Inlet pressure attenuator for single plunger fuel pump

Abstract

An attenuator diaphragm assembly for a fuel injection pump, comprising a diaphragm formed of two half-shells, having mated flat rims that are welded together along their peripheral edges and a compression joint formed at inward, unwelded portions of the rims, and a carrier that captures the joined and welded rims.

Description

RELATED APPLICATION

This application claims priority under 35 U.S.C. 119(e) from U.S. Provisional Application No. 60/879,738 filed Jan. 10, 2007 for “Inlet Pressure Attenuator for Single Plunger Fuel Pump”, the entire disclosure of which is hereby incorporated by reference.

BACKGROUND

The present disclosure relates generally to fuel pumps, and is more particularly concerned with a new and improved single plunger fuel pump.

Practitioners in the field of fuel pump design and development for vehicles readily understand the main components of a typical single plunger pump and their function and operation. The engine drive shaft carries a lobed cam that reciprocates the pumping plunger within a pumping sleeve secured to the housing, between charging (intake) and discharging (output) phases. The pumping end of the plunger is situated in the pumping chamber, which fills with fuel at a feed pressure of up to about 4 bar during the charging phase and, preferably subject to initial spill control, pressurizes the fuel in the pumping chamber up to about 200 bar for delivery to, e.g., a common rail.

The feed fuel is fed directly to the pumping chamber through an inlet valve, which receives flow from an inlet damping chamber. The fuel passes one or more attenuator diaphragms in the damping chamber along the flow path to the pumping chamber. The diaphragms encapsulate fixed masses of gas, such as helium at two bars. The flexibility of the diaphragms can adjust the volumes of the gas in response to pressure variations in the feed line and thereby maintain a substantially constant feed pressure to the inlet valve.

A problem encountered with known welded diaphragms, is that the substantially continual accommodation of normal pressure fluctuations and the occasional attenuation of spurious pressure transients, stresses the welds and causes leakage, with resulting deterioration of performance or even failure.

SUMMARY

It is an object of the present invention to provide an improved technique for stress relieving the junction of juxtaposed thin rims of a pressurized bellows type diaphragm attenuator that is integrated with the inlet feed train of a single plunger fuel pump.

One embodiment is directed to an attenuator diaphragm assembly for a fuel injection pump. The diaphragm assembly includes a diaphragm formed of two half-shells, having mated flat rims that are welded together along their peripheral edges. A compression joint is formed at inward, unwelded portions of the rims and a carrier or frame captures the joined and welded rims.

Another embodiment is directed to a fuel pump having a single plunger that reciprocates into and out of a pumping chamber situated within a pump housing. The pump features a pressurized inlet line through the housing to an inlet valve that feeds the pumping chamber. A damping chamber is integrated with the housing, in which fuel passes around at least one gas filled and sealed attenuator diaphragm along a flow path to the inlet valve. Each diaphragm is formed of two half-shells, having central convex bulges and mated flat rims which are supported in a diaphragm carrier within the damping chamber. The rims are welded together along their outer edges and a compression joint is formed at inward, unwelded portions of the rims to reduce stresses transmitted to the welded edges.

Preferably, each half-shell is substantially circular and each rim circumscribes a respective convex bulge. The rims are bent over at a circumferential bend line that forms the compression joint. The bent over portion of the rims forms a circumferential ridge that is substantially coaxial with the axis of the diaphragm. The diaphragm carrier has a radial slot including upper and lower walls between which the ridge is captured. Each rim has a flat portion radially inward of the bend line. The upper wall extends closely over said flat portions of the rims and the welded outer edges are supported by the lower wall.

