CN111600406A - Rotor for an electric machine and electric machine having such a rotor - Google Patents

Abstract

The invention relates to a rotor (10) for an electric machine (12), comprising a base body (20) which extends concentrically around an axial rotor shaft (14), wherein the base body (20) consists of individual axially stacked plate laminations (32), wherein magnet recesses (18) are formed in the radially outer regions (23) of the plate laminations, into which permanent magnets (16) engage, and wherein pole covers (40) having an outer contour (11) are formed radially outside the magnet recesses (16), wherein axial welds (55) are formed in the pole covers (40) which connect at least the two uppermost plate laminations (32) to one another in a material-locking manner in the axial direction (8).

Description

Rotors of electric machines and electric machines with such rotors

technical field

The present invention relates to a rotor of an electric machine and an electric machine having such a rotor.

Background technique

An electric motor having a rotor with a laminated core is known from DE 10 2007 005 032 A1, wherein the magnets are arranged in recesses in the laminated core. The magnets are constructed longer in the circumferential direction than in the radial direction and are held in the recesses by means of elastic webs. Arranged radially outside the magnets are rotor poles, which are formed axially by stacking individual plate laminations. The plate stacks are axially connected to each other. In certain application cases, however, undesired axial movements of the sheet metal laminations relative to one another can occur in the radially outer region, which are associated with disturbing noise generation or, in extreme cases, fatigue of the pole caps. /break associated. This disadvantage should be eliminated by the solution according to the invention.

SUMMARY OF THE INVENTION

In contrast to this, the rotor and the electric machine according to the invention with the features of the independent claims have the advantage that, by welding through the pole shields in the axial direction, the plate laminations are also securely connected to each other in the radially outer region. connect. This prevents, during operation, that the plate laminations vibrate relative to one another in the axial direction and thus create a rattling noise. Contrary to the opinion common in the art, the detent torque of the rotor can at the same time be reduced by axial welding with a high magnetic flux radially inside the pole shield. Therefore, such rotors are also suitable for applications with high stopping torque requirements, such as for example for servo steering.

Advantageous developments and refinements of the embodiments specified in the independent claims can be achieved by the measures recited in the dependent claims. It is therefore particularly advantageous if the axial weld is formed in the central region of the pole shield with respect to its circumferential direction. By centrally arranging the axial welds, the pole shields are optimally connected to each other in the axial direction in order to dampen axial vibrations of the plate laminations. Meanwhile, the circumferential area in the middle of the pole shield is the area with the maximum magnetic flux density. Contrary to the know-how common to date, it has been shown that the retaining torque can be positively influenced by changing the material by welding in the pole shield in the region of the greatest magnetic flux. By arranging the axial weld in the region of the greatest magnetic flux, the magnetic flux is formed more uniformly with respect to the circumferential direction of the rotor.

This effect is particularly advantageous in the case of magnet recesses which are designed to be completely closed over their entire circumference transversely to the rotor axis. In this case, the pole shield is located radially outside the magnet recess and is connected on its two tangential sides to the radially inner region of the plate stack by means of radial retaining webs. In this embodiment, the extension of the pole cap in the circumferential direction is significantly greater than its extension in the radial direction. This also applies to permanent magnets that are pressed into magnet recesses.

In this arrangement, in which the substantially square permanent magnets have a greater extent in the tangential direction than in the radial direction, the magnetic field lines extend radially from the permanent magnets through the pole shields to the outer contour of the rotor. Here, the permanent magnets have magnetizations in the radial direction, such that in the circumferential direction pole caps with north poles alternate with pole caps with south poles.

In principle, it is also conceivable that, in the case of permanent magnet storage assemblies, the pole segments between the tangentially magnetized permanent magnets are arranged in the radially outer region by means of such an axial welding, so that the sheet metal laminations are formed. In the radially outer region, they are fixedly connected to each other in the axial direction.

