Electric machine

Abstract

The invention relates to an electric machine (10) comprising: a stator unit (14) with a ferromagnetic stator body (18), a multi-part plastic holding body (24) surrounding the stator body (18), wherein the plastic holding body (24) has two axially adjacent plastic holding elements (241, 242), and at least one stator winding (22) arranged on the plastic holding body (24); a rotor unit (16) with a rotor shaft (40), which is rotatably mounted on the plastic holding body (24) via a shaft radial bearing (25), and a rotor body (42) which is secured to the rotor shaft (40) and is arranged inside the stator body (18), with the plastic holding body (24) having at least two axially spaced-apart separating planes (241, 242), in which the two plastic holding elements (241, 242) are axially adjacent to one another.

Description

[0001] DESCRIPTION

[0002] Electric machine

[0003] The present invention relates to an electrical machine, in particular an electric motor. The electrical machine comprises a stator unit with a ferromagnetic stator body, a multi-part plastic holding body surrounding the stator body, the plastic holding body having two axially adjacent plastic holding elements, and at least one stator winding arranged on the plastic holding body. Furthermore, the electrical machine comprises a rotor unit with a rotor shaft rotatably mounted on the plastic holding body via a radial shaft bearing, and a rotor body fastened to the rotor shaft and arranged within the stator body.

[0004] Such an electrical machine is disclosed, for example, in DE 40 215 99 A1, wherein the electrical machine has a stator unit with a plurality of stator teeth, which form the ferromagnetic stator body, and a plastic holding body. The plastic holding body has two shell-shaped plastic holding elements, which axially adjoin one another at a parting plane arranged centrally in the axial direction of the stator. The plastic holding elements serve to position the stator teeth relative to one another and to accommodate the stator winding, wherein the wound stator winding is electrically insulated from the stator teeth by the plastic holding elements. The plastic holding elements are fixed in the circumferential direction via a pin fastened to one of the plastic holding elements and an opening provided in the other plastic holding element, wherein the pin engages in the opening.The electric machine also includes a rotor unit, which has a rotor shaft and a rotor body attached to the rotor shaft. The rotor shaft is rotatably mounted on the plastic retaining elements via two rolling bearings.

[0005] The disadvantage of a central division of the plastic holding body is that the stator unit has a relatively low torsional rigidity, i.e. a relatively low rigidity in the circumferential direction.

[0006] The present invention is based on the object of creating a relatively cost-effective and easily assembled electrical machine which has a high torsional rigidity.

[0007] This object is achieved by an electrical machine having the features of main claim 1.

[0008] The electric machine according to the invention comprises a fixed stator unit and a rotatable rotor unit.

[0009] The stator unit comprises a ferromagnetic stator body and a multi-part plastic holding body that surrounds the stator body. Typically, the stator body defines a plurality of stator poles distributed along a circumference of the rotor unit. The stator body can be designed as a solid body. However, the stator body preferably consists of a plurality of sheet metal parts. A stator body constructed in this way is also referred to as a laminated stator body or a laminated stator body and exhibits particularly low eddy currents during operation of the electrical machine. The stator body is generally made of a ferromagnetic metal. The stator body typically comprises a plurality of winding support sections on which an electromagnetic stator winding is arranged. The plastic holding body has two plastic holding elements, which are preferably produced by an injection molding process.The plastic retaining elements are preferably identical. The plastic retaining elements are axially adjacent to one another and are directly or indirectly connected to one another in a form-fitting manner in the circumferential direction, with a first plastic retaining element being pushed onto the stator base body on a first axial side and a second plastic retaining element being pushed onto the stator body on a second axial side.

[0010] The plastic holding body serves, among other things, to provide electrical insulation between the stator body and the stator windings, which is why at least a section of the plastic holding body surrounding the stator body is preferably made of a plastic material with good electrical insulation properties, i.e. with a high specific electrical resistance, typically at least 10 10 Qcm, and a high dielectric strength.

[0011] The rotor unit comprises a rotor shaft, which is mounted in the plastic holding body via a radial shaft bearing, and a rotor body, which is fastened to the rotor shaft and arranged within the stator body. The radial shaft bearing can be designed exclusively for radial support, or can be designed for radial and axial support of the rotor shaft. Typically, the rotor shaft is mounted in a housing part of the electric machine via another radial shaft bearing, which is arranged on a side of the rotor body opposite the radial shaft bearing arranged on the plastic holding body. The rotor body can be designed as a solid, permanent-magnetic body, can be designed to support at least one permanent magnet, or can be designed to support at least one electromagnetic rotor winding.In the last two cases, the rotor body is generally made of a ferromagnetic metal and can be either a solid body or consist of several interconnected individual parts, typically sheet metal parts.

