Position determining sensor unit

Abstract

A position determining sensor unit having a number of sensors arranged at predetermined positions along a path, and a transducer. The transducer has a first end which is moveable at least along the entire path, and a length running parallel to the path. Each sensor has a first supply voltage connection, a second supply voltage connection and a switching output, and wherein the switching output is switched into an On-state or an Off-state as a function of the threshold value of a sensor signal being exceeded or undershot. The supply voltage connection of each sensor is connected to a supply voltage, and a first sensor is arranged at a beginning of the path and a last sensor is arranged at an end of the path so that the second supply voltage connection of the first sensor is connected to a reference potential and the first sensor has a power consumption.

Claims

1. A position determining sensor comprising: a current measuring unit; a plurality of sensors arranged at predetermined intervals at positions along a path, each of the plurality of sensors comprises a first supply voltage connection, a second supply voltage connection, and a switching output; and a transducer that has a first end, which is at least movable along an entire path and a length extending from the first end in parallel to the path, wherein a switching output is switched into an On-state or an Off-state as a function of a sensor signal exceeding or falling below a threshold value, wherein the first supply voltage connection of each of the plurality of sensors is connected to a supply voltage, wherein a first sensor of the plurality of sensors is arranged at a beginning of the path and a last sensor of the plurality of sensors is arranged at an end of the path, wherein a second supply voltage connection of the first sensor of the plurality of sensors is connected to a reference potential, and the first sensor of the plurality of sensors has a power consumption, wherein the first sensor of the plurality of sensors is always in a switched-on state when the position determining sensor is in operation, wherein the second supply voltage connection of each further sensor of the plurality of sensors is connected to the switching output of a preceding sensor of the each further sensor of the plurality of sensors, wherein a respective further sensor of the plurality of sensors is adapted to be switched on or off via the switching output of the preceding sensor, wherein the respective further sensor of the plurality of sensors has a power consumption in a switched-on state, wherein the current measuring unit is arranged before the first supply voltage connection of the first sensor of the plurality of sensors or before the second supply voltage connection of the first sensor of the plurality of sensors, wherein the power consumption of all switched-on sensors contribute to an aggregate current measured via the current measuring unit, and wherein the aggregate current is a multiple of the power consumption and is proportional to a position of the first end of the transducer.

2. The position determining sensor unit according to claim 1, wherein the On-state of the switching output of each of the plurality of sensors is switched when a first threshold value is exceeded, wherein the Off-state of the switching output of each of the plurality of sensors is switched when the first threshold value falls short, wherein the length of the transducer extends from the first end at least up to the first sensor of the plurality of sensors, wherein a position of the first end of the transducer in a region of the position of the m-th sensor, m being an integer greater than zero, corresponds to an aggregate current:
Isum=(m+1)*Isup, and wherein Isum is the aggregate current and Isup is the power consumption.

3. The position determining sensor unit according to claim 1, wherein, for increasing the accuracy of the position determination, each of the plurality of sensors has at least a first threshold value and a second threshold value, wherein the length of the transducer extends from the first end to at least the first sensor of the plurality of sensors, wherein the second threshold value is less than the first threshold value, wherein the On-state of the switching output of each of the plurality of sensors is switched when the first threshold value is exceeded, wherein the Off-state of the switching output of each of the plurality of sensors is switched when the second threshold value falls short, wherein the On-state of the switching output of each of the plurality of sensors is pulse-width-modulated for sensor signals lying between the second threshold value and the first threshold value, wherein a duty cycle of the pulse width modulation is proportional to the sensor signals, wherein the power consumption of a sensor connected to the pulse-width-modulated switching output is proportional to the duty cycle and less than the power consumption in the On-state, wherein a position of the first end of the transducer in the region of the position Pm of the m-th sensor Sm corresponds to an aggregate current:
Isum=I/Isup+Ipwm, and wherein Ipwm is a power consumption of a sensor connected to the pulse-width-modulated switching output.

