Method for determining the torque applied between two rotating parts

Abstract

The invention relates to a method for determining the torque applied between two components rotating about a geometric axis of rotation. The method comprises that each sensor (4, 5) delivers a reference pulse (S3) from a set of pulses defining a known reference angular deviation between tracks (2a, 3a) and the following steps: detection of a set of pulses and comparison of the position signals corresponding to said detection to determine the angular deviation of said pulse set; calculation of the difference between the reference angular deviation and the determined angular deviation; correction of the angular deviation resulting from the position signal comparison device with the calculated difference before determining the applied torque. Figure 1

Description

Title of the invention: Method for determining the torque applied between two rotating parts

[0001] The invention relates to a method for determining a torque applied between two elements rotating around a geometric axis of rotation.

[0002] The invention applies in particular to the determination of a torque applied between two components 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 electrically assisted bicycle.

[0003] To do this, it is known to use a test body having a first -respectively a second - portion fixed in rotation to a first -respectively a second - of the organs, said portions being connected by a deformable structure which is arranged to transmit the torque between the organs while allowing an angular deflection between said portions.

[0004] Such a test body can be instrumented with a torque determination system comprising, for each of the portions: - an encoder carrying a track capable of emitting a periodic signal representative of the rotational displacement of the corresponding portion; and - a sensor comprising a pattern of sensitive elements arranged at a reading distance from the track to deliver a signal representative of the angular position of the corresponding encoder.

[0005] 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 deviation between the portions, and therefore the applied torque in that it induces said angle by twisting the deformable structure.

[0006] The limitation of this solution lies in the incremental nature of the torque value which is determined by comparison of position signals, in that the absence of a reference frame for this comparison can induce a shift in the value of said torque, particularly in the case where a torque is initially applied to its determination.

[0007] The invention aims to solve the problems of the prior art by proposing in particular a method for determining a torque in an absolute manner as a function of a reference value.

[0008] To this end, the invention proposes a method for determining a torque applied between two elements rotating about a geometric axis of rotation, said method providing: - to use a test body presenting a first - respectively a second - portion fixed in rotation to a first - respectively to a second - of said organs, said portions being connected by a deformable structure which is arranged to transmit the torque between the organs while allowing an angular deflection between said portions; - to equip the test body with a torque determination system comprising, for each of the portions: • an encoder carrying a track capable of emitting a periodic signal representative of the rotational displacement of the corresponding portion; and • a sensor comprising a pattern of sensitive elements arranged at a reading distance from the track to deliver a signal representative of the angular position of the corresponding encoder;

[0009] said determination system comprising a device for comparing the position signals delivered by each of the sensors, said device being capable of determining an angular deviation between the portions which is a function of the applied torque; - that each of the sensors also delivers a reference pulse from a set of pulses defining a known reference angular gap between the tracks;

[0010] said process comprising the steps of: - detection of a set of pulses and comparison of the position signals corresponding to said detection to determine the angular deviation of said set of pulses; - calculation of the difference between the reference angular deviation and the determined angular deviation; - correction of the angular deviation resulting from the position signal comparison device with the difference calculated before determining the applied torque.

[0011] Other objects and advantages of the invention will become apparent from the following description, made with reference to the accompanying figures, in which:

[0012] [Fig-1] schematically illustrates the implementation of a method according to the invention to determine a torque applied between two elements rotating around a geometric axis of rotation;

[0013] [Fig.2] shows a front view of two encoders for implementing a determination method mination of a couple according to the invention.

[0014] In particular, the method allows the determination of a torque applied between two components 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 electrically assisted bicycle.

[0015] To achieve this, the method uses a test specimen having a first - respectively a second - portion fixed in rotation to a first - respectively of a second - of the organs, said portions being connected by a deformable structure 1 which is arranged to transmit the torque between the organs while allowing angular movement between said portions.

[0016] According to one embodiment, the test body may have an inner ring fixed in rotation to means for mounting said test body on one component, and an outer ring extending around the inner ring by having means for mounting said test body on the other component, said rings being connected by at least one deformable arm.

