GB2570154A

GB2570154A - High pressure diesel fuel pump

Info

Publication number: GB2570154A
Application number: GB1800600.7A
Authority: GB
Inventors: J Lane David; Ying Wai Ma Antonio
Original assignee: Delphi Technologies IP Ltd
Current assignee: Delphi Technologies IP Ltd
Priority date: 2018-01-15
Filing date: 2018-01-15
Publication date: 2019-07-17
Also published as: CN110043409A; GB201800600D0

Abstract

A high-pressure pump for i.c. engine fuel injection equipment has a camshaft 14 defining a longitudinal axis X and two, three or more pumping units 16, 18 arranged perpendicular to the axis X, the axes Z16, Z18 of the pumping units being offset both longitudinally (OL, fig.3) and angularly (OAP, fig.2) with respect to each other. The pump may be a V-type pump with two identical pumping units angularly offset by 45o and cooperating with a dedicated cam 28, 30 of the camshaft 14. The cams 28, 30 may be single lobe or bi-lobe cams. The major axes of the cams 28, 30 may be offset angularly with respect to one another; the angular offset OAC may be different from the angular offset (OAP) of the pumping axes. Each pumping unit 16, 18 may be longitudinally larger than the longitudinal offset (OL, fig.3) between the pumping units.

Description

HIGH PRESSURE DIESEL FUEL PUMP

TECHNICAL FIELD

The present invention relates to multi-high-pressure-head-diesel-pump .

BACKGROUND OF THE INVENTION

A fuel injection equipment (FIE) of an internal combustion engine is provided with a HP pump wherein fuel enters at low pressure and is pressurised to several thousands of bars prior to be delivered to a common rail that distributes said HP fuel to fuel injectors.

The pump typically comprises a rotating camshaft urging a piston perpendicular to the camshaft to reciprocate between BDC and TDC extreme positions so to vary the volume of a compression chamber defined in a pumping head further provided with a fuel inlet, a fuel outlet, an electric connector and screws for fixing said head on the body of the pump.

Engine size and other fuel injection equipment’s parameters have lead toward HP multi-head-pumps having a single camshaft cooperating with several pistons, as many as there are pumping heads.

In a first embodiment, a multi-head-pump has a coplanar arrangement of the camshaft and the piston axes, in said “in-line” pumps each piston cooperates with a dedicated cam, the camshaft being provided with as many cams as there are pistons and pumping heads.

The simple architecture of in-line pumps enable easy manufacturing of the pump body and, easy assembly with straight inlet lines and easy HP outlet lines,. Said pumps have a rather thin width transversal to the camshaft but an important axial length driven by the tessellation of the heads next to one another. Also, the pump designer is provided with a design-to-operation freedom thanks to the plurality of cam-piston pairs. This freedom enables tuning the pump to each specific engine application with individual cam profile and individual cam angular orientation.

In a second embodiment another multi-head-pump architecture is a startype pump wherein the camshaft axis is normal to the plan wherein all the pistons axes are angularly distributed. This architecture enables a smaller pump length and reduced pump weight since the camshaft has only one cam cooperating which all the pistons, the star array enabling the arrangement of the multiple large pumping heads. An problem with said star-type embodiment is that said one cam sees the load from all the pistons generating fatigue cracks, wear and durability issues. V-type or flat-twin are well known architectures for two-head pumps.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to resolve the above mentioned problems in providing a pump for fuel injection equipment of an internal combustion engine, said pump being provided with a camshaft defining a longitudinal axis and a plurality of pumping units each extending along a pumping axis perpendicular to the longitudinal axis. Said pumping axes are offset longitudinally and angularly with respect to each other.

In another aspect of the invention, each pumping unit may define a compression chamber which volume is cyclically varied by a dedicated piston reciprocally moving along one of the pumping axes between and the foot end of said piston with a cam of the camshaft via a cam follower.

The camshaft may comprise a plurality of cams longitudinally offset with one another, each cam cooperating with one pumping unit each cam being a single lobe cam or a multi-lobe cam.

Each of said cam defines a major axis, said major axes being offset longitudinally and angularly with respect to one another, said major axes angular offset differing from the pumping axes angular offset and, the pumping axes and the cam major axes having same longitudinal offset.

