PUMP

Abstract

A pump comprising a check valve, which check valve comprises: an axially extending valve bore defined within a pump body of the pump and having an inner surface, a seat member defining an axially extending valve channel and having a mounting portion being press-fitted into the valve bore so that it engages the inner surface and a seat portion disposed proximal with respect to the mounting portion, the seat portion defining a seat surface around a proximal opening of the valve channel, wherein a pilot radius, which is a maximum radius of the seat portion, is at least 95% but less than 100% of valve-bore radius of the valve bore so that the seat portion is out of contact with the inner surface, and a valve member movable with respect to the seat member and engaging the seat surface in a closed position.

Claims

1. A pump comprising a check valve extending along a valve axis from a proximal side to a distal side, the check valve comprising: a. an axially extending valve bore defined within a pump body of the pump and having an inner surface, b. a seat member defining an axially extending valve channel and having a mounting portion being press-fitted into the valve bore so that it engages the inner surface, and a seat portion disposed proximal with respect to the mounting portion, the seat portion defining a seat surface around a proximal opening of the valve channel, wherein a pilot radius, which is a maximum radius of the seat portion, is at least 95% but less than 100% of valve-bore radius of the valve bore so that the seat portion is out of contact with the inner surface, and c. a valve member movable with respect to the seat member and engaging the seat surface in a closed position to close the valve channel, wherein a groove portion is axially interposed between the seat portion and the mounting portion, which groove portion defines a groove extending radially inwards between the seat portion and the mounting portion so that the groove portion is at least partially radially spaced from the inner surface by the groove.

2. The pump according to claim 1, wherein the check valve is a relief valve, and the pump is a fuel pump with a pumping chamber connected to a high-pressure outlet via an outlet valve, wherein the distal side is in fluid communication with the high-pressure outlet and the proximal side is in fluid communication with a location upstream of the outlet valve via a relief passage.

3. The pump according to claim 1, being adapted to generate a pressure of at least 200 bar on the distal side of the check valve.

4. The pump according to claim 1, wherein the groove extends circumferentially around the valve axis.

5. The pump according to claim 1, wherein an axial groove length of the groove is between 40% and 100% of an axial seat-portion length of the seat portion.

6. The fuel pump according to claim 1, wherein a minimum groove-portion radius of the groove portion is between 40% and 70% of the pilot radius.

7. The pump according to claim 1, wherein the groove is delimited by sidewalls facing each other along the valve axis, each sidewall being disposed at an angle of at least 75 relative to the valve axis.

8. The pump according to claim 1, wherein the seat portion comprises a pilot portion defining the pilot radius, and a cone portion that is disposed proximal to the pilot portion and that conically tapers towards the proximal side.

9. The pump according to claim 8, wherein a cone angle of the cone portion is between 35 and 50.

10. The pump according to claim 1, wherein an axial seat-member length of the seat member is less than 200% of the valve-bore radius.

11. The pump according to claim 1, wherein the mounting portion has a press-fit portion engaging an inner surface of the valve bore, and a tapered portion disposed proximal to the press-fit portion and adjacent the groove portion, the tapered portion having a smaller radius than the press-fit portion.

12. The fuel pump according to claim 1, wherein the seat-portion length is between 10% and 30% of the seat-member length.

13. The pump according to claim 1, wherein a channel radius of the valve channel is between 15% and 35% of the valve-bore radius.

14. The pump according to claim 1, wherein the valve-member channel has a proximal first channel section with a first channel radius which is reduced with respect to a second channel radius of a distal second channel section, which first channel section extends from an axial position of the seat portion to an axial position of the mounting portion.

