Magnetic brake with reduced elastic return hysteresis

Abstract

Magnetic hysteresis brake (10), comprising at least a first element (11.1) carrying magnets (17.1) and a second element (12) made of magnetic material, a first surface (15.1) of the first element (11.1) being opposite a second surface (14) of the second element (12), so that the magnets (17.1) generate a magnetic flux induced in the second element (12) through said surfaces, characterized in that the magnets (17.1) are separated from each other by teeth (18.1) which are made of a material conducting the magnetic flux and which have a free surface close to the first surface (15.1). Control instrument and vehicle comprising such a brake. FIGURE OF THE ABSTRACT: Fig. 2

Description

Title of the invention: Magnetic brake with reduced elastic return hysteresis

[0001] The present invention relates to a magnetic hysteresis brake which can be used, for example, in human / machine interfaces, to generate a force resisting the movement of an object, such as a control instrument, manipulated by a user. BACKGROUND OF THE INVENTION

[0002] The resistive force in question is the result of a hysteretic loss imitating friction exerted on a part connected to the object to be braked.

[0003] A magnetic hysteresis brake comprises two elements facing each other and movable relative to each other, namely a rotor and a stator: one of the elements, for example the stator has magnetic poles facing the rotor and the rotor is made of a material which has magnetic properties such as: - when the material is subjected to an exciting magnetic field, a magnetic field is induced in the material, and - when the excitation field varies, the corresponding induced field describes a hysteresis cycle, that is to say that when the excitation field returns to its initial value (zero), the induced field remains (we say that the material retains a remanent induction).

[0004] Thus, the magnetic poles of the stator impose a magnetic field in the rotor. When the rotor is in motion, the magnetic field remains unchanged relative to the stator and therefore variable in the rotor. This variation creates hysteretic losses proportional to the movement of the rotor. In other words, this results in a constant force that opposes the movement of the rotor.

[0005] Such magnetic hysteresis brakes are used, for example, in control instruments. The rotor is then connected to a lever of the control instrument, this lever being moved by a user, for example, to control a device such as a motor. The induced magnetic field produces resistance to the movement of the rotor and therefore resistance to the movement of the lever manipulated by the user. This resistance allows the user to better control the movement he imparts to the lever of the control instrument.

[0006] Document FR-A-2998347 describes a magnetic brake in which the poles are formed by electromagnetic windings.

[0007] The magnetic poles can also be formed by permanent magnets, which allows for a simpler structure without the need for power supply.

[0008] However, magnetic hysteresis brakes have an elastic return ma magnetic which causes the rotor to move in the opposite direction to the movement applied by the user to the lever once it is released. This magnetic elastic return must have the smallest possible amplitude to allow the lever to remain in the position in which it was released. Indeed, if the magnetic elastic return amplitude is high, the lever moves back after being released and the engine thrust setpoint is incorrect. Furthermore, magnetic elastic return is defined as a physical phenomenon due to the hysteresis cycle of the magnetic material used and the number of magnetic poles. Increasing the number of magnetic poles would reduce magnetic elastic return. However, increasing the number of magnetic poles would proportionally increase the size and mass of the hysteresis magnetic brake. SUBJECT OF THE INVENTION

[0009] The invention particularly aims at providing a magnetic hysteresis brake which at least partially overcomes the aforementioned drawbacks. Summary of the invention

[0010] To this end, according to the invention, a magnetic hysteresis brake is provided, comprising at least a first element carrying magnets and a second element made of magnetic material, a first surface of the first element facing a second surface of the second element, so that the magnets generate an induced magnetic flux in the second element through said surfaces. The magnets are separated from each other by teeth which are made of a material which conducts the magnetic flux and which have a free surface close to the first surface.

[0011] Thus, these teeth are provided with a polarity opposite to that of the magnets and therefore make it possible to increase the number of poles in a smaller footprint...

[0012] A brake is further provided in which the first element and the second element are mounted to rotate relative to each other about an axis of rotation.

