Rotor assembly, electric machine and electric drive system

Abstract

The application relates to a rotor assembly (1) of an electric machine for a motor vehicle drive system, comprising a rotor (5), a rotor body (6) fixedly arranged on a rotor shaft (7), and a cooling circuit (8) partially penetrating the rotor (5), wherein the cooling circuit (8) is provided with a plurality of rotor cooling channels (9) distributed in the circumferential direction and extending in the axial direction of the rotor body (6) in the rotor body (6), the rotor (5) is provided with a fluid discharge port (51) in the region of the outer cylindrical surface (50) of the rotor (5), cooling liquid (11) can flow out of the rotor (5) under the action of gravity, and the fluid discharge port (51) is provided with a discharge valve (52) configured to open the fluid discharge port (51) when the rotor (5) is stationary and close the fluid discharge port (51) when the rotor (5) rotates.

Description

[0001] This invention relates to a rotor assembly for an electric motor in a motor vehicle drive system, comprising a rotor having a rotor body fixedly mounted on a rotor shaft, a cooling circuit partially passing through the rotor, wherein the cooling circuit has a plurality of circumferentially distributed rotor cooling channels extending axially along the rotor body within the rotor body. The invention also relates to an electric motor and an electric drive system.

[0002] In motor vehicles, electric motors are increasingly being used as drive systems to replace internal combustion engines that require fossil fuels. Significant efforts have been made to improve the everyday usability of electric drives and provide users with a familiar driving experience.

[0003] For a detailed introduction to electric drives, please refer to the article "Highly Integrated and Flexible Electric Drive Units for Electric Vehicles" by Erik Schneider, Frank Fickl, Bernd Cebulski, and Jens Liebold, ATZ Magazine, Volume 113, Issue 5, 2011, pp. 360-365. These drive units are also known as electric axles or electric drive systems.

[0004] In addition to pure electric drive systems, hybrid drive systems are also known. These hybrid vehicles typically combine an internal combustion engine and an electric motor, enabling pure electric operation in urban areas while ensuring sufficient range and availability for long-distance travel. Furthermore, under certain operating conditions, both the internal combustion engine and the electric motor can drive the vehicle simultaneously.

[0005] For the development of motors used in electric shafts and hybrid power modules, there is a continuous need to increase their power density, making motor cooling increasingly important. Due to the required cooling capacity, most solutions employ hydraulic fluids (such as cooling oil) to remove heat from the heated areas of the motor.

[0006] For example, for the stator of an electric motor, it is known that cooling of the motor via hydraulic fluid is achieved by using casing cooling and winding end cooling. Casing cooling transfers the generated heat from the outer surface of the rotor core to the cooling circuit, while winding end cooling directly exchanges heat between the conductors (winding ends) outside the core and the fluid.

[0007] In addition to cooling the stator, it is also known in principle to cool the rotor of the motor. During this process, a lack of sealing between the rotor cores can lead to increased drag forces in the air gap between the rotor and stator, as well as uncontrollable losses of the coolant, which is undesirable.

[0008] In addition to the liquid-cooled rotor with a hollow shaft described above, air-cooled rotors, such as those with impellers mounted axially on the rotor, are also known in the prior art. For a description of the current state of the relevant technology, see DE 10 2018 220 810 A1.

[0009] Furthermore, it is known to utilize centrifugal force to guide the cooling medium within the rotor. For example, US11146133B2 employs cooling channels with increasing pitch circle diameters, while DE102017112348A1 describes a tapered, enlarged shaft. In these cases, the delivery of the cooling medium is accomplished by the motor itself, rather than by an external oil pump.

[0010] For separately excited synchronous motors (FSMs) with liquid-cooled rotors, it is known that uneven distribution of coolant within the rotor body can lead to rotor imbalance during passive operation. For example, if the cooling channel outlet is not located at the outermost diameter, some coolant may remain in the cooling system when the rotor shaft stops rapidly. However, it is generally advisable to avoid placing the outlet at the outermost diameter, as this would generate excessive pumping action during rotor operation, causing the coolant in the rotor cooling channels to empty itself at high speeds, thus negatively impacting cooling performance.

[0011] Under certain operating conditions and drive system configurations, it may occur that the vehicle moves but the rotor is not actively energized, such as when the vehicle has a second motor mounted on another axle, or when the vehicle is coasting downhill. When the passive rotor shaft, which is fixedly connected to the vehicle axle, restarts after the vehicle has stopped and the cooling pump has been turned off, the residual oil distributed in the cooling channels may cause rotor imbalance. This imbalance can place a significant load on bearings and components at high speeds.

[0012] Therefore, the objective of this invention is to avoid or at least alleviate the problems known in the prior art and to provide a correspondingly improved rotor assembly. Furthermore, this invention also aims to achieve an optimized motor and an improved electric drive system.

[0013] The present invention achieves the above-mentioned task by a rotor assembly for an electric motor for a motor vehicle drive system. The rotor assembly includes a rotor, the rotor body is fixedly mounted on a rotor shaft, a cooling circuit partially passes through the rotor, wherein the cooling circuit has a plurality of rotor cooling channels distributed circumferentially and extending axially along the rotor body within the rotor body, the rotor has a fluid discharge port in the region of its outer cylindrical surface, through which coolant can flow out under gravity, and a discharge valve is provided in the fluid discharge port, the discharge valve being configured to open the fluid discharge port when the rotor is stationary and close the fluid discharge port when the rotor is rotating.

[0014] Therefore, in addition to the "conventional" fluid outlet, the valve is also installed on the outer diameter of the rotor and closes the fluid discharge port as the rotational speed increases. In the stationary state, the valve is opened by a spring, thereby allowing the coolant inside the rotor to be drained.

