GB2540549A

GB2540549A - Novel fuel pump design

Info

Publication number: GB2540549A
Application number: GB1512685.7A
Authority: GB
Inventors: Foord Gary
Original assignee: Delphi International Operations Luxembourg SARL
Current assignee: Delphi International Operations Luxembourg SARL
Priority date: 2015-07-20
Filing date: 2015-07-20
Publication date: 2017-01-25
Also published as: EP3325797A1; WO2017012836A1; GB201512685D0

Abstract

A fuel pump including a housing comprises at least a first flow path and the second flow path formed within the housing, wherein at least two flow paths are arranged substantially adjacent. The first and second flow paths may have respective inlets from different pressure sources. One of the flow paths may be a lubrication path from the front or rear bearing of the pump drive shaft 19,21, which may include a bore from one or more of the bearings to the inlet of the flow path. The second flow 12 path may include an inlet from one or more of the cambox 5, inlet metering valve, or injector backleak 16, and may include a Venturi arrangement. The first and second flow paths may be parallel and provided by a common component 33 formed as an insert, which may include a Venturi or diffuser portion. Outlets of the flow paths may converge to form a pump backleak path.

Description

Novel Fuel Pump Design

Field of the Invention

This disclosure relates to fuel pumps and has particular but not exclusive application to common rail (CR) Diesel fuel pumps.

Background to the Invention

On existing CR pumps, the hydraulic circuitry usually employs numerous separate, machined holes within the pump envelope (i.e. machined into the pump housing/body) which connect various low or high pressure flow paths. In some parts of the flow circuit there may also be provided further separate, flow control devices; for example in order to provide a Venturi or similar functions. A problem with this is that it is difficult and expensive to machine flow paths in housings such as the pump body, especially where the flow paths incorporate comers. Furthermore, the flow paths require space in the housing to be provided for.

It is one objective of the invention to overcome these problems.

Statement of the Invention

In one aspect is provided a fuel pump including a housing and including at least a first flow path and a second flow path formed within said housing where at least two flow paths are arranged substantially adjacent.

The said first flow path may have an inlet from one pressure source and said second flow path has an inlet from another pressure source.

One of said flow paths may be a lubrication path.

The said inlet may be from a front or rear bearing of the pump drive shaft.

The pump may include a bore from one or more of said bearings to the inlet of said flow path The outlets of said flow paths may converge.

The outlet of said flow paths may form a pump backleak path.

The second flow path may include an inlet from one or more the cambox, inlet metering valve or injector backleak.

The pump may include a Venturi arrangement in said second flow path The first and second flow paths are preferably substantially parallel.

Preferably said first and second paths are provided by a common component. The common component may be provided as an insert.

The said insert may include a Venturi or diffuser portion The pump housing may enclose a pressurised cambox area.

The said flow paths are preferably arranged in the same region of the housing relative to the cambox.

Examples of the invention provide one or more flow paths that can be provided in a compact and intelligent manner to reduce the above mentioned problems.

Brief Description of Drawings

The invention will now be described by way of example and with reference to the following examples of which:

Figure 1 shows a cross sectional view across a known example fuel pump unit with the physical arrangement of the flow paths;

Figure 2 diagrammatically shows relevant flow paths (in relation to pump unit components) for example pump shown in figure 1;

Figure 3 diagrammatically shows relevant flow paths for a revised circuit incorporating the invention;

Figure 4 shows a simple schematic representation of part of arrangement shown in figure 2 and figure 1;

Figure 5 shows a cross sectional view across a revised example fuel pump unit with the physical arrangement of the flow paths according to one example of the invention;

Figure 6 shows a simple schematic representation according to one example of the invention such as the arrangement shown in figure 3 and figure 5;

Figure 7 shows an example of the invention in more detail;

Figure 8 shows the device according to one example in greater detail; and Figure 9a andb shows views of the assembly of device of figure 8.

Detailed Description of the Invention

Figure 1 shows a cross sectional view across a known example fuel pump unit with the physical arrangement of the flow paths. Such a fuel pump may have application as a Diesel fuel pump for a common rail system. The pump may include a drive shaft 2 that is driven by a belt (from an engine) attached to the belt gear 3, and an eccentric cam 4, that drives a reciprocating pump portion (not shown) via a corresponding cam mechanism. The figure shows a cambox 5 which is effectively a space within a pump housing/body 6 that contains the eccentric cam and cam mechanism. The driveshaft is located in the housing on a rear bearing (not shown) and sealed into the housing by a front plate 18, which also houses/incorporates a front bearing (not shown). A lubrication flow path from front and rear bearings 19 is shown, which combines with a high pressure flow path 12 (shown dashed) from the cambox, after passing through a cooling orifice (not shown), to provide a flow path to a Venturi 14, after which it joins a flow from the backleak injector source 16. These have a common outflow (backleak) at outlet 9.

