Magnetic hysteresis brake with adjustable air gap

Abstract

The invention relates to a magnetic hysteresis brake comprising an inner element (12) and an outer element (1111) which defines a cavity for receiving the inner element (11) such that the inner element (11) and the outer element (12) are rotatable about a pivoting axis (4) relative to each other. One of the elements is provided with magnets (15) and the other is made of semi-remanent material such that the magnets (15) generate in the semi-remanent material an induced magnetic field through the opposing surfaces (14, 16). The brake comprises a member (22) for adjusting the axial position of one of the elements relative to the other one of the elements in order to adjust a degree of depression of the inner element (11) into the outer element (12) and therefore an intensity of the induced magnetic field. The invention also relates to a control instrument and to a vehicle comprising such a brake.

Description

[0001] MAGNETIC BRAKE WITH ADJUSTABLE AIR GAP HYSTERESIS

[0002] 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.

[0003] BACKGROUND OF THE INVENTION The resistive force in question is the result of magnetic friction exerted on a part connected to the object to be braked.

[0004] A magnetic hysteresis brake comprises two elements that move opposite each other, namely a rotor and a stator: one of the elements, for example the stator, has magnetic poles opposite the rotor and the rotor is made of a material with high magnetic remanence. It should be remembered that such a material has magnetic properties such as:

[0005] - when the material is subjected to an exciting magnetic field, a magnetic field is induced in the material, and

[0006] - 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).

[0007] Thus, the magnetic poles of the stator generate the activating magnetic field and the induced field in the rotor produces resistance to the movement of the rotor.

[0008] Such hysteresis magnetic 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 instrument manipulated by the user. This resistance allows the user to better control the movement he imparts to the lever of the control instrument.

[0009] Document FR-A-2998347 describes a magnetic brake in which the poles are formed by electromagnetic windings.

[0010] Magnetic poles can also be formed by permanent magnets, which allows for a simpler structure.

[0011] However, the resistance force depends on the power of the magnets used and the air gap between the rotor and the stator. However, the sizing and adjustments necessary to obtain the desired resistance force are relatively complex.

[0012] SUBJECT OF THE INVENTION

[0013] The invention particularly aims at providing a magnetic hysteresis brake whose resistive force is adapted to the applications envisaged.

[0014] SUMMARY OF THE INVENTION

[0015] To this end, the invention provides a hysteresis magnetic brake, comprising an inner element having an outer surface centered on a pivot axis and an outer element having an inner surface that is centered on the pivot axis and that delimits a housing for receiving the inner element in such a way that the inner element and the outer element are rotatable about the pivot axis relative to each other. One of the elements is provided with magnets and the other of the elements is made of semi-remanent material in such a way that the magnets generate in the semi-remanent material an induced magnetic field through said surfaces when said surfaces are facing each other. The brake comprises an adjustment member in the axial position of one of the elements relative to the other of the elements to adjust a degree of penetration of the inner element into the outer element and therefore an intensity of the induced magnetic field.

[0016] So :

[0017] - if the internal surface and the external surface are frustoconical, the axial offset of the internal element relative to the external element makes it possible to modify in particular the air gap between them (i.e. the distance between the internal surface and the external surface);

[0018] - if the internal surface and the external surface are cylindrical, the axial offset of the internal element relative to the external element makes it possible to modify the rate of coverage of the internal surface by the external surface and therefore the surface available for the passage of the field lines.

[0019] As a result, adjusting the axial position of the internal element relative to the external element makes it possible to adjust the resistive force in a simple and economical manner.

[0020] The invention also relates to a control instrument equipped with such a brake and to a vehicle equipped with such a control instrument.

[0021] Other characteristics and advantages of the invention will emerge on reading the following description of a particular and non-limiting embodiment of the invention.

[0022] BRIEF DESCRIPTION OF THE DRAWINGS

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

[0024] Figure 1 is a partial schematic view of a vehicle cockpit, provided with a control instrument according to the invention; Figure 2 is a perspective view, in diametrical half-section, of a brake equipping the control instrument, according to a first embodiment of the invention;

[0025] Figure 3 is a schematic cross-sectional view of this brake showing the field lines in one of the brake magnets;

[0026] Figure 4 is a partial schematic view, in axial section, of this brake with a first axial positioning of the rotor;

[0027] Figure 5 is a partial schematic view, in axial section, of this brake with a second axial positioning of the rotor;

[0028] Figure 6 is a partial schematic view, in axial section, of this brake with a third axial positioning of the rotor;

[0029] Figure 7 is a partial schematic view, along a first axial section plane, of this brake;

[0030] Figure 8 is a partial schematic view, along a second axial section plane, of this brake;

[0031] Figure 9 is a partial schematic view, along a third axial section plane, of this brake;

[0032] Figure 10 is a partial schematic view, in axial section, of a brake according to a second embodiment of the invention.

