Patent Publication Number: US-2022224260-A1

Title: Method for detecting the rotary angle positions of rotating parts of a wiper motor, and wiper motor

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is filed under 35 U.S.C. § 371 U.S. National Phase of International Application No. PCT/EP2020/062350 filed May 4, 2020 (published as WO2020233974), which claims priority benefit to German application No. 102019113549.4 filed on May 21, 2019, the disclosures of which are herein incorporated by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     The invention relates to a method for detecting the rotary angle positions of rotating parts of a wiper motor having the features of the precharacterizing clause of claim  1 . The invention furthermore relates to a wiper motor which is configured to carry out a method according to the invention. 
     BACKGROUND ART 
     A wiper motor which is configured to carry out a method according to the precharacterizing clause of claim  1  is known from DE 10 2017 121 222 A 1 by the applicant. The known wiper motor or the known method is distinguished in that two sensor devices are provided for detecting the rotary angle positions of a rotor of a brushless electric motor and of a gear wheel which is driven by the electric motor and serves at least indirectly for driving a wiper. Each of the two sensor devices comprises a signal generating element and a sensor element for detecting a changing physical parameter of the signal generating element. Typically, sensor devices are configured in the form of Hall sensors, in which the Hall sensor detects the changes of an element which moves past the Hall sensor and generates a magnetic field. A further significant feature of the known sensor devices is that, when a magnetic field is first detected or when the electric motor is started, said sensor devices are not capable of detecting an absolute angle position of the rotating part (rotor or gear wheel). On the contrary, further information or a certain rotary angle of the rotating part is needed before an evaluating unit of the sensor device can draw a conclusion regarding an absolute angle of the rotating part. 
     In particular in conjunction with brushless electric motors, it is desirable or required to know the rotary angle position as rapidly and exactly as possible for the energizing or activating of the individual wire windings of the stator. This is similarly also desirable in order to detect a rotary angle position of a driven shaft of the wiper motor, said driven shaft being connected to the wiper motor. 
     SUMMARY 
     The method according to the invention for detecting the rotary angle positions of rotating parts of a wiper motor having the features of claim  1  has the advantage of permitting a very rapid and precise detection of an absolute rotary angle of a rotating part, in particular when starting up a wiper motor. This is made possible according to the invention in accordance with the teaching of claim  1  in that an absolute rotary angle position of the rotating part is detected by means of at least one of the sensor devices. What is meant here is that a conclusion can be drawn regarding the absolute rotary angle of the rotating part with respect to an angle reference (0 degrees) just from first information or a first detection of a physical parameter. This in particular even includes the situation in which the electric motor is still not rotating, i.e. that the angle position can be detected even in a stationary state of the otherwise rotating part. 
     Advantageous developments of the method according to the invention for detecting the rotary angle positions of rotating parts of a wiper motor are presented in the dependent claims. 
     In a preferred refinement of the method according to the invention, it is provided that a change of a magnetic field of the signal generating element is detected by means of the sensor device that detects the absolute angle position In particular, it is therefore possible, for example, to draw a conclusion about an absolute angle position of the rotating part from the magnitude of the magnetic flux density of the magnetic field in combination with the orientation thereof. 
     However, other physical operative principles are also conceivable, for example optically operating measuring devices or sensor devices which detect other physical parameters, such as inductance or the like. 
     A further preferred method provides that the rotary angle positions of the two rotating parts (in particular rotor and gear wheel) are matched with each other in such a manner that a specific rotary angle position of the one part (for example of the gear wheel or of the driven shaft) is matched with at least one specific rotary angle position of the other part (for example of the rotor), that currently matched rotary angle positions of the two rotating parts are compared to values stored in a storage unit and that a signal, an error message or the like is generated when a stored limit value between current values and stored values is exceeded. 
     The background of this preferred method is that typically in the new state or in a state of the wiper motor in which the rotating parts are disposed with little play or no play with respect to one another, the matched rotary angle positions of the parts have only small tolerances with respect to one another. However, with increasing wear or increasing play between the rotating parts, the detected rotary angle positions of the rotating parts change in such a manner that, for example, there is a greater angular offset or a greater angular difference between the rotary angle positions than is the case in the new state or when there is no play. The preferred method provided therefore makes it possible to be able to draw a conclusion regarding the wear of the rotating parts of the wiper motor and, for example, because of a corresponding error message read within the scope of inspections or similar measures, to be able to undertake a repair or a corresponding replacement of the wiper motor. Furthermore, such a method moreover makes it fundamentally possible, for example, also to adapt or to modify a temporal or angle-conforming activation of wire windings of the stator, in order to be able to always obtain the same movement sequence at the wiper motor and therefore at the wipers. 
