DE102008022369B4 - electric motor - Google Patents

Abstract

Electric motor with- a motor shaft,- a sensor unit for detecting the speed and/or the angle of rotation of the motor shaft,- a fan wheel fastened to the motor shaft, and an electromagnetically actuable brake for the motor shaft, the fan wheel having at least one permanent magnet which moves with the fan wheel, wherein the magnetic field of the at least one permanent magnet can be detected by the sensor unit,wherein the sensor unit is arranged between the electromagnetically actuatable brake and the fan wheel,and the sensor unit has a shielding element,wherein the shielding element protects the sensor unit on its sides facing the motor shaft and the electromagnetically actuatable brake and the shields the sides oriented in the direction of rotation of the motor shaft against magnetic fields and forms a passage opening for magnetic fields at least in regions on the side of the sensor unit oriented towards the fan wheel, characterized in that the shielding element consists of is made of a soft magnetic powder composite material with a ferromagnetic core material produced by powder metallurgy in a sintering process, with the shielding element being designed in one piece, with the shielding element having a base plate which magnetically shields the sensor unit for the electromagnetically actuatable brake, and with a double-walled collar made of a soft magnetic Powder composite material is formed, which surrounds the sensor unit in at least three mutually perpendicular spatial directions and magnetically shields it, one of the spatial directions pointing to the motor shaft and the other two spatial directions pointing in the direction of rotation of the motor shaft.

Description

The invention relates to an electric motor with a motor shaft, a sensor unit for detecting the speed and/or the angle of rotation of the motor shaft, a fan wheel attached to the motor shaft and an electromagnetically actuable brake for the motor shaft, the fan wheel having at least one permanent magnet which moves with the fan wheel. the magnetic field of the at least one permanent magnet can be detected by the sensor unit, the sensor unit is arranged between the electromagnetically actuable brake and the fan wheel, and the sensor unit has a shielding element, with the shielding element protecting the sensor unit on its sides located towards the motor shaft and the electromagnetically actuable brake and on the in Shields the sides oriented in the direction of rotation of the motor shaft against magnetic fields and, at least in some areas, forms a passage opening for magnetic fields on the side of the sensor unit oriented towards the fan wheel, in particular at least the Fan wheel oriented side of the sensor unit is not shielded.

Such electric motors are known as the closest prior art from DE 10 2006 030 737 A1 wherein a Wiegand sensor is provided in a thin pocket made of sheet steel or the like to provide the sensor very close to the brake.

The general use of pulse wire counters as revolution counters is, for example, from DE 10 2005 006 419 A1 known.

From the DE 10 348 810A1 discloses a method of manufacturing metal powders having nano-scale grains and excellent in high-frequency characteristics, and a method of manufacturing a high-frequency soft magnetic core using such powders.

From the DE 694 18 07 U a magnetically shielded cable is known.

The object of the invention is to create an electric motor with a cost-effective speed sensor that can be operated with little interference.

According to the invention, the object is achieved with the electric motor according to the features specified in claim 1.

An important feature of the invention of an electric motor of the type mentioned at the outset is that the shielding element is made from a soft magnetic powder composite material. A ferromagnetic core material produced by powder metallurgy in a sintering process can be used as the soft-magnetic powder composite material. The shielding element is preferably preformed as a green compact by pressing and then sintered, ie compacted and hardened by heat treatment below the melting temperature. Shielding is beneficial of pure iron powdered iron core, 81% nickel 17% iron 2% molybdenum MPP core, 50% nickel 50% iron high flux core, 85% iron sendust core , 9.5% silicon and 5.5% aluminum or an aluminum cast iron core can be produced, with the specified weight percentages being only approximate and deviations from this can also be used advantageously.

The shielding advantageously prevents the strong magnetic fields from the stator, which are routed to the outside through the rotor shaft, and from the electromagnetically actuable brake from interfering with an angular position determination of the rotor shaft by the sensor unit. A higher accuracy of the angular position determination can thus be achieved. With the shielding described, it is only possible to use a Wiegand sensor for the sensor unit, which enables increased angular resolution through the multi-stage folding process in the sheath and core of the measuring wire that is typical for it.

