WO2012103882A2 - Rotor for an electric motor and electric motor - Google Patents

Abstract

The invention relates to a rotor (1) for an electric motor, having a first substantially cylindrical region (3), and a second region (5) which is connected to the first region (3) and comprises a connection region (7) for coupling to a drive shaft (9).

Description

 Rotor for an electric motor and electric motor

The invention relates to a rotor for an electric motor according to the preamble of claim 1 and to an electric motor according to the preamble of claim 12.

Rotors and electric motors of the type discussed here are known. Known rotors for electric motors typically have a first, substantially cylindrical region, to which a second region is connected. This comprises a connection region which serves to couple with a drive shaft. In particular, if such rotors are provided as external rotors of an electric motor, they are preferably designed cup-shaped, wherein the first region is substantially tubular and the second region forms a kind of flange, which is connected to the drive shaft and quasi represents the pot bottom. At least the first region of the rotor consists of a magnetically good conductive, preferably soft magnetic material and is made of a material and solid. During operation of the electric motor, variable magnetic forces act on this first region, which change their attack position on the latter due to the rotation of the rotor. As a result, the rotor is excited to vibrate, which leads to body and thus airborne sound. The first region of the rotor preferably has a small wall thickness, because this saves mass, installation space and costs and at the same time ensures a sufficient magnetic flux. However, if the first region of the rotor is thin-walled, it becomes all the more efficient

Vibrations excited, so that a structure-borne noise level and thus ultimately a level of the radiated airborne sound is particularly high. Larger wall thicknesses shift due to the increased mass, the resonance frequencies in the direction of the low-frequency range, thus causing a distance thereof to critical high resonance frequencies, but increase the total mass of the rotor and thus the motor, the space and the cost.

The object of the invention is therefore to provide a rotor and an electric motor, which do not have the disadvantages mentioned. To solve this problem, a rotor with the features of claim 1 is proposed. This is characterized in that at least the first region has at least a first and a second part, wherein the parts are delimited from one another by an imaginary peripheral surface. At least the first region of the rotor is thus formed at least in two parts. This creates a kind of internal friction effect between the at least two parts of the rotor by a parting line, if vibrations continue over the parting line. This leads to an efficient damping of vibrations and thus of the body and ultimately the radiated airborne sound. A high wall thickness is not required in this solution, but may be useful as an additional measure.

Preferred is a rotor, which is characterized in that the first part is formed as an inner part. This is then encompassed by the second part, which is designed as an outer part, at least partially. This means a particularly favorable construction of the rotor.

Particularly preferred is a rotor in which the inner part - seen in the circumferential direction - is completely encompassed by the outer part. In this way, a large-scale contact of the outer part is effected on the inner part, so that the vibration damping due to the internal friction between the at least two parts is particularly efficient.

Also, a rotor is preferred, which is characterized in that the outer part also extends - seen in the axial direction - over the entire length of the inner part. Such a rotor is designed quasi in sandwich construction. Internal friction is generated here over a large area, so that the structure-borne sound damping is highly efficient.

It is also preferred a rotor, which is characterized in that the at least two parts have different materials. In particular, materials are preferred which have different impedances for structure-borne sound vibrations or different resonance frequencies. They can also have different densities or different moduli of elasticity. This leads to, That vibrations of the first part can not be efficiently introduced into the second part, because the vibration coupling due to the different impedances, resonance frequencies, densities or elastic moduli is extremely low. The second part therefore does not participate or only slightly participates in the oscillation movement of the first part. As a result, the parts are at least partially displaced from each other, which in turn internal friction occurs. Ultimately, this leads to an efficient damping of structure-borne noise and thus of radiated airborne sound.

A rotor is preferred, which is characterized in that the first part comprises a soft magnetic material, preferably soft iron. Particularly preferably, the first part consists of a soft magnetic material, preferably of soft iron. Thus, the first part is magnetically well conductive and can be easily penetrated by the magnetic flux occurring in the operation of the electric motor, which is essential for the operation of the engine.

Furthermore, a rotor is preferred in which the second part comprises an elastomer material, for example rubber or plastic, or a composite material made of rubber and sheet metal. Particularly preferably, the second part consists of an elastomeric material, for example of rubber or plastic, or a composite material of rubber and sheet metal. An elastomer material, in particular rubber or plastic, has a particularly favorable loss factor, so that the attenuation of structure-borne noise is very efficient if the second part comprises or consists of an elastomer material, for example rubber or plastic. The loss factor describes the loss of vibration energy per oscillation period. Also, a composite material made of rubber and sheet metal has a high loss factor. Particularly preferably, the material is applied to the first part, that the rubber between the first part and the sheet is arranged. The metal sheet then forms the outermost layer - seen in the radial direction. In this case, the rubber is mechanically protected by the sheet.

