Fuel cell system

Abstract

In a fuel cell system equipped with a full-water determination unit that determines whether or not the water storage tank for the generated water produced by the fuel cell is full, the system suppresses a decrease in the accuracy of the full-water determination unit's judgment even if the water level of the generated water in the storage tank is unstable. [Solution] The full-water determination unit Cw counts up the first count value C1 when the signal output from the float sensor Sf is at a high level, and counts down the first count value C1 when the signal output from the float sensor Sf is at a low level. When the first count value C1 is equal to or greater than the first threshold C1th, it determines that the water storage tank WT is full.

Description

Technical Field

[0006] , ,

[0001] The present invention relates to a fuel cell system.

Background Art

[0002] As a fuel cell system, there is one including a water storage tank for storing generated water generated by a fuel cell, a float sensor that outputs a high-level signal when the float rises as the water level of the generated water in the water storage tank rises, and a full-water determination unit that determines that the inside of the water storage tank is in a full-water state when the signal output from the float sensor is continuously at a high level for a certain period of time. As a related technique, there is Patent Document 1.

[0003] By the way, when the water level of the generated water in the water storage tank is unstable, the state of the signal output from the float sensor also becomes unstable, so there is a possibility that the accuracy of the determination of the full-water determination unit may decrease.

[0004] For example, when the fuel cell system is mounted on a moving body such as a vehicle, when the moving body vibrates or turns, the water storage tank may shake or tilt, causing the water level of the generated water in the water storage tank to fluctuate. When the water level of the generated water in the water storage tank fluctuates, even though the inside of the water storage tank is actually in a full-water state, the signal output from the float sensor may not continuously become high level for a certain period of time, and there is a possibility that the full-water determination unit may not determine that it is in a full-water state.

[0005] Also, when the moving body is tilted with respect to the horizontal, the water storage tank is also tilted. Therefore, depending on the mounting position of the float sensor, the float of the float sensor may rise even though the inside of the water storage tank is not actually in a full-water state, or the float of the float sensor may not rise even though the inside of the water storage tank is actually in a full-water state, and there is a possibility that the state inside the water storage tank may be misjudged by the full-water determination unit.

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] Japanese Patent Publication No. 2024-083027 [Overview of the project] [Problems that the invention aims to solve]

[0007] One aspect of the present invention is to suppress a decrease in the accuracy of the full-water determination unit's determination even when the water level of the generated water in the storage tank is unstable, in a fuel cell system that includes a full-water determination unit that determines whether or not the storage tank for the generated water produced by the fuel cell is full. [Means for solving the problem]

[0008] One embodiment of the fuel cell system according to the present invention includes a water storage tank for storing water discharged from a fuel cell, a float sensor provided in the water storage tank, and a full-water determination unit that counts up a first count value when the signal output from the float sensor is at a high level, counts down the first count value when the signal output from the float sensor is at a low level, and determines that the water storage tank is full when the first count value is equal to or greater than a first threshold.

[0009] As a result, even when the water storage tank is actually full, the full-water determination unit can still determine that the water storage tank is full, even if the level of the signal output from the float sensor fluctuates due to changes in the water level of the generated water inside the tank. In other words, even if the water level of the generated water inside the tank is unstable, it is possible to suppress a decrease in the accuracy of the full-water determination unit's judgment.

[0010] Furthermore, one embodiment of the present invention is a fuel cell system mounted on a mobile body, comprising: a water storage tank for storing water discharged from the fuel cell; a float sensor provided in the water storage tank; a tilt determination unit for determining whether the mobile body is tilted relative to the horizontal; and a full-water determination unit for determining that the water storage tank is full when the signal output from the float sensor is at a high level, counts up a first count value when the signal output from the float sensor is at a low level, counts down the first count value when the signal output from the float sensor is at a low level, and determines that the water storage tank is full when the first count value is equal to or greater than a first threshold, wherein the full-water determination unit changes the first threshold when the tilt determination unit determines that the mobile body is tilted relative to the horizontal.

[0011] Thus, since the system is configured to determine that the water storage tank is full when the first count value is equal to or greater than the first threshold, even if the water level of the generated water in the water storage tank fluctuates and the level of the signal output from the float sensor changes, the full-water determination unit can still determine that the water storage tank is full when the water storage tank is actually full. Furthermore, since the system is configured to change the first threshold when it is determined that the moving body is tilted relative to the horizontal, even if the signal output from the float sensor becomes low level due to the tilt of the moving body, even though the water storage tank is actually full, the first count value is more likely to become equal to or greater than the first threshold, thereby preventing the full-water determination unit from mistakenly determining that the water storage tank is not full. Furthermore, since the system is configured to change the first threshold when it is determined that the moving body is tilted, even if the signal output from the float sensor becomes high level due to the tilt of the moving body, even though the water storage tank is not actually full, the first count value is less likely to become equal to or greater than the first threshold, thereby preventing the full-water determination unit from mistakenly determining that the water storage tank is full. In other words, even if the water level of the generated water in the storage tank is unstable, it is possible to suppress a decrease in the accuracy of the full-tank detection unit's judgment.

[0012] Furthermore, the full-water determination unit may be configured to increment a second count value when the signal output from the float sensor is low level, to decrement the second count value when the signal output from the float sensor is high level, and to determine that the water storage tank is not full when the second count value is equal to or greater than a second threshold.

