Circuit and method for controlling an electric motor for driving a windshield wiper

Abstract

Control circuit (3) for an electric motor (4) for driving a windshield wiper, comprising a control means (16), comprising an output for controlling the electric motor (4), wherein the control means (16) is suitable to adjust the angle (θ) of the motor between a given minimum value (θ) min ) and a given maximum value (θ max ) to vary, wherein the control means (16) has an input for receiving a speed setpoint (dθ / dt) c includes and is suitable to determine the angular velocity (dθ / dt) of the motor (4) according to the speed setpoint (dθ / dt) c to control, wherein the control circuit (3) also has a setpoint averaging (14), comprising an input for receiving the motor angle (θ) values ​​and an output for supplying a speed setpoint (dθ / dt) c to the control means (16), wherein the setpoint means (14) is suitable to determine the speed setpoint (dθ / dt) cto be determined on the basis of a continuous function of the motor angle (θ), characterized in that the speed setpoint (dθ / dt) c is achieved at a predetermined motor angle value.

Description

[0001] The present invention relates to circuits and methods for controlling an electric motor for driving a windshield wiper. The invention also relates to a drive device for performing an alternating rotary movement in one direction and then in another, as well as to a windshield wiper device. Such movements are typically used for wiping windshields of vehicles, for example, cars, trucks, trains, airplanes, etc. In particular, the invention relates to a circuit according to the preamble of claim 1 and a method according to the preamble of claim 10, as known, for example, from US 2009 / 0248243 A1.

[0002] In particular, for driving the rear windshield wiper of a motor vehicle, it is known to use a motor that performs a pendulum motion. The motor angle is then proportional to the angle of the wiper arm, according to a constant reduction ratio. One such example is described in particular in patent US 4,271,381. The reduction gear can thus be a wheel connected to a continuous worm, and the changes in the wiper's wiping direction can be controlled by electrical supply switches connected to the motor's output shaft, which supply the motor with direct current. Other examples are also described in documents FR 2 893 575, WO 98 / 30422, WO 99 / 06251, FR 2 744 685, WO 02 / 22409, and WO 96 / 07566.In these devices, the motor is controlled as a function of the angle of the motor, in particular the two angles that limit the wiping area of ​​the windscreen wiper and the rest angle, or as a function of mechanical stops that embody these characteristic angles.

[0003] The motor is now controlled in on-off mode or vice versa. However, these devices are not suitable for applications where the torque, especially the aerodynamic torque, the inertia, and the length of the wiper arm are greater. In these applications, the wiper cannot complete half a revolution by simply switching. Furthermore, the motors operate in an open loop and thus at maximum torque, which reduces their operating performance at low rotation speeds.

[0004] Devices are also known, generally comprising a motor and a mechanical converter, which, on the one hand, reduces the speed of the electric motor and, on the other hand, converts the rotary motion into a reciprocating motion. In such a device, the motor axis always rotates in the same direction, at a greater or lesser speed. A connecting rod-type system, for example, ensures the conversion of the rotary motion into a reciprocating motion. Furthermore, aircraft devices also have a rest position (called a parking position), generally located outside the windshield wiping area. For this purpose, the connecting rod mechanism may include an eccentric cam and a detent.With such devices, the direction of rotation of the motor determines the operating mode of the windshield wiper: wiping the windshield area when the motor rotates in a given direction and placing it in the rest position when the motor rotates in the other direction.

[0005] Devices that incorporate a connecting rod system have several disadvantages. These devices comprise numerous parts and are designed for a specific geometry (wiping angle, parking position, etc.). Such devices are expensive, complex, bulky, and require sufficient space to convert rotary motion into reciprocating motion. Furthermore, due to the numerous parts, the mechanical converter has a significant mass, which is usually housed on board a vehicle. Finally, since the device is designed for a specific geometry, it is necessary to recreate several parts when manufacturing such a device for a new application.

[0006] An object of the present invention is therefore to propose a circuit that allows a motor for driving a windshield wiper to be controlled more efficiently, for example, limiting power consumption and motor heating. Furthermore, an object of the invention is to propose a compact, reliable, and easy-to-install drive device that can be adapted to any type of application, requiring few or no structural modifications.

