Rotor for electric motor

Abstract

The utility model relates to a rotor (10) for an electric motor, which comprises a shell (12) and a base (14) integrally connected with the shell (12), the base (14) is provided with a socket (16) used for a rotor shaft (18), the shell (12) and the base (14) are formed into a whole by injection-molded plastic materials, the plastic materials comprise embedded magnetic particles, and the magnetic particles are magnetized so that the magnetic particles can be inserted into the socket (16) in the circumferential direction. The magnetic poles (20) are formed at a distance from one another, and the inner contour (22) and the outer contour (24) of the housing (12) lie between two concentric circles (32) defined by a maximum outer radius (34) and a minimum inner radius (36) of the housing (12) when viewed in a cross-section perpendicular to the rotor shaft (18). At least one of the contours (22, 24) extends in a curved manner such that it has a periodically varying distance from the central axis of the rotor shaft (18).

Description

Technical Field

[0001] The utility model relates to a rotor for an electric motor, in particular to a driving motor for a hydraulic pump. The rotor comprises a shell formed by injection-molded plastic material, wherein the plastic material comprises embedded magnetic particles. Background Art

[0002] In particular, it is conceivable to produce the housing by an injection molding process of a plastic material. In this process, the magnetic particles can be added as a powder to the plastic material. The plastic material then serves as a matrix for the magnetic particles.

[0003] The magnetic particles may be, for example, NdFeB or ferrite particles.

[0004] Since suitable magnetic particles are not available in unlimited quantities and represent a considerable cost factor for electric motors of this type, it is desirable to use the magnetic particles in a resource-saving manner. Utility Model Content

[0005] It is therefore an object of the present invention to provide a rotor which manages to provide at least approximately the same performance as a rotor of conventional construction, using fewer magnetic particles.

[0006] According to the present invention, this object is achieved by a rotor for an electric motor, particularly a drive motor for a hydraulic pump, comprising a housing and a base integrally connected thereto. The base is provided with a receptacle for the rotor shaft and is integrally formed with the housing from an injection-molded plastic material including embedded magnetic particles. In this case, the magnetic particles are magnetized so that the magnetic poles are formed at a certain distance from each other in the circumferential direction. When viewed in a cross-section perpendicular to the rotor shaft, the inner and outer contours of the housing lie between two concentric circles defined by the maximum outer radius and the minimum inner radius of the housing. At least one contour extends in a curved manner, such that it has a periodically varying distance from the central axis of the rotor shaft.

[0007] The present invention is based on the discovery that magnetic particles arranged in the rotor housing contribute to different degrees to the rotor's available magnetic field, depending on their circumferential position. Therefore, in the rotor according to the present invention, as little material as possible is used in the housing regions that contribute less to the available magnetic field.

[0008] Since the inner and / or outer contour is provided with a periodically varying distance from the central axis of the rotor shaft and magnetic particles are saved, plastic material is also saved, which also leads to a reduction in the overall weight of the rotor.

[0009] In one variant, the housing has an outer contour with a circular cross-section, and the inner contour is extended by a centrally projecting inner projection and an intervening inner recess. In this variant, material is saved in the region of the inner recess, that is, on the inner side of the rotor. This has a lesser impact on the rotor's function than saving material on the outer side of the rotor, since the magnetic field region on the outer side of the rotor, closer to the stator, is particularly relevant for the drive.

[0010] It can be provided that the inner projection has a continuous curvature. The curvature can follow, for example, the course of the magnetic field lines, which has a positive effect on the flux density distribution of the rotor magnetic field.

[0011] In addition, it can also be provided that the inner recess is formed as a variable. In this context, the term "variable" should be understood to mean that the inner recess is conical and / or has a tip radius that is much smaller than the curvature of the inner protrusion. By means of this geometric design, a large amount of material can be saved.

[0012] In this case, the inner recesses can be oriented relative to the magnetic poles. In particular, they can be positioned between the magnetic poles and the rotor axis. This allows the inner contour of the housing and the magnetic field distribution to be tailored to each other. This design has been found to have a positive impact on the motor's driving characteristics.

[0013] Alternatively, the housing can have an inner contour with a circular cross-section, and an outer contour with recesses equidistant from one another in the circumferential direction. The recesses save material on the outer side of the rotor. The resulting additional space between the rotor and stator can, for example, have coolant flowing through it and thus be used for cooling. Furthermore, CFD simulations have shown that wet rotors with corresponding recesses have lower drag losses, which has a positive impact on motor performance.