[0013] This allows the full-water level determination unit to determine that the water tank is not full, even if the water level of the generated water in the tank fluctuates, causing the signal level output from the float sensor to change. In other words, it further suppresses the decrease in the accuracy of the full-water level determination unit's judgment, even if the water level of the generated water in the tank is unstable.

[0014] Alternatively, the moving body may be a vehicle, and the tilt determination unit may be configured to determine whether the moving body is tilted relative to the horizontal based on the power request from the moving body, the speed of the moving body, the accelerator opening of the moving body, and the acceleration of the moving body. [Effects of the Invention]

[0015] According to the present invention, in a fuel cell system equipped with a full-water determination unit that determines whether or not the water storage tank for storing generated water produced by a fuel cell is full, it is possible to suppress a decrease in the accuracy of the full-water determination unit's determination even if the water level of generated water in the storage tank is unstable. [Brief explanation of the drawing]

[0016] [Figure 1] This figure shows an example of a fuel cell system according to the first embodiment. [Figure 2] This is a flowchart showing an example of the operation of the water level determination unit in the first embodiment. [Figure 3] This figure shows an example of the float sensor output signal, first count value, second count value, and full water status flag. [Figure 4]It is a flowchart showing a modification example of the operation of the full water determination unit in the first embodiment. [Figure 5] It is a diagram showing an example of a fuel cell system of the second embodiment. [Figure 6] It is a flowchart showing an example of the operation of the full water determination unit in the second embodiment. [Figure 7] It is a diagram showing an example of an output signal of a float sensor, a first count value, a second count value, an inclination state flag, and a full water state flag. [Figure 8] It is a flowchart showing a modification example of the operation of the full water determination unit in the second embodiment.

Mode for Carrying Out the Invention

[0017] Hereinafter, embodiments will be described in detail based on the drawings.

[0018] <First Embodiment> FIG. 1 is a diagram showing an example of a fuel cell system of the first embodiment.

[0019] The fuel cell system FCS shown in FIG. 1 is mounted on a moving body M such as a vehicle or an aircraft, and supplies electric power to a load Lo mounted on the vehicle. For example, the vehicle is a forklift, a towing tractor, or an automatic guided vehicle (AGV). Also, the aircraft is a drone or the like. When the moving body M is a vehicle, the load Lo shown in FIG. 1 is, for example, a cargo handling device or an inverter circuit that drives a traveling motor. When the moving body M is an aircraft, the load Lo is an inverter circuit that drives a flying motor or the like.

[0020] The fuel cell system FCS also includes a fuel cell FC as a main unit and a plurality of auxiliary machines for generating power from the fuel cell FC.

[0021] In other words, the fuel cell system (FCS) includes, as auxiliary components of the fuel gas system, a hydrogen tank (HT), an injector (INJ), a gas-liquid separator (GLS), a hydrogen circulation pump (HP), an exhaust and drain valve (EDV), a diluent (DIL), and a water storage tank (WT).

[0022] Furthermore, the fuel cell system (FCS) includes an air compressor (ACP) and an air pressure regulating valve (ARV) as auxiliary equipment for the oxidizer gas system.

[0023] Furthermore, the fuel cell system (FCS) includes a radiator (R) and a water pump (WP) as auxiliary cooling system components.

[0024] Furthermore, the fuel cell system (FCS) includes a DC-DC converter (CNV) and an energy storage device (B) as electrical auxiliary equipment.

[0025] Furthermore, the fuel cell system (FCS) includes a memory device (Str) and a control device (Cnt).

[0026] A fuel cell (FC) consists of multiple fuel cell cells connected in series, and generates electricity or liquid water through an electrochemical reaction between hydrogen contained in hydrogen gas and oxygen contained in an oxidizing gas.

[0027] The hydrogen tank (HT) is a storage container for hydrogen gas. The hydrogen gas stored in the hydrogen tank (HT) is supplied to the fuel cell (FC) via the injector (INJ).

[0028] The injector (INJ) adjusts the flow rate of hydrogen gas supplied to the fuel cell (FC).

[0029] The gas-liquid separator GLS separates hydrogen gas containing unreacted hydrogen discharged from the fuel cell (FC) from the generated water.

[0030] The hydrogen circulation pump (HP) resupplies the hydrogen gas separated by the gas-liquid separator (GLS) back to the fuel cell (FC).

[0031] The exhaust and drain valve EDV sends the generated water, separated by the gas-liquid separator GLS, to the diluent DIL.

[0032] The diluent (DIL) dilutes hydrogen gas containing unreacted hydrogen emitted from the fuel cell (FC) by mixing it with an oxidizer gas and then discharges it to the outside or inside of the fuel cell system (FCS).

[0033] The water storage tank WT is a container for storing the generated water sent to the diluent DIL. A float sensor Sf is also installed inside the water storage tank WT. The float sensor Sf is equipped with a float (not shown) and outputs a low-level signal to the control device Cnt when the float is descending without being affected by the buoyancy of the generated water in the water storage tank WT, and outputs a high-level signal to the control device Cnt when the float is rising due to buoyancy as the generated water in the water storage tank WT rises.

[0034] The air compressor (ACP) compresses the oxidizer gas present around the fuel cell system (FCS) and supplies it to the fuel cell (FC).

[0035] The air pressure regulating valve (ARV) adjusts the pressure and flow rate of the oxidizer gas supplied to the fuel cell (FC).

