Inductive sensor device for detecting changes in the position of actuator elements

Abstract

This invention relates to an inductive sensor device for detecting changes in the position of an actuating element. The sensor device comprises: - an LC resonant circuit having an inductive element (L) and a capacitive element (C); - an excitation supply for exciting the LC resonant circuit by coupling an excitation voltage (U) to the LC resonant circuit; - a decoupling element arranged between the excitation supply and the LC resonant circuit; and - an evaluation device for evaluating signal attenuation in the resonant circuit. The invention also relates to an actuation device.

Description

Technical Field

[0001] This invention relates to an inductive sensor device. It also relates to an actuation device. Background Technology

[0002] Inductive sensor devices are playing an increasingly important role in modern motor vehicles, for example, in detecting actuation of so-called fixed door handles and triggering the opening of the door. The working principle of inductive sensor devices is based on detecting changes in an electromagnetic field as a metallic or ferromagnetic actuating element moves within it. The underlying physical effect is the change in inductance and / or inductive mass caused by the positional change of the conductive and / or ferromagnetic element relative to the component generating the inductance. The conductive or ferromagnetic element can be, for example, the actuation region of the door handle or a portion of the actuation region of the door handle. Because inductive sensors can also be used to detect minute changes in position, such as in the micrometer range, their use is particularly interesting for the increasingly prevalent use of so-called fixed door handles.

[0003] When providing actuators with inductive sensor devices, reliable detection of position changes in the metal actuator element is important. Furthermore, low manufacturing cost of the actuator components is also desirable. Summary of the Invention

[0004] The object of this invention is to provide an alternative to existing actuation devices. The considerations to be adopted should satisfy the expectation of sufficiently reliable detection of position changes in the actuating element, and allow for the production of the actuation device with reasonable economic efficiency.

[0005] This objective is achieved by an inductive sensor device having the features of claim 1. This objective can also be achieved by an actuation device having the features of claim 8.

[0006] An inductive sensor device is provided for detecting position changes of an actuating element, particularly a metal actuating element. The sensor device has at least the following components:

[0007] - An LC resonant circuit having an inductive element (L), preferably a coil or a combination of several coils, and a capacitive element (C), such as one or more capacitors;

[0008] - An excitation source (Anregungsversorger) is coupled to the LC resonant circuit via an excitation voltage (U) to excite the LC resonant circuit.

[0009] - A decoupling element placed between the excitation source and the LC resonant circuit.

[0010] - An evaluation device for evaluating a signal that decreases through a resonant circuit.

[0011] Specifically, a high-impedance series resistor (Vorwiderstand) can be provided as a decoupling element, connected between the excitation source and the resonant circuit. The high-impedance series resistor can, for example, have a resistance value between 1 kiloohm and 10 kiloohms, preferably between 3 kiloohms and 1 kiloohms. Of course, the decoupling element can also have multiple components, with the primary function being high-impedance decoupling.

[0012] The excitation voltage is preferably output as a sequence of voltage pulses from an excitation source, and particularly preferably as a sequence of square wave pulses. The voltage pulses can be output at an operating frequency of, for example, 1 MHz to 10 MHz, preferably 5 MHz to 10 MHz, and particularly preferably 7 MHz to 9 MHz. However, alternatively, other forms of excitation voltage are conceivable, such as using an excitation signal that follows a sinusoidal curve, i.e., using an excitation voltage described as a time-dependent sine function or a sinusoidal oscillation. In this case, the operating frequency can also be between 1 MHz and 10 MHz, preferably 5 MHz to 10 MHz, and particularly preferably 7 MHz to 9 MHz.

[0013] For example, an NOC (numerically controlled oscillator), often also referred to as a DCO (digitally controlled oscillator), can be used as an excitation source. Its advantage is that the timer required for the output voltage pulses is already an integral part of the excitation source. The excitation source can also be called a signal source; the term signal source is common in contexts related to the operation of resonant circuits.

