Electric motor transmission device

Abstract

A powertrain of a vehicle is provided that includes an electric motor, a final drive, a gearing system having two degrees of freedom configured to transfer power from the electric motor to the final drive, the gearing system including a one-way mechanism, and a mechanical friction brake connected to the gearing system. The powertrain further includes a control system. The power assembly can achieve power driving, motor-free dragging sliding and braking with regenerative braking. A method for controlling a braking mode in a vehicle including such a powertrain is also provided.

Description

Technical Field

[0001] The present disclosure relates generally to electric motor transmissions having two degrees of freedom, and more particularly to electric motor gear transmissions having two degrees of freedom arranged to enable coasting as well as regenerative braking. Background Art

[0002] Current electric vehicles use an electric motor connected via a direct drive connection to the final drive, or a 'one-way clutch' or 'one-way clutch' gear system. Direct drive is common in cars and motorcycles, which inherently allows for regenerative braking, but has the disadvantage of always dragging the motor, thus preventing an effective coasting mode as the motor is constantly 'engaged' to the final drive.

[0003] A one-way clutch gear drive connection is common on e-bikes, which enables coasting without dragging the motor, but prohibits regenerative braking.

[0004] There is a need for a transmission that can achieve coasting without motor drag and can convert kinetic energy into electrical energy during braking processes, thereby providing an energy-efficient transmission for electric vehicles. Summary of the invention

[0005] The present disclosure provides a powertrain including a gear transmission system with two degrees of freedom. The powertrain of the present disclosure, more specifically, the gear transmission system of the present disclosure is arranged to enable coasting and regenerative braking.

[0006] The present disclosure provides a powertrain for a vehicle, the powertrain comprising an electric motor, a final drive, a gear transmission system having two degrees of freedom, the gear transmission system comprising at least three components configured to rotate relative to each other. The gear transmission system may be configured to transmit power from the electric motor to the final drive, wherein the gear transmission system comprises a one-way mechanism connected to one of the at least three rotating components of the gear transmission system, the one-way mechanism may be configured to reduce one of the two degrees of freedom by limiting the rotation of one component in a first direction during a power drive mode of the powertrain, while the one-way mechanism may be configured to enable one component to rotate freely in a second opposite direction during a coasting mode of the powertrain, thereby avoiding dragging of the electric motor. The powertrain may further comprise a mechanical friction brake connected to the gear transmission system via a component of the at least three components, the mechanical friction brake being configured to reduce one of the two degrees of freedom by limiting the rotation of the component to which the mechanical friction brake is connected during a braking mode of the powertrain, so as to cause movement of the electric motor, thereby regenerating energy through the electric motor.

[0007] Optionally, the mechanical friction brake is connected to the gear train and not to the final drive.

[0008] Optionally, the one-way mechanism is an overrunning clutch.

[0009] Alternatively, the gear train may include planetary gears, and the at least three components may include a sun gear rotatably connected to the electric motor and at least one planetary gear rotatably connected to a planet carrier.

[0010] Alternatively, the one-way mechanism may be a one-way bearing incorporated as part of the planet carrier, the one-way bearing being configured to allow the planet carrier to rotate in a first direction and prevent the planet carrier from rotating in a second direction, the second direction being opposite to the first direction.

[0011] Optionally, a mechanical friction brake is connected to the planet carrier, which mechanical friction brake may be configured to slow down the rotation of the planet carrier and thereby mechanically force the electric motor to rotate via the forced rotation of the sun, thereby achieving regenerative braking.

[0012] Optionally, the mechanical friction brake comprises a disc brake.

[0013] Optionally, the gear transmission system includes a differential gear system, wherein the at least three components include a first side gear rotatably connected to the electric motor and a horizontal planetary gear, the horizontal planetary gear is rotatably connected to the rack, and wherein the horizontal planetary gear is further rotatably connected to the second side gear.

[0014] Optionally, the one-way mechanism is a one-way bearing incorporated as part of the second side gear, the one-way bearing being configured to allow the second side gear to rotate in a first direction and prevent the second side gear from rotating in a second direction, the second direction being opposite to the first direction.

[0015] Optionally, the mechanical friction brake comprises a disc brake connected to the second side gear, the disc brake being configured to slow down the rotation of the second side gear and thereby mechanically force the electric motor to rotate via forced rotation of the first side gear, thereby achieving regenerative braking.

[0016] The present disclosure further provides a vehicle gear transmission system, comprising: an electric motor, a final drive, and a gear transmission system having two degrees of freedom, the gear transmission system comprising at least three components configured to rotate relative to each other, the gear transmission system being configured to transfer power from the electric motor to the final drive. The gear transmission system comprises a one-way mechanism connected to one of the at least three rotating components of the gear transmission system, the one-way mechanism being configured to reduce one of the two degrees of freedom by limiting the rotation of one component in a first direction during a power drive mode of the powertrain, while the one-way mechanism being configured to enable one component to rotate freely in a second opposite direction during a coasting mode of the powertrain, thereby avoiding dragging of the electric motor. The powertrain may further comprise a mechanical friction brake connected to the gear transmission system via a component of the at least three components, the mechanical friction brake being configured to reduce one of the two degrees of freedom by limiting the rotation of the component to which the mechanical friction brake is connected during a braking mode of the powertrain, thereby causing movement of the electric motor, thereby regenerating energy through the electric motor. The powertrain may further include a control system configured to control the amount of power supplied by the electric motor during the driving mode and to control the amount of negative torque applied by the electric motor during the regenerative braking mode. The control system includes a processor configured to: Detecting braking mode; predefining a setpoint value based on (i) a gear ratio of the vehicle and (ii) a parameter modifiable according to a desired regeneration ratio; calculating a process value based on a ratio between a motor speed and a final drive speed; and An amount of negative torque required to equalize the process value to the set point value is determined, the negative torque being applied by the electric motor during the regenerative braking mode.

[0017] Optionally, the desired regeneration ratio is determined by at least one of battery / capacitor state of charge (SOC), power rating, drive speed, motor load, terrain, temperature, or any combination thereof.

[0018] The present disclosure may further include a method for controlling a braking mode in a vehicle, the vehicle including an electric motor, a final drive, and a gear system having two degrees of freedom, the gear system including at least three components configured to rotate relative to each other, the gear system configured to transfer power from the electric motor to the final drive. The gear system includes a one-way mechanism connected to one of the at least three rotating components of the gear system, the one-way mechanism configured to reduce one of the two degrees of freedom by limiting the rotation of one component in a first direction during a power drive mode of the powertrain, while the one-way mechanism is configured to enable one component to rotate freely in a second opposite direction during a coasting mode of the powertrain, thereby avoiding dragging of the electric motor. The vehicle may further include a mechanical friction brake connected to the gear system via a component of the at least three components, the mechanical friction brake configured to reduce one of the two degrees of freedom by limiting the rotation of the component to which the mechanical friction brake is connected during a braking mode of the powertrain to cause movement of the electric motor, thereby regenerating energy through the electric motor and the processor.

[0019] The method may include Detecting braking mode; predefining a setpoint value based on (i) a gear ratio of the vehicle and (ii) a parameter modifiable according to a desired regeneration ratio; calculating a process value based on a ratio between a motor speed and a final drive speed; and An amount of negative torque required to equalize the process value to the set point value is determined, the negative torque being applied by the electric motor during the regenerative braking mode.

[0020] Optionally, detecting the braking mode includes determining that the motor is rotating and further determining that the user is not applying throttle.

[0021] Optionally, the step of calculating the process value comprises detecting the motor speed and detecting the final drive speed via respective speed sensors.

[0022] Optionally, the method further comprises calculating an error representing a difference between the process value and the set point value.

[0023] Optionally, the desired regeneration ratio is determined by at least one of battery / capacitor state of charge (SOC), power rating, drive speed, motor load, terrain, temperature, or any combination thereof. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Some non-limiting exemplary embodiments or features of the disclosed subject matter are illustrated in the following drawings.

