DE102022213709A1 - Electromotor drive arrangement with increased service life - Google Patents

Abstract

The present invention relates to an electromotive drive arrangement with an increased service life, in particular for a braking device of a vehicle. The electromotive drive arrangement comprises a stator with permanent magnets, a rotatably mounted drive shaft with grooves for receiving coil windings and a contact arrangement. The contact arrangement comprises at least one slip ring.

Description

The present invention relates to an electric motor drive arrangement with increased service life, in particular for a braking device of a vehicle.

Modern braking systems for motor vehicles, such as electromechanical wheel brakes, can have various electrically actuated elements, such as ABS pumps, which require an electromotor drive arrangement. The electromotor drive arrangement can be used, for example, as a pump motor to operate a hydraulic unit of a brake control unit for ABS or ESP applications. The electromotor drive arrangement can also be designed, for example, to control valves of a wheel brake.

An electric motor drive arrangement in the automotive sector can comprise a direct current machine, in particular a permanent magnet direct current machine. These direct current machines can be designed as an internal rotor arrangement and comprise a stator with permanent magnets as well as coils or coil windings that are assigned to the drive shaft or the rotor. Such motors are comparatively simple and inexpensive to manufacture.

For cost reasons, the coil windings are often still supplied with current via a mechanical commutation device or a mechanical commutator.

In addition to the commutator, such mechanical commutation devices usually contain metal-containing graphite brushes to supply the coils with electricity. A typical embodiment also provides for laminations arranged on the rotor for commutation, which can then be electrically contacted via the metal brushes.

However, such electromotive drive arrangements with mechanical contact via lamellae and brushes have some disadvantages.

There is a risk of sparking at the commutator. This can impair and reduce electromagnetic compatibility, for example through high-frequency interference.

Likewise, the service life of such drive arrangements can also be reduced, as erosion can lead to increased wear.

Finally, the control or the selection of an optimal operating point of the electromotive drive arrangement depending on the functions and load conditions of the connected devices, for example a braking device, via such a commutator is also difficult.

What is desirable is an electric motor drive arrangement that reduces these disadvantages or, ideally, does not have them.

An object of the invention is therefore to provide a cost-effective electromotive drive arrangement, in particular for a braking device of a vehicle, which allows simple and reliable control and contacting.

This also increases the service life of the drive assembly, which is particularly beneficial.

In addition, the electromagnetic compatibility of the drive arrangement is to be improved.

The inventors have taken on this task.

This object is achieved surprisingly simply by an electromotive drive arrangement, in particular a permanent magnet direct current machine, and a method for operating such an electromotive drive arrangement according to one of the independent claims.

Preferred embodiments and further developments of the invention can be found in the respective subclaims.

The present invention therefore relates in a first aspect to an electromotive drive arrangement, in particular a permanent magnet direct current machine, which can be used in or together with a braking device of a vehicle.

If a direct current machine is mentioned below, this refers to the basic structure of the electric machine rather than the type of power supply. In particular, it is intended that the electromotive drive system according to the invention or the permanent magnet electric motor can also be operated with three-phase alternating current.

• - einen Stator mit zumindest einem, bevorzugt einer Mehrzahl von Permanentmagneten,
• - eine rotierbar gelagerte Antriebswelle mit zumindest einer, bevorzugt einer Mehrzahl von auf der Außenwandung der Antriebswelle angeordneten Zähnen und Nuten zur drehfesten Aufnahme von Spulenwicklungen, und
• - eine Kontaktierungsanordnung

umfassen.The electric motor drive arrangement can be used

• - a stator with at least one, preferably a plurality of permanent magnets,
• - a rotatably mounted drive shaft with at least one, preferably a plurality of teeth and grooves arranged on the outer wall of the drive shaft for the rotationally fixed reception of coil windings, and
• - a contact arrangement

include.

According to a preferred embodiment of the invention, the coil windings are in electrical contact with the contact arrangement. The coil windings are insulated from one another. The winding wires can be insulated with varnish, for example. The lamellae of the contact arrangement can be insulated by means of saw gaps, for example, and the base body can comprise a thermosetting plastic. The coil windings of the electromotive drive arrangement are designed as a ring in a known manner. A coil can be provided for the lamellae of the contact arrangement, and each of the two coil ends can be connected to a lamella. At the same time, this represents the beginning of the next coil. The lamella can comprise a hook into which the wire can be hooked and then welded. The beginning and end of the complete coil winding can then be in one of the hooks.