[0007] For this purpose, a control circuit for an electric motor for driving a windscreen wiper according to claim 1 is proposed.

[0008] A continuous function is one in which, as the motor angle approaches a given angle, the speed setpoint approaches the setpoint for the given angle. In particular, this means that the speed setpoint varies depending on the motor angle without sudden changes in value. Thus, the circuit is suitable for controlling the motor speed in such a way that the electrical power consumed by the motor is limited while maintaining a compact, lightweight, and reliable device. For example, the variation in the speed setpoint for a given change in the motor angle can be less than or equal to a certain value.

[0009] The variation of the speed setpoint may be less than or equal to one quarter, preferably one sixth, preferably one eighth and more preferably one tenth of the maximum speed setpoint, for each variation of the motor angle equal to one twentieth of the difference between the maximum and the minimum value of the motor angle, ie for each variation of the motor angle equal to one twentieth of the wiping range.

[0010] If the control circuit is an analog circuit and the motor angle is provided by a position sensor that sends a continuous signal, the speed command can be a continuous function of the motor angle.

[0011] If the control circuit is a digital circuit and the motor angle is a sampled signal, the speed command can also be a sampled function, but determined for each sample of the motor angle according to a continuous function.

[0012] Specifically, at half-revolutions of the motor, the speed setpoint decreases, cancels itself, and changes sign. This avoids sudden changes in the direction of rotation and significant energy losses. Furthermore, to control the motor speed according to the speed setpoint, the motor torque is adjusted, making it possible to use only the necessary and sufficient torque.

[0013] The setpoint means may be adapted to determine a first angle value of the motor which is greater than the minimum value and a second angle value which lies between the first angle value and the maximum value, to provide a speed setpoint which varies with the value of the motor angle when this lies between the minimum value and the first value or between the second value and the maximum value, and to provide a speed setpoint with a constant absolute value (which corresponds to the maximum desired speed setpoint in absolute value) when the value of the motor angle lies between the first value and the second value.The speed setpoint now has three parts depending on the motor angle: a first increasing part, corresponding to an increase in motor speed until the desired maximum speed is reached; a second constant part, corresponding to wiping the windshield at the desired speed; and a third decreasing part, corresponding to a decrease in motor speed before changing direction. Such a speed setpoint makes it possible, in particular, to obtain a uniform rotational movement between the first and second values, i.e., in the center of the wiping area, thus ensuring visual comfort for the user. Furthermore, the effects of inertia on the motor and energy losses are limited, since the motor speed is controlled to increase or decrease progressively.

[0014] The setpoint means may also include an input for selecting a user mode, wherein the maximum desired speed setpoint, the maximum value, the minimum value, the first value, and the second value of the motor angle can be determined depending on the selected user mode. The user mode corresponds to an operating mode of the windshield wiper, for example, depending on the intensity of the rain falling on the windshield.

[0015] The control means may also include an input for receiving the motor's angular velocity values ​​and may be suitable for controlling the motor torque as a function of the difference between the motor's angular velocity and the speed setpoint. The motor's angular velocity is then controlled in a closed loop by the control means. In other words, the motor's angular velocity is subject to the control of the control means. This results in a better angular velocity, particularly with respect to the speed setpoint.

[0016] The control means may also include an input for receiving a motor angle setpoint and an input for receiving the motor angle values. During motor idle phases, the control means may be adapted to control the motor depending on the difference between the motor angle and the motor angle setpoint. The motor angle is then controlled by the control means in a closed loop.

[0017] The circuit may also comprise a determining means comprising an input for receiving the values ​​of the motor angle and an output for supplying the angular velocity of the motor to the control means, wherein the determining means is suitable for calculating the angular velocity of the motor from values ​​of the motor angle.

[0018] According to a further aspect, the invention also relates to a drive device for carrying out an alternating rotary movement, comprising a circuit as previously described and an electric drive motor.

[0019] The motor can be a synchronous motor, preferably without brushes.

