HIGH PRESSURE FUEL PUMP FOR A FUEL SYSTEM

Abstract

The present invention relates to a high pressure fuel pump comprising an inlet channel in connection with a first chamber, through which inlet channel fuel is led to the first chamber, a second chamber arranged in connection with the first chamber, an outlet valve arranged in connection with the second chamber and an inlet valve comprising a piston, with a first end section and a second end section. The piston is moveably arranged with the first end section in a third chamber, and the second end section is moveably arranged between the first chamber and the second chamber. A press element is arranged to act on the piston with a mechanic force, so that the piston strives to be positioned with the second end section closing the connection between the first chamber and the second chamber. The inlet valve is in a closed state and may be controlled via an electromagnetic unit.

Claims

1. A fuel system comprising a high pressure fuel pump and a low pressure circuit, from which fuel is arranged to be supplied to the high pressure fuel pump, wherein the high pressure fuel pump comprises: an inlet channel in connection with a first chamber, and through which fuel is led to the first chamber with a feeding pressure; a second chamber arranged in connection with the first chamber; an outlet valve arranged in connection with the second chamber; and an inlet valve comprising a piston, with a first end section and a second end section, wherein the piston is moveably arranged with the first end section in a third chamber, and the second end section is moveably arranged between the first chamber and the second chamber, wherein a press element is arranged to act on the piston with a mechanic force, so that the piston strives to be positioned with the second end section closing the connection between the first chamber and the second chamber, and so that the inlet valve is thus in a closed state, wherein the inlet valve is controllable using a controllable electromagnetic unit arranged in the third chamber, in order to act with a magnetic force on the piston, so that the piston moves, wherein the fuel system is arranged in such a manner that the feeding pressure entails a flow force acting on the piston in a direction opposed to the mechanic force, wherein the electromagnetic unit is arranged to: act with the magnetic force on the piston in a direction opposed to the mechanic force, in order to achieve an open state of the inlet valve, wherein the fuel system is arranged to increase the feeding pressure of the fuel from the low pressure circuit in cases where the electromagnetic unit is out of order, so that the flow force becomes greater than the mechanic force; or act with the magnetic force on the piston in the same direction as the mechanic force, in order to achieve a closed state of the inlet valve, wherein the mechanic force is smaller than the flow force caused by the feeding pressure at normal operation.

2. A fuel system according to claim 1, wherein the press element is arranged to act on the first end section of the piston.

3. A fuel system according to claim 1, wherein the magnetic force is arranged to act on the first end section of the piston.

4. A fuel system according to claim 1, wherein the magnetic force is achieved by way of an electric current being led through the electromagnetic unit.

5. A fuel system according to claim 1, wherein, if the electromagnetic unit is arranged to act with the magnetic force on the piston in the same direction as the spring force in order to achieve a closed state of the inlet valve, a passage is arranged between the inlet channel and the third chamber, so that fuel which is fed through the inlet channel may flow to the third chamber.

6. A fuel system according to claim 1, wherein the outlet valve is a check valve.

7. A fuel system according to claim 1, wherein a pressure element is moveably arranged in the second chamber, in connection with a camshaft in a combustion engine.

8. A fuel system according to claim 7, wherein the pressure element is arranged to increase the pressure of the fuel in the second chamber, and thus to facilitate feeding of the fuel through the outlet valve.

9. A fuel system according to claim 1, wherein the press element is a spring element and the mechanic force is a spring force.

10. A combustion engine comprising a fuel system, wherein the fuel system comprises a high pressure fuel pump and a low pressure circuit, from which fuel is arranged to be supplied to the high pressure fuel pump, wherein the high pressure fuel pump comprises: an inlet channel in connection with a first chamber, and through which fuel is led to the first chamber with a feeding pressure; a second chamber arranged in connection with the first chamber; an outlet valve arranged in connection with the second chamber; and an inlet valve comprising a piston, with a first end section and a second end section, wherein the piston is moveably arranged with the first end section in a third chamber, and the second end section is moveably arranged between the first chamber and the second chamber, wherein a press element is arranged to act on the piston with a mechanic force, so that the piston strives to be positioned with the second end section closing the connection between the first chamber and the second chamber, and so that the inlet valve is thus in a closed state, wherein the inlet valve is controllable using a controllable electromagnetic unit arranged in the third chamber, in order to act with a magnetic force on the piston, so that the piston moves, wherein the fuel system is arranged in such a manner that the feeding pressure entails a flow force acting on the piston in a direction opposed to the mechanic force, wherein the electromagnetic unit is arranged to: act with the magnetic force on the piston in a direction opposed to the mechanic force, in order to achieve an open state of the inlet valve, wherein the fuel system is arranged to increase the feeding pressure of the fuel from the low pressure circuit in cases where the electromagnetic unit is out of order, so that the flow force becomes greater than the mechanic force; or act with the magnetic force on the piston in the same direction as the mechanic force, in order to achieve a closed state of the inlet valve, wherein the mechanic force is smaller than the flow force caused by the feeding pressure at normal operation.

