EP3353412A1

EP3353412A1 - Fuel pump assembly

Info

Publication number: EP3353412A1
Application number: EP16763528.3A
Authority: EP
Inventors: Benjamin P. WEST; Gunay CICEK
Original assignee: Delphi Technologies IP Ltd
Current assignee: Borgwarner US Technologies LLC
Priority date: 2015-09-21
Filing date: 2016-09-13
Publication date: 2018-08-01
Anticipated expiration: 2036-09-13
Also published as: JP2018527515A; CN108350846B; WO2017050608A1; KR20180053399A; GB201516704D0; EP3353412B1; CN108350846A; KR102659828B1; JP6806769B2

Abstract

A fuel pump assembly (30) for an internal combustion engine, the fuel pump assembly comprising a pump chamber (36) for fuel; a plunger (32) which is driven by means of a drive arrangement to cause pressurization of fuel within the pump chamber (36); and a first housing part (40) provided with a recess (38a, 38b) which defines the pump chamber (36) in an upper region (38a) thereof and which receives a second elongate housing part (44) in a lower region thereof, wherein the second housing part (44) defines a plunger bore (34) for receiving the plunger (32). The second housing part (44) projects from the recess (38a, 38b) so that a greater proportion of the second elongate housing part (44) extends from the recess (38a, 38b) than is received within the recess (38a, 38b).

Description

FUEL PUMP ASSEMBLY TECHNICAL FIELD

The present invention relates to fuel pump assembly which is suitable for use in pumping fuel in an internal combustion engine, and particularly in a compression ignition internal combustion engine.

BACKGROUND OF THE INVENTION

A known fuel pump assembly 10 for a compression ignition internal combustion engine is shown in Figure 1. The pump assembly forms a part of a larger pump assembly (not shown) which may include a plurality of similar pump heads arranged to be driven by a common drive shaft for the pump.

Each pump head includes a pumping plunger 12 which is driven by means of a cam (not shown) mounted on the drive shaft. The pumping plunger 12 reciprocates within a bore 14 provided in a pump head 18 to cause pressurization of fuel within a pump chamber 16 defined at one end of the bore 14. An inlet valve 20 extends into the pump chamber and is actuable to move towards and away from an inlet valve seating defined at the uppermost end of the bore 14 so as to control the flow of low pressure fuel into the pump chamber 16, prior to pressurisation. When the inlet valve 20 is moved away from the inlet valve seating 22 during a plunger return stroke (i.e. as the plunger moves downwardly within the plunger bore 14), low pressure fuel is drawn into the pump chamber 16 past the inlet valve 20 ready for pressurization during a subsequent pumping stroke of the plunger 12. When the inlet valve 20 is seated against the inlet valve seating 22 during the plunger pumping stroke, fuel within the pump chamber 16 is pressurized and is delivered through an outlet valve (not shown) to the downstream components of the fuel injector.

The outlet valve extends tangentially to the plunger 12 to supply a delivery path for pressurized fuel which also extends tangentially to the pumping plunger 12. The inlet and delivery paths to/from the pump chamber 16 are therefore arranged tangentially to one another. The pump head 18 is a forged housing part within which the plunger bore 14 is drilled. The pump head 18 takes the form of a substantially flat horizontal structure 18a with a vertically extending nose portion 18b extending downwards from the underside of the horizontal structure. The majority of the plunger bore 14 is disposed within the nose portion 18b, with the pump chamber 16 residing centrally within the horizontal structure 18a.

In some pump assemblies, whilst it is fuel that is pressurized within the pump chamber 16, the intermediate drive components and the drive shaft are lubricated by engine oil which leads to complications with cross contamination of the fuel unless a relatively long plunger sealing length is used. However, this creates a problem because the inlet valve seating 22, which is formed at the upper end of the plunger bore 14, is then relatively inaccessible due to the requirement for a long sealing length for the plunger 12 which extends the full length of the nose 18b. Machining of the inlet valve seating 22 is therefore difficult, and is especially difficult to machine with accuracy.

It is an object of the invention to provide a fuel pump assembly which provides a solution to the aforementioned problem.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a fuel pump assembly for an internal combustion engine, the fuel pump assembly comprising a pump chamber for fuel; a plunger which is driven by means of a drive arrangement to cause pressurization of fuel within the pump chamber; and a first housing part provided with a recess which defines the pump chamber in an upper region thereof and which receives a second elongate housing part in a lower region thereof. The second housing part defines a plunger bore for receiving the plunger and projects from the recess so that a greater proportion of the second housing part extends from the recess than is received within the recess.

