The invention relates to a method for producing a high-pressure fuel pump according to the preamble of claim 1.
Fuel systems for internal combustion engines, in which fuel is pumped from a fuel tank at high pressure into a high-pressure accumulator (“rail”) by means of a pre-supply pump and a mechanically driven high-pressure fuel pump, are known on the market. A pressure damper device is customarily arranged on or in a pump housing of such a high-pressure fuel pump. A pressure damper device of this type generally comprises a cover element and a membrane damper which is arranged between cover element and pump housing, is customarily in the form of a gas-filled membrane capsule and is supported on the pump housing via a support element. The pressure damper device here is fluidically connected to a low-pressure region. The pressure damper device serves for damping pressure pulsations in the low-pressure region of the fuel system, said pressure pulsations being caused, for example, by opening and closing operations of valves, for example of an inlet valve, in the high-pressure fuel pump. An integrally bonded connection between the pump housing and the cover element is produced according to the prior art by means of a laser welding process.
The present invention has the advantage that the production of the high-pressure fuel pump is simpler and more reliable and makes it possible to design the pump more advantageously.
In the case of the laser welding process known from the prior art, measures have to be taken to avoid welding splashes inside the pump. By contrast, in the case of the proposed capacitor discharge press-fit welding process (CDPF welding process), only a weld expulsion in the form of a firm burr arises at the connecting point. The CDPF welding process therefore does not result in any additional admission of dirt into the pump. Further measures in this respect can be omitted. Furthermore, the CDPF welding process has a shorter cycle time than the previously known laser welding process.
According to the invention, in order to produce a high-pressure fuel pump comprising a pump housing and a cup-shaped cover element, wherein the pump housing the cover element are connected to each other by an encircling weld seam (360°), it is provided that the process steps indicated in claim 1 are carried out.
The method can be further simplified in that the collet chuck and the electrode as a whole are realized by a single tool.
It can furthermore be provided that the inside diameter of the cover element has an excess size in relation to the outside diameter of the pump housing. In association therewith, it can be provided that the cover element is pushed over the pump housing. This reduces the height of the high-pressure fuel pump by the amount of the overpressing. The high-pressure fuel pump thereby becomes more compact as a whole, which is an important requirement for the integration of the high-pressure fuel pump in an internal combustion engine. At the same time, this measure also increases the effective diameter of the cover element. It is thereby possible to provide an enlarged pressure damper between the cover element and the pump housing, which has a positive effect on the functionality of said pressure damper.
It is provided in a development of the process that, during the process, a relative movement between the cover element and the pump housing is detected and evaluated. Additionally or alternatively, a current profile can also be detected and evaluated. In this connection, it is provided in particular that the detected process features are compared with predetermined reference data and it is then determined on the basis of the comparison whether the process has taken place in a defective or error-free manner.
Further features, application possibilities and advantages of the invention emerge from the description below of exemplary embodiments of the invention. In the figures:
A piston 34 of the high-pressure fuel pump 22 can be moved up and down along a piston longitudinal axis 38 by means of a drive 36, which here is in the form of a cam disk, this being illustrated schematically by an arrow having the reference sign 40. An outlet valve 44 is arranged hydraulically between the piston chamber 26 and an outlet connecting branch 42 of the high-pressure fuel pump 22, which outlet valve can open toward a high-pressure accumulator 46 (“rail”). The high-pressure accumulator 46 and the piston chamber 26 can be connected fluidically via a pressure-limiting valve which opens when a limit pressure in the high-pressure accumulator 46 is exceeded.
The high-pressure fuel pump 22 is shown in a sectional illustration in
The connecting region 56 runs around the pump housing in a circumferential direction. A membrane damper capsule 60 is held between the cover element 54 and the pump housing 52 by means of two holding elements.
The CDPF weld seam between the metallic cover element and the metallic pump housing 52 is produced, as illustrated schematically in
As an alternative to the use of the mechanical stop 90, the sinking of the collet chuck or of the electrode can be detected by means of other suitable sensor arrangements, for example travel sensors, and the pressing is ended after a predetermined sinking distance. There is then likewise no further sinking.
In an alternative embodiment, see
Number | Date | Country | Kind |
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10 2016 212 469.2 | Jul 2016 | DE | national |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2017/061272 | 5/11/2017 | WO | 00 |