In an embodiment, the longitudinal offset between two adjacent pumping axes may be constant.

Each pumping unit may be longitudinally larger than said longitudinal offset.

In a particular embodiment, the pump may only have two pumping units angularly offset by substantially 45°.

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 3D view of a V-type pump as per the invention, the pump body not being represented to enable better visualization.

Figure 2 is a section of the pump of figure 1 through a plan transverse to the longitudinal axis of the pump.

Figure 3 is a section of the pump of figures 1 and 2 through a longitudinal plan of the pump.

Figure 4 is a plot of the pumping cycles of the pump of figure 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In reference to the figures is described a V-type high pressure pump 10 adapted to be arranged in a fuel injection equipment of an internal combustion engine. Said pump 10 has a body 12, not shown on figure 1, in which is arranged a camshaft 14 extending along a longitudinal axis X and cooperating with two pumping units 16, 18.

The camshaft 14 comprises a cylindrical front wheel 20 engaged in a front bushing to form a front bearing 22, a cylindrical rear wheel 24 engaged in a rear bushing to form a rear bearing 26 and, between said front 20 and rear 24 wheels the camshaft comprises a first cam 28 and a second cam 30, the wheels 20, 24 and the cams 28, 30 being coaxially arranged adjacent to one another. A front end member 32 of the camshaft 14 extends beyond the front wheel 20 defining a sloped face and a threaded end adapted to engage with driving means such as a gear or a pulley. Depending on the application, the cams can be single or multilobe cam, the cams represented in the example shown being bi-lobe cams, the two lobes of each cam being diametrically opposed each defining a major axis A28, A30 joining the summit of said two lobes.

A single lobe cam also defines a major axis intersecting the longitudinal axis and joining the lobe summit and, in the case of a cam having three or more lobes, the major axis intersects the longitudinal axis and joins one of the lobe summit. On the example shown, the major axis A28, A30 are angularly offset OAC by 135°.

The two pumping units are identical, the first pumping unit 16 cooperating with the first cam 28 and, the second pumping unit 18 cooperating with the second cam 30.

The first pumping units 16 is elongated along a first pumping axis Z16 comprising a piston extending from a foot that cooperates with a first cam follower 16F to a head protruding in a compression chamber. Said first cam follower 16F is urged against the outer face of said first cam 28 by a first spring compressed between said first cam follower 16F and a face of a first pumping head 16H that internally defines said compression chamber. The first pumping head 16H further comprises a first inlet 161, a first electric connector 16C internally connected to an electro-actuator cooperating with an inlet valve, and also two screws 34 for fixing the first pumping head 16H onto the pump body 12.

Similarly, the second pumping unit 18 is elongated along a second pumping axis Z18 comprising a piston extending from a foot that cooperates with a second cam follower 18F to a head protruding in a compression chamber. Said second cam follower 18F is urged against the outer face of said second cam 30 by a second spring compressed between said second cam follower 18F and a face of a second pumping head 18H that internally defines said compression chamber. The second pumping head 18H further comprises a second inlet 181, a second electric connector 18C internally connected to an electro-actuator cooperating with an inlet valve, and also two screws 34 for fixing the second pumping head 18H onto the pump body 12.

The first Z16 and second Z18 pumping axes are both perpendicular to the longitudinal axis X and are longitudinally offset OL by a distance that is the longitudinal distance between the first 28 and second 30 cam and, they are also angularly offset by an angle OAP with one another. In the example shown the angular offset OAP between the pumping axes is 45°.

In use, the camshaft 14 rotates about said longitudinal axis X and, figure 4 represents the plots the pumping cycles of the first 16 and of the second 18 pumping units on an x-y diagram, the x-axis being the angles of rotation of the camshaft and, the y-axis being the displacements between BDC and TDC. The first and second pistons reciprocate along their respective pumping axes Z16, Z18, the pumping cycles ranging between BDC and TDC. The curves may be sinusoids or other depending on the cam profile. The cams being symmetrical bi-lobes cams, in one rotation of the camshaft, each piston travels twice between BDC and TDC, said curves having a period of 180°. Also, the two curves are offset to one another to achieve, in this case of a bi-lobe cam setup, a 90° phasing between the instant alternate pump modules reach TDC. This is achieved by designing the sum of the pumping angular offset (OAP) and the cam angular offset (OAC) relative to Z16 to be 90°. In the illustrated embodiment, the sum of OAP (45°) and the cam angular axis OAC (135°) achieves the desired value of 90°.

