WO2018091488A1

WO2018091488A1 - High pressure fuel pump with venturi flow circuit

Info

Publication number: WO2018091488A1
Application number: PCT/EP2017/079248
Authority: WO
Inventors: Stephen Joseph MACLANE; James McHattie
Original assignee: Delphi Technologies Ip Limited
Priority date: 2016-11-17
Filing date: 2017-11-15
Publication date: 2018-05-24
Also published as: GB2556078A; GB201619492D0; GB2556078B; EP3542048A1

Abstract

A high pressure fuel pump (12) has a housing (38) in which a camshaft (18) is arranged rotatable between a front bearing (20) and a rear bearing (22), the camshaft (18) cooperating with a piston sliding in a bore to alternatively vary the volume of a compression chamber. In use, part of the inlet flow remains in the pump for lubricating the bearings, said lubricating flow circulating in a plurality of channels (28, 30, 32) and merging prior to join a pump return outlet (36) adapted to be connected to a return line. The pump (12) further comprises a venturi (34) arranged in said return channels.

Description

HIGH PRESSURE FUEL PUMP WITH VENTURI FLOW CIRCUIT

TECHNICAL FIELD

The present invention relates to a high pressure fuel pump of a fuel injection equipment and, more particularly to means for attenuating the pressure fluctuations around within the pump. BACKGROUND OF THE INVENTION

A fuel injection equipment is provided with a pump that receives low pressure fuel from a tank and delivers high pressure fuel to fuel injectors. The pump typically comprises a pumping head and a cambox, a piston collaborating with a camshaft rotating in the cambox reciprocally slides in a bore of the head to vary the volume of a compression chamber wherein majority of the fuel is pressurised and, the complementary portion leaks and lubricates the piston sliding in the bore, the cambox and the bearings of the camshaft. Said low pressure fuel forms return flows that merge prior to exit the pump to return to the tank. Pressure fluctuations generated by the reciprocal displacement of the piston propagate in said return flows and alter the performance of the pump. Damping systems generally arranged within the return line, enable to only partially attenuate said fluctuations, pressure waves still being noticeable within the cambox and around the bearings. SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to resolve the above mentioned problems in providing a high pressure fuel pump of a fuel injection equipment of an internal combustion engine, the pump having a housing defining a cambox in which a camshaft is arranged rotatable between a front bearing aligned with a rear bearing, the camshaft cooperating with a piston sliding in a bore to alternatively vary the volume of a compression chamber. In use, part of the inlet flow lubricates the front and rear bearings or the piston and the bore, said lubricating flow circulating in a plurality of channels, comprising a front channel and a rear channel joining into a single bearing channel and, in a central channel, said channels being defined in the pump housing and merging prior to join an outlet adapted to be connected to a return line.

The pump further comprises a venturi arranged in said return channels, the venturi pulling fuel from the bearings and lowering the pressure in the front and rear bearing channels.

According to a further aspect of the invention, all the channels merge into said venturi.

According to a further aspect of the invention, the venturi has a diabolo shape conduit with a large section inlet portion narrowing to a central portion forming a restriction which connects to an outlet portion having an enlarging section.

According to a further aspect of the invention, the venturi is arranged so the return flow from the front and rear bearings both enter the inlet portion.

According to a further aspect of the invention, the return flow from the cambox directly enters the central portion.

Moreover, the venturi is defined a cylindrical member inserted in a recess provided in the housing.

According to a further aspect of the invention, said recess opens in an outer face of the housing, the recess defining a cylindrical peripheral face extending from said opening to an opposed bottom face.

According to a further aspect of the invention, the front, rear and single bearing channels open in said bottom face. In use, the fuel lubricating the bearings flows in said channels

According to a further aspect of the invention, the central channel opens in said peripheral face, the cambox lubricant flowing, in use, in said central channel.

According to a further aspect of the invention, the venturi is a distinct cylindrical member having a cylindrical outer face extending from a transverse under face to a transverse outer face, the venturi inlet portion opening in the under face and, the enlarging outlet portion opening in the outer face.

According to a further aspect of the invention, the venturi member is further provided with another connecting channel extending radially from the cylindrical outer face to the central restricted portion of the venturi. According to a further aspect of the invention, said cylindrical outer face further defines an annular space, said another connecting channel opening in said annular space.