4. The Position determining sensor unit according to claim 1, wherein the Off-state of the switching output of each of the plurality of sensors is switched when a first threshold value is exceeded, wherein the On-state of the switching output of each of the plurality of sensors is switched when the first threshold value is undershot, wherein the transducer extends from the first end at least along a partial region of the path in the direction of the last of the plurality of sensors, and wherein a position of the first end of the transducer in the region of the position of an m-th sensor corresponds to an aggregate current:
Isum=m*Isup.

5. The position determining sensor unit according to claim 1, wherein, in order to increase an accuracy of the position determination, each of the plurality of sensors has at least a first threshold value and a second threshold value, wherein the transducer extends from the first end at least along a partial region of the path in the direction of the last of the plurality of sensors, wherein the second threshold value is less than the first threshold value, wherein the Off-state of the switching output of each of the plurality of sensors is switched when the first threshold value is exceeded, wherein the On-state of the switching output of each of the plurality of sensors is switched when the second threshold value falls short, wherein the Off-state of the switching output of each of the plurality of sensors is pulse-width-modulated for sensor signals lying between the first threshold value and the second threshold value, wherein a duty cycle of the pulse width modulation is inversely proportional to the sensor signals, wherein the power consumption of a sensor connected to the pulse-width-modulated switching output is proportional to the duty cycle and less than the power consumption in the On-state, and wherein a position of the first end of the transducer in the region of the position of the m-th sensor corresponds to an aggregate current:
Isum=(m1)*Isup+Ipwm.

6. The position determining sensor unit according to claim 1, wherein the power consumption of the plurality of sensors has a mutual variance of at most 10%.

7. The position determining sensor unit according to claim 1, wherein the power consumption of each of the plurality of sensors is stabilized or trimmed.

8. The position determining sensor unit according to claim 1, wherein the intervals between each of the plurality of sensors are substantially identical.

9. The position determining sensor unit according to claim 1, wherein the first end of the transducer is designed as a tip or as an edge.

10. The position determining sensor unit according to claim 1, wherein a distance of the transducer from a path along the entire length of the transducer is constant or at least increases in the region of the first end.

11. The position determining sensor unit according to claim 1, wherein the plurality of sensors are magnetic field sensors.

12. The position determining sensor unit according to claim 1, wherein the plurality of sensors are Hall sensors with laterally or vertically measuring Hall plates.

13. The position determining sensor unit according to claim 1, wherein the switching output has an open-drain transistor.

14. The position determining sensor unit according to claim 13, wherein a current-carrying capacity of an open-drain output of the open-drain transistor is at least 100 mA.

15. The position determining sensor unit according to claim 13, wherein an input resistance of the open-drain transistor is at most 100 m.

16. The position determining sensor unit according to claim 1, wherein the last sensor of the plurality of sensors is a resistor.

17. The position determining sensor unit according to claim 1, wherein the sensors are capacitive sensors or inductive sensors or temperature sensors or force sensors or pressure sensors.

18. The position determining sensor unit according to claim 1, wherein the plurality of sensors are identical or substantially identical to one another.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) 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:

(2) FIG. 1 is a schematic view of an embodiment of a position determining sensor unit according to the invention;

(3) FIG. 2 is a schematic view of an embodiment of a position determining sensor unit according to the invention;

(4) FIG. 3 is a schematic view of an embodiment of a position determining sensor unit according to the invention;

(5) FIG. 4 is a schematic view of an embodiment of a position determining sensor unit according to the invention,

DETAILED DESCRIPTION

(6) The diagram of FIG. 1 shows a schematic view of an inventive position determining sensor unit 10, comprising a number N=5 of identical sensor units Sn=1 . . . N, a transducer 20 and a current measuring unit 40.

(7) The sensors are arranged along a path 30 at even intervals at positions Pn=1 . . . N, wherein a first sensor S1 is arranged at a beginning of the path and a last sensor SN is arranged at one end of the path 30.