According to a preferred embodiment of the invention, the coil windings can be designed as a three-phase three-phase winding with a delta connection. A star connection is also conceivable. In this way, when electrical current is applied, the coil windings can interact with the at least one permanent magnet of the stator in such a way that a torque can be generated on the drive shaft during operation, which can set the drive shaft in rotation. The grooves can in particular be assigned to the rotor or armature of the electromotive drive arrangement and thus represent a central component of the drive shaft.

The stator can be designed with a peripheral yoke and an even number of means for generating a permanent excitation field protruding inwards from the yoke. These are preferably permanent magnets. It is advantageous if adjacent permanent magnets are magnetized in opposite directions. The invention makes it possible to use inexpensive ferrite magnets. It is of course also possible to use stronger magnets, for example neodymium-iron-boron magnets. The stator and/or the rotor can be made either from laminated or solid materials.

The contacting arrangement according to the invention comprises at least one slip ring. If the electromotive drive arrangement is operated with three-phase alternating current, according to a preferred embodiment of the invention, one slip ring is provided for each phase. The slip rings are electrically insulated from each other. One coil winding is electrically connected to a slip ring. This contacting arrangement, also referred to below as a slip ring arrangement, can also be connected to a corresponding operating voltage source with electronic commutation in order to be able to supply current to the coil windings.

The drive arrangement according to the invention can be supplied electronically via the three slip rings, so that during operation of the drive arrangement a magnetic rotating field can be generated in the drive shaft or in the rotor, which causes the rotation.

For control, appropriate power electronics with a bridge circuit can be provided in an advantageous manner, as is known from brushless synchronous machines. In this way, the drive arrangement according to the invention can be controlled very precisely. When the electromotive drive arrangement is used in or together with a braking device of a vehicle, the control can be carried out, for example, via a B6 bridge of a vehicle.

The electric motor drive arrangement according to the invention offers many advantages.

The invention makes it possible to continue to use brush machines modified in this way instead of brushless DC motors, which are significantly more expensive. The electromotive drive arrangement according to the invention offers properties which in certain aspects are close to those of brushless DC motors.

Electrical contact via slip rings leads to significantly less wear and is less abrasive than contact via individual, spaced-apart lamellas in conjunction with carbon brushes. In particular, this can increase the service life of the brushes.

Electronic commutation can also counteract sparking, thereby improving electromagnetic compatibility the electric motor drive arrangement can be improved.

As a result, the service life of the electromotive drive arrangement according to the invention can be significantly increased overall. While the service life of brush motors can be in a range of, for example, 300 to 1,000 hours, the invention can achieve a service life of around 3,000 to 5,000 hours. The service life can thus be in the range of brushless motors, which can be around 5,000 hours or more.

Furthermore, field weakening is possible for certain load situations, which reduces the current requirement at high torques. The motor is designed in such a way that it cannot reach the maximum operating speed without field weakening because the flux linkage and thus the induced voltage would be too high. At the same time, the current required for the required maximum torque decreases proportionally with the increasing flux linkage. For operating cases that require particularly high speeds for a short time, the field weakening range can be opened up by pre-commutation. With pre-commutation, the winding voltage can be reversed before the rotor has reached the neutral position. However, an increased current is then required in this range. With appropriate design of the motor parameters, in particular the flux linkage, the inductance and the current limit of the converter, a constant power range can be used that promises a constant output power up to infinite speeds without taking losses into account. In reality, factors of 3 to 5 times the idle speed can be achieved.

The electromotive drive arrangement according to the invention can be used in or with motor vehicle brake systems, for example in electronically controlled braking devices. These can include, for example, anti-lock braking systems (ABS), anti-skid control systems (ARS), electronic stability programs (ESP) or electrohydraulic or electromechanical braking systems.

The slip rings can be arranged axially offset from the at least one coil winding. In a preferred embodiment of the invention, the slip rings are arranged outside the stator or outside the yoke and protrude from it. In other words, the slip ring arrangement can be located outside the housing or yoke. In this way, particularly simple lateral contact is possible. In addition, easier access, for example for maintenance, is possible, and brush abrasion can be kept away from the motor.