The advantage here is that the grain boundaries between the granular components of the sintered material prevent the occurrence of eddy currents, as a result of which the shielding and the entire sensor unit only heat up slightly despite the strong magnetic fields present from the electric motor and brake. Furthermore, the shield can be designed with a shape that is more complex than an embodiment made of ferritic sheet metal and is better adapted to the problem and the space conditions in an electric motor. In particular, the shape allows space-saving shielding of the sensor unit, since no minimum bending radii have to be observed, as is the case when using ferritic sheets. Finally, cost-effective production is made possible because, under certain circumstances, post-processing of the sintered pieces can be dispensed with.

The sensor unit is preferably arranged in the space between the fan wheel and the brake, which is provided for the manual release lever of the brake.

According to the invention, it is provided that the shielding element, ie the shield, has a preferably flat base plate which magnetically shields the sensor unit for the electromagnetically actuable brake. The level, flat Shaped design of the base plate offers the advantage that an area is formed above the base plate near the base plate, which is essentially free of magnetic interference fields. This base plate can advantageously be used as a mechanically stable mounting surface for the components of the sensor unit.

According to the invention, a double-walled collar made of a soft magnetic powder composite material is formed onto the base plate, which surrounds and magnetically shields the sensor unit in at least three mutually perpendicular spatial directions, with one of the spatial directions pointing towards the motor shaft and the other two spatial directions pointing in the direction of rotation of the motor shaft . The outer wall of the double-walled collar diverts most of the magnetic interference field lines past the sensor unit. The inner wall is magnetically decoupled from the interference fields through the gap between the outer and inner walls, with both walls being firmly connected to the base plate. The shielding of the sensor unit against interference from the drive unit is thus improved once again. The use of insulating intermediate layers with Nomex paper or the like is not necessary.

According to one embodiment of the invention, it can be provided that the base plate carries a circuit board with the electronic components of the sensor unit. Thus, the electronic switching elements for the evaluation or conversion of the sensor signals are magnetically shielded and mechanically protected.

According to one embodiment of the invention, it can be provided that the electronic components of the sensor unit are arranged on a circuit board, with the circuit board being aligned parallel to the running plane of the fan wheel. The sensor elements can thus be distributed on the circuit board and, in particular, arranged in an offset manner, which makes it possible to determine the direction of rotation of the rotor shaft. In addition, by aligning the circuit board parallel to the running plane of the fan wheel, the sensor unit's external dimensions are small.

According to one embodiment of the invention, it can be provided that the sensor unit has a Wiegand sensor and/or at least one Hall element, in particular at least two Hall sensors arranged crossed and/or spaced apart radially and/or in the circumferential direction, and/or the at least one Hall sensor and the Wiegand sensor are arranged on opposite sides of a board and/or evaluation electronics, in particular at least one semiconductor module, are arranged on the board with which the signals of the sensors can be evaluated. The combination of Hall sensors and Wiegand sensors enables the angle of rotation to be detected using two different measuring methods, which means that the detection accuracy can be increased and the failure rate reduced. The combination also enables simple, improved detection of the sense of rotation, and the high angular resolution of the Wiegand sensor can be accompanied by a rough pre-measurement with the Hall sensors, with the Wiegand sensor only being evaluated in the trigger windows of the Hall sensor or the Hall sensors is done. Due to the crossed arrangement of Hall sensors, different components of the moving magnetic fields of the magnetic flags in the fan wheel can be detected, and the direction of rotation and absolute instantaneous value of the rotation of the rotor shaft can be determined by offsetting the sensors against each other. By arranging the evaluation electronics or parts thereof in the shielded area, the induction of interference signals in the sensor leads can also be avoided.

According to one embodiment of the invention, it can be provided that the at least one Hall sensor is arranged on the side of the board facing the at least one permanent magnet of the fan wheel, i.e. printed circuit board, and/or the Wiegand sensor is arranged on the side facing away from the at least one permanent magnet of the fan wheel Side of the board is arranged. The Wiegand sensor is therefore protected, while the Hall sensor can better detect the magnetic field from the fan wheel.

