High pressure pump for alternative fuels

Abstract

TITLE: High-pressure pump for alternative fuels High-pressure pump (1) for alternative fuels, in particular for methanol or ammonia, comprising a housing (2) with a bore (3) receiving a piston (4) in a reciprocating movement. The piston (4) is connected to a piston rod (5) guided in a leakage chamber (6) adjacent to the bore (3) and surrounded at least by segments by a bellows with corrugations or pleats (7) securely connected at one end to the piston rod (5) and at the other end to the housing (2). The bellows (7) has a hydraulic diameter (DB) adapted to the outside diameter (DK) of the piston (4) so that during the movement of the piston (4), the bellows (7) performs volumetric compensation. Figure 1

Description

Title of the invention: High pressure pump for alternative fuels FIELD OF THE INVENTION

[0001] The present invention relates to a high pressure pump for alternative fuels, in particular for methanol or ammonia, comprising a casing with a bore receiving a pump piston in a reciprocating movement,

[0002] - the pump piston being connected to a piston rod guided in a leak chamber, adjacent to the bore and surrounded at least by segments by a bellows with corrugations or folds, securely connected at one end to the piston rod and at the other end to the casing.

[0003] The preferred field of application of the invention is that of engines, in particular large engines powered by an alternative fuel. STATE OF THE ART

[0004] In the field of thermal engines, fuel injection systems are known that transfer fuel at high pressure with a high-pressure pump. The supply fuel must be separated from a medium of the transmission mechanism, for example lubricating oil. In the case of a high-pressure pump with a reciprocating piston, the separation of the media can be achieved with a corrugated or pleated bellows. The corrugated or pleated bellows is then the movable seal that allows the movements of the pump piston to be received and at the same time separate one medium from the other.

[0005] The movement of the pump piston displaces a volume which depends on the stroke and the geometry of the pump piston. This volume displacement results in pressure variations applied to the corrugated or pleated bellows and which influence the stability and reliability of this corrugated or pleated bellows. The amplitude of the pressure variations applied to the corrugated or pleated bellows also depends, among other things, on the compressibility of the medium. The greater this compressibility of the medium, the greater the pressure variations. Alternative fuels such as, for example, methanol or ammonia have a lower compressibility compared to air. In the high-pressure pump applied to alternative fuels, the separation of the media is carried out with a corrugated or pleated bellows which is thus exposed to significant pressure variations and thus to high stress.

[0006] PURPOSE OF THE INVENTION

[0007] The present invention aims to reduce the stress on a corrugated or pleated bellows of a high pressure alternative fuel pump and thus improve its reliability.

[0008] DISCLOSURE AND ADVANTAGES OF THE INVENTION

[0009] To this end, the invention relates to a high-pressure pump for alternative fuels, in particular for methanol or ammonia, comprising a casing with a bore receiving a reciprocating pump piston,

[0010] - the pump piston being connected to a piston rod guided in a leak chamber, adjacent to the bore and surrounded at least by segments by a bellows with corrugations or folds securely connected at one end to the piston rod and at the other end to the casing,

[0011] pump characterized in that

[0012] the corrugated or pleated bellows has a hydraulic diameter adapted to the external diameter of the pump piston so that during the movement of the pump piston, the corrugated or pleated bellows provides volumetric compensation.

[0013] Thanks to the volumetric compensation, the volume of the leak chamber does not change during the reciprocating movement of the pump piston. This means that there are no pressure variations or only a substantially small pressure variation applied to the corrugated or pleated bellows. This results in an improvement in the reliability of the corrugated or pleated bellows.

[0014] For volumetric compensation, the outer diameter of the pump piston and the hydraulic diameter of the corrugated or pleated bellows are matched and ideally they are equal. Therefore, care must be taken that the hydraulic diameter of the corrugated or pleated bellows does not correspond to either the outer diameter or the inner diameter of the corrugated or pleated bellows. The hydraulic diameter is by construction between the outer diameter and the inner diameter.

[0015] According to a preferred development of the invention, the corrugated or pleated bellows separates the leak chamber and the annular volume filled with air. This means that the exterior of the corrugated or pleated bellows is exposed to a less compressible medium than the interior. Volumetric compensation is thus achieved in the volume in which the risk of pressure variation is particularly high.

[0016] According to another feature, the bore of the high pressure pump casing is stepped to form the leak chamber. This stepped construction creates the volume receiving the corrugated or pleated bellows whose outside diameter must be larger than the outside diameter of the pump piston.

[0017] The leak chamber is connected to a return path, preferably by a bore made in the crankcase. The bore and the return path allow fuel from leaks in the leak chamber to be evacuated, preferably to a fuel tank. The drilling can be in particular radial or inclined relative to the bore.

[0018] Preferably, the corrugated or pleated bellows is securely connected at least at one end to the piston rod and / or the housing by an annular-shaped part. This annular-shaped part can support the corrugated or pleated bellows in the axial direction. In addition, it facilitates the connection of the corrugated or pleated bellows to the piston rod or the housing. The annular component is, for example, a washer.

[0019] Preferably, the casing receives a guide member, in particular in the area of the leak chamber, preferably pressed and passing over the piston rod. Since the piston rod has a certain length, it is advantageous to have such another guide. The first guide is produced by guiding the pump piston in the bore. The other guide is produced with the casing, preferably pressed into it. The guide member is thus ideally produced at the end of the piston rod opposite that of the pump piston. Between the guide member and the pump piston there is thus sufficient space to receive the bellows with corrugations or pleats.