Particularly preferred is also a rotor in which the second part has pores. Materials that have pores have particularly favorable sound-absorbing or damping properties. Here, for example, elastomeric foams or aluminum foams can be used.

Furthermore, a rotor is preferred in which the second part is connected to the first part by gluing, pressing, vulcanization, shrinking or soldering. In this way, a secure and permanent connection of the two parts can be ensured.

Also preferred is a rotor which is designed as an external rotor of an electric motor. Especially in connection with this construction results in a particularly efficient damping of body or radiated airborne sound.

Finally, a rotor is preferred which has at least one permanent magnet in the region of a circumferential surface facing a stator of an electric motor. Particularly preferably, the rotor has a plurality of bar magnets in this area. The rotor is then suitable for use in a DC motor, in particular in a brushless DC motor.

The object is also solved by an electric motor with the characteristics of

Claim 12 is created. This is characterized in that it comprises a rotor according to one of claims 1 to 1 1. Due to the design of the rotor, in which a first region has at least a first and a second part, wherein the parts are delimited from each other by an imaginary peripheral surface, structure-borne noise and thus ultimately radiated airborne sound due to occurring at least in the first region of the rotor inner Friction efficiently damped. The electric motor is therefore very quiet.

It is also preferred an electric motor, which is characterized in that it is designed as a DC motor. In particular, permanently excited DC motors have a very high energy density.

An electric motor is preferred which acts as a brushless DC motor

is trained. The commutation of the electric motor is effected electronically, so that highly susceptible parts such as brushes omitted. The engine is thus low maintenance and cost effective in operation, as well as durable.

Finally, a brushless and sensorless electric motor is preferred. This has a particularly inexpensive and advantageous construction.

The invention will be explained in more detail below with reference to the drawing. Show it:

Figure 1 is a schematic longitudinal sectional view of one of the prior

 Technique known rotor;

Figure 2 is a schematic longitudinal sectional view of a first embodiment of a rotor, and

Figure 3 is a partially broken, schematic detail view in the longitudinal

 Section of a second embodiment of a rotor.

Figure 1 shows a schematic view in longitudinal section of a rotor 1 for an electric motor, not shown here. Preferably, this is designed as a DC motor, so that it has a high energy density. Particularly preferably, the electric motor is designed as a brushless DC motor. In this case, its commutation is effected electronically, so that wear-prone parts such as brushes can be dispensed with.

The rotor 1 has a first region 3. This is essentially cylindrical. The rotor 1 also has a second region 5. This is connected to the first area 3. It also has a connection region 7, which serves to couple the rotor 1 to a drive shaft 9. The drive shaft 9 can be in operative connection with a device, not shown here, to be driven by the electric motor to drive them. The device may be, for example, a pump. In the illustrated embodiment, the rotor 1 is cup-shaped. In this case, the first region 3 constitutes a quasi tubular section which forms the peripheral wall of the pot. The second region 5 is formed in the manner of a flange, and constitutes, as it were, the bottom of the pot. In a curved transition region 11, the first region 3 and the second region 5 merge into one another. In the embodiment shown here, the rotor 1 is formed in one piece, wherein in particular the first region 3 and the second region 5 are regions of the same part. In other embodiments, it is possible that the rotor 1 is formed at least in two parts, wherein preferably the first region 3 is provided as a separate, connected to the second region 5 part. In order to ensure a function of the electric motor, it is preferably provided that the first region 3 comprises a magnetically conductive, preferably soft magnetic material. It particularly preferably comprises soft iron or consists of this. The second region 5, on the other hand, need not necessarily comprise a magnetically conductive material. It can therefore be provided that only the first region 3 comprises soft magnetic material, while the second region 5 comprises a material which does not have this property.

In the connecting region 7, the rotor 1 has a through hole 13 which is provided in a collar 15. Through the through hole 13, a projection 17 of the drive shaft 9, on which the rotor 1 is attached to the collar 15 extends. The rotor 1 can be connected to the drive shaft 9 by pressing, shrinking, gluing, soldering, welding or in any other suitable manner. It is also possible to provide a positive connection in the connecting region 7 between the drive shaft 9 and the rotor 1, so that increased torques can be transmitted.

The drive shaft 9 is rotatably mounted about a longitudinal axis 19.

