System for determining information on the rotation of an organ

Abstract

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

Description

Title of the invention: System for determining information on the rotation of an organ

[0001] The invention relates to a system for determining information on the rotation 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 integral in rotation with the member, having a track capable of emitting a periodic signal representative of the rotational movement of said member, the sensor comprising a sensitive pattern arranged at a reading distance from the track to deliver the rotation information as a function of said movement.

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

[0004] To do this, it is known to use a test body having an inner section integral in rotation with a member, and an outer section extending around the inner section while 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 movement 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 a track. 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.

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

[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 difference between the sections, and therefore the torque applied in that it induces said angle by torsion of the deformable structure.

[0008] In known systems, the problem arises of adjusting the reading distance between the sensitive pattern and the track of the corresponding encoder, which must be carried out 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 making it possible to make the reading distance of the sensitive patterns more reliable, and to do so in a particularly simple manner.

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

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

[0013] Other objects and advantages of the invention will appear in the following description, given with reference to the appended figures, in which:

[0014] [Fig-1] is a partial representation in exploded perspective of the crankset of an electrically assisted bicycle equipped with a system according to the invention for determining the rotational torque between two members rotating around an axis of rotation;

[0015] [Fig. 1a] shows the assembly of the rolling 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 in partial axial section the pedal assembly of an electrically assisted bicycle equipped with the system for determining the previous figures;

[0020] [Fig.5a],

[0021] [Fig.5b] and

[0022] [Fig.5c] represent, in a view similar to [Fig.5], a bicycle crankset with electrical resistance equipped with a determination system according to a respective variant embodiment of the invention.

[0023] In relation to these figures, a system for determining rotation information of a member 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 R of rotation. In particular, the terms “interior” and “exterior” are relative to an arrangement respectively close to and at a distance from this axis R, and the terms "axial" and "radial" are relative to an arrangement respectively along this axis R and moving away from or approaching it. Furthermore, the terms "internal" and "external" are relative to an arrangement respectively on one side and the other along the axis R, in particular downwards and upwards in figures 5.

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

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

[0027] According to the embodiment shown, one of the members 1 is equipped with a part 2 for actuating its rotation. In particular, [Fig.l] represents a crankset of an electrically assisted bicycle comprising a crank 2 equipped with a pedal 3, 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.

[0028] The system comprises a test body 50 which makes it possible to transmit the pedaling torque M+ to the second member. In particular, the second member may comprise a sleeve arranged concentrically around the shaft 1a, said sleeve being for example connected to a satellite carrier of an epicyclic train of a motorized gearbox, by 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 1,500 N which, with a crank length 2 of 165 mm, generates a pedaling 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 by the arrow M+ in the figures), insofar as the other direction corresponds to the freewheel of the bicycle.

[0030] The test body 50 has an inner section 4 integral in rotation with the first member 1, as well as 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 internal section 4 has a bore 6 equipped with coupling means on the shaft 1a, 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 member, [Fig. 1] represents an external section 5 whose internal circumferential wall has at least one radial lobe 8 which is equipped with a means 9 for fixing said outer section on a sleeve of said second member, as described previously. In particular, three lobes 8 at 120° are provided, each of them having a fixing orifice 9, in particular by a pin or by screwing into a complementary orifice of such a sleeve.

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

[0034] In particular, the torque resulting from the pedaling torques M+ on the inner section 4 and the torque applied by the second member to the outer section 5 induces a torsion between the sections 4, 5, and therefore a relative angular displacement of said sections according to 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 the sections 4, 5. In particular, the branches 10 and the sections 4, 5 are formed in a single piece, in particular by stamping and / or by cutting a blank of metallic material.

[0036] The branches 10 are inclined in the opposite direction to the rotation, which generates a lever arm which, by stressing the branches 10 in traction, reduces the constraints in a very effective manner with the counterpart of an increase in the stiffness.

[0037] In [Fig.l], the test body 50 comprises three branches 10 which each have a curved geometry arranged to guarantee an effective lever arm effect while having a reduced radial size, the lobes 8 each extending radially in an external bend of respectively one branch 10.

[0038] The system comprises 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 torque applied.

[0039] To do this, the device comprises two concentric encoders carried by a section 4, 5 of the test body 50 respectively, including an internal encoder 11 - respectively external 12 - integral in rotation with the internal section 4 - respectively external 5 -, each having a track 11a, 12a capable of emitting a signal representative of the rotational movement of a member 1 respectively.

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

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

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

[0043] In relation to [Fig.l], 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 while being angularly offset from the lobes 8 for attachment to the second member, each section 4, 5 having three attachment orifices 4a, 5a arranged at 120° from each other while being formed on each of the lobes 13, 14.

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

[0045] The coders 11, 12 may 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 11a, 12a.

[0046] The determination device further comprises a sensor comprising at least two sensitive patterns, respectively inner 15 and outer 16, each arranged at a reading distance d from the track, respectively inner 11a and outer 12a, to deliver the rotation information of the corresponding member 1 as a function of its movement.

[0047] In the embodiments shown, each sensitive pattern 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 difference between said sections, which is a function of the torque applied.

[0048] According to one embodiment, each pattern 15, 16 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.

