BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to a stator for an electric machine, in particular for driving an electric or hybrid vehicle. The invention furthermore relates to a cooling apparatus for such a stator and to an electric machine having such a stator and having such a cooling apparatus.

An electric machine, such as for example an electric or electromotive drive machine, usually has an electric motor, which for its part typically has a stator provided with a stator winding (rotating-field winding) and a rotor mounted so as to be rotatable about a motor axis, which generates a static magnetic field by means of permanent magnets, for example. During operation of the electric motor, in which an electric alternating current flows through the stator winding, which is therefore energized, the rotor rotates in a magnetic rotating field generated by the stator or the stator winding thereof.

When such a drive machine is used in an electrically or electromotively operated or driven vehicle (electric or hybrid vehicle), it is typically necessary to cool the stator and/or the rotor by way of a gaseous or liquid coolant (cooling medium) in order to ensure the desired long-term efficiency for such vehicle applications.

To cool the stator, it is possible, for example, to arrange what is known as a water or coolant jacket as a cooling apparatus on the outer circumference of the stator. Such a jacket cooling apparatus has the disadvantage that it cools the stator only from the outside, that means in the region of the outer circumference thereof. In this case, the problem of the stator winding and/or the rotor not being cooled to a sufficient extent arises.

Furthermore, cooling apparatuses are known in which a coolant, in particular a motor or transmission oil, is applied to the stator and/or the rotor during operation of the electric motor. Such direct cooling (oil spray cooling) requires additional components of the machine, such as for example an oil cooler and/or an oil pump, as a result of which additional costs and an increased installation space requirement arise. Furthermore, cooling apparatuses in which the lines forming the stator winding are embodied as pipe-like or pipe-shaped waveguides, through which a coolant flows during operation, are contemplated. As a result, the winding density of the stator windings is reduced, which has a disadvantageous effect on the performance of the electric machine.

In order to dissipate the waste heat from a stator designed as a (stator) laminated core with individual laminations, it is known from EP 2 003 764 A2 to introduce a number of axially running cooling channels into the laminated core. The cooling channels are coupled to one another in terms of flow technology on the opposite stator face sides by way of annular or crown-like distributor structures and a coolant flows through said cooling channels. In this case, for example, the cooling channels are introduced in a stator yoke of the laminated core. In such a cooling apparatus for a stator of an electric motor, it is disadvantageous that the stator winding and, in particular, the rotor are not cooled to a sufficient extent. Furthermore, the magnetic properties of the stator are disadvantageously reduced due to the introduction of the cooling channels into the laminated core.

The invention is based on the object of providing a particularly suitable stator for an electric machine, in particular for an electromotive drive machine for an electric or hybrid vehicle. Furthermore, a suitable cooling apparatus for such a stator and an electric machine having such a stator as well as a motor vehicle, which has a drive machine with improved stator cooling, are intended to be specified.

The object is achieved by a stator, by a cooling apparatus for a stator, by an electric machine having the stator and cooling apparatus, and by a motor vehicle having such an electric machine, in accordance with the claimed invention. Here, the statements in connection with the stator also apply accordingly to the cooling apparatus, to the electric machine, and to the motor vehicle, and vice versa.

The stator according to the invention is suitable and configured for an electric machine, in particular for an electric or electromotive drive machine for an electric or hybrid vehicle. To this end, the stator has a stator laminated core having a stator yoke and having a number of radially oriented stator teeth. In this case, the stator laminated core has a corresponding number of stator slots between the stator teeth to receive a stator winding or rotating-field winding. The stator may also have a bevel. A cooling apparatus having a number of cooling channels (coolant channels) is furthermore provided. In this case, the cooling channels are each arranged so as to run at least substantially axially in one of the stator slots. During operation, a gaseous or liquid coolant flows through the cooling channels. Here, the coolant absorbs heat from the stator and dissipates it to the outside. For this purpose, the cooling channels are expediently produced from a thermally conductive material and preferably have the lowest possible (channel) wall thickness, with the result that effective heat exchange or heat transfer between the guided coolant and the respective environment of the cooling channel is ensured. As a result thereof, efficient and reliable cooling of the stator is ensured, as a result of which the lifetime and performance of the stator is substantially improved.

