DEVICE FOR DETERMINING A POSITION OF A MOVING PART AND METHOD FOR THE OPERATION THEREOF

Abstract

A device for determining a position of a moving part, having a position detector for detecting a position of the moving part relative to a reference position, wherein the position detector has a transmitter which is fixedly connected with the moving part. The position detector is designed such that it is operable in a position detection state for detecting the position of the moving part relative to the reference position and in a power saving state to save power. A capacitive sensor includes the transmitter, and the transmitter and the remainder of the capacitive sensor are designed to coordinate with each other and are arranged in such a way that in the power-saving state of the position detector, a movement of the moving part relative to the reference position is detected by the capacitive sensor and the position detector is transferred automatically from a power-saving state to a position-detecting state.

Claims

1. A device for determining a position of a moving part, the device comprising: a position detector to detect a position of the moving part relative to a reference position, the position detector having a transmitter fixedly connected to the moving part, the position detector being designed such that it is operated in a position detection state for detecting the position of the moving part relative to the reference position and in a power-saving state to save power; and a capacitive sensor comprising the transmitter, and the transmitter and the remainder of the capacitive sensor are formed to be coordinated with each other and are arranged such that in the power-saving state of the position detector, a movement of the moving part relative to the reference position is detectable via the capacitive sensor and, as a function of this detection, the position detector is automatically transferred from its power-saving state to its position-detecting state.

2. The device according to claim 1, wherein the position detector is designed as an inductive and/or magnetic and/or optical sensor.

3. The device according to claim 2, wherein the position detector is formed as an inductive sensor with a transmitter coil and a plurality of sensor coils and wherein the capacitive sensor at least partially includes the transmitter coil and the sensor coils of the inductive sensor for capacitive evaluation.

4. The device according to claim 1, wherein the capacitive sensor has a plurality of transmitter electrodes and a sensor electrode, wherein the transmitter electrodes and the sensor electrode of the capacitive sensor are formed at least partially independent of the position detector.

5. The device according to claim 1, wherein the device is configured to determine a rotation angle and/or torque of the moving part formed as a rotating part, comprising a position detector formed as an angle detector for detecting an angular position of the rotating part relative to a reference position and at least one indexer for indexing at a predetermined rotation, preferably a 360 rotation, of the rotating part relative to the reference position, wherein the angle detector has a transmitter which is non-rotatably connected with the rotating part and which is formed as a rotor with a base body for attachment to the rotating part and a plurality of vanes extending radially outwardly from the base body, and wherein at least one of the vanes of the rotor has a marker that is detected via the indexer.

6. The device according to claim 5, wherein the transmitter electrodes and the sensor electrode of the capacitive sensor are each designed as at least one circular sector, wherein the circular sectors are arranged concentrically about an axis of rotation of the rotor.

7. The device according to claim 5, wherein the transmitter electrodes and the sensor electrode of the capacitive sensor are each designed as at least one circular segment, and wherein the circular segments are arranged concentrically about an axis of rotation of the rotor.

8. The device according to claim 7, wherein the indexer includes two directly adjacent circular segments and the rotor, wherein the rotor and the two directly adjacent circular segments are suitably configured and arranged for indexing at a predetermined rotation, preferably a 360 rotation, of the rotating part relative to the reference position.

9. The device according to claim 1, wherein the position detector and the capacitive sensor are each at least partially arranged on a common printed circuit board and wherein the printed circuit board is designed as a multilayer printed circuit board.

10. A method comprising: providing a device according to claim 1; and automatically transferring the position detector from a power-saving state to a position detection state via the capacitive sensor as a function of the detection of a movement of the moving part relative to the reference position.

11. The method according to claim 10, wherein the position detector is automatically transferred from its position detection state to its power-saving state via the position detector as a function of the detection of a movement of the moving part relative to the reference position.