[0020] The invention also relates to a windshield wiper device, in particular for a motor vehicle or an aircraft, comprising at least one drive device as described above and a windshield wiper arm driven by the drive device, possibly with the aid of a mechanical transmission. The mechanical transmission is preferably a fixed reduction gear. The mechanical transmission can be a wheel or a continuous worm gear, or a direct gear train device.

[0021] According to a further aspect, a control method for an electric motor according to claim 10 is proposed. Preferably, a first angle value of the motor which is greater than the minimum value and a second angle value which lies between the first angle value and the maximum value are determined, a speed command value which varies with the value of the motor angle when this lies between the minimum value and the maximum value or between the second value and the maximum value is determined, a constant speed command value (which corresponds to a maximum desired speed command value) is provided when the value of the motor angle lies between the first and the second value.

[0022] The value of the constant speed setpoint, the maximum value, the minimum value, the first value and the second value of the motor angle can be determined depending on a user mode.

[0023] Preferably, the motor torque is also controlled as a function of the difference between the angular velocity of the motor and the speed setpoint.

[0024] The motor can also be controlled depending on the difference between the motor angle and a motor angle setpoint during the motor's rest phases.

[0025] The invention will be better understood by studying a particular embodiment, which is in no way to be considered as a limiting example and is illustrated by the accompanying drawings, in which: - Fig. Figure 1 schematically shows a windscreen wiper device according to the invention; - Fig. Figure 2 schematically shows an embodiment of a drive device according to the invention; - Fig. Figure 3 shows an example of a speed setpoint as a function of the motor angle according to the invention; and - Fig. 4 shows the variation of the motor angle as a function of time according to the invention.

[0026] In Fig. Figure 1 schematically shows a windshield wiper device 1. The windshield wiper device 1 comprises a drive device 2, comprising a control circuit 3 and a drive motor 4, and a windshield wiper arm 5, which is driven by the motor 4 and wipes the surface of a windshield 6, for example, of an aircraft.

[0027] More precisely, the wiper arm 5 moves back and forth across a wiping area of ​​the windshield defined by a first position 7 and a second position 8 of the wiper arm. The first and second positions of the wiper arm correspond to the two edges of the wiping area: they are the boundaries of the wiping surface and the position of the wiper where the direction of rotation is reversed. In the following description, it is assumed that the first position 7 corresponds to a minimum value θ min of the motor angle and the second position 8 a maximum value θ max of the motor angle. Furthermore, the windscreen wiper arm 5 can also be arranged in a rest position 9, so-called parking position, which corresponds to a motor angle θ park The rest position 9 can be arranged in particular outside the wiping area of ​​the windscreen or outside the windscreen 6, as shown in Fig. 1 is shown.

[0028] Depending on the intended use of the drive device, particularly with regard to torque and speed, the drive device 2 may also comprise a reduction gear 10 mounted between the motor 4 and the windshield wiper arm 5. The angular reduction gear 10 may, for example, be formed, on the one hand, by an endless screw rigidly connected to the output shaft of the motor 4 and, on the other hand, by a gear connected to the windshield wiper 5, or even by three direct gear trains.

[0029] The motor 4 is a motor capable of driving its output shaft in a first direction of rotation and in the reverse direction. The motor 4 thus performs a reciprocating or reverse rotation. The motor 4 can be an electric motor, for example a synchronous motor, preferably without brushes. This type of motor is suitable for the present use and allows rotation in one direction and then in the other with great reliability, even with frequent changes of direction. This brushless motor is preferably of the type comprising an external coil stator and a central magnetic rotor.

[0030] According to one embodiment, the motor 4 can also include a static brake, for example a power-default brake (not shown), which allows the angle of the motor to be kept constant when the power supply is no longer available. The static brake is used in particular during rest periods to limit the rotation of the motor under the action of external influences, such as wind. The motor then consumes no energy to keep the wiper in its rest position.

[0031] The motor 4 may also include a sensor 11. The sensor 11 may be an encoder or a function sensor located on the axis of the magnetic rotor. The sensor 11 allows, for example, the angular position θ or the angular velocity (dθ / dt) of the motor 4 to be measured and transmits the measured values ​​to the control circuit 3. It may also be a magnetic, mechanical, optical, etc. type sensor.