15. A check valve for a pump, the check valve extending along a valve axis from a proximal side to a distal side and comprising in assembled state: a. an axially extending valve bore defined within a pump body of the pump and having an inner surface, b. a seat member defining an axially extending valve channel and having a mounting portion being press-fitted into the valve bore so that it engages the inner surface, and a seat portion disposed proximal with respect to the mounting portion, the seat portion defining a seat surface around a proximal opening of the valve channel, wherein a pilot radius, which is a maximum radius of the seat portion, is at least 95% but less than 100% of valve-bore radius of the valve bore so that the seat portion is out of contact with the inner surface, and c. a valve member movable with respect to the seat member and engaging the seat surface in a closed position to close the valve channel, wherein a groove portion is axially interposed between the seat portion and the mounting portion, which groove portion defines a groove extending radially inwards between the seat portion and the mounting portion so that the groove portion is at least partially radially spaced from the inner surface by the groove.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

[0032] FIG. 1: is a sectional view of an inventive fuel pump;

[0033] FIG. 2: is a sectional view of a detail of the fuel pump of FIG. 1 with an inventive relief valve;

[0034] FIG. 3: is a side view of a first embodiment of a member for the relief valve of FIG. 2;

[0035] FIG. 4: is a perspective view of the seat member of FIG. 3;

[0036] FIG. 5: is a sectional side view of the seat member of FIG. 3; and

[0037] FIG. 6: is a sectional side view of a second embodiment of a seat member.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0038] FIG. 1 shows a fuel pump 1 according to the present invention. The general structure and operating principle of the fuel pump 1 are generally known and thus will only be briefly described here. The fuel pump 1 is typically part of a fuel system (not shown) of an internal combustion engine, which generally includes a fuel tank holding a volume of fuel to be supplied to the engine for operation thereof. A low-pressure fuel pump draws fuel from fuel tank and elevates the pressure of the fuel (e.g. up to 5 bar) for delivery to the (high-pressure) fuel pump 1 which in turn further elevates the pressure of the fuel (e.g. to between 10 bar an 50 bar) for delivery to the fuel injectors, which then directly inject the fuel into the combustion chambers of the cylinders of the engine.

[0039] The fuel pump 1 comprises a pump body 2 with various parts, most of which are made of metal, e.g., stainless steel. The pump body 2 defines a pumping chamber 3 with a pumping plunger 4, which is adapted to reciprocate within the pumping chamber 3 and may be mechanically linked to a rotating camshaft (not shown) of the engine. The pumping chamber 3 is connected to an inlet passage 5 with an inlet valve 6. The inlet passage 5 is connected to a low- pressure inlet (not visible) of the fuel pump 1, via which the fuel pump 1 can be connected to the abovementioned low-pressure pump. The fuel enters the pump through the low-pressure inlet and is guided to the inlet passage via a damping volume 8, which is arranged in a damper cup mounted to the pump body 2.

[0040] The pump body 2 also defines an outlet passage 30 with an outlet valve (not shown), which outlet passage 30 connects the pumping chamber 3 to a high-pressure outlet 31 of the fuel pump 1. Furthermore, the pump body 2 defines a relief passage 25 with a relief valve 10. The outlet valve is a check valve that enables fuel flow from the pumping chamber 3 to the outlet 31 if the pressure in the pumping chamber 3 exceeds the pressure in the outlet passage 30. The relief valve 10 also is a check valve that enables flow from the outlet passage 30 through the relief passage 25 back to the pumping chamber 3 in case the pressure in the outlet passage 30 exceeds the pressure in the pumping chamber 3 and the difference is greater than a defined opening pressure.

[0041] During operation, the reciprocating movement of the pumping plunger 4 causes fuel to be drawn from the inlet passage 5 into the pumping chamber 3 during an intake stroke. During a following pumping or compression stroke, the fuel in the pumping chamber 3 is pressurized and expelled through the outlet valve and the outlet passage 30. The fuel can then be supplied via the outlet 31 to a fuel rail that is connected to the above-mentioned injectors. During the compression stroke, the inlet valve 6 prevents backflow through the inlet passage 5. If at any time the pressure difference between the outlet passage 30 and the pumping chamber 3 exceeds the predefined opening pressure, the relief valve 10 opens to release fuel from the outlet passage 30 through the relief passage 25 into the pumping chamber 3, thereby preventing possible damage to any components downstream of the fuel pump 1.

