Adjustment device for a head rest of a motor vehicle seat

The invention relates to an adjustment device for a headrest of a vehicle seat.

A headrest is used in a motor vehicle seat to support the head of a vehicle occupant using the seat in a crash and thus to avoid kinking of the cervical spine backwards. The saving from the headrest safety gain is in full but only reached when the headrest is adjusted with respect to the vertical head position at the right height, so that the head in a crash essentially hitting a purpose must be the center of the headrest. An incorrectly adjusted headrest can, however, result in a crash injuries in the neck and head area. To minimize the risk of a head injury, such as a concussion during the impact of the head on the headrest, the headrest should be arranged in a horizontal direction as close to the head of the vehicle occupant, but nevertheless allow a clear head movement.

For correct positioning of a headrest, this is usually adjustable in a vertical direction and partially in the horizontal direction with respect to the seat back. In a high-quality automotive seat adjustment of the headrest is frequently motorized.

To avoid incorrect positioning of the headrest of a modern headrest moving device a detector device is sometimes associated with that detects the head position of a vehicle occupant relative to the associated headrest. For example, one of<patcit id="pcit0001" dnum="EP1857318A2"><text>EP 1857318 A2</text></patcit> known headrest moving device a detector device assigned in the form of an integrated in the headrest capacitive proximity sensor. This proximity sensor comprises three electrodes that are spaced in the vertical direction to each other are arranged on the front side of the headrest. The two outer electrodes here serve as transmitting electrodes for radiating an alternating electric field in a arranged in front of the headrest room area. The middle electrode serves as a common receiving electrode for measuring the capacitance formed between each of the transmitting electrodes and the receiving electrode. The known adjusting device based on the principles that will change the capacitance of the electrode assembly by the presence of the head in the alternating electric field in a characteristic manner. The deviation of the headrest position from a predetermined desired vertical position relative to the head of the vehicle occupant is determined by comparison of the two transmitting electrodes respectively associated capacitance values. As desired position for the headrest in this case that of headrest position is detected when these capacitance values ​​are identical.

Similar headrest moving devices with a comprehensive three electrode capacitive proximity sensor for detecting the head position are further also from <patcit id="pcit0002" dnum="FR2884775A1"><text>FR 2884775 A1</text></patcit> and <patcit id="pcit0003" dnum="DE19916804C1"><text>DE 199 16 804 C1</text></patcit> known.

The invention has for its object to provide an improved contrast headrest moving device.

This object is according to a first variant of the invention achieved by the features of claim 1. Accordingly, the headrest moving device includes an integrated in the headrest or for integration provided in the headrest capacitive proximity sensor, said proximity sensor at least three mutually spaced vertically arranged transmitting electrodes and a common receiving electrode having. The term "vertical" is based on high the intended installation position of the proximity sensor in a motor vehicle.

The adjustment device further comprises an actuator for motorized adjustment of the headrest in the vertical direction relative to the vehicle seat and a control unit for controlling the actuator in accordance with a detected by the proximity sensor head position of the vehicle seat-use vehicle occupants. The control unit is in this case - in terms of circuitry and / or programming technology - designed to carry out a control method in which the transmitting electrodes are driven to emit an alternating electric field, are at whatever detected by the receiving electrode receiving electric signals respectively associated measured capacitance values ​​determined, the information on included between each of the transmitting electrodes and the receiving electrode are each formed capacitance, and wherein in accordance with these measured capacitance values ​​of the actuator is actuated for setting a desired vertical position of the headrest relative to the head position.

According to a second variant of the invention the above object is independently achieved by the features of claim 3. The subsequently specified headrest moving means corresponds substantially to the variant of the invention described above. Instead of the at least three transmitting electrodes but includes the proximity sensor according to the second variant of the invention at least three mutually spaced vertically disposed receiving electrodes. Instead of the common receiving electrode is a common transmitter electrode is provided according to the second variant of the invention.

With regard to the underlying physical principles and of the invention aimed at in accordance effect both variants of the invention are substantially equivalent to those described above. In particular, the exchange of transmitting and receiving electrodes - except for a sign change - not affect the characteristics of the propagating due to the proximity sensor in the space in front of the headrest alternating electric field.

The inventive electrode arrangement of the proximity sensor are systemic maladjustments of the headrest, which can not be excluded in the known adjusting devices, safely avoided. Namely, while a purely extensive three electrode proximity sensor by comparing the capacitances formed between these electrodes only parts of the body of the vehicle occupant are detected, their distance from the sensor arrangement (ie, minimum or maximum) is extremal, can be detected in addition to the inventive electrode arrangement, whether the sensor opposite body portion of the vehicle occupant is convexly or concavely curved. This in turn allows a clear distinction to the desired target position, in the center of the head restraint at about the level of the (convex) head of the vehicle occupant is adjusted by an undesired headrest position in which the headrest about the same level as the (concave) neck of the vehicle occupant is set.