It is particularly advantageous if the individual sheet metal laminations each have insulating surfaces which bear against each other in the axial direction. As a result, eddy currents inside the rotor are reliably suppressed. Such an insulating coating can be achieved, for example, by thermal treatment of individual sheet laminates, or by means of a carbon-containing coating, like for example a C ₃ or C ₅ coating. In the region of the axial weld, the pole caps are connected to one another in the axial direction in a cohesive manner, so that the insulation is also destroyed in this region, and thus the sheet metal laminations are to one another along the weld curvature in the axial direction electrical contact.

The axial weld is particularly advantageously carried out by means of laser welding, wherein the laser beam penetrates the first plate lamination completely in the axial direction from the axial end face of the rotor cover and penetrates in the axial direction as far as the second, or third, Either the fourth, or the fifth plate lamination. This results in a welding point, which is configured in the axial direction as an axial welding camber, which is preferably arranged radially inside the outer contour of the rotor.

It is particularly advantageous if the axial weld is arranged inside the pole shield in the vicinity of the permanent magnet. The detent torque is influenced particularly advantageously if the center point of the axial weld is arranged between 20% and 45% with respect to the radial height of the pole hood in the radially inner region of the radial height. It has surprisingly been found that by arranging the center point of the axial weld closer to the permanent magnet, the detent torque can be significantly reduced. However, the center point of the axial weld cannot be arranged arbitrarily close to the permanent magnet so that it is not affected so strongly during the welding process.

The laser weld has, for example, a circular cross-section on the axial end face of the pole shield, which is larger than the cross-section in the underlying plate stack. The axial weld therefore has a tapering cone in the axial direction, which preferably has a circular cross-section.

Depending on the size of the rotor, the diameter of the axial weld on the axial end side of the pole shield is, for example, 0.8 mm to 1.8 mm. The diameter of this axial weld decreases with its axial depth, so that, for example, its diameter is only 0.1 to 0.5 mm in the second or third plate laminate.

In order to influence the locking torque of the rotor in a targeted manner, the outer contour of the individual pole shields has an approximately sinusoidal shape or a so-called Richter contour. Thereby, the circumference of the rotor deviates from an exact circle, so that the radius of the rotor is smaller at the edge regions of the circumference of the permanent magnets than in the middle circumferential region of the permanent magnets.

For a mechanically stable embodiment of the rotor, exactly one axial weld is formed on each pole cover, wherein the axial weld is preferably formed on two opposite axial end faces of the pole cover. In this way, the plate stacks are prevented from colliding axially with each other in each individual pole cap. Here, the axial weld extends axially through the plurality of plate laminations.

The extension of the permanent magnets in the axial direction is preferably greater than the extension in the tangential direction and in the radial direction. To assemble the permanent magnets, the permanent magnets are simply pressed axially into the magnet recesses, wherein the permanent magnets are pressed radially outwards against the pole shields by means of spring webs formed on the plate laminations. Preference is given to using rare earth magnets, in particular with NdFeB, as permanent magnets.

Such a rotor according to the invention is preferably arranged within a stator, which is part of the electric machine. The electric machine is preferably designed as an electrically commutated electric motor, wherein the stator has electronically commutated windings which bring the rotor and the permanent magnets into motion. Such an EC motor is preferably used in a motor vehicle as a steering auxiliary drive, but can also be used for other actuating drives of components in the motor vehicle or for rotating rotary drives. Such electric machines with low detent torque can of course also be used for applications other than motor vehicles.

Description of drawings

In the following description, preferred exemplary embodiments of the invention are explained in detail with reference to the drawings, in which corresponding elements are provided with corresponding reference numerals. which shows:

Figure 1 shows a view of a rotor according to the invention of an electric machine,

Figure 2 shows a detail view of an axial top view of the rotor, and

Figure 3 shows another embodiment of the rotor in side view.

