Integrated regenerative drive system with kinematically synchronized axial flux motor-generator unit

Abstract

Integrated regenerative drive system for an electric vehicle, including: a) a planetary gear set with a fixed gear ratio of at least 5:1, wherein a carrier of the gear set is operationally coupled to a vehicle axle; b) an axial flux motor-generator unit (MGU), comprising: i) a stationary stator; ii) a first rotor arranged on one side of the stator; iii) a second rotor located on the opposite side of the stator; iv) a kinematic synchronization system driven by a central drive shaft and configured to induce synchronized rotation in the same direction in the first and second rotors, resulting in a counter-rotation of the first and second rotors relative to the stator; c) wherein a sun gear output of the planetary gear set is operationally coupled to the central drive shaft of the axial flux MGU; d) wherein the MGU has a rated power between 2.2 and 4.5 times the continuous rated power of a primary drive motor of the vehicle; characterized in that the combination of the planetary gear and the rated power of the MGU is configured to generate a regenerative charging current during a positive torque output of the drive motor and thereby generate a reactive braking torque on the axle of less than 5 Nm at vehicle speeds of 20 km / h.

Description

1. Title:

[0001] Integrated regenerative drive system with kinematically synchronized axial flux motor-generator unit 2. Priority claim:

[0002] This application claims the priority advantage of the applications with file numbers 20 2025 002 595.3, 20 2025 002 598.8, 20 2025 002 596.1 and 20 2025 002 599.6. 3. Technical field:

[0003] The invention relates to the field of powertrains and energy management systems for electric vehicles. More specifically, it relates to a regenerative drive system comprising a specialized axial flux motor-generator unit (MGU) with kinematically synchronized, counter-rotating rotors, configured for continuous energy generation with minimal mechanical resistance. The system is particularly suitable for use in urban driving cycles to significantly increase the operating range. 4. State of the art:

[0004] Conventional regenerative braking systems, such as those exemplified in the prior art, e.g., DE102017005A1, utilize motor-generators directly coupled to the vehicle's drivetrain. A significant disadvantage is the generation of a substantial electromagnetic braking torque (back EMF) at low vehicle speeds, which acts as a parasitic load, hinders vehicle coasting, and reduces overall efficiency.

[0005] Furthermore, attempts to improve efficiency with dual-rotor machines are hampered by complexity, as multiple independent motors or complex electronic control systems are required to synchronize the rotors, increasing costs, weight, and potential sources of error.

[0006] There is a significant unmet need for a fully integrated system that combines highly efficient recuperation with a robust, purely mechanical solution for managing MGU counter-torque and rotor synchronization. 5. Summary of the invention:

[0007] The present invention offers a solution to the aforementioned problems by disclosing an integrated regenerative drive system.

[0008] The system is characterized by a regenerative drive system according to patent 20 2025 002 595.3, wherein the motor-generator unit (MGU) is specifically an electric axial flux machine according to patent 20 2025 002 598.8. The axial flux MGU comprises a stationary stator arranged between a first and a second rotor and driven by a kinematic synchronization system from a single central drive shaft.

[0009] The system is further characterized by the fact that the central drive shaft of the axial-flux MGU is operationally coupled to the sun gear output of a planetary gear set, which in turn is driven by the differential crown gear of the vehicle. The combination of the planetary gear set (with a gear ratio of at least 5:1), the oversized rated power of the MGU, and the intrinsic counter-rotation of the axial-flux MGU leads to a drastic reduction in the current density required for power generation. This minimizes the back EMF, resulting in a reactive torque on the drivetrain that is low enough for continuous operation during propulsion.

[0010] An electromagnetic clutch and flywheel are integrated on the central drive shaft of the MGU to eliminate any remaining resistance during sailing, braking and stopping.

[0011] Optionally, a photovoltaic system and associated circuits according to patent 20 2025 002 596.1 can be integrated to directly supply power to the MGU terminals and thus actively compensate for the remaining electromagnetic resistance.

[0012] A radial flow version of the MGU according to patent 20 2025 002 599.6 is also disclosed as a complementary configuration for the system. The invention protects the synergistic integration of the physical components and the configuration of the overall system to achieve the technical advantages.

