System for determining a torque applied between two rotating parts
The torque determination system addresses precision issues by using a guide bearing and concentric rings with magnetic tracks and sensors to accurately measure torque, enhancing accuracy in compact designs.
Patent Information
- Application Number
- FR2023005020
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2023-05-22
- Publication Date
- 2025-10-24
- Estimated Expiration
- 2043-05-22
AI Technical Summary
Existing torque determination systems face precision issues due to eccentricity induced by radial forces on deformable structures, particularly in compact designs, which affect the angular movement and torque measurement accuracy.
A torque determination system with a deformable structure that includes a guide bearing for radial retention and a mechanism to minimize radial oscillations, using a concentrically connected inner and outer rings with magnetic tracks and sensors to accurately measure angular displacement.
The system enhances precision in torque measurement by limiting eccentricity and radial movements, maintaining structural integrity while allowing angular movement, thus improving the accuracy of torque determination.
Smart Images
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Abstract
Description
Title of the invention: System for determining a torque applied between two rotating members
[0001] The invention relates to a system for determining a torque applied between two rotating members, as well as a module comprising such a system with a rotating shaft and a second member between which a torque to be determined is transmitted.
[0002] The invention applies in particular to the determination of a torque applied between two members integrated in a transmission of a motor torque to a vehicle, for example between the electric motor or the pedal assembly and the mechanical transmission of an electrically assisted bicycle.
[0003] To do this, it is known to use a test body having an inner ring equipped with a device for coupling in rotation to a first of the members and an outer ring intended to drive in rotation the second of the members, said outer ring extending around the inner ring and said rings being connected concentrically by a deformable structure which is arranged to transmit the torque between the members while allowing an angular movement between said rings as a function of the torque applied between said members.
[0004] Such a test body can be instrumented with an encoder by equipping each of the rings with a ring carrying a magnetic track, respectively inner and outer, which is capable of emitting a periodic signal representative of the rotational movement of the corresponding ring. In particular, each of the tracks has a succession of pairs of North and South poles to form a multipolar magnetic track delivering a pseudo-sinusoidal magnetic signal.
[0005] The determination system then comprises a sensor having a first - respectively a second - pattern of sensitive elements arranged at a reading distance from the inner track - respectively from the outer track - to form a signal representative of the angular position of the corresponding ring.
[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 difference between the rings, and therefore the torque applied in that it induces said angle by twisting the deformable structure.
[0007] In certain applications, the torque applied between the members may comprise a radial component which stresses the deformable structure. In particular, the planet carrier of a gearbox of an electrically assisted bicycle may be mounted floating relative to a shaft and therefore apply a radial force to the deformable structure. of a test body whose outer ring rotates said planet carrier and the inner ring is mounted on the shaft.
[0008] Thus, in addition to the angular movement necessary for determining the torque, the deformable structure may have a radial movement which induces an eccentricity of the rings and therefore of the magnetic tracks, which has a direct negative impact on the precision of the determination of the angle between the rings and therefore of the torque.
[0009] This problem is all the more critical in the case of a test body of reduced size, in particular radially, which further constrains the production of the deformable structure, in particular in relation to its radial rigidity compared to its torsional deformation which must induce a movement of the order of a few degrees of angle while resisting a torque of the order of 250 Nm.
[0010] The invention aims to improve the prior art by proposing in particular a determination system in which the eccentricity under stress of the rings is limited without constraining the design of the deformable structure, in particular in relation to the angular movement of the rings which is necessary for the precision of the determination of the torque.
[0011] To this end, according to a first aspect, the invention proposes a system for determining a torque applied between two rotating members, said system comprising: - a test body having an inner ring equipped with a device for rotating coupling to a first of the members and an outer ring intended to rotate the second of the members, said outer ring extending around the inner ring and said rings being concentrically connected by a deformable structure which is arranged to transmit the torque between the members while allowing angular movement between said rings as a function of the torque applied between said members; - a device for determining an angle between the rings which is a function of the torque applied;
[0012] said system comprising an interface part provided with a mechanism for driving the second member in rotation and a device for coupling it in rotation to the outer ring, said interface part being equipped with a bearing for guiding its rotation relative to the first member, said bearing being arranged to ensure radial retention of said interface part on said first member.
