Magnetic brake with hysteresis and reduced elastic return

Abstract

A hysteresis magnetic 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), such 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) made of a material that conducts magnetic flux and having a free surface adjacent to the first surface (15.1). A control instrument and vehicle comprising such a brake. FIGURE IN ABRIDGED FORM: Fig. 2

Description

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

[0001] The present invention relates to a hysteresis magnetic brake usable, 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 resisting force in question is the result of a hysteretic loss imitating a friction exerted on a part connected to the object to be braked.

[0003] A hysteresis magnetic brake comprises two facing elements that are 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 that has magnetic properties such as: - when the material is subjected to an excitation 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 is therefore variable in the rotor. This variation creates hysteretic losses proportional to the rotor's motion. In other words, this results in a constant force opposing the rotor's motion.

[0005] Such hysteresis magnetic brakes are used, for example, in control instruments. The rotor is then connected to a lever on 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 imparted 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 and without the need for a power supply.

[0008] However, magnetic brakes with hysteresis exhibit a magnetic springback that causes the rotor to move in the opposite direction to the movement imparted by the user on the control lever once it is released. It is necessary for this magnetic springback to have the smallest possible amplitude to allow the control lever to remain in the position in which it was released. Indeed, if the magnetic springback amplitude is high, the control lever recoils after being released, and the engine thrust command is incorrect. Furthermore, the magnetic springback is defined as a physical phenomenon due to the hysteresis loop of the magnetic material used and the number of magnetic poles. Increasing the number of magnetic poles would reduce the magnetic springback.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 aims in particular at a magnetic hysteresis brake which at least partially remedies the aforementioned disadvantages. Summary of the invention

[0010] To this end, the invention provides a hysteresis magnetic brake comprising at least a first element bearing magnets and a second element made of magnetic material, a first surface of the first element being opposite 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 made of a material that conducts the magnetic flux and whose free surface is adjacent to the first surface.

[0011] Thus, these teeth have 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 proposed in which the first element and the second element are mounted to rotate relative to each other around an axis of rotation.

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

[0014] A brake is further proposed 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 proposed in which the first surface and the second surface are flat; the magnets of the first element being arranged in a circle and the magnetic flux being axial.

[0016] We further propose a brake comprising several first elements and several second elements.

[0017] A control instrument is further proposed comprising a frame, a lever mounted movable on the frame, and a brake, one of the first element and the second element being mounted fixed relative to the frame and the other of the first element and the second element being linked to the lever.

[0018] A control instrument is also proposed in which the lever is mounted on the frame to pivot.

[0019] A control instrument is further proposed comprising a reducer having a first shaft linked to said other of the first element and of the second element and a second shaft linked to the lever.

[0020] A vehicle comprising a control instrument is also proposed.

[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 features and advantages of the invention will become apparent from the following description of particular, non-limiting embodiments of the invention. Brief description of the drawings

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

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

[0025] [Fig.2] [Fig.2] is a perspective view of a brake equipping the control instrument, 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 equipping the control instrument, according to a second embodiment;

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

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

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

[0031] The control instrument 1 includes 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 a rotation axis 4, here horizontal.

[0033] The control instrument 1 further includes a brake 10 comprising two stators 11.1, 11.2 rotationally linked to the frame 2 and a rotor 12 rotationally linked to the handle 3.

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

[0035] According to the first embodiment shown in Figures 2 and 3, the rotor 12 is here a bell having an external cylindrical surface 14 and an internal cylindrical 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 principal surfaces of the rotor 12.

[0036] The rotor 12 is made of a magnetic material, and more specifically, in this case, a semi-remanent material. The material chosen is called "semi-remanent" because its major hysteresis loop is close to that of a magnet. The material is, for example, that produced under the brand name MAGNETOFLEX (and more specifically MAGNETOFLEX 35 U) or CROVAC by the manufacturer VACUUMSCHMELZE.

[0037] The rotor 12 further includes a tubular hub which is centered on the axis of rotation 4 and which links the rotor 12 to the handle 3.

