Electric Motor

Abstract

The invention relates to an electric motor (2) having a stator (3) and a rotor (4). The rotor (4) is equipped with permanent magnets (7) which are surrounded by a rotor group (8). A heat sink element (14) is attached to the rotor group (8). A gap seal (16) is formed between the outer diameter of the heat sink element (14) and the inner diameter of a component (6) connected to the stator (3).

Description

Technical Field

[0001] The invention relates to an electric motor having a stator and a rotor of the type defined in more detail in claim 1 . Background Art

[0002] An electric motor according to the introduction is known from DE 10 2007 060 011 A1.

[0003] WO 2007 / 028684 A1 describes an electric motor having a stator and a rotor, the rotor being connected to a shaft in a rotationally fixed manner. The shaft is mounted in a bearing, which is received in a bearing plate. An air gap is provided between the bearing plate and the shaft, which serves to conduct part of the heat from the rotor.

[0004] Another electric motor is known from DE 10 2016 123 272 A1.

[0005] DE 10 2014 202 187 A1 describes a similar electric motor which is provided with a cooling unit for cooling a drive unit or an electronic unit of the electric motor.

[0006] A further brushless electric motor having a fan is known from WO 2017 / 173075 A1, which is formed as a single piece with the rotor assembly and consists of a plastic material.

[0007] Such brushless electric motors have a rotor equipped with permanent magnets and are usually encapsulated to protect the rotor from contamination, in particular from metal dust attracted by the permanent magnets. Due to magnetic reversal effects in the rotor and heat transfer from the stator to the rotor, the rotor in such electric motors heats up quite significantly in most cases. Therefore, a particular problem is that as the output of the electric motor increases, the temperature of the rotor also increases, and the high temperatures thus generated within the electric motor can damage the permanent magnets. Due to the encapsulation of the motor, in particular the rotor, it is very difficult to keep the rotor at an acceptable temperature.

[0008] Most of the technical solutions known from the prior art are also very complicated in terms of cooling the rotor, or the encapsulation of the rotor is insufficient, so that the rotor is easily contaminated, which reduces the working life of the rotor.

[0009] With regard to the general prior art relating to cooling of electric motors, reference may additionally be made to WO 2006 / 072 489 A1, EP 0425 492 B1, WO 2009 / 059 863 A1, DE 21 2013 000 108 U1 or DE 10 2007 012395 A1. Some of these documents also describe non-brushless motors. Summary of the invention

[0010] An object of the present invention is to provide a brushless electric motor which avoids overheating of the rotor.

[0011] According to the invention, this object is achieved by the features mentioned in claim 1 .

[0012] The heat dissipation element attached to the rotor assembly according to the invention ensures that heat is reliably conducted away when the rotor heats up during operation, thereby avoiding overheating of the rotor.

[0013] The gap seals present between the heat dissipating element and the components connected to the stator prevent contaminants, such as metal dust, from reaching the rotor. The rotor is thus encapsulated without the risk of overheating.

[0014] Since the gap seal is formed between the heat dissipating element and the coil body connected to the stator, existing components are conveniently used, and thus no additional cost expenditure is required to form the gap seal.

[0015] In order to be able to dissipate particularly large amounts of heat away from the rotor, it can further be provided that the heat dissipation element consists of a material with high thermal conductivity.

[0016] It has been found that it is particularly advantageous, on the one hand, with regard to the heat dissipation of the rotor and, on the other hand, with regard to a low mass of the electric motor, if the cooling element is made of aluminum.

[0017] A particularly advantageous embodiment of the invention in terms of construction may consist in that the heat dissipating element is attached to a flat surface of the rotor stack.

[0018] Furthermore, it can be provided that the heat sink element is connected to the fan wheel or is formed in one piece with the fan wheel. The connection of the fan wheel to the heat sink element leads to a significant increase in the surface area of ​​the heat sink element, so that a correspondingly larger amount of heat can be removed from the rotor.

[0019] This heat transfer from the rotor can be further increased if the fan wheel consists of a material with high thermal conductivity.

[0020] In order to form a gap seal, it can also be provided that the distance between the component connected to the stator and the heat dissipation element is 0.05 mm to 1 mm, preferably 0.3 mm to 0.6 mm. A gap seal of this size prevents contaminants from entering the region of the rotor on the one hand, and allows air to flow through on the other hand, thereby ensuring cooling of the rotor.