[0013] The present combined application has the specific objective of expressly claiming the synergistic integration of the regenerative drive system with the dual-rotor MGU as a physical apparatus. Specifically, the invention disclosed and claimed herein is designed to protect all combinations of the physical components.

[0014] This comprehensive approach ensures protection for the integrated system as a whole, offering benefits that cannot be achieved by the individual components alone. 6. Brief description of the drawings: Fig. 1: Isometric exploded view of the integrated system assembly. Fig. 2: Sectional view of the axial flow MGU with flow paths. Arrows: Direction of magnetic flux, indicating "flux tunneling," where the flux forms paths of low magnetic resistance between the opposite poles of the two rotors, passing through the stator. This configuration is the source of the cogging torque reduction and power increase. Effective counter-rotation: Although both rotors physically rotate in the same direction (COUNTER-CLOCKWISE), the 180° mounting means that, viewed from the fixed reference frame of the stator, they appear to rotate in opposite directions (counter-rotation). Fig. 3: Diagram of the power flow and the kinematic train. Solid arrow lines: Path of kinetic energy (mechanical power) from the vehicle axle to the rotors of the MGU. Dashed arrow line: Path of generated electrical energy from the stator to the battery. COUNTERCLOCKWISE: Indicates that both rotor L [134L] and rotor R Fig.4: Schematic block diagram of the optional photovoltaic integration circuit. Function: The solar-generated current supplied to the MGU terminals compensates for the current required for the MGU's own excitation (to generate its magnetic field). This reduces the net current draw from the battery, which directly reduces the back EMF and thus the reactive braking torque (resistance) on the vehicle axle. 7. Detailed description of the invention: 7.1 Core Components number component Description 100 Vehicle drive shaft Entry from the wheels of the vehicle. 102 Differential assembly Standard vehicle differential. 104 Differential crown gear Output element of the differential

[102] . 106 bevel gear Engages with the differential crown gear

[104] . 108 planetary gear carrier Input element of the planetary gear, driven by the bevel gear

[106] . 110 planetary gears They are in engagement with both the ring gear

[112] and the sun gear

[114] . 112 ring gear Fixed component of the planetary gear system. 114 sun wheel Output element of the planetary gear. 116 MGU central drive shaft Drive shaft for the axial flux MGU, driven by the sun wheel

[114] . 118 Electromagnetic coupling Configurable to disengage the MGU assembly from the drive shaft. 120 flywheel Storage element for kinetic energy, rotationally fixed to the MGU central drive shaft

[116] . 122 central wheel Large diameter gear mounted on the MGU central drive shaft

[116] . 124L, 124R gears Mounted on the intermediate shafts [126L, 126R]. 126L, 126R Parallel intermediate waves They are driven by the central wheel

[122] . 128L, 128R shaft-mounted bevel gears Engage with the rotor-mounted bevel gears [130L, 130R]. 130L, 130R rotor-mounted bevel gears Engage the shaft-mounted bevel gears [128L, 128R]. 132L, 132R Rotor shafts They are driven directly by the rotor-mounted bevel gears [130L,130R]. 134L First rotor Disc-shaped rotor with permanent magnets. 134 R Second rotor Disc-shaped rotor with permanent magnets, mounted in a 180° orientation relative to the first rotor [134L]. 136 stator Stationary disc-shaped core with windings, arranged between the first and second rotors. 138 MGU housing It carries the components of the axial flux MGU. 140 battery The vehicle's main energy storage system. 142 Upgrade switch DC-DC converter to raise the output voltage of the MGU to the voltage level of the battery

[140] . 144 control unit Electronically controls the state of the electromagnetic coupling

[118] . 146 PV system Optional roof-mounted photovoltaic module assembly. 148 MPPT controller Optional Maximum Power Point Tracking controller for the PV system

[146] . 150 PV boost converter Optional DC-DC converter to boost the PV system voltage to the MGU terminal voltage. 152 diode Optional unidirectional current device to prevent backflow. 7.2 Functionality & Integration:

[0015] The functionality of the integrated system results from the interaction of its physical components: The optional PV system