11. A vehicle comprising a fuel system, wherein the fuel system comprises a high pressure fuel pump and a low pressure circuit, from which fuel is arranged to be supplied to the high pressure fuel pump, wherein the high pressure fuel pump comprises: an inlet channel in connection with a first chamber, and through which fuel is led to the first chamber with a feeding pressure; a second chamber arranged in connection with the first chamber; an outlet valve arranged in connection with the second chamber; and an inlet valve comprising a piston, with a first end section and a second end section, wherein the piston is moveably arranged with the first end section in a third chamber, and the second end section is moveably arranged between the first chamber and the second chamber, wherein a press element is arranged to act on the piston with a mechanic force, so that the piston strives to be positioned with the second end section closing the connection between the first chamber and the second chamber, and so that the inlet valve is thus in a closed state, wherein the inlet valve is controllable using a controllable electromagnetic unit arranged in the third chamber, in order to act with a magnetic force on the piston, so that the piston moves, wherein the fuel system is arranged in such a manner that the feeding pressure entails a flow force acting on the piston in a direction opposed to the mechanic force, wherein the electromagnetic unit is arranged to: act with the magnetic force on the piston in a direction opposed to the mechanic force, in order to achieve an open state of the inlet valve, wherein the fuel system is arranged to increase the feeding pressure of the fuel from the low pressure circuit in cases where the electromagnetic unit is out of order, so that the flow force becomes greater than the mechanic force; or act with the magnetic force on the piston in the same direction as the mechanic force, in order to achieve a closed state of the inlet valve, wherein the mechanic force is smaller than the flow force caused by the feeding pressure at normal operation.

12. A method to control a fuel system comprising a high pressure fuel pump and a low pressure circuit, from which fuel is fed to the high pressure fuel pump, wherein the high pressure fuel pump comprises an inlet channel in connection with a first chamber, and through which fuel is led to the first chamber with a feeding pressure, a second chamber arranged in connection with the first chamber, an outlet valve arranged in connection with the second chamber and an inlet valve comprising a piston, with a first end section and a second end section, wherein the piston is moveably arranged with the first end section in a third chamber, and the second end section may be moved between the first chamber and the second chamber, wherein the method comprises: a) providing a press element arranged to act on the piston with a mechanic force, so that the piston strives to be positioned with the second end section closing the connection between the first chamber and the second chamber, and so that the inlet valve is thus in a closed state; and b) controlling the inlet valve with an electromagnetic unit arranged in the third chamber, which unit acts with a magnetic force on the piston of the inlet valve, so that the piston moves, so that the feeding pressure entails a flow force acting on the piston in a direction opposed to the mechanic force, wherein the electromagnetic unit is arranged to: act with the magnetic force on the piston in a direction opposed to the mechanic force, in order to achieve an open state of the inlet valve, wherein the method comprises the step to increase the feeding pressure of the fuel from the low pressure circuit in cases where the electromagnetic unit is out of order, so that the flow force becomes greater than the mechanic force; or act with the magnetic force on the piston in the same direction as the mechanic force, in order to achieve a closed state of the inlet valve, wherein the mechanic force is smaller than the flow force caused by the feeding pressure at normal operation.

13. A method according to claim 12, wherein the inlet valve is controlled by controlling the supply of electric current through the electromagnetic unit.

14. A method according to claim 12, wherein, in case the electromagnetic unit is out of order, an open state of the inlet valve is achieved by ensuring that the flow force is greater than the mechanic force.

