System for determining the rotational information of an organ

Abstract

The invention relates to a system for determining rotation information of an organ (1) around an axis (R) by means of a device comprising an encoder (11, 12) carried by a body (50) fixed in rotation to said organ, said encoder having a track (11a, 12a) capable of emitting a periodic signal representative of the rotational displacement of said organ; a sensor comprising a sensitive pattern (15, 16) disposed at a reading distance (d) from the track (11a, 12a) to deliver the information as a function of said displacement; said system comprising a housing (17) in which said component is rotatably mounted by means of a bearing (18) and, fixed in the housing (17), a module (19) to which the sensor is attached, the guide bearing (18) being carried by the module (19), a spacer (26) for adjusting the reading distance (d) being disposed between the body (50) and the guide bearing (18). Figure 5

Description

Title of the invention: System for determining the rotational information of an organ

[0001] The invention relates to a system for determining rotation information of an organ around an axis by means of a device comprising an encoder and a sensor.

[0002] In particular, the encoder is carried by a body fixed in rotation to the organ, presenting a track capable of emitting a periodic signal representative of the rotational displacement of said organ, the sensor comprising a sensitive pattern disposed at a reading distance from the track to deliver the rotation information as a function of said displacement.

[0003] According to a particular application, the system allows the determination of a torque applied between two rotating parts, in particular integrated into 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.

[0004] To do this, it is known to use a test body having an inner section fixed in rotation to a member, and an outer section extending around the inner section having means for coupling said body to the second member, said sections being connected concentrically around the axis by a deformable structure which is arranged to transmit a torque between the members while allowing an angular deflection between said sections as a function of the torque applied between said members.

[0005] Such a test body can be instrumented with two concentric encoders, each having one track. In particular, each track has a succession of North and South pole pairs to form a multipolar magnetic track delivering a pseudo-sinusoidal magnetic signal.

[0006] The sensor comprises two sensitive patterns arranged respectively at a reading distance from a track, said sensor comparing the displacements of the sections to determine the applied torque.

[0007] Documents FR-2 816 051, FR-2 821 931 and FR-2 862 382 describe the comparison of such signals to determine an angular gap between the sections, and therefore the applied torque in that it induces said angle by torsion of the deformable structure.

[0008] In known systems, there is a problem of adjusting the reading distance between the sensitive pattern and the corresponding encoder track, which must be done precisely.

[0009] In particular, for the determination of the torque, the reading distance must be stable and equivalent for both sensors, so as not to distort the determination.

[0010] The invention aims to improve the prior art by proposing in particular a determination system allowing the reading distance of sensitive patterns to be made more reliable, and in a particularly simple way.

[0011] To this end, the invention proposes a system for determining the rotational information of an organ around an axis by means of a device comprising: - an encoder carried by a body fixed in rotation to said organ, said encoder having a track capable of emitting a periodic signal representative of the rotational displacement of said organ; - a sensor comprising a sensitive pattern arranged at a reading distance from the track to deliver information according to said displacement;

[0012] said system comprising a housing in which said organ is mounted for rotation by means of a guide bearing and, fixed in the housing, a module on which the sensor is associated, the guide bearing being carried by the module, a spacer for adjusting the reading distance being disposed between the body carrying the encoder and said bearing.

[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 exploded perspective representation of the crankset of an electric assisted bicycle equipped with a system according to the invention for determining the rotational torque between two organs rotating around an axis of rotation;

[0015] [Fig. la] shows the assembly of the bearing in the module;

[0016] [Fig.2] is a perspective and axial sectional representation of the module of the [Fig.l];

[0017] [Fig.3] shows in exploded perspective the assembly of the sensor on the module of the previous figures;

[0018] [Fig.4] shows in exploded perspective the assembly in the casing of the assembly module / bearing / sensor of the previous figures;

[0019] [Fig. 5] shows a partial axial section of the electric assist bicycle crankset equipped with the system for determining the previous figures;

[0020] [Fig.5a],

[0021] [Fig.5b] and

[0022] [Fig.5c] represent, following a view similar to [Fig.5], a bicycle crankset electric assistance equipped with a determination system according respectively to a variant embodiment of the invention.

