The invention refers - in general - to a braking, and preferably energy recovery, system for a vehicle equipped with an electric propulsion motor. In particular, the electric vehicle is a wheeled vehicle, e.g. a car or an electric bicycle.

It is known to recover the kinetic energy of an electric vehicle while it is braking. Instead of dissipating the energy with the friction of the brakes, the electric motor is used as a generator to recharge the power supply batteries.

Current systems control energy recovery circuits by a binary signal (ON/ OFF) which indicates the braking condition. However, the binary signal does not bring other information and the efficiency of the system is affected because, for example, the batteries are not able to absorb at best or always the reverse energy during the entire braking phase. An excessive or incorrect charge can damage the batteries, or at least limit a lot the recovered energy.

In the case of a bicycle assisted by an electric motor, a further problem is that the known systems do not evaluate the rider's intention to brake. The electric motor responds only to the pedal stroke, and if unfortunately, especially at turns, one brakes without stopping pedaling, the bicycle falls because the motor keeps pushing it.

It is then desired to propose a system to remedy one or more of these problems, with a system and/ or method according to the appended claims, in which the dependent ones define advantageous variants.

In particular, it is desired to make the ride of a bicycle assisted by an electric motor safer, by solving the problem of an insecure or uncontrolled braking.

Then, a system is proposed for a bicycle assisted by an electric propulsion motor, comprising

a manually operated brake to brake the bicycle,

a position sensor for detecting the, e.g. angular, position of the brake, an electronic board configured (e.g. programmed) to detect said position by means of the sensor and controlling the power supplied by the electric motor according to this position.

A clear advantage is that the bicycle no longer has a dangerous behavior during braking, because the rider's pedaling does not induce the action of the motor anymore.

By manually it is meant an operation in which it is required the active intervention of an operator (as opposed to automatic). The manually operable element may have many variations. E.g. it's a pedal, a rotary knob or a lever. Preferably the kinetic energy of the braking vehicle is converted into electric energy, through the electric motor, or thermal energy if and when it gets dissipated. In a preferred variant, the electronic board is configured for controlling the conversion of the kinetic energy of the vehicle during braking by modulating the electrical power generated by the electric motor (used here as a generator) as a function of said position.

The electronic board may be a discrete-element analog circuit, but, for more calculation power and versatility, preferably il comprises a programmable microprocessor, programmed to run a program that implements the control actions defined here.

The electric bicycle is preferably equipped with a handlebar with which to steer a directional wheel, and the manually operable element for comfort is placed on the handlebars, especially in the form of a lever mounted oscillating with respect to the handlebar. In this case the position sensor is prepared for example to detect the angular position of the lever with respect to handlebar or with respect to a fixed part of the operable element itself.

Preferably the lever or the manually operable element is mounted to control a bicycle braking circuit, with double action on the system.

In particular, the lever comprises a portion cooperating with an activating member of hydraulic or pneumatic circuit, which serves for activating a vehicle brake when operating the lever. To prevent that the braking circuit is inserted at the beginning of the braking, when it is desired instead to recover kinetic energy, preferably said portion is mounted with mechanical play with respect to the activating member, so that said portion, along an initial segment of its stroke, travels through the mechanical play without engaging the activating member. The activating member gets activated by said portion after this initial segment.

E.g. said portion is a protrusion integral with the lever, rotatable with it and sized to activate by contact the activating member.

As a variant, the electronic board is configured to detect said position via the sensor and

- if a braking action is detected, to control temporarily the power supplied by the electric motor regardless of the rider's pedalling; and/ or

- while a braking action is detected, to control the conversion of kinetic energy of the bicycle during braking as a function of such position, that is to control how and/ or how much the electric motor converts the kinetic energy of the bicycle into supplied electrical energy (e.g. to a battery or a heatsink). Preferably, the electronic board is configured via software program instructions.

It is understood that the board may then be programmed for

- limiting or nulling the power supplied by the electric motor towards the bicycle's wheels, and/ or

- optimizing the energy conversion process, e.g. by using in a first braking phase the motor as a generator for the battery and in a second and subsequent braking phase dissipating the energy to safeguard the batteries; or vice-versa.