According to a preferred embodiment of the invention - in the case of the first variant of the invention - at least three transmitting electrodes sequentially in time, ie according to a time division process, driven. The signal received by the common receiving electrode total received signal thus divided into temporally well separated individual receive signals which are each assigned to a particular transmitting electrode. From each of these single-reception signals can be calculated very simply, the capacitance formed between the receiving electrode and the associated transmitting electrode. In the case of the second variant of the invention, the single transmitting electrode there is expediently driven continuously or periodically pulsed to emit the alternating field. In this case, the control unit of each of the at least three receiving electrodes is supplied with a separate receiving signal from which, in turn, can calculate the capacitance formed between the associated receiving electrode and the common transmitting electrode. The receiving electrodes are preferably respectively read at the same time. To simplify the implemented in the control unit readout circuit, the receiving electrodes can also be read out sequentially in time.

Other further developments are described in the following for reasons of simplicity, only the first variant of the invention in more detail. Each of these embodiments is, however, correspondingly applicable in the invention also to the second variant of the invention, whereby the advantages described below can be realized. Pursuant to the second variant of the invention, the terms "transmitting electrode" and "receiving electrode" to exchange in the text below, mutatis mutandis.

In order to enable a particularly simple numerical evaluation of the received signals, the electrodes of the proximity sensor according to the invention are preferably arranged spatially to one another, that all transmitting electrodes to the common receiving electrode have the same distance. This is achieved in a particularly advantageous solution provides that the common receiving electrode is formed by an elongated vertically electrodes field that at least substantially covers the area occupied by all transmitting electrodes vertical portion of the headrest surface. Optionally, the common receiving electrode also comprise a plurality of such electrode arrays which are shorted together.

The or each electrode array of the common receiving electrode can here flank the at least three transmitting electrodes outside. To achieve a particularly large sensor range but showing an alternative sensor arrangement has proven to be especially advantageous, wherein each of the at least three transmitting electrodes positioned in two on the same vertical height and horizontal spaced-apart electrode arrays is divided between which the common receiving electrode - in particular approximately centrally - runs , This sensor array is - regardless of the other characteristics of the headrest moving device - regarded as an independent invention.

to order based on the received signals to determine the target position of the headrest in a particularly simple and precise manner, at least two of the transmitting electrodes in the vertical direction are expediently symmetrical with respect to the center of the headrest, ie, disposed above or below the headrest. As part of the implemented in the control unit control method that these transmitting electrodes associated measured capacitance values ​​and at least one other measured capacitance value to be comparatively evaluated to recognize the achievement of the desired vertical position.

By comparing the measured capacitance values ​​of the two symmetrically arranged transmitting electrodes a headrest position with extremalem, ie minimum or maximum distance from the center to the vehicle occupant is thereby recognized it conveniently by the control unit that the values ​​of these two measured capacitance values ​​intersect on reaching this headrest position, ie assume the same value , Whether the distance formed in this headrest position between the vehicle occupant and the center of the headrest is minimal or maximal, ie whether the proximity sensor opposite body portion is convex or concave, is suitably recognized at the amount of the third measured capacitance value in comparison to the amount of the intersecting measured capacitance values , The headrest position is only accepted as the setpoint position, if this analysis shows that the distance between the vehicle occupant and the center of the headrest in this headrest position is minimal.

To quickly, but precisely to approach the target position of the headrest, without headrest overshoot to a significant degree on the desired position, the displacement of the actuator under the implemented in the control unit control method is based on the measured capacitance values ​​preferably before reaching the target position continuously or in several stages reduced.

In a first embodiment of this variant of the method comprises the associated proximity sensor more than three, in particular five, to each other with vertical spaced transmitting electrodes. The control unit in this case the travel speed of the actuator is then lowered by a predetermined amount when the measured capacitance values ​​of two adjacent terminal electrodes cross magnitude.

Alternatively or additionally, is optionally provided that in the course of the control process by the control unit, the travel speed of the actuator is reduced when the measured capacitance value of the at least three transmitting electrodes an extreme value, ie a minimum or maximum exceeds.

In a preferred embodiment of the implemented in the control unit control method is tested by the control unit first determines whether there is ever the head of a vehicle occupant within the detection range of the proximity sensor. For example, the control unit for this purpose by a so-called scan, in which continuously or periodically repeated vertical the headrest at least one measured capacitance value, preferably all measured capacitance values ​​are compared with a stored threshold value, which indicates the presence of the vehicle occupant in the detection area of ​​the proximity sensor. Alternatively, the change of one or more measured capacitance values ​​over the adjustment of the headrest can be detected, and concluded from this change in the presence or absence of a vehicle occupant in the detection area of ​​the proximity sensor. According to the method, the control unit in this case a whenever the whole control range of the headrest no head position can be determined, the headrest to a stored standard setpoint position. With this standard target position is in particular a so-called 2/3 of position, in which the headrest is extended to about two-thirds of its vertical displacement path upward. These 2/3 position has been found to be the optimum for the average vehicle occupant adjustment of the headrest. In Figure 2/3 position, therefore, an at least acceptable protective effect is obtained even without occupant-specific adjustment of headrest height for most vehicle occupants. The setting of Figure 2/3 position in the case of failing detecting a head position for this paragraph is generally considered without the other features of the adjustment as an independent invention.