Detailed ways

A rotor 10 is shown in FIG. 1 as it is used, for example, in an electric machine 12 . The rotor 10 has a rotor shaft 14 on which a base body 20 is arranged concentrically therewith. The base body 20 is, for example, press-fitted onto the rotor shaft 14 . The base body 20 consists of individual plate laminations 32 which are stacked axially on top of each other in the axial direction 8 . The individual sheet metal laminations 32 are stamped, for example, from electrical steel sheets and are pressed together with respect to the axial direction 8 preferably by means of stamping stacks.

For this purpose, caulking points 80 are preferably formed radially within the permanent magnets 16 , which caulking points connect all the sheet metal laminations 32 to one another. In the radially inner region 22 , the basic body 20 has a relatively large cutout 24 , so that the radially outer region 23 is connected to the hub 28 of the basic body 20 only by relatively thin radial webs 26 . Therefore, the rotor size and inertia moment of the rotor are mainly reduced. In the radially outer region 23 , a magnet recess 18 is hollowed out in the base body 20 , into which the permanent magnet 16 engages axially. In this exemplary embodiment, the permanent magnets 16 have a substantially rectangular cross-section whose extent 34 in the circumferential direction 9 is greater than the extent 35 of the permanent magnets 16 in the radial direction 7 . The magnet recesses 18 have a closed circumference such that the permanent magnets 16 are arranged completely inside the circumferential surface of the rotor 10 . A pole cover 40 is formed radially outside the magnet recess 18 , via which the magnetic flux is transmitted from the permanent magnet 16 to the outer contour 11 of the pole cover 40 . The pole shield 40 cooperates, for example, with a stator 42 which is arranged radially outside the rotor 10 . The stator 42 here has, for example, electronically commutated stator coils 43 which interact magnetically with the pole shield 40 . Between the magnet recesses 18 in the circumferential direction 9 , holding tabs 19 are formed, which are part of the circumference of the magnet recess 18 . The permanent magnets 16 preferably bear against the holding tabs 19 in the circumferential direction 9 . The retaining lugs 19 transition into the pole shields 40 in the circumferential direction 9 , so that the permanent magnets 16 are retained in the fully closed magnet recess 18 towards the rotor shaft 14 . An axial welded connection 55 is formed on the pole cap 40 , which axially extends through the at least two sheet metal laminations 32 in order to connect them to one another in a cohesive manner. The axial welded connections 55 preferably do not extend over the entire axial length of the rotor 10 , but only over the first two to five plate laminations 32 starting from the end sides 56 , 57 of the rotor 10 . According to the invention, the axial welded connection 55 is formed by means of laser welding, wherein the laser beam penetrates axially on the end face 56 of the rotor 10 and completely axially welds one or more sheet metal laminations 32 to one another. In this case, the weld bead 58 is designed as a weld seam, which extends in the axial direction through the laminated core 32 . Only the end face 56 of the rotor 10 with the axial welded connection 55 is visible in FIG. 1 . Preferably, however, an axial welded connection 55 is also formed on the pole shield 40 on the opposite end side 57 . In FIG. 1 , on each pole shield 40 exactly one axial welded connection 55 is formed over the entire circumference on the end sides 56 , 57 in each case. This prevents that the plate stacks 32 can move axially relative to each other on the outer contour 11 during operation of the electric machine 12 .

Another embodiment of a rotor 10 according to the invention is shown as a partial detail in FIG. 2 . The permanent magnet 16 engages in the magnet recess 18 and is here tensioned radially in the magnet recess 18 by means of clamping clips 38 .