[0021] A handheld power tool device having an electric motor according to the invention is specified in claim 8 .

[0022] Such an electric hand tool may, for example, be in the form of an angle grinder which, due to the above-mentioned good heat transfer from the electric motor, may be operated at a very high output.

[0023] In order to improve the air supply within the handheld power tool device, it can also be provided that an air gap is present between the stator and the housing surrounding the stator.

[0024] Further features and advantages of the present invention will become apparent from the following description of exemplary embodiments of the invention and from the dependent claims.

[0025] In addition, it should be pointed out that terms such as "including", "having" or "having" do not exclude other features or steps. In addition, the terms "one" or "the" indicating a single number of steps or features do not exclude multiple features or steps, and conversely, terms indicating multiple numbers of features or steps do not exclude a single number of features or steps. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention will be described in more detail below with reference to the accompanying drawings. The accompanying drawings show multiple features of the present invention in combination with each other. However, those skilled in the art can of course consider these multiple features separately from each other without inventive activity and optionally combine these multiple features to form further advantageous sub-combinations.

[0027] In the accompanying diagrammatic form:

[0028] Figure 1 Shown is a section through a handheld power tool device according to the invention which has an electric motor according to the invention. DETAILED DESCRIPTION

[0029] Figure 1 A handheld power tool device 1 is shown, which in the present example is in the form of an angle grinder. The handheld power tool device 1 can in principle also be designed in a different manner, for example as a hand drill, a jigsaw or the like.

[0030] The hand-held electric tool device 1 has an electric motor 2, in this example a brushless electric motor 2. The electric motor 2 in turn has a stator 3 and a rotor 4 arranged in the stator 3. The electric motor 2 is an electric motor 2 operated with normal mains power supply, and the electrical insulation of the electric motor 2 is good compared to electric motors operated by batteries or accumulators, so the above-mentioned problems with high temperatures of the rotor 4 are increased in most cases.

[0031] In addition to the winding 5 known per se, the stator 3 also has a coil body 6 known per se. As is conventional in brushless electric motors 2, the rotor 4 is equipped with permanent magnets 7, which are surrounded by a metal cover plate or rotor group 8 in a manner known per se. A rotor shaft 9 extends through the rotor 4, which drives an output shaft 11 of the handheld power tool device 1 via a transmission 10. The rotor shaft 9 is mounted in the housing 12 of the handheld power tool device 1 by means of two bearing devices 13 spaced apart from each other. In the exemplary embodiment shown, the housing 12 of the handheld power tool device 1 is two-piece and has a motor housing 12a and a transmission housing 12b. Thus, the drive components of the handheld power tool device 1, in particular the electric motor 2 and its components, the transmission 10, the output shaft 11 and the bearing device 13, can be assembled.

[0032] In the present example, the heat dissipation element 14 is attached to the rotor group 8 of the rotor 4. The heat dissipation element 14 is preferably made of a material with high thermal conductivity, for example aluminum, and is used to transfer heat away from the rotor 4. The heat dissipation element 14 should also be made of a non-magnetizable material to avoid magnetic short circuits of the rotor 4. In the present example, in order to dissipate heat from the rotor 4, the heat dissipation element 14, which is preferably in a rotationally symmetrical form, is attached to the flat surface 8a of the rotor group 8. In other words, the heat dissipation element 14 is arranged as an axial extension of the rotor group 8. Due to this arrangement of the heat dissipation element 14, the heat generated in the rotor 4 is transferred to the heat dissipation element 14 via the rotor group 8. However, the heat dissipation element 14 can also have one or more contact surfaces that contact the rotor group 8 at positions other than the flat surface 8a, for example, the heat dissipation element 14 has one or more protrusions that are axially engaged in the rotor group 8. In addition, the heat dissipation element 14 can also be multi-piece, or one or more additional components can be arranged between the heat dissipation element 14 and the rotor group 8, which additional components should have thermal conductivity in the present example. For example, the heat sink element 14 may be attached to the rotor stack 8 by means of a suitable, preferably thermally conductive adhesive. In the present example, an insulating material 15 is located between the heat sink element 14 and the rotor shaft 9 , which ensures electrical insulation of the heat sink element 14 .

[0033] The cooling element 14 can also be used for balancing the rotor 4 , wherein depressions or similar material removal areas are introduced into the cooling element or are realized on the cooling element.

