Patent Application
20060138040
This application is based on German Patent Application 10 2004 062 008.3 filed Dec. 23, 2004, upon which priority is claimed.
1. Field Of The Invention
The invention relates to a fuel filter, which is embodied in particular as a rodlike filter body and which can be introduced into an inlet conduit, in particular of a fuel injection valve of a common rail system; the filter body has at least one inlet opening and at least one outlet opening.
The invention further relates to the use of the known hydroerosive process for producing rounded places in fuel filters.
2. Description of the Prior Art
To prevent damage to fuel injection valves from contaminants in the fuel, the fuel filters known from the prior art and also known in a version as a rod filter, are typically placed in each fuel injection valve.
The rodlike filter body described in German Patent Disclosure DE 198 32 940 A1 is press-fitted into an inlet conduit of a fuel injection valve. The fuel filter itself has at least one inlet opening, through which the fuel, which is at high pressure, is introduced. Any chips and contaminants entrained with the fuel remain in the filter body, since the outlet openings have a substantially smaller diameter than the inlet opening.
Especially embodied fuel injection systems require fuel filters in which only slight pressure variations occur. The fuel filters known until now from the prior art comprise the aforementioned filter body, which has outlet openings on its circumference. Because of the constant pressure and the varying pressure pulses that are exerted by the fuel inside the fuel filter, nonlaminar flows occur, especially at the transitions from the interior of the filter body to the outlet openings. These nonlaminar flows occur particularly at the points where there is a change in cross section or a change of direction. Because of this constant stress, over the service life of the fuel filter rounded places occur at these points, so that the flow coefficient changes over the service life.
It is a prerequisite for certain fuel injection systems that the flow coefficient be constant over the service life.
The object of the invention is to refine a fuel filter of the type defined at the outset such that it has a virtually constant flow coefficient over its service life.
For attaining this object it is therefore important that the flow coefficient inside the fuel filter be set sufficiently precisely. It is therefore proposed that a known fuel filter be refined such that the transitions of the outlet openings, particularly relative to the inner wall, not have sharp edges but instead have rounded places, and these rounded places can be produced by means of a known hydroerosive rounding process.
A substantial advantage of the invention is that the flow coefficient can be set precisely, since the outlet openings have rounded places toward the inner wall of the filter body that allow a nearly laminar flow inside the filter body. As a result, throttling inside the filter body because of turbulence that occurs, especially at edges, is avoided.
With the aid of the hydroerosive process (HE rounding process) known per se, these rounded places are produced, specifically in such a way that already during the production process, the flow coefficient of the filter body can be measured. In this hydroerosive process, a fluid that contains grinding bodies is pressed with pressure through the previously made outlet openings, causing the edges of the outlet openings to be rounded by being ground off, namely in the region of the transition from the inner wall of the filter body to the outlet opening.
By the above-described hydroerosive rounding process, any wear at the edges that might occur during use is produced in advance by the process so that the flow of fuel from the inlet opening to the outlet opening changes only slightly or not at all over the running life of the filter.
It has also been found that by employing the hydroerosive rounding process, the flow coefficient of the fuel filter is improved, so that high throughput rates can be attained with smaller outlet openings, or with only a few outlet openings.
A preferred embodiment advantageously provides that in a filter body, the outlet openings are first made by means of a laser drilling process. In a further ensuing machining process, hydroerosive rounding process is employed, and the flow coefficient is measured during the process.
Another advantage of the invention is that there is a damping system inside the fuel filter. In a preferred exemplary embodiment, this damping system is embodied such that star-shaped damping elements that suitably damp the various pressure pulses are located inside the fuel filter. The fuel filter itself furthermore has a corresponding damping property, since the diameter of the outlet openings is substantially less than that of the inlet opening.
The invention will be better understood and further objects and advantages thereof will become more apparent from the ensuing detailed description of a preferred embodiment taken in conjunction with the drawings, in which:
The fuel filter 1 in
In the view shown in
The outlet openings 8 shown in
According to the invention, it is provided that the rounded places of the outlet openings 8 (that is, the edges between the inner face 7b of the filter body 2 and the respective outlet opening 8, as shown in
The invention is not limited to the exemplary embodiment described. On the contrary, the invention extends to filter bodies whose edges, which are created in the region of the inner wall to the outlet opening, are rounded. In particular, the use of the hydroerosive process is proposed for this purpose.
The foregoing relates to a preferred exemplary embodiment of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2004 062 008.3 | Dec 2004 | DE | national |
