EP3542450A1

EP3542450A1 - Gear motor, associated wiper system and associated control method

Info

Publication number: EP3542450A1
Application number: EP17801374.4A
Authority: EP
Inventors: Jose-Luis Herrada
Original assignee: Valeo Systemes dEssuyage SAS
Current assignee: Valeo Systemes dEssuyage SAS
Priority date: 2016-11-21
Filing date: 2017-11-06
Publication date: 2019-09-25
Also published as: JP2020513720A; WO2018091302A1; JP6949958B2; CN110168875B; FR3059174B1; CN110168875A; US11063538B2; FR3059174A1; US20200067432A1

Abstract

The present invention relates to a gear motor (101), in particular for a wiper system, comprising: - a brushless DC electric motor (103) including: - a rotor (15); - a stator (13) having coils (17) for electromagnetically exciting the rotor (15); - a device (25) for determining the angular position of the rotor (15) with respect to the stator (13); - a control unit (21) configured to generate control signals for supplying power to the electromagnetic excitation coils (17) according to the angular position of the rotor (15) determined by the device (25) for determining the angular position of the rotor (15); - a reduction gear mechanism (104) linked, on one side, to the rotor (15) of the electric motor (103) and, on the other side, to an output shaft (109) that is intended to be linked to an external mechanism, in particular a wiper system, the reduction gear mechanism (104) having a predefined reduction ratio, said device (25) for determining the angular position of the rotor (15) comprises at least one Hall effect sensor (27, 27a, 27b) associated with a control magnet (29, 29a, 29b) that rotates with the rotor (15) and the gear motor (101) also comprises a processing unit (26) connected to the device (25) for determining the angular position of the rotor (15) and configured to determine the angular position of the output shaft (109) on the basis of the angular position of the rotor (15) determined by taking the predefined reduction ratio of the reduction gear mechanism (104) into account.

Description

MOTOR-REDUCER, WIPING SYSTEM AND METHOD OF

ASSOCIATED ORDER

The present invention relates to a geared motor and in particular a motor gear reducer for wiper systems of a motor vehicle.

Geared motors are essentially composed of an electric motor coupled to a gear mechanism to speed down the speed to obtain a high torque transmission.

Different types of electric motors can be used in a geared motor and in particular brushless DC electric motors which have many advantages such as a long service life, reduced space and consumption and a low noise level.

However, the control of electric motors is more complex compared to electric brush motors because to allow proper operation, it is necessary to know precisely the angular position of the rotor of the brushless direct current electric motor.

Indeed, such electric motors comprise electromagnetic excitation coils disposed at the stator and fed alternately via an inverter to allow the drive of permanent magnets arranged on the rotor.

However, in order to be able to switch the inverter switches and thus the supply of the electromagnetic coils at optimal times to obtain the desired drive of the rotor, it is necessary to know the position of the rotor at least in sectors with some specific points during state switching (generally, for trapezoidal excitation, six switches at each revolution of the rotor). In Figure la is shown a diagram of an angular detection device of the rotor of an electric motor comprising three Hall effect sensors according to the state of the art. As seen in this figure, three Hall effect sensors denoted Hi, H2 and H3 are disposed on the stator ST around a control magnet AC, by an annular magnet, integral with the rotor of the DC electric motor of which only the X axis is visible in Figure la. The control magnet AC comprises two poles marked S for the South pole and N for the North pole.

The three Hall effect sensors Ηι, H2 and H3 are angularly distributed at 120 ^° from each other so as to obtain the six switching moments of the electromagnetic excitation coils per cycle corresponding to a rotation angle of 60 ° of the rotor.

FIG. 1b represents, in its upper part, the signals coming from the three Hall effect sensors Ηι, H2 and H3 and, in its lower part, the supply signals of the electromagnetic excitation coils during a 360 ⁰ cycle. of the rotor. The cycle is divided into 6 steps of 60 ° delimited by the vertical dashed lines.

In a first step denoted 1 ranging from 0 to 60 ° corresponding to a high signal of the sensor H3 and a low signal of the sensors Hi and H2, the current flows from the phase A to the phase B (the signal corresponding to the phase A is at 1, the signal corresponding to phase B is at -1 and the signal corresponding to phase C is at o).

In a second step denoted 2 ranging from 60 to 120 ⁰ corresponding to a high signal of the sensors H2 and H3 and to a low signal of the sensor Hi, the current flows from phase A to phase C (the signal corresponding to phase A is at 1, the signal corresponding to phase B is at o and the signal corresponding to phase C is at -1).

In a third step denoted 3 ranging from 120 to 180 ⁰ corresponding to a high signal of the sensor H2 and a low signal of the sensors Hi and H3, the current flows from phase B to phase C (the signal corresponding to phase B is at 1, the signal corresponding to phase A is at o and the signal corresponding to phase C is at -1).

In a fourth step denoted 4 ranging from 180 to 240 ⁰ corresponding to a high signal of the sensors Hi and H2 and to a low signal of the sensor H3, the current flows from phase B to phase A (the signal corresponding to phase B is at 1, the signal corresponding to phase C is at o and the signal corresponding to phase A is at -1).

