GB2579220A

GB2579220A - A pump assembly

Info

Publication number: GB2579220A
Application number: GB1819174.2A
Authority: GB
Inventors: T D Mchattie James
Original assignee: Delphi Technologies IP Ltd
Current assignee: Borgwarner US Technologies LLC
Priority date: 2018-11-26
Filing date: 2018-11-26
Publication date: 2020-06-17
Anticipated expiration: 2038-11-26
Also published as: GB2579220B; GB201819174D0

Abstract

A pump head assembly 30 for a high pressure pump of a compression ignition internal combustion engine comprises a pump chamber 36 to pressurise fuel by means of a piston or plunger pumping element (20, figure 1) and inlet 40 and outlet 42 valve members. The valve members are aligned along a common longitudinal axis and movable within a common bore 44 provided in the pump head. One valve member is movable within the other, to open and close respective seats 64, 48. Preferably the inlet valve member is provided with a bore 58 wherein the outlet valve member is movable within. The inlet valve member has a cross drilling hole(s) to allow fuel into the bore and force the member towards its respective seat which may also be in association with a spring 62. The outlet valve member may have a spring 50 that urges the member towards its respective seat. The force of the inlet valve spring is preferably less than the outlet valve spring. The valve seats may be frusto-conical. Preferably the inlet valve forms parts of a digital inlet metering valve.

Description

A PUMP ASSEMBLY

TECHNICAL FIELD

The present disclosure relates to pump assembly for a fuel injection system. In particular, the invention relates to a pump assembly for a fuel injection system of a compression ignition internal combustion (diesel) engine, or for a diesel engine in a hybrid vehicle also having an electric battery to power the vehicle in addition to the diesel engine.

BACKGROUND

Referring to Figure 1, in a conventional pump assembly 10 for a compression ignition internal combustion engine, a pump head 12 includes an inlet valve 14 and an outlet valve 16 to regulate the flow into, and the delivery from, a high pressure pump chamber 18. A pumping plunger 20 extends along a plunger axis and is received within a plunger bore 22 provided in the pump head 12 and is driven, by means of a cam drive arrangement (not shown), to reciprocate within the plunger bore 22 through a pumping cycle. The plunger bore 22 defines, at one end, the high pressure pump chamber 18. The inlet valve 14 is arranged to control the supply of fuel into the pump chamber 18 during a filling stroke and the outlet valve 16 is arranged to control the delivery of high pressure fuel to the downstream elements of the fuel injection system (e.g. a common rail).

It is common to arrange the inlet valve 14 within the pump head so that it moves along the same axis as the outlet valve 16, as shown in Figure 1. In other arrangements the inlet valve extends along and/or moves parallel with the axis of the plunger 20, whereas the outlet valve 16 extends along an axis which is perpendicular to the axis of movement of the inlet valve. In both cases the pump head 12 occupies a relatively large volume that, for some applications, is incompatible with the available space within the engine. This is especially the case where the inlet valve 14 is aligned with the plunger axis, but the same problem also arises with the layout shown in Figure 1.

Space is a particular problem in a hybrid vehicle when a battery/electric motor setup is also required and takes considerable volume. Also, there is an increasing demand to improve rail pressure stability which is most easily addressed using multi-head pumps which further increases the demands on space.

It is an object of the invention to provide a pump assembly which address at least these concerns.

SUMMARY OF THE INVENTION

According to an aspect of the invention there is provided a pump assembly for a high pressure pump of a compression ignition internal combustion engine, the pump head assembly comprising a pump chamber in which fuel is pressurised by a pumping element, an inlet valve member for controlling a flow of relatively low pressure fuel into the pump chamber and an outlet valve member for controlling a flow of pressurised fuel out of the pump chamber, the inlet valve member being aligned along a common longitudinal axis with the outlet valve member, and both the inlet valve member and the outlet valve member being movable within a common bore provided in the pump head, with one valve member being movable within the other valve member, to open and close respective inlet and outlet valve seats.

Typically the pump assembly takes the form of a pump head assembly which attaches to a main pump body or housing.