12. The method according to claim 10, wherein the capacitive sensor is used in the position detection state of the position detector to detect the position of the moving part relative to the reference position.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:

[0031] FIG. 1 shows an exemplary embodiment of the device according to the invention in a partial plan view, without a transmitter,

[0032] FIG. 2 shows the embodiment according to FIG. 1 in a partial plan view of a transmitter embodied as a first rotor,

[0033] FIG. 3 is an exemplary illustration of a multilayer printed circuit board in the first embodiment,

[0034] FIG. 4 shows a current flow in the exemplary embodiment shown by way of example,

[0035] FIG. 5 is an exemplary embodiment of the device according to the invention in a partial plan view of a second rotor as an alternative to the first rotor,

[0036] FIG. 6a shows the exemplary embodiment in a partial side view,

[0037] FIG. 6b shows the exemplary embodiment in a further partial side view,

[0038] FIG. 7 shows an exemplary embodiment of the device according to the invention in a partial plan view, without a transmitter,

[0039] FIG. 8 shows an exemplary embodiment of the device according to the invention in a partial plan view, without a transmitter and

[0040] FIG. 9 shows the exemplary embodiment in a partial plan view of a third rotor as an alternative to the first and the second rotor.

DETAILED DESCRIPTION

[0041] FIG. 1 shows a first embodiment of a device according to the invention in a partial view. The device is designed to determine an angle of rotation and a torque of a rotating part, namely a steering shaft of a power steering system (not shown) for a motor vehicle. The device comprises two angle detector, each designed as an inductive sensor, for detecting an angular position of the rotating part relative to a reference position and an indexer designed as a capacitive sensor for indexing during a 360 rotation of the rotating part relative to the reference position, wherein the angle detector each have a rotor that is fixedly connected to the rotating part, comprising a base body for attachment to the rotating part and a plurality of vanes extending radially outward from the base body. Correspondingly, the moving part is a part rotating about an axis of rotation and the respective position detector are designed as angle detector. Furthermore, the transmitter is embodied as the rotor.

[0042] FIG. 1 only partially shows one of the two angle detector, namely its stator 1, with an annular transmitter coil 1.1 and a total of three sensor coils 1.2, 1.3 and 1.4, which are identical to each other but are each arranged rotated with respect to each other at a certain angle about the axis of rotation of the rotating part. The rotor 2 that corresponds thereto is shown with the base body 2.1 and the vanes 2.2 in FIG. 2. The reference position is symbolized in FIG. 2 by means of a dot 5. The indexer and the rotating part, i.e. the steering shaft, are not shown. The axis of rotation is symbolized in FIGS. 1 and 2 by a cross 3, wherein the axis of rotation 3 runs perpendicular to the image planes of FIGS. 1 and 2.

[0043] The rotating part, i.e. the steering shaft, is divided into two parts in a manner known to those skilled in the art, wherein one part of the steering shaft is non-rotatably connected with one of the angle detector, namely with its rotor 2, and the other part of the steering shaft is non-rotatably connected with the other of the angle detector, namely with its rotor. The indexer is assigned to one of the two parts of the steering shaft. The two parts of the steering shaft are connected to one another in a force-transmitting manner known to those skilled in the art by means of a torsion bar. FIG. 2 shows only the rotor 2 of the angle detector, which is assigned with the indexer to the same part of the steering shaft. Each rotor 2 is made in one piece from a sheet metal suitable for inductive coupling. The rotor 2 shown in FIG. 2 has a total of nine vanes 2.2 which extend radially outward from the base body 2.1. A gap 4 is formed in each case between the individual vanes 2.2. The vanes 2.2 are arranged uniformly around the circumference of the base body 2.1 of the rotor 2. As can be seen from FIG. 2, one of the vanes 2.2 of the rotor 2 has an opening 6 which is delimited by a circumferential edge. This opening 6 is a marker 6 that can be detected by means of the indexer.

