High-pressure pump for alternative fuels

Abstract

The invention relates to a high-pressure pump (1) for alternative fuels, in particular for methanol or ammonia, having a housing (2) with a cylinder bore (3) in which a pump piston (4) is guided to move back and forth, wherein the pump piston (4) is connected to a piston rod (5) which is guided through a leakage space (6) adjacent to the cylinder bore (3) and is at least partially surrounded by a corrugated or folded bellows (7) which is fixedly connected at one end to the piston rod (5) and at the other end to the housing (2). According to the invention, the corrugated or folded bellows (7) has a hydraulic diameter (DB) which is adapted to an outer diameter (DK) of the pump piston (4) such that a volumetric compensation can be achieved via the corrugated or folded bellows in the event of a movement of the pump piston (4).

Description

[0001] Description

[0002] title

[0003] High-pressure pump for alternative fuels

[0004] The invention relates to a high-pressure pump for alternative fuels, in particular for methanol or ammonia, having the features of the preamble of claim 1.

[0005] The preferred field of application of the invention is engines, in particular large engines, which must be supplied with an alternative fuel.

[0006] State of the art

[0007] Fuel injection systems are known from the field of internal combustion engines, which use a high-pressure pump to deliver fuel at high pressure. The fuel to be delivered must be separated from an engine medium, such as lubricating oil. In the case of a high-pressure pump with a reciprocating pump piston, media separation can be achieved, in particular, with the help of a corrugated seal or bellows. As a movable seal, the corrugated seal or bellows is able to absorb the movements of the pump piston and simultaneously separate two media from each other.

[0008] The movement of the pump piston displaces a volume that depends on the stroke and geometry of the pump piston. This volume displacement leads to pressure fluctuations in the corrugated or bellows, which influence the stability and durability of the corrugated or bellows. The extent of the pressure fluctuations in the corrugated or bellows depends, among other things, on the compressibility of the medium. The lower the compressibility of the medium, the greater the pressure fluctuations. Alternative fuels, such as methanol or ammonia, have a low compressibility compared to air. In a high-pressure pump for alternative fuels, a corrugated or bellows used for media separation is therefore exposed to high pressure fluctuations and thus to high stress.

[0009] The present invention is concerned with the object of reducing the load on a corrugated or bellows in a high-pressure pump for alternative fuels and thereby improving its durability.

[0010] The object is achieved by the high-pressure pump having the features of claim 1. Advantageous further developments of the invention can be found in the subclaims.

[0011] Disclosure of the invention

[0012] The proposed high-pressure pump for alternative fuels, in particular for methanol or ammonia, has a housing with a cylinder bore in which a pump piston is guided for reciprocating movement. The pump piston is connected to a piston rod, which is guided through a leakage chamber adjoining the cylinder bore and is surrounded at least in sections by a corrugated or bellows that is firmly connected at one end to the piston rod and at the other end to the housing. According to the invention, the corrugated or bellows has a hydraulic diameter that is adapted to an outer diameter of the pump piston, so that volumetric compensation can be achieved when the pump piston moves over the corrugated or bellows.

[0013] Thanks to volumetric compensation, the volume of the leakage chamber remains constant as the pump piston moves back and forth. This means that there are virtually no pressure fluctuations that place stress on the bellows or corrugated seal. This, in turn, improves the durability of the bellows or corrugated seal.

[0014] To achieve volumetric compensation, the outer diameter of the pump piston and the hydraulic diameter of the bellows or corrugated sleeve must be matched, ideally equal. It should be noted that the hydraulic diameter of the bellows or corrugated sleeve does not correspond to either the outer or inner diameter of the bellows or corrugated sleeve. Due to the design, the hydraulic diameter lies between the outer and inner diameters.

[0015] According to a preferred embodiment of the invention, the corrugated or bellows seal separates the leakage chamber from an annular space filled with air. This means that the outside of the corrugated or bellows seal contains a less compressible medium than the inside. Volumetric equalization is thus achieved in the space where the risk of pressure fluctuations is particularly high.

[0016] Furthermore, it is proposed that the cylinder bore in the housing of the high-pressure pump be stepped to create the leakage chamber. This stepped design creates space for the bellows, since its outer diameter must be larger than the outer diameter of the pump piston.

[0017] The leakage chamber is preferably connected to a return path via a bore formed in the housing. The fuel accumulating in the leakage chamber due to leakage can then be discharged via the bore and the return path, preferably returned to a fuel tank. The bore can, in particular, run radially or obliquely to the cylinder bore.

[0018] Preferably, the corrugated or bellows is firmly connected to the piston rod and / or the housing at at least one end via an annular component. The at least one annular component can support the corrugated or bellows in the axial direction. Furthermore, it facilitates the connection of the corrugated or bellows to the piston rod or the housing. The annular component can be a disc, for example.

[0019] Furthermore, a guide body is preferably inserted, preferably pressed into, the housing, particularly in the area of ​​the leakage chamber, over which the piston rod is guided. Since the piston rod can have a certain length, further guidance is advantageous. A first guide is achieved via the pump piston accommodated in the cylinder bore, which is guided via this bore. The further guidance with the aid of the guide body inserted, preferably pressed into, the housing is therefore ideally achieved at the end of the piston rod facing away from the pump piston. This also leaves a sufficiently large space between the guide body and the pump piston to accommodate the corrugated or bellows seal.