[0013] A brake is further proposed in which the first surface and the second surface are cylindrical with a circular section; the magnets of the first element being arranged in a cylinder and the magnetic flux being radial.

[0014] A brake is further provided in which the second element is tubular in shape with a circular cross-section and the brake comprises a second first element which is disposed in the second element and which has a third surface opposite a fourth surface of the second element, said fourth surface being opposite the second surface of the second element.

[0015] A brake is further provided in which the first surface and the second surface are planar; the magnets of the first element are arranged in a circle and the flux magnetic being axial.

[0016] A brake is further provided comprising several first elements and several second elements.

[0017] A control instrument is further provided comprising a frame, a lever movably mounted on the frame, and a brake, one of the first element and the second element being fixedly mounted relative to the frame and the other of the first element and the second element being connected to the lever.

[0018] A control instrument is further provided in which the lever is mounted on the frame for pivoting.

[0019] A control instrument is further provided comprising a reducer having a first shaft connected to said other of the first element and the second element and a second shaft connected to the handle.

[0020] A vehicle comprising a control instrument is further provided.

[0021] The invention also relates to a control instrument equipped with such a brake and a vehicle equipped with such a control instrument.

[0022] Other characteristics and advantages of the invention will emerge from reading the following description of particular and non-limiting embodiments of the invention. Brief description of the drawings

[0023] Reference will be made to the accompanying drawings, among which:

[0024] [Fig-1] [Fig. 1] is a partial schematic view of a cockpit of vehicle, provided with a control instrument according to the invention;

[0025] [Fig.2] [Fig.2] is a perspective view of a brake fitted to the instrument of order, according to a first embodiment;

[0026] [Fig.3] [Fig.3] is a perspective view of a portion of the brake according to the first embodiment;

[0027] [Fig.4] [Fig.4] is a perspective view of a brake fitted to the instrument of command, according to a second embodiment;

[0028] [Fig.5] [Fig.5] is an exploded perspective view of the brake according to the second mode of realization;

[0029] [Fig.6] [Fig.6] is another perspective view of the brake according to the second mode of realization. DETAILED DESCRIPTION OF THE INVENTION

[0030] With reference to Figures 1 to 6, the invention is described here in application to a control instrument, generally designated 1, equipping the cockpit of a vehicle V such as an air, land or naval vehicle. The control instrument 1 is here arranged to control the engine of said vehicle (the control instrument 1 is here what is commonly called the throttle).

[0031] The control instrument 1 comprises a frame 2 which is fixed to the structure of the vehicle V, in the cockpit, within easy reach of the pilot.

[0032] A lever 3 is mounted on the frame 2 to pivot around an axis of rotation 4 here horizontal.

[0033] The control instrument 1 further comprises a brake 10 comprising two stators 11.1, 11.2 linked in rotation to the frame 2 and a rotor 12 linked in rotation to the lever 3.

[0034] The brake 10 is a magnetic hysteresis brake.

[0035] According to the first embodiment shown in Figures 2 and 3, the rotor 12 is here a bell comprising a cylindrical external surface 14 and a cylindrical internal surface 16 which is coaxial with the external surface 14 and which defines an internal housing of the rotor 12. The external surface 14 and the internal surface 16 form main surfaces of the rotor 12.

[0036] The rotor 12 is made of a magnetic material and more particularly here a semi-remanent material. The material chosen is called “semi-remanent” because its major hysteresis cycle is similar to that of a magnet. The material is for example that produced under the brand name MAGNETOFLEX (and more particularly MA-GNETOFLEX 35 U) or CROVAC by the manufacturer VACUUMSCHMELZE.

[0037] The rotor 12 further comprises a tubular hub which is centered on the axis of rotation 4 and which connects the rotor 12 to the lever 3.

[0038] The stator 11.1 is an outer stator extending around the rotor 12 and the stator 11.2 is an inner stator which extends into the housing of the rotor 12.

