Electric machine, especially for the propulsion system of a motor vehicle

Abstract

An electric machine (1) comprising a stator (2) and a rotor (3) and a Peltier element (5) with at least one Peltier element (15) for cooling the machine (1). The stator (2) comprises a stator body (12) and a stator winding (22) mounted on the stator body (12). The Peltier element (15) is arranged on a radial outer surface (32) of the stator body (12) and has a cold side (25) facing the outer surface (23) of the stator body (12), which is actively cooled when current flows. An induction device (6) comprises at least one induction loop (16) connected to the Peltier element (15), by means of which the current flow required for the Peltier element (15) can be provided from at least one magnetic field (11) present during operation of the machine (1).The induction loop (16) is arranged adjacent to the winding head arrangement (62) of the stator winding (22), so that the winding head field induces a voltage in the induction loop (16) which provides the current flow.

Description

The present invention relates to an electric machine with a stator and a rotor rotatable relative to the stator and a Peltier device with at least one Peltier element for cooling the machine. Such a machine is known, for example, from DE 10 2008 057 567 A1. There, the Peltier element generates electricity by utilizing the Seebeck effect when the laminated cores heat up during machine operation. The electricity generated in this way can be used for the machine itself, for other components, or for charging a battery. To achieve the highest possible temperature gradient, the cold side of the Peltier element is connected to the cooling motor housing. In addition to energy generation, an electrical voltage can be applied to the Peltier element to prevent an emergency shutdown of the machine due to overheating, thus actively cooling one side. In this case, the Peltier element itself forms the housing. Alternatively, the Peltier element can be mounted externally on the motor housing. German patent application DE 10 2012 217 444 A1 discloses a cooling device with Peltier elements for an electrical conductor of a generator. The Peltier elements are arranged such that their cold side is thermally connected to the conductor, while their hot side dissipates heat to the generator's laminated core. Current is generated by a conductor loop that induces a voltage through the changing magnetic field of the generator, which in turn generates the current flow in the Peltier elements. A rectifier or a Graetz bridge ensures that the current flow in the Peltier elements is always in one direction to maintain the cooling effect. In contrast, the object of the present invention is to provide improved cooling for an electric machine, particularly for the drive system of a motor vehicle. Preferably, the aim is to enable the most efficient and energy-saving cooling possible. In particular, the solution should be structurally simple, space-saving, and preferably also lightweight. This problem is solved by an electric machine having the features of claim 1. Preferred embodiments of the invention are the subject of the dependent claims. Further advantages and features of the present invention will become apparent from the general description and the description of the exemplary embodiment. The electric machine according to the invention is intended in particular for the propulsion of a motor vehicle, and preferably a passenger car. For example, the motor vehicle is designed as a battery-electric passenger car or a hybrid passenger car. The electric machine comprises a stator and, in particular, a rotor rotatable relative to the stator. The electric machine includes a Peltier element with at least one Peltier element for cooling the machine. The stator comprises a stator body and at least one stator winding mounted on the stator body. The at least one Peltier element is arranged on a radial outer surface of the stator body, facing away from the rotor and / or towards a cooling device. In particular, the cold side is arranged on the outer surface. In particular, the stator body comprises at least one radial inner surface facing the rotor.The Peltier element comprises at least one cold side that can be actively cooled (due to the Peltier effect) when an electric current flows through it. The cold side faces the outside of the stator body. The electric machine comprises at least one induction device. The induction device comprises at least one induction loop, which is connected to or electrically contacted with the at least one Peltier element. The current flow required for the at least one Peltier element can be supplied (by induction) from at least one (rotating) magnetic field present during operation of the machine by means of the at least one induction loop. The stator winding comprises at least one winding head assembly, from which a winding head field emanates when the stator winding is energized. The at least one induction loop is arranged radially and / or axially adjacent to the winding head assembly.The winding head field induces a voltage in at least one induction loop, which provides the current flow. In particular, the magnetic field induces a voltage in the induction loop. A current then flows through the connection of the induction loop to the Peltier element or through a short circuit of the induction loop. This induced current, in particular, at least partially provides active cooling of the cold side. Specifically, a voltage can be induced in the induction loop by a magnetic field emanating from the stator winding and / or the rotating rotor, thus providing the current flow. The present invention offers many advantages. A significant advantage is the induction device. This allows the machine's operating magnetic field to be used to provide the electrical energy required for cooling the Peltier element. This makes the machine particularly energy-efficient and, at the same time, highly efficient in its cooling. Furthermore, complex electrical contacting or control of the Peltier element is unnecessary. Overall, the present invention saves on components, installation space, and weight, while simultaneously enabling higher continuous power output. Preferably, the at least one induction loop includes at least one rectifier unit. This enables uninterrupted or continuous cooling of the cold side. In particular, the rectifier unit comprises at least one diode and / or at least one other component suitable for rectification. Specifically, the rectifier is integrated into the induction loop with respect to the magnetic field present during machine operation, taking into account the desired polarity of the Peltier element. The polarity is specifically chosen to ensure