EP3283764B1

EP3283764B1 - High pressure diesel fuel pumps

Info

Publication number: EP3283764B1
Application number: EP16714431.0A
Authority: EP
Inventors: Stephen MACLANE
Original assignee: Delphi Technologies IP Ltd
Current assignee: Delphi Technologies IP Ltd
Priority date: 2015-04-13
Filing date: 2016-04-05
Publication date: 2022-07-13
Anticipated expiration: 2036-04-05
Also published as: EP3283764A1; GB201506194D0; WO2016165985A1

Description

BACKGROUND

Technical Field

The present invention relates generally to the field of high pressure diesel fuel pumps. More particularly, but not exclusively, the present invention concerns low pressure inlets for high pressure diesel fuel pumps.

Description of the Related Art

Known high pressure diesel fuel pumps comprise one or more plungers movable within plunger bores, to pressurise fuel within respective pumping chambers. Those chambers deliver the fuel onwards to a fuel injection system of an engine as disclosed in DE10356262 A1 and in DE102012222450A1 .
As shown in Figures 1 and 2, each plunger (not shown) of pump 1 is reciprocally movable along a pumping axis by a cam arrangement (driven by a drive shaft 15) to perform a fuel-pressurising pumping stroke and a plunger return spring to effect a plunger return stroke. In a tappet arrangement, each of the plungers are driven within its bore via a tappet member 20. A return spring acts on the top of the tappet member 20 to allow it to follow the cam profile to a dropped position. A tappet vent 40 is provided within a wall of a drivetrain housing 5 between a spring chamber 30, housing the return spring above the tappet 20, and the cambox 10, below the tappet 20. The tappet vent 40 typically allows pressurised lubrication fluid, such as fuel or oil, and air to escape from above the tappet 20 and return to the cambox 10.
In current single plunger pumps, to deliver lubrication fluid to the driveshaft components, a low pressure inlet 50 feeds either directly into the cambox 10 (inlet 50b) or into a lower portion of the vent 40 close to an opening into the cambox 10 (inlet 50a). The inlet 50a/ 50b provides cooling flow of fluid to the driveshaft components.
In such arrangements, as the cam rotates and the tappet-plunger arrangement oscillates, a pressure wave is created in the cambox 10. Due partially to the return flow of fluid through the tappet vent 40 and the pressure wave, the fluid can be carried back through the low pressure inlet 50a/ 50b and down the inlet connector to other (upstream) fuel system components. These pressure waves will attenuate as they travel further away from the source of the wave, but due to current engine packaging restrictions, long pipe/ connector lengths are not always available in a system. Accordingly, the attenuation is often minimal and the pressure wave can have detrimental effects on those upstream components. Therefore, it is now desired to provide an improved arrangement for high pressure diesel fuel pump to minimise the effects of such pressure waves.

