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Title:
PUMPING ASSEMBLY TO FEED FUEL, PREFERABLY DIESEL FUEL, TO AN INTERNAL COMBUSTION ENGINE
Document Type and Number:
WIPO Patent Application WO/2017/216142
Kind Code:
A1
Abstract:
A pumping assembly to feed fuel, preferably diesel fuel, to an internal combustion engine has at least one cylinder (14), a piston (15) engaged slidingly in the cylinder (14), and a delivery valve (30) for selectively controlling the feed of the fuel to the internal combustion engine; the piston (15) being axially delimited by a free end face (42), which faces towards a shutter (38) of the delivery valve (30) and is inclined at least in part by an angle different to 90° with respect to a longitudinal axis (8) of the cylinder (14).

Inventors:
BELGIOVINE, Valeria Cecilia (Via delle Ortensie 19, Modugno, 70026, IT)
Application Number:
EP2017/064368
Publication Date:
December 21, 2017
Filing Date:
June 13, 2017
Export Citation:
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Assignee:
ROBERT BOSCH GMBH (Postfach 30 02 20, Stuttgart, 70442, DE)
International Classes:
F04B1/04; F02M59/06; F02M59/10; F02M59/46; F04B11/00
Foreign References:
US6238190B12001-05-29
DE102015116677A12016-05-12
DE102010063363A12012-06-21
DE102012200708A12013-07-25
US20160146170A12016-05-26
Other References:
None
Download PDF:
Claims:
Claims

1. Pumping assembly to feed fuel, preferably diesel fuel, to an internal combustion engine, the pumping assembly comprising a pump body (4, 9); at least one cylinder (14) formed in the pump body (4, 9) and having a longitudinal axis (8); a piston (15) engaged slidingly in the cylinder (14) and axially delimited by a free end face (42); an actuating device (16) to move the piston (15) with an intake stroke of the fuel into the cylinder (14) and with a compression stroke of the fuel present in said cylinder (14); an intake valve (29) for selectively controlling the feed of the fuel into the cylinder (14); and a delivery valve (30) for selectively controlling the feed of the fuel to the internal combustion engine; the delivery valve (30) comprising a shutter (38) facing axially towards the end face (42) of the piston (15); and being characterized in that the end face (42) is inclined at least in part by an angle different to 90° with respect to the longitudinal axis (8) of the cylinder (14).

2. Pumping assembly according to Claim 1 and further comprising a delivery duct (13b), which is coaxial with the cylinder (14) and is engaged slidingly by the shutter (38). 3. Pumping assembly to feed fuel, preferably diesel fuel, to an internal combustion engine, the pumping assembly comprising a pump body (4, 9); at least one cylinder (14) formed in the pump body (4, 9) and having a longitudinal axis (8); a piston (15) engaged slidingly in the cylinder (14) and axially delimited by a free end face (42); an actuating device (16) to move the piston (15) with an intake stroke of the fuel into the cylinder (14) and with a compression stroke of the fuel present in said cylinder (14); an intake valve (29) for selectively controlling the feed of the fuel into the cylinder (14); and a delivery valve (30) for selectively controlling the feed of the fuel to the internal combustion engine; the intake valve (29) comprising a shutter (35) facing towards the end face (42); and being characterized in that the end face (42) is inclined at least in part by an angle different to 90° with respect to the longitudinal axis (8) of the cylinder (14).

4. Pumping assembly according to Claim 3 and further comprising an intake duct (31), which is coaxial with the cylinder (14) and is engaged slidingly by the shutter (35).

5. Pumping assembly according to any one of the preceding claims, wherein the end face (42) has an inclination which is symmetrical with respect to the longitudinal axis (8) of the cylinder (14).

6. Pumping assembly according to any one of the preceding claims, wherein the end face (42) is tapered in the direction of said shutter (35; 38).

7. Pumping assembly according to any one of the preceding claims, wherein the end face (42) is frustoconical.

8. Pumping assembly according to Claim 7, wherein the end face (42) has a substantially flat central portion (43) perpendicular to the longitudinal axis (8) of the cylinder (14), and a frustoconical lateral portion (44).

