Arrangement for a means of transport and method for determining an angular error of a geared motor due to an axial play of a spindle

Abstract

An arrangement for a means of transport and a method for determining an angular error of a geared motor (1) due to axial play of a spindle (2) are proposed. The method comprises the steps of operating the geared motor (1), determining an operating parameter (M), and determining the angular error (X°) using a predefined reference describing a relationship between the operating parameter (M) and the axial play (S).

Description

State of the art

[0001] The present invention relates to an arrangement for a means of transport and a method for determining an angular error of a geared motor due to axial play of a spindle. In particular, the present invention relates to a simple yet precise determination of an angular error and an automatic correction of a measured angle in a geared motor.

[0002] The ongoing miniaturization is impacting electric drives, which are becoming ever smaller. Accordingly, the components of electric drives are also becoming ever smaller. Furthermore, brushless drives are becoming increasingly common. Their operation requires precise methods and devices for detecting the rotary motion and angular position of the electric drive. Furthermore, magnetic field-based sensors are known to be used to detect the rotary position and / or angular position. Common sensor technologies include:

[0003] Hall, xMR, Circular Hall, Hall Array, GMR, and AMR sensors. Each of the aforementioned sensor technologies has specific application possibilities. These applications arise from the interaction of a magnet with the sensor, as well as from the magnetic field generated by the magnet and its components, and their conversion into electrical signals.

[0004] DE 10 2019 212 122 A1 discloses a device for detecting a rotational movement and / or an angular position, wherein a tunnel magnetoresistive (TMR) sensor is used to detect the magnetic field of an exciter.

[0005] Axial play in a spindle, such as that which drives a windscreen wiper in a vehicle, can result in the rotational position of the spindle and / or an output gear via which the wiper is driven not being known exactly.

[0006] This results in problems in controlling the electric motor used.

[0007] It is an object of the present invention to alleviate or eliminate the disadvantages of the prior art.

[0008] The above object is achieved according to the invention by a method for determining an angular error of a geared motor due to an axial play of a spindle having the features according to claim 1 and by an arrangement for a means of transport having the features according to claim 11.

[0009] The subclaims show preferred developments of the invention.

[0010] The output gear can be provided to drive a wiper unit of a means of transport. The spindle can be provided as the drive for the output gear. It can be mounted in a housing of a geared motor. According to the invention, the geared motor is initially operated as intended, resulting in an axial force acting on the spindle. This axial force acting depends on the current torque and the direction of rotation of the spindle. Depending on the load the geared motor currently has to move, the axial play of the spindle becomes more or less noticeable. In a further step, an operating parameter is determined, for example using a sensor unit. The operating parameter can be determined, for example, as an electrical parameter of an electric motor within the geared motor.In other words, a sensor unit can be used to measure the current and / or voltage and / or frequency and / or torque of the electric motor. In a third step, the angular error of the geared motor is determined using a predefined reference that represents a relationship between the motor's operating parameter and the axial play. For example, the predefined reference can represent a mathematical relationship and / or a look-up table for the operating parameter and the resulting angular error. This relationship can be determined experimentally or derived from a model. An exact measurement of the spindle's axial position is not required.Rather, an exact rotational position of the spindle and thus of the electric motor of the gear motor can be determined based on a measurement result, for example, from an angle sensor of an output gear.

[0011] Preferably, the angular error can arise due to the axial play of the spindle as a function of a torque, which is why the angular error can also be determined based on the predefined reference as a function of a measured and / or calculated torque of the geared motor. The output gear can have an angle sensor arranged in the region of its axis for precise rotational position determination. Alternatively or additionally, an angle value determined via an exciter (e.g., a permanent magnet) arranged on the spindle in conjunction with a stationary / fixed sensor can be corrected by the angular error correction value determined according to the invention based on the reference.