[0038] The stator 11.1 is an external stator extending around the rotor 12 and the stator 11.2 is an internal stator extending 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 on the inner periphery of the cylindrical armature so as to have a free surface forming a principal surface 15.1, substantially cylindrical, of said stator 11.1 surrounding the external surface 14 of the rotor 12. The armature includes teeth 18.1 which separate the magnets 17.1 from each other and which have a free surface close to the principal surface 15.1 of said stator 11.1. The free surface of the teeth 18.1 is flush with the free surface of the magnets 17.1 and therefore coincides with the principal surface 15.1 of the stator 11.1. The magnets 17.1 are positioned so that their magnetization vector extends in a radial direction from the stator 11.1 to produce a radial magnetic flux, or axially 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 have a polarity opposite to that of the magnets. This architecture allows optimal feedback of the magnetic flux.

[0040] The stator 11.1 includes an external cylindrical 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 external surface 14 of the rotor 12.

[0041] The stator 11.2 has a similar structure to the stator 11.1 and is coaxial with it and with the rotor 12. However, the stator 11.2 is disposed within the internal housing of the rotor 12 and comprises an armature carrying magnets 17.2 on its outer periphery. The magnets 17.2 have a free surface defining a principal 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 having teeth 18.2 separating the magnets 17.2 from each other.

[0042] As before, the teeth 18.2 have a free surface close to the main surface 15.2 of the stator 11.2. The free surface of the teeth 18.2 is 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 from the stator 11.2 to produce a radial magnetic flux. Furthermore, the magnets 17.2 all have the same pole oriented towards the rotor 12. This arrangement allows for optimal magnetic flux feedback.

[0043] The stator 11.2 includes an internal cylindrical 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 locally saturates opposite the poles, which will generate dry friction.

[0045] It should be noted that the teeth 18.1, 18.2 increase the number of poles, channel the magnetic flux, and reduce elastic springback. More specifically, the increased number of poles allows the bell to align more closely with the poles when it is remanent.

[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 are disc-shaped, and the stators 11.1, 11.2 have main flat surfaces opposite the main flat surfaces of the rotor 12. As a result, the rotor 12 has a central position between the stators 11.1, 11.2.

[0047] As before, 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 having 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 according to 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 reduction gear can be associated with the brake to further reduce the magnitude of the magnetic elastic return effect. In such an embodiment, the reduction gear comprises a first shaft connected to the rotor and a second shaft connected to the lever. The transmission ratio x of the reduction gear, from the lever 3 to the rotor 12, is greater than 1, so that a return of the rotor 12 with an angular amplitude of 0 will result in a displacement of the lever 3 with a smaller 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 different structure from that described above.

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

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

[0054] The stator can constitute the internal element and the rotor the external element or Conversely, the brake may consist of a drum-shaped stator and two annular rotors, one extending inside 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 the stator and the rotor. To this end, 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 can be fixed in rotation and mobile in translation while the rotor is mobile 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 teeth, as well as the number of rotor(s) and / or stator(s) depend on the desired performance according to the intended application (braking torque, size, mass, effect of magnetic elastic return).

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

Claims

Demands

1. A control instrument (1) comprising a frame (2), a lever (3) movably mounted on the frame (2), and a hysteresis magnetic brake (10), said brake 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), such 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) made of a magnetic flux-conducting material and having a free surface adjacent to the first surface (15.1), one of the first element (11.1) and of the second element (12) being fixedly mounted relative to the frame (2) and the other of the first element (11.1) and the second element (12) being linked to the controller (3).

2. Control instrument (1) 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. Control instrument (1) according to claim 2, wherein the first surface (15.1) and the second surface (14) are cylindrical with a circular cross-section; the magnets (17.1) of the first element (11.1) being arranged in a cylinder and the magnetic flux being radial.

4. Control instrument (1) 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 disposed 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. Control instrument (1) 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. Control instrument (1) according to any one of claims 1, 2 and 5, wherein the brake comprises several first elements (11.1) and several second elements (12).

7. Control instrument according to any one of the preceding claims, wherein the lever (3) is mounted on the frame (2) to pivot.

8. Control instrument according to claim 7, comprising a reducer having a first shaft linked to said other of the first element (11.1) and of the second element (12) and a second shaft linked to the lever.

9. Vehicle comprising a control instrument according to any one of claims 1 to 8.