DE102018121664A1 - Brushless DC motor with magnetic material in a gap or shield plate - Google Patents

Abstract

Brushless DC motor (1), at least comprising: - a stator (2), - a rotor (3) with a plurality of magnets (4), the rotor (3) being arranged coaxially to the stator (2) and relative to the stator (2 ) is rotatable about an axis of rotation (5) and wherein a gap (6) is formed between the stator (2) and the rotor (3) and a magnetic material (7) which is arranged in the gap (6), or - A shield plate (8) which is arranged orthogonally to the axis of rotation (5) at a longitudinal end (9) of the rotor (3).

Description

The present invention relates to a brushless DC motor (BLDC motor). Such brushless DC motors are regularly constructed like a three-phase synchronous machine with excitation by permanent magnets.

Due to larger inaccuracies / tolerances, an air gap of the BLDC motor must be enlarged. This results in larger stray fields outside the stator / rotor, which can interfere with locally present sensors or electronics.

It is therefore an object of the invention to at least partially solve the problems described with reference to the prior art and, in particular, to provide a brushless DC motor whose stray fields are at least reduced.

This object is achieved with a brushless DC motor according to the features of the independent claim. Further advantageous embodiments of the invention are specified in the dependent claims. It should be pointed out that the features listed individually in the dependent claims can be combined with one another in any technologically expedient manner and define further refinements of the invention. In addition, the features specified in the claims are specified and explained in more detail in the description, further preferred embodiments of the invention being illustrated.

• - einen Stator,
• - einen Rotor mit einer Mehrzahl von Magneten, wobei der Rotor koaxial zum Stator angeordnet und relativ zum Stator um eine Drehachse drehbar ist und wobei zwischen dem Stator und dem Rotor ein Spalt ausgebildet ist sowie
• - ein magnetisches Material, das in dem Spalt angeordnet ist, oder
• - ein Schirmblech, das orthogonal zu der Drehachse an einem längsseitigen Ende des Rotors angeordnet ist.

A brushless DC motor with at least the following components contributes to this:

• - a stator,
• a rotor with a plurality of magnets, the rotor being arranged coaxially to the stator and being rotatable relative to the stator about an axis of rotation and a gap being formed between the stator and the rotor and
• a magnetic material arranged in the gap, or
• - A shield plate, which is arranged orthogonally to the axis of rotation at a longitudinal end of the rotor.

In the case of brushless DC motors, the rotor is equipped with (permanent) magnets and the fixed stator encompasses the coils. In addition to the inner rotor, the structure as an outer rotor is also often used. The winding is usually designed as a three-phase system and, depending on the speed range, with a low to very high number of poles. The (permanent) magnets that are required to generate the torque in brushless DC motors lead to undesired stray fields at the ends of the rotor. These stray fields influence e.g. the sensors for determining the current rotor position. The stray fluxes should be shielded to such an extent that the disruptive influence on the sensors is minimized or excluded. This is intended to dispense with a larger axial distance or an adaptation of the sensor magnets. For this purpose, the brushless DC motor can have a magnetic material which is arranged in an (air) gap between the stator and the rotor. Alternatively or cumulatively, the brushless DC motor can have a shield plate. The shield plate is (essentially) orthogonal to an axis of rotation of the rotor and / or to the (air) gap. As a result, the magnetic field strengths acting orthogonally to the air gap are damped or magnetically short-circuited. In addition to the shield plate, a magnetic material can be on the rotor. As a result, the above-mentioned disturbance variables - based on the rotor magnets - or stray fields can also be minimized.

The magnetic material can be sleeve-shaped.

The magnetic material can be arranged on stator teeth of the stator. In particular, the magnetic material can (directly) rest on the stator teeth.

The magnetic material can be formed on the rotor. In particular, the magnetic material can rest on the rotor. In addition, the magnetic material can be designed, for example, in the manner of a burst protection sleeve.

