Force sensor comprising specific capacitive sensors, and input device

Abstract

One aspect of the invention relates to a force sensor (3) comprising a first electrode pair (4) which has a first electrode (5) and a first counter-electrode (6), which electrodes are movable relative to each other and form a first capacitive sensor (14), wherein the force sensor (3) comprises at least one second electrode pair (15) which has a second electrode (16) and a second counter-electrode (17), which are movable relative to each other and form a second capacitive sensor (18), wherein the two electrode pairs (4, 15) are coupled on the basis of a contradirectional distance change concept for the contradirectional adjustment of the respective capacitance.

Description

[0001] Force sensor with specific capacitive sensors, as well as input device

[0002] One aspect of the invention relates to a force sensor with a first electrode pair comprising a first electrode and a first counter electrode. The first electrode and the first counter electrode are arranged to be movable relative to one another and form a first capacitive sensor of the force sensor.

[0003] US 2017 / 268946 A1 discloses a force sensor comprising a pair of electrodes. One electrode, which is arranged cantilevered horizontally and movable at a distance from an electrode of the electrode pair arranged stationary on a circuit board, is integrally connected to an actuating element of the force sensor. If a force is exerted on this actuating element, this actuating element deforms, and this deformation automatically initiates a movement of the electrode.

[0004] Such a force sensor is limited in its functionality.

[0005] With such force sensors, reliable detection of the applied force is only possible with relatively high levels of accuracy. Relatively low forces, which result in even a slight change in the actuating element, cannot be detected or can only be detected with insufficient accuracy.

[0006] It is an object of the present invention to provide a force sensor and an input device for a motor vehicle, in which the precise detection of an acting force over a larger area is possible.

[0007] This object is achieved by a force sensor and an input device according to the independent claims.

[0008] One aspect of the invention relates to a force sensor with a first electrode pair. The first electrode pair has a first electrode and a separate first counterelectrode. The first electrode and the first counterelectrode are arranged so as to be movable relative to one another. They form a component of a first capacitive sensor of the force sensor. The force sensor has at least one second electrode pair that is different from the first electrode pair. The second electrode pair has a second electrode and a second counterelectrode. The second electrode and the second counterelectrode are arranged so as to be movable relative to one another. The second electrode and the second counterelectrode form a component of a second capacitive sensor of the force sensor.The two electrode pairs of the force sensor are coupled together on the basis of a distance change concept, in particular a change in the distance of an electrode to a counter electrode, for the automatic mutual influence of the respective capacitance.

[0009] In particular, they are coupled together to adjust the respective capacity in opposite directions.

[0010] This creates a force sensor that can detect the application of force very precisely, or even more precisely, both for larger and smaller forces. The mere fact that two separate capacitive sensors are part of the force sensor enables the expanded detection of different acting forces. It is particularly advantageous that these two capacitive sensors of the force sensor are also functionally coupled to one another. This also means that whenever the distance between an electrode and a counter electrode of a capacitive sensor changes, a simultaneous, opposing change in the distance between the electrode and the counter electrode of the other capacitive sensor occurs, in particular, automatically.As a result, the sensitive detection of the force sensor is coordinated in a particularly advantageous manner and the precise detection of both low forces acting on the force sensor and higher forces acting on the force sensor can be improved.

[0011] In one embodiment, the first counter electrode is arranged in a fixed position on a circuit board of the force sensor. The first electrode is arranged to be movable relative to this first counter electrode, so that the capacitance of the first capacitive sensor can be changed depending on the distance between the first electrode and the first counter electrode.

[0012] In one embodiment, the first electrode is designed as the actuating element of the force sensor. This actuating element is thus intended to be subjected to a force, particularly directly. By actuating this actuating element, the force acting on the force sensor is characterized and detectable, or is intended to be detected, or is detected.

[0013] This makes this element particularly multifunctional. On the one hand, it is an electrical component that is part of this first capacitive sensor. On the other hand, it is a mechanical functional part that is intended to be directly acted upon in order to sense the force generated.