[0042] Details of the relief valve 10 will now be discussed with reference to FIGS. 2 to 5. The relief valve 10 comprises a valve bore 11, which is part of the relief passage 25 or directly connected thereto. The valve bore 11 is aligned along a valve axis A, which defines an axial direction, and has a circular cross-section with a valve-bore radius r.sub.b of e.g. 2.5 mm in this embodiment. The main elements of the valve mechanism are a seat member 15 and a valve member 20. The seat member 15 is stationary and is connected to the pump body 2 by press-fitting it into the valve bore 11. The valve member 20, on the other hand, is axially movable and is biased against the seat member 15 by a spring member 21. The valve member here takes the form of a ball. Specifically, in a closed position, which is shown in FIGS. 1 and 2, the valve member 20 engages a seat surface 15.1 of the seat member 15. As can also be seen in FIGS. 3 to 5, the seat surface 15.1 has an overall annular shape and is disposed around a proximal opening 18 of a valve channel 17 that traverses the seat member 15. The valve channel 18 is symmetrical about the valve axis A and has a circular cross-section with a channel radius r.sub.c. In this exemplary embodiment, the channel radius r.sub.c is 0.58 mm, corresponding to about 23% of the valve-bore radius r.sub.b. In other embodiments, this ratio could be different, e.g., between 15% and 35%.

[0043] Along the axial direction A, three different portions of the seat member 15 can be distinguished. The seat surface 15.1 is disposed on a seat portion 15.2 which is out of contact with an inner surface 12 of the valve bore 11, while a mounting portion 15.6 engages the inner surface 12 by a press fit. A groove portion 15.5 is interposed between the seat portion 15.2 and the mounting portion 15.5. It defines a single groove 16 that extends radially inwards. The groove portion 15.5 is radially spaced from the inner surface by the groove.

[0044] The shape and dimensions of the seat member 15 and its portions 15.2, 15.5, 15.6 will now be described in more detail. It is understood that these dimensions are exemplary and can be modified depending on many factors, like the overall size and performance of the fuel pump 1. An axial seat-member length I.sub.sm of the seat member 15 is 3.6 mm, which corresponds to less than 200% of the valve-bore radius r.sub.b, in this case 144%. The seat portion 15.2 has an overall axial seat-portion length I.sub.sp of 0.7 mm, which is about 19% of the seat-member length I.sub.sm, but could otherwise be, e.g., between 10% and 30%. It comprises a pilot portion 15.4 disposed adjacent the groove 16 and defining a pilot radius r.sub.p, of 2.46 mm, and a cone portion 15.3 that is disposed proximal to the pilot portion 15.4 and that conically tapers towards the proximal side P. Specifically, the cone portion 15.3 has a frusto-conical shape with a cone angle of about 42, which could otherwise be, e.g., between 35 and 50. Since the pilot radius r.sub.p is only minimally smaller than the valve-bore radius r.sub.b, corresponding to 98% thereof, the pilot portion 15.4 facilitates piloting or guiding of the seat member 15 during its insertion into the valve bore 11.

[0045] The mounting portion 15.6 has a press-fit portion 15.7 and a tapered portion 15.8. In its undeformed state, i.e. before insertion into the valve bore, a mounting-portion radius r.sub.b of the press-fit portion 15.7 is 2.52 mm, i.e., somewhat larger than the valve-bore radius r.sub.b. Accordingly, after insertion into the valve bore 11, the press-fit portion 15.7 engages the inner surface 12 of the valve bore 11. The tapered portion 15.8, which is disposed proximal to the press-fit portion 15.7 and adjacent the groove portion 15.5, has a smaller radius than the press-fit portion 15.7. Accordingly, it remains out of contact with the inner surface 12 but may complement the guiding function by the pilot portion 15.4 during the insertion and press-fitting process.

