Patent Application
20120007453
The present invention relates to a double rotor motor according to the preamble of claim 1.
Double rotor motors which have an individual tooth technology and a high efficiency but a low strength and poor heat dissipation are known from WO 06/083097, U.S. Pat. No. 6,002,192, WO04/004098 and U.S. Pat. No. 5,982,070. These motors are characterised by a high efficiency of the magnetic circuit, since with the impression of a current in the stator tooth, a torque is generated by two rotors. Individual teeth in the exciting circuit are particularly advantageous, as stated in the above-mentioned applications.
Double rotors can be configured for high outputs and torques. For this, the excitation teeth, coils and attachments must have a high degree of rigidity. For high torques and a compact construction, the excitation teeth with coils have to be constructed close together. Since the stator is self-supporting in the case of a double rotor motor with individual teeth, the teeth and coils have to be supported on the housing with a high degree of rigidity. Furthermore, the variation in the magnetic flux in double rotor motors is very high so that electrically conductive materials are undesired in the magnetic circuit, because very high eddy currents are generated therein. For this reason, electrically conducive materials with a large cross section are to be avoided particularly in the region of the greatest changes in flux, as occur in the poles and in the air gaps.
WO2006/083097 discloses a double rotor motor of this type. In this case, the self-supporting coils are injection moulded with the coil bodies and yoke to produce a stator. The application does not show a cross section through the coils to detect the distance to the adjacent yoke. It can therefore be assumed that the illustrated wall thickness also applies in the circumferential direction and thus there is a large distance to the adjacent coil. The torque is substantially supported by the insert moulded bodies and the ribbing on the side of the housing. Since very high moments are primarily effective in the outer region, the stator can only support torques to a limited extent.
WO 2004/004098 also discloses a double rotor motor, in which the yokes are insert moulded with the coil bodies. The coil bodies are centred with the wound coils in a housing by positioning webs of a plastics material body (
Furthermore, the dissipation of heat is very limited in the case of the prior art motors, because the stator is disadvantageously connected to the housing. As shown in FIG. 9C (WO 2006/083097), the stator is connected to the radially inwardly offset housing by plastics material over a great path length. Consequently, the output of the motor is very limited, since the heat cannot be removed from the coils. Moreover, since the thermal conductivity of cast resin or injection moulded plastics material is very low, a large spacing between coil and metal housing has a thermally insulating effect. The same applies similarly to WO2006/083097.
Double rotor motors which have a high degree of rigidity and efficiency are already known from EP 1879283 (Matsushita), EP 1191673 (Denso) and U.S. Pat. No. 5,260,642 (Huss). From EP 1879283 and EP 1191673 a stator construction is in each case already known, in which two rotors provided with permanent magnets are joined to one another via a shaft. In this respect, the rotors are driven by a stator wound with excitation coils. The stator is configured as a single part and consists of inner and outer teeth with pole shoes and a tangential connecting web between the yoke arms. An excitation coil is in each case wound in the circumferential direction on each connecting web, as illustrated in FIG. 8 of EP 1879283 and in FIG. 38 of EP 1191673. Due to this coil arrangement, the magnetic flux is generated tangentially in the connecting web. The magnetic flux is at the same time divided into two magnetic partial fluxes in the yoke teeth. One of the partial fluxes goes radially outwardly to the outer rotor and is closed via the outer rotor, and goes radially inwardly via the adjacent stator tooth to the connecting web. The second partial flux leads radially inwardly and is closed via the inner rotor, and is led radially outwardly via the adjacent stator tooth and is closed via the connecting web.
In EP 1191673, in contrast to the stator structure of EP 1879283, the rotors are not joined to one another via a shaft. Instead, the relative rotor position of the outer and inner rotors is regulated by a control algorithm.
A further double rotor is known from U.S. Pat. No. 5,260,642. Here a plurality of rotors equipped with permanent magnets are arranged axially with respect to one another and are driven via an external excitation stator.
The winding technique known from EP 1191673 and EP 1879283 is disadvantageous. The tangential winding technique is on the one hand very complicated, and on the other hand a good copper space factor cannot be achieved with automated winding, since the space covered by the pole shoes is very difficult to fill during winding. In addition, the magnetic flux is generated in the tangential direction from the connecting web and is then deflected by 90° in the radial direction. This is unfavourable for the efficiency of the magnetic circuits and prevents the use of soft magnetic material with grain orientation.
The object of the invention is to provide a double rotor motor for high torques and output.
This object is advantageously achieved with a double rotor motor which has the features of claim 1. Advantageous configurations of the double rotor according to claim 1 are provided by the features of the subclaims.