According to one embodiment of the invention, it can be provided that a protrusion made of a soft-magnetic powder composite material is formed on the base plate and faces the sensor unit, in particular the circuit board, and protrudes from the base plate, through which the field lines of the at least one permanent magnet of the fan wheel when passing the sensor unit in be bundled in one area of the sensor unit, in particular with the formation on the base plate being arranged below the at least one Hall sensor. At its free end protruding above the base plate, the shape forms a truncated tip, on the curved surfaces of which the exiting magnetic field lines have a particularly high surface density. If the formation is now arranged below a sensor or in close proximity to the sensor, the field lines to be measured preferably emerge from the shielding material close to the sensor and thus lead to a stronger measurement signal in the sensor. The signal-to-noise ratio is thus improved. Due to the arrangement of the formation on the base plate, the formation is necessarily surrounded by the collar-shaped edge of the shield. Thus, only mag magnetic field lines in and out of it, originating from a dipole located directly above the formation. Other magnetic field lines are guided around the formation by the base plate. The shape therefore only bundles the magnetic field lines to be measured from a passing magnetic flag in the fan wheel and not the interfering field lines of the electric motor or the brake.

The fan wheel preferably has two, three, four, five, or more than five, for example twenty-four or more, such flags.

According to one embodiment of the invention, it can be provided that the at least one Hall sensor or the at least two Hall sensors can be used to detect the component of a Manet field that is perpendicular to the circuit board and/or a component of a Manet field that is aligned parallel to the circuit board can be detected by the Wiegand sensor Magnetic field, preferably the radial component or the component pointing in the circumferential direction, can be detected. With the arrangement described, increased selectivity for the measurement signal with respect to the interfering influences can be achieved. In addition, the Hall sensors can be arranged parallel to the circuit board to save space.

According to one embodiment of the invention, provision can be made for fastening ears to be formed on the outside of the shield, in particular on sides of the shield that lie opposite one another in the circumferential direction. These fastening ears allow the sensor unit to be fastened to a housing part of the electric motor. In particular, it can be provided that the shielding is fastened to the B end shield of the electric motor, in particular via at least one rod or similar rod-shaped holding element fastened to a fastening ear, and/or the shielding is fastened to the brake housing or is designed in one piece with it. In this case, the B end shield is the end shield opposite the outlet of the end of the rotor shaft of the electric motor provided for the drive. The sensor unit is thus mechanically decoupled from the housing parts of the brake, which are severely shaken during operation, and protected from damage. Since most of the magnetic field lines are bundled in the rotor shaft, the interfering magnetic fields are routed around the B end shield and thus around the sensor unit attached to it.

On the other hand, attachment to the brake offers the advantage of an arrangement of the sensor unit that is protected against mechanical damage.

According to one embodiment of the invention, it can be provided that the permanent magnets of the fan wheel are aligned radially and/or are arranged in pairs with opposite polarity. This arrangement has proven to be particularly advantageous for the low-error triggering of the flip measurement signal in the Wiegand wire.

According to one embodiment of the invention, it can be provided that the shielding has a recess on its radially outer side, which forms an opening to the sensor or sensors of the sensor unit. This creates an easily accessible option for routing the connecting cables.

According to one embodiment of the invention, it can be provided that the shielding is open on the side facing the fan wheel. Thus, the measurement signal of the flag can be detected without interference.

According to the invention, the shielding is designed in one piece. A mechanically stable shielding unit is thus provided which can be produced in a few production steps and which can therefore be produced inexpensively, in particular without post-processing from a green body.

According to one embodiment of the invention, it can be provided that the shielding protrudes axially beyond the sensor unit on the open side or terminates with it. This achieves the most comprehensive possible shielding of the sensor elements of the sensor unit while at the same time maintaining the sensor sensitivity for the magnetic flags in the fan wheel.