In a fifth step denoted by 240 to 300 ⁰ corresponding to a high signal of the sensor Hi and a low signal of the sensors H2 and H3, the current flows from the phase C to the phase A (the signal corresponding to the phase C is at 1, the signal corresponding to phase B is at o and the signal corresponding to phase A is at -1).

In a sixth step denoted 6 ranging from 300 to 360 ⁰ corresponding to a high signal of the sensors Hi and H3 and at a low signal of the sensor H2, the current flows from phase C to phase B (the signal corresponding to phase C is at 1, the signal corresponding to phase A is at o and the signal corresponding to phase B is -1).

Thus, the use of three Hall effect sensors Ηι, H2 and H3 makes it possible to precisely determine the six positions of the rotor corresponding to the six switching change instants of the electromagnetic excitation coils.

Such a solution therefore appears costly because of the large number of sensors required to control the electric motor.

In order to reduce the number of necessary sensors, it is also known, for determining the position of the rotor, to use a sensorless method based on the measurement of the counter-electromotive forces of the stator excitation coils.

However, such a solution requires startup of the brushless DC electric motor in synchronous mode until the rotational speed of the rotor and therefore the counter-electromotive forces are sufficient to be measured and to be able to be used for the control of switching times.

However, such a startup in synchronous mode is only possible for applications where the load is low at startup and relatively known (for example for the control of a fan). It is thus clear that this solution is not applicable to a geared motor for a motor vehicle wiper system which requires a load and a high torque force from the start and which can be started with virtually zero loads (as in the case of wet windows) or with high loads (as in the case of brooms glued due to ice or snow).

In addition, an associated problem is the determination of the position of the output shaft of the reduction mechanism on which the wiper system is arranged in order to decide on the control to be applied to the electric motor and in particular its direction of rotation. For this, it is known to use an additional sensor, for example an analog angular sensor, located at the output shaft of the reduction mechanism. The cost of such a sensor is also high and contributes to increasing the overall cost of the geared motor.

The present invention is therefore aimed at providing a solution that makes it possible to reduce overall cost of a geared motor while allowing efficient control and proper operation of the wiper system.

For this purpose, the present invention relates to a geared motor, in particular for a wiper system, comprising:

a brushless direct current electric motor comprising:

- a rotor,

a stator having coils of electromagnetic excitation of the rotor,

a device for determining the angular position of the rotor relative to the stator,

a control unit configured to generate control signals for supplying the electromagnetic excitation coils according to the angular position of the rotor determined by the device for determining the angular position of the rotor,

a reduction mechanism connected on one side to the rotor of the electric motor and on the other side to an output shaft intended to be connected to an external mechanism, in particular a wiper system, the reduction mechanism having a predefined reduction ratio ,

said device for determining the angular position of the rotor comprises at least one Hall effect sensor associated with a control magnet fixed to rotate with the rotor, and the geared motor also comprises a processing unit connected to the device for determining the angular position of the rotor. rotor and configured to determine the angular position of the output shaft from the angular position of the rotor determined by taking into account the predefined reduction ratio of the reducing mechanism.

Determining the angular position of the output shaft from the angular position of the rotor makes it possible to dispense with a precise position sensor at said output shaft.

According to another aspect of the present invention, the device for determining the angular position of the rotor comprises two Hall effect sensors respectively associated with a control magnet fixed to rotate the rotor. The use of two Hall effect sensors makes it possible to determine the direction of rotation of the rotor. According to a further aspect of the present invention, the control magnet comprises a number of pairs of poles greater than the number of pairs of magnetic poles of the rotor of the brushless direct current electric motor.

According to an additional aspect of the present invention, the device for determining the angular position of the rotor comprises a single Hall effect sensor associated with a control magnet comprising a number of pairs of poles equal to three times the number of pairs of magnetic poles. of the rotor of the electric motor, the poles of the control magnet being configured to be in phase with the magnetic poles of the rotor of the electric motor so that the state changes of the Hall effect sensor are synchronized with the changes of state control signals generated by the control unit for supplying the electromagnetic excitation coils.

Such a configuration makes it possible to drive the electric motor with a single Hall effect sensor.

According to another aspect of the present invention, the device for determining the angular position of the rotor comprises two Hall effect sensors associated with a control magnet comprising a number of pairs of poles equal to three times the number of pairs of magnetic poles. rotor of the electric motor, the two sensors being offset by an angle of 30 ⁰ , the magnetic poles of the rotor of the control magnet being configured to be in phase with the magnetic poles of the rotor so that the changes of states of one of the Hall effect sensors are synchronized with the state changes of the control signals generated by the control unit for supplying the electromagnetic excitation coils.

