Patent Description:
A wiper motor which is configured to carry out a method according to the precharacterizing clause of Claim <NUM> is known from <CIT> 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.

The patent application publications <CIT> and <CIT> illustrate other exemplary wiper motors known in the state of the art.

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.

The method according to the invention for detecting the rotary angle positions of rotating parts of a wiper motor having the features of claim <NUM> 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 <NUM> 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 (<NUM> 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.

The method according to the invention further 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 method according to the invention 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.

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:.

Identical elements or elements having an identical function are provided with the same reference numbers in the figures.

<FIG> illustrate the essential components of a wiper motor <NUM> for driving a wiper (not illustrated). The wiper motor <NUM> has a brushless electric motor <NUM> which has a rotor <NUM> which rotates about an axis of rotation <NUM> and has magnetic elements <NUM>. The rotor <NUM> is surrounded radially by a stator <NUM> which is illustrated only in <FIG> and which in a known manner has a plurality of wire windings <NUM> in such a manner that the rotor <NUM> is set into a rotational movement by a phase-displaced or temporally consecutive energizing of the individual wire windings <NUM>.

The rotor <NUM> is connected to a rotor shaft <NUM> for rotation therewith, the rotor shaft being mounted rotatably in a bearing device <NUM>, for example, on the side facing away from the rotor <NUM>. In a central section of the rotor shaft <NUM>, the latter has a worm toothing <NUM> which meshes with a mating toothing on a gear wheel <NUM>. The gear wheel <NUM> is connected to a driven shaft <NUM> for rotation therewith and is mounted rotatably about an axis of rotation <NUM>. The driven shaft <NUM> 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 <NUM> or the rotor shaft <NUM> is disposed close to the rotor <NUM> in operative connection with a first magnetic element arrangement <NUM>. In particular, the first magnetic element arrangement <NUM> is connected to the rotor shaft <NUM> for rotation therewith. The first magnetic element arrangement <NUM> is part of a first sensor device <NUM> for detecting the rotary angle position of the rotor shaft <NUM> and therefore of the rotor <NUM>. For this purpose, the first magnetic element arrangement <NUM> interacts, for example, with a sensor element <NUM>. The sensor element <NUM> comprises, for example, a Hall sensor arrangement which is configured to draw a conclusion regarding the absolute rotary angle position of the rotor <NUM> or of the rotor shaft <NUM> directly from the rotary angle position of the first magnetic element arrangement <NUM>. The absolute rotary angle position is required in order to permit a phase-conforming or angle-conforming energizing of the wire windings <NUM> of the stator <NUM>. An absolute rotary angle position is understood as meaning a rotary angle of the rotating part with respect to a fixed reference position (<NUM> degrees angle position).

Furthermore, a second magnetic element arrangement <NUM> is provided on an end surface <NUM> of the driven shaft <NUM>. The second magnetic element arrangement <NUM> is part of a second sensor device <NUM> which is configured to detect an absolute angle position of the driven shaft <NUM> and therefore of the gear wheel <NUM>. For this purpose, the second magnetic element arrangement <NUM>, for example, likewise interacts with a sensor element <NUM> 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 <NUM> or of the gear wheel <NUM> on the basis of the changing magnetic field of the second magnetic element arrangement <NUM>.

The two sensor elements <NUM> and <NUM> are disposed in an electrically conductive manner on a shared circuit board <NUM>. The plane of the circuit board <NUM> runs parallel to the axis of rotation <NUM> of the rotor <NUM> and perpendicular to the axis of rotation <NUM> of the driven shaft <NUM>. In the exemplary embodiment illustrated in <FIG>, the two sensor elements <NUM>, <NUM> are each disposed on the lower side <NUM> of the circuit board <NUM>, said lower side facing the rotor shaft <NUM>. Furthermore, components for activating or for driving the wiper motor <NUM> are disposed, as known per se, on the circuit board <NUM>. Said components comprise, by way of example, an IC <NUM> or a similar logical circuit which is configured to activate or to energize in particular wire windings <NUM> of the stator <NUM>. For this purpose, the information from the two sensor devices <NUM> of <NUM> is supplied as an input variable to the IC <NUM>.

<FIG> illustrate different arrangements of the two sensor devices <NUM> and <NUM>. It is illustrated in <FIG> that the circuit board 42a has a rectangular cutout <NUM>, on the edge of which the sensor element 32a is disposed. The first magnetic element arrangement 30a enters at least in regions into the cutout <NUM>. Furthermore, it can be seen that the sensor element 40a is disposed so as to align with the axis of rotation <NUM>, i.e. so as to cover the second magnetic element arrangement <NUM>.