15. A method to claim 12, wherein the mechanic force is a spring force, which is provided via a spring element.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Below is a description, as an example, of preferred embodiments of the invention with reference to the enclosed drawings, in which:

[0037] FIG. 1 shows a schematic side view of a vehicle, which comprises a fuel system for a combustion engine according to the present invention,

[0038] FIG. 2 shows a schematic cross sectional view of a high pressure fuel pump according to one aspect of the present invention,

[0039] FIG. 3 shows a schematic cross sectional view of a high pressure fuel pump according to one aspect of the present invention,

[0040] FIG. 4 shows a schematic cross sectional view of a high pressure fuel pump according to one aspect of the present invention, and

[0041] FIG. 5 schematically shows a fuel system; and

[0042] FIG. 6 shows a flow chart of a method for a high pressure fuel pump according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0043] FIG. 1 shows a schematic side view of a vehicle 1, which vehicle comprises a fuel system 4 for a combustion engine 2. In the combustion engine 2 a high pressure fuel pump 12 is arranged according to the present invention. The combustion engine 2 is connected to a gearbox 6, which is further connected to the driving wheels 8 of the vehicle 1 via a transmission. The vehicle also comprises a chassis 10.

[0044] FIG. 2 shows a schematic cross sectional view of a high pressure fuel pump 12 according to one aspect of the present invention. The high pressure fuel pump 12 comprises an inlet channel 14 in connection with a first chamber 16, and through which fuel (symbolized with enlarged arrows) from a low pressure circuit 110 (see FIG. 5) in a fuel system 4 is led to the first chamber 16, a second chamber 18 arranged in connection with the first chamber 16, an inlet valve 20 arranged in connection with the second chamber 18, in order to achieve that fuel flows from the first chamber 16 to the second chamber 18, and an outlet valve 40 arranged in connection with the second chamber 18, in order to feed fuel further along to the combustion engine 2. The inlet valve 20 comprises a piston 22 with a first end section 24 and a second end section 26, wherein the piston 22 is moveably arranged with the first end section 24 in a third chamber 28, and the second end section 26 is moveably arranged between the first chamber 16 and the second chamber 18. When the inlet valve 20 is in a closed state, the second end section 26 closes the connection between the first chamber 16 and the second chamber 18, and when the inlet valve 20 is in an open state (illustrated with dashed lines), fuel may flow from the first chamber 16 to the second chamber 18 through an inlet passage 30. The second end section 26 is suitably adapted like a truncated cone, with a bottom 32 having an area at least equivalent to the cross sectional area of a first chamber 16 at the connection with the second chamber 18. When the inlet valve 20 is in the closed state, the bottom 32 of the second end section 26 is thus arranged in a tightly fitting manner between the first chamber 16 and the second chamber 18. When the inlet valve 20 is in an open state, the second end section 26 of the piston 22 has been moved into the second chamber 28, so that the inlet passage 30 is formed.

[0045] A spring element 34 is arranged to act on the first end section 24 of the piston 22 with a spring force F.sub.s, so that the piston 22 strives to be positioned with the second end section 26 closing the connection between the first chamber 16 and the second chamber 18, and so that the inlet valve 20 is thus in a closed state. The forces are symbolized with arrows in the drawings. The spring element 34 is arranged in the third chamber 28 and acts on the first end section 24 of the piston 22. The first end section 24 is suitably T-shaped. The spring force F.sub.s is determined based on the performance of the pump and the dimensions of the piston. Fuel is fed from the low pressure circuit 110 into the inlet channel 14 with a feeding pressure P, which entails that the fuel acts on the piston 22 with a flow force F.sub.f in a direction opposed to the spring force F.sub.s. The feeding pressure P and the flow force F.sub.f are also determined based on the performance of the pump and the dimensions of the piston. The flow force F.sub.f that acts on the piston 22 depends on the feeding pressure P and the area of the angled sides 36 of the second end section 26, on which area the feeding pressure P acts. Generally, the larger the area, the greater the flow force F.sub.f.