[0012] The geared motor can be a wiper motor and, in particular, comprise an electronically commutated electric motor. The electrically commutated motor can, for example, be arranged in a housing with the spindle and the output gear. The angle sensor (on the output gear and / or on the spindle) can also be located in the housing. Sensors / measurement equipment for measuring the operating parameters can also be arranged in the housing. The electronics for controlling the electronically commutated motor can also be located in the housing.

[0013] The operating parameter may include a state of motion of a rotor shaft (rotational state, standstill and / or angular acceleration) and / or an angular velocity, in particular of the spindle, and / or a current and / or a voltage.

[0014] The aforementioned variables can be measured directly on the electric motor. The state of motion and angular velocity can be measured on the spindle.

[0015] For example, the direction in which the angular error arises due to the torque can be determined from a model and / or a measurement. Accordingly, the sign of the offset can be automatically reversed in response to a reversal of the load condition. This way, a two-way dependency of the angular error on the torque, a voltage, or the current drawn by the electric motor does not necessarily have to be stored separately in the case of symmetrical dependencies, which can roughly halve the storage space.

[0016] The predefined reference can, for example, include a 2D / 3D characteristic map and / or a complex model of the geared motor or an assembly containing the geared motor. If a simple calculation unit is to be used, a look-up table for specific input operating parameters (torque, current, voltage, frequency, power, etc.) can be used, via which the angle error can be read or read out. The angle error can then be added to or subtracted from an otherwise determined (erroneous) angle value, angle measurement, or angle calculation result.

[0017] The predefined reference can alternatively or additionally represent a relationship between the angular error and an axial offset of the spindle (spindle backlash), and alternatively or additionally a relationship between the torque or current of the electric motor on the one hand and the angular error on the other. This relationship can be defined in a conversion table / value table or as a mathematical function (f (angular error)) of torque or current. In this way, comprehensive information can be created based on a few, easily determined input operating parameters.

[0018] The spindle can preferably have an excitation unit, which, for example, has one or more permanent magnet poles. These poles can interact with a stationary sensor arranged in the area of ​​the excitation unit. The stationary sensor can, for example, comprise a TMR sensor arranged in the same housing as the output gear, the spindle, and the electric motor. Alternatively, it can be a 3D magnetic sensor (Hall sensor). The only important thing is that the rotational state / angle of the spindle can be determined using the resulting magnetic sensor unit.

[0019] Preferably, in a further step, a measured rotor angle / spindle angle can be corrected using the determined angular error. For example, the angular error of the output gear of a wiper can be determined if the value determined via the angle sensor arranged on the spindle is assumed to be correct. Alternatively, the position of the geared motor and / or the position of a rotor of the electric motor and / or the position of the output gear and / or the position of a wiper for the vehicle can be determined using the determined angular error. Since the wiper experiences different friction values ​​on the windshield depending on the dry conditions, wetness (rain), and icing, the torques to be applied by the output gear are highly dependent on the weather, temperature, and operating conditions (also note the wind load on the wiper blade as a function of the vehicle's travel speed).Such information can be obtained, for example, from a speedometer, a precipitation sensor, a thermometer, etc., and used to roughly estimate the current load torque of the geared motor. In particular, this can be used to feed or create a model that can be used to determine a comprehensive operating state of the geared motor based on the electric motor's electrical input variables.

[0020] According to a second aspect of the present invention, an arrangement for a means of transport (e.g., a car, van, truck, aircraft, and / or watercraft) is proposed, which arrangement comprises an electric motor, a spindle with axial play, an output gear, an excitation unit on the spindle, an evaluation unit, a stationary sensor, and an operating parameter sensor. The spindle engages with an output gear and is thus configured to cause the output gear to rotate at low speed but with high torque. The excitation unit is configured to interact with the stationary sensor in such a way that a rotational position / rotational state of the spindle can be determined. The operating parameter sensor is configured to determine an operating parameter during operation of the motor.For example, the operating parameter sensor can determine the current consumption, a voltage drop, and / or motor power and / or torque using measurement and / or computation. The stationary sensor is configured to determine a spindle angle, and the evaluation unit, in turn, is configured to correct the angle based on a predefined reference describing a relationship between the operating parameter and the angle error. In this way, the arrangement (device) according to the invention is configured to implement the features, feature combinations, and the resulting advantages of the method according to the invention in a manner that is clearly evident; to avoid repetition, reference is made to the above explanations. Disclosure of the invention