In the region of a peripheral surface 21 facing a stator of the electric motor, not shown here, the rotor 1 has at least one permanent magnet, which is designed here as a bar magnet 23. As viewed in the circumferential direction of the rotor 1, a plurality of permanent magnets, in particular in the area of the peripheral surface 21, are preferred. special bar magnets 23, provided. The permanent magnets are - seen in the circumferential direction - preferably provided at a constant angular distance from each other. FIG. 1 shows four bar magnets 23, 23 ', 23 ", 23"'. The magnets may preferably - as seen in the axial direction - comprise individual segments. It is also possible to provide a homogeneous ring, viewed in the circumferential direction of the rotor 1, which comprises or consists of magnetizable material. The permanent magnets, preferably bar magnets 23, 23 ', 23 ", 23"' can be glued to the peripheral surface 21, let into this, be connected by soldering or welding or in any other way with the peripheral surface 21. They cooperate with the windings of the stator of the electric motor to transmit a torque to the drive shaft 9 during operation of the electric motor. The operation of an electric motor is known, so it will not be discussed further.

In particular, on the first region 3 of the rotor 1 act during operation of the

Electric motor variable magnetic forces that change due to the rotation of the rotor 1 about the longitudinal axis 19 and their attack position on the same. As a result, vibrations are introduced into the rotor 1, which lead to structure-borne noise, which ultimately makes noticeable by radiated airborne sound. This is particularly problematic if the first region 3 is thin-walled, so that it can be excited to vibrate particularly efficiently.

In particular, to make the electric motor quieter during operation, the rotor 1 should be made less susceptible to structure-borne noise and vibrations.

FIG. 2 shows a first exemplary embodiment of a rotor 1 according to the invention in a schematic longitudinal sectional view. Identical and functionally identical elements are provided with the same reference numerals, so that reference is made to the preceding description. The first area 3 here has a first part 25 and a second part 27. The two parts are delimited from each other by an imaginary peripheral surface. This coincides with a peripheral surface 29 of the first part 25 in the illustrated embodiment. If the first part 25 is excited to vibrate, this leads to internal friction in a contact region 31, in which the first part 25 and the second part 27 preferably abut each other. by virtue of This internal friction vibrations are damped in the first part 25, so that a structure-borne noise level or ultimately a level of radiated airborne sound is attenuated.

The second part 27 is formed here as a sleeve 33, which surrounds the first part 25. This is therefore designed here as an inner part, which is encompassed by the outer part formed as a second part 27. In the illustrated embodiment, the first part 25 - seen in the circumferential direction - completely encompassed by the cuff 33 formed as outer part.

In other embodiments, it is possible that - seen in the circumferential direction - only partially, at least a second part 27 is provided. It is also possible that more than one second part 27 is provided, preferably seen in the circumferential direction.

The first part 25 preferably comprises a magnetically conductive material, more preferably a soft magnetic material. Most preferably, the first part comprises 25 soft iron. It is also possible that the first part 25 consists of a magnetically conductive material, a soft magnetic material, in particular soft iron. In this way, the first part 25, which is embodied here as an inner part, can absorb the magnetic flux generated by the stator (not shown), as a result of which a rotation of the rotor 1 is effected in conjunction with the bar magnets 23, 23 ', 23 ", 23"'.

It already causes a significant reduction of structure-borne noise, when the first and the second part 25, 27 have identical materials, which are separated by a parting line. The reduction is then substantially due to the internal friction generated in the contact area 31.

However, the second part 27 preferably comprises a material which is of the

Material - in particular with regard to its modulus of elasticity and / or its density - is different, the first part 25 has. This results in an even more efficient damping of structure-borne noise. In addition, in the contact 31 relative displacements between the two parts 25, 27, so that an increased internal friction is given.

Particularly preferably, the second part 27 on an elastomeric material, preferably rubber or plastic, on, or consists of this. Such a material has a particularly favorable loss factor, so that the structure-borne sound damping is very efficient. The second part 27 may also comprise bitumen, which is also a material with a high loss factor. Aluminum is also preferred as the material for the second part 27.

It is also possible that the second part 27 has a layer structure, in particular layers of different materials. Depending on the selection and combination of the different materials of the individual layers, a particularly efficient damping can thus be effected. Particularly preferably, the second part 27 comprises or consists of a composite material made of rubber and sheet metal. Such a construction is also referred to as a sandwich sheet. If the rubber layer faces the first part 25, so that the sheet-metal layer faces outwards-as viewed in the radial direction-the inner rubber layer is protected against mechanical damage by the sheet-metal layer. The rubber layer is in this case namely - viewed in the radial direction - between the first part 25 and the sheet-metal layer of the second part 27 is arranged.

Preferably, the second part 27 has pores. Porous materials have particularly good sound-absorbing properties. This also leads to a highly efficient damping. The second part 27 may preferably comprise foam or consist of foam. It is also possible that the second part 27 comprises elastomer foam or aluminum foam or consists of these materials. Other metallic foams or sintered materials are possible.