[0014] In one embodiment, the first electrode, in a non-actuated basic state, is at a maximum distance from the first counter electrode. Following an actuation, this electrode is designed to automatically return to the basic state. This eliminates the need for a user to return to the actuated state and reset the basic state. The electrode is primarily designed and arranged such that, when it is in the actuated state and the force applied is subsequently terminated or reduced, it automatically returns from the actuated state to the basic state.

[0015] In one embodiment, the electrode has an edge that defines its shape or contour. The edge rests on the circuit board of the force sensor both in the basic state and in the actuated state. This enables the first electrode to be positioned in a consistently advantageous manner. The relative movement to the first counterelectrode is thereby guided particularly advantageously, and dynamic changes in the first electrode relative to the counterelectrode can be maintained more effectively. This is particularly advantageous in that the first electrode remains stably positioned, even when dynamically deformed by the applied force. This is also advantageous with regard to the distance variation concept. This allows deformation of the first electrode to be transmitted to the second capacitive sensor in a very defined and targeted manner.

[0016] In one embodiment, the first electrode is a metal spring. It can, in particular, be dome-shaped, at least in some areas. This specific shape supports the aforementioned advantages. This also facilitates easy actuation and uniform deformation.

[0017] In one embodiment, the second counter electrode is arranged in a stationary manner on a circuit board of the force sensor. In particular, the second electrode is arranged so as to be movable. The capacitance of the second capacitive sensor can be changed depending on the distance between the second electrode and the second counter electrode. In one embodiment, the distance between the second electrode and the second counter electrode can be changed automatically depending on a movement of the first electrode relative to the first counter electrode. This coupling principle makes it particularly advantageous to achieve the above-mentioned change in distance in opposite directions, so that an increase in capacitance occurs automatically and simultaneously in one capacitive sensor and a decrease in capacitance in the other.

[0018] In one embodiment, by mechanically coupling the first electrode to the second electrode in this distance-changing concept, the distance between the second electrode and the second counterelectrode can be increased when the distance between the first electrode and the first counterelectrode is reduced. Additionally or instead of this, it is provided that by mechanically coupling the first electrode to the second electrode in a distance-changing concept, the distance between the second electrode and the second counterelectrode can be reduced when the distance between the first electrode and the first counterelectrode is increased. This creates very short-path mechanical operating principles between the electrodes, which then lead to the automatic, opposing adjustment of the respective capacitance.This allows for a compact design of the force sensor and minimizes tolerances in the transmission path of the movement from the first electrode to the second electrode, resulting in the corresponding opposing adjustments of the respective capacitances of the capacitive sensors. This achieves a particularly simple, short-acting, and particularly precise force sensor principle. The range of a value interval over which different force values ​​can be determined precisely and quickly is thus significantly improved.

[0019] In one embodiment, the second electrode is pivotably arranged, so that a relative movement of the second electrode to the second counter electrode for changing the distance is a pivoting movement. In particular, this provides a movement concept for the second electrode in which the second electrode is not deformed during the movement, but is moved as a whole. The pivoting movement or folding movement is very advantageous here, as it enables the distance to be adjusted and the relative movement to the second counter electrode to be carried out very smoothly and precisely. On the other hand, such a pivoting movement can also be achieved very easily by acting on a mechanical coupling between the first electrode and the second electrode. Complex movements of the second electrode can thus be avoided. In one embodiment, the first counter electrode is designed as a ring electrode.This enables, on the one hand, a simple electrical coupling with the second counter electrode to realize the capacitive sensor, and, on the other hand, especially with a specific design of the first electrode, both the movement principle of the first electrode and the coupling with the second capacitive sensor are very easily enabled.

[0020] In one embodiment, the second counter electrode and / or the second electrode are each formed as a plate, in particular a square plate.

[0021] In one embodiment, the first electrode has a curved central part, on which at least one wing part protruding therefrom is arranged. This also supports the aforementioned advantages and particularly effectively fulfills the multifunctionality of the first electrode.