[0014] The LC resonant circuit is preferably a parallel resonant circuit, but in principle, the sensor device can also be used with an LC resonant circuit designed as a series resonant circuit.

[0015] Preferably, there is a simple structural form in which exactly one coil forms the inductor and exactly one capacitor forms the LC resonant circuit as the capacitor. Alternatively, multiple inductors and / or multiple capacitors can be provided, in which case, within the consideration of the equivalent circuit diagram, the capacitor represents the overall capacitance effect and the inductor represents the overall inductance effect.

[0016] Specifically, it can be specified that at least the excitation source, resonant circuit, wiring connections, and / or decoupling elements are contained within the same microcontroller, and preferably, an evaluation device is also included. Providing all or many of the functions of the sensor device within the microcontroller means that the sensor device can be provided very economically through microcontroller programming.

[0017] In one embodiment, the evaluation device has a rectifier circuit.

[0018] Therefore, an inductive sensor device for detecting position changes of an actuating element is proposed. The electromagnetic characteristics of an LC resonant circuit are measured to determine the position change of the actuating element, wherein the LC resonant circuit detunes when the position changes, exhibiting the following characteristics:

[0019] - An LC resonant circuit with an inductor (L) and a capacitor (C).

[0020] - An excitation source coupled to the LC resonant circuit via an excitation voltage (U) to excite the LC resonant circuit. The excitation source is preferably a pin-controller whose output pin is coupled to the LC resonant circuit via a conductor, and has a high-resistance decoupling resistor, for example between 1 kΩ and 10 kΩ, preferably between 4 kΩ and 6 kΩ, connected between the output pin and the LC resonant circuit.

[0021] - An evaluation apparatus for evaluating a signal that decreases through a resonant circuit. The evaluation apparatus is preferably a series circuit consisting of a rectifier circuit and an ADC (Analog-Digital-Converter), wherein the rectifier circuit and the ADC are particularly preferably smoothed by additional capacitive elements, optionally supplemented by high-impedance resistors.

[0022] The rectifier circuit produces a DC voltage signal instead of a high-frequency AC voltage. In a preferred embodiment, the rectifier circuit consists of a diode and a capacitor arranged in parallel with a resonant circuit. The voltage drop across the rectifier capacitor is a measure of the AC voltage amplitude, provided, of course, that the capacitor is large enough—a responsibility of the designer. The voltage across the capacitor is determined at the ADC and, for example, compared with a target value and / or checked for being below a lower threshold and / or checked for being above an upper threshold. In this invention, this is the signal dropped across the resonant circuit, i.e., indirectly through the evaluation of the rectified voltage value. When one or more conditions are met in a predetermined manner, and in a manner depending on the specific design of the sensor device, the actuating element is identified as deviating from a non-actuated position, and thus actuation is determined. This can cause a trigger circuit coupled to the evaluation device to output an actuation signal.

[0023] A key advantage of the described process is that it transforms the complex and error-prone time-resolved measurement of high-frequency, time-dependent voltages into a measurement of a rectified signal (which significantly reduces time dependence). Therefore, this measurement results in robust detection of position changes that is less dependent on deviations in the time recording or the accuracy of the timer.

[0024] In a preferred embodiment, the excitation source is configured to output an excitation voltage corresponding to the natural frequency of the resonant circuit or an operating frequency tuned to that natural frequency. Tuning to the natural frequency preferably means finding, practically, an excitation voltage that produces a significant effect with the smallest possible positional variation. Specifically, this means, for example, finding the operating point of the excitation voltage with the maximum possible slope in the signal frequency curve (signal on the y-axis). Typically, this is a frequency close to the natural frequency. For example, the excitation voltage can be specified to deviate from the natural frequency of the resonant circuit by less than five percent. An operating frequency close to the natural frequency of the resonant circuit means that even small changes in the inductance and / or inductance quality of the inductor element will cause a strong change in the signal drop across the resonant circuit, thus resulting in high measurement sensitivity of the sensing sensor device.

