Method for manufacturing a rotor for an electrical machine with a contactless power transmission system, and rotor, electrical machine and motor vehicle

Abstract

A method for manufacturing a rotor for an electric machine with a contactless power transmission system, wherein an end winding cover is arranged on one end face of a laminated core of the rotor. The invention provides that a secondary unit (SEC) of the power transmission system is integrated in the end winding cover and, as a result, after the end winding cover has been arranged, the secondary unit (SEC) is held on the rotor indirectly via the end winding cover.

Claims

1. A method for manufacturing a rotor for an electric machine with a contactless power transmission system, comprising steps of providing an end winding cover; providing a rotor; providing a laminated core, the laminated core being part of the rotor; providing a secondary unit (SEC), the secondary unit (SEC) being part of the power transmission system; providing a cavity delimited by the laminated core; and providing a filling compound; arranging the end winding cover on an end face of the laminated core of the rotor; integrating the secondary unit (SEC) of the power transmission system in the end winding cover such that after the end winding cover has been arranged on the end face of the laminated core of the rotor, the secondary unit (SEC) is held on the rotor indirectly via the end winding cover; filling the laminated core and the cavity delimited by the laminated core and the end winding cover with the filling compound such that the end winding cover is held on the laminated core by curing the filling compound.

2. The method of claim 1, further comprising the steps of: providing a through-opening which is part of the end winding cover; and providing the secondary unit (SEC) to be a ring; inserting the ring into the through-opening.

3. The method of claim 1, further comprising the steps of: providing a sleeve; using the sleeve to hold the end winding cover on the laminated core as the wound laminated core and the cavity delimited by the laminated core and the end winding cover are filled with the compound.

4. The method of claim 1, further comprising the steps of: providing a shaft of the rotor; providing an annular gap between the secondary unit (SEC) and the shaft of the rotor; and providing an annular plug; closing the annular gap with the annular plug to fill the rotor.

5. The method of claim 1, further comprising the steps of providing the filling compound to further comprise a potting compound.

6. The method of claim 1, further comprising the steps of: providing the filling compound to further comprise an injection-molding compound; filling the wound laminated core and the cavity delimited by the laminated core and the end winding cover with the injection-molding compound using an injection-molding process.

7. The method of claim 1, further comprising the steps of: providing a first fastening tool; providing a second fastening tool; providing at least one electrical connection contact of an excitation winding of the rotor; and providing a respective contact element of a rectifier of the secondary unit (SEC); arranging the end winding cover with the secondary unit (SEC) arranged therein; holding the end winding cover a distance from the end face of the rotor; moving the first fastening tool along a radial direction between the end face and the end winding cover; moving the second fastening tool along an axial direction between the end winding cover and a shaft surface of the rotor; using the fastening tools to connect the at least one electrical connection contact of the excitation winding of the rotor to the respective contact element of the rectifier of the secondary unit (SEC).

8. The method of claim 7, further comprising the steps of using the fastening tools to fasten the at least one connection contact to the respective contact element by at least one of soldering or welding or crimping or clamping.

9. The method of claim 7, further comprising the steps of: providing the second fastening tool to be a tube; slipping the tube over a shaft end of the rotor.

10. The method of claim 7 further comprising the steps of: providing a winding hook to be the respective contact element; and providing a rectifier board; inserting the winding hook into the rectifier board of the rectifier.

11. The method of claim 10, further comprising the steps of providing a metal core in the rectifier board.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) An exemplary embodiment of the invention is described below, the figures showing:

(2) FIG. 1 a schematic representation of a longitudinal section of an externally excited rotor with brushless power transmission;

(3) FIG. 2 a schematic representation of a longitudinal section of a secondary unit of a power transmission system of the rotor from FIG. 1;

(4) FIG. 3 a schematic representation of the rotor during its completion when the secondary unit is being assembled;

(5) FIG. 4 a schematic representation of the rotor during its completion after the assembly of the secondary unit and before potting;

(6) FIG. 5 a schematic representation of the rotor during its completion when potting;

(7) FIG. 6 a schematic representation of a perspective view of the rotor with a partial section;

(8) FIG. 7 a schematic representation of a perspective view of the rotor;

(9) FIG. 8 a schematic representation of a perspective view of the rotor as a partial section;

(10) FIG. 9 a schematic representation of a perspective view of the rotor as a partial section;

(11) FIG. 10 a schematic representation of a perspective view of the rotor as a partial section; and

(12) FIG. 11 a schematic representation of an embodiment of the motor vehicle according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(13) The following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.