Further advantages result from the dependent claims. The invention is not limited to the combination of features of the claims. For the person skilled in the art, there are further meaningful combinations of claims and/or individual claim features and/or features of the description and/or the figures, in particular from the task and/or the task arising from comparison with the prior art.

The invention will now be explained in more detail with reference to figures:

• 1 eine erfindungsgemäße Sensoreinheit in Gebrauchslage in Aufsicht auf Bremse und B-Lagerschild,
• 2 die erfindungsgemäße Sensoreinheit gemäß 1 mit Bremse und B-Lagerschild von der Seite,
• 3 eine Einzelansicht der Sensoreinheit gemäß 1 aus axialer Richtung,
• 4 eine Einzelansicht der Sensoreinheit gemäß 3 von der Seite,
• 5 eine weitere erfindungsgemäße Sensoreinheit in einer Schrägansicht und
• 6 die Sensoreinheit gemäß 5 in einer Schnittansicht.

It shows

• 1 a sensor unit according to the invention in the position of use with a view of the brake and B end shield,
• 2 according to the sensor unit according to the invention 1 with brake and B end shield from the side,
• 3 a detail view of the sensor unit according to FIG 1 from the axial direction,
• 4 a detail view of the sensor unit according to FIG 3 of the page,
• 5 another sensor unit according to the invention in an oblique view and
• 6 the sensor unit according to 5 in a sectional view.

1 shows a motor unit designated as a whole with 1 in a plan view of the B end shield with the fan wheel removed. The B end shield is covered in the illustration by the coil body 2 of an electromagnetically actuated brake. The rotor shaft, not shown, is inserted through the central opening in coil body 2 .

The brake can also be actuated manually by a release mechanism 3 with a hand lever 4 .

A transmitter 5 designed as a sensor unit is fastened to the B end shield 18 with pins 10 engaging the ears 9 . The transmitter 5 has a U-shaped shield 6 and a parallel shield 7, which are separated from one another by a groove 8 filled with air.

The outer shield 6 and the inner shield 7 surround a circuit board 11 on three sides. The printed circuit board 11 has a Hall sensor 12 on its upper side and other electronic components for setting the operating point of the sensors of the transmitter 5 and for reading out the sensor signals.

The shields 6, 7 are open radially outwards and provide space for the supply of electrical connection cables.

2 shows a side view of the motor unit 1 according to FIG 1 . For the sake of clarity, the rotor shaft of motor unit 1 has not been drawn in.

The encoder 5 is arranged in the space between the coil body 2 and the fan wheel 17, which is usually provided for the manual release mechanism 3 of the brake. The encoder 5 is held by two pins 10 on the B end shield 18 of the motor unit 1, the pins 10 overlapping the coil former 2 and protrude axially without touching it. The pins 10 are positively connected to the ears 9, for example by rivets or screws or the like. For this purpose, a bore 20 is made in each of the ears 9, which receives the ends of the pins 10.

The ears 9 are molded onto the outer shield 6 .

In the fan wheel 17, permanent magnets that are not visible are introduced or cast in at regular intervals along the circumference, which generate a magnetic signal when passing the transmitter 5 and thus act as magnetic transmitter flags. The radial position of the transmitter 5 is determined by the radial position of these magnetic transmitter flags, with the shielding of the transmitter 5 being open towards the fan wheel 17 in order to detect the magnetic field of the transmitter flags.

3 shows a detailed view of the encoder 5 from above, that is from the fan wheel 17, and 4 the encoder 5 obliquely in a side view.

A Hall sensor 12, a programmable memory module or FPGA, ie field programmable gate array, 12 and other electronic modules 22 are arranged on the printed circuit board 11.

The printed circuit board 11 is placed on a shoulder 15 in the inner shield 7 and thus closes a cavity 23 against the fan wheel 17 . A Wiegand sensor 13 is arranged in the cavity 23 and thus below the printed circuit board 11 .

The printed circuit board 11 is glued to the shoulder 15 along its edge and is thus held in place.

