Drive system with gearing for e-bikes or e-trikes or muscle-powered vehicles

Abstract

The invention relates to a drive system with gearing for e-bikes or e-trikes in particular with variable transmission ratio or muscle-powered vehicles. The aim of the invention is to provide a drive system which provides sufficient torque and sufficient power in all rotational speed ranges and all driving situations with the best possible efficiency of the overall system, and which is also lightweight and compact. According to the invention, in a drive system having an electric drive assistance and electric motors that are generally centrally arranged drive motors, which act on a pedal axle (6) with a chain ring (20) arranged thereon, a battery pack and at least one power electronics system (16) are interconnected and mounted on the vehicle in order to supply energy. In a novel manner, one electric motor (1) is optimised for lower rotational speeds and a second electric motor (2) is optimised for higher rotational speeds. Both are designed in such a way that an improved optimised torque curve is achieved when the two electric motors (1) and (2) are suitably controlled. The two electric motors (1) and (2) are coupled to a gearing (3) on a common drive shaft (4). The advantage is that one electric motor is optimised in such a manner that in a relatively low travel-speed range it feeds in a maximum torque and is operated in the optimum operating point range of the motor characteristic curve. The second electric motor is optimised for higher speeds, wherein a corresponding torque can be fed in at higher travel speeds and the motor can likewise be operated largely in the optimum operating point range. By splitting the working ranges among the respective optimised motors, the performance of the entire system can be increased and the energy provided by the battery can be better utilised.

Description

[0001] Drive system with gearbox for eBikes or eTrikes or muscle-powered vehicles

[0002] The invention relates to a drive system with gearbox for eBikes or eTrikes or muscle-powered vehicles, in particular with constant or variable gear ratio.

[0003] There are numerous drive systems for electric bicycles that have been offered and advertised on the market in recent years. A significant number of these electric bicycles have an electric drive located near the bottom bracket or integrated directly into the bottom bracket as a complete drive system. These drive systems are often referred to as mid-drive motors. With these systems, the torque generated by the rider's muscle power and the torque provided by the electric motor are typically combined and added using a gearbox, then transmitted via a chain or belt to the rear wheel of an e-bike or e-trike. To ensure a consistent cadence for the rider, adapted to their physical condition and regardless of terrain, these bicycles, like regular bicycles, are equipped with gears.Derailleur gears are typically the preferred choice for e-bikes. However, derailleur gears have the disadvantage of wearing out relatively quickly, especially when used with high-performance electric motors. In addition to derailleur gears, hub gears are also increasingly being used. These usually contain switchable planetary gears within the hub housing at the center of the rear wheel or rear axle. However, gear systems require a certain amount of installation space and increase the weight of the e-bike.

[0004] High-performance mid-drive motors now often deliver torque between 80 and 120 Newton meters. Generating this torque energy-efficiently from the limited battery capacity and converting it into desired performance and advantageous handling is a complex process. This often involves accepting power losses, or the drive motors are rarely optimized due to space constraints. Electric motors currently available on the market often represent compromises, exhibiting relatively low efficiency depending on their operating point and consuming unnecessary energy, which can reduce the driving range depending on the battery size.Therefore, the requirements are twofold: to provide the highest possible torque, to make the drives as small and compact as possible, and to keep the battery size from becoming too large, as this is not only inefficient but also negatively impacts the overall weight of the vehicle. Commercially available shifting or transmission systems also have the disadvantage of often only allowing for certain fixed, discrete gear ratios. However, different users in different work environments require different gear ratios and optimized drive torques. Depending on the specific application, the overall bandwidth of the drive system can also pose problems. The lowest universal gear, for example on an electric mountain bike, should be 32 / 50 (1 / i = 0.64). This means that the rear wheel only travels 32 / 50 of its circumference with each crank revolution.So-called "speed pedelecs," on the other hand, have a top speed of 45 km / h. If these fast electric bicycles also have a small wheel circumference, they require an overall gear ratio of 60 / 10. To meet these requirements, it is essential that the drive systems used not only operate energy-efficiently at a single operating point but exhibit optimized energy efficiency across the entire speed and power range. Achieving all these points is difficult simply through variations of existing gearbox designs.