[0021] Further details of the invention are disclosed below without any limiting character: The magnetic field applied to a sensor for rotor position detection is strongly influenced by mechanical play and axial deflection under load. The accuracy of rotor position detection using TMR technology is severely impaired, resulting in a highly inaccurate rotor position. High-quality commutation of the EC motor cannot be guaranteed. Therefore, the use of cost-effective TMR technology is only possible to a limited extent. In the prior art, two Hall sensors are often used, as this ensures greater robustness and the rotor position is detected with sufficient accuracy. Using a correction algorithm, the technology disclosed here makes cost-effective TMR technology usable for rotor position sensing (RPS), allowing it to be used for an EC motor with a flange-mounted helical gear (spindle drive with output gear).According to the invention, omitting one of the sensors can result in a cost advantage. Another advantage of using a TMR sensor is the significantly lower power consumption compared to two Hall sensors. The angular error caused by the axial movement of the spindle / rotor shaft can be corrected, for example, as follows: - Detection of the angle error depending on the direction of rotation and the torque; - Determination of the correction value based on a predefined reference; and - Correction of the measured angle via software algorithm using current and speed. Short description of the drawings

[0022] Embodiments of the invention are described in detail below with reference to the accompanying drawings. They show: Fig. 1 is a partially cutaway perspective 3D view of an electric geared motor for an arrangement according to a first embodiment of the present invention; Fig. 2 a schematic detailed representation of functional groups of an arrangement according to the invention for a means of transport according to a second embodiment of an arrangement according to the invention; Fig. 3 an example diagram of the angular error X° versus the axial offset; Fig. 4 a diagram illustrating the correction value for the measured angle error versus the torque applied by the electric motor or the current consumed by the electric motor; and Fig. 5 a flowchart illustrating steps of an embodiment of a method according to the invention for determining an angular error of a geared motor due to an axial play of a spindle. Embodiments of the invention

[0023] Fig. 1 shows a partially cutaway perspective view of a geared motor 1, in whose housing 9 an electric motor 10 is operatively connected to a spindle 2. An excitation unit 6 with permanent magnet poles (not shown) is arranged on the spindle 2, which interact with a stationary sensor 13. The angular position of the spindle 2 and its direction of rotation can be determined via the stationary sensor 13. The spindle 2 is operatively connected to an output gear 3, on whose axis an output shaft sensor 11 is arranged. The rotational position of the output gear 3 can be determined via the output shaft sensor 11 and used as a basis for determining the position of the wiper blade. However, since the output shaft sensor 11 incurs costs, the output shaft sensor 11 can be dispensed with by correcting the angular value determined by the stationary sensor 13 according to the invention.

[0024] Fig. 2 shows a schematic representation of a second embodiment of an arrangement according to the invention. The electric motor 10 is powered by an evaluation unit 8, which also monitors the voltage, current, power, and rotational frequency of the electric motor 10. The electric motor 10 rotates the spindle 2 clockwise, as indicated by the arrow P3. The rotational position of the spindle 2 can be determined via the excitation unit 6 and the fixed sensor 13. Due to the axial play P1 of the spindle 2, which also manifests itself as axial play P2 of the excitation unit 6, the determination of a rotational position / angular position P4 of the output gear 3 is not sufficiently accurate for all applications. Therefore, a reference (not shown) is also consulted via the evaluation unit 8, via which the determined angle can be corrected. The fixed sensor 13 is provided as an SMD component on a PCB 12.The arrangement shown enables a cost-reduced architecture of a geared motor 1.

