High-pressure connective device, high-pressure fuel pump, and method for producing a high-pressure connection device for a high-pressure fuel pump

Abstract

The invention relates to a high-pressure connection device (50) for a high-pressure fuel pump (10), having the following: an outlet device (18) for discharging fuel (14) from the high-pressure fuel pump (10); a connection device (22) for connecting the outlet device (18) to elements arranged downstream of the outlet device; a welding seam (30) for connecting the outlet device (18) and the connection device (22); and a pretensioning device (52) for exerting a pretension force (F.sub.v) onto the welding seam (30) in the direction of the outlet device (18). The invention further relates to a high-pressure fuel pump (10) which has such a high-pressure connection device (50) and to a method for producing such a high-pressure connection device (50).

Claims

1. A high-pressure connection device for connecting a high-pressure fuel pump to one or more elements of a fuel injection system, the high-pressure connection device comprising: an outlet which discharges fuel from the high-pressure fuel pump; a connector connecting the outlet to the one or more elements of the fuel injection system; a weld seam which connects the outlet and the connector; and a pretensioner configured to exert a tension force on the weld seam, the pretensioner directly contacting the connector and directing connected to the outlet.

2. The high-pressure connection device of claim 1, further comprising a fuel inlet volume in the connector, and a pressure-relief valve disposed in the outlet such that the pressure-relief valve opens into the fuel inlet volume, wherein the fuel inlet volume is configured to admit fuel that flows out of the outlet and into the connector.

3. The high-pressure connection device of claim 1, wherein the pretensioner has a pretensioning face directed toward the outlet and which applies the tension force to the weld seam, the weld seam being supported by a contact face of the connector.

4. The high-pressure connection device of claim 3, wherein the pretensioning face and the contact face of the connector are in contact in a contact region disposed so as to have the same distance from a flow axis of fuel through the high pressure connection device and a longitudinal axis of the connector as a distance of the weld seam to the flow axis and the longitudinal axis.

5. The high-pressure connection device of claim 3, wherein the pretensioning face and the contact face of the connector are in contact in a contact region disposed so as to be substantially perpendicular to a flow direction of fuel through the high-pressure connection device.

6. The high-pressure connection device of claim 3, wherein the pretensioning face and the contact face of the connector are in contact in a contact region disposed so as to be between 30 degrees and 80 degrees to a flow direction of fuel through the high-pressure connection device.

7. The high-pressure connection device of claim 6, wherein the contact region is disposed at 45 degrees to the flow direction of fuel through the high-pressure connection device.

8. The high-pressure connection device of claim 1, further comprising a recess on the outlet, wherein the pretensioner is configured to engage the recess, the recess has an external recess thread and the pretensioner has an internal pretensioning installation thread.

9. The high-pressure connection device of claim 1, further comprising a substantially circular groove disposed in the outlet, wherein the weld seam is disposed in at least one of the groove and a flow axis of fuel in the high-pressure connection device beside the circular groove so as to be perpendicular to the flow axis of fuel.

10. The high-pressure connection device of claim 1, further comprising a protrusion region disposed on a first end of the connector, the protrusion region contacting the outlet, wherein the protrusion region comprises a welding face on which the weld seam is located.

11. The high-pressure connection device of claim 10, wherein a connection region of the connector for connecting the connector to the one or more elements of the fuel injection system is disposed on a second end of the connector opposite the first end thereof, and the second end of the connector has an external thread.

12. The high-pressure connection device of claim 10, wherein a connection region of the connector for connecting the connector to the one or more elements of the fuel injection system is disposed on a second end of the connector opposite the first end thereof, and an external diameter of the connector at the first end thereof is larger than an external diameter of the connector at the second end of the connector.

13. A high-pressure fuel pump for charging a fuel with high pressure, comprising: a high-pressure connection device for connecting the high-pressure fuel pump to one or more elements of a fuel injection system, the high-pressure connection device including: an outlet, which discharges fuel from the high-pressure fuel pump; a connector connecting the outlet to the one or more elements of the fuel injection system; a weld seam which connects the outlet and the connector; and a pretensioner configured to exert a tension force on the weld seam, the pretensioner directly contacting the connector and directing connected to the outlet.