(8) Each sensor Sn has a first supply voltage connection 32, a second supply voltage connection 34 and a switching output 36, wherein the switching output 36 has an On-state and an Off-state. In the illustrated exemplary embodiment, as a function of a first threshold value, the switching output 36 of each sensor Sn switches to the On-state when a threshold value exceeds the sensor signal of the sensor Sn, and to the Off-state when the first threshold value falls short.

(9) The first supply voltage connection 32 of the first sensor S1 is connected to a supply voltage Vsup, and the second supply voltage connection 34 of the first sensor S1 is connected to a reference potential GND, so that the first sensor S1 is always switched on during commissioning of the position determining sensor unit 10, therefore always having a power consumption Isup.

(10) All further sensors Sn=2 . . . N are also connected by means of the respective first supply voltage connection 32 to the supply voltage Vsup. The second supply voltage connection 34 of the further sensors Sn=2 . . . N is connected in each case to the switching output 36 of the sensor Sn1 immediately preceding along the path 30. As a result, the further sensors Sn=2 . . . N are switched on in each case by means of the immediately preceding sensor Sn1, on the basis of exceeding the threshold value detected by the immediately preceding sensor. In the switched-on state, the further sensors Sn=2 . . . N also have a power consumption Isup, wherein the respective power consumption of all sensors Sn exhibits low variance due to the uniformity of the sensors.

(11) To reduce costs, the last sensor SN can also be designed as a more cost-effective power consumer, e.g. as a resistor with a resistance value adapted to the supply voltages and without a connection corresponding to the switching output.

(12) In the illustrated embodiment, the transducer 20 is a magnet, which has a first end 22 and a length 24. The transducer 20 is moveable parallel to the path 30, wherein the first end 22 can be moved along the entire path 30 and the length 24 of the magnet is greater than or equal to the path 30.

(13) In the exemplary embodiment shown, the current measuring unit 40 is looped into the line of the first supply voltage Vsup, immediately before a first voltage node of the first sensor S1. Alternatively, the current measuring unit 40 can also be looped into the line for the reference potential GND before the second supply voltage connection 34shown by dashed lines.

(14) In both embodiments, an aggregate current Isum can be determined by means of the current measuring unit 40 in a simple manner, wherein the aggregate current is derived from the power consumption Isup of all switched-on sensors Sn. The aggregate current Isum thus corresponds to one multiple m of the power consumption Isup of a single sensor Sn:
Isum=m*Isup

(15) In the illustrated exemplary embodiment, from the following equation using the measurable factor m, it is possible to determine over which sensor Sn the first end 22 of the transducer 20 is located:
n=m1

(16) Thus, the first end 22 is at the position Pm1 of the (m1)-th sensor Sm1.

(17) If the first end 22 of the transducer 20 is, as shown in the exemplary embodiment, above the third sensor S3, i.e., at the position P3 of the third sensor S3, then the transducer 20 covers the sensors S1, S2 and S3. The respective sensor signal for the sensors S1, S2, S3 is above the first threshold value; the respective switching output is switched to the On-state so that the sensors S1 to S4 are in the switched-on state. Only sensor S5 is still in a switched-off state. Thus, the four sensors contribute to the aggregate current Isum; the factor m is thus four.

(18) To increase the accuracy of the position determination, according to a further development the sensors Sn=1 . . . N each have a second threshold value, the second threshold value being less than the first threshold value. When the first threshold value is exceeded, the switching output of each sensor is switched to the On-state; when the second threshold value falls short, the switching output is in each case switched to the Off-state.

(19) For sensor signals located between the first threshold value and the second threshold value, the switching output is switched from the Off-state to the On-state in a pulse-width-modulated manner. The pulse width modulation has a duty cycle which is proportional to the sensor signal of the respective sensor.

(20) The power consumption Ipwm of a sensor Sn switched in a pulse-width-modulated manner, i.e. of a sensor Sn which is connected to a pulse-width-modulated switching output of an immediately preceding sensor Sn1, is less than the power consumption Isup of a fully switched-on sensor Sn.

