Method of manufacturing a test body comprising a nut for coupling to a rotating member

Abstract

The invention relates to a manufacturing method providing: forming a test body (1) having two rings (2, 3) connected by a deformable structure arranged to transmit a torque applied in one direction between the rings (2, 3) while allowing their angular movement, the inner ring (2) having a bore (4) of nominal diameter Dnom; forming a nut (9) having an outer wall (11) extending axially along a nominal diameter (dnom); the fitting of the wall (11) into the bore (4) following an axial stroke allowing the rotational coupling of said test body on said nut, the nominal diameter dnom being such that: 98%×Dnom ≤ dnom ≤ 99.95%×Dnom and teeth (13) being angularly distributed in the bore (4) extending radially in a circumscribed diameter Ddents such that: 90%×dnom ≤ Ddents ≤ 99%×dnom. Figure 5

Description

Title of the invention: Method for manufacturing a test body comprising a nut for coupling to a rotating member

[0001] The invention relates to a method for manufacturing a test body comprising a nut, as well as a system for determining a torque applied in one direction between two rotating members which comprises a test body manufactured by implementing such a method.

[0002] The organs can in particular be integrated into a transmission of engine torque to a vehicle, for example at the level of the pedal assembly of an electrically assisted bicycle.

[0003] To do this, it is known to use a test body having an inner ring integral in rotation with means for coupling said test body to a first of the members, and an outer ring extending around the inner ring while having means for coupling 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 angular movement between said rings as a function of the torque applied between the 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] Document FR-2 821 931 describes the use of a device for comparing such signals which is capable of determining an angle of relative displacement of the rings, and therefore the torque applied in that it induces said angle by twisting the deformable structure.

[0007] In certain applications, particularly in relation to the transmission of an electrically assisted bicycle, the space available for installing the test body is severely limited. This results in the need to design test bodies with reduced bulk, particularly by cutting out a blank of material.

[0008] This constraint is all the more critical for the realization of the means coupling, especially those of the inner ring, as long as the maximum available space is used for the deformable structure in order to optimize the quality of the torque determination.

[0009] To solve these problems, test bodies are known whose inner ring has a bore in which a coupling nut with the first member is attached, said nut being fixed to said test body by fitting into said bore and / or by riveting on the inner ring.

[0010] The invention aims to improve the prior art by proposing in particular a method of manufacturing a test body in which a nut can be coupled to the inner ring in a particularly simple manner, while making the coupling necessary for the transmission of the torque to be measured more reliable.

[0011] To this end, according to a first aspect, the invention proposes a manufacturing method of a test body comprising a nut, said method providing: - to form a test body having an inner ring connected to an outer ring by means of a deformable structure which is arranged to transmit a torque applied in one direction between the rings while allowing angular movement of said rings as a function of said torque, said inner ring having a bore of nominal diameter Dnom; - to form a nut having an outer wall extending axially along a nominal diameter dnom; - the fitting of the outer wall into the bore following an axial stroke allowing the rotational coupling of said test body on said nut;

[0012] said method providing an outer wall of nominal diameter dnom which is such that: 98%xDnom < dnom < 99.95%xDnom, and, prior to fitting, forming teeth distributed angularly in the bore extending radially in a circumscribed diameter Ddents which is such that: 90%xdnom < Ddents < 99%xdnom.

[0013] According to a second aspect, the invention proposes a system for determining a torque applied in one direction between two rotating members, said system comprising a test body manufactured by implementing such a method, the nut and the outer ring being arranged to be coupled in rotation to a member respectively, said system further comprising a device for determining an angle between the rings which is a function of the torque applied.

