Method for measuring the water level of a water trap in a fuel cell

Abstract

Method for measuring the water level of a water trap (10) wherein the method comprises the following steps: i) Acquisition of output data from a water level sensor (12) at a reference temperature by a control unit which uses an algorithm to correct the output value of the water sensor; ii) Acquisition of output value data from the water level sensor (12) for each ambient temperature by the control unit, which uses a water sensor output value correction algorithm; iii) Calculating a correction value for the output value of the water level sensor (12) for each ambient temperature based on an output value of the water level sensor (12) at the reference temperature by the control unit, which uses a water sensor output value correction algorithm; and iv) Correcting the output value of the water level sensor (12) for each ambient temperature by the control unit, which uses a water sensor output value correction algorithm, based on the calculated correction value, wherein step iii) includes: iii-1) a method of setting a temperature in a chamber to a temperature lower than the reference temperature (Ta) and then increasing the temperature in the chamber to a predetermined temperature higher than the reference temperature (Ta) at predetermined temperature step intervals, in a condition in which the water trap (10) on which the water level sensor (12) with a temperature sensor (20) is mounted is placed in an ambient chamber, the temperature in the ambient chamber being increased while each temperature step is maintained for a predetermined time; iii-2) a method of recording the output value of the water level sensor (12) and the current temperature data at the time at which each temperature step ends; and iii-3) a method of subtracting the output value of the water level sensor (12) at the time when each temperature step ends from the output value of the water level sensor (12) at the reference temperature in order to calculate the correction value for correcting the output value of the water level sensor (12).

Description

BACKGROUND(a) Technical field

[0001] The present invention relates to a method for detecting the water level of a water trap, in particular to a method for detecting the water level of a water trap in a fuel cell, which can accurately output the water level of the water collected in the water trap by the reaction of the fuel cell. (b) Description of the state of the art

[0002] A primary energy source for a fuel cell vehicle is provided by a generating device called a fuel cell stack, and the fuel cell stack is a device in which oxygen in air and hydrogen supplied from outside react chemically to produce energy.

[0003] When hydrogen is supplied as fuel to the anode of the fuel cell stack and air as an oxidant to the cathode, the supplied hydrogen is split into hydrogen ions and electrons through an oxidation reaction in the catalyst layer of the anode. The generated hydrogen ions are supplied to the cathode through a polymer electrolyte membrane in the fuel cell stack, and the electrons are supplied to the cathode via an external circuit. As a result, electricity is generated in the cathode through a process in which the supplied oxygen and electrons combine to produce oxygen ions via a catalyst layer reduction reaction, and the hydrogen ions and oxygen ions combine to produce water.

[0004] Since the water produced in the fuel cell stack interrupts the flow of oxygen and hydrogen, it must be removed. Therefore, the water falls by gravity according to the design of the fuel cell stack and is collected in a water trap.

[0005] When the water collected in the water trap reaches a predetermined water level or more, an opening control of a drain valve is carried out to release the water to the outside by detecting through a water level sensor that the collected water has reached the predetermined water level or more.

[0006] As described above, only by accurately recording the water level stored in the water trap can the current water level in the water trap be precisely determined, and furthermore, the timing of the water release to the outside can be precisely controlled.

[0007] The water level sensor mounted on the water trap, a capacitive analog water level sensor, displays a water level that is output within a normal range of room temperature conditions, but shows an output that differs from the actual water level when the temperature of the water and the ambient temperature change.

[0008] For example, the water level sensor tends to output a water level that is higher than the actual water level when the temperature of the water increases.

[0009] From JP 2013 - 088 222 A, a method for detecting a water level is known, comprising the steps of: acquiring output data of a water level sensor at a reference temperature by a control unit; acquiring output value data of the water level sensor for each ambient temperature by a control unit; calculating a correction value for the output value of the water level sensor for each ambient temperature based on an output value of the water level sensor at the reference temperature by a control unit; and correcting the output value of the water level sensor for each ambient temperature by a control unit based on the calculated correction value.