The fuel pump assembly of the invention provides a particular advantage that the two part nature of the housing for the plunger means that the valve seating of an inlet valve, which is arranged to control fuel flow into the pump chamber prior to pressurization, can be machined more easily. This is because the inlet valve seating is accessible through the recess, whereas in known fuel pump assemblies the inlet valve seating is accessible only through the plunger bore which is necessarily of long length and of limited diameter.

In one embodiment of the invention, at least two-thirds of the length of the second housing part may extend from the recess.

In another embodiment of the invention, at least three-quarters of the length of the second housing part may extend from the recess.

The fuel pump assembly may comprise an inlet valve arranged vertically above an end surface of the plunger within the pump chamber. The inlet valve may be operable to control a supply of fuel into the pump chamber prior to pressurization. The inlet valve may be cooperable with an inlet valve seating defined at an entry port to the pump chamber.

One advantage of the invention is that the inlet valve seating is much easier to machine due to the two-part construction of the housing of the assembly.

Typically, the inlet valve seating may be defined within the first housing part. The fuel pump assembly may comprise an outlet valve arranged within the first housing part to extend tangentially from the pump chamber. The inlet valve may be operable to control a supply of pressurized fuel from the pump chamber. The second housing part may include a sleeve. The sleeve may define an upper portion of the plunger bore.

The sleeve may be fixed to the second housing part. The sleeve may define, together with the recess in the first housing part, a clearance for fuel. The clearance for fuel may permit fuel flow around the outside of the sleeve. The plunger bore in the second housing part may be provided with an annular recess to collect leakage fuel within the plunger bore. The annular recess and the collection of leakage fuel controls fuel losses.

The fuel pump assembly may comprise a plunger return spring for effecting a return stroke of the plunger. During the return stroke of the plunger, the plunger is retracted from the pump chamber., which permits fuel to be drawn into the pump chamber.

The plunger return spring may receive that greater proportion of the second housing part which extends from the recess.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 has already been described and shows a cross sectional view of a fuel pump assembly known in the prior art. The present invention will now be described by way of example only with reference to the accompanying drawings in which; and

Figure 2 is a cross sectional view of a fuel pump assembly of an embodiment of the invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS

It will be appreciated that references in this following description to up, down, higher, lower, left, right, vertical and horizontal, for example, are not intended to be limiting and are used merely in relation to the orientation shown in the drawings.

Referring to Figure 2, a fuel pump assembly 30 of an embodiment of the invention includes a pumping plunger 32 which is driven by means of an intermediate drive arrangement (not shown) under the influence of a cam mounted on an engine drive shaft (also not shown). The cam cooperates with the pumping plunger 32 to cause the plunger 32 to reciprocate within a plunger bore 34. Typically the intermediate drive arrangement includes a tappet which is coupled to the plunger 32. As the cam rotates with the drive shaft, the tappet is driven through cooperation with the cam and the plunger 32 is caused to move within the plunger bore 34 to pressurize fuel within a pump chamber 36 defined at the end of the plunger bore 34.

The pump chamber 36 is defined within a recess provided in a first, upper housing part 40 for the pump assembly. The first housing part 40 takes the form of a relatively flat, disc-like housing of relatively large width dimension and the recess is centrally positioned. The recess is of stepped form, defining an upper region 38a of relatively narrow diameter which defines the pump chamber 36 and a lower region 38b of relatively enlarged diameter. The relatively large width dimension ensures there is adequate volume of material of the first housing part 40 within which to form a delivery passage 42 for high pressure fuel exiting the pump, as will be described in further detail later.

The lower region of the recess 38b receives a second, lower housing part 44 in the form of an elongate housing part having a sleeve 46 arranged at its upper end. The elongate housing part 44 is provided with a bore which defines the majority of the length of a plunger bore 34 for the plunger, with the sleeve 46 defining the upper end of the plunger bore 34. The outer diameter of the elongate housing part 44 is stepped so as to match the stepped diameter of the recess 38a, 38b in the first housing part 40. The elongate housing part 44 is joined to the first housing part 40 by any suitable means, such as brazing or welding, or may be joined by an interference fit.

The elongate housing part 44 is of relatively long length compared to the first housing part 40 and a greater proportion of the elongate housing part 44 projects from the recess 38b than is received within the recess. In the example shown in Figure 2, approximately two thirds of the length of the elongate housing part 44 extends below the recess 38a, 38b with approximately one third of the elongate housing part residing within the recess 38a, 38b. As a result, a greater proportion of the plunger bore 34 is defined external to the first housing part 40 than is actually defined within the first housing part 40. Because the drive arrangement is typically immersed in lubricating engine oil, where as the pump chamber 36 is filled with injectable fuel, the long length of the plunger bore 34 is advantageous as it helps to reduce cross contamination between the different fluids. It is a particular concern that lubricating oil may contaminate the injectable fuel. To further reduce the risk of cross contamination between the fluids, the plunger bore 34 within the elongate housing part is provided with an annulus (not shown) to collect fuel which leaks down the plunger bore 34 (defined as the plunger sealing length). Excess fuel which collects in the annulus can be drained from the annulus via a drilling (not shown) which transports fuel to a low pressure drain.