[0014] Provision can be made for the outer contour to extend at a constant radius between the outer recesses. In particular, the rotor's magnetic poles can be arranged in a region with a constant radius. In this arrangement, the electric motor's magnetic poles are close to the stator. As a result, and due to the resulting equal gap distance between the rotor and stator in the magnetic pole region, efficiency is maximized.

[0015] Furthermore, it is conceivable that the outer recess has a continuous curvature that transitions discontinuously into a section extending at a constant radius. This curvature adapts the outer contour of the rotor to the field lines between the magnetic poles. This allows for a favorable flux density distribution in the rotor magnetic field, which has a positive impact on the drive characteristics.

[0016] Furthermore, it can be provided that the outer recess is arranged offset from the magnetic poles in the circumferential direction. Thus, material can be selectively saved between the magnetic poles. As a result, this material saving has only a minor effect on the drive characteristics of the motor.

[0017] In another variant, it is provided that the housing has an outer contour comprising an outer recess and an inner contour comprising an inner protrusion. In this case, when viewed in the circumferential direction, the outer recess and the inner protrusion are located on the same radius.

[0018] In this embodiment, the outer recess and the inner protrusion can of course also have the above-mentioned characteristics and the advantages associated therewith.

[0019] This geometric design allows for significant material savings both on the outside and on the inside of the rotor.

[0020] Since the outer recess and the inner projection are located on the same radius when viewed in the circumferential direction, it is also ensured that the housing has sufficient thickness and stability over its entire circumference.

[0021] Furthermore, a housing geometry adapted to the magnetic field distribution is thereby provided, which can have a positive influence on the drive characteristics of the motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Further features and advantages of the present invention will become apparent from the following description and the accompanying drawings, to which reference will be made. In the accompanying drawings:

[0023] - Figure 1 is a three-dimensional view of a rotor known in the prior art;

[0024] - Figure 2 yes Figure 1 Axial cross-sectional view of the middle rotor;

[0025] - Figure 3 yes Figure 1 End plan view of the middle rotor;

[0026] - Figure 4 yes Figure 1 Cross-sectional view of the middle rotor;

[0027] - Figure 5 yes Figure 1 An enlarged schematic cross-sectional view of the rotor housing, wherein arrows indicate the contours of the magnetic field;

[0028] - Figure 6 is a three-dimensional view of a first embodiment of a rotor according to the present invention, comprising an inner recess and an inner protrusion;

[0029] - Figure 7 yes Figure 6 Axial cross-sectional view of the middle rotor;

[0030] - Figure 8 yes Figure 6 End plan view of the middle rotor;

[0031] - Figure 9 yes Figure 6 Cross-sectional view of the middle rotor;

[0032] - Figure 10 yes Figure 6 An enlarged schematic cross-sectional view of the rotor housing, wherein arrows indicate the contours of the magnetic field;

[0033] - Figure 11 is a three-dimensional view of a second embodiment of a rotor according to the present invention including an external protrusion;

[0034] - Figure 12 yes Figure 11 Axial cross-sectional view of the middle rotor;

[0035] - Figure 13 yes Figure 11 End plan view of the middle rotor;

[0036] - Figure 14 yes Figure 11 Cross-sectional view of the middle rotor;

[0037] - Figure 15 yes Figure 11 An enlarged schematic cross-sectional view of the rotor housing, wherein arrows indicate the contours of the magnetic field;

[0038] - Figure 16 is a three-dimensional view of a third embodiment of a rotor according to the present invention, comprising an inner recess, an inner bulge, and an outer protrusion;

[0039] - Figure 17 yes Figure 16 Axial cross-sectional view of the middle rotor;

[0040] - Figure 18 yes Figure 16 End plan view of the middle rotor;

[0041] - Figure 19 yes Figure 16 a cross-sectional view of the middle rotor; and

[0042] - Figure 20 yes Figure 16 Enlarged schematic cross-sectional view of the rotor housing, where arrows indicate the contours of the magnetic field. DETAILED DESCRIPTION

[0043] Figures 1 to 5 A cup-shaped rotor 10 as known in the art is shown. The rotor 10 comprises a housing 12 and a base 14.

[0044] The base 14 has a socket 16 for a rotor shaft 18. In the figure shown, the rotor shaft 18 is located in the socket 16.

[0045] The rotor 10 comprises five pole pairs formed by poles 20 arranged on opposite sides of the rotor. Figure 5 Only parts of the magnetic poles 20 and the field lines are shown by arrows.

[0046] The housing 12 has a circular inner contour 22 and a circular outer contour 24 .

