Dual-state drivetrain based on power-split hybridisation for electric bikes and control system thereof

Abstract

The invention firstly relates to a dual-state drivetrain based on power-split hybridisation for e-bikes comprising a gearbox (CS), with an electric motor (eM), a reducer (ReM), and a power-split mechanism (PS) based on planetary gears, pedalling power entering through the ring gear, the power-split mechanism including a free wheel (Fwps) to prevent the ring gear from moving faster than the sun gear, thereby generating a rigid solid state that varies the transmission ratio and protects the motor from stresses that would cause same to brake. The invention also relates to a control system based on cadence (Nn) for the hybrid drivetrain (0), which allows the user to select a programmed cadence Nn(prog); and a control method that distinguishes a proportional-power parallel mode and an adaptive mode such that the gearbox (CS) is converted into an assisted selector.

Description

[0001] Dual-State Drive via Power Divider Hybridization for Electric Bicycles and Their Control System Technical Field

[0002] The present invention belongs to the field of technology relating to hybrid drive systems and mechanisms for vehicles, and more specifically, to its application to electric bicycles, known as e-bikes.

[0003] Within hybrid drive systems: series, parallel, and by means of a power divider; the present invention focuses on the latter case, also known as power-split hybridization, in its application to e-bikes, where a human power input — at low speed and with very high torque peaks — is combined with a power input by means of an electric motor — at high speed —, to achieve a mechanical output power towards a wheel — at low speed —.

[0004] STATE OF THE ART

[0005] In the field of e-bikes, the following four hybridization systems are widely known:

[0006] • Parallel hybridization: where an electric motor adds torque to boost power output. This configuration is the one most commonly used in e-bikes on the market.

[0007] • Series hybridization: where the mechanical energy from pedaling is used solely to generate electricity via an electric generator. The power output is provided exclusively by an electric motor, which uses energy supplied by a battery or by the aforementioned generator. This system is used in Schaeffler's "Free Drive" chainless electric drive system for bicycles (patent DE102011082082A1).

[0008] • Power-split hybridization: where an electric machine—motor / generator—adds / subtracts speed from another power source, at least partially muscular. In this case, an overlapping gear—also called a power-split mechanism, speed coupling, or simply "power-split"—is used, such as a planetary gear. This transmission has a first member, where at least the muscular power of a cyclist is received, either directly from the crankset or through any interposed transmission mechanism, such as a chain and sprocket; a second member, where the power from the electric machine is received; and a third transmission member, where the power, the sum of the two previous ones, is output, with the corresponding torques, or moments, always remaining proportional between any two of the three members.In the e-bike market, its application in bicycles with a single electric motor is not well known, but there are many patents proposing its use, such as US9758212B2 from BOSCH. Also worth mentioning is patent WO2024170938A1, from the same inventor as the present invention, which addresses power-split hybridization using a "bicyclic" gear, and Spanish patent P202430744, which employs a bicyclic-epicycloidal combination to achieve a higher multiplication ratio.

[0009] • e-CVT systems: These combine power-split and parallel hybridization, with the former providing additional speed and the latter additional torque. The result is electric assistance with a wide gear range, effectively functioning as a gearbox. Currently, the only system available in the bicycle market is the E2 Drives system — WO2016034574A1, US11383791B2 and US2022274670A1 — marketed by Decathlon under the OWURll brand. This is an e-CVT with parallel hybridization at the input.

[0010] Since regulations stipulate that all electric bicycles must cut off their assistance once they exceed 25 km / h, e-bikes are equipped with a speed sensor. This sensor can be external or internal to the bicycle's drive system, and it typically measures the wheel's rotational speed, calculating the bicycle's speed based on the wheel's diameter.

[0011] In the present invention, we focus on a powersplit hybrid system with a single electric motor. Therefore, these are bicycle systems that combine this electric drive with conventional mechanical gear changes, whether by means of a derailleur and cassette, internal gears, or other means, and whether actuated mechanically or electronically.

[0012] As is already widely known, parallel hybrid electric drive systems, conventional in electric bicycles, have the drawback that they need a torque sensor, which, in addition to increasing the cost, generates delays both to start and to stop pushing when the cyclist suddenly stops pedaling in the face of a potential obstacle; thus resulting in a critical component in terms of the perceived quality of use and the overall reliability of the system.

