WO2001011756A1

WO2001011756A1 - Electrical motor of a fuel pump for an internal-combustion engine

Info

Publication number: WO2001011756A1
Application number: PCT/EP2000/006933
Authority: WO
Inventors: Giancarlo Fasola
Original assignee: Bitron S.P.A.
Priority date: 1999-08-06
Filing date: 2000-07-20
Publication date: 2001-02-15
Also published as: ITTO990154V0; ITTO990154U1

Abstract

An electrical brushless motor of a fuel pump for an internal-combustion engine presents the rotor (2) consisting basically of a packet of stator core laminations (4) the surface of which is basically that of a prism and on the faces of which are located corresponding magnetic segments (5) with basically rectangular axial section and plane sides; the magnetic segments (5) being assembled to the stator core laminations (4) by means of co-forging by a resin (6) which is preferably an acetalic resin and covers them so that it makes the rotor present a basically cylindrical shape.

Description

ELECTRICAL MOTOR OF A FUEL PUMP FOR AN INTERNAL-COMBUSTION ENGINE

DESCRIPTION

The present invention refers to an electrical motor, more in particular to a brushless motor, which is part of the fuel pump of an internal-combustion engine.

According to the state of the art, fuel pumps buried into the tanks are moved by direct current motors of the brush contact type which, at the moment, represent the best compromise between functionality, life and costs of production.

However, while electrical motors of the brush contact type imply low production costs, and the car industry is therefore quite interested in them, they present problems related to their life and to the moving parts. Brush wear, in fact, involves the substitution of the whole engine-pump unit. Besides, the mass of the rotors of motors of this type is quite big so that it increases the time needed to reach the steady condition with a consequent delay in the feeding of fuel to the thermal motor.

This is the reason why fuel pump manufacturers are more and more eager to use brushless electrical motors which last considerably longer and present less inertia.

The main problem that the manufacturer still has to solve is that the cost of these motors is very high, and such a high cost is not compatible with the lower costs policy adopted by the car industry.

It is an object of the present invention to provide a brushless electrical motor which ensures a reasonable performance and the production cost of which is equal to that of the motors which are generally used.

Said object is achieved by means of the present invention which relates to an electrical motor assembled to a fuel pump for an internal-combustion engine, consisting of a rotor rotatably coupled to a stator in order to rotate around an axis of rotation, and of an electronic device feeding and controlling the electrical motor itself, which is characterised by what set forth in claim 1.

Further characteristics and advantages will become clear from the following description referring to the appended figures provided as non-restrictive example, and in which: figure 1 is a radial sectional view of the motor together with the external body; figures 2 and 3 are a radial section and an axial section, respectively, of the rotor of the motor in figure 1 and figure 4 shows a front view of the rotor. With reference to the figures, reference number 1 indicates the shaft of the electrical motor on which the rotor 2 rotates. Said rotor consists of a packet 4 of stator core laminations the shape of which, according to the embodiment provided as non-restrictive example, is basically that of a regular hexagon. Magnetic segments 5 are positioned on the faces of the hexagon, said segments presenting a basically rectangular axial section, alternate polarity and being in axis to the planes of the packet hexagon 4.

The length of the side of the hexagon is basically equal to the length of longest side of the rectangle so that each magnetic segment 5 presents an internal edge adjacent to the edge of the following magnetic segment 5. It is obvious that in case the shape of the packet of stator core laminations is that of a pentagon or an octagon or else, the number of the magnetic segments 5 will be equal to the number of the faces of the packet 4. The magnetic segments 5 are assembled to the packet of the stator core laminations 4 by co-forming, by means of a resin which is adapted to this use, and preferably by means of an acetalic resin. Co-forming serves for:

1. protecting the magnets from the fluid fuel

2. smoothing the rotating surfaces in order to minimise losses due to viscose losses

3. facilitating the balancing of the rotor both in case of removal and addition of material

4. preventing centrifugation of the magnets.