According to a further aspect of the present invention, the device for determining the angular position of the rotor comprises two Hall effect sensors, the first hall effect sensor being associated with a first control magnet comprising a number of pairs of poles equal to three times the number of pairs of magnetic poles of the rotor of the electric motor, the second hall effect sensor being associated with a second magnet control unit comprising a number of pole pairs equal to nine times the number of magnetic pole pairs of the electric motor rotor, the poles of the first control magnet being configured to be in phase with magnetic poles of the electric motor rotor so that that the state changes of the first Hall effect sensor are synchronized with the state changes of the control signals generated by the control unit to supply the electromagnetic excitation coils, the second Hall effect sensor and the second magnet are configured so that the state changes of the first Hall sensor occur mid-way mps between two state changes of the second Hall effect sensor. According to an additional aspect of the present invention, the device for determining the angular position of the rotor relative to the stator is configured to:

determining the angular position of the rotor from the signals from the Hall effect sensor (s) for rotational speeds of the rotor below a predetermined threshold, and

determining the angular position of the rotor from a measurement of the counter-electromotive forces coming from the electromagnetic excitation coils for rotational speeds of the rotor equal to or greater than the predetermined threshold. The use of counter electromotive forces makes it possible to improve the accuracy of the determination of the position of the rotor

According to another aspect of the present invention, the counter-electromotive force of the at least one unpowered electromagnetic excitation coil is measured and transmitted to the device for determining the angular position of the rotor, said position determining device angular rotor being configured to compare the measured counter-electromotive force value with a predetermined threshold associated with a predetermined position of the rotor. According to a further aspect of the present invention, the device for determining the angular position of the rotor is configured to correct the angular measurement resulting from the Hall sensor (s) from the measurement of the counter-electromotive forces of the coils of the rotor. electromagnetic excitation to calibrate the Hall effect sensor (s) from said counterelectromotive force measurements.

According to an additional aspect of the present invention, the geared motor also comprises an additional magnet said output magnet rotatably connected to the output shaft and at least one additional Hall effect sensor called output sensor associated with the magnet of the output, the at least one output sensor and the output magnet being configured such that the at least one output sensor detects a first position of the output magnet corresponding to a first stop position of the mechanism external connector intended to be connected to the output shaft and a second position of the output magnet corresponding to a second abutment position of the external mechanism intended to be connected to the output shaft, the, at least one output sensor being connected to the control unit and said control unit being configured to generate the control signals as a function also of the signals from said at least one output sensor.

The present invention also relates to a wiper system, particularly for a motor vehicle comprising a geared motor as described above.

The present invention also relates to a method for controlling an electric motor of a geared motor, particularly for wiping systems, the geared motor comprising:

a brushless direct current electric motor comprising:

- a rotor,

a stator having coils of electromagnetic excitation of the rotor,

a reduction mechanism connected on one side to the rotor of the electric motor and on the other side to an output shaft intended to be connected to an external mechanism, in particular a wiper system, the reduction mechanism having a predefined reduction ratio,

a device for determining the angular position of the rotor with respect to the stator, comprising at least one Hall effect sensor associated with a control magnet integral in rotation with the rotor,

said method comprising the following steps:

(a) for rotational speeds of the rotor below a predetermined threshold:

the angular position of the rotor is determined from the signals originating from the Hall effect sensor (s),

(b) for rotational speeds of the rotor equal to or greater than the predetermined threshold,

the angular position of the rotor is determined from a measurement of the counter-electromotive forces coming from the electromagnetic excitation coils,

control signals are generated to feed the electromagnetic excitation coils according to the angular position of the rotor determined during the preceding steps,

the angular position of the output shaft is determined from the angular position of the rotor determined during the preceding steps and taking into account the predefined reduction ratio of the reducing mechanism.

According to another aspect of the present invention, the angular measurement of the Hall sensor (s) is corrected from the measurement of the electromotive forces coming from the electromagnetic excitation coils of the rotor. According to a further aspect of the present invention, the gear motor also comprises an additional magnet said output magnet disposed at the output shaft of the gear mechanism and at least one additional Hall effect sensor called output sensor associated with the output gear. the output magnet, the at least one output sensor and the at least one output magnet being configured so that the at least one output sensor detects a first position of the output magnet when the output shaft is in a first position corresponding to a first stop position of the external mechanism to be connected to the output shaft and detects a second position of the output magnet when the output shaft is in a second position corresponding to a second abutment position of the external mechanism intended to be connected to the output shaft and in which the step of generating the control signals for supplying the electromagnetic excitation coils is also performed according to signals of said at least one output sensor.

Other characteristics and advantages of the invention will emerge from the following description, given by way of example and without limitation, with reference to the accompanying drawings, in which: FIG. 1 is a diagram of an angular rotor detection device. an electric motor comprising three Hall effect sensors according to the state of the art,

FIG. 1b represents a diagram of the signals supplied by the sensors of FIG. 1a and the control signals of the electromagnetic excitation coils of the electric motor,

FIG. 2 represents a diagram of a geared motor, FIGS. 3a, 3b and 3c show functional diagrams of an electric motor,

FIG. 4 represents a diagram of a Hall effect sensor associated with a control magnet according to a first embodiment,

FIG. 5 represents a graph of the signal supplied by the Hall effect sensor of FIG. 4 as a function of the angular position of the rotor as well as the control signals of the electromagnetic excitation coils,

FIG. 6 shows two Hall effect sensors associated with a control magnet according to a second embodiment,

FIG. 7 represents a graph of the signals supplied by the Hall effect sensors of FIG. 6 as a function of the angular position of the rotor as well as the control signals of the electromagnetic excitation coils, FIG. 8a shows a first Hall effect sensor associated with a first control magnet according to a third embodiment, FIG. 8b shows a second Hall effect sensor associated with a second control magnet according to the third embodiment; FIG. 8c represents a schematic view of the first and second Hall effect sensors associated with a first and a second control magnet and their positioning with respect to the axis of the rotor,

FIG. 9 represents a graph of the signals supplied by the Hall effect sensors of FIG. 8 as a function of the angular position of the rotor as well as the control signals of the electromagnetic excitation coils,

FIG. 10 shows a schematic representation of a windshield and the stop positions of a wiping arm,

Figures 11a, 11b and 11c show a reduction mechanism comprising two hall effect sensors disposed at its gear in three distinct positions.