[0005] From DE 10 2010 009 649 A1, an electric auxiliary drive for vehicles with pedal crank drive is known, in which two pedal cranks are arranged on a bottom bracket shaft and an electrically driven motor is arranged in the immediate vicinity of the bottom bracket shaft, the motor shaft being arranged parallel and not coaxial to the bottom bracket shaft. A hollow shaft is arranged parallel to the bottom bracket shaft, which has at least one drive wheel for a traction transmission, the at least one drive wheel being connected via a traction element to the wheel that propels the vehicle on the road. At least one intermediate shaft is located between the motor shaft and the hollow shaft. The motor shaft is located in front of the bottom bracket shaft in the direction of travel. The bottom bracket shaft, the hollow shaft, and at least one intermediate shaft are arranged in a cylindrical installation space formed by the rotation of the crank arms.This solution is structurally complex and requires a considerable amount of installation space in the area of ​​the bottom bracket.

[0006] From US Patent 2012 / 0012412 A1, a different drive system is known in which two electrically driven motors are arranged near the bottom bracket axle. A planetary gear set is located inside a housing, with the ring gear of the set forming the output, and the drive power is transmitted to a sprocket for the rear wheel only via a hollow shaft. In this system, neither the electrically driven motor nor its intermediate shafts are directly connected to the bottom bracket axle; instead, the electrically driven motor and its intermediate shafts are directly connected to the output gear. This system has the disadvantage that the motor connected to the sun gear, for example, has to absorb high reaction torques when pedaling out of the saddle. Torques of up to 250 Nm are generated when pedaling out of the saddle. This would then feel like a slight "slippage" because the respective coupled motor cannot maintain the target speed.Another way of describing this disadvantageous circumstance would be an unwanted change in gear ratio when the driver applies high pedal forces.

[0007] Other technical solutions, for example according to DE 10 2009 045 447 Al, or according to DE 10 2016 224 314 Al or according to DE 10 2017 219 398 Al, also have similar disadvantages.

[0008] Drive systems according to EP 3 168 125 A1 and similar designs are known in various configurations, wherein exactly one electrically driven motor and its intermediate shafts are connected to the bottom bracket axle via a freewheel, and wherein no electrically driven motor and its intermediate shafts are directly connected to the output wheel. If an electrically driven motor is directly connected to the output wheel, as shown in US 2012 / 0012412 A1, this is a disadvantage because, for example, during steep uphill riding at low speed, this motor cannot operate at its optimal operating point. It is therefore indirectly connected to the rear wheel without a gear system and its rotational speed must cover the entire rotational range of the rear wheel. This disadvantage is also precisely described in DE 10 2010 009 649 A1 and corresponds to the disadvantage of a wheel hub motor.

[0009] According to the technical solution of the EP 3 168 125 Al, an electric motor connected to the bottom bracket axle can be operated close to its operating point, as its rotational speed is always proportional to the rider's cadence and is almost at a specific point. The varying riding speed, depending on the terrain, is adjusted in the EP 3 168 125 Al via the downstream hub gear or derailleur gear system.

[0010] The object of the invention is to create a drive system with a gearbox for e-bikes, e-trikes, or muscle-powered vehicles that provides sufficient torque in all speed ranges and all driving situations with the best possible overall system efficiency, and is also energy-efficient, lightweight, and compact. This object is achieved according to the invention by the features of the first claim. Further advantageous embodiments of the invention are the subject of the dependent claims.In the drive system according to the invention, with a gearbox for e-bikes or e-trikes or other muscle-powered vehicles with electric drive assistance, and with the electric motors generally arranged as a central drive acting on a pedal axle 6 with a chainring 20 or pulley mounted thereon, a battery pack and at least one control unit 16 are arranged and connected on the vehicle for energy supply. In a novel manner, one electric motor 1 is optimized exclusively for lower speeds and a second electric motor 2 is optimized only for higher speeds. Both are designed such that, with suitable control of the two electric motors 1 and 2, an improved torque curve is achieved with optimized energy efficiency. The two electric motors 1 and 2 are also coupled to a gearbox with a constant or variable gear ratio 3 via a common drive shaft 4.

[0011] In a particularly advantageous embodiment of the drive system according to the invention, one electric motor 1 is designed as an external rotor motor and the other electric motor 2 as an internal rotor motor. The external rotor motor, in particular, can generate high torques with optimal efficiency at low speeds, which is especially advantageous when starting, driving off-road, and driving uphill. If, on the other hand, a higher speed is required, for example, when the vehicle being driven is traveling at high speeds, the internal rotor motor, with its optimized efficiency at higher speeds, is used to provide drive support. According to the invention, both motors can operate together in driving situations with particularly high torque or power requirements.

[0012] Depending on the type of vehicle to be driven or its design, the two electric motors 1 and 2 can optionally be arranged on a common drive axle 4 of the drive system on only one side of the drive system or also on the left and right outer sides of the drive system.