When the headrest is preferably a four-way head restraint is adjustable both vertically and horizontally, ie up, down, front and back. The terms "vertical" and "horizontal" are in this case be regarded as approximations to the adjustment of the headrest. In particular, the vertical adjustment of the headrest is arranged approximately parallel to the orientation of the backrest of the vehicle seat, and can therefore be also slightly inclined to the vertical of the surrounding space. The horizontal adjustment of the head restraint is in particular approximately perpendicular to the horizontal displacement, and can therefore also be slightly tilted with respect to the horizontal direction of the surrounding space. Also can be a formed of 90 ° slightly divergent angle between the horizontal displacement and vertical displacement. The horizontal actuator degree of freedom of the headrest can also be formed by a tilting of the headrest about a horizontal axis.

To activate the four-way headrest adjustment which preferably comprises a further actuator, with which the headrest, ie, at least one of the vehicle occupant as intended facing front surface of the headrest can be adjusted horizontally. As part of the implemented in the control unit control method in this case the headrest of further actuator is actuated for setting a horizontal target position of the headrest preferably after setting the desired vertical position. This horizontal target position is in this case determined by comparing at least one measured capacitance value with a stored threshold. For this purpose, by the control unit, in particular a measured capacitance value used, which is associated with a medium, in particular approximately in the center of the head restraint arranged transmitting or receiving electrode.

Erkan Term Ate show the measured capacitance values ​​of the capacitive proximity sensor also systemic, ie. Without the presence of a vehicle occupant, a certain dependence on the horizontal headrest position Reason for this system-related function are especially metal components of the headrest. Such metal components forming the electrodes of the proximity sensor parasitic capacitances whose size varies from the horizontal the headrest from the spacing changing to the electrodes of the proximity sensor.

To eliminate or at least reduce these disturbances, in the context of the proximity sensor according to the invention - as per se already made <patcit id="pcit0004" dnum="EP1957318A2"><text>EP 1957318 A2</text></patcit> known - a metal, in particular grounded shield be provided behind the electrodes of the proximity sensor. However, experiments have shown that such a shield disadvantageously limits the detection range of the proximity sensor.

Preferably, therefore, the system-related function of the or each relied on for adjusting the horizontal target position measured capacitance value is compensated numerically. For this purpose the said measured capacitance value is normalized by the control unit and in particular a stored system characteristic that reflects the systemic, ie unaffected by a vehicle occupant during the measured capacitance value depending on the horizontal headrest position.

For fast, but precise Anfahrung the horizontal target position and the positioning speed of the further actuator is reduced when approaching the horizontal target position continuously or in several steps in an expedient embodiment of the control method by the control unit. The control unit controls the actuator speed in this case in particular by comparing the measured capacitance value with multiple staggered thresholds, the setting speed of another actuator is always lowered intermittently in several steps if the measured capacitance value exceeds one of these thresholds.

All procedural aspects of the invention described above are also considered in itself, in particular, irrespective of their automated execution by the control unit, as an independent invention.

Embodiments of the invention are explained in detail using a drawing. Therein:<dl id="dl0001" compact="compact"><dt>Fig. 1</dt><dd>in a roughly schematic cross-section of the head of a vehicle occupant and a headrest with an associated adjusting device which comprises a capacitive proximity sensor, a control unit, a vertical actuator for adjustment of the vertical headrest position and a hori- tal-actuator for adjustment of horizontal headrest position,</dd><dt>FIG. 2</dt><dd>in a schematic block diagram of a first embodiment of the adjusting device according to <figref idrefs="f0001">Fig. 1</figref>.</dd><dt>Fig. 3</dt><dd>according to a schematically simplified block diagram of a control unit of the adjustment <figref idrefs="f0002">FIG. 2</figref>.</dd><dt>Fig. 4</dt><dd>in two superimposed charts against the vertical headrest position the course of five measured capacitance values ​​of the proximity sensor (top graph) and the course of the function of these measurements set by the control unit actuating speed of the vertical actuator (lower diagram)</dd><dt>Fig. 5</dt><dd>in a schematic side view of the head of the vehicle occupants and positioned at head height headrest, as well as a schematic diagram in comparison to the respective amount of the estimated in this position measured capacitance values,</dd><dt>Fig. 6</dt><dd>according to representation <figref idrefs="f0004">Fig. 5</figref> the head and the neck height here positioned on the headrest and again in comparison to the respective amount of the estimated in this position measured capacitance values,</dd><dt>Fig. 7</dt><dd>in three diagrams superimposed the history of a measured capacitance value in the presence of a head and accordingly this one (system) characteristic of the system-related function of the measured capacitance value of the horizontal headrest position (top graph), the course of the same measured capacitance value in the presence of the head normalized against the horizontal headrest position, on the system characteristic (middle panel), and the course of the set as a function of normalized measured capacitance value setting speed of the horizontal actuator (lower diagram) </dd><dt>Fig. 8</dt><dd>according to representation <figref idrefs="f0002">FIG. 2</figref> A second embodiment of the adjusting device,</dd><dt>Fig. 9</dt><dd>according to representation <figref idrefs="f0002">Fig. 3</figref> the control unit of the adjusting device according to <figref idrefs="f0005">Fig. 8</figref>.</dd><dt>Fig. 10-12</dt><dd>Various other embodiments of the proximity sensor.</dd></dl>