[0032] The drive device also includes control circuit 3. Control circuit 3 includes an output for controlling motor 4. This may be an output for supplying electrical power to motor 4. In this case, the current and voltage applied to motor 4 may allow control of the torque and angular velocity of the motor.

[0033] The control circuit 3 also includes a first input for selecting a user mode MU. This user mode can be selected by the user located behind the windshield and adjusts the wiper speed depending on meteorological conditions: for example, intermittent wiping, slow wiping, fast wiping, or no wiping. The user mode can also be provided by a rain sensor mounted on the windshield, which determines the required wiping speed for wiping the windshield.

[0034] The control circuit also includes an input for receiving the values ​​from sensor 11. The values ​​of the motor angle θ or the motor speed (dθ / dt) of the motor 4 are used to subsequently control the motor and / or perform a closed-loop control. Alternatively, the control circuit can also detect the motor's rest positions using mechanical stops 12, 13 located near the wiper arm's rest position and near the wiper arm's second position, respectively. The stops 12, 13 can allow the control means, each time the power is switched off, to position the motor in a specific reference position, detecting a zero angular velocity.

[0035] The control circuit 3 comprises in particular a setpoint means 14 comprising an input for receiving the user mode MU, an input for receiving the signal of the position sensor 11 and an output for supplying a speed setpoint (dθ / dt) c The control circuit 3 also includes a determination means 15, comprising an input for receiving the signals from the position sensor 11 and an output for supplying angular velocity values ​​calculated based on the data from the position sensor 11. Finally, the control circuit includes a control means 16, comprising an input for receiving the speed setpoint (dθ / dt). c supplied by the setpoint means 14, an input for receiving the angular velocity values ​​(dθ / dt) supplied by the determining means 15, and an output for controlling the motor 4, for example an output for the electrical supply of the motor 4.

[0036] Fig. Figure 2 schematically describes an embodiment of the control circuit 3. In particular, Fig. 2 an example of a control means 16.

[0037] The control means 16 comprises a first comparator 17 which is suitable for comparing the angular velocity (dθ / dt) determined by the determining means 15 and the speed setpoint (dθ / dt) c , which was supplied by the setpoint means 14. The first comparator 17 provides a value at the output which represents the difference between the angular velocity (dθ / dt) and the speed setpoint (dθ / dt) crepresentative, to a first corrector 18. The first corrector 18 makes it possible to modify the control of the motor 4 in order to reduce or eliminate the difference between the angular velocity of the motor and the speed setpoint. The first comparator 17 and the first corrector 18 thus form a closed-loop control of the angular velocity of the motor in order to obtain an angular velocity of the motor as close as possible to the speed setpoint.

[0038] Closed-loop control of the motor's speed and angle can also make it possible to detect vibration phenomena of the windshield wiper arm based on the torque setpoint. Depending on the arm's mass and the torsional rigidity of the mechanical transmission, a "mass-spring" type vibration phenomenon may be observed, caused by friction between the arm and the windshield. Such vibration can generate excessive torque and damage the device. The control means 3 can be suitable for detecting such vibration and subsequently controlling the motor to limit or eliminate this phenomenon.

[0039] The first corrector 18 thus delivers a current, called active current, I q_ref . The current I q_refAllows the torque of motor 4 to be controlled: this is a first current corresponding to a vectorial control of the motor. In the case of vectorial control, the motor torque is controlled by the current, and the speed is controlled by the voltage. However, the torque can also allow the motor speed to be controlled. The angular speed of the motor can be controlled by the motor's power supply current due to the various torques exerted on the windshield wiper arm, which can reduce the motor's angular speed: the motor torque counteracts these torques and thus obtains the desired angular speed.

[0040] Thus, the control circuit 3 allows the torque and thus the supply current of the motor 4 to be adjusted as needed. It is not necessary to apply the maximum motor torque at all times to ensure that the desired angular velocity is achieved. By thus limiting the motor torque and thus the supply current, the control circuit allows the electrical power delivered to the motor 4 to be reduced, thus increasing the device's performance. Furthermore, by limiting the motor supply current, the control circuit also limits the heat losses caused by the motor's internal resistance. This results in better conduction and less heating of the motor.