[0013] According to a second aspect, the invention proposes a module comprising a rotating shaft and a second member between which a torque is transmitted, said module comprising such a system for determining said torque in which the interface part drives the second member in rotation by being coupled in rotation to the outer ring of the test body, the inner ring of said test body having an association bore around the rotating shaft, the guide bearing being mounted in rotation substantially without radial play around said shaft.
[0014] Other objects and advantages of the invention will appear in the following description, given with reference to the appended figures, in which:
[0015] [Fig-1] is a partial perspective representation of the crankset of an electrically assisted bicycle equipped with a torque determination system according to one embodiment of the invention,
[0016] [Fig. la] being an exploded view of [Fig.l],
[0017] [Fig.lb] being a partial longitudinal sectional view of [Fig.l];
[0018] [Fig.2] is an exploded representation of a test body equipped with a device for angular measurement for a system according to the invention;
[0019] [Fig.3] is a partial exploded representation of the pedal assembly of an assisted bicycle electric vehicle equipped with a torque determination system according to a second embodiment of the invention,
[0020] [Fig.3a] being a partial longitudinal sectional view of [Fig.3];
[0021] [Fig.4] is a partial exploded representation of the pedal assembly of an assisted bicycle electric vehicle equipped with a torque determination system according to a third embodiment of the invention,
[0022] [Fig.4a] being a partial longitudinal sectional view of [Fig.4].
[0023] In relation to these figures, a system for determining a torque applied between two rotating members 1, 2 is described below, as well as a module comprising two members 1, 2 and such a system for determining the torque transmitted between said members.
[0024] In this description, the terms of positioning in space are taken with reference to the axis R of rotation of the first member 1. In particular, the terms “interior” and “exterior” relate to an arrangement respectively close to and at a distance from this axis R, and the terms “axial” and “radial” relate to an arrangement respectively along this axis R and moving away from or approaching it.
[0025] In particular, the system allows the determination of a torque applied between two members 1, 2 of a module integrated in a transmission of a motor torque to a vehicle, for example between the electric motor or the pedal assembly and the mechanical transmission of an electrically assisted bicycle.
[0026] [Fig.l] represents a crankset of an electrically assisted bicycle comprising a crank 3 equipped with a pedal 4, said crank being mounted on a shaft 1a driven in rotation along the axis R to form a member 1 for applying a pedaling torque M+ depending on the direction of pedaling.
[0027] The system comprises a test body which makes it possible to transmit the pedaling torque M+ to the other of the members 2 of the module, which, in the figures, is represented in the form: - a sleeve 2a, for example a satellite carrier of an epicyclic gear train of a motorized gearbox, exerting a torque Mbv (figures 1, 1a, 1b); or - a pinion 2b, for example from a motorized gearbox (figures 3, 3a, 4, 4a).
[0028] In this application, the pedaling force F at the end of the pedal 4 to be considered according to standard EN15194: 2017 is 1,500 N which, with a crank length Lm of 165 mm, generates a torque M+ of the order of 250 Nm. In particular, the torque to be transmitted by the test body is only in one direction of rotation (that represented M+ in the figures), insofar as the other direction corresponds to the freewheel of the bicycle.
[0029] The test body presents: - an inner ring 5 equipped with a device for rotating coupling to the first member 1; and - an outer ring 6 extending around the inner ring 5 and intended to drive the second member 2 in rotation.
[0030] In relation to the figures, the inner ring 5 has a bore 7 equipped with coupling means on the shaft, for example in the form of a thread or grooves.
[0031] According to one embodiment, a coupling nut of the test body with the first member 1 can be attached by being fixed in the bore 7, said nut having a bore allowing coupling, for example by being equipped with a thread or grooves.
[0032] The nut can be held in the bore 7: - by riveting, by presenting for this purpose a flange in which orifices are formed, the edge of the bore being provided with complementary orifices allowing the riveting of said nut by means of rivets; or - by crimping, or by being held in said bore by welding.