The pump assembly is particularly compact because the inlet and outlet valve members are configured to move one within the other. One way to improve rail pressure stability is to fit more pumping heads to the pump, but the cost of the valve arrangements in the pump head, and the number of parts, can make the cost of such multi-pump-head pumps prohibitive. By providing a more compact and cheaper valve arrangement in the pump head, as in the present invention, the option to provide multiple pump heads in a pump is achievable with acceptable cost.

In one particular embodiment, for example, the outer valve member is movable within a bore provided in the inner valve member. For example, the inlet valve member may be provided with an inlet valve bore and the outlet valve member may be movable within the inlet valve bore.

The inlet valve member may be provided with a cross drilling which communicates with the inlet valve bore to allow fuel to flow into the inlet valve bore and urge the inlet valve member towards the inlet valve seat.

The pump assembly may further comprise an inlet valve spring which serves to urge the inlet valve member against the inlet valve seat, and wherein the outlet valve member includes an elongate body which extends, at least partially, through the inlet valve spring.

The pump may further comprise an outlet valve spring which serves to urge the outlet valve member against the outlet valve seat.

In an embodiment, the inlet valve spring has a spring force which is less than a spring force of the outlet valve spring so that a lower force is required to overcome the spring force of the inlet valve spring to move it away from the inner valve seat.

The plunger typically has a plunger axis and the inlet valve member and the outlet valve member are movable along a common axis. At least one of the outlet valve member and the inlet valve member intersects the plunger axis at least in a position in which one of valve members is seated against its respective seat.

The outlet valve member intersects the plunger axis both when it is seated against the outlet valve seat and when it is moved away from the outlet valve seat.

In an example, the inlet valve seat and the outlet valve seat may be frustoconical valve seats which are defined within the common bore concentrically with one another.

The inlet valve member may form a part of a digital inlet metering valve It will be appreciated that the preferred and/or optional features of the invention may be incorporated alone or in appropriate combination in the various embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The background art has already been described with reference to Figure 1 which shows a sectional view of a pump head assembly known in the prior art.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 2 is a sectional view of a pump head assembly of an embodiment of the invention, with an inlet valve of the pump head assembly in a closed position and an outlet valve of the pump head assembly in a closed position; Figure 3 is a sectional view of the pump head assembly in Figure 2, with the inlet valve in an open position and the outlet valve in a closed position; Figure 4 is sectional view of the pump head assembly in Figures 2 and 3 with the inlet valve in a closed position and the outlet valve in an open position; Figure 5 is a perspective view of a pump head assembly of an embodiment of the invention when comprising a digital inlet metering valve, and with a coil of the digital inlet metering valve partly removed; and Figure 6 is a perspective view of the pump head assembly in Figure 5 with the coil shown in full.

DETAILED DESCRIPTION

Referring to Figure 2, a pump head assembly 30 of an embodiment of the invention includes a pump head (or pump head housing) 32 which is mounted upon a main pump housing (not shown). The pump head 32 takes the form of a block with a nose region 32a projecting to the left hand side of the pump head 32 (in the illustration shown). The pump head is provided with a longitudinal plunger bore 34, extending along an axis A -A, which extends vertically in the orientation shown. At the upper end of the plunger bore 34 (in the orientation shown), a pump chamber 36 is defined within which fuel is pressurised during a pumping cycle. The plunger bore 34 receives a pumping plunger (not shown) which extends along the axis A-A and which is driven to move within the plunger bore 34 by means of a drive arrangement (also not shown) in a conventional manner. As the plunger is driven within the plunger bore 34, it moves through the plumping cycle which includes a return stroke, in which relatively low pressure fuel is drawn into the pump chamber 36, and a pumping stroke in which fuel within the pump chamber 36 is pressurised to a high level, typically in excess of 2500-3000 bar.

The flow of fuel into, and out of, the pump chamber 36 is controlled by means of a valve assembly. The valve assembly includes an inlet valve member 40 and an outlet valve member 42, both of which are arranged within a common bore 44 provided in the pump head 32, with the inlet valve member 40 being arranged within, and slidable within, the outlet valve member 42. The common bore 44 extends along an axis B-B which extends perpendicularly to the axis A -A of the plunger bore 34. By arranging the common bore 44 along the axis B-B, the overall height of the pump head 32 is relatively low (compared with many prior art arrangements).