[0020] Furthermore, the guide body preferably has at least one through-flow opening. The at least one through-flow opening enables ventilation or venting of the air-filled annular space, which is separated from the leakage space by the corrugated or bellows. The guide body preferably has a plurality of through-flow openings arranged at equal angular spacing from one another.

[0021] Preferred embodiments of the invention are explained in more detail below with reference to the accompanying drawings. These show:

[0022] Fig. 1 is a longitudinal section through a first high-pressure pump according to the invention,

[0023] Fig. 2 shows a highly simplified longitudinal section through a second high-pressure pump according to the invention and

[0024] Fig. 3 shows an enlarged section of Figure 2.

[0025] Detailed description of the drawings

[0026] Figure 1 shows a high-pressure pump 1 according to the invention for alternative fuels, for example, for methanol. The high-pressure pump 1 comprises a housing 2 with a stepped cylinder bore 3. A pump piston 4 is accommodated and guided in an upper section of the cylinder bore 3 for reciprocating movement. In a lower section, the cylinder bore 3 forms a leakage chamber 6, which receives fuel escaping from the guide area of ​​the cylinder bore 3 by way of leakage. This fuel is discharged from the leakage chamber 6 via a bore 9.

[0027] The pump piston 4 is connected to an engine (not shown) via a piston rod 5. The piston rod 5 is guided through the leakage chamber 6. In order to separate the leakage occurring in the leakage chamber 6 from a medium of the engine, for example lubricating oil, the piston rod 5 is partially surrounded by a corrugated or bellows 7. This separates the leakage chamber 6 from an annular chamber 8 filled with air. The corrugated or bellows 7 is able to absorb the movements of the pump piston 4 or the piston rod 5. At one end, the corrugated or bellows 7 is firmly connected to the piston rod 5 via an annular first component 10, and at the other end to the housing 2 via an annular second component 11. The annular second component 11 has an inner diameter that is larger than the outer diameter of the piston rod 5, so that air can flow through.Furthermore, a guide body 12 is inserted, preferably pressed into, the leakage chamber 6, over which the piston rod 5 is guided. Flow openings 13 formed in the guide body 12 also allow air to flow through.

[0028] The flow of air through enables a volume shift when the pump piston 4 moves downwards, so that the corrugated or bellows 7 is compressed and air is displaced from the annular space 8. The volume of the leakage space 6, on the other hand, is enclosed between the pump piston 4 and the lower annular component 11, so that the movement of the pump piston 4 cannot be compensated by a volume shift. Usually, pressure fluctuations occur instead, which lead to a high load on the corrugated or bellows 7. This is not the case with the high-pressure pump 1 according to the invention shown in Figure 1. Here, the corrugated or bellows 7 has a hydraulic diameter DB that is adapted to an outer diameter DK of the pump piston 4, so that volumetric compensation is created via the corrugated or bellows 7 when the pump piston 4 moves.This means that no volume is shifted, but also no pressure fluctuations occur in the leakage chamber 6, so that the corrugated or bellows 7 is subjected to less stress. The service life of the corrugated or bellows 7 is correspondingly increased.

[0029] Figure 2 shows a further high-pressure pump 1 according to the invention. This also has a housing 2 with a cylinder bore 3 and a pump piston 4 guided to move back and forth in the cylinder bore 3. The pump piston 4 is connected to a piston rod 5, which is guided through a leakage chamber 6 and is partially surrounded by a corrugated or bellows 7. This separates the leakage chamber 6 from an annular space 8 filled with air. The corrugated or bellows 7 is connected at each end to the piston rod 5 and to the housing 2 via annular components 10, 11. As can be seen in particular from Figure 3, the corrugated or bellows 8 has a hydraulic diameter DB that is equal to an outer diameter DK of the pump piston 4. Thus, when the pump piston 4 moves, volumetric compensation is achieved via the corrugated or bellows 7.

Claims

Claims 1. A high-pressure pump (1) for alternative fuels, in particular for methanol or ammonia, comprising a housing (2) with a cylinder bore (3) in which a pump piston (4) is guided to move back and forth, wherein the pump piston (4) is connected to a piston rod (5) which is guided through a leakage chamber (6) adjoining the cylinder bore (3) and is surrounded at least in sections by a corrugated or bellows (7) which is firmly connected at one end to the piston rod (5) and at the other end to the housing (2), characterized in that the corrugated or bellows (7) has a hydraulic diameter (DB) which is adapted to an outer diameter (DK) of the pump piston (4), so that when the pump piston (4) moves via the corrugated or bellows (7), volumetric compensation can be achieved.

2. High-pressure pump (1) according to claim 1, characterized in that the corrugated or bellows (7) separates the leakage space (6) from an annular space (8) which is filled with air.

3. High-pressure pump (1) according to claim 1 or 2, characterized in that the cylinder bore (3) is stepped to form the leakage chamber (6).

4. High-pressure pump (1) according to one of the preceding claims, characterized in that the leakage chamber (6) is connected to a return path via a bore (9) formed in the housing (2).

5. High-pressure pump (1) according to one of the preceding claims, characterized in that the corrugated or bellows (7) is firmly connected at at least one end to the piston rod (5) and / or the housing (2) via an annular component (10, 11).

6. High-pressure pump (1) according to one of the preceding claims, characterized in that a guide body (12) is inserted, preferably pressed, into the housing (2), preferably in the region of the leakage chamber (6), over which the piston rod (5) is guided.

7. High-pressure pump (1) according to claim 6, characterized in that the guide body (12) has at least one flow opening (13), preferably a plurality of flow openings (13) arranged at the same angular distance from one another.

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