[0010] DE 10 2007 039 557 A1 discloses the invention. The invention relates to a method and a device for determining a fill level for level control of a liquid accumulating in a system, wherein emptying is triggered when an upper switching point is exceeded, emptying is terminated when a lower switching point is undershot, and at least one switching point is predicted as a function of at least one current physical state variable of the system. The invention relates in particular to a method for determining a switching point for level control of a separator in a fuel cell system.

[0011] CN 1 256 404 A describes a level gauge comprising a pressure transmitter, a power supply, a housing, a push button, an LED display, and circuitry connected via signal and power cables. The circuitry includes pressure and temperature transmitters, multi-channel analog switches, analog-to-digital converters, a monochip computer, data and program memory, a serial interface, a keypad / display interface, and an LED display. Error compensation involves first measuring the output signals of the pressure and temperature transmitters, and then compensating for the nonlinear error, temperature error, and zero-point drift error of the pressure signal using a compensation program developed within the monochip computer.

[0012] US Patent 4,601,201 A further discloses a device for measuring the level and quantity of fuel oil stored in a tank, comprising a pair of electrodes, one being a number of segmented electrodes, while the other is an elongated electrode to form a number of capacitors; a source for applying a high-frequency voltage to the electrodes, one after the other, to generate electrical signals; means for converting the signals into corresponding high-frequency signals; means for calculating the liquid level from the frequencies of the signals; and means for calculating the fuel quantity. The capacitor probe is manufactured by attaching an elongated flexible substrate, printed with the electrodes, around a rigid rod, covering its outer surface with insulating material, and attaching a metal tube. The segmented electrodes are arranged longitudinally in two rows in a zigzag pattern and partially overlapping.

[0013] The above information disclosed in this background section is intended only to improve the understanding of the background of the invention and may therefore contain information that does not constitute the prior art already known to a person skilled in the art in this country. OVERVIEW

[0014] It is an object of the present invention to provide a method for detecting the water level of a water trap which can detect a change in the ambient temperature of a water level sensor by attaching a separate temperature sensor to the water level sensor and can accurately output the water level in the water trap independently of the change in the ambient temperature by means of a water sensor output value correction algorithm based on a detected temperature.

[0015] The problem is solved by a method for detecting the water level of a water trap with the features of claim 1. Advantageous further developments are found in the dependent claims.

[0016] According to one aspect of the present invention, a method for detecting the water level of a water trap is provided, the method comprising the following steps: i) acquiring data from a water level sensor at a reference temperature by a control unit using a water sensor output value correction algorithm; ii) acquiring output value data from the water level sensor for each ambient temperature by the control unit using a water sensor output value correction algorithm; iii) calculating a correction value for the output value of the water level sensor for each ambient temperature based on an output value of the water level sensor at the reference temperature by the control unit using a water sensor output value correction algorithm;and iv) Correcting the output value of the water level sensor for each ambient temperature by the control unit, which uses a water sensor output value correction algorithm, based on the calculated correction value. Step iii) includes: iii-1) a method of setting a temperature in a chamber to a temperature lower than the reference temperature (Ta), and then increasing the temperature in the chamber to a predetermined temperature higher than the reference temperature (Ta) at a predetermined temperature step interval, in a state where the water trap, on which the water level sensor with a temperature sensor is mounted, is placed in an ambient chamber, with the temperature in the ambient chamber being increased while each temperature step is maintained for a predetermined time;iii-2) a method of recording the output value of the water level sensor and the current temperature data at the time each temperature step ends; and iii-3) a method of subtracting the output value of the water level sensor at the time each temperature step ends from the output value of the water level sensor at the reference temperature in order to calculate the correction value for correcting the output value of the water level sensor.

[0017] In step i), the output signal of the water level sensor can be an output value of the water level sensor for a state in which the water level in the water trap is a low water level or a full water level at the reference temperature, and an output value of the water level sensor in a range between the low water level and the full water level.

[0018] In step ii), the output data of the water level sensor can be recorded for each ambient temperature under the condition that the water level in the water trap is low.

