Method for determining the switching state of a valve and solenoid valve assembly

Abstract

The present invention relates to a method for determining the switching state of a valve actuated by a coil, wherein the method comprises the following steps: determining a current flowing through the coil and a voltage applied to the coil at times following each other at predefined time intervals, calculating an inductance variable of the coil based on the current, the voltage, and the time interval, and determining the switching state based on the inductance variable. The present invention also relates to a solenoid valve assembly.

Description

Technical Field

[0001] The invention relates to a method for determining a switching state of a valve as claimed in claim 1 and to a solenoid valve assembly as claimed in claim 8 . Background Art

[0002] In particular, the valve can be actuated by an electromagnet. For this purpose, a corresponding electromagnetic valve assembly can be established, which generally has a valve and a coil for actuating the valve.

[0003] It is known in the prior art to switch valves by applying a current suitable for switching to the corresponding coil. The magnetic field generated in this manner typically switches the valve or holds it in a specific state. However, in prior art embodiments, it is often assumed that a set or desired switching state is actually assumed. This is not checked.

[0004] Known normally open inlet valves close the hydraulic connection to the brake caliper as needed if the system pressure is higher than the pressure that should prevail in the brake caliper. This can be the case, for example, during ABS control.

[0005] In modern inlet valves, a non-return valve is usually responsible for reliably reducing the pressure in the brake caliper when the brake is released, for example in the event of a stuck valve.

[0006] However, it is then necessary to provide additional valves which are responsible for shutting off the pressure in the wheels (for example during the reintroduction of the LAC). In addition, a so-called "cross flow" occurs, in which case... Summary of the Invention

[0007] Therefore, an object of the present invention is to provide a method for determining the switching state of a valve. Another object of the present invention is to provide an associated solenoid valve assembly.

[0008] The present invention relates to a method for determining the switching state of a valve, which is actuated by a coil. The method comprises the following steps:

[0009] - determining the current flowing through the coil and the voltage applied to the coil, respectively, at times following each other at pre-specified time intervals,

[0010] - calculating the inductance variable of the coil based on the currents, the voltage and the time interval, and

[0011] - determining the switching state based on the inductance variable.

[0012] The present invention is based on the knowledge that an inductance variable can be determined by measuring the current and voltage at a given time, wherein the switching state of the valve can be determined based on this inductance variable. This allows monitoring the switching state, i.e., for example, whether the valve is open or closed. A valve switching event can be inferred or detected based on a change in the switching state.

[0013] The current and / or voltage can be determined, for example, by measurement. Suitable measuring devices can be used for this purpose. However, the current and voltage can each be determined using predefined values. This is particularly the case when the values are predefined and set using a device suitable for this purpose. Thus, for example, a regulated current source can be used to set a defined current. The same applies to the voltage. In this case, it is no longer absolutely necessary to measure the actual set value, but it should be noted that such a value can still be measured.

[0014] A physical inductance can be used as the inductance variable. However, a variable representing inductance, such as a variable that is proportional to the actual inductance but is easier to calculate or process, can also be used. The inductance variable and the actual inductance typically have a relationship, such as a linear relationship.

[0015] It should be noted that the inductance variable may be easier to determine than the inductance in a strict physical sense, wherein the inductance variable or another variable that is easier to calculate than the inductance and is based on the inductance may also be used to determine the switching state.

[0016] Since a non-return valve is no longer required, an additional valve for shutting off the pressure in the wheel is also saved. In addition, there is no longer any "cross-flow" effect, and costs are reduced due to the elimination of the non-return valve.

[0017] In a preferred development of the method, the switching of the valve is detected based on a change in the switching state.

[0018] In a preferred development of the method, the switching state of the valve is monitored by detecting voltage peaks. This is based on the knowledge that voltage peaks occur when the switching state changes. In particular, these can be detected by a suitable sensor system and used accordingly. For example, this can be used to control the opening of the tappet.

[0019] It will be appreciated that identifying switching states by identifying voltage peaks may represent an independent aspect of the present invention, which may also be used independently of the other features and embodiments disclosed herein, but may also be combined with them as desired.

[0020] As an alternative or in addition, the switching state of the valve can be detected based on a test signal. The test signal can be applied to the coil so that the switching state can be detected.

[0021] In a preferred development of the method, the coil is driven by pulse width modulation. In this case, the current and voltage are preferably each averaged within a pulse width modulation period. It has been shown that in this case, the method can also be advantageously used with coils driven by pulse width modulation.