[0025] In the attached picture:

[0026] Figure 1 is a schematic diagram of a two degree-of-freedom powertrain according to some embodiments of the present disclosure;

[0027] Figure 2 is a schematic diagram of an isometric view of a transmission system according to an embodiment of the present disclosure;

[0028] Figure 3 is a schematic diagram of a pattern detection method according to an embodiment of the present disclosure;

[0029] Figure 4 is a schematic diagram of a braking mode control algorithm according to an embodiment of the present disclosure;

[0030] Figure 5A-5C is a schematic diagram of a cross-sectional view and an isometric view of a transmission system implemented in an electric bicycle according to an embodiment of the present disclosure;

[0031] Figure 6A-6C is a schematic diagram of a cross-sectional view and an isometric view of a transmission system implemented in an electric motorcycle according to an embodiment of the present disclosure;

[0032] Figure 7A-7D are schematic diagrams of several configurations of transmission systems according to embodiments of the present disclosure; and

[0033] Figure 8 It is a summary of the embodiments according to the present disclosure. Figure 7A-7D Table of characteristics of transmission system configurations, all of which are capable of achieving a drive mode, a coasting mode, and a regenerative braking mode.

[0034] Now with specific reference to the drawings in detail, it should be emphasized that the details shown are by way of example and for the purpose of illustrative discussion of the embodiments of the present disclosure. In this regard, the description in conjunction with the drawings makes it clear to those skilled in the art how the embodiments of the present disclosure can be practiced.

[0035] Identical or repeated or equivalent or similar structures, elements or components appearing in one or more figures are generally marked with the same reference numerals (optionally with one or more additional letters to distinguish similar entities or variations of entities) and may not be repeatedly marked and / or described. Reference to previously presented elements is implicit without necessarily further reference to the figure or description in which they appear.

[0036] The dimensions of the components and features shown in the drawings are selected for convenience or clarity of presentation and are not necessarily shown to scale or true perspective. For convenience or clarity, some elements or structures are not shown or are only partially and / or shown in different perspectives or from different viewpoints. DETAILED DESCRIPTION

[0037] The present disclosure provides a transmission system or gear transmission system configured to be implemented in a vehicle having an electric motor, and further configured to achieve coasting and regenerative braking during operation of the vehicle. Such a transmission system can provide an energy-efficient vehicle that benefits from coasting without dragging the motor and thus reducing kinetic energy waste during such coasting motion, and benefits from regenerating electrical energy during braking operations, which is also energy-efficient.

[0038] The present disclosure provides two aspects, the first being the mechanical aspects of a gear transmission system, the purpose of which is to connect between the electric motor and the final drive (e.g., wheels of a vehicle) during a driving mode, and to disconnect between the electric motor and the final drive during a coasting mode, and finally, to gradually reconnect between the electric motor and the final drive during a braking mode.

[0039] The second aspect of the disclosure is a control aspect, the purpose of which is to determine the amount of braking (negative) torque to be applied to the vehicle's electric motor in order to slow the vehicle and regenerate energy.

[0040] Thus, in braking mode, because the moving final drive (eg, the moving wheels) is connected to the electric motor, and the motor resists the motion via the control system, the final drive or wheels will slow down, thereby slowing the vehicle.

[0041] The term "vehicle" as used herein refers to any vehicle including an electric motor. The vehicle may be a fully electric vehicle, a hybrid vehicle (e.g., a hybrid car), or a manual vehicle with electric motor assistance (e.g., a manual bicycle with motor assistance).

[0042] Throughout the description, the terms "gear," "gear system," and "transmission system" may be used interchangeably.

[0043] Reference now Figure 1 , Figure 1A powertrain of a vehicle including a gear transmission system with two degrees of freedom according to some embodiments of the present disclosure is schematically shown. According to the present disclosure, via the powertrain, the vehicle can have at least three operating modes, which can include power drive, coasting and regenerative braking. The present disclosure provides a powertrain 10 with two degrees of freedom, which can include an electric motor 12 configured to convert electricity or electrical energy into mechanical power or mechanical energy, a final drive 20, and a gear transmission system 14 with two degrees of freedom. The gear transmission system 14 can be configured to transfer mechanical power from the electric motor 12 to the final drive 20. According to some embodiments, the powertrain 10 can further include a one-way mechanism 16, which can typically be an overrunning clutch, a one-way clutch or a one-way bearing that can be incorporated as part of the gear transmission system 14. For the power drive mode, the one-way mechanism 16 can be configured to reduce the degrees of freedom of the gear transmission system 14. According to some embodiments, the powertrain 10 can further include a mechanical friction brake 18 connected to the gear transmission system 14. According to the present disclosure, the mechanical friction brake 18 is not connected to the final drive 20. For the regenerative braking mode, the mechanical friction brake 18 can be controlled by the user to partially or completely reduce the degrees of freedom of the gear transmission system 14. In some embodiments, the mechanical friction brake 18 can include any of a disc brake, a drum brake, a block brake, or any other friction braking mechanism, or any combination thereof.

[0044] According to some embodiments, the powertrain 10 may further include a control system 22 configured to control the operation of the electric motor 12 during various operating modes of the powertrain 10. In some embodiments, the control system 22 may include a processor 24 configured to determine an amount of negative torque that may be applied by the electric motor 12 during the regenerative braking mode. According to some embodiments, the gear transmission system 14 may include a planetary gear, a differential gear, and any other similar gear transmission system having two degrees of freedom.

[0045] According to some embodiments of the present disclosure, the mechanical friction brake 18 may be connected to an element of the gear train 14 and not to the final drive, so that the powertrain 10 may achieve regenerative braking while the powertrain 10 further achieves coasting via the one-way mechanism 16 .

[0046] According to some embodiments, the control system 22 can be configured to receive various inputs that are typically speed-related, such as the speed of the electric motor 12, the speed of the final drive 20, the speed of any other component of the gear train, or the speed of any component of the mechanical friction brake 18, and / or any combination thereof. In some embodiments, the inputs received by the control system 22 can be received from different sensors that can be connected to different elements of the powertrain 10. According to what will be referred to below Figure 4 To describe the braking mode control algorithm, the received input may be analyzed by at least one processor 24 that may be incorporated as part of the control system 22. In some embodiments, the control system 22 may be configured to analyze the received input data and provide instructions to the powertrain 10 to control the amount of power that the electric motor 12 should apply depending on the specific operating mode (e.g., power drive, coasting, and regenerative braking).

[0047] Reference now Figure 2 , Figure 2 Schematically illustrates an isometric view of a transmission system according to some embodiments of the present disclosure. According to some embodiments, the transmission system of the present disclosure can be a gear transmission system 100 with two degrees of freedom, which can include planetary gears. The planetary gear 100 can include a sun gear 101 and one or more pinion gears or planetary gears 102 configured to rotate relative to the rotation of the sun gear 101. In some embodiments, the sun gear 101 can be connected to an electric motor (e.g., an electric motor 12 ( Figure 1 )), the electric motor can rotate relative to the vehicle chassis represented by reference numeral 107. According to some embodiments, the gear transmission system 100 can further include a planet carrier 122, which can be configured to rotate relative to the vehicle chassis 107 along the one-way bearing 103 ( Figure 1 In some embodiments, the gear transmission system 100 may include a ring gear 105, which may be attached to a final drive (e.g., Figure 1 In some embodiments, the final drive may be a wheel, such as a bicycle wheel.

[0048] In some embodiments, the gear transmission system 100 can be a gear transmission system with two degrees of freedom, because one component can rotate two other components. In this case, in one example, the sun gear 101 can be the input, and the output can be the ring gear 105, the planet carrier 122, or both, depending on the degrees of freedom enabled or restricted by the gear transmission system 100 in its different operating modes.

[0049] According to some embodiments, if the rotation direction of the planet carrier 122 is enabled by the one-way bearing 103, the rotation of the sun gear 101 can cause one or more planet gears 102 to rotate, thereby rotating the planet carrier 122. Through the rotation of the sun gear 101, the rotation of one or more planet gears 102 can also cause the ring gear 105 to rotate.