     A further preferred refinement of the method according to the invention, in which, for example, a conclusion can be drawn regarding increased friction or blocking of rotating parts of the wiper motor, provides that during operation of the wiper motor, a rotary angle velocity of at least one of the two rotating parts is detected and that the motion of the wiper motor is stopped and/or a signal and/or an error message or the like is generated when the rotary angle velocity falls short of a limit value. Damage or overloading of the wiper motor can thereby be prevented. 
     The invention furthermore comprises a wiper motor which is preferably operated in accordance with a method according to the invention described to this extent. The wiper motor is distinguished, as known per se, by a brushless electric motor which has a rotor and which drives a driven shaft by means of a gear wheel, and comprising two sensor devices each having a signal generating element and a sensor element for detecting a changing physical parameter of the signal generating element, the sensor devices being configured to detect the rotary angle positions of the rotor and of the driven shaft. The wiper motor according to the invention is distinguished in that at least one of the two sensor devices is configured to measure an absolute angle. 
     It is particularly preferred that the at least one sensor device is matched to the rotor of the electric motor for measuring the absolute angle. This therefore relates to the fact that, for the activation of the wire windings of the stator correctly in terms of time, it is essential to know the (absolute) rotary angle position of the rotor as rapidly as possible. Furthermore, it should be taken into consideration here that, owing to the reduction in the rotational speed of the electric motor, one and the same absolute rotary angle position of the gear wheel or of the driven shaft can optionally be matched with a plurality of different rotary angle positions of the rotor. From the knowledge of the absolute rotary angle of the gear wheel or of the driven shaft, it is therefore not inevitably possible to be able to draw a conclusion regarding the absolute rotary angle position of the rotor. 
     In a structurally preferred refinement of the wiper motor, at least one of the signal generating elements of the two sensor devices is configured to generate a magnetic field that is detectable by the sensor element and that changes as a function of the rotary angle position. 
     In a structurally preferred arrangement and configuration of the wiper motor, it is moreover provided that the two sensor elements are disposed in the area of a shared circuit board and are connected to the circuit board in an electrically conductive manner. 
     There are various possibilities in respect of the specific arrangement of the sensor elements. In a development of the last proposal for use of a shared circuit board, it can be provided that at least one sensor element is disposed so as to not cover the axis of rotation of the rotor or the driven shaft. 
     In this case, it is moreover provided that the sensor element detecting the rotary angle position of the driven shaft or of the rotor is disposed so as to cover the axis of rotation of the driven shaft. 
     Furthermore, it can be provided in an advantageous structural refinement of the circuit board that the latter has a cutout and that the signal generating element assigned to the rotor is disposed in the area of the cutout. A particularly compact construction of the wiper motor can thereby be made possible. 
     With regard to as compact an arrangement or configuration of the wiper motor as possible, it is moreover of advantage if the plane of the circuit board runs parallel to the axis of rotation of the rotor and perpendicular to the axis of rotation of the driven shaft. 
     In order to obtain additional functionalities of the wiper motor, it can moreover be provided that an storage and evaluating unit is provided which is at least configured to match a rotary angle position of the driven shaft with at least one rotary angle position of the rotor and to compare it to stored matched values of the driven shaft and of the rotor during operation of the wiper motor, and that a signal, an error message or the like can be generated when a stored limit value between current matched values and stored matched values is exceeded. 
     A development of the last proposal provides that the storage and evaluating unit is additionally configured to detect a rotary angle velocity of at least one of the rotating parts during operation of the wiper motor and to generate a signal, an error message or the like and/or to reduce the power output of the wiper motor and/or to stop its operation when the rotary angle velocity falls short of a predefined limit value. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further advantages, features and details of the invention will emerge from the following description of preferred exemplary embodiments and with reference to the drawing, in which: 
         FIG. 1  shows a perspective, partially sectioned view of a wiper motor, 
         FIG. 2  shows a perspective, partially sectioned view of a wiper motor according to  FIG. 1 , 
         FIG. 3  to  FIG. 6  each show, in simplified illustrations, different arrangements of sensor devices for detecting the rotary angle position of a rotor and a gear wheel, 
         FIG. 7  shows a diagram for explaining the matching of different rotary angle positions of a rotor and of a gear wheel for detecting a possible wear, and 
         FIG. 8  shows a diagram for explaining the detection of a rotary angle velocity of rotating parts of the wiper motor for detecting a possible blockage of rotating parts. 