In all the figures, the identical elements bear the same reference numbers.

The following achievements are examples. Although the description refers to one or more embodiments, this does not necessarily mean that each reference relates to the same embodiment or that the features apply only to a single embodiment. Simple features of different embodiments may also be combined or interchanged to provide other embodiments.

In the description, it is possible to index certain elements or parameters, such as for example first element or second element as well as first parameter and second parameter, or first criterion and second criterion, and so on. In this case, it is a simple indexing to differentiate and name elements or parameters or criteria close but not identical. This indexing does not imply a priority of one element, parameter or criterion in relation to another, and it is easy to interchange such denominations without departing from the scope of this description. This indexing does not imply either an order in time for example to appreciate such or such criteria.

FIG. 2 represents an example of a law geared motor intended to equip a wiper system of a motor vehicle.

The gear motor law comprises a housing 102 on which is mounted an electric motor 103 coupled to a reduction mechanism 104 having a predefined reduction ratio, for example typically a ratio 1/69.

The reduction mechanism 104 comprises a worm gear 107 driven in rotation by the electric motor 103 and a toothed wheel 108 integral with an output shaft 109 rotatably mounted along an axis substantially perpendicular to the axis of rotation of the screw without end 107.

The reduction mechanism 104 is arranged in such a way that the worm gear 107 engages meshing with the toothed wheel 108, so that the output shaft 109 is able to be driven indirectly in rotation by the electric motor 103.

The output shaft 109 is generally connected either directly or via a linkage to a wiper arm on which a wiper blade is attached.

In the context of the present invention, the electric motor 103 is a brushless motor (brushless motor).

As represented in FIG. 3a, which represents a schematic cross-sectional view, the electric motor 103 comprises a cylindrical stator 13 in the center of which a rotor 15 is housed.

The rotor 15 is rotatably mounted around the central axis X of the electric motor 103 and comprises a permanent magnet 16 whose magnetic poles are represented by the letters N for the North Pole and S for the South Pole. However, the present invention is not limited to a permanent magnet 16 of the rotor 15 comprising a pair of magnetic poles but also extends to a permanent magnet having a higher number of pairs of magnetic poles.

The stator 13 comprises electromagnetic excitation coils 17 arranged around the rotor 15. The electromagnetic excitation coils 17 are evenly distributed on the circumference of the stator 13. The electric motor 103 is here a three-phase motor whose phases are denoted A, B and C. The electromagnetic excitation coils 17 are six in number (two coils being associated to form a phase) and are connected in a star assembly or Y mount.

Of course, a different number of electromagnetic excitation coils 17 and a different mounting, for example in a triangle can also be used.

As shown in FIG. 3b, the electromagnetic excitation coils 17 may be powered by an inverter 19 managed by a control unit 21.

The inverter 19 comprises for example three branches denoted Βι, B2 and B3 for supplying the respective phases A, B and C of the stator 13.

Each branch Βι, B2 or B3 comprises two switches 23 whose switching causes the power supply or not the electromagnetic excitation coils 17 of phase A, B or C associated.

The switches 23 of the inverter 19 are controlled by the control unit 21 to obtain a sequence of six switching steps represented by arrows numbered 1 to 6 in FIG. 3c.

The first step 1 corresponds to the passage of the current of the phase A to the phase B, the second step 2 corresponds to the passage of the current of the phase C to the phase B, the third step 3 corresponds to the passage of the current of the phase C to phase A, the fourth 4 corresponds to the passage of the current from phase B to phase A, the fifth step 5 corresponds to the passage of the current from phase B to phase C and the sixth step 6 corresponds to the passage of the current of the phase A to phase C.

The six switching steps correspond to a rotation of 360 ⁰ electrical, that is to say a complete rotation of 360 ⁰ of the rotor 15 in the case where the permanent magnet 16 comprises a single pair of magnetic poles, called here pair of motor poles. In the case of a permanent magnet 16 comprising two pairs of magnetic poles, the six switching steps, corresponding to 360 ⁰ electrical, correspond to a rotation of 180 ⁰ of the rotor 15 and in the case of a permanent magnet 16 comprising three pairs of poles, the six switching steps, corresponding to 360 ⁰ electrical, correspond to a rotation of 120 ⁰ of the rotor 15. The passage from one switch to another is therefore performed at each rotation of an angle of 6o ° electric of the rotor 15.

At each stage, the current passes through two phases while the third has a floating potential. The sequence of the six switching steps allows the creation of a rotating magnetic field at the stator 13 which allows the rotational drive of the rotor 15. Although this six-step switching scheme is the best known with a phase conduction of 120 ^° and a non-excitation of 60 °, the present invention is not limited to this single switching scheme but also extends to other types of switching for example with a conduction of phases of 180 ⁰ or intermediate or different dosage excitation during conduction up to sinusoidal progression.