[146] generates electricity, which is optimized by the MPPT

[148] and boosted to MGU voltage by the converter

[150] . The diode

[152] ensures that this current is fed directly into the MGU terminals, compensating for its excitation current requirement and further reducing the reactive braking torque on the axis. The system configuration enables the operating states described below. 1. Power transmission & speed multiplication:

[0016] Vehicle motion drives the axle

[100] and the differential

[102] . The crown gear

[104] of the differential drives the bevel gear

[106] , which is attached to the carrier

[108] of the planetary gear set. The planet gears

[110] rotate within the stationary ring gear

[112] and drive the sun gear

[114] at a multiplied speed (e.g., 5:1 ratio). The sun gear

[114] directly drives the central drive shaft

[116] of the axial flux MGU. 2. Kinematic synchronization & counter-rotation:

[0017] Rotation of the MGU central drive shaft

[116] rotates the central gear

[122] . This central gear

[122] drives the gears [124L, 124R] on the parallel intermediate shafts [126L, 126R]. The rotation of these shafts is deflected by a 90° angle by the bevel gear sets [128L, 128R] and [130L, 130R] to drive the rotor shafts [132L, 132R]. Due to the 180° mounting of the rotors [134L, 134R], their identical physical rotation results in an effective counter-rotation relative to the stationary stator

[136] . This doubles the relative magnetic field velocity and increases the generation efficiency. 3. Continuous low-resistance recuperation:

[0018] The oversizing of the MGU, combined with the high operating speed of the gearbox and the efficient design of the axial flux machine, ensures that the current requirement for a given power output is minimized. This configuration results in a very low back EMF and thus a negligible reactive braking torque at the axis

[100] during drive and constant speed operation, which enables continuous energy recovery. 4. Zero resistance operation:

[0019] The system is further configured such that, upon detection of a sailing or braking condition, the control unit

[144] issues the command to disengage the clutch

[118] . This isolates the entire MGU / flywheel

[120] assembly from the drivetrain and eliminates all mechanical resistance. The kinetic energy stored in the flywheel

[120] feeds the MGU for further power generation. 7.3 Technical advantages:

[0020] Synergy efficiency: The combination of the 5:1 gearbox, the MGU oversizing and the counter-rotating design of the axial flux machine results in a highly efficient recuperation system with minimal parasitic losses.

[0021] Mechanical robustness: The kinematic synchronization of the MGU rotors is achieved passively with gears, eliminating the need for complex, failure-prone electronic synchronization.

[0022] Maximized urban range: The system configuration enables continuous "rolling recuperation" in urban traffic, significantly extending the operating range. Flexible implementation: The disclosure includes the primary axial-flow design and confirms the radial-flow design (Patent 4) as an alternative, thus strengthening the scope of protection of the patent.

[0023] Comprehensive system protection: The invention claims the physical device in its various combinations and configurations. This protection of the apparatus covers its ability to achieve the novel operating states of continuous energy harvesting and zero-resistance operation, thus securing all commercially valuable combinations of the invention. Key to Fig. 1:

[100] Vehicle axle: Primary input from the wheels of the vehicle.

[102] Differential assembly: Standard vehicle differential.

[104] Crown gear: Output element of the differential.

[106] Bevel gear: Transmits the torque from the crown gear to the planetary gear.

[108] Planet carrier: Input element of the planetary gear.

[110] Planet gears: Engage with the ring gear

[112] and the sun gear

[114] .

[114] Sun gear: Output element of the planetary gear, drives the MGU.

[116] MGU central drive shaft: Primary input for the kinematic system of the axial flux MGU.

[118] from the electromagnetic clutch: selectively disengages the MGU / flywheel assembly from the drive train.

[120] Flywheel: Storage element for kinetic energy.

[122] Central gear: Driven by the central shaft

[116] , drives the parallel intermediate shafts. [124L, 124R] Gears: Transmit the rotation from the central gear to the intermediate shafts. [126L, 126R] Parallel intermediate shafts: Transmit the torque along axes parallel to the central shaft. [128L, 128R] Shaft-mounted bevel gears: Engage with rotor-mounted bevel gears [130L, 130R] to redirect the torque by 90°. [130L, 130R] Rotor-mounted bevel gears: Engage with shaft-mounted bevel gears [128L, 128R] to drive the rotor shafts. [132L, 132R] Rotor shafts: Drive the rotors directly. [134L] First rotor: Disc-shaped rotor with permanent magnets. [134R] Second rotor: Disc-shaped rotor with permanent magnets, mounted in a 180° orientation relative to [134L].

