System for determining the torque applied between two organs

Abstract

The invention relates to a system for determining the torque applied between two elements (1, 2) about an axis of rotation (R), comprising a test body having two rings (5, 6) rotationally fixed to each element (1, 2), and connected concentrically by a deformable structure; two encoders (23, 24) fixed to each ring (5, 6) by means of an armature (23b, 24b), at least one armature (23b, 24b) having tabs (31) extending under the track (23a, 24a) of the encoder (23, 24), the ring (5, 6) being equipped with a bearing surface (5a, 6a) for axial support of the armature (23b, 24b), said bearing surface having pockets in which each tab (31) is fixed to connect said encoder to said ring. Figure 2a

Description

Title of the invention: System for determining the torque applied between two components

[0001] The invention relates to a system for determining a torque applied between two components around an axis of rotation.

[0002] The invention applies in particular to the determination of a torque applied between two rotating elements which are integrated in a transmission of a motor torque to a vehicle, for example between the electric motor or the crankset and the mechanical transmission of an electric assisted bicycle.

[0003] To do this, it is known to use a test body having an inner ring fixed in rotation to coupling means of said test body to a first of the members, and an outer ring extending around the inner ring having coupling means of said test body to the second of the members, said rings being connected concentrically around the axis of rotation by a deformable structure which is arranged to transmit the torque between the members while allowing an angular deflection between said rings as a function of the torque applied between the members.

[0004] Such a test body can be instrumented with two encoders by equipping each of the rings with a ring carrying an inner and outer magnetic track, respectively, which is capable of emitting a periodic signal representative of the rotational displacement of the corresponding ring. In particular, each of the tracks has a succession of North and South pole pairs to form a multipolar magnetic track delivering a pseudo-sinusoidal magnetic signal.

[0005] The determination system then includes a torque determination device, which may in particular include a support carrying two sensors respectively inside and outside, each comprising a pattern of sensitive elements arranged at a reading distance from the inside or outside track to deliver a signal representative of the angular position of the corresponding encoder.

[0006] Documents FR-2 816 051, FR-2 821 931 and FR-2 862 382 describe the use of a device for comparing such signals which is capable of determining an angular gap between the rings, and therefore the applied torque in that it induces said angle by twisting the deformable structure.

[0007] In known systems, the magnetic rings of the encoders are each associated with a ring by means of an armature which is fixed to said ring by a mechanical linking element, in particular by screwing or riveting.

[0008] These solutions are not entirely satisfactory, as they require numerous operations to mount the encoders on the test body, which generates a cycle time incompatible with mass production.

[0009] Furthermore, these solutions require forming a recess on the mounting surfaces of the encoders on the test body, in order to avoid interference of the screw or rivet heads with the measuring sensors during rotation, which forces the production of smaller connecting parts, and further complicates the production of these systems.

[0010] The invention aims to improve the prior art by proposing in particular a system for determining a torque in which the fixing of the encoders to the test body is carried out in a simple and reliable manner.

[0011] To this end, the invention proposes a system for determining a torque applied between two components around an axis of rotation, said system comprising: - a test body having an inner ring fixed in rotation to coupling means of said test body to a first of the members, and an outer ring extending around the inner ring having coupling means of said test body to the second of the members, said rings being connected concentrically around the axis by a deformable structure which is arranged to transmit the torque between the members while allowing an angular deflection between said rings as a function of the torque applied between said members; - two encoders respectively internally fixed in rotation to the inner ring and externally fixed in rotation to the outer ring, each of said encoders comprising an armature carrying a track capable of emitting a periodic signal representative of the rotational displacement of the corresponding ring; - a torque determination device comprising an inner sensor and an outer sensor each comprising a pattern of sensitive elements arranged at a reading distance from the inner or outer track to deliver a signal representative of the angular position of the corresponding encoder, said device comprising means for comparing the signals delivered by each of the sensors to determine an angular gap between the rings which is a function of the applied torque;

[0012] the armature of at least one encoder having tabs extending under the track, the corresponding ring being equipped with an axial support bearing surface of the armature, said bearing having pockets in which respectively a tab is fixed to associate said encoder with said ring.