[0044] The rotor of the other, not shown, angle detector has a total of eighteen vanes. This rotor has no marker detectable by an indexer or of the indexer, for example in the form of an opening delimited by a circumferential edge in one of its vanes. By means of a differential angle determination known well to those skilled in the art between the angle detector partially shown in FIG. 2 and said non-shown angle detector, the torque with which the steering shaft is acted upon can be determined. The angle of rotation of the steering shaft is determined by means of the angle detector, namely stator 1 and rotor 2, each shown partially in FIGS. 1 and 2. The indexer also serves to detect angles of rotation of 360 and more. This is necessary, for example, for commercial vehicles such as trucks or the like.

[0045] In addition to the rotor, for example rotor 2, each of the angle detector also has a stator, for example stator 1. The stator 1 is constructed in a manner known to the person skilled in the art and includes the transmission coil 1.1 and the three sensor coils 1.2, 1.3, 1.4. In the present exemplary embodiment, the respective stator 1 is arranged on a single multilayer printed circuit board 8, which is shown by way of example in FIG. 3. The multilayer printed circuit board 8 has a total of six layers, which are designated in FIG. 3 with a, b, c, d, e and f. The individual layers a to f are applied to printed circuit board material, which is symbolized in FIG. 3 by means of different textures for the purpose of better clarity. The stator 1 of the angle detector partially shown in FIG. 1 is arranged on layers a and b of the printed circuit board 8 and the stator of the angle detector, not shown in FIG. 1, is arranged on layers e and f of the printed circuit board 8. On the one hand, the indexer embodied as a capacitive sensor is arranged on layers c and d of the printed circuit board 8. On the other hand, the layers c and d of the printed circuit board 8 are also designed as a shield, by means of which undesired interaction between the angle detector designed as inductive sensors is at least reduced, the stators 1 of which are arranged on layers a and b and on layers e and f of the printed circuit board 8. In FIG. 3, only layers a to f are shown, but not the stators 1 and the indexer designed as a capacitive sensor.

[0046] Furthermore, the respective angle detector is designed such that it can be operated in a position detection state designed as an angle detection state for detecting the angle of the rotating part relative to the reference position 5 and in a power-saving state for power saving, wherein the device has an additional capacitive sensor comprising the rotor 2, and the rotor 2 and the remainder of the additional capacitive sensor are designed to be coordinated with one another and are arranged in such a manner that in the power-saving state of the respective angle detector, a movement of the rotating part relative to the reference position 5 can be detected by means of the additional capacitive sensor, and the respective angle detector can be transferred automatically from its power-saving state to its angle detection state as a function of this detection. The two angle detecting means, for example, the angle detector partially shown in each case in FIGS. 1 and 2 with the stator 1 and the rotor 2, can thus be automatically transferred by means of the additional capacitive sensor from the respective power-saving state to the respective angle detection state.

[0047] In the first exemplary embodiment, as already explained above, the respective position detector designed as angle detector is designed as an inductive sensor, for example the angle detector shown with the stator 1, the transmission coil 1.1 and the three sensor coils 1.2, 1.3 and 1.4, wherein the additional capacitive sensor includes the transmitter coil 1.1 and the sensor coils 1.2, 1.3 and 1.4 of the stator 1 for capacitive evaluation. The additional capacitive sensor according to the present first exemplary embodiment does not have sensor structures that are separate from this angle detector. Accordingly, the angle detector shown and the additional capacitive sensor are each arranged on the common printed circuit board 8.

[0048] The device according to the invention is explained in more detail below in accordance with the first exemplary embodiment and with reference to FIGS. 1 to 4.

[0049] When the steering shaft rotates, for example due to a steering intervention by a vehicle driver of the motor vehicle, the steering shaft rotates relative to the reference position 5, so that the angle of rotation of the steering shaft can be determined in a manner known to those skilled in the art by means of the one angle detector partially shown in FIGS. 1 and 2. On the other hand, the two parts of the steering shaft twist towards each other, which leads to a torsion of the torsion bar, so that by determining the differential angle between the angle detected by means of the aforementioned angle detector and the angle detected by means of the not-shown angle detector in a manner known to those skilled in the art, the torque introduced in the steering shaft can be determined. When determining the angle by means of the angle detector partially shown in FIGS. 1 and 2, the opening 6 arranged in the one vane 2.2, i.e. the marker detectable by means of the indexer, is not a hindrance, since the current flow relevant for the inductive sensor follows the geometry shown in FIG. 4. As can be seen from this, the current flows along the outer contour of the rotor 2 shown in the image plane of FIGS. 2 and 4. The current flow required for the inductive sensor system is therefore not impeded by the opening 6.

