WO2019120887A1

WO2019120887A1 - Pump for feeding high-pressure fuel to an internal-combustion engine

Info

Publication number: WO2019120887A1
Application number: PCT/EP2018/082482
Authority: WO
Inventors: Alessandro De Luca; Antonio Grimaldi; Vittorio Caroli
Original assignee: Robert Bosch Gmbh
Priority date: 2017-12-21
Filing date: 2018-11-26
Publication date: 2019-06-27

Abstract

Pump (1) for feeding high-pressure fuel to an internal combustion engine, of the type comprising a pump body (2) and an actuating shaft (3) which is housed in an axially rotatable manner inside the pump body (2); the pump body (2) being provided with one or more internal fuel flow ducts (17,21) through which the fuel flows to and from a variable-volume pumping chamber (12); and being at least partially made of metallic material by means of 3D printing; at least one of said internal fuel flow ducts (17, 21) being formed during stratification of the part.

Description

Title

PUMP FOR FEEDING HIGH-PRESSURE FUEL TO AN INTERNAL-

COMBUSTION ENGINE

The present invention relates to a pump for feeding high-pressure fuel to an internal-combustion engine.

In greater detail, the present invention relates to a high-pressure pump for fuel supply systems of the "common rail" type, to which the description below will make specific reference without thereby losing its general character.

As is known, high-pressure pumps for the latest common rail systems comprise: a pump body which is usually structured so as to be fixed onto the engine block of the combustion engine; an actuating shaft, which is inserted in an axially rotatable manner inside the pump body, is provided with at least one lobe-shaped cam and is designed to be connected to the driving shaft of the combustion engine so as to be rotationally driven by it; and a plurality of head-pieces each of which is placed so as to close the distal end/inlet of a respective radial cylindrical cavity which extends inside the pump body perpendicularly with respect to the longitudinal axis of the actuating shaft and has the inlet/proximal end directly facing the peripheral surface of the lobe-shaped cam of the actuating shaft.

Usually the radial cylindrical cavities are moreover angularly spaced at the same distance from each other around the longitudinal axis of rotation of the actuating shaft.

The aforementioned feed pumps in addition comprise, for each radial cylindrical cavity of the pump body, also a pumping piston and a helical opposition spring. The pumping piston has an oblong form and is inserted in an axially sliding manner inside a cylindrical cavity which extends inside the head-piece coaxially with the corresponding radial cylindrical cavity of the pump body and is closed at the top so that the piston forms/defines, inside the said head-piece, a variable- volume pumping chamber.

The piston is also designed with dimensions such as to protrude from the head- piece and extend projecting inside the corresponding radial cylindrical cavity of the pump body until it is arranged against the peripheral surface of the lobe shaped cam of the actuating shaft.

Each helical opposition spring, instead, is positioned inside the radial cylindrical cavity, with a first end bearing against the head-piece and a second end bearing against the bottom end of the pumping piston, and is structured so as to oppose the return upward movement of the piston inside the cylindrical cavity of the head-piece and at the same time keep the bottom end of the piston always in contact with the peripheral surface of the lobe-shaped cam.

Each head-piece of the pump moreover is provided with an intake valve and a delivery valve which are positioned alongside the variable-volume chamber and control the entry and exit of the fuel into/from the variable-volume chamber.

In greater detail, the intake valve is arranged between the variable-volume chamber and a fuel supply duct, which extends inside the head-piece and the pump body as far as the delivery of an auxiliary gear pump, which is in turn fixed directly onto the pump body, on the outside thereof, and is rotationally driven by the actuating shaft of the high-pressure pump.

The delivery valve, instead, is arranged between the variable-volume chamber and a fuel discharge duct which extends inside the head-piece and the pump body as far a hydraulic connector which is intended to be connected directly to the high-pressure fuel distribution header of the common rail system. At present the pump body is made by means of die- casting and the internal fuel flow ducts are produced subsequently by forming directly in the die-cast part a series of blind cylindrical holes or through-holes which intersect each other and are hermetically closed off at the ends by special screw-type closing plugs and washers made of copper.