[0033] In relation to the figures, the bore 7 is directly provided with splines 7a for coupling with the shaft 1a of the first member 1.
[0034] 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 angular movement between said rings as a function of the torque applied between said members.
[0035] In particular, the torque resulting from the pedal torque M+ applied to the inner ring 5 and the torque Mbv applied to the sleeve 2a or the pinion 2b by the ring external 6 induces a torsion between the rings 5, 6 and therefore a relative angular displacement of said rings according to an angle of torsion which is a function of said torque.
[0036] The system comprises 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 torque applied.
[0037] According to one embodiment, the determination device comprises: - an encoder produced by equipping each of the rings 5, 6 with a ring 9, 10 carrying a magnetic track, respectively inner 9a and outer 10a, which is capable of emitting a periodic signal representative of the rotational movement of the corresponding ring 5, 6; - a sensor comprising a first 11 - respectively a second 12 - pattern of sensitive elements arranged at a reading distance from the inner track 9a - respectively from the outer track 10a - to form a signal representative of the angular position of the corresponding ring 9, 10; - a device for comparing the signals delivered by the sensor, said device being capable of determining an angle between the rings 5, 6 which is a function of the torque applied.
[0038] In relation to the figures, the axis of the pedal assembly is mounted in rotation in a casing 13 on which the sensor is implanted with the patterns 11, 12 at a reading distance from the corresponding tracks 9a, 10a.
[0039] According to one embodiment, each of the rings 9, 10 is carried by an inner 9b and outer 10b frame respectively, the inner ring 5 - or outer 6 - respectively having means for fixing the inner - or outer - frame to it.
[0040] In particular, each of the rings 5, 6 has orifices 5a, 6a for fixing the reinforcements 9b, 10b, in particular by rivets 14 or by screwing. In relation to the figures, the inner ring 5 - respectively outer ring 6 - has an outer circumferential wall - respectively inner - provided with three radial lobes 15, 16, as well as three fixing orifices 5a, 6a arranged at 120° from each other and being formed on each of the lobes 15, 16.
[0041] According to one embodiment, a succession of pairs of North and South poles is magnetized on a ring 9, 10 respectively to form a multipolar magnetic track 9a, 10a capable of emitting a magnetic signal of pseudo-sinusoidal shape.
[0042] The rings 9, 10 may 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 9a, 10a.
[0043] Each pattern 11, 12 may comprise at least two sensitive elements, in particular a plurality of aligned sensitive elements, as described in documents FR-2 792 403, EP-2 602 593 and EP-2 602 594.
[0044] The sensitive elements may be based on a magnetoresistive material whose resistance varies according to the magnetic signal of the track 9a, 10a to be detected, for example of the AMR, TMR or GMR type, or a Hall effect probe.
[0045] According to one embodiment, the angular position can be determined incrementally by means of the signal emitted by a magnetic track 9a, 10a. According to another 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 9, 10.
[0046] The system further comprises a device for comparing the signals delivered by the sensor, said device being capable of determining an angle between the rings 5, 6 which is a function of the torque applied. In relation to the figures, the sensor comprises a card 17 on which the patterns 11, 12 of sensitive elements are implanted in an electronic circuit.
[0047] According to one embodiment, the sensors deliver incremental square signals in quadrature, the comparison device comprising counting means indicating the angular position of each of the rings 9, 10 and subtraction means making it possible to calculate the difference between said angular positions, in particular as described in documents FR-2 816 051, FR-2 821 931 and FR-2 862 382.
[0048] The deformable structure comprises a set of branches 18 distributed angularly between the rings 5, 6. In particular, the branches 18 and the rings 5, 6 are formed in a single piece, for example by cutting with a wire machine or by stamping a blank of metallic material, or by laser cutting or by water jet.
[0049] In the figures, the branches 18 are inclined in the opposite direction to the rotation, which generates a lever arm which, by stressing the branches 18 in traction, reduces the stresses in a very effective manner with the counterpart of an increase in stiffness.