The electric motor 103 also comprises a device for determining the angular position of the rotor 25 (see FIG. 3b) connected to the control unit 21 to enable the control unit 21 to determine the different switching times and to order accordingly. the switches 23 of the inverter 19.

The device for determining the angular position of the rotor 25 is configured to determine the position of the rotor 15 with respect to the stator 13 from at least one Hall effect sensor associated with a control magnet fixed in rotation with the rotor 15.

The angular position of the rotor 15 thus determined is then transmitted by the device 25 for determining the angular position of the rotor 15 to the control unit 21 to enable the switching moments of the inverter 19 to be determined.

In addition, the geared motor 101 also comprises a processing unit 26 connected to the device 25 for determining the angular position of the rotor 15 and to the control unit 21 and configured to determine the angular position of the output shaft 109. from the angular position of the rotor 15 determined by taking into account the predefined reduction ratio of the gear mechanism 104. The angular position of the output shaft 109 is then used by the control unit 21 to determine the rotational speed to apply to the rotor 15 and in particular to determine the times when the wiper arm arrives in an abutment position and for which the direction of rotation of the electric motor 103 must be reversed. l) Determination of switching times of the inverter 19

A) First embodiment: a single Hall sensor 27

Referring to FIGS. 4 and 5, according to a first embodiment, the electric motor 103 comprises a single Hall effect sensor 27. This single sensor 27 is used by the device 25 for determining the angular position of the rotor 15, this in particular for determining the position of the rotor 15 for low speeds of rotation, that is to say less than a predetermined threshold, for example for speeds less than 10% of the maximum speed of the electric motor 103. here of the starting phase of the electric motor 103 DC brushless.

For rotation speeds equal to or greater than the predetermined threshold, that is to say after the starting phase, the device 25 for determining the angular position of the rotor 15 can determine the angular position of the rotor 15 from the forces against electromotive devices measured at electromagnetic excitation coils 17.

The force against electro-motor is measured at a coil 17 unpowered. For example, in the case of step 1 of FIG. 3c, the current is transmitted from phase A to phase B so that the electromotive force is measured at the level of the electromagnetic excitation coil 17 associated with the phase C. The measurement of the electromotive force is then transmitted to the device 25 for determining the angular position of the rotor 15.

The device 25 for determining the angular position of the rotor 15 then compares the value of the electromotive force measured against a predetermined threshold associated with a predetermined position of the rotor 15. For example, in the case of a symmetrical power supply, the instantaneous switching means corresponds to the zero crossing (transition from a positive level to a negative level or vice versa) of the voltage value of the back electromotive force at the terminals of the electromagnetic excitation coil 17 which is not powered.

In addition, the measured electromotive forces can be used to correct or even calibrate the Hall effect sensor 27.

According to a variant, it is possible to continue to exploit the position of the rotor 15 determined from the signals delivered by the Hall effect sensor 29 even for rotational speeds equal to or greater than the predetermined threshold.

The Hall effect sensor 27 is disposed at the level of the stator 13 and is associated with a control magnet 29 integral in rotation with the rotor 15 as shown in FIG. 4.

The control magnet 29 has a number of magnetic poles equal to three times the number of magnetic poles of the rotor 15. In this case, the number of poles of the control magnet 29 therefore comprises six magnetic poles denoted Ni, N2. and N3 for the north poles and Si, S2 and S3 for the south poles as shown in Fig. 4. Each magnetic pole of the control magnet 29 occupies an angular section of 60 °.

Due to the six magnetic poles of the control magnet 29, the Hall effect sensor 27 can detect a precise angular position of the rotor every 6o °. The electric motor 103 is thus configured so that the signal state changes provided by the single Hall effect sensor 27 correspond to the switching changes of the inverter 19 as shown in the graph of FIG. 5.

In fact, FIG. 5 represents, in its upper part, the signal h coming from the Hall effect sensor 27 as a function of the angular position a of the rotor 15.

The six steps corresponding to the switching cycle of the electromagnetic excitation coils 17 are also shown in the lower part of FIG.

The changes in state of the signal h from the Hall effect sensor 27 thus make it possible to determine the times at which the switching changes of the inverter 19 must be made.

B) Second Embodiment: Two Hall Effect Sensors 27a and 27b in a First Configuration

According to a second embodiment illustrated in FIGS. 6 and 7, the electric motor 103 comprises two Hall effect sensors 27a and 27b associated with a control magnet 29 whose number of magnetic poles is equal to three times the number of magnetic poles. of the rotor 15 and is therefore similar to the control magnet 29 of the first embodiment. In the present case, the number of poles of the control magnet 29 therefore comprises six magnetic poles as shown in FIG. 6. The two Hall effect sensors 27a and 27b are for example arranged around the rotor 15 and offset by one. angular position such that the signals from the two Hall effect sensors 27a and 27b are offset by an angle of 90 ⁰ electrical, that is to say an offset of 30 ⁰ in the case of a control magnet 29 comprising three pairs of magnetic poles.

The electric motor 103 is moreover similar to the first embodiment and only the differences in operation will now be described.

The electric motor 103 is configured such that the signal state changes provided by one of the two Hall effect sensors 27a or 27b, for example the sensor 27b, correspond to the switching changes of the inverter 19 as shown in FIG. the graph of Figure 7.