However, the arrangement and the dimensions (diameter and/or length) of the single holes formed in the pump body are dependent on the form of the die-cast part, with all the associated problems as regards the fuel flow to and from the variable-volume chamber. The right-angled bends and sudden changes in diameter of the ducts in fact result in significant head losses in the fuel flow to and from the variable-volume chamber.

In addition, the positioning of the closing plugs in the die-cast part is a relatively delicate and laborious operation which, if performed incorrectly, may result in the long run in fuel leakages which may also be of a major nature, thus adversely affecting operation of the pump.

Finally, the closing plugs and the washers increase the overall weight of the pump body.

The object of the present invention is to provide a pump body in which the fuel flow ducts have dimensions such as to minimize the head losses of the fuel flow entering and exiting the variable-volume chamber and which is also lighter and stronger than the currently known pump bodies.

In accordance with these aims, according to the present invention, a pump for feeding high-pressure fuel to an internal-combustion engine is provided, as defined in Claim 1 and preferably, but not necessarily, in any one of the claims dependent thereon.

The present invention will now be described with reference to the accompanying drawings which illustrate a non-limiting example of embodiment thereof, in which: - Figure 1 is a side view, with parts cross-sectioned and parts removed for greater clarity, of a pump for feeding high-pressure fuel to an internal-combustion engine, provided in accordance with the principles of the present invention;

- Figure 2 is a side view of the bottom part of the pump shown in Figure 1, with parts cross-sectioned and parts removed for greater clarity; while

- Figures 3 and 4 are two cross-sectional views of a part of the pump body shown in Figure 2, during production of the part.

With reference to Figures 1 and 2, the number 1 denotes overall a fuel pump which is able to feed high-pressure fuel to an internal-combustion engine (not shown) and which may be advantageously used in plants for feeding the fuel to a combustion engine.

In greater detail, the pump 1 may be advantageously used in modern-day fuel feed systems of the common rail type which are usually used to feed high- pressure diesel fuel to a diesel combustion engine.

The pump 1 firstly comprises: an outer casing or pump body 2 which is preferably structured so as to be fixed to the engine block of the internal-combustion engine (not shown); and an actuating shaft 3 which is housed in an axially rotatable manner inside the pump body 2, preferably with special bearings and/or bushes arranged in between, so as to be able to rotate freely about its longitudinal axis A. At least one lobe-shaped cam 4 is also positioned along the section/segment of the actuating shaft 3 situated inside the pump body 2 and is preferably formed as one piece with the said actuating shaft 3.

In addition, the actuating shaft 3 is preferably structured/designed with dimensions so as to protrude projecting from the pump body 2 with a first axial end. Preferably this axial end is also structured so as to be mechanically connected to the driving shaft of the combustion engine (not shown) so that the actuating shaft 3 is rotationally driven by the combustion engine. The outer casing or pump body 2 is therefore provided with a longitudinal oblong cavity 5 for receiving/containing at least the segment of the actuating shaft 3 provided with the lobe-shaped cam(s) 4.

The pump 1 in addition also comprises at least one head-piece 6, which is firmly fixed on the pump body 2 so as to close the distal end/opening of an oblong radial cavity 7, preferably with a substantially cylindrical shape, which branches off from the longitudinal cavity 5 and extends inside the pump body 2 coaxial with a reference axis B transverse to the longitudinal axis A of the actuating shaft 3.

In greater detail, the axis B of the oblong radial cavity 7 is preferably substantially perpendicular to the longitudinal axis A of the actuating shaft 3.

The proximal end/opening of the oblong radial cavity 7 also directly faces the periphery of the lobe-shaped cam 4 positioned on the actuating shaft 3.

With reference to Figures 1, 2, 3 and 4, in the example shown, in particular, the pump body 2 preferably comprises: a monobloc 8 of metallic material which is provided with an oblong seat designed to receive/contain at least the segment of the actuating shaft 3 provided with the lobe-shaped cam(s) 4 and is preferably structured so as to be fixed onto the engine block of the internal-combustion engine (not shown); and an annular locking ring 9 which is fitted onto the actuating shaft 3 preferably in a fluid-tight manner and is also firmly fixed in a fluid-tight manner on the monobloc 8, so as to close off the inlet opening of the oblong seat of the latter.