Figure 2 diagrammatically shows relevant flow paths (in relation to pump unit components) for example pump shown in figure 1. This shows a pump (fuel inlet) flow path into the pressurised cambox 5 and the front and rear bearings are 7 and 8 respectively. There are flow paths provided from the cambox through the bearings to a pump backleak path 9 which are used to provide lubrication to the bearings. There is a flow path 10 from via an inlet metering valve (IMV) 11 to the pump hydraulic head. There is also a high pressure flow path 12 from the cambox to the pump backleak which includes a cooling orifice 13 for providing cooling circulation. A Venturi 14 may be provided in flow paths, and is typically used in flow paths going from high to low pressure, such as providing low pressure suction for injector backleak flow 16. The pump inlet feeds into the cambox and is outlet to the hydraulic head via an inlet metering valve. Fuel is pressurised in the hydraulic head by means of reciprocating plungers in contact with a cam on driveshaft, which runs in front and rear bearings. The bearings are lubricated via flow paths from the cambox, which combine to give a common return flow to pump backleak port 9. In order to cool the cambox, flow may be provided via a flow path 12 and cooling orifice 13 which also flows to the pump backleak. A Venturi is often provided for the backleak flow from the bearings/cooling orifice. There may be an inlet to the flow circuit to pump backleak from the injector backleak, returning excess fuel from the injectors which may be under pressure. This injector backleak may be input via a Venturi using pump backleak flow from bearings and cambox.

Figure 3 diagrammatically shows relevant flow paths for a revised circuit incorporating the invention. Here the flow path from the rear bearing to the pump backleak is removed and the flow from the rear bearing is returned to the pressurised cambox. The bearing may be designed such that it is self-lubricating and does not need separate fuel lubrication and also the cooling orifice may also be removed. A flow path from cambox and injector backleak are combined in the same portion with a Venturi. The flow path provided for rear bearing lubrication now returns to the cambox (as it is no longer required), instead of connecting to pump backleak via the Venturi.

Figure 4 shows a simple schematic representation of part of arrangement shown in figure 2 and figure 1. The cambox 5 is shown located towards the centre of the housing and forms a space for the cam arrangement. In the upper portion of the pump housing is located a flow path machined into the housing which may include a Venturi arrangement 15 and connects the high pressure portion(s) from inlet 12 such as connection from the cambox and/or the injector backleak to the low pressure back-leak outlet 9. The Venturi or general path may include a lower pressure path from the inlet metering valve (not shown). Below the cambox is located also the low pressure path to the backleak outlet 19 from the front/rear bearing for lubrication purposes. The Venturi also provides low pressure suction for injector backleak flow 16.

Detailed Description of Examples

According to aspects of the invention one or more pathways which may be high/and or low pressure pathways) are co-located e.g. so as to be adjacent and preferably parallel. This allows more efficient use of space, requires less machining and is simpler and cheaper to manufacture.

So in aspects, the invention locates certain pathways and preferably so that at least two pathways are arranged adjacently. This allows space to be saved and obviates in some cases the need to provide complex machining including providing non straight pathways. Additionally the pathways or portion thereof may be provided in single component or component assembly further saving costs an making manufacturing quicker and more efficient.

In the example of figure 5 it shows how the low pressure flow path 19 from the bearing(s) of figure 1 is re-located above the cambox and in the embodiment is also adjacent to the flow path from other e.g. higher pressure pathways, designated with reference numeral 20, e.g. including the high pressure from the cambox pressure and/or via the IMV 11. In preferred embodiments the adjacent/parallel pathways are located above the cambox; they may be located elsewhere and in the same region of the pump housing but adjacent to one another.

In further embodiments the adjacent pathways are provided by a common component or flow element regulator 33. This is preferably provided as an insert which makes manufacture far simpler as the pathways do not need to be directly machined in the housing/pump body.

In the figure the common component 33 e.g. as an insert, is shown, through which separate flow paths are provided, where one flow path 20 may be from a high pressure source and the other 21 may be from a low pressure source 19. The flow paths may themselves be provided with more than one inlet. In the example shown, high pressure inlet/source may be from the IMV 11 and/or cambox and the low pressure inlet may be from front or rear or both bearings. Thus the path from the bearing (low pressure 19) is colocated with the high pressure path 12 from the cambox/IMV . Preferably at least two flow paths 20 and 21 are generally parallel. In enhanced examples the flow paths are provided using a common component. In the example the flow paths converge in the pump housing and exit to the backleak outlet

Figure 6 shows a schematic view of the figure 5 arrangement with corresponding reference numerals and generally with the same connections. The lubrication 19 / low pressure path 21 has been located adjacent to the conduit /flow path from the high pressure portion 12 providing substantial space saving. In the example the lubrication 19/low pressure path 21 has been provided in the top portion (above the cambox).