14. A method for providing a high-pressure connection for a high-pressure fuel pump, the method comprising: providing an outlet for discharging a fuel from the high-pressure fuel pump; providing a connector configured to connect the outlet to at least one element of a fuel injection system; generating a weld seam that connects the outlet to the connector; and exerting a pretensioning force on the weld seam in a direction of the outlet, comprising directly connecting a pretensioner to the outlet such that a pretension face of the pretensioner contacts a contact face of the connector and applies the pretensioning force to the weld seam.

15. The high-pressure connection device as claimed in claim 1, wherein the pretensioner comprises one of a nut which has a threaded engagement with the outlet and a flange assembly with at least one through-bore in which at least one fastener is disposed that engages with the outlet.

16. The high-pressure fuel pump of claim 13, wherein the connector has a contact face and the pretensioner has a pretensioning face that contacts the contact face and is directed toward the outlet and applies the tension force to the weld seam, and the pretensioning face and the contact face of the connector are in contact in a contact region disposed so as to be at least one of at an oblique angle relative to a longitudinal axis of the connector and a flow axis of fuel through the connector, and the same distance from the flow axis of fuel and the longitudinal axis of the connector as a distance of the weld seam to the flow axis and the longitudinal axis.

17. The high-pressure fuel pump of claim 16, wherein the oblique angle is between 30 degrees and 80 degrees to the flow direction and the longitudinal axis of the connector.

18. The high-pressure fuel pump of claim 13, wherein the connector has a contact face and the pretensioner has a pretensioning face that contacts the contact face and is directed toward the outlet and applies the tension force to the weld seam, and the pretensioning face and the contact face of the connector are in contact in a contact region disposed so as to be at a first oblique angle relative to a longitudinal axis of the connector and a flow axis of fuel through the connector, and the weld seam is at a second oblique angle relative to the longitudinal axis and the flow axis.

19. The high-pressure fuel pump of claim 13, wherein the outlet includes a recess, the pretensioner is configured to engage the recess, and the recess has an external recess thread and the pretensioner has an internal pretensioning installation thread.

20. The high-pressure fuel pump of claim 13, further comprising a substantially circular groove disposed in the outlet, wherein the weld seam is disposed in at least one of the groove and a flow axis of fuel in the high-pressure connection device beside the circular groove so as to be perpendicular to the flow axis of fuel.

Description

(1) Advantageous design embodiments of the invention will be explained in more detail below by means of the appended drawings. In the drawings:

(2) FIG. 1 shows a perspective view of a high-pressure fuel pump having an outlet installation for discharging a fuel that in the high-pressure fuel pump is charged with pressure;

(3) FIG. 2 shows a perspective view of a detail of the high-pressure fuel pump of FIG. 1, having a connection installation that is disposed on the outlet installation;

(4) FIG. 3 shows a sectional view through the high-pressure fuel pump having a connection installation of FIG. 2;

(5) FIG. 4 shows a further sectional view of a high-pressure fuel pump having a connection installation, an outlet valve, and a pressure-relief valve;

(6) FIG. 5 shows a sectional view of a high-pressure connection device on a high-pressure fuel pump as shown in FIG. 1, according to a first embodiment;

(7) FIG. 6 shows a schematic illustration of stress distribution in individual regions of the high-pressure connection device according to FIG. 5;

(8) FIG. 7 shows a sectional view of a high-pressure connection device on a high-pressure fuel pump as shown in FIG. 1, according to a second embodiment;

(9) FIG. 8 shows a schematic illustration of stress distribution in individual regions of the high-pressure connection device according to FIG. 7;

(10) FIG. 9 shows a sectional view of a high-pressure connection device on a high-pressure fuel pump as shown in FIG. 1, according to a third embodiment;

(11) FIG. 10 shows a schematic illustration of stress distribution in individual regions of the high-pressure connection device according to FIG. 9;

(12) FIG. 11 shows a perspective view of a high-pressure connection device on the high-pressure fuel pump according to FIG. 1, according to a fourth embodiment; and

(13) FIG. 12 shows a further perspective view of the high-pressure connection device of FIG. 11.

(14) FIG. 1 shows a perspective view of a high-pressure fuel pump 10 such as is used in a fuel injection system, for example. A pressurized chamber 24 (see FIG. 3) that is not visible in the perspective view of FIG. 1 is present in a housing 12 of the high-pressure fuel pump 10, a fuel 14 being charged with high pressure in said pressurized chamber 24.