[0050] The opening 6, that is to say the marker, can be detected by means of the indexer designed as a capacitive sensor. Correspondingly, the indexer can be used to detect 360 rotations of the rotating part, that is to say the steering shaft, and thus also to detect angles of rotation of the steering shaft of 360 and more. For example, this can always take place when the vane 2.2 of the rotor 2 passes the reference position 5 with the opening 6.

[0051] If the steering shaft does not rotate, for example, for the duration of a predetermined time interval, then the respective position detector designed as angle detector is automatically transferred from its position detection state to its power-saving state. In the power-saving state of the two angle detector, position detection, that is to say detection of the angle of rotation, takes place only by means of the additional capacitive sensor.

[0052] In contrast to the position detection state of this angle detector, which is designed as an angle detection state, instead of inductive sensing, capacitive sensing takes place in the power-saving state, wherein for example the capacitive coupling of two of the sensor coils to one another, i.e. 1.2 and 1.3 or 1.2 and 1.4 or 1.3 and 1.4, are detected and evaluated in a manner known to those skilled in the art. For this purpose, the two sensor coils, for example the transmission coils 1.2 and 1.3, are each switched as transmitter electrodes. The remaining sensor coil 1.4 is then used as a sensor electrode. The transmitter electrodes, for example 1.2 and 1.3, are connected to different potentials; the transmitter electrodes, for example 1.2 and 1.3, are preferably each connected to one of the supply voltages of the angle detector. However, the use of divided or multiplied potentials that result from the two supply voltages is also conceivable. Depending on the rotational position of the rotor 2 about the axis of rotation 3, the capacitance between the transmitter electrode 1.2 and the sensor electrode 1.4 of the additional capacitive sensor on the one hand and between the transmitter electrode 1.3 and the sensor electrode 1.4 of the additional capacitive sensor on the other is different. For example, see FIGS. 6a and 6b in which the coupling of the aforesaid pairs by means of the illustrated rotor 2 exemplifies two mutually different rotational positions of the rotor 2, and thus the steering shaft. This difference can then be used in a manner known to the person skilled in the art to determine the position, that is to say, for example, to determine the angle.

[0053] To increase the accuracy of the position determination, that is to say the position detection, the individual sensor coils 1.2, 1.3 and 1.4 can be used alternately as transmitter electrodes and as a sensor electrode, for example via a multiplex process. Accordingly, a total of three measurement results would be achieved in the present first exemplary embodiment.

[0054] In other embodiments, it is possible that the three sensor coils 1.2, 1.3 and 1.4 are used as transmitter electrodes and the transmitter coil 1.1 is used as the sensor electrode of the additional capacitive sensor. For example, a time-division multiplex process can be used for this.

[0055] Furthermore, it is also possible that, for example, the annular transmission coil 1.1 with an electrode 1.5 arranged in an interior delimited by the sensor coils 1.2, 1.3 and 1.4 forms the additional capacitive sensor. See FIG. 1. In this case, the sensor coils 1.2, 1.3 and 1.4 form intermediate capacitances which, as a function of the rotational position of the rotor 2, receive different proportions of a transmission signal from the transmitter electrode 1.1 and/or the transmitter electrode 1.5 of the additional capacitive sensor. In principle, this is also possible by simultaneously emitting a magnetic field to be inductively sensed by means of the angle detector designed as inductive sensors.

[0056] By evaluating the capacitive coupling, conclusions can be drawn about a change in the rotational position of the rotor 2 and thus of the steering shaft. This can be done with very little power expenditure during the power-saving state. Triggered by the aforementioned detection, the more power-intensive inductive angle detections can then be started during the position detection state.