[0013] Electric drive systems with power-split hybridization have a number of disadvantages that have led to their limited or nonexistent use to date. These disadvantages have been minimized by the present inventor's patent ES3034822A1, relating to a cadence control procedure for a power-split hybrid drive applicable to electric bicycles. However, there are still two aspects in which these types of systems can be improved:

[0014] • The first problem to solve would be minimizing the sudden acceleration of the cyclist's legs in the event that the motor cannot overcome a torque peak induced by the cyclist, since in that case the motor would brake rapidly and be perceived by the user as motor slippage; and

[0015] • The second problem to solve would be to minimize the negatively perceived effect on the cyclist when selecting an increase in the level of electric assistance, since, with the torques linked by the power-split, when the motor induces significant acceleration, the cyclist has to endure an additional strain due to the sudden increase in torque, which is not perceived as assistance.

[0016] SUMMARY OF THE INVENTION

[0017] The present invention relates to electric assistance in the propulsion of bicycles and other pedal-powered vehicles that have at least one mechanical gear-changing system — regardless of whether it is electrically / electronically operated, by cable pull, or other means — constituting a hybrid system, where human mechanical power is combined with the power of an electric machine, comprising a hybrid drive and a control system.

[0018] This invention applies both to drives located upstream of the gear change of the pedal vehicle — in the area of ​​the bottom bracket, usually called mid-drive motors — and to drives located downstream of the gear change — such as the drives on the rear wheel of the bicycle in the case of hub motors —. A first object of the present invention consists of a hybrid drive by means of power-split.

[0019] A second object of the present invention consists of a control system for said drive.

[0020] The hybrid power-split drive will employ an electric machine — eM — , a reducer — ReM — , a power-split mechanism — PS — , and at least one one-way clutch element or freewheel mechanism.

[0021] The control system comprises at least some means of measuring certain external variables, an electronic control unit or ECU, a human-machine interface or HMI, and a control procedure.

[0022] — FIRST OBJECT OF THE PRESENT INVENTION:

[0023] For the hybrid drive that is the subject of the present invention, the use of a power-split mechanism is proposed, consisting of an epicyclic or planetary gear, comprising a sun gear, a ring gear, planet gears (simple or compound), and a planet carrier.

[0024] Where said power-split mechanism has:

[0025] • a first transmission member, which integrally comprises the crown gear with a number of teeth Zr, and in use, is responsible for receiving the muscular power of a cyclist, either from a bottom bracket axle or through any interposed transmission mechanism, for example, a chain and a sprocket;

[0026] • a second transmission member, which integrally comprises the sun gear with a number of teeth Zs, and in use, receives power from the motor or electric machine through a reducer comprising one or more stages with a total reduction ratio equal to GReM, and, preferably, also through some one-way clutch element or freewheel mechanism (known as “Free-wheel” or “one-way clutch” in English) which, when pedaling without electric assistance, would mechanically disconnect the motor, preventing it from being pulled along, which we will call the “motor freewheel”;

[0027] • A third transmission member, integrally comprising the planet carrier, transmits an output power that is the sum of the two previous members minus mechanical transmission losses. Furthermore, this hybrid drive incorporates at least one freewheel mechanism between any two of the three transmission members, preventing the first transmission member from achieving a rotational speed higher than that of either of the other two. In this way, either the three transmission members behave as a rigid body with a single rotational speed, or the speed of the third member—N3—is obtained from the combination of the speeds of the first—Ni—and the second member—N2—, as indicated by Willis' equation for planetary gears.Preferably, this freewheel will be located between the second and first transmission members, as this is where it will have to bear the least load when the freewheel operates, resulting in the second member being driven by the first member. We will refer to this freewheel as the "power-split freewheel."