The two Hall effect sensors 27a and 27b arranged at 30 ^° thus make it possible to obtain a detection of the position of the rotor 15 every 30 ^° .

The six steps corresponding to the switching cycle of the electromagnetic excitation coils 17 are also represented on the lower part of FIG. 7.

Thus, one of the Hall effect sensors, for example the sensor 27b, makes it possible to provide the switching change times of the inverter 19 as in the first embodiment and the other Hall effect sensor, for example the 27a sensor, provides the direction of rotation of the rotor 15.

The measured electromotive forces can also be used to determine the position of the rotor 15 and to correct and / or calibrate the Hall effect sensors 27a and 27b.

C) Third embodiment: two Hall effect sensors 27a and 27b according to a second configuration. According to a third embodiment illustrated in FIGS. 8a, 8b and 9, the electric motor 103 comprises a first Hall effect sensor 27a associated with a first control magnet 29a comprising a number of pairs of magnetic poles equal to nine times the number of pairs of motor poles and a second Hall effect sensor 27b associated with a second control magnet 29b comprising a number of pairs of magnetic poles equal to three times the number of pole pairs of the electric motor 103. In this case, the number of poles of the first control magnet 29a comprises 18 magnetic poles denoted Ni, N2, N3, N4, N5, N6, N7, N8 and N9 for the north poles and Si, S2, S3, S4, S5, S6, S7, S8 and S9 for the south poles as shown in Figure 8a. Each magnetic pole of the first control magnet 29a occupies an angular section of 20 ^° . The number of poles of the second control magnet 29b comprises six magnetic poles denoted Ni, N2 and N3 for the north poles and Si, S2 and S3 for the south poles as shown in FIG. 8a. Each magnetic pole of the second control magnet 29b occupies an angular section of 60 °. The first 29a and the second 29b control magnets are integral in rotation with the rotor 15 and arranged coaxially as shown in Figure 8b.

The electric motor 103 is also similar to the second embodiment and only the differences in operation will now be described.

The electric motor 103 is for example configured so that the state changes of the signal h_b provided by the second Hall effect sensor 27b correspond to the switching changes of the inverter 19 as shown in the graph of FIG. 9.

The first Hall effect sensor 27a and the first control magnet 29a are for example configured so that the state changes of the second Hall effect sensor 29b occur half-way between two state changes of the first effect sensor. Hall 27a as shown in FIG.

The second Hall effect sensor 27b thus makes it possible to provide the instants of the switching changes of the inverter 19 and the first Hall effect sensor 27a makes it possible to determine the direction of rotation of the rotor 15. The combination of the two sensors 27a and 27b makes it possible to determine to obtain the position of the rotor every 10 ° or 20 ^° .

The six steps corresponding to the switching cycle of the electromagnetic excitation coils 17 are also represented on the lower part of FIG. 9.

As for the second embodiment, the measured electromotive forces can also be used to determine the position of the rotor 15 and to correct and / or calibrate the Hall effect sensors 27a and 27b. Other embodiments comprising one or two Hall effect sensors 27, 27a, 27b associated with one or two control magnets 29, 29a, 29b comprising a number of magnetic poles of greater or lesser size are also conceivable in the context of FIG. present invention. The Hall effect sensors 27, 27a, 27b for determining the switching times of the inverter 19.

In practice, the device 25 for determining the angular position of the rotor 15, the control unit 21 and the processing unit 26 can be combined in a single piece of equipment, for example a microprocessor, a microcontroller or an ASIC (a circuit application-specific integrated) or any other suitable processing means known to those skilled in the art.

In addition, it should be noted that the example shown for the various embodiments corresponds to an electric motor 103 with two magnetic poles and a unit reduction ratio but the present invention is not limited to such an example but extends to other configurations having a different number of magnetic poles and a different reduction ratio.

2) Determination of the position of the output shaft 109 of the reducing mechanism 104

As indicated above, the position of the rotor 15 determined by the device 25 for determining the angular position of the rotor 15 is transmitted to the processing unit 26 which is configured to determine the position of the output shaft 109 of the gear mechanism 104 This determination is made taking into account the reduction ratio of the gear mechanism 104, for example 1/69 so that 69 rotations of the rotor 15 correspond to a revolution of the output shaft 109 of the gear mechanism 104. The determined position of the output shaft 109 of the reduction mechanism 104 makes it possible to estimate the position of the fitting arm 114 and thus to define the times when the speed of rotation must be reduced as well as the times when the direction of rotation of the electric motor 103 must be reversed for the wiper arm to make the desired back and forth motion. The processing unit 26 is thus coupled to the control unit 21 to generate the control signals making it possible to obtain a change in the direction of rotation of the electric motor 103 at the level of a predefined stop position of the output shaft 109 of the gear mechanism 104.

The mechanism comprises for example two abutment positions denoted A and B as shown in FIG. 10. A first abutment position A corresponds, for example, to a position of the low wiping arm close to the lower edge of the windshield 112 or the glass window associated with the wiper arm 114. The second stop position B corresponds for example to a high position of change of direction of the wiper arm 114 when the latter is in operation.

Thus, from the signals from the Hall effect sensor or sensors 17, 27a, 27b, the processing unit 26 can determine the number of revolutions made by the rotor 15 and deduce the position of the wiper arm 114 from reduction ratio.