The invention is based on the concept that the coil supports which also form the poles and the yoke are insert moulded with a plastics material, the plastics material forming a support structure which is also formed between the individual coil supports and coils. During the insert moulding procedure, the plastics material joins with the housing or with a part connected to the housing, thereby producing a stable unit. The plastics material is preferably a high-strength plastics material. The plastics material composition injected between the coil supports forms supports in each case, the cross section of which is advantageously U-shaped, T-shaped or double-T-shaped.
The configuration of the double rotor motor for high torques, output and a compact construction requires specific solutions in terms of rigidity and heat dissipation, since the insert moulding/encapsulating alone of coil supports and yoke is not sufficient for this. For a high rigidity, a high geometrical moment of inertia Ia for a low bending of the stator and a high modulus of elasticity is required. In the prior art, the coil body was used as the support and is connected to the housing by the encapsulating compound, or an insert moulding of the stator teeth which produces the rigidity.
In contrast to this, the invention provides using the production-related space or spacing between the coils which is filled by the injected plastics material and forms a support structure or a support. This produces a geometrical moment of inertia Ia which is greater than the coil body by a factor of four. The entire yoke or the external pole can also be insert moulded with a relatively thin wall of plastics material. In contrast to the prior art, the reinforcement is supported by a high-grade plastics material. However, it is also possible for a filler with a high modulus of elasticity to be additionally injected. A thermosetting plastics material is preferably used in which an effective heat-conducting filler, for example boron-nitride is embedded. The insert moulding is connected to the housing with suitable profiled parts and anchors. The use of plastics material advantageously minimises the eddy current losses to achieve a good efficiency.
For further reinforcement, parts which are of a particularly thin-walled configuration, with a high modulus of elasticity can be embedded or incorporated in the injection moulding.
Also advantageous is a stator tooth with a body-less coil or with insulation parts only on the tooth neck wall and front with a corresponding spacing to the external and internal poles. The material is then injected into this space formed by the spacing.
All the individual yokes with their coils are connected to the housing and centred accordingly by the previously described insert moulding procedure. The free space or spacing between the coils and yokes, like the front of the coil, is then sheathed or filled with plastics material, it being possible for a corresponding structure and contour of the plastics material with respect to the outer reinforcement to be formed.
In a particularly advantageous configuration of the invention, the free space or spacing between the individual yokes and the coils forms a double-T-support-shaped space which is filled by the plastics material. Thus, after injection, the plastics material forms in cross section a double-T-support-shaped support which is anchored in the housing or in the part joined to the housing. A particularly good rigidity is thus achieved by this cross-sectional contour. The cross-sectional contour of the supports can advantageously extend into the correspondingly formed recesses in the housing or in the part joined thereto, thereby producing a particularly good rigidity of the supports. In this respect, the cross-sectional area of the recesses can be larger than the support cross-sectional area in the region of the rotor, so that a type of widened base is produced on the support which extends into the recesses in the housing or housing part.
Likewise, to reinforce the plastics material composition, reinforcing elements can be provided, one end of which extends in each case up into a recess and the other end extends as far as the stator tooth or up into the gap between the adjacent stator teeth. In this respect, the reinforcing elements can be embedded in the region of the external pole shoe and/or the internal pole shoe.
It is optionally possible to obtain an even more rigid construction by additionally insert moulding the poles with the plastics material. The plastics material sheathing the poles or pole shoes is joined to the supports by radially and axially extending walls. Although the length of the air gap is increased by the sheathing of the pole shoes, this is compensated by the increased rigidity and thus the greater power of the motor.
In the embodiment according to the invention, individual stator teeth which in cross section can advantageously have a double-T shape, i.e. they have radially outer and inner pole shoes, are initially wound axially and then positioned in the injection moulding die. Unlike double rotors with a high output and rigidity (prior art (EP 1879283 (Matsushita), EP 1191673 (Denso) and U.S. Pat. No. 5,260,642 (Huss)), the stator does not have any tangential connecting webs. In this embodiment, the magnetic flux is generated radially and is closed via the outer rotor, the adjacent stator teeth and the inner rotor.
The individual teeth are firmly anchored to the housing and are held in position by the supports and support elements injected from plastics material.
The injected support elements are preferably T-shaped of more preferably double-T-support-shaped so that the stator is provided with a very high rigidity for radial and tangential loads. To ensure a very efficient heat dissipation, the plastics material is preferably formed from materials which have a high thermal conductivity but a low electrical conductivity.
The construction according to the invention has the following advantages over the prior art:
In the following, various embodiments of the double rotor motor according to the invention are described with reference to drawings, in which:
a is a plan view of the reinforcing element;
a shows a support structure with a reinforcing element;
b is a sectional view of the housing part and of two supports;
c shows the motor with externally and internally insert moulded pole shoes.