[0028] This allows for a mechanical system in which two distinct operating states can be defined based on the speed ratio between its members:

[0029] • Rigid state: we define this as the state in which Ni = N2 = N3, so the power-split mechanism functions kinematically as a rigid body — generally when the power-split freewheel is engaged —. In the preferred case where there is also a motor freewheel, the motor could be either stationary, moving at a certain speed without applying torque to the second transmission member, or applying a certain torque to the second transmission member, which would always be less than a critical torque T2 C The critical pair T2 C is obtained as a multiple K2 of the input pair through the first member (T2 C= K2 T1). The multiple is calculated as K2 = 1 / b where b is the “basic ratio” of the reducer — in the case of a simple planetary gear it is b=Zr / Zs, and in the case of a compound planetary gear of the “stepped planets” type b=(ZprZr) / (Zs Zp2) — . In the non-preferred case in which a freewheel of the motor is not used, when pedaling without assistance the motor would be driven, either without excitation, or generating electrical power — for example to recharge the battery — .

[0030] • Power-split state: We define this as the state in which N2 > Ni, so it is known that the power-split's freewheel has ceased to act and the torque in the second transmission member remains permanently proportional to Ti, with T2=K2'TI — logically coinciding with the critical torque —. In this state, the power-split combines the two inputs — first and second transmission members — into the output — third transmission member —, according to Willis' equation: (1+b)' N3= N2+ b' Ni. In this state, the torque or moment ratios obtained between any two of the three transmission members are constant. Between the third and the first, we have T3 / T1 = K3 = (1 +b) / b > 1. Between the second and first members, we have T2 / T1 = K2 = 1 / b < 1.

[0031] Therefore, we can define the first object of the present invention as “dual state drive by means of power-split hybridization”, which we will also refer to simply as “hybrid drive”.

[0032] The freewheeling of the power-split is key to the operation of the system since it is what allows the existence of the two states.

[0033] The fact that human power input is through the crown gear and not the planet carrier has two implications that are not obvious:

[0034] • When power is applied, the directions of rotation of the three transmission members are the same, making it possible to use the power-split freewheel.

[0035] • When transitioning from the solid state to the power-split state, the torque ratio between the third and first transmission members changes from 1:1 to Ks:1, with K3 always greater than one. Therefore, the torque the cyclist must withstand is reduced compared to that imposed by the bicycle's dynamics. This change of state is equivalent to shifting to a lower gear.

[0036] In a first preferred embodiment, to prevent the motor from being dragged when pedaling without electric assistance, the aforementioned motor freewheel would be used, connected to the mechanical transmission between the electric motor and the second transmission member. In a second embodiment, this freewheel would not be used, allowing the motor's drag to generate electricity to recharge the batteries.

[0037] Regarding the hybrid drive architecture, it can have either a mid-drive motor or a hub motor configuration—mounted on the drive wheel. In the first case, the power-split unit can be coaxial with the bottom bracket axle, but this is not mandatory. The motor, in turn, can be coaxial, parallel, or in some other configuration relative to the power-split unit. In the case of a hub motor, both the power-split unit and the motor are coaxially configured with the axle of the drive wheel.

[0038] — SECOND OBJECT OF THE PRESENT INVENTION: With regard to the second object of the present invention, the control system employs the so-called “rigid state” to mitigate sudden accelerations in pedaling cadence in response to torque peaks that exceed the capacity of the electric motor. To this end, a control system based on pedaling cadence is implemented, such that significant assistance is only provided to the power-split — and, consequently, the “power-split state” is activated — at a cruising cadence — preselected by the user — and not when the cadence is low, when high torque peaks occur.

[0039] To approximate this desired behavior under all conditions, we establish at least two operating modes at the control procedure level:

[0040] • PARALLEL mode, which includes in one case the rigid state; and in another case the power-split state when the rotational speed is very close to that of the rigid state (N2 > Ni, but N2 ~ Ni);

[0041] • ADAPTIVE mode, which always occurs in power-split mode. In this way, as a preferred option, the user could choose to select assistance primarily in torque until reaching the selected cruising speed, or forgo assistance until that threshold is reached.

[0042] The control system comprises at least:

[0043] • A main control procedure, programmed in the electronic control unit, which is responsible for acquiring signals, processing them and calculating the electrical output magnitudes to control the electric motor.

[0044] • Sensors or measuring devices that, either directly or indirectly, allow the determination of the rotational speeds (Ni, Nh) corresponding to the first member of the transmission and the bottom bracket axle—that is, the pedaling cadence Nh. In the case of mid-drive motors, those with the bottom bracket axle fixed to the first member, the pedaling cadence, Nh, and the rotational speed of the first transmission member coincide, Ni; and for other mid-drive motor configurations, both speeds will necessarily be proportional. In any case, only two measuring devices are needed for mid-drive motors, since knowing the cadence allows determining the rotational speed of the first member, and vice versa. These measuring devices can be internal or external to the hybrid drive system.