For example, clamping lugs 38 are formed here on the circumference of the magnet recesses 18 , which clamp the permanent magnets 16 in the corresponding magnet recesses 18 . In order for the clamping webs 38 to be designed elastically, they are stamped, for example, only in every second or every n laminations, so that free spaces are formed between the clamping webs 38 in the axial direction 8 . The permanent magnets 16 rest on the holding tabs 19 on both sides in the circumferential direction 9 . Profiles 60 are each freed from magnet recesses 18 in circumferential direction 9 in order to reduce flux leakage losses. It can be seen in FIG. 2 that the outer contour 11 of the pole cap 40 differs from the circular shape 62 . For example, the pole cap 40 has a sinusoidal profile 64 or a so-called corrector profile, by means of which the blocking torque of the rotor 10 can be influenced accordingly. The axial welded connection 55 is arranged at the axial side 66 of the pole cap 40 approximately centrally with respect to the extent of the pole cap 40 in the circumferential direction 9 . The pole shield 40 has a radial height H which extends radially from the magnet recess 18 to the outer contour 11 of the pole shield 40 . The radial height H is configured to the greatest extent in the central region with respect to the circumferential direction 9 . The axial welded connection has a center point 54 which, starting from the magnet recess 18 , is arranged in the range between 20% and 50% of the radial height H. In order to have a positive influence on the detent torque, starting from the magnet recess 18 , the center point 54 of the axial weld 55 lies in the range between 25% and 40% of the radial height H. The cross section 53 of the laser welding 55 is preferably circular, but can also have a shape different from this. Since the center point 54 of the axial welded connection 55 is arranged radially inside the radial height H of the pole cap 40 , the outer contour 11 of the pole cap 40 has no welds in this region.

In an alternative, not shown embodiment, more than one axial weld 55 can also be arranged inside a pole cap 40 and/or the center point 54 of the welded connection 55 can also be arranged with respect to the circumferential direction 9 are arranged eccentrically.

Another embodiment of the rotor 10 according to the invention is shown in FIG. 3 as a side view. The weld 55 is not visible on the outer contour 11 of the pole cap 40 . On the other hand, the axial welding portion 55 is arranged radially inside the pole cover 40 so that the cross-section 55 of the axial welding portion 55 does not intersect the outer contour 11 .

The axial weld 55 is shown here in phantom as a type of weld bevel 58 , the cross-section 53 of which, starting from the axial end face 56 of the rotor 10 , in the axial direction 8 from the plate laminations 32 towards the plate laminations 32 decrease. For example, the diameter 52 of the substantially circular cross-section 53 of the laser weld 55 is 0.7 mm to 2.0 mm on the axial end side 66 of the pole shield 40 of the first plate stack 31 . In the second plate lamination 33 the diameter is already smaller, and in the third plate lamination 36 the diameter 51 is for example only between 0.1 and 0.5 mm. The welding arch 58 ends in the third plate laminate 36 in FIG. 3 . Alternatively, however, the welding curvature 58 can also extend to the fourth or fifth plate stack 32 . The welding bead 58 is conical in the side view shown, wherein an arcuate welding point 70 can be formed on the end face 66 of the pole cap 40 . In this embodiment, the individual plate stacks 32 have an insulating coating 72 so that eddy currents in the axial direction 8 are suppressed. The coating 72 can be designed, for example, as a carbon-containing covering, which, for example, contains C ₃ or C ₅ . In the region of the axial weld bead 58 , the insulating coating 72 is melted, so that in the region of the axial weld 55 the individual sheet metal laminations 32 are connected to one another in an electrically conductive manner in the axial direction 8 . A typical thickness 74 of these plate stacks 32 in the axial direction 8 is, for example, about 0.5 mm.

It is to be noted that with regard to the embodiments shown in the drawings and in the description, various combinations of individual features with one another are possible. Thus, for example, the specific configuration, arrangement and number of permanent magnets 16 with corresponding pole shields 40 may vary. The specific location and configuration of the axial weld 55 within the pole shield 40 can likewise be adapted to the requirements and manufacturing possibilities of the electric machine 12 . With the aid of the specific design of the outer contour 11 of the pole shield 40 , the desired locking torque of the electric machine 12 can be designed in conjunction with the arrangement of the axial welding cambers 58 . The invention is particularly suitable for the rotational drive of assemblies or the adjustment of components in motor vehicles, but can also be used for other applications, such as for the drive of bicycles or powered wheels. The electric machine 12 is preferably designed as a synchronous motor, which can be used as a drive for various applications, in particular as a steering assist motor for a servo steering.