According to a further aspect of the invention, the venturi is inserted in the recess provided in the housing, the under face of the venturi being against the bottom face of the recess, the return channel opening in said recess peripheral face facing the annular space of the venturi.

According to a further aspect of the invention, the pump further comprises a return connection member arranged on said recess and protruding from the housing.

According to a further aspect of the invention, said connection member is a tubular member adapted to complementary receive a return line.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is now described by way of example with reference to the accompanying drawings in which:

Figure 1 is a general sketch of a high pressure fuel pump as per a first embodiment in which is arranged a damper as per the invention.

Figure 2 is a general sketch of a high pressure fuel pump as per a second embodiment in which is arranged a damper as per the invention.

Figure 3 is a plot of the lubricant pressure fluctuations when there is no damper.

Figure 4 is similar to figure 3 but with a damper.

Figure 5 is a section of a housing of a fuel pump enabling to visualise the return flow channels and an embodiment of the venturi damper.

Figure 6 is a magnified view of the venturi of figure 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A fuel injection equipment 10 of an internal combustion engine comprises a pump 12 pressurising and delivering to injectors fuel received from a low pressure tank.

A typical pump 12 sketched on figures 1 and 2 has a pumping head 14 fixed on a cambox 16 wherein a camshaft 18 aligned between a front 20 and a rear bearing 22 cooperates with a piston to reciprocally slide in a guiding bore for varying the volume of a compression chamber arranged in the pumping head 14.

The embodiments shown on figures 1 and 2 differ by the position of a general fuel inlet 24 and the routing of the inlet flow inside the pump. On the first embodiment, figure 1, said inlet 24 is arranged in the pumping head 14 and the fuel directly gets in the compression chamber. In the second embodiment, figure 2, said inlet 24 is arranged in the cambox 16 then the fuel upwardly transfers to the compression chamber.

Whatever the embodiment, a majority of the fuel entering the pump 12 is pressurized then expelled via an outlet 26, a smaller portion forming a lubricating flow splits for lubricating the piston-and-camshaft cooperation means, the front bearing 20 and the rear bearing 22. Afterward, said lubricating flow follows a central channel 28 as from the cambox 16, a front channel 30 as from the front bearing 20 and, a rear channel 32 as from the rear bearing 22, said channels 28, 30, 32 converging toward a damper 34 arranged before a return outlet 36 connected to the tank via a return line.

The damper 34 is a venturi defining a restriction through which the return fuel flow goes and, due to the traditional venturi effect, the venturi pulls in fuel from the bearings, lowering the pressure in the front 30 and rear 32 bearing channels said low pressure on the backleak side of the bearings 20, 22 providing an opportunity to reduce the bearing clearance as now there is more of a pressure differential and therefore more cooling/lubricating flow.

Experiments have been conducted where pressure in the cambox have been measured, without a damper 34, figure 3, said pressure fluctuating between 0 and 28 bars and, with a damper 34, figure 4, said fluctuations having a much smaller amplitude ranging between 3 to 7 bars.

An exemplary embodiment is presented on figures 5 and 6, a section of the housing 38 of the cambox 16 enables to visualise an inner space wherein cooperate, in use, the piston and the camshaft, the two bearings, the three channels 28, 30, 32, the damper 34 and the return outlet 36.

The damper 34 is an elongated cylindrical member inserted in a deep recess 40 having a cylindrical peripheral face 42 extending from a bottom face 44 to an opening 46 in an outer face of the housing 38. The front 30 and rear 32 channels extending from the front and rear bearings merge in a T-junction and form a single bearing channel 33 that opens in said recess bottom face 44 and, the central channel 28 extends directly from said pump inner space and radially opens in the recess peripheral face 42.

The damper 34 is arranged in said recess 40 together with a return outlet connection member 48. Said connection member 48 is a tubular member having an inner portion 50 inserted with press-fit in the recess 40, so that it is fixed to the housing 17 and, a protruding outer potion 52 ready for connection to a hose of the return line. Said connection member 48 defines an outlet channel 54 extending through both inner and outer portions and it is further provided with a collar 56 arranged between the inner 50 and the outer 52 portions, said collar 56 defining an annular outer shoulder face 58 abutting against the outer face of the housing around the opening 46 of the recess. Moreover, the outlet channel 54 is larger within the inner portion 50 than within the outer portion 52 so that an inner shoulder face 60 is defined in planar continuity with the outer shoulder face 58 although said planar continuity is not an obligation.