[0020] According to another characteristic, the guide member has at least one through-orifice. This through-orifice allows ventilation or evacuation of the annular volume filled with air and which is thus separated from the bellows with corrugations or pleats relative to the leak chamber. Preferably, the guide member comprises several through-orifices distributed equiangularly. Brief description of the drawings

[0021] The present invention will be described below with the aid of the embodiment shown in the accompanying drawings in which:

[0022] [Fig.l] longitudinal section of a first high-pressure pump according to the invention,

[0023] [Fig.2] greatly simplified longitudinal section of a second high-pressure pump according to the invention,

[0024] [Fig.3] enlarged detail of [Fig.2].

[0025] DESCRIPTION OF AN EMBODIMENT

[0026] [Fig.l] shows a high-pressure pump 1 according to the invention for alternative fuels, for example methanol. The high-pressure pump 1 comprises a housing 2 with a stepped bore 3. The upper segment of the bore 3 receives a pump piston 4 guided in its reciprocating movement. In the lower segment, the bore 3 forms a leakage chamber 6 which receives the fuel leaking from the guide zone of the bore 3. The bore 3 returns this fuel from the leakage chamber 6 through a bore 9.

[0027] The pump piston 4 is connected by a piston rod 5 to the transmission (not shown). The piston rod 3 is guided in the leak chamber 6. To separate the leaks arriving in the leak chamber 6 from the transmission medium, such as the lubricating oil, the piston rod 5 is surrounded by segments by a bellows with corrugations or pleats 7. This bellows separates the leak chamber 6 from the annular volume 8 filled with air. The bellows with corrugations or pleats 7 absorbs the movements of the pump piston 4 or the piston rod 5.

[0028] One end of the bellows with corrugations or pleats 7 is connected by a first annular part 10 integrally to the piston rod 5. The other end is connected to the casing 2 by a second part 11 of annular shape. The second part 11 of annular shape has an internal diameter larger than the external diameter of the piston rod 5, which allows the passage of air. The leak chamber 6 further has a guide member 12, preferably pressed, to guide the piston rod 5. The passage orifices 13 made in the guide member 12 also allow the passage of air.

[0029] The passage of air allows the displacement of a volume when the pump piston 4 descends, thus compressing the corrugated or pleated bellows 7 and pushing air out of the annular volume 8. The volume of the leak chamber 6 is on the other hand between the pump piston 4 and the lower annular component 1 so that the movement of the piston 4 cannot be compensated by a volume displacement. Usually, pressure variations are encountered instead, which result in a strong stress on the corrugated or pleated bellows 7. This is not the case with the high-pressure pump 1 shown in [Fig.l]. Indeed, the corrugated or pleated bellows 7 has a hydraulic diameter DB adapted to the external diameter DK of the pump piston 4 so that the corrugated or pleated bellows 7 performs volumetric compensation when the pump piston 4 moves.This means that there is no volume displacement but also no pressure variations in the leak chamber 6 so that the bellows with corrugations or pleats is less heavily stressed, which results in an increase in the service life of the bellows with corrugations or pleats 7.

[0030] [Fig.2] shows another embodiment of a high pressure pump 1. This pump also has a casing 2 with a bore 3 as well as a pump piston 4 guided in its reciprocating movement in the bore 3. The pump piston 4 is connected to a piston rod 5 guided in the leak chamber 6 and surrounded by segments, by the bellows with corrugations or pleats 7. The bellows separates the leak chamber 6 and the annular volume 8 filled with air. The bellows with corrugations or pleats 7 is connected respectively at the end by an annular part 10, 11 to the piston rod 5 and to the casing 2.

[0031] As appears in particular in [Fig. 3], the corrugated or pleated bellows 7 has a hydraulic diameter DB equal to the external diameter DK of the pump piston 4. Thus during the movement of the pump piston 4 there is a volumetric compensation by the bellows with waves or folds 7.

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[0046] NOMENCLATURE OF THE MAIN ELEMENTS 1 High pressure pump 2 Casing 3 Bore 4 Piston 5 Piston rod 6 Leakage chamber 7 Bellows with waves or folds Db Hydraulic diameter of the bellows Dk Outside diameter of the piston 9 Bore 10 Annular shaped part 11 Annular shaped part 12 Guide member 13 Through hole

Claims

Claims

1. High-pressure pump (1) for alternative fuels, in particular for methanol or ammonia, comprising a housing (2) with a bore (3) receiving a pump piston (4) in a reciprocating movement, - the pump piston (4) being connected to a piston rod (5) guided in a leakage chamber (6) adjacent to the bore (3) and surrounded at least by segments by a bellows with corrugations or pleats (7) which is securely connected at one end to the piston rod (5) and at the other end to the housing (2), characterized in that the bellows with corrugations or pleats (7) has a hydraulic diameter (DB) which is adapted to the outer diameter (DK) of the pump piston (4) so that during the movement of the pump piston (4), the bellows with corrugations or pleats (7) performs a volumetric compensation.

2. High pressure pump (1) according to claim 1, characterized in that the bellows with corrugations or pleats (7) separates the leak chamber (6) from the annular volume (8) filled with air.

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

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

5. High-pressure pump (1) according to one of the preceding claims, characterized in that the bellows with corrugations or pleats (7) is securely connected at at least one end to the piston rod (5) and / or to the housing (2) by an annular-shaped part (10, 11).

6. High pressure pump (1) according to one of the preceding claims, characterized in that a 7 guide member (12) is preferably installed in the leak chamber (6) in particular by clamping while being guided on the piston rod (5).

7. High pressure pump (1) according to claim 6, characterized in that the guide member (2) has at least one through-orifice (13) preferably several through-orifices (13) distributed equiangularly.

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