[0013] Other objects and advantages of the invention will become apparent from the following description, made with reference to the accompanying figures, in which:

[0014] [Fig-1] is a partial perspective representation of the crankset of an electrically assisted bicycle equipped with a torque determination system according to the invention;

[0015] [Fig.2a],

[0016] [Fig.2b] and

[0017] [Fig.2c] represent the proof body of [Fig.1], respectively in axial section ([Fig.2a]), exploded perspective ([Fig.2b]) and top view before encoder mounting ([Fig.2c]);

[0018] [Fig.3a],

[0019] [Fig.3b] and

[0020] [Fig. 3c] Figures 3a, 3b and 3c represent a proof body of a system of torque determination according to another embodiment of the invention, respectively in exploded perspective ([Fig.3a]), in axial section ([Fig.3b]) and in top view before mounting the encoders ([Fig.3c]).

[0021] In relation to these figures, a system for determining a torque applied between two organs 1, 2 around an axis of rotation R is described below.

[0022] In this description, the terms of positioning in space are taken with reference to the axis R of rotation. In particular, the terms "inside" and "outside" are related to an arrangement respectively close to and at a distance from this axis R, and the terms "axial" and "radial" are related to an arrangement respectively along this axis R and moving away from or towards it.

[0023] In particular, the system allows the determination of a torque applied between two rotating parts 1, 2 which are integrated into a transmission of a motor torque to a vehicle, for example at the level of the crankset of an electric assisted bicycle.

[0024] Fig. 1 represents a crankset of an electric assisted bicycle comprising a crank 3 equipped with a pedal 4, said crank being mounted on a shaft la driven in rotation around the axis R to form an element 1 for applying a pedaling torque M+ according to the direction of pedaling.

[0025] The system includes a test body which allows the pedaling torque M+ to be transmitted to the other of the organs 2, which, in the figures, is represented in the form of a pinion 2a, for example a freewheel of a motorized gearbox.

[0026] In this application, the pedaling force F at the end of the pedal 4, to be considered according to standard EN15194:2017, is 1500 N, which, with a crank length Lm of 165 mm, generates a pedaling torque M+ of approximately 250 Nm. In particular, the torque to be transmitted by the test body is only in one direction of rotation (that represented by the arrow M+ in the figures), insofar as the other direction corresponds to the freewheel of the bicycle.

[0027] The test body has an inner ring 5 rotationally fixed to coupling means of said test body to the first member 1, and an outer ring 6 extending around the inner ring 5 and having coupling means of said test body to the second member 2.

[0028] The rings 5, 6 are connected concentrically around the axis R by a deformable structure which is arranged to transmit the torque between the members 1, 2, while allowing an angular deflection between said rings as a function of the torque applied between said members.

[0029] In particular, the resulting torque from the pedaling torques M+ on the inner ring 5 and the torque applied by the sprocket 2a on the outer ring 6 induces a torsion between the rings 5, 6, and therefore a relative angular displacement of said rings along an angle of torsion which is a function of said torque.

[0030] In the embodiment shown, the deformable structure comprises a set of arms 7 distributed angularly between the rings 5, 6. In particular, the arms 7 and the rings 5, 6 are formed in one piece, in particular by stamping and / or by cutting a blank in metallic material (figures 2a to 2c).

[0031] The arms 7 are inclined in the opposite direction of the rotation, which generates a lever arm which, by stressing the arms 7 in tension, reduces the stresses very effectively with the corresponding increase in stiffness.

[0032] In the figures, the proof body comprises three branches 7 which are separated by a branchless sector. In particular, the branchless sectors extend over an angle which is greater than 60°.

[0033] The inner ring 5 has a bore 8 in which is brought a coupling nut 9 of the test body with the rotating shaft of the first member 1, said nut being fixed in said bore, in particular by being fitted into said bore.

[0034] This embodiment allows for simplified manufacturing of the rings 5, 6 and the deformable structure, particularly by deep drawing, and for separate machining of the coupling nut 9 before its attachment. In addition to the economic benefit of forming the test body by deep drawing, the inner ring 5 can be made with a dimension just sufficient for attaching the nut 9, thus providing a compact test body while maximizing the length of the deformable arms 7.

[0035] In particular, the nut 9 may have a bore 10 allowing the test body to be coupled to the shaft la of the first member 1, said bore being equipped with a thread or coupling splines. In [Fig. 1], the nut 9 is mounted axially against the rotating shaft la, for example on a radial shoulder formed at this effect on said rotating shaft, and is axially immobilized between said radial shoulder and an elastic washer 11 of the "circlip" type mounted in an annular groove formed peripherally on said rotating shaft.