[0022] It is possible for the wing part to be a coupling part in which the first electrode is mechanically coupled to the second electrode. In one embodiment, this wing part is, on the one hand, compact and space-saving, while, on the other hand, it represents a cantilevered, very stable, and essentially rigid component. This ensures that deformation of the curved central part caused by the application of a force does not lead to undesired deformation of the wing part. Instead, the force acting directly on the curved central part is transmitted very directly to the second capacitive sensor, in particular the second electrode, via this wing part.

[0023] It is possible for several separate, protruding wing parts, in particular four wing parts, to be formed on the curved central part. These can be arranged equidistant from one another in the circumferential direction around a longitudinal axis of the curved central part.

[0024] A further aspect of the invention relates to an input device for a motor vehicle with at least one force sensor according to the above-mentioned aspect or an advantageous embodiment thereof. The input device can also be referred to as a motor vehicle input device.

[0025] A further aspect of the invention relates to a motor vehicle with a force sensor according to the above-mentioned aspect or an advantageous embodiment thereof and / or with an input device according to the above-mentioned aspect or an advantageous embodiment thereof.

[0026] Embodiments of the invention are explained in more detail below with reference to schematic drawings. They show:

[0027] Fig. 1 is a schematic plan view of an embodiment of a vehicle according to the invention with an embodiment of an input device according to the invention and / or an embodiment of a force sensor according to the invention;

[0028] Fig. 2 is a schematic plan view of an embodiment of a force sensor according to the invention, which can be part of an embodiment of an input device according to the invention;

[0029] Fig. 3 the top view according to Fig. 2, but only with partial components of the force sensor;

[0030] Fig. 4 is a schematic vertical sectional view through the force sensor according to Fig. 2 in a first operating state of the force sensor;

[0031] Fig. 5 shows the representation according to Fig. 4 in a second operating state of the force sensor which is different from Fig. 4; and

[0032] Fig. 6 is a schematic diagram showing the capacitance of the force sensor as a function of the stroke or the distance from electrodes of the force sensor to counter electrodes of the force sensor.

[0033] In the figures, identical or functionally identical elements are provided with the same reference symbols.

[0034] Fig. 1 shows a schematic representation of a motor vehicle 1. The motor vehicle 1 can be, for example, a passenger car or a truck. The motor vehicle 1 has an exemplary embodiment of an input device 2 according to the invention. In one exemplary embodiment, this input device 2 can have at least one force sensor 3. Fig. 2 shows a schematic representation of an exemplary embodiment of a force sensor 3 in a plan view. The force sensor 3 has a first pair of electrodes 4.

[0035] The first electrode pair 4 comprises a first electrode 5 and a first counter electrode 6. In the exemplary embodiment, the first counter electrode 6 is arranged stationary on a circuit board 7 of the force sensor 3. The first electrode 5 is arranged so as to be movable relative to the first counter electrode 6.

[0036] As can be seen in the exemplary embodiment, the first electrode 5 is formed with a central part 8. The central part 8 can preferably be dome-shaped. In the exemplary embodiment, several wing parts, here wing parts 10, 11, 12, and 13, extend freely projecting outward from an edge 9 of this central part 8.

[0037] This first electrode 5 and the first counter electrode 6 form a first electrode pair 4. This forms a first capacitive sensor 14 of the force sensor 3.

[0038] In addition, the force sensor 3 has a second electrode pair 15. The second electrode pair 15 has a second electrode 16. Furthermore, the second electrode pair 15 has a second counter electrode 17. The second counter electrode 17, which is arranged separately and at a distance from the first counter electrode 6, is fixedly mounted on the circuit board 7 in the exemplary embodiment. The second electrode 16 is arranged so as to be movable relative to the second counter electrode 17.

[0039] This second pair of electrodes 15 forms a second capacitive sensor 18 of the force sensor 3.