Corresponding parts and quantities are always provided in all figures with the same reference numerals.

<figref idrefs="f0001">Fig. 1</figref> shows in a schematically simplified representation of a (vehicle) seat 1, is shown by the excerpts of only the upper part of a seat back. 2 <figref idrefs="f0001">Fig. 1</figref> continues to show a mounted on the seat back 2 Headrest 3 for the head 4 of the seat 1-use vehicle occupant 5. In the seat 1 is in particular to the driver or passenger seat of a passenger car.

The headrest 3 is a so-called 4-way headrest, both in a vertical direction 6 and in a horizontal direction 7 is adjustable relative to the seat. 1 The terms "vertical" and "horizontal" are here understood as "gritty" details the approximate specification of the adjustment directions. In particular, the vertical direction 6 is oriented approximately parallel to the longitudinal extension of the seat back 2, and slightly inclined with the respect to the space vertical. The horizontal direction 7 is arranged approximately at right angles thereto and extending in the installed state of the headrest 3 is approximately parallel to the longitudinal direction of the vehicle. The vertical direction 6 is directed to as upward, the horizontal direction 7 as directed forwards assumed wherein the terms "top", "bottom" refer, "front" and "back" to the intended installation position of the headrest 3 in the motor vehicle , As front or front side corresponding to the side of the headrest 3 is referred to, which faces the head 4 of the vehicle occupant. 5

The headrest 3 comprises an approximately cup-shaped back part 8 of metal and / or a contract-resistant plastic and a held therein forming front part 9. On the back part 8, two runs in the vertical direction 6 support rods 10 attached, with which the headrest 3 in the usual manner on the seat back 2 is anchored. About the support rods 10, the headrest 3 in the vertical direction 6 is slidably guided in a headrest support 11 of the seat back. 2

The front part 9 of the headrest 3 comprises a support shell 13, which is formed in particular by a contract proof plastic part. The carrier shell 13 carries on its front a bolster 14 to bolster 14 is again a coating 15 made of textile material, leather or the like. When applied, the outer skin forms the front of the headrest 3 toward the same.

The front part 9 of the headrest 3 is performed in the horizontal direction 7 slidably mounted on the back. 8 This guide is for example formed among others by a fixed to the front part 8 rack 16, which runs in a support 17 of the back section. 8

<figref idrefs="f0001">Fig. 1</figref> shows the headrest 3 at the top of its vertical displacement path V and the rear edge of its horizontal displacement path H. The opposite positions of the back portion 8 at the bottom of the vertical displacement path V and the front portion 9 are at the leading edge of the horizontal displacement path H in <figref idrefs="f0001">Fig. 1</figref> indicated by dashed lines. Within the vertical displacement path V and the horizontal displacement path H, the headrest position is continuously adjustable.

To adjust the headrest 3 that is associated with an adjusting 20th This comprises a capacitive proximity sensor 21, a (vertical) Actuator 22 for vertical adjustment of the headrest 3, a (horizontal) Actuator 23 for horizontal adjustment of the headrest 3 and a control unit 24th

The proximity sensor 21 is arranged inside the headrest 3 between the carrier shell 13 and the bolster 14th It can alternatively also between the bolster 14 and the coating 15, and thus be directly placed under the front surface of the headrest. 3

The actuator 22 is disposed within the seat back 2 and acts in a known manner to the support bars 10 of the headrest 3. The actuator 23 is arranged inside the headrest 3 and acts to adjust the front portion 9 with respect to the back portion 8 with the rack 16 together ,

The preferably also arranged in the headrest 3 control unit 24 is connected via data lines 25, 26 and 27 with the proximity sensor 21 and the actuator 22 and the actuator 23rd The data line 26 is in this case guided by one of the support rods 10 of the headrest 3 in the seat back the second By one of the support rods 10 (not shown) supply lines for the electrical supply of the actuator 23 and the control unit 24 are also guided.