[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 cross-sectional representation of a test body before em handle of a nut according to the invention, [Fig.1a] being an enlarged view centered on zone B of this [Fig.1];

[0016] [Fig.2] is a cross-sectional representation of a nut arranged to be fitted into the bore of the inner ring of the test body of [Fig.l];

[0017] [Fig.3] represents in exploded perspective the nut and the test body as represented in the preceding figures;

[0018] [Fig.4] represents the geometric arrangement of a tooth formed in the inner bore of the test body of the preceding figures;

[0019] [Fig.5] is a cross-sectional representation of the test body comprising the nut according to the preceding figures,

[0020] [Fig.5a] being an enlarged view centered on zone A of this [Fig.5],

[0021] [Fig.5b] being an enlarged view centered on zone B of [Fig.5a];

[0022] [Fig.6] is an axial sectional view of the test body of [Fig.5];

[0023] [Fig.6a] being an enlarged view centered on zone B of this [Fig.6];

[0024] [Fig.7] schematizes the interference of a tooth with a nut according to the previous figures.

[0025] In relation to these figures, a system for determining a torque Mbv applied between two rotating members in a direction S around a geometric axis of rotation R is described below.

[0026] In this description, the terms of positioning in space are taken with reference to the axis R of rotation. 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.

[0027] In particular, the system allows the determination of a torque applied between two components integrated in a transmission of engine torque to a vehicle, for example at the level of the pedal assembly of an electrically assisted bicycle.

[0028] In a known manner, such a crankset comprises a crank equipped with a pedal, said crank being mounted on a shaft driven in rotation along the axis R to form a first member for transmitting a pedaling torque along the pedaling direction S.

[0029] The system comprises a test body 1 which makes it possible to transmit the pedaling torque to the other of the members, this second member being for example a sleeve equipping a satellite carrier of an epicyclic train of a motorized gearbox, said second member exerting in reaction a torque Mbv.

[0030] In this application, the torque Mbv to be transmitted by the test body 1 is only in one direction S of rotation, insofar as the other direction corresponds to the freewheel of the bicycle.

[0031] The test body has an inner ring 2 integral in rotation with means for coupling said test body to the first member, and an outer ring 3 extending around the inner ring 2 while presenting means for coupling said test body to the second member.

[0032] In relation to the figures, the inner ring 2 has a bore 4 to allow the coupling of the test body 1 on the rotating shaft.

[0033] With regard to the coupling to the second member, the figures represent an inner circumferential wall of the outer ring 3 which has at least one radial lobe 5 which is equipped with a means 6 for fixing said outer ring to the sleeve of said second member. In particular, three lobes 5 at 120° are provided, each of them having an orifice 6 for fixing, in particular by a pin or by screwing, in a complementary orifice of the sleeve.

[0034] The rings 2, 3 are 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.

[0035] In particular, the applied torque Mbv induces a torsion between the rings 2, 3, and therefore a relative angular displacement of said rings according to a torsion angle which is a function of said torque.

[0036] The system comprises a device for determining the angle between the rings 2, 3 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 2, 3 with a ring carrying a magnetic track, respectively internal and external, which is capable of emitting a periodic signal representative of the rotational movement of the corresponding ring 2, 3; - a sensor comprising 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; - a device for comparing the signals delivered by the sensor, said device being capable of determining an angle between the rings 2, 3 which is a function of the torque Mbv applied.

[0038] In a known manner, the pedal axle can be mounted in rotation in a casing on which the sensor is installed with the patterns at a reading distance from the corresponding tracks.

[0039] Furthermore, each of the rings can be carried by an inner and outer frame respectively, the inner ring 2 - or outer ring 3 - having means 2a, 3a for fixing the inner frame - or outer ring - on it respectively. In the figures, each ring 2, 3 has orifices 2a, 3a for fixing the reinforcements, for example by screwing or riveting, and in particular three orifices 2a, 3a arranged at 120° to each other on the corresponding ring 2, 3.

[0040] In particular, the orifices 3a are formed on each of the lobes 5 of the outer ring 3. Similarly, the outer circumferential wall of the inner ring 2 also has radial lobes 7 on which the orifices 2a for fixing the inner frame are formed.