[0015] First, the various elements of the subject matter of the invention will be described in sequence according to their relevance or order of reference in the claims, followed by a description of particularly preferred embodiments of the subject matter of the invention.

[0016] The rotor is the rotating part of an electric motor. The rotor, in particular, includes the rotor shaft. The rotor shaft can be designed as a hollow structure, which reduces weight and allows for the delivery of lubricant or coolant to the rotor body.

[0017] In this invention, the rotor body refers to a rotor excluding the rotor shaft. The rotor body is particularly composed of a rotor core lamination, a permanent magnet embedded in or fixed circumferentially within the rotor core lamination slots, and an axial end cap (if any) for closing the slot openings.

[0018] Preferably, the rotor comprises multiple rotor bodies. Particularly preferred are these rotor bodies to be substantially equal in number, and especially substantially identical. Most preferred are the rotor bodies to be composed of equally divided, and especially substantially identical, rotor laminations. Therefore, the rotor body preferably comprises a rotor core bundle, which is composed of multiple layers of laminations, typically made of electrical steel, stacked together, i.e., the so-called rotor core bundle. Individual laminations can be fixed within the core bundle by bonding, welding, or bolting. The rotor core bundle may also include permanent magnets embedded in core bundle slots or fixed circumferentially within the core bundle. The rotor core bundles can be staggered relative to each other, i.e., arranged at an angle. This staggering can be linear or V-shaped to avoid or at least reduce axial forces.

[0019] The rotor can be designed as a permanent magnet excited rotor or a separately excited rotor.

[0020] A separately excited rotor, especially a component of a radial flux motor, is used to convert electrical energy into mechanical energy or vice versa. A separately excited rotor is a rotor powered by an independent power source (usually DC). Unlike a self-excited rotor (which obtains excitation from AC power on the stator side), a separately excited rotor typically requires an external DC power source.

[0021] Preferably, the separately excited rotor may have a cylindrical rotor body, preferably made of laminated iron, to reduce eddy current losses. Multiple slots or gaps may be provided on the surface of the rotor body for housing the rotor windings. These rotor windings are preferably made of insulated copper or aluminum wire and guided through the slots or gaps to ensure mechanical stability.

[0022] The rotor windings of a separately excited rotor are preferably divided into multiple coils, which are electrically connected. The coils are wound along the rotor axis and are typically multiphase windings to achieve efficient conversion of electrical energy to mechanical energy. The number of coils and their arrangement depend on the specific requirements of the machine.

[0023] An external DC power supply can be connected to the rotor windings via slip rings and carbon brushes. The carbon brushes ensure a low-friction electrical connection between the static power supply and the rotating rotor windings. The external DC power supply generates a magnetic field in the rotor, which interacts with the magnetic field of the stator-side winding system, thereby affecting the machine's torque and power.

[0024] The advantage of separately excited rotors is that the excitation of the rotor can be externally controlled. By adjusting the DC current input to the rotor, the power and torque of the motor can be precisely controlled.

[0025] The rotor body may consist of one or more rotor core claddings. A rotor core cladding refers to a stack of multiple layers of laminations, typically made of electrical steel, arranged in a single layer. Individual laminations can be fixed within the core cladding by bonding, welding, or bolting. Rotor core claddings for permanent magnet excitation rotors may also include magnetic elements embedded in or fixed circumferentially within the core cladding slots, and axial end caps (if present) for closing the slot openings.

[0026] An electric motor can be specifically designed as a rotary motor. A rotary motor can be specifically designed as a radial flux motor. A radial flux motor is characterized by magnetic field lines extending radially in the air gap between the rotor and stator. The air gap refers to the gap that exists between the rotor and stator. In a radial flux motor, this air gap is annular in cross-section, and its radial width is equal to the distance between the rotor bodies.

[0027] The electric motor is particularly suitable for hybrid or pure electric vehicle drive systems. Specifically, the motor's dimensions are designed to achieve vehicle speeds greater than 50 km / h, preferably greater than 80 km / h, and especially greater than 100 km / h. Particularly preferred is that the motor's power is greater than 50 kW, preferably greater than 80 kW, and especially greater than 150 kW. Furthermore, it is preferable that the motor can provide speeds greater than 8,000 rpm, particularly preferably greater than 12,000 rpm, and more preferably greater than 15,000 rpm.

[0028] The term "motor vehicle" as used in this application refers to a land vehicle that is driven by mechanical power and does not rely on rails. For example, a motor vehicle may be selected from passenger cars (PKW), trucks (LKW), mopeds, light motor vehicles, motorcycles, buses (KOM), or tractors, etc.

[0029] The rotor assembly may also include a control unit. The control unit, as used in this invention, is particularly used for electronic control and / or regulation of one or more technical systems of the rotor assembly and / or the motor, such as controlling / regulating the energization of the coolant pump and / or the rotor windings.

[0030] The control unit particularly includes a wired or wireless signal input terminal for receiving, in particular, electrical signals, such as sensor signals. Furthermore, the control unit preferably also includes a wired or wireless signal output terminal for transmitting, in particular, electrical signals.

[0031] Control and / or adjustment operations can be performed within the control unit. Particularly preferred is that the control unit includes hardware for executing software. Preferably, the control unit includes at least two electronic processors for executing program flows defined in their respective software. These two processors can also be integrated as cores within a processor, wherein each core is considered a processor in the context of this invention.

[0032] The control unit may also include one or more electronic memories for storing and retrieving data contained in signals transmitted to the control unit. Furthermore, the control unit may also include one or more electronic memories for variable and / or immutable storage of data.

