The invention relates to a fuel pump, in particular for a fuel system of a piston engine, as generically defined by the preamble to claim 1.
Internal combustion engines, such as Diesel or gasoline piston engines, that have a high-pressure fuel system are on the market. The fuel system in turn includes a high-pressure fuel pump, with which the fuel is aspirated from a fuel tank and delivered under high pressure to one or more injectors. As the high-pressure fuel pumps, piston pumps, which for instance have a geared pump or a vane cell pump on the low-pressure side, or are supplied by such a pump, are used as a rule.
In such pumps, at least one of the parts that is in motion in operation, such as gear wheels (in the case of a geared pump) or a rotor (in the case of a vane cell pump), rests laterally on a housing region of the fuel pump, so that in operation they slide along that housing region. For reasons of weight, the housings of the known high-pressure fuel pumps are made partly of aluminum. To ensure adequate wear resistance of the housing region along which the parts that are in motion in operation slide, these housing regions, also called “runup faces” are made for instance from steel or gray cast iron.
It is the object of the invention to create a high-pressure fuel pump which has a long service life, is low in cost, and requires little space.
This object is attained by the high-pressure fuel pump having the characteristics of claim 1. Advantageous refinements are recited in dependent claims. Characteristics important to the invention are also found in the ensuing description and the drawings. The characteristics may be important for the invention both on their own and in various combinations, without explicit mention being made thereof.
The coating provided according to the invention is extremely wear-resistant and is therefore very well suited as a running face particularly for rotating parts, such as gear wheels or rotors of corresponding types of pump. The elimination of a separate running face, for instance of steel or gray cast iron or the like, such as aluminum/nickel or anodized aluminum, leads to cost savings. With the elimination of an intermediate disk of steel or gray cast iron as a running face, the space required is reduced as well; thus the high-pressure fuel pump has comparatively small dimensions. If the coating of plastic is applied directly to the housing region, without the use of a coated intermediate disk as a running face for the moving part, a sealing region toward the outside is eliminated as well, which simplifies construction, reduces costs, and increases the operating reliability.
A first refinement of the invention provides that the plastic is a thermoplastic, in particular a polyether ether ketone. Such a material is especially wear-resistant and therefore provides for a long service life of the high-pressure fuel pump.
This advantage can be enhanced further if the thermoplastic is reinforced with fibers, in particular carbon fibers.
The material of at least the housing region onto which the coating is applied includes aluminum or is aluminum. Aluminum is comparatively simple to machine, which reduces the production costs. Moreover, it has a low weight, and thus the weight of the high-pressure fuel pump is low. Nevertheless, by means of the plastic coating provided according to the invention, wear is kept slight, and a long service life of a high-pressure fuel pump that is for by far the most part made of aluminum is ensured.
The refinement of the high-pressure fuel pump of the invention in which a region of the coating is embodied as a sealing region, which cooperates with another region of the housing is especially advantageous. The plastic coating provided according to the invention performs a dual function in such a case: Besides the wear-reduced function, it also performs a sealing function. Separate sealing, for instance by means of an O-ring, including the attendant metal-cutting machining after suitable O-ring grooves have been made is thus not necessary. This too simplifies construction, facilitates assembly, reduces sources of mistakes, and so forth.
The sealing region can include an encompassing sealing bead or an encompassing sealing lip. Such embodiments are easy to produce with conventional plastics, especially thermoplastics, and ensure reliable sealing off even with major pressure differences.
The plastic coating can be produced simply in that the coating is melted onto the housing region.
It is also possible that the housing region onto which the coating is applied includes a comparatively thin support plate, which is secured to another housing region, preferably glued to it. In specific applications, depending on what until now was the complex geometry of the housing region and/or of the region to be sealed off, this makes individualized, reliable construction possible.
Embodiments of the invention are described in further detail below in conjunction with the drawings. In the drawings:
In
On the low-pressure side, the high-pressure fuel pump 14 includes a geared pump 15. In exemplary embodiments not shown, the high-pressure fuel pump can also include a vane cell pump or any other suitable type of pump on its low-pressure side. The high-pressure fuel pump 14, including the geared pump 15 on the low-pressure side, is driven directly and mechanically by the engine. In an exemplary embodiment not shown, the geared pump on the low-pressure side can also have a separate drive mechanism, such as an electric motor.
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Number | Date | Country | Kind |
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10 2007 044 499.2 | Sep 2007 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP08/61470 | 9/1/2008 | WO | 00 | 3/11/2010 |