[0025] Especially in improved designs that incorporate a rectifier circuit as part of the evaluation apparatus, parameters dependent on the rectified signal can be evaluated. It is preferable to measure the rectified voltage. It is recommended that this evaluation be performed only when the rectified signal has already saturated, for example, after at least five, preferably at least ten, excitation cycles have elapsed.

[0026] The rectifier circuit preferably has a diode and a capacitor (C_D) preferably connected in parallel with the resonant circuit. The advantage of this design is that it is particularly simple and therefore inexpensive.

[0027] The rectifier circuit is preferably arranged between the LC resonant circuit and the ADC of the evaluation device, which is configured to use the ADC to detect the voltage value rectified at the rectifier and identify the location change based on the detected voltage.

[0028] Preferably, the evaluation device is an ADC that exists in the microcontroller, or has an ADC as a component.

[0029] The evaluation device is particularly preferably configured to identify the presence of a positional change when the voltage exceeds an upper threshold voltage value or when it falls below a lower threshold voltage value.

[0030] According to one embodiment of the sensor device, the evaluation device is configured to accurately identify position changes when the voltage exceeds an upper threshold voltage value or falls below a lower threshold voltage value. In particular, it can be specified that the position change is accurately identified when the voltage exceeds the upper threshold voltage value or falls below the lower threshold voltage value.

[0031] In an alternative embodiment of the invention, the evaluation device does not have a rectifier circuit, and the ADC of the evaluation device detects the voltage drop at the resonant circuit. In this embodiment, the retardation characteristic of the ADC must be adapted to the operating frequency of the excitation supply, such that the minimum measurement duration of the ADC lasts for at least one cycle of the resonant circuit excitation, preferably 5 to 1000 resonant circuit excitation cycles, particularly preferably 5 to 100 resonant circuit excitation cycles, and more preferably 5 to 20 resonant circuit excitation cycles. In simulations, a resonant circuit excitation of 10 cycles and adjacent values ​​have proven to be particularly suitable. The effect of this is that the ADC cannot follow the voltage change over time; instead, for the ADC, the voltage change over time results in a voltage measurement that is essentially time-independent. Therefore, this embodiment takes advantage of the disadvantage of relatively inexpensive ADCs, namely poor time resolution.

[0032] One idea of ​​the present invention relates to an actuation device, particularly in a motor vehicle, having a sensor device according to one of the preceding claims and a metal actuation element, wherein the metal actuation element (4) changes position relative to an inductive element (L) when actuated.

[0033] The electromagnetic field of a metal actuator relative to an inductive element is movable or deformable, both of which are encompassed within the overarching concept of position change. This position change results in a change in the inductance and / or equivalent inductance and / or inductive mass of the inductive element, as explained earlier. This, in turn, detunes the LC resonant circuit, causing a change in the rectified voltage amplitude compared to the voltage amplitude present in the equilibrium state. The change in voltage amplitude can then be used to directly infer the position change of the metal actuator. For example, an evaluation device might consider a position change detected if it exceeds an upper threshold voltage and / or falls below a threshold voltage determined by a technician based on the required accuracy and / or permissible false positive measurements.

[0034] The actuation device is preferably a door handle or a vehicle cover, wherein the sensing sensor device is arranged inside the door handle. The actuation element is particularly preferably arranged on the door handle or as part of the door handle, preferably as part of the door handle housing. Attached Figure Description

[0035] Figure 1a and 1b : Schematic diagram of the principle of actuator 1;

[0036] Figure 2 Schematic circuit diagram of an inductive sensor device. Detailed Implementation

[0037] exist Figure 1aA schematic cross-sectional view of an actuation device 1 for a motor vehicle is shown. In the embodiment shown as an example, the actuation device 1 is a door handle, shown in cross-section. Inside the handle 1, an inductive sensor device 2 is shown, which, in the illustrated embodiment, is integrally arranged on a circuit board. The inductive sensor device has a resonant circuit with a coil L. A metal actuation element 4, designed as a metal foil, is arranged on the housing portion of the door handle and on the inner side of the door handle. The metal actuation element 4 is arranged opposite to the coil L of the inductive sensor device 2. Due to the elastic properties of the housing portion of the door handle, the metal actuation element 4 can move relative to the sensor device 2.