[0033] The control unit may include multiple controllers, which are distributed particularly within the vehicle's interior space. Controllers, also known as electronic control units (ECUs) or electronic control modules (ECMs), preferably include electronic microcontrollers for performing data processing operations, and are particularly preferably implemented via software. Controllers are preferably interconnected to enable wired and / or wireless data exchange. In particular, controllers can also be interconnected via existing bus systems within the vehicle, such as CAN bus or LIN bus.

[0034] Particularly preferred is that the control unit includes at least a processor and at least one memory, the memory containing computer program code, the memory and the computer program code being configured to cooperate with the processor to enable the control unit to execute the computer program code.

[0035] The control unit may also preferably include power electronics for energizing the stator or rotor. The power electronics are preferably a combination of components for controlling or regulating the motor current, and preferably include necessary peripheral components such as cooling elements or power supplies. In particular, the power electronics or one or more components thereof are used for controlling or regulating the current. One or more power switches, such as power transistors, are particularly preferred. It is particularly preferred that the power electronics have two or more, especially three, independent phase or current paths, each with at least one independent power electronic component. The power electronics are preferably designed to control or regulate at least 10 W, preferably at least 100 W, and particularly preferably at least 1000 W of peak power per phase, and preferably continuous power.

[0036] According to another particularly preferred embodiment of the invention, the rotor can be configured to achieve separate excitation via energized rotor windings, and the rotor assembly includes a control unit for energizing the rotor windings. By enabling the rotor to achieve separate excitation via energized rotor windings, greater flexibility in machine control can be achieved. The control unit can adjust the rotor current, thereby adjusting the machine's torque, speed, or other operating parameters. This allows for more precise adaptation to different operating conditions, load requirements, or control objectives.

[0037] Preferably, a coolant pump is provided in the cooling circuit to deliver coolant through the cooling circuit. Furthermore, a control unit can be provided to control the coolant pump, thereby achieving precise control of the rotor's cooling capacity.

[0038] Advantageous embodiment of the invention: "discharge valve" According to a preferred embodiment of the invention, the discharge valve can be configured to open the fluid discharge port when the rotor speed is below 100-200 rpm. The advantage of this embodiment is that it achieves a good balance between avoiding imbalance and providing good cooling performance at low rotor speeds.

[0039] According to a further preferred improvement of the invention, the discharge valve can also be configured as a check valve loaded by a spring element. Furthermore, according to another preferred embodiment of the invention, the spring element can be configured as a disc spring, which exhibits particular advantages in terms of the required spring force and characteristic curve. Therefore, it is particularly preferred that the ball of the check valve, under centrifugal force, pushes the slotted disc spring, thereby closing the fluid discharge port when the rotational speed reaches at least 100-200 rpm.

[0040] According to another particularly preferred embodiment of the invention, the rotor may be configured to have multiple fluid discharge ports, each of which is provided with a discharge valve.

[0041] Because the rotor has multiple fluid discharge ports, coolant can be safely discharged regardless of the rotor's position, as this increases the probability that at least one fluid discharge port is located at the lowest point of the rotor when it is stationary. This simplifies rotor control and improves operational safety for effective coolant discharge. If one discharge port is blocked or restricted (e.g., due to dirt or deposits), the others can still serve as coolant outlets, further enhancing system safety. For rotors where air bubbles may exist in the cooling circuit, multiple discharge ports also facilitate system venting.

[0042] By providing multiple outlets, fluid can be distributed more evenly and efficiently across the entire rotor, thereby improving the performance and efficiency of the motor. Furthermore, coolant flowing through multiple outlets distributes pressure and mechanical load more evenly across the rotor, helping to reduce undesirable loads and vibrations inside or on the rotor's surface. In high-performance rotors or when the rotor is operating at its performance limits, heat dissipation can be critical; multiple outlets facilitate more efficient coolant flow across the rotor, achieving better cooling. With multiple fluid outlets, the coolant flow rate at each outlet can be reduced, optimizing flow patterns and reducing the likelihood of cavitation. Multiple fluid outlets also reduce localized overheating zones (so-called "hot spots") because uniform coolant flow minimizes temperature differences across the rotor.

[0043] Furthermore, the present invention can be further improved such that the rotor body has a first rotor end cover on its first front side, wherein at least one fluid discharge port, preferably multiple fluid discharge ports, and more preferably all fluid discharge ports are disposed in the end cover. By centrally arranging all fluid discharge ports in the rotor end cover, centralized management of fluid flow can be achieved, thereby simplifying and improving the efficiency of liquid guidance and control. Integrating the openings directly into the rotor end cover reduces or eliminates the need for additional accessories or piping systems, thereby simplifying the structure and reducing production and assembly costs. Centralizing the fluid openings in the rotor end cover also reduces the number of required seals and connections, thereby reducing the risk of leakage. In addition, by centrally integrating the openings in the rotor end cover, the overall rotor design can be made more compact and space-saving. The rotor end cover also has a certain degree of modular adaptability, because with the rotor end cover as the central element of the fluid openings, it is easier to implement or replace specific end cover designs for different applications or operating conditions.

[0044] The invention can be further improved by making the rotor end caps from plastic. Plastics are generally lighter than metals, so lighter rotor end caps reduce the overall mass of the rotor, thereby improving efficiency and performance and reducing the mechanical load on the entire system. Plastics are also easy to process into complex shapes, providing a high degree of flexibility in rotor end cap design. This is particularly useful for achieving specific hydrodynamic characteristics related to the coolant. Furthermore, plastics are better at damping vibrations and reducing noise than many metals, contributing to quieter operation. In addition, plastics are generally non-conductive, thus providing electrical insulation, which is particularly advantageous in cases involving separately excited rotors. In many cases, plastic rotor end caps are less expensive to manufacture than metals, both in terms of material costs and manufacturing processes. Some plastics also have low thermal conductivity, which helps provide thermal insulation or reduce heat conduction in rotor assembly applications.

