Fuel Cell Systems

Abstract

To provide a fuel cell system capable of detecting a voltage of a power storage device with high accuracy.SOLUTION: An electronic control unit 41 includes an actuator drive circuit 43 that receives electric power from a power storage device 38 to drive a hydrogen circulation pump 36, and a microcomputer 42 that is connected to the power storage device 38 together with the actuator drive circuit 43 and detects a voltage of the power storage device 38 on the upstream side of the actuator drive circuit 43. The microcomputer 42 samples the voltage of the power storage device 38 at intervals obtained by dividing the driving cycle of the hydrogen circulation pump 36. The microcomputer 42 averages the sampled voltage of power storage device 38.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] Attempts have been made to detect the varying power supply voltage in detail (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-214898 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, when the circuit configuration is such that voltage fluctuations are likely to occur, there is a demand for improving the accuracy of voltage detection by considering the causes of the fluctuations. Particularly in fuel cell systems, which are equipped with a drive circuit for driving auxiliary devices such as pumps, the load acting on the drive circuit may change depending on the load of the auxiliary devices, causing the detected voltage to