[0050] According to some embodiments, the gear transmission system 100 may include a mechanical friction brake system 104 ( Figure 1 18). In some embodiments, the mechanical friction brake system 104 may include a disc brake 114 and a caliper 124. In some embodiments, the disc brake 114 may be attached to the planet carrier 122 so that the disc brake 114 and the planet carrier 122 may rotate together as one element. In some embodiments, the disc brake 114 may be attached to the planet carrier 122 via bolts, screws 134, or any other fastening means.

[0051] In some embodiments, the caliper 124 can be fixed to the electric vehicle chassis 107. The caliper 124 can include two brake pads, each located on one of two opposite sides of the disc brake 114, which can be clamped onto the disc brake 114 once the user activates the friction braking system 104 (e.g., via a brake handle or brake pedal). According to some embodiments, the brake handle or brake pedal (through which the friction braking system 104 can be operated) can be an inherent component of the vehicle, which does not need to be changed once the gear transmission system 100 is implemented into a vehicle with an electric motor.

[0052] According to some embodiments, in the 'power drive' mode, the motor rotates because it is driven by electricity, that is, the electric motor 12 and its subordinate sun gear 101 rotate, which means that during the 'power drive' period, the sun gear 101 is the input of the gear transmission system 100. In one example, the electric motor 12 can rotate in the direction opposite to the forward driving direction of the final drive 20. During the 'power drive' mode, the planet carrier 122 can be prevented from rotating in the same direction as the electric motor 12 by the one-way mechanism 16 (e.g., one-way bearing 103), thereby forcing the planet carrier 122 to be stationary. Therefore, the gear transmission system 100 reduces one degree of freedom. That is, all torque is transmitted from the electric motor 12 and its subordinate gears (e.g., sun gear 101) to the final drive 20 and its subordinate gears (e.g., ring gear 105) via one or more planetary gears 102. In the driving mode or power drive mode, the ring gear 105 is the output of the gear transmission system 100.

[0053] According to some embodiments, in the 'coasting' mode, the ring gear 105 is the input to the gear train 100, as the ring gear 105 rotates without being driven by the electric motor 12. When the ring gear 105 rotates, it can cause one or more of the planet gears 102 to rotate, which in turn can cause the planet carrier 122 to rotate freely in a direction enabled and dictated by the one-way bearings 103. In this example, the direction of enabled rotation is the forward drive direction of the final drive 20. Therefore, during the coasting mode, no torque is transmitted to the sun gear 101 via the planet carrier 122, thereby allowing the sun gear 101 and thus the electric motor 12 connected to the sun gear 101 to be stationary.

[0054] According to some embodiments, in the 'brake' mode, the user may apply a mechanical braking force to the planet carrier 122. For example, via the use of a brake handle or brake pedal, the user may operate the mechanical friction brake system 104. In some embodiments, the brake handle or brake pedal may be connected to the mechanical friction brake system 104, which may include a caliper 124 and a disc brake 114. In the 'brake' mode, the ring gear 105 is an input to the gear transmission system 100 because the ring gear 105 rotates without being driven by the electric motor 12. When the ring gear 105 rotates, it may rotate one or more planet gears 102, which may not be able to rotate the planet carrier 122 freely in the 'brake' mode because the planet carrier 122 is restrained by the friction brake system 104. Therefore, torque is transmitted from the ring gear 105, which is still rotating due to the vehicle's motion, to the electric motor 12 through the sun gear 101 via the one or more planet gears 102, thereby rotating the sun gear 101 and thus rotating the electric motor 12.

[0055] In some embodiments, once the user stops starting the electric motor 12, for example, stops operating the accelerator handle or the accelerator pedal, the operating mode changes from driving to coasting, for example, when the electric motor 12 slows down, the planet carrier 122 starts to rotate. When the user operates the mechanical friction brake system 104, the calipers 124 can be clamped onto both sides of the disc brake 114, and a mechanical braking force can be applied to the planet carrier 122 because the disc brake 114 as part of the mechanical friction brake system 104 is connected to the planet carrier 122, so that the disc brake 114 and the planet carrier 122 rotate as a single unit.

[0056] For example, a user may depress the brake handle, causing the caliper 124 to slow the free rotation of the disc brake 114 and the planet carrier 122, since they are connected to each other to form a single unit. Thus, torque is transmitted from the ring gear 105, which is still rotating due to the motion of the vehicle, through the sun gear 101 via one or more planet gears 102 to the electric motor 12, thereby rotating the sun gear 101 and thus rotating the electric motor 12. The control system (e.g., the control system 22) may cause the electric motor 12 to apply a negative torque to the sun gear 101 to slow the vehicle and regenerate energy. That is, since the planet carrier 122 is forced to slow down by the mechanical friction brake system 104, the gear transmission system 100 is reduced to one degree of freedom, and since the ring gear 105 rotates, the ring gear 105 forces the sun gear 101 to rotate via the rotation of one or more planet gears 102 and thus rotates the electric motor 12. Energy can be regenerated by forcing the sun gear 101 to rotate and thus the electric motor 12 to rotate through the rotation of the ring gear 105, because the electric motor 12 is not rotated by electrical drive (such as in the drive mode), but the electric motor 12 is mechanically forced to rotate, thereby regenerating energy. In some embodiments, the regenerated energy can be stored in an energy storage device such as a battery or capacitor for later use.

[0057] According to the present disclosure, the disc brake 114 does not directly slow down the vehicle, but is used to restrict one of the two degrees of freedom. Therefore, most of the braking energy can be regenerated, and only a small amount of energy can be wasted due to friction and heat, which will be referred to in detail. Figure 4 Detailed description is given in Figure 2 In the illustrated gear transmission system 100, by connecting the disc brake 114 to one of the elements of the planetary gear transmission system (e.g., the planet carrier 122), when the brakes are applied, the electric motor 12 is forced to rotate, not by electrical drive, but due to the reduction of one of the two degrees of freedom. Therefore, the electric motor 12 generates electrical energy during the braking mode.

[0058] According to some embodiments, during the driving mode, the user may apply the throttle and the electric motor 12 may generate positive torque depending on the position of the throttle. During the gliding mode, the user may release the throttle and the electric motor 12 may eventually slow to a complete stop. And finally, during the braking mode, the user may apply the friction braking system 104 to slow down the elements of the transmission system connected to the friction braking system 104. For example, according to Figure 2, the element slowed by the friction braking system 104 is the planet carrier 122. Slowing the planet carrier 122 causes the electric motor 12 to rotate. The control system 22 can detect that the electric motor 12 is being rotated by an external force other than a throttle command, and can therefore respond by applying a controlled negative torque to the electric motor 12, which can cause the electric motor 12 to act as a generator, thereby achieving regenerative braking.

[0059] Therefore, in order for the control system 22 to properly control the operation of the electric motor 12 while switching between operating modes, these modes must be determined and distinguished from one another.

[0060] Reference now Figure 3 , Figure 3 Schematically illustrates a mode detection method according to some embodiments of the present disclosure. In some embodiments, the mode detection method 300 can be performed by the control system 22 (e.g., via the processor 24). In some embodiments, the mode detection method 300 can include, for example, determining whether the electric motor 12 is rotating (302) by sensing the electric motor speed (e.g., via a speed sensor that can be connected to the electric motor 12). If the control system 22 or processor 24 determines that the electric motor 12 is not rotating, the control system 22 can identify that the vehicle is in a gliding mode (306). If the control system 22 or processor 24 determines that the electric motor 12 is rotating, it is necessary to determine the throttle position (304). In the case where the control system 22 or processor 24 determines that the electric motor 12 is rotating and the throttle position is not equal to '0' (i.e., the throttle is activated), the control system 22 or processor 24 can identify that the vehicle is in a driving or power drive mode (308). However, if the control system 22 or processor 24 determines that the electric motor 12 is rotating and the throttle position is equal to '0', the control system 22 or processor 24 can identify that the vehicle is in a braking mode (310). This is because the electric motor 12 is rotating but not due to throttle activation, e.g., the throttle position is not zero, but due to external forces, namely the friction brake system (e.g., friction brake 18 ( Figure 1 ) or friction system 104 ( Figure 2 )) operation.