The pump chamber 36 is provided at the end of the plunger bore 34 (the upper end in the illustration) and is supplied with fuel at relatively low pressure through an inlet port 48 under the control of an inlet valve 50. The inlet port 48 is positioned centrally and vertically above an upper end surface of the plunger 32. A seating for the inlet valve (not labeled) is defined within the port 48. The inlet valve 50 is arranged within an inlet passage 54 provided in the first housing part 40, and the inlet valve passage 54 communicates with an inlet drilling 56. The inlet drilling 56 meets the inlet valve passage 54 at an angle and receives fuel from a relatively low pressure fuel supply (not shown). In the vicinity of the inlet port 48, in the region of intersection between the inlet valve passage 54 and the pump chamber 36, it is important to achieve a good surface finish at the inlet valve seating.

The pump chamber 36 is also provided with an outlet port 58 through which pressurized fuel is delivered, under the control of an outlet valve 60, to the delivery passage 42 defined within the first housing part 40, and onwards to the downstream parts of the fuel injection system. The delivery passage 42 extends tangentially to the plunger 32 to communicate with the pump chamber 36 through a side wall thereof. The outlet valve 60 takes the form of a ball valve and is located within the delivery passage 42 and biased by means of an outlet valve spring 62 into a closed position, in which it seats against an outlet valve seating (not labeled) and in which communication between the pump chamber 36 and the delivery passage 42 is closed. In the vicinity of the outlet port 58, in the region of intersection between the delivery passage 42 and the pump chamber 36, it is important to achieve a good surface finish so as to minimize stress at the intersection. The inlet valve 50 is biased towards a closed position, in which fuel is unable to flow into the pump chamber 36, by means of an inlet valve spring 64. The inlet valve 50 is moveable away from the inlet valve seating by means of an actuator (not shown) against the force of the spring 64. The actuator may be an electromagnetic actuator of conventional type and includes an armature (not shown), moveable under an electromagnetic force, which is coupled to the inlet valve 50.

In use, the plunger 32 performs a pumping cycle including a pumping stroke and a return stroke. During the pumping stroke, in which the plunger 32 is driven inwardly within the plunger bore 34, the volume of the pump chamber 36 is reduced and fuel within the pump chamber 36 is pressurized. During the return stroke of the plunger 32, the plunger 32 is retracted from the bore 34, increasing the volume of the pump chamber 36 and causing relatively low pressure fuel to be drawn through the open inlet valve 50. The plunger return stroke is effected by means of a plunger return spring 70 through which the elongate housing part 44 extends. The lower end of the spring 70 is attached to a retainer in the form of a top hat shaped part 72 having a central opening through which the lower end of the plunger 32 protrudes. The plunger 32 carries a collar 74 which is press-fitted to the plunger 32. The collar 74 is sized so that it cannot pass through the opening in the retainer 72 and so in this way the plunger is indirectly secured to the lower end of the spring 70.

The sleeve 46 at the upper end of the elongate housing part 44 is integrally formed with the main body of the housing part 44, and so forms a permanent part of the housing part 44, and defines the upper portion of the plunger bore 34. The sleeve 46 is positioned within the upper region of the recess 38a, and the outer diameter is selected so as to define an outer annular clearance with the internal wall of the recess 38a. The outer annular clearance is not visible within the dimensions of the figures, but receives high pressure fuel due to its communication with the pump chamber 36 and is necessary so as to ensure that fuel within the pump chamber 36 is able to flow around the sleeve 46 and exit the pump chamber 36 via the outlet port 58, which communicates with the outer annular clearance. The inner diameter of the sleeve 46 is selected so as to define an inner annular clearance with the plunger 32. Fuel within the pump chamber 36 is also able to fill the inner annular clearance which applies a radially outwards force to the sleeve 46 which is substantially equal to the radially inwards force due to fuel within the outer annular clearance. Although some dilation of the upper end of the recess 38a will occur, the provision of the sleeve 46 reduces the dilation effect. This dilation effect gives rise to leakage through the plunger bore 34 in the prior art design in Figure 1 , but in the present invention, where the housing is formed from two parts 40, 44 and with the sleeve 46 in place, it is possible to reduce the impact of the dilation so that higher pressurization levels are achievable without excessive loss.