The electrical contact of the slip rings can be made in a known manner, for example by means of brushes.

For electronic commutation of the drive arrangement according to the invention, the precise orientation of the drive shaft or the rotor position is required. The invention offers the possibility of being operated both with and without position sensors.

Commutation without position sensors offers the advantage that the position sensors and their installation in the housing are not required, so that this embodiment of the invention can be implemented very cost-effectively. To determine the current rotor position, in the simplest case, the proportion of the induced voltage can be observed from the measured currents and voltages using a motor model and the current angle of rotation for control can be determined from this. The method cannot be used below a certain speed because the induced voltage is too small. A voltage/frequency ramp or current/frequency ramp is therefore usually used to start up until the aforementioned model delivers a valid angle, after which the system switches to closed-loop operation or regular operation.

However, it is also possible to detect the current rotor position in a known manner using sensors. Position sensors can be used for this purpose, for example magnetosensitive sensors such as Hall sensors. Here, it can be provided that three Hall sensors mounted on the stator interact and are scanned with an encoder wheel that is connected to the drive shaft in a rotationally fixed manner.

For example, a so-called resolver can be used, in which two coils can be attached to the stator at a 90 degree angle and a third coil to the drive shaft. When this third coil is energized, a magnetic field is created during operation, which can induce a voltage in the other two coils when they rotate. The maxima of these voltage amplitudes can then be scanned, and the rotor position or the orientation of the drive shaft can be determined with sufficient accuracy.

Incremental encoders based on optical principles can also be used to determine the current rotor position.

Depending on the orientation of the drive shaft, the coil windings can be controlled or energized using the power electronics so that a corresponding torque can be generated. Electronic commutation also offers the advantage that the electromotor drive arrangement can also be operated at very low speeds.

The invention makes it possible to achieve a very compact design of the electromotive drive arrangement while at the same time maintaining a high energy density, which is particularly advantageous for certain uses in braking devices. Here it is often advantageous if the extension in the axial direction, i.e. the length of the drive shaft or yoke, can be kept as short as possible, whereas the extension in the radial direction can be less limited.

In this way, the drive arrangement according to the invention can be very well integrated into existing braking systems.

In a further aspect, the invention comprises a method for operating an electromotive drive arrangement, comprising an electromotive drive arrangement as described above. The drive arrangement can be operated with three-phase alternating current and is electronically commutated.

Further details of the invention emerge from the description of the illustrated embodiments and the appended claims.

The drawings show:

• 1 schematically shows essential components of an electromotive drive arrangement according to the invention in a sectional view perpendicular to the longitudinal axis,
• 2 schematically a winding scheme with three coil windings and a contact arrangement with three slip rings,
• 3 schematically in an oblique view an electric motor drive arrangement according to the invention, and
• 4 schematically in a further oblique view the electromotive drive arrangement according to the invention from 3 .

In the following detailed description of preferred embodiments, like reference numerals designate substantially like parts in or on those embodiments for the sake of clarity. However, to better illustrate the invention, the preferred embodiments shown in the figures are not always drawn to scale.

1 shows schematically essential components of an electromotive drive arrangement 10 according to the invention in a sectional view perpendicular to the longitudinal axis. The electromotive drive arrangement 10 is designed as a permanent magnet direct current machine and can be used together with or for a braking device of a vehicle.

• einen Stator 20 mit zumindest einem, bevorzugt einer Mehrzahl von Permanentmagneten M_j,
• eine rotierbar gelagerte Antriebswelle 30 mit zumindest einer, bevorzugt einer Mehrzahl von auf der Außenwandung der Antriebswelle 30 angeordneten Zähnen S_k und Nuten N_i zur drehfesten Aufnahme von Spulenwicklungen SW_x, und eine Kontaktierungsanordnung 40,
• wobei die Spulenwicklungen SW_x in elektrischen Kontakt mit der Kontaktierungsanordnung 40 stehen und dazu ausgebildet sind, bei Beaufschlagung mit elektrischem Strom mit dem zumindest einen Permanentmagneten M_j derart zusammen zu wirken, dass im Betrieb ein Drehmoment auf die Antriebswelle 30 erzeugt werden kann, und wobei die Kontaktierungsanordnung 40 zumindest einen Schleifring 41 umfasst.