[0061] As a safety measure, an on / off sensor can be added to the brake handle / pedal to force the throttle position to zero whenever the brake is applied. In this case, once the mechanical brake is applied, the brake sensor senses the operation of the mechanical brake. Figure 1 The control system 22 in the braking mode will override any other commands, such as operating the electric motor 12 via the throttle. That is, regardless of the user throttle position, once the brake sensor detects the operation of the mechanical brakes, the control system 22 will enter the braking mode (310) and the vehicle will begin to slow down.

[0062] Reference now Figure 4 , Figure 4 4 is a schematic diagram of a braking mode control algorithm according to an embodiment of the present disclosure. According to an embodiment of the present disclosure, in order to provide a smooth braking motion, the amount of negative torque applied by the electric motor 12 in a continuous manner can be determined by the control system 22 (e.g., via the processor 24) according to the braking mode control algorithm 400.

[0063] In some embodiments, the braking mode control algorithm 400 may be a feedback loop. The braking mode control algorithm 400 may include a calculation loop process value (PV) 406, which may represent the ratio between the motor speed and the final drive speed, which may be calculated according to equation (1): (1)PV=ωm / ωd in: ωm represents the motor speed; and ωd represents the final drive speed.

[0064] In some embodiments, the motor speed may be provided by a motor speed sensor 416 and the final drive speed may be provided by a final drive speed sensor 422. The ratio between the motor speed and the final drive speed may be calculated in operation 418 according to equation (1).

[0065] In some implementations, the braking mode control algorithm 400 may include setting a circuit set point (SP) ratio 402, which may have a value calculated according to equation (2): (2) SP = Regen × Gear in: Regen represents a parameter having a value less than 1, which represents the ratio between the motor speed and the final drive speed; and Gear represents the transmission ratio of a gear system with two degrees of freedom in drive mode when the degrees of freedom are fully reduced. According to some embodiments, when 'Regen' has a value close to '1', this indicates that most of the kinetic energy will be regenerated by the electric motor 12 , and when 'Regen' has a value close to '0', this indicates that most of the kinetic energy will be dissipated as heat through the mechanical braking system 104 . In some embodiments, in order to provide an energy efficient gear transmission system, 'Regen' should be a number as close to 1 as possible but less than 1.

[0066] In some embodiments, the energy regenerated by the electric motor 12 can be stored in an energy storage device such as a battery or capacitor. When the storage device reaches or is about to reach its maximum capacity, or when the regenerative power approaches the maximum rating specified by the manufacturer of any component of the electrical system, 'Regen' can be set to a low value, thereby minimizing regenerative braking power and maximizing mechanical braking power. That is, in some embodiments, 'Regen' can be changed or modified by the control system 22 (e.g., via the processor 24) during vehicle operation to comply with various system limitations.

[0067] In some embodiments, 'Regen' may be a parameter modifiable according to the desired regeneration ratio, which may be varied by the control system 22 based on battery / capacitor state of charge (SOC), power rating, drive speed, motor load, terrain, temperature, or any combination thereof. Other and / or additional parameters may affect 'Regen'.

[0068] In some embodiments, the braking mode control algorithm 400 may include receiving an error 408 via a controller 410, which may be incorporated as part of the control system 22. The error 408 may be calculated by subtracting a process value (PV) from a set point (SP). In response to receiving the error 408, the controller 410 may control the braking mode control algorithm 400 to be controlled by an electric motor 414 (e.g., Figure 1 The amount of negative torque 412 applied by the electric motor 12 in order to achieve equality between the SP ratio and the PV ratio, resulting in error 408 being equal to zero.

[0069] The amount of negative torque applied by the electric motor 414 (e.g., electric motor 12) is proportional to the negative error 408. The larger the negative error 408, the larger the negative torque applied by the electric motor 414. In the case where the error 408 is positive, i.e., the absolute value of PV is less than the absolute value of SP, no negative torque is applied, but no positive torque is applied either. That is, the maximum positive torque defined by the control system 22 during the braking mode is '0' because during the braking mode, only negative torque should be applied by the electric motor to slow the vehicle while regenerating energy.

[0070] In some embodiments, the greater the braking pressure applied by the user, the more the speed of the planet carrier 122 is reduced. The reduction in the planet carrier speed can be reflected as an increase in PV because the motor speed increases when the planet carrier speed decreases. In response, the controller 410 can increase the negative torque acting on the motor 414, thereby increasing the braking force to reduce the PV value and achieve equality between PV and SP.

[0071] Conversely, the less brake pressure applied by the user, the less the speed of the planet carrier 122 decreases. The less speed reduction of the planet carrier 122 can be reflected as a decrease in PV, which can cause the controller 410 to reduce the negative torque acting on the motor 414, thereby reducing the braking force.

[0072] For example, the planetary gear type gear transmission system 100 can be represented by the following equation (3): (3) (R+S)×Tc=R×Tr+Ts×S in: R represents the number of teeth of the ring gear; S represents the number of teeth of the sun gear; Tc represents the number of turns of the planet carrier; Tr represents the number of turns of the ring gear; and Ts represents the number of turns of the sun gear. For this example, the gear transmission system can achieve the following number of teeth on the sun gear and the number of teeth on the ring gear: S=16, R=64. A reduction ratio of '-4' is achieved, that is, in the driving mode, the final drive rotates 1 circle in the first direction, and the sun gear rotates 4 circles in the second direction opposite to the first direction, that is, Gear = -4. Alternatively, it can coast at 200 RPM, that is, ωd = 200. Since the operating mode is coasting, the electric motor is stationary and not rotating, therefore: ωm=0. Therefore, according to equation (3), for a ring speed of 200 RPM and a motor speed of 0 RPM, the planet carrier speed (Tc) is 160 RPM. In this example, 'Regen' is predefined as follows: Regen=0.9. According to this example, when the user applies the brakes, the planetary carrier (e.g., planetary carrier 122) can slow down, the electric motor 414 or the electric motor 12 can begin to rotate, and the control system 22 can adjust the motor braking torque (i.e., negative torque) so that the electric motor can rotate at a speed that meets the SP requirement. (2)SP=Regen×Gear=0.9*(-4)=-3.6 To meet the SP requirement, PV should be equal to SP to avoid error 408: (1)PV=ωm / ωd=ωm / 200=-3.6 = >ωm = -720 Therefore, the desired brake mode motor speed for the vehicle speed of this example is -720 RPM, which means that the electric motor should rotate at a speed of 720 RPM in a direction opposite to the direction of rotation of the ring (eg, final drive 20). Therefore, according to equation (3), for a ring speed of 200 RPM and a motor speed of -720 RPM, the planet carrier speed will be 16 RPM.

[0073] If the user applies more pressure to the brake, the planet carrier 122 will reduce its speed, and therefore the electric motor 12 will increase its speed, for example, to -730RPM. Therefore, the control system 22 will need to increase the braking torque to bring the motor speed back to -720RPM in order to continue to meet the SP requirement by maintaining equality between PV and SP. If the user applies less pressure to the brake, the planet carrier will increase its speed, and therefore the motor will reduce its speed, for example, to -710RPM. Therefore, the control system will reduce the braking torque to bring the motor speed back to -720RPM in order to continue to meet the SP requirement. Therefore, the more pressure the user applies to the brake, the more braking torque the control system 22 increases, and the less pressure applied to the brake, the less braking torque the control system 22 applies, which enables the user to intuitively operate the brake.

[0074] In some embodiments, control system 22 (eg, via processor 24 ) responds to changes in electric motor speed by adjusting the braking / negative torque applied to electric motor 12 in a continuous manner so as to maintain the SP demand being met throughout operation of the vehicle.