[0046] In this embodiment, the groove 16 extends circumferentially around the valve axis A and has an axial groove length I.sub.g of 0.5 mm, corresponding to 71% of the seat-portion length I.sub.sp. However, this ratio could be different, e.g. between 40% and 100%. A minimum groove-portion radius r.sub.g of the groove portion 15.5 is 1.2 mm, corresponding to 48% of the pilot radius r.sub.p. Alternatively, this ratio could be, e.g., between 40% and 70%. A radial depth of the groove 16 is about 1.27 mm. The groove 16 is delimited by sidewalls 15.9 facing each other along the valve axis A, each sidewall 15.9 being perpendicular to the valve axis A.

[0047] By the presence of the groove 16, the seat portion 15.6 is mechanically decoupled from the deformation of the mounting portion 15.2 during the press-fitting procedure. Accordingly, a precise shape of the seat surface 15.1 is maintained, as is necessary to maintain a sealing engagement of the valve member 20 with the seat surface 15.1. Considering the channel radius r.sub.c and the minimum groove-portion radius r.sub.g, a remaining material thickness radially inside the groove 16 is about 0.61 mm, which is sufficient to maintain an overall structural stability of the seat member 15.

[0048] FIG. 6 shows a second embodiment of a seat member 15 for the relief valve 10. Apart from minor differences, which will not be discussed here, this embodiment is mostly identical to the first embodiment. However, the valve channel 17 does not have a constant radius. Rather, it has a proximal first channel section 17.1 with a first channel radius r.sub.c1 which is reduced with respect to a second channel radius r.sub.c2 of a distal second channel section 17.2. In this embodiment, first channel radius r.sub.c1 is 0.58 mm and the second channel radius r.sub.c2 is 1.00 mm. The first channel section 17.1 extends from an axial position of the seat portion 15.2, along the groove portion 15.5 and to an axial position of the mounting portion 15.6. Accordingly, the seat member 15 is reinforced near the groove 16, which may help to prevent deformation of the seat portion 15.2. Possibly, the depth of the groove 16 could even be increased, i.e., the groove-portion radius r.sub.g could be decreased without destabilizing the seat member 15 in an unwanted way. On the other hand, the greater second channel radius r.sub.c2reduces the flow resistance inside the valve channel 17 and reduces the overall volume of the seat member 15.

[0049] LEGEND OF REFERENCE NUMBERS [0050] 1 fuel pump [0051] 2 pump body [0052] 3 pumping chamber [0053] 4 pumping plunger [0054] 5 inlet passage [0055] 6 inlet valve [0056] 8 damping volume [0057] 10 relief valve [0058] 11 valve bore [0059] 12 inner surface [0060] 15 seat member [0061] 15.1 seat surface [0062] 15.2 seat portion [0063] 15.3 cone portion [0064] 15.4 pilot portion [0065] 15.5 groove portion [0066] 15.6 mounting portion [0067] 15.7 press-fit portion [0068] 15.8 tapered portion [0069] 15.9 sidewall [0070] 16 groove [0071] 17 valve channel [0072] 17.1 first channel portion [0073] 17.2 second channel portion [0074] 18 proximal opening [0075] 20 valve member [0076] 21 spring member [0077] 25 relief passage [0078] 30 outlet passage [0079] 31 outlet [0080] A valve axis [0081] D distal side [0082] I.sub.g groove length [0083] I.sub.sm seat-member length

[0084] I.sub.sp seat-portion length [0085] P proximal side [0086] r.sub.b valve-bore radius [0087] r.sub.c channel radius [0088] r.sub.c1 first channel radius [0089] r.sub.c2 second channel radius [0090] r.sub.g groove-portion radius [0091] r.sub.m mounting-portion radius [0092] r.sub.p pilot radius [0093] cone angle