METHOD AND DEVICE FOR DETERMINING THE PRESSURE PREVENT IN A TANK

Description

[0001] The present invention relates to a method for determining the pressure prevailing in a tank. The present invention further relates to a corresponding device, a corresponding computer program product, and a corresponding storage medium. State of the art

[0002] State-of-the-art hydrogen-powered vehicles use pressure tanks made of carbon fiber-reinforced plastic, for example, that can withstand pressures of up to 800 bar. The resulting storage density gives this type of vehicle a range of more than 500 km.

[0003] DE102006027712A1 discloses an electromagnetic shut-off valve ( shut-off valve), which has particular application for opening and closing a pressurized hydrogen storage tank. In one embodiment, the valve comprises two valve sealing elements, with one side of one valve sealing element located on the high-pressure side of the valve and an opposite side of the other valve sealing element located on the high-pressure side of the valve. Therefore, the pressure applied to the two valve sealing elements is balanced, so less force is required to open the valve against the high pressure.

[0004] Also known are so-called directly operated solenoid valves, whose drive acts directly on a sealing element in the form of a needle-shaped valve piston. When the electromagnet is deactivated, a compression spring keeps the valve closed by pressing the valve piston against the valve seat. The flow direction of the medium through the valve is determined in such a way that, when the valve is closed, the differential pressure building up between the inlet and outlet of the valve additionally presses the valve piston against the valve seat. To open the valve, the piston must be lifted from the valve seat solely by the electromagnetic drive; the drive must therefore work against the compression spring and against the differential pressure applied to the valve piston. The minimum force required by the electromagnetic drive to open such a valve depends primarily on the spring force, the valve seat size, and the maximum differential pressure when the valve is closed. Disclosure of the invention

[0005] The invention provides a method for determining the pressure prevailing in a tank, a corresponding device, a corresponding computer program product and a corresponding storage medium according to the independent claims.

[0006] The proposed method is based on the finding that compressed gas tanks in mobile applications, such as hydrogen tank systems, typically use a shut-off valve. The valve is designed to close when stationary, thus sealing the tank. During operation, the valve opens, allowing the gas to be extracted to supply fuel to the propulsion system.

[0007] A shut-off valve of this type can, for example, be designed as a solenoid-controlled control valve of the type outlined above. When stationary, the valve is closed, with the spring pressing the valve needle onto the valve seat as described above, thus sealing the tank container. To open the valve during operation, an electrical voltage is applied to the solenoid coil. The resulting magnetic force overcomes the closing spring and pressure forces, thereby opening the valve.

[0008] The inventive approach further addresses the need to measure the gas temperature and pressure of the tank container in order to check or monitor its condition. In conventional tank systems with multiple tank containers, however, not every container is equipped with a pressure sensor. Instead, often only a single high-pressure sensor is installed in the high-pressure line to measure the pressure therein. During operation, when the tank valves of all tank containers are open, the pressure in the tank containers can be calculated or at least estimated from the measured pressure in the high-pressure line. However, before the tank valves are opened, e.g. when the vehicle is started, the pressure in the tank containers is unknown without a pressure sensor. This is particularly disadvantageous if the pressure in the individual tank containers differs during start-up.In such a situation, due to large pressure differences between the tank containers and the high-pressure line, some tank valves may be delayed in opening, which may delay the start of the vehicle as a whole.

[0009] The procedure described below, however, allows the tank valves in individual tanks to be opened in a specific sequence when the vehicle is started while the tank valves are still closed, and thus the tank system to be put into operation smoothly.

[0010] The measures listed in the dependent claims allow advantageous refinements and improvements of the basic concept stated in the independent claim. For example, it may also be advantageous to detect the pressure in the individual tank containers during startup without pressure sensors in order to determine the exact fuel level in the respective tank container.

[0011] According to a further aspect, a software function can be provided to determine the pressure in a tank container in which no pressure sensor is installed before the tank valve, designed as a solenoid-controlled shut-off valve, is opened. This function can partially replace a pressure sensor in the tank container to enable the smooth opening of the tank system and the determination of the fill level of the tank system at startup. Short description of the drawings

[0012] Embodiments of the invention are illustrated in the drawings and explained in more detail in the following description. It shows: Figure 1 a decrease in the current through the solenoid coil, which is characteristic of the opening of a solenoid valve. Figure 2 the flowchart of a method according to a first embodiment. Figure 3 schematically shows a control device according to a second embodiment. Embodiments of the invention

[0013] Figure 1 illustrates a decrease (13) in the current (11) through the solenoid coil, characteristic of the opening (12) of a shut-off solenoid valve. When the shut-off valve is closed, the spring force, which presses the valve needle onto the valve seat, and the pressure force prevail. When an electrical voltage (10) is applied to the solenoid coil, a magnetic force is generated. As soon as this force overcomes the spring and pressure forces, the valve begins to open.