[0023] In relation to these figures, a system for determining rotation information of an organ 1 around an axis R is described below.

[0024] In this description, the terms of positioning in space are taken with reference to the axis of rotation R. In particular, the terms "inside" and "outside" refer to an arrangement respectively close to and at a distance from this axis R, and the terms "axial" and "radial" refer to an arrangement respectively along this axis R and away from or towards it. Furthermore, the terms "internal" and "external" refer to an arrangement respectively on one side and the other along the axis R, specifically downwards and upwards in Figures 5.

[0025] According to a particular application, the system allows the determination of a torque applied between two organs 1 rotating around the axis R, said organs being integrated into a transmission of a motor torque to a vehicle, for example at the level of the crankset of an electric assisted bicycle.

[0026] According to other applications, the system allows the determination of different information such as the position or rotational speed of a rotating part.

[0027] According to the embodiment shown, one of the components 1 is equipped with a part 2 for actuating its rotation. In particular, [Fig. 1] represents a crankset of an electric-assisted bicycle comprising a crank 2 equipped with a pedal 3, said crank being mounted on a shaft la driven in rotation about the axis R to form a component 1 for applying a pedaling torque M+ in the direction of pedaling.

[0028] The system includes a test body 50 which allows the pedaling torque M+ to be transmitted to the second element. In particular, the second element may include a sleeve arranged concentrically around the shaft la, said sleeve being, for example, connected to a planet carrier of an epicyclic gear train of a motorized gearbox, exerting a rotational torque oriented in a direction opposite to that of the pedaling torque M+.

[0029] In this application, the pedaling force F at the end of the pedal 3, to be considered according to standard EN15194:2017, is 1500 N, which, with a crank length 2 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), since the other direction corresponds to the freewheel of the bicycle.

[0030] The test body 50 has an inner section 4 fixed in rotation to the first member 1, and an outer section 5 extending around the inner section 4 and having means for coupling said test body to the second member.

[0031] In relation to the figures, the inner section 4 has a bore 6 equipped with coupling means on the shaft la, in particular in the form of grooves 7a arranged to engage with complementary ribs 7b formed circumferentially and in relief on the periphery of said shaft.

[0032] With regard to the coupling to the second component, [Fig. 1] represents an outer section 5 whose inner circumferential wall has at least one radial lobe 8 which is equipped with a means 9 for fixing said outer section to a sleeve of said second component, as described above. In particular, three lobes 8 at 120° are provided, each of them having a fixing hole 9, notably by a pin or by screwing into a complementary hole of such a sleeve.

[0033] Sections 4, 5 are connected concentrically around the axis R by a deformable structure which is arranged to transmit a torque between the members, while allowing an angular deflection between said sections, depending on the torque applied between said members.

[0034] In particular, the resulting torque from the pedaling torques M+ on the inner section 4 and the torque applied by the second component on the outer section 5 induces a torsion between sections 4, 5, and therefore a relative angular displacement of said sections along a torsion angle which is a function of said torque.

[0035] In the embodiments shown, the deformable structure comprises a set of branches 10 distributed angularly between sections 4, 5. In particular, the branches 10 and the sections 4, 5 are formed from a single piece, in particular by stamping and / or by cutting a blank in metallic material.

[0036] The arms 10 are inclined in the opposite direction of the rotation, which generates a lever arm which, by stressing the arms 10 in tension, reduces the stresses very effectively with a corresponding increase in stiffness.

[0037] In [Fig.1], the proof body 50 comprises three branches 10, each of which has a curved geometry arranged to ensure an effective lever arm effect while having a reduced radial footprint, the lobes 8 each extending radially in an external bend of a branch 10 respectively.

[0038] The system includes a device for determining the angle between sections 4, 5 which, in particular taking into account the stiffness of the deformable structure, is a function of the applied torque.

[0039] To do this, the device includes two concentric encoders carried by respectively a section 4, 5 of the test body 50, among which an inner encoder 11 - respectively outer 12 - fixed in rotation to the inner section 4 - respectively outer 5 -, each presenting a track 1la, 12a capable of emitting a signal representative of the rotational displacement of respectively a member 1.