[0039] The stator 11.1 comprises a cylindrical armature, made of a magnetic flux-conducting material, centered on the axis of rotation 4, and a set of permanent magnets 17.1 which are fixed to the internal periphery of the cylindrical armature to have a free surface forming a main surface 15.1, substantially cylindrical, of said stator 11.1 surrounding the external surface 14 of the rotor 12. The armature comprises teeth 18.1 which separate the magnets 17.1 from each other and which have a free surface close to the main surface 15.1 of said stator 11.1. The free surface of the teeth 18.1 is here flush with the free surface of the magnets 17.1 and therefore coincides with the main surface 15.1 of the stator 11.1. The magnets 17.1 are positioned so that their magnetization vector extends in a radial direction of the stator 11.1 to produce a radial or axial magnetic flux in the case illustrated in Figures 4 to 6. In addition, the magnets 17.1 all have the same pole oriented towards the rotor 12. The teeth 18 interposed between the magnets 17 are provided with a polarity opposite to that of the magnets. This architecture allows optimal looping of the magnetic flux.

[0040] The stator 11.1 comprises a cylindrical external surface 13.1 coaxial with the main surface 15.1 constituting the internal surface of the stator 11.1. The diameter of the main surface 15.1 of the stator 11.1 is slightly greater than the diameter of the surface external 14 of rotor 12.

[0041] The stator 11.2 has a structure similar to the stator 11.1 and is coaxial with it and with the rotor 12. The stator 11.2 is however arranged in the internal housing of the rotor 12 and comprises an armature carrying magnets 17.2 on its external periphery. The magnets 17.2 have a free surface defining a main surface 15.2 (which is the external surface of the stator 11.2 and not the internal surface as in the stator 11.1) and comprising teeth 18.2 separating the magnets 17.2 from each other.

[0042] As previously, the teeth 18.2 have a free surface close to the main surface 15.2 of said stator 11.2. The free surface of the teeth 18.2 is here flush with the free surface of the magnets 17.2 and therefore coincides with the main surface 15.2 of the stator 11.2. The magnets 17.2 are positioned so that their magnetization vector extends in a radial direction of the stator 11.2 to produce a radial magnetic flux. In addition, the magnets 17.2 all have the same pole oriented towards the rotor 12. This architecture allows optimal looping of the magnetic flux.

[0043] The stator 11.2 comprises a cylindrical internal surface 13.2 coaxial with the main surface 15.2 constituting the external surface of the stator 11.2.

[0044] It is understood that when the pilot moves the lever 3, the lever 3 moves the rotor 12 in rotation. Under the effect of the rotation of the rotor 12 relative to the stators 11.1 and 11.2, the bell saturates locally opposite the poles which will generate dry friction.

[0045] It is noted that the teeth 18.1, 18.2 make it possible to increase the number of poles, to channel the magnetic flux and to reduce the elastic return. More particularly, the number of poles allows the bell to align itself more, when it is remanent, on the poles.

[0046] In the second embodiment of Figures 4 to 6, the stators 11.1, 11.2 and the rotor 12 are not arranged in the same way. Indeed, the stators 11.1, 11.2 and the rotor 12 have a disc shape and the stators 11.1, 11.2 have planar main surfaces facing opposite planar main surfaces of the rotor 12. As a result, the rotor 12 has a central position between the stators 11.1, 11.2.

[0047] As previously, the main surfaces 15.1, 15.2 of the stators 11.1, 11.2 are formed by the free surfaces of the magnets 17.1, 17.2 which are carried by an armature comprising teeth 18.1, 18.2 separating the magnets 17.1, 17.2 from each other. The teeth 18.1, 18.2 have a free surface flush with the main surfaces 15.1, 15.2 of the stators 11.1, 11.2. The magnets 17.1, 17.2 of the stators 11.1 and 11.2 are arranged in a circle and have a magnetization vector parallel to the axis of rotation 4 and whose direction is oriented towards the rotor 12 to produce an axial magnetic flux.

[0048] The aforementioned friction torque is adjustable by offsetting one stator 11 relative to the other 11.2.