[0019] The method may further include: after step iii-3), iii-4), a method of adjusting the temperature in the ambient chamber to a temperature higher than the reference temperature, and then lowering the temperature in the ambient chamber to a predetermined temperature lower than the reference temperature, with the predetermined temperature step interval, wherein the temperature in the ambient chamber is reduced while each temperature step is maintained for a predetermined time; iii-5) a method of recording the output value of the water level sensor and the current temperature data at the time at which each temperature step ends; iii-6) a method of subtracting the output value of the water level sensor at the time each temperature step ends from the output value of the water level sensor at the reference temperature in order to calculate the correction value for correcting the output value of the water level sensor; and iii-7) Calculating a final correction value by averaging the correction value calculated in step iii-3) and the correction value calculated in step iii-6).

[0020] Step iv) can be obtained by finding, when a current temperature detected by a temperature sensor differs from the reference temperature, the correction value corresponding to the current temperature in a memory of a control unit, and outputting a water level sensor output value on which the found correction value is reflected.

[0021] The present invention provides the following effects through the means of solving the problems.

[0022] First, a separate temperature sensor is installed inside a water level sensor to detect changes in the ambient temperature of the water level sensor, and to correct and output an output value of the water level sensor for each currently detected temperature according to an output value of the water level sensor at a reference temperature, and as a result, the water level sensor can continuously and accurately output a water level in a water trap regardless of changes in the ambient temperature.

[0023] Secondly, the accuracy of an output value indicating the water level of a capacitive analog water level sensor can be improved, and a problem where a state-of-the-art water level sensor shows an output that differs from an actual water level when the temperature of the water and an ambient temperature are changed can be resolved.

[0024] Further aspects and preferred embodiments of the invention are explained below. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The above and further features of the present invention will now be described in detail with reference to certain exemplary embodiments shown in the accompanying drawings, which are provided below for illustrative purposes only and thus do not limit the present invention and in which: Fig. 1 (Related technology) is a schematic view showing a water trap of a fuel cell system and a water level sensor according to the related technology attached to the water trap; Fig. 2 is a schematic view showing a water trap of a fuel cell system and a water level sensor attached to the water trap; Fig. 3 is a graph showing a change in an output value of the water level sensor at a reference temperature according to a water level in the water trap; Fig. 4 is a graph showing a change in the output value of the water level sensor for each ambient temperature when the water level in the water trap is in a low water level state; Fig. 5 is a graph showing an example of the correction of the output value of the water level sensor according to a current temperature as a method for detecting a water level according to the present invention; Fig. 6 is a graph showing a comparison of the output value of the water level sensor for each ambient temperature of the present invention for a specific water level and the output value of the water level sensor according to the related technology; and Fig. Figure 7 is a flowchart that provides an example of the calculation of a correction value K for the output value of the water level sensor in the present invention.

[0026] It is understood that the accompanying drawings are not necessarily to scale and represent a somewhat simplified depiction of various preferred features that constitute the basic principles of the invention. The specific embodiments of the present invention, as disclosed herein, including, for example, specific dimensions, orientations, positions, and shapes, are partly determined by the specific intended application and usage environment.

[0027] In the figures, the reference numerals refer to the same or equivalent parts of the present invention in the different figures of the drawing. DETAILED DESCRIPTION

[0028] It is understood that the term "vehicle" or "vehicle-" or other similar expressions, as used herein, include motor vehicles in general, such as passenger cars, including all-terrain vehicles (SUVs), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft and the like, and hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles and other alternative fuel vehicles (for example, fuels derived from resources other than petroleum). As used herein, a hybrid vehicle is a vehicle with two or more propulsion sources, for example, both gasoline and electric vehicles.

[0029] The terminology used herein serves only to describe specific embodiments and is not intended to limit the disclosure. As used herein, the singular forms "a," "an," and "the" are also intended to include the plural forms, unless the context clearly indicates otherwise. Furthermore, it is understood that the expressions "includes" and / or "comprehensive," when used in this specification, specify the presence of the indicated features, numbers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, numbers, steps, operations, elements, components, and / or groups thereof. As used herein, the expression "and / or" includes any and all combinations of one or more of the associated listed elements.Unless explicitly stated otherwise, the term "include" and variations such as "includes" or "comprehensive" are understood to mean the inclusion of specified elements but not the exclusion of other elements. Additionally, the terms "unit," "-er," "-or," and "module" as described in the specification refer to units for performing at least one function and operation, and can be implemented by hardware components or software components and combinations thereof.