[0047] Figures 6 to 10 A first embodiment of a rotor 10 according to the invention is shown. For similar or functionally similar features, the same reference numerals as in the previously described figures are used, and in this respect reference is made to the above explanations.

[0048] Figures 6 to 10 The rotor 10 shown is used for a drive motor of a hydraulic pump. This is of course not to be understood as a limitation. Other fields of application are also conceivable.

[0049] The rotor 10 comprises a housing 12 and a base 14 integrally connected to the housing 12. The base 14 has a socket 16 for a rotor shaft 18, in which the rotor shaft 18 is located in the figure shown.

[0050] from Figures 6 to 9 It can be seen that the base 14 is provided with a plurality of through-holes 26, which connect the volume arranged inside the housing 12 to the outside of the rotor 10. Internal cooling of the rotor 10 by means of a cooling fluid is thereby possible, for example.

[0051] Furthermore, base 14 includes recesses 28. Recesses 28 also serve to save material. Connectors 30 are located between recesses 28. Connectors 30 extend between housing 12 and socket 16, respectively. Despite this material saving, connectors 30 ensure sufficient mechanical stability for rotor 10. Connectors 30 and recesses 28 are both optional features and should not be construed as limiting.

[0052] The housing 12 and the base 14 are composed of a thermoplastic material containing embedded magnetic particles, such as NdFeB or ferrite powder (not shown). In this case, the plastic material acts as a matrix for the magnetic particles. The housing 12 and the base 14 are injection-molded parts of plastic material produced as a single piece.

[0053] The magnetic particles are magnetized so that the magnetic poles 20 are formed at a distance from each other in the circumferential direction.

[0054] Similar to Figures 1 to 5 The rotor 10 shown, Figures 6 to 10 The rotor 10 according to the invention shown also comprises five pole pairs. For the sake of clarity, in this case again, Figure 10Only some of the magnetic poles 20 and field lines are schematically shown in FIG. 1 by arrows. The exemplary embodiment shown should of course not be understood as limiting. It is also conceivable that the rotor 10 according to the invention comprises more or fewer pole pairs.

[0055] The embodiment shown is special in that, when viewed in a section perpendicular to the rotor axis 18 , the inner contour 22 and the outer contour 24 of the housing 12 lie between two concentric circles 32 defined by a maximum outer radius 34 and a minimum inner radius 36 of the housing 12 . Figure 8 A circle 32 and radii 34 , 36 are schematically shown in FIG.

[0056] The inner contour 22 extends in a curved manner such that it has a periodically varying distance from the center axis of the rotor shaft 18 .

[0057] In the exemplary embodiment, housing 12 has an outer profile 24 that includes a circular cross-section.

[0058] However, the inner contour 22 is extended with an inner projection 38 protruding toward the center and an intervening inner recess 40. In particular, by means of the inner recess 40, material can be saved compared to a conventional rotor 10.

[0059] like Figures 6 to 10 As shown, the inner protrusion 38 has a continuous curvature.

[0060] However, the inner recesses 40 are formed to be variable. This means that they extend from the inside to a point or extend into the housing 12 with a small tip radius.

[0061] In this case, if Figure 10 As shown, the inner recesses 40 are oriented relative to the poles 20. They are located between the poles 20 and the axis of the rotor 10, respectively.

[0062] from Figure 10 It can be seen that, in the case of this geometric design, the inner contour 22 essentially follows the contour of the magnetic field. This allows a particularly slim and efficient rotor design.

[0063] Figures 11 to 15 A second embodiment of a rotor 10 according to the invention is shown. This corresponds in several essential respects to Figures 6 to 10 For similar or functionally similar features, the same reference numerals as in the previously described figures are used, and in this respect reference is made to the above explanations.

[0064] The peculiarity of the second embodiment is that it is not the inner contour 22 but the outer contour 24 that has a curved gradient.

[0065] In the exemplary embodiment, the inner profile 22 has a circular cross-section.

[0066] However, the outer contour 24 has outer recesses 42 which are equidistant from one another in the circumferential direction.

[0067] Between the outer recesses 42 , the outer contour 24 comprises a portion 44 in which the outer contour 24 extends with a constant radius, in this case the outer radius 34 .

[0068] like Figure 11 、 13 , 14 and 15 , the outer recess 42 has a continuous curvature that transitions with a discontinuity 46 into a portion 44 extending at a constant radius.

[0069] In this case, the outer recess 42 is arranged to be offset from the magnetic pole 20, as shown in FIG. Figure 15 shown.