(14) The exemplary embodiment is a preferred embodiment of the invention. In the exemplary embodiment, the described components of the embodiment each represent individual features of the invention which are to be considered independently of one another and which each also develop the invention independently of one another and may therefore also be considered to be a constituent part of the invention, either individually or in a combination other than that shown. Furthermore, the embodiment described may also be supplemented by further features of the invention from among those which have already been described.

(15) In the figures, functionally identical elements are respectively provided with the same reference signs.

(16) As an overview, reference is first made to FIG. 11. FIG. 11 shows a motor vehicle 10, which may be a motor car, such as for example a passenger car. The motor vehicle 10 may have an electric traction drive 11, which may be formed on the basis of an electric machine 12. In addition, an inverter 13 and a traction battery 14 are shown. The traction battery 14 may be for example a high-voltage battery, which may provide an electrical voltage greater than 60 V, such as greater than 100 V. The inverter 13 may generate phase currents for a stator winding 15 of a stator 16 of the electric machine 12 from the DC voltage of the traction battery 14 in a manner known per se. The phase currents of the inverter 13 are used to generate a rotating magnetic field in an interior of the stator 16 using the stator winding 15.

(17) A rotor 17 may be rotatably mounted in the interior of the stator 16. The electric machine 12 may be an externally excited synchronous machine. For this purpose, an excitation winding 18, through which a DC current may flow, is provided in the rotor 17. The rotor 17 then generates magnetic poles on its outer circumference, interacting with the rotating magnetic field of the stator 16, which results in a rotary movement of the rotor 17. The rotor then rotates about an axis of rotation 19 and thereby turns a shaft 20, via which a drive torque is transmitted to wheels of the motor vehicle 10.

(18) In order to generate the current in the excitation winding 18, the electric machine 12 may have a power transmission system 21. Using the power transmission system 21, electrical energy is transmitted to the rotor 17 contactlessly, on the basis of an inductive transmission. For this purpose, the power transmission system 21 may have a rotary transformer with a primary-side winding 22 on a housing part or end shield 24 and a secondary-side winding 23 on the rotor 17.

(19) FIG. 1 illustrates in this respect the power transmission system 21 in a longitudinal section. FIG. 1 is mirror-symmetrical with respect to the axis of rotation 19, so that the reference signs are in each case only indicated on one side of the axis of rotation 19. They also apply mirror-symmetrically to the opposite side.

(20) The power transmission system 21 may have been manufactured by a manufacturing method that may have the following advantageous properties: It is a manufacturing method for traction drives with externally excited synchronous machines with contactless power transmission with an excitation current transmission system or power transmission system that is provided at low cost and a high temperature resistance and speed stability (over 15 000 rpm). A special sealing concept is provided, allowing the rotor to be potted with an epoxy resin or filled with a plastic by an injection-molding process. A special geometry of the rotary transformer of the power transmission system and the special axial sealing of the rotor in the region of the rotary transformer guarantee the reliable potting or injection-molding process as well as the axial and radial air gap of the rotary transformer. The rotary transformer is centered radially during the potting process with the aid of a cover of the end windings. A special manufacturing method (for welding the winding wire to the winding hook) for contacting the winding wire of the rotor winding with the secondary side of the power transmission system is provided. A special concept for accommodating the winding hooks on the rectifier board is provided. For better heat dissipation from all of the components of the rotary transformer, including the winding and electronic parts of the secondary side of the rotary transformer, a special epoxy resin or special plastic (preferably with a higher thermal conductivity than air) is used in the potting or plastic injection-molding process. A special geometry of the cover of the end winding is produced at low cost and allows for example the accommodation of a sensor track and a balancing ring (see the publications mentioned at the beginning DE 20 2012 002 024 U1 and DE 20 2012 002 027 U1). However, another type of rotor position encoder may also be provided. In this case, the sensor track is substituted by another position-giving element. With an axial signal transmission (from the encoder wheel, which is accommodated on the rotor, to a rotor position encoder), the cover of the end winding is designed as one part with the sensor track (optional), a balancing ring and a special seat for the rotary transformer. A suitable material composition of the cover of the end winding may in this case be considered (see documents DE 20 2012 002 024 U1 and DE 20 2012 002 027 U1 for the material composition).