SUMMARY OF THE INVENTION

In a first aspect of the present invention there is provided a high pressure diesel fuel pump comprising a drivetrain assembly within a drivetrain housing and a pumping assembly, the drivetrain assembly comprising a cam mounted in a cambox, a tappet member arranged for reciprocal movement with the cam within a tappet chamber, and a spring mounted in a spring chamber acting on an upper surface of the tappet member, the pumping assembly comprising a pump housing and a plunger mounted within a bore formed in the pump housing for reciprocal movement along a pumping axis under the influence of the reciprocating tappet member, wherein the drivetrain housing comprises a vent arranged to connect said spring chamber and/or said tappet chamber with the cambox and a low pressure inlet for delivery of fluid to the drivetrain assembly, characterised in that the low pressure inlet is arranged to feed into the spring chamber, and wherein the inlet is located within 90° rotation of the vent around the pumping axis, wherein the inlet comprises an internal opening into the spring chamber and, wherein the internal opening is disposed towards a bottom end of the spring chamber.
With this arrangement, the feed of fluid through the inlet of the spring chamber makes use of the typical tappet vent (channel) between the spring chamber and the cambox to provide cooling flow of fluid to the top of the tappet and to the drivetrain assembly. With the inlet distanced from the source of the pulsation, being the cam in the cambox, the pressure pulsations have time to attenuate to a level that has minimal effect on the rest of the system. In addition, the flow of fluid is encouraged to take a defined path through the cambox, tappet chamber and vent, thereby minimising reverse flow. The arrangement helps improve lubrication and durability of the pump components and reduces flow fluctuations and cavities often caused by reversing flow.
Preferably, the inlet comprises a conduit leading to an external opening on an external surface of the housing.
Preferably, the internal opening is disposed close to the tappet chamber.
Preferably, the vent comprises an open-ended channel. Preferably, a first open end of the channel is located in the spring chamber. The first open end of the channel may alternatively be located in the tappet chamber. Preferably, the channel comprises a second open end located in the cambox.
Preferably, at least a portion of the internal opening is provided at a level between opposing top and bottom walls or loci of the first open end of the channel. Most preferably, a bottom wall or locus of the internal opening is biased towards a level defined by a bottom wall or locus of the first open end. Alternatively, a top wall or locus of the internal opening may be biased towards a level defined by a bottom wall or locus of the first open end.
Preferably, the first open end comprises a height defined between opposing top and a bottom walls or loci). The height of the first open end may be greater than a height of the inlet.
The top and bottom walls/ loci are defined by reference to the pumping axis.
Preferably, the internal opening of the inlet is disposed towards a tappet end of the spring chamber.
Preferably, the internal opening is distanced from the first end of the channel. Most preferably, the internal opening is disposed approximately 90° rotation away from the first end.
Preferably, the inlet is adapted to attach to a connector (not shown), which in turn connects with a fluid reservoir (not shown).
Preferably, the cambox and the spring and tappet chambers are generally open to one another, e.g. flow of fluid is permissible therebetween and around the drive assembly.
Preferably, the housing comprises a fluid outlet. Preferably, the fluid outlet comprises an internal opening into the cambox. Preferably, the outlet comprises a conduit leading to an external opening on an external surface of the housing. Preferably, the outlet is adapted to attach to a connector (not shown), which in turn connects with a hydraulic head (not shown).
In a second aspect of the present invention there is provided a drivetrain housing for a high pressure diesel fuel pump, the drivetrain housing comprising a cambox adapted to receive a rotating cam, a tappet chamber adapted to receive a tappet member for reciprocal movement with the cam, and a spring chamber adapted to receive a spring for acting on an upper surface of the tappet member, wherein the drivetrain housing comprises a vent arranged to connect said spring chamber and/or said tappet chamber with the cambox and a low pressure inlet for delivery of fluid to the drivetrain assembly, characterised in that the low pressure inlet is arranged to feed into the spring chamber.
It will be appreciated that the preferred features described in relation to the first aspect of the invention apply to the second aspect of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention, and to show how exemplary embodiments may be carried into effect, reference will now be made to the accompanying drawings in which:

