Title of Invention	AN ELECTRONICALLY COMMUTATED MOTOR FOR A FUEL PUMP
Abstract	The invention relates to an electronically commutated motor for a fuel pump, comprising a rotor (1) which is connected to a shaft (2) in a rotationally fixed manner and has a plastic bonded ferrite, in which the rotor (1) has a fuel- resistant shaped body (6) which is formed by the plastic-bonded ferrite (4), characterized in that a magnetic ret urn element (14) which can be adjusted in relation to the shaped body (6) by being moved on the shaft (2) is provided, with the shaped body having an axial recess (12) in which the return element (14) engages, with the axial recess (12) having an opening side (18) and a base side (20) which is situated opposite the opening side (18) and at which the shaped body (6) is connected to the shaft (2), and with the axial recess (12) forming a funnel (22) which widens conically toward the opening side (18), and in that the return element (14) forms a cone (24) which tapers toward the base side (20) of the recess (12).

Title of Invention

AN ELECTRONICALLY COMMUTATED MOTOR FOR A FUEL PUMP

Abstract

The invention relates to an electronically commutated motor for a fuel pump, comprising a rotor (1) which is connected to a shaft (2) in a rotationally fixed manner and has a plastic bonded ferrite, in which the rotor (1) has a fuel- resistant shaped body (6) which is formed by the plastic-bonded ferrite (4), characterized in that a magnetic ret urn element (14) which can be adjusted in relation to the shaped body (6) by being moved on the shaft (2) is provided, with the shaped body having an axial recess (12) in which the return element (14) engages, with the axial recess (12) having an opening side (18) and a base side (20) which is situated opposite the opening side (18) and at which the shaped body (6) is connected to the shaft (2), and with the axial recess (12) forming a funnel (22) which widens conically toward the opening side (18), and in that the return element (14) forms a cone (24) which tapers toward the base side (20) of the recess (12).

