EP3158185B1 - High-pressure fuel pump for a fuel system for an internal combustion engine - Google Patents

Description

State of the art

The invention relates to a high-pressure fuel pump according to the preamble of claim 1.

From the market known fuel high-pressure pumps for fuel systems of internal combustion engines, for example, for a gasoline direct injection. A high-pressure fuel pump can deliver fuel from a low-pressure region, for example downstream of a prefeed pump, into a high-pressure region, in particular into a high-pressure reservoir (rail). For this purpose, high-pressure fuel pumps frequently have a pressure-limiting valve which can limit a fuel pressure in the high-pressure region to a predefinable maximum value. Thus, operation of the high-pressure fuel pump can be improved and possible damages of the fuel system can be prevented.

The DE 197 10 891 A1 discloses a fuel injection pump.

Disclosure of the invention

The problem underlying the invention is achieved by a high pressure fuel pump according to claim 1, and by a pressure relief valve according to the independent claim. Advantageous developments are specified in subclaims. For the invention important features can be further found in the following description and in the drawings, wherein the Features both alone and in different combinations may be important to the invention, without being explicitly referred to again.

The invention relates to a fuel high-pressure pump for a fuel system for an internal combustion engine, having a pressure-limiting valve arranged hydraulically between an outlet and an area upstream of the outlet in a housing and opening to the upstream area, which has a closing element which is in the closing direction by a valve spring is applied, and has a stopper body which limits the maximum opening travel of the closing element. According to the invention, the stop body is supported axially on the housing and is acted upon by the valve spring against the housing. As a result, the pressure limiting valve according to the invention can be produced and mounted in a particularly simple manner, whereby costs can be saved. By limiting the maximum opening travel of the closing element by means of the stopper body, a hydraulic dead volume in the high-pressure fuel pump can be reduced and thus a pumping efficiency ("delivery rate") of the high-pressure fuel pump can be improved. In addition, as a result of the present invention limited opening travel of the closing element on the one hand, a closing speed of the closing element is reduced, whereby a fatigue strength of the pressure relief valve can be improved. On the other hand, the closing time of the pressure relief valve is shortened, whereby the delivery rate can be further increased.

In one embodiment of the high-pressure fuel pump, the stop body is solid. As a result, the stopper body can transmit comparatively large forces and yet be manufactured simply and cheaply. For example - but not mandatory - the stopper body is made of a plastic material.

In a further embodiment of the high-pressure fuel pump, a closing body is arranged between the closing element and the valve spring, which cooperates with the stop body and which preferably - but not necessarily - is made massive. By means of the closing body can through the Valve spring exerted force to be transmitted to the closing element, whereby the function of the pressure relief valve can be improved.

Furthermore, it may be provided that an end portion of the closing body and / or an end portion of the stopper body are made plate-shaped / is, wherein an outer diameter of the end portion is larger than an inner diameter of the valve spring. The thus executed end portions can define defined with associated end portions of the valve spring. As a result, the pressure limiting valve can be made particularly simple, cheap and at the same time robust.

Furthermore, it may be provided that a guide portion of the closing body and / or a guide portion of the stopper body are designed peg-shaped / is, wherein an outer diameter of the respective guide portion is smaller than an inner diameter of the valve spring. This makes it possible to arrange the respective guide portion at least partially radially within the valve spring, wherein the guide portions can abut each other with a respective end portion and thus the maximum opening travel of the closing body can be limited according to the invention. As a result, the pressure limiting valve can be made particularly robust, at the same time saving space. Overall, the pressure limiting valve according to the invention can have comparatively few and easily manufactured components, which can be arranged in a simple manner in the housing, without additional connection techniques are required.

The high-pressure fuel pump can be further simplified and cheapened when the closing body and the stopper body are made at least substantially identical, wherein at least the closing body on the closing element facing side preferably, however, has a centering for radial retention of the closing element. If the centering recess on the plate-shaped end portion of the closing body only spares a comparatively small volume of material, the stopper body can also have a similar recess without being impaired in terms of functionality. In this case, the closing body and the stopper body can therefore be made completely identical.

According to the invention, the closing element cooperates with a valve seat, which is formed on a valve body which is frictionally held in the housing. This is preferably done by pressing. Thereby, an assembly of the pressure relief valve can be simplified and cheapened. Preferably, the closing element is designed as a "free-flying" valve ball. The said pressing in addition has the advantage that a bias of the valve spring at a known spring constant can be easily, accurately and permanently specified by means of the press-fit.

Figur 1

eine schematische Darstellung eines Kraftstoffsystems für eine Brennkraftmaschine; und

Figur 2

einen Längsschnitt durch ein Druckbegrenzungsventil einer Kraftstoff-Hochdruckpumpe des Kraftstoffsystems von Figur 1.

