Capacitive sensor device for switching a door opening on a motor vehicle and bumper therewith

Abstract

Sensor device for detecting movement gestures on a motor vehicle (1), comprising a first capacitive electrode arrangement (2) and at least one control and evaluation device (4) coupled to the first electrode arrangement (2), which detects a change in the capacitance of the first electrode arrangement (2) relative to a reference potential by periodically charging and discharging the first electrode arrangement (2) at a predetermined frequency and evaluating at least one parameter of a current or voltage curve dependent on the periodic charging and discharging of the first electrode arrangement (2) in order to detect the change in capacitance, characterized in that the first capacitive electrode arrangement (2) is an elongated, sectionally segmented electrode arrangement (2), wherein the segments are arranged in the longitudinal direction and enable sectionally different capacitive detection.

Description

[0001] The invention relates to a capacitive sensor device with an electrode arrangement, with the aid of which the intrusion of an object into a space in front of the electrode arrangement is to be detected, a control and evaluation circuit coupled to the electrode arrangement, which detects a change in the capacitance of the electrode arrangement with respect to a reference potential by periodically charging and discharging the electrode arrangement at a predetermined frequency and evaluates at least one parameter of a current or voltage curve dependent on the periodic charging and discharging of the electrode arrangement in order to detect the change in capacitance.

[0002] A capacitive sensor device with an electrode, with the aid of which the approach of an object is to be detected, and with a control and evaluation circuit coupled to the electrode, which detects a change in the capacitance of the electrode with respect to ground by periodically coupling the electrode to an operating voltage at a predetermined frequency and evaluating at least one parameter of a current or voltage curve dependent on the periodic charging and discharging of the electrode in order to detect the change in capacitance, is known, for example, from US patent 5,730,165 or the corresponding patent specification DE 196 81 725 B4.The parameter of a current or voltage curve dependent on the periodic charging and discharging of the electrode is a voltage measurable across a capacitor, which depends on the charge accumulated on the capacitor. This charge is accumulated by periodically charging the electrode by coupling it to the operating voltage and then discharging it via the capacitor by coupling it to the capacitor. Another such capacitive sensor is known from patent EP 1 339 025 B1.

[0003] A capacitive sensor device comprising an electrode, a ground background electrode arranged at a distance behind the electrode, and a shielding electrode arranged between the electrode and the ground background electrode, which is coupled to the electrode via a control and evaluation circuit such that its potential tracks the potential of the electrode, is known, for example, from publications EP 0 518 836 A1, US 6,825,752 B2, DE 101 31 243 C1, and DE 10 2006 044 778 A1. The provision of a shielding electrode between the electrode and the background electrode at ground potential, as known from these publications, has the advantage of increasing the sensitivity of the capacitive sensor thus formed to changes in the space in front of the electrode, for example, due to the introduction of objects.This is primarily due to the fact that the field propagating from the electrode extends more strongly into the space in front of the electrode (detection zone), because a large portion of the field is no longer short-circuited to the background electrode, which is at ground potential, as would be the case without a shield electrode. Due to the fact that the shield electrode is coupled to the electrode in such a way that it tracks its potential, the strong electric field is created between the shield electrode and the background electrode; more importantly, however, practically no field develops between the electrode and the potential-tracking shield electrode.

[0004] The known arrangement of electrode, shielding electrode and background electrode is usually enclosed by an electrical insulator, for example a plastic, so that an insulator layer, for example a plastic layer, is located on the electrode and thus between the electrode and the space to be monitored in front of the electrode, i.e. the detection area.

[0005] Such electrodes can be used to operate a motor vehicle door, such as the tailgate. Electrodes can be used to detect the approach of a body part, such as a swinging movement of a leg under the bumper, and transmit this information to a control device in the vehicle as a command to open or close the tailgate.

