High-pressure pump

Abstract

A high-pressure pump including a drive shaft (2) supported about an axis of rotation (26) and having at least one cam (3). The pump includes at least two pistons (5); at least two cylinders (6) supporting the pistons (5); wherein the pistons (5) have longitudinal axes (16) oriented at an angle to each other in a projection of the piston longitudinal axes (16) in the direction of the axis of rotation (26) onto a fictitious projection plane perpendicular to the axis of rotation (26). Each of the pistons (5) is supported on a shaft rolling surface (4) of the drive shaft (2) having the at least one cam (3) indirectly by means of a respective supporting element (14) having a supporting rolling surface (15), such that a translational motion can be performed by the pistons (5) as the result of a rotational motion of the drive shaft (2), wherein the piston longitudinal axes (16) have an axial distance in the direction of the axis of rotation (26).

Claims

1. A high-pressure pump (1), comprising a drive shaft (2) mounted rotatably about a rotation axis (26) and having at least one cam (3), at least two pistons (5), at least two cylinders (6) for mounting of the at least two pistons (5), the pistons (5) each having a piston longitudinal axis (16), wherein on a projection of the piston longitudinal axes (16) in a direction of the rotation axis (26) of the drive shaft (2) onto a theoretical projection plane perpendicular to the rotation axis (26), the piston longitudinal axes (16) are oriented at an angle to each other, wherein the at least two pistons (5) rest indirectly, each by means of a support element (14) having a support rolling face (15), on a shaft rolling face (4) of the drive shaft (2) having the at least one cam (3), so that the at least two pistons (5) can perform a translational movement as a result of rotational movement of the drive shaft (2), characterized in that the piston longitudinal axes (16) have an axial spacing (17) in the direction of the rotation axis (26) of the drive shaft (2), contact rolling faces (18), of the support rolling faces (15) of the support elements (14) on the shaft rolling face (4) of the drive shaft (2) are separate from each other along the rotation axis (26) so as not to overlap each other, and all support elements (14) with the support rolling faces (15) rest on just one common shaft rolling face (4) of the drive shaft (2) having the at least one cam (3).

2. The high-pressure pump as claimed in claim 1, characterized in that the axial spacing (17) of the piston longitudinal axes (16) of the pistons (5) in the direction of the rotation axis (26) of the drive shaft (2) amounts to at least 30% of an axial extension (40) of the support rolling faces (15) in the direction of the rotation axis (26) of the drive shaft (2).

3. The high-pressure pump as claimed in claim 1, characterized in that on a projection of the piston longitudinal axes (16) in the direction of the rotation axis (26) of the drive shaft (2) onto the theoretical projection plane, the piston longitudinal axes (16) are oriented at a minimum angle to each other of between 0 and 180.

4. The high-pressure pump as claimed in claim 1, characterized in that all pistons (5) rest indirectly, each by means of the support element (14) with the support rolling face (15), on the shaft rolling face (4) of just one drive shaft (2) having the at least one cam (3).

5. The high-pressure pump as claimed in claim 1, characterized in that each one of a plurality of theoretical straight lines oriented parallel to the rotation axis (26) and lying continuously without interruption on the common shaft rolling face (4) has a constant distance from the rotation axis (26) of the drive shaft (2) in the direction of the rotation axis (26) of the drive shaft (2).

6. The high-pressure pump as claimed in claim 1, characterized in that, on the projection of the piston longitudinal axes (16) in the direction of the rotation axis (26) of the drive shaft (2) onto the theoretical projection plane, all piston longitudinal axes (16) are arranged within an angular range of 120.

7. A high-pressure injection system (36) for an internal combustion engine (39), comprising a high-pressure pump (1), a high-pressure rail (30), and a pre-delivery pump (35) for delivering a fuel from a fuel tank (32) to the high-pressure pump (1), characterized in that the high-pressure pump (1) is configured as a high-pressure pump (1) as claimed in claim 1.

8. The high-pressure pump as claimed in claim 1, characterized in that the axial spacing (17) of the piston longitudinal axes (16) of the pistons (5) in the direction of the rotation axis (26) of the drive shaft (2) amounts to at least 50% of an axial extension (40) of the support rolling faces (15) in the direction of the rotation axis (26) of the drive shaft (2).

9. The high-pressure pump as claimed in claim 1, characterized in that the axial spacing (17) of the piston longitudinal axes (16) of the pistons (5) in the direction of the rotation axis (26) of the drive shaft (2) amounts to at least 70% of an axial extension (40) of the support rolling faces (15) in the direction of the rotation axis (26) of the drive shaft (2).

10. The high-pressure pump as claimed in claim 1, characterized in that the axial spacing (17) of the piston longitudinal axes (16) of the pistons (5) in the direction of the rotation axis (26) of the drive shaft (2) amounts to at least 100% of an axial extension (40) of the support rolling faces (15) in the direction of the rotation axis (26) of the drive shaft (2).