[0075] In some embodiments, the energy loss percentage on the friction brake (eg, mechanical friction brake system 104) is proportional to the 'brake mode' planet carrier speed and the 'glide mode' planet carrier speed, which is 10% in this example: 16 / 160=10%. That is, only 10% of the braking energy will be dissipated through the friction brakes, while the rest of the energy can be used for regenerative braking.

[0076] Therefore, by adjusting the value of 'Regen' to be as close to 1 as possible while 'Regen' is still less than 1 so that the braking torque can be adjusted by the control system 22, the energy loss due to friction braking can be minimized, which means that the gear transmission system 100 of the present disclosure is highly energy-efficient. The value of 'Regen' must be less than 1 because the controller 410 or control system 22 (e.g., via the processor 24) determines the amount of negative torque applied to the electric motor 12 based on the value of the error 408, which is proportional to the amount that the PV is above the SP. In other words, in order to generate negative torque, a negative error 408 is required. If the value of 'Regen' is equal to 1, then the PV ratio cannot be greater than the SP ratio, and the error 408 cannot be negative, which means that no braking torque will be applied to the electric motor 12. According to some embodiments, the electric motor 12 may have a non-zero minimum braking torque, and a braking torque below this minimum braking torque may be achieved by applying slight pressure to the brake system, thereby transferring only a portion of the torque from the final drive 20 to the electric motor 12. According to the above example, when coasting at 200 RPM, the user may apply the brakes very lightly, thereby slowing the planet carrier from its coasting speed of 160 RPM to a slightly lower speed (e.g., 150 RPM), causing the electric motor to rotate slowly at -50 RPM according to equation (3). In this case, the absolute value of PV is less than the absolute value of SP, so the error 408 is positive. Therefore, the control system 22 will apply zero negative torque and will not regenerate energy. However, because the electric motor 12 has some internal friction, it will slowly slow the vehicle in proportion to the speed of the electric motor, which is controlled by the amount of braking force applied by the user.

[0077] In some embodiments, the vehicle does not require a designated sensor to detect the brake handle / pedal position. Instead, the adjustment of the braking torque applied to the electric motor 12 can be determined by the control system 22 in response to the amount of braking applied by the user to the brake handle / pedal, as described above. Therefore, no changes to the existing brake mechanism are required.

[0078] According to some embodiments, when the braking process is initiated, the electric motor needs to accelerate from zero to the braking RPM (e.g., -720 RPM according to the above example). This increase in electric motor speed can be gradual and can be controlled by the amount of braking force applied by the user, as described above with respect to the braking mode control algorithm 400. That is, unlike some current designs that include a solenoid used as an electromagnetic clutch (which is an instantaneous engagement of the motor, which has an unpleasant 'on / off' or '0 / 1' operation), the present disclosure provides a gradual increase in motor speed, which enables the electric motor 12 to be smoothly engaged according to user input, which is further consistent with the natural user operation of current braking systems.

[0079] According to some embodiments of the present disclosure, the powertrain system of the present disclosure provides continuously variable braking torque from zero negative torque to the maximum negative torque capability of the electric motor 12 by responding to brake pressure applied by the user in a seamless and intuitive manner via the brake mode control feedback loop 400 .

[0080] Reference now Figure 5A-5C , Figure 5A-5CSchematic diagrams of a transmission system implemented in an electric bicycle (bicycle) according to an embodiment of the present disclosure, a cross-sectional view, an isometric view with a partial hub, and an isometric view with a complete hub, respectively. In some embodiments, the transmission system of the present disclosure can be implemented as part of an electric bicycle geared hub motor system 500. In some embodiments, the electric bicycle geared hub motor system 500 can include an electric motor rotor 501, which can be attached to a gear transmission system with two degrees of freedom, which can be similar to the gear transmission system 100 ( Figure 2 ). The gear transmission system may include a sun gear 511, at least one planet gear 502 (e.g., two planet gears 502), and a planet carrier 522. The final drive 20 may include a ring gear 505 located within and attached to a hub or housing 515. In some embodiments, the electric motor rotor 501 may be attached to the sun gear 511. In some embodiments, the planet carrier 522 may rotate around a static axis 507 equivalent to the chassis of the electric bicycle via a one-way mechanism (e.g., a one-way bearing 503). In some embodiments, a friction brake mechanism (which may include a disc brake 514) may be attached to the planet carrier 522, such as via bolts, rivets, screws 534, or any other fastening means.

[0081] In some embodiments, the hub or cover 515 can be configured to cover the components of the gear train while maintaining the disc brake 514 as the only component outside the space defined by the hub 515.

[0082] In some embodiments, the electric bicycle geared hub motor system 500 can further include a bearing 560, which can be part of the hub 515, and the disc brake 514 can be connected to the planet carrier 522 through the bearing 560. The bearing 560 can enable the disc brake 514 to rotate with the planet carrier 522 as a single unit that can rotate independently of the hub 515.

[0083] Reference now Figure 6A-6C , Figure 6A-6C Schematic diagrams of a transmission system implemented in an electric motorcycle according to an embodiment of the present disclosure, in a cross-sectional view and an isometric view, respectively. In some embodiments, the transmission system 660 can be implemented as part of the rear wheel hub of the electric motorcycle, which is externally driven by the mid-drive motor system 600. According to some embodiments, the gear transmission system 660 with two degrees of freedom implemented as part of the electric motorcycle motor system 600 is implemented in a form similar to a power differential gear, however, it includes the same basic principles of the transmission system of the present disclosure, which enables free sliding as well as regenerative braking.

[0084] In some embodiments, the electric motorcycle motor system 600 may include a motor 670 ( Figure 6B ), the motor 670 may be externally linked to the sprocket 601 (eg, via a chain 672 or any other mechanism). Fig. 6A ). The sprocket 601 can be attached to the gear transmission system 660 via the first side gear 611. The rotation of the first side gear 611 is enabled by the first side gear bearing 661. The rotation of the first side gear 611 causes the rotation of the horizontal planetary gear 602, which can be mounted on the rack 622. The rack 622 can be attached to the final drive 605. The rotation of the horizontal planetary gear 602 can cause the rotation of the rack 622. The rotation of the horizontal planetary gear 602 can be enabled via the bearing 662. The rotation of the horizontal planetary gear 602 can further cause the rotation of the second side gear 604. In some embodiments, the second side gear 604 can be mounted on a one-way bearing 603, which is configured to provide for the second side gear 604 to rotate in only one direction. The second side gear 604 can rotate relative to the static shaft or chassis 607. The rotation of the rack 622 relative to the first side gear 611 and the second side gear 604, respectively, can be enabled by the bearing 682. In some embodiments, the disc brake 614 can be attached to the second side gear 604 , for example, via bolts, rivets, or screws 634 .

[0085] Figure 6A-6C The power differential gear transmission system shown can be expressed by the following equation (4): (4) Trc = (T1 + T2) / 2 in: T1 represents the number of turns of the first side gear (eg, the first side gear 611) T2 represents the number of revolutions of the second side gear (eg, the second side gear 604) Trc represents the number of turns of the rack (eg, rack 622).

[0086] During the drive mode, the electric motor 670 can supply power to operate the rotation of the sprocket 601, which in turn can rotate the first side gear 611. The second side gear 604 can be prevented from moving during the drive mode due to the rotation limit provided by the one-way bearing 603. In some embodiments, the one-way bearing 603 can allow the second side gear 604 to rotate only in a single direction (e.g., the direction in which the first side gear 611 rotates). Therefore, the rotation of the first side gear 611 can cause the one or more horizontal planetary gears 602 to rotate, which can cause the rack 622 to rotate, thereby rotating the final drive 605 and the wheel 680.