In preferred examples the adjacent paths can be provided as a bypass flow control device which may be provided as an insert 33 that provides at least two flow paths as shown by the shaded area. This allows substantial space to be saved.

As can be seen the flow control device provides two adjacent paths - in examples one of the paths is a low pressure path 21 that connects the bearing flow to the pump backleak and the other path 20 combines high pressure source from cambox 12 with the injector backleak 16 and then connects to the pump backleak. The device 33 providing the flow paths may thus include two or more inlets.

As can be seen a Venturi 15 or other arrangement can be incorporated into one of the flow paths. Preferably the common component/arrangement provides flow paths together in parallel and/or adjacent arrangement and preferably by the same component or component assembly unit. Alternatively the flow paths may be machined in the pump adjacent each other rather than being provided by a separate flow control device. Although this would involve higher machining costs with respect to the pump body, this still provides space saving.

In changing from the existing use of multiple, relatively long, separate machined holes in a pump housing (for high and low pressure flow paths connected to a limited function, flow control device) to a method combining the holes required for said high and low pressure flow paths employing a more versatile multipressure, flow control bypass device (insert), thus allows reducing the number or length of separate flow paths required, and the space required to accommodate them. As a consequence, the shape or form of the housing can be optimized for material savings, reducing the overall pump envelope & permit simplified machining operations leading to savings on overall manufacturing costs.

The multi-pressure, flow control bypass device may be a molded component enabling special features to be used that are not easily achieved or possible compared with machined features made to the housing (6) in the traditional manner. So in preferred examples the flow paths are formed within a common component/insert or component assembly i.e. forming the flow control device.

Figure 7 shows an example of the invention in more detail. It shows a cross section through the pump unit body above the cambox and shows flow pathways. The invention is positioned in the body of the pump unit above the cambox, but of course it may be positioned in any appropriate place. It shows the low pressure flow 21 from the front bearing into device (see arrow A) and high pressure path 12 comprising flow into the device 33 from IMV/cambox (arrows B) and flow from the injector backleak (arrows C). These converge along the flow path 20. There may be devices such as one or more Venturi in the path from the IMV valve and or the injector backleak flow. The flow paths 20 and 21 are arranged such that they exit the device at near equalised pressure & the combined backleak flow is shown by arrow D and exits the pump. The flow paths such as bearing flow and injector backleak/IMV flow are provided in parallel and adjacent by way of an insert.

The insert (device) 33 is shown in greater detail in figure 8.. It may be provided with an annular face seal 30 with front plate 18 by means of plug seal bung 31. The plug seal bung seals between regions of high and low pressure both within the device and between it and the front plate 18. Views of the insert 33 are shown in figure 9a and b and may include circular recesses 35 for providing requisite sealing via e.g. standard O-rings between the device and pump housing bore. The plug seal bung may be provided as a moulded unit. As can be seen from figure 9 b one or more of the pathways 21 may have a non-circular cross section.

Claims

1. A fuel pump including a housing and including at least a first flow path and a second flow path formed within said housing where at least two flow paths are arranged substantially adjacent.

2. A pump as claimed in claim 1 where said first flow path has an inlet from one pressure source and said second flow path has an inlet from another pressure source.

3. A pump as claimed in claims 1 or 2 wherein one of said flow paths is a lubrication path.

4. A pump as claimed in claim 3 wherein said inlet is from a front or rear bearing of the pump drive shaft.

5. A pump as claimed in claim 4 including a bore from one or more of said bearings to the inlet of said flow path

6. A pump as claimed in any preceding claim wherein the outlets of said flow paths converge.

7. A pump as claimed in claim 6 wherein said outlet of said flow paths forms a pump backleak path.

8. A pump as claimed in any previous claim where said second flow path includes an inlet from one or more the cambox, inlet metering valve or injector backleak.

9. A pump as claimed in any previous claim which includes a Venturi arrangement in said second flow path

10. A pump as claimed in any previous claim wherein said first and second flow paths are substantially parallel.

11. A pump as claimed in any previous claim wherein said first and second paths are provided by a common component.

12. A pump as claimed in claim 11 wherein said common component is provided as an insert.

13. A pump as claimed in claim 12 wherein said insert includes a Venturi or diffuser portion

14. A pump as claimed in any preceding claim wherein said pump housing is enclosing a pressurised cambox area.

15. A pump as claimed in claim 14 wherein said flow paths are arranged in the same region of the housing relative to the cambox.