Full Text	FIELD OF INVENTION The invention relates to an electronically commutated motor for a fuel pump, comprising a rotor which is connected to a shaft in a rotationally fixed manner and has a plastic-bonded ferrite. BACKGROUND OF INVENTION Electronically commutated motors in the form of commutatorless DC motors, so called electronic motors, are known. Such brushless DC motors are distinguished in that they do not require servicing and the cost of producing them is comparatively low. It is also known to provide such motors with a rotor which is arranged on a shaft and is composed of a permanent-magnet material, for example a plastic-bonded barium ferrite. One problem with the known motors is that the rotor is permanently damaged when it comes into contact with gasoline or diesel fuel as is unavoidable when the motors are used to drive fuel pumps. Furthermore, the motors have a large spectrum of efficiency which is dependent on further system parameters. US-A-6 220 826 discloses an electronically commutated motor for a fuel pump of the type mentioned in the introduction. US-A-6 204 584 discloses a rotor for an electrically commutated motor which has a tubular permanent magnet body with alternating poles on the circumference and a return element protruding into its continuous cylindrical through opening, said return element having a circular basic cross section and one or more pairs of flat areas on its lateral surface. Air gaps between the return element and the tubular permanent magnet body are formed by the flat areas. The return element can be adjusted by rotating the return element in the permanent magnet body. US 6,455,975 Bl discloses a generator with a conical hub which is composed of a magnetic steel, whose lateral surface has a constant wall thickness and on which magnets are arranged. OBJECT OF THE INVENTION The object of the invention is therefore to provide a motor of the type mentioned in the introduction for a fuel pump, which motor is highly efficient and at the same time has long service life. SUMMARY OF INVENTION According to the invention, this object is achieved in that the rotor has a fuel resistant shaped body which is formed by the plastic bonded ferrite, and in that a magnetic return element which can be adjusted in relation to the shaped body by being moved on the shaft is provided, with the shaped body having an axial recess in which the return element engages, with the axial recess having an opening side and a base side which is situated opposite the opening side and at which the shaped body is connected to the shaft, and with the axial recess forming a funnel which widens conically toward the opening side, and in that the return element forms a cone which tapers toward the base side of the recess. -3 The ability to adjust the return element in relation to the plastic-bonded ferrite which forms a shped body makes it possible to match the magnetic flux specifically to the motor system while optimizing the efficiency of the motor. In this case, the shaped body allows deliberate interaction between the return element and the rotor which has two or more magnetic poles. The shaped body itself permanently retains its shape even in a fuel environment, as a result of which not only the electromagnetic properties and the power output of the motor remain constant over time, but also an unbalance of the rotor which increases wear is reliably avoided. Particularly exact association of the shaped body and return element along with the high stability of the motor arrangement is achieved by moving the return element. A particularly compact structure is achieved by the return element engaging in the recess. It is possible to imaging forming the recess and shaped body in such a way that the return element engages fully through the shaped body. However, particularly high stability and easy installation of the motor arrangement are achieved when the axial recess has an opening side and a base side which is situated opposite the opening side and at which the shaped body is connected to t he shaft. The ability to adjust the return element in relation to the shaped body is considerably simplified by the recess being in the form of a funnel and the return element being in the form of a cone. If, according to one advantageous development of the invention, the opening angle of the funnel corresponds to the cone angles of the cone, the magnetic flux can be matched particularly exactly to the motor system; the lateral surface of the cone and the corresponding inner face of the funnel are always parallel to one another in this case. In principle, any desired fuel-resistant plastics which have high deformation rersistance can be used as a support for the ferrite. However, polyphenylene sulfide (PPS) is a particularly advantageous plastic which bonds the ferrite, especially for providing the shaped body with a high degree of chemical resistance and very high dimensional stability. A further advantage of PPS is its inherent flame resistance. Since the ferrite is responsible for the permanent magnet properties of the rotor, it is also expedient if it has a high coercive force. According to one advantageous development of the invention which was discovered from experiments, the