The electric motor drive arrangement comprises 10

• a stator 20 with at least one, preferably a plurality of permanent magnets M _j ,
• a rotatably mounted drive shaft 30 with at least one, preferably a plurality of teeth S _k and grooves N _i arranged on the outer wall of the drive shaft 30 for the rotationally fixed reception of coil windings SW _x , and a contact arrangement 40,
• wherein the coil windings SW _x are in electrical contact with the contacting arrangement 40 and are designed to interact with the at least one permanent magnet M _j when supplied with electrical current such that a torque can be generated on the drive shaft 30 during operation, and wherein the contacting arrangement 40 comprises at least one slip ring 41.

In the 1 In the embodiment shown, the drive shaft 30 comprises a total of nine teeth S _k with k = 1, ..., 9, as well as nine corresponding grooves N _i with i = 1, ..., 9. The contact arrangement 40 is in the 1 not shown.

A total of three coil windings SW _x with x = 1, ..., 3 (only indicated in the illustration shown) are alternately held by this arrangement. The coil windings SW _x are in electrical contact with the contact arrangement 40. The coil windings SW _x are designed as a three-phase three-phase winding with a delta connection.

2 shows schematically the corresponding winding scheme with three coil windings SW ₁ , SW ₂ and SW ₃ as well as the contact arrangement 40 with three slip rings 41, 42 and 43. Accordingly, one slip ring 41, 42, 43 is provided for each phase. Power electronics with bridge circuit 50 are provided for control, in the example a B6 bridge of a vehicle.

The contact arrangement 40 is connected to a corresponding operating voltage source in order to be able to supply current to the coil windings. A star connection is also conceivable and possible.

In this way, when electrical current is applied to the coil windings SW _{x ,} they can interact with the permanent magnets M _j of the stator 20 in such a way that, during operation, a torque can be generated on the drive shaft 30, which can set the drive shaft 30 in rotation.

The teeth S _k and the corresponding grooves N _i are, as shown in the 1 recognizable, are assigned to the rotor of the electromotive drive arrangement 10 and thus represent a central component of the drive shaft 30.

The stator 20 is designed with permanent magnets M _j arranged inside. In the exemplary embodiment, a total of six permanent magnets M _j with j = 1, ..., 6 are provided. Neighboring permanent magnets, in the exemplary embodiment, for example M ₁ and M ₂ , are magnetized in opposite directions. The permanent magnets M _j are designed as ferrite magnets and can therefore be manufactured very inexpensively. The stator 20 is arranged coaxially to the drive shaft 30.

The supply of the electromotive drive arrangement 10 according to the invention is therefore via the three slip rings 41, 42, 43, so that during operation of the drive arrangement a magnetic rotating field is generated in the rotor, which sets the drive shaft 30 in rotation.

According to a preferred embodiment, the slip rings 41, 42, 43 are arranged axially offset from the at least one coil winding. 3 shows schematically in an oblique view an electromotive drive arrangement 10 according to the invention using the example of an electric motor 60. The electric motor 60 is designed as a permanent magnet direct current machine.

The electric motor 60 comprises a housing 65 with holding means 66, which are 3 are only indicated, for easy attachment, for example to a braking device. The drive shaft 30 is led out of the yoke and out of the housing 65. The slip rings 41, 42, 43 are arranged at least partially outside the stator or outside the housing 65 on the drive shaft 30, thus essentially on the section 64 of the drive shaft 30 protruding from the housing 65. This enables easy lateral contact via brushes 61, 62, 63.

4 shows schematically in a further oblique view the electromotive drive arrangement according to the invention from 3 , whereby the housing 65 is not shown for better illustration.

In the 4 the contacts 71, 72, 73 of the brushes 61, 62, 63 are shown. In addition, magnetic elements 67, 68 and 69 are shown, which are each magnetized differently at their opposite ends and thus each comprise two oppositely polarized permanent magnets M _j . The magnetic element 67 thus integrates the permanent magnets M ₁ and M ₂ .

In the embodiment shown, the orientation of the drive shaft 30 or the rotor position is detected without position sensors, which means that no position sensors are required in the housing 65.