The common bore 44 includes an enlarged diameter section 44a which projects into the nose region 32a of the pump head 32 and a relatively smaller diameter section 44b which connects with the enlarged diameter section 44a at a frusto-conical intersection 46. The frusto-conical intersection 46 defines a seating for an outlet valve member (referred to as the outlet valve seat 48).

The outlet valve member 42 is an elongate member including an elongate outlet valve body 42a and an outlet valve head 42b. The outlet valve body 42a extends along the axis B-B and across the top of the plunger bore 34 so that it intersects the longitudinal axis A-A of the plunger bore 34. The outlet valve head 42b defines an enlarged end surface 42c of the outlet valve member 42 and also a frusto-conical surface which tapers to the outlet valve body 42b. The frusto-conical surface of the outlet valve head 42a is engageable, in use, with the outlet valve seat 48.

The enlarged end surface 42c of the outlet valve head 42b defines an abutment surface for one end of an outlet valve spring 50. A spring seating member 52 is received in the enlarged diameter section 44a of the common bore 44 and is fixed therein. The seating member 52 is of annular form so that a central flow passage is defined through the seating member 52. Downstream of the seating member 52, the enlarged diameter section 44a defines an outlet flow passage 54 from the pump assembly which, in use, delivers pressurised fuel to the downstream parts of the fuel injection system. One face of the seating member defines an abutment surface 56 for the end of the outlet valve spring 50 remote from the outlet valve member 42.

At the opposite end from the outlet valve head 42b, the outlet valve body 42a extends into a blind bore (referred to as the inlet valve bore 58) provided in the inlet valve member 40. The inlet valve member 40 is received within the reduced diameter section 44b of the common bore 44. The inlet valve member 40 extends longitudinally along the axis B-B, coaxially with the outlet valve member 42. The outlet valve member 42 is slidably received within the inlet valve bore 58 so that the two valve members move relative to one another, one inside the other. In the embodiment shown the outlet valve member 40 moves inside the inlet valve member 42.

The inlet valve bore 58 communicates, at its blind end, with a cross drilling which extends tangentially to the axis B-B. The cross drilling 60 opens into the reduced diameter section 44b of the common bore 44.

The outlet valve body 42a is received, at least partially, within an inlet valve spring 62 which is engaged between the outlet valve head 42b and one end of the inlet valve spring 62. At the end of the inlet valve member 40 remote from the inlet valve spring 62, the inlet valve member 40 terminates in a tip region 40a which defines a seating surface of the inlet valve member 40. The seating surface is engageable with a frusto-conical seating surface (the inlet valve seat 64) defined by the common bore 44. The inlet valve seat 64 leads into an inlet passage 66 which communicates, in use, with a source of low pressure fuel (e.g. a transfer pump).

The inlet and outlet valve springs 62, 50 are selected so that the spring force of the inlet valve spring 62 is lower than the spring force of the outlet valve spring 50, as will be appreciated from the following description of the pump head assembly, in use.

Referring also to Figures 3 and 4, the plunger of the pump head assembly 30 is driven in a conventional manner so that it performs a pumping cycle, moving through a return (filling) stroke followed by a forward (pumping) stroke, with the strokes repeating in a cycle. Initially, as the plunger is retracted from the plunger bore 34 to perform the return stroke, the pressure in the pump chamber 36 reduces so that the inlet valve member 40 is urged to open, against the force of the inlet valve spring 62, due to the pressure of incoming fuel in the inlet passage acting on the inlet valve member 40. The inlet valve member 40 therefore moves away from the inlet valve seat 64, against the spring force (which is compressed), and fuel is able to flow into the pump chamber 36.

Throughout this phase of operation the inlet valve spring 62 is compressed as the inlet valve member 40 is caused to move, within the reduced diameter section 44b of the bore, away from the inlet valve seat 64. The higher spring force of the outlet valve spring 50 ensures that the outlet valve member 42 remains seated against the outlet valve seat 48 as the pump chamber 36 receives incoming fuel through the inlet passage 66. This is the configuration shown in Figure 3 (i.e. the inlet valve member 40 is unseated and the outlet valve member 42 is seated).