[136] Stator: Stationary disk-shaped core with windings, arranged between the rotors. Legend to Fig. : [134L] Rotor L: Rotates counterclockwise. The north (N) and south (S) poles of its permanent magnets are shown. [134R] Rotor R: Rotates counterclockwise. Due to its 180° mounting relative to Rotor L, the poles of its magnets are reversed, so that its north pole is opposite the south pole of Rotor L.

[136] Stator: Stationary central component with windings (not shown in detail). Key to Fig. : [134R] rotate in the same physical direction (COUNTERCLOCKWISE). Their effective counter-rotation relative to the stator results from the 180° mounting, not from an opposite physical rotation.

[100] Vehicle axle: Primary input from the wheels of the vehicle.

[104] Differential ring gear: Output element of the vehicle's differential gear.

[106] Bevel gear: Transmits the torque from the ring gear to the planetary gear.

[108] Planet carrier: Input element of the planetary gear set, driven by the bevel gear.

[110] Planetary gears: Rotate around the sun gear, driven by the planet carrier.

[114] Sun gear: Output element of the planetary gear set, drives the MGU central shaft.

[116] MGU central drive shaft: Primary drive shaft for the kinematic system of the axial flux MGU.

[122] Central gear: Large gear on the central shaft that drives the parallel intermediate shafts. [124L, 124R] Gears: Transfer the rotation from the central gear to the left and right intermediate shafts. [126L, 126R] Parallel intermediate shafts: Transmit the torque along the axes parallel to the central shaft. [128L, 128R] Shaft-mounted bevel gears: Attached to the ends of the intermediate shafts. [130L, 130R] to redirect the torque by 90° and drive the rotor shafts. Rotor-mounted bevel gears: Engage with the shaft-mounted bevel gears [128L, 128R] [132L, 132R] Rotor shafts: Output shafts that are driven directly by the rotor-mounted bevel gears. [134L] First rotor (Rotor L): Left disc-shaped rotor with permanent magnets. [134R] Second rotor (Rotor R): Right-hand disc-shaped rotor with permanent magnets, mounted in a 180° orientation relative to rotor L.

[136] Stator: A stationary, disk-shaped core with windings, arranged between the rotors. Generates the electrical output.

[142] Boost converter: A DC-DC converter that increases the voltage of the MGU to the higher voltage level of the battery.

[140] Battery: The vehicle's main traction battery. Legend for Fig. :

[146] PV system: Roof-mounted photovoltaic module arrangement with a nominal output voltage that is lower than the operating voltage of the MGU.

[148] MPPT controller: Maximum Power Point Tracking controller. Optimizes the power output of the PV system under variable light conditions.

[150] PV boost converter: A DC-DC converter that increases the voltage from the output of the MPPT controller to the nominal operating voltage of the MGU terminals (e.g. 48V to 72V).

[152] Diode: A unidirectional current-carrying component. It allows current to flow from the PV system to the MGU terminals, but prevents reverse current from the MGU or the battery into the PV circuit at low light intensity.

[136] MGU terminals: The electrical input / output terminals of the motor-generator. This is where the solar-generated electricity is fed in.

[142] Booster: The main DC-DC converter that increases the output voltage of the MGU to the higher voltage level of the main traction battery

[140] . QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 102017005A1

[0004]