[0046] The inlet valve 20 is actively controllable since an electromagnetic unit 38 is arranged in the third chamber 28, in order to act with a magnetic force F.sub.m on the first end section 24 of the piston 22, so that the piston 22 moves. The electromagnetic unit 38 is arranged in such a manner that the magnetic force F.sub.m acts on the first end section 24 of the piston 22 in a direction opposed to the spring force F.sub.s. The magnetic force F.sub.m is achieved by way of an electric current I being led through the electromagnetic unit 38. In order to achieve an open state of the inlet valve 20, the sum of the magnetic force F.sub.m and the flow force F.sub.f must exceed the spring force F.sub.s. The spring force F.sub.s, the flow force F.sub.f and the magnetic force F.sub.m are illustrated as arrows in the direction, in which the respective force acts on the piston 22. By controlling the supply of electric current I through the electromagnetic unit 38, the magnetic force F.sub.m may be controlled, and the inlet valve 20 may thus be actively controlled to an open state, so that fuel may be supplied to the second chamber 18. In order to achieve a closed state of the inlet valve 20, the supply of electric current I through the electromagnetic unit 38 is stopped, and the magnetic force F.sub.m is accordingly zero. The spring force F.sub.s is greater than the flow force F.sub.f, and the piston 22 thus moves to a closed state. Should the electromagnetic unit 38 fail to function, the magnetic force F.sub.m becomes zero, and to achieve an open state of the inlet valve 20, the flow force F.sub.f must in this case exceed the spring force F.sub.s. This may be achieved by increasing the feeding pressure P of the fuel from the low pressure circuit, and thus increasing the flow force F.sub.f that acts on the piston 22. This ensures that redundancy is obtained and that the combustion engine 2 is supplied with fuel, even in cases where the active control of the inlet valve 20 does not function.

[0047] The high pressure fuel pump 12 also comprises a pressure element 42, which is moveably arranged in the second chamber 18. The pressure element 42 is arranged in connection with a camshaft 44 in the combustion engine 2, and when the camshaft 44 rotates the pressure element 42 in the second chamber 18 moves in a direction towards and away from the first chamber 16. When the pressure element 42 moves in a direction towards the first chamber 16, the inlet valve 20 is controlled to a closed state, the volume of the second chamber 18 decreases and the pressure of the fuel in the second chamber 18 increases. The increased pressure of the fuel in the second chamber 18 acts on the outlet valve 40, so that it opens and fuel may be fed further along to the combustion engine 2. The outlet valve 40 suitably consists of a check valve comprising a spring loaded ball 46. When the pressure element 42 moves in a direction away from the first chamber 16, the volume of the second chamber 18 increases and the inlet valve 20 is controlled to an open state, so that fuel may flow from the first chamber 16 to the second chamber 18.

[0048] FIG. 3 shows a schematic cross sectional view of a high pressure fuel pump 12 according to one aspect of the present invention. The high pressure fuel pump 12 is adapted as described in FIG. 2, with the difference that the electromagnetic unit 38 is arranged in such a manner that the magnetic force F.sub.m acts on the first end section 24 of the piston 22 in the same direction as the spring force F.sub.s, and thus moves the piston 22 to a closed state. The spring force F.sub.s, the feeding pressure P, with which fuel is fed, and the flow force F.sub.f are determined based on the pump's performance and dimensions. In order to achieve an open state of the inlet valve 20, the supply of current I through the electromagnetic unit 38 is controlled in such a manner that the magnetic force F.sub.m becomes zero. When the flow force F.sub.f is greater than the spring force F.sub.s, an open state is therefore created in the inlet valve 20. In order to achieve a closed state of the inlet valve 20, the supply of electric current I through the electromagnetic unit 38 is controlled in such a manner that the sum of the magnetic force F.sub.m and the spring force F.sub.s exceeds the flow force F.sub.f, and the piston 22 thus moves to the closed state. Should the electromagnetic unit 38 fail to function, the magnetic force F.sub.m becomes zero, and thus the open state of the inlet valve 20 is not impacted. This ensures that the combustion engine 2 is supplied with fuel, even in cases where the active control of the inlet valve 20 does not function.

[0049] FIG. 4 shows a schematic cross sectional view of a high pressure fuel pump 12 according to one aspect of the present invention. The high pressure fuel pump 12 is adapted as described in FIG. 3, with the addition that a passage 48 is arranged between the inlet channel 14 and the third chamber 28. Thus, fuel may flow from the inlet channel 14 to the third chamber 28 and act on the first end section 24. In this manner, the area of the piston 22 on which the fuel acts becomes larger than when the passage 48 to the third chamber 28 is missing. Since the fuel acts on a larger area, the total flow force F.sub.f acting on the piston 22 increases, so that an open state of the inlet valve 20 is achieved in a simpler manner.