[0017] Alternatively, the deformable structure 1 can be in the form of at least one torsion bar, each end of which has a portion attached to a member respectively, said bar being arranged to deform in torsion according to the torque applied between said members.

[0018] To determine the angular displacement of the portions, which is a function of the applied torque, the test body is equipped with a system comprising, for each of the portions: - an encoder 2, 3 carrying a track 2a, 3a capable of emitting a periodic signal representative of the rotational displacement of the corresponding portion; and - a sensor 4, 5 comprising a pattern of sensitive elements arranged at a reading distance from track 2a, 3a to deliver a signal representative of the angular position of the corresponding encoder 2, 3.

[0019] In particular, each of the encoders 2, 3 is rotationally fixed to the corresponding portion, for example by being fixed to said portion or by being rotationally fixed to a guiding element of said portion.

[0020] According to one embodiment, each of the encoders 2, 3 carries a main track 2a, 3a having a succession of pairs of North N and South S poles forming a multipolar magnetic track 2a, 3a capable of emitting a magnetic displacement signal of pseudo-sinusoidal shape, each of the sensors 4, 5 delivering two periodic signals - in particular incremental square SI, S2 - in quadrature for the determination of the signal representative of the angular position of the corresponding encoder 2, 3.

[0021] Advantageously, the sensors 4, 5 comprise a pattern of 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.

[0022] The sensitive elements can be based on a magnetoresistive material whose resistance varies according to the magnetic signal of the track to be detected, for example of the type anisotropic magnetoresistance (AMR), tunnel magnetoresistance (TMR) or giant magnetoresistance (GMR), or of a Hall effect probe.

[0023] The torque determination system includes a device for comparing the position signals delivered by each of the sensors 4, 5, said device being capable of determining an angular deviation between the portions which is a function of the applied torque. In particular, the angular deviation corresponds to the angle of twist which, knowing the stiffness of the deformable structure 1, makes it possible to calculate the applied torque.

[0024] In relation to [Fig.1], the comparison device includes counting means 6 providing the angular position of each of the encoders 2, 3 and subtraction means 7 allowing the difference between said angular positions to be calculated as a function of the angle of rotation, said difference being an image of the angle of torsion and therefore of the applied torque.

[0025] In particular, the torque determination system may include means for applying an interpolation factor fi and f2 to the signal delivered by a sensor 4, 5 respectively, the counting means 6 measuring a number of edges ni and n2 in each of said interpolated signals.

[0026] In relation to main multipolar tracks 2a, 3a comprising respectively Nppi and Npp2 pairs of North N and South S poles, the subtraction means 7 perform for example the operation DIFF = Npp2.f2.ni - Nppi.fi.n2 to calculate the difference between the angular positions.

[0027] In particular, the determination system includes means for applying interpolation factors such as: f2 / fi = Nppi / Npp2. When tracks 2a, 3a have the same number of pole pairs (Nppi = Npp2), the calculation can be performed by simply subtracting the edges ni and n2 with the same interpolation factor (fi = f2).

[0028] Each of the sensors 4, 5 also delivers, in particular at least once per rotation of the test body, a reference pulse S3 from a set of pulses defining a reference angular deviation between tracks 2a, 3a, said reference angular deviation being known.

[0029] Thus, after the detection of a set of pulses, the method provides for the comparison of the position signals corresponding to said detection in order to determine the angular deviation of said set of pulses, then the calculation of the difference between the reference angular deviation and the determined angular deviation in order to, before determining the applied torque, correct the angular deviation from the position signal comparison device with the calculated difference, in particular by subtracting said difference from said angular deviation.

[0030] This solution allows, while the angular positions are determined incrementally by means of the signal emitted by the main magnetic tracks 2a, 3a, to determine the torque absolutely with respect to the reference from the known angular deviation for the pulses S3 of a set.

[0031] According to one embodiment, the reference angular deviation between the S3 impulses of a set is known under zero applied torque. Thus, even in the case where a torque is initially applied during the determination, the determined torque is corrected according to a zero-torque reference.

[0032] In particular, if the determination process is started while a torque is applied, for example if the cyclist applies force on the pedals, the determination takes into account this initial value by delivering an absolute torque.