[0040] According to other applications, the body 50 can be equipped with one or more encoders 11, 12 to determine rotation information of the organ 1, such as position or its speed of rotation.

[0041] In the embodiment shown, each encoder 11,12 is fixed to a section 4, 5 respectively and carries an inner magnetic track 1a and an outer magnetic track 12a respectively which is capable of emitting a periodic signal representative of the rotational displacement of the corresponding section 4, 5.

[0042] Each of the encoders 11,12 is carried by an inner armature 11b and an outer armature 12b respectively, the inner section 4 - and outer section 5 - having means for fixing the inner armature 11b - and outer section 12b - to it, in particular in the form of screwing or riveting holes 4a, 5a.

[0043] In relation to [Fig.1], the inner section 4 has an outer circumferential wall provided with three radial lobes 13, and the outer section 5 has three radial lobes 14 which are formed on its inner circumferential wall by being angularly offset from the lobes 8 for attachment to the second organ, each section 4, 5 having three attachment orifices 4a, 5a arranged at 120° to each other by being formed on each of the lobes 13, 14.

[0044] According to one embodiment, a succession of North and South pole pairs is magnetized on an encoder 11,12 respectively to form a multipolar magnetic track lia, 12a capable of emitting a magnetic signal of pseudo-sinusoidal shape.

[0045] The encoders 11,12 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 1a, 12a.

[0046] The determination device further includes a sensor comprising at least two sensitive motifs respectively inner 15 and outer 16 arranged each at a reading distance d from the track respectively inner 1 la and outer 12a to deliver the rotation information of the corresponding member 1 as a function of its displacement.

[0047] In the embodiments shown, each sensitive motif 15, 16 is arranged to deliver a signal representative of the angular position of the corresponding encoder 11, 12, and the sensor uses said signals to compare the displacements of the corresponding sections 4, 5, in order to determine an angular gap between said sections, which is a function of the applied torque.

[0048] According to one embodiment, each motif 15, 16 may comprise 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.

[0049] The sensitive elements can be based on a magnetoresistive material whose resistance varies according to the magnetic signal of the track lia, 12a to be detected, for example of type AMR, TMR or GMR, or a Hall effect probe.

[0050] According to one embodiment, the angular position can be determined incrementally by means of the signal emitted by a magnetic track 1a, 12a. In particular, the sensitive patterns 15, 16 can be arranged to deliver incremental quadrature square signals, the sensor comprising comparison means which have counting means indicating the angular position of each of the encoders 11, 12, as well as subtraction means allowing the difference between said angular positions to be calculated, in particular as described in documents FR-2 816 051, FR-2 821 931 and FR-2 862 382.

[0051] 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 washer of an encoder 11, 12, a pattern of the sensor being able to be arranged at a reading distance d from said track or said coding.

[0052] In relation to the figures, the determination system further comprises a housing 17 in which the member 1 is mounted for rotation by means of a guide bearing 18 and, fixed in the housing 17, a module 19 on which the sensor is associated.

[0053] In particular, the housing 17 includes an outer wall 20 provided with a bore 21 through which the rotating shaft is mounted in rotation by means of the bearing 18, said rotating shaft having an end 22 projecting from said outer wall which is equipped with the crank 2 for applying a pedaling torque M+.

[0054] The housing 17 has a cavity 23 forming a recess 24 in which the module 19 and the test body 50 are arranged. In the figures, the outer wall 20 of the housing 17 is surrounded by a skirt 25 which delimits the recess 24, the module 19 and the sensor being arranged in said recess and circumferentially surrounded by said skirt, so as to be entirely contained within said housing.

[0055] Furthermore, the guide bearing 18 is supported by the module 19, and a spacer 26 for adjusting the reading distance d is disposed between the test body 50 and said bearing.

[0056] This arrangement makes it possible to make the reading distance d reliable and therefore the accuracy of the delivered signals, insofar as it allows the positioning between the bearing 18 and the sensitive patterns 15, 16 relative to the module 19 to be defined, the positioning of the tracks 1a, 12a relative to the body 50, and the distance d directly by the length of the spacer 26.