The stator consists of individual stator teeth 1 with pole shoes 1a in the outer region and pole shoes 1b in the inner region, which are wound with excitation coils 4. In addition, the motor comprises an outer rotor 3a provided with permanent magnets 2a and an inner rotor 3b provided with permanent magnets 2b. Furthermore, two back-circuit elements 24a, 24b are shown which are optional. The back iron can also take place via the rotors 3a, 3b. Air gaps 1f are in each case between the pole shoes 1a, 1b and the rotors 3a, 3b as well as the optional back-circuit elements 24a, 24b.
A pressed screen 23 can also be provided which is also insert moulded for contacting purposes, so that the contacting of the coils 4 takes place before the insert moulding procedure and thus the tool configuration is simplified. In a multi-part injection process, it is to be provided that the injection moulding compositions interlock. A corresponding interlocking region and separating region of the moulded compositions is shown at 35d.
Furthermore, the housing 12 in region 12a is to be configured such that the spacing between coil side 4a and housing region 12a is minimised. Therefore, the housing region 12a widens towards the rotation axis to be adapted to the coil contour. This ensures that the wall 35w, produced by insert moulding, is as thin as possible for a good heat transfer. The wall region 35w can also be produced by a plastics material with good heat conduction properties.
Injection moulded on the inside is a reinforcing insert 36 with a high modulus of elasticity and heat conduction which, during injection moulding, is pressed positively onto the stator teeth 1 by suitable tools. In addition, a further outer insert part 37 is optionally provided which is also joined to the injection moulding in region 35c by one or a plurality of recesses 40 also in the inner insert part. A connecting web or connecting ring 38 can also be provided between the insert parts 36 and 37 for further reinforcement.
The insert part 36, 37 can also project laterally out of the housing 12 and rest resiliently against the housing 12 to maintain a bias. This improves the bond, in particular when a metallic material is used as the insert parts 36, 37. To reduce eddy currents, the insert part 36, 37 is thin and is provided with stamped-out elongated slots 37a, as shown in
On the front 4b, remote from the housing, the coil 4 is also insert moulded, the injection composition forming reinforcing ribs 35b. These enhance the rigidity and enlarge the surface for heat dissipation by air cooling. The air cooling is furthered by a fan impeller 21. For an appropriate air guidance, recesses 39 can be made in the rotor and in the housing 12.
The magnetic back irons 24a and 24b are mounted such that they are fixed to the housing. There are two air gaps if in each case between stator, rotors 3a and 3b and back irons 24a and 24b. The rotors 3a and 3b are configured with thin walls. This reduces the mass of inertia of the rotor and the cooling channels 18 can extend axially in the housing, thereby improving the rotor cooling.
The support structures 35 configured as double-T supports extend as far as the inside of the yoke to increase the geometrical moment of inertia Ia and thus to improve the tangential load. For a radial load, the radial web height of the supports 35 is to be configured as high as possible, which results in a high degree of rigidity.
For the structure, it is necessary for the stator tooth to be previously wound and positioned relative to the housing.
a shows the double-T support 35 with a radially outer reinforcing element 37. Alternatively, the reinforcing element 37 can be arranged relative to the excitation coils 4, but can also be arranged radially inside. Of course, reinforcing elements 37 can also be arranged outside and inside and injection moulded. The reinforcing element 37 is preferably made of a poorly conductive metallic material, for example stainless steel, with stamped-out areas 37a to reduce the current conductivity and thus the eddy current losses.
b shows the cut-off T-supports 35 with a thickening 35a as well as the contour of the housing recess 12b which is configured in terms of injection moulding so that a high degree of rigidity is obtained. The contour of the housing recess 12b should correspond to the cross-sectional contour of the supports 35, so that a high degree of rigidity results and the supports extend up into or through the housing wall. In this respect, attention should also be paid to a minimum use of material, while bearing in mind the necessary rigidity.
c shows a widening of the T-support structure 35. The supports 35 are connected to an outer ring 35e as part of the injection moulding over the regions 35s, which comprise the external poles 1a including the outer reinforcing ring 35e. Even in the case of a small wall thickness, this ring 35e is also very effective for reinforcement with a tangential load. In region Z-Z, a further alternative is shown, in which both the external and the internal yoke poles 1a, 1b are insert moulded through rings 35e in a thin-walled manner and are connected to webs between the coils. A thermosetting plastics material is preferably suitable for producing a thin wall thickness. For the injection procedure, the region E between the poles can be configured to be slightly recessed if appropriate due to the formation of burrs.
As a result of the above-mentioned measures, the coil space between the poles can be fully utilised, which increases the efficiency. These measures make it possible to achieve a great rigidity with good heat dissipation, so that it is possible to realise a motor with high output, a small diameter and relatively long self-supporting coils.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2009 011 383.5 | Mar 2009 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2010/001383 | 3/5/2010 | WO | 00 | 9/6/2011 |