The damper 34 has a cylindrical peripheral face 62 extending between transverses under 64 and outer 66 faces and, said damper 34 is inserted in the inner portion of the outlet channel 54 so the outer face 66 abuts against the inner shoulder face 60 and, the under face 64 is in close proximity to the recess bottom face 44. To ensure sealing of the area, an upper O-ring 68 is arranged between the damper peripheral face 62 and the inner face of the outlet channel 54 and, a lower O-ring 70 is arranged between the damper peripheral face 62 and the peripheral face 42 of the recess so that, as per the arbitrary orientations of the figures, the the central channel 28 opens between said two O-rings 68, 70.

The damper 34 itself defines a through conduit opening in both under 64 and outer faces 66, said through conduit defining the venturi with a large lower inlet portion 72 opening in the under face 64, a central restriction portion 74, an enlarging outlet portion 76 opening in the outer face 66 and, at least one radial channels 78, two being shown on the figures, extending between the damper peripheral face 62 and said restriction portion 74.

The opening of the inlet portion 72 faces the opening of the bearing channels 33 in the recess bottom face 44 and, both openings have substantially equal cross-section, for instance typically about 5 mm in diameter. Said inlet portion 72 is rather short, maybe a quarter of the total length of the damper 34 straightly upwardly extending in a constant cross-section, or slightly narrowing, toward a beveled end where said cross section abruptly reduces, for instance from said 5mm diameter to 1 mm diameter.

The central restriction portion 74 is a calibrated orifice extending on an even shorter length, maybe a tenth of the length of the damper and keeping constant said reduced section, for instance 1mm.

The outlet portion 76 that is lengthy portion upwardly extending and gradually enlarging from a narrow extremity wherein opens the central restriction to a large opening in the outer face of the damper, said large opening having a cross-section substantially equal to the section of the tubular outer portion 52 of the connection member 48.

The radial channels 78 are calibrated orifices with constant small diameters, substantially equal to the section of the central restriction portion 74, and joining said central portion 74 very near its end where said central portion 74 opens in the narrow end of the outlet portion 76.

In the embodiment presented, the peripheral face 62 of the damper comprises a long upper portion having a slightly reduced diameter in comparison to a short bottom portion that is a little larger, the upper O-ring 68 being arranged in the upper portion and the lower O-ring 70 being in the bottom portion. Thus is defined an annular space 80 surrounding the damper 34, the central channel 28 and the radial channels 78 opening in said annular space 80.

In use, return flow from the bearings enters the recess 40 via the opening in the bottom face 44 and, because being stopped by the lower O-ring 70, said flow enters the inlet portion 72 of the venturi 34, at the end of which said flow forces its way through the restriction 74 then gets into the outlet portion 76 continuing toward the hose of the return line.

The central flow from the cambox 16 enters the recess 40 in said annular space 80 and, from there it gets into the radial channels 78 and into said outlet portion 76. All the return flow enter the narrow end of the outer portion 76 where said gradually enlarging long outer portion 76 favors mixing of the flows. As it is visible on the on the figures, the radial channels 78 are angularly drilled relative to the main axis on the damper conduit. This enables the flow coming from the cambox to more easily merge into the flow from the bearings than a 90° Iⁿjunction. Also, the central restriction 74 serves majorly to attenuate the pressure fluctuations in the bearing areas while the fluctuations in the cambox are attenuated by the small section radial channels.