[0087] During the gliding mode, the wheels 680 and the final drive 605 rotate together with the rack 622, and the torque is transmitted to the second side gear 604 via the horizontal planetary gear 602 in the direction allowed by the one-way bearing 603. Therefore, the second side gear 604 and the disc brake 614 connected to the second side gear 604 rotate as a single unit. Therefore, the rotation of the horizontal planetary gear 602 makes the first side gear 611 and the sprocket 601 directly connected to the first side gear 611 stationary, thereby allowing the motor 670 to be stationary.

[0088] During the braking mode, the final drive 605 and the wheel 680 rotate together with the rack 622. Since the brakes are applied during the braking mode, the movement of the disc brake 614 and the second side gear 604 connected to the disc brake 614 is restricted, and the torque is transmitted to the first side gear 611 via the horizontal planetary gear 602, and thus to the sprocket 601, thereby rotating the motor 670.

[0089] In the braking mode, the motor 670 does not rotate due to the power supplied to the motor 670 as in the driving mode. Instead, during the braking mode, the motor 670 is mechanically forced to rotate, thereby regenerating energy.

[0090] In some embodiments, the braking mode control feedback loop 400 ( Figure 4 ) can be compared to Figure 6A-6C The power differential gear transmission system is further realized. The differential topology can be realized according to equation (4) with a reduction ratio of 2, that is, in the driving mode, the final drive rotates 1 circle in the first direction, and the first side gear (T1) rotates 2 circles in the same direction, that is, Gear=2.

[0091] Alternatively, it is possible to coast at 200 RPM, ie, ωd=200.

[0092] Since the operating mode is coasting, the electric motor is stationary and not rotating, therefore: ωm=0.

[0093] According to equation (4), for a case where the rack speed (Trc) is 200 RPM and the first side gear speed (T1) is 0 RPM, the second side gear speed (T2) is 400 RPM.

[0094] In this example, 'Regen' is predefined as follows: Regen=0.9.

[0095] According to this example, when the user applies the brakes, the second side gear (T2) may slow down, the electric motor may begin to rotate, and the control system (e.g., the control system 22 ( implemented by the brake mode control feedback loop 400) may be activated. Figure 1)) can adjust the motor braking torque (ie, negative torque) so that the electric motor 670 can rotate at a speed that meets the SP requirement.

[0096] According to equation (2), for this example, SP = Regen × Gear = 0.9 * 2 = 1.8

[0097] To meet the SP requirement, PV should be equal to SP to avoid error 408: PV=ωm / ωd=ωm / 200=1.8 = >ωm = 360 Therefore, the desired brake mode motor speed according to the vehicle speed of this example is 360 RPM, which means that the electric motor rotates at a speed of 360 RPM in the same direction as the rack.

[0098] Therefore, according to equation (4), for a rack speed (Trc) of 200 RPM and a first side gear speed (T1) of 360 RPM, the second side gear speed (T2) is 40 RPM.

[0099] In some embodiments, the energy loss percentage on the friction brake (e.g., mechanical friction brake system 104, in this case, disc brake 614) is proportional to the 'brake mode' speed of the second side gear (T2) and the 'coasting mode' speed of the second side gear (T2), which is 10% in this example: 40 / 400=10% That is, only 10% of the braking energy will be dissipated through the friction brakes, while the rest of the energy can be used for regenerative braking.

[0100] Reference now Figure 7A-7D , Figure 7A-7D Schematic diagrams of several transmission system configurations according to embodiments of the present disclosure, all of which are capable of achieving a driving mode, a coasting mode, and a regenerative braking mode. Each of configurations 7A, 7B, 7C, and 7D may include a gear transmission system having two degrees of freedom, the gear transmission system may include a one-way mechanism (e.g., a one-way bearing) configured to limit the rotation of one of the elements of the gear transmission system during the driving mode, and further include a braking system configured to limit the rotation of one of the elements of the gear transmission system during the braking and regenerative braking modes.

[0101] In some embodiments, Fig. 7A The configuration is equivalent to a planetary gear transmission system, similar to Figure 2 The planetary gear system 100 and Figure 5A-5CThe gear transmission system 500 in the embodiment of the present invention. Configuration 7A includes a motor 12, which is configured to rotate a sun gear 101, which in turn can rotate one or more planetary gears 102, which in turn can rotate a planet carrier 122 and a ring gear 105, depending on the relevant operating mode. According to configuration 7A, the planet carrier 122 includes a one-way bearing 103, and the planet carrier 122 can rotate relative to the vehicle chassis 107 along the one-way bearing 103.

[0102] In some embodiments, Figure 7B The configuration is equivalent to a differential gear transmission system, such as Figure 6A-6C Configuration 7B includes a one-way bearing 603 , and the second side gear 604 can rotate along the one-way bearing 603 relative to the vehicle chassis 607 .

[0103] In some embodiments, Figure 7C The configuration is equivalent to a planetary gear transmission system, which includes a planet carrier 122, and the planet carrier 122 includes a one-way bearing 103, and the planet carrier can rotate relative to the sun gear 101 along the one-way bearing 103.

[0104] In some embodiments, Fig.7D The configuration is equivalent to a differential gear transmission system, which includes a rack 622 , the rack 622 includes a one-way bearing 603 , and the rack 622 can rotate relative to the first side gear 611 along the one-way bearing 603 .

[0105] Reference now Figure 8 , Figure 8 It is a summary of the embodiments according to the present disclosure. Figure 7A-7D Table 800 summarizes the details of the transmission system configurations, all of which are capable of achieving a driving mode, a coasting mode, and a regenerative braking mode. Figure 7A-7D The characteristics of different transmission systems that can achieve driving mode, coasting mode and regenerative braking mode.

[0106] According to some embodiments, 'motor' in table 800 represents a component of the transmission system that is equivalent to a motor, or a component that is directly connected to a motor. 'final drive' represents a component of the transmission system that is equivalent to a final drive, or a component that is directly connected to a final drive. 'unidirectional' represents a component of the transmission system that is forced to rotate in only one direction and relative to other components of the transmission system during a drive mode. 'brake component' represents a component of the transmission system that is connected to a mechanical brake system and is forced to reduce its rotational speed when the mechanical brake system is operated.

[0107] For example, configuration 'A' in table 800 represents a transmission system implementing a planetary gear, such as Fig. 7A and Figure 8 In configuration 'A', the components representing the electric motor 12 and connected to the electric motor 12 are sun gear 101 (similar to Figure 5A The sun gear 501 in FIG. 1 is represented by its speed 'Ts'. According to configuration 'A', the component representing the final drive is the ring gear 105 (similar to Figure 5A The ring gear 505 in the drive mode is represented by 'Tr'. According to configuration 'A', the component forced to move in only one direction during the drive mode is the planet carrier 122 (similar to Figure 5A According to configuration 'A', the planet carrier 122 is forced relative to the chassis 107 of the vehicle (similar to Figure 5A The chassis 507 in the planet carrier 122 moves in one direction. Therefore, the speed of the planet carrier 122 can be equal to or greater than zero 'Tc≥0'. In some embodiments, the one-way direction of the planet carrier 122 can be provided by a one-way bearing 103 (similar to Figure 5A In some embodiments, the brake component in the planetary gear system of configuration 'A' is the planet carrier 122. Therefore, the speed of the planet carrier 122 can be reduced to zero (Tc→0) to rotate the electric motor 12 for energy regeneration. The control parameters of configuration 'A' that can be implemented by the braking mode control algorithm 400 and equation (3) can be Gear=(-R) / S, and 0 <Regen<1。

[0108] According to some embodiments, configuration 'B' in table 800 represents a transmission system implementing a differential gear, such as Figure 7B and Figure 8 As shown and Figure 6A-6CDetailed in . In configuration 'B', the component representing the electric motor 12 and connected to the electric motor 12 is the first side gear 611, whose speed is represented by 'T1'. According to configuration 'B', the component representing the final drive is the rack 622, whose speed is represented by 'Trc'. According to configuration 'B', the component that is only allowed to move in a single direction during the driving mode is the second side gear 604. According to configuration 'B', the second side gear is forced to move in one direction relative to the chassis 607 of the vehicle. Therefore, the speed of the second side gear 604 can be equal to or greater than zero 'T2≥0'. In some embodiments, the unidirectional direction of the second side gear 604 can be specified by a one-way bearing 603. In some embodiments, the braking component in the differential gear system of configuration 'B' is the second side gear 604. Therefore, the speed of the second side gear 604 can be reduced to zero (T2→0) so as to cause the rotation of the electric motor 12 via the first side gear 611 for energy regeneration by the electric motor 12.

