Patent Application
20180073477
The disclosure relates to a piston-type fuel pump.
Fuel systems of internal combustion engines in which the fuel is delivered from a fuel tank into a fuel rail at high pressure by means of a mechanically driven piston-type fuel pump are known from the market. For this purpose, the piston-type fuel pump has at least one inlet valve and one outlet valve. The outlet valve is in the form of a spring-loaded non-return valve, normally with a ball-shaped valve element.
The problem addressed by the present disclosure is solved by means of a piston-type fuel pump. Advantageous refinements of the disclosure are specified in the claims. Further features of importance for the disclosure furthermore emerge from the following description and from the drawing.
The piston-type fuel pump according to the disclosure has the advantage that the production thereof can be simplified, and production costs thereby reduced, because the guide element is held securely in the pump housing without additional joining measures. By means of the guide element, reliability during the operation of the piston-type fuel pump is furthermore increased, because jamming is prevented and sealed closure is ensured. The guidance of the valve element by the guide element also reduces wear. The guidance of the valve element also ensures a temporally short closing process, which increases the efficiency of the piston-type fuel pump.
A first refinement is characterized in that the guide element has a guide section for guiding the valve element and has a retention section for retention in the opening of the pump housing, wherein the guide section and the retention section are arranged axially at different points of the guide element. The “guidance” function is thus spatially separate from the “retention” function. In this way, the quality of the “guidance” function is maintained even if radial deformation occurs in the “retention” region owing to said region being radially pressed in.
In a refinement of this, it is proposed that the guide element is pressed into a holding ring which in turn is pressed into the pump housing, wherein the holding ring preferably has fuel passage openings. The latter may be in the form of axially running ducts or in the form of intermediate spaces between the radially outwardly extending vane-like or lamellar fastening sections. The guide element can thus be of very simple construction, reducing the costs for the production thereof, because the fuel passage function is performed by the separate holding ring.
It is also proposed that the guide element has a stroke stop which limits the opening stroke of the valve element to a predefined value. This has the advantage that the closing impetus of the valve element onto the valve seat is reduced by virtue of the flight path of the valve element being reduced by the stroke stop. The occurring accelerations thus act only over a limited distance, which leads to a lower closing speed of the valve element. This reduces the damaging effects during the closing process, in particular the wear generated both on the valve element and also on the valve seat as a result of the closing impact. Furthermore, the reduced flight path results in a temporally shortened closing process, which increases the efficiency of the piston-type fuel pump. Furthermore, the lower closing speed leads to a lower impact speed of the valve element against the valve seat, which leads to a reduction in noise during the operation of the piston-type fuel pump.
A further advantageous refinement of the piston-type fuel pump according to the disclosure is distinguished by the fact that the guide element is arranged coaxially with respect to and radially outside the valve element and has a radially inwardly directed shoulder that forms the stroke stop. A guide element of said type is simple to produce, and the radially inwardly directed stroke stop may be formed for example by an annular shoulder with which the valve element comes into contact over the largest possible area, whereby the loads on the valve element are kept low. Furthermore, a guide element of said type does not pose an obstruction to the accommodation of the valve spring.
As an alternative to this, it is also possible for the guide element to have, at least in sections, a smaller internal diameter than the valve element and to be arranged coaxially with respect to the valve element, and for that end of the guide section which points toward the valve element to form the stroke stop, or for it to have a radially outwardly directed shoulder that forms the stroke stop. This, too, is simple to manufacture and assemble, and furthermore has the advantage of the relatively small radial dimensions.
Here, it is particularly advantageous for a valve spring to also be guided by the guide element. In this way, the guide element performs not just one but two or possibly even three tasks. Owing to the integration of the different functions, components and thus manufacturing and assembly costs are saved.
This integration of different functions into said guide element can be further enhanced if it has a support section on which that end of the valve spring which is situated opposite the valve element is supported.