[0045] In another preferred embodiment of the invention, the number of fluid discharge ports can be set to be equal to the number of rotor cooling channels. If the number of fluid discharge ports is exactly equal to the number of rotor cooling channels, a one-to-one correspondence between cooling channels and discharge ports can be achieved, bringing several technical advantages. Each rotor cooling channel can have a dedicated discharge port, allowing the coolant flowing through a specific channel to be directly and without detours discharged from the rotor. This ensures efficient and rapid heat dissipation for each cooling channel.

[0046] The invention can be further improved such that the fluid discharge port extends radially along the rotor, which is beneficial for the coolant to flow out of the rotor as completely as possible.

[0047] The present invention also achieves the above-mentioned task by an electric motor comprising a rotor assembly according to any one of claims 1-8.

[0048] Finally, the present invention can also achieve the above-mentioned task by a motor vehicle drive system comprising the motor according to claim 9.

[0049] Circular Channel Implementation According to another preferred embodiment of the invention, the rotor assembly of the motor for the motor vehicle drive system may also be configured to include a rotor, the rotor body being fixedly mounted on a rotor shaft, a cooling circuit partially passing through the rotor, wherein the cooling circuit has a plurality of rotor cooling channels distributed circumferentially and extending axially along the rotor body within the rotor body, and the rotor body is provided with a hydraulic channel extending circumferentially, the hydraulic channel connecting the rotor cooling channels to each other circumferentially.

[0050] The advantage of this is that, through the circumferentially extending hydraulic channels, coolant can be distributed within the rotor cooling channels during rotor operation, ensuring that all rotor cooling channels are either full or completely emptied, thus preventing imbalance when the rotor starts from a standstill. Particularly advantageous is the hydraulic connection of the rotor cooling channels at their maximum diameter via an annular hydraulic channel, as this allows for optimal circumferential coolant distribution.

[0051] The rotor cooling channels are hydraulically connected by hydraulic channels extending circumferentially, so that the coolant accumulated in the rotor cooling channel below the direction of gravity can be evenly distributed to other rotor cooling channels connected to the hydraulic channels at the rotational speed.

[0052] The hydraulic passage can be divided into multiple independent passages or it can be a single passage. It is particularly preferred that the hydraulic passage be designed as a single passage, so that the coolant can be guided in a very specific and precise manner inside the rotor.

[0053] According to a preferred embodiment of the present invention, the hydraulic channel can be configured as an annular channel. The advantage of this embodiment is that the annular channel structure is particularly simple, thus reducing manufacturing costs. To ensure rotor balance, it is preferable to design the annular channel as annular. Multiple annular channels can also be arranged coaxially to further improve the distribution of coolant during rotor startup.

[0054] According to a further preferred improvement of the invention, annular channels can be configured to connect the outermost rotor cooling channels to each other. Annular channels can also be configured to connect the rotor cooling channels to each other in the radially outer region, especially when these channels themselves have radial extension. This allows for particularly rapid and complete elimination of rotor imbalance during startup.

[0055] Furthermore, according to another preferred embodiment of the invention, the rotor body may be provided with a first rotor end cap on its first front side, and an annular channel may be disposed in the end cap. The advantage of this embodiment is that the annular channel is particularly easy to manufacture on the rotor end cap. In particular, the rotor end cap can also be designed as a plastic injection molded part, which makes the manufacture of the annular channel particularly simple.

[0056] According to another particularly preferred embodiment of the invention, the first rotor end cover may be provided with a plurality of radially extending fluid channels that converge into an annular channel and are hydraulically connected to the rotor cooling channel in the first rotor end cover mounting state, which helps to distribute the coolant particularly effectively when the rotor starts.

[0057] The invention can be further improved by providing a fluid outlet on the front side of the first rotor end cover, through which coolant can flow, thus realizing a rotor cooling circuit with a simple structure.

[0058] In another preferred embodiment of the invention, the rotor body may be provided with a second rotor end cap on the second front side. This end cap has a radially extending fluid channel that hydraulically connects the rotor shaft, which is designed as a hollow shaft and through which coolant can flow, to the rotor cooling channel. This also achieves a rotor cooling circuit with a simple structure. The second rotor end cap is also preferably a plastic injection molded part.

[0059] The invention can be further improved by arranging multiple rotor cooling channels on the same circle, which again helps to balance the rotor.

[0060] As mentioned above, after a prolonged period of stillness, a certain amount of coolant may remain in the rotor cooling channels below the direction of gravity. Prolonged stillness, especially at low temperatures, can cause changes in coolant viscosity, leading to a decrease in flow rate and thus slower emptying or refilling. Therefore, the coolant in the rotor cooling channels can be heated by targeted rotor coil excitation. Heating can also be performed before rotor startup or vehicle startup, such as when the vehicle is unlocked or the brake or clutch pedal is depressed. Therefore, in addition to the coolant pump's delivery status, the control unit can also heat the rotor body before the second start signal appears and / or when the rotor accelerates from a standstill.

[0061] In another preferred embodiment of the invention, the rotor shaft may be rotatably supported by at least one rolling bearing, through which the cooling circuit passes. This allows for better lubrication and cooling of the rolling bearing, thereby further improving the efficiency of the rotor assembly.

[0062] Check valve implementation method In another preferred embodiment, the rotor assembly of the motor for a motor vehicle drive system includes a rotor body fixedly mounted on a rotor shaft, a cooling circuit partially passing through the rotor, wherein the cooling circuit has a plurality of circumferentially distributed rotor cooling channels extending axially along the rotor body within the rotor body, the rotor having at least one fluid outlet through which the cooling circuit passes, such that coolant leaves the rotor after flowing through the rotor cooling channels, and a valve is provided within the fluid outlet, the valve being configured to close the fluid outlet when the rotor speed is below a predetermined value and open the fluid outlet when the speed is above the predetermined value.