[0006] DE 20 2006 013 337 U1 describes an anti-pinch device for a motor vehicle, consisting of a motor for actuating a pivoting actuator, a sensor for contactless obstacle detection, and a control unit. The sensor comprises an electrode with several radially arranged segments that generate an external electric field. The segments can be evaluated individually, so that an interference signal can be used to control the motor to stop or modify the movement of the actuator when an obstacle is detected.

[0007] DE 10 2007 026 307 A1 discloses an arrangement for generating a signal indicating the presence of an object in an observation area. The arrangement comprises a transmitting electrode device for emitting an alternating field and a receiving electrode device connected to an amplifier circuit. This configuration is intended to reduce false detections due to external influences, such as water exposure.

[0008] DE 20 2006 009 188 U1 describes an anti-pinch sensor with an evaluation circuit for obstacle detection in vehicle systems. The anti-pinch sensor comprises an electrode for generating an external electric field against a counter electrode and a pressure-sensitive sensor that detects mechanical pressure independently of the electrode.

[0009] EP 2 159 362 A1 relates to a motor vehicle with automatic flap operation. Horizontal and vertical capacitive sensors are used to trigger an opening or closing signal by changing the capacitive coupling in their surroundings.

[0010] DE 10 2008 063 366 A1 discloses a contactless device for actuating movable vehicle parts, such as trunk lids or side doors. The device uses two capacitive sensors with separately definable detection areas to activate the actuation by detecting objects in the respective areas.

[0011] One problem with the known devices is that they can lead to false detections, which trigger unwanted switching or actuation processes if movements of objects are misinterpreted by the sensors.

[0012] The object of the invention is to provide a reliable sensor system that reduces the error detection of actuation requests.

[0013] According to the invention, this object is achieved by a capacitive sensor device having the features of claim 1.

[0014] The sensor device according to the invention comprises a capacitive electrode arrangement and at least one control and evaluation device coupled to the electrode arrangement. The control and evaluation device detects a change in the capacitance of the electrode arrangement relative to a reference potential by periodically charging and discharging the electrode arrangement at a predetermined frequency and evaluating at least one parameter of a current or voltage curve dependent on the periodic charging and discharging of the electrode arrangement to detect the change in capacitance.

[0015] At least one elongated, sectionally segmented, capacitively detecting first electrode arrangement is formed, wherein the segments are arranged in the longitudinal direction and enable sectionally different capacitive detection.

[0016] The control and evaluation device carries out the periodic charging and discharging, for example, by periodically coupling the electrode of the first electrode arrangement to a predetermined potential, for example, the operating voltage potential, at the predetermined frequency. The voltage curve can, for example, be the voltage curve at the terminal of the first electrode. The parameter can, for example, be a voltage measured across a charge-accumulating capacitor or a specific number of charging and discharging periods until a switching threshold is exceeded by a voltage measured at the first electrode arrangement.

[0017] The segmented electrode array has regions with different capacitive sensitivities along its length or is formed from alternating sections of multiple electrodes. This means that the segmented electrode array allows for different detection in the direction of the first electrode's length, depending on its position along the first electrode. A body part that is moved along the first electrode array generates different detectable signals at the first electrode array depending on its position, provided the distance of the body part from the electrode array does not change. This device therefore allows the detection of a movement along the segmented electrode array by repeatedly interrogating this segmented electrode array.If changes in signal values ​​occur at the segmented electrode array during repeated scans, this indicates movement along the electrode array. This allows movements that represent an operating gesture to be more reliably distinguished from other movements.

[0018] The segmented electrode arrangement can be formed as a continuous electrode with segmented insulation or shielding (e.g., coaxial cable with segmented shielding removed). Alternatively, multiple segments of separately controlled and interrogated electrodes can be arranged in a line or offset by segments. The number of segments is at least two, but there is no upper limit.

[0019] The first electrode array is positioned, for example, in a rear bumper to monitor the area behind and below the bumper. The environment of the devices describes the installation environment of the devices in the vehicle. This covers both the environment in the rear area and the area below the rear area of ​​the vehicle. The signal patterns of the first electrode array are repeatedly queried (e.g., in response to the detection of an ID transmitter from a keyless entry system).

