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Title:
PUMP UNIT FOR FEEDING FUEL, PREFERABLY DIESEL FUEL, TO AN INTERNAL COMBUSTION ENGINE
Document Type and Number:
WIPO Patent Application WO/2016/124295
Kind Code:
A1
Abstract:
A pump unit for feeding fuel, preferably diesel fuel, to an internal combustion engine (3) is provided with a gear pump (7) having an inner gear (36) mounted inside a outer gear formed in a rotor (27) of an electric motor (24) for actuating said gear pump (7); the rotor (27) having an inner annular element (28) defining the outer gear and an outer magnetic ring (32) engaged rotatably in a stator (25) of the electric motor (24).

Inventors:
MEDORO, Nello (Via Martiri di via Fani 45, Trinitapoli, 71049, IT)
Application Number:
EP2015/080517
Publication Date:
August 11, 2016
Filing Date:
December 18, 2015
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
ROBERT BOSCH GMBH (Postfach 30 02 20, Stuttgart, 70442, DE)
International Classes:
F04C2/08; F04C2/10; F04C15/00
Foreign References:
DE102010041995A12012-04-05
DE102009028154A12011-02-03
DE102006037177A12008-02-14
DE10334003A12004-02-05
Download PDF:
Claims:
CLAI MS

1. Pump unit for feeding fuel, preferably diesel fuel, to an internal combustion engine (3), the pump unit comprising a high-pressure pump (6) for feeding the fuel to the internal combustion engine (3); and a gear pump (7) for feeding the fuel to the high-pressure pump (6); the gear pump (7) comprising an electric motor (24) comprising, in turn, a stator (25), an annular rotor (27) engaged rotatably in the stator (25) so as to rotate about a first axis of rotation (26), and an outer gear formed on the rotor (27); and an inner gear (36) mounted inside and engaged with said outer gear so as to rotate about a second axis of rotation (37) parallel to and separate from said first axis of rotation (26); and being characterized in that the rotor (27) comprises an inner annular element (28) on which the outer gear is formed and an outer magnetic ring (32) joined in angularly fixed manner to the inner annular element (28).

2. Pump unit according to Claim 1, wherein the outer magnetic ring (32) is joined in an angularly fixed manner to the inner annular element (28) by means of bonding and/or an interference fit and/or a splined joint.

3. Pump unit according to Claim 1 or 2, wherein the rotor (27) further comprises a coating layer (35) which is applied onto an outer surface (34) of the outer magnetic ring (32) and is arranged between the outer magnetic ring (32) and the stator (25).

4. Pump unit according to Claim 3, wherein the coating layer (35) is made of metallic material, in particular nickel.

5. Pump unit according to Claim 3, wherein the coating layer (35) is made of ceramic material.

6. Pump unit according to any one of the preceding claims, wherein the outer magnetic ring (32) comprises a ferromagnetic material incorporated within a plastic material.

7. Pump unit according to any one of the preceding claims, wherein the inner annular element (28) is bounded by a cylindrical outer surface (30) coaxial with the first axis of rotation (26) and the outer magnetic ring (32) is bounded by a cylindrical inner surface (33) and by a cylindrical outer surface (34) which are coaxial with said first axis of rotation (26).

8 . Pump unit according to any one of the preceding claims, wherein the inner gear (36) has outer teeth (38) meshing with inner teeth (29) of the outer gear.

9 . Pump unit according to Claim 8, wherein the two sets of teeth (29, 38) are formed so as to define a plurality of variable-volume chambers (39) which are joined together in a fluid-tight manner and are connected hydraulically partly to a fuel inlet (40) of the gear pump (7) and partly to a fuel outlet (41) of said gear pump (7).

Description:
Description

Title

PUMP UNIT FOR FEEDING FU EL, PREFERABLY DIESEL FU EL, TO AN INTERNAL COMBUSTION ENGINE

The present invention relates to a pump unit for feeding fuel, preferably diesel fuel, from a storage tank to an internal combustion engine.

In particular the present invention relates to a pump unit of the type comprising a high-pressure pump, for example a piston pump, designed to supply the fuel to an internal combustion engine; and a pre-feed pump designed to supply the fuel from a storage tank to the high-pressure pump. The pump unit is further provided with a hydraulic circuit comprising a first branch for connecting together the storage tank and the pre-feed pump, a second branch for connecting together the pre-feed pump and the high- pressure pump, and a third branch for connecting together the high-pressure pump and the internal combustion engine.

The pre-feed pump is an electric gear pump comprising a pump body, and a synchronous, brushless, permanent-magnet, electric motor housed inside said pump body.

The electric motor comprises an annular-shaped stator engaged rotatably by an annular-shaped rotor mounted so as to rotate about an axis of rotation coinciding with a longitudinal axis of said stator.

The rotor has inner teeth and defines an outer gear of the gear pump which further comprises an annular-shaped inner gear seated inside the rotor. The inner gear is mounted so as to rotate about an axis of rotation which is eccentric with respect to the axis of rotation of the rotor and has outer teeth meshing with the inner teeth of said rotor.

The two sets of teeth are formed so as to define a plurality of variable- volume chambers which are distributed around the axis of rotation of the rotor, are joined together in a fluid-tight manner and are connected hydraulically partly to a fuel inlet of the gear pump and partly to a fuel outlet of said gear pump.

The rotor further comprises a plurality of pockets which are configured to each seat inside them a respective permanent magnet and are distributed around the axis of rotation of said rotor.

Each pocket is formed by means of stock removal machining of the rotor, and each permanent magnet is bonded inside the associated pocket.