[0063] Therefore, the valve at the rotor outlet prevents coolant from flowing out when the rotor is stationary. This ensures that the rotor cooling channels are always evenly filled with coolant, preventing imbalances caused by uneven coolant distribution within the rotor during startup. This plays a crucial role in reducing bearing load during rotor acceleration, extending rotor assembly life, and improving reliability.

[0064] According to a preferred embodiment of the present invention, the valve can be configured to close the fluid outlet when the rotor speed is below 100-200 rpm.

[0065] The advantage of this implementation is that it achieves a good balance between avoiding imbalance and providing good cooling performance at low rotor speeds.

[0066] According to a further preferred improvement of the invention, the valve can also be configured as a spring-loaded check valve. The spring force of the check valve is preferably designed to close the check valve when the rotor speed is below 100-200 rpm. When the speed is above 100-200 rpm, the check valve can be opened by the pressure under centrifugal force and / or the additional pump pressure of the coolant pump.

[0067] Furthermore, according to another preferred embodiment of the invention, the cooling circuit may include a coolant pump that delivers coolant through the cooling circuit, and the valves and coolant pump are configured to open the valves by the hydraulic pressure established in the cooling circuit by the coolant pump. Therefore, for example, to cool electronic components or to heat the coolant to operating temperature (pre-conditioning), the check valve can be opened by the coolant pump even when the rotor is stationary. The valve at the rotor outlet prevents coolant from flowing out when the rotor is stationary and the coolant pump is off. Thus, the rotor cooling channels of the rotor body are always uniformly filled.

[0068] According to another particularly preferred embodiment of the invention, the rotor can be configured to have multiple fluid outlets, each equipped with a valve. This achieves better cooling, reduces pressure loss in the cooling circuit, and ensures uniform flow of coolant from the rotor.

[0069] Furthermore, the invention can be further improved such that the rotor body has a first rotor end cover on its first front side, wherein at least one fluid outlet, preferably multiple fluid outlets, and more preferably all fluid outlets are disposed in the end cover. The advantage of this embodiment is that the fluid outlets are particularly easy to manufacture on the rotor end cover. In particular, the rotor end cover can also be designed as a plastic injection molded part, which makes the manufacture of the fluid outlets particularly simple. Here, the fluid outlets preferably extend axially along the rotor end cover.

[0070] In another preferred embodiment of the invention, the number of fluid outlets can be set to be equal to the number of rotor cooling channels, which is particularly advantageous in reducing cooling circuit pressure loss and improving cooling performance.

[0071] The invention can be further improved by having multiple fluid outlets, preferably all fluid outlets, arranged on the same circle, which also helps the coolant to flow out of the rotor evenly.

[0072] Preferably, the fluid outlet or multiple fluid outlets are arranged in the radially inner region of the rotor, which can reduce the unexpected pumping effect of the fluid outlets during rotor operation.

[0073] Orifice Implementation According to another embodiment of the present invention, the rotor assembly of the motor for a motor vehicle drive system may be configured to include a rotor, the rotor body being fixedly mounted on a rotor shaft, a cooling circuit partially passing through the rotor, wherein the cooling circuit has a plurality of rotor cooling channels distributed circumferentially and extending axially along the rotor body within the rotor body, the rotor having a fluid outlet having a first flow cross-section, through which the cooling circuit passes, such that coolant leaves the rotor through the fluid outlet after flowing through the rotor cooling channels, and the rotor also having a fluid discharge port having a second flow cross-section, the fluid discharge port being arranged radially outward of the fluid outlet, and the first flow cross-section being larger than the second flow cross-section.

[0074] In addition to the cooling circuit outlet, which is "conventionally" located at the smaller inner diameter, a smaller fluid outlet is also provided at the outermost diameter of the rotor, functioning similarly to a hydraulic throttle orifice. Through this outlet, the rotor cooling channels can be slowly emptied when the rotor is stationary. The pumping effect generated during normal rotor operation is limited by the ratio of the cross-sectional area of ​​the fluid outlet to the fluid outlet.

[0075] By draining coolant when the rotor is stationary, the risk of imbalance caused by hydraulic pressure during rotor startup and rotation can be significantly reduced. Incorporating openings in the rotor also provides a safe and cost-effective way to effectively reduce this imbalance.

[0076] Preferably, the fluid discharge port can be controlled so that it is located at the lowest point of the ground when the rotor is stationary, which is conducive to the safe and complete drainage of the rotor coolant.

[0077] According to a preferred embodiment of the invention, the first flow cross-section can be set to be 5-50 times the size of the second flow cross-section. This can particularly effectively reduce the pumping effect at high rotor speeds, while ensuring the coolant flow rate through the fluid outlet and the rotor's cooling performance. At the same time, the cross-sectional area of ​​the discharge port remains large enough to allow coolant to flow out when the rotor is stationary.

[0078] The dimensions of the outlet should be at least 0.1mm / 0.01mm. 2 This is to ensure a sufficiently fast evacuation rate, but it should not exceed 0.6mm / 0.28mm. 2 This is to prevent excessive bypass flow and pumping effect through the throttling orifice.

[0079] According to a further preferred improvement of the invention, the fluid outlet may extend axially along the rotor axis and / or the fluid discharge port may extend axially along the rotor axis. Axial extension reduces pressure loss in the cooling circuit section within the rotor, allowing the coolant pump to be designed more compactly and energy-efficiently. Furthermore, axial extension of the fluid discharge channel also facilitates good coolant discharge while further reducing the pumping effect during rotor operation. If both the fluid outlet and discharge port are axially oriented, rotor manufacturing can be simplified, for example, by co-directional drilling or injection molding.

