METHOD FOR DETERMINING A SWITCHING STATE OF A VALVE, AND SOLENOID VALVE ASSEMBLY

Abstract

A method for determining a switching state of a valve that is actuated by a coil, wherein the method includes: respectively ascertaining a current flowing through the coil and a voltage applied to the coil at several times which follow one another with a prespecified time interval, calculating an inductance variable of the coil based on the currents, the voltage and the time interval, and determining the switching state based on the inductance variable. Also disclosed is a solenoid valve assembly.

Claims

1. A method for determining a switching state of a valve that is actuated by a coil, wherein the method comprises: respectively ascertaining a current flowing through the coil and a voltage applied to the coil at several times which follow one another with a prespecified time interval, p1 calculating an inductance variable of the coil based on the currents, the voltage and the time interval, and p1 determining the switching state based on the inductance variable.

2. The method as claimed in claim 1, p1 wherein switching of the valve is identified from a change in the switching state.

3. The method as claimed in claim 1, p1 wherein a switching state of the valve is further monitored by identifying a voltage peak and/or wherein the switching state of the valve is identified from a test signal.

4. The method as claimed in claim 1, wherein the coil is driven by pulse-width modulation, wherein current and voltage are each averaged over a pulse-width modulation period.

5. The method as claimed in claim 1, which is executed continuously or continually repeatedly.

6. The method as claimed in claim 1, wherein the inductance variable is compared with a first end value and a second end value, wherein a first switching state is determined if the inductance variable is at most at a predetermined distance from the first end value, and wherein a second switching state is determined if the inductance variable is at most at a predetermined distance from the second end value.

7. The method as claimed in claim 6, wherein the switching states are end states of the valve.

8. A solenoid valve assembly, comprising: a valve, a coil for actuating the valve, a control device for applying a current and/or a voltage to the coil, and a state determination device which is configured to execute a method as claimed in claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Further features and advantages will be gathered by a person skilled in the art from the exemplary embodiment described below with reference to the appended drawing, in which:

[0039] The FIGURE shows a hydraulic circuit diagram of a brake system that functions merely with use of an inlet valve without a non-return valve.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] Owing to an aspect of the invention, it is possible to provide a normally open inlet valve without a non-return valve, but with tappet opening control.

[0041] In order to implement a normally open inlet valve without a non-return valve, monitoring is advantageously performed as to whether the tappet of the inlet valve falls back to its starting position (open), after the coil is switched off. This can occur, for example, as described further above in accordance with one or more of the embodiments shown. However, this can also occur as described below for example.

[0042] A voltage is induced in the coil due to an opening movement of the tappet. The opening point (upper stop of the tappet) can typically be clearly identified by a voltage peak in this case.

[0043] In the event that no opening has been detected, for example because the tappet is stuck, the outlet valve can be switched in order to reliably reduce the pressure in the brake caliper.

[0044] The advantages of an inlet valve without a non-return valve are, in particular, the saving in respect of further valves that are responsible for shutting the pressure in the wheel (e.g. during re-induction of an LAC), the prevention of a so-called “crossflow” and a reduction in costs owing to the non-return valve being dispensed with.

[0045] An exemplary hydraulic circuit diagram for a brake system that functions merely with use of an inlet valve without a non-return valve is illustrated in the FIGURE. This will not be described further here, but rather reference may be made to the clearly comprehensible hydraulic circuit diagram.