Several alternative embodiments not shown can be provided for a similar purpose of attenuating the pressure fluctuations either as an independent member inserted in a recess or provided right after the pump outlet. Another possibility is to provide the pump with several venturi, for instance one arranged in the front channel for the flow of the front bearing, one in the rear channel for the flow of the rear bearing and a third venturi in the central channel for the flow of the cambox. Moreover, said venturi can either one or many can be provided integral to the pump housing. LIST OF REFERENCES

10 fuel injection equipment

12 pump

14 pumping head

16 cambox

18 camshaft

20 front bearing

22 rear bearing

24 inlet

26 HP outlet

28 central channel

30 front channel

32 rear channel

33 bearing channel

34 damper - venturi

36 return outlet

38 housing of the cambox

40 recess

42 peripheral face bottom face

opening of the recess

return outlet connection member inner portion

outer portion

outlet channel

collar

outer shoulder face

inner shoulder face

cylindrical peripheral face of the damper under face of the damper

outer face of the damper

upper O-ring

lower O-ring

inlet portion

central portion - restriction

outlet portion

radial channel

annular space

Claims

CLAIMS:

1. High pressure fuel pump (12) of a fuel injection equipment (10) of an internal combustion engine, the pump (12) having a housing (38) defining a cambox (16) in which a camshaft (18) is arranged rotatable between a front bearing (20) aligned with a rear bearing (22), the camshaft (18) cooperating with a piston sliding in a bore to alternatively vary the volume of a compression chamber,

wherein, in use, part of the inlet flow lubricates the front (20) and rear (22) bearings or the piston and the bore, said lubricating flow circulating in a plurality of channels (28, 30, 32, 33) comprising a front channel (30) and a rear channel (32) merging into a single bearing channel (33) and, a central channel (28), said channels being defined in the pump housing (38) and merging prior to join an outlet (36) adapted to be connected to a return line;

characterised in that the pump (12) further comprises a venturi (34) arranged in said return channels, the venturi pulling fuel from the bearings (20, 22) and lowering the pressure in the front (30) and rear (32) bearing channels.

2. Pump (12) as claimed in the preceding claim wherein all the return channels (28, 30, 32, 33) merge into said venturi (34).

3. Pump (12) as claimed in any one of the preceding claims wherein the venturi (34) has a diabolo shape conduit with a large section inlet portion (72) narrowing to a central portion (74) forming a restriction which connects to an outlet portion (76) having an enlarging section.

4. Pump (12) as claimed in claim 3 wherein the venturi (34) is arranged so the return flow from the front and rear bearings both enter the inlet portion (72). 5. Pump (12) as claimed in any one of the claims 3 or 4 wherein the return flow from the cambox directly enters the central portion (74).

6. Pump (12) as claimed in claim 5 wherein the venturi (34) is defined a cylindrical member inserted in a recess (40) provided in the housing (38).

7. Pump (12) as claimed in claim 6 wherein said recess (40) opens (46) in an outer face of the housing, the recess (40) defining a cylindrical peripheral face

(42) extending from said opening (46) to an opposed bottom face (44).

8. Pump (12) as claimed in claim 7 wherein the front, rear and single bearing channels (30, 32, 33) open in said bottom face (44).

9. Pump (12) as claimed in any one of the claims 7 or 8 wherein the central channel (28) opens in said peripheral face (42), the cambox lubricant flowing, in use, in said central channel (28). 10. Pump (12) as claimed in any one of the claims 7 to 9 wherein the venturi (34) is a distinct cylindrical member having a cylindrical outer face (62) extending from a transverse under face (64) to a transverse outer face (66), the venturi inlet portion (72) opening in the under face (64) and, the enlarging outlet portion (76) opening in the outer face (66).

11. Pump (12) as claimed in claim 10 the venturi (34) member is further provided with another connecting channel (78) extending radially from the cylindrical outer face (62) to the central restricted portion (74) of the venturi. 12. Pump (12) as claimed in claim 11 wherein said cylindrical outer face (62) further defines an annular space (80), said another connecting channel (78) opening in said annular space (80).

13. Pump (12) as claimed in claim 12 combined with claim 9 wherein the venturi (34) is inserted in the recess (40) provided in the housing (38), the under face (64) of the venturi being against the bottom face (44) of the recess, the return channel (78) opening in said recess peripheral face (62) facing the annular space (80) of the venturi (34).

14. Pump (12) as claimed in any one of the claims 7 to 13 further comprising a return connection member (48) arranged on said recess (40) and protruding from the housing (38).

15. Pump (12) as claimed in claim 14 wherein said connection member (48) is a tubular member adapted to complementary receive a return line.