Fuel cell system for a mobile work machine

Abstract

The invention relates to a fuel cell system (1) for a mobile work machine, in particular an industrial truck, comprising a hydrogen-powered fuel cell device (4), a hydrogen tank (5) which is connected to the fuel cell device (4) by means of a supply line (6), and a flushing system (10) which is designed to flush the fuel cell device (4). The flushing system (10) has a flushing valve (11) which is arranged in a flushing line (12) connected to the fuel cell device (4). A pressure sensor (15) is provided which is designed to detect the pressure in the flushing line (12) between the fuel cell device (4) and the flushing valve (11). The pressure sensor (15) is connected to an electronic controller (20) which is designed to monitor the function of the flushing valve (11) using the measurement values of the pressure sensor (15).

Description

[0001] Description

[0002] Fuel cell system for a mobile work machine

[0003] The invention relates to a fuel cell system for a mobile work machine, in particular an industrial truck, comprising a hydrogen-operated fuel cell device, a hydrogen tank connected to the fuel cell device by means of a supply line, and a purging system designed to purge the fuel cell device, wherein the purging system has a purge valve arranged in a purge line connected to the fuel cell device.

[0004] In mobile work machines, in particular industrial trucks, with an electric drive system, it is known to use a fuel cell system to supply energy to the electric drive system.

[0005] Known fuel cell systems comprise a hydrogen-powered fuel cell device, to which oxygen or ambient air is supplied at a cathode region and hydrogen from a hydrogen tank is supplied at an anode region. In the fuel cell device, the oxygen from the ambient air is reacted with the hydrogen, generating electrical energy and waste heat. To dissipate this waste heat from the fuel cell device, it is known to design the fuel cell device as an air-cooled fuel cell device with a cooling system comprising a fan device, wherein the fan device generates a cooling air flow through the fuel cell device.

[0006] A fuel cell system with a hydrogen-powered fuel cell device also requires a purging system that regularly purges the fuel cell device, particularly in the anode area, in order to flush out and thus remove unwanted foreign gas components and / or water that negatively affect the performance and service life of the fuel cell device. The purging system has a purge valve that is arranged in a purge line connected to the fuel cell device. During a purge process of the fuel cell device, the purge system generates purge gas that contains hydrogen. During a purge process, this hydrogen-containing purge gas is released into the environment via the purge line. During operation of the fuel cell system, hydrogen is thus released with the purge gas.In order to reduce the hydrogen concentration to permissible values, it is known to mix the purge gas released during a purging process with another air flow, for example the cooling air flow of the fuel cell device, and thereby dilute the hydrogen concentration.

[0007] Since the purge valve seals a hydrogen area of ​​the fuel cell device from the environment, it must be ensured and monitored that the purge valve closes properly again after a purge process and reliably seals the hydrogen area of ​​the fuel cell device in order to prevent uncontrolled escape of hydrogen into the environment via the purge valve.

[0008] For this purpose, a documented fault exclusion can be requested from the manufacturer of the flush valve, which demonstrates that improper closing of the flush valve can be ruled out in all possible situations. While such a fault exclusion represents a theoretical alternative, no manufacturer of suitable flush valves has yet been found that would provide such a fault exclusion. Alternatively, the flush valve can be used with position detection and position feedback in order to detect the closing of the flush valve after the flushing process. This requires the provision and integration of valve position monitoring on the flush valve, which significantly increases the complexity of the flush valve and thus the costs and installation space of the flush valve.

[0009] The present invention is based on the object of providing a fuel cell system for a mobile work machine, in particular an industrial truck, of the type mentioned at the outset, in which the closing of the purge valve can be monitored after a purge process of the fuel cell device with little installation space and cost.

[0010] This object is achieved according to the invention in that a pressure sensor is provided which is designed to detect the pressure in the purge line between the fuel cell device and the purge valve, wherein the pressure sensor is connected to an electronic control device which is designed to monitor the function of the purge valve on the basis of the measured values ​​of the pressure sensor.

[0011] According to the invention, a pressure sensor is provided that is arranged in the purge line between the fuel cell device and the purge valve, and thus in the purge line upstream of the purge valve. Based on the measured values ​​measured by the pressure sensor arranged in the purge line upstream of the purge valve, the function of the purge valve can be monitored in a simple and cost-effective manner, thus requiring minimal space and cost. In particular, closing of the purge valve after a purge process of the fuel cell device can be detected and thus monitored.

[0012] According to an advantageous embodiment of the invention, the purge valve has an open position in which the purge line is open, and a shut-off position in which the purge line is shut off. The purge valve is actuated to the open position during a purge process of the fuel cell device and to the shut-off position during normal operation of the fuel cell device. With such a purge valve having an open position and a shut-off position, a purge process of the fuel cell device can be carried out in a simple manner.

[0013] According to an advantageous embodiment of the invention, the purge valve is controlled by the electronic control device into the open position and the shut-off position. The control device thus controls the purge valve into the open position and the shut-off position by means of corresponding control signals, thus controlling the purge process. This allows the control device to easily determine the end of the purge process of the fuel cell device based on the purge valve control signal, which actuates the purge valve into the shut-off position.