In contrast to the prior art, the cooling channels are therefore arranged not inside the stator laminated core but rather outside, in particular in the free spaces, which are formed by the stator slots, between two respective adjacent stator teeth. As a result, the magnetic properties of the stator laminated core or of the stator are not disadvantageously influenced by the cooling channels. Since during electromotive operation heat develops in the region of the stator winding, the arrangement of the cooling channels according to the invention ensures that the stator is cooled to a sufficient extent in this region. Furthermore, the arrangement of the cooling channels in the stator slots does not bring about an additional installation space requirement of the stator.

In an advantageous development, the cooling channels of the cooling apparatus are produced from a thermally conductive and electrically non-conductive material, in particular a ceramic or a ceramic material or a plastic, preferably a glass fiber reinforced plastic (GRP). On account of the electrically non-conductive, in particular non-magnetic, embodiment of the cooling channels, it is ensured that no electric leakage currents are induced during the electromotive operation, in which the stator winding generates a magnetic rotating field. In other words, the cooling channels therefore do not cause undesired power losses in the stator.

In an expedient configuration, the cooling channels of the cooling apparatus are coupled to the respective stator teeth in a thermally conductive manner by means of a potting compound. In other words, a respective gap region in the stator slot between the cooling channel and a stator tooth is at least partly filled by the potting compound. In this case, it is preferably contemplated, for example, for the respective cooling channel in the stator slot to also be connected to the stator winding in a thermally conductive manner by the potting compound. This improves the effected cooling power of the cooling apparatus during operation of the stator.

The cooling apparatus has at least one collector ring, in a preferred configuration two single-piece collector rings (end ring, distributor ring), which are arranged on the opposite face sides of the stator laminated core. The circular or crown-like collector rings couple the cooling channels arranged between them to one another in terms of flow technology. The collector rings and the cooling channels therefore form an approximately cage-like or cage-shaped cooling apparatus of the stator. This ensures particularly uniform and efficient cooling of the stator.

In a suitable configuration, one of the collector rings has an inlet for coupling in terms of flow technology to a coolant supply line for supplying with the coolant or the cooling medium. The collector ring arranged opposite accordingly has an outlet for discharging the coolant. By way of the collector rings, the fed coolant is distributed substantially equally across all cooling channels and discharged again. This ensures reliable dissipation of the heat produced during operation within the stator.

In an alternative embodiment, it is likewise contemplated, for example, for the cooling channels to be contact-connected in terms of flow technology by means of hollow spaces or coolant conducting structures of a stator housing or motor housing provided for this purpose. In addition or as an alternative, it is possible for the cooling apparatus to have in addition to the cooling channels in the stator slots a coolant jacket on the outer circumference of the stator laminated core, wherein the cooling channels and the coolant jacket are coupled to one another in terms of flow technology. As a result, particularly reliable and effective cooling of the stator is possible.

In an expedient design, the collector rings each have an annular body having an integrated collector channel and a number of axially integrally formed connecting receptacles corresponding to a number of coolant channels. The collector channels of the collector rings are therefore arranged in an encircling manner in the region of the opposite end sides of the cooling channels. In this case, the end sides of the cooling channels are coupled to the respective collector channel in terms of flow technology by means of the connecting receptacles. This means that the cooling channels are arranged parallel to one another in terms of flow technology between the collector channels. In other words, the collector channels and the cooling channels form a substantially closed coolant system for guiding the coolant. This ensures a uniform distribution and guidance of the coolant in a constructively simple manner. This consequently advantageously translates to cooling of the stator.

In the assembled state, the collector rings are arranged on the opposite face sides of the stator laminated core. This means that the annular bodies are arranged substantially in the region of the end windings of the stator winding and/or of an end shield. The coolant flows through the collector channels integrated into the annular bodies of the collector rings during operation. This effects an additional cooling effect of the cooling apparatus in the region of the end windings and/or of the end shield.

In an expedient development, the cooling channels are joined on the end side to connecting receptacles of the collector rings. The cooling channels are thus, for example, soldered or adhesively bonded on the end side to the connecting receptacles. The cooling channels are preferably inserted into the connecting receptacles. As a result, expedient securing and coupling that are reduced in terms of outlay during assembly are realized.

