High pressure pump for alternative fuels

Abstract

A high-pressure pump (1) for alternative fuels, particularly methanol or ammonia, has a housing (2) having a cylinder bore (3) in which a pump piston (4) is reciprocally guided. The pump piston (4) is connected to a piston rod (5) which is guided through a leakage space (6) connected to the cylinder bore (3) and is at least sectionally surrounded by a corrugated or pleated tube (7) 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 pleated tube (7) has a hydraulic diameter (D). B The hydraulic diameter is related to the outer diameter (D) of the pump piston (4). K The bellows or pleated tube (7) is matched so that volume compensation can be achieved when the pump piston (4) moves.

Description

Technical Field

[0001] The present invention relates to a high-pressure pump for alternative fuels, particularly methanol or ammonia, having the features of the preamble of claim 1.

[0002] The preferred application of this invention is in engines, especially large engines, which must be supplied with alternative fuels. Background Technology

[0003] Fuel injection systems are known in the field of internal combustion engines, which deliver fuel to high pressure using a high-pressure pump. The fuel to be delivered must be separated from the medium (e.g., lubricating oil) of the power mechanism. In the case of a high-pressure pump with a reciprocating piston, medium separation can be achieved, in particular, by means of bellows or pleats. Because, as a movable seal, the bellows or pleats can receive the movement of the pump piston while simultaneously separating the two media from each other.

[0004] The movement of the pump piston displaces a volume of material, depending on the stroke and the piston's geometry. This displacement causes pressure fluctuations at the bellows or pleats, affecting their stability and durability. The magnitude of these pressure fluctuations is particularly dependent on the compressibility of the medium. The lower the compressibility, the greater the pressure fluctuation. Alternative fuels, such as methanol or ammonia, have lower compressibility than air. Therefore, in high-pressure pumps used for alternative fuels, the bellows or pleats used for medium separation are subjected to high pressure fluctuations, thus bearing high loads. Summary of the Invention

[0005] The objective of this invention is to reduce the load on the corrugated or pleated tubes in high-pressure pumps used for alternative fuels, thereby improving their durability.

[0006] This task is accomplished by a high-pressure pump having the features of claim 1. Advantageous extensions of the invention can be found in the dependent claims.

[0007] The proposed high-pressure pump for alternative fuels, particularly methanol or ammonia, has a housing with a cylinder bore in which a pump piston is reciprocally guided. The pump piston is connected here to a piston rod, which is guided through a leakage space connected to the cylinder bore and is at least sectionally surrounded by a corrugated or pleated tube fixed at one end to the piston rod and at the other end to the housing. According to the invention, the corrugated or pleated tube has a hydraulic diameter that matches the outer diameter of the pump piston, thereby enabling volume compensation through the corrugated or pleated tube during pump piston movement.

[0008] Through volume compensation, the volume of the leakage space remains unchanged as the pump piston reciprocates. This means that there are no or almost no pressure fluctuations that would subject the bellows or pleats to load. This, in turn, improves the durability of the bellows or pleats.

[0009] To achieve volume compensation, the outer diameter of the pump piston and the hydraulic diameter of the bellows or pleats must be coordinated, ideally chosen to be the same size. It is important to note that the hydraulic diameter of the bellows or pleats does not correspond to either its outer or inner diameter. Structurally, the hydraulic diameter lies between the outer and inner diameters.

[0010] According to a preferred embodiment of the invention, a corrugated or pleated tube separates the leakage space from the air-filled annular space. This means that a less compressible medium acts outside the corrugated or pleated tube than inside. Volume compensation is thus achieved in spaces where pressure fluctuations are particularly dangerous.

[0011] Furthermore, it is proposed that the cylinder bore in the high-pressure pump housing be implemented in a stepped manner to construct a leakage space. This stepped implementation creates space for accommodating bellows or pleats, since their outer diameter must be larger than the outer diameter of the pump piston.

[0012] The leak space is preferably attached to the return path via a hole constructed in the housing. Through the hole and the return path, fuel present in the leak space due to leakage can be discharged, preferably returned to the fuel reservoir. The hole may extend radially or obliquely relative to the cylinder bore.

[0013] Preferably, the corrugated or pleated tube is fixedly connected to the piston rod and / or housing at at least one end by an annular member. The corrugated or pleated tube can be supported in the axial direction by at least one annular member. Furthermore, it facilitates the connection of the corrugated or pleated tube to the piston rod or housing. The annular member can be, for example, a disc.

[0014] Furthermore, preferably, a guide body is installed, preferably pressed in, within the housing, preferably in the area of ​​the leakage space, through which the piston rod is guided. Since the piston rod can have a certain length, further guidance is advantageous. The first guide portion is realized by a pump piston housed in a cylinder bore, through which the pump piston is guided. Thus, further guidance by means of the guide body, preferably pressed in, installed in the housing, is ideally achieved at the end of the piston rod opposite to the pump piston. Therefore, a sufficiently large space is left between the guide body and the pump piston to accommodate a corrugated or pleated tube.