(21) For further explanation of the method, FIG. 1 specifically shows a movable bearing side (non-driving side) of the electric machine 12. The end shield or motor housing 24 and a spring element 25 are shown.

(22) The shaft 20 of the rotor 17 is rotatably mounted on the end plate or motor housing 24 via a bearing 26. Circlips 27 fix the bearing 26 in the axial direction 28 along the axis of rotation 19. Of the rotor 17, also shown are a laminated core 29, end windings 30 of the excitation winding 18, a cover 31 of the end windings 30 with a potting compound 32 arranged therein and wires 33 of the excitation winding 18. The wires 33 may be connected to the power transmission system 21. Each wire 33 thus represents a connection contact.

(23) The power transmission system has a primary unit PRIM fastened on the end plate or motor housing 24 and a secondary unit SEC fastened on the rotor. The primary unit PRIM provides a primary side and the secondary unit a secondary side of a rotary transformer. The primary unit PRIM and the secondary unit SEC are each formed as rings, which are arranged around the shaft 20. The secondary unit SEC may be arranged on one end face 17′ of the rotor 17.

(24) Of the power transmission system 21, shown from the primary unit PRIM are the primary-side winding 22, a heat sink 34, a connection board 35 for providing a supply voltage (outgoing electrical lines are not shown), metal pins 36 for through-contacting the connection board 35 to a winding board 37 of the primary-side winding 22 and a primary ferrite core 38.

(25) A radial air gap 40, via which a flux generated by the primary winding 22 may change over into the ferrite core 39 of the secondary unit SEC, is obtained in a magnetic circuit. Since it is a radial air gap 40, its gap dimension does not change when there is an axial movement of the shaft 20 in the axial direction 28. With the axial movement, an axial air gap 40′ changes. The ferrite cores 38, 39 each have an L profile. This also allows radial tolerances to be compensated.

(26) Also shown from the secondary unit SEC are: a winding board 41 of the secondary-side winding 23, a heat sink 42, a rectifier board 43 with a rectifier circuit that includes capacitors 44 and diodes 45, metal pins 46, via which the winding board 41 is electrically connected to the rectifier board 43, and hooks 47, at which the wires 33 of the excitation winding 18 are contacted. Each hook 47 thus represents a contact element. The hooks 47 are also referred to as winding hooks. They each represent a connection contact of the rectifier circuit. The rectifier board 43 may be connected directly to the heat sink 42 by metal screws (an associated countersink with a thread 48 is shown). The heat sink 42 bears against the cover 31 with a coupling surface 42′. It may be a press fit. The cover may be made of a non-magnetizable metal or a non-magnetizable metal alloy.

(27) The winding 23 may be realized on the winding board 41 as a flat coil having conductor tracks. For this purpose, the winding board 41 may be of a single-layer or multi-layer design.

(28) FIG. 2 shows the upper section of the secondary unit SEC, as shown in FIG. 1, on an enlarged scale. It shows how intermediate spaces are filled or filled up with a potting compound of an epoxy resin or are filled or filled up with plastic using an injection-molded filling. This potting or injection-molded filling 32′ on the one hand allows the secondary unit SEC to be stabilized for a high speed. The power transmission system 21 is thereby provided with speed stability for speeds greater than 15,000 revolutions per minute. Furthermore, the potting or the injection-molded filling 32′ offers a solid-based heat transfer from the electronic parts and the winding via the heat sink into the end winding cover. A special cooling of the components via the following “heat path” is proposed: from the components via heat sinks of the power transmission system and special highly heat-conducting epoxy resin or special highly heat-conducting plastic, then to the cover of the end winding and thereafter into the engine compartment of the electric machine.