By comparison with the installation position of the encoder 5 according to 1 it is clear that the Wiegand sensor 13 is arranged in the circumferential direction with respect to the rotation of the motor unit 1, while the Hall sensor 12 detects a component of the magnetic field which is perpendicular to the circuit board 11. The FPGA 21 evaluates the sensor signals and uses them to determine preferably digitally processable values that characterize the speed and/or the angular position and/or the direction of rotation of the fan wheel 17 and thus the rotor shaft to which it is firmly connected.

The cavity 23 is closed off towards the brake by a floor 16 forming a base plate, to which the inner shield 7 and the outer shield 6 are connected in one piece. Shields 6 and 7 and the bottom 16 thus form a shielding element.

For this purpose, the shields 6, 7 are formed as a double-walled collar on the base 16 and project approximately at right angles from it. The double wall is formed by a separating groove 8 that reaches to the bottom 16 and extends along the shielding.

An approximately cylindrical formation 14 is formed on the floor 16 in the cavity 23 below the Hall sensor 12 . Cuboid formations can also be provided. This formation 14 bundles magnetic field lines that pass through the printed circuit board 11 in the vicinity of the Hall sensor 12 in such a way that they preferably run through the Hall sensor 12 .

The shielding of the encoder 5 formed by the shields 6 and 7 and the base is made of a soft magnetic powder material or of a sintered metal composite material SMC and forms an opening 19 on the radially outward-facing side through which the connecting cables for operating the encoder 5 can be routed. and can pass through the magnetic field lines from the passing magnetic encoder flags in the fan wheel 17 into the measurement-sensitive space of the encoder 5.

5 and 6 show another embodiment of the invention, which instead of the encoder 5 in 1 and 2 can be used.

5 shows a view from above while 6 shows a sectional view in oblique representation.

The transmitter 5 has a shielding element made of soft magnetic powder material, which is formed by a base plate 53 and a wall 50 integrally formed thereon, projecting at right angles in a collar shape and extending over the entire circumference of the base plate 53 .

The wall 50 forms a cable opening 52 which is separated from the inside of the base plate 53 by a step 57 . In the position of use on the motor unit 1 , the cable opening 52 points radially outwards and the outside of the base plate 53 points toward the coil body 2 .

At the free end of the wall 50, a circumferential shoulder 51 is formed, in which a printed circuit board 54 is inserted, which is firmly connected to the wall 50.

A cavity 23 is thus formed inside the encoder 5, in which a Wiegand sensor 56 is arranged on the underside of the printed circuit board 54. The longitudinal axis of the Wiegand sensor 56 is aligned perpendicular to the radial and axial direction of the motor unit, i.e. in the circumferential direction in relation to the rotation of the fan wheel 17.

A Hall sensor 55, evaluation electronics 21 and other electronic components 22 are arranged on the upper side of the printed circuit board 11 facing the fan wheel 17 .

In the electric motor 1, a sensor unit 5 is provided for detecting a periodic magnetic signal emitted by the fan wheel 17 during operation, which, to protect against the interfering magnetic field of the stator and that of a magnetically actuable brake 2, is covered by a shield made of a soft-magnetic, sintered powder material at least axially to the Brake and is shielded radially to the rotor shaft. The sensor unit 5 can have a Hall sensor 12, 55 and a Wiegand sensor 11, 56, wherein at least in the vicinity of the Hall sensor 12, 55 a protrusion can be formed on the shield 16, 53 which has a has a strongly curved surface and thereby bundles the magnetic field lines in the vicinity of the sensor 11, 12, 55, 56 and thus amplifies the measurement signal.

reference list

1

motor unit

2

bobbin

3

ventilation mechanism

4

hand lever

5

giver

6

shielding

7

shielding

8th

groove

9

Ear

10

Pen

11

circuit board

12

Hall sensor

13

Wiegand sensor

14

molding

15

Unit volume

16

floor

17

fan wheel

18

B end shield .