Eventually, as the pressure of fuel introduced via the inlet passage 66 and the pressure of fuel in the pump chamber 36 equalise, the force of the inlet valve spring 62 causes the inlet valve member 40 to move to the right in the illustration shown and the inlet valve member 40 seats against the inlet valve seat 64 to terminate the flow into the pump chamber 36. This is the configuration shown in Figure 2. As the plunger reaches bottom-dead-centre (BDC) at the end of the return stroke, the plunger is momentarily stationary, the inlet valve member 40 is seated and so too is the outlet valve member 42.

Once the plunger has reached the end of its return stroke and it commences its pumping stroke, with both the inlet valve member 40 and the outlet valve member 42 seated against their respective seats 64, 48, the pressure of fuel within the pump chamber 36 starts to increase. As the pressure builds in the pump chamber 36 the inlet valve member 40 experiences an increased seating force due to (a) the pressure of fuel acting on its outlet-valve-receiving end of the inlet valve member 40 and (b) the pressure of fuel within the cross drilling 60 and the inlet valve bore 58. The exposed frusto-conical surface of the outlet valve head 42b within the common bore 44 also experiences an increased force due to high pressure fuel within the pump chamber 36. In addition, due to fuel within the cross drilling 60 in the inlet valve member 40, the end of the outlet valve member 42 that is received within the inlet valve member 40 also experiences the increased force due to high pressure fuel within the pump chamber 36.

Eventually, the increased force acting on the outlet valve head 42b, together with the increased force acting on the end remote from the outlet valve head 42b, is sufficient to overcome the force of the outlet valve spring 50 so that the outlet valve member 42 is caused to lift away from the outlet valve seat 48, compressing the outlet valve spring 50. Once the outlet valve member 42 is moved away from the outlet valve seat 48, pressurised fuel within the pump chamber 36 is able to flow past the outlet valve seat 48, through the outlet flow passage 54 defined within the enlarged diameter section 44a of the common bore 44, and on to the downstream parts of the engine. This is the configuration of the pump head assembly shown in Figure 4, with the inlet valve member 40 seated and the outlet valve member 42 unseated.

The combined assembly of the inner valve member 40 and the outlet valve member 42 intersects the axis A -A of the plunger bore 34 when the outlet valve member 42 is in the seated position, but also when the outlet valve member 42 is moved away from the outlet valve seat 48 to open the communication path between the pump chamber 36 and the outlet flow passage 54.

The plunger continues through the pumping stroke until it reaches the top of the stroke (top-dead-centre -TDC), at which point the pressure in the pump chamber 36 starts to reduce as the fuel is delivered through the outlet passage. As the plunger passes TDC it is momentarily stationary, the outlet valve member 42 is caused to close against the outlet valve seat 48 under the force of the outlet valve spring 50 and the pump head assembly again adopts the configuration shown in Figure 2.

It is one benefit of the invention that the common bore 44 within which both the inlet valve member 40 and the outlet valve member 42 can be machined using a single forming tool. Furthermore, because the inner valve seat 64 and the outer valve seat 48 are machined in the same common bore 44, the use of the single machining tool means that excellent concentricity of the valve seats can be achieved. A further benefit of the common bore 44 for the inlet and the outlet valve members 40, 42 is that both are aligned tangentially to the longitudinal (and long) axis of the pump head assembly so that the overall height of the pump head can be reduced compared to some existing designs where typically the inlet valve member is coaxial with the plunger axis. The invention also removes the need for a head cap on the pump head, as is required in some arrangements where the inlet valve member is coaxial with the plunger axis. A guided inlet valve stem component is also no longer required as in conventional arrangements. The cost and weight of the pump head assembly of the invention is therefore reduced compared to conventional arrangements and may allow for multiple pump heads to be used (e.g. to ensure smooth pumping and good rail pressure), but without prohibitive cost.