The pumping heads 16H, 18H are quite large members considering the fuel inlets, the connector and the screws arranged at the periphery of the heads. Thanks to the pumping units angular offset OAP the heads are away from one another and, the longitudinal offset OL can be minimized to be smaller than the longitudinal width of the heads. Therefore the overall longitudinal length of the Vtype pump 10 is smaller than the length of an equivalent “in-line” pump of the prior art, equivalent meaning having same number of pumping units. Also, the pump arrangement wherein each of the pumping heads cooperates with a dedicated cam halves the duty cycle of the cam lobe resolving the durability issues of known V-type pumps and it provides a design freedom wherein said cam angular offset OAC is chosen upon each application of injection equipment. The designer can choose each pumping curve independently from the other pumping curves. In a V-type pump of the prior art wherein the two heads cooperate with the same cam, the angular offset between the curves of the pumping cycles is the angular offset between the pumping axes and, there is no freedom of choice between the compactness of the pump and the pump efficiency requiring a particular pumping curve offset.

Similar benefits of design freedom can be achieved with pumps having three or more pumping units, each unit being angularly offset OAP relative to the others and, each of said units cooperating with a dedicated cam of the camshaft, each cam having a specific special orientation.

LIST OF REFERENCES

X longitudinal axis

Z16 first pumping axis

Z18 second pumping axi s

A28 major axis of the first cam

A30 major axis of the second cam

OLC longitudinal offset

OAC angular offset between the cams

OAP angular offset between the pumping units high pressure pump body camshaft first pumping unit

16F first cam follower

16H first pumping head

161 first inlet

16C first electric connector second pumping unit

18F second cam follower

18H second pumping head

181 second inlet

18C second electric connector front wheel front bearing rear wheel rear bearing first cam second cam front end member screw

Claims

CLAIMS:

1. Pump (10) for fuel injection equipment of an internal combustion engine, said pump being provided with a camshaft (14) defining a longitudinal axis (X) and a plurality of pumping units (16, 18) each extending along a pumping axis (Z16, Z18) perpendicular to the longitudinal axis (X), said pumping axes (Z16, Z18) being offset longitudinally (OL) and angularly (OAP) with respect to each other.

2. Pump (10) as claimed in the preceding claim wherein each pumping unit (16, 18) defines a compression chamber which volume is cyclically varied by a dedicated piston reciprocally moving along one of the pumping axes (Z16, Z18) between BDC and TDC, the foot end of said piston with a cam (28, 30) of the camshaft via a cam follower (16F, 18F).

3. Pump (10) as claimed in claim 2 wherein the camshaft (14) comprises a plurality of cams (28, 30) longitudinally offset (OL) with one another, each cam cooperating with one pumping unit (16, 18).

4. Pump (10) as claimed claim 3 wherein each cam is a single lobe cam.

5. Pump (10) as claimed claim 3 wherein each cam is a multi-lobe cam.

6. Pump (10) as claimed in any one of the claims 4 or 5 wherein each of said cam (28, 30) defines a major axis (A28, A30), said major axes being offset longitudinally (OL) and angularly (OAC) with respect to one another.

7. Pump (10) as claimed in claim 6 wherein said major axes angular offset (OAC) differs from the pumping axes angular offset (OAP).

8. Pump (10) as claimed in claim 7 wherein the pumping axes (Z16, Z18) and the major axes (A28, A30) have same longitudinal offset (OL).

9. Pump (10) as claimed as in any one of the preceding claims wherein the longitudinal offset (OL) between two adjacent pumping axes is constant.

10. Pump (10) as claimed in claim 9 wherein the each pumping unit is

5 longitudinally larger than said longitudinal offset (OL).

11. Pump (10) as claimed in any one of the preceding claims wherein the pump (10) has only two pumping units (16, 18) angularly offset (OAP) by substantially 45°.