[0012] According to the invention, the plastic holding body has two axially spaced-apart parting planes, at which the two plastic holding elements axially adjoin or bear against one another. Preferably, both plastic holding elements each have at least a first, short axial section and at least one second, long axial section, wherein the first axial section of the first plastic holding element and the second axial section of the second plastic holding element define a first parting plane and the first axial section of the second plastic holding element and the second axial section of the first plastic holding element define a second parting plane. The total length of the two axial sections of the two plastic holding elements that are axially adjacent to one another, i.e. arranged in alignment with one another, always remains the same.

[0013] When the stator unit is subjected to torsional stress, the two axially spaced-apart parting planes ensure that there is no transverse plane at which the two plastic retaining elements exclusively slide in the circumferential direction. Although the two plastic retaining elements would slide against each other in the circumferential direction at the first parting plane, the two axial sections defining the second parting plane support the area of ​​the first parting plane in the rotational direction. Likewise, the two plastic elements at the second parting plane support each other in the rotational direction through the axial sections defining the first parting plane.

[0014] This increases the rigidity of the stator unit in the direction of rotation in a simple way.

[0015] Preferably, the stator body has a plurality of radial projections distributed over the circumference, and the plastic retaining body has a radial opening for each radial projection, such that the plastic retaining elements are positively connected to the stator body in the circumferential direction by the engagement of the radial projections in the radial openings. This allows the plastic retaining body to be easily fastened to the stator body in the circumferential direction.

[0016] In a preferred embodiment, the first axial section is arranged in the circumferential direction on a first side of a radial projection of the stator body, and the second axial section is arranged on a second side of the radial projection. In this way, the plastic retaining element is divided at each radial projection of the stator body in both parting planes, so that increased rigidity of the stator unit is present at each radial projection. Preferably, the same axial section of a plastic retaining element is arranged in the circumferential direction on the two mutually facing sides of the adjacent radial projections.

[0017] Preferably, one plastic retaining element has a section in the circumferential direction between two axial sections, which has a recess into which a projection of a section of the other plastic retaining element arranged in the circumferential direction between two axial projections engages. This creates an additional positive connection between the two plastic retaining elements, which further increases the torsional rigidity, i.e., the rigidity in the circumferential direction, of the stator unit.

[0018] Preferably, the plastic retaining elements are each made in one piece. This allows for simple and cost-effective production. The plastic retaining elements are preferably manufactured using an injection molding process.

[0019] In a preferred embodiment, the plastic retaining elements are axially secured to one another by the stator winding wound onto the plastic retaining body. The coil winding is wound around the sections of the plastic retaining elements in the area of ​​the radial projections, thereby axially securing the plastic retaining elements to one another. This allows the plastic retaining elements to be axially connected to one another easily and cost-effectively, eliminating the need for additional, cost-intensive joining elements.

[0020] Preferably, the plastic holding elements are each pot-shaped, wherein the plastic holding elements each have an end section and a casing section surrounding the base body. At least one of the plastic holding elements has an opening on the end section through which the rotor unit can be pushed when a stator unit is finally assembled. Alternatively, the rotor unit could first be inserted into the through-opening of the stator unit and then at least one of the two plastic holding elements can be finally assembled. In this case, an opening for pushing the rotor unit through on one of the plastic holding elements would not be necessary. In a preferred embodiment, the first plastic holding element and / or the second plastic holding element has a bearing section for the plain bearing of the rotor shaft.The bearing section is a bore into which the rotor shaft is inserted, with the rotor shaft being supported radially on the circumferential surface of the bore. Preferably, the bearing section is formed by a plastic injection-molded onto the plastic retaining element, which allows for improved sliding properties of the plain bearing.

[0021] Preferably, the end face section comprises a spoke structure. The spoke structure makes it possible to create a mechanically stable end face section with relatively little material. This allows for the creation of a relatively lightweight electric machine. The spoke structure also makes it possible to form the entire plastic support body with a relatively uniform wall thickness. This relatively uniform wall thickness, in turn, enables particularly simple production of the plastic support body using the injection molding process.