[0015] Furthermore, preferably, the guide body has at least one flow-through opening. The at least one flow-through opening allows for the inflation or deflation of an annular space filled with air, which is separated from a leakage space by corrugations or pleats. Preferably, the guide body has a plurality of flow-through openings arranged at equal angular intervals. Attached Figure Description

[0016] Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. These drawings show: Figure 1 The longitudinal section of the first high-pressure pump according to the present invention is shown. Figure 2 The significantly simplified longitudinal section of the second high-pressure pump according to the present invention, and Figure 3 for Figure 2 A magnified partial view. Detailed Implementation

[0017] from Figure 1 The image shows a high-pressure pump 1 according to the invention for an alternative fuel, such as methanol. The high-pressure pump 1 includes a housing 2 having a stepped cylinder bore 3. In the upper section of the cylinder bore 3, a pump piston 4 is reciprocally received and guided. In the lower section, the cylinder bore 3 forms a leakage space 6, which contains fuel that escapes from the guiding region of the cylinder bore 3 due to leakage. This fuel is discharged from the leakage space 6 through a hole 9.

[0018] The pump piston 4 is connected to a power unit (not shown) via a piston rod 5. The piston rod 5 is guided through a leakage space 6. To separate the leakage in the leakage space 6 from the medium (e.g., lubricating oil) of the power unit, the piston rod 5 is sectionally surrounded by a corrugated or pleated tube 7. The corrugated or pleated tube separates the leakage space 6 from the air-filled annular space 8. The corrugated or pleated tube 7 absorbs the movement of the pump piston 4 or the piston rod 5. The corrugated or pleated tube 7 is fixedly connected to the piston rod 5 at one end via an annular first member 10, and connected to the housing 2 at the other end via an annular second member 11. The annular second member 11 has an inner diameter larger than the outer diameter of the piston rod 5, allowing air to flow through. A guide body 12 is also installed, preferably pressed in, in the leakage space 6, through which the piston rod 5 is guided. A flow-through opening 13 constructed in the guide body 12 also allows air to flow through.

[0019] As the pump piston 4 moves downward, the airflow achieves volume displacement, thereby compressing the bellows or pleats 7 and expelling air from the annular space 8. In contrast, the leakage space 6 is enclosed between the pump piston 4 and the lower annular member 11, so the movement of the pump piston 4 cannot be compensated for by volume displacement. Typically, this results in pressure fluctuations, leading to high loads on the bellows or pleats 7. Figure 1 This is not the case in the high-pressure pump 1 according to the present invention. Because here, the corrugated or pleated tube 7 has a hydraulic diameter D. B The hydraulic diameter is related to the outer diameter D of the pump piston 4. K This matching mechanism allows for volume compensation via the bellows or pleats 7 when the pump piston 4 moves. This means no volume is displaced, and no pressure fluctuations occur in the leakage space 6, thus reducing the load on the bellows or pleats 7. Consequently, the service life of the bellows or pleats 7 is increased.

[0020] from Figure 2 Another high-pressure pump 1 according to the invention can be seen. This high-pressure pump also has a housing 2 and a cylinder bore 3, and a pump piston 4 reciprocally guided within the cylinder bore 3. The pump piston 4 is connected to a piston rod 5, which is guided through a leakage space 6 and is at least sectionally surrounded by a corrugated or pleated tube 7. The corrugated or pleated tube separates the leakage space 6 from an air-filled annular space 8. The corrugated or pleated tube 7 is connected at its end sides to the piston rod 5 and to the housing 2 via annular members 10 and 11, respectively.

[0021] Especially from Figure 3 As can be seen, the corrugated or pleated tube 7 has a hydraulic diameter D. B The hydraulic diameter is equal to the outer diameter D of the pump piston 4. K Therefore, volume compensation is also achieved here through the bellows or pleated tube 7 during the movement of the pump piston 4.

Claims

1. A high-pressure pump (1) for alternative fuels, particularly methanol or ammonia, having a housing (2) having a cylinder bore (3) in which a pump piston (4) is reciprocally guided, wherein, The pump piston (4) is connected to the piston rod (5), which is guided through a leakage space (6) connected to the cylinder bore (3) and is at least sectionally surrounded by a corrugated or pleated tube (7), which is fixedly connected to the piston rod (5) at one end and to the housing (2) at the other end. The corrugated or pleated tube (7) is characterized in that it has a hydraulic diameter (D). B The hydraulic diameter is related to the outer diameter (D) of the pump piston (4). K The bellows or pleated tube (7) is matched so that volume compensation can be achieved through the bellows or pleated tube (7) when the pump piston (4) moves.

2. The high-pressure pump (1) according to claim 1, characterized in that, The corrugated or pleated tube (7) separates the leakage space (6) from the air-filled annular space (8).

3. The high-pressure pump (1) according to claim 1 or 2, characterized in that, The cylinder bore (3) is stepped to construct the leakage space (6).

4. The high-pressure pump (1) according to any one of the preceding claims, characterized in that, The leakage space (6) is attached to the return path through a hole (9) constructed in the housing (2).

5. The high-pressure pump (1) according to any one of the preceding claims, characterized in that, The corrugated or pleated tube (7) is fixedly connected to the piston rod (5) and / or the housing (2) at at least one end by an annular member (10, 11).

6. The high-pressure pump (1) according to any one of the preceding claims, characterized in that, In the housing (2), preferably in the area of ​​the leakage space (6), a guide (12) is installed, preferably pressed in, through which the piston rod (5) is guided.

7. The high-pressure pump (1) according to claim 6, characterized in that, The guide (12) has at least one flow-through opening (13), preferably having a plurality of flow-through openings (13) arranged at the same angular intervals.

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