[0045] • An electronic control unit (ECU) where signals from the sensors are acquired, and all the calculations necessary for system control are performed, as well as all the power electronics for controlling the electric motor. • A control device or HMI (Human Machine Interface), which will have at least the means to: turn the system on and off; and to select the desired cruising speed, which we will call the "programmed speed," Nh(prog); the user will be able to modify the programmed speed at any time using the HMI. In addition, it will preferably have the means to configure PARALLEL mode, and to apply, as a priority, an extraordinary mode of maximum torque delivery for a very limited time, which we will call BOOST mode.

[0046] Preferably to comply with regulations and to be able to offer this information to the user, means will also be available to measure the rotational speed N w , of the vehicle's drive wheel.

[0047] Depending on the operation of the power-split's freewheel, the system will be in one of two previously defined states: rigid or power-split. The motor's rotational speed, NeM, at which the motor's freewheel disengages, is called the "critical motor speed" and is denoted by NeMc, calculated as NeMc = GReM'Ni. When the motor's rotational speed, NeM, exceeds the critical speed, NeMc, the system leaves the rigid state and enters the power-split state.

[0048] For the control of the electric motor, a setpoint speed NeM(con) is defined, which is the rotational speed that a secondary control procedure tends to impose on the electric motor, for example, by means of a PID.

[0049] In PARALLEL mode, a setpoint speed NeM(con) of the electric motor (eM) is established proportional to the speed Ni of the first transmission member (1), with NeM(con) = X- Ni, and assistance may or may not be provided depending on whether X is greater or less than GReM, that is, either the power-split freewheel (FWps) is not acting (N2 > Ni), or the power-split freewheel (FWps) is acting (N2 = Ni);

[0050] The selection of parameter X can be set as a constant in the control procedure, or preferably selected either via the HMI or a user application. This selection constitutes the PARALLEL mode configuration, and two basic configurations can be chosen:

[0051] i. Configuration with assistance in PARALLEL mode.

[0052] X = (1+ <p)' GReM. Es decir, X se elige igual a una fracción mayor o ligeramente mayor que GR6M, mediante el parámetro 0 < cp < 0,25. En este caso hay una asistencia desde el inicio en forma de una asistencia en par de valor K3 (T3= KyTh) y además una pequeña asistencia en velocidad, correspondiente al valor elegido (<p) .

[0053] < < <

[0054] >

[0055]

[0056] i. Unassisted configuration in PARALLEL mode.

[0057] or X = 0. In this configuration, minimum power consumption or maximum range is achieved. Parallel assistance (in pairs) is not available until ADAPTIVE mode is switched — when the programmed cadence is reached —.

[0058] or A = (1-s)' GReM. That is, X is chosen to be equal to a fraction less than or slightly greater than GR6M, using the parameter 0 < s < 0.25. In this case, the minimum reaction time is achieved when switching to ADAPTIVE mode, but parallel assistance is not obtained until switching to ADAPTIVE mode.

[0059] or A = a transition function between 0 and (1-s)-GR6M as the cadence approaches the programmed cadence. This preferred case attempts to obtain the combined advantages of the two previous ones.

[0060] In ADAPTIVE mode, a setpoint speed NeM(con) for the electric motor (eM) is established, which depends on the current and past ratio of the cyclist's cadence, Nh, to the programmed cadence, Nh(prog). The minimum setpoint value will be higher than the value that characterizes PARALLEL mode, i.e., NeM(con) > X-Ni.

[0061] The set speed is calculated by taking advantage of the fact that when the electric motor delivers more or less power to the power-split gear, a greater or lesser resistive torque is generated on the human power input. This causes the pedaling cadence to slow down or speed up, potentially maintaining a value close to the programmed cadence Nh(prog) within a wide range of operating conditions. The ADAPT VO mode will not always attempt to maintain the programmed cadence, as the control system internally operates according to a "set cadence", Nh(con), which is the cadence the control system tries to maintain through the electric motor's action. This will generally be equal to the programmed cadence and may temporarily have a different value.This could be due, on the one hand, to the cyclist intentionally stopping pedaling, in which case the motor should stop immediately; or, on the other hand, to the motor reaching its maximum power output, or to the electric assist system exceeding one of its limits. These limits may include reaching the motor's maximum revolutions per minute (RPM), the maximum permissible current, or a temperature that puts the system at risk. In such cases, the control system should establish a new, higher cadence than the programmed one, and / or reduce the motor's RPM, thus decreasing the load on the entire electrical system.