[0036] Advantageously, the bore 8 of the inner ring 5 may have geometric means, for example grooves 12 (figures 3a, 3b), the outer periphery of the nut 9 having complementary geometric means, for example complementary grooves 13, to make the rotational holding of said nut in said bore reliable.

[0037] In Figures 1, 2a, 2b and 2c, the nut 9 is held in the bore 8 by riveting. To this end, the nut 9 has a flange 14 in which orifices 16 are formed, the edge of the bore 8 being provided with additional orifices 17 allowing the riveting of said nut by means of rivets 15.

[0038] Alternatively, the nut 9 can be held in the bore 8 by crimping by being held in said bore by welding.

[0039] With regard to the coupling to the second member 2, the outer ring 6 is provided with geometric means 18 for meshing with said second member. In particular, the geometric means for meshing 18 extend over an outer circumferential wall of the outer ring 6.

[0040] In the figures, the geometric means of gearing include teeth 18 so that the outer ring 6 forms a pinion meshed with the pinion 2a of the transmission.

[0041] In Figures 1, 2a, 2b and 2c, the system comprises a matrix 19, in particular of polymer material, for example based on polyoxymethylene (POM), which has an inner ring 20 in which the inner ring 5 is disposed, and an outer ring 21 in which the outer ring 6 is disposed, the gear teeth 18 of the outer ring 6 with the pinion 2a being formed on an outer peripheral wall of said outer ring.

[0042] In particular, in these figures, the test body is produced by stamping a metallic material, for example steel-based, and is arranged in the die 19, in particular by overmolding the polymer material forming said polymeric die.

[0043] In Figures 3a to 3b, the test body is made in one piece 22 with the geometric gearing means 18, said piece being made by molding a polymer material, for example based on polyoxymethylene (POM). In particular, the polymer piece 22 has an outer peripheral wall on which the gear teeth 18 are formed.

[0044] The system includes a device for determining the angle between the rings 5, 6 which, in particular taking into account the stiffness of the deformable structure, is a function of the applied torque.

[0045] To do this, the system includes two encoders, among which an inner encoder 23 fixed in rotation to the inner ring 5 and an outer encoder 24 fixed in rotation to the outer ring 6.

[0046] Each encoder 23, 24 comprises a ring fixed, for example by overmolding or by being attached, respectively to a ring 5, 6 by means of an armature 23b, 24b, forming respectively an inner magnetic track 23a and an outer magnetic track 24a which is capable of emitting a periodic signal representative of the rotational displacement of the corresponding ring 5, 6.

[0047] According to one embodiment, a succession of North and South pole pairs is magnetized on a ring of the encoders 23, 24 respectively to form a multipolar magnetic track 23a, 24a capable of emitting a magnetic signal of pseudo-sinusoidal shape.

[0048] The rings of the encoders 23, 24 can each comprise an annular matrix, for example made from a plastic or elastomer material, in which magnetic particles are dispersed, in particular ferrite or rare earth particles such as NdFeB, said particles being magnetized to form the magnetic tracks 23a, 24a.

[0049] The system further includes a torque determination device which comprises: - a support 25 carrying an inner sensor 26 and an outer sensor 27, each of said sensors comprising a pattern of sensitive elements arranged at a reading distance from the inner track 23a - respectively from the outer track 24a - to deliver a signal representative of the angular position of the corresponding encoder 23, 24; - means of comparing the signals delivered by each of the sensors 26, 27 to determine an angular gap between the rings 5, 6 which is a function of the applied torque.

[0050] Each sensor 26, 27 may comprise a pattern of at least two sensitive elements, including a plurality of aligned sensitive elements, as described in documents FR-2 792 403, EP-2 602 593 and EP-2 602 594.

[0051] The sensitive elements can be based on a magnetoresistive material whose resistance varies according to the magnetic signal of the track to be detected, for example of type AMR, TMR or GMR, or a Hall effect probe.

[0052] According to one embodiment, the angular position can be determined incrementally by means of the signal emitted by a magnetic track 23a, 24a. In particular, the sensors 26, 27 can be arranged to deliver incremental quadrature square wave signals, the comparison means comprising counting means indicating the angular position of each of the encoders 23, 24 and means subtraction methods allow for calculating the difference between these angular positions, particularly as described in the documents FR-2 816 051, FR-2 821 931 and FR-2 862 382.

[0053] According to one embodiment, the angular position can be determined absolutely, that is to say with respect to a reference position, by providing a secondary magnetic track or a specific coding on the ring of an encoder 23, 24.