Referring to Figure 5 and 6, in some embodiments of the invention the inlet valve member may be controlled by a digital inlet metering valve 70. A coil 72 of the digital inlet metering valve 70 is arranged with its axis aligned with the axis of the inlet valve member 40 (and hence the outlet valve member 42). The pump assembly together with the digital inlet metering valve 70 is a more expensive assembly compared to a hydraulically controlled inlet metering valve of previous figures, but for some applications could provide a beneficial arrangement. For other applications where a low cost arrangement is desired, the hydraulically operable inlet valve shown in Figures 2 to 4 is preferable.

It will be appreciated that various modifications may be made to the aforementioned embodiments without departing from the scope of the invention as set out in the accompanying claims.

LIST OF REFERENCES

pump head assembly 32 pump head 32a nose region 34 plunger bore 36 pump chamber inlet valve member 42 outlet valve member 42a outlet valve body 42b outlet vale head 42c enlarged end surface 44 common bore 44a enlarged diameter section of common bore 44b reduced diameter section of common bore 46 frusto-conical intersection 48 outer valve seat outlet valve spring 52 seating member 54 outlet flow passage 56 abutment surface 58 inlet valve bore 60 cross drilling 62 inlet valve spring 64 inlet valve seat 66 inlet passage digital inlet metering valve 72 coil A-A plunger axis B-B axis of the common bore

Claims

CLAIMS: 1. A pump assembly (30) for a high pressure pump of a compression ignition internal combustion engine, the pump head assembly (30) 5 comprising; a pump chamber (36) in which fuel is pressurised by a pumping element, an inlet valve member (40; 70) for controlling a flow of relatively low pressure fuel into the pump chamber (36) and an outlet valve member (42) for controlling a flow of pressurised fuel out of the pump chamber (36), the inlet valve member (40) being aligned along a common longitudinal axis (A -A) with the outlet valve member (42), and both the inlet valve member (42) and the outlet valve member (42) being movable within a common bore (44) provided in the pump head (32), with one being movable within the other, to open and close respective inlet and outlet valve seats (64, 48).
2. The pump assembly (30) as claimed in claim 1, wherein the inlet valve member (40) is provided with an inlet valve bore (58) and wherein the outlet valve member (42) is movable within the inlet valve bore (58).
3. The pump assembly (30) as claimed in claim 2, wherein the inlet valve member (40) is provided with a cross drilling (60) which communicates with the inlet valve bore (58) to allow fuel to flow into the inlet valve bore (58) and urge the inlet valve member towards the inlet valve seat (62).
4. The pump assembly (30) as claimed in any of claims 1 to 3, further comprising an inlet valve spring (62) which serves to urge the inlet valve member (42) against the inlet valve seat (64), and wherein the outlet valve member (42) includes an elongate body (42a) which extends, at least partially, through the inlet valve spring (62).
5. The pump assembly (30) as claimed in claim 4, further comprising an outlet valve spring (50) which serves to urge the outlet valve member (42) against the outlet valve seat (48).
6. The pump assembly (30) as claimed in claim 5, wherein the inlet valve spring (62) has a spring force which is less than a spring force of the outlet valve spring (50) so that a lower force is required to overcome the spring force of the inlet valve spring (62) to move it away from the inner valve seat (64).
7. The pump assembly (30) as claimed in any of claims 1 to 6, wherein the plunger has a plunger axis (A-A) and wherein the inlet valve member (40) and the outlet valve member (42) are movable along a common axis (B-B), and wherein at least one of the outlet valve member (42) and the inlet valve member (42) intersects the plunger axis (A-A) at least in a position in which one of valve members (40, 42) is seated against its respective seat (48, 64).
8. The pump assembly (30) as claimed in claim 7, wherein the outlet valve member (42) intersects the plunger axis (A-A) both when it is seated against the outlet valve seat (48) and when it is moved away from the outlet valve seat (48).
9. The pump assembly as claimed in any of claims 1 to 8, wherein the inlet valve seat (64) and the outlet valve seat (48) are frusto-conical valve seats which are defined within the common bore (44) concentrically with one another.
10. The pump assembly (60) as claimed in any of claims 1 to 9, wherein the inlet valve member (40) forms a part of a digital inlet metering valve (70).