     
    
    
     DETAILED DESCRIPTION 
     Identical elements or elements having an identical function are provided with the same reference numbers in the figures. 
       FIGS. 1 and 2  illustrate the essential components of a wiper motor  10  for driving a wiper (not illustrated). The wiper motor  10  has a brush less electric motor  12  which has a rotor  15  which rotates about an axis of rotation  14  and has magnetic elements  16 . The rotor  15  is surrounded radially by a stator  18  which is illustrated only in  FIG. 1  and which in a known manner has a plurality of wire windings  19  in such a manner that the rotor  15  is set into a rotational movement by a phase-displaced or temporally consecutive energizing of the individual wire windings  19 . 
     The rotor  15  is connected to a rotor shaft  20  for rotation therewith, the rotor shaft being mounted rotatably in a bearing device  21 , for example, on the side facing away from the rotor  15 . In a central section of the rotor shaft  20 , the latter has a worm toothing  22  which meshes with a mating toothing on a gear wheel  24 . The gear wheel  24  is connected to a driven shaft  26  for rotation therewith and is mounted rotatably about an axis of rotation  28 . The driven shaft  26  is coupled in turn in a manner known per se, for example, to a wiper linkage or else directly to the wiper to be moved. 
     The rotor  15  or the rotor shaft  20  is disposed close to the rotor  15  in operative connection with a first magnetic element arrangement  30 . In particular, the first magnetic element arrangement  30  is connected to the rotor shaft  20  for rotation therewith. The first magnetic element arrangement  30  is part of a first sensor device  31  for detecting the rotary angle position of the rotor shaft  20  and therefore of the rotor  15 . For this purpose, the first magnetic element arrangement  30  interacts, for example, with a sensor element  32 . The sensor element  32  comprises, for example, a Hall sensor arrangement which is configured to draw a conclusion regarding the absolute rotary angle position of the rotor  15  or of the rotor shaft  20  directly from the rotary angle position of the first magnetic element arrangement  30 . The absolute rotary angle position is required in order to permit a phase-conforming or angle-conforming energizing of the wire windings  19  of the stator  18 . An absolute rotary angle position is understood as meaning a rotary angle of the rotating part with respect to a fixed reference position (0 degrees angle position). 
     Furthermore, a second magnetic element arrangement  36  is provided on an end surface  34  of the driven shaft  26 . The second magnetic element arrangement  36  is part of a second sensor device  38  which is configured to detect an absolute angle position of the driven shaft  26  and therefore of the gear wheel  24 . For this purpose, the second magnetic element arrangement  36 , for example, likewise interacts with a sensor element  40  which likewise has, for example, a Hall sensor arrangement which is configured to draw a conclusion regarding an absolute angle position of the driven shaft  26  or of the gear wheel  24  on the basis of the changing magnetic field of the second magnetic element arrangement  36 . 
     The two sensor elements  32  and  40  are disposed in an electrically conductive manner on a shared circuit board  42 . The plane of the circuit board  42  runs parallel to the axis of rotation  14  of the rotor  15  and perpendicular to the axis of rotation  28  of the driven shaft  26 . In the exemplary embodiment illustrated in  FIG. 2 , the two sensor elements  32 ,  40  are each disposed on the lower side  43  of the circuit board  42 , said lower side facing the rotor shaft  20 . Furthermore, components for activating or for driving the wiper motor  10  are disposed, as known per se, on the circuit board  42 . Said components comprise, by way of example, an IC  44  or a similar logical circuit which is configured to activate or to energize in particular wire windings  19  of the stator  18 . For this purpose, the information from the two sensor devices  31  of  38  is supplied as an input variable to the IC  44 . 
       FIGS. 3 to 6  illustrate different arrangements of the two sensor devices  31  and  38 . It is illustrated in  FIG. 3  that the circuit board  42   a  has a rectangular cutout  46 , on the edge of which the sensor element  32   a  is disposed. The first magnetic element arrangement  30   a  enters at least in regions into the cutout  46 . Furthermore, it can be seen that the sensor element  40   a  is disposed so as to align with the axis of rotation  28 , i.e. so as to cover the second magnetic element arrangement  36 . 
       FIG. 4  illustrates the case in which the sensor element  40   b  is disposed laterally offset with respect to the axis of rotation  28  of the driven shaft  26  while the arrangement of the first magnetic element arrangement  30   b  and of the sensor element  32   b  corresponds to that of the first magnetic element arrangement  30   a  of  FIG. 3 . 