[0054] In relation to the figures, the determination system further comprises a housing 28 in which are housed the test body, the encoders 23, 24 and the torque determination device.

[0055] In particular, the housing 28 includes an outer wall 29 having an opening 30 through which the rotating shaft is mounted for rotation, in particular by means of a bearing, said rotating shaft having an end projecting from said outer wall which is equipped with the crank 3 for applying a pedaling torque M+, which is arranged opposite said outer wall.

[0056] Each encoder 23, 24 comprises an inner armature 23b and an outer armature 24b respectively, on which is fixed the magnetic ring of the corresponding encoder 23, 24, the inner armature 23b - or outer armature 24b - being fixed on the inner ring 5 - or outer ring 6 respectively.

[0057] The armature 23b, 24b of at least one encoder 23, 24 has tabs 31 extending under the track 23a, 24a, i.e. in particular opposite the sensors 26, 27. The corresponding ring 5, 6 is equipped with a bearing surface 5a, 6a for axial support of the armature 23b, 24b, said bearing having pockets 32 in which respectively a tab is fixed to associate said encoder with said ring.

[0058] Thus, the means for attaching the encoder 23, 24 to the ring 5, 6 are located within the thickness of said ring, thereby avoiding the presence of protruding attachment means at the air gap between the magnetic tracks 23a, 24a and the reading faces of the sensors 26, 27, and thus the risk of interference during rotation. This arrangement also helps to limit the overall axial size of the instrumented test body.

[0059] Advantageously, in each of the embodiments shown, each of the armatures 23b, 24b has tabs 31, and each of the rings 5, 6 is equipped with pockets 32 for receiving said tabs.

[0060] Each armature 23b, 24b is formed by folding and / or stamping a metal sheet, in particular steel, and has a radial annular plate 33 on which is fixed the magnetic ring of the sensor 23, 24, as well as folds 34 which extend axially from an outer peripheral edge of said plate to form the tabs 31, said plate being axially supported on the bearing surface 5a, 6a of the corresponding ring 5, 6.

[0061] In the embodiments shown, the bearing surfaces 5a, 6a and the pockets 32 are formed in the polymer matrix 19 overmolding the test body (Figures 1, 2a, 2b and 2c) or in the polymer piece 22 forming the test body (Figures 3a to 3b), and extend angularly along a circular arc geometry around the axis R.

[0062] In particular, the outer crown 21 and inner crown 20 of the matrix 19 (Figures 1, 2a, 2b and 2c) or the rings 5, 6 of the polymeric proof body 22 (Figures 3a to 3c) each comprise radial lobes 5b, 6b extending angularly between two adjacent branches 7 and on which the corresponding reinforcement 23b, 24b is axially supported. Each inner lobe 5b comprises a pocket 32 ​​for the attachment of an inner tab 31, the outer crown 21 or ring 6 having pockets 32 each extending angularly outward from an outer lobe 6b.

[0063] In figures 1, 2a, 2b and 2c, the metallic proof body also includes lobes 5c, 6c which each extend between two adjacent branches 7, each lobe 5c, 6c being overmolded respectively by a lobe 5b, 6b of the corresponding crown 20, 21.

[0064] Advantageously, each armature 23b, 24b has at least three tabs 31 angularly equidistant under the track 23a, 24a, so as to ensure reliable fixing of the armature 23b, 24b to the test body over the entire circumference of said armature, and thus prevent any relative rotation of the encoders 23, 24 with respect to the corresponding ring 5, 6.

[0065] In the embodiments shown, the polymer crowns 20, 21 or rings 5, 6 each have three lobes 5b, 6b which each extend radially and angularly in a branch-free sector of the proof body, a pocket 32 ​​being formed in each inner lobe 5b and outer lobe 6b.

[0066] In particular, two adjacent tabs 31 are separated by a slot 36 extending over an angular sector whose angle is at least equal to the angle of the angular sector in which each of said tabs extends.

[0067] Advantageously, the tabs 31 are overmolded in the pockets 32 to ensure their fixation by anchoring in the polymeric material forming the matrix 19 or the test body 22, which makes it possible to fix the armatures 23b, 24b of the encoders 23, 24 to said test body reliably and in a minimum of operations, and thus to facilitate the industrial manufacture of the torque determination system.

[0068] To do this, the encoders 23, 24 and the possible metallic test body can be placed in a molding cavity into which a thermoplastic polymer material is then injected, in order to form by molding the polymer matrix 19 enveloping said metallic test body or the polymer piece 22 forming the test body, by overmolding the tabs of said encoders.