[0036] The radiator R exchanges heat between the refrigerant (such as water), which has been heated by the heat generated by the fuel cell (FC), and the outside air.

[0037] The water pump (WP) supplies the refrigerant cooled by the radiator (R) to the fuel cell (FC).

[0038] The DC-DC converter CNV converts the voltage output from the fuel cell FC to a predetermined voltage. The power output from the DC-DC converter CNV is supplied to the load Lo, as well as auxiliary equipment such as the hydrogen circulation pump HP and the energy storage device B.

[0039] Energy storage device B is composed of a lithium-ion battery or lithium-ion capacitor and is connected between the DC-DC converter CNV and the load Lo. If the supplied power, which is the difference between the power output from the DC-DC converter CNV and the total power supplied to each auxiliary device, is greater than the required power Pr requested by the external control device Cm that controls the operation of the load Lo, then the required power Pr is supplied to the load Lo, and the remaining power is supplied to energy storage device B. When power is supplied from the DC-DC converter CNV to energy storage device B, energy storage device B is charged and its charge rate (the ratio of remaining capacity to the full charge capacity of energy storage device B [%]) increases. Also, when regenerative power supplied from the load Lo to the fuel cell system FCS is supplied to energy storage device B, energy storage device B is charged and its charge rate increases. Furthermore, if the supplied power, which is the difference between the power output from the DC-DC converter CNV and the total power supplied to each auxiliary device, is less than the required power Pr requested by the external control device Cm, then that supplied power is supplied to the load Lo, and the remaining power is supplied to the load Lo from the energy storage device B. When power is supplied to the load Lo from the energy storage device B, the energy storage device B is discharged and its charge level decreases.

[0040] The memory device Str is composed of, for example, RAM (Random Access Memory) or ROM (Read Only Memory), and stores the cumulative value of the first count value C1, the cumulative value of the second count value C2, the first threshold C1th, and the second threshold C2th, as described later.

[0041] The control device Cnt is composed of, for example, a microcomputer and comprises a power generation control unit Cp and a water level determination unit Cw. For example, the power generation control unit Cp and the water level determination unit Cw are realized when the microcomputer executes a program stored in the memory device Str.

[0042] The power generation control unit Cp controls the operation of each auxiliary device in order to control the power generation of the fuel cell FC. For example, the power generation control unit Cp changes the target power generation power according to the charge level of the energy storage device B, and controls the operation of each auxiliary device so that the power generation power of the fuel cell FC follows the target power generation power through PI (Proportional-Integral) control, etc.

[0043] The full-water determination unit Cw determines whether the water storage tank WT is full or not based on the level of the signal output from the float sensor Sf.

[0044] Figure 2 is a flowchart showing an example of the operation of the water level determination unit Cw in the first embodiment. Note that each of the processes in steps S11 to S18 shown in Figure 2 is executed at arbitrary control timings (for example, at each clock cycle of the microcomputer).

[0045] First, when the full-water level determination unit Cw determines that the signal output from the float sensor Sf is at a high level (step S11: Yes), it increments the first count value C1 and decrements the second count value C2 (step S12). For example, each time the full-water level determination unit Cw increments the first count value C1, it accumulates the first count value C1 by 1 or two or more arbitrary values ​​(per unit time). Also, each time the full-water level determination unit Cw decrements the second count value C2, it subtracts the second count value C2 by 1 or two or more arbitrary values ​​(per unit time).

[0046] On the other hand, when the full-water level determination unit Cw determines that the signal output from the float sensor Sf is at a low level (step S11: No), it counts down the first count value C1 and counts up the second count value C2 (step S13). For example, each time the full-water level determination unit Cw counts down the first count value C1, it subtracts 1 or more arbitrary values ​​(per unit time) from the first count value C1. Also, each time the full-water level determination unit Cw counts up the second count value C2, it accumulates 1 or more arbitrary values ​​(per unit time) from the second count value C2.

[0047] Next, the full-water determination unit Cw determines that the water storage tank WT is full if the first count value C1 is greater than or equal to the first threshold C1th (step S14: Yes), sets the full-water status flag to high level (step S15), resets the second count value (step S16), and waits until the next control timing. For example, the first threshold C1th is any period within the time frame from when the signal output from the float sensor Sf switches from low level to high level until it switches from high level to low level, when the moving body M is not vibrating or rotating, for example, several tens of seconds. The control device Cnt may be configured to notify the user that the water storage tank WT is full when the full-water status flag is high level, using a display or speaker (not shown). Alternatively, the control device Cnt may be configured to notify the user of an alarm that the water storage tank WT is full when the full-water status flag is high level. This allows users to be encouraged to remove the generated water from the water storage tank (WT), thereby suppressing the reduction in the power generation capacity of the fuel cell (FC) caused by water clogging that occurs when the generated water in the water storage tank (WT) is not removed.

[0048] On the other hand, the full-water determination unit Cw determines that the water storage tank WT is not full if the second count value C2 is greater than or equal to the second threshold C2th (step S14: No, step S17: Yes), sets the full-water status flag to a low level (step S18), and waits until the next control timing. For example, the second threshold C2th is any period within the time from when the signal output from the float sensor Sf switches from a high level to a low level until it switches from a low level to a high level, when the moving body M is not vibrating or rotating, for example, a few minutes. The control device Cnt may be configured to notify the user that the water storage tank WT is not full when the full-water status flag is at a low level, using a display or speaker not shown. Alternatively, the control device Cnt may be configured to cancel the alarm indicating that the water storage tank is full when the full-water status flag is at a low level.