Figure 1 is a perspective partial cross-sectional view of a prior art high pressure fuel diesel pump;
Figure 2 is a schematic view of a prior art high pressure fuel diesel pump showing the direction of fluid flow; and
Figure 3 is a side view of an exemplary embodiment of a high pressure fuel diesel pump according to the invention;
Figure 4 a schematic view of a high pressure fuel diesel pump according to Figure 3;
Figure 5 is a perspective partial cross-sectional view of an exemplary embodiment of a high pressure fuel diesel pump according to Figure 3.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Figure 3 is a side view of a high pressure diesel fuel pump 100 according to an exemplary embodiment. As shown in Figure 3, the pump 100 comprises a drivetrain assembly within a drivetrain housing 105 and a pumping assembly (not shown), the drivetrain assembly comprising a cam mounted in a cambox 110, a tappet member 120 arranged for reciprocal movement with the cam within a tappet chamber 125, and a spring mounted in a spring chamber 130 acting on an upper surface of the tappet member 120, the pumping assembly comprising a pump housing and a plunger mounted within a bore formed in the pump housing for reciprocal movement along a pumping axis A-A' under the influence of the reciprocating tappet member 120, wherein the drivetrain housing 105 comprises a vent 140 arranged to connect said spring chamber 130 and/or said tappet chamber 125 with the cambox 110 and a low pressure inlet 150 for delivery of fluid to the drivetrain assembly, the low pressure inlet 150 being arranged to feed into the spring chamber 130.
The drivetrain assembly is packaged within the drivetrain housing 105. Accordingly, the housing 105 comprises the cambox 110, the tappet chamber 125 and the spring chamber 130. The cambox 110 and the chambers 125, 130 are generally open to one another, e.g. flow of fluid is permissible therebetween and around the drive assembly.
The cambox 110 comprises a substantially cylindrical compartment of varying diameter across its length within the drivetrain housing 105. A drive shaft 115 with the cam thereon is mounted within the cambox 110. The drive shaft 115 is attached at a first end to a drive means (not shown), which dictates a rotational axis B-B' of the drive shaft 115 and therefore, the rotational path of the cam fitted thereon.
As visible on figure 3, on the left the camebox 110 in which in use the cam is rotating comprises the camshaft which is guided in a bearing and a back chamber (not referenced) is drawn on the right of the figure 3. When the camshaft is in place, there is no fluid communication between said back chamber and the cambox 110. As visible in figure 3, the vent 140 creates a non-restricted fluid communication between the cambox 110 and the spring chamber 130 and / or the tappet chamber 125.
The tappet chamber 125 comprises a substantially cylindrical compartment of substantially equal diameter within the drivetrain housing 105. The tappet chamber 125 is disposed perpendicularly to the cambox 110 so as to be generally upstanding above the cam. Accordingly, the pumping axis A-A' and the drive shaft rotational axis B-B' are disposed substantially perpendicularly to one another.
The spring chamber 130 comprises a substantially cylindrical compartment of substantially equal diameter within the drivetrain housing 105 and is provided coaxially with the tappet chamber 125, so as to be generally in line with the tappet chamber 125 and along the pumping axis A-A'.
The vent 140 comprises an open-ended passage 141 provided in the housing 105. In an exemplary embodiment, a first end 142 of the passage 141 communicates with a lower end of the spring chamber 130, whilst a second end 143 of the passage 141 opens up into an upper part of the cambox 110.
The low pressure inlet 150 comprises a first opening 151 into a lower end of the spring chamber 130, a conduit (not shown) through the housing 105 and a second opening (not shown) on an external surface of the housing 105. The second opening of the inlet 150 is attached to an inlet connector (not shown), which in turn connects with a fluid reservoir (not shown).
The inlet 150 is ideally located within 90° rotation of the vent 140.
The housing 105 provides an outlet 155 leading from the cambox 110. The outlet 155 comprises a first opening 156 extending from the cambox 110, a conduit 157 through the housing 105 and a second opening 158 on an external surface of the housing 105. The second opening 158 of the outlet 155 is connected to a hydraulic head (not shown).
In use, fluid is fed into the spring chamber 130 through the low pressure inlet 150 in the housing 105. Due to the positioning of the inlet 150, the fluid flows downwardly into the tappet chamber 125 to provide cooling flow to the upper surface of the tappet member 120. During reciprocal movement of the tappet member 125 along the axis A-A' through the rotation of the cam via the driveshaft 115, the fluid above the tappet member 125 is pushed upwardly towards the spring chamber 130. Excess fluid flows into the first open end 142 of the tappet vent 140 to flow downwardly through the passage 141 and exit into the cambox 110 (via second open end 143) where it provides cooling flow to the drivetrain assembly components (the cam, driveshaft 115, bearings, etc.).
The rotation of the cam on the driveshaft 115, drives the reciprocal movement of the tappet member 120 and since the cambox 110 and the tappet chamber 125 are connected, fluid is pushed upwardly into the tappet chamber 125. Therefore, a positive cyclical flow of fluid through the housing 105 is achieved. Excess fluid can exit the cambox 110 via outlet 155.
The rotation of the cam typically causes pressure pulses in the cambox 110, and can lead to reverse flow back through the tappet vent 140 and up into the tappet chamber 125. However, since a positive flow of fluid is established, such reverse flow is minimised. Furthermore, since the inlet 150 is distanced from the cambox 110, any such pulses are weakened before reaching the inlet 150 and any reverse flow back up the inlet connector has a minimal effect on any upstream components.
The repositioning of the low pressure inlet 150 (from the prior art position of directly into the cambox 110) to the spring chamber 130 provides a low pressure cooling/ lubrication flow of fluid into the housing 105 and around the drivetrain assembly without putting the upstream pump and engine components at risk of damaging pressure pulses. This in turn improves durability of the components. The positive fluid flow path through the housing 105, provides for improved cooling and lubrication to the drivetrain assembly and minimises reverse flow that can cause cavities.