shaped body has stabilizing fiber material. A proportion by volume of approximately 2% of glass fibres has proven particularly suitable and also cost effective. It is possible to imagine placing the shaped body, for example, onto the shaft and adhesively bonding them. In contrast, a particularly simple and long-lasting connection between the rotor and the shaft while at the same time avoiding an unbalance of the rotor is ensured when, according to another advantageous development of the invention, the shaped body is injection molded onto the shaft has a pattern which increases its surface roughness. This pattern may be, for example, a roughened section or - particularly advantageously knurled formation. -4A The motor can be produced in a particularly simple and cost effective manner when, according to another advantageous development of the invention the return element is pressed onto the shaft. In this case, the return element can be pressed onto the shaft. In this case, the return element can be pressed onto the shaft, after the shaped body and shaft are connected, so as to ensure exact adjustment in relation to the shaped body. BRIEF DESCRIPTION OF ACCOMPANYING DRAWING One exemplary embodiment of the invention is illustrated in the drawing and described in greater detail in the following text. In the drawing, the single figure shows a partial sectional view of a motor for a fuel pump. The figure is a schematic view of a rotor 1 of an electronically commutated motor (not illustrated in any more detail) for a fuel pump, said rotor having two or more magnetic poles. The rotor 1 is connected to a shaft 2 in a rotationally fixed manner and has a plastic-bonded ferrite 4 which is admixed with a stabilizing fiber material. The plastic-bonded ferrite 4 forms a fuel-resistant shaped body 6 which is injection molded onto the shaft 2 and at the same time is magnetized, so that it forms a multipole permanent magnet. In a connecting region 8 between the shaft 2 and the shaped body 6, the shaft 2 has a pattern 10 which increases its surface roughness and is in the form of a knurl. The shaped body 6 also has an axial recess 12 in which a return element 14 which is composed of a soft-magnetic material 16 engages. The return element 14 increases the magnetic flux and, in accordance with requirements, may be dimensioned as a function of the shaped body 6 and the motor/pump system. The axial recess 12 in the shaped body 6 has an opening side 18 at one end and a base side 20, which is situated opposite the opening side 18, at the other end. The shaped body 6 is connected to the shaft 2 at the base side 20 of the recess 12. It can also be seen that the return element 14 is arranged entirely within the shaped body 6. In order to adjust the return element 14 in relation to the shaped body 6, the axial recess 12 in said shaped body forms a funnel 22 which widens conically toward the opening side 18. In a manner which corresponds to the funnel 22, the return element 14 forms a cone 24 which tapers toward the base side 20 of the recess 12. In this case, the opening angle (3 of the funnel 22 and the cone angle (3 of the cone 24 correspond, so that an air gap 26 is bounded by parallel faces. When the return element 14 which is pressed onto the shaft 2 is adjusted in relation to the shaped body 6, which is done by moving said return element in the directions indicated by the double-headed arrow 28, the air gap 26 is therefore uniformly changed. The width of the air gap 26 directly influences the magnetic flux. WE CLAIM : 1. An electronically commutated motor for a fuel pump, comprising a rotor (1) which is connected to a shaft (2) in a rotationally fixed manner and has a plastic bonded ferrite, in which the rotor (1) has a fuel-resistant shaped body (6) which is formed by the plastic-bonded ferrite (4), characterized in that a magnetic ret urn element (14) which can be adjusted in relation to the shaped body (6) by being moved on the shaft (2) is provided, with the shaped body having an axial recess (12) in which the return element (14) engages, with the axial recess (12) having an opening side (18) and a base side (20) which is situated opposite the opening side (18) and at which the shaped body (6) is connected to the shaft (2), and with the axial recess (12) forming a funnel (22) which widens conically toward the opening side (18), and in that the return element (14) forms a cone (24) which tapers toward the base side (20) of the recess (12). 2. Motor as claimed in Claim 1, wherein the opening angle (a) of the funnel (22) corresponds to the cone angle (P) of the cone (24). 3. Motor as claimed in any of the preceding claims, wherein the plastic which bonds the ferrite (4) is polyphenylene sulfide. 4. Motor as claimed in any of the preceding claims wherein the shaped body (6) has stabilizing fiber material. 5. Motor as claimed in any of the preceding claims wherein the shaped body (6) us injection molded onto the shaft (2), and in that, in a connecting region (8) between the shaft (2) and the shaped body (6), the shaft (2) has a pattern (10) which increases its surface roughness. 6. Motor as claimed in any of the preceding claims, wherein the return element (14) is pressed onto the shaft (2).