However, such an operation may not be satisfactory, especially if the wiper arm 114 is not reduced to a predetermined rest position, for example the position A at each deactivation of the wiper system. Indeed, it is necessary for the control unit 11 to know the position of the wiper arm 114 during activation of the wiper system to be able to properly control the electric motor 113 of the geared motor 101.

For this, it is possible to use at least one additional Hall sensor called output sensor associated with one or more control magnets called output magnets rotatably coupled to the output shaft 109 of the gear mechanism 104. The or the sensors and output magnets make it possible, for example, to determine the stop positions. The output sensor or sensors are for example connected to the processing unit 26.

FIG. 11a shows an exemplary embodiment comprising two output Hall effect sensors 127a and 127b and a control magnet 129 comprising two south poles Si and S2 situated at the stop positions of the toothed wheel 108 associated with the transmission shaft. exit 109 and a north pole N located between the two south poles Si and S2.

Figures 11b and 11c show the gear wheel 108 respectively in first and second stop positions. The use of two Hall effect sensors 127a and 127b makes it possible to detect the presence of a stop and to determine whether it is the first stop or the second stop. Indeed, when the gear wheel 108 is in the first stop position (fig.iib), the first output sensor 127a is in view of the south pole Si and the second output sensor 127b is opposite the north pole N while in the second stop position (fig.nc), the first output sensor 127a is opposite the north pole N and the second sensor output 127b is opposite the south pole S2. Thus, depending on whether a south pole is detected by the first 127a or the second 127b output sensor, it is possible to determine whether the wiper arm is in the first or second stop position. In addition, during the operation of the wiper system, the processing unit 26 can determine the position of the wiper arm between the two stop positions given by the output sensors 127a, 127b by means of the sensor (s). ) Hall effect 27, 27a, 27b associated with the rotor 15 as previously described.

Thus, the present invention reliably drives a geared motor 101 using a limited number of Hall effect sensors 27, 27a, 27b, 127a, 127b. These Hall effect sensors 27, 27a, 27b, 127a, 127b make it possible to determine both the position of the rotor 15 of the electric motor 103 as well as the position of the output shaft 109 of the reduction mechanism 104.

Claims

1. Moto-reducer (law), in particular for a wiper system, comprising:

a brushless direct current electric motor (103) comprising:

a rotor (15),

a stator (13) presenting coils (17) for electromagnetic excitation of the rotor (15),

a device (25) for determining the angular position of the rotor (15) with respect to the stator (13),

a control unit (21) configured to generate control signals for supplying the electromagnetic excitation coils (17) as a function of the angular position of the rotor (15) determined by the angular position determining device (25) rotor (15),

a reduction mechanism (104) connected on one side to the rotor (15) of the electric motor (103) and on the other side to an output shaft (109) intended to be connected to an external mechanism, in particular a control system wiping, the reducing mechanism (104) having a predefined reduction ratio,

characterized in that said device (25) for determining the angular position of the rotor (15) comprises at least one Hall sensor (27, 27a, 27b) associated with a control magnet (29, 29a, 29b) integral with rotation of the rotor (15) and in that the geared motor (101) also comprises a processing unit (26) connected to the device (25) for determining the angular position of the rotor (15) and configured to determine the angular position the output shaft (109) from the angular position of the rotor (15) determined by taking into account the predefined reduction ratio of the reduction mechanism (104).

The geared motor (101) according to claim 1, wherein the device (25) for determining the angular position of the rotor (15) comprises two Hall effect sensors (27a, 27b) respectively associated with a control magnet ( 29, 29a, 29b) integral in rotation with the rotor (15).

A geared motor (law) according to claim 1 or 2, wherein the control magnet (29, 29a, 29b) comprises a number of pairs of poles greater than the number of pairs of magnetic poles of the rotor (15) of the brushless direct current electric motor (103).

The geared motor (101) according to claim 3 in combination with claim 1, wherein the device (25) for determining the angular position of the rotor (15) comprises a single Hall effect sensor (27) associated with a control magnet (29) comprising a number of pairs of poles equal to three times the number of magnetic pole pairs of the rotor (15) of the electric motor (103), the poles of the control magnet (29) being configured to being in phase with the magnetic poles of the rotor (15) of the electric motor (103) so that the state changes of the Hall effect sensor (27) are synchronized with the state changes of the control signals generated by the control unit (21) for supplying the electromagnetic excitation coils (17).

The geared motor (101) according to claim 3, wherein the device (25) for determining the angular position of the rotor (15) comprises two Hall effect sensors (27a, 27b) associated with a control magnet (29). ) comprising a number of pairs of poles equal to three times the number of pairs of magnetic poles of the rotor (15) of the electric motor (103), the two sensors (27a, 27b) being offset by an angle of 30 ⁰ , the magnetic poles of the rotor (15) of the control magnet (29) being configured to be in phase with the magnetic poles of the rotor (15) so that the state changes of one of the Hall effect sensors (27a , 27b) are synchronized with the state changes of the control signals generated by the control unit (21) for supplying the electromagnetic excitation coils (17).