[0049] Furthermore, if the full-water tank determination unit Cw finds that the first count value C1 is less than the first threshold C1th and the second count value C2 is less than the second threshold C2th (step S17: No), it maintains the state of the water storage tank WT determined before the previous control timing and waits until the next control timing.

[0050] Figure 3(a) shows an example of the output signal of the float sensor Sf in the first embodiment, Figure 3(b) shows an example of the first count value C1 in the first embodiment, Figure 3(c) shows an example of the second count value C2 in the first embodiment, and Figure 3(d) shows an example of the full water state flag in the first embodiment. In the two-dimensional coordinates shown in Figures 3(a) and 3(d), the horizontal axis represents time and the vertical axis represents voltage. The solid line in Figure 3(a) represents the output signal of the float sensor Sf, and the solid line in Figure 3(d) represents the full water state flag. In the two-dimensional coordinates shown in Figures 3(b) and 3(c), the horizontal axis represents time and the vertical axis represents the count value. The solid line in Figure 3(b) represents the first count value C1, and the solid line in Figure 3(c) represents the second count value C2. Furthermore, the lower limit of the first count value C1 is set to zero, and the upper limit of the first count value C1 is set to the same value as the first threshold C1th. Furthermore, the lower limit of the second count value C2 is set to zero, and the upper limit of the second count value C2 is set to the same value as the second threshold C2th. Furthermore, the full water status flag is set to an indeterminate state (initial state) greater than the low level and high level (NULL). Furthermore, it is assumed that the water storage tank WT is actually full during the period from time t10 to time t12 and from time t14 onwards. Furthermore, it is assumed that the water storage tank WT is not actually full during the period from time t12 to time t14. Furthermore, it is assumed that the signal output from the float sensor Sf changes from a high level to a low level three times during the period from time t10 to time t12 due to the vibration of the moving body M. Furthermore, it is assumed that the signal output from the float sensor Sf changes from a high level to a low level from time t14 onwards due to the rotation of the moving body M.

[0051] As shown in Figure 3(b), at time t11, when the first count value C1 becomes equal to or greater than the first threshold C1th, the full-water determination unit Cw determines that the water storage tank WT is full, and sets the full-water status flag to a high level, as shown in Figure 3(d). In this way, even when the water storage tank WT is actually full, the full-water determination unit Cw can still determine that the water storage tank WT is full, even if the output signal of the float sensor Sf changes from a high level to a low level three times due to the vibration of the moving body M.

[0052] Furthermore, as shown in Figure 3(c), when the second count value C2 becomes equal to or greater than the second threshold C2th at time t13, the full-water determination unit Cw determines that the water storage tank WT is not full, and sets the full-water status flag to a low level, as shown in Figure 3(d).

[0053] Furthermore, as shown in Figure 3(b), when the first count value C1 becomes equal to or greater than the first threshold C1th at time t15, the full-water determination unit Cw determines that the water storage tank WT is full, and sets the full-water status flag to a high level, as shown in Figure 3(d). In this way, even when the water storage tank WT is actually full, the full-water determination unit Cw can be made to determine that the water storage tank WT is full, even if the output signal of the float sensor Sf changes from a high level to a low level due to the rotation of the moving body M.

[0054] Thus, in the first embodiment, the full-water determination unit Cw counts up the first count value C1 when the signal output from the float sensor Sf is at a high level, counts down the first count value C1 when the signal output from the float sensor Sf is at a low level, and determines that the water storage tank WT is full when the first count value C1 is equal to or greater than the first threshold C1th.

[0055] As a result, even when the water storage tank WT is actually full, the water fullness determination unit Cw can determine that the water storage tank WT is full, even if the level of the signal output from the float sensor Sf fluctuates due to fluctuations in the water level of the generated water in the water storage tank WT. In other words, even if the water level of the generated water in the water storage tank WT is unstable, a decrease in the accuracy of the determination by the water fullness determination unit Cw can be suppressed. Furthermore, because a decrease in the accuracy of the determination by the water fullness determination unit Cw can be suppressed, a reduction in the operating time of the mobile unit M by the user can be prevented.

[0056] Furthermore, in the first embodiment, the full-water determination unit Cw counts up the second count value C2 when the signal output from the float sensor Sf is at a low level, counts down the second count value C2 when the signal output from the float sensor Sf is at a high level, and determines that the water storage tank WT is not full when the second count value C2 is equal to or greater than the second threshold C2th.

[0057] As a result, even if the water level of the generated water in the storage tank WT is not actually full, the full-water determination unit Cw can still determine that the water storage tank WT is not full, even if the level of the signal output from the float sensor Sf fluctuates due to fluctuations in the water level of the generated water in the storage tank WT. In other words, even if the water level of the generated water in the storage tank WT is unstable, the decrease in the accuracy of the full-water determination unit Cw's judgment can be further suppressed.

[0058] <Modified form of the first embodiment> Figure 4 is a flowchart showing a modified example of the operation of the water level determination unit Cw in the first embodiment. Note that each of the processes in steps S11 to S15 shown in Figure 4 is executed at arbitrary control timings (for example, at each clock cycle of the microcomputer).