(15) Once the fuel 14 has been charged with high pressure, said fuel is discharged from the high-pressure fuel pump 12 by way of an outlet installation 18 that is disposed in the housing 12 and has an outlet bore 20, so as to be directed onward to elements which in the flow direction 48 of the fuel 14 are downstream of the high-pressure fuel pump 10.

(16) FIG. 2 shows a perspective view of a detail of the high-pressure fuel pump 10 of FIG. 1, wherein a connection installation 22 by way of which the outlet installation 18 is to be connected to the downstream elements of the fuel injection system is disposed on the outlet installation 18.

(17) FIG. 3 shows a sectional view through the perspective detailed view in FIG. 2, wherein the pressurized chamber 24, an inflow 26 to the pressurized chamber 24, and the outlet bore 20 in the outlet installation 18 of the housing 12 can now be seen in the housing 12 of the high-pressure fuel pump 10. It can furthermore be seen that the connection installation 22 at a first end 28 is connected to the outlet installation 18 by way of an encircling weld seam 30. At a second end 32, the connection installation 22 has a region by way of which the former can be connected to downstream elements of the fuel injection system. For example, an external thread 34 for connection to the downstream elements can be provided here.

(18) FIG. 4 shows a further sectional view of a high-pressure fuel pump 10 having a connection installation 22, wherein an outlet valve 36 is disposed in the outlet installation 18, in particular in the outlet bore 20. Furthermore provided in the outlet installation 18 is a pressure-relief valve 38 which prevents that elements downstream of the high-pressure fuel pump 10 are impinged upon with excessive fuel pressure and thus are damaged. The pressure-relief valve 38 has a valve opening 40 which opens into a fuel inlet volume 42 of the connection installation 22. The outlet bore 20 also opens into this fuel inlet volume 42. The fuel inlet volume 42 tapers down from the first end 28 of the connection installation 22 toward the second end 32 of the connection installation 22, thus supplying the pressurized fuel 14 to the downstream elements of the fuel injection system.

(19) The connection installation 22 for guiding the fuel 14 has a longitudinal axis 44 which is congruent with a flow axis 46 which runs along the flow direction 48 of the fuel 14.

(20) The outlet installation 18 and the connection installation 22, when interconnected, form a high-pressure connection device 54 by way of which the high-pressure fuel pump 10 can be connected to elements of the fuel injection system that are downstream of the high-pressure fuel pump 10.

(21) In order for the outlet installation 18 and the connection installation 22 to be connected, no longer is only the weld seam 30 as shown in FIG. 3 now used, but a pretensioning installation 52 which is disposed such that the latter can apply a pretensioning force F.sub.v to the weld seam 30 is additionally applied. The combination of the weld seam 30 and the pretensioning installation 52 will be explained in more detail hereunder by means of FIG. 5 to FIG. 12.

(22) The features of the elements of the high-pressure connection device 50 that will be initially described hereunder are common to all embodiments described in the following.

(23) The outlet installation 18 has a recess 54 in which a wall 56 of the connection installation 22 that is disposed so as to be parallel with the flow axis 46 of the fuel 14 can engage, so as to be supported on said recess 54. The recess 54 herein preferably has a depth of at least 5 mm, so as to be able to guarantee positive support of the connection installation 22 on the outlet installation 18.

(24) A groove 58 is additionally disposed in the outlet installation 18, in order to provide flexibility for the assembly and the welding procedure when attaching the weld seam 30, that is to say in order to make available more spatial degrees of freedom for attaching the weld seam 30. The groove is preferably disposed in an encircling manner on a surface of the outlet installation 18.

(25) The connection installation 22 has a protrusion region 60 which on a side that is directed toward the outlet installation 18 comprises a welding face 62 on which the weld seam 30 is disposed. The connection installation 22 on the opposite side of the protrusion region 60, that is to say the side that is disposed so as to be directed away from the outlet installation 18, has a contact face 64 by way of which said connection installation 22 is in contact with the pretensioning installation 52. The protrusion region 60 is disposed on the first end 28 of the connection installation 22. Opposite the protrusion region 60 on the second end 32 of the connection installation 22, the connection installation 22 has a connection region 66 by way of which the high-pressure connection device 50 can be connected to downstream elements of the fuel injection system. A neck region in which the connection installation 22 has the smallest external diameter is provided between the connection region 66 and the protrusion region 60. The connection region 66 can optionally have the external thread 34, and moreover has a smaller external diameter than the protrusion region 60.