[0041] The first correction means 18 may also be capable of determining, based on the differences between the speed setpoint and the angular velocity of the motor, the torque required by the motor and thus the braking torque corresponding to the friction of the arm on the windshield and / or the friction of the air on the arm. To the extent that the friction torque of the arm on the windshield is the same in both directions of operation of the arm, the friction torque of the air is driving or braking depending on the direction of operation of the arm. The correction means can distinguish between the two torques and deduce from them, for example, the speed of the vehicle (depending on the friction torque of the air and at a given air pressure) or the surface condition of the windshield, dry or wet (depending on the friction torque of the wiper arm on the windshield).

[0042] The Stream I q_refis then supplied to a second comparator 19, which also measures the current I q supplied to the motor by the control circuit. The second comparator 19 is adapted to receive the reference current I q_ref and the applied current I q The second comparator 19 delivers a value representative of the difference between these two values ​​to a second corrector 20. The second corrector 20 also makes it possible to modify the control of the motor 4 in order to compensate for the difference between the desired current value I q_ref and the actual invested value I q The second comparator 19 and the second corrector 20 thus form a control of the active current I q to supply the motor in a closed loop.

[0043] The control means 16 can also regulate the current I d_ref, which is the second current corresponding to the vectorial control of motor 4, in a closed loop. The current I d_ref is supplied to a third comparator 21, which also measures the current I d which is supplied to the motor by the control circuit. The third comparator 21 is adapted to receive the reference current I d_ref and the applied current I d The third comparator 21 provides at its output a value representative of the difference between these two values ​​to a third corrector 22. The third corrector 22 also makes it possible to modify the control of the motor 4 in order to compensate for the difference between the desired current value I d_ref and the actual invested value I d The third comparator 21 and the third corrector 22 thus form a control of the active current I d to supply the motor in a closed loop.

[0044] The second corrector 20 thus provides a corrected active current I at the output q_corr and the third corrector 22 provides a corrected active current I at the output d_corr . The Currents I q_corr and I d_corr allow the torque of motor 4 to be controlled: this is the vector control of the motor. This vector control is then converted into a scalar control, which is applied to the three phases of the motor.

[0045] Thus, the control means 16 also comprises a conversion means 23. The conversion means 23 comprises an input for receiving the motor angle values ​​θ and two inputs for receiving the currents I q_corr and I d_corr . The conversion means 23 makes it possible to convert the vector control into a scalar control, with the three currents I a , I b , I c The currents I a , I b , I care the currents supplied by the control means 16 and applied directly to the motor 4 to achieve the rotation of the motor's output shaft. The conversion means 23 can also use a Park transformer to convert the currents I a , I b , I c depending on the currents I q_corr and I d_corr the vector control.

[0046] Finally, the control means 16 comprises a fourth comparator 24 and an inversion means 25 which, at the input, receives the currents I a , I b and θ and at the output the corresponding currents I q and I d The fourth comparator 24 and the inverter 25 enable closed-loop control of the motor's control currents. In this case, the inverter 25 can use an inverse Park transform.

[0047] Fig. Figure 3 shows an example of a speed setpoint provided by the setpoint means 14 for a given user mode when the windshield wiper arm wipes the wiping surface.

[0048] The speed setpoint comprises a first part 26 for motor angle values ​​θ between θ min and a first value θ1. In the first part, the speed setpoint increases continuously with the motor angle θ. The first part corresponds to the speed setpoint of the wiper arm when it is in the first position 7 (the θ min corresponds) and towards the second position 8 (which corresponds to θ max The first part 26 corresponds to a progressive acceleration phase of the wiper arm until the maximum desired angular velocity (dθ / dt) max) is reached when the position of the wiper arm is at the first value θ1. In particular, the control circuit 16 applies a progressively increasing current to the motor 4 to achieve the desired angular velocity, limiting the electrical power consumed by the motor. Preferably, the acceleration of the wiper arm is constant throughout the duration of the first part 26.