[0059] The difference between the operation of the full-water level determination unit Cw shown in Figure 4 and the operation of the full-water level determination unit Cw shown in Figure 2 is that it does not determine whether or not the water storage tank WT is full.

[0060] Specifically, first, when the full-water level determination unit Cw determines that the signal output from the float sensor Sf is at a high level (step S11: Yes), it increments the first count value C1 (step S12').

[0061] On the other hand, if the full-water level determination unit Cw determines that the signal output from the float sensor Sf is at a low level (step S11: No), it counts down the first count value C1 (step S13').

[0062] Next, the full-water determination unit Cw determines that the water storage tank WT is full if the first count value C1 is greater than or equal to the first threshold C1th (step S14: Yes), sets the full-water status flag to high level (step S15), and waits until the next control timing. When the full-water status flag is high level, the control device Cnt notifies the user that the water storage tank WT is full using a display or speaker (not shown). The user may configure the system to send a notification to the control device Cnt (full-water determination unit Cw) using an input device (not shown) that the generated water in the water storage tank WT has been removed after the generated water has been removed from the water storage tank WT. Alternatively, the full-water determination unit Cw may be configured to switch the full-water status flag from high level to low level when it receives notification that the generated water in the water storage tank WT has been removed.

[0063] On the other hand, the full-water level determination unit Cw waits until the next control timing if the first count value C1 is less than the first threshold C1th (step S14: No).

[0064] Thus, in the modified version of the first embodiment, the full-water determination unit Cw counts up the first count value C1 when the signal output from the float sensor Sf is at a high level, counts down the first count value C1 when the signal output from the float sensor Sf is at a low level, and determines that the water storage tank WT is full when the first count value C1 is equal to or greater than the first threshold C1th.

[0065] As a result, even when the water storage tank WT is actually full, the water fullness determination unit Cw can determine that the water storage tank WT is full, even if the level of the signal output from the float sensor Sf fluctuates due to fluctuations in the water level of the generated water in the water storage tank WT. In other words, even if the water level of the generated water in the water storage tank WT is unstable, a decrease in the accuracy of the determination by the water fullness determination unit Cw can be suppressed. Furthermore, because a decrease in the accuracy of the determination by the water fullness determination unit Cw can be suppressed, a reduction in the operating time of the mobile unit M by the user can be prevented.

[0066] <Second Embodiment> Figure 5 shows an example of a fuel cell system (FCS) according to the second embodiment. In Figure 5, components identical to those shown in Figure 1 are denoted by the same reference numerals, and their descriptions are omitted.

[0067] In the fuel cell system FCS shown in Figure 5, the difference from the fuel cell system FCS shown in Figure 1 is that the control device Cnt further includes a tilt determination unit Cs. For example, the tilt determination unit Cs is realized by a microcomputer executing a program stored in the memory device Str.

[0068] The inclination determination unit Cs determines whether the moving body M is inclined relative to the horizontal. For example, if the moving body M is a vehicle, the inclination determination unit Cs determines whether the moving body M is inclined relative to the horizontal (whether the moving body M is going up or down a slope) based on the required power Pr requested from the external control device Cm, the speed V of the moving body M, the accelerator opening D of the moving body M, and the acceleration A of the moving body M.

[0069] In other words, the external control device Cm determines the amount of accelerator pedal operation by the driver, which is detected by a potentiometer or the like connected to the accelerator pedal of the mobile body M, as the accelerator opening degree D, and sends this accelerator opening degree D to the control device Cnt.

[0070] Furthermore, the external control device Cm determines the required power Pr (the power required to drive the load Lo). For example, the external control device Cm may use the product of the output voltage of the energy storage device B and the current flowing from the energy storage device B to the load Lo, or the power consumed by the load Lo as predicted from the operation control of the load Lo, as the required power Pr.

[0071] Furthermore, the external control device Cm determines the velocity V [m / s] and acceleration A [m / s²] of the mobile body M. For example, the external control device Cm uses the result of the calculation (rotational speed of the driving motor [rpm] × tire outer diameter [m] × pi) / (gear ratio × reduction ratio) as the velocity V. The external control device Cm also uses the amount of change in velocity V per second as the acceleration A. Alternatively, the external control device Cm may be configured to determine the acceleration A based on the output values ​​of an acceleration sensor (not shown) mounted on the mobile body M or a torque sensor connected to the driving motor.

[0072] Generally, the greater the gradient [%] of an uphill slope, the greater the power consumed by the drive motor. In particular, when the vehicle M is an industrial vehicle, the weight of the vehicle M is relatively large, so the greater the gradient of the uphill slope, the greater the power consumed by the drive motor tends to be. Also, the greater the gradient of an uphill slope, the greater the speed of the vehicle M tends to be. Furthermore, when the vehicle M is traveling uphill, its speed is lower than when it is traveling on a flat road, so the driver tends to press the accelerator pedal more to maintain the same speed as on a flat road. Also, when the vehicle M is traveling uphill, its speed tends to remain constant, so its acceleration tends to be relatively small. In other words, when the vehicle M is traveling uphill, the required power Pr and accelerator opening D are relatively large, while the speed V and acceleration A are relatively small.