Es werden für funktionsäquivalente Elemente und Größen in allen Figuren auch bei unterschiedlichen Ausführungsformen die gleichen Bezugszeichen verwendet.
Figur 1 zeigt ein Kraftstoffsystem 10 für eine weiter nicht dargestellte Brennkraftmaschine in einer vereinfachten schematischen Darstellung. Aus einem Kraftstofftank 12 wird Kraftstoff über eine Saugleitung 14, mittels einer Vorförderpumpe 16, über eine Niederdruckleitung 18, über einen Einlass 20 eines von einer elektromagnetischen Betätigungseinrichtung 22 betätigbaren Mengensteuerventils 24 einem Förderraum 26 einer Kraftstoff-Hochdruckpumpe 28 zugeführt. Beispielsweise kann das Mengensteuerventil 24 ein zwangsweise öffenbares Einlassventil der Kraftstoff-Hochdruckpumpe 28 sein.Hereinafter, exemplary embodiments of the invention will be explained with reference to the drawings. In the drawing show:

FIG. 1

a schematic representation of a fuel system for an internal combustion engine; and

FIG. 2

a longitudinal section through a pressure relief valve of a high-pressure fuel pump of the fuel system of FIG. 1 ,

The same reference numerals are used for functionally equivalent elements and sizes in all figures, even in different embodiments.
FIG. 1 shows a fuel system 10 for a further not shown internal combustion engine in a simplified schematic representation. Fuel is supplied from a fuel tank 12 via a suction line 14, by means of a prefeed pump 16, via a low-pressure line 18, via an inlet 20 of a quantity control valve 24 which can be actuated by an electromagnetic actuating device 22 to a delivery chamber 26 of a high-pressure fuel pump 28. For example, the quantity control valve 24 may be a forcibly openable inlet valve of the high-pressure fuel pump 28.

In the present case, the high-pressure fuel pump 28 is designed as a piston pump, wherein a piston 30 can be moved vertically by means of a cam 32 in the drawing. Hydraulically between the delivery chamber 26 and an outlet 36 of the high-pressure fuel pump 28 is a in the FIG. 1 arranged as a spring-loaded check valve drawn outlet valve 40 and a likewise drawn as a spring-loaded check valve pressure relief valve 42. The outlet 36 is connected to a high-pressure line 44 and via this to a high-pressure accumulator 46 ("common rail").

The exhaust valve 40 may open to the outlet 36 and the pressure relief valve 42 to the pumping chamber 26 out. The electromagnetic actuator 22 is controlled by a control and / or regulating device 48. Deviating from the presentation of FIG. 1 can one in the FIG. 1 left terminal of the pressure limiting valve 42 alternatively instead of the outlet (without reference numeral) of the high-pressure fuel pump 28 may also be connected to the delivery chamber 26 or any other element upstream of the high-pressure fuel pump 28.

During operation of the fuel system 10, the prefeed pump 16 delivers fuel from the fuel tank 12 into the low pressure line 18. The quantity control valve 24 may be closed and opened in response to a respective demand for fuel. As a result, the amount of fuel delivered to the high-pressure accumulator 46 is influenced. Normally, the pressure relief valve 42 is closed.

If, in a normal case deviating operation, a fuel pressure in the high pressure line 44 is higher than a fuel pressure in a region of the delivery chamber 26 (plus a spring force of a valve spring 60 of the pressure relief valve 42, see also the FIG. 2 ), so the pressure relief valve 42 can open and thus fuel can flow from the high pressure line 44 back into the delivery chamber 26 and from there optionally back into the low pressure line 18. As a result of the expansion, the fuel pressure in the high-pressure line 44 can drop to a permissible value and the pressure-limiting valve 42 can close again.

FIG. 2 shows a longitudinal section through the pressure relief valve 42 of the high-pressure fuel pump 28 of FIG. 1 , The pressure relief valve 42 is hydraulically disposed between the outlet 36 and an upstream of the outlet 36 portion of the high-pressure fuel pump 28 and can open to the upstream region. The pressure relief valve 42 and its elements described in more detail below are designed essentially rotationally symmetrical.

The pressure limiting valve 42 comprises a housing 50 which is designed essentially as a cylindrical sleeve. At one in the FIG. 1 left end face, the housing 50 has an axial first opening 52, wherein a radius of the opening 52 corresponds to an inner radius of the cylindrical sleeve. The first opening 52 is hydraulically associated with the outlet 36 and, respectively, the high-pressure region downstream thereof. At one in the FIG. 2 right end wall 54, the housing 50 is executed closed. In a right lower portion, the housing 50 has a radial second opening 56. The second opening 56 is hydraulically associated with said upstream portion of the high-pressure fuel pump 28 and connected, for example, to the delivery space 26. In the present case, the housing 50 is made in one piece.

In one in the FIG. 2 horizontal middle section, the pressure relief valve 42 has a closing element 58 which is acted upon by a valve spring 60 designed as a helical spring by means of a closing body 62 in the closing direction, ie in the FIG. 2 to the left. In the present case, the closing element 58 is a "free-flying" valve ball.

In the FIG. 2 on the right is a stop body 64 of the pressure relief valve 42 is arranged, which cooperates with the closing body 62. The stopper 64 is axially supported on the end wall 54 of the housing 50 and is acted upon by the valve spring 60 against the end wall 54 of the housing 50, that is to the right. For this purpose, a portion of the housing 50 in the region of the end wall 54 on a reduced inner diameter, whereby the stopper body 64 and thus also the valve spring 60 are kept defined.