[0013] Furthermore, it is advantageous if, in a specific embodiment of the drive system according to the invention with a transmission with constant or variable ratio 3, the electric motors 1 and 2 are coupled to the common drive shaft 4 by means of interposed freewheels 22. This allows one or, optionally, both electric motors 1 and 2 to be decoupled, so that, for example, at high speeds the electric motor intended for low speeds does not have to be driven. Depending on the type of vehicle and its respective area of ​​application or purpose, it is possible in the drive system according to the invention to optionally design the transmission with constant or variable ratio 3 as a single-, two- or multi-stage spur gear transmission 14, or as a planetary gear transmission, or as a continuously variable transmission, or as a manual transmission, or any other transmission, or as a combination of the aforementioned.

[0014] It is a significant advantage if, in a drive system with a gearbox, both electric motors 1 and 2 are designed to be controllable via a common, connected control unit 16 with only one controller 23. However, it is also possible to design and connect a separate control unit 16 for electric motor 1 and a second separate control unit 16 for electric motor 2. A preferred control unit 16 advantageously includes at least one controller 23 for calculating the timing of the phase control of the respective electric motors 1 and 2, and two power drivers 24 for supplying the motor currents. The controller 23 acquires the signals from the sensors installed and connected in the electric motors 1 and 2 (in particular for determining rotor angle, speed, torque, etc.) and calculates the optimal motor currents from this data.According to these calculations, the controller 23 controls the two power drivers 24 in such a way that each of the two electric motors 1, 2 can be operated with optimal efficiency according to the selected driving situation. This ensures that, as a rule, only one electric motor is driven during acceleration, which has a high starting torque.

[0015] While the other electric motor can propel the vehicle alone at higher speeds, both electric motors operate at or near their optimal operating point according to their motor characteristics. If needed, both electric motors can also be operated simultaneously to achieve even higher torques or power outputs.

[0016] It is advantageous if the two electric motors 1 and 2 are designed so that they can both be controlled by a common commutation sensor 13. However, it is also possible to control them with separate commutation sensors 13.

[0017] The control unit 16, which belongs to the drive system with gearbox and is connected to the electrical components, is designed such that the torque sensors 25, and / or speed sensors 11, and / or tilt sensors 12, and / or commutation sensors 13, arranged at suitable locations on the drive system or on the vehicle, can be evaluated and appropriately controlled or displayed. Preferably, these sensors 11, 12, 13, and / or 25 are also installed and connected in the control unit 16. Furthermore, the drive system according to the invention has suitable interfaces to other active components of the e-bike, e-trike, or human-powered vehicle, which can influence the behavior of the entire drive system as needed.In the drive system according to the invention, the circuit of the eBike can provide signals for the currently set switching state, which can then be evaluated for controlling the optimal operating point of the drive system and included in the control.

[0018] Furthermore, suitably arranged interfaces can be used to coordinate the transmission and drive system in such a way that, when changing gears, the torque of the entire drive system or the electric motor currently driving the transmission is briefly reduced to enable smooth, quiet and low-wear shifting during the shifting process.

[0019] Additionally, it is also possible to evaluate the brake activation status and control the behavior of the drive system accordingly, so that, for example, no drive torque is generated when the brake is applied. Generally, it is sufficient to evaluate only the front wheel brake (18), even if an ABS system is sometimes installed there.

[0020] The advantage of the drive system according to the invention, with a gearbox and these two differently designed electric motors 1 and 2 as the drive, is that one electric motor is optimized to deliver maximum torque at relatively low speeds and can operate largely within its optimal operating point. The second electric motor, on the other hand, is optimized for operation at higher speeds, allowing it to deliver a correspondingly adjusted torque at these higher speeds and also operate largely within its optimal operating point. This division of operating ranges between the respective optimized electric motors increases the performance of the entire system and allows for better utilization of the energy supplied by the battery.It is conceivable to either achieve a greater driving range with a battery of the same size or, for the same driving range, to build a smaller battery to save weight. This also enables faster acceleration from a standstill, which improves traffic flow on public roads. The two electric motors are controlled in such a way that they can be operated individually or together as needed to provide the required torque and power. By using a special low-speed motor in one of the electric motors, it can provide more torque than conventional drive systems. There is no reduction in battery range.Due to the operation of the two electric motors near their optimal operating points and their continuous high-efficiency operation, the supplied energy is used optimally, thus increasing the battery range. Furthermore, it is possible to implement a simple circuit for controlling the two electric motors 1 and 2. It is also advantageous to position various sensors 11, 12, 13, and 25 at suitable locations to detect the driving situation. Their signals can be individually or appropriately combined and evaluated, and then integrated into the control characteristics to optimize their regulation.