[0073] Therefore, the incline determination unit Cs determines that the mobile body M is traveling uphill if the requested power Pr is equal to or greater than a predetermined requested power Pr1, the speed V is equal to or less than a predetermined speed V1, the accelerator opening D is equal to or greater than a predetermined accelerator opening D1, and the acceleration A is equal to or less than a predetermined acceleration A1. Conversely, the incline determination unit Cs determines that the mobile body M is not traveling uphill if the requested power Pr is less than a predetermined requested power Pr1, or the speed V is greater than a predetermined speed V1, or the accelerator opening D is less than a predetermined accelerator opening D1, or the acceleration A is greater than a predetermined acceleration A1. The predetermined accelerator opening is not limited to 100% (fully open accelerator), but is set after experimentally and empirically determining the opening that is estimated when the mobile body M is traveling uphill.

[0074] Furthermore, generally speaking, the greater the gradient [%] of a downhill slope, the less power is consumed by the drive motor (the greater the power regenerated from the drive motor). In particular, when the vehicle M is an industrial vehicle, the weight of the vehicle M is relatively large, so the greater the gradient of the downhill slope, the less power is consumed by the drive motor. Also, the greater the gradient of a downhill slope, the greater the speed V of the vehicle M tends to be. Moreover, when the vehicle M is traveling downhill, the speed V of the vehicle M is greater than when it is traveling on a flat road, so the driver tends to press the accelerator pedal more than usual in an attempt to maintain the same speed as on a flat road. Also, when the vehicle M is traveling downhill, the acceleration A of the vehicle M tends to be relatively large. In other words, when the vehicle M is traveling downhill, the required power Pr is relatively small, while the regenerated power, speed V, accelerator opening D, and acceleration A are relatively large.

[0075] Therefore, the incline determination unit Cs determines that the moving body M is traveling downhill if the required power Pr is less than or equal to a predetermined required power Pr2, the speed V is greater than or equal to a predetermined speed V2, the accelerator opening D is greater than or equal to a predetermined accelerator opening D2, and the acceleration A is greater than or equal to a predetermined acceleration A2. Conversely, the incline determination unit Cs determines that the moving body M is not traveling downhill if the required power Pr is greater than a predetermined required power Pr2, or the speed V is less than a predetermined speed V2, or the accelerator opening D is less than a predetermined accelerator opening D2, or the acceleration A is less than a predetermined acceleration A2.

[0076] Figure 6 is a flowchart showing an example of the operation of the full-water level determination unit Cw in the second embodiment. Steps S11 to S18 shown in Figure 6 are the same as steps S11 to S18 shown in Figure 2, so their explanation is omitted.

[0077] First, the full-water level determination unit Cw, when it is determined by the tilt determination unit Cs that the moving body M is tilted relative to the horizontal (step S21: Yes), changes the first threshold C1th (step S22), and then executes the processes from step S11 onwards. When it is determined by the tilt determination unit Cs that the moving body M is not tilted relative to the horizontal (step S21: No), it executes the processes from step S11 onwards without changing the first threshold C1th.

[0078] For example, consider a case where, when the tilt determination unit Cs determines that the moving object M is not tilted relative to the horizontal, the signal output from the float sensor Sf becomes high level, but when the tilt determination unit Cs determines that the moving object M is tilted relative to the horizontal, the signal output from the float sensor Sf becomes low level.

[0079] In this case, the modified first threshold C1th' is set to any value smaller than the first threshold C1th. For example, the first threshold C1th' may be determined based on the frequency at which the signal output from the float sensor Sf becomes high or low when the moving body 1 is tilted relative to the horizontal and the water level in the water storage tank WT is unstable due to vibration or rotation of the moving body M.

[0080] In other words, when the full water level determination unit Cw determines that the moving body M is tilted relative to the horizontal by the tilt determination unit Cs (step S21: Yes), it changes the first threshold C1th to the first threshold C1th' (step S22), and then in step S14, it compares the first count value C1 with the first threshold C1th'.

[0081] This makes it easier to raise the first count value C1 to the first threshold C1th' or higher when the water storage tank WT is actually full. Therefore, it is possible to prevent the full-water determination unit Cw from mistakenly determining that the water storage tank WT is not full when it is actually full.

[0082] Alternatively, consider a scenario where, for example, when the tilt determination unit Cs determines that the moving object M is not tilted relative to the horizontal, the signal output from the float sensor Sf becomes low level, but when the tilt determination unit Cs determines that the moving object M is tilted relative to the horizontal, the signal output from the float sensor Sf becomes high level.

[0083] In this case, the modified first threshold C1th'' is set to any value greater than the first threshold C1th. For example, the first threshold C1th'' may be determined based on the frequency at which the signal output from the float sensor Sf becomes high or low when the moving body 1 is tilted relative to the horizontal and the water level in the water storage tank WT is unstable due to vibration or rotation of the moving body M.

[0084] In other words, when the tilt determination unit Cs determines that the moving body M is tilted relative to the horizontal (step S21: Yes), the full water level determination unit Cw changes the first threshold C1th to the first threshold C1th'' (step S22), and then in step S14, compares the first count value C1 with the first threshold C1th''.

[0085] This makes it difficult for the first count value C1 to exceed the first threshold C1th'' when the water storage tank WT is actually full, thus preventing the full-water determination unit Cw from mistakenly determining that the water storage tank WT is full when it is not actually full.