[0050] In the embodiments shown, the test body comprises three branches 18 which are separated by a branch-free sector. In particular, the branch-free sectors extend over an angle which is greater than 60°, the lobes 15, 16 each extending into a branch-free sector.
[0051] Alternatively, the branches 18 may have an S-shaped geometric conformation, two respectively inner and outer bent sections each connected to the inner ring 5 and the outer ring 6 respectively. This arrangement makes it possible to limit the radial size of the test body while increasing the length of the branches 18 in order to reduce their stiffness, in particular by maximizing the amplitude of the bent sections.
[0052] The system further comprises an interface part 19 which is provided with a mechanism for driving the second member 2 in rotation and a device for coupling it in rotation to the outer ring 6, said interface part also being provided with a bearing 20 for guiding its rotation relative to the first member 1, said bearing being arranged to ensure radial retention of said interface part on said first member.
[0053] In particular, the guide bearing comprises a bore 20a to allow it to be mounted in rotation substantially without radial play around the shaft 1a of the first member 1, which makes it possible to limit the transmission to the outer ring 6 of the radial oscillations of the second member 2, and thus to improve the precision of the measurements carried out by the sensor to determine the torque applied between the members 1, 2.
[0054] In the figures, the interface part 19 is mounted in rotation on the shaft 1a by means of a plain bearing arranged to ensure the rotational guidance of said part by sliding. Alternatively, the interface part 19 may be mounted in rotation on the shaft 1a by means of a rolling bearing, in particular a needle roller bearing.
[0055] In the embodiments shown, the interface part 19 has a discoidal geometry which has a central bore 21 in which an outer crown 22 of the bearing 20 is associated substantially without radial play, in particular by being shrunk into the bore 21 of the interface part 19.
[0056] In particular, in Figures 4, 4a, the interface part 19 has a barrel 23 which extends axially at the center of its discoidal geometry, the bore 21 for mounting the bearing 20 being formed in said barrel.
[0057] The interface part 19 and the bearing 20 are held axially on the shaft 1a by means of a radial washer 24 which is integral with said bearing (figures 1, 1a, 1b, 3, 3a) or formed from a separate part (figures 4, 4a), as well as an elastic washer 25 of the “circlip” type which is arranged in axial abutment against the washer 24 while being mounted in a radial groove 26 provided for this purpose in the periphery of said shaft.
[0058] The discoidal geometry of the interface part 19 is mounted coaxially opposite the test body axially, and the device for coupling said interface part to the outer ring 6 comprises a mechanism with pins 28 engaged in orifices 6b of said outer ring.
[0059] To the extent that manufacturing tolerances may cause the pins 28 not to be perfectly concentric with the outer ring 6, a clearance may be provided in this coupling device in order to facilitate assembly. A second advantageous aspect of this coupling device is that any deformations of the shaft 1a under load are not transmitted or are transmitted only slightly to the outer ring 6.
[0060] In particular, the interface part 19 and the outer ring 6 respectively comprise three pin orifices and three orifices 6b spaced 120° apart, the orifices 6b of said outer ring being in particular each formed on a lobe 16 respectively.
[0061] In Figures 1, 1a, 1b, the mechanism for driving the second member 2 in rotation by the interface part 19 comprises a mechanism with pins 27 engaged in orifices 29. To do this, the sleeve 2a comprises three blind orifices 29 spaced 120° apart, the interface part 19 carrying three pins 27 formed opposite the pins 28 for coupling to the outer ring 6.
[0062] In relation to [Fig.lb], the pins 27, 28 are carried by axes which allow the torque to be taken up directly, said axes also being able to be located with good precision.
[0063] This achievement thus makes it possible to obtain an electrically assisted bicycle with two means of propulsion: - muscular propulsion generated by the cyclist's pedaling, which enters through the pedal axle, which is transmitted via the test body to the reducer and then by the transmission (chain, cardan, belt) to the rear wheel; - an electric motor, the torque of which goes directly into the reducer (second component 2) and is added to the torque of the muscular propulsion.