(26) The external diameter of the protrusion region 60 is defined by the required fuel inlet volume 42 into which not only the outlet bore 20 of the high-pressure fuel pump 12 but also the valve opening of the pressure-relief valve 38 open, as is shown in FIG. 4. On account thereof, an internal diameter in the protrusion region 60 of 16 mm results, for example, the latter defining the external diameter of the protrusion region 60.

(27) The pretensioning installation 52 has a pretensioning face 70 with which the contact face 64 is in contact so as to apply the pretensioning force F.sub.v to the weld seam 30. An internal diameter of the pretensioning installation 52 is larger than the external diameter on the connection region 66 such that the pretensioning installation can be pulled over the connection installation 22. At the same time, the smallest internal diameter of the pretensioning installation 52 is smaller than the external diameter of the protrusion region 60 such that the pretensioning installation 52 can be supported on the protrusion region 60.

(28) By way of the pretensioning installation 52, a pretensioning force of approximately 4 kN-8 kN, for example, can be applied to the weld seam 30 which has a linkage length of approximately 1.9 mm to 2.2 mm, for example, and a width of approximately 0.2 mm to 0.4 mm, for example.

(29) FIG. 5 and FIG. 6 show sectional views of a first embodiment of the high-pressure connection device 50.

(30) The pretensioning installation 52 here is configured as a nut 72, wherein the recess 54 has an external recess thread 74 and the nut 72 has an internal pretensioning installation thread 76 which engages in the external recess thread 74. The contact face 64 of the connection installation 22 and the pretensioning face 70 of the pretensioning installation 52 are in contact in a contact region 78 which is disposed so as to be perpendicular to the flow direction 48 of the fuel 14. Furthermore, the contact region 78 in the embodiment shown in FIG. 5 and FIG. 6 in the flow direction 48 of the fuel 14 is disposed so as to be substantially perpendicularly above the weld seam 30 and thus has approximately the same spacing d from the flow axis 46 as does the weld seam 30. On account thereof, the weld seam 30 is destressed as efficiently as possible, since lifting or rupturing of the weld seam can be effectively counteracted. The pretensioning force F.sub.v required therefor is simultaneously reduced as compared to the case in which the weld seam 30 is not destressed and a higher pretensioning force F.sub.v thus has to be applied in order for the weld seam 30 to be stabilized. Thus, a mean stress which engages on the external thread 34 in the connection region 66 also becomes lower and therefore the integrity of operation becomes higher. In the case of the arrangement illustrated in FIG. 5, almost all potential weld seam angles of a contact face of the weld seam with the outlet installation 18 in relation to the flow direction 48 in the range from 0 to 90 are also possible in the case of the connection of the outlet installation 18 and the connection installation 22.

(31) FIG. 6 shows a fragment of the sectional view in FIG. 5 with stresses acting in the individual regions illustrated, wherein the stresses are lower as the coloration becomes darker. The weld seam 30 in the embodiment according to FIG. 5/FIG. 6 runs in the groove 58.

(32) In the first embodiment shown in FIG. 5 and FIG. 6, a weld seam 30 that is welded conventionally from the outside, having a nut as a union nut, is thus illustrated. It is particularly advantageous in the case of this embodiment that known arrangements of high-pressure connection devices 50 and the processes associated therewith which are known from the production of high-pressure fuel pumps 10 of lower pressure levels can be appropriated without any major modifications. Despite the increase in pressure, there is furthermore the potential of maintaining the installation space and thus any optionally available components below the connection installation 22. Besides the outlet valve 36, the pressure-limiting valve 38 that in most instances is likewise installed below this connection installation 22 becomes particularly significant herein, since said pressure-limiting valve 38 to some extent safeguards components that are downstream of the high-pressure fuel pump 10, such as the injectors and the rail, for example, against excessive pressure peaks. The excess medium is then conveyed away in a controlled manner by way of the high-pressure region of the pump.