<figref idrefs="f0002">FIG. 2</figref> shows a first embodiment of the adjusting device 20 in greater detail. As this illustration in conjunction with<figref idrefs="f0001">Fig. 1</figref> It is apparent from a flat support 30. On includes the proximity sensor 21 to the carrier, an electrode assembly is applied, which is formed of five transmitting electrodes 31a to 31e and a common receiving electrode 32nd The support 30 is formed of a preferably flexible plastic film. The electrodes 31 a to 31 e and 32 are formed by preferably also flexible metal foils, which are glued to the carrier 30, for example. Alternatively, the electrodes may be 31 a to 31 e and 32 applied in the form of a coating on the carrier 30th

The carrier 30 extends both in the vertical direction 6 and in a perpendicular thereto vehicle transverse direction 33 over a vast area of ​​the headrest 3. In particular, the carrier 30 is located approximately centered at a center 34 of the headrest 3, the determination according to the head 4 in crash to open case.

The electrodes 31 a to 31 e and 32 are arranged in turn distributed over a large part of the surface of the carrier 30th The receiving electrode 32 is formed in the form of an elongate strip in this case by an electrode array 35 which is disposed in the vehicle transverse direction 33 centrally on the carrier 30 and extending in the vertical direction 6 over the whole of the transmitting electrodes 31 a to 31 e occupied height range. Each of the transmitting electrodes 31 a to 31 e is divided into two mutually shorted electrode pads 36 and 37, with the electrode pads 36 and 37 of the same transmitting electrode 31a extend to 31 e respectively on the same vertical height in vehicle transverse direction 33 left or right of the receiving electrode 32nd The electrode arrays 36 and 37 of the various transmitting electrodes 31 a to 31 e are mutually respectively aligned with distance stacked in the vertical direction. The electrode arrays 36 and 37 of the transmitting electrode 31 a in this case are at the bottom, the electrode arrays 36 and 37 of the transmitting electrode 31 disposed uppermost e. The transmitting electrode 31 c is arranged in the vertical direction approximately centered with the center of the 34th d between the adjacent transmitting electrodes 31 and 31b or 31 b and 31 c and 31 c and 31 d or 31 and 31 e is formed in each case the same vertical distance. Also there are all electrode arrays 36 and 37 of the various transmitting electrodes 31 a to 31 e in always equidistant from the receiving electrode 32nd

Each of the transmitting electrodes 31 a to 31 e is connected to the control unit 24 under the data line 25 via a single line 38a to 38d separately. The receiving electrode 32 is connected as part of the data line 25 via a single line 39 to the control unit 24th To avoid parasitic capacitance in the data line 25, the single line 39 is electrically shielded by a so-called guard screen 40 in the form of a set at the ground potential M head, the single line 39 - in particular coaxially - surrounds. The guard screen 40 is both short-circuited to a ground input of the control unit 24th On the other hand, the guard screen 40 is optionally substituted with a - connected guard electrode 41 that surrounds the receiving electrode 32 annularly - optionally provided.

As <figref idrefs="f0002">FIG. 2</figref> is also clear, each is 22 and 23, a Hall sensor 42 associated with the actuators. The Hall sensors 42 respectively generate in cooperation with a (not shown) ring magnet which is coupled to the shaft of each actuator 22 and 23, a measurement signal on the basis of this, state variables of the respective actuator 22 or 23, such as the rotational position, calculate the speed and the distance adjustment path. Each of the data lines 26 and 27 accordingly comprises in addition to a control line 43 for driving the respective actuator 22 and 23, a measuring line 44 for returning the Hall signal to the control unit 24th

In the <figref idrefs="f0002">Fig. 3</figref> Control unit shown in detail 24 of the adjusting device 20 according to <figref idrefs="f0002">FIG. 2</figref> includes a frequency generator 45, a time multiplexer 46, a (capacitance) measurement module 47, two Hall modules 48 for controlling a respective one of the Hall sensors 42 as well as for evaluation of the returned Hall signal, and two motor control 49 for driving each of the actuators 22 and 23. the control unit 24 further comprises a microcontroller 50 which is control-connected to the frequency generator 45, the time multiplexer 46, the measurement module 47, the Hall-modules 48 and the motor controls 49th

In the microcontroller 50 is using software, a (more detail below described) implemented control program - focus - by triggering the proximity sensor 21 detects the position of the head 4 relative to the current headrest position and the headrest 3 according to the detected head position by driving the actuators 22 and 23 drives in a (vertical and horizontal) target position.

The implemented in the microcontroller 50 control process is started, for example by the starting of the motor vehicle engine. Optionally it is provided that the control method can also be started during vehicle operation at regular intervals and / or at the request of a user of the vehicle (for example, by pressing an appropriate control key).

In a first phase of the control method, the vertical target position of the headrest 3 is first set. For this purpose, the control unit 24 initially a search through. At the beginning of the search, the headrest 3 is at the bottom of its vertical displacement path V and the rear edge of its horizontal displacement path H. Otherwise, the headrest 3 is driven by the control unit 24 in this position.

