GB2564868A

GB2564868A - Fuel pump

Info

Publication number: GB2564868A
Application number: GB1711906.6A
Authority: GB
Inventors: Hennig Christian; Giorgetti Basilio
Original assignee: Delphi International Operations Luxembourg SARL
Current assignee: Delphi International Operations Luxembourg SARL
Priority date: 2017-07-24
Filing date: 2017-07-24
Publication date: 2019-01-30
Also published as: GB201711906D0

Abstract

A high pressure fuel pump (10) comprising a cambox (12), a pumping head (14) and an inlet metering valve (16) adapted to receive a flow (F1) incoming from the cambox via a first conduit (C1). The flow is split into a fraction (F2) delivered to the inlet chamber (42) and a complementary in-excess fraction (F3) returned to a drain, and the first conduit (C1) opens in the lower part of the inner space (S). The opening of the first conduit may be below the axis of rotation of the cam, it may be within 45 degrees of vertical and it may be exactly on the vertical axis. The pumping axis may be 45 degrees from the horizontal. There may be a venting conduit from the inner space.

Description

TECHNICAL FIELD

The present invention relates to a high pressure pump of a fuel injection equipment of an internal combustion engine and, more particularly to an arrangement aiming at removing bubbles from a part of the fuel.

BACKGROUND OF THE INVENTION

In a diesel fuel injection equipment of an internal combustion engine, diesel fuel enters a cambox of a high pressure pump wherefrom an inlet metering valve (IMV) sucks the necessary quantity and sends it to a pumping head where it is pressurised and delivered to fuel injectors.

The cambox has a body wherein a camshaft driven in rotation between aligned bearings urges a piston guided in a bore defined in a pumping head to reciprocal displacements that cyclically vary the volume of a compression chamber defined at a blind end of said bore. Fuel flowing from the IMV enters said compression chamber via an opening controlled by an inlet valve.

In a typical embodiment of the HP pump, under the stresses generated by the pressure and the high rate of pumping cycles, cavitation occurs in the pumping head and, bubbles generated in the low pressure side travel in the cambox, enter the pumping head and exit with the pressurised fuel. Said cavitation and bubbles flowing in the main fraction alter the fuel equipment performance and pressure overshoot have been measured.

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, said pump comprising

- a cambox defining an inner space wherein a camshaft is adapted to be driven in rotation between bearings aligned along a camshaft axis set to be substantially horizontal;

- a pumping head fixed on said cambox, and comprising a piston reciprocally guided in a bore along a pumping axis perpendicular to the camshaft axis, the piston cooperating with the camshaft for varying the volume of a compression chamber wherein an inlet and an outlet open,

- an inlet valve assembly fixed on said pumping head, and comprising an inlet valve member for controlling said inlet opening from an inlet chamber to the compression chamber and,

- an inlet metering valve fixed on said cambox and adapted to receive an flow incoming from the cambox via a first conduit and, to split said flow into a main fraction delivered to the inlet chamber via a second conduit and a complementary in-excess fraction returned to a drain via a venting third conduit and wherein, the first conduit opens in the lower part of the inner space.

Also, said first conduit opens in the inner space below an horizontal plane defined by the camshaft axis and another horizontal axis perpendicular to the camshaft axis.

Also, said bottom opening of the first conduit in the inner space is within a 90° angular sector that is symmetric about a vertical axis intersecting said horizontal camshaft axis.

Preferably, said first conduit opens in the inner space on said vertical axis.

Also, said another horizontal axis and the pumping axis substantially defines a 45° between them.

Also, the inlet metering valve is arranged atop the cambox, substantially opposite the first conduit bottom opening at the bottom in the inner space.

For preventing bubbles from entering the IMV and the pumping head, the bottom entry of the first conduit and the venting opening are opposed preferably defining the vertical axis. It is not essential for the IMV to be set exactly atop the cambox not for the pumping head to be at 45°, said orientation being a suggested orientation.

Also, the high pressure fuel pump further comprises another venting conduit from the inner space, said another venting opening in upper part of the inner space.

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 sketch of a HP pump as per the invention. Figure 2 is a side view of a HP pump as per the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In reference to the figures is now described a high pressure pump 10 of a fuel injection equipment of an internal combustion engine, said pump 10 comprising a cambox 12, a pumping head 14 and an inlet metering valve (IMV) 16.

The cambox 12 has a body 18 defining an inner space S in which a camshaft 20 aligned between a front 22 and a rear bearing 24 is adapted to rotate about a camshaft axis X which, in a typical arrangement configuration is horizontal when the pump 10 is fixed in a vehicle staying of an horizontal plane.

The pumping head 14 also had a body 26 defining a blind bore 28 extending about a pumping axis P transverse to the camshaft axis X, the blind end of the bore defining partially a compression chamber 30 wherein open an inlet 32 and an outlet 34. In the bore 28 is guided a piston 36 extending from a head partially defining said compression chamber to a foot end protruding in the inner space S via an open end of the bore and cooperating with the camshaft 20 so that, in use, as the camshaft rotates about its axis X, the piston 36 reciprocally slides in the bore performing pumping cycles and alternatively varying the volume of the compression chamber. Atop the pumping head 14 is fixed an inlet valve assembly 38 which in a top hat 40 houses an inlet chamber 42 and an inlet valve member 44 controlling the inlet 34 fluid communication between the compression chamber 30 and said inlet chamber 42.