[0062] To switch from PARALLEL mode to ADAPTIVE mode, the cyclist's cadence must reach the setpoint cadence, which in this state change will normally be the same as the programmed cadence. At that moment, the setpoint speed of the NeM(con) motor will increase relative to the base speed N.m or when the cyclist is attempting to accelerate—trying to reach a cadence higher than the setpoint—until either a critical state is reached or the cyclist stops accelerating—either due to fatigue or having reached a desired speed. If the cadence remains within a range around the setpoint, the motor's setpoint speed will remain approximately constant. If the cyclist begins applying less power than is necessary to maintain the bicycle's speed, the cadence will tend to drop below the setpoint cadence, so the control system will decrease the motor's setpoint speed, attempting to maintain the cyclist's cadence until either the cyclist reaches the setpoint cadence or the motor's setpoint speed reaches the base speed, N. m or, in which case the system will switch to PARALLEL mode.

[0063] — Said ADAPTIVE mode is described in Spanish patent P202530027 and its application in the present invention corresponds to claim 2 — .

[0064] In conclusion, we can affirm that the existence of the power-split freewheel, which in itself represents an implicit gear change, and which together with the control system practically eliminates the aforementioned problems to be solved, specifically:

[0065] • In the first problem to be solved, the possibility of the cyclist's legs accelerating in the event of motor slippage is minimized, since the power-split's freewheel limits this slippage until the decreasing speed of the second member is matched by that of the first. Because the peak torque exerted by the cyclist usually occurs at relatively low cadences, if we take advantage of this rigid state through the control system, both members will travel at very similar speeds, and slippage will be minimal.

[0066] • In the second problem to be solved, the additional strain on the cyclist when the electric motor induces acceleration on the bicycle is practically eliminated, since the extra torque on the chainring is compensated by the new torque ratio, which changes from 1:1 to K3:1.

[0067] BRIEF DESCRIPTION OF THE FIGURES

[0068] FIG. 1 schematically represents a section of an electric bicycle motor according to the present invention, in a mid-drive configuration, showing: the hybrid drive (0), with an electric motor (eM) with its rotor (R) and stator (E); a mechanical transmission system with a reduction gear (ReM), in which a freewheel (FWeM) is used; a power-split mechanism (PS) with a first transmission member (1) comprising the crown gear (A) and a bottom bracket axle (10); a second transmission member (2) comprising the sun gear (S); a freewheel (FWps) between the first (1) and second (2) transmission members of the power-split (PS); a third transmission member (3) comprising the planet carrier (C) and being integral with a power output chainring (100). This output is connected by a chain to a cassette (CS).Also shown is a cadence sensor (SS), pedals (111, 112), and cranks (11, 12) attached to the bottom bracket axle (10).

[0069] FIG. 2 schematically represents a section of a hybrid drive (0) for an electric bicycle, a particularization of the case in FIG. 1, in a coaxial motor configuration showing: a reduction gear (ReM) consisting of a bicloidal type reducer, arranged coaxially with the power-split gear (PS). The motor's freewheel (FWeM) is located directly at the power input to the second transmission member (2).

[0070] Figures 3A and 3B show three-dimensional views of the internal parts of a motor according to an embodiment of Figure 1. The power-split gear (PS) is located around the bottom bracket axle (10). A second parallel shaft is also shown, on which the motor and an epicyclic gearbox are mounted. At its output is a sprocket for a toothed belt that transmits power to another sprocket on the main shaft. This second sprocket forms part of the second member (2) of the power-split gear (PS). The system includes a tensioner pulley.

[0071] FIG. 4 shows a cross-section of the mechanism corresponding to FIG. 3A and FIG. 3B. In this case, the mechanical transmission system (ReM) consists of two stages: an epicyclic reduction gear and a toothed belt drive. The motor freewheel (FWeM) is located between the two stages. The power-split freewheel (FWps) is located between the second transmission member (2) and the bottom bracket axle (10).