       FIG. 5  illustrates an arrangement approximately according to  FIG. 2  in which the rectangular circuit board  42  is provided on the side facing the first magnetic element arrangement  30  with the sensor element  32   c  which is disposed at a distance from the axis of rotation  14  of the rotor shaft  20 . The first magnetic element arrangement  30  is located outside the circuit board  42  on the side of the circuit board  42  that faces away from the rotor  15 . The arrangement of the sensor element  40   c  corresponds to that of the sensor element  40   a  according to  FIG. 3 . 
     Finally,  FIG. 6 , as a modification of the arrangement in  FIG. 5 , illustrates the case in which the two sensor elements  32   d  and  40   d  are disposed so as not to cover the axes of rotation  14  and  28  of the rotor shaft  20  and of the driven shaft  26 , respectively. 
     The IC  44  optionally has a storing and evaluating unit  48  which permits additional functionalities of the wiper motor  10 .  FIG. 7  thus illustrates one above the other the signals SR and SG detected by the sensor devices  31  and  38  over the absolute rotary angle a of the rotor  15  and  13  of the gear wheel  24 , respectively. It is seen here that, at a revolution about 360Q of the gear wheel  24  (maximum of the signal SG), the rotor  15  in the new state of the components or not having any play between the components has rotated, for example, twelve times. Furthermore, the dashed illustration of the signal profile of the signal SG in the lower part of  FIG. 7  shows the situation which arises after a certain operating duration or when wear occurs between those parts of the rotor shaft  20  or of the rotor  15  and of the driven shaft  26  or of the gear wheel  24  that are operatively connected to one another. In particular, it is seen that, after twelve revolutions of the rotor  12 , the signal SG of the gear wheel  24  has not yet reached its maximum, that is to say that the gear wheel  24  is still not revolving about 360° . This is the case only after an additional angle offset σ. 
     As soon as the angle offset a exceeds a limit value stored in the storing and evaluating unit  48 , a conclusion is drawn regarding wear at the components of the wiper motor  10  and so that this is stored, for example, in an error memory as an error message, a corresponding signal is generated or the like. 
     Finally, it is explained with regard to  FIG. 8  that the storing and evaluating unit  48  can furthermore be configured to detect a rotary angle velocity ω of the rotor shaft  20  and/or of the driven shaft  26  over the time t of the wiper motor  10 . If, during the operation of the wiper motor  10 , the rotary angle velocity ω1 falls short of, for example, a lower limit value GW, a conclusion is drawn that the wiper motor  10  has increased friction values or a tendency to block due to an internal error or else that the wiper motor  10  is prevented from operating correctly due to external force influences, for example a snow load or the like. Also in this case, the storing and evaluating unit  48  can deposit, for example, a corresponding error in an error memory, can generate a signal or else can stop the operation of the wiper motor  10 . 
     The wiper motor  10  described so far can be altered or modified in a wide variety of ways without departing from the concept of the invention. This consists in that at least one sensor device which serves to detect the rotary angle position of the rotor shaft  20  or of the rotor  15  and of the driven shaft  26  or of the gear wheel  24  uses an absolute angle sensor. It can thus be provided, for example, for the rotary angle information of the two sensor devices  31  and  38  and the activation of the wire windings of the stator  18  to be brought about not (internally) by the wiper motor  10 , but rather by an external control device or the like. Furthermore, the sensor devices  31  and  38  can also be based on different physical operative principles and/or can have different specifications. 
     List of reference signs 
       10  Wiper motor 
       12  Electric motor 
       14  Axis of rotation 
       15  Rotor 
       16  Magnetic element 
       18  Stator 
       19  Wire winding 
       20  Rotor shaft 
       21  Bearing device 
       22  Worm gearing 
       24  Gear wheel 
       26  Driven shaft 
       28  Axis of rotation 
       30 /a/b Magnetic element arrangement First sensor device 
       31  First sensor device 
       32 /a/b/c/d Sensor element 
     End surface of the driven shaft 
     Magnetic element arrangement 
     Second sensor device 
       40 /a/b/c/d Sensor element 
       42 /a Circuit board 
       43  Lower side of the circuit board 
       44  IC 
       46  Cutout 
       48  Evaluating unit 
     α Angle 
     β Angle 
     σ Angle offset 
     ω Rotary angle velocity 
     DW Rotary angle 
     GW Limit value 
     S Signal 
     t Time