[0049] The first value θ1 can be determined by the setpoint means 14, particularly depending on the user mode. The speed setpoint must be equal to the maximum angular speed desired by the user (dθ / dt). maxwhen the arm is at the first value θ1. If the user speed is high, the setpoint means 14 can select a higher first value θ1 to provide a larger angular sector to increase the motor's angular speed. Moderate acceleration and thus lower electrical power are now obtained.

[0050] Conversely, if the user speed is low, the first value θ1 can be chosen smaller, since a small angular sector is necessary to reach the desired angular velocity.

[0051] Once the maximum specified angular speed is reached, the speed setpoint now has a second part 27 in which it remains constant for motor angle values ​​θ between the first value θ1 and a second value θ2. This angular sector corresponds to the central sector of the wiping surface. Having a constant angular speed in this sector allows for greater visual comfort for the user.

[0052] When the angle value reaches the second value θ2, the speed command now has a third part 28 for motor angle values ​​θ between the second value θ2 and the value θ max In the third part, the speed setpoint decreases continuously with the motor angle θ. The third part corresponds to the speed setpoint of the wiper arm when it is in the second position 8 (the θ max) and prepares to perform half a revolution. The third part 28 corresponds to a progressive deceleration phase of the wiper arm until the zero angular velocity is reached, when the position of the wiper arm is at the value θ max In particular, the control circuit 16 applies a current to the motor 4 that progressively decreases until the zero angular velocity is reached. The deceleration of the wiper arm can, for example, be constant throughout the entire duration of the third part 28.

[0053] The second value θ2 can be determined by the setpoint means 14 depending on the deceleration characteristics of the angular velocity and the user speed.

[0054] The speed setpoint includes a fourth part 29 for values ​​of the motor angle θ between θ maxand the second value θ2. In the fourth part, the speed setpoint increases continuously with the motor angle θ. The fourth part corresponds to the speed setpoint of the windscreen wiper arm when it is in the second position 8 (the θ max corresponds) and towards the first position 7 (which corresponds to θ min The fourth part 29 corresponds to a progressive acceleration phase of the wiper arm until the determined constant angular velocity is reached (which corresponds to the maximum desired angular velocity (-(dθ / dt) max )) when the position of the wiper arm is at the second value θ2. In particular, the control circuit 16 applies a progressively increasing current to the motor 4 to obtain the desired angular velocity, reducing the electrical power consumed by the motor.

[0055] The second value θ2 can be determined differently to limit the third part 28 and the fourth part 29. In the third part 28, the second value θ2 is determined depending on the deceleration characteristics, while in the fourth part 29, the second value θ2 is determined depending on the acceleration characteristics. Thus, the second value θ2 can be changed by the setpoint means 14 when the direction of the windshield wiper arm changes to the second position 8.

[0056] When the maximum angular velocity is reached, the speed setpoint now has a fifth part 30 in which it remains constant for motor angle θ values ​​between the second value θ2 and the first value θ1. This angular sector still corresponds to the central sector of the wiping surface.

[0057] When the angle value reaches its first value θ1, the speed command now has a sixth part 31, for values ​​of the motor angle θ that lie between the first value θ1 and the value θ min In the sixth part, the speed setpoint decreases continuously with the motor angle θ. The sixth part corresponds to the speed setpoint of the windscreen wiper arm when it is in the first position 7 (the θ min ) and prepares to perform half a revolution. The sixth part 31 corresponds to a progressive deceleration phase of the wiper arm until the zero angular velocity is reached, when the position of the wiper arm is at the value θ min In particular, the control circuit 16 applies a current to the motor 4 which progressively decreases until the zero angular velocity is reached.

[0058] The first value θ1 of the sixth part 31 may also be different from the first value θ1 of the first part 26.

[0059] Fig. 4 shows the variation of the motor angle as a function of time when the motor is running according to a speed setpoint such as that shown in Fig. 3 shown.

[0060] In Fig. 4, it can be seen that the angle θ has a general sinusoidal or quasi-sinusoidal shape with straight sections between the values ​​θ1 and θ2. Thus, the angle θ does not vary abruptly over time: it is now possible to keep the motor torque at a low value and thus achieve higher power.