[0057] In the embodiments shown, the module 19 includes a shaft 27 which has an outer wall disposed in the bore 21 and an inner wall carrying the guide bearing 18.

[0058] To prevent, on the one hand, leaks of lubricant disposed inside the housing 24 of the casing 17, and on the other hand, the penetration into said housing of pollutants external elements such as water, dust and / or mud, the outer wall of the barrel 27 is equipped with a sealing element 28 of its interface with the bore 21.

[0059] In the embodiments shown, the system includes an O-ring 28 which is disposed in an annular groove 29 formed for this purpose on the outer wall of the barrel 27 (Figures 2, 5, 5a) and / or on the inner wall of the bore 21 (Figures 5b, 5c), in order to ensure the sealing of the interface between the module 19 and said bore.

[0060] Similarly, the inner wall of the barrel 27 is equipped with an annular sealing element 30 of its interface with the organ 1, said sealing element resting axially on an annular rim 31 formed for this purpose on said inner wall.

[0061] In Figures 5 and 5a, the module 19 is formed by molding, in particular from a polymer material. In Figures 5b and 5c, the module 19 is formed by stamping a sheet metal plate made of metallic material, the shaft 27 being formed by two axial walls, inner 27a and outer 27b, connected to each other by an external fold 27c.

[0062] The guide bearing 18 comprises an inner ring 32 mounted around the member 1 and an outer ring 33 carried by the module 19, rolling bodies, in particular in the form of balls 34, being arranged between said rings to guide their relative rotation.

[0063] In figures 5, 5a, 5b, the outer ring 33 is associated on a wall of the module, in particular by means of a circlip-type washer 35a (figures 5, 5a) or by means of an internal radial fold 35b formed by stamping an internal end of the inner wall 27a ([Fig.5b]).

[0064] In [Fig. 5c], module 19 has a wall, in particular the inner wall 27a of its barrel 27, which itself forms the outer ring 33. To do this, the outer bearing track of the balls 34 is formed by stamping in the inner wall 27a, and the annular rim 31 is formed on an outer part of said track.

[0065] The inner ring 32 is fitted around the shaft 1a and has an outer wall 32a which is axially retained on said shaft. In particular, the crank 2 has an axial stop 2a against which the outer wall 32a bears, optionally via a ring 36 disposed between said stop and said wall.

[0066] Advantageously, the ring 36 is fitted onto the shaft la with the interposition of a sealing element, in particular in the form of an O-ring 37.

[0067] The spacer 26 is arranged in axial support against an internal wall 32b of the inner ring 32. In figures 5, 5b and 5c, the spacer 26 is arranged in axial support against an external wall of the body 50, as well as on a radial wall formed in the external part of the gear ribs 7b of the shaft la with said body.

[0068] In [Fig. 5a], the spacer 26 is formed in one piece with the body 50, which for this purpose it features a nose 38 extending axially to form said spacer. Alternatively, the inner ring 32 may have a similar nose to form the spacer 26 and / or said spacer may include a shoulder formed around the shaft la.

[0069] In relation to the figures, the body 50 has an internal wall 39a which is held axially on the member 1 by means of a washer 39.

[0070] In particular, the washer 39 is a circlip-type elastic washer mounted in an annular groove 40 formed peripherally on the rotating shaft, and is arranged to apply an axial clamping force of the spacer 26 on the guide bearing 18.

[0071] In the figures, the module 19 further presents a plate 41 which extends radially, presenting an internal wall on which the sensor is fixed.

[0072] Advantageously, the plate 41 is screwed into blind holes 42 in the housing 17. This arrangement leaves the outer wall 20 of the housing 17 free of any protruding fasteners, thus preventing any risk of collision with the crank 2, and also preventing the risk of lubricant leakage and / or the entry of external contaminants through any openings in said outer wall. Furthermore, the sensor is thus precisely positioned with reference to the axis of rotation R by being fixed directly into the housing 17, in particular by positioning the plane of the sensing motifs 15, 16 perpendicular to the axis R.