[0109] The control parameters of configuration 'B' that can be implemented by the braking mode control algorithm 400 and equation (4) can be Gear=2, and 0 <Regen<1。

[0110] According to some embodiments, configuration 'C' of table 800 represents a transmission system implementing a planetary gear system that includes a dual gear ratio, such as Figure 7C and Figure 8 As shown. According to configuration 'C', the component of the transmission system connected to the motor 12 is the sun gear 101, where the sun gear speed is represented by 'Ts'. The component connected to the final drive is the ring gear 105, whose speed is represented by 'Tr'. Unlike configuration 'A', in configuration 'C', the one-way bearing 103 is connected to the planet carrier 122, and the planet carrier 122 can be rotated relative to the sun 101 (such as Figure 7C ) rather than relative to the chassis 107 (as shown Fig. 7A ) as shown. That is, according to configuration 'C', the planet carrier 122 (whose speed is represented by 'Tc') is allowed to rotate in only one direction relative to the sun 101, for example via the one-way bearing 103, thereby enforcing the condition Tc ≥ Ts. In configuration 'C', the component connected to the mechanical braking system is the planet carrier 122. Therefore, the speed of the planet carrier 122 can be reduced to zero (Tc→0) in order to cause the electric motor 12 to rotate for energy regeneration by transferring torque to the electric motor 12. The control parameters of configuration 'C', which can be implemented as part of the braking mode control algorithm 400 and equation (3), can be Gear=-R / S, and 0 <Regen<1。 According to configuration 'C', during the drive mode, due to the one-way bearing 103, the sun 101 can rotate the planet carrier in the same direction at a 1:1 ratio, and therefore, according to equation (3), the planet carrier 122 can rotate the ring in the same direction at a 1:1 ratio, that is, a 1:1 ratio of the sun to the final drive is achieved. For example, according to equation (3), in the case where the motor 12 or the sun 101 rotates at a speed of 200RPM, Ts=Tc=Tr=200RPM.

[0111] According to configuration 'C', during the coasting mode, the planet carrier 122 rotates freely. Therefore, the ring 105 can rotate the planet gears 102, and the planet carrier 122 rotates according to equation (3), thereby making the sun 101 stationary and thus the electric motor 12 stationary. As in the example of configuration 7A, where the number of teeth of the sun gear is 16 and the number of teeth of the ring gear is 64, in the embodiment of the planetary gear, during the coasting mode, if the ring speed 'Tr' is 200RPM, the planet carrier speed 'Tc' is 160RPM, so as to make the sun gear speed 'Ts' equal to 0, because the sun gear 101 or the electric motor 12 should be stationary during the coasting mode.

[0112] According to configuration 'C', during the braking mode, the planet carrier 122 is restrained by the friction brake 114 because the friction brake 114, which is operated during the braking mode, is connected to the planet carrier 122. Therefore, the ring gear 105 can rotate the planet gears 102, which in turn can rotate the sun gear 101 according to equation (3) in the direction opposite to the direction of the ring rotation, and thus will not violate the restriction Tc≥Ts imposed by the one-way bearing 103. Rotating the sun 101 by mechanical force rather than electrical force enables the vehicle to regenerate energy during the braking mode. For example, if the ring speed is equal to 200RPM (for example, after coasting), and assuming that the speed of the planet carrier 'Tc' is equal to 16RPM, then according to equation (3), the motor speed 'Ts' should be equal to -720RPM, that is, the speed of the motor in the direction opposite to the direction in which the ring rotates is 720RPM.

[0113] According to configuration 'C', a low gear mode may exist. During the low gear mode, the brake may be fully engaged, thereby locking the planet carrier 122 and limiting the rotation of the planet carrier 122. The electric motor 12 may supply power in the reverse direction (i.e., opposite to the forward drive direction of the ring 105). The planetary gear 102 may be rotated by the sun 101, and the planetary gear 122 may cause the ring gear 105 according to equation (3) to rotate in the direction opposite to the sun rotation (i.e., in the forward drive direction) at a ratio determined by the properties of the planetary gear. For example, if the ring speed 'Tr' is equal to 200RPM and the planet carrier speed 'Tc' is equal to 0, then according to equation (3), the speed of the sun gear or the speed of the electric motor 'Ts' is equal to -800RPM, without violating the limit Tc≥Ts.

[0114] According to some embodiments, configuration 'D' of table 800 represents a transmission system implementing a semi-regenerative differential gear, such as Fig.7D As shown. According to configuration 'D', the component of the transmission system connected to the electric motor 12 is the first side gear 611, whose speed is represented by 'T1'. The component connected to the final drive is the rack 622, whose speed is represented by 'Trc'. In configuration 'D', the one-way bearing 603 is connected to the rack 622. That is, according to configuration 'D', the rack 622 is allowed to rotate only in one direction relative to the first side gear 611, for example, via the one-way bearing 103, so that the condition Trc≥T1 is satisfied. In configuration 'D', the component connected to the mechanical brake system 114 is the second side gear 604. Therefore, the speed of the second side gear 604 can be reduced to zero (T2→0) so as to rotate the electric motor 12 via the first side gear 611 for energy regeneration by the electric motor 12, and in this case, at least half of the kinetic energy is also dissipated via the mechanical brake, because Regen is defined as being greater than zero and less than 0.5.

[0115] The control parameters of configuration 'D' that can be implemented by the braking mode control algorithm 400 and equation (4) can be Gear=2, and 0 <Regen<0.5。

[0116] According to configuration 'D', during the driving mode, the electric motor 12 can be operated to drive the first side gear 611 to rotate. The rotation of the first side gear 611 can force the rack 622 to rotate in the allowed direction at a 1:1 ratio via the one-way bearing 603 to which the rack 622 is connected. The rotation of the rack 622 causes the rotation of the final drive, thereby enabling the vehicle in which the transmission gear of configuration 'D' is implemented to move. For example, if the number of turns of the first side gear 'T1' is equal to 1, then due to the 1:1 ratio, the number of turns of the rack 'Trc' is also equal to 1, and according to equation (4), the number of turns of the second side gear 'T2' is equal to 1.

[0117] According to configuration 'D', during the coasting mode, the rack 622 rotates freely, which can cause the second side gear 604 to rotate, thereby allowing the first side gear 611 to be stationary according to equation (4). For example, the number of turns of the rack can be the same as the number of turns in the driving mode, for example, Trc=1. And, in order to make the number of turns of the first side gear 'T1' equal to 0, that is, to make the first side gear in a stationary state, according to equation (4), the number of turns of the second side gear 'T2' should be equal to 2.

[0118] According to configuration 'D', during the braking mode, the rotation of the second side gear 604 is limited by the friction brake 614 (and possibly the caliper 624). Since the one-way bearing forces the condition Trc ≥ T1, it is obvious from equation (4) that Trc ≤ T2. That is, in the forward driving condition, braking the second side gear 'T2' to a stop will also stop the rack 'Trc', and the best energy regeneration ratio will be achieved when T1 = T2.

[0119] Therefore, the friction brakes will dissipate at least 50% of the energy, as shown by Regen < 0.5, since the friction brakes cannot rotate slower than the electric motor 12. However, on the other hand, the mechanical brakes can slow a vehicle implementing a transmission system of configuration 'D' to a complete stop.

[0120] It is noteworthy that operation under load is possible with any configuration of the transmission system according to the present disclosure, as the user can disengage the brakes at any time by simply releasing the brake handle or brake pedal.