[0040] The two electrode pairs 4 and 15 and thus the capacitive sensors 14 and 18 are coupled to one another on the basis of a distance variation concept for adjusting the respective capacitances, in particular in opposing values. For this purpose, a mechanical coupling unit or coupling 19 of the force sensor 3 is provided. In the exemplary embodiment, the wing part 10 of the first electrode 5 is mechanically, in particular directly, coupled to the second electrode 16. In addition, the force sensor 3 has an electrical contact 20, by means of which the capacitive sensors 14 and 18 are electrically connected to an evaluation unit. Fig. 3 shows a representation according to Fig. 2, although the electrodes 5 and 16 and the mechanical coupling 19 are not shown here. It can be seen that the first counter electrode 6 is designed as a ring electrode.The second counter electrode 17 is designed here as a polygonal surface, in particular as a square plate.

[0041] Fig. 4 shows a vertical sectional view of the force sensor 3 as shown in Fig. 2. In this state, a distance a1 between the first electrode 5, in particular the central part 8, and the first counter electrode 6 is maximum. The first electrode 5 is shown in Fig. 4 in its unactuated basic state. In this operating state, however, a distance a2 between the second electrode 16 and the second counter electrode 17 is minimal, here 0. This means that in this operating state, the second electrode 16 rests directly on the second counter electrode 17.

[0042] As can be seen in the simplified diagram in Fig. 6, in which the capacitance is plotted on the vertical axis and the distance between an electrode and a counter electrode is shown on the horizontal axis, the opposite principle of changing capacitances is illustrated. For the first capacitive sensor 14, the horizontal axis is directed to the right, meaning that the values ​​increase from left to right. For the second capacitive sensor 18, the horizontal axis is directed to the left, meaning that the values ​​increase from right to left.

[0043] In the characteristic curve I shown in Fig. 6, which applies to the first capacitive sensor 14, the capacitance increases with increasing distance a1. In contrast, the further characteristic curve II, which applies to the second capacitive sensor 18, shows that the capacitance increases with increasing distance a2.

[0044] In the operating state of the force sensor 3 shown in Fig. 4, the distance a1 is large, so that the capacitance of the first capacitive sensor 14 is large. At the same time, the distance a2 is small, so that the capacitance is small.

[0045] Starting from the illustration in Fig. 4, a force K is now exerted on the first electrode 5, which is intended to serve as the confirmation element here. This changes the distance a1, namely is reduced here. The capacitance of the first capacitive sensor 14 decreases. Due to the mechanical coupling 19, when this force K is applied to the first electrode 5, here in particular the central part 8, this central part 8 is deformed, namely spread in the radial direction. As a result, the wing part 10 and the mechanical coupling 19 produce an effect on the second electrode 16 such that the distance a2 between the second electrode 16 and the second counter electrode 17 is increased. As can be seen in this context from the diagram in Fig. 6, the capacitance increases according to characteristic curve II of the second capacitive sensor 18 with increasing stroke, i.e. with increasing distance a2. This is shown in Fig.6 shows that, according to the basic state in Fig. 4, in which the first electrode 5 is not actuated, the smallest distance a2 is set for the second capacitive sensor 18 and thus, according to characteristic curve II, the smallest capacitance is present. On the other hand, the first capacitive sensor 14 has simultaneously set the largest distance a1 between the electrode 5 and the first counter electrode 6, so that, according to characteristic curve I in Fig. 6, it simultaneously has the highest capacitance.

[0046] If, as already explained in Fig. 5, a force K is then applied to the first electrode 5, both capacitances of the first capacitive sensor 14 and the second capacitive sensor 18 change continuously according to the characteristic curves I and II. Due to the characteristic curves shown in Fig. 6, one capacitance decreases, whereas the other capacitance increases simultaneously.

[0047] Electrodes 5 and 16 are preferably metal electrodes. In particular, the first electrode 5 can be a metal spring. It can preferably be connected to an electrical potential of, for example, between 4V and 6V, in particular 5V. The counter electrode 6 can, for example, be connected to an electrical potential of 0V. The same can be provided for the second electrode 16 and the second counter electrode 17. For very small counter-rotating strokes, the force can therefore be determined very precisely, in particular via the second capacitive sensor 18, whereas for very large strokes and thus larger force effects, this force can be determined in particular by the first capacitive sensor 14.