[0020] A predetermined gesture from a user, e.g. a simulated kick under the bumper, is intended to trigger an opening or closing action. For this purpose, the first electrode array is interrogated. Due to its segmented design, this array detects not only an approach but also movement along the array's longitudinal axis. If, for example, the electrode segments are a few centimeters long, a rapid change in signal strength (either due to segmented shielding or due to interrogation of segmented electrode sections) indicates movement along the longitudinal axis. This makes it possible to filter out a gesture that, for example, would be performed by a child playing kicking a ball behind the vehicle or would be caused by an animal.

[0021] It is crucial that the segmented electrode array allows for the detection of a change in the position of the detected body along the array's length through repeated signal interrogation. If the segmented electrode array is formed from three different electrodes with alternating segments (in the pattern 1-2-3-1-2-3- etc.), even the directional detection of the movement is possible.

[0022] In a preferred embodiment, the first electrode arrangement consists of an elongated continuous conductor which has alternating sections with different shielding.

[0023] Such electrode arrays are particularly easy to manufacture, since the insulation or shielding (e.g., braiding in coaxial cables) only needs to be removed in sections from commercially available cables. Furthermore, a wire can also be used that is mounted in a holder with varying shielding along its length. The wire then acquires its segmented properties as an electrode array by being inserted into the holder with different shielding effects in each segment.

[0024] In another design, the first electrode arrangement consists of two electrodes, each segmented at different distances from the detection area or provided with opposing shielding. Such an electrode arrangement can be realized, for example, by wrapping two separate electrodes around a rod in a phase-shifted manner. The electrodes run longitudinally at different distances and with different shielding (alternating between those in front of and behind the rod).

[0025] Such an electrode arrangement allows not only the detection of an approach but also the detection of the direction of movement in front of the electrode arrangement. For this purpose, the sequence of sensor signals is recorded and the direction of travel of a signal maximum is determined.

[0026] Advantageous and / or preferred embodiments are characterized in the subclaims.

[0027] The invention will now be explained in more detail with reference to the accompanying figures. Fig. 1 shows the arrangement of a first embodiment of the sensor device according to the invention on a motor vehicle; Fig. 2 shows the arrangement of Fig. 1 in a schematic plan view; Fig. Figure 3a shows a first segmented electrode arrangement for use in a device according to the invention; Fig. Figure 3b shows a schematic signal curve when detecting a longitudinal movement with an electrode arrangement of Fig. 3a; Fig. Figure 4a shows a second segmented electrode arrangement for use in a sensor device according to the invention; Fig. Figure 4b shows a schematic signal curve when detecting a longitudinal movement with an electrode arrangement of Fig. 4a;

[0028] In Fig. 1 shows the rear of a vehicle 1. A segmented electrode arrangement 2 is mounted in the area of ​​the rear bumper. A further electrode arrangement 3 is arranged below the electrode arrangement 2. The electrode arrangements 2 and 3 are each connected to control and evaluation devices located in a vehicle control unit 4 (see Fig. 2). The electrodes are charged via this device, and their capacitance change upon approach of a body, e.g., a part of the operator's body, can be detected by charge analysis. This principle of a capacitive sensor is well known in the field of automotive engineering.

[0029] The electrode arrangement 3 runs essentially parallel to the electrode arrangement 2. However, the arrangement 2 is segmented. The segmented design is such that the arrangement 2 has regions with varying detection sensitivity in the direction of the bumper's extension. This electrode arrangement 2 can therefore detect both an approach (through an absolute change in the detected signal) and a movement of a body along the segments. If the body is positioned in front of the electrode arrangement in such a way that more segments or larger sections with higher detection sensitivity lie behind the body than segments with lower detection sensitivity, the detected signal is higher than if the body is positioned in front of the electrode arrangement in such a way that more segments or larger sections with lower detection sensitivity lie behind the body than segments with higher detection sensitivity.If the body moves along the array, this is detected by a signal fluctuation that can be measured with the evaluation device. The segments' longitudinal dimensions should be adjusted to the desired detection accuracy; for example, they can each have a length of 5 cm to 30 cm.