[0073] In the figures, the plate 41 includes three orifices 43 angularly equidistant to allow its attachment to the external wall 20 by means of suitable screws 44.

[0074] The sensor is mounted on a card 45 of a printed circuit board, said card being fixed to the module 19. In particular, the card 45 is fixed by two screws 46 to the inner wall of the tray 41.

[0075] In the case of a module 19 formed by stamping a sheet of metallic material (Figures 5b, 5c), the plate 41 is formed by axially stacking at least two walls connected by folds, in order to guarantee said plate a thickness sufficient to ensure its rigidity, particularly with respect to screwing into the housing 17 and / or screwing the sensor board 45. Furthermore, this embodiment provides sufficient threaded length for the screws securing the electronic board 45, while remaining recessed from the encoders 11, 12.

Claims

Demands

1. System for determining rotation information of an organ (1) around an axis (R) by means of a device comprising: - an encoder (11, 12) carried by a body (50) fixed in rotation to said organ, said encoder having a track (lia, 12a) capable of emitting a periodic signal representative of the rotational displacement of said organ; - a sensor comprising a sensitive pattern (15, 16) disposed at a reading distance (d) from the track (lia, 12a) to deliver the information as a function of said displacement; said system comprising a housing (17) in which said organ is mounted for rotation by means of a guide bearing (18) and, fixed in the housing (17), a module (19) on which the sensor is associated, said system being characterized in that the guide bearing (18) is carried by the module (19), and in that a spacer (26) for adjusting the reading distance (d) is disposed between the body (50) and the guide bearing (18).

2. A determination system according to claim 1, characterized in that the housing (17) comprises a bore (21) in which the member (1) is mounted for rotation, the module (19) having a shaft (27) having an outer wall disposed in said bore and an inner wall carrying the guide bearing (18).

3. A determination system according to any one of claims 1 or 2, characterized in that the guide bearing (18) comprises an inner ring (32) mounted around the member (1) and an outer ring (33) carried by the module (19), rolling bodies (34) being arranged between said rings to guide their relative rotation.

4. A determination system according to claim 3, characterized in that the outer ring (33) is associated on a wall of the module (19).

5. Determination system according to claim 3, characterized in that the module (19) has a wall (27a) forming the outer ring (33).

6. A determination system according to any one of claims 3 to 5, characterized in that the spacer (26) is arranged in axial support against an internal wall (32b) of the inner ring (32).

7. A determination system according to any one of claims 3 to 6, characterized in that the inner ring (32) has an outer wall (32a) which is held axially on the member (1).

8. A determination system according to any one of claims 1 to 7, characterized in that the spacer (26) is arranged in axial support against an external wall of the body (50).

9. A determination system according to any one of claims 1 to 8, characterized in that the body (50) has a nose (38) extending axially to form the spacer (26).

10. A determination system according to any one of claims 1 to 9, characterized in that the body (50) has an internal wall (39a) which is held axially on the member (1) by means of a washer (39).

11. A determination system according to any one of claims 1 to 10, characterized in that the module (19) has a radially extending platform (41), said platform having an internal wall on which the sensor is fixed.

12. Determination system according to claim 11, characterized in that the plate (41) is fixed by screwing into blind holes (42) in the housing (17).

13. A determination system according to any one of claims 1 to 13, characterized in that the sensor is implanted on a card (45) of a printed circuit board, said card being fixed to the module (19).

14. A determination system according to any one of claims 1 to 13, characterized in that the body (50) carries two concentric encoders (11, 12) each having a track (lia, 12a), the sensor comprising at least two sensitive motifs (15, 16) arranged respectively at a reading distance (d) from a track (lia, 12a).

15. A determination system according to claim 14, characterized in that the body (50) has an inner section (4) rotationally fixed to the member (1), and an outer section (5) extending around the inner section (4) and having means (9) for coupling said body to a second member, said sections being connected concentrically around the axis (R) by a deformable structure (10) which is arranged to transmit a torque between the members (1) while allowing angular deflection between said sections as a function of the torque applied between said components, the encoders (11, 12) being respectively carried by a section (4, 5) and the sensor comparing the displacements of said sections to determine the applied torque.

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