ELECTRIC MOTOR FOR ELECTRIC VEHICLE

Abstract

An electric motor is described comprising a central stator and a rotor formed by an outer casing of the motor. A ring is integral with the outer surface of the casing and a braking member integral with the stator can to brake the ring. An electronic circuit mounted on/in the stator generates a resistant torque to brake the rotor through the motor acting as brake and the braking member.

Claims

1. Electric motor comprising: a central stator with electric windings for generating a magnetic field that hits a rotor, the rotor being formed by an outer casing of the motor which is rotatably pivoted about the stator to rotate about an axis, a ring integral with the outer surface of the casing and arranged coaxially to said axis, a braking member which is integral with the stator and configured to brake the ring, an electronic circuit mounted on/in the stator comprising an electronic power stage for driving the stator windings to control the rotation of the rotor, an electronic control stage for the braking member, a logic unit configured to control the electronic power stage and the electronic control stage so as to generate a resistant torque to brake the rotor by driving the stator windings so that the motor acts as an electric power-generating brake and driving the electronic control stage to activate the braking member on the ring to brake the ring.

2. Motor according to claim 1, wherein the braking member is an electromechanical member or a pneumatic member.

3. Motor according to claim 1, wherein the logic unit is configured to control the electronic power stage and the electronic control circuit to simultaneously generate the resistant torque through the braking member and the braking action developed by the electric motor.

4. Motor according to claim 1, wherein the motor comprises a sensor configured to detect the relative position of the braking member with respect to the ring and to send to the logic unit a signal indicative of the relative potion.

5. Motor according to claim 1, wherein the logic unit is configured to control the electronic power stage and the electronic control stage so that the resisting torque follows a desired course over time.

6. Motor according to claim 1, wherein said electronic circuit is mounted inside a fixed casing from which the stator protrudes.

7. Motor according to claim 6, wherein the casing is finned to dissipate heat.

8. Motor according to claim 1, wherein the logic unit is configured to control the electronic power stage so as to impose on the rotor a driving torque which follows a desired course over time.

9. Motor according to claim 1, wherein the electric motor is an axial-flow electric motor, the stator being equipped with windings arranged in a circular series around said rotation axis, each winding to create a magnetic field, with a polar axis parallel to the rotation axis, through which to rotate the rotor thanks to the magnetic interaction between the generated magnetic fields and a corresponding circular series of magnetic elements of the rotor.

10. Motor according to claim 2, wherein the logic unit is configured to control the electronic power stage and the electronic control circuit to simultaneously generate the resistant torque through the braking member and the braking action developed by the electric motor.

11. Motor according to claim 2, wherein the motor comprises a sensor configured to detect the relative position of the braking member with respect to the ring and to send to the logic unit a signal indicative of the relative potion.

12. Motor according to claim 3, wherein the motor comprises a sensor configured to detect the relative position of the braking member with respect to the ring and to send to the logic unit a signal indicative of the relative potion.

Description

[0030] The advantages of the invention will be clearer from the following description of a preferred embodiment, referring to the attached drawing in which

[0031] FIG. 1 shows a cross-sectional view of an electric motor.

[0032] The motor MC shown in FIG. 1 serves to allow—and also to brake—the rotation of a wheel (not shown) of a vehicle not shown, e.g. a car or a truck.

[0033] The motor MC comprises a central stator 10 and a rotor 20 rotatably pivoted via bearings 12 around the stator 10 to rotate about an axis X.

[0034] The stator 10, which protrudes from a casing 40, comprises well-known electric windings in order to push the rotor 30 into rotation through a magnetic field generated by the windings.

[0035] The rotor 20 comprises an outer casing 22 of the motor MC, e.g. a bell, on whose outer surface 24 a ring 50 is fixed and arranged coaxially to the axis X.

[0036] On the ring 50 can act a caliper 60 which is integral with the stator 10 (and/or with the casing 40) and configured to tighten the ring 50.

[0037] Inside the casing 40 is placed an electronic circuit 80 composed of [0038] an electronic power stage 82 to drive the stator windings 10, [0039] an electronic control stage 84 to control the caliper 60 via a line 88, e.g. an electrical line; [0040] a microprocessor 86 programmed to control the electronic power stage 82 and the electronic control stage 84.

[0041] The microprocessor 86 is programmed in a known way to drive the electronic power stage 82 to rotate the rotor 10. For example, the microprocessor 86 can impose a torque on the rotor 10 following a reference signal, e.g. generated by a speed level sensor that can be operated by a person, such as a lever or an accelerator pedal.

[0042] The microprocessor 86 is in particular programmed to drive the electronic power stage 82 and the electronic control stage 84 to brake the rotor 10.

[0043] The braking action may be generated by driving the electronic power stage 82 so that the motor MC acts as an electric power-generating brake, and/or by driving the electronic control stage 84 to tighten the caliper 60 on the ring 50.

[0044] In the first case, the electric energy generated by the motor MC is derived from the conversion of kinetic energy of the wheel and/or vehicle, and e.g. it can be stored in a battery (not shown).

[0045] In the second case the kinetic energy of the wheel and/or vehicle is converted by the friction between the caliper 70 and the ring 60 into heat.

[0046] An example of a control algorithm executed by the microprocessor 86 during a braking phase is the following. Defined

[0047] RT_Target the braking torque required to the motor MC,

[0048] RT_Mmax the maximum braking torque manageable by the motor MC,

[0049] RT_Mder the derating torque according to motor/stator temperature,

[0050] RT_Bms the braking torque limit determined by the battery charge state,

[0051] RT_Rmax the torque limit obtainable by regenerative means,

[0052] RT_C the braking torque on the rotor 10 to be applied via the caliper 60,

[0053] at each sampling interval (e.g. with a control frequency of 1 KHz) the microprocessor 86 calculates:

RT_Rmax=min{|RT_Mmax|−|RT_Mder|,|RT_Bms|}e

RT_C=min(0,RT_Target−RT_Rmax}.