[0033] DETAILED DESCRIPTION OF THE INVENTION

[0034] With reference to Figures 1 to 9, 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). The control instrument 1 comprises a frame 2 which is fixed to the structure of the vehicle, in the cockpit, within easy reach of the pilot.

[0035] A lever 3 is mounted on the frame 2 to pivot around a pivot axis 4 here horizontal.

[0036] The control instrument 1 further comprises a brake 10 comprising a stator 11 rotationally connected to the frame 1 and a rotor 12 rotationally connected to the lever 3.

[0037] Brake 10 is a hysteresis magnetic brake.

[0038] The stator 11 is formed from a stack of laminations which are stacked along the pivot axis 4 and are each pierced with a hole so as to form a housing 13 delimited by an internal surface 14 of the stack of laminations forming the stator 11. The internal surface 14 is of truncated cone shape centered on the pivot axis 4. The laminations are made of a semi-remanent material. The material chosen for the stack of laminations of the yoke 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 MAGNETOFLEX 35 U) or CROVAC by the manufacturer VACUUMS CHMEL ZE.

[0039] The rotor 12 comprises a tubular hub, made of steel, which is centered on the pivot axis 4 and which has a frustoconical peripheral surface on which magnets 15 are fixed. The magnets 15 are positioned so that their magnetization vector extends in a radial direction of the hub and are oriented north-south and south-north alternately in a circumferential direction of the hub. Thus, in this circumferential direction, the north pole of a magnet 15 is framed by the south poles of the two adjacent magnets 15, and so on... to form poles of alternating magnetization on an external surface 16 of the rotor 12.

[0040] The rotor 12 and the stator 11 are mounted relative to each other to be movable, not only in rotation about the pivot axis 4, but also in translation along the pivot axis 4. For this purpose, the hub of the rotor 12 is mounted to slide axially on a tubular shaft 17 connected in rotation, here via internal teeth, to the handle 3 and mounted in the frame 2 to pivot about the pivot axis 4. The amplitude of the translational movement of the hub 12 is such that the rotor 12 and the stator 11 have two extreme relative positions:

[0041] - a position of maximum insertion in which the rotor 12 is received in the housing 13 of the stator 11 and comes to bear against a front stop 18 (here a stop ring) integral with the tubular shaft 17 so that the internal surface 14 and the external surface 16 extend opposite one another with a minimal air gap between them (see figure 4);

[0042] - a minimum depression position in which the rotor 12 is partly disengaged from the housing 14 of the housing 13 of the stator 11 and is close to a collar 19 secured to the tubular shaft 17 so that the internal surface 14 and the external surface 16 are offset from each other with a maximum air gap between them (see figure 6).

[0043] An intermediate position has also been shown in Figure 5. It will be noted that the depth of insertion of the rotor 12 into the stator 11 also conditions the area of ​​the external surface 16 opposite the internal surface 14, and therefore the degree of coverage of these two surfaces. It is recalled that the degree of coverage of the two surfaces is representative of the passage section available for the field lines (the field lines have been shown in Figure 3). Thus, the more the rotor 12 is inserted into the stator 11, the greater the resistance to pivoting of the rotor 12 will be.

[0044] The rotor 12 is linked in rotation to the shaft 17 and guided in translation by means of pins 20 each extending parallel to the pivot axis 4 and each having an end section embedded in the collar

[0045] 19 and an end section received in a bore 21 of the rotor 12 sliding parallel to the pivot axis 4 (see figure 7). The pins 20 are here three in number and are symmetrically arranged around the pivot axis 4.

[0046] Adjusting the rotor position 12 along the pins

[0047] 20 is ensured by means of two screws 22 which extend parallel to the pivot axis 4 in two diametrically opposite positions (see figure 9 where only one of the screws is visible). Each screw 22 comprises two end sections threaded in opposite directions and engaged respectively for one in a thread 23 of the rotor 12 and for the other in a thread 24 of the collar 19. The rotation of the screws 22 brings the rotor 12 closer or further away from the collar 19 depending on the direction of rotation.

[0048] The locking of the adjustment in axial position is ensured by point screws 25 engaged in threads 26 of the collar 19 to project from the collar 19 and bear against the rotor 12. When the point screws 25 are tightened against the rotor 12, they put the screws 22 under tension and prevent them from loosening once the adjustment in axial position has been carried out.