A further benefit of forming the housing from two parts (the first housing part 40 and the elongate housing part 44) is that access to the inlet valve seating in the region of the inlet port 48 is more straightforward. In addition, access to the outlet valve 58 and its transition to the recess 38a, 38b is improved. This improved access means that beneficial techniques can be used for the seat formation, such as electro chemical machining (ECM) techniques and shot peening, improving the seat contact.

In use, the plunger 32 is driven as the cam rotates, driving the tappet and causing the plunger 32 to reciprocate within the plunger bore 34 through the pumping cycle. During the return stroke of the plunger 32, the plunger 32 is withdrawn from the plunger bore 34 under the influence of the return spring 70 and the inlet valve 50 is actuate to open, allowing relatively low pressure fuel to flow into the pump chamber 36. During this stage of the pumping cycle the outlet valve 60 is closed under the force of the outlet valve spring 62 because fuel pressure in the pump chamber 36 is relatively low. On the subsequent plunger stroke, the inlet valve 50 is closed under the force of the inlet valve spring 64 and the plunger 32 is driven inwardly within the plunger bore 34 as it rides over the nose of the cam. As the volume of the pump chamber 36 is reduced, the pressure of fuel within the pump chamber 36 is increased until such time as the force due to fuel pressure in the pump chamber 36 overcomes the force due to the outlet valve spring 62 and the outlet valve 60 is lifted away from its seating. Pressurised fuel within the pump chamber 36 is then able to flow past the open outlet valve 60 through the delivery passage 42 to the downstream parts of the fuel injection system.

The dilation effects of high pressure fuel within the pump chamber 36 are mitigated due to the presence of the sleeve 46 at the upper end of the elongate housing part 40, and so it is possible to pressurize fuel to a higher level without comprising on fuel leakage losses through the plunger bore 34. This reduces the risk of cross contamination of fuel and engine lubricating oil which is used to lubricate the drive components.

It will be appreciated by a person skilled in the art that the invention could be modified to take many alternative forms to that described herein, without departing from the scope of the appended claims.

Claims

1 . A fuel pump assembly for an internal combustion engine, the fuel pump assembly comprising: a pump chamber (36) for fuel; a plunger (32) which is driven by means of a drive arrangement to pressurization of fuel within the pump chamber (36); a first housing part (40) provided with a recess (38a, 38b) which defines the pump chamber (36) in an upper region thereof and which receives a second elongate housing part (44) in a lower region thereof, wherein the second elongate housing part (44) defines at least in part a plunger bore (34) for receiving the plunger (32); and wherein the second elongate housing part (44) projects from the recess (38a, 38b) so that a greater proportion of the second housing part (44) extends from the recess (38a, 38b) than is received within the recess (38a, 38b); and wherein the fuel pump assembly comprises an inlet valve (50) arranged vertically above an end surface of the plunger (32) within the pump chamber (36) and operable to control a supply of fuel into the pump chamber (36) prior to pressurization, wherein the inlet valve (50) is cooperable with an inlet valve seating defined at an entry port (48) to the pump chamber (36).

2. The fuel pump as claimed in claim 1 , wherein at least two-thirds of the length of the second elongate housing part (44) extends from the recess (38a, 38b).

3. The fuel pump as claimed in claim 2, wherein at least three quarters of the length of the second elongate housing part (44) extends from the recess (38a, 38b).

4. The fuel pump assembly as claimed in claim 1 , wherein the inlet valve seating is defined within the first housing part (40).

5. The fuel pump assembly as claimed in any of claims 1 to 4, comprising an outlet valve (60) arranged within the first housing part (40) to extend tangentially from the pump chamber (36) and operable to control a supply of pressurized fuel from the pump chamber (36).

6. The fuel pump assembly as claimed in any of claims 1 to 5, wherein the second elongate housing part (44) includes a sleeve (46) which defines an upper portion of the plunger bore (34).

7. The fuel pump assembly as claimed in claim 6, wherein the sleeve (46) is fixed to the second elongate housing part (44).

8. The fuel pump assembly as claimed in claim 6 or claim 7, wherein the sleeve (46) defines, together with the recess (38a) in the first housing part (40), a clearance for fuel to permit fuel flow around the outside of the sleeve (46).

9. The fuel pump assembly as claimed in any one of claims 1 to 8, wherein the plunger bore (34) in the second elongate housing part (44) is provided with an annular recess (46) to collect leakage fuel within the plunger bore (46).

10. The fuel pump assembly as claimed in any of claims 1 to 9, comprising a plunger return spring (70) for effecting a return stroke of the plunger (32) during which the plunger (32) is retracted from the pump chamber (36) to permit fuel to be drawn into the pump chamber (36).

1 1 . The fuel pump assembly as claimed in claim 10, wherein the plunger return spring (70) receives the greater proportion of the second elongate housing part (44) which extends from the recess (38a, 38b).