[0030] Furthermore, the control logic of the present invention can be implemented as non-volatile, computer-readable media on a computer-readable medium containing executable program instructions that are executed by a processor, a controller / controller unit, or the like. Examples of computer-readable media include, but are not limited to, ROM, RAM, compact disc (CD)-ROMs, magnetic tapes, floppy disks, memory sticks, memory cards, and optical data storage devices. The computer-readable recording medium can also be distributed across computer systems linked via a network, allowing the computer-readable media to be stored and executed in a distributed manner, for example, by a telematics server or a controller area network (CAN).

[0031] The following section describes in detail various embodiments of the present invention, examples of which are illustrated in the accompanying drawings and described below. While the invention is described in conjunction with exemplary embodiments, it is understood that the present description is not intended to limit the invention to these exemplary embodiments. On the contrary, the invention is intended to encompass not only the exemplary embodiments but also various alternatives, modifications, equivalents, and other embodiments that may be included within the scope and protection of the invention as defined by the accompanying claims.

[0032] Preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0033] First, an operating sequence of a water trap installed in a fuel cell system and a water level sensor attached to the water trap are described with reference to Fig. 1 (prior art) described to aid in understanding the present invention.

[0034] First, when hydrogen is supplied to an anode of the fuel cell stack, unreacted hydrogen is discharged to an outlet port of the anode, and in this case, water contained in the unreacted hydrogen falls off by gravity to be collected in the water trap, and hydrogen from which droplets have been removed is returned to an inlet port of the anode.

[0035] In this case, the water level of the water collected in a water trap 10 is detected in real time by a water level sensor 12, which is attached to the water trap 10, and the water level sensor 12 consists of a water level detection electrode 12-1 and a printed circuit board (PCB) 12-2, which transmits a water level detection signal to a control unit.

[0036] Therefore, if the control unit determines that the water level in the water trap 10 is a predetermined level or higher, based on the water level detection signal sent by the water level sensor 12, the water in the water trap is discharged to the outside through an opening control of a drain valve 14 located at the bottom of the water trap.

[0037] The water level sensor 12, mounted on the water trap 10 as a capacitive analog water level sensor, shows a water level output within a normal range at room temperature, but shows an output that differs from the actual water level when the temperature of the water and the ambient temperature change.

[0038] For example, the water level sensor 12 tends to output a water level that is higher than the actual water level when the temperature of the water increases.

[0039] To solve the problem, the present invention focuses on detecting a change in the ambient temperature of a water level sensor by placing a separate temperature sensor in the water level sensor and accurately outputting the water level in the water trap regardless of the change in the ambient temperature through a temperature correction algorithm based on a detected temperature.

[0040] The water level sensor for the water trap and an operating flow thereof according to the present invention are described below.

[0041] Referring to Fig. 2 is a separate temperature sensor 20 attached to the water level sensor 12, which is mounted in the water trap 10.

[0042] The water level sensor 12 is used as the capacitive, analog water level sensor, which consists of the water level sensing electrode 12-1 and the printed circuit board (PCB) 12-2, which sends the water level detection signal to the control unit, and the temperature sensor 20 is attached to an adjacent part of the electrode 12-1 of the water level sensor 12.

[0043] The reason for mounting the temperature sensor 20 on the adjacent part of the electrode 12-1 of the water level sensor 12 is that an output value of the water level sensor 12 is influenced by a temperature of the electrode 12-1.

[0044] Therefore, the output value of the water level sensor 12, which is influenced by the temperature, is corrected using a detection value from the temperature sensor 20, and as a result, the output value of the water level sensor 12 can be output to accurately display a water level in the water trap regardless of any change in the ambient temperature.

[0045] A method for correcting the output value of the water level sensor in accordance with the ambient temperature according to the present invention is described below.

[0046] First, the output data of the water level sensor are recorded for a state in which the water level in the water trap is a low water level (empty) and a full water level (full) at a reference temperature Ta.