[0086] Figure 7(a) shows an example of the output signal of the float sensor Sf in the second embodiment, Figure 7(b) shows an example of the first count value C1 in the second embodiment, Figure 7(c) shows an example of the second count value C2 in the second embodiment, Figure 7(d) shows an example of the tilt state flag, and Figure 7(e) shows an example of the full water state flag in the second embodiment. In the two-dimensional coordinates shown in Figures 7(a), 7(d), and 7(e), the horizontal axis represents time and the vertical axis represents voltage. The solid line in Figure 7(a) represents the output signal of the float sensor Sf, the solid line in Figure 7(d) represents the tilt state flag, and the solid line in Figure 7(e) represents the full water state flag. In the two-dimensional coordinates shown in Figures 7(b) and 7(c), the horizontal axis represents time and the vertical axis represents the count value. The solid line in Figure 7(b) represents the first count value C1, and the solid line in Figure 7(c) represents the second count value C2. The lower limit of the first count value C1 is set to zero, and the upper limit of the first count value C1 is set to the same value as the first threshold C1th. The lower limit of the second count value C2 is set to zero, and the upper limit of the second count value C2 is set to the same value as the second threshold C2th. The full water status flag is set to an indeterminate state (initial state) greater than the low level and high level (NULL). The water storage tank WT is not actually full during the period from time t20 to time t24. The signal output from the float sensor Sf changes from a low level to a high level three times during the period from time t20 to time t22, even though the water storage tank WT is not actually full, due to the vibration of the moving body M. The water storage tank WT is actually full after time t24. Furthermore, it is assumed that from time t24 onward, the signal output from the float sensor Sf changes from a high level to a low level due to the rotation of the moving object M.

[0087] As shown in Figure 7(d), at time t21, the tilt determination unit Cs determines that the moving body M is tilted relative to the horizontal, and when the tilt state flag switches from a low level to a high level, the water level determination unit Cw increases the first threshold C1th, as shown in Figure 7(b).

[0088] As a result, as shown in Figure 7(b), at time t21, the first count value C1 does not exceed the first threshold C1th, thus preventing the full-water determination unit Cw from mistakenly determining that the water storage tank WT is full, even though the water storage tank WT is not actually full.

[0089] Furthermore, as shown in Figure 7(c), when the second count value C2 becomes equal to or greater than the second threshold C2th at time t23, the full-water determination unit Cw determines that the water storage tank WT is not full, and sets the full-water status flag to a low level, as shown in Figure 7(e).

[0090] Furthermore, as shown in Figure 7(b), when the first count value C1 becomes equal to or greater than the first threshold C1th at time t25, the full-water determination unit Cw determines that the water storage tank WT is full, and sets the full-water status flag to a high level, as shown in Figure 7(e).

[0091] Thus, in the second embodiment, the full-water determination unit Cw counts up the first count value C1 when the signal output from the float sensor Sf is at a high level, counts down the first count value C1 when the signal output from the float sensor Sf is at a low level, and determines that the water storage tank WT is full when the first count value C1 is equal to or greater than the first threshold C1th.

[0092] As a result, even when the water storage tank WT is actually full, the water fullness determination unit Cw can determine that the water storage tank WT is full, even if the level of the signal output from the float sensor Sf fluctuates due to fluctuations in the water level of the generated water in the water storage tank WT. In other words, even if the water level of the generated water in the water storage tank WT is unstable, a decrease in the accuracy of the determination by the water fullness determination unit Cw can be suppressed. Furthermore, because a decrease in the accuracy of the determination by the water fullness determination unit Cw can be suppressed, a reduction in the operating time of the mobile unit M by the user can be prevented.

[0093] Furthermore, in the second embodiment, the full-water determination unit Cw counts up the second count value C2 when the signal output from the float sensor Sf is at a low level, counts down the second count value C2 when the output from the float sensor Sf is at a high level, and determines that the water storage tank WT is not full when the second count value C2 is equal to or greater than the second threshold C2th.

[0094] As a result, even if the water level of the generated water in the storage tank WT is not actually full, the full-water determination unit Cw can still determine that the water storage tank WT is not full, even if the level of the signal output from the float sensor Sf fluctuates due to fluctuations in the water level of the generated water in the storage tank WT. In other words, even if the water level of the generated water in the storage tank WT is unstable, the decrease in the accuracy of the full-water determination unit Cw's judgment can be further suppressed.

[0095] Furthermore, in the second embodiment, the full-water determination unit Cw is configured to change the first threshold C1th when the inclination determination unit Cs determines that the moving body M is inclined relative to the horizontal.

[0096] As a result, even if the water storage tank WT is actually full, the tilt of the moving body M makes it easier for the first count value C1 to exceed the first threshold C1th, even if the signal output from the float sensor Sf is at a low level. This prevents the full-water tank determination unit Cw from mistakenly determining that the water storage tank WT is not full. Furthermore, even if the water storage tank WT is not actually full, the tilt of the moving body M makes it difficult for the first count value C1 to exceed the first threshold C1th, even if the signal output from the float sensor Sf is at a high level. This prevents the full-water tank determination unit Cw from mistakenly determining that the water storage tank WT is full. In other words, even if the water level of the generated water in the water storage tank WT is unstable, the accuracy of the full-water tank determination unit Cw's judgment can be further suppressed.

[0097] <Modified form of the second embodiment> Figure 8 is a flowchart showing a modified example of the operation of the water level determination unit Cw in the second embodiment. Note that the processes in steps S21 to S22 and steps S11 to S18 shown in Figure 8 are executed at arbitrary control timings (for example, at each clock cycle of the microcomputer).

[0098] The difference between the operation of the full-water level determination unit Cw shown in Figure 8 and the operation of the full-water level determination unit Cw shown in Figure 6 is that it does not determine whether or not the water storage tank WT is full.

[0099] Specifically, first, the full-water level determination unit Cw, when it is determined by the tilt determination unit Cs that the moving body M is tilted relative to the horizontal (step S21: Yes), changes the first threshold C1th (step S22), and then executes the processes from step S11 onwards. If it is determined by the tilt determination unit Cs that the moving body M is not tilted relative to the horizontal (step S21: No), it executes the processes from step S11 onwards without changing the first threshold C1th.

[0100] Next, when the full-water level determination unit Cw determines that the signal output from the float sensor Sf is at a high level (step S11: Yes), it increments the first count value C1 (step S12').

[0101] On the other hand, if the full-water level determination unit Cw determines that the signal output from the float sensor Sf is at a low level (step S11: No), it counts down the first count value C1 (step S13').

[0102] Next, the full-water determination unit Cw determines that the water storage tank WT is full if the first count value C1 is greater than or equal to the first threshold C1th (step S14: Yes), sets the full-water status flag to high level (step S15), and waits until the next control timing.

[0103] On the other hand, the full-water level determination unit Cw waits until the next control timing if the first count value C1 is less than the first threshold C1th (step S14: No).

[0104] Thus, in the modified version of the second embodiment, the full-water determination unit Cw counts up the first count value C1 when the signal output from the float sensor Sf is at a high level, counts down the first count value C1 when the signal output from the float sensor Sf is at a low level, and determines that the water storage tank WT is full when the first count value C1 is equal to or greater than the first threshold C1th.

[0105] As a result, even when the water storage tank WT is actually full, the water fullness determination unit Cw can determine that the water storage tank WT is full, even if the level of the signal output from the float sensor Sf fluctuates due to fluctuations in the water level of the generated water in the water storage tank WT. In other words, even if the water level of the generated water in the water storage tank WT is unstable, a decrease in the accuracy of the determination by the water fullness determination unit Cw can be suppressed. Furthermore, because a decrease in the accuracy of the determination by the water fullness determination unit Cw can be suppressed, a reduction in the operating time of the mobile unit M by the user can be prevented.

[0106] Furthermore, in the second embodiment, the full-water determination unit Cw is configured to change the first threshold C1th when the inclination determination unit Cs determines that the moving body M is inclined relative to the horizontal.

[0107] As a result, even if the water storage tank WT is actually full, the tilt of the moving body M makes it easier for the first count value C1 to exceed the first threshold C1th, even if the signal output from the float sensor Sf is at a low level. This prevents the full-water tank determination unit Cw from mistakenly determining that the water storage tank WT is not full. Furthermore, even if the water storage tank WT is not actually full, the tilt of the moving body M makes it difficult for the first count value C1 to exceed the first threshold C1th, even if the signal output from the float sensor Sf is at a high level. This prevents the full-water tank determination unit Cw from mistakenly determining that the water storage tank WT is full. In other words, even if the water level of the generated water in the water storage tank WT is unstable, the accuracy of the full-water tank determination unit Cw's judgment can be further suppressed.

[0108] It should be noted that the present invention is not limited to the embodiments described above, and various improvements and modifications are possible without departing from the spirit of the invention. [Explanation of Symbols]

[0109] FCS Fuel Cell System Lo load FC fuel cell HT Hydrogen Tank INJ Injector GLS gas liquid separator HP Hydrogen Circulation Pump EDV Exhaust Drain Valve DIL Diluent WT Water storage tank ACP Air Compressor ARV Air Pressure Regulating Valve CNV DC-DC converter B Energy storage device Str storage Cnt control unit Cp power generation control unit Cw Full Water Level Judgment Unit Cs slope judgment part

Claims

1. A water storage tank for storing the water generated by the fuel cell, A float sensor is installed inside the water storage tank, A full-water determination unit that counts up a first count value when the signal output from the float sensor is at a high level, counts down the first count value when the signal output from the float sensor is at a low level, and determines that the water storage tank is full when the first count value is equal to or greater than a first threshold, A fuel cell system equipped with the following features.

2. A fuel cell system mounted on a mobile vehicle, A water storage tank for storing the water generated by the fuel cell, A float sensor is installed inside the water storage tank, An inclination determination unit that determines whether the moving body is inclined relative to the horizontal, A full-water determination unit that counts up a first count value when the signal output from the float sensor is at a high level, counts down the first count value when the signal output from the float sensor is at a low level, and determines that the water storage tank is full when the first count value is equal to or greater than a first threshold, Equipped with, The full-water determination unit changes the first threshold when the tilt determination unit determines that the moving body is tilted relative to the horizontal. Fuel cell system.

3. A fuel cell system according to claim 1 or claim 2, The full-water determination unit counts up the second count value when the signal output from the float sensor is low level, counts down the second count value when the signal output from the float sensor is high level, and determines that the water storage tank is not full when the second count value is equal to or greater than the second threshold. Fuel cell system.

4. A fuel cell system according to claim 2, The aforementioned moving object is a vehicle, The tilt determination unit determines whether the moving body is tilted relative to the horizontal based on the power request from the moving body, the speed of the moving body, the accelerator opening of the moving body, and the acceleration of the moving body. Fuel cell system.

Images