[0069] Advantageously, each tab 32 has a central cutout 35 into which the injected polymer material is intended to be inserted during the molding of the die 19 or the test body 22, in order to provide additional anchoring of said tab in the polymer material to prevent any axial displacement of the encoders 23, 24 relative to said die or test body.

Claims

1. Claims System for determining a torque applied between two members (1, 2) around an axis of rotation (R), said system comprising: - a test body having an inner ring (5) integral in rotation with means for coupling said test body to a first of the members (1), and an outer ring (6) extending around the inner ring (5) while having means for coupling said test body to the second of the members (2), said rings being concentrically connected around the axis (R) by a deformable structure which is arranged to transmit the torque between the members (1, 2) while allowing angular movement between said rings as a function of the torque applied between said members; - two encoders respectively inner (23) integral in rotation with the inner ring (5) and outer (24) integral in rotation with the outer ring (6), each of said encoders comprising an armature (23b, 24b) carrying a track (23a, 24a) capable of emitting a periodic signal representative of the rotational movement of the corresponding ring (5, 6); - a torque determination device comprising an inner sensor (26) and an outer sensor (27) each comprising a pattern of sensitive elements arranged at a reading distance from the inner track (23a) or outer track (24a) to deliver a signal representative of the angular position of the corresponding encoder (23, 24), said device comprising means for comparing the signals delivered by each of the sensors (26, 27) to determine an angular difference between the rings (5, 6) which is a function of the applied torque; said system being characterized in that the armature (23b, 24b) of at least one encoder (23, 24) has tabs (31) extending under the track (23a, 24a), the corresponding ring (5, 6) being equipped with a bearing surface (5a, 6a) for axial support of the armature (23b, 24b), said scope having pockets (32) in which respectively a tab (31) is fixed to associate said encoder with said ring.

2. A torque determination system according to claim 1, characterized in that each of the armatures (23b, 24b) has tabs (31), each of the rings (5, 6) being equipped with pockets (32).

3. System for determining a torque according to one of claims 1 or 2, characterized in that the armature (23b, 24b) has a radial annular plate (33) on which the track (23a, 24a) is formed, and axial folds (34) forming the tongues (31), said plate being in axial support on the bearing surface (5a, 6a) of the corresponding ring (5, 6).

4. System for determining a torque according to any one of claims 1 to 3, characterized in that two adjacent tabs (31) are separated by a notch (36) extending over an angular sector whose angle is at least equal to the angle of the angular sector in which each of said tabs extends.

5. System for determining a torque according to any one of claims 1 to 4, characterized in that the tabs (31) have a central cutout (35).

6. A torque determination system according to any one of claims 1 to 5, characterized in that the tabs (31) are overmolded in the pockets (32) to ensure their fixing.

7. A torque determination system according to any one of claims 1 to 6, characterized in that it comprises a die (19) having an inner crown (20) in which the inner ring (5) is arranged, and an outer crown (21) in which the outer ring (6) is arranged, the pockets (32) being formed in said crowns.

8. A torque determination system according to claim 7, characterized in that the test body is overmolded in a polymer matrix (19).

9. A torque determination system according to any one of claims 1 to 6, characterized in that the pockets (32) are formed in the rings (5, 6).

10. A torque determination system according to claim 9, characterized in that the test body is made of polymeric material.

11. System for determining a torque according to any one of claims 1 to 10, characterized in that the deformable structure comprises a set of branches (7) distributed angularly between the rings (5, 6).

12. A torque determination system according to claim 11, characterized in that the pockets (32) are made in radial lobes (5b, 6b) which extend angularly between the branches (7), the corresponding armature (23b, 24b) being axially supported on said lobes.

13. System for determining a torque according to any one of claims 1 to 12, characterized in that the outer ring (6) is provided with geometric means (18) for gearing with the second member (2).

14. System for determining a torque according to any one of claims 1 to 13, characterized in that the inner ring (5) has a bore (8) in which a nut (9) for coupling with the first member (1) is fitted.

15. System for determining a torque according to any one of claims 1 to 14, characterized in that the tracks (23a, 24a) of the encoders (23, 24) are each formed of a ring on which a succession of pairs of North and South poles is magnetized to form a multipolar magnetic track (23a, 24a) capable of emitting a magnetic signal of pseudo-sinusoidal shape, said ring being fixed on the armature (23b, 24b).

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