Operating device for an electrical apparatus, in particular for a vehicle component

The operating device for an electrical apparatus or a system, in particular for a vehicle component, is provided with at least one elastically mounted operating element (12), a counter-element (14), relative to which the at least one operating element (12) is movable when actuated, thereby varying the distance, namely as seen in the movement direction, and at least one capacitor (38) which comprises a first carrier body (20) with a first capacitor electrode (34) and an elastically bendable second carrier body (22), designed as a bending bar, having a first end (26) and a second end (32) opposite said first end and having a second capacitor electrode (36) opposite the first capacitor electrode (34). Connected to the first and second capacitor electrode (34, 36) is an evaluation unit (42) for determining the capacitance and/or a change in the capacitance of the at least one capacitor (38) upon actuation of the at least one operating element (12).

The invention relates to an operating device for an electrical apparatus or for a system, said operating device being provided in particular for a vehicle component.

The present application claims the priority of German Patent Application 10 2013 225 436.9 of Dec. 10, 2013, the contents of which are herewith included by reference in the content of the present PCT application.

Operating devices with operating elements of the most various designs are generally known. Particularly in the automotive field, operating concepts have been established wherein use is made of operating elements in the form of keys. Recently, it has been increasingly demanded to design such key-type operating elements to the effect that, when actuated, their surfaces should move, as far as possible, in a manner imperceptible to the user. Thus, it is desired to realize movement strokes as small as possible and, further, to allow these to be detected. On the basis of the path covered, it can then be determined whether the respective operating element has been correctly actuated; thereupon, the function of the device or system that is assigned to the operating element will be performed.

If, in such a system, its resilience (stiffness) is known, the detected displacement/movement of the operating element out of its rest position makes it possible to conclude on the actuating force. In case of a high system stiffness, the displacement is relatively small (which ultimately is even intended in some cases); thus, the challenge arises to find ways for a precise measurement of small displacements.

In DE-A-10 2011 089 693, an operating device is described wherein, in response to a press-down movement, a cut-free bending bar integrated into the circuit board will be deformed. On that end of the bending bar that is not rigidly connected to the circuit board and thus is free, the bending bar carries a capacitor electrode which, together with a further capacitor electrode arranged on the rigid circuit board area facing toward the free end of the bending bar and thus arranged laterally to the free end, forms a capacitor. The change of the capacitance of this capacitor is used for detection of the actuation of the operating element.

DE-A-10 2013 100 649 discloses a touch-type operating element with tactile feedback of a touch of the operating element. Herein, a capacitor is provided whose rigid electrode surfaces will be displaced so that the capacitance will be changed.

Thus, it is an object of the invention to provide an operating device for an electrical apparatus or for a system, particularly for a vehicle component, wherein, in spite of the smallest possible movement strokes of an operating element, a reliable conclusion can be drawn on the movement stroke of this operating element.

To achieve the above object, the invention proposes an operating device for an electrical apparatus or for a system, particularly for a vehicle component, wherein the operating device is provided withat least one elastically mounted operating element,a counter-element, relative to which the at least one operating element is movable when actuated, thereby varying the distance, namely as seen in the movement direction,at least one capacitor which comprises a first carrier body with a first capacitor electrode and an elastically bendable second carrier body, designed as a bending bar, said second carrier body having a second capacitor electrode opposite the first capacitor electrode,whereinthe capacitor is held on the at least one operating element and upon actuation of the operating element can be moved along with the operating element in that the two carrier bodies are fastened by their first ends to the at least one operating element, and the second carrier body on its second end opposite to the first end is in operative connection with the counter-element, for movement of the second end of the elastically bendable second carrier body away from the first carrier body performed upon actuation of the at least one operating element (see e.g.FIG. 1, where the first carrier body and the first end of the elastically bendable second carrier body are fastened to the at least one operating element for movement of the first carrier body and the first end of the elastically bendable second carrier body together with the at least one operating element, and the second end of the second carrier body opposite to the first end of the elastically bendable second carrier body is arranged on the counter-element and, respectively, is supported/held by the latter upon actuation of the at least one operating element and, upon actuation of the at least one operating element, moves away from the first carrier body),orthe capacitor is held on the counter-element in that the two carrier bodies are fastened by their first ends to the counter-element, and the second carrier body on its second end opposite to the first end is in operative connection with the at least one operating element, for movement of the second end of the second carrier body away from the second end of the first carrier body performed upon actuation of the at least one operating element (see e.g.FIG. 4, where the first carrier body is held on the counter-element and the at least one operating element is movable relative to the first carrier body, and the elastically bendable second carrier body on its first end is held by the counter-element and, on its second end opposite to the first end, is in operative connection with the at least one operating element for movement of the second end of the elastically bendable second carrier body away from the first carrier body performed upon actuation of the at least one operating element),wherein the second end of the elastically bendable second carrier body undergoes a deflection oriented away from the first carrier body, upon actuation of the at least one operating element and a resultant generation and/or enlargement of a distance between the first and second capacitor electrodes, andan evaluation unit connected to the first and second capacitor electrodes for determining the capacitance and/or a change of the capacitance of the at least one capacitor upon actuation of at least one operating element.