11. The high-pressure pump as claimed in claim 1, characterized in that in the direction of the rotation axis (26) of the drive shaft (2), the support rolling faces (15) of the support elements (14) have an axial spacing (41) of at least 1% of an axial extension (40) of the support rolling faces (15) in the direction of the rotation axis (26) of the drive shaft (2).

12. The high-pressure pump as claimed in claim 1, characterized in that in the direction of the rotation axis (26) of the drive shaft (2), the support rolling faces (15) of the support elements (14) have an axial spacing (41) of at least 3% of an axial extension (40) of the support rolling faces (15) in the direction of the rotation axis (26) of the drive shaft (2).

13. The high-pressure pump as claimed in claim 1, characterized in that in the direction of the rotation axis (26) of the drive shaft (2), the support rolling faces (15) of the support elements (14) have an axial spacing (41) of at least 5% of an axial extension (40) of the support rolling faces (15) in the direction of the rotation axis (26) of the drive shaft (2).

14. The high-pressure pump as claimed in claim 1, characterized in that in the direction of the rotation axis (26) of the drive shaft (2), the support rolling faces (15) of the support elements (14) have an axial spacing (41) of at least 10% of an axial extension (40) of the support rolling faces (15) in the direction of the rotation axis (26) of the drive shaft (2).

15. The high-pressure pump as claimed in claim 1, characterized in that all contact rolling faces (18) of the support rolling faces (15) of the support elements (14) on the shaft rolling face (4) of the drive shaft (2) have axial spacing therebetween.

16. The high-pressure pump as claimed in claim 1, characterized in that on the projection of the piston longitudinal axes (16) in the direction of the rotation axis (26) of the drive shaft (2) onto the theoretical projection plane, the piston longitudinal axes (16) are oriented at a minimum angle to each other of between 2 and 178.

17. The high-pressure pump as claimed in claim 1, characterized in that on the projection of the piston longitudinal axes (16) in the direction of the rotation axis (26) of the drive shaft (2) onto the theoretical projection plane, the piston longitudinal axes (16) are oriented at a minimum angle to each other of between 10 and 120.

18. The high-pressure pump as claimed in claim 1, characterized in that on the projection of the piston longitudinal axes (16) in the direction of the rotation axis (26) of the drive shaft (2) onto the theoretical projection plane, the piston longitudinal axes (16) are oriented at a minimum angle to each other of between 20 and 100.

19. The high-pressure pump as claimed in claim 1, characterized in that the support elements (14) with the support rolling faces (15) are configured as running rollers (10) with roller rolling faces (11).

20. The high-pressure pump as claimed in claim 19, characterized in that, on the projection of the piston longitudinal axes (16) in the direction of the rotation axis (26) of the drive shaft (2) onto the theoretical projection plane, all piston longitudinal axes (16) are arranged within an angular range of 120.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Exemplary embodiments of the invention are described below with reference to the enclosed drawings. These show:

(2) FIG. 1 a cross section of a high-pressure pump at a piston,

(3) FIG. 2 a section A-A according to FIG. 1 of a running roller with roller shoe and a drive shaft,

(4) FIG. 3 a greatly simplified view of the drive shaft with two running rollers,

(5) FIG. 4 a side view of the drive shaft with two running rollers each in a roller shoe, and

(6) FIG. 5 a highly diagrammatic view of a high-pressure injection system.

DETAILED DESCRIPTION

(7) FIGS. 1 and 2 show a cross section of a high-pressure pump 1 for a high-pressure injection system 36. The high-pressure pump 1 serves to deliver fuel, e.g. petrol or diesel, under high pressure to an internal combustion engine 39. The pressure which can be generated by the high-pressure pump 1 lies for example in a range between 1000 and 3000 bar.

(8) The high-pressure pump 1 has a drive shaft 2 having two cams 3, which executes a rotational movement around a rotation axis 26. The rotation axis 26 lies in the drawing plane of FIG. 1 and stands perpendicular to the drawing plane of FIG. 2. The high-pressure pump 1 has a total of two pistons 5 mutually oriented in a V-shape. Each piston 5 is mounted in a cylinder 6 formed by a housing 8. A working chamber 29 is delimited by the cylinder 6, the housing 8 and the piston 5. An inlet channel 22 with an inlet valve 19, and an outlet channel 24 with an outlet valve 20, open into the working chamber 29. The fuel flows under high pressure into the working chamber 29 through the inlet channel 22 and back out of the working chamber 29 through the outlet channel 24. The inlet valve 19, e.g. a check valve, is configured so that fuel can only flow into the working chamber 29, and the outlet valve 20, e.g. a check valve, is configured so that fuel can only flow out of the working chamber 29. The volume of the working chamber 29 changes because of the oscillating stroke movement of the piston 5. The piston 5 rests indirectly on the drive shaft 2. A roller shoe 9 with a running roller 10 is fixed at the end of the piston 5 or pump piston 5. The running roller 10 is mounted in the roller shoe 9 by means of a plain bearing 13. The running roller 10 can execute a rotational movement, the rotation axis 25 of which lies in the drawing plane according to FIG. 1 and stands perpendicular to the drawing plane of FIG. 2. The drive shaft 2 with the two cams 3 has a shaft rolling face 4 and the running roller 10 as a support element 14 has on the outside a roller rolling face 11 as a support rolling face 15.