(29) The secondary unit SEC may be held on the rotor 17 indirectly by the end winding cover 31 and the potting compound 32.

(30) A balancing ring 50 may be arranged in the end winding cover 31. The balancing ring 50 may have an L-profile. With respect to the axial direction of the laminated core 29, the balancing ring 50 may have an undercut in which the potting compound 32 may engage. As a result, the end winding cover 31 is held on the laminated core 29.

(31) As shown in FIGS. 3 to 5, the rotor 17 may be assembled with the secondary unit of the power transmission system in the following order and with the following manufacturing steps.

(32) First, the laminated rotor core 29 is wound with the winding wire of the excitation winding 18. Since a DC current is fed into the rotor 17 of an externally excited synchronous machine during operation, the rotor 17 has two winding ends for contacting, i.e. two wires 33. State of the art is to wind an externally excited rotor with a round wire. Other types of winding may also be used.

(33) The end winding cover 31 is joined to the laminated rotor core 29 along the axial direction 28 (fitting-on direction or sliding direction) (FIG. 3). After that or before that, the secondary unit SEC of the rotary transformer of the power transmission system 21 is inserted into the end winding cover 31. It is conceivable that the end winding cover 31 and the secondary unit SEC of the rotary transformer are joined to the laminated rotor core 29 at the same time, or first the secondary unit SEC of the rotary transformer and then the end winding cover 31. By inserting the secondary unit SEC into the end winding cover, the manufacturing method allows both an integrated solution and a stand-alone solution for the secondary unit SEC.

(34) A defined distance 51 between the laminated rotor core 29, the end winding cover 31 and the secondary unit SEC of the rotary transformer allows the winding wire 33 to be placed onto the winding hooks 47 and a clearance for a welding electrode 52 during the welding process. In FIG. 3, the welding electrode 52 is inserted along a radial direction 54 (perpendicularly in FIG. 3). The welding electrode 52 represents a first fastening tool. A tubular electrode 55 is proposed as the counter electrode. The tubular electrode 55 represents a second fastening tool. The secondary unit SEC is designed and arranged in such a way that the tubular electrode 55 does not touch the rotor shaft 20 and the ferrite core 39 of the rotary transformer. The tubular electrode 55 also serves as support for the winding hook 47 during the placement of the winding wire 33 onto the hook 47 and during the welding process. The winding hook 47 is pressed together during the welding process by the radially acting electrode 52. When the current is applied and the hook is pressed together during welding, the insulation of the winding wire 33 is burned off. This creates a secure electrical connection.

(35) During the winding process, the two ends of the winding wire 33 are placed onto the two winding hooks 47, which are connected directly to the rectifier board 43. The electrode 52, aligned vertically in FIG. 3, presses the winding hook 47 from above and current is applied between the vertical electrode 52 and the tubular electrode 55.

(36) FIG. 4 shows how, after the welding process, the end winding cover 31 and the secondary unit SEC of the rotary transformer are brought into an end position by being pushed in the axial direction 28 toward the laminated core 29.

(37) As an alternative to the welding described, other connecting techniques may be used for connecting the winding wire 33 and the winding hook 47: brazing, crimping or clamping.

(38) In the case of this manufacturing method with an industrialization concept, the winding hooks 47 have three functions they must be able to absorb and withstand the winding forces when the winding wire 33 is placed on them; they must allow the welding process; they must ensure a secure electrical connection to the rectifier board 43.

(39) The winding hooks 47 are preferably connected directly to the rectifier board 43. A rectifier board 43 with an aluminum core is additionally proposed. As an alternative, a rectifier board 43 with a copper core may also be used, as a result of which the heat dissipation is improved.

