Device and method for detecting an end of a movement of a valve piston in a valve

1. A device for detecting an end of a movement of a valve piston in at least one valve, comprising:

the device being connected to the least one valve and embodied for:

detecting a first variable being representative of an induced voltage induced by the movement of the valve piston in a coil of the valve;

determining a second variable being representative of a first derivation of the first variable according to time; and

detecting the end of the movement of the valve piston in the valve if the first variable is greater than a predetermined first threshold value and the second variable falls below a predetermined second threshold value.

2. The device according to claim 1 , further comprising:

a first impedance converter having an input impedance being greater than an output impedance, said first impedance converter having an output and an input for receiving the induced voltage; and

a second impedance converter having an input impedance being less than an output impedance, said second impedance converter having an output, an input and a series circuit connected to said input, said series circuit containing a resistor and a capacitor, said input of said second impedance converter connected to said output of said first impedance converter, the first variable being detectable at said output of said first impedance converter and the second variable being detectable at said output of said second impedance converter.

3. The device according to claim 1 , further comprising:

a device input; and

a low-pass filter connected to said device input.

4. The device according to claim 1 , further comprising a voltage divider electrically connected between a supply potential and a ground potential, said voltage divider having a series circuit containing at least three resistors and at which the predetermined first threshold value and predetermined second threshold value can be tapped off between two succeeding ones of said three resistors in each case.

5. The device according to claim 1 , further comprising:

a device output;

a first and a second comparator, each of said first and second comparator having an open-collector output, an inverting input, and a non-inverting input, the first variable being applied to said non-inverting input of said first comparator, the predetermined first threshold value being applied to said inverting input of said first comparator, the second variable being applied to said inverting input of said second comparator and the predetermined second threshold value being applied to said non-inverting input of said second comparator, said open-collector output of said first comparator and said open-collector output of said second comparator are connected together and form said device output.

6. The device according to claim 1 , further comprising:

a device input; and

a protective circuit connected to said device input and including at least one diode and one resistor, said protective circuit embodied so that if an excessive supply voltage occurs at said device input said diode becomes conducting and a current flow through said diode is limited by said resistor.

7. The device according to claim 1 , wherein the device is embodied such that the predetermined first threshold value and/or the predetermined second threshold value are determined in dependence on the first variable.

8. The device according to claim 7 , wherein the device is embodied such that the predetermined first threshold value or the predetermined second threshold value are only determined in dependence on the first variable if the first variable is greater than a predetermined third threshold value.

9. A method for detecting an end of a movement of a valve piston in a valve, which comprises the steps:

detecting a first variable being representative of an induced voltage induced by the movement of the valve piston in a coil of the valve;

determining a second variable being representative of a first derivation of the first variable according to time; and

detecting the end of the movement of the valve piston in the valve if the first variable is greater than a predetermined first threshold value and the second variable drops below a predetermined second threshold value.

10. The method according to claim 9 , which further comprises determining at least one of the predetermined first threshold value and the predetermined second threshold value in dependence on the first variable.

11. The method according to claim 9 , which further comprises determining one of the predetermined first threshold value and the predetermined second threshold value in dependence on the first variable if the first variable is greater than a predetermined third threshold value.

12. A device for detecting an end of a movement of a valve piston in at least one valve, the device being connected to the least one valve, the device comprising:

means for detecting a first variable being representative of an induced voltage induced by the movement of the valve piston in a coil of the valve;

means for determining a second variable being representative of a first derivation of the first variable according to time; and

means for detecting the end of the movement of the valve piston in the valve if the first variable is greater than a predetermined first threshold value and the second variable falls below a predetermined second threshold value.

13. A device for detecting an end of a movement of a valve piston in at least one valve, the device being connected to the least one valve, the device comprising:

a device input for receiving an induced voltage induced by the movement of the valve piston in a coil of the valve;

a first device coupled to said device input and detecting a first variable being representative of the induced voltage;

a second device coupled to said device input and determining a second variable being representative of a first derivation of the first variable according to time; and

a third device for detecting the end of the movement of the valve piston in the valve if the first variable is greater than a predetermined first threshold value and the second variable falls below a predetermined second threshold value, said third device connected to said output of both said first and second devices.

14. The device according to claim 13 , further comprising a low-pass filter connected between said device input and said first device.

15. The device according to claim 13 ,

further comprising a first impedance converter having an input impedance being greater than an output impedance, said first impedance converter having an output and an input for receiving the induced voltage, said first impedance device connected between said device input and said first device; and

wherein said second device having a second impedance converter with an input impedance being less than an output impedance, said second impedance converter having an output, an input and a series circuit connected to said input of said second impedance converter, said series circuit containing a resistor and a capacitor, said input of said second impedance converter connected to said output of said first impedance converter, the first variable being detectable at said output of said first impedance converter and the second variable being detectable at said output of said second impedance converter.

16. The device according to claim 15 , wherein said second device containing a voltage divider having an input connected to said output of said second impedance device, said voltage divider electrically connected between a supply potential and a ground potential, said voltage divider having a series circuit containing at least three resistors and at which the predetermined first threshold value and predetermined second threshold value can be tapped off between two succeeding ones of said three resistors in each case, said voltage dividers having outputs connected to said first and second devices.

17. The device according to claim 16 , wherein:

said first device contains a first comparator; and

said second device contains a second comparator, each of said first and second comparators having an open-collector output, an inverting input, and a non-inverting input, the first variable being applied to said non-inverting input of said first comparator, the predetermined first threshold value being applied to said inverting input of said first comparator, the second variable being applied to said inverting input of said second comparator and the predetermined second threshold value being applied to said non-inverting input of said second comparator.

18. The device according to claim 17 , further comprising a protective circuit disposed between said device input and said first impedance converter, said protective circuit having at least one diode and one resistor, said protective circuit embodied so that if an excessive supply voltage occurs at an input side said diode becomes conducting and a current flow through said diode is limited by said resistor.

19. The device according to claim 17 , wherein said third device is an AND gate having inputs each connected to said open-collector output of said first and second comparators.