Starting from there, causing the microcontroller 50 under the control of the actuator 22 via the respective engine control 49 a the headrest 3 upwards. The microcontroller 50 causes the frequency generator 45 for generating an alternating voltage with a frequency of preferably about 10 MHz, which is passed through the time division multiplexer 46 sequentially in time to each of the transmitting electrodes 31 a to 31 e of the proximity sensor 21st

Under the influence of this voltage, the transmitting electrodes 31a to 31e generate alternately in one of the headrest 3 upstream spatial area an alternating electric field F. In this alternating field F of each of the transmitting electrodes acts 31a to 31e with the receiving electrode 32 in an electrical sense as a condenser together, whose capacitance is detected by the measurement module 47th

Due to the sequential activation of the transmitting electrodes 31a to 31e decomposes due to the alternating field F in the receiving electrode 32 generated electrical signal in well-timed separate reception signals S_i (I = 1,2 ..., 5), each one of the transmitting electrodes 31 a to 31 e assigned. The following are, by definition, the received signal S₁ the transmitting electrode 31a, the reception signal S₂ the transmission electrode 31 b, the received signal S₃ the transmitting electrode 31 c, the reception signal S₄ the transmitting electrode 31 d and the reception signal S₅ the transmitting electrode associated 31e.

From each of these received signals S_i calculates the measurement module 47 an associated measured capacitance value C_i (I = 1,2, .... 5), and outputs this measured capacitance values ​​C_i continuously to the microcontroller 50 from. When the measured capacitance values ​​C_i is it generally to any measured variables that make up the capacitance formed between the associated transmitting electrode 31a to 31e and the receiving electrode 32 can be calculated. In the hereinafter described variant of the control method is in the measured capacitance values ​​C_i particular sizes, which are inversely proportional to the respective capacitance.

Located during the search of the head 4 of the vehicle occupant 5 within a detection range 51 (in <figref idrefs="f0001">Fig. 1</figref> indicated by dashed lines) of the proximity sensor 21, so influenced the head 4, the capacitances formed between the transmitting electrodes 31a to 31e and the receiving electrode 32nd This is partly due to the fact that the head 4 acts in the alternating electric field F as a dielectric, whereby the respectively considered capacity is increased. On the other hand, the influence of the head 4 due to the fact that the head 4 acts due to the ionic mobility in the human body and are always present in some extent grounding of the human body as a counter electrode, whereby the measurable capacitances between the transmitting electrodes 31 a to 31 e and the receiving electrode 32 lowered. In general, the latter effect predominates. Accordingly, the amount of the measured capacitance values ​​C increases_i all the more so the closer the head to the associated transmitting electrode 31 a to 31 e is approximated.

This effect is exploited during the search, in order to test whether any head position can be detected. Each of the measured capacitance values ​​C_i is determined using a stored threshold value C₀ (<figref idrefs="f0003">Fig. 4</figref>) compared. If all measured capacitance values ​​C_i over the entire vertical adjusting the threshold value V C₀ below, this is interpreted as an indication of this, that no head 4 is located within the detection range 51st The headrest 3 is advanced in this case, in the horizontal direction 7, after which the search is repeated. If over the entire adjustment range H and vertical adjustment can not determine head position V, moves the controller 24, the headrest 3 in the so-called 2/3 of-position in which the headrest 3 in the vertical direction 6 is about one-third of the vertical displacement path V to is extended toward the top. A corresponding value h_2/3 the vertical headrest position h is in <figref idrefs="f0003">Fig. 4</figref> schematically plotted. In Figure 2/3 position the headrest 3 is retracted to the rear edge of the horizontal adjustment travel H.

Unless otherwise the head 4 of a vehicle occupant 5 is within the detection range 51, through each measured capacitance value C₁ -C₅ in the vertical the headrest 3 is a characteristic maximum (see. <figref idrefs="f0003">Fig. 4</figref>). The maximum of the measured capacitance value C₃ this coincides with the adjusted nominal vertical position h_s together, namely those vertical headrest position h, at the center 34 of the headrest in the vertical direction 6 is arranged in the minimum distance to the head 4, while approximately the same height with the eye-ear-line of the head 4, (s. <figref idrefs="f0001">Fig. 1</figref>).

Since erkan purportedly due to measurement noise, the determination of the maximum of the measured capacitance value C₃ is associated with a comparatively large measurement errors, the attainment of the target position h_s not based on the measured capacitance value C₃But a more specific reference to the transmitting electrodes 31 b and 31 c associated measured capacitance values ​​C₂ and C₄ determined. As<figref idrefs="f0003">Fig. 4</figref> It can be seen, namely drops the target position h_s also about having crossing point 52 of the measured capacitance values ​​C₂ and C₄ together.