The second part 27 is preferably connected to the first part 25 by gluing, pressing or soldering. If it comprises an elastomeric material, preferably rubber, it may also be vulcanized onto the first part 25. It is also possible to cool the first part 25 and / or to heat the second part 27 to the second part 27 on the first part 25 shrink. In this case, preferably, the first part 25 in thermal equilibrium with the second part 27 on a slight excess in terms of its outer diameter with respect to the inner diameter of the second part 27 on. Thus, when shrinking a particularly firm connection between the two parts 25, 27 are effected. It is also possible that the second part 27 comprises a shrinkable plastic, for example consists of shrink film. This can then be shrunk onto the first part 25 in a manner known per se, for example with the aid of hot air.

FIG. 3 shows a second exemplary embodiment of a rotor 1 according to the invention in a schematic, partially broken away longitudinal sectional view. Identical and functionally identical elements are provided with the same reference numerals, so that reference is made to the preceding description. Also in this embodiment, the first part 25 is formed as an inner part, which is encompassed by the second part 27, which is designed as an outer part. Here, however, the inner part is not only completely encompassed by the outer part, as viewed in the circumferential direction, but the second part 27 formed as an outer part also extends over the entire length of the first part 25 formed as an inner part, seen in the axial direction. The axial direction Here, the direction, which is defined by the longitudinal axis 19. The rotor 1 is constructed in this case in sandwich construction. This results in a particularly large contact area between the two parts 25, 27 in the contact region 31. As a result, the internal friction in this area is significantly increased, so that the attenuation of structure-borne noise and thus ultimately of radiated air jet is very efficient.

Regardless of the realized embodiment, it is always possible between the two parts 25, 27 to realize not only a frictional connection, but also a positive connection. For example, the parts 25, 27 may have projections or recesses which engage in one another in a known manner. As a result, the internal friction acting between the parts 25, 27 can still be increased. For the second part 27, materials with a high loss factor are preferred. Particular care is taken to ensure that the heat flow from the first part 25 to the second part 27 is not impaired. Thus, heat generated in the first part 25 can be dissipated via the second part 27.

Preferably, the rotor 1 is designed as an external rotor of an electric motor. Especially with such a construction, high structure-borne sound levels occur, so that the solution proposed here for damping structure-borne noise is particularly efficient.

Overall, it turns out that the rotor 1 proposed here and the electric motor have a particularly efficient damping with respect to structure-borne noise and thus also with respect to radiated airborne sound, wherein increased costs are avoided by a higher mass, larger installation space or complex constructive measures.

LIST OF REFERENCE NUMBERS

I rotor

 3 area

 5 area

 7 connection area

 9 drive shaft

 I I transition area

13 through hole

15 collar

 17 lead

 19 longitudinal axis

 21 peripheral surface

 23 bar magnet

 25 part

 27 part

 29 peripheral surface

 31 touch area

 33 cuff

Claims

claims Rotor for an electric motor, with  a first substantially cylindrical portion (3) and a second portion (5) connected to the first portion (3) and having a connecting portion (7) for coupling to a drive shaft (9),  characterized in that  at least the first region (3) has at least a first and a second part (25; 27), the parts being delimited from one another by an imaginary peripheral surface. Rotor according to claim 1, characterized in that the first part (25) is designed as an inner part, which is encompassed by the second, formed as an outer part part (27) at least partially. Rotor according to claim 2, characterized in that the inner part - seen in the circumferential direction - is completely encompassed by the outer part. Rotor according to claim 3, characterized in that the outer part also - seen in the axial direction - extends over the entire length of the inner part. Rotor according to one of the preceding claims, characterized in that the at least two parts (25; 27) have different materials. 6. Rotor according to one of the preceding claims, characterized in that the first part (25) comprises a soft magnetic material, preferably soft comprises iron, particularly preferably made of a soft magnetic material, preferably soft iron exists. 7. Rotor according to one of the preceding claims, characterized in that the second part (27) comprises an elastomeric material, such as rubber or plastic, or a composite material of rubber and sheet metal, more preferably of an elastomeric material, such as rubber or plastic , or a composite material made of rubber and sheet metal. 8. Rotor according to one of the preceding claims, characterized in that the second part (27) has pores. 9. Rotor according to one of the preceding claims, characterized in that the second part (27) with the first part (25) is connected by gluing, pressing, vulcanization, shrinking or soldering. 10. Rotor according to one of the preceding claims, characterized in that the rotor (1) is designed as an external rotor of an electric motor. 1 1. Rotor according to one of the preceding claims, characterized in that the rotor (1) in the region of a stator of an electric motor facing peripheral surface (21) at least one permanent magnet, preferably a bar magnet (23; 23 ', 23 ", 23"') , 12. Electric motor, characterized by a rotor (1) according to one of claims 1 to 1 1st 13. Electric motor according to claim 12, characterized in that the electric motor is a DC motor. 14. Electric motor according to claim 13, characterized in that the electric motor is a brushless DC motor. 15. Electric motor according to claim 14, characterized in that the electric motor is a brush and sensorless DC motor.