The known pump units of the type described above have a number of drawbacks mainly arising from the fact that the processes for stock removal machining of the rotor and bonding the permanent magnets inside the associated pockets are relatively complex and costly.

The object of the present invention is to provide a pump unit for feeding fuel, preferably diesel fuel, to an internal combustion engine, which does not have the aforementioned drawbacks and is simple and inexpensive to produce.

According to the present invention, a pump unit for feeding 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 example of embodiment thereof, in which:

Figures 1 is a hydraulic diagram of a preferred embodiment of the pump unit according to the present invention;

Figure 2 is an exploded perspective view of a detail of the pump unit according to Figure 1; and

Figure 3 is a front view of a detail of Figure 2.

With reference to Figure 1, 1 denotes in its entirety a pump unit for feeding fuel, preferably diesel fuel, from a storage tank 2 to an internal combustion engine 3, in the case in question a diesel combustion engine comprising a fuel distribution manifold 4, commonly referred to by the term "common rail", and a plurality of injectors 5 connected to the manifold 4 and designed to atomize the fuel inside associated combustion chambers (not shown) of the said engine 3.

The pump unit 1 comprises a high-pressure pump 6, in the case in question a piston pump, designed to feed the fuel to the engine 3, and a low-pressure or pre-feed pump 7 designed to feed the fuel from the tank 2 to the pump 6. The pump 6 comprises a plurality of cylinders 8 (in the case in question two cylinders 8) which are formed in a pump body 9 and are each slidably engaged by a respective piston 10.

The pistons 10 are displaced along the associated cylinders 8 by an actuating device 11 of the known type housed inside the pump body 9 with an alternating rectilinear movement comprising an outward stroke for drawing the fuel into the associated cylinders 8 and a return stroke for compressing the fuel contained in said associated cylinders 8.

The pump unit 1 further comprises a hydraulic circuit 12 for feeding the fuel comprising, in turn, a first branch 13 for connecting together the tank 2 and the pump 7; a second branch 14, which connects together the pumps 6 and 7, extends through the pump body 9 in order to lubricate the actuating device 11 and is connected to each cylinder 8 by means of an associated intake valve 15; and a third branch 16 which extends between the pump 6 and the manifold 4 and is connected to each cylinder 8 by means of an associated delivery valve 17.

The branch 14 is provided with a device 18 for filtering the fuel fed to the pump 6 and a metering electrovalve 19 which is mounted upstream of the valves 15 in a direction 20 of feeding of the fuel along the branches 13, 14 and 16 and is movable between a closed position and an open position for selectively controlling the instantaneous fuel flow fed to the pump 6 depending on the values of a plurality of operating parameters of the engine 3.

The circuit 12 further comprises a fourth branch 21 which extends between the manifold 4 and the tank 2 and is provided with a metering electrovalve 22 which cooperates with the electrovalve 19 in order to control selectively the fuel flow fed to the injectors 5 and allows the amount of fuel exceeding that required by the injectors 5 to be discharged into the tank 2.

The pump 7 is an electric gear pump comprising a pump body 23, and a synchronous, brushless, permanent-magnet, electric motor 24 housed inside the said pump body 23.

The motor 24 comprises an annular-shaped stator 25 which has a longitudinal axis 26 and is rotatably engaged by an annular-shaped rotor 27 mounted coaxially with said axis 26.

The rotor 27 comprises an inner ring 28 which has inner teeth 29 and is bounded by a cylindrical outer surface 30 coaxial with the axis 26; and an outer sleeve 31 bonded onto said surface 30.

Obviously the ring 28 and the sleeve 31 may be joined together in an angularly fixed manner by means of methods other than bonding, for example by means of an interference fit or a splined joint or by means of a combination of the aforementioned methods and bonding.

The sleeve 31 comprises a magnetic ring 32 which is made, in the case in question, by means of injection-moulding of a ferromagnetic material in a plastic material and is radially bounded by a cylindrical inner surface 33 arranged in contact with the surface 30 and a cylindrical outer surface 34 opposite said surface 33.

The ring 32 is coated with a coating layer 35 which is applied on the surface 34, is arranged in contact with the stator 25 and is made, preferably, but not necessarily, of nickel, namely a material having a relatively high wear resistance.

According to a variant not shown, the layer 35 is made using materials other than nickel, for example ceramic materials.

The rotor 27 defines an outer gear of the pump 7 which further comprises an annular-shaped inner gear 36 seated inside said rotor 27.

The gear 36 is mounted so as to rotate about an axis 37 parallel to and separate from said axis 26 and has outer teeth 38 meshing with the inner teeth 29 of the rotor 27.

The two sets of teeth 29, 38 are formed so as to define a plurality of variable-volume chambers 39 which are distributed around the axis 26, are joined together in a fluid-tight manner and are connected hydraulically partly to a fuel inlet 40 of the pump 7 and partly to a fuel outlet 41 of said pump 7. In connection with the above comments it should be pointed out that the volume of the chambers 39 associated with the inlet 40 increases in a direction 42 of rotation of the rotor 27 about the axis 26 and the gear 36 about the axis 37 and that the volume of the chambers 39 associated with the outlet 41 diminishes in the direction 42 so as to compress the fuel.

Since the inner ring 28 has solely the teeth 29, the magnetic ring 32 is formed by means of injection-moulding of a ferromagnetic material in a plastic material and the coating layer 35 is applied onto said magnetic ring 32 by means of a chemical deposition process, the rotor 27 has a relatively simple and low-cost structure and requires relatively simple and rapid assembly operations.