Claims (14)

1. A rotor (10) for an electric machine (12) having a base body (20) which extends concentrically around an axial rotor shaft (14), wherein the base body (20) consists of a single axially stacked plate lamination (32), in the radially outer region (23) of which a magnet recess (18) is formed, into which a permanent magnet (16) engages, and radially outside the magnet recess (16) a pole housing (40) having an outer contour (11) is formed,

characterized in that an axial weld (55) is formed in the pole housing (40), which connects at least two uppermost plate laminations (32) to one another in a material-locking manner in the axial direction (8).

2. The rotor (10) as claimed in claim 1, characterized in that the axial weld (55) is arranged substantially centrally in the pole shield (40) with respect to the circumferential direction (9) of the rotor (10) and in particular radially inside the outer contour (11).

3. The rotor (10) according to one of the preceding claims, characterized in that the magnet recess (18) is configured to be completely closed and the pole cover (40) is configured to be larger in the circumferential direction (9) than in the radial direction (7).

4. The rotor (10) according to any one of the preceding claims, characterized in that the permanent magnets (16) are magnetized in a radial direction (7) such that magnetic field lines (50) of the permanent magnets extend radially outwards through the pole housing (40) to the outer contour (11).

5. The rotor (10) according to any one of the preceding claims, characterised in that the permanent magnets (16) have a greater dimension in the circumferential direction (9) than in the radial direction (7).

6. Rotor (10) according to one of the preceding claims, characterized in that the plate stack (32) has an insulation layer (72) which electrically insulates the plate stacks (32) relative to one another in the axial direction (8), in particular made of carbon C₃Or C₅Is produced and two axially adjacent plate laminations (32) are connected to each other in an electrically conductive manner locally on the axial weld (55).

7. The rotor (10) according to one of the preceding claims, characterized in that the axial weld (55) is configured as a laser weld arch (58) which, proceeding from the axial end side (56) of the uppermost plate lamination (32), penetrates axially at least into the second or third plate lamination (32).

8. The rotor (10) according to one of the preceding claims, characterized in that the pole shield (40) has a radial height (H) from the magnet recess (18) up to its outer contour (11), and the center point (54) of the axial weld (55) is arranged within an inner half (H/2), in particular within an inner third, of the radial height (H).

9. The rotor (10) according to any one of the preceding claims, characterized in that the cross section (53) of the axial weld (55) is substantially circular and the diameter (52) of the cross section (53) decreases with the axial depth (59) of the axial weld (55) starting from the outer axial end side (56) of the uppermost plate lamination (32).

10. The rotor (10) as recited in any one of the preceding claims, characterized in that the diameter (52) of the cross section (53) of the axial weld (55) is about 1.0 to 2.0 mm on the outer axial end side (56) of the uppermost plate lamination (32) and about 0.1 to 0.4 mm within the third plate lamination (32).

11. The rotor (10) according to any one of the preceding claims, characterized in that the circumferential profile of the rotor (10) differs from the exact circular shape (13) and in particular the individual pole covers (40) have a sinusoidal or rectifier profile (64) or other spline curve profile.

12. The rotor (10) according to one of the preceding claims, characterized in that exactly one axial weld (55) is arranged in each pole cap (40) with respect to the circumferential direction (9), in particular on both axial end sides (56, 57) of the rotor (10).

13. The rotor (10) according to one of the preceding claims, characterized in that the permanent magnets (16) are pressed radially outwards against the pole housing (40) inside the magnet recess (18) by means of clamping tabs (38) formed on the plate pack (32).

14. An electrical machine (12), in particular an electric motor, wherein the rotor (10) according to any of the preceding claims is arranged radially inside a stator (42) having electronically commutated electrical windings (43).

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