cooling of the cold side. It is possible and advantageous for the at least one induction loop to be arranged relative to or on the stator body in such a way that a voltage can be induced in the induction loop by a magnetic field present during the intended operation of the machine, thus providing the required current flow. The magnetic field is, in particular, a rotor field and / or a stator field and / or a winding head field. In an advantageous embodiment, the at least one induction loop is at least partially integrated into the stator body and preferably into a laminated core, and is, for example, embedded. In particular, the induction loop is integrated such that a magnetic field penetrating the stator body or the laminated core can induce a voltage in the induction loop to provide the current flow. According to the invention, the stator winding comprises at least one winding head assembly. In particular, the winding head assembly comprises winding heads which project at least partially beyond the stator body at one or both axial ends of the stator. According to the invention, the at least one induction loop is arranged radially and / or axially adjacent to the at least one winding head assembly. According to the invention, a winding head field emanates from the winding head assembly when the stator winding is energized. According to the invention, the winding head field can induce a voltage in the at least one induction loop, which can provide the current flow. It is possible that the at least one induction loop is arranged (directly) on a winding head. In particular, the at least one induction loop is arranged (directly or spaced apart) on a radial outer side of the winding head assembly. In particular, the at least one induction loop is arranged within a winding head array. In particular, the induction loop then extends from the winding head assembly to the Peltier element, the cold side of which is arranged on the outer side of the stator body. In an embodiment with a plurality of induction loops, the induction loops can be at least partially integrated into the stator body and arranged at least partially adjacent to the winding head assembly. In an advantageous embodiment, the stator body comprises at least one laminated core or is designed as such. Preferably, the outer surface is provided at least partially by the laminated core. In particular, the stator winding extends at least partially through the laminated core. In particular, at least one Peltier element and / or at least one induction loop are arranged and preferably attached directly to and / or within the laminated core. It is preferred and advantageous that the Peltier element, with its cold side, is in thermally conductive contact with the outside of the stator body, preferably the laminated core. In particular, a direct thermally conductive connection is provided. The Peltier element can be thermally connected to the outside by its mounting. Additionally or alternatively, the Peltier element can also be mounted externally on the machine. For example, the Peltier element can be mounted to a (machine) housing, while its cold side is in thermally conductive contact with the outside of the stator body. In particular, a plurality of Peltier elements are arranged distributed on the outside of the stator body. Specifically, at least two, and preferably a plurality, of Peltier elements are distributed circumferentially around the outside (resulting in an annular arrangement). In the axial direction, at least one, at least two, or a plurality of Peltier elements can be arranged in a row. Preferably, at least two, at least three, or even more of the annular arrangements described above are arranged axially adjacent to one another. In particular, the Peltier elements are arranged coaxially to a longitudinal axis or to an (imaginary) axis of rotation of the machine on the outside of the stator body. In particular, the Peltier element comprises at least one hot side that heats up during operation. Preferably, the hot side faces away from the outside of the stator body. Particularly preferably, the hot side faces a cooling device that serves to dissipate waste heat from the machine. In particular, the cold side and the hot side face away from each other and are opposite each other. In particular, the hot side can be heated when current flows through the Peltier element. In particular, the hot side is (directly) thermally connected to the cooling device. In an advantageous embodiment, the cooling device is designed and configured to actively dissipate heat from the hot side of the at least one Peltier element. In particular, the heat is dissipated from the hot side by means of a cooling medium (for example, air or a liquid coolant). Specifically, the cooling device provides an airflow and / or a liquid coolant flow. In particular, the cooling device includes a guide for the cooling medium so that it can be directed along the hot side. In particular, the cooling device is designed to cool a stator housing. For example, the cooling device comprises at least one cooling fin assembly and / or a heat exchanger through which the cooling medium flows. In particular, the hot side is in direct thermal contact with the cooling fin assembly and / or the heat exchanger. In a preferred embodiment, the cooling device is at least partially provided by a stator housing. In particular, the stator housing is equipped with cooling fins and / or flow channels for a cooling medium. It is possible and advantageous for the Peltier device to include at least one connection unit for contacting the vehicle's electrical system. In particular, this allows the current flow required for the at least one Peltier element to also be supplied by the vehicle's electrical system. This enables the current flow provided by the induction device to be supplemented or even completely supplied by the vehicle's electrical system in certain operating conditions, for example, below a defined rotational speed. The applicants reserve the right to claim an electric drive system for a motor vehicle that is at least partially electrically powered, comprising at least one electric machine. In particular, the outer surface corresponds to a radially outward-facing surface of the stator body. The stator body can also be referred to as the stator yoke. In particular, the stator body comprises stator teeth between or along which the stator winding runs, at least partially. In particular, the stator body and the stator winding are at least partially housed in a stator casing. In particular, the stator casing is part of a machine casing or connected to one. In particular, the induction device is suitable and designed to provide an electrical voltage and / or an electrical current depending on the