[0061] However, the invention is not limited to this embodiment. In particular, the setpoint means can also provide a speed setpoint comprising a certain duration during which, when the angle of the motor θ min or θ maxis, the speed setpoint remains zero. In this case, the control means can regulate the position of the motor rather than its speed, for more precise positioning. Furthermore, the static brake allows the motor to be kept in the desired stopped position, thus preventing the motor from running continuously to return to the desired position. A speed setpoint equal to zero for a certain period of time at half a revolution can allow the motor to be cooled, in particular limiting heat losses due to the Joule effect.

[0062] This makes it easy to change the wiper arm's wiping frequency: for example, wiping can be intermittent at low speed, intermittent at low speed, intermittent at high speed, intermittent at high speed, or even in a half-cycle (stopping the ram every half revolution). In the latter two cases, motor heating is limited while maintaining efficient and regular wiping of the windshield.

[0063] Likewise, the setpoint means may also be suitable for providing a speed setpoint with which the wiping range is changed depending on the frequencies, ie that the half revolutions of the windscreen wiper arm for different angles of θ min and θ max Thus, if the wiping frequency selected by the user is high speed, the angles θmin and θ maxFor example, they may be closer to each other, meaning that the wiping area may be smaller to compensate for the elastic deformation of the wiper arm at each half turn under the effect of inertia.

[0064] Thanks to the control circuit according to the invention, it is possible to limit the current peak during acceleration phases, thus using the motor with better performance. Joule effect losses are reduced. Furthermore, since the wiping speed never exceeds the maximum specified speed, visual comfort is achieved for the user compared to the device comprising a crank-rod system whose speed varies quasi-sinusoidally with the angle of the wiper arm. Finally, it is easy to improve the arm acceleration / maximum wiping speed compromise or to change the angles of the wiping surface and the parking position.

[0065] The device also has fewer mechanical parts than a connecting rod system, thus reducing costs and requiring less space. It is no longer necessary to develop a new device for each vehicle type. Furthermore, it is possible to use the same device to operate the left and right windshield wipers of a vehicle. The device is also easier to assemble, thanks to an electronics block, a motor block, and an arm, which can be controlled separately and are more independent than those of the prior art. Thus, apart from the motor position sensor, which sends a signal to the control circuit, each block of the device is independent and requires less wiring with the others.

[0066] Finally, the first correction means may also be capable of determining, based on the differences between the speed setpoint and the angular velocity of the motor, the torque required by the motor and thus the braking torque corresponding to the friction of the arm on the windshield and / or the friction of the air on the arm. Since the braking torque has the same magnitude in both directions of operation of the arm, while the friction torque of the air can be driving or braking depending on the direction of operation of the arm, the first correction means can distinguish between these two moments and derive from them, for example, the vehicle speed (depending on the friction torque of the air and for a given air pressure) or the surface condition of the windshield, dry or wet (depending on the friction torque of the wiper arm on the windshield).

[0067] Controlling the motor's speed and angle in a closed loop also makes it possible to detect vibration phenomena in the wiper arm. Depending on the arm's mass and the system's rigidity, a "mass-spring" vibration phenomenon may occur due to friction between the arm and the windshield. Such vibration can generate excessive torque and damage the device. Controlling the arm's wiping speed in a closed loop makes it possible to detect such vibration and subsequently control the motor to directly eliminate, prevent, or mitigate this phenomenon when it occurs.