(9) The roller running face 11 of the running roller 10 rolls on the shaft rolling face 4 of the drive shaft 2 having the two cams 3, so that a contact face 12 is present between the roller rolling face 11 and the shaft rolling face 4. The roller shoe 9 is mounted in a roller shoe bearing as a plain bearing formed by the housing 8. A spring 27 or coil spring 27, as an elastic element 28, clamped between the housing 8 and the roller shoe 9, applies a pressure to the roller shoe 9 so that the roller rolling face 11 of the running roller 10 is in constant contact with the shaft rolling face 4 of the drive shaft 2. The rolling shoe 9 and the piston 5 thus execute a common oscillating stroke movement.

(10) FIG. 3 shows a view radially onto the drive shaft 2 with two running rollers 10, and FIG. 4 depicts an axial side view of the drive shaft with two running rollers 10 each in a roller shoe 9. The drawing plane of FIG. 3 lies parallel to the rotation axis 26, and the drawing plane of FIG. 4 stands perpendicular to the rotation axis 26. The high-pressure pump 1 has two pistons 5 mutually oriented in a V-shape. In a projection in the direction of the rotation axis 26 of the piston longitudinal axes 16, which also form a piston movement axis 16, onto a theoretical projection plane perpendicular to the rotation axis 26, the piston longitudinal axes 16 are oriented at an angle of around 60 to each other. The theoretical projection plane corresponds to the drawing plane of FIG. 4. The piston longitudinal axes 16 are here oriented centrally on the running rollers 10 in the direction of the rotation axis 26 of the drive shaft 2. The axial spacing 17 of the piston longitudinal axes 16 in the direction of the rotation axis 26 of the drive shaft 2 is greater than the axial extension 40 of the roller rolling face 11 of the running roller 10 or the axial extension 40 of the running roller 10 as a support element 14 with the support rolling face 15. Thus there is an axial distance 41 between the two roller rolling faces 11 or support rolling faces 15, or the two running rollers 10. The roller rolling faces 11 of the running rollers 10 rest or roll on the shaft rolling face 4 of the drive shaft 2, so that in this way at the contact region between the running roller 10 and the drive shaft 2, a contact rolling face 18 of the running roller 10 is present on the drive shaft 2, i.e. the shaft rolling face 4. Because of the axial distance between the running rollers 10, the axial distance 41 also exists between the contact rolling faces 18 of the running rollers 10 on the shaft rolling face 4. The contact rolling faces 18 of the two running rollers 10 on the shaft rolling face 4 of the drive shaft 2 are thus different, i.e. there is no overlap of the contact rolling faces 18 of the two running rollers 10 on the shaft rolling face 4 of the drive shaft 2. The two piston longitudinal axes 16 of the two pistons 5 are arranged within an angular range of 90.

(11) FIG. 5 shows highly diagrammatically the high-pressure injection system 36 for a motor vehicle (not shown) with a high-pressure rail 30 or a fuel distribution pipe 31. From the high-pressure rail 30, the fuel is injected by means of valves (not shown) into the combustion chamber of the internal combustion engine 39. A pre-delivery pump 35 delivers fuel from a fuel tank 32 through a fuel line 33 to the high-pressure pump 1 according to the exemplary embodiment described above. The high-pressure pump 1 and the pre-delivery pump 35 are here driven by the drive shaft 2. The drive shaft 2 is coupled by means of a crankshaft of the internal combustion engine 39. The high-pressure rail 30as already describedserves to inject the fuel into the combustion chamber of the internal combustion engine 39. The fuel delivered by the pre-delivery pump 35 is conducted through the fuel line 33 to the high-pressure pump 1. The fuel not required by the high-pressure pump 1 is then returned through a fuel return line 34 to the fuel tank 32. A metering unit 37 controls and/or regulates the quantity of fuel supplied to the high-pressure pump 1, so that in a further embodiment (not shown), the fuel return line 34 may be omitted.

(12) Viewed as a whole, considerable advantages are achieved with the high-pressure pump 1 according to the invention and the high-pressure injection system 36 according to the invention. The two running rollers 10 rest or roll on a common shaft rolling face 38 of the drive shaft 2. The contact rolling face 18 of one running roller 10 on the shaft rolling face 4 is completely separate from the contact rolling face 18 of the second or other running roller 10, so that in this way the shaft rolling face 4 of the common shaft rolling face 38 is in each case separately mechanically loaded by just one running roller 10. On a rotational movement of the drive shaft 2 with a complete rotation of 360, thus only a single roll on the shaft rolling face 4 takes place in a section perpendicular to the rotation axis 26. The mechanical load on the shaft rolling face 4 from the running rollers 10 is thus substantially reduced so that the high-pressure pump 1 advantageously has a substantially longer life.