METHOD FOR OPENING A VALVE ASSEMBLY FOR A FUEL TANK

Abstract

The invention relates to a method for opening a valve assembly for a fuel tank, comprising a pilot valve (V.sub.1) and at least one additional valve (V.sub.2), in particular for use in a fuel cell-operated vehicle, having the steps of applying (30) an amplification voltage (S.sub.1) in order to open the pilot valve (V.sub.1) in an opening phase (P.sub.1) of the pilot valve (V.sub.1), deactivating (32) the amplification voltage (S1) in order to terminate the opening phase (P.sub.1) of the pilot valve (V.sub.1), applying (34) a pull-in voltage (S.sub.2) in a pull-in phase (P.sub.2) of the pilot valve (V.sub.1) in order to hold the pilot valve (V.sub.1) open, and activating and deactivating (36) the pull-in voltage (S.sub.2) in an alternating manner in order to hold the pilot valve (V.sub.1) open and in order to open the at least one other value (V.sub.2) and hold same open in a readjustment phase (P.sub.3) such that the hold-open energy required on average for holding the pilot valve (v.sub.1) open and the opening energy and/or hold-open energy required on average for the at least one other valve (V.sub.2) is provided.

Claims

1. A method for opening a valve assembly for a fuel tank, said valve assembly comprising a pilot valve (V.sub.1) and at least one further valve (V.sub.2), , comprising the following steps: applying (30) a booster voltage (S.sub.1) for opening the pilot valve (V.sub.1) in an opening phase (P.sub.1) of the pilot valve (V.sub.1), switching off (32) the booster voltage (S.sub.1) for concluding the opening phase (P.sub.1) of the pilot valve (V.sub.1), applying (34) an energizing voltage (S.sub.2) for keeping the pilot valve (V.sub.1) open in an energizing phase (P.sub.2) of the pilot valve (V.sub.1), alternating switching off and on (36) of the energizing voltage (S.sub.2) for keeping the pilot valve (V.sub.1) open and for opening and keeping open the at least one further valve (V.sub.2) in a post-control phase (P.sub.3), so that the mean requisite keep-open energy for keeping the pilot valve (V.sub.1) open and also the mean requisite opening energy and/or keep-open energy of the at least one further valve (V.sub.2) is made available.

2. The method as claimed in claim 1, wherein the booster voltage (S.sub.1) is numerically greater than the energizing voltage (S.sub.2), the booster voltage (S.sub.1) preferentially having an absolute value of more than 12 V.

3. The method as claimed in claim 1, wherein the opening phase (Pi) lasts for more than 2 ms.

4. The method as claimed in claim 1, wherein the energizing voltage (S.sub.2) is lower than the booster voltage (Si), the energizing voltage (S.sub.2) preferentially having a value of 12 V or less.

5. The method as claimed in claim 1, wherein the alternating switching of the energizing voltage (S.sub.2) off and on is undertaken in a post-control phase (P.sub.3) in such a manner that an opening current and/or keep-open current of at least 2 amperes on average is set.

6. The method as claimed in claim 1, wherein the frequency and/or the amplitude of the alternating switching of the energizing voltage (S.sub.2) off and on in the keep-open phase (P.sub.3) is varied as a function of the operating conditions.

7. A system (1) for opening a valve assembly for a fuel tank for use in a fuel-cell-powered vehicle, the system, comprising: a pilot valve (V.sub.1), at least one further valve (V.sub.2), a control unit for applying a booster voltage (S.sub.1) for opening the pilot valve (V.sub.1) and also for applying an energizing voltage (S.sub.2) for keeping the pilot valve (V.sub.1) open and for opening and keeping open the at least one further valve (V.sub.2), the control unit having been designed and arranged within the system (1) in such a manner that the mean requisite keep-open energy for keeping the pilot valve (V.sub.1) open and for opening and keeping open the at least one further valve (V.sub.2) is capable of being made available by an alternating switching of the energizing voltage (S.sub.2) off and on.

8. The system (1) as claimed in claim 7, wherein the pilot valve (V.sub.1) and/or the at least one further valve (V.sub.2) take the form of self-closing valves, preferentially solenoid valves.

9. The system as claimed in claim 7, wherein a detection unit is provided for detecting measured values for determining a suitable point in time for applying a variable voltage.

10. The system as claimed in claim 7, wherein a processing unit is provided for determining a suitable point in time for applying a variable voltage on the basis of measured values detected by means of the detection unit.

11. A motor vehicle including a system comprising: a pilot valve (V.sub.1), at least one further valve (V.sub.2), a control unit for applying a booster voltage (S.sub.1) for opening the pilot valve (V.sub.1) and also for applying an energizing voltage (S.sub.2) for keeping the pilot valve (V.sub.1) open and for opening and keeping open the at least one further valve (V.sub.2), the control unit having been designed and arranged within the system (1) in such a manner that the mean requisite keep-open energy for keeping the pilot valve (V.sub.1) open and for opening and keeping open the at least one further valve (V.sub.2) is capable of being made available by an alternating switching of the energizing voltage (S.sub.2) off and on .