[0080] Furthermore, according to another preferred embodiment of the invention, the rotor can be configured to have multiple fluid outlets and / or multiple fluid discharge ports. This can improve both the rotor's balance and its cooling performance.

[0081] By providing multiple outlets, fluid can be distributed more evenly and efficiently across the entire rotor, thereby improving the performance and efficiency of the motor. Furthermore, coolant flowing through multiple outlets distributes pressure and mechanical load more evenly across the rotor, helping to reduce undesirable loads and vibrations inside or on the rotor's surface. In high-performance rotors or when the rotor is operating at its performance limits, heat dissipation can be critical; multiple outlets facilitate more efficient coolant flow across the rotor, achieving better cooling. With multiple fluid outlets, the coolant flow rate at each outlet can be reduced, optimizing flow patterns and reducing the likelihood of cavitation. Multiple fluid outlets also reduce localized overheating zones (so-called "hot spots") because uniform coolant flow minimizes temperature differences across the rotor.

[0082] Because the rotor has multiple fluid discharge ports, coolant can be safely discharged regardless of the rotor's position, as this increases the probability that at least one fluid discharge port is located at the lowest point of the rotor when it is stationary. This simplifies rotor control and improves operational safety for effective coolant discharge. If one discharge port is blocked or restricted (e.g., due to dirt or deposits), the others can still serve as coolant outlets, further enhancing system safety. For rotors where air bubbles may exist in the cooling circuit, multiple discharge ports also facilitate system venting.

[0083] According to another particularly preferred embodiment of the invention, the number of fluid outlets can be set to be equal to the number of rotor cooling channels and / or the number of fluid discharge ports can be equal to the number of rotor cooling channels. If the number of fluid outlets and / or fluid discharge ports is exactly equal to the number of rotor cooling channels, a one-to-one correspondence between cooling channels and outlets can be achieved, bringing several technical advantages. Each rotor cooling channel can have a dedicated outlet or discharge port, allowing the coolant flowing through a specific channel to be directly and without detours discharged from the rotor. This ensures efficient and rapid heat dissipation for each cooling channel. Since each cooling channel has its own outlet, the temperature distribution throughout the rotor is more uniform, contributing to improved rotor thermal efficiency and structural integrity. Each rotor cooling channel has an independent outlet, which also optimizes the flow rate of the coolant within each channel, avoiding efficiency problems or cavitation caused by excessively fast or slow flow rates.

[0084] The invention can be further improved by arranging multiple fluid outlets, preferably all fluid outlets, on the same first circle, and multiple fluid discharge ports, preferably all fluid discharge ports, on the same second circle, with the diameter of the first circle being smaller than the diameter of the second circle. This configuration is particularly helpful in improving the rotor's balance performance. In this context, it is especially preferred that the diameter of the second circle is slightly smaller than the rotor body diameter, so that the fluid discharge ports are located at the lowest point when the rotor is stationary, which facilitates the complete drainage of the rotor coolant. Preferably, the first and second circles are coaxially arranged, which also contributes to the rotor's balance.

[0085] In another preferred embodiment of the invention, the rotor body may also be provided with a first rotor end cap on its first front side, wherein at least one fluid outlet, preferably multiple fluid outlets, more preferably all fluid outlets are disposed in the end cap, and / or at least one fluid discharge port, preferably multiple fluid discharge ports, more preferably all fluid discharge ports are disposed in the end cap. By centrally distributing all fluid outlets and / or discharge ports in the rotor end cap, centralized management of fluid flow can be achieved, thereby simplifying and improving the efficiency of liquid guidance and control. Integrating the openings directly into the rotor end cap reduces or eliminates the need for additional accessories or piping systems, thereby simplifying the structure and reducing production and assembly costs. Centralizing the fluid openings in the rotor end cap also reduces the number of required seals and connections, thereby reducing the risk of leakage. Furthermore, by centrally integrating the openings in the rotor end cap, the overall rotor design can be made more compact and space-saving. The rotor end cap also has a certain degree of modular adaptability, because with the rotor end cap as the central element of the fluid openings, it is easier to implement or replace specific end cap designs for different applications or operating conditions.

[0086] The invention can be further improved by making the rotor end caps from plastic. Plastics are generally lighter than metals, so lighter rotor end caps reduce the overall mass of the rotor, thereby improving efficiency and performance and reducing the mechanical load on the entire system. Plastics are also easy to process into complex shapes, providing a high degree of flexibility in rotor end cap design. This is particularly useful for achieving specific hydrodynamic characteristics related to the coolant. Furthermore, plastics are better at damping vibrations and reducing noise than many metals, contributing to quieter operation. In addition, plastics are generally non-conductive, thus providing electrical insulation, which is particularly advantageous in cases involving separately excited rotors. In many cases, plastic rotor end caps are less expensive to manufacture than metals, both in terms of material costs and manufacturing processes. Some plastics also have low thermal conductivity, which helps provide thermal insulation or reduce heat conduction in rotor assembly applications.

[0087] The invention will be further described below with reference to the accompanying drawings, but this is not intended to limit the overall concept of the invention. Attached image description: Figure 1 A schematic diagram of a motor vehicle equipped with an electric drive system; Figure 2 A schematic diagram of an electric motor; Figure 3 A schematic diagram of an axial cross-section of a rotor assembly; Figure 4 A perspective view of a rotor end cover; Figure 5 A schematic diagram of an axial cross-section of a rotor assembly; Figure 6 A schematic diagram of an axial cross-section of a rotor assembly; Figure 7 A schematic diagram of an axial cross-section of a rotor assembly.