[0057] In the following, further embodiments of the invention are shown by way of example. Components that are the same or have the same effect as the first exemplary embodiment are provided with the same reference numbers. The further exemplary embodiments are each explained only to the extent of the differences from the preceding exemplary embodiments. Otherwise, reference is made to the explanations about the previous exemplary embodiments.

[0058] FIG. 5 shows a second embodiment of the inventive device, wherein the second embodiment is different from the first embodiment by means of the rotor.

[0059] The second exemplary embodiment essentially corresponds to the first exemplary embodiment, so that reference is made to the above statements as far as possible. In contrast to the first exemplary embodiment, all of the vanes 2.2 except for a single vane 2.2 of the rotor 2 have an opening 6 delimited by a circumferential edge. The rotor 2 of the second exemplary embodiment is thus formed inversely to the rotor 2 of the first exemplary embodiment. Correspondingly, in the second exemplary embodiment, the single vane 2.2 without opening 6 acts as a marker that can be detected by means of the indexer. Otherwise, the structure and the mode of operation of the second exemplary embodiment correspond to those of the first exemplary embodiment.

[0060] FIG. 7 illustrates a third embodiment of the device according to the invention. In contrast to the first and second embodiment, the additional capacitive sensor has a structure 7 with a plurality of transmitter electrodes 7.1, 7.2 and 7.3 and a sensor electrode 7.4, wherein the transmitter electrodes 7.1, 7.2 and 7.3 and the sensor electrode 7.4 of the additional capacitive sensor are designed independently of the position detector, that is, independently of the two angle detector. This means that the transmitter coil 1.1 and the sensor coils 1.2, 1.3 and 1.4 of the stator 1 of the shown angle detector are not capacitively evaluated, but instead, a separate structure of the additional capacitive sensor, namely the structure 7, is used. According to the third embodiment, the transmitter electrodes 7.1, 7.2 and 7.3 and the sensor electrode 7.4 of the additional capacitive sensor 7 are each formed as two circular sectors, wherein said circular sectors are concentrically arranged about the rotation axis 3 of the rotor 2. In the present exemplary embodiment, the two circular sectors, which are each assigned to the transmitter electrode 7.1, 7.2 and 7.3 and the sensor electrode 7.4, are arranged opposite one another and are connected to one another in an electrically conductive manner. See FIG. 7. For example, the same supply connections can be used for the additional capacitive sensor during the power-saving state of the two angle detector, which is generally referred to as so-called pin sharing.

[0061] This separate structure 7 of the additional capacitive sensor can for example be arranged at least partially on the printed circuit board 8 together with the structures of the two angle detector and the indexer, wherein the additional capacitive sensor is arranged in at least one layer of the printed circuit board 8, not shown, that is different from the first and second layer.

[0062] The capacitive coupling between all electrodes 7.1, 7.2, 7.3 and 7.4 that are not connected to one another can now be detected cyclically and evaluated in a manner known to those skilled in the art, which in turn depends on the rotational position of the rotor 2 about the axis of rotation 3, i.e. about the axis of rotation of the steering shaft.

[0063] In a fourth embodiment of the inventive device shown in FIGS. 8 and 9, the transmitter electrodes 7.1, 7.2 and 7.3 and the sensor electrode 7.4 of the additional capacitive sensor are in each case formed as two mutually opposite circular segments and are electrically conductive connected, wherein the circular segments are arranged concentrically about the axis of rotation 3 of the rotor 2. As can be seen in FIG. 9, the rotor 2 of this embodiment is modified such that a vane 2.2 of the rotor 2, as compared to the remaining vanes 2.2 of the rotor 2, extends radially outwardly.