[0072] Figure 5 shows a graph presenting various vehicle curves as a function of time. It was generated by integrating the equations of motion of a simplified model. The simulation was performed assuming a mid-motor configuration with K3 assistance from the start in PARALLEL mode. One of the simplifications is that the cyclist contributes a constant power of 220 W from the very beginning. Due to this simplification, the torque provided by the cyclist (Th) is quite high at the initial moments. The gear ratio is also constant with a 28-tooth chainring (100), a 38-tooth sprocket on the cassette (CS), and a 10% incline.Presented are the cyclist's cadence (Nh), measured with the cadence sensor (SS); the third member revolutions (N3) corresponding to the chainring, the revolutions of the electric motor (N6M), the speed of the bicycle (Vbike), the torques of the cyclist (Th) and of the motor (T6M), the power of the motor (P6M) and the time (tobj) in which the programmed cadence is reached.

[0073] Figure 6 schematically shows a preferred embodiment of a complete e-bike system incorporating a hybrid drive in a mid-motor configuration. It depicts an electric motor (eM), a reduction gear (ReM), a motor freewheel (FWeM), a remote control (HMI), an electrical power source (Bat), and an electronic motor control unit (ECU). Also shown are a power-split gear (PS), a power-split freewheel (FWps), a bicycle speed measurement device (WS) that measures the rotational speed of a drive wheel (W), a cadence sensor (SS), and a mechanical gear shifter (CS).

[0074] Figure 7 schematically shows a preferred embodiment of a complete e-bike system incorporating a hybrid drive system with a hub motor configuration for the rear wheel. Shown are an electric motor (eM), a gearbox (ReM), a motor freewheel (FWeM), a remote control (HMI), an electrical power supply (Bat), and a motor controller (control). Also shown are a power-split gear (PS) and a power-split freewheel (FWps), a bicycle speed measurement device (WS) that measures the rotational speed of a drive wheel (W), a cadence sensor (SS), and a first-member rotational speed sensor (NiS).

[0075] PREFERRED EMBODIMENT OF THE INVENTION

[0076] For the first object of the present invention, a dual-state drive is proposed using power-split hybridization, also referred to as hybrid drive (0), applicable to bicycles and other pedal-powered vehicles equipped with a mechanical gear-changing system (CS), to provide them with electric assistance.

[0077] Specifically, this preferred embodiment consists of a hybrid drive (0), in which the power-split mechanism (PS) comprises an epicyclic gear system with a sun gear (S) having 36 teeth, a ring gear (A) having 90 teeth, six simple planet gears (P), and a planet carrier (C). This power-split mechanism incorporates:

[0078] • a first transmission member (1) comprising the crown gear (A), and a bottom bracket axle (10) integrally. In use it will receive muscle power (Ph) from pedals (111, 112) through the cranks (11, 12);

[0079] • a second transmission member (2) comprising the sun gear (S), and in use, receives power (P6M) from an electric motor (eM) through a reducer (ReM) with two stages and a reduction ratio GR6M=10.3125:1 — speed reduction —, incorporating a motor freewheel (FWeM) to mechanically disconnect it and prevent it from being dragged when pedaling without assistance;

[0080] • a third transmission member (3) comprising the planet carrier (C) through which an output power is transmitted that is the sum of the two previous ones, the human power (Ph) and the electrical power (P6M), less the mechanical losses in the transmission. This member incorporates a chainring (100) to transmit the power by chain.

[0081] From the data above, when the system is operating in power-split mode, we have a gear reduction from the motor to the chainring of 36.09:1; and a reduction ratio from the motor to the bottom bracket of 25.78:1, resulting in a gear reduction from the bottom bracket to the chainring of 1.40:1. It is precisely this latter gear reduction that provides the additional torque when transitioning from the rigid to the power-split mode. The critical torque in this case will be T2. C = 0.4 Ti = 0.4 Th Within this preferred embodiment, we consider the following configurations:

[0082] • Central drive with the motor on a shaft parallel to that of the bottom bracket (10), and the power-split (PS) coaxial with the bottom bracket shaft (10) — examples FIG.3A, FIG.3B and FIG.4 — , where a first stage of the reducer (ReM), at the output of the motor (eM), can be of epicyclic, or gear train, bicyclic or other type; and where the transmission of power between both shafts can be carried out by means of straight or helical gears; pulleys and belt; or by means of corresponding chain sprockets.