(21) Due to the proportionality of the duty cycle of the pulse width modulation to the sensor signal, the power consumption Ipwm of the pulse-width-modulated sensor is also proportional to the sensor signal, and thus proportional to the position of the first end 22 of the transducer in the region above the preceding sensor Sn1. As a result, the position Pp of the first end 22 of the transducer 20 is more precisely resolved in the region of a single sensor.

(22) When the first end 22 is located above the third sensor, as shown in FIG. 1, for the embodiment variant with pulse width modulation, the aggregate current Isum is composed of the power consumption Isup of the fully switched-on sensors S1, S2, S3 and the power consumption Ipwm of the sensor S4, since the sensor S4 is not switched on completely, but is switched on, accordingly pulse-width-modulated, by the pulse-width modulated switching output of the sensor S3. The sensor S5 does not contribute to the aggregate current Isum:
I=3*Isup+Ipwm

(23) Consequently, based on the multiple m of the power consumption Isup, here three, one can read off above which sensor Sn the first end 22 of the transducer is located. By mapping all possible values of the current Ipwm to a path corresponding to a width of a sensor along the path or to the distance between two sensors, and by determining the measured current Ipwm proportion of the width or path, the position of the first end 22 of the transducer 20 in the region of the third sensor can be more precisely determined.

(24) The illustrations of FIGS. 2 and 3 show advantageous embodiments of the embodiments shown in FIG. 1. In the following, only the differences from the illustration of FIG. 1 are explained. While the transducer 20 shown in FIG. 1 has a constant distance to the path 30 along the entire length 24 of the transducer 20, the distance of the transducer 20 shown in FIG. 2 increases in the direction of the first end 22, since the transducer 20 is bent in an area before the first end 22. Furthermore, in FIG. 2, the course of a first pole 26 and a second pole 28 is sketched within the transducer 20, which is designed as a magnet.

(25) In FIG. 3, a position determining sensor unit 10 is sketched in a plan view. For better clarity, only the transducer 20 and the sensors Sn are shown. The transducer 20 shown in FIG. 3 has a tapering first end 22.

(26) The embodiments of the first end 22 of the transducer 20 shown in FIGS. 2 and 3 make it possible to increase the accuracy of the position determination in a pulse-width-modulated operation.

(27) The diagram of FIG. 4 shows a further embodiment of a position determining sensor unit. In the following, only the differences from the illustration of FIG. 1 are explained. The illustrated sensors Sn are inverting, so that the switching outputs of the sensors each switch into the Off-state when the first threshold value is exceeded, and into the On-state, when the first threshold value falls short.

(28) The transducer 20 extends from the first end 22 in the direction of the last sensor SN, wherein the length 24 of the transducer 20 covers only a partial region of the path 30.

(29) In the absence of the transducer 20, all sensors Sn are in the switched-on state, since the first threshold value falls short for each sensor Sn and the output signal 36 is switched to the On-state.

(30) If the first end 22 of the transducer is located in a region of an m-th sensor, e.g. as shown in the region of the third sensor S3, i.e. at the position P3, the sensor signal of the third sensor S3 exceeds the first threshold value, and the output signal 36 of the third sensor S3 is switched to the Off-state. As a result, all subsequent sensors S4, S5 are in the switched-off state and have no power consumption Isup. Only the power consumption Isup of the sensors S1 and S2 preceding along the path contributes to the aggregate current Isum. Thus, by means of the factor m of Isum=m*Isup, the sensor Sn or the position Pn of the sensor Sn, on which the first end 22 of the transducer 20 is located, can be determined as follows:
n=m

(31) The pulse width modulation described with regard to the exemplary embodiment according to FIG. 1 and the embodiments of the first end of the transducer 20 described in FIGS. 2 and 3 for increasing the accuracy of the position determinations are equally possible in the inverted mode illustrated in FIG. 4.

(32) 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.