(40) When the laminated core 29 is wound, the two ends of the winding wire 33 are placed onto the two winding hooks 47, which are connected directly to the rectifier board 43. Placement generally involves a great force effect by the winding machine. For this reason, the aluminum or copper cores are not only used for cooling the electronic parts or components of the rectifier board 43, but also serve as a reinforcing layer of the circuit board of the rectifier board 43 when the winding wire 33 is placed and welded. The winding hooks 47 are preferably pushed through the rectifier board 43 and mechanically and electrically connected on the other side (connecting side with copper layer for conductor tracks) of the rectifier board 43. For example, the following connecting techniques may be used: screwing, soldering, clamping and welding. A reliable electrical contact with the copper tracks of the circuit board of the rectifier board 43 is realized both on the winding hook side and on the other side (connecting side). The winding hooks may also be electrically contacted on both sides of the rectifier board.

(41) In order, due to high centrifugal forces, to be able to guarantee rotational speed stability (over 15 000 per minute) for traction drives, the externally excited rotor 17 may be potted with an epoxy resin or filled with a plastic using an injection-molding process.

(42) If the secondary unit SEC of the rotary transformer is to be considered as a separate part (stand-alone solution), the parts of the secondary unit SEC are potted together or overmolded with a plastic independently of the rotor 17 (see FIG. 2). Thereafter, the potted or overmolded secondary part SEC is contacted with the two winding ends 33 of the rotor 17 and accommodated in the already potted laminated core 29 in the end winding cover 31. Such a stand-alone solution makes sense, for example, if a number of rotors have a different geometry or power and it makes no sense to use different geometries for the rotary transformer of the power transmission system 21.

(43) In the following description, only the integrated solution for the rotary transformer is described as a more cost-effective solution on the basis of FIG. 5 (without considering a stand-alone solution).

(44) When potting or filling the externally excited rotor 17, the rotor 17 must be sealed off with respect to the outside, in order that the potting or injection-molding compound does not escape from the outer geometry of the rotor 17.

(45) In order that the rotor is potted together with the secondary unit SEC of the rotary transformer, the geometry and structure shown of the rotor with the rotary transformer are proposed. In the publications 20 2012 002 024 U1 and DE 20 2012 002 027 U1, it is proposed that the two end windings of the rotor 17 with the end winding covers (made of a special stainless steel, as described in the publications) are secured against centrifugal forces using a potting compound or using a plastic injection compound (general filling compound). The end winding covers are secured against axial slipping and radial forces with the aid of the undercuts of the balancing rings and the potting 32.

(46) The geometry of the secondary unit SEC of the rotary transformer is designed in such a way that reliable sealing during the potting process and the axial and radial air gap 40, 40′ are ensured.

(47) Axial and radial air gaps 40, 40′ between rotating and stationary parts of the contactless power transmission system 21 are the decisive factors of the contactless power transmission. The smaller the two air gaps 40, 40′ are, the less losses occur during the power transmission.

(48) At the same time, the mechanical tolerances of the individual parts and assemblies of the electric machine 12 (see FIG. 1) rather require an enlargement of the axial and radial air gap 40, 40′, in order that the rotating and stationary parts (for example the rotor 17 and the stator 16 of the machine 12) do not touch during operation. The smaller the radial air gap 40 between the stator and the rotor of the electric machine (the rotary transformer itself is not meant here), the more expensive it is to manufacture the machine 12. The development of an economical manufacturing concept is faced with the challenge of finding a compromise between these two opposing demands.

(49) The structure or the geometry of the power transmission system 21 allows a sealing concept of the rotor 17 during the potting with epoxy resin or injection molding with a plastic.

(50) FIG. 4 shows in this respect how, after the welding, brazing, crimping or clamping of the winding wire 33 onto the winding hook 47, the cover 31 of the end winding (and the secondary unit SEC) is placed axially onto the laminated rotor core 29 as far as it will go. The interface or contact point between the laminated rotor core 29 and the cover 31 of the end winding must be sealed in the potting or plastic molding tool. For this purpose, a silicone ring or a silicone sleeve 56 is pulled onto the rotor 17, for example when potting, in the region of the interface with the end winding cover 31. After potting, the sleeve 56 is removed. Since the cured potting compound 32 does not stick to the silicone, the sleeve 56 may be used several times.