[0022] Particularly preferably, the spoke structure is axially flowable in order to enable efficient cooling of the electric machine.

[0023] An embodiment of the present invention is described below with reference to the accompanying figures. Herein:

[0024] Figure 1 is an exploded view of an electrical machine according to the invention, and Figure 2 is a perspective view of a fully assembled stator unit of an electrical machine from Figure 1.

[0025] Figure 1 shows an electrical machine 10 with a stator unit 14, also shown in Figure 2, and a rotatable rotor unit 16.

[0026] The stator unit 14 comprises a stator body 18, which consists of a plurality of ferromagnetic sheet metal parts 181 stacked in the axial direction to form a laminated core 182. The stator body 18 comprises six radial projections 20 distributed over the circumference, which extend axially from a first end face to the second end face of the laminated core 182. Each radial projection 20 forms a winding support section 183, on which a stator winding 22 is arranged.

[0027] The stator unit 14 further comprises a plastic holding body 24, which is composed of a first plastic holding element 241 and a second plastic holding element 242. The plastic holding elements 241, 242 are each pot-shaped and have an end face section 26 and a covering section 28. Both plastic holding elements 241, 242 have

[0028] Enclosure section 28 has six radially projecting sections 29 distributed over the circumference, each of which includes an open radial opening 30. In the final assembled state, the radial projections 20 of the stator body 18 are arranged within the radial openings 30 of the plastic holding elements 241, 242.

[0029] During assembly of the stator unit 14, the pot-shaped first plastic retaining element 241 is pushed onto the laminated core via the first end face of the stator body 18 with the enclosing section 28. The pot-shaped second plastic retaining element 242 is also pushed onto the laminated core 182 via the second end face of the stator body 18 with the enclosing section 28. In the final assembled state, the two plastic retaining elements 241, 242 abut or rest against one another with the axial end facing away from the end face section 26 and are axially connected to one another by the wound stator winding 22.

[0030] According to the invention, the plastic holding body 24 has two axially spaced-apart parting planes E1, E2, at which the two plastic holding elements 241, 242 axially adjoin or bear against one another. For this purpose, both plastic holding elements 241, 242 each have six first, short axial sections 321, 341 and six second, long axial sections 322, 342, wherein the first axial sections 321, 341 all have the same length and the second axial sections 322, 342 also all have the same length. The first axial sections 321 of the first plastic holding element 241 and the second axial sections 342 of the second plastic holding element 242 define the first parting plane E1. The first axial sections 341 of the second plastic holding element 242 and the second axial sections 322 of the first plastic holding element 241 define a second parting plane E2. The total length of the two axially adjacent, ieaxial sections 321, 342 and 322, 341 of the two plastic holding elements 241, 242, which are arranged in alignment with one another, always remain the same.

[0031] The axial sections 321, 322, 341, 342 are arranged in the circumferential direction on the radial projections 20 of the stator body 18 such that the first axial section 321, 341 is arranged on a first side of a radial projection 20 and the second axial section 322, 342 is arranged on a second side of the same radial projection 20, wherein the same axial section 321, 322, 341, 342 is arranged on the sides of the adjacent radial projections 20 that face each other in the circumferential direction. For example, the first axial section 321, 341 is arranged on the sides of the adjacent radial projections 20 that face each other in the circumferential direction. Otherwise, the second axial section 322, 342 is arranged on the sides of the adjacent radial projections 20 facing each other in the circumferential direction.

[0032] In addition, both plastic holding elements 241, 242 have a plurality of sections 36 in the circumferential direction between the two axial sections 321, 322, 341, 342, each of which has a recess 361 or a projection 362, wherein each projection 362 of a plastic holding element 241, 242 engages in a recess 361 of the other plastic holding element 241, 242.

[0033] The end section 26 of the first plastic retaining element 241 has a spoke structure 261 through which air can flow to provide a cooling air flow. The spoke structure 261 comprises a plurality of spokes 2611 and openings 2612 formed between the spokes 2611, through which air can flow axially through the spoke structure 261. Furthermore, the end section 26 of the first plastic retaining element 241 has, radially inwardly, a bearing section 262 forming a shaft radial bearing 25 for supporting the rotor unit 16.