[0049] It is understood from Figure 3 that the flux lines of the magnetic field generated by the magnets 15 pass through the surfaces 16 and 14 and close in the stator 11 to induce a magnetic field there. Under the effect of the rotation of the rotor 12 relative to the stator 11, the semi-remanent material of the stator 11 will therefore behave like a magnet and generate a stator magnetic field opposing the rotor magnetic field in the air gap: this opposition of the fields will create a dry friction torque whose value does not depend on the rotation speed. This dry friction produces resistance to the relative pivoting of the rotor 12 and the stator 11.

[0050] Between the two extreme positions, we understand that there are intermediate positions in which magnetic friction is present but is less than in the maximum depression position, the magnetic friction increasing as we move away from the minimum depression position and approach the maximum depression position.

[0051] In the embodiment of Figure 10, the surfaces 14 and 16 are cylindrical centered on the pivot axis 4.

[0052] As previously, the rotor 12 is adjustable in axial position relative to the stator 11 between two extreme relative positions:

[0053] - a maximum insertion position in which the rotor 12 is received in the housing 13 of the stator 11 and comes to bear against a stop 18 (here a stop ring) integral with the tubular shaft 17 so that a maximum of the internal surface 14 is located opposite the external surface 16;

[0054] - a minimum depression position in which the rotor 12 is partly disengaged from the housing 14 of the housing 13 of the stator 11 and is close to a collar 19 secured to the tubular shaft 17 so that a minimum of the internal surface 14 is located opposite the external surface 16.

[0055] It will be noted that, in this embodiment, the air gap does not depend on the depth of insertion of the rotor 12 into the stator 11. Only the degree of coverage of the two surfaces 14, 16 is modified.

[0056] 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. In particular, the brake may have a structure different from that described above.

[0057] The control instrument lever may, for example, be a button, a steering wheel, a lever, or other. The invention is also applicable to the control of control surfaces and more generally to any device that must implement dry friction.

[0058] The stator can be the inner element and the rotor the outer element.

[0059] The stator can be fixed in rotation and mobile in translation while the rotor is mobile in rotation and fixed in translation.

[0060] The rotor can be shaped like a solid cylinder rather than a hollow hub.

[0061] The stator can carry the magnets and the rotor can be made of semi-remanent material.

[0062] The locking in position of the hub on the shaft can be obtained by tightening the hub of the shaft (tightening by screwing or keying for example) or by any other locking means. There can be one or more locking means. There can be one or more position adjustment members.

[0063] The position adjustment can result from the sliding of the rotor 12 on the shaft 17 but also from the screwing of the rotor 12 onto the shaft 17.

Claims

DEMANDS 1. A hysteresis magnetic brake, comprising an internal element (12) having an external surface (16) centered on a pivot axis (4) and an external element (11) having an internal surface (14) which is centered on the pivot axis (4) and which delimits a housing for receiving the internal element (12) such that the internal element (12) and the external element (11) are free to rotate about the pivot axis (4) relative to each other, one of the elements being provided with magnets (15) and the other of the elements being made of semi-remanent material such that the magnets (15) generate in the semi-remanent material an induced magnetic field through said surfaces (14, 16) when said surfaces (14, 16) are facing each other,the brake comprising an adjustment member (22) in the axial position of one of the elements relative to the other of the elements to adjust a degree of penetration of the internal element (12) into the external element (11) and therefore an intensity of the induced magnetic field and at least one of the internal element (12) and the external element (11) being adjustable in position and mounted to slide on a shaft (17),characterized in that the axial position adjustment member comprises at least one screw (22) extending parallel to the pivot axis (4) and comprising two end sections threaded in opposite directions and engaged respectively in a tapped hole (23) of the internal element (12) carried by the shaft (17) and for the other in a tapped hole (24) of a flange (19) of the shaft (17), and a locking of the axial position adjustment is ensured by set screws (25) engaged in tapped holes (26) of the flange (19) to protrude from the flange (19) and bear against the element (12) mounted on the shaft (17).

2. Brake according to claim 1, wherein the internal surface (14) and external surface (16) are frustoconical surfaces having respective axes aligned on the pivot axis (4).

3. Brake according to claim 1, wherein the internal surface (14) and the external surface (16) are cylindrical surfaces having generatrices extending parallel to the pivot axis (4).

4. Brake according to claim 1, wherein the element (12) carried by the shaft (17) is rotationally linked to the shaft (17) and guided in translation by means of pins (20) each extending parallel to the pivot axis (4) and each having an end section embedded in a collar (19) of the shaft (17).

5. Control instrument comprising a frame, a lever mounted to pivot on the frame, and a brake according to any one of the preceding claims, one of the internal and external elements of the brake being rotationally linked to the frame and the other of the internal and external elements of the brake being rotationally linked to the lever.

6. Vehicle comprising a control instrument according to the preceding claim.

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