[0041] According to one embodiment, a succession of pairs of North and South poles is magnetized on a ring respectively to form a multipolar magnetic track capable of emitting a magnetic signal of pseudo-sinusoidal shape.

[0042] The rings 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.

[0043] Each pattern of the sensor 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 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. According to another embodiment, the angular position can be determined absolutely, i.e. relative to a reference position, by providing a secondary magnetic track or specific coding on the ring.

[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 2, 3 which is a function of the torque applied. In particular, the sensor may comprise a card on which the patterns 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 and subtraction means making it possible to calculate the difference between said angular positions, in particular as described in document FR-2 821 931.

[0048] The deformable structure comprises a set of branches 8 distributed angularly between the rings 2, 3. In particular, the branches 8 are inclined to generate a lever arm which, by stressing the branches 8 in traction, reduces the constraints in a very effective manner with the counterpart of an increase in the stiffness.

[0049] In the figures, the test body 1 comprises three branches which are separated by a sector without a branch. In particular, the sectors without a branch extend over an angle which is greater than 60°, the lobes 5, 7 each extending into a sector without a branch.

[0050] To facilitate the coupling of the inner ring 2 to the first member, a nut 9 for coupling the test body with said first member is fitted in the bore 4.

[0051] This embodiment makes it possible to fix the nut in the bore 4, in particular in a non-removable manner, by controlling its axial position relative to the inner ring 2, so as to guarantee the reading distance of the inner magnetic track by the first sensor.

[0052] This embodiment also allows simplified manufacturing of the rings 2, 3 and the deformable structure, in particular in a single piece, and to machine the coupling nut 9 separately before its fixing. In addition to the economic benefit of forming the body 1 in a single piece, the inner ring 2 can be produced with a dimension just sufficient for fixing the nut 9, in order to benefit from a compact test body 1 while maximizing the length of the deformable branches 8.

[0053] In particular, the nut is arranged to be coupled in rotation to the first member. To do this, as shown in the figures, the nut 9 has a bore 10 in which a rotating shaft, in particular as described previously in relation to an electrically assisted bicycle crankset, is intended to be fitted.

[0054] Advantageously, the bore 10 can be equipped with geometric means for rotational coupling around the shaft, for example in the form of a thread or coupling splines.

[0055] In a variant not shown, the nut 9 can be integrated into a rotating shaft.

[0056] A method of manufacturing a test body 1 comprising a nuts 9 as previously described.

[0057] The method provides for forming a test body 1 having an inner ring 2 and an outer ring 3 connected by a deformable structure as described previously, the inner ring 2 having a bore 4 of nominal diameter Dnom.

[0058] In particular, the method provides for forming the test body 1 (rings 2, 3 and deformable structure) in a single piece by cutting a blank of material, in particular metal, said cutting being able to be carried out with a wire machine, by stamping, by laser, by water jet.

[0059] This arrangement makes it easier to manufacture the test body 1, and thus to reduce the production costs of the determination system.

[0060] In particular, the method provides for forming by cutting the following elements in the test body: - an outer ring 3 with means 6 for coupling to a second member exterior, as well as holes 3a for fixing an external encoder frame; - an inner ring 2 with holes 2a for fixing an outer encoder armature; - the outer ring 3 around the inner ring 2 with a deformable structure comprising a set of branches 8 distributed angularly between the rings 2, 3, in particular according to a geometry as described previously.

[0061] The method provides for forming a nut 9 arranged to be mechanically coupled to an internal member, in particular a rotating shaft as described previously, said nut having an external wall 11 which extends axially along a nominal diameter dnom.

[0062] Then, the method provides for assembling the nut 9 to the test body 1 by fitting the outer wall 11 into the bore 4, following an axial stroke allowing the rotational coupling of said test body on said nut.

