Keystroke detection device, keyboard, and keystroke detection method

Apparatus (1) for detecting a key press comprising a circuit substrate (2), a key module (4) attached to the circuit substrate (2) with a key cap (3), and a movement mechanism (15) for moving the key cap (3) relative to the circuit substrate (2) between a rest position and an actuation position, and a device (10) for detecting the movement of the key cap (3) relative to the circuit substrate (2),

• wherein the movement mechanism (15) has at least one one-part or multi-part movement element (5) which, when the key cap (3) moves relative to the circuit substrate (2), also moves at least in some regions relative to the circuit substrate (2) and comprises or consists of a conductive material, wherein the conductive material encloses a continuous recess (13) so that a current flow around the recess (13) is possible,
• wherein the device (10) for detecting the movement of the key cap (3) relative to the circuit substrate (2) comprises an electrical resonance circuit (11) with at least one capacitor (C1) and with at least one primary coil (L1) stationary in relation to the circuit substrate (2) with one or more coil windings and comprises at least one secondary coil (L2) with a short-circuited winding,
• wherein the primary coil (L1) is arranged on a rear side of the key module (4) opposite the key cap (3) on or in the circuit substrate (2),
• wherein the at least one movement element (5) forms the at least one secondary coil (L2), wherein the conductive material surrounding the recess (13) is the corresponding short-circuited winding of the secondary coil (L2),
• wherein the primary coil (L1) and the at least one secondary coil (L2) are inductively coupled to one another, and the strength of the inductive coupling between the primary coil (L1) and the at least one secondary coil (L2) and thus at least one physical variable of the resonance circuit (11) change during the movement of the key cap (3) and thus of the at least one movement element (5) forming the at least one secondary coil (L2) between the rest position and the actuation position,
• wherein the device (10) for detecting the movement of the key cap (3) relative to the circuit substrate (2) comprises a measuring device for detecting and/or processing at least one physical variable of the electrical resonance circuit, which variable changes during the movement of the key cap (3) between the rest position and the actuation position (11), and outputs at least one electrical signal that is dependent on the change in the physical variable.