With reference to Figure 1, the pump 1 also comprises a pumping piston 10 with an oblong shape which is inserted in an axially sliding manner inside a corresponding oblong cavity 11 which extends inside the head-piece 6 so as to be aligned and facing the oblong radial cavity 7 of the pump body 2.

In greater detail, the oblong cavity 11 extends inside the head-piece 6, preferably remaining coaxial with a reference axis C which is substantially parallel and optionally also coincides with the longitudinal axis B of the oblong radial cavity 7. The oblong cavity 11 also has a cross-section complementing that of the piston 10 and is closed at the top so that the piston 10 forms/defines, inside the head- piece 6, a small closed variable-volume chamber 12 intended to receive the fuel to be pumped to the internal-combustion engine (not shown).

The pumping piston 10 therefore extends inside the head-piece 6 coaxial with the axis C.

Preferably, the piston 10 is also designed with dimensions such as to protrude from the head-piece 6 and extend projecting inside the oblong radial cavity 7 of the pump body 2, towards the actuating shaft 3, until it reaches and is arranged with the bottom end bearing against the peripheral surface of the lobe-shaped cam 4 of the actuating shaft 3.

In the example shown, in particular, the piston 10 has preferably a substantially cylindrical shape.

With reference to figure 1, the pump 1 also comprises a resilient opposition member 13 which is designed to oppose the return upward movement of the piston 10 inside the oblong cavity 11 and at the same time keep the bottom end of the piston 10 always resting on the peripheral surface of the lobe-shaped cam 4.

Rotating about the axis A, the actuating shaft 3 is therefore able to impart to the piston 10 an alternating rectilinear movement inside the cylindrical cavity 11, with a consequent cyclical variation of the volume of the variable-volume chamber 12 present inside the head-piece 6.

With reference to Figure 1, in the example shown, in particular, the bottom end of the piston 10 preferably rests on the peripheral surface of the lobe-shaped cam 4 by means of a revolving tappet assembly 14 which is arranged in between and is preferably integral with the bottom end of the piston 10 and engages in an axially slidable manner the bottom section of the radial cavity 7. The resilient opposition member 13 instead preferably consists of a helical spring which extends inside the oblong radial cavity 7, remaining locally coaxial with the pumping piston 10 so as to have a first end in bearing contact against the head- piece 6 and a second end bearing against the revolving tappet assembly 14 which, in turn, is rigidly fixed to the bottom end of the pumping piston 10. Preferably the helical spring is also fitted onto an ogive-shaped end portion of the head-piece 6 which extends inside the oblong radial cavity 7.

With reference to Figure 1, the head-piece 6 of the pump 1 is also provided with an intake valve 15 and a delivery valve 16 which are preferably positioned alongside the variable-volume chamber 12 and respectively control the entry and exit of the fuel into/from the variable-volume chamber 12.

In greater detail, the intake valve 15 is structured so as to allow the automatic entry of the low-pressure fuel inside the variable-volume chamber 12, when the piston 10 moves down inside the oblong cavity 11, causing an increase in the volume of the variable-volume chamber 12. The delivery valve 16, instead, is structured so as to allow the automatic expulsion of the high-pressure fuel from the variable-volume chamber 12, when the piston 10 moves back up inside the oblong cavity 11, causing a reduction in the volume of the variable-volume chamber 12.

With reference to Figures 1, 2, 3 and 4, the outer casing or pump body 2 is also provided with one or more internal fuel flow ducts through which the fuel flows to and from the variable-volume chamber 12, and is at least partially made of metallic material by means of 3D printing. In addition said one or more internal fuel flow ducts is/are formed during 3D printing of the pump body 2, namely during stratification of the part.

In greater detail, the pump body 2 is at least partially made of metallic material by means of three-dimensional sintering printing.

In other words the pump body 2 is preferably at least partially made of metallic material by means of 3D printing using DMLS (Direct Metal Laser Beam Sintering) technology or using LENS (Laser Engineered Net Shaping) technology or using MMLD (Multi-Materials Laser Densification) technology or using SLS (Selective Laser Sintering) technology.

In greater detail, in the example shown the monobloc 8 of the pump body 2 is preferably made of metallic material by means of 3D printing, and at least one of the internal fuel flow ducts extends inside the monobloc 8 and is formed during 3D printing of the monobloc 8.