The approach to be realized by the operating device of the invention resides in determining a displacement of the operating element in a capacitive manner in that the change of the capacitance of a capacitor is metrologically detected with the aid of an elastic electrode. The special feature herein resides in that, upon movement of an operating element out of its rest position, the capacitor will change its capacitance from high values to low values. Hence, the capacitor will “open up” when the operating element is actuated.

According to the invention, the operating device comprises at least one elastically supported operating element. In the normal case, this operating element is designed as a key body and can be moved in a translatory manner; however, also deflections of the operating element can be metrologically detected by use of the concept of the invention. The operating element, when actuated, will be moved in the direction of a counter-element and, respectively, the operating element will again move back from said counter-element when no actuating force is exerted on the operating element anymore.

Between the operating element and the counter-element, there is arranged, in the moving path, a capacitor comprising a first and a second carrier body, wherein each carrier body comprises a capacitor electrode (hereunder referred to as a first and respectively second capacitor electrode). While the first carrier body is of a rigid design, the second carrier body is formed in the manner of a bending bar and thus is elastically bendable. The two capacitor electrodes are arranged opposite to each other.

Upon actuation of the operating element, the second carrier body will be deflected to an increasing extent. This will cause an increase of the distance between the two capacitor electrodes which in the rest condition of the operating element should be as small as possible. Thus, notably, in the rest condition of the operating element, the capacitor has a relatively high electrical capacitance which will decrease relatively quickly, particularly also when the operating element is moved only minimally. This relatively large drop of the electrical capacitance of the capacitor can be reliably used for detecting an actuation of the operating element and respectively the displacement path of the operating element and, thus (provided that the stiffness of the system is known), the actuating force.

In case that, for reasons of the design and its tolerances, minimum distances have to be maintained between the electrodes, which normally will result in an air gap that will reduce the capacitance of the capacitor, this invention has the advantage that such a minimum distance needs to be maintained only on one side, namely the side that is opening. On the opposite side, the air gap can be omitted so that the capacitance of the capacitor will be high.

The above mentioned concept of the operating device of the invention can be realized, according to a first alternative, e.g. in that the first carrier body is held immobile relative to the operating element and the at least one operating element is movable relative to the second carrier body, and this elastically bendable second carrier body is by its first end held on the operating element and, on its second end opposite to the first end, is in operative connection with the counter-element upon movement of the elastically bendable second carrier body performed upon actuation of the operating element. In this variant, the first carrier body and the first end of the elastically bendable second carrier body are fastened to the at least one operating element so that, upon actuation of the operating element, both will move along with the latter. In this arrangement, the second end of the elastically bendable second carrier body is in abutment on the counter-element. The two carrier bodies are disposed above each other, wherein the elastically bendable second carrier body is arranged between the operating element and the first carrier body. Consequently, the farther the operating element is moved, the more second carrier body will be defected.

In a second variant of the operating device of the invention, it is provided that the first carrier body and the first end of the elastically bendable second carrier body are held on the counter-element. The second end of the elastically bendable second carrier body is in operative connection with the at least one operating element when the latter is actuated. In this variant, the two carrier bodies again are disposed on top of each other but are held on the counter-element. The second end of the elastically bendable second carrier body is arranged—with respect to the moving direction of the operating element upon actuation—behind the first carrier body and, further, has its second end arranged in abutment on the operating element. Again, upon actuation of the operating element, the second carrier body will be deflected to an increasing extent.

For both variants of the invention, it thus holds true that, upon actuation of the at least one operating element while a distance is generated between the first and second capacitor electrodes and/or said distance is enlarged, the second end of the elastically bendable second carrier body undergoes a deflection directed away from the first carrier body. By means of an evaluation unit connected to the first and second capacitor electrodes, it is now possible to determine the capacitance and/or a change of the capacitance of the at least one capacitor upon actuation of the at least one operating element.