[0063] As shown in Figures 3, 5, 6 and 6a, the method provides for the formation of a nut 9 which has a radial flange 12 at the rear of the outer wall 11 of said nut, said flange being arranged to come into abutment on the inner ring 2 at the end of said fitting.

[0064] In the description, the terms “front” and “rear” are taken with reference to the direction of fitting of the nut 9 into the test body 1.

[0065] The method provides an outer wall 11 of nominal diameter dnom which is such that: 98%xDnom < dnom < 99.95%xDnom, so as to produce a fitting with a clearance which in particular facilitates the centering of the nut 9 in the bore 4.

[0066] Furthermore, prior to fitting, the method provides for forming teeth 13 distributed angularly in the bore 4 extending radially in a circumscribed diameter Ddents which is such that: 90%xdnom < Ddents < 99%xdnom.

[0067] This arrangement makes it possible to create an interference between the outer wall 11 of the nut 9 and the teeth 13 at the time of fitting, the rotational coupling being ensured by plastic deformation and shearing of said outer wall by the teeth by providing anchoring grooves.

[0068] Thus, the need to form geometric coupling means on the nut 9 is eliminated, which makes it possible to simplify manufacturing, and therefore to reduce production costs.

[0069] Advantageously, the teeth 13 are formed in the bore 4 at the time of cutting the test body 1 from a blank of material, which makes it possible to simplify manufacturing even more.

[0070] In relation to Figures 3, 6 and 6a, the method further provides for the formation of a

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[0082] clearance groove 14 at the rear of the outer wall 11 of the nut 9, so as to collect in said groove the shavings of material detaching from said outer wall under the effect of interference with the teeth 13 during the axial fitting of said nut into the test body 1. In particular, the groove 14 is formed on the flange 12 from the junction with the outer wall 11. As shown more particularly in Figures 1, 1a, 3, 5 and 5a, the method provides for the formation of teeth 13 which are angularly equidistributed in the bore 4, each extending axially along the fitting stroke. Furthermore, the method provides for forming teeth 13 which each have a peak 17, through which the circumscribed diameter Ddents passes. Advantageously, the method further provides for forming teeth 13 of identical geometry, which makes it easier to manufacture the test body 1, but also guarantees balanced mechanical stresses exerted on the outer wall 11 of the nut 9. The method provides for the formation of a number N of teeth 13 which is such that each of the teeth 13 has, during fitting, an interference surface Sdent_interf with the outer wall 11 which represents between 3% and 10% of the total interference surface Sinterf of all the N teeth with said wall. In particular, 10 to 40 teeth can be formed. In particular, the total interference surface Sinterf satisfies the following equation, since the teeth 13 all have identical geometry: Sinterf NxSdent_interf Advantageously, the method provides for the formation of teeth 13 whose radial section has a surface Sdent such that, during fitting, between 75% and 95% of the surface Sdent interferes with the outer wall 11. This arrangement makes it possible to anchor each tooth 13 deeply in the outer wall 11, and thus to improve the resistance of the coupling of the nut 9 in the bore 4 against the torque Mbv applied between the members. Advantageously, the method provides for the formation of teeth 13 having a total interference surface Sinterf with the outer wall 11 which is such that 10 3%xS nom — Simerf — 9x10 %XSnom, UVCC S^^^^ — 7F ÏX f In relation to [Fig.4], the method provides for the formation of teeth 13 each having a triangular radial section, said section having an upstream face 15 in the direction of application of the torque Mbv and a downstream face 16 which are connected by a vertex 17. In particular, the process provides for: - the formation of an upstream face 15 forming an angle a with the radial direction A (vertical in [Fig.4]), said angle a being between 0° and 10°; and / or - the formation of a downstream face 16 forming an angle at the top [3 with the upstream face 15, said angle [3 being between 20° and 60°.

[0083] In particular, the value of the angle a makes it possible to benefit from a tooth 13 with a substantially radial upstream wall 15, which makes it possible to guarantee increased resistance of the coupling of the nut 9 in the bore 4.