Preferably the monobloc 8 of the pump body 2 is also made of aluminium or aluminium alloy.

With reference to Figures 1 and 2, in particular, the intake valve 15 is preferably arranged between the variable-volume chamber 12 and a fuel supply duct 17 which extends in succession inside the head-piece 6 and the pump body 2, and at least one section of the fuel supply duct 17 is preferably formed during 3D printing of the pump body 2.

In greater detail, in the example shown, at least one section of the fuel supply duct 17 extends inside a wall of the monobloc 8 and is preferably formed inside said wall during 3D printing of the monobloc 8.

In other words, the fuel supply duct 17 is one of the internal fuel flow ducts through which the fuel flows to and from the variable-volume chamber 12.

Preferably the fuel supply duct 17 also communicates with the delivery of an auxiliary feed pump 19 which is preferably fixed directly onto the pump body 2, on the outside of the said pump body 2.

In greater detail the pump body 2 is preferably provided externally with an interface seat or area 20 structured so as to be able to be connected to the auxiliary feed pump 19, and the fuel supply duct 17 preferably terminates in said interface seat or area 20. Preferably, the auxiliary feed pump 19 is also mechanically connected to the actuating shaft 3 so as to be rotationally driven by the latter.

In greater detail, in the example shown, the interface seat or area 20 is preferably formed directly on the monobloc 8, on the opposite side to the inlet opening of the oblong seat which houses the actuating shaft 3 and the lobe-shaped cam 4, so as to be aligned with the actuating shaft 3.

Preferably a second axial end of the actuating shaft 3 moreover protrudes projecting from the interface seat or area 20, and the auxiliary feed pump 19 is preferably connected to said second axial end of the actuating shaft 3 so as to be rotationally driven by the latter.

In the example shown, moreover, the auxiliary feed pump 19 is preferably a gear pump.

With reference to Figures 1, 2, 3 and 4, preferably the pump body 2 is moreover provided also with at least one damping cavity 22 which communicates directly with the fuel supply duct 17 and has dimensions such as to be able to dampen the pressure peaks of the fuel which flows along the fuel supply duct 17 towards the intake valve 15.

In the same way as for the fuel supply duct 17, the damping cavity 22 is preferably formed during 3D printing of the pump body 2.

In greater detail, in the example shown, the damping cavity 22 is preferably positioned inside a wall of the monobloc 8 and is preferably formed during 3D printing of the monobloc 8.

In the example shown, in particular, the damping cavity 22 has preferably a substantially spherical shape and is preferably positioned inside the pump body 2, adjacent to the fuel supply duct 17. Preferably, the damping cavity 22 also communicates with the fuel supply duct 17 by means of a small connecting duct 23 which is preferably formed during 3D printing of the monobloc 8. With reference to Figures 1 and 2, the delivery valve 16 instead is arranged between the variable-volume chamber 12 and a fuel delivery duct 21 which is able to convey the high-pressure fuel outside of the pump 1 and extends inside the head-portion 6 and optionally also inside the pump body 2, preferably as far as a hydraulic connector (not shown) which allows the pump 1 to be connected in a known manner to the high-pressure fuel distribution header (not shown) of the common rail system.

Preferably also any section of the fuel delivery duct 21 which extends inside the pump body 2, or more particularly inside the monobloc 8, is preferably formed during 3D printing of the pump body 2 or more particularly inside the monobloc 8.

The operating principle of the pump 1 may be easily determined from that described above and does not require further explanation.

The advantages associated with the manufacture of the pump body 2 by means of three-dimensional printing are considerable.

Firstly, 3D printing of the pump body 2 allows the formation at the same time of the internal fuel flow ducts, simplifying the production of the component.

In fact, the blind cylindrical holes or through-holes which intersect each other to form the internal fuel flow ducts need no longer be formed on the monobloc 8. In addition it is no longer necessary to insert the various closing plugs in the monobloc 8, reducing the overall weight of the part.

In addition, owing to 3D printing, it is possible to optimize the shape and cross- section of the internal fuel flow ducts so as to minimize the head losses in the fuel flow to and from the variable-volume chamber 12.