Claims

Patent claims 1 . Force sensor (3) with a first electrode pair (4) having a first electrode (5) and a first counter electrode (6) which are arranged to be movable relative to one another and form a first capacitive sensor (14), characterized in that the force sensor (3) has at least a second electrode pair (15) having a second electrode (16) and a second counter electrode (17) which are arranged to be movable relative to one another and form a second capacitive sensor (18), wherein the two electrode pairs (4, 15) are coupled on the basis of a distance change concept for adjusting the respective capacitance.

2. Force sensor (3) according to claim 1, characterized in that the first counter electrode (6) is arranged in a fixed position on a circuit board (7) of the force sensor (3) and the first electrode (5) is arranged to be movable thereto, so that the capacitance of the first capacitive sensor (14) can be changed depending on the distance (a1) between the first electrode (5) and the first counter electrode (6).

3. Force sensor (3) according to claim 1 or 2, characterized in that the first electrode (5) is designed as an actuating element, by the actuation of which the force occurring thereby acts on the force sensor (3).

4. Force sensor (3) according to claim 3, characterized in that the first electrode (3) in an unactuated basic state has a greatest distance (a1) from the first counter electrode (6), and starting from an actuated state reached by an actuation is designed to return automatically to the basic state.

5. Force sensor (3) according to claim 3 or 4, characterized in that the first electrode (5) has an edge (9), wherein the edge (9) in the basic state and / or in an actuated state of the first electrode (5) sits on a circuit board (7) of the force sensor (3).

6. Force sensor (3) according to one of the preceding claims, characterized in that the first electrode (5) is a metal spring, in particular a dome-shaped metal spring.

7. Force sensor (3) according to one of the preceding claims, characterized in that the second counter electrode (17) is arranged in a stationary manner on a circuit board (7) of the force sensor (3) and the second electrode (16) is arranged to be movable thereto, so that the capacitance of the second capacitive sensor (18) can be changed depending on the distance (a2) of the second electrode (16) to the second counter electrode (17).

8. Force sensor (3) according to one of the preceding claims, characterized in that in the distance change concept a distance (a2) of the second electrode (16) to the second counter electrode (17) can be changed automatically, in particular in the opposite direction, depending on a movement of the first electrode (5) to the first counter electrode (6).

9. Force sensor (3) according to one of the preceding claims, characterized in that by a mechanical coupling (19) of the first electrode (5) to the second electrode (16) in the distance change concept, a distance (a2) of the second electrode (16) to the second counter electrode (17) can be increased if the distance (a1) between the first electrode (5) and the first counter electrode (6) is reduced, and / or a distance (a2) of the second electrode (16) to the second counter electrode (17) can be reduced if the distance (a1) between the first electrode (5) and the first counter electrode (6) is increased.

10. Force sensor (3) according to one of the preceding claims, characterized in that the second electrode (16) is arranged pivotably, so that a relative movement of the second electrode (16) to the second counter electrode (17) for changing the distance is a pivoting movement.

11. Force sensor (3) according to one of the preceding claims, characterized in that the first counter electrode (6) is designed as a ring electrode.

12. Force sensor (3) according to one of the preceding claims, characterized in that the second counter electrode (17) and / or the second electrode (16) is designed as a plate, in particular a square plate.

13. Force sensor (3) according to one of the preceding claims, characterized in that the first electrode (5) has a curved central part (8) on which at least one wing part (10, 11, 12, 13) projecting therefrom is arranged.

14. Force sensor (3) according to claim 13, characterized in that the wing part (10) is a coupling part with which the first electrode (5) is mechanically coupled to the second electrode (16).

15. Input device (2) for a motor vehicle (1) with at least one force sensor (3) according to one of the preceding claims.

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