machine's rotational speed. Specifically, the induction device provides an increasing voltage and / or current as the rotational speed increases. In this way, the cooling effect is adapted to the machine's rotational speed without additional components or complex control technology. The Peltier device comprises, in particular, at least two Peltier elements and preferably a plurality of Peltier elements. In particular, each Peltier element has at least one cold side and at least one hot side. In particular, each Peltier element is associated with at least one induction loop. It is also possible that at least two or more Peltier elements can be supplied with current by at least one common induction loop. In particular, at least one Peltier element and at least one induction loop together form a separate (pre-assemblable) mounting unit. In particular, the mounting units can be arranged and preferably mounted independently of one another on the outside. In particular, the mounting units are independent of one another with respect to their power supply and / or control. The induction loop comprises, in particular, at least one conductor. In particular, the conductor is in contact with the Peltier element at its ends. In particular, the Peltier element is short-circuited via the conductor. In particular, the Peltier element has supply terminals for power supply. In particular, the supply terminals of the Peltier element are short-circuited by the induction loop. The conductor may comprise at least one coil. In particular, the induction loop extends, at least in sections, transversely to the field lines of the magnetic field. Further advantages and features of the present invention will become apparent from the exemplary embodiments, which are explained below with reference to the accompanying figures. The figures show: Fig. 1 a purely schematic representation of an electrical machine according to the invention in a cutaway side view; and Fig. 2 a purely schematic detail representation of a Peltier device of the machine. Fig. 1 shows an electric machine 1 according to the invention, which here is configured as a drive system 10 or traction motor of a battery-electric passenger car. The machine 1 comprises a stator 2 and a rotor 3 with a rotor shaft 13. The machine 1 is shown here only above a central longitudinal axis or axis of rotation. The lower part is essentially analogous to or symmetrical with the upper part. The stator 2 comprises a stator body 12, here designed as a laminated core 42, and a stator winding 22, which extends through the stator body 12 along stator teeth 72. At the axial ends of the stator 2, the stator winding 22 forms a winding head assembly 62 with several winding heads that protrude from the stator body 12. The stator body 12 and the stator winding 22 are housed here in a stator casing 52, which is shown only schematically. The stator casing 52 can, for example, be part of a housing of the machine 1 (so-called machine casing), which is not shown in detail here. To actively dissipate the waste heat generated during the operation of machine 1, a cooling device 4 is provided. The cooling device 4 includes, for example, cooling fins (not shown in detail here) formed on an outer surface of the stator housing 52. The cooling device 4 can supply the stator housing 52 with an airflow via a fan (not shown in detail here). Alternatively, the cooling device 4 can circulate a liquid cooling medium, e.g., through channels in the stator housing 52. To increase the continuous power output of machine 1 and to efficiently and energy-savingly support the cooling effect of the cooling device 4, machine 1 is equipped with a Peltier element 5 and an induction loop 6. The Peltier element 5 comprises several Peltier elements 15 arranged coaxially to the rotor shaft 13, of which only two axially arranged Peltier elements 15 are visible here. A single Peltier element 15 and the attached induction loop 16 are shown in more detail in Fig. 2. The magnetic field lines 11 of machine 1 are also sketched there. The Peltier elements 15 each have a cold side 25 and a hot side 35. The cold side 25 can be cooled by the Peltier effect when current flows and is thermally connected to a radial outer surface 32 of the stator body 12. The hot side 35 is thermally connected to the stator housing 52. The current flow required for the Peltier effect is provided by short-circuiting the Peltier element 15 via the induction loop 16. The rotating magnetic field during operation of the machine 1 induces a voltage in the induction loop 16, which, due to the short circuit, leads to a current flow. Each induction loop 16 is equipped with a rectifier unit 26 and, for example, a diode or similar component, so that the current flow is limited to one direction only. This ensures a continuous cooling effect on the outer surface 32. The induction device 6 comprises several induction loops 16, so that one induction loop 16 is available for each Peltier element 15. For example, one induction loop 16 and one Peltier element 15 are pre-assembled into assembly units. This significantly reduces manufacturing effort. The cooling effect increases with increasing rotational speed of machine 1. Depending on the operating point of machine 1, the induced voltage in the induction loop 16 increases due to the increasing rotational speed. Consequently, the current flow in the Peltier element 15 also increases with increasing rotational speed, thus increasing the cooling effect. The size, shape, and positioning of the Peltier elements 15 and the induction loops 16 are tailored to the requirements of machine 1 shown here. The induction loops 16 are integrated into the laminated core 42. The rectifier units 26 can also be integrated, as shown here. However, designs in which the rectifier units 26 are located outside the stator body 12 are also possible and advantageous. In an embodiment not shown in detail here, some or all of the Peltier elements 15 can be arranged radially above the winding head assembly 62. This allows the winding head stray field to be used to operate the Peltier device 5. In a further development shown in dashed lines in Fig. 2, the Peltier element 15 can be equipped with a connection unit 36 ​​which can be connected to the vehicle's electrical system. This allows the Peltier element 15 to be supplied with electrical energy additionally or alternatively to the induction device 6. Reference symbol list: 1 Machine 2 Stator 3 Rotor 4 Cooling unit 5 Peltier unit 6 Induction unit 10 Drive unit 11 Field line 12 Stator body 13 Rotor shaft 15 Peltier element 16 Induction loop 22 Stator winding 25 Cold side 26 Rectifier unit 32 Outer side 35 Hot side 36 Connection unit 42 Laminated core 52 Stator housing 62 Winding head assembly 72 Stator tooth