Information about "how much" the rider is braking is preferably provided on the electronic board in real time, e.g. by choosing for said sensor an incremental position sensor.

By acquiring this data the board can then be programmed for modulating the power supplied by the electric motor to the wheels of the bicycle depending on how much the rider is braking or pulling the brake, with the advantage of natural braking and immediate feedback to the human being. E.g. the power supplied by the electric motor to the bicycle's wheels can be reduced proportionally to how much the rider is braking or is pulling the brake.

Preferably the board can be programmed to optimize the energy conversion process, e.g. by controlling the motor in a first braking phase so that the motor acts as a battery-recharging generator, and controlling the motor in a second following braking phase to dissipate the energy on a heat sink, to safeguard the batteries; or viceversa.

The position sensor, incremental or not, may be, for example, a potentiometer, a digital rotary encoder, a capacitive or inductive sensor or a proximity sensor. The sensor is e.g. adapted to output an analog or digital electrical signal that contains the information about the angular position.

Another aspect of the invention is an aforementioned electric bicycle provided with the system defined here.

Another aspect of the invention is a control method for the electric motor of an electric bicycle as defined herein, comprising the phases of

detecting the, e.g. angular, position of a manually operable brake for braking the bicycle,

controlling the power supplied by the electric motor according to such position.

Preferred phases are:

- converting the kinetic energy of the bicycle during braking into electric energy, through the electric motor, or thermal energy by dissipating it; and / or - detecting said position by means of the sensor and

if a braking action is detected, controlling temporarily the power supplied by the electric motor regardless of the rider's pedaling; and/ or

while a braking action is detected, controlling the conversion of kinetic energy of the bicycle during braking as a function of such position.

The advantages of the invention will be clearer from the following description of a preferred embodiment, referring to the attached drawing in which

- Fig. 1 shows a schematic diagram with components illustrated as in use. The illustrated system MC serves to brake the rotation of a wheel of a bicycle, which comprises a handlebar 10 with which to steer e.g. the front wheel, in a known manner.

A sleeve 30 is mounted on the handlebars 10 and, on a portion 32, hingedly mounts a lever 20, which can then rotate about a pivot axis. The angular position of the lever 20 with respect to sleeve 30 (or to the handlebar 10) is indicated by the angle W.

The lever 20 comprises an integral portion or finger 22 for pushing a piston 40 connected to a hydraulic circuit which sends oil to brakes 90 of the bicycle to brake. When pulling the lever 20 towards the sleeve 30, the portion 22 approaches the piston 40, but with a certain delay due to a mechanical play G present in the initial part of the stroke of the portion 22.

The lever 20 is preferably kept at an end-of-travel position away from the sleeve 30 by an elastic element. On the lever 20, e.g. in correspondence of the rotation fulcrum, an angular position sensor 70 is present, connected by an electric line 60 to an electronic control unit 50, which drives an electric motor 52 used to give the bicycle propulsion.

To brake the bicycle, the user closes one hand on the lever 20 to bring it closer to the sleeve 30 (the angle W decreases). In this first phase the user wins the resistance of the elastic element alone (if any), because the portion 22 moves without obstacles along the play G.

At the same time the sensor 70 detects the progressive variation of the angle

W and transmits a signal with such information to the unit 50. At this point it begins a sequence of operations designed to drive the motor 52 in order to reduce or limit its power, and preferably also for optimizing the energy recovery of the kinetic energy possessed by the bicycle. Subsequently the portion 22 reaches the piston 40 and mechanical braking begins by the brakes 90.

The aforementioned combined actions have several advantages. Primarily, the mechanical braking action is delayed to allow maximum freedom to the electronic circuitry to manage as much recoverable energy as possible. Secondly, the continuous detection of the angle W allows the unit 50 to modify the dynamic behavior of the motor and the energy recovery process, e.g. by avoiding abrupt responses from the motor 52 and / or accelerating the braking if the angle W varies quickly (the user wants to brake quickly) and/or by adjusting the braking to the variation of the angle W (so the user creates a natural braking corresponding to the action of his hand, and without the motor acting with opposite effect).