<FIG> illustrates the case in which the sensor element 40b is disposed laterally offset with respect to the axis of rotation <NUM> of the driven shaft <NUM> while the arrangement of the first magnetic element arrangement 30b and of the sensor element 32b corresponds to that of the first magnetic element arrangement 30a of <FIG>.

<FIG> illustrates an arrangement approximately according to <FIG> in which the rectangular circuit board <NUM> is provided on the side facing the first magnetic element arrangement <NUM> with the sensor element 32c which is disposed at a distance from the axis of rotation <NUM> of the rotor shaft <NUM>. The first magnetic element arrangement <NUM> is located outside the circuit board <NUM> on the side of the circuit board <NUM> that faces away from the rotor <NUM>. The arrangement of the sensor element 40c corresponds to that of the sensor element 40a according to <FIG>.

Finally, <FIG>, as a modification of the arrangement in <FIG>, illustrates the case in which the two sensor elements 32d and 40d are disposed so as not to cover the axes of rotation <NUM> and <NUM> of the rotor shaft <NUM> and of the driven shaft <NUM>, respectively.

The IC <NUM> optionally has a storing and evaluating unit <NUM> which permits additional functionalities of the wiper motor <NUM>. <FIG> thus illustrates one above the other the signals SR and SG detected by the sensor devices <NUM> and <NUM> over the absolute rotary angle α of the rotor <NUM> and β of the gear wheel <NUM>, respectively. It is seen here that, at a revolution about 360º of the gear wheel <NUM> (maximum of the signal SG), the rotor <NUM> 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> shows the situation which arises after a certain operating duration or when wear occurs between those parts of the rotor shaft <NUM> or of the rotor <NUM> and of the driven shaft <NUM> or of the gear wheel <NUM> that are operatively connected to one another. In particular, it is seen that, after twelve revolutions of the rotor <NUM>, the signal SG of the gear wheel <NUM> has not yet reached its maximum, that is to say that the gear wheel <NUM> is still not revolving about <NUM>°. This is the case only after an additional angle offset δ.

As soon as the angle offset δ exceeds a limit value stored in the storing and evaluating unit <NUM>, a conclusion is drawn regarding wear at the components of the wiper motor <NUM> 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> that the storing and evaluating unit <NUM> can furthermore be configured to detect a rotary angle velocity ω of the rotor shaft <NUM> and/or of the driven shaft <NUM> over the time t of the wiper motor <NUM>. If, during the operation of the wiper motor <NUM>, the rotary angle velocity ω1 falls short of, for example, a lower limit value GW, a conclusion is drawn that the wiper motor <NUM> has increased friction values or a tendency to block due to an internal error or else that the wiper motor <NUM> 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 <NUM> 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 <NUM>.

Claim 1:
Method for detecting the rotary angle positions (α, β) of rotating parts of a wiper motor (<NUM>), the wiper motor (<NUM>) having a brushless electric motor (<NUM>) as a first part which comprises a rotor (<NUM>) rotating about a first axis of rotation (<NUM>) and which drives a gear wheel (<NUM>) as a second part which rotates about a second axis of rotation (<NUM>) and which comprises a driven shaft (<NUM>), and the rotary angle positions (α, β) of the two rotating parts being detected by means of two sensor devices (<NUM>, <NUM>) each having a signal generating element (<NUM>; 30a; 30b, <NUM>) and a sensor element (<NUM>; 32a to 32d; <NUM>; 40a to 40d) for detecting a changing physical parameter of the signal generating element (<NUM>; 30a; 30b, <NUM>), an absolute angle position (α, β) of both rotating parts is detected by means of a respective one of the sensor devices (<NUM>, <NUM>), the rotary angle positions (α, β) of the two rotating parts being matched with each other in such a manner that a specific rotary angle position (β) of the driven shaft (<NUM>) is matched with at least one specific rotary angle position (α) of the rotor (<NUM>), that currently matched rotary angle positions (α, β) of the two rotating parts are compared to values stored in a storage and evaluation unit (<NUM>) a signal or an error message is generated when a stored limit value (σ) between current values and stored values is exceeded, characterized in that a conclusion is drawn regarding a wear state of the rotating parts of the wiper motor and/or the temporal or angle-conforming activation of the wire windings of the stator are adapted or modified in response to said signal or error message.