[0038] exist Figure 1b The diagram illustrates how the application of force affects the housing portion (indicated by arrow 3). As a result of the applied force, the metal actuator 4, designed as a metal foil, changes its position. This positional change is a result of a change in the cross-section of the actuator 4 relative to the sensor device 2, caused by deformation of the actuator 4. This positional change of the actuator is also specifically relative to the coil L of the sensor device 2. The sensor device 2 is used to identify the actuation indicated by the deformation of the actuator 4.

[0039] Figure 2 An exemplary embodiment of an inductive sensor device according to the present invention is shown. The sensor device has an LC resonant circuit 5 having an inductive element L and a capacitive element C. The sensing element represents a part of the sensor device and provides functionality for detecting positional changes of metallic and / or ferromagnetic actuating elements. In the illustrated embodiment, the resonant circuit 5 is a parallel resonant circuit coupled to an excitation source 6 via a decoupling resistor 7. The excitation source 6 is a pin controller whose output pin provides an excitation signal to the resonant circuit 5. In the illustration, the resistance value of the decoupling resistor is 5 kΩ. An evaluation device for evaluating the signal drop across the resonant circuit includes a rectifier 8 and a capacitor C. D (Also known as C_D), together they form the rectifier circuit, as well as ADC 10 and resistor 9 and capacitor CG, which are used to smooth the signal, but are not absolutely necessary for the actual function.

Claims

1. A motor vehicle having an actuation device (1) mounted thereon, the actuation device being a door handle or a vehicle cover, the actuation device having an inductive sensor device for detecting positional changes of an actuating element, and a metal actuating element (4) that, upon actuation, changes position relative to the inductive element L, characterized in that: The sensor device has at least the following components: - An LC resonant circuit with an inductor L and a capacitor C; - An excitation source, coupled to the LC resonant circuit via an excitation voltage U, to excite the LC resonant circuit. -A decoupling element placed between the excitation source and the LC resonant circuit. - An evaluation device for evaluating a signal that decreases through a resonant circuit. The operating frequency of the excitation source is 5 MHz to 10 MHz, and it is either a square wave pulse sequence output or a sine curve excitation signal.

2. The motor vehicle according to claim 1, characterized in that: The excitation source is configured to output an excitation voltage U having an operating frequency f corresponding to the natural frequency of the resonant circuit or tuned to the natural frequency of the resonant circuit.

3. The motor vehicle according to claim 1 or 2, characterized in that: The evaluation device has a rectifier circuit.

4. The motor vehicle according to claim 3, characterized in that: The rectifier circuit has a diode D and a capacitor C, which is connected in parallel to the resonant circuit.

5. The motor vehicle according to claim 3, characterized in that: The rectifier circuit is arranged between the LC resonant circuit and the ADC of the evaluation device, which is configured to use the ADC to detect the voltage value rectified at the rectifier circuit and identify the location change based on the detected voltage.

6. The motor vehicle according to claim 5, characterized in that: The evaluation device is configured to identify a positional change when the voltage exceeds an upper threshold voltage value or when it falls below a lower threshold voltage value.

7. The motor vehicle according to claim 1 or 2, characterized in that: The evaluation device does not have a rectifier circuit, and the analog-to-digital converter (ADC) of the evaluation device detects the voltage drop at the resonant circuit. The delay characteristics of the ADC are adapted to the operating frequency of the excitation source such that the minimum measurement duration of the ADC lasts for at least one cycle of the resonant circuit excitation.

8. The motor vehicle according to claim 7, characterized in that: The minimum measurement duration of the ADC ranges from 5 to 1000 resonant circuit excitation cycles.

9. The motor vehicle according to claim 7, characterized in that: The minimum measurement duration of the ADC ranges from 5 to 20 resonant circuit excitation cycles.

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