The seal-tightness of the cooling apparatus for preventing coolant leaks is ensured, for example, by way of a press-fit assembly of the cooling channels in the connecting receptacles or by use of a potting or an adhesive. In a particularly coolant-tight configuration, at least one sealing element is provided between the collector rings and cooling channels. In this case, a respective sealing element is suitably arranged between an end side of a coolant channel and an inner wall of a corresponding connecting receptacle of a collector ring. In this case, the sealing elements are designed, for example, as sealing rings or sealing hoses. This advantageously and easily counteracts an undesired escape of coolant in the stator.

The collector rings are suitably embodied in one piece. However, a collector ring may also be made of several pieces. For example, in an alternative embodiment of the cooling apparatus, each two of the cooling channels can be connected in terms of flow technology in pairs to a collector ring on a face side by means of a deflection body. In this case, the deflection bodies have plug receptacles for forming a plug connection with the cooling channels. In order to prevent coolant leaks, a sealing element is provided here between the cooling channels and the plug receptacles. Alternatively, the cooling channels are connected to the plug receptacles of the corresponding deflection body by means of a press-fit assembly or by means of an adhesive.

On the opposite face side, a respective cooling channel of the cooling channels connected in pairs is then connected, for example by means of a hose, to an intake for the coolant from a coolant circuit of the motor vehicle and the respective other cooling channel of the cooling channels connected in pairs is connected to an outlet for the coolant to the coolant circuit. In other words, the coolant is accordingly fed to or discharged from the cooling channels only at a face side. This makes possible, in particular, an alternative embodiment for the connection of the cooling apparatus to the coolant circuit, which can better satisfy an installation space requirement of the electric machine.

The deflection bodies have a collector channel through which coolant flows during operation of the cooling apparatus and, for example, a shape such that the deflection bodies at least partly cover the corresponding face side. In addition, the hoses are arranged on the corresponding face side in a suitable manner, with the result that the end windings of the stator winding are cooled by means of the hoses or deflection bodies through which coolant flows. In this embodiment, the deflection bodies together form the collector ring there at the corresponding end side of the stator.

In a suitable embodiment, the cooling channels have a circular cross-sectional shape. In this case, the cooling channels preferably bear at least in sections in the region of their respective outer circumference against the stator teeth of the respective stator slot and/or the stator winding arranged therein. In this case, the cooling channels preferably have the lowest possible wall thickness, with the result that a particularly effective heat exchange takes place between the stator teeth and the coolant within the cooling channel.

In an advantageous development, the cooling channels are guided to a rotor side of the stator laminated core in a manner radially offset to the stator winding. The rotor side is to be understood as meaning, in particular, the surface of the stator or of the stator laminated core that faces toward a rotor in an assembled or installed situation. In other words, the cooling channels are arranged in the region of an air gap or a pole shoe of the stator laminated core. This means that the cooling channels are arranged in the case of an inner rotor radially on the inside in the stator slots of the stator laminated core, with the result that the rotor is surrounded substantially in the manner of a cage by the cooling apparatus. In the case of an outer rotor, the cooling channels are accordingly arranged radially on the outer side of the stator laminated core. As a result, the cooling channels are arranged close to the rotor in an installed or assembled situation. As a result, the rotor is cooled during electromotive operation by means of the coding apparatus of the stator by means of an air gap and/or the resulting cooler ambient air of the stator.

The cooling apparatus according to the invention is suitable and configured for a stator described above. In this case, the cooling apparatus has a number of cooling channels, which in the assembled state are each arranged so as to run axially in a stator slot. As a result, a particularly efficient cooling apparatus that is compact in terms of installation space is realized.

The electric machine according to the invention is designed, in particular, as an electromotive drive machine for an electrically driven or drivable motor vehicle, in particular an electric or hybrid vehicle. The electric machine is embodied, for example, as an asynchronous machine with a brushless electric motor having a stator and having a rotatably mounted rotor. In this case, the stator is provided with a cooling apparatus described above. As a result, a particularly suitable electric machine, which is improved with respect to the lifetime and running time thereof, is realized.

In a preferred application, the electric drive machine is part of a motor vehicle, in particular an electrically or electromotively operated or driven motor vehicle. The motor vehicle is, in particular, an electric or hybrid vehicle, wherein at least one of the vehicle axles thereof is driven by the electric drive machine.

Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.

