Sensor for a motor vehicle

Abstract

A sensor for a motor vehicle having an evaluation unit which is connected to an output of the sensor. The sensor should be able to activate at least one control unit and/or a sensor at low power consumption without significant delay. This is achieved by connecting a switching signal unit to the output of the sensor in parallel with the evaluation unit.

Claims

1. A sensor for a motor vehicle, the sensor comprising: an evaluation unit connected to a first output of the sensor, the evaluation unit connected to a control unit via a first connection; and a switching signal unit connected to a second output of the sensor in parallel with the evaluation unit, the switching signal unit connected to the control unit via a second connection.

2. The sensor according to claim 1, wherein the sensor comprises a Wheatstone bridge.

3. The sensor according to claim 2, wherein tunnel magnetoresistive elements are interconnected in the Wheatstone bridge.

4. The sensor according to claim 1, wherein the switching signal unit is permanently connected to voltage, and wherein the sensor is permanently connected to voltage.

5. The sensor according to claim 1, wherein the sensor is a position sensor.

6. The sensor according to claim 1, wherein the sensor is associated with a clutch or brake pedal, a steering angle sensor or a seat belt.

7. The sensor according to claim 1, wherein the switching signal unit is integrated in the control unit.

8. The sensor according to claim 1, wherein a switch of the switching signal unit includes a transistor.

9. The sensor according to claim 8, wherein the switch of the switching signal unit includes a MOSFET or a bipolar transistor.

10. The sensor according to claim 1, wherein the sensor has a clock-based sleep phase and a clock-based awake phase in an idle modes.

11. The sensor according to claim 1, wherein the switching signal unit activates the control unit and other sensors based on the second output signal.

12. The sensor according to claim 2, wherein only the Wheatstone bridge and the switching signal unit are permanently supplied with voltage.

13. The sensor according to claim 1, wherein the evaluation unit is connected to a power supply only when an ignition of the motor vehicle is switched on, the evaluation unit processing the first output of the sensor when connected to the power supply.

14. The sensor according to claim 1, wherein a change of signal from the sensor closes a switch of the switching signal unit, so that the switching signal unit outputs an activation command to the control unit.

15. A sensor unit, comprising: a sensor having a first signal output and a second signal output; an evaluation unit connected to the first output of the sensor, the evaluation unit connected to a control unit via a first connection; and a switching signal unit connected to the second output of the sensor, the switching signal unit connected to the control unit via a second connection, wherein the first signal output and the second signal output are supplied to the evaluation unit and the switching signal unit in parallel, wherein the first connection and the second connection to the control unit are in parallel, and wherein only the sensor and the switching signal unit are supplied with voltage in an idle mode, the evaluation unit being supplied with voltage in an normal mode with an ignition switched on.

16. The sensor unit according to claim 15, wherein the sensor has a clock-based sleep phase and a clock-based awake phase in the idle mode.

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 circuit diagram of a sensor; and

(3) FIG. 2 is a circuit diagram of a switching signal unit.

DETAILED DESCRIPTION

(4) As can be seen from FIG. 1, a sensor comprises, e.g., a position sensor, a Wheatstone bridge 1, at the output 4 of which an evaluation unit 2 and a switching signal unit 3 are connected in parallel. The sensor is arranged in a motor vehicle and assigned, for example, to a clutch or brake pedal.

(5) The Wheatstone bridge 1 comprises, as usual, four first resistors 5, which are interconnected to form a closed square. In a first diagonal of the Wheatstone bridge 1, a voltage source 6 is connected and in a second diagonal, the output 4 is connected, which outputs signals in the form of an output voltage (in_n and in_p).

(6) The voltage source 6 is permanently, that is, independent of an ignition switching position, connected to a power supply of the motor vehicle (terminal 30). In order to reduce the power requirements of the assembly even further, it is further possible to clock the voltage source 6, that is, to realize a disconnected sleep phase with a closed-circuit current very close to zero, and a preferably short awake phase with low power consumption.

(7) The first resistors 5 are designed to be of high impedance in the form of tunnel magnetoresistive elements (TMR).

(8) The evaluation unit 2 is connected to the power supply via a terminal VCC only when the ignition is switched on, and processes the Wheatstone bridge 1 signals in_n and in_p into position information 7 of the sensor. As usual, the position information 7 is transmitted analogously, digitally or by means of pulse width modulation (PWM) to an associated control unit.

(9) Like the Wheatstone bridge 1, the switching signal unit 3 is permanently connected to the power supply via the terminal 30, and processes a change in the signals in_n and in_p into a switching command. As an alternative to the illustration in FIG. 1, the switching signal unit 3 may be spatially separated from the sensor and, for example, be arranged in a control unit.

(10) A circuit diagram of the switching signal unit 3 is shown in FIG. 2. The signals in_n and in_p are fed into an operational amplifier 9 via a respective second resistor 8a, 8b. The signal in_n is connected via a third resistor 10 to an electrical ground between the associated second resistor 8a and a minus input of the operational amplifier 9. An output of the operational amplifier 9 is connected to a plus input of a comparator 11. The signal in_p is connected via a fourth resistor 12 to the output of the operational amplifier 9 between the associated second resistor 8b and a plus input of the operational amplifier 9. A minus input of the comparator 11 is connected via a voltage stabilizer 13 and a fifth resistor 14 to terminal 30, and via a sixth resistor 15 to ground, and is thus permanently supplied with power. A switch 16 is connected to an output of the comparator 11.

(11) The voltage stabilizer 13 outputs a voltage of, for example, 3.3V or 5.0V.

(12) The switch 16 is, e.g., a transistor, in particular a MOSFET.

(13) The sensor function is as follows:

(14) In normal operation, i.e., with the ignition switched on, both the Wheatstone bridge 1 and the switching signal unit 3 as well as the evaluation unit 2 are connected to voltage. As usual, the signals in_n and in_p of the Wheatstone bridge 1 are processed in the evaluation unit 2 into corresponding positions, and the position information 7 is relayed to a master control unit.

(15) In idle mode, i.e., with the ignition off, only the Wheatstone bridge 1 and the switching signal unit 3 are connected to voltage via the terminal 30. The power consumption in this case is very low. Once a mechanism associated with the sensor is actuated, such as the clutch or brake pedal, the signals in_n and in_p that are output from the Wheatstone bridge 1, which are introduced into the switching signal unit 3, change. This change of the signals has the effect of closing the switch 16 in the switching signal unit 3 and outputting an activation command 17 to at least one predetermined control unit. A switching point for closing the switch 16 is set by the fifth resistor 14 and the sixth resistor 15.

(16) 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.