Moreover, the possibility of connecting the fuel supply duct 17 to one or more damping cavities 22 improves the performance of the pump 1. Furthermore, owing to 3D printing, it is possible to vary locally the composition of the alloy during stratification of the monobloc 8 so as to increase the hardness and/or strength in specific points of the part. Finally, owing to 3D printing, it is possible to obtain a monobloc 8 which has a porosity substantially less than that of a similar die-cast part, increasing substantially the overall rigidity of the part.

Finally it is clear that the pump 1 may be subject to modifications and variations without departing from the scope of the present invention.

For example, the pump body 2 may be provided with a plurality of oblong radial cavities 7, each of which is closed by a respective head-piece 6 which in turn houses a pumping piston 10 able to be moved by the actuating shaft 3. Preferably the oblong radial cavities 7 are angularly spaced at the same distance from each other around the longitudinal axis A of the actuating shaft 3.

Claims

1. Pump (1) for feeding high-pressure fuel to an internal combustion engine, of the type comprising a pump body (2) and an actuating shaft (3) which is housed in an axially rotatable manner inside the pump body (2); the pump body (2) being provided with one or more internal fuel flow ducts (17, 21) through which the fuel flows to and from a variable-volume pumping chamber (12);

said pump (1) being characterized in that the pump body (2) is at least partially made of metallic material by means of 3D printing, and at least one of said internal fuel flow ducts (17, 21) is formed during 3D printing of the said pump body (2).

2. Pump according to Claim 1, characterized in that the pump body (2) is at least partially made of metallic material by means of three-dimensional sintering printing.

3. Pump according to Claim 2, characterized in that the pump body (2) is at least partially made by means of Direct Metal Laser Beam Sintering or by means of Laser Engineered Net Shaping or by means of Multi-Materials Laser Densification or by means of Selective Laser Sintering.

4. Pump according to any one of the preceding claims, characterized in that the pump body (2) comprises a monobloc (8) which is provided with an oblique seat able to receive the actuating shaft (3) and is also made of metallic material by means of 3D printing; at least one of the internal fuel flow ducts (17, 21) extending inside the monobloc (8) and being formed during 3D printing of said monobloc (8).

5. Pump according to Claim 4, characterized in that the pump body (2) also comprises an annular locking ring (9) which is fitted onto the actuating shaft (3) and is also fixed onto the monobloc (8) so as to close the inlet opening of the oblong seat of said monobloc (8).

6. Pump according to any one of the preceding claims, characterized in that at least one lobe-shaped cam (4) is positioned on a segment of the actuating shaft (3) inside the pump body (2).

7. Pump according to any one of the preceding claims, characterized in that it comprises at least one head-piece (6) which is positioned so as to close the distal end of a corresponding oblong radial cavity (7) which branches off from the longitudinal cavity (5) of the pump body (2) housing the actuating shaft (3) and extends inside the pump body (2) coaxial with a reference axis (B) transverse to the longitudinal axis (A) of said actuating shaft (3).

8. Pump according to Claim 7, characterized in that it also comprises, for each head-piece (6): an oblong pumping piston (10) which is inserted in an axially sliding manner inside the head-piece (6) forming said pumping chamber (12) and extends projecting from the head-piece (6) and along the oblong radial cavity (7) as far as the actuating shaft (3); and an intake valve (15) and a delivery valve (16) which are positioned in the head-piece (5) and control respectively the entry and exit of the fuel into/from the pumping chamber (12).

9. Pump according to Claim 8, characterized in that the intake valve (15) is arranged between the pumping chamber (12) and a fuel supply duct (17) which communicates with the delivery of an auxiliary feed pump (19) fixed on the outside of the pump body (2); said fuel supply duct (17) being one of the internal fuel flow ducts (17, 21) formed during 3D printing of the pump body (2).

10. Pump according to Claim 9, characterized in that it also comprises at least one damping cavity (22) which communicates directly with the fuel supply duct (17) and has dimensions such as to be able to dampen the pressure peaks of the fuel which flows along the fuel supply duct (17) towards the intake valve (15).

11. Pump according to Claim 10, characterized in that said damping cavity (22) is formed during 3D printing of the pump body (2).