[0021] The invention will be described in more detail below with reference to Figures 1 to 4 in preferred embodiments.

[0022] Fig. 1 schematically shows a drive system with both electric motors 1 and 2 on one side.

[0023] Fig. 2 schematically shows a drive system with electric motors 1 and 2 arranged on both sides externally.

[0024] Fig. 3 shows a side view of a drive system with the electric motors 1 and 2 arranged externally on the central drive axis 4, where electric motor 1 is designed as an external rotor and electric motor 2 as an internal rotor.

[0025] Fig. 4 shows the other side of the drive system with two electric motors 1 and 2 on a common drive shaft 4.

[0026] Fig. 5 shows two electric motors 1, 2 with a three-stage spur gear unit 14

[0027] Fig. 6 shows two electric motors with electronics for motor control and also for additionally arranged sensors.

[0028] Fig. 7 shows a stylized drawing of an eBike with a mid-drive motor, which is combined with other active components.

[0029] Components, such as the brake and gearshift, communicate with each other. Fig. 8 schematically shows the structure and function of a control unit 16. Fig. 1 schematically shows, as a first embodiment, the structure of a drive system with both electric motors 1 and 2 on one side. This has the advantage that, for example, on the side opposite the electric motors 1 and 2, there is enough space for an arrangement of a chainring 20 or pulley as an output on the pedal axle 6. A three-stage spur gear transmission 14 is arranged between the common drive shaft 4 and the pedal axle 6. This has the advantage of a simple transmission design and can be made small and compact in terms of volume. It is suitable for translating or transmitting the torques generated by the two electric motors 1 and 2, arranged on a common electric motor shaft 5, to the pedal axle 6 with minimal loss.In this embodiment of the invention, the electric motor shaft 5 and the drive shaft 4 are designed as a single continuous shaft. However, these can also be designed as segmented shafts. As is generally known, a freewheel 22, or two freewheels 22, are installed in the pedal shaft 6, which is designed as a hollow shaft, in order to completely decouple the electric motors 1 and 2 from the pedals in certain driving situations.

[0030] Figure 2 schematically shows another drive system with electric motors 1 and 2 arranged on both outer sides. Here too, both electric motors 1 and 2, one being an internal rotor and the other an external rotor, are arranged on a continuous drive shaft 4, but on the left and right outer sides. The three-stage spur gear transmission 14 is designed here with a constant gear ratio, but it is also possible to design the drive so that other transmissions with variable gear ratios 8 can be integrated and arranged. The arrangement of two freewheels 22, each between the two electric motor shafts 5 and the drive shaft 4, and one or two further freewheels 22 in the pedal shaft 6, is also shown here in order to decouple one or the other, or both, as well as the transmission, from the pedals, depending on the driving situation.

[0031] Fig. 3 shows an external view of a drive system with the electric motors 1 and 2 arranged externally on the central drive shaft 4, with electric motor 1 being an external rotor and electric motor 2 an internal rotor. The gearbox 3 is enclosed in a separate gearbox housing 8. The pedal axle 6 with the pedal mount 7, the chainring mount 9, and the bearing 10 are visible. The covers of the two electric motors are not shown. Four drive block mounts 17 are arranged on the gearbox housing 8, with which the drive block 15 can be attached to the frame 21 of an e-bike, e-trike, or human-powered vehicle. Fig. 4 shows the other side of the drive system with two electric motors 1 and 2 on a common drive shaft 4 and the gearbox housing 8, including the bearing 10 of the pedal axle 6 with the pedal mount 7 mounted thereon.

[0032] Figure 5 shows the two electric motors 1 and 2 with a preferably arranged three-stage spur gear unit 14 without a gearbox housing 8, i.e., the internal structure of a drive system according to the invention with a possible configuration of the individual gears. The bearings 10 of both the pedal axle 6 and the electric motor shaft 5 are visible. The pedal mounts 7 are formed on the pedal axle 6, and the chainring mount 9, which is secured with a union nut, is shown. A helical gear is preferably arranged on the drive shaft 4 to enable optimal torque transmission from the drive shaft 4 to the spur gear unit 14.

[0033] Fig. 6 shows the same internal structure from the other side, with the two electric motors 1, 2 and the control unit 16. Its electronic circuit board contains all components for motor control and preferably also for the arrangement of additional sensors, such as one or two commutation sensors 13 and / or speed sensors 11, at least one tilt sensor 12, and optionally a torque sensor 25, as well as a controller 23 and two power drivers 24. Their exact arrangements are variable and therefore not immediately apparent from the drawing. On this side of the drive system, the bearings 10 of the pedal axle 6 and a transmission shaft are visible. These bearings 10 are correspondingly fixed in recesses in the transmission housing 8.