[0025] Fig. 3 shows an exemplary relationship between the angular error X° and the axial play S of the spindle 2 (see Fig. 2). This angular error X° is caused by the axial play S.

[0026] Fig. Figure 4 shows the relationship between the motor torque M and the current I consumed by the electric motor, on the one hand, and the angle correction value Φkorr, on the other. The relationship shown can be used to determine the angle correction value measured by the fixed sensor 13 (see Fig. 2). Therefore, sufficiently good results can be achieved with fewer sensors or less precise sensors, thereby reducing the costs of an arrangement according to the invention.

[0027] Fig.5 shows steps of an exemplary embodiment of a method according to the invention for determining an angular error of a geared motor due to axial play in a spindle thereof. In step 100, the geared motor is operated as intended. This implies a load condition corresponding to the current intended use. In step 200, an operating parameter is determined which is also determined by the load condition. For example, the operating parameter can be a motor torque. In step 300, an angular error is determined using a predefined reference, wherein the reference describes a relationship between the operating parameter (e.g., torque) and the axial play of the spindle. The predefined reference can be stored, for example, as a look-up table, mathematical model, or otherwise.In step 400, the measured rotor angle is corrected based on the determined angle error and thus in step 500 the basis is created to determine a position of the gear motor and / or an output gear and / or a wiper for a means of transport without having to use multiple angle sensors. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2019 212 122 A1

[0004]

Claims

[1] Method for determining an angular error (X°) of a geared motor (1) due to an axial play (S) of a spindle (2) comprising the steps - Operating (100) the gear motor (1), - Determining (200) an operating parameter (M), and - Determining (300) the angular error (X°) using a predefined reference describing a relationship between the operating parameter (M) and the axial play (S). [2] Method according to claim 1, wherein the angular error (X°) arises due to an axial play (S) of the spindle (2) which is in engagement with an output gear (3), as a function of a torque (M). [3] Method according to claim 1 or 2, wherein the geared motor (1) is a wiper motor, and in particular comprises an electronically commutated motor (4). [4] Method according to one of the preceding claims, wherein the operating parameter - a state of motion of a rotor shaft (5) and / or - an angular velocity and / or - a current and / or - includes a voltage. [5] Method according to one of the preceding claims, wherein the predefined reference - a model and / or - includes a map. [6] Method according to one of the preceding claims, wherein the predefined reference comprises a relationship between - the angular error (X°) and an axial offset and / or - the moment or current on the one hand and the angular error on the other hand. [7] Method according to one of the preceding claims, wherein the spindle (2) has an excitation unit (6) which cooperates in particular with a fixed sensor (13). [8] Method according to claim 7, wherein the excitation unit (6) comprises a ring magnet and the fixed sensor (13) comprises a TMR sensor and / or a multi-dimensional magnetic sensor. [9] Method according to one of the preceding claims further comprising - Correcting (400) a measured rotor angle by means of the determined angle error (X°) and - Determining (500) a position of the geared motor (1) and / or an output gear (3) and / or a wiper for a means of transport. [10] Method according to one of the preceding claims, wherein the predefined reference defines a relationship between a position of the spindle (2) and a torque of the motor (10). [11] Arrangement for a means of transport comprising - an engine (10) - a spindle (2) with an axial play (S), - an output gear (3), - an excitation unit (6) on the spindle (2), - an evaluation unit (8), - a fixed sensor (13), and - an operating parameter sensor (9), wherein the spindle (2) is in engagement with the output gear (3), the excitation unit (6) is arranged to interact with the fixed sensor (13), - wherein the operating parameter sensor (9) is designed to determine an operating parameter during operation of the engine (10), and - the fixed sensor (13) is configured to determine an angle of the spindle (2) and the evaluation unit (8) is configured to correct the angle using a predefined reference describing a relationship between the operating parameter and an angle error.

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