[0064] Thus the pins 28, 27 transmit the torque from the test body to the reducer.
[0065] In Figures 3, 3a, 4, 4a, the interface part 19 drives the second member 2 in rotation by means of a gear mechanism.
[0066] In Figures 3, 3a, the discoidal geometry of the interface part 19 has a periphery which is provided with gear teeth 30a to cooperate with the pinion 2b of the second member 2.
[0067] In Figures 4, 4a the mechanism for driving the pinion 2b in rotation by the interface part 19 comprises a separate toothed wheel 31 which is mounted in rotation on the central barrel 23 of said interface part by means of a freewheel device 32.
Claims
Claims
1. Module comprising a rotating shaft (1a) and a second member (2, 2a, 2b) between which a torque is transmitted, said module comprising a system for determining said torque, said system comprising: - a test body having an inner ring (5) equipped with a device for coupling in rotation to the rotating shaft (1a) and an outer ring (6) intended to drive in rotation the second member (2, 2a, 2b), said outer ring extending around the inner ring (5) and said rings being concentrically connected by a deformable structure which is arranged to transmit the torque between the rotating shaft (1a) and the second member (2, 2a, 2b) while allowing an angular movement between said rings as a function of the torque applied between said rotating shaft and said second member; - a device for determining an angle between the rings (5, 6) which is a function of the torque applied;said module being characterized in that the system comprises an interface part (19) provided with a mechanism (27, 30, 31) for driving the second member (2, 2a, 2b) in rotation and a device (27, 28) for coupling it in rotation to the outer ring (6), said interface part being equipped with a bearing (20) for guiding its rotation relative to the rotating shaft (la), said bearing being arranged to ensure radial retention of said interface part on said rotating shaft, the inner ring (5) having a bore (7) for association around the rotating shaft (la), the guide bearing (20) being mounted in rotation substantially without radial play around said shaft.;
2. Module according to claim 1, characterized in that the bore (7) is equipped with means (7a) for coupling to the shaft (la), the guide bearing (20) having a mounting bore (20a) substantially without radial play around said shaft.
3. Module according to one of claims 1 or 2, characterized in that the interface part (19) has a bore (21) in which a outer crown (22) of the bearing (20) is associated substantially without radial play.
4. Module according to any one of claims 1 to 3, characterized in that the interface part (19) has a discoidal geometry which is mounted coaxially opposite the test body axially.
5. Module according to any one of claims 1 to 4, characterized in that the device for coupling the interface part (19) to the outer ring (6) comprises a mechanism with pins (28) engaged in orifices (6b).
6. Module according to any one of claims 1 to 5, characterized in that the mechanism for driving the second member (2) in rotation by the interface part (19) comprises a mechanism with pins (27) engaged in orifices (29).
7. Module according to any one of claims 1 to 5, characterized in that the mechanism for driving the second member (2) in rotation by the interface part (19) comprises a gear mechanism (30, 31).
8. Module according to claim 7, characterized in that the interface part (19) has a periphery which is provided with gear teeth (30a) for cooperating with a pinion (2b) of the second member (2).
9. Module according to any one of claims 1 to 8, characterized in that the mechanism (31) for driving the second member (2) in rotation by the interface part (19) is mounted on the interface part (19) by means of a freewheel device (32).
10. Module according to any one of claims 1 to 9, characterized in that the deformable structure comprises a set of branches (18) distributed angularly between the rings (5, 6).
11. Module according to any one of claims 1 to 10, characterized in that the determination device comprises: an encoder produced by equipping each of the rings (5, 6) with a ring (9, 10) carrying a magnetic track, respectively inner (9a) and outer (10a), which is capable of emitting a periodic signal representative of the rotational movement of the corresponding ring (5, 6); a sensor comprising a first (11) - respectively a second (12) - pattern of sensitive elements arranged at a reading distance from the inner track (9a) - respectively from the outer track (10a) - to form a signal representative of the angular position of the corresponding ring (9, 10); a device for comparing the signals delivered by the sensor, said device being capable of determining an angle between the rings (5, 6) which is a function of the torque applied.