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Further advantages, features and particulars of the invention arise out of the following description, in which embodiments of the invention are described in detail with reference to the drawings. In this connection, the features mentioned in the claims and in the description may be essential for the invention, individually in each instance or in any combination.

[0018] Shown are:

[0019] FIG. 1 a schematic representation of the individual steps of a method according to the invention for opening a valve assembly for a fuel tank,

[0020] FIG. 2 a schematic representation of the activation profile for the pilot valve,

[0021] FIG. 3 a schematic representation of the activation profile for further tank valves.

DETAILED DESCRIPTION

[0022] FIG. 1 shows a schematic representation of the individual steps of a method according to the invention for opening a valve assembly for a fuel tank, said valve assembly comprising a pilot valve V.sub.1 and at least one further valve V.sub.2, in particular for use in a fuel-cell-powered vehicle.

[0023] The method includes the step of applying 30 a booster voltage S.sub.1 for opening the pilot valve V.sub.1 in an opening phase P.sub.1 of the pilot valve V.sub.1. The booster voltage S.sub.1 is advantageously numerically greater than an energizing voltage S.sub.2 to be applied subsequently, the booster voltage S.sub.1 preferentially having an absolute value of more than 12 V, particularly preferably an absolute value of more than 65 V, in particular an absolute value of at least 400 V.

[0024] In a subsequent second step of the method according to the invention, a switching off 32 of the booster voltage S.sub.1 is undertaken for concluding the opening phase P.sub.1 of the pilot valve V.sub.1. The opening phase P.sub.1 may last, for instance, for more than 2 ms, preferentially more than 5 ms, in particular more than 10 ms.

[0025] According to a subsequent third step of the method according to the invention, an application 34 of an energizing voltage S.sub.2 is undertaken for keeping the pilot valve V.sub.1 open in an energizing phase P.sub.2 of the pilot valve V.sub.1. The energizing voltage S.sub.2 is advantageously lower than the booster voltage S.sub.1, the energizing voltage S.sub.2 preferentially having a value of 12 V or less.

[0026] According to the fourth step of the method according to the invention, an alternating switching off and on 36 of the energizing voltage S.sub.2 is undertaken for keeping the pilot valve V.sub.1 open and for opening and keeping open the at least one further valve V.sub.2 in a post-control phase P.sub.3, so that the mean requisite keep-open energy for keeping the pilot valve V.sub.1 open and also the mean requisite opening energy and/or keep-open energy of the at least one further valve V.sub.2 is made available. The alternating switching of the energizing voltage S.sub.2 off and on in the post-control phase P.sub.3 is preferentially undertaken in such a manner that an opening current and/or keep-open current of at least 2 A on average is set. The frequency and/or the amplitude of the alternating switching of the energizing voltage S.sub.2 off and on in the keep-open phase P.sub.3 can be varied, in particular, as a function of the operating conditions, for instance as a function of the counterpressure or of the temperature or such like.

[0027] FIG. 2 shows a schematic representation of the activation profile for the pilot valve V.sub.1.

[0028] The pilot valve V.sub.1 is initially supplied with a booster voltage S.sub.1 of, in the present case, 65 V in an opening phase P.sub.1, so that the current I rises to over 10 A for a short time. The opening phase P.sub.1 of the pilot valve lasts for about 10 ms before the booster voltage S.sub.1 of 65 V is switched off, and in the energizing phase P.sub.2 only a voltage of about 12 V is applied. After the energizing phase P.sub.2, the energizing voltage S.sub.2 of, in the present case, 12 V is alternately switched off and on in the commencing post-control phase P.sub.3, so that the mean requisite keep-open energy for the pilot valve V.sub.1 is still continuously made available.

[0029] FIG. 3 shows the activation profile of the further tank valves V.sub.2. After the pilot valve V.sub.1 has been opened, the pilot valve V.sub.1 ensures that the pressure in the high-pressure circuit rises, so that the remaining tank valves V.sub.2 can be opened contrary to an equalized pressure, and with distinctly less energy. No booster voltage V.sub.1 of, for instance, 65 V is then necessary for this purpose; rather, the energizing voltage S.sub.2 of 12 V is sufficient. By the alternating switching of the energizing voltage S.sub.2 of, in the present case, 12 V, on and off, the further valves V.sub.2 are supplied on average with a current of about 2 A, which ensures that the valves are opened and kept open securely.

[0030] This post-control phase P.sub.3 lasts until such time as the valves V.sub.2 and the pilot valve V.sub.1 are closed again at the end of a journey. This is undertaken by the 12 V supply being set. The frequencies, phases and amplitudes, represented in the present case, of the voltage supply with the energizing voltage S.sub.2 can furthermore be varied, depending upon the operating conditions, in particular as a function of the counterpressure and/or of the temperature. In the case of an emergency opening contrary to a particularly high pressure (for instance, during or shortly after an accident with outbreak of fire and associated increase in pressure in the tank), the booster voltage S.sub.1 of the pilot valve V.sub.1 can also be applied distinctly longer and more frequently, in order to ensure the opening and keeping open.