Claims

Claims

1. A method of manufacturing a test body (1) comprising a nut (9), said method providing: - forming a test body (1) having an inner ring (2) connected to an outer ring (3) by means of a deformable structure which is arranged to transmit a torque (Mbv) applied in one direction between the rings (2, 3) while allowing angular movement of said rings as a function of said torque, said inner ring having a bore (4) of nominal diameter (Dnom); - forming a nut (9) having an outer wall (11) extending axially along a nominal diameter (dnom); - fitting the outer wall (11) into the bore (4) along an axial stroke allowing rotational coupling of said test body on said nut; said method being characterized in that it provides an outer wall (11) of nominal diameter (dnom) which is such that: 98%xDnom < dnom < 99.95%xDnom, and, prior to fitting, to form teeth (13) distributed angularly in the bore (4) extending radially in a circumscribed diameter (Ddents) which is such that: 90%xdnom < Ddents < 99%xdnom.

2. Manufacturing method according to claim 1, characterized in that it provides for the formation of teeth (13) which are angularly equidistributed in the bore (4).

3. Manufacturing method according to one of claims 1 or 2, characterized in that it provides for the formation of teeth (13) extending axially along the fitting stroke.

4. Manufacturing method according to any one of claims 1 to 3, characterized in that it provides for the formation of a number N of teeth (13) which is such that each of the teeth (13) has, during fitting, an interference surface (Sdent_interf) with the outer wall (11) which represents between 3% and 10% of the total interference surface Sinterf of said teeth with said wall.

5. Manufacturing method according to any one of claims 1 to 4, characterized in that it provides for the formation of teeth (13) whose section radial has a surface (Sdent) which is such that, during fitting, between 75% and 95% of the surface (Sdent) interferes with the outer wall (11).

6. Manufacturing method according to any one of claims 1 to 5, characterized in that it provides for the formation of teeth (13) having a total interference surface Sinterf with the outer wall (11) which is such that 10 3%xSnom < Sinterf < 9x10 2%xSnom, with S nom = JT x ( "

7. Manufacturing method according to any one of claims 1 to 6, characterized in that it provides for the formation of teeth (13) having a triangular radial section, said section having an upstream face (15) in the direction of application of the torque (Mbv) and a downstream face (16) which are connected by a vertex (17).

8. Manufacturing method according to claim 7, characterized in that it provides for the formation of an upstream face (15) forming an angle (a) with the radial direction (A), said angle (a) being between 0° and 10°.

9. Manufacturing method according to one of claims 7 or 8, characterized in that it provides for the formation of a downstream face (16) forming an angle at the apex (|3) with the upstream face (15), said angle (|3) being between 20° and 60°.

10. Manufacturing method according to any one of claims 1 to 9, characterized in that it provides for forming the outer ring (3) around the inner ring (2) with a deformable structure comprising a set of branches (8) distributed angularly between the rings (2, in

11. Manufacturing method according to any one of claims 1 to 10, characterized in that the test body (1) is formed by cutting a blank of material, the teeth (13) being formed during said cutting.

12. Manufacturing method according to any one of claims 1 to 11, characterized in that it provides for the formation of a clearance groove (14) at the rear of the outer wall (11) of the nut (9).

13. System for determining a torque (Mbv) applied in one direction between two rotating members, said system comprising a test body (1) manufactured by implementing a method according to any one of claims 1 to 12, the nut (9) and the outer ring (3) being arranged to be coupled in rotation to respectively a organ, said system further comprising a device for determining an angle between the rings (2, 3) which is a function of the torque (Mbv) applied.

14. Determination system according to claim 13, characterized in that the nut (9) has a bore (10) in which a rotating shaft is intended to be fitted.

15. Determination system according to claim 14, characterized in that the bore (10) of the nut (9) is equipped with geometric means for coupling in rotation around the shaft.

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