[0070] In the exemplary embodiment, material is saved in the region of the outer recess 42 compared to a conventional rotor 10. Consequently, material is saved on the outer side of the rotor between the poles 20. The influence on the driving characteristics is therefore minimal.

[0071] In experiments, it has been found that with the rotor 10 according to the second embodiment, a lower drag torque can be achieved in a wet-running motor compared to a conventional rotor 10 with a circular outer contour 24 .

[0072] For example, this may be due to the fact that in an electric motor (not shown), additional clearance is provided between the rotor 10 and the stator (not shown) by the outer recess 42, thereby reducing friction losses, while the distance between the magnetic poles 20 of the rotor 10 and the stator does not change in the process. However, this reasoning is merely speculative and should not be construed as limiting.

[0073] Figures 16 to 20 A third embodiment of a rotor 10 according to the invention is shown. This corresponds in many essential respects to the first and second embodiments. For similar or functionally similar features, the same reference numerals as in the previously described figures are used, and in this respect reference is made to the above explanations.

[0074] The third embodiment is special in that both the inner contour 22 and the outer contour 24 extend in a curved manner in the circumferential direction.

[0075] Therefore, the inner contour 22 and the outer contour 24 each have a periodically varying distance from the central axis of the rotor shaft 18 .

[0076] Similar to the first embodiment, the inner profile 22 of the third embodiment includes an inner protrusion 38 with an intervening inner recess 40 .

[0077] Furthermore, the third embodiment comprises an outer recess 42 in its outer contour 24 , which is formed similarly to the second embodiment.

[0078] Thus, in this exemplary embodiment, material is saved in the region of the inner recess 40 and the outer recess 42 compared to a conventional rotor 10. Thus, material is saved both on the inside and on the outside of the rotor. Consequently, a significant amount of material can be saved.

[0079] like Figure 16 、 18 , 19 and 20, when viewed in the circumferential direction, the outer recess 42 and the inner protrusion 38 are located on the same radius. In other words, the outer recess 42 and the inner recess 40 are offset from each other in the circumferential direction.

[0080] This ensures that, despite the material saving, the housing 12 has sufficient thickness and is therefore mechanically stable over its entire circumference.

Claims

1. A rotor for an electric motor, comprising a housing (12) and a base (14) integrally connected thereto, the base (14) being provided with a socket (16) for a rotor shaft (18), the housing (12) and the base (14) being formed integrally with each other from an injection-molded plastic material, the plastic material comprising embedded magnetic particles, the magnetic particles being magnetized in such a way that in the circumferential direction, magnetic poles (20) are formed at a distance from each other, the inner contour (22) and the outer contour (24) of the housing (12) being located between two concentric circles (32) defined by a maximum outer radius (34) and a minimum inner radius (36) of the housing (12) when viewed in a cross section perpendicular to the rotor shaft (18), characterised in that At least one of the profiles (22, 24) extends in a curved manner such that it has a periodically varying distance from the center axis of the rotor shaft (18).

2. The rotor according to claim 1, characterized in that The housing (12) has an outer contour (24) with a circular cross section, and the inner contour (22) is extended with an inner protrusion (38) protruding toward the center and an inner recess (40) inserted therein.

3. The rotor according to claim 2, characterized in that The inner protrusion (38) has a continuous curvature.

4. The rotor according to claim 2 or 3, characterized in that The inner recess (40) is formed to be variable.

5. The rotor according to claim 2 or 3, characterized in that: The inner recess (40) is oriented relative to the magnetic pole (20).

6. The rotor according to claim 1, characterized in that The housing (12) has an inner contour (22) with a circular cross section, and the outer contour (24) is provided with outer recesses (42) equidistant from one another in the circumferential direction.

7. The rotor according to claim 6, characterized in that The outer contour (24) extends with a constant radius between the outer recesses (42).

8. The rotor according to claim 6 or 7, characterized in that The outer recess (42) has a continuous curvature that transitions with a discontinuity (46) into a portion (44) extending with a constant radius.

9. The rotor according to claim 6 or 7, characterized in that The outer recess (42) is arranged offset from the magnetic pole (20) in the circumferential direction.

10. The rotor according to claim 1, wherein: The housing (12) has an outer contour (24) including an outer recess (42) and an inner contour (22) including an inner protrusion (38), wherein the outer recess (42) and the inner protrusion (38) are located on the same radius when viewed in the circumferential direction.

11. The rotor according to claim 5, characterized in that The inner recesses (40) are each arranged between a magnetic pole (20) and a rotor axis of the rotor (10).

12. The rotor according to claim 1, wherein The rotor is used for a drive motor of a hydraulic pump.

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