9. Pumping assembly according to any one of Claims 1 to 6, wherein the end face (42) is conical.

Description:
Description Title

PUMPING ASSEMBLY TO FEED FU EL, PREFERABLY DIESEL FU EL, TO AN INTERNAL COMBUSTION ENGINE

The present invention relates to a pumping assembly to feed fuel, preferably diesel fuel, to an internal combustion engine.

In particular, the present invention relates to a pumping assembly of the type comprising a pump body; at least one cylinder formed in the pump body; a piston engaged slidingly in the cylinder; and an actuating device to move the piston with an intake stroke of the fuel into the cylinder and with a compression stroke of the fuel present in said cylinder.

The pumping assembly further comprises a duct for the intake of the fuel inside the cylinder; an intake valve mounted along the intake duct for selectively controlling the feed of the fuel into the cylinder; a duct for delivering the fuel to the internal combustion engine; and a delivery valve mounted along the delivery duct for selectively controlling the feed of the fuel to the internal combustion engine.

The delivery duct is coaxial with a longitudinal axis of the cylinder and is engaged slidingly by a shutter of the delivery valve.

The shutter of the delivery valve therefore faces axially towards the piston and is movable between a position for opening and a position for closing the delivery duct. When it is arranged in its closing position, the shutter is coupled in a fluid- tight manner to a conical seat formed in the delivery duct. The known pumping assemblies of the type described above have a number of disadvantages mainly arising from the fact that, during its compression stroke, the piston generates pressure waves inside the cylinder.

Since the piston is axially delimited by a free end face perpendicular to the longitudinal axis of the cylinder, the pressure waves bounce off between the shutter and the piston parallel to the longitudinal axis of the cylinder at least during the initial phase of the compression stroke of the piston, i.e. when the delivery valve is still closed.

The reciprocating motion of the pressure waves between the shutter and the piston causes the formation of vapour pockets, the implosion of said vapour pockets at the conical seat of the delivery duct and, as a result, cavitation wear to the shutter and to the conical seat, and therefore jeopardizes the correct fluid- tight coupling between the shutter and said conical seat.

It is an object of the present invention to provide a pumping assembly to feed fuel, preferably diesel fuel, to an internal combustion engine, which does not have the above-described disadvantages and is simple and inexpensive to produce.

According to the present invention, a pumping assembly to feed fuel, preferably diesel fuel, to an internal combustion engine is provided as claimed in the accompanying claims.

The present invention will now be described with reference to the accompanying drawings, which illustrate a non-limiting exemplary embodiment thereof, in which:

Figure 1 is a first schematic sectional view, with parts removed for clarity, of a preferred embodiment of the pumping assembly of the present invention; and

Figure 2 is a second schematic sectional view, with parts removed for clarity, of the pumping assembly shown in Figure 1. With reference to Figures 1 and 2, 1 denotes in its entirety a pumping assembly to feed fuel, preferably diesel fuel, to an internal combustion engine (not shown). The pumping assembly 1 comprises a piston pump 2 to feed the fuel to said internal combustion engine (not shown); and a pre-feed pump 3, for example a gear pump, to feed the fuel to said pump 2.

The pumping assembly 1 has a pump body comprising a support casing 4, which is provided with a central hole 5 having a longitudinal axis 6 and with at least one lateral hole 7 (normally a plurality of holes 7 distributed uniformly about the axis 6), which has a longitudinal axis 8 transverse to the axis 6 and extends radially towards the outside of the casing 4 proceeding from said hole 5.

Each hole 7 is closed by a cylinder head 9, which is arranged in contact with the casing 4 and has an extended portion 10 projecting inside the hole 7 coaxially with the axis 8.

The cylinder head 9 has a central hole 11, which is formed through the cylinder head 9 coaxially with the axis 8, and comprises an intermediate narrower portion 12 arranged between two wider portions 13a, 13b, of which the portion 13a faces towards the hole 5 and defines a cylinder 14 of the piston pump 2.

The cylinder 14 is engaged slidingly by a piston 15, which is movable, under the thrust of an actuating device 16, with a reciprocating rectilinear movement, comprising an intake stroke of the fuel into the cylinder 14 and a compression stroke of the fuel present inside said cylinder 14.