[0083] • Central drive with the motor (eM) arranged coaxially with the pedal assembly (10) — example FIG.2 — , where the reduction gear (ReM) in the power transmission system can be of the bicycloidal or epicyclic type, either simple or compound.

[0084] For the second object of the present invention, a control system based on the cadence (Nh) applicable to dual-state drives using power-split hybridization is proposed. This control system comprises at least:

[0085] • an electronic control unit (ECU) that: acquires signals from the sensors (WS, SS, and / or NiS); acquires or determines signals directly from the motor (N6M, UM); performs all the calculations necessary to control the system; and houses all the power electronics necessary to govern the electric motor (eM);

[0086] • a control device (HMI) that allows the user, at least, to select a programmed cadence Nh(prog), which is the cruise cadence that the user would like to maintain; that has means to select the PARALLEL mode configuration, setting the determination of X — constant value or function of the ratio between the cadence Nh and the setpoint cadence Nh(con) — ; and also means to activate the BOOST mode.

[0087] • measuring devices that, directly or indirectly, allow the rotation speeds to be known (Ni, N w and Nh) corresponding to the first transmission member (1), to the drive wheel (W) of the vehicle, and to the bottom bracket axle (10) — i.e., the pedaling cadence — ;

[0088] • a main control procedure programmed in the ECU that distinguishes at least three operating modes:

[0089] or a first mode called PARALLEL; or a second mode called ADAPTIVE;

[0090] or a third mode called BOOST;

[0091] OTHER ACHIEVEMENTS

[0092] With respect to the embodiment of the present invention described above, other modifications may be employed without departing from the scope of the present invention as defined in the appended claims. For example, the size, shape, location, or orientation of the various components may vary. Components shown as directly connected or in contact with each other may have intermediate structures arranged between them. The functions of one element may be performed by two, and vice versa. Therefore, the scope of the invention should not be limited by the specific embodiments described, but rather by the appended claims.

[0093] In another preferred embodiment, the freewheel (FWeM) would not be used. In this way, pedaling would generate motor drag, and through appropriate configuration of the electronic control unit (ECU), a suitable voltage would be available to recharge the batteries. Preferably, the human-machine interface (HMI) would have sufficient means for the user to select the bicycle speed at which generation would occur, by controlling the motor / generator's rotational speed.In another embodiment, a dual-state drive is proposed using power-split hybridization configured in the hub of a rear bicycle wheel, where the mechanical gearbox (CS) comprises sprockets arranged in a cassette, and where the motor is arranged coaxially with the first transmission member (1) and, in use, will rotate together with the gearbox sprockets (CS), where the reduction gear (ReM) is of the bicycloidal type, or of the epicyclic type.

[0094] In another embodiment, the control system would also include an Industrial Measurement Unit (IMU), which allows for measuring the accelerations and gradients to which the control system is subjected. This enables, for example, more agile management on steep gradients in PARALLEL mode, and more robust management in ADAPTIVE mode—for example, by reducing the parameter value. <p — .

[0095] In another, non-preferred embodiment, the PARALLEL mode configuration is not done from the HMI, but from a user application. In yet another non-preferred embodiment, instead of controlling the electric motor (eM) by speed during PARALLEL mode, the motor could be controlled by torque such that N6M = GReM'Ni. This would provide parallel assistance from the start, but with a more or less constant assist torque, always less than the critical torque T2C. Since the torque is not measured, open-loop control is implemented.