• 1: eine erste Variante eines bürstenlosen Gleichstrommotors in einer Draufsicht;
• 2: die erste Variante des bürstenlosen Gleichstrommotors in einer Schnittdarstellung;
• 3: eine zweite Variante eines bürstenlosen Gleichstrommotors in einer Draufsicht;
• 4: die zweite Variante des bürstenlosen Gleichstrommotors in einer Schnittdarstellung;
• 5: eine dritte Variante eines bürstenlosen Gleichstrommotors in einer Draufsicht;
• 6: die dritte Variante des bürstenlosen Gleichstrommotors in einer Schnittdarstellung;
• 7: eine vierte Variante eines bürstenlosen Gleichstrommotors in einer Draufsicht; und
• 8: die vierte Variante des bürstenlosen Gleichstrommotors in einer Schnittdarstellung.

The invention and the technical environment are explained in more detail below with reference to the figures. It should be noted that the figures show particularly preferred variants of the invention, but this is not restricted to this. The same components are provided with the same reference numerals in the figures. Exemplarily and schematically, they show:

• 1 : a first variant of a brushless DC motor in a plan view;
• 2 : the first variant of the brushless DC motor in a sectional view;
• 3 : a second variant of a brushless DC motor in a plan view;
• 4 : the second variant of the brushless DC motor in a sectional view;
• 5 : a third variant of a brushless DC motor in a plan view;
• 6 : the third variant of the brushless DC motor in a sectional view;
• 7 : a fourth variant of a brushless DC motor in a plan view; and
• 8th : the fourth variant of the brushless DC motor in a sectional view.

The 1 shows a first variant of a brushless DC motor 1 in a top view. The brushless DC motor 1 includes a stator 2 and a rotor 3 , The rotor 3 is coaxial with the stator 2 arranged and relative to the stator 2 about an axis of rotation 5 rotatable. The axis of rotation 5 runs orthogonal to the plane of the drawing. The rotor 3 has a plurality of magnets on its outer peripheral surface 4 on, which are designed here in the manner of permanent magnets. Between the rotor 3 and the stator 2 is an (air) gap 6 trained in which a magnetic material 7 is arranged. The magnetic material 7 can be ferromagnetic or paramagnetic. Furthermore, the magnetic material 7 parallel to the axis of rotation 5 sleeve-shaped and (directly) on stator teeth 10 of the stator 2 arranged. This leads to a reduction in the magnetic (air) gap 6 and thus to an increase in the torque of the brushless DC motor 1 , However, arise between the individual stator teeth 10 also magnetic connections, which are created by the inserted magnetic material in the air gap and lead to stray fluxes and thus again to a reduction in the torque. Through a clever design of the magnetic material 7 can compare the torque to the brushless DC motor 1 without sleeve made of magnetic material 7 or a sleeve made of non-magnetic material. By reducing the (air) gap 6, the stray fields at the edge of the rotor ( 3 ) less, which means that the sensors not shown here are less influenced.

The 2 shows the first variant of the brushless DC motor 1 in a sectional view. The rotor can be seen here 3 with the magnet 4 and the stator 2 , Between the stator 2 and the rotor 3 is the magnetic material 7 in the gap 3 arranged.

The 3 shows a second variant of the brushless DC motor 1 in a top view. The second variant of the brushless DC motor 1 differs from the first variant of the brushless DC motor 1 only in that the magnetic material 7 on the magnet 4 of the rotor 3 is attached. The magnetic material 7 is also sleeve-shaped or in the form of a rotor sleeve (also called burst protection). Furthermore, the magnetic material 7 here on the rotor 3 pushed. This leads to a reduction in the (air) gap 6 and thus to an increase in the torque of the brushless DC motor 1 , However, arise directly above the magnet 4 magnetically conductive bridges that lead to stray fluxes and thus to a reduction in torque. About the saturation field strength of the magnetic material 7 Especially in these areas, the stray fluxes can be reduced and thus the loss of torque can be limited. Furthermore, the magnetic material 7 be designed so that the torque increase by reducing the (air) gap 6 the stray flows across the bridges between the magnets 4 compensated. Here, too, is the leakage flow at the edge of the rotor through the smaller (air) gap 3 smaller and thus the influence on the sensor system not shown here is also less.