[0049] The sensitive elements may be based on a magnetoresistive material whose resistance varies according to the magnetic signal of the track 11a, 12a to be detected, for example of the AMR, TMR or GMR type, 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 11a, 12a. In particular, the sensitive patterns 15, 16 can be arranged to deliver incremental square signals in quadrature, 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 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.

[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 casing 17 in which the member 1 is mounted in rotation by means of a guide bearing 18 and, fixed in the casing 17, a module 19 on which the sensor is associated.

[0053] In particular, the casing 17 comprises an external wall 20 provided with a bore 21 through which the rotating shaft 1a is mounted in rotation by means of the bearing 18, said rotating shaft having an end piece 22 projecting from said external wall which is equipped with the crank 2 for applying a pedaling torque M+.

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

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

[0056] This arrangement makes it possible to make the reading distance d and therefore the precision of the delivered signals more reliable, insofar as it makes it possible to define the positioning between the bearing 18 and the sensitive patterns 15, 16 relative to the module 19, the positioning of the tracks 11a, 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 comprises a barrel 27 which has an outer wall arranged 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 external pollutants such as water, dust and / or mud, the external 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 comprises an O-ring 28 which is arranged 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 for its interface with the member 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 barrel 27 being formed by two inner 27a and outer 27b axial walls 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 with a wall of the module, in particular by means of a washer 35a of the “circlip” type (Figures 5, 5a) or by means of an internal radial fold 35b formed by stamping an internal end of the internal wall 27a ([Fig.5b]).

[0064] In [Fig.5c], the 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 rolling track of the balls 34 is formed by stamping in the inner wall 27a, and the annular rim 31 is formed on an external part of said track.

[0065] The inner ring 32 is associated by fitting around the shaft 1a, and has an external wall 32a which is held axially on said shaft. In particular, the crank 2 has an axial stop 2a on which the external wall 32a bears, possibly by means of a ring 36 arranged between said stop and said wall.

[0066] Advantageously, the ring 36 is fitted onto the shaft 1a 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 FIGS. 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 1a with said body.

[0068] In [Fig.5a], the spacer 26 is formed in one piece with the body 50, which has for this purpose 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 comprise a shoulder formed around the shaft 1a.

[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 at the periphery on the rotating shaft 1a, and is arranged to apply an axial force for pressing the spacer 26 onto the guide bearing 18.

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

[0072] Advantageously, the plate 41 is fixed by screwing into blind orifices 42 of the casing 17. This arrangement makes it possible to leave the external wall 20 of the casing 17 free of any projecting fixing element, in order to avoid any risk of collision with the crank 2, but also to avoid the risks of lubricant leakage and / or entry of external pollutants through any orifices passing through said external wall. Furthermore, the sensor is thus positioned in a precise manner with reference to the axis of rotation R by fixing directly in the casing 17, in particular by arranging the plane of the sensitive patterns 15, 16 perpendicular to the axis R.

[0073] In the figures, the plate 41 comprises three orifices 43 equally distributed angularly to allow its fixing to the external wall 20 by means of appropriate screws 44.

[0074] The sensor is installed on a card 45 of a printed circuit, said card being fixed to the module 19. In particular, the card 45 is fixed by two screws 46 on the internal wall of the plate 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 axial stacking of at least two walls connected by folds, in order to guarantee said plate a thickness which is sufficient to ensure its rigidity, in particular with respect to the screwing in the casing 17 and / or the screwing of the card 45 of the sensor. In addition, this embodiment makes it possible to have sufficient threaded length for the screws for fixing the electronic card 45, while remaining set back from the encoders 11, 12.

Claims

Claims

1. System for determining information on the rotation of a member (1) around an axis (R) by means of a device comprising: - an encoder (11, 12) carried by a body (50) integral in rotation with said member, said encoder having a track (11a, 12a) capable of emitting a periodic signal representative of the rotational movement of said member; - a sensor comprising a sensitive pattern (15, 16) arranged at a reading distance (d) from the track (11a, 12a) to deliver the information as a function of said movement; said system comprising a casing (17) in which said member is mounted in rotation by means of a guide bearing (18) and, fixed in the casing (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 arranged between the body (50) and the guide bearing (18).

2. Determination system according to claim 1, characterized in that the casing (17) comprises a bore (21) in which the member (1) is mounted in rotation, the module (19) having a barrel (27) having an outer wall arranged in said bore and an inner wall carrying the guide bearing (18).

3. Determination system according to 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. Determination system according to claim 3, characterized in that the outer ring (33) is associated with 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. 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. 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. 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. 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. 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. Determination system according to any one of claims 1 to 10, characterized in that the module (19) has a plate (41) extending radially, said plate 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) of the casing (17).

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

14. 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 (11a, 12a), the sensor comprising at least two sensitive patterns (15, 16) arranged respectively at a reading distance (d) from a track (11a, 12a).

15. Determination system according to claim 14, characterized in that the body (50) has an inner section (4) integral in rotation with 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 an angular movement between said sections as a function of the torque applied between said members, the encoders (11, 12) being respectively carried by a section (4, 5) and the sensor comparing the movements of said sections to determine the torque applied.

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