[0047] The output values ​​C1 and C2 of the water level sensor for the state in which the water level in the water trap is the low water level (empty) and the full water level (full) at the reference temperature Ta, and an output value (C = F (x)) of the water level sensor in a range between the low water level (empty) and the full water level (full), are output essentially linearly, as shown in Fig. 3 shown.

[0048] Therefore, the output values ​​C1 and C2 of the water level sensor for the state in which the water level in the water trap is the low water level (empty) and the full water level (full) at the reference temperature Ta, and the output value (C = f (x)) of the water level sensor in the range between the low water level (empty) and the full water level (full) are stored in a memory of the control unit.

[0049] Next, the initial value data of the water level sensor are recorded for each ambient temperature in the state where the water level in the water trap is the low water level.

[0050] In this case, the reason for recording the output value of the water level sensor for each ambient temperature only under the condition of low water level is that the output values ​​of the water level sensor for each ambient temperature are changed in a similar way in the state where the water in the water trap is at low water level, in the state between low water level and full water level, and in the state of full water level.

[0051] Referring to Fig. 4. In the event of a change in the water level sensor output for each ambient temperature in the low water level (empty) state, the output value at a temperature T_LOW lower than the reference temperature Ta is output to be lower than the output value C3 at the reference temperature Ta, and the output value at a temperature T_HIGH higher than the reference temperature Ta is output to be higher than the output value C3. This demonstrates that the water level sensor output changes according to the ambient temperature.

[0052] Subsequently, a correction value K for the output value of the water level sensor is calculated for each ambient temperature (for example, for each ambient temperature of the electrode) based on the output value of the water level sensor at the reference temperature Ta.

[0053] An example of a procedure for calculating the correction value K is given below with reference to a flowchart according to Fig. 7 described.

[0054] The water trap, on which the water level sensor including the temperature sensor is mounted, is used in an environmental chamber (S101).

[0055] Next, the temperature in the chamber is set to T_LOW, which is lower than the reference temperature Ta, and then increased to a predetermined temperature T_HIGH, which is higher than the reference temperature Ta, at a temperature step interval of 2 °C, with each temperature step being held for a minimum of 180 seconds (S102).

[0056] In this case, the output value of the water level sensor and the current temperature data are recorded at the time when each temperature step ends (S103).

[0057] The output value of the water level sensor at the time each temperature step ends is then subtracted from the output value of the water level sensor at the reference temperature to calculate the correction value K to correct the output value of the water level sensor (S104).

[0058] Meanwhile, the temperature in the chamber is set to the temperature T_HIGH, which is higher than the reference temperature Ta, and then the correction value is recalculated to increase the accuracy of the calculation of the correction value K.

[0059] For this purpose, the temperature in the chamber is set to the temperature T_HIGH, which is higher than the reference temperature Ta, and then reduced to a predetermined temperature T_LOW, which is lower than the reference temperature Ta, at a temperature step interval of 2 °C, with each temperature step being held for a minimum of 180 seconds per step (S105).

[0060] Even in this case, the output value of the water level sensor and the current temperature data are recorded at the time when each temperature step ends (S106).

[0061] Similarly, the output value of the water level sensor at the time each temperature step ends is subtracted from the output value of the water level sensor at the reference temperature to calculate the correction value K to correct the output value of the water level sensor (S107).

[0062] As described above, the step of calculating the correction value is repeated twice, and the resulting values, which have been repeated twice, are averaged to calculate a final correction value K (S108).

[0063] The finally calculated correction value K is applied to a table or equation that is to be stored in the memory of the control unit.

[0064] Accordingly, the output value of the water level sensor can be corrected for any ambient temperature based on the calculated correction value.

[0065] Especially when the current temperature Tb detected by the temperature sensor differs from the reference temperature Ta, as in Fig. As shown in Figure 5, the correction value K, which corresponds to the current temperature Tb, is found in the memory of the control unit and an output value from the water level sensor, on which the found correction value K is reflected, is output.