(33) FIG. 7 and FIG. 8 show a sectional view of a second embodiment of the high-pressure connection device 50 which is of substantially the same construction as the high-pressure connection device 50 of FIG. 5 and FIG. 6, the difference being that the weld seam 30 here does not run within the groove 58 but is disposed so as to be offset away from the groove 58 in the direction toward the flow axis 46 of the fuel 14. The groove 58 here contributes to directing forces that act on the weld seam 30 away from the weld seam 30 and to thus destressing the latter even more intensely.

(34) The stresses acting in this embodiment are schematically illustrated in FIG. 8 in a manner analogous to FIG. 6.

(35) FIG. 9 and FIG. 10 each show a sectional view of a third embodiment of the high-pressure connection device 50, wherein the contact region 78 here is not aligned so as to be perpendicular to the flow direction 48 of the fuel 14, but at an angle which is within a range from 30 to 80, in the present example of 45. The arrangement in the high-pressure connection device 50 otherwise corresponds to the arrangement that is shown in FIG. 7.

(36) FIG. 10, in a manner analogous to that of FIG. 6 and FIG. 8, herein schematically shows the stresses acting in the third embodiment.

(37) The protrusion region 60 in the embodiment in FIG. 9 has a smaller internal diameter and also a smaller external diameter than in the preceding embodiments, on account of which the weld seam 30 moves inward in the direction toward the flow axis 46 such that the introduction of the pretensioning force F.sub.v directly above the weld seam 30, as is shown in the embodiment according to FIG. 5, is no longer possible. This is because the pretensioning installation 52 which is intended to be pulled over the connection installation 22 requires a minimum internal diameter in order to be able to pass the connection region 66 having the external thread 34 disposed thereon. It is therefore proposed in the embodiment according to FIG. 9 that an oblique weld seam 30 and a contact face 64 or a pretensioning face 70, respectively, that is embodied at a similar angle thereto is provided. On account thereof, the forces can be introduced and distributed in such a targeted manner that the weld seam 30 and the further participating components are not excessively stressed. The weld seam 30 here was generated by means of capacitor discharge welding.

(38) FIG. 11 and FIG. 12 show perspective views of a fourth embodiment, in which a flange-screw assembly 80 instead of a nut 72 is used as the pretensioning installation 52, in the case of which a flange 82 by way of its pretensioning face 70 is supported on the contact face 64 of the connection installation 22 and screw bores 84 through which screws can engage into the housing 12 of the high-pressure fuel pump 10 or into the outlet installation 18, respectively, are provided.

(39) Accordingly, a flange-screw assembly 18 can also be used instead of a nut 72 as the pretensioning installation 52. As opposed to the flange-screw assembly 80, the nut 72 offers the advantage that the pretensioning force F.sub.v introduced is introduced uniformly into all regions. This is most often not the case when a flange 82 is used. However, a flange 82 does have the advantage that the latter in terms of the installation space can be designed in a significantly more flexible manner.

(40) In known arrangements, the high-pressure connection that by welding (for example by way of an electron beam or a laser beam) is fixedly connected to the housing 12 of the high-pressure fuel pump 10 is highly stressed in mechanical terms in and beside the weld seam 30 by the forces that are generated by the high pump pressure that arises in the high-pressure connection.

(41) To date, circular weld seams 30 have been generated by way of a beam direction that is in a direction perpendicular or angular in relation to the longitudinal axis 44 of the connection installation 22 and from the outside in the direction of the longitudinal axis 44 along the contact line of the two parts to be connected. The penetration depth when welding could thus be maximized, this in turn leading to the forces resulting axially from the internal pressure stress being minimized. Despite the consistent projected face, the loads and the stresses

(42) Engaging on account thereof on the weld seam 30 increase in the case of comparatively high pressures. This face could be further minimized by a method in which the high-pressure connection is welded from the inside (for example by capacitor discharge welding).

(43) By minimizing the projected axial face and by way of a construction that is tailored to stress and offers operational integrity, the construction of the high-pressure connection device 50 as described attempts to minimize the loads that engage on the weld seam 30.

(44) In order for the maximum resilience to be able to be further increased, the high-pressure connection device 50 which by using a pretensioning installation 52 such as, for example, a nut 72 or a flange-screw assembly 80 causes pretensioning of the weld seam 30 is proposed, such that a simple welding process can continue to be used for sealing and for materially-integral connecting at a consistent axial face and an increased pressure level.