Erkan Term Ate is the intersection of the measured capacitance values ​​C₂ and C₄ but only a sufficient, not a necessary criterion for reaching the target position h_s, Rather, there is an intersection of the measured capacitance values ​​C₂ and C₄ - As a comparison of <figref idrefs="f0004">FIGS. 5 and 6</figref> shows - even if the center is 34 of the headrest 3 incorrectly set in the vertical direction 6 on the neck of the vehicle occupant 5 (<figref idrefs="f0004">Fig. 6</figref>). To switch between the target position h_s to distinguish and an incorrect adjustment of the headrest 3 to the neck of the vehicle occupant 5 is within the framework of the implemented in the microcontroller 50 control method in addition the measured capacitance value C₃ evaluated, which is associated with the mean transmission electrode 31 c. As a comparison of<figref idrefs="f0004">FIGS. 5 and 6</figref> shows the value of this measured capacitance value C₃ at the target position h_s greater than the value of the measured capacitance values ​​C₂ and C₄, Whereas in the case of an incorrect adjustment of the headrest 3 to the neck area of ​​the vehicle occupant 5 is reversed.

In an advantageous embodiment of the control method, the control unit 24 Notes recognizes the meaning of the above reaching the target position h_s because, in the headrest 3 upwards Conditions C₄ &lt;C₂ and C₃ &gt; C₄ are fulfilled. Once these conditions are met, the control unit 24 turns off according to the actuator 22nd

To prevent the headrest 3 when approaching the desired vertical position h_s This "overshoot", the microcontroller 50 by appropriate control of the actuator 22 associated motor controller 49 in consideration of the 48 supplied from the respective Hall-module speed values ​​the displacement d_v the actuator 22 before reaching the target position h_s in several stages successively reduced. As<figref idrefs="f0003">Fig. 4</figref> It can be seen, a first reduction of the adjustment takes place d_v when the top transmitting electrode 31e associated measured capacitance value C₅ the next lower transmitting electrode 31d associated measured capacitance value C₄ crosses. The adjustment speed d_v is once again lowered when the measured capacitance value C₄ the measured capacitance value C₃ crosses. To a possible "soft", ie jerk-free adjustment of the headrest to realize 3, the displacement d is_v intervening optional lowered a second time when the measured capacitance value C₄ the maximum exceeds (see dashed line in the lower diagram of <figref idrefs="f0003">Fig. 4</figref>).

When the vertical setpoint h_s the microcontroller 50 in a second phase of the control method, a horizontal reference position I_s on. To determine the desired position I_s starts the microcontroller 50 under the control of the actuator 23 is a horizontal scan, under which the front part 9 of the headrest 3 is moved up to the head. 4 Meanwhile pursuing the microcontroller 50 to the upper diagram of<figref idrefs="f0003">Fig. 7</figref> History measured capacitance value C shown₃,

For the numerical compensation of parasitic capacitances due to the metallic components of the headrest 3, the microcontroller 50 normalizes the detected measured capacitance value C₃ on a system characteristic K that the system-related function of the measured capacitance value C₃ reproduces from the horizontal headrest position. The system characteristic K is stored in the form of a list of nodes in the microcontroller 50, between which interpolates the microcontroller 50th AIternativ can also be stored in the form of an approximated model function, the system characteristic K. The course of a correspondingly normalized measured capacitance value C '₃ = C₃ / K (Question: Is that right) is in the middle diagram of <figref idrefs="f0003">Fig. 7</figref> shown.

To determine the horizontal target position I_s compares the microcontroller 50, the normalized measured capacitance value C '₃ with a stored threshold value C_H and switches the actuator 23 off when this threshold C_H is exceeded (see lower diagram in <figref idrefs="f0003">Fig. 7</figref>).

In order to prevent that, when the horizontal adjustment, the headrest 3, the set value I_S "Overshoot", the microcontroller 50 and the adjustment speed d_H the actuator 23 stepwise down before the target position I_S is achieved. The adjustment speed d_H Here is then lowered when the normalized measured capacitance value C '₃ one over the threshold C_H lowered threshold Cp exceeds (see <figref idrefs="f0003">Fig. 7</figref>).

<figref idrefs="f0005">Fig. 8</figref> shows a second embodiment of the adjusting device 20. This embodiment is similar - if not described in the following in deviation - in connection with the <figref idrefs="f0002">FIG. 2</figref> described embodiment of the adjusting device 20. Instead of the local transmitting electrodes 31a to 31e are in accordance <figref idrefs="f0005">Fig. 8</figref> but - with the same geometric arrangement of the electrode pads 36 and 37 on the carrier 30 - provided five receiving electrodes 60a-60e. Instead of the receiving electrode 32 of the embodiment according to<figref idrefs="f0002">FIG. 2</figref> is according <figref idrefs="f0005">Fig. 8</figref> - Provided a common transmitting electrode 61 - with the same geometric arrangement of the associated electrode array 35th A screening of the individual line 39 is not needed here. Also, the in<figref idrefs="f0002">FIG. 2</figref> illustrated Guard electrode 41 omitted. Instead, here are preferably the individual lines 38a to 38e, the control unit 24 here with the receiving electrodes 60a to 60e connect - electrically shielded - especially individually. An appropriate shield 53 is in<figref idrefs="f0005">Fig. 8</figref> schematically indicated.