The IMV 16 has a body 46 fixed to the cambox and in which is guided a plunger regulating the fuel flow.

On figure 1, wherein the axes are referenced with angular values of a trigonometric circle, the horizontal plane is defined by the camshaft axis X, perpendicular to the figure, and an axis H (axis 0°). The IMV 16 fixed atop the cambox is arranged on the vertical axis Z (axis 90°) perpendicular to said horizontal plane. The pumping axis P (axis 45°) upwardly extends at 45° between the IMV and the horizontal plane.

The HP pump 10 further defines a first fuel conduit Cl that mainly extends in the cambox from a bottom opening 48 (axis 270°) arranged in the lower part of the inner space S to an upper opening 50 that is an inlet to the IMV. A possible routing of said first conduit Cl is presented in the side view of figure 2, the bottom opening 48 being in the bottom front area of the inner space S and said first conduit Cl extending in several portions to the other end entering the IMV. A first flow Fl corresponding to the engine needs flows in said first conduit Cl enters the IMV then is delivered to the pumping head 14 .

The pump is further provided with a venting opening 52 arranged in the upper part of inner space S, on the vertical axis Z, enabling bubbles present in the cambox following an upward natural path to exit the pump and not entering the pumping head .

The locations of the bottom opening 48 and of the venting 52 can be arranged within an angular sector of 90° around the preferred vertical values set above. The bottom opening 48 can be arranged between the axes 225° and 315° while, on the upper side, the venting 52 is between the axes 45° and 135°.

Thanks to said arrangement, bubbles generated in the LP circuit move up in the inner space S and exit the cambox 12 via said venting 52 while a the first fuel flow Fl is bubble free.

LIST OF REFERENCES

X	camshaft axis - horizontal axis
H	horizontal axis
Z	vertical axis
P	pumping axis
s	inner space
Cl	first conduit
C2	second conduit
C3	third conduit
Fl	fuel flow entering the pump
F2	main fraction
F3	in-excess fraction
10	high pressure pump
12	cambox
14	pumping head
16	inlet metering valve - IMV

body of the cambox camshaft front bearing rear bearing body of the pumping head bore compression chamber inlet outlet piston inlet valve assembly top hat inlet chamber inlet valve member body of the IMV bottom opening of the first conduit upper opening of the first conduit venting opening

Claims

1. High pressure fuel pump (10) of a fuel injection equipment of an internal combustion engine, said pump (10) comprising a cambox (12) defining an inner space (S) wherein a camshaft (20) is adapted to be driven in rotation between bearings (22, 24) aligned along a camshaft axis (X) set to be substantially horizontal, a pumping head (14) fixed on said cambox, and comprising a piston (36) reciprocally guided in a bore (28) along a pumping axis (P) perpendicular to the camshaft axis (X), the piston (36) cooperating with the camshaft (20) for varying the volume of a compression chamber (30) wherein an inlet (32) and an outlet (34) open, an inlet valve assembly (38) fixed on said pumping head (14), and comprising an inlet valve member (44) for controlling said inlet opening (32) from an inlet chamber (42) to the compression chamber (30) and, an inlet metering valve, IMV, (16) fixed on said cambox (12), and adapted to receive an flow (Fl) incoming from the cambox via a first conduit (Cl) and, to split said flow (Fl) into a main fraction (F2) delivered to the inlet chamber (42) via a second conduit (C2) and a complementary in-excess fraction (F3) returned to a drain via a venting third conduit (C3), and wherein, the first conduit (Cl) opens in the lower part of the inner space (S).

2. High pressure fuel pump (10) as claimed in the preceding claim wherein said first conduit (Cl) opens in the inner space (S) below an horizontal plane (X, H) defined by the camshaft axis (X) and another horizontal axis (H) perpendicular to the camshaft axis (X).

3. High pressure pump (10) as claimed in claim 2 wherein said bottom opening (48) of the first conduit in the inner space (S) is within a 90° angular sector that is symmetric about a vertical axis intersecting said horizontal camshaft axis (X).

4. High pressure fuel pump (10) as claimed in claim 3 wherein, preferably, said first conduit (Cl) opens in the inner space (S) on said vertical axis.

5. High pressure fuel pump (10) as claimed in any of the claims 2 to 4

5 wherein said another horizontal axis (H) and the pumping axis (P) substantially defines a 45° between them.

6. High pressure fuel pump (10) as claimed in any of the preceding claims wherein the inlet metering valve (16) is arranged atop the cambox (12),

10 substantially opposite the first conduit bottom opening (48) at the bottom in the inner space (S).

7. High pressure fuel pump (10) as claimed in any of the preceding claims further comprising another venting conduit (52) from the inner space (S), said

15 another venting opening (52) in upper part of the inner space (S).