Claims

CLAIMS 1. A dual-state drive using power-split hybridization, hereinafter also referred to simply as a hybrid drive (0), applicable to electric bicycles and other pedal-powered vehicles having at least one mechanical gear-shifting system (CS), comprising at least: an electric motor (eM); a reduction gear (ReM) — with one or more stages and a total reduction ratio GReM —; and a power-split mechanism (PS) built on an epicyclic gear comprising a sun gear (S), a ring gear (A), planet gears (P) — whether simple or compound — and a planet carrier (C); b being the value of its basic ratio; and where: This power-split mechanism includes: • a first transmission member (1) comprising the crown gear (A) and, in use, is responsible for receiving the muscle power (Ph) of a cyclist, either from a bottom bracket axle (10) or through any interposed transmission mechanism; • a second transmission member (2) comprising integrally the sun gear (S), and in use, receives power from the motor (P6M), through the reducer (ReM); • a third transmission member (3) comprising the planet carrier (C) through which an output power is transmitted which is the result of the sum of the two previous ones (Ph+ P6M) minus the mechanical losses in the transmission; This drive is characterized by: incorporating at least one freewheel mechanism, which we will call the power-split freewheel (FWps), located between any two of the three transmission members (1, 2, 3), preferably between the second (2) and the first transmission member (1), which, in any case, acts in such a way as to prevent the first transmission member (1) from reaching a rotational speed Ni, higher than that of either of the other two N2 or N3, for which reason while said power-split freewheel (FWps) is acting, all the members (1, 2, 3) of the power-split mechanism (PS) will rotate together as a rigid body;2.A dual-state drive using power-split hybridization according to claim 1, characterized in that it incorporates a freewheel, which we call the motor freewheel (FWeM), connected in the mechanical transmission between the electric motor (eM) and the second transmission member (2) to prevent the electric motor (eM) from being dragged when pedaling when there is no electric assistance.

3. A dual-state drive by power-split hybridization according to claim 1 or 2, characterized in that said hybrid drive (0) is configured as an electric bicycle central motor.

4. A dual-state drive according to claim 3, wherein said first transmission member (1) is coaxial with the bottom bracket axle (10) and rotates in unison with it.

5. A cadence-based control system (Nh) for a hybrid drive (0) according to any of the preceding claims, comprising at least: an electronic control unit (ECU); a human-machine interface (HMI) that allows the user to select at least a programmed cadence Nh(prog), which is the cruise cadence the user would like to maintain; and a main control procedure programmed in the ECU that distinguishes at least two operating modes: • a first mode called PARALLEL, in which it establishes a setpoint speed N e M(con) of the electric motor (eM) proportional to the speed Ni of the first transmission member (1), with NeM(con) = X- Ni, being able to provide assistance or not depending on whether X is greater or less than GReM, that is, either the power-split freewheel (FWps) does not act (N2 > Ni), or the power-split freewheel (FWps) is acting (N2 = Ni); • a second mode called ADAPTIVE in which the set speed NeM(con) of the electric motor (eM) depends on what is and has been the ratio of the cyclist's cadence, Nh, with respect to the programmed cadence, Nh(prog).

6. A cadence-based control system (Nh) according to claim 5, comprising at least: • measuring devices that, directly or indirectly, allow the rotation speeds to be known (Ni, N w and Nh) corresponding to the first transmission member (1), to the drive wheel (W) of the vehicle, and to the bottom bracket axle (10) — i.e., the pedaling cadence —; • said electronic control unit (ECU) performs the acquisition of signals from the sensors (WS, SS, and / or NiS); acquires or determines signals directly from the motor (N6M, UM); performs all the calculations necessary to control the system; and houses all the power electronics necessary to govern the electric motor (eM); 7. A control system based on cadence (Nh) according to claim 5 or 6, wherein: • This control procedure will also incorporate an extraordinary mode of maximum torque delivery for a sufficiently limited time, called BOOST mode; • said HMI, will have means to apply said BOOST mode.

8. A control system based on cadence (Nh) according to claims 5, 6 or 7, wherein: • This control procedure will allow the user to set the value of X, either from the HMI or from a user application, thus configuring the behavior of the PARALLEL mode.

9. A dual-state drive using power-split hybridization according to claim 1, characterized in that when the freewheel (FWps) is acting, since the electric motor (eM) is being driven, under an action in the HMI, which would have means for this, the control procedure activates a mode in which the electronic control unit (ECU) allows the generation of electrical energy in the motor.

10. A dual-state drive by means of power-split hybridization according to claims 1, 2 or 9, wherein said hybrid drive (0) is arranged in the hub of a wheel, and wherein the mechanical gear change (CS) comprises sprockets arranged in a cassette, and characterized in that said first transmission member (1) in use rotates together with the sprockets of the gear change (CS).

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