19

opening

20

drilling

21

FPGA

22

Electronic Components

23

cavity

50

screening wall

51

Unit volume

52

cable opening

53

base plate

54

circuit board

55

Hall sensor

56

Wiegand sensor

57

Step

Claims (12)

Electric motor with - a motor shaft, - a sensor unit for detecting the speed and/or the angle of rotation of the motor shaft, - a fan wheel fastened to the motor shaft - and an electromagnetically actuable brake for the motor shaft, the fan wheel having at least one permanent magnet which moves together with the fan wheel, wherein the magnetic field of the at least one permanent magnet can be detected by the sensor unit, wherein the sensor unit is arranged between the electromagnetically actuatable brake and the fan wheel, and the sensor unit has a shielding element, wherein the shielding element protects the sensor unit on its side facing the motor shaft and the electromagnetically actuatable brake and shields the sides oriented in the direction of rotation of the motor shaft against magnetic fields and at least partially forms a passage opening for magnetic fields on the side of the sensor unit oriented towards the fan wheel, characterized in that the shielding element ment is made of a soft-magnetic powder composite material with a ferromagnetic core material produced by powder metallurgy in a sintering process, with the shielding element being designed in one piece, with the shielding element having a base plate which magnetically shields the sensor unit for the electromagnetically actuatable brake, and with a double-walled collar on the base plate a soft magnetic powder composite material, which surrounds and magnetically shields the sensor unit in at least three mutually perpendicular spatial directions, with one of the spatial directions pointing towards the motor shaft and the other two spatial directions pointing in the direction of rotation of the motor shaft. Electric motor according to the preceding claim, characterized in that the base plate carries a circuit board with the electronic components of the sensor unit. Electric motor according to one of the preceding claims, characterized in that the electronic components of the sensor unit are arranged on a circuit board, the circuit board being aligned parallel to the running plane of the fan wheel. Electric motor according to one of the preceding claims, characterized in that the sensor unit has a Wiegand sensor and/or at least one Hall element, in particular at least two Hall sensors arranged crossed and/or spaced apart radially and/or in the circumferential direction and/or the at least one Hall sensor and the Wiegand sensor are arranged on opposite sides of a board and/or evaluation electronics, in particular at least one semiconductor module, are arranged on the board with which the signals of the sensors can be evaluated. Electric motor according to one of the preceding claims, characterized in that the at least one Hall sensor is arranged on the side of the circuit board facing the at least one permanent magnet of the fan wheel and/or the Wiegand sensor is arranged on the side of the circuit board facing away from the at least one permanent magnet of the fan wheel is arranged. Electric motor according to one of the preceding claims, characterized in that a protrusion made of a soft-magnetic powder composite material which faces the sensor unit, in particular the board, and protrudes from the base plate is formed on the base plate and through which the field lines of the at least one permanent magnet of the fan wheel pass when passing the sensor unit are bundled in one area of the sensor unit, in particular with the formation on the base plate being arranged below the at least one Hall sensor. Electric motor according to one of the preceding claims, characterized in that the component of a Manet field perpendicular to the circuit board can be detected by the at least one Hall sensor or the at least two Hall sensors and/or a component aligned parallel to the circuit board by the Wiegand sensor of a magnetic field, preferably the radial component or the component pointing in the circumferential direction, can be detected. Electric motor according to one of the preceding claims, characterized in that fastening ears are formed on the outside of the shielding element, in particular on opposite sides of the shielding element in the circumferential direction. Electric motor according to one of the preceding claims, characterized in that the shielding element is fastened to the B end shield of the electric motor, in particular via at least one rod or similar rod-shaped holding element fastened to a fastening ear, and/or the shielding element is fastened to the brake housing or is integral with it is executed. Electric motor according to one of the preceding claims, characterized in that the permanent magnets of the fan wheel are aligned radially and/or are arranged in pairs with opposite polarity. Electric motor according to one of the preceding claims, characterized in that the shielding element has a recess on its radially outer side which forms an opening to the sensor or sensors of the sensor unit and/or the shielding element is open on the side facing the fan wheel. Electric motor according to one of the preceding claims, characterized in that the shielding element protrudes axially beyond the sensor unit on the open side or terminates with it.

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