Pumps, especially fuel injection pumps

Abstract

The invention relates to a pump (1), in particular a fuel injection pump, having a housing part (2) with a cylinder bore (3) in which a stroke rod (4) is received for reciprocating movement and in which a rod seal (5) is integrated for media separation, in particular for separating a first medium, fuel, from a second medium, lubricant, according to the invention, the housing part (2) forms a first stop surface (6) for limiting the stroke of the stroke rod (4), the first stop surface (6) being arranged to form a stop together with a second stop surface (7) formed on the stroke rod (4), at least one of the stop surfaces (6, 7) being formed with at least one relief groove (8), and when the stroke rod (4) abuts against the stop surface (6) of the housing part (2), the cylinder bore (3) is connected via the relief groove (8) to a pressure chamber (9) for guiding a medium.

Description

[Technical field]

[0001] The present invention relates to a pump, in particular a fuel injection pump, which is used to supply fuel to an internal combustion engine, which can for example drive a vehicle. [Background technology]

[0002] DE 10 2004 13 2005 A1 describes, for example, a fuel injection pump with a piston guided for reciprocating movement in a cylinder, whereby fuel is sucked into the pump working chamber and then compressed by the action of the piston.

[0003] The movement of the piston requires a drive mechanism. A suitable drive mechanism has, for example, a camshaft with a cam, on which the piston is supported at its end facing away from the pump work chamber. The rotary movement of the camshaft is converted into a linear movement of the piston. The reset is brought about by means of the spring force of a piston spring. Regardless of the specific design of the drive mechanism, the piston must be guided into the drive mechanism chamber, which is loaded by the lubricant during the operation of the fuel injection pump. Since fuel is not normally used as a lubricant, measures must be taken to ensure media separation. For example, annular sealing elements are arranged in the guide area of ​​the piston. Since such sealing elements are dynamically loaded via the movement of the piston, a particularly robust sealing element must be provided. So-called rod seals are therefore generally used. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] European Patent Publication No. 1722098 Summary of the Invention [Problem to be solved by the invention]

[0005] Starting from the above-mentioned prior art, the object of the present invention is to reduce the load on rod seals used for media separation in pumps, in particular in fuel injection pumps, so that the robustness and thus the service life of the pump are ultimately increased. [Means for solving the problem]

[0006] To achieve this goal, a pump is proposed having the features of claim 1. Preferred embodiments of the invention are set forth in the dependent claims.

[0007] The proposed pump, in particular a fuel injection pump, has a housing part with a cylinder bore, in which a stroke rod is received for reciprocating movement. A rod seal for medium separation, in particular for separating the fuel as a first medium from the lubricant as a second medium, is integrated in the cylinder bore. According to the invention, the housing part forms a first stop surface for limiting the stroke of the stroke rod, which first stop surface forms a stop in cooperation with a second stop surface formed on the stroke rod. In this case, at least one stop surface forms at least one relief groove, and when the stroke rod abuts against the stop surface of the housing part, the cylinder bore is connected via the relief groove to a pressure chamber for guiding the medium.

[0008] When the stroke rod reaches the stop, the medium present between the two stop faces escapes via the at least one relief groove into the pressure chamber which guides the medium. In this way, the at least one relief groove counteracts the fluid blockage in front of the rod seal in the stop area as well as in the cylinder bore. By means of the at least one relief groove, pressure peaks in the cylinder bore, which can have a detrimental effect on the sealing function and the service life of the rod seal, are thus avoided. The at least one relief groove thus produces a relief of the rod seal. The relief of the rod seal not only increases the service life of the seal itself, but also the service life of the pump. The relief effect of the at least one relief groove increases with the size of the stop face, since the displacement volume also increases with the size of the stop face.

[0009] The stop formed by the two stop surfaces together can be a stop which defines the top or bottom dead center of the stroke rod. The medium which escapes via the at least one relief groove into the pressure chamber for guiding the medium can in particular be the fuel to be injected.

[0010] Preferably, the at least one relief groove extends radially relative to the longitudinal axis of the cylinder bore and / or the stroke rod. If the at least one relief groove is formed in the stop surface of the housing part, this preferably extends radially relative to the longitudinal axis A of the housing part. If the at least one relief groove is formed in the stop surface of the stroke rod, this preferably extends radially relative to the longitudinal axis A of the stroke rod. In the ideal case, the stroke rods are aligned coaxially with the cylinder bores, so that their respective longitudinal axes coincide together with a common longitudinal axis A. The radial path of the at least one relief groove corresponds to the shortest connection between the cylinder bore and the pressure chamber for guiding the medium, so that the medium present between the stop surfaces is displaced into the pressure chamber over the shortest path.

[0011] In a preferred embodiment, the relief grooves are arranged at equal angular intervals on at least one of the two stop surfaces, for example in the form of a cross or a star, such that the medium present in the stop area is displaced uniformly into the pressure chamber which guides the medium, so that no pressure cushions form between the stop surfaces.

[0012] At least one relief groove has an angular, e.g. triangular or rectangular, trapezoidal or circular cross section. Angular cross-sectional shapes have the advantage that they can be produced particularly simply by material removal methods and allow large flow cross sections. Circular cross sections are particularly optimal for flow.

[0013] According to a preferred embodiment of the invention, the stop surface of the stroke rod is formed on an annular collar of the stroke rod, which is formed by a diameter enlargement of the stroke rod or by a separate element arranged on the stroke rod. The annular collar is in any case firmly connected to the stroke rod, so that it can form a stop in cooperation with a stop surface of the housing part. The designed configuration has the advantage that it simplifies the manufacture of the stroke rod as well as the assembly of the pump.

[0014] According to another preferred embodiment of the invention, the stop surface of the housing part is formed on a plateau surrounding the cylinder bore. At least one relief groove can be produced simply, since it can be formed by a corresponding opening in the plateau. The plateau preferably has a circular basic shape arranged concentrically relative to the cylinder bore. In this way, an annular stop surface surrounding the cylinder bore is obtained, which has the same annular width and is interrupted only by at least one relief groove.

[0015] It is further proposed that the pressure chamber for guiding the medium, which is connected to the bore via at least one relief hole, is loaded with fuel as the first medium during operation of the pump. The stop is therefore preferably arranged on the fuel side of the bore. The fuel is in particular the fuel to be injected. A rod seal integrated in the bore prevents the fuel present in the pressure chamber from mixing with another medium on the other side of the bore, in particular a lubricant for lubricating the drive mechanism of the pump.

[0016] It is therefore proposed according to an embodiment of the invention that the bore opens at its end opposite the stop surface into a pressure chamber which is loaded with lubricant during pump operation. A rod seal integrated in the bore ensures a permanent separation of fuel and lubricant. By providing at least one relief groove on at least one stop surface, fluid blockage in front of the rod seal and thus increased loading of the rod seal due to pressure peaks is avoided. [Brief description of the drawings]

[0017] [Figure 1] 2 is a schematic longitudinal section of a pump according to the invention in the region of a rod seal for media separation integrated in the cylinder bore; [Diagram 2] 2 is a schematic plan view of a housing portion having a cylinder bore of the pump shown in FIG. 1. [Diagram 3] 2 a) to 2 c) show various cross-sectional shapes of relief grooves for a pump according to the invention; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0019] The pump 1 shown in FIG. 1 can in particular be a fuel injection pump, by means of which fuel can be injected into the combustion chamber of an internal combustion engine. The pump 1 shown has a housing part 2 with a cylinder bore 3, in which a stroke rod 4 is received or guided so as to be reciprocally movable. A first section of the stroke rod 4 penetrates into a first pressure chamber 9, which is loaded with a first medium, for example fuel, during operation of the pump 1. A second section of the stroke rod 4 penetrates beyond the cylinder bore 3 into a second pressure chamber 12, which is loaded with another medium, for example lubricant, during operation of the pump 1. For reliable media separation, a rod seal 5 is integrated into the cylinder bore 3.

[0020] The housing part 2 forms a plateau 11 with a stop surface 6 surrounding the cylinder bore 3, which forms a stop in conjunction with a stop surface 7 formed on an annular collar 10 of the stroke rod 4. If the stroke rod 4 moves towards the stop during operation of the pump 1, fluid blockage occurs in the stop area as well as in the cylinder bore 3. The resulting pressure peaks then place a high load on the rod seal 5, so that its sealing action is impaired. To avoid this, the stop surface 6 of the housing part 2 has a number of relief grooves 8 formed by the relief of the plateau 11. When the stroke rod 4 abuts against the stop, the medium present between the two stop surfaces 6, 7 escapes via the relief grooves 8 into the pressure chamber 9.

[0021] As shown by way of example in FIG. 2, the relief grooves 8 may be arranged in a cross shape and each extend radially outward from the cylinder bore 3. As an example, four relief grooves 8 are shown in FIG. 2. This number may also be less than four, for example two or three, or more than four, for example five or six. Furthermore, any groove cross-section may be selected. Several examples are shown in FIGS. 3a), 3b) and 3c), where FIG. 3a) shows a round cross-section, FIG. 3b) shows a rectangular cross-section and FIG. 3c) shows a trapezoidal cross-section.

[0022] As an alternative to the embodiment shown in figures 1 to 3, at least one relief groove 8 can also be formed in the stop surface 7 of the annular flange 10 of the stroke rod 4. Therefore, in figures 2 and 3, the number 7 is written in brackets after the number 6. Similarly, in figure 2, the number 10 is written in brackets after the number 11. [Explanation of symbols]

[0023] 1 Pump 2 Housing part 3 Cylinder hole 4 stroke rod 5 Rod Seal 6,7 Stopper surface 8 Relief Groove 9. First Pressure Chamber 10 Annular brim 11 Plateau 12 Second pressure chamber A Vertical axis

Claims

1. A pump (1), in particular a fuel injection pump, having a housing part (2) with a cylinder bore (3) in which a stroke rod (4) is received for reciprocating movement, in which a rod seal (5) for media separation, in particular for separating a fuel as a first medium from a lubricant as a second medium, is integrated, a housing part (2) that forms a first stop surface (6) that limits the stroke of the stroke rod (4), the first stop surface (6) being adapted to cooperate with a second stop surface (7) formed on the stroke rod (4) to form a stop, at least one of the stop surfaces (6, 7) being formed with at least one relief groove (8), and when the stroke rod (4) abuts against the stop surface (6) of the housing part (2), the cylinder bore (3) is connected to a pressure chamber (9) that guides a medium via the relief groove (8).

2. 2. The pump (1) according to claim 1, characterized in that at least one of the relief grooves (8) extends radially with respect to the longitudinal axis (A) of the cylinder bore (3) and / or the stroke rod (4).

3. 3. The pump (1) according to claim 1 or 2, characterized in that a number of relief grooves (8) are arranged in at least one of the two stop surfaces (6, 7) at equal angular intervals from one another, for example in the form of a cross or a star.

4. 3. The pump (1) according to claim 1 or 2, characterized in that at least one of the relief grooves (8) has an angular, e.g. triangular or rectangular, trapezoidal or circular cross section.

5. 3. The pump (1) according to claim 1 or 2, characterized in that the stop surface (7) of the stroke rod (4) is formed on an annular flange (10) of the stroke rod (4), which is formed by a diameter enlargement of the stroke rod (4) or by a separate element arranged on the stroke rod (4).

6. 3. The pump (1) according to claim 1 or 2, characterized in that the stop surface (6) of the housing part (2) is formed on a plateau (11) surrounding the cylinder bore (3).

7. 3. The pump (1) according to claim 1 or 2, characterized in that the pressure chamber (9) for guiding a medium, which is connected to the cylinder bore (3) via at least one of the relief grooves (8), is loaded with fuel as a first medium during operation of the pump (1).

8. 3. The pump (1) according to claim 1 or 2, characterized in that the cylinder bore (3) opens at its end opposite the stop surface (6) into a pressure chamber (12) which is loaded with lubricant during operation of the pump (1).

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