Claims

[1] Control circuit (3) for an electric motor (4) for driving a windscreen wiper, comprising a control means (16) comprising an output for controlling the electric motor (4), the control means (16) being suitable for controlling the angle (θ) of the motor between a given minimum value (θ min ) and a given maximum value (θ max ), wherein the control means (16) has an input for receiving a speed setpoint (dθ / dt) c and is suitable for controlling the angular speed (dθ / dt) of the motor (4) according to the speed setpoint (dθ / dt) c to control, wherein the control circuit (3) also comprises a setpoint means (14) comprising an input for receiving the values ​​of the motor angle (θ) and an output for supplying a speed setpoint (dθ / dt) c to the control means (16), wherein the setpoint means (14) is suitable for determining the speed setpoint (dθ / dt) cbased on a continuous function of the motor angle (θ), characterized by that the speed setpoint (dθ / dt) c at a predetermined motor angle value. [2] Circuit according to claim 1, wherein the setpoint means (14) is adapted to provide a first angle value (θ1) of the motor (4) which is greater than the minimum value (θ min ), and a second angle value (θ2) between the first angle value (θ1) and the maximum value (θ max ) to determine a speed setpoint (dθ / dt) c , which varies with the value of the motor angle (θ) when it is between the minimum value (θ min ) and the first value (θ1) or between the second value (θ2) and the maximum value (θ max ) and a speed setpoint (dθ / dt) c with a constant absolute value when the value of the motor angle (θ) lies between the first (θ1) and the second (θ2) value. [3] A circuit according to claim 2, wherein the setpoint means (14) also comprises an input for selecting a user mode, and wherein the constant speed setpoint (dθ / dt) c , the maximum value (θ max ), the minimum value (θ min ), the first value (θ1) and the second value (θ2) of the motor angle are determined depending on the user mode. [4] Circuit according to one of the preceding claims, in which the control means (16) also comprises an input for receiving the values ​​of the angular velocity (dθ / dt) of the motor (4) and is suitable for adjusting the motor torque as a function of the difference between the angular velocity (dθ / dt) of the motor (4) and the speed setpoint (dθ / dt) c to control. [5] Circuit according to the preceding claim, also comprising a determining means (15) comprising an input for receiving the values ​​of the motor angle (θ) and an output for supplying the angular velocity (dθ / dt) of the motor (4) to the control means (16), wherein the determining means (15) is suitable for calculating the angular velocity (dθ / dt) of the motor (4) on the basis of the values ​​of the motor angle (θ). [6] Circuit according to claim 4 or 5, wherein the control means (16) also comprises an input for receiving a motor angle setpoint and an input for receiving the motor angle values ​​and may be suitable for controlling the motor (4) during the rest phases of the motor as a function of the difference between the motor angle (0) and the motor angle setpoint. [7] Drive device (2) for performing an alternating rotary movement, comprising a circuit according to one of claims 1 to 6 and an electric drive motor (4). [8] Drive device (2) according to the preceding claim, wherein the motor (4) is a synchronous motor. [9] Windscreen wiper device (1) for a motor vehicle or an aircraft, comprising at least one drive device (2) according to one of claims 7 to 8 and a windscreen wiper arm (5) driven by the drive device (2). [10] Control method for an electric motor (4) for driving a windscreen wiper, in which the motor (4) is controlled in such a way that the motor angle (θ) is between a given minimum value (θ min ) and a given maximum value (θ max ) is varied, whereby the angular speed dθ / dt) of the motor (4) is also varied according to a speed setpoint (dθ / dt) c is controlled, where the speed setpoint (dθ / dt) c is determined based on a continuous function of the motor angle, characterized by that the speed setpoint (dθ / dt) cat a predetermined motor angle value. [11] Method according to claim 10, wherein a first angle value (θ1) of the motor (4) which is greater than the minimum value (θ min ), and a second angle value (θ2) between the first angle value (θ1) and the maximum value (θ max ), a speed setpoint (dθ / dt) c which varies with the value of the motor angle when it is between the minimum value (θ min ) and the maximum value (θ max ) or between the second value (θ2) and the maximum value (θ max ) and a constant speed setpoint (dθ / dt) c is delivered when the value of the motor angle is between the first (θ1) and the second (θ2) value. [12] Method according to claim 11, wherein the value of the constant speed setpoint (dθ / dt) c , the maximum value (θ max ), the minimum value (θ min), the first value (θ1) and the second value (θ2) of the motor angle are determined depending on a user mode. [13] Method according to one of claims 10 to 12, in which the motor torque is also determined as a function of the difference between the angular speed (dθ / dt) of the motor (4) and the speed setpoint (dθ / dt) c is controlled. [14] Method according to one of claims 10 to 12, wherein the motor (4) is controlled as a function of the difference between the motor angle and a motor angle setpoint during the rest phases of the motor (4).

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