In fact, as it can be seen more in particular in figures 3 and 4, the way the co-forming of the rotor 2 is performed in such that the covering resin 6 extends to the two ends of the body of the rotor and the corresponding annular appendixes 19, made in the plastic for co-forming, which allow to balance the rotor by means of addition of material, for instance by placing balancing material at the very points along the subfra es 20 of the two annular portions 19 (see figure 3) or in special holes 21 (see figure 4) made frontally in the annular portions themselves 19; the balancing can be achieved also by means of removing part of the resin from the annular portions themselves 19.

In the rotor which is here shown, the distance between the upper edges of the magnetic segments 5, is kept such that it is a good compromise in order to make the motor keep a cogging couple low enough thanks also to the help of the toothing 18 (see figure of the pole shoes 10) . At the same time, the cost of production of these magnetic segments 5, the section of which is that of a parallelepiped with plane sides, is significantly lower than the cost of the magnetic segments of the bent tile type which are normally used on electrical motors, so that the total cost of production of the whole engine is considerably lowered.

In fact, the cost of production of the bent tiles which are known to present curved shape and reduced thickness, is surely high, much higher than that of the magnetic segments with the parallelepiped section with plane sides and greater thickness, even if it is evident that bent tiles are more efficient than the magnetic segments of the type of the present invention.

Reference number 10 indicates the polar shoes of the stator, four in the example shown, each one of which is formed by a pile of basically T-shaped metal stator core laminations, where the foot 17 of the T consists of the part of said polar shoes 10 which, while in use, points towards the rotor 2. The polar shoes are covered by means of co-forging with a plastic material serving as electrical insulator 12, around which the skeins 13 constituting the stator winding are wind.

As it can be observed in figure 2, each polar shoe 10 is provided with a basis 15, opposite to the T-shaped foot 17, which allows the shoe to be placed into a corresponding notch in the body 14 of the stator after the winding is completed. In fact, due to the peculiar shape of the stator it is preferable to make the windings 13 on each polar shoe 10 separately and afterwards locate the shoes in their own seats or notches in the body 14 of the stator .

The polar shoes 10 are placed radially equidistant around the rotor 2 and are separated by sectors or false teeth 16 made in the body 14 of the stator.

While the present invention has been described in relation to what is currently considered the preferred and most practical embodiment, it is to be understood that the invention is not limited to the embodiment here shown but can modified and applied to equivalent arrangements without going beyond the scope of the appended claims.

Claims

CLAIM

1. Electrical brushless motor of a fuel pump for an internal-combustion engine, characterised in that the rotor (2) consists basically of a packet of stator core laminations (4) the surface of which is basically that of a prism and on the faces of which are located corresponding magnetic segments (5) with basically rectangular axial section and plane sides.

2. Motor as claimed in claim 1 characterised in that the magnetic segments (5) are assembled to the stator core laminations (4) by means of co-forging by a resin (6) which is preferably an acetalic resin and covers the magnetic segments (5) so that it makes the rotor present a basically cylindrical shape.

3. Motor as claimed in claim 1 characterised in that the surface of the stator core laminations (4) is hexagonal in shape .

4. Motor as claimed in claim 1 characterised in that the length of each side of the packet of the stator core laminations (4) is basically equal to the length of one of the sides of the magnetic segment (5) applied on it.

5. Motor as claimed in claim 1 characterised in that each magnetic segment (5) is parallelepiped in shape.

6. Motor as claimed in claim 1 characterised in that the polar shoes (10) are wind while detached from the body

(14) of the stator and afterwards applied on it.

7. Motor as claimed in claim 1 characterised in that the polar shoes (10) present a basis (15) which is opposite to the foot (17), facing the rotor (2), provided with an enlargement adapted to be fixed longitudinally into a special notch in the body (14) of the stator.

8. Motor as claimed in claim 1 characterised in that the polar shoes (10) of the stator are separated by false teeth (16) which are part of the stator.

9. Motor as claimed in claim 1 characterised in that the polar shoes (10) present a toothed surface (18) at the magnetic gap.

10. Motor as claimed in claim 2 characterised in that the resin (6) extends by means of annular appendixes (19) on both ends of the body of the rotor.

11. Motor as claimed in claim 10 characterised in that the rotor is balanced by means either of addition or removal of material at said annual appendixes (19).