[0034] Figure 7 shows a stylized e-bike with a mid-drive motor, i.e., the drive unit 15 is arranged and attached to the bottom bracket area on or within the frame 21 of an e-bike. Suitable sensors are also provided on both the brakes 18 and the gear shifter 19 so that their signals can be transmitted to the control unit 16 via connecting lines 26. By enabling communication between the individual components, such as the brakes 18 and gear shifter 19, and the control unit, the torque of the entire drive system, or of the currently driving electric motor 1 or 2, is briefly reduced when changing gears. This ensures smooth, quiet, and low-wear shifting during the shifting process. Additionally, the control unit 16 can detect whether braking is being initiated, so that when one or both brakes 18 are applied, no drive torque is generated. Figure 7 illustrates this.Figure 8 schematically shows the structure and operation of a preferred embodiment of a simple control unit 16. The signals from a number of different possible sensors (1, 2, n), which are installed depending on the embodiment, are connected to this unit. The controller 23 processes all the incoming signals and controls the two power drivers 24 so that the electric motors 1 and 2 are controlled according to the selected driving characteristics.

[0035] The drive system according to the invention with gearbox and the two correspondingly designed electric motors 1 and 2 is preferably applicable for eBikes, eTrikes or muscle-powered vehicles.

[0036] Reference symbol list

[0037] 1 electric motor 1

[0038] 2 electric motors

[0039] 3 gearboxes with constant or variable ratio

[0040] 4 common drive shaft

[0041] 5 Electric motor shaft

[0042] 6 Pedal axle

[0043] 7 Pedal mount

[0044] 8 Gearbox housings

[0045] 9 chainring mount

[0046] 10 storage locations

[0047] 11 Speed ​​sensor

[0048] 12 Tilt sensor

[0049] 13 Commutation sensor

[0050] 14 Spur gear units

[0051] 15 Drive block

[0052] 16 Control unit

[0053] 17 Drive block suspension

[0054] 18 brake

[0055] 19 Circuit

[0056] 20 chainring

[0057] 21 frames

[0058] 22 Freewheel

[0059] 23 controllers

[0060] 24 performance drivers

[0061] 25 Torque sensor

[0062] 26 connecting lines

Claims

Patent claims:

1. Drive system with gearbox for eBikes, eTrikes or muscle-powered vehicles with two drive motors (1 and 2), a chainring or pulley which are coupled via a gearbox (3) and connected power electronics (16), characterized in that an electric motor (1) is optimized for lower speeds and an electric motor (2) is optimized for higher speeds and the electric motors (1, 2) are coupled to a gearbox (3) by means of a common drive shaft (4).

2. Drive system with gearbox according to claim 1, characterized in that the electric motor (1) is designed as an external rotor motor and the electric motor (2) as an internal rotor motor.

3. Drive system with gearbox according to claim 1, characterized in that the electric motors (1 and 2) are arranged on one side of the drive system on a common drive shaft (4).

4. Drive system with gearbox according to claim 1 characterized in that the electric motors (1 and 2) are arranged on a common drive shaft (4) to the left and right of the drive system.

5. Drive system with gearbox according to claim 1, characterized in that the electric motors (1 and 2) are coupled directly or by means of intermediate freewheels (22) to the common drive shaft (4).

6. Drive system with transmission according to claim 1, characterized in that the transmission (3) is designed as a single-, two- or multi-stage spur gear transmission (14) or as a planetary gear transmission or as a continuously variable transmission or gearbox or any other transmission or as a combination of the aforementioned.

7. Drive system with gearbox according to claim 1, characterized in that both electric motors (1 and 2) are connected to a common control unit (16) or separate controllers (23) are connected to each electric motor (1 and 2).

8. Drive system with gearbox according to claim 7, characterized in that a controller (23) and two power drivers (24) are arranged and switched in the control unit (16).

9. Drive system with gearbox according to claim 1, characterized in that the electric motors (1 and 2) are controlled by a common commutation sensor (13) or by separate commutation sensors (13).

10. Drive system with gearbox according to claim 1, characterized in that one or more speed sensors (11) and / or one or more tilt sensors (12) are arranged at suitable locations.

11. Drive system with gearbox according to claim 1, characterized in that the drive system has suitable interfaces to other active components of the eBike or eTrike that influence the behavior of the drive system.

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