Claims

An electric machine (1), in particular for a drive system (10) of a motor vehicle, comprising a stator (2) and a rotor (3) rotatable relative to the stator (2), and a Peltier device (5) with at least one Peltier element (15) for cooling the machine (1), wherein the stator (2) has a stator body (12) and at least one stator winding (22) mounted on the stator body (12), and wherein the Peltier element (15) is arranged on a radial outer surface (32) of the stator body (12) and has at least one cold side (25) which can be actively cooled when current flows and which faces the outer surface (23) of the stator body (12), characterized by at least one induction device (6) with at least one induction loop (16) connected to the at least one Peltier element (15).wherein the current flow required for the Peltier element (15) can be provided by means of the induction loop (16) from at least one magnetic field (11) present during the operation of the machine (1), and that the stator winding (22) comprises at least one winding head arrangement (62) from which a winding head field emanates when the stator winding (22) is energized, and that the at least one induction loop (16) is arranged radially and / or axially adjacent to the winding head arrangement (62), and that the winding head field induces a voltage in the at least one induction loop (16) which provides the current flow. Electric machine (1) according to the preceding claim, wherein the induction loop (16) comprises at least one rectifier unit (26). Electric machine (1) according to one of the preceding claims, wherein the at least one induction loop (16) is at least partially integrated into the stator body (12), preferably into a laminated core (42). Electric machine (1) according to one of the preceding claims, wherein the stator body (12) comprises at least one laminated core (42) and wherein the outer surface (32) is provided at least sectionally by the laminated core (42). Electric machine (1) according to one of the preceding claims, wherein the Peltier element (15) is in thermal conductivity with its cold side (25) against the outside (32) of the stator body (12), preferably of the laminated core (42). Electric machine (1) according to one of the preceding claims, wherein the Peltier element (15) comprises at least one hot side (35) which heats up during operation of the Peltier element (15) and wherein the hot side (35) is turned away from the outside (32) of the stator body (12) and / or is turned towards a cooling device (4) for dissipating waste heat from the machine (1). Electric machine (1) according to the preceding claim, wherein heat can be actively dissipated from the hot side (35) by means of the cooling device (4). Electric machine (1) according to one of the two preceding claims, wherein the cooling device (4) is provided at least partially by a stator housing (52). Electric machine (1) according to one of the preceding claims, wherein the Peltier device (6) comprises at least one connection unit (36) for contacting an on-board power supply of a motor vehicle, so that the current flow required for the Peltier element (15) can also be provided by the on-board power supply.

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