[0033] In order to facilitate the discrimination of the S3 impulses of a set, the method provides for determining a maximum angular deviation under maximum applied torque, the reference angular deviation between the S3 impulses of a set being fixed at a value which is less than said maximum angular deviation.

[0034] Advantageously with respect to the risk of variation of the torque applied during the determination of a set of pulses, the method provides that the reference angular deviation between the pulses S3 of a set is as small as possible and ideally zero.

[0035] According to one embodiment, the method provides that each of the sensors 4, 5 delivers a reference pulse S3 per rotation of the test body, in order to be able to benefit from the determination of the absolute torque at the latest after one rotation of the test body.

[0036] To accelerate this absolute determination, the method provides that each of the sensors 4, 5 delivers several reference pulses S3 per revolution in order to define several reference angular deviations which are distributed along the tracks 2a, 3a, the difference being able to be calculated with the first set of pulses detected.

[0037] Advantageously, the angular separation between the S3 pulses of the sets has the same value. Furthermore, a sensor 4, 5 can deliver additional S3 pulses that are not taken into account in the determination, in that they are not associated with a set with an S3 pulse delivered by the other sensor 5, 4.

[0038] In addition, the method can be made more reliable by periodically calculating a new difference to update the correction of the angular deviation.

[0039] According to one embodiment, the method further provides for a calibration procedure for determining the torque, said procedure being initiated and / or terminated depending on the determination of a reference angular position, in particular by detecting a singularity delivered by a sensor 4, 5 on a rotation of the test body.

[0040] In particular, the calibration procedure provides for: - rotate the test body through at least one revolution under a constant calibration torque, and in particular substantially zero, between the components; - use the determination system to define calibration values ​​of the angular deviation between portions as a function of the angle of rotation of the test body.

[0041] Thus, the subsequent determination of the applied torque can be obtained by correcting the angular deviation determined at a given angle with the corresponding calibration value, so as to be able to eliminate errors arising from possible relative defects between the portions, the encoders 2, 3 and / or the sensors 4, 5.

[0042] In particular, the calibration procedure is simple to perform, notably not requiring an angular and / or torque reference sensor or rotating the test specimen at a constant speed. The correction applied during operation is also simple to implement, particularly in that it does not introduce any delay in the real-time torque determination.

[0043] According to an advantageous implementation, an encoder 3 carries a reference track 3b capable of emitting one or more pulses S3 and / or the singularity to be detected.

[0044] In particular, each of the encoders 2, 3 can have at least one magnetic irregularity on one rotation and, when two irregularities are successively detected by respectively a sensor 4, 5, their angular difference is calculated using the signals SI, S2 of said sensors which are measured between these two detection instants.

[0045] Alternatively, at least one sensor 4, 5 can be arranged to deliver a pulse S3 in relation to a single main multipolar track 2a, 3a, for example at each North South magnetic transition, by means of a separate magnet and a Hall effect switch, a mechanical index and a proximity detector or an optical sensor.

[0046] In relation to [Fig.2], an encoder 3 carries a main track 3a having a succession of pairs of North N and South S poles forming a multipolar magnetic track 3a and a succession of pairs of North N and South S poles forming a reference multipolar magnetic track 3b having at least one magnetic irregularity I detected by the sensor 4, 5 to deliver a reference pulse S3.

[0047] In particular, and as described in particular in document EP-1 403 622, at least one magnetic transition of the N, S poles of the main inner track 3a and outer reference track 3b may be different from the others to form the magnetic irregularity I, in particular by being angularly offset.

[0048] The multipolar magnetic reference track 3b may have several magnetic irregularities I distributed angularly along said track, in particular an irregularity I associated with each of the pole pairs N, S of the main track 3a.

[0049] Furthermore, a pair of poles N, S can be associated with a different irregularity I or with an absence of irregularity I detected by the sensor 4, 5 to deliver a singularity per turn of rotation of the test body, for example by providing as in [Fig.2] that a magnetic transition T of the poles is not shifted or shifted by a different value.