According to a further advantageous embodiment of the invention, there can be provided a feedback unit acting on the at least one operating element for generating a tactile confirmation of an actuation of the at least one operating element, wherein said feedback unit is adapted to be controlled depending on the amount of the capacitance or depending on the degree of the change of capacitance that the capacitor assumes and respectively undergoes upon actuation of the at least one operating element. This feedback can also be given acoustically or visually and, optionally, acoustically and visually in combination and, if desired, additionally in combination with a tactile feedback. A tactile feedback unit can be realized e.g. as a solenoid whose armature can be fastened to the operating element and whose coil with yoke can be fastened to the housing—or vice versa—or as an unbalance motor or vibration unit.

On the at least one elastically supported operating element of the operating device of the invention, there can be arranged a plurality of operating fields with respectively one symbol. Irrespective of which of the operating fields is currently contacted, e.g. by a finger of a hand, for actuating the operating element so that the operating element will be actuated, the operating element will perform a movement which, as described above, will be capacitively detected as provided by the invention. Now, for detecting which operating field is acted on by the finger of a hand when the operating element is actuated, the use of a capacitive touch sensor arrangement is of advantage, its evaluation being formed particularly in the evaluation unit.

InFIG. 1, there is shown a first exemplary embodiment of an operating device10. This operating device10comprises an elastically supported operating element12which is movable in the direction towards a counter-element14and away from the latter when, as indicated at16inFIG. 1, an actuating force is acting on the operating element12and, respectively, when this actuating force is released. InFIG. 1, the elastic support of operating element12is schematically represented by the springs18.

Fastened to the operating element12are a—particularly rigid—first carrier body20and elastically bendable second carrier bony22superposed arrangement. Said first carrier body20can be e.g. a circuit board while the second carrier body22can be formed as a strip of sheet metal. As can be seen inFIG. 1, the two carrier bodies20,22are fastened, in the area of their first ends24,26, to a projection28of the otherwise plate-shaped operating element12. Said projection28is oriented in the direction towards counter-element14. The two carrier bodies20,22further comprise second ends30,32opposite to their respective first ends24and26, respectively, wherein the end32of the elastically bendable second carrier body22extends beyond the second end30of the first carrier body20.

In the area of the second end30of the first carrier body20, a first capacitor electrode34is arranged. Opposite to said first capacitor electrode, a portion of the second carrier body22is located that, within this portion, forms a second capacitor electrode36. Thus, there is formed a capacitor38(with electronically insulated electrodes).

As can be further seen inFIG. 1, the second end32of the second carrier body22rests on a deflection element40of counter-element14. When, now, the operating element12is pressed, i.e. actuated, the second carrier body22will increasingly bend due to the abutment of its second end32on the deflection element40, which is evident by a comparison betweenFIGS. 2 and 3. InFIG. 2, there is shown the situation of the capacitor configuration when the operating element12is in its rest position.FIG. 3shows the case where the operating element12is pressed and thus is actuated. This defines the actuation stroke s. The deflection element40does not necessarily have to abut on the second end32of the second carrier body22but can also touch and deflect the second carrier body at another position wherein, for this purpose, the deflection element40extends through an opening or the like cutout through the first carrier body20so as to come into abutment with the second carrier body22.

Said actuation stroke s can now be detected on the basis of the changing capacitance of capacitor38. InFIG. 2, “A” indicates the level of the average electrode distance Waverage nin the situation where the operating element12is in its rest position or normal position. InFIG. 3, “B” indicates the level of the average capacitor-electrode distance Waverage bwhich is reached when the operating element12is actuated. The difference between the two levels “A” and “B” is denoted by Δwaverage; it can be seen that Δwaverageis smaller than the stroke s, which, however, is not absolutely necessary according to the invention.

InFIG. 1, it is further schematically represented that the two capacitor electrodes34,36are electrically connected to an evaluation unit42. In this evaluation unit42, there is performed the detection of the capacitance and respectively the change of capacitance upon actuation of operating element12. For tactile feedback, a corresponding feedback unit44can be provided which comprises an electromechanical drive for causing the operating element12to perform vibrations.

InFIG. 4, a concept is shown that is inverse to the actuation detection concept according toFIG. 1. Thus, in the corresponding operating device10ofFIG. 4, the capacitor38and respectively the mutually superposed carrier bodies20and22will not move along with the operating element12when the latter is actuated (except for the bending of the elastically bendable second carrier body22). Besides, inFIG. 4, those elements that are constructionally and functionally similar to the elements of the operating device10ofFIG. 1are marked by the same reference numerals as inFIGS. 1 to 3.