[0034] The plastic holding elements 241, 242 can each consist of a single plastic material, which advantageously has both relatively good electrical insulation properties and relatively good tribological properties. Alternatively, a different plastic material, which advantageously has particularly good tribological properties, could be injection-molded onto the bearing section 262. The rotor unit 16 comprises a rotor shaft 40 and a rotor body 42 fastened to the rotor shaft 40. The rotor shaft 40 is mounted on a first axial side of the rotor body 42 via the shaft radial bearing 25 on the plastic holding body 24, in particular on the first plastic holding element 241, wherein the rotor shaft 40 extends through the bearing section 262 of the first plastic holding element 241 and an outer surface of the rotor shaft 40 is in frictional contact with a sliding surface 251.The rotor shaft 40 is rotatably mounted on a second axial side of the rotor body 42 via a further bearing element not shown in the figures on a housing (also not shown). Alternatively, the rotor shaft 40 could also be rotatably mounted on the plastic holding body 24, in particular on the second plastic holding element 242. The second plastic holding element 242 has an opening 32 designed such that the rotor unit 16 can be inserted into the stator unit 14.

[0035] This creates an electrical machine that is cost-effective and easy to assemble and has a stator unit with a high torsional rigidity.

Claims

PATENT CLAIMS 1. Electrical machine (10), comprising: - a stator unit (14) with • a ferromagnetic stator body (18), • a multi-part plastic holding body (24) which surrounds the stator body (18), wherein the plastic holding body (24) has two axially adjacent plastic holding elements (241, 242), and • at least one stator winding (22) which is arranged on the plastic holding body (24), - a rotor unit (16) with • a rotor shaft (40) which is rotatably mounted on the plastic holding body (24) via a shaft radial bearing (25), and • a rotor body (42) which is fastened to the rotor shaft (40) and is arranged within the stator body (18), characterized in that the plastic holding body (24) has at least two axially spaced-apart parting planes (El, E2) in which the two plastic holding elements (241, 242) axially adjoin one another.

2. Electrical machine (10) according to claim 1, wherein both plastic holding elements (241, 242) each have at least one first, short axial section (321, 341) and at least one second, long axial section (322, 342), wherein the first axial section (321) of the first plastic holding element (241) and the second axial section (342) of the second plastic holding element (242) define a first parting plane (El) and the first axial section (341) of the second plastic holding element (242) and the second axial section (322) of the first plastic holding element (241) defines a second parting plane (E2).

3. Electrical machine (10) according to claim 1 or 2, wherein the stator body (18) has a plurality of radial projections (20) distributed over the circumference and the plastic holding body (24) has a radial opening (30) for each radial projection (20), such that the plastic holding elements (241, 242) are positively connected to the stator body (18) in the circumferential direction by the engagement of the radial projections (20) in the radial openings (30).

4. Electrical machine (10) according to claim 2 and 3, wherein the first Axial section (321, 341) is arranged in the circumferential direction on a first side of a radial projection (20) and the second axial section (322, 342) is arranged on a second side of the radial projection (20).

5. Electrical machine (10) according to claim 4, wherein in the circumferential direction on the two mutually facing sides of the mutually adjacent radial projections (20) the same axial section of a plastic holding element (241, 242) is arranged.

6. Electrical machine (10) according to claim 5, wherein the one plastic holding element (241, 242) has a section (36) in the circumferential direction between two axial sections (321, 341, 322, 342), which section has a recess (361) into which a projection (362) of a section (36) of the other plastic holding element (241, 242) arranged in the circumferential direction between two axial sections (321, 341, 322, 342) engages.

7. Electrical machine (10) according to one of the preceding claims, wherein the plastic holding elements (241, 242) are each designed in one piece.

8. Electrical machine (10) according to one of the preceding claims, wherein the plastic holding elements (241, 242) are axially fastened to one another by the stator winding (22) wound onto the plastic holding body (24).

9. Electrical machine (10) according to one of the preceding claims, wherein the plastic holding elements (241, 242) are each pot-shaped, wherein the plastic holding elements (241, 242) each have an end face section (26) and a covering section (28) surrounding the stator body (18).

10. Electrical machine (10) according to one of the preceding claims, wherein the first plastic holding element (241) and / or the second plastic holding element (242) has a bearing section (262) for sliding bearing of the rotor shaft (40).

11. Electrical machine (10) according to one of the preceding claims, wherein a spoke structure (261) is provided on the end face portion (26).

12. Electrical machine (10) according to claim 11, wherein the spoke structure (261) can be flowed through axially.

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