Full Text

FIELD OF INVENTION
The invention relates to an electronically commutated motor for a fuel pump,
comprising a rotor which is connected to a shaft in a rotationally fixed manner
and has a plastic-bonded ferrite.
BACKGROUND OF INVENTION
Electronically commutated motors in the form of commutatorless DC motors, so
called electronic motors, are known. Such brushless DC motors are distinguished
in that they do not require servicing and the cost of producing them is
comparatively low. It is also known to provide such motors with a rotor which is
arranged on a shaft and is composed of a permanent-magnet material, for
example a plastic-bonded barium ferrite.
One problem with the known motors is that the rotor is permanently damaged
when it comes into contact with gasoline or diesel fuel as is unavoidable when
the motors are used to drive fuel pumps. Furthermore, the motors have a large
spectrum of efficiency which is dependent on further system parameters.
US-A-6 220 826 discloses an electronically commutated motor for a fuel pump of
the type mentioned in the introduction.
US-A-6 204 584 discloses a rotor for an electrically commutated motor which has
a tubular permanent magnet body with alternating poles on the circumference
and a return element protruding into its continuous cylindrical through opening,
said return element having a circular basic cross section and one or more pairs of

flat areas on its lateral surface. Air gaps between the return element and the
tubular permanent magnet body are formed by the flat areas. The return
element can be adjusted by rotating the return element in the permanent
magnet body.
US 6,455,975 Bl discloses a generator with a conical hub which is composed of a
magnetic steel, whose lateral surface has a constant wall thickness and on which
magnets are arranged.
OBJECT OF THE INVENTION
The object of the invention is therefore to provide a motor of the type mentioned
in the introduction for a fuel pump, which motor is highly efficient and at the
same time has long service life.
SUMMARY OF INVENTION
According to the invention, this object is achieved in that the rotor has a fuel
resistant shaped body which is formed by the plastic bonded ferrite, and in that a
magnetic return element which can be adjusted in relation to the shaped body
by being moved on the shaft is provided, with the shaped body having an axial
recess in which the return element engages, with the axial recess having an
opening side and a base side which is situated opposite the opening side and at
which the shaped body is connected to the shaft, and with the axial recess
forming a funnel which widens conically toward the opening side, and in that the
return element forms a cone which tapers toward the base side of the recess.
-3

The ability to adjust the return element in relation to the plastic-bonded ferrite
which forms a shped body makes it possible to match the magnetic flux
specifically to the motor system while optimizing the efficiency of the motor. In
this case, the shaped body allows deliberate interaction between the return
element and the rotor which has two or more magnetic poles. The shaped body
itself permanently retains its shape even in a fuel environment, as a result of
which not only the electromagnetic properties and the power output of the motor
remain constant over time, but also an unbalance of the rotor which increases
wear is reliably avoided.
Particularly exact association of the shaped body and return element along with
the high stability of the motor arrangement is achieved by moving the return
element.
A particularly compact structure is achieved by the return element engaging in
the recess.
It is possible to imaging forming the recess and shaped body in such a way that
the return element engages fully through the shaped body. However, particularly
high stability and easy installation of the motor arrangement are achieved when
the axial recess has an opening side and a base side which is situated opposite
the opening side and at which the shaped body is connected to t he shaft.
The ability to adjust the return element in relation to the shaped body is
considerably simplified by the recess being in the form of a funnel and the return
element being in the form of a cone.

If, according to one advantageous development of the invention, the opening
angle of the funnel corresponds to the cone angles of the cone, the magnetic
flux can be matched particularly exactly to the motor system; the lateral surface
of the cone and the corresponding inner face of the funnel are always parallel to
one another in this case.
In principle, any desired fuel-resistant plastics which have high deformation
rersistance can be used as a support for the ferrite. However, polyphenylene
sulfide (PPS) is a particularly advantageous plastic which bonds the ferrite,
especially for providing the shaped body with a high degree of chemical
resistance and very high dimensional stability. A further advantage of PPS is its
inherent flame resistance. Since the ferrite is responsible for the permanent
magnet properties of the rotor, it is also expedient if it has a high coercive force.
According to one advantageous development of the invention which was
discovered from experiments, the shaped body has stabilizing fiber material. A
proportion by volume of approximately 2% of glass fibres has proven particularly
suitable and also cost effective.
It is possible to imagine placing the shaped body, for example, onto the shaft
and adhesively bonding them. In contrast, a particularly simple and long-lasting
connection between the rotor and the shaft while at the same time avoiding an
unbalance of the rotor is ensured when, according to another advantageous
development of the invention, the shaped body is injection molded onto the shaft
has a pattern which increases its surface roughness. This pattern may be, for
example, a roughened section or - particularly advantageously knurled
formation.
-4A