Claims

1. Demands A method for determining the torque applied between two components rotating about a geometric axis of rotation, said method comprising: - to use a test body having a first - respectively a second - portion fixed in rotation to a first - respectively a second - of said organs, said portions being connected by a deformable structure (1) which is arranged to transmit the torque between the organs while allowing an angular deflection between said portions; - to equip the test body with a torque determination system comprising, for each portion: • an encoder (2, 3) carrying a track (2a, 3a) capable of emitting a periodic signal representative of the rotational displacement of the corresponding portion; and • a sensor (4, 5) comprising a pattern of sensitive elements arranged at a reading distance from the track (2a, 3a) to deliver a signal representative of the angular position of the corresponding encoder (2, 3); said determination system comprising a device for comparing the position signals delivered by each of the sensors (4, 5), said device being capable of determining an angular deviation between the portions which is a function of the applied torque; - that each of the sensors (4, 5) also delivers a reference pulse (S3) from a set of pulses defining a known reference angular deviation between the tracks (2a, 3a); said process includes the steps of: - detection of a set of pulses and comparison of the position signals corresponding to said detection to determine the angular deviation of said set of pulses; - calculation of the difference between the reference angular deviation and the determined angular deviation; - correction of the angular deviation from the position signal comparison device with the difference calculated before determining the applied torque.

2. A method for determining a torque according to claim 1, characterized in that it provides that each of the sensors (4, 5) delivers a reference pulse (S3) per rotation of the test body.

3. Method for determining a torque according to claim 1, characterized in that it provides that each of the sensors (4, 5) delivers several reference pulses (S3) per rotation of the test body in order to define several reference angular deviations which are distributed along the tracks (2a, 3a).

4. Method for determining a torque according to any one of claims 1 to 3, characterized in that it provides that at least one encoder (3) carries a reference track (3b) capable of emitting the pulse (S3) to be detected.

5. A method for determining a torque according to any one of claims 1 to 4, characterized in that it provides for a procedure for calibrating the determination of the torque, said procedure being initiated and / or terminated as a function of the determination of a reference angular position.

6. Method for determining a torque according to claim 5, characterized in that the reference angular position is determined by detection of a singularity delivered by a sensor (4, 5).

7. Method for determining a torque according to claim 6, characterized in that it provides that an encoder (3) carries a reference track (3b) capable of emitting the singularity to be detected.

8. Method for determining a torque according to any one of claims 1 to 7, characterized in that the comparison device comprises counting means (6) providing the angular position of each of the encoders (2, 3) and subtraction means (7) allowing the difference between said angular positions to be calculated as a function of the angle of rotation.

9. A method for determining a torque according to any one of claims 1 to 8, characterized in that it comprises each of the encoders (2, 3) carrying a main track (2a, 3a) having a succession of pairs of North (N) and South (S) poles forming a ma- multipolar genetic (2a, 3a) capable of emitting a pseudo-sinusoidal shape magnetic displacement signal, each of the sensors (4, 5) delivering two periodic quadrature signals (SI, S2) for determining the signal representative of the angular position of the corresponding encoder (2, 3).

10. Method for determining a torque according to claim 9, characterized in that it provides that at least one encoder (3) further carries a multipolar magnetic reference track (3b) having at least one magnetic irregularity (I) detected by the sensor (4, 5) to deliver the reference pulse (S3).

11. Method for determining a torque according to claim 10, characterized in that the multipolar magnetic reference track (3b) has several magnetic irregularities (I) distributed angularly along said track.

12. Method for determining a torque according to claim 11, characterized in that the multipolar magnetic reference track (3b) has an irregularity (I) associated with each of the pole pairs (N, S) of the main track (3a).

13. Method for determining a torque according to claim 12, characterized in that a pair of poles (N, S) is associated with a different irregularity (I) or with an absence of irregularity (I) detected by the sensor (4, 5) to deliver a singularity per rotation of the test body.

14. Method for determining a torque according to any one of claims 1 to 13, characterized in that it provides that the reference angular deviation between the impulses (S3) of a set is known under zero applied torque.

15. Method for determining a torque according to any one of claims 1 to 14, characterized in that it provides that the reference angular deviation between the impulses (S3) of a set is zero.

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