[0022] In a preferred development of the invention, the method is performed continuously or repeatedly. This means that the state of the valve can be monitored continuously.

[0023] In a preferred development of the invention, the following steps are performed:

[0024] - comparing the inductance variable with a first end value and a second end value,

[0025] - determining a first switching state if the inductance variable is at most a predetermined distance from the first end value, and

[0026] If the inductance variable is at most a predetermined distance from the second end value, a second switching state is determined.

[0027] In a preferred development of the method, the switching state is the end state of the valve. However, intermediate states can also be determined.

[0028] The present invention also relates to a solenoid valve assembly, which comprises:

[0029] -valve,

[0030] - a coil for actuating the valve,

[0031] - control means for applying a current and / or a voltage to the coil, and

[0032] - A state determination device configured to carry out the method according to one of the preceding claims.

[0033] The present invention also relates to a solenoid valve assembly. The solenoid valve assembly comprises a valve and a coil for actuating the valve. The solenoid valve assembly further comprises a control device for applying a current and / or voltage to the coil. As a result, the valve or the coil can be actuated.

[0034] The solenoid valve assembly further comprises a state determination device which is configured to carry out the method according to the invention.All embodiments and variants described herein can be used here.

[0035] By means of the solenoid valve assembly according to the invention, the advantages mentioned further above can be used for the solenoid valve assembly.

[0036] The invention also relates to a non-volatile computer-readable storage medium having a program code stored thereon, during the execution of which the method according to the invention is performed.With regard to the method according to the invention, all embodiments and variants described herein can be used. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] A person skilled in the art will derive further features and advantages from the exemplary embodiments described below with reference to the accompanying drawings, in which:

[0038] Figure 1 : shows a hydraulic circuit diagram of a brake system that functions only by using an inlet valve without a one-way valve. DETAILED DESCRIPTION

[0039] Thanks to the invention, it is possible to provide a normally open inlet valve without a non-return valve but with tappet opening control.

[0040] To implement a normally open inlet valve without a check valve, it is advantageous to monitor whether the tappet of the inlet valve has returned to its starting position (open) after the coil is deactivated. This can occur, for example, as described further above with respect to one or more of the illustrated embodiments. However, it can also occur, for example, as described below.

[0041] As the tappet opens, a voltage is induced in the coil. In this case, the opening point (top dead center of the tappet) can usually be clearly identified by a voltage peak.

[0042] In the event that opening is not detected (for example due to a stuck tappet), the outlet valve can be switched in order to reliably reduce the pressure in the brake caliper.

[0043] The advantages of an inlet valve without a non-return valve are in particular the saving of an additional valve responsible for shutting off the pressure in the wheel (for example during reintroduction of the LAC), the avoidance of so-called "cross-flow" and the reduction of costs due to the omission of a non-return valve.

[0044] Figure 1 An exemplary hydraulic circuit diagram of a brake system is shown, which functions only by using an inlet valve without a one-way valve. No further description will be given here, but reference can be made to the hydraulic circuit diagram which is clear and easy to understand.

Claims

1. A method for determining a switching state of an inlet valve, the inlet valve being actuated by a coil, wherein: The method comprises the following steps: - determining the current flowing through the coil and the voltage applied to the coil, respectively, at times following each other at pre-specified time intervals, - calculating the 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 and monitoring whether the tappet of the inlet valve falls back into its starting position after the coil is closed, in order to implement a normally open inlet valve without a non-return valve, The switching state of the inlet valve is further monitored by detecting voltage peaks.

2. The method according to claim 1, wherein the switching of the inlet valve is detected based on a change in the switching state.

3. The method according to claim 1 or 2, - In this case, the switching state of the inlet valve is also detected based on the test signal.

4. The method according to claim 1 or 2, - wherein the coil is driven by pulse width modulation, - in, The current and voltage are each averaged over the PWM period.

5. The method according to claim 1 or 2, - Execute the method continuously or repeatedly.

6. The method according to claim 1 or 2, - in, comparing the inductance variable with a first end value and a second end value, - wherein a first switching state is determined if the inductance variable is at most a predetermined distance from the first end value, and wherein a second switching state is determined if the inductance variable is at most a predetermined distance from the second end value.

7. The method according to claim 6, - wherein the switching state is the end state of the inlet valve.

8. A solenoid valve assembly comprising: - a normally open inlet valve without a non-return valve, - a coil for actuating the inlet valve, - control means for applying a current and / or voltage to the coil, and - A state determination device configured to carry out the method according to one of the preceding claims.

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