The motor can be produced in a particularly simple and cost effective manner
when, according to another advantageous development of the invention the
return element is pressed onto the shaft. In this case, the return element can be
pressed onto the shaft. In this case, the return element can be pressed onto the
shaft, after the shaped body and shaft are connected, so as to ensure exact
adjustment in relation to the shaped body.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWING
One exemplary embodiment of the invention is illustrated in the drawing and
described in greater detail in the following text. In the drawing, the single figure
shows a partial sectional view of a motor for a fuel pump.
The figure is a schematic view of a rotor 1 of an

electronically commutated motor (not illustrated in any more
detail) for a fuel pump, said rotor having two or more magnetic
poles. The rotor 1 is connected to a shaft 2 in a rotationally
fixed manner and has a plastic-bonded ferrite 4 which is
admixed with a stabilizing fiber material. The plastic-bonded
ferrite 4 forms a fuel-resistant shaped body 6 which is
injection molded onto the shaft 2 and at the same time is
magnetized, so that it forms a multipole permanent magnet. In a
connecting region 8 between the shaft 2 and the shaped body 6,
the shaft 2 has a pattern 10 which increases its surface
roughness and is in the form of a knurl.
The shaped body 6 also has an axial recess 12 in which a return
element 14 which is composed of a soft-magnetic material 16
engages. The return element 14 increases the magnetic flux and,
in accordance with requirements, may be dimensioned as a
function of the shaped body 6 and the motor/pump system. The
axial recess 12 in the shaped body 6 has an opening side 18 at
one end and a base side 20, which is situated opposite the
opening side 18, at the other end. The shaped body 6 is
connected to the shaft 2 at the base side 20 of the recess 12.
It can also be seen that the return element 14 is arranged
entirely within the shaped body 6.
In order to adjust the return element 14 in relation to the
shaped body 6, the axial recess 12 in said shaped body forms a
funnel 22 which widens conically toward the opening side 18. In
a manner which corresponds to the funnel 22, the return element
14 forms a cone 24 which tapers toward the base side 20 of the
recess 12. In this case, the opening angle (3 of the funnel 22
and the cone angle (3 of the cone 24 correspond, so that an air
gap 26 is bounded by parallel faces. When the return element 14
which is pressed onto the shaft 2 is adjusted

in relation to the shaped body 6, which is done by moving said
return element in the directions indicated by the double-headed
arrow 28, the air gap 26 is therefore uniformly changed. The
width of the air gap 26 directly influences the magnetic flux.

WE CLAIM :
1. An electronically commutated motor for a fuel pump, comprising a
rotor (1) which is connected to a shaft (2) in a rotationally fixed
manner and has a plastic bonded ferrite, in which the rotor (1) has a
fuel-resistant shaped body (6) which is formed by the plastic-bonded
ferrite (4), characterized in that a magnetic ret urn element (14) which
can be adjusted in relation to the shaped body (6) by being moved on
the shaft (2) is provided, with the shaped body having an axial recess
(12) in which the return element (14) engages, with the axial recess
(12) having an opening side (18) and a base side (20) which is
situated opposite the opening side (18) and at which the shaped body
(6) is connected to the shaft (2), and with the axial recess (12)
forming a funnel (22) which widens conically toward the opening side
(18), and in that the return element (14) forms a cone (24) which
tapers toward the base side (20) of the recess (12).
2. Motor as claimed in Claim 1, wherein the opening angle (a) of the
funnel (22) corresponds to the cone angle (P) of the cone (24).
3. Motor as claimed in any of the preceding claims, wherein the plastic
which bonds the ferrite (4) is polyphenylene sulfide.
4. Motor as claimed in any of the preceding claims wherein the shaped
body (6) has stabilizing fiber material.

5. Motor as claimed in any of the preceding claims wherein the shaped
body (6) us injection molded onto the shaft (2), and in that, in a
connecting region (8) between the shaft (2) and the shaped body (6),
the shaft (2) has a pattern (10) which increases its surface roughness.
6. Motor as claimed in any of the preceding claims, wherein the return
element (14) is pressed onto the shaft (2).

AN ELECTRONICALLY COMMUTATED MOTOR FOR A FUEL PUMP

Documents:

Inventors:

PCT Conventions: