PUMP, ESPECIALLY FUEL INJECTION PUMP

Description

[0001] The invention relates to a pump, in particular a fuel injection pump.

[0002] Fuel injection pumps supply fuel to an internal combustion engine. The engine can be used to power a vehicle, for example. State of the art

[0003] EP 1 722 098 A1 and DE102015201444 A1 provide examples of fuel injection pumps with a piston that is guided back and forth within a cylinder. The piston's movements draw fuel into a pump working chamber and subsequently compress it.

[0004] The movements of the piston require a drive mechanism. A suitable drive mechanism could, for example, comprise a camshaft with a cam on which the piston is supported at the end facing away from the pump working chamber. The rotary movement of the camshaft is then converted into a linear movement of the piston. The return movement can be achieved using the spring force of a piston spring. Regardless of the specific design of the drive mechanism, the piston must be guided into the drive chamber, which is supplied with a lubricating medium during operation of the fuel injection pump. Since fuel is not generally used as a lubricating medium, measures must be taken to ensure media separation. For example, an annular sealing element can be arranged in the area of the piston guide. Since this is subjected to dynamic loads via the movements of the piston, a particularly robust sealing element must be provided.So-called rod seals are therefore usually used.

[0005] Based on the aforementioned prior art, the present invention is based on the object of reducing the loads on a rod seal used for media separation in a pump, particularly in a fuel injection pump. As a result, the robustness and thus the service life of the pump are to be increased.

[0006] To achieve this object, the pump having the features of claim 1 is proposed. Advantageous further developments of the invention can be found in the subclaims. Disclosure of the invention

[0007] The proposed pump, in particular a fuel injection pump, comprises a housing part with a cylinder bore in which a lifting rod is accommodated for reciprocating movement. A rod seal is integrated into the cylinder bore for media separation, in particular for separating the fuel as the first medium from a lubricating medium as the second medium. According to the invention, the housing part forms a first stop surface that limits the stroke of the lifting rod and interacts with a second stop surface formed on the lifting rod to form a stop. At least one relief groove is formed in at least one stop surface, via which the cylinder bore is connected to a media-carrying pressure chamber when the lifting rod comes into contact with the stop surface of the housing part.

[0008] When the stroke rod reaches the stop, a medium located between the two stop surfaces can escape into the media-carrying pressure chamber via the at least one relief groove. In this way, the at least one relief groove counteracts the formation of fluid backups in the stop area and in front of the rod seal within the cylinder bore. This means that with the help of the at least one relief groove, high pressure peaks within the cylinder bore are avoided, which could negatively affect the sealing function and the service life of the rod seal. The at least one relief groove therefore relieves the rod seal. Relieving the rod seal not only increases the service life of the seal itself, but also the service life of the pump.The relieving effect of at least one relief groove increases with the size of the stop surfaces, since the displacement volume also increases with the size of the stop surfaces.

[0009] The stop formed by the two stop surfaces together can be a stop that defines the top or bottom dead center of the lifting rod. The medium that escapes into the media-carrying pressure chamber via the at least one relief groove can, in particular, be the fuel to be injected.

[0010] The at least one relief groove preferably runs radially with respect to a longitudinal axis of the cylinder bore and / or the lifting rod. If the at least one relief groove is formed in the stop surface of the housing part, it preferably runs radially with respect to the longitudinal axis A of the housing part. If the at least one relief groove is formed in the stop surface of the lifting rod, it preferably runs radially with respect to the longitudinal axis A of the lifting rod. Since ideally the lifting rod is aligned coaxially to the cylinder bore, the respective longitudinal axes coincide on a common longitudinal axis A. The radial course of the at least one relief groove corresponds to the shortest connection between the cylinder bore and the media-carrying pressure chamber, so that medium located between the stop surfaces is displaced into the pressure chamber via the shortest route.

[0011] Advantageously, several relief grooves are arranged at equal angular spacing from one another, for example, in a cross or star pattern, in at least one of the two stop surfaces. This arrangement at equal angular spacing from one another results in a uniform displacement of the medium in the stop area into the media-carrying pressure chamber, so that no pressure cushion can build up between the stop surfaces.

[0012] The at least one relief groove can have a square cross-section, for example, triangular or square, trapezoidal, or round. The square cross-section has the advantage of being particularly easy to manufacture using a material-removing process and allowing for large flow cross-sections. The round cross-section is primarily flow-optimized.

[0013] According to a preferred embodiment of the invention, the stop surface of the lifting rod is formed on an annular collar of the lifting rod, which is formed by a diameter step in the lifting rod or by a separate body arranged on the lifting rod. In any case, the annular collar is firmly connected to the lifting rod, so that it can interact with the stop surface of the housing part to form a stop. The assembled design has the advantage of simplifying the manufacture of the lifting rod and the assembly of the pump.

[0014] According to a further preferred embodiment of the invention, the stop surface of the housing part is formed on a plateau surrounding the cylinder bore. The at least one relief groove can then be created by a corresponding recess in the plateau, making it easy to manufacture. The plateau preferably has a circular basic shape that is arranged concentrically with respect to the cylinder bore. In this way, an annular stop surface surrounding the cylinder bore is created, which has the same width all the way around and is interrupted only by the at least one relief groove.

[0015] Furthermore, it is proposed that the media-carrying pressure chamber, to which the cylinder bore is connected via the at least one relief groove, be pressurized with fuel as the first medium during operation of the pump. The stop is therefore preferably arranged on the fuel side of the cylinder bore. The fuel can, in particular, be the fuel to be injected. The rod seal integrated into the cylinder bore prevents the fuel in the pressure chamber from mixing with another medium on the other side of the cylinder bore, in particular with a lubricating medium for lubricating a pump drive mechanism.