Is also proposed that the valve spring be a spiral-type or stellate flat diaphragm spring that is fastened to the guide element or directly to the pump housing. In this way, the axial structural height of the outlet valve can be reduced.
The guide element may be a sintered or MIM part. Such a part exhibits considerable mechanical robustness and thus permanently only very low wear.
Finally, it is also proposed that the valve element be of pot-shaped form. The encircling wall of a valve element of said type is particularly suitable as a guide wall in interaction with the above-mentioned guide element. Nevertheless, a valve element of said type has a relatively low mass and thus good dynamics, which in turn is to the benefit of the efficiency of the piston-type fuel pump according to the disclosure.
Examples of the present disclosure will be explained in more detail below with reference to the appended drawings, in which:
A fuel system of an internal combustion engine is denoted as a whole in
The piston-type fuel pump 18 comprises a pump housing 26 (only partially indicated) in which a pump piston 28 is guided. The latter can be set in a reciprocating motion by a drive (not illustrated), as indicated by a double arrow 30. The pump piston 28 and the pump housing 26 delimit a delivery chamber 32. The latter is connected via an inlet valve 34 to the low-pressure line 16. Furthermore, the delivery chamber 32 is connected via a high-pressure duct 36 to an outlet valve 38, which in turn is connected at the outlet side to the high-pressure line 20.
Both the inlet valve 34 and the outlet valve 38 are in the form of spring-loaded non-return valves. Here, an embodiment of the inlet valve as a flow-rate control valve is not illustrated but is possible. In the case of such a valve, the inlet valve 34 can be positively opened during a delivery stroke of the pump piston 28, such that the fuel is delivered not into the fuel rail 22 but back into the low-pressure line 16. The fuel flow rate delivered by the piston-type fuel pump 18 into the fuel rail 22 can be adjusted in this way.
The design of the outlet valve 38 is of particular significance in the present case. This will therefore now be discussed in more detail with reference to
The outlet valve 38 also comprises a cylindrical guide element in the form of a sleeve 50, which in the present case is of stepped form. Said sleeve has a first section 52 (“guide section”) on the left in
At its right-hand end in
The outlet valve 38 furthermore comprises a holding ring 66 which is pressed by way of its outer wall 68 into the opening 41 in the pump housing 26. The second section 54 of the guide element 50 is in turn pressed into the inner opening 70 of the holding ring 66. Here, the connecting section 56 bears by way of its side pointing to the right in
During operation of the piston-type fuel pump 18, the valve element 44 lifts off from the valve seat 42 when the pressure in the delivery chamber 32 reaches a corresponding opening value during a delivery stroke of the pump piston 28. The stroke of the valve element 44 is however limited by the stroke stop 58 to a predefined value H which corresponds to the spacing between the stroke stop 58 and the projecting edge of the guide wall 48 of the valve element 44 when the outlet valve 38 is closed. When the outlet valve 38 is open, the fuel flows through the inlet duct 43 into the counterplate 40, through the gap between the valve seat 42 and base 46 of the valve element 44, through the annular chamber between the first section 52 of the guide element 50 and the inner wall of the opening 41 in the pump housing 26, through the fuel passage openings 71, and finally into the high-pressure line 20.
The outlet valve 38 of
In the embodiments of
In the embodiments of
In the embodiments of
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2012 211 107.7 | Jun 2012 | DE | national |
| 10 2012 222 826.8 | Dec 2012 | DE | national |
This application is a continuation application of copending U.S. patent application Ser. No. 14/410,078, which was filed on Dec. 20, 2014 and is a 35 U.S.C. § 371 National Stage Application of PCT/EP2013/062578, filed on Jun. 18, 2013, which claims the benefit of priority to (i) patent application no. DE 10 2012 211 107.7, filed on Jun. 28, 2012 in Germany and (ii) patent application no. DE 10 2012 222 826.8, filed on Dec. 11, 2012 in Germany. The disclosures of each of the above-identified patent applications are incorporated herein by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 14410078 | Dec 2014 | US |
| Child | 15817698 | US |