[0050] FIG. 5 illustrates schematically a fuel system 4, comprising a low pressure circuit 110 from which fuel is supplied to a high pressure pump 12 according to the above. The high pressure pump is a part of the fuel system's 4 high pressure circuit 120, from which fuel is supplied to the combustion engine 2 with a high pressure.

[0051] FIG. 6 shows a flow chart over a method for a high pressure fuel pump 12 in a fuel system 4 for a combustion engine 2, comprising an inlet channel 14 in connection with a first chamber 16, and through which fuel from a low pressure circuit in the fuel system 4 is led to the first chamber 16, a second chamber 18 arranged in connection with the first chamber 16, an outlet valve 40 arranged in connection with the second chamber 18, and an inlet valve 20 comprising a piston 22 with a first end section 24 and a second end section 26, wherein the piston 22 is moveably arranged with the first end section 24 in a third chamber 28, and the second end section 26 is movably arranged between the first chamber 16 and the second chamber 18. The method comprises the steps of a) providing a spring element 34 arranged to act on the first end section 24 with a spring force F.sub.s, so that the piston 22 strives to be positioned with the second end section 26 closing the connection between the first chamber 16 and the second chamber 18, and so that the inlet valve 20 is thus in a closed state; and b) controlling the inlet valve 20 with an electromagnetic unit 38 arranged in the third chamber 28, which may act with a magnetic force F.sub.m on the piston 22 of the inlet valve 20, so that the piston 22 moves.

[0052] Preferably, the feeding pressure P, with which fuel is supplied to the first chamber 16, entails a flow force F.sub.f, which acts on the piston 22 in a direction opposed to the spring force F.sub.s.

[0053] The inlet valve 20 is suitably controlled by controlling the supply of electric current I through the electromagnetic unit 38.

[0054] According to one aspect of the present invention, the electromagnetic unit 38 is arranged in such a manner that the magnetic force F.sub.m acts on the piston 22 in a direction opposed to the spring force F.sub.s. By controlling the supply of electric current I through the electromagnetic unit 38, so that a magnetic force F.sub.m is obtained, an open state of the inlet valve 20 may be achieved. A closed state of the inlet valve 20 may be achieved by stopping the supply of electric current I through the electromagnetic unit 38, so that the magnetic force F.sub.m becomes negligible and does not act on the piston 22. The spring force F.sub.s is then greater than the flow force F.sub.f, so that the piston 22 is moved to the closed state.

[0055] According to one aspect of the present invention, the electromagnetic unit 38 is arranged in such a manner that the magnetic force F.sub.m acts on the piston 22 in the same direction as the spring force F.sub.s. By controlling the supply of electric current I through the electromagnetic unit 38 so that a magnetic force F.sub.m is obtained, a closed state of the inlet valve 20 may be achieved. An open state of the inlet valve 20 may be achieved by stopping the supply of electric current I through the electromagnetic unit 38, so that the magnetic force F.sub.m becomes negligible and does not act on the piston 22. The spring element 34 is adapted, so that the flow force F.sub.f is greater than the spring force F.sub.s, and so that the piston 22 is moved to an open state thanks to the flow force F.sub.f.

[0056] Preferably, an open state of the inlet valve 20 is achieved, in the event that the electromagnetic unit 38 is out of order, by way of ensuring that the flow force F.sub.f is greater than the spring force F.sub.s. In the event that the electromagnetic unit 38 is arranged to act with the magnetic force F.sub.m in a direction opposed to the spring force F.sub.s, it is ensured that the flow force F.sub.f is greater than the spring force F.sub.s, suitably by way of increasing the feeding pressure P, with which fuel is being fed. In the event that the electromagnetic unit 38 is arranged to act with the magnetic force F.sub.m in the same direction as the spring force F.sub.s, it is ensured that the flow force F.sub.f is greater than the spring force F.sub.s, by way of providing a spring element 34 with a spring force F.sub.s, which is lower than the flow force F.sub.f.

[0057] The components and features specified above may, within the framework of the invention, be combined between different embodiments specified.