[0034] A gap seal 16 is formed between the outer diameter of the heat dissipation element 14 and the inner diameter of the component connected to the stator 3 (in this example, the coil body 6), which prevents contaminants (such as metal dust) from entering the area of ​​the rotor 4, especially the area of ​​the permanent magnet 7. In order to form the gap seal 16, the distance between the component connected to the stator 3 (i.e., the coil body 6) and the heat dissipation element 14 can be 0.05mm to 1mm, preferably 0.3mm to 0.6mm. Therefore, a good seal can be obtained over the length of the gap formed between the coil body 6 and the heat dissipation element 14. At the end opposite to the heat dissipation element 14, the rotor 4 or the rotor group 8 and the permanent magnet 7 are also encapsulated, that is, the coil body 6 is connected to the bearing flange 17 and thus prevents contaminants from entering from that side as well. One of the two bearing devices 13 is accommodated in the bearing flange 17.

[0035] Adjacent to the heat sink element 14 is a fan wheel 18, which is arranged on the rotor shaft 9. On the side facing the fan wheel 18, the heat sink element 14 is provided with an inflow geometry, which in the present example is in the form of a curved portion, which improves the inflow of air into the fan wheel 18. Due to the flow on the surface forming the inflow geometry, good cooling of the heat sink element 14 is achieved. The inflow geometry of the heat sink element 14 thus begins at the end of the coil body 6, which is axially shorter than the heat sink element 14. The air flowing through the housing 12 of the handheld power tool device 1 can therefore flow through the heat sink element 14 to cool the heat sink element.

[0036] In order to further improve the heat dissipation of the rotor 4, the heat dissipation element 14 can be connected to a fan wheel 18. Therefore, at least some of the heat dissipated by the rotor assembly 8 to the heat dissipation element 14 is further transferred to the fan wheel 18, and the heat can be dissipated from the fan wheel to the air flowing through the housing 12 of the handheld power tool device 1. In the present example, the fan wheel 18 is preferably made of a material with high thermal conductivity, such as aluminum, and can also be used to balance the rotor 4. Of course, the fan wheel 18 can also be made of a plastic material.

[0037] In order to improve the air flow through the housing 12 of the handheld power tool device 1, an air gap 19 is provided between the stator 3 and the housing 12. The air flowing through the air gap 19 directly reaches the heat dissipation element 14, so that heat can be transferred away from the heat dissipation element.

Claims

1. An electric motor (2) comprising a stator (3) and a rotor (4), wherein: The rotor (4) is equipped with permanent magnets (7) which are surrounded by a rotor group (8), wherein a heat dissipation element (14) is attached to the rotor group (8), Characterized in that a gap seal (16) is formed between the outer diameter of the heat dissipation element (14) and the inner diameter of a coil body (6) connected to the stator (3), wherein the gap seal (16) is formed between the heat dissipation element (14) and the coil body (6) connected to the stator (3), wherein the heat dissipation element (14) can also be used to balance the rotor (4), wherein recesses or similar material removal areas are introduced into the heat dissipation element or are realized on the heat dissipation element.

2. The electric motor according to claim 1, It is characterized in that The heat dissipation element (14) is made of a material with high thermal conductivity.

3. The electric motor according to claim 2, It is characterized in that The heat dissipation element (14) is made of aluminum.

4. The electric motor according to any one of claims 1 to 3, It is characterized in that The heat dissipation element (14) is attached to the flat surface (8a) of the rotor assembly (8).

5. The electric motor according to any one of claims 1 to 3, It is characterized in that The heat dissipation element (14) is connected to the fan wheel (18) or is formed as an integral piece.

6. The electric motor according to claim 5, It is characterized in that The fan wheel (18) is made of a material with high thermal conductivity.

7. An electric motor according to any one of claims 1 to 3, It is characterized in that In order to form the gap seal (16), the distance between the coil body (6) connected to the stator (3) and the heat dissipation element (14) is 0.05 mm to 1 mm.

8. The electric motor according to claim 7, It is characterized in that In order to form the gap seal (16), the distance between the coil body (6) connected to the stator (3) and the heat dissipation element (14) is 0.3 mm to 0.6 mm. 9 . A hand-held power tool device ( 1 ) comprising an electric motor ( 2 ) according to claim 1 .

10. The handheld power tool device according to claim 9, It is characterized in that An air gap (19) exists between the stator (3) and a housing (12) surrounding the stator (3).

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