The 4 shows the second variant of the brushless DC motor 1 in a sectional view along the in the 3 shown cutting line IV-IV , The rotor can be seen here 3 with the magnet 4 and the stator 2 , Between the stator 2 and the rotor 3 is the magnetic material 7 in the gap 3 arranged.

The 5 shows a third variant of a brushless DC motor 1 in a top view. The third variant of the brushless DC motor 1 differs from the first variant of the brushless DC motor 1 only by the fact that on the rotor 3 an edge-side shield plate 8th is arranged and there is no magnetic material in the air gap. The shield plate 8th (e.g. shape of a washer) with a high permeability lies on the side of the rotor facing the sensor system (not shown here) 3 on. Here the stray fluxes are short-circuited, which reduces the influence on the sensors.

The 6 shows the third variant of the brushless DC motor 1 in a sectional view along the in the 5 shown cutting line VI-VI , The rotor can be seen here 3 with the magnet 4 and the stator 2 between the rotor 3 and the stator 2 is a crack 6 educated. On the rotor 3 is the shield plate 8th arranged.

The 7 shows a fourth variant of a brushless DC motor 1 in a top view. The fourth variant of the brushless DC motor 1 differs from the third variant of the brushless DC motor 2 just because the rotor 3 a two-part rotor sleeve 11 having. The two-part rotor sleeve 11 can at least partially as a burst protection for the rotor 3 be trained. One to the axis of rotation 5 parallel section of the rotor sleeve 11 can consist of a non-magnetic material or a material with low permeability. As with the second variant of the brushless DC motor, this takes over 1 mechanical tasks and reduces the magnetic (air) gap 6. At one longitudinal end 9 or an end face of the rotor 3 , which points in the direction of a sensor, not shown here, as in the third variant of the brushless DC motor 1 , a shield plate 8th made of a material with high permeability. This shield plate 8th , e.g. B. formed like a disc, the edge-side stray flows "short" and thus prevents the influence of stray flows on the sensors. The shield plate protrudes 8th in a radial direction over the magnets 4 of the rotor 3 , this also short-circuits parts of the air gap flow as stray flows and thus reduces the torque. For this reason, the shield plate is not useful 8th in an axial direction, ie parallel to the axis of rotation 5 , about the magnets 4 to push, but should only go so far over the magnets 4 protrude, as is absolutely necessary for strength, support, etc.

The 8th shows the fourth variant of the brushless DC motor 1 in a sectional view along the in the 7 shown cutting line VIII-VIII , The rotor can be seen here 3 with the magnet 4 and the rotor sleeve 11 as well as the stator 2 , The rotor sleeve 11 is formed in two parts and has at the longitudinal end 9 of the rotor 3 the shield plate 8th on.

Reference list

1

Brushless DC motor

2

stator

3

rotor

4

magnet

5

Axis of rotation

6

gap

7

magnetic material

8th

Shield plate

9

longitudinal end

10

Stator tooth

11

Rotor sleeve

Claims (4)

Brushless DC motor (1), at least comprising: - a stator (2), - A rotor (3) with a plurality of magnets (4), the rotor (3) being arranged coaxially to the stator (2) and being rotatable relative to the stator (2) about an axis of rotation (5) and wherein between the stator (2 ) and the rotor (3) a gap (6) is formed and - A magnetic material (7) which is arranged in the gap (6), or - A shield plate (8) which is arranged orthogonally to the axis of rotation (5) at a longitudinal end (9) of the rotor (3). Brushless DC motor (1) Claim 1 , wherein the magnetic material (7) is sleeve-shaped. Brushless DC motor (1) according to one of the preceding claims, wherein the magnetic material (7) is arranged on stator teeth (10) of the stator (2). Brushless DC motor (1) according to one of the preceding claims, wherein the magnetic material (7) is formed on the rotor (3).

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