(51) The silicone ring or the silicone sleeve 56 centers the end winding cover 31 radially during the potting process, and at the same time the secondary unit SEC of the rotary transformer integrated in the cover 31.

(52) Axially, a silicone ring or silicone plug 57 (see FIG. 5) is proposed for sealing an annular gap 58 between the secondary unit SEC and the shaft 20, and ultimately the entire rotor 17.

(53) The rotor 17 may now be potted or filled by injection molding. Such a rotor system is preferably potted upright (see FIG. 5) with epoxy resin under a vacuum. The rotor is thereby (preferably) placed on the other side of the rotor (upright) in the potting tool. The potting compound is preferably injected into the evacuated rotor from bottom to top under pressure along a potting direction 59. When potting or injection molding, the rotor must be vented, in order that the interior is completely filled without air pockets. For this purpose, venting openings 60 are provided, for example in the end winding cover 31. The air may escape along a venting direction 61.

(54) In the case of injection molding with a plastic, the silicone ring (sleeve 56) shown in FIG. 5 is substituted by a sealing part in the injection-molding tool. Just like the sleeve 56 in the region of the interface, the silicone plug 57 is substituted by a sealing part in the injection-molding tool.

(55) In general, the silicone sealing parts may be removed after potting and used again. When injection molding with a plastic, the (horizontal or vertical) position of the rotor 17 is irrelevant.

(56) The axial sealing concept described above plays an important role for the radial and axial air gap 40, 40′ between the two ferrite cores 38, 39 (see FIG. 1). If for example when the rotor 17 is potted, the potting compound escapes in the region of the silicone plug 57, the radial air gap 40 between the two ferrite cores 38, 39 becomes smaller. The narrowed air gap may lead to the rotary transformer being damaged.

(57) FIG. 6, FIG. 7, FIG. 8, FIG. 9 and FIG. 10 show the completely assembled rotor 17. Generally, in the case of externally excited synchronous machines, a rotor requires a rotor position encoder. The accommodation of a sensor track 62 and the balancing ring 50 has already been described in the publications DE 20 2012 002 024 U1 and DE 20 2012 002 027 U1. However, the sensor track is just an example. A special material composition for the end winding cover 31 of the end winding 30, the rolled-in balancing ring 50 and (optionally) a sensor track 62, which are applied to the end winding cover 31 by the cold-gas spraying process, are preferably also used in the case of the manufacturing method presented here. The cited documents are therefore to be regarded as part of the present description.

(58) Overall, the example shows how a manufacturing method for a traction drive with an externally excited synchronous machine and with contactless excitation current transmission and high temperature resistance and speed stability may be provided by the invention.

(59) The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.

LIST OF REFERENCE SIGNS

(60) 10 Motor vehicle 11 Electric traction drive 12 Electric machine 13 Inverter 14 Traction battery 15 Stator winding 16 Stator 17 Rotor 17′ End face 18 Excitation winding 19 Axis of rotation 20 Shaft 21 Power transmission system 22 Primary winding 23 Secondary winding 24 Motor housing 25 Spring element 26 Bearing 27 Rings 28 Axial direction 29 Laminated rotor core 30 End windings (of the excitation winding 18) 31 Cover 32 Potting compound 32′ Injection-molded filling 33 Wires 34 Heat sink 35 Connection board 36 Metal pin 37 Winding board 38 Ferrite core 39 Ferrite core 40 Radial air gap 40′ Axial air gap 41 Winding board 42 Heat sink 43 Rectifier board 44 Capacitors 45 Diodes 46 Metal pins 47 Hooks 48 Metal screw 49 Conductor tracks 50 Balancing ring 51 Distance 52 Welding electrode 54 Radial direction 55 Tubular electrode 56 Sleeve 57 Silicone plug 58 Annular gap 59 Potting direction 60 Venting opening 61 Venting direction 62 Sensor track PRIM Primary unit SEC Secondary unit