Of course, the invention also makes it possible to detect the current rotor position in a known manner by means of sensors, for which position sensors, for example magnetosensitive sensors such as Hall sensors, are preferably provided.

Here, for example, it can be provided that three Hall sensors mounted on the stator interact with and are scanned by an encoder wheel that is connected to the drive shaft in a rotationally fixed manner. The invention makes it possible to achieve a very compact design of the electromotive drive arrangement while at the same time maintaining a high energy density, which is particularly advantageous for certain uses in braking devices.

In this way, the drive arrangement according to the invention can be very well integrated into existing braking systems.

The invention also provides a method for operating an electric motor drive arrangement 10, which comprises an electric motor drive arrangement 10 as described above.

List of reference symbols

10

Electromotor drive arrangement

20

stator

30

drive shaft

40

Contact arrangement

41

Slip ring

42

Slip ring

43

Slip ring

50

B6 bridge circuit

60

Electric motor

61

brush

62

brush

63

brush

64

Section

65

Housing

66

Holding devices

67

Magnetic element

68

Magnetic element

69

Magnetic element

71

Contacting

72

Contacting

73

Contacting

No

Groove, i = 1, ..., 9

Mj

Permanent magnet, j = 1, ..., 6

Sk

Tooth, k = 1, ..., 9

SWx

Coil winding, x = 1, ..., 3

Claims (12)

Electromotive drive arrangement (10), in particular a permanently excited direct current machine, preferably for a braking device of a vehicle, comprising - a stator (20) with at least one, preferably a plurality of permanent magnets (M _j ), - a rotatably mounted drive shaft (30) with at least one, preferably a plurality of teeth (S _k ) and grooves (N _i ) arranged on the outer wall of the drive shaft (30) for the rotationally fixed reception of coil windings (SW _x ), and - a contacting arrangement (40), wherein the coil windings (SW _x ) are in electrical contact with the contacting arrangement (40) and are designed to interact with the at least one permanent magnet (M _j ) when supplied with electrical current in such a way that a torque can be generated on the drive shaft (30) during operation, and wherein the contacting arrangement (40) comprises at least one slip ring (41, 42, 43). Electromotive drive arrangement (10) according to the preceding claim, characterized in that the electromotive drive arrangement (10) can be operated with three-phase alternating current. Electromotive drive arrangement (10) according to one of the preceding claims, characterized in that the coil windings (SW _x ) are designed as a three-phase three-phase winding with delta connection or star connection. Electromotive drive arrangement (10) according to one of the preceding claims, characterized in that the contacting arrangement (40) comprises a slip ring (41, 42, 43) for each phase. Electromotive drive arrangement (10) according to one of the preceding claims, characterized in that the slip rings (41, 42, 43) are arranged axially offset to the at least one coil winding, preferably outside the stator (20) or outside the housing (65). Electromotive drive arrangement (10) according to one of the preceding claims, characterized in that the electrical contacting of the slip rings (41, 42, 43) of the contacting arrangement (40) takes place by means of brushes (61, 62, 63). Electromotive drive arrangement (10) according to one of the preceding claims, characterized in that the contacting arrangement (40) comprises power electronics with a bridge circuit (50) for control. Electromotive drive arrangement (10) according to one of the preceding claims, characterized in that the commutation takes place without a position sensor, wherein the current inductance is preferably measured to determine the current rotor position and is used to determine the rotor position. Electromotive drive arrangement (10) according to one of the preceding Claims 1 until 7 , characterized in that the commutation is sensor-supported, wherein the current rotor position is detected by means of sensors, in particular position sensors, for example magnetosensitive sensors such as Hall sensors, or by means of a resolver. Electromotive drive arrangement (10) according to one of the preceding claims, characterized in that the diameter of the stator is equal to or greater than the length of the stator, preferably larger by a factor of two and particularly preferably larger by a factor of 2.5 or even 3, or more. Electromotive drive arrangement according to one of the preceding claims, characterized in that the electromotive drive arrangement (10) is designed as an internal rotor arrangement. Method for operating an electromotive drive arrangement (10), wherein the method comprises or interacts with an electromotive drive arrangement (10) according to one of the preceding claims.

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