[0014] The time of this first valve needle lift can be seen in the diagram according to Figure 1This can be identified by a kink in the current strength graph (11). At this point, the pressure force can be determined by comparing the spring, pressure, and magnetic forces. The spring force is generally known as a design parameter; the magnetic force can be determined from the electrical current (11) and the parameters of the solenoid coil. The tank pressure can be determined from the pressure force calculated in this way and the pressure measured in the high-pressure line.

[0015] Based on this interaction, the commissioning of a hydrogen-powered vehicle with several tanks connected by a common pressure line, each filled with fuel to varying degrees and sealed by a solenoid valve, can be optimized. This application example will now be illustrated using the flow diagram according to Figure 2 explained.

[0016] First, a predetermined voltage (10 - Figure 1 ) is applied (process 21) and the current flowing through the solenoid coil (11 - Figure 1 ) measured (process 22) until a value for the opening (12 - Figure 1 ) of the solenoid valve characteristic decrease (13) of the current (11 - Figure 1 ), which indicates the beginning of the valve needle's stroke movement against the spring force exerted by the valve spring. In addition, the line pressure prevailing in the common pressure line is measured once using the pressure sensor provided for this purpose.

[0017] Based on the data collected during the decline (13 - Figure 1 ) measured current (11 - Figure 1) by the coil on the one hand and the structurally determined and thus essentially known force of the spring loading the valve on the other hand, the pressure difference between the respective tank and the pressure line is calculated, from which the tank pressure can be directly derived in view of the known line pressure (process 23). From the tank pressure calculated in this way, the fuel level in the respective tank can be deduced or the order in which the opening (12 - Figure 1 ) of the solenoid valves for the purpose of supplying fuel to the fuel cell or engine.

[0018] This method (20) can be implemented, for example, in software or hardware or in a mixed form of software and hardware, for example in a control unit (30), as the schematic representation of the Figure 3 clarified.

Claims

1. Method (20) for determining a tank pressure prevailing in a tank, characterized by the following features: - a predefined voltage (10) is applied (21) to a solenoid of a solenoid valve closing the tank, - the current (11) flowing through the solenoid is measured (22) until a decrease (13) of the current (11), which is characteristic of an opening (12) of the solenoid valve, is registered, and - the tank pressure is calculated (23) based on the current (11) measured during the decrease (13).

2. Method (20) according to Claim 1, characterized by the following features: - the solenoid valve is loaded by a valve spring and - the calculation (23) is also carried out based on a structurally induced spring force exerted by the valve spring.

3. Method (20) according to Claim 2, characterized by the following features: - the spring force acts on a valve needle of the solenoid valve and - the decrease (13) occurs upon a lifting movement of the valve needle.

4. Method (20) according to one of Claims 1 to 3, characterized by the following features: - the solenoid valve connects the tank to a pressure line, - the line pressure prevailing in the pressure line is measured and - the calculation (23) is carried out by first calculating the pressure difference between the tank and the pressure line and then the tank pressure is calculated from the line pressure and the pressure difference.

5. Method (20) according to Claim 4, characterized by the following features: - the pressure line is connected to other tanks by other solenoid valves and - the method (20) is applied successively to each of the tanks.

6. Method (20) according to Claim 5, characterized by the following features: - the tanks are at least partially filled with a fuel and - the calculated tank pressure indicates the level of the fuel in the respective tank.

7. Method (20) according to Claim 6, characterized by the following features: - the fuel is used to drive a motor vehicle and - the solenoid valves of the tanks are opened (12) during start-up of the motor vehicle in a sequence depending on the tank pressure determined in each case.

8. Device (30) configured to carry out the method (20) according to one of Claims 1 to 7.

9. Computer program product comprising instructions that cause the device in Claim 8 to carry out the method steps according to one of Claims 1 to 7.

10. Machine-readable storage medium on which the computer program product according to Claim 9 is stored.