The compression joint isolates the weld from excessive stresses associated with the expansion and contraction of the diaphragm, thereby avoiding leakage of the gas and deterioration or failure of pressure attenuating capability of the diaphragm.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawing, like elements are numbered alike in the several Figures:

FIG. 1 is a perspective view of a one plunger fuel pump having a substantially cubic housing or body, with the fuel inlet connector projecting on the right, the single plunger actuation assembly projecting from the left, and the inlet control valve projecting from the top;

FIG. 2 is staggered section view of the pump of FIG. 1, through the inlet connection with associated attenuator, and the inlet control valve;

FIGS. 3A and 3B are enlarged plan and section views of the split diaphragm carrier for the two pressurized diaphragms shown in FIG. 2, with the section line indicated by A-A;

FIG. 4 is an enlarged view of the attenuator diaphragm, showing the preferred bending at the rims for stress relief;

FIG. 5 is an enlarged view of an alternative technique for reducing the stresses at the weld of the diaphragm rims;

DETAILED DESCRIPTION

FIG. 1 shows a one plunger fuel pump 10 having a substantially cubic housing or body 12, with the fuel inlet connector 14 projecting on the right, the single plunger actuation assembly 16 projecting from the left, and the inlet control valve 18 projecting from the top. In FIG. 1, plunger 20 can be seen projecting slightly from the single plunger actuation assembly 16.

With further reference to FIG. 2, the feed fuel is fed directly to the pumping chamber 22 through the solenoid controlled inlet valve 18, which receives flow through a first internal passage 24 of the housing, from the inlet damping chamber 26. The damping chamber receives feed fuel through an inlet fitting 28, and the fuel passes around the attenuator diaphragms 30 on its way to the first internal passage 24. The diaphragms encapsulate fixed masses of gas, such as helium at two bars, but the flexibility of the diaphragms can adjust the volumes of the gas in response to pressure variations in the feed line and thereby maintain a substantially constant feed pressure to the inlet valve 18.

The improvement with respect to the damping chamber 26 will now be described in greater detail with reference to FIGS. 1, 2, 3 and 4. The substantially cylindrical chamber is in part defined by a cup cover 32 welded to the inlet fitting 28 and to the wall of a shallow bore in the housing 12. A diaphragm carrier 36 is annularly disposed against the inside surface 36 of the cup cover 32. The carrier has upper and lower annular grooves or slots 38, for receiving the rims 40 of respective diaphragms 30. Each slot includes upper and lower walls 42a and 42b that closely confront the inner radial portion of each respective diaphragm rim. Each diaphragm is formed of two substantially circular half-shells 44, having central convex bulges 45 and mated flat rims 40. In an environment at about two bar pressure, a helium balloon is placed between the half-shells 44, the shells are urged together, and the rims are TIG welded at the outer circumferences, as indicated by reference numeral 46. This forms a central, substantially cylindrical helium volume and a flat rim having a radial dimension outside of the helium cylinder. While this embodiment features upper and lower slots, it should be clear to those skilled in the art that the object of the disclosure may be practiced with any number of slots.

The improvement comprises that an annular compression joint is formed on a radially inward, unwelded portion of the rim to reduce stresses transmitted to the welded circumference.

In one embodiment, after welding along the outer edges of the half-shells 44, the joined rims 40 are bent over to form a circumferential ridge 48, preferably enough to nearly align the bent over circumferential ridge with the axis of the cylinder, shown by reference numeral 50. The bend line L forms the compression joint 41. In general, the circumferential bend line is located within the radially inward 75 percent of the radial dimension of the rim. The joined rims have a flat portion 52 radially inward of the bend line. Generally, the circumferential ridge 48 is captured between the upper and lower walls 42a and 42b of a carrier annular groove 38 with the upper wall 42a extending closely over the rim flat portion 52 while the lower wall 42b supports the welded outer edges 46 of the rim.

This technique of forming the diaphragm avoids stress at the weld 46 arising from the use environment, where a constant internal pressure of about 2 bars acts in the direction of separating the rims, and the diaphragm 30 undergoes continual contraction and expansion, because the weld 46 is axially offset from the separation plane between the rims.