The opposite <figref idrefs="f0002">FIG. 2</figref> reversed electrode function in accordance with a modified version of the control unit 24 <figref idrefs="f0005">Fig. 9</figref> causes. In contrast to<figref idrefs="f0002">Fig. 3</figref> 47 is connected via the individual lines 38a to 38e with the receiving electrodes 60a to 60e here the capacitance measurement module. This measurement module 47 is for the simultaneous detection of separately via the individual lines 38a to 38e provided here received signals S₁ to S₅ educated. The time multiplexer 46 in accordance with the embodiment<figref idrefs="f0005">FIGS. 8 and 9</figref> not required. The frequency generator 45 is - also deviating from<figref idrefs="f0002">Fig. 3</figref> - Via the single line 39 with the transmitting electrode 61st

Apart from these differences, the operation of the control unit 24 corresponds according to <figref idrefs="f0005">Fig. 9</figref> the embodiment described above. In particular, the control method described above is in the same way, in the microcontroller 50 in accordance with<figref idrefs="f0005">Fig. 9</figref> implemented.

The <figref idrefs="f0006">Fig. 10-12</figref> finally show variants of the proximity sensor 21 with respect to <figref idrefs="f0002">FIG. 2</figref> modified electrode configuration. In all illustrated here variants of the proximity sensor 21, the transmitting electrodes 31 a to 31 e can be 32 used as receiver electrodes 60a to 60e, and the common receiving electrode as a common transmitting electrode 61st

LIST OF REFERENCE NUMBERS

<dl id="dl0002" compact="compact"><dt>1</dt><dd>(Vehicle) seat</dd><dt>2</dt><dd>seatback</dd><dt>3</dt><dd>headrest</dd><dt>4</dt><dd>head</dd><dt>5</dt><dd>vehicle occupant</dd><dt>6</dt><dd>vertical direction</dd><dt>7</dt><dd>horizontal direction</dd><dt>8th</dt><dd>back</dd><dt>9</dt><dd>front</dd><dt>10</dt><dd>supporting rod</dd><dt>11</dt><dd>Headrest Mount</dd><dt>13</dt><dd>support tray</dd><dt>14</dt><dd>upholstery</dd><dt>15</dt><dd>coating</dd><dt>16</dt><dd>rack</dd><dt>17</dt><dd>holder</dd><dt>20</dt><dd>adjustment</dd><dt>21</dt><dd>Proximity sensor</dd><dt>22</dt><dd>(Vertical) Actuator</dd><dt>23</dt><dd>(Horizontal) Actuator</dd><dt>24</dt><dd>control unit</dd><dt>25</dt><dd>data line</dd><dt>26</dt><dd>data line</dd><dt>27</dt><dd>data line</dd><dt>30</dt><dd>carrier</dd><dt>31a-31e</dt><dd>transmitting electrodes</dd><dt>32</dt><dd>receiving electrode</dd><dt>33</dt><dd>Vehicle transverse direction</dd><dt>34</dt><dd>center</dd><dt>35</dt><dd>electrode array</dd><dt>36</dt><dd>electrode array </dd><dt>37</dt><dd>electrode array</dd><dt>38a-38e</dt><dd>Single line</dd><dt>39</dt><dd>Single line</dd><dt>40</dt><dd>Guard Screen</dd><dt>41</dt><dd>Guard electrode</dd><dt>42</dt><dd>Hall sensor</dd><dt>43</dt><dd>control line</dd><dt>44</dt><dd>measuring line</dd><dt>45</dt><dd>frequency generator</dd><dt>46</dt><dd>multiplexer</dd><dt>47</dt><dd>(Capacity) measurement module</dd><dt>48</dt><dd>Hall modules</dd><dt>49</dt><dd>motor control</dd><dt>50</dt><dd>Microcontroller</dd><dt>51</dt><dd>Detection distance</dd><dt>52</dt><dd>intersection</dd><dt>53</dt><dd>shielding</dd><dt>60a - 60e</dt><dd>receiving electrodes</dd><dt>61</dt><dd>transmitting electrode</dd><dt>d_H</dt><dd>adjustment</dd><dt>d_v</dt><dd>adjustment</dd><dt>H</dt><dd>(Vertical) position headrest</dd><dt>H_2/3</dt><dd>value</dd><dt>H_s</dt><dd>target position</dd><dt>I</dt><dd>(Horizontal) position headrest</dd><dt>I_s</dt><dd>target position</dd><dt>C₀</dt><dd>threshold</dd><dt>C_H</dt><dd>threshold</dd><dt>C_i</dt><dd>Measured capacitance value (i = 1,2, ..., 5)</dd><dt>C_p</dt><dd>threshold</dd><dt>F</dt><dd>alternating electric field</dd><dt>H</dt><dd>(Horizontal) displacement</dd><dt>K</dt><dd>System characteristic curve </dd><dt>M</dt><dd>ground potential</dd><dt>S_i</dt><dd>Received signal (i = 1,2, ..., 5)</dd><dt>V</dt><dd>(Vertical) displacement</dd></dl>