[0089] Figure 2 A rotor assembly 1 for an electric motor 2, which is part of the drive system 3 of a motor vehicle 4, is shown. Figure 1 As shown. In Figure 1 In the embodiment shown, the motor 2 is coupled with the gear assembly 26 to form a structural unit, which can also be called a shaft drive system.

[0090] like Figure 2-3 As shown, rotor assembly 1 includes a rotor 5, the rotor body 6 of which is fixedly mounted on rotor shaft 7. The cooling circuit 8 partially passes through the rotor 5, and the cooling circuit 8 has multiple circumferentially distributed rotor cooling channels 9 within the rotor body 6 and extending axially along the rotor body 6. Furthermore, in the illustrated embodiment, the rotor assembly 1 also includes a coolant pump 10 disposed in the cooling circuit 8, which delivers coolant 11 through the cooling circuit 8, and includes a control unit 12 for controlling the coolant pump 10. In the illustrated embodiment, the motor 2 is a radial flux motor with a hollow cylindrical stator 23 in which the rotor 5 is rotatably mounted.

[0091] like Figure 3 As shown, the hollow cylindrical rotor shaft 7 has multiple openings on its cylindrical surface, through which coolant 11 flows radially into the annular fluid channel 38 of the rotor 5. This fluid channel 38 is connected to the rotor cooling channel 9. On the opposite axial side, the coolant 11 is discharged from the rotor 5 through the radially inner outlet 35 and can be further transported to… Figure 3 The rolling bearing 20 shown.

[0092] In this design, when the rotor 5 is stationary, a portion of coolant 11 remains in the rotor cooling channel 9 located below the direction of gravity. During prolonged periods of stillness and at low temperatures, the viscosity of the coolant 11 may change, leading to a decrease in flow rate and slower drainage. Therefore, the coolant 11 within the rotor cooling channel 9 can be heated by targeted rotor coil excitation. This heating process can also be performed before the rotor starts or the vehicle starts, for example, when the vehicle is unlocked or the accelerator, brake, or clutch pedals are pressed.

[0093] The rotor 1 is separately excited via an energized rotor winding 19. The rotor assembly 1 includes a control unit with a rotor power supply 24 for energizing the rotor winding 19. This power supply can be electrically connected to the rotor shaft 7 or the rotor winding 19 via a slip ring 25. The rotor power supply 24 is connected to the control unit 12. Before the second start signal 13 occurs and / or when the rotor 5 accelerates from rest, the rotor body 6 can be heated by the energized rotor winding 19. The rotor shaft 7 is rotatably supported by at least one rolling bearing 20, through which the cooling circuit 8 passes.

[0094] The control unit 12 for controlling the rotor assembly 1 includes a processor 21 and a memory 22 containing computer program code. The memory and computer program code are configured to cooperate with the processor 21 to enable the control unit 12 to perform the methods described further below. The control unit 12 may have multiple signal inputs 13, 15, 17 through which the operation of the rotor assembly 1 is controlled or regulated.

[0095] Figure 3-4 Circular channel The rotor body 6 also includes a circumferentially extending hydraulic channel 30 that connects the rotor cooling channels 9 circumferentially to each other. This connection can also be achieved through... Figure 3-4 This was observed through comparative study.

[0096] The hydraulic channel 30 is designed as an annular channel 31, connecting the outermost rotor cooling channels 9 to each other. The rotor body 6 has a first rotor end cap 33 on its first front side 32, within which the annular channel 31 is located. Figure 4 As shown, the first rotor end cover 33 is provided with a plurality of radially extending fluid channels 40, which converge into the annular channel 31 and are hydraulically connected to the rotor cooling channel 9 when the first rotor end cover 33 is installed.

[0097] A fluid outlet 35 is provided on the front side 32 of the first rotor end cover 33, through which coolant 11 can flow. The rotor body 6 is also provided on the second front side 36 with a second rotor end cover 37, which has a radially extending fluid channel 38, and hydraulically connects the rotor shaft 7, which is designed as a hollow shaft 39 through which coolant 11 can flow, to the rotor cooling channel 9.

[0098] Figure 5 Check valve Figure 5 Another embodiment of the rotor assembly 1 is shown, wherein the rotor 5 has at least one fluid outlet 35 through which the cooling circuit 8 passes, allowing the coolant 11 to exit the rotor 5 through the fluid outlet 35 after flowing through the rotor cooling channel 9. A valve 41 is provided within the fluid outlet 35, which is configured to close the fluid outlet 35 when the rotor 5 rotates below a predetermined value and to open the fluid outlet 35 when the rotational speed is above the predetermined value.

[0099] Valve 41 is configured to close fluid outlet 35 when the rotor 5 rotates at speeds below 100-200 rpm. For example... Figure 5 As shown, valve 41 is a spring-loaded check valve.

[0100] like Figure 5 As shown, the cooling circuit 8 includes a coolant pump 10, which delivers coolant 11 through the cooling circuit 8. Valve 41 and the coolant pump 10 are configured to open valve 41 by the hydraulic pressure established in the cooling circuit 8 by the coolant pump 10. The rotor 5 has multiple fluid outlets 35, each containing a valve 41.

[0101] In addition, such as Figure 5 As shown, the rotor body 6 has a first rotor end cover 33 on its first front side 32, and all fluid outlets 35 are disposed in this end cover. In the illustrated embodiment, the number of fluid outlets 35 is equal to the number of rotor cooling channels 9. The fluid outlets 35 are also arranged on the same circle.

[0102] Figure 6 Discharge valve Figure 6 In the illustrated embodiment, the rotor 5 has a fluid outlet 51 on its outer cylindrical surface 50, through which coolant 11 can flow out under gravity. The fluid outlet 51 extends radially along the rotor 5.