The device 16 comprises a tubular sleeve 17, which is engaged slidingly on the inside of the hole 7 coaxially with the axis 8, extends about the cylinder 14, and has an inner annular flange 18, which projects radially from an inner surface of the sleeve 17 and divides said sleeve 17 into two cylindrical portions 19, 20, of which the portion 19 faces towards the hole 5. The device 16 further has a tappet 21, comprising a substantially cylindrical coupling block 22, which is blocked by interference on the inside of the portion 19, is arranged in contact with the flange 18, and supports a cam follower 23. The cam follower 23 projects from the block 22 towards the hole 5 and is coupled in a rotatable manner to the block 22 to rotate, with respect to said block 22, about a longitudinal axis 24 thereof substantially perpendicular to the axis 8.

The flange 18 supports an annular plate 25, which extends about the piston 15, is inserted into the portion 20 of the sleeve 17 coaxially with the axis 8, and has an outer perimetral edge facing axially towards the flange 18 and an inner perimetral edge facing axially towards a head of said piston 15.

The device 16 further comprises a compression spring 26, which is mounted between the extended portion 10 and the sleeve 17 coaxially with the axis 8, and is interposed between the cylinder head 9 and the plate 25 to move, and normally keep, the plate 25 in contact with the flange 18 and the cam follower 23 in contact with a cam 27 formed on an outer surface of an intermediate portion of a drive shaft 28 mounted through the hole 5 to rotate, with respect to the casing 4, about the axis 6.

The cylinder head 9 internally houses a valve 29 for the intake of the fuel into the cylinder 14 and a valve 30 for the delivery of the fuel to the internal combustion engine (not shown).

The valve 29 is mounted on the inside of an intake duct 31 having a longitudinal axis 32 perpendicular to the axis 8, and comprises a cylindrical valve body 33, which extends about the axis 32 and is blocked axially along the duct 31 by a closing cover 34 screwed into said duct 31.

The valve 29 further comprises a shutter 35 mounted through the valve body 33 to move between a position for opening and a position for closing the valve 29. The shutter 35 is moved, and normally kept, in its closing position by a spring 36 interposed between the valve body 33 and an annular plate 37 mounted on the shutter 35 transversely to the axis 32. The valve 30 is housed inside the portion 13b and comprises a cup-shaped shutter 38, which is engaged slidingly into the portion 13b and is movable between a position for opening and a position for closing the valve 30.

The shutter 38 is moved, and normally kept, in its closing position by a spring 39 interposed between the shutter 38 and an end-stop sleeve 40 mounted on the inside of said portion 13b.

When it is arranged in its closing position, the shutter 38 is coupled in a fluid-tight manner to a conical seat 41 formed in the hole 11 between the portions 12 and 13b.

The piston 15 is axially delimited by a free end face 42, which faces towards the shutter 38 and has a shape inclined at least in part by an angle different to 90° with respect to the axis 8.

The face 42 has an inclination which is symmetrical with respect to the axis 8 and tapered towards the shutter 38. In other words, the diameter of the piston 15 decreases along the axis 8 towards the shutter 38.

In the case in question, the face 42 has a substantially flat central portion 43 perpendicular to the axis 8, and a substantially frustoconical lateral portion 44, which extends about the portion 43 coaxially with said axis 8.

According to a variant which is not shown, the face 42 has a conical shape.

In use, during its compression stroke, the piston 15 generates pressure waves inside the cylinder 14.

At least during the initial phase of the compression stroke of the piston 15, that is to say when the delivery valve 30 is still closed, the pressure waves bounce off from the face 42 mainly in directions inclined with respect to the axis 8. In other words, the pressure waves bounce off from the face 42 mainly against the side wall of the cylinder 14 and only to a limited extent against the shutter 38.

As a result, the shape of the face 42 makes it possible to limit the cavitation wear to the shutter 38 and to the conical seat 41, and thereby ensures correct fluid- tight coupling between the shutter 38 and said conical seat 41.

It goes without saying that the form of the face 42 of the piston 15 can also be utilized when the pumping assembly 1 is produced with the shutter 35 of the intake valve 29 facing towards the piston 15 and coaxial with the axis 8, and with the shutter 38 of the delivery valve 30 perpendicular to said axis 8.