[0030] At the operator's request, for example, an operator can move their lower leg in a pivoting motion under the bumper. This movement and approach is detected by both the segmented electrode array 2 and the electrode array 3, as the capacitance change is repeatedly queried and evaluated over time.

[0031] However, an opening command is only generated by the central control unit 4 if the device 2 does not register a transverse movement above a permissible threshold during a time query. Only a straight gesture directed toward the vehicle should be interpreted as an opening command. Accordingly, the entirety of the detected signals is evaluated to enable a reliable interpretation of an opening gesture.

[0032] The arrangement can be supplemented with further segmented electrode arrangements.

[0033] Fig. Figure 3a schematically shows a possible design of a segmented electrode arrangement. An electrode 10 is guided in a holder 11. The holder 11 surrounds the electrode 10 in sections, thus forming segments with greater and lesser shielding.

[0034] An object 15 can move transversely in front of the segmented electrode array. Depending on its position, it is primarily located in front of more or less shielded areas.

[0035] Fig. Figure 3b shows an idealized temporal signal curve for evaluating the signal during a uniform movement of the object in front of the electrode array. The average signal strength (or offset) is determined by the proximity of the object to the electrode array. However, the fluctuation is caused by the object's movement in the longitudinal direction of the electrode array. Through appropriate empirical evaluation and determination of characteristic values, a signal curve 20 caused by a moving object can be distinguished from a curve 21 caused by a targeted movement (swinging the leg toward the electrode array).

[0036] Fig. Figure 4a shows an alternative design of a segmented electrode arrangement with two separate capacitively sensed electrodes 30, 31. These are located in sections at varying distances from the object 15 to be detected.

[0037] Fig. Figure 4b again shows a signal curve that represents the temporal signals from both electrodes during a transverse movement (solid lines) and a directed operating gesture (dashed lines). Here, too, the different signal curves are clearly distinguishable, increasing the reliability of interpreting the sensor signals.

Claims

[1] Sensor device for detecting movement gestures on a motor vehicle (1), comprising a first capacitive electrode arrangement (2) and at least one control and evaluation device (4) coupled to the first electrode arrangement (2), which detects a change in the capacitance of the first electrode arrangement (2) relative to a reference potential by periodically charging and discharging the first electrode arrangement (2) at a predetermined frequency and evaluating at least one parameter of a current or voltage curve dependent on the periodic charging and discharging of the first electrode arrangement (2) to detect the change in capacitance, characterized by that the first capacitive electrode arrangement (2) is an elongated, sectionally segmented, electrode arrangement (2), wherein the segments are arranged in the longitudinal direction and enable sectionally different capacitive detection. [2] Sensor device according to claim 1, wherein the segmented first electrode arrangement (2) is formed by a shielding (11) of an electrode (10) which is different in sections in the longitudinal direction. [3] Sensor device according to claim 1, wherein the segmented first electrode arrangement (2) is formed by alternating longitudinal arrangement of at least two separately controllable electrodes (30, 31). [4] Sensor device according to one of the preceding claims, wherein the segmented first electrode arrangement (2) can be interrogated by the evaluation device (4) in order to detect a temporal signal profile (20, 21). [5] Sensor device according to one of the preceding claims, wherein a second electrode arrangement (3) is provided which is arranged spatially offset from the segmented first electrode arrangement (2). [6] Sensor device according to claim 5, wherein the second electrode arrangement (3) is formed from a homogeneous electrode. [7] Sensor device according to claim 5, wherein the second electrode arrangement (3) is also a segmented electrode arrangement. [8] Sensor device according to one of claims 5 to 7, wherein a third electrode arrangement is present which is formed from a homogeneous electrode and is arranged offset from the first two electrode arrangements (2, 3). [9] A bumper with a sensor device according to any one of the preceding claims, wherein the segmented first electrode arrangement (2) is arranged in the bumper.

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