[0066] For example, if it is assumed that the reference temperature Ta is 10°C and the output value of the water level sensor at the reference temperature Ta of 10°C is 100, and assuming that the current temperature Tb, which is detected by the temperature sensor, is -10°C and that the output value of the water level sensor at the current temperature Tb of -10°C is 50, the correction value becomes 50, and consequently the output value of the water level sensor, on which the correction value of 50 is reflected, becomes 100.

[0067] As described above, the separate temperature sensor is installed in the water level sensor to detect changes in the current ambient temperature of the water level sensor, and to correct and output the output value of the water level sensor for each currently detected temperature according to the output of the water level sensor at the reference temperature, and thus the water level sensor can continuously and accurately output the water level in the water trap regardless of changes in the ambient temperature.

[0068] In other words, the output value of the water level sensor varies for each ambient temperature for a specific water level compared to the output value at the reference temperature Ta, as shown in Fig.6 as shown in the related technology, however, according to the present invention, a constant output value of the water level sensor at the specific water level can be output in comparison to the output value at the reference temperature Ta, regardless of the ambient temperature, whereby the accuracy of the output value indicating the water level of the capacitive analog water level sensor can be improved.

Claims

[1] Method for measuring the water level of a water trap (10) wherein the method comprises the following steps: i) Acquisition of output data from a water level sensor (12) at a reference temperature by a control unit which uses an algorithm to correct the output value of the water sensor; ii) Acquisition of output value data from the water level sensor (12) for each ambient temperature by the control unit, which uses a water sensor output value correction algorithm; iii) Calculating a correction value for the output value of the water level sensor (12) for each ambient temperature based on an output value of the water level sensor (12) at the reference temperature by the control unit, which uses a water sensor output value correction algorithm; and iv) Correcting the output value of the water level sensor (12) for each ambient temperature by the control unit, which uses a water sensor output value correction algorithm, based on the calculated correction value, wherein step iii) includes: iii-1) a method of setting a temperature in a chamber to a temperature lower than the reference temperature (Ta) and then increasing the temperature in the chamber to a predetermined temperature higher than the reference temperature (Ta) at predetermined temperature step intervals, in a condition in which the water trap (10) on which the water level sensor (12) with a temperature sensor (20) is mounted is placed in an ambient chamber, the temperature in the ambient chamber being increased while each temperature step is maintained for a predetermined time; iii-2) a method of recording the output value of the water level sensor (12) and the current temperature data at the time at which each temperature step ends; and iii-3) a method of subtracting the output value of the water level sensor (12) at the time when each temperature step ends from the output value of the water level sensor (12) at the reference temperature in order to calculate the correction value for correcting the output value of the water level sensor (12). [2] Method according to claim 1, wherein in step i) the output data of the water level sensor (12) are an output value of the water level sensor (12) for a state in which a water level in the water trap (10) is a low water level or a full water level at the reference temperature, and an output value of the water level sensor (12) in a range between the low water level and the full water level. [3] Method according to claim 1, wherein in step ii) the output value data of the water level sensor (12) are recorded for each ambient temperature under the condition that the water level in the water trap (10) is the low water level. [4] Method according to claim 1, further comprising: after step iii-3), iii-4) a method of setting the temperature in the ambient chamber to a temperature higher than the reference temperature and then lowering the temperature in the ambient chamber to a predetermined temperature lower than the reference temperature, with the predetermined temperature step interval, wherein the temperature in the ambient chamber is reduced while each temperature step is maintained for a predetermined time; iii-5) a method of recording the output value of the water level sensor (12) and the current temperature data at the time at which each temperature step ends; iii-6) a method of subtracting the output value of the water level sensor (12) at the time when each temperature step ends from the output value of the water level sensor (12) at the reference temperature in order to calculate the correction value for correcting the output value of the water level sensor (12); and iii-7) Calculating a final correction value by averaging the correction value calculated in step iii-3) and the correction value calculated in step iii-6). [5] Method according to claim 1, wherein step iv) is obtained by finding, when a current temperature detected by a temperature sensor (20) differs from the reference temperature, the correction value corresponding to the current temperature in a memory of a control unit, and outputting an output value of the water level sensor (12) on which the found correction value is reflected.

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