[0049] Alternatively, a reducer may be associated with the brake in order to further reduce the amplitude of the effect of the magnetic elastic return. In such an embodiment, the reducer comprises a first shaft connected to the rotor and a second shaft connected to the handle. The transmission ratio x of the reducer, from the handle 3 to the rotor 12, is greater than 1 so that a return of the rotor 12 over an angular amplitude 0 will result in a displacement of the handle 3 of a lesser amplitude equal to 0 / x.

[0050] Of course, the invention is not limited to the embodiments described but encompasses any variant falling within the scope of the invention as defined by the claims.

[0051] In particular, the brake may have a structure different from that described above.

[0052] The control instrument lever may for example be a button, a steering wheel, a lever, or other. The invention is also applicable to control surfaces and more generally to any device that must implement dry friction.

[0053] The handle may be mounted on the frame to slide along a linear axis.

[0054] The stator may constitute the internal element and the rotor the external or in payment. The brake may comprise a stator in the form of a drum and two annular rotors, one extending into the drum and the other around the drum.

[0055] The rotor 12 and the stator 11 can be mounted relative to each other to be movable, not only in rotation about the axis of rotation 4, but also in translation along the axis of rotation 4 to allow adjustment of the air gap between stator and rotor. For this purpose, the hub of the rotor 12 is mounted to slide axially on a tubular shaft connected in rotation, here via internal teeth, to the handle 3 and mounted in the frame 2 to pivot about the axis of rotation 4.

[0056] Alternatively, the stator may be fixed in rotation and movable in translation while the rotor is movable in rotation and fixed in translation.

[0057] The rotor may have the shape of a solid cylinder and not a hollow hub.

[0058] The rotor can carry the magnets and the stator can be made of semi-remanent or low-remanent material. residual.

[0059] The number of magnets and therefore of teeth, as well as the number of rotor(s) and / or stator(s) depend on the desired performance according to the envisaged application (braking torque, size, mass, effect of magnetic elastic return).

[0060] Another possible architecture may be the successive alternation of a stator then a rotor, at a frequency defined according to the desired performance according to the envisaged application.

Claims

Claims

1. Magnetic hysteresis brake (10), comprising at least a first element (11.1) carrying magnets (17.1) and a second element (12) made of magnetic material, a first surface (15.1) of the first element (11.1) being opposite a second surface (14) of the second element (12), so that the magnets (17.1) generate an induced magnetic flux in the second element (12) through said surfaces, characterized in that the magnets (17.1) are separated from each other by teeth (18.1) which are made of a material conducting the magnetic flux and which have a free surface close to the first surface (15.1).

2. A brake according to claim 1, wherein the first element (11.1) and the second element (12) are mounted to rotate relative to each other about an axis of rotation (4).

3. Brake according to claim 2, in which the first surface (15.1) and the second surface (14) are cylindrical with a circular section; the magnets (17.1) of the first element (11.1) being arranged in a cylinder and the magnetic flux being radial.

4. A brake according to claim 3, wherein the second element (12) is tubular in shape with a circular cross-section and the brake (10) comprises a second first element (11.2) which is arranged in the second element (12) and which has a third surface (15.2) opposite a fourth surface (16) of the second element (12), said fourth surface (16) being opposite the second surface (14) of the second element (12).

5. Brake according to claim 2, wherein the first surface (15.1) and the second surface (14) are planar; the magnets (17.1) of the first element (11.1) being arranged in a circle and the magnetic flux being axial.

6. Brake according to any one of claims 1, 2 and 5, comprising several first elements (11.1) and several second elements (12).

7. Control instrument (1) comprising a frame (2), a lever (3) mounted movably on the frame (2), and a brake (10) according to any one of the preceding claims, one of the first element (11.1) and the second element (12) being mounted fixed relative to the frame (2) and the other of the first element (11.1) and the second element (12) being linked to the lever (3).

8. A control instrument according to claim 7, wherein the handle (3) is mounted on the frame (2) for pivoting.

9. A control instrument according to claim 8, comprising a reducer having a first shaft connected to said other of the first element (11.1) and the second element (12) and a second shaft connected to the lever.

10. Vehicle comprising a control instrument according to any one of claims 7 to 9.

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