[0103] A discharge valve 52 is provided within the fluid discharge port 51. This valve is configured to open the fluid discharge port 51 when the rotor 5 is stationary and close the fluid discharge port 51 when the rotor 5 is rotating. The discharge valve 52 is also configured to open the fluid discharge port 51 when the rotor 5 rotates at a speed below 100-200 rpm. In the illustrated embodiment, the discharge valve 52 is a check valve loaded by a spring element 53, wherein the spring element 53 is a disc spring.

[0104] The rotor 5 is provided with multiple fluid discharge ports 51, and each discharge port is provided with a discharge valve 52.

[0105] like Figure 6 As shown, the rotor body 6 has a first rotor end cover 33 on its first front side 32, and a fluid discharge port 51 is disposed in the end cover. The number of fluid discharge ports 51 is equal to the number of rotor cooling channels 9.

[0106] Figure 7 throttle orifice Figure 7 Another embodiment of the rotor assembly 1 is shown, wherein the rotor 5 is provided with a fluid outlet 35 having a first flow cross-section 60, through which the cooling circuit 8 passes, such that the coolant 11 exits the rotor 5 through the fluid outlet 35 after flowing through the rotor cooling channel 9. The rotor 5 is also provided with a fluid discharge port 61 having a second flow cross-section 62, the fluid discharge port 61 being arranged radially outward of the fluid outlet 35, and the first flow cross-section 60 being larger than the second flow cross-section 62.

[0107] Fluid outlet 35 and fluid discharge port 61 extend axially along rotor 5, and rotor 5 is provided with multiple fluid outlets 35 and multiple fluid discharge ports 61.

[0108] In the illustrated embodiment, the number of fluid outlets 35 is equal to the number of rotor cooling channels 9, and the number of fluid discharge outlets 61 is also equal to the number of rotor cooling channels 9.

[0109] All fluid outlets 35 are arranged on the same first circle, and all fluid discharge ports 61 are arranged on the same second circle, with the diameter of the first circle being smaller than the diameter of the second circle.

[0110] The rotor body 6 has a first rotor end cap 33 made of plastic on the first front side 32, and all fluid outlets 35 and fluid discharge ports 61 are located in the end cap.

[0111] It should be understood that Figure 2-7 The features of the illustrated embodiments can be combined arbitrarily, even if not explicitly shown in the embodiments.

[0112] This invention is not limited to the embodiments shown in the figures. The above description should not be considered restrictive but rather illustrative. The following patent claims should be understood as indicating that the described features are present in at least one embodiment of the invention. This does not exclude the presence of other features. If the patent claims and the above description define "first" and "second" features, such designations are used only to distinguish two identical features and do not indicate any order of priority. Explanation of reference numerals in the attached figures 1 Rotor assembly 2 machines 3. Drive System 4 Motor vehicles 5 rotors 6. Rotor body 7. Rotor shaft 8 Cooling Circuit 9 Rotor cooling channels 10 Coolant Pump 11 Coolant 12 Control Units 13 Start signal 15 Stop signal 17 Stop signal 19 Rotor windings 20 Rolling bearings 21 processors 22 Memory 23 Stator 24 Rotor power supply 25 slip ring 26 Gear Assembly 30 Hydraulic channels 31. Circular Channel 32 Anterior side 33 Rotor end cover 35 Fluid outlet 36 Front 37 Rotor end cover 38 Fluid Channels 39 Hollow Shaft 40 Fluid Channels 41 Valves 50 Cylindrical surface 51 Fluid discharge port 52 Discharge Valve 53 Spring elements 60 Flow cross section 61 Fluid discharge port 62 Flow cross section

Claims

1. A rotor assembly (1) for a motor (2) in a drive system (3) of a motor vehicle (4), comprising: • A rotor (5) with a rotor body (6) mounted on a rotor shaft (7) in a rotationally fixed manner. • A cooling circuit (8) that partially passes through the rotor (5), wherein the cooling circuit (8) has multiple rotor cooling channels (9) distributed circumferentially and extending axially through the rotor body (6) within the rotor body (6). Its features are, The rotor (5) has a fluid discharge port (51) in the area of ​​its outer peripheral surface (50), and the coolant (11) can flow out from the rotor (5) under the action of gravity. A discharge valve (52) is provided in the fluid discharge port (51) and is configured to release the fluid discharge port (51) when the rotor (5) is stationary and close the fluid discharge port (51) when the rotor (5) is rotating.

2. The rotor assembly (1) according to claim 1, characterized in that, The discharge valve (52) is configured to open the fluid discharge port (51) when the rotational speed of the rotor (5) is lower than a value selected as 100-200 rpm.

3. The rotor assembly (1) according to claim 1 or 2, characterized in that, The discharge valve (52) is designed as a one-way valve loaded by a spring element (53).

4. The rotor assembly (1) according to claim 3, characterized in that, The spring element (53) is a disc spring.

5. The rotor assembly (1) according to any of the preceding claims, characterized in that, The rotor (5) has multiple fluid discharge ports (51), and each fluid discharge port (51) is provided with a discharge valve (52).

6. The rotor assembly (1) according to any of the preceding claims, characterized in that, The rotor body (6) has a first rotor cover (33) on the first front side (32), wherein at least one fluid discharge port (51), preferably multiple fluid discharge ports (51), and more preferably all fluid discharge ports (51) are formed in the rotor cover (33).

7. The rotor assembly (1) according to any of the preceding claims, characterized in that, The number of fluid discharge ports (51) is equal to the number of rotor cooling channels (9).

8. The rotor assembly (1) according to any of the preceding claims, characterized in that, The fluid discharge port (51) extends radially through the rotor (5).

9. An electric motor (2) comprising a rotor assembly (1) according to any of the preceding claims.

10. A drive system (3) for a motor vehicle (4) comprising a motor (2) according to claim 9.

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