The geared motor (101) according to claim 3, wherein the device (25) for determining the angular position of the rotor (15) comprises two Hall effect sensors (27a, 27b), the first hall effect sensor ( 27a) being associated with a first control magnet (29a) comprising a number of pairs of poles equal to three times the number of magnetic pole pairs of the rotor (15) of the electric motor (103), the second hall effect sensor (27b) being associated with a second control magnet (29b) comprising a number of pairs of poles equal to nine times the number of magnetic pole pairs of the rotor (15) of the electric motor (103), the poles of the first control magnet (29) being configured to being in phase with magnetic poles of the rotor (15) of the electric motor (103) so that the state changes of the first Hall effect sensor (27a) are synchronized with the state changes of the control signals generated by the control unit (21) for supplying the electromagnetic excitation coils (17), the second Hall effect sensor (27b) and the second control magnet (29b) being configured so that the state changes of the first sensor to effe t Hall (27a) occur halfway between two state changes of the second Hall effect sensor (27b).

7. Moto-reducer (101) according to one of the preceding claims, wherein the device (25) for determining the angular position of the rotor (15) relative to the stator (13) is configured to:

determining the angular position of the rotor (15) from the signals from the Hall effect sensor (s) (27, 27a, 27b) for rotational speeds of the rotor below a predetermined threshold, and

- Determining the angular position of the rotor (15) from a measurement of the counter-electromotive forces from the electromagnetic excitation coils (17) for rotational speeds of the rotor (15) equal to or greater than the predetermined threshold.

The geared motor (101) according to claim 7, wherein the counter electromotive force of the at least one unpowered electromagnetic excitation coil (17) is measured and transmitted to the device (25) for determining the angular position of the rotor (15), said device (25) for determining the angular position of the rotor (15) being configured to compare the measured counter-electromotive force value with a predetermined threshold associated with a predetermined position of the rotor (15).

9. Gear motor (101) according to claim 7 or 8, wherein the device for determining the angular position of the rotor (15) is configured to correct the angular measurement from the Hall sensor (s) (27). , 27a, 27b) from the measurement of the counter electromotive forces of the electromagnetic excitation coils (17) so as to calibrate the Hall effect sensor or sensors (27, 27a, 27b) from said counter force measurements. electromotive.

10. Moto-reducer (101) according to one of the preceding claims, also comprising a supplementary magnet said output magnet (129) rotatably connected to the output shaft (109) and at least one additional Hall effect sensor said an output sensor (127a, 127b) associated with the output magnet (129), the at least one output sensor (127a, 127b) and the output magnet (129) being configured so that the at least one at least one output sensor (127a, 127b) detects a first position of the output magnet (129) corresponding to a first stop position of the external mechanism to be connected to the output shaft (109) and a second position of the output magnet (129) corresponding to a second stop position of the external mechanism to be connected to the output shaft, the, at least one output sensor (127a, 127b) being connected to the unit control unit (21) and said control unit (21) being configured to generate the control signals also according to signals from said at least one output sensor (127a, 127b).

11. A wiper system, especially for a motor vehicle comprising a geared motor (101) according to one of the preceding claims.

12. A method of controlling an electric motor (103) of a geared motor (101), especially for wiping systems, the geared motor (101) comprising:

a brushless direct current electric motor (101) comprising:

a rotor (15),

a stator (13) presenting electromagnetic excitation coils (17) of the rotor (15),

a device (25) for determining the angular position of the rotor (15) with respect to the stator (13) comprising at least one Hall effect sensor (27, 27a, 27b) associated with a control magnet (29, 29a, 29b) integral in rotation with the rotor (15),

said method comprising the following steps:

(a) for rotational speeds of the rotor below a predetermined threshold:

the angular position of the rotor (15) is determined from the signals originating from the Hall effect sensor (s) (27, 27a, 27b),

the angular position of the rotor (15) is determined from a measurement of the counter-electromotive forces originating from the electromagnetic excitation coils (17),

control signals are generated for supplying the electromagnetic excitation coils (17) as a function of the angular position of the rotor (15) determined during the preceding steps,

the angular position of the output shaft (109) is determined from the angular position of the rotor (15) determined during the preceding steps and taking into account the predefined reduction ratio of the reducing mechanism (104).

13. A method of controlling an electric motor (103) of a geared motor (101) according to the preceding claim, wherein the angular measurement of the sensor (s) Hall effect (s) (27, 27a, 27b) is corrected. ) from the measurement of the electromotive forces from the coils (17) of electromagnetic excitation of the rotor (15).

14. A control method according to claim 12 or 13 wherein the motorcycle reducer (101) also comprises an additional magnet said output magnet (129) disposed at the output shaft (109) of the gear mechanism (104) and at least one additional Hall effect sensor said output sensor (127a, 127b) associated with the output magnet (129), the at least one output sensor (127a, 127b) and the at least one output magnet (129) being configured such that the at least one , output sensor (127a, 127b) detects a first position of the output magnet (129) when the output shaft (109) is in a first position corresponding to a first stop position of the external mechanism to be connected to the output shaft (109) and detects a second position of the output magnet (129) when the output shaft (109) is in a second position corresponding to a second stop position of the external mechanism intended to be connected to the output shaft (109) and wherein the generator stage control signals for supplying the electromagnetic excitation coils (17) are also produced as a function of the signals of said at least one output sensor (127a,