[0064] By means of this design of the additional capacitive sensor and the rotor 2 according to the fourth exemplary embodiment, it is possible, for example, that the indexer comprises two directly adjacent circular segments, for example the circular segments 7.1 and 7.2, and the rotor 2, wherein the rotor 2 and these two directly adjacent circular segments are suitably designed and arranged for indexing during a 360 rotation of the rotating part, i.e. the steering shaft, relative to the reference position 5. Correspondingly, an additional indexer, for example the indexer designed as a capacitive sensor of the first, second and third exemplary embodiment, is unnecessary. In contrast to the present fourth exemplary embodiment, it is also possible for a plurality of index positions to be detectable in the aforementioned manner. For this, a corresponding modification of the rotor is then required.

[0065] The invention is not limited to the present exemplary embodiments. For example, the angle of rotation and/or torque of other rotating parts can also be advantageously determined by means of the device according to the invention. Instead of detecting the angle of rotation and the torque, it is possible to detect only the angle of rotation or the torque. In addition to angles of rotation, the invention also includes other types of position detection, for example in the case of linearly moving parts. The invention can also be used in other fields of application apart from the automotive industry.

[0066] As already explained, the at least one angle detector and the at least one indexer can be freely selected within wide, suitable limits. This also applies to the sensor principle used. The at least one angle detector is preferably designed as an inductive and/or magnetic and/or optical sensor. The same applies, if present, to the at least one indexer. Accordingly, various combinations of sensor principles can be used simultaneously, for example for a plurality of angle detector and/or a plurality of indexer.

[0067] For example, it is conceivable that a single vane extends radially further outward from the base body than the other vanes into a detection area of the indexer, or that all vanes except for a single vane extend radially further outward from the base body than the single vane into a detection area of the indexer. In this case, the angle detector can be designed as an inductive sensor and the indexer as an optical sensor, and a single vane can extend radially further outward from the base body than the other vanes or all vanes except for one single vane can extend radially further outward from the base body than the single vane. For example, the optical sensor could be arranged offset radially outward relative to the rotor in such a way that the optical sensor can detect the marker detectable by means of the optical sensor, that is to say, the only longer or the only shorter vane of the rotor.

[0068] In another embodiment of the device according to the invention, it could be that the angle detector and the indexer are each designed as an inductive sensor, and that a stator of the indexer has at least one sensor coil, wherein the sensor coil and the at least one marker of the rotor are designed to be coordinated with each other and are arranged relative to one another in such a manner that the sensor coil only acts as a sensor coil for the indexer. For example, the sensor coil for detecting the marker could be designed to be locally limited in such a way that this sensor coil, in contrast to at least one further sensor coil of the angle detector, has a detection area which comprises only one vane and a gap adjacent to this vane according to one of the above embodiments. In the case of a rotor according to FIG. 2, a substantially constant voltage would therefore always be induced in this sensor coil when the rotating part rotates. Only when the vane with the opening passes through the detection area would a voltage deviating from the otherwise-induced voltage be induced in the sensor coil. The same would apply to an embodiment in which a rotor according to FIG. 5 would be used. Only when the vane without an opening passes through the detection area would a voltage deviating from the otherwise-induced voltage be induced in the sensor coil.

[0069] In particular in the two last-named embodiments of the device according to the invention in which a plurality of inductive sensors are used, it is advantageous that the angle detector has a first operating frequency and the indexer has a second operating frequency, wherein the first operating frequency and the second operating frequency are different from one another. For example, the first operating frequency could be 3-4 MHz and the second operating frequency could be 6-8 MHz. Due to the significant deviation of the first from the second operating frequency, undesired interaction between the two inductive sensors would be effectively prevented. This development of the arrangement according to the invention could also be used advantageously in the case of a plurality of inductive angle detector.

[0070] The components of the at least one angle detector and of the at least one indexer do not necessarily have to be arranged at least partially on a single printed circuit board, in particular a multilayer printed circuit board. Depending on the requirements of the individual case, the components of the at least one angle detector and of the at least one indexer can also be arranged on printed circuit boards or the like, which are different from one another, in one or more layers. The same applies to the capacitive sensor for the automatic transfer of the position detector from its power-saving state to its position detection state. In addition, an indexer is not absolutely necessary.

[0071] The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.