Another embodiment is shown in FIG. 5, where the welded rims are not bent over, but a different type of diaphragm carrier 34 has a radial slot 38 such that the walls 42 of the slot along the radially inner portion of the slot closely confront, or are preferably clamped against, the inner radial portion of the rim 40. This clamping is an alternative to the bend line of the embodiment of FIG. 4, whereby the weld on the outer edges of the rim is isolated from the forces associated with the pressure in and flexing of the diaphragm 30, by the radially inner clamping. Such clamping would typically leave a space or gap 54 along the radially outer portion of the slot surrounding the weld 46.

While preferred embodiments have been set forth for purposes of illustration, the foregoing description should not be deemed a limitation of the disclosure herein, or of the scope of disclosure or claims that may be presented in a regular application based on the present application. Accordingly, various modifications, adaptations and alternatives may occur to one skilled in the art without departing from the spirit and scope of the present disclosure.

Claims

1. In a fuel pump having single plunger that reciprocates into and out of a pumping chamber situated within a pump housing; a pressurized inlet line through the housing to an inlet valve that feeds the pumping chamber; a damping chamber integrated with the housing, in which fuel passes around at least one gas filled and sealed attenuator diaphragm along a flow path to the inlet valve; each diaphragm being formed of two half-shells, having central convex bulges and mated flat rims which are supported in a diaphragm carrier within the damping chamber; wherein the improvement comprises that the rims are welded together along their outer edges and a compression joint is formed at inward, unwelded portions of the rims to reduce stresses transmitted to the welded edges.

2. The fuel pump of claim 1, wherein the rims are bent over at a bend line that forms said compression joint.

3. The fuel pump of claim 1, wherein each half-shell is substantially circular and each rim circumscribes a respective convex bulge.

4. The fuel pump of claim 3, wherein the rims are bent over at a circumferential bend line that forms said compression joint.

5. The fuel pump of claim 4, wherein the bent over portion of the rims forms a circumferential ridge that is substantially coaxial with the axis of the diaphragm.

6. The fuel pump of claim 4, wherein the circumferential bend line is located within the radially inward 75 percent of the radial dimension of the rim.

7. The fuel pump of claim 3, wherein the diaphragm carrier has a radial slot including upper and lower walls that closely confront the inner radial portion of the rim but not the circumferential weld.

8. The fuel pump of claim 7, wherein the radial slot circumferentially surrounds said weld.

9. The fuel pump of claim 8, wherein the slot has a radially inner portion where the walls are clamped against the rim and a radially outer portion forming a space surrounding said weld.

10. The fuel pump of claim 7, wherein the radial slot is one of a plurality of said slots circumferentially spaced apart around the rim.

11. The fuel pump of claim 10, wherein each slot has a radially inner portion where the walls are clamped against the rim and a radially outer portion forming a space surrounding said weld.

12. The fuel pump of claim 1, wherein each half-shell is substantially circular; each rim circumscribes a respective convex bulge; the rims are bent over at a circumferential bend line that forms said compression joint; the bent over portion of the rims forms a circumferential ridge that is substantially coaxial with the axis of the diaphragm; the diaphragm carrier has a radial slot including upper and lower walls; and the ridge is captured between the upper and lower walls.

13. The fuel pump of claim 12, wherein each rim has a flat portion radially inward of the bend line; the upper wall extends closely over said flat portions of the rims; and the welded outer edges are supported by the lower wall.

14. An attenuator diaphragm assembly for a fuel injection pump, comprising: a diaphragm formed of two half-shells, having mated flat rims that are welded together along their peripheral edges and a compression joint formed at inward, unwelded portions of the rims; and a carrier that captures the joined and welded rims.

15. The attenuator diaphragm of claim 14, wherein each half-shell is substantially circular; each rim circumscribes a respective convex bulge; the rims are bent over at a circumferential bend line that forms said compression joint; the bent over portion of the rims forms a circumferential ridge that is substantially coaxial with the axis of the diaphragm; the diaphragm carrier has a radial slot including upper and lower walls; and the ridge is captured between the upper and lower walls.

16. The attenuator diaphragm of claim 15, wherein each rim has a flat portion radially inward of the bend line; the upper wall extends closely over said flat portions of the rims; and the welded outer edges are supported by the lower wall.