Claims

A high pressure diesel fuel pump (100) comprising a drivetrain assembly within a drivetrain housing (105) and a pumping assembly, the drivetrain assembly comprising a cam mounted in a cambox (110), a tappet member (120) arranged for reciprocal movement with the cam within a tappet chamber (125), and a spring mounted in a spring chamber (130) acting on an upper surface of the tappet member (120), the pumping assembly comprising a pump housing and a plunger mounted within a bore formed in the pump housing for reciprocal movement along a pumping axis (A-A') under the influence of the reciprocating tappet member (120), wherein the drivetrain housing (105) comprises a vent (140) arranged to connect said spring chamber (130) and/or said tappet chamber (120) with the cambox (110) and a low pressure inlet (150) for delivery of fluid to the drivetrain assembly, characterised in that the low pressure inlet (150) is arranged to feed into the spring chamber (150) and wherein the inlet (150) is located within 90° rotation of the vent (140) around the pumping axis (A-A'),
wherein the inlet (150) comprises an internal opening into the spring chamber (130) and,

wherein the internal opening is disposed towards a bottom end of the spring chamber (130).
The pump according to claim 1, wherein the inlet (150) comprises a conduit leading to an external opening on an external surface of the housing (105).
The pump according to any one of claims 1 to 2, wherein the vent (140) comprises an open-ended channel (141).
The pump according to claim 3, wherein a first open end (142) of the channel (141) is located in the spring chamber (130).
The pump according to any one of claims 3 to 4, wherein the channel (141) comprises a second open end (143) located in the cambox (110).
The pump according to claim 5, wherein the second open end (143) is located in the cambox (110) opens up into the upper part of the cambox (110).
The pump according to any one of claims 1 to 6, wherein at least a portion of the internal opening is provided at a level between opposing top and bottom walls or loci of the first open end (142) of the channel (141).
The pump according to claim 7, wherein a bottom wall or locus of the internal opening is biased towards a level defined by a bottom wall or locus of the first open end (142).
The pump according to any one of claims 1 to 8, wherein the internal opening of the inlet (150) is disposed towards a tappet end of the spring chamber (130).
The pump according to any one of claims 4 to 9, wherein the internal opening is distanced from the first end (142) of the channel (141).
The pump according to any one of claims 1 to 10, wherein the internal opening is disposed at least approximately 90° rotation away from the first end (142).
The pump according to any one of claims 1 to 11, wherein the cambox (110) and the spring and tappet chambers (125, 130) are generally open to one another.
The pump according to any one of claims 1 to 12, wherein the housing (105) comprises a fluid outlet (155).