The closing body 62 and the stopper body 64 are made substantially identical. In particular, an end portion 62 a of the closing body 62 and an end portion 64a of the stopper body 64 is carried out plate-shaped, wherein an outer diameter of the respective end portion 62a and 64a is greater than an inner diameter of the valve spring 60th

Furthermore, the closing body 62 comprises a pin-shaped guide portion 62b and the stopper body 64 a pin-shaped guide portion 64b, both of which are arranged radially adjacent to each other within the valve spring 60. Correspondingly, a respective outer diameter of the guide sections 62b and 64b is smaller than an inner diameter of the valve spring 60. As a result, among other things, an improved guidance of the valve spring 60 is made possible.

In the present case, the closing body 62 on the plate-shaped end portion 62a has a centering recess 66 for the radial retention of the closing element 58 and is otherwise identical to the stop body 64. By means of the closing body 62 or the centering recess 66, a pressure force generated by the valve spring 60 can be optimally transmitted to the closing element 58 (valve ball).

In one in the FIG. 2 left portion of the housing 50, a valve body 68 is arranged, which is frictionally held on a radially outer circumferential surface in the housing 50 and preferably is pressed therein. The valve body 68 has a continuous axial central longitudinal channel 70 which has a constant inner diameter in sections. The longitudinal channel 70 is hydraulically connected through the first opening 52 to the outlet 36. At one in the FIG. 2 right end portion of the longitudinal channel 70, a radially encircling valve seat 72 is formed on the valve body 68, which cooperates with the closing element 58.

In the present case, the closing body 62 and the stopper body 64 are solid and, for example, made of a plastic material. In one embodiment, not shown, of the pressure relief valve 42, the closing body 62 and / or the stopper body 64 at least partially on one or more cavities, whereby weight can be saved. In a further embodiment, not shown, the closing body 62 and the closing element 58 are made together in one piece. This is the dish-shaped end portion 62 a of the closing body 62 is made partially conical or peg-shaped, so that it can seal to the valve seat 72.

In another embodiment, not shown, the housing 50 of the pressure limiting valve 42 is an integral part of the high-pressure fuel pump 28 and thus not a separate element. For this purpose, the high-pressure fuel pump 28, for example, a cylindrical bore, in which the functional elements of the pressure relief valve 42 are added.

The function of the pressure limiting valve 42 has already been described above in the FIG. 1 generally described. Like in the FIG. 2 To recognize the geometries of the closing body 62 and the stopper body 64 are dimensioned such that a maximum opening travel of the closing body 62 and thus of the closing element 58 is limited. In this case, the guide portions 62b and 64b of the closing body 62 and the stopper body 64 can abut flat against one another at respective end portions. In this way, a compressive stress of the valve spring 60 can be reduced. In addition, a hydraulic dead volume of the high-pressure fuel pump 28 can be reduced and a so-called "delivery rate" can be improved. Preferably, the maximum opening travel of the closing element 58 and the geometries of the valve body 68 and the closing body 62 are dimensioned such that the closing element 58 (valve ball) can be kept and / or defined defined ("flight path").

Claims (6)

1. High pressure fuel pump (28) for a fuel system (10) for an internal combustion engine, having a pressure relief valve (42) which is arranged hydraulically between an outlet (36) and a region in a housing (50), which region is upstream of the outlet (36), which pressure relief valve (42) opens towards the upstream region and has a closing element (58), which is loaded in the closing direction by a valve spring (60), and also has a stop body (64) which limits the maximum opening travel of the closing element (58), the stop body (64) being supported axially on the housing (50) and being loaded against the housing (50) by the valve spring (60), characterized in that the closing element (58) interacts with a valve seat (72) which is configured on a valve body (68) which is held in the housing (50) in a frictionally locking manner.
2. High pressure fuel pump (28) according to Claim 1, characterized in that the stop body (64) is of solid configuration.
3. High pressure fuel pump (28) according to at least one of Claims 1 and 2, characterized in that a closing body (62) is arranged between the closing element (58) and the valve spring (60), which closing body (62) interacts with the stop body (64) and is of solid configuration.
4. High pressure fuel pump (28) according to at least one of the preceding claims, characterized in that an end section (62a) of the closing body (62) and/or an end section (64a) of the stop body (64) are/is of plate-shaped configuration, an external diameter of the end section (62a, 64a) being greater than an internal diameter of the valve spring (60).
5. High pressure fuel pump (28) according to at least one of the preceding claims, characterized in that a guide section (62b) of the closing body (62) and/or a guide section (64b) of the stop body (64) are/is of pin-shaped configuration, an external diameter of the respective guide section (62b, 64b) being smaller than an internal diameter of the valve spring (60).
6. High pressure fuel pump (28) according to at least one of the preceding claims, characterized in that the closing body (62) and the stop body (64) are of at least substantially identical configuration, and, however, at least the closing body (62) on the side which faces the closing element (58) has a centring recess (66) for radially securing the closing element (58).

Images