[0121] According to some embodiments, no electrical energy is required to apply the friction brake system. Braking torque can be applied by the user via a brake handle or brake pedal at a level similar to current brake systems.

[0122] For any flow chart cited herein, it should be understood that the illustrated method is divided into discrete operations represented by the blocks of the flow chart only for convenience and clarity. Alternative methods of dividing the illustrated method into discrete operations can also obtain equivalent results. Such alternative methods of dividing the illustrated method into discrete operations should be understood to represent other embodiments of the illustrated method.

[0123] Similarly, it should be understood that, unless otherwise indicated, the order of execution of the operations represented by the blocks of any flowchart referenced herein is selected for convenience and clarity only. The operations of the illustrated method may be performed in an alternative order, or simultaneously, with equivalent results. Such reordering of the operations of the illustrated method should be understood to represent other embodiments of the illustrated method.

[0124] Different embodiments are disclosed herein. Features of certain embodiments may be combined with features of other embodiments; therefore, certain embodiments may be a combination of features of multiple embodiments. The foregoing description of the embodiments of the present disclosure is presented for the purpose of illustration and description. It is not intended to be exhaustive or to limit the disclosure to the precise form disclosed. It will be appreciated by those skilled in the art that, in view of the above teachings, many modifications, variations, substitutions, changes, and equivalents are possible. Therefore, it will be appreciated that the appended claims are intended to cover all such modifications and changes that fall within the true spirit of the disclosure.

[0125] While certain features of the disclosure have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will now occur to those of ordinary skill in the art. It is therefore to be understood that the appended claims are intended to cover all such modifications and changes that fall within the true spirit of the disclosure.

Claims

1. A powertrain for a vehicle, comprising: Electric motor; Final drive; a gear system having two degrees of freedom, the gear system comprising at least three components configured to rotate relative to each other, the gear system configured to transfer power from the electric motor to the final drive, wherein the gear transmission system includes a one-way mechanism connected to one of the at least three rotating components of the gear transmission system, the one-way mechanism being configured to reduce one of the two degrees of freedom by limiting rotation of the one component in a first direction during a powered driving mode of the powertrain, while the one-way mechanism is configured to enable free rotation of the one component in a second opposite direction during a coasting mode of the powertrain, thereby avoiding dragging of the electric motor; as well as a mechanical friction brake connected to the gear transmission system via a component of the at least three components, the mechanical friction brake being configured to reduce one of the two degrees of freedom by limiting rotation of the component to which the mechanical friction brake is connected during a braking mode of the powertrain to cause movement of the electric motor, thereby regenerating energy through the electric motor. 2 . The powertrain of claim 1 , wherein the mechanical friction brake is connected to the gear train and is not connected to the final drive.

3. The powertrain of claim 1, wherein the one-way mechanism is an overrunning clutch.

4. The powertrain of claim 1 , wherein the gear train includes planetary gears, and the at least three components include a sun gear rotatably connected to the electric motor and at least one planetary gear rotatably connected to a planet carrier.

5. The powertrain of claim 4, wherein the one-way mechanism is a one-way bearing incorporated as part of the planet carrier, the one-way bearing being configured to allow the planet carrier to rotate in a first direction and prevent the planet carrier from rotating in a second direction, the second direction being opposite to the first direction.

6. The powertrain of claim 5, wherein the mechanical friction brake is connected to the planet carrier, the mechanical friction brake being configured to slow down the rotation of the planet carrier and thereby mechanically force the electric motor to rotate via the forced rotation of the sun, thereby achieving regenerative braking.

7. The powertrain of claim 4, wherein the mechanical friction brake comprises a disc brake.

8. The powertrain of claim 1 , wherein the gear transmission system comprises a differential gear system, wherein the at least three components include a first side gear rotatably connected to the electric motor and a horizontal planetary gear, the horizontal planetary gear is rotatably connected to a rack, and wherein the horizontal planetary gear is further rotatably connected to a second side gear.

9. The powertrain of claim 8, wherein the one-way mechanism is a one-way bearing incorporated as part of the second side gear, the one-way bearing being configured to allow the second side gear to rotate in a first direction and prevent the second side gear from rotating in a second direction, the second direction being opposite to the first direction.

10. The powertrain of claim 8, wherein the mechanical friction brake comprises a disc brake connected to the second side gear, the disc brake being configured to slow down rotation of the second side gear and thereby mechanically force the electric motor to rotate via forced rotation of the first side gear, thereby achieving regenerative braking.

11. A vehicle gear transmission system, comprising: Electric motor; Final drive; a gear system having two degrees of freedom, the gear system comprising at least three components configured to rotate relative to each other, the gear system configured to transfer power from the electric motor to the final drive, wherein the gear transmission system includes a one-way mechanism connected to one of the at least three rotating components of the gear transmission system, the one-way mechanism being configured to reduce one of the two degrees of freedom by limiting rotation of the one component in a first direction during a powered driving mode of the powertrain, while the one-way mechanism is configured to enable free rotation of the one component in a second opposite direction during a coasting mode of the powertrain, thereby avoiding dragging of the electric motor; as well as a mechanical friction brake connected to the gear transmission system via a component of the at least three components, the mechanical friction brake configured to reduce one of the two degrees of freedom by limiting rotation of the component to which the mechanical friction brake is connected during a braking mode of the powertrain to cause movement of the electric motor to regenerate energy by the electric motor; as well as a control system configured to control the amount of the power supplied by the electric motor during the driving mode and to control the amount of negative torque applied by the electric motor during the regenerative braking mode, the control system comprising a processor configured to: Detecting braking mode; predefining a setpoint value based on (i) a gear ratio of the vehicle and (ii) a parameter modifiable according to a desired regeneration ratio; calculating a process value based on a ratio between a motor speed and a final drive speed; and An amount of negative torque required to make the process value equal to the set point value is determined, the negative torque being applied by the electric motor during the regenerative braking mode.

12. The vehicle gear transmission system of claim 11, wherein the desired regeneration ratio is determined by at least one of battery / capacitor state of charge (SOC), power rating, drive speed, motor load, terrain, temperature, or any combination thereof.

13. A method for controlling a braking mode in a vehicle, the vehicle comprising an electric motor, a final drive and a gear system, a mechanical friction brake, the gear system having two degrees of freedom, the gear system comprising at least three components configured to rotate relative to each other, the gear system configured to transfer power from the electric motor to the final drive, wherein the gear transmission system includes a one-way mechanism connected to one of the at least three rotating components of the gear transmission system, the one-way mechanism being configured to reduce one of the two degrees of freedom by limiting rotation of the one component in a first direction during a powered driving mode of the powertrain, while the one-way mechanism is configured to enable free rotation of the one component in a second opposite direction during a coasting mode of the powertrain, thereby avoiding dragging of the electric motor; the mechanical friction brake being connected to the gear transmission system via a component of the at least three components, the mechanical friction brake being configured to reduce one of the two degrees of freedom by limiting rotation of the component to which the mechanical friction brake is connected during a braking mode of the powertrain to induce movement of the electric motor to regenerate energy through the electric motor and a processor; The method comprises: Detecting braking mode; predefining a setpoint value based on (i) a gear ratio of the vehicle and (ii) a parameter modifiable according to a desired regeneration ratio; calculating a process value based on a ratio between a motor speed and a final drive speed; and An amount of negative torque required to make the process value equal to the set point value is determined, the negative torque being applied by the electric motor during a regenerative braking mode.

14. The method of claim 13, wherein detecting the braking mode comprises determining that the motor is rotating and further determining that the user is not applying throttle.

15. The method of claim 13, wherein the step of calculating the process value includes sensing a motor speed and sensing a final drive speed via respective speed sensors.

16. The method of claim 13, further comprising calculating an error representing a difference between the process value and the set point value.

17. The method of claim 13, wherein the desired regeneration ratio is determined by at least one of battery / capacitor state of charge (SOC), power rating, drive speed, motor load, terrain, temperature, or any combination thereof.

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