Claims

[1] Integrated regenerative propulsion system for an electric vehicle, comprising: a) a planetary gear set with a fixed gear ratio of at least 5:1, wherein a carrier of the gear set is operationally coupled to a vehicle axle; b) an axial flux motor-generator unit (MGU), comprising: i) a stationary stator; ii) a first rotor arranged on one side of the stator; iii) a second rotor located on the opposite side of the stator; iv) a kinematic synchronization system driven by a central drive shaft and configured to induce synchronized rotation in the same direction in the first and second rotors, resulting in a counter-rotation of the first and second rotors relative to the stator; c) wherein a sun gear output of the planetary gear set is operationally coupled to the central drive shaft of the axial flux MGU; d) wherein the MGU has a rated power between 2.2 and 4.5 times the continuous rated power of a primary drive motor of the vehicle; characterized by , that the combination of the planetary gear and the rated power of the MGU is configured to generate a regenerative charging current during a positive torque output of the drive motor, while generating a reactive braking torque on the axle of less than 5 Nm at vehicle speeds of 20 km / h. [2] System according to claim 1, characterized by , that it further includes an electromagnetic clutch configured to disconnect the MGU from the vehicle axle, and a flywheel that is non-rotatably connected to the central drive shaft. [3] System according to claim 2, characterized bythat the flywheel is configured to drive the MGU for a period of at least 10 seconds after separation from the axle. [4] System according to claim 2 or 3, characterized by , that it further includes a control unit configured to: i) Detecting a sailing state, a braking state or a vehicle standstill state based on pedal positions of an accelerator pedal and a brake pedal; and ii) Triggering the disengagement of the clutch upon detection of the state. [5] System according to any one of the preceding claims, characterized by , that it further includes: a) a photovoltaic (PV) system; b) a maximum power point tracking (MPPT) controller that is electrically connected to the PV system; c) a first DC-DC boost converter configured to boost an output voltage of the MPPT controller to a nominal operating voltage of MGU terminals; d) a unidirectional current element arranged to direct an output of the first boost converter to the terminals of the MGU and to prevent reverse current flow; wherein the photovoltaic system is electrically connected directly to the terminals of the MGU to compensate for any excitation current requirement of the MGU. [6] System according to any one of the preceding claims, characterized by , that the vehicle axle is coupled to the carrier of the planetary gear via a bevel gear which engages with a crown gear of a vehicle differential. [7] System according to any one of the preceding claims, characterized by , that the kinematic synchronization system includes: a central gear mounted on the central drive shaft; a left and a right intermediate shaft, parallel to the central drive shaft, which are driven by the central gear; a first set of bevel gears, which is operationally coupled to the left and right intermediate shafts; and a second set of bevel gears, which engages with the first set and is operationally coupled to a first and a second rotor shaft; whereby a rotation is transmitted from the central drive shaft to the rotor shafts. [8] System according to claim 7, characterized by that the bevel gears of the first set are integrally formed with the intermediate shafts. [9] System according to any one of the preceding claims, characterized by , that the planetary gear increases the speed of the MGU to over 3000 rpm at vehicle speeds of 50 km / h or less. [10] System according to any one of the preceding claims, characterized bythat the reactive braking torque during positive torque delivery is sufficiently low to allow continuous operation of the MGU as a generator during urban driving cycles without a net reduction in vehicle range. [11] System according to any one of the preceding claims, characterized by that the first and second rotors comprise permanent magnets in Halbach arrays. [12] Integrated regenerative propulsion system for an electric vehicle, comprising: a) a regenerative drive subsystem comprising a planetary gear unit with a fixed gear ratio of at least 5:1, operationally coupled to a vehicle axle; b) a dual rotor motor generator unit (MGU) with a rated power between 2.2 and 4.5 times the continuous rated power of a primary traction motor of the vehicle, characterized by , that the MGU is an axial flux machine which includes: a stationary stator positioned between a first and a second rotor, and a kinematic synchronization system, driven and configured by a central drive shaft, a synchronized counter-rotation of the first and to induce a second rotor relative to the stator; c) wherein the planetary gear is operationally coupled to drive the MGU drive shaft. [13] Integrated regenerative propulsion system for an electric vehicle, comprising: a) a regenerative drive subsystem comprising a planetary gear unit with a fixed gear ratio of at least 5:1, operationally coupled to a vehicle axle; b) a dual rotor motor generator unit (MGU) with a rated power between 2.2 and 4.5 times the continuous rated power of a primary traction motor of the vehicle, characterized by , that the MGU is a radial flux machine which includes: a stationary stator arranged concentrically between an inner and an outer rotor, and a kinematic synchronization system configured to induce a synchronized counter-rotation of the inner and outer rotors relative to the stator; c) wherein the planetary gear is operationally coupled to drive a drive shaft of the MGU. [14] System according to claim 13, characterized by , that the kinematic synchronization system includes cardan joints configured to accommodate shaft misalignment.

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