[0016] In a further development of the invention, it is therefore proposed that the cylinder bore, at its end facing away from the stop surface, open into a pressure chamber, which is pressurized with a lubricating medium during pump operation. With the help of the rod seal integrated into the cylinder bore, the fuel and the lubricating medium can be permanently and safely separated. By providing at least one relief groove in at least one stop surface, fluid buildup in front of the rod seal and thus increased stress on the rod seal due to pressure peaks can be avoided.

[0017] Preferred embodiments of the invention are explained in more detail below with reference to the accompanying drawings. These show: Fig. 1 a schematic longitudinal section through a pump according to the invention in the area of a rod seal integrated into a cylinder bore for media separation, Fig. 2a schematic plan view of the housing part of the pump with the cylinder bore of the Fig. 1 and Fig. 3 a) to c) different cross-sectional shapes of a relief groove for a pump according to the invention. Detailed description of the drawings

[0018] In the Figure 1The pump 1 shown can in particular be a fuel injection pump with the aid of which fuel can be injected into a combustion chamber of an internal combustion engine. The pump 1 shown comprises a housing part 2 with a cylinder bore 3 in which a lifting rod 4 is received or guided so as to be movable back and forth. A first section of the lifting rod 4 extends into a first pressure chamber 9 which, during operation of the pump 1, is pressurised with a first medium, for example fuel. A second section of the lifting rod 4 extends beyond the cylinder bore 3 into a second pressure chamber 12 which, during operation of the pump 1, is pressurised with a further medium, for example a lubricating medium. For reliable media separation, a rod seal 5 is integrated into the cylinder bore 3.

[0019] The housing part 2 forms a plateau 11 surrounding the cylinder bore 3 with a stop surface 6, which interacts with a stop surface 7 formed on an annular collar 10 of the lifting rod 4 to form a stop. If the lifting rod 4 moves towards the stop during operation of the pump 1, a fluid backup can occur in the stop area and within the cylinder bore 3. The resulting pressure peaks lead to a high load on the rod seal 5, so that the sealing effect is compromised. To prevent this, the stop surface 6 of the housing part 2 has several relief grooves 8, which are formed by clearances in the plateau 11. If the lifting rod 4 comes to rest against the stop, any medium present between the stop surfaces 6, 7 can escape via the relief grooves 8 into the pressure chamber 9.

[0020] As exemplified in the Figure 2As shown, the relief grooves 8 can be arranged in a cross shape and each extend radially outwards from the cylinder bore 3. Figure 2 shows four relief grooves 8 as an example. However, the number can also be less than four, for example two or three, or more than four, for example five or six. Furthermore, any groove cross-section can be selected. Examples of embodiments are shown in the Figures 3a) to 3c ), where Figure 3a ) a round cross-section, the Figure 3b ) a square cross-section and the Figure 3c ) show a trapezoidal cross-section.

[0021] As an alternative to the representations of the Figures 1 to 3 the at least one relief groove 8 can also be formed in the stop surface 7 of the annular collar 10 of the lifting rod 4. In the Figures 2 and 3 Therefore, reference number 7 is given in parentheses after reference number 6. Analogously, in the Figure 2The reference number 10 is given in brackets after the reference number 11.

Claims

1. Pump (1), in particular a fuel-injection pump, comprising a housing part (2) with a cylinder bore (3), in which a reciprocating rod (4) is received for back- and-forth movement, wherein a rod seal (5) is integrated in the cylinder bore (3) for media-separation purposes, in particular for separating the fuel - the first medium - from a lubricating medium - the second medium, characterized in that the housing part (2) forms a first stop surface (6), which limits the stroke of the reciprocating rod (4) and interacts with a second stop surface (7), which is formed on the reciprocating rod (4), to provide stopping action, wherein at least one stop surface (6, 7) contains at least one relief groove (8), via which the cylinder bore (3) is connected to a media-carrying pressure chamber (9) when the reciprocating rod (4) comes into abutment against the stop surface (6) of the housing part (2).

2. Pump (1) according to Claim 1, characterized in that the at least one relief groove (8) runs radially with respect to a longitudinal axis (A) of the cylinder bore (3) and / or of the reciprocating rod (4).

3. Pump (1) according to Claim 1 or 2, characterized in that a plurality of relief grooves (8) are arranged at equal angular distances from one other, for example in the form of a cross or star, in at least one of the two stop surfaces (6, 7).

4. Pump (1) according to one of the preceding claims, characterized in that the at least one relief groove (8) has a polygonal, for example triangular or quadrilateral, a trapezoidal or round cross section.

5. Pump (1) according to one of the preceding claims, characterized in that the stop surface (7) of the reciprocating rod (4) is formed on an annular collar (10) of the reciprocating rod (4), the annular collar being formed by a marked change in diameter of the reciprocating rod (4) or by a separate body arranged on the reciprocating rod (4).

6. Pump (1) according to one of the preceding claims, characterized in that the stop surface (6) of the housing part (2) is formed on a plateau (11) surrounding the cylinder bore (3).

7. Pump (1) according to one of the preceding claims, characterized in that the media-carrying pressure chamber (9), to which the cylinder bore (3) is connected via the at least one relief groove (8), is charged with fuel - the first medium - during operation of the pump (1).

8. Pump (1) according to one of the preceding claims, characterized in that, at its end which faces away from the stop surface (6), the cylinder bore (3) opens out into a pressure chamber (12), which is charged with a lubricating medium during operation of the pump (1).