Thus, as evident from the above, the invention makes it possible to detect, through measurement technology, a small displacement with the aid of relatively simple means, namely a circuit board, a sheet-metal strip and a capacitance measurement device. For this purpose, it is merely required that one of the two elements “circuit board” and “sheet-metal strip” can be displaced relative to the other with known stiffness.

Force measurements (or the determining of a force) as rendered possible by the invention are increasingly provided in connection with touch operating functions. Therefore, the hardware and software required for the touch operating functions can be used also for said force measurements. In comparison with known capacitive systems, the change of capacitance relative to the covered path is considerably larger when using the approach provided by the invention, which is achieved because of the physical principle utilized by the invention, so that the accuracy of the force determination is enhanced.

The features of the invention include particularly the following, which can be realized individually and also in any desired combination:The decrease of capacitance is used for path measurement.In the starting position, the two plates of the capacitor have a smaller distance.A strong capacitive change is achieved because:the distance between the boards is enlarged anda second dielectric, which herein is air, will enter into the gap between the capacitor plates.One capacitor plate is elastic.The air gap between the capacitor plates is formed by the bending of the elastic capacitor plate, e.g. a metal sheet. Thereby, there is effected a mechanical translation between the mechanical displacement of the overall system and the real average change of distance in the capacitor.Tolerances of the component parts are compensated by the elasticity of the capacitor metal sheet; by this compensation of tolerances, an idle stroke of the key is avoided, thus making it possible to detect minimal movements within the measurement accuracy.

Hereunder, in a quite general manner, the physical/electrotechnical principles of the inventive approach shall be outlined once more.

The merely minimally displaceable operating element whose displacement is to be metrologically detected, is elastically connected to another component, e.g. to a casing or, as expressed above, a counter-element. The stiffness of this connection (represented in the figures by the springs18) is known. On the basis of the force/path interrelationship. i.e.
F=D×s,
wherein D represents the stiffness and s the path, the applied force F can be calculated with the aid of the displacement S.

The capacitor for path measurement comprises a plane capacitor plate, e.g. a copper conduction path on a circuit board. On this circuit board, also the electronics for measurement of the capacitance are accommodated. In electronic insulation to the first capacitor plate, e.g. a sheet-metal strip is arranged, forming the second capacitor plate. The capacitance of the capacitor is calculated as follows:
C=∈0×∈r×A/w,
wherein ∈0represents the electronic field constant, ∈rrepresents the relative permeability of the material in the gap (in the normal case, air), A represents the surface area of the capacitor and w represents the distance of the capacitor plates. Now, when a force is applied onto the operating element, there is covered—via the elastic deformation of the springs—the path s. Thus, the (upwardly projecting actuation) pin will be displaced relative to the circuit board with the copper conduction path and relative to the sheet-metal strip. Thereby, the sheet-metal strip will be lifted off the copper conduction path. Due to the one-sided tight clamping attachment, the sheet-metal strip will undergo a corresponding deformation and will form a bending line (seeFIGS. 1 to 4). The gap between the copper conduction path on the circuit board and the sheet-metal strip will now have a height which depends on the site on the sheet-metal strip (seeFIGS. 2 and 3). Now, when an average distance before and after displacement is detected, this distance is smaller than the displacement s of the operating element. Thus, due to the bending line, the displacement s is translated into the average distance w of the capacitor (seeFIGS. 2 and 3).

Since, with increasing path s, the capacitor will open ever further, i.e. the sheet-metal strip will be bent farther away from the circuit board, no actuating forces will be transferred to the circuit board, thus protecting it from damage.

If the path measurement is combined with a haptic feedback which acts in the direction of the actuation, this additional path of the operating element for haptic feedback will open the capacitor still more (seeFIGS. 1 to 4).

According to the invention, in contrast to systems working with “closing” capacitors and thus with increasing capacitance, the actuating path provided for actuation and optionally feedback and thus as an “allowance” as is the case in a “closing” capacitor, does not have to be provided, so that the capacitor gap in the rest position can be designed to be very small, thus rendering possible a high output capacitance.

At46inFIGS. 1 to 4, there is schematically depicted a capacitive touch sensor system which makes it possible to detect on which site e.g. the finger of a hand is located when the operating element12is actuated.

LIST OF REFERENCE NUMERALS

10operating device10′ operating device12operating element14counter-force16actuating force18spring20carrier body22carrier body24first end of first carrier body26first end of second carrier body28projection30second end of first carrier body32second end of second carrier body34first capacitor electrode36second capacitor electrode38capacitor40deflection element for second carrier body42evaluation unit44feedback unit46touch sensor arrangements actuation strokew distanceF actuating force