[0014] According to an advantageous embodiment of the invention, the electronic control device is designed to detect a malfunction of the purge valve during normal operation of the fuel cell device and / or at the end of a purge process if the pressure measured by the pressure sensor falls below a predetermined pressure value. During normal operation of the fuel cell device and / or at the end of a purge process, the purge valve is actuated to the shut-off position. If the purge valve does not close properly and is fully actuated to the shut-off position, the pressure in the purge line between the fuel cell device and the purge valve drops.If the pressure sensor measures a pressure that falls below a predetermined pressure value, in particular one stored in the control device, the control device can determine the malfunction of an open purge valve and thus monitor the closing of the purge valve after a purge process of the fuel cell device.

[0015] According to an advantageous embodiment of the invention, the electronic control device is designed to transfer the fuel cell system to a safe state, in particular to shut down the fuel cell device, upon a detected malfunction of the purge valve. Since hydrogen escapes uncontrollably into the environment via the open purge valve during normal operation of the fuel cell system upon a detected malfunction of the purge valve, further escape of hydrogen via the incorrectly opened purge valve can be prevented by transferring the fuel cell system to a safe state, for example, by shutting down the fuel cell device.

[0016] The invention further relates to a mobile work machine, in particular an industrial truck, having an electric drive system and a fuel cell system according to the invention, wherein the fuel cell system is designed to supply the electric drive system of the work machine with electrical energy, and wherein the fuel cell system has a housing which is designed to be inserted into a battery receiving space of the work machine.

[0017] In such work machines, the fuel cell system can be installed in the battery compartment of the work machine instead of a traction battery, for example, a lead-acid battery. Due to the limited space and size of the battery compartment, the fuel cell system intended as a replacement for a traction battery also requires little installation space. Due to the limited installation space required for such a fuel cell system intended as a replacement for a traction battery, the function of the purge valve can be monitored with the pressure sensor arranged in the purge line, while requiring minimal installation space.

[0018] The invention has a number of advantages.

[0019] The pressure sensor located upstream of the flush valve in the flushing line allows for simple and space-saving diagnostics and monitoring of the flush valve. This makes it possible to use a simple and cost-effective valve as the flush valve. This eliminates the need for a complex and expensive flush valve with integrated valve position monitoring.

[0020] Further advantages and details of the invention are explained in more detail with reference to the embodiment shown in the schematic figures.

[0021] Figure 1 is a perspective view of the fuel cell system according to the invention and

[0022] Figure 2 is a schematic representation of the fuel cell system of Figure 1.

[0023] Figure 1 shows a fuel cell system 1 according to the invention for a mobile work machine, in particular an industrial truck, with an electric drive system that can be used as a replacement for a traction battery in a battery receiving space of the work machine.

[0024] The fuel cell system 1 has a rectangular housing 2 within which the components of the fuel cell system 1 are installed.

[0025] The fuel cell system 1 has - as can be seen in more detail in connection with Figure 2 - a hydrogen-operated fuel cell device 4.

[0026] The fuel cell device 4 is preferably designed as a fuel cell stack. The fuel cell device 4 is preferably designed as an air-cooled fuel cell device 4, which is cooled by a cooling air flow generated by a fan device (not shown in detail).

[0027] The fuel cell system 1 further comprises a hydrogen tank 5, which is connected to the fuel cell device 4 via a supply line 6. A tank valve 7, which has an open position and a shut-off position, can be arranged in the supply line 6.

[0028] The fuel cell system 1 further comprises a purge system 10 configured to purge the fuel cell device 4. The purge system 10 comprises a purge valve 11 arranged in a purge line 12 connected to the fuel cell device 4. The outlet of the purge valve 11 is connected to the environment via the purge line.

[0029] The fuel cell system 1 has a pressure sensor 15 which is designed to detect the pressure in the purge line 12 between the fuel cell device 4 and the purge valve 11.

[0030] The flushing valve 11 has an open position in which the flushing line 12 is opened, and a shut-off position in which the flushing line 12 is shut off,

[0031] The fuel cell system 1 has an electronic control device 20 which is connected to the pressure sensor 15 and receives the measured values ​​of the pressure sensor 15.

[0032] The flush valve 11 is controlled by the electronic control device 20 to move it into the open position and into the shut-off position. For this purpose, the flush valve 11 is preferably electrically actuated into the open position and into the shut-off position by means of an electrical actuating device, wherein the electrical actuating device of the flush valve 11 is controlled by means of corresponding control signals generated by the control device 20 to move the flush valve 11 into the open position and into the shut-off position.

[0033] In the fuel cell system 1, the fuel cell device 4 must be purged at regular intervals. For this purpose, the electronic control device 20 actuates the purge valve 11 to the open position at the beginning of a purge process and the purge valve 11 to the shut-off position at the end of the purge process. During the purge process, the purge valve 11 is thus actuated to the open position, with a hydrogen-containing purge gas escaping through the purge line 12.

[0034] During normal operation of the fuel cell system 1, i.e. in all operating states that do not involve a purging process, the purge valve 11 is controlled by the electronic control device 20 into the shut-off position.

[0035] In the fuel cell system 1, it must be ensured and monitored that the purge valve 11 is actuated into the shut-off position again at the end of the purge process and thus after the purge process and thus closes properly in order to seal the hydrogen area of ​​the fuel cell device 4.

[0036] In the fuel cell system according to the invention, this monitoring is carried out by means of the pressure sensor 15, wherein the electronic control device 20 is designed to monitor the function of the purge valve 11 based on the measured values ​​of the pressure sensor 15.

[0037] Based on the measured values ​​detected by the pressure sensor 15 and thus the pressure in the flushing line 12 upstream of the flushing valve 11, the control device 20 can monitor the opening and subsequent closing of the flushing valve 11 during a flushing process, as described below.

[0038] During normal operation of an air-cooled fuel cell device 4, with the purge valve 11 in the shut-off position blocking the purge line 12, only small volume flows flow through the fuel cell device 4, so that the pressure at the inlet of the fuel cell device 4 can be determined from the pressure at the outlet of the fuel cell device 4 measured by the pressure sensor 15. During the purge process, with the purge valve 11 in the open position opening the purge line 12, the closed hydrogen region of the fuel cell device 4 is opened to the environment via the open purge line 12. As a result, significantly higher volume flows flow through the fuel cell device 4. The increased volume flows result in a pressure loss between the inlet and the outlet of the fuel cell device 4.By positioning the pressure sensor 15 in the purge line 12 downstream of the outlet of the fuel cell device 4, this pressure loss can be detected. For this purpose, a predefined pressure value is stored in the control device 20, with which the pressure measured by the pressure sensor 15 is compared. If the pressure measured by the pressure sensor 15 is above the predefined pressure value, a closed purge valve 11 in the shut-off position can be closed. If the pressure measured by the pressure sensor 15 is below the predefined pressure value, an open purge valve 11 in the open position can be closed.

[0039] The electronic control device 20 is particularly designed to detect a malfunction of the purge valve 11 during normal operation of the fuel cell device 4 and / or at the end of a purge process if the pressure measured by the pressure sensor 15 falls below the predetermined pressure value. During normal operation of the fuel cell device 4 or at the end of the purge process, the purge valve 11 is actuated to the shut-off position. If a malfunction of the purge valve 11 occurs and the purge valve 11 is not properly actuated to the shut-off position and thus does not close properly, the pressure sensor 15 detects a pressure below the predetermined pressure value.At the end of a purging process and thus after a purging process of the fuel cell device 4, the control device 20 can thus monitor the closing of the purging valve 11 based on the pressure in the purging line 12 detected by the pressure sensor 15 and can detect a malfunction in the form of a non-closing of the purging valve 11.

[0040] The electronic control device 20 is further configured to transfer the fuel cell system 4 to a safe state, in particular to shut down the fuel cell device 4, upon a detected malfunction of the purge valve 11. This can prevent further hydrogen from escaping from the incorrectly opened purge valve 11.

Claims

Patent claims 1. A fuel cell system (1) for a mobile work machine, in particular an industrial truck, comprising a hydrogen-powered fuel cell device (4), a hydrogen tank (5) connected to the fuel cell device (4) by means of a supply line (6), and a purging system (10) designed to purge the fuel cell device (4), wherein the purging system (10) has a purge valve (11) arranged in a purge line (12) connected to the fuel cell device (4), characterized in that a pressure sensor (15) is provided which is designed to detect the pressure in the purge line (12) between the fuel cell device (4) and the purge valve (11), wherein the pressure sensor (15) is connected to an electronic control device (20) designed to monitor the function of the purge valve (11) based on the measured values ​​of the pressure sensor (15).

2. Fuel cell system according to claim 1, characterized in that the purge valve (11) has an open position in which the purge line (12) is open, and a shut-off position in which the purge line (12) is shut off, wherein the purge valve (11) is actuated into the open position during a purge process of the fuel cell device (4) and is actuated into the shut-off position during normal operation of the fuel cell device (4).

3. Fuel cell system according to claim 2, characterized in that the purge valve (11) is controlled by means of the electronic control device (20) into the open position and into the shut-off position.

4. Fuel cell system according to one of claims 1 to 3, characterized in that the electronic control device (20) is designed to detect a malfunction of the purge valve (11) during normal operation of the fuel cell device (4) and / or at the end of a purge process if the pressure measured by the pressure sensor (15) falls below a predetermined pressure value.

5. Fuel cell system according to claim 4, characterized in that the electronic control device (20) is designed to transfer the fuel cell system (4) into a safe state, in particular to switch off the fuel cell device (4), in the event of a detected malfunction of the purge valve (11).

6. Mobile work machine, in particular industrial truck, with an electric drive system and a fuel cell system (1) according to one of the preceding claims, wherein the fuel cell system (1) is designed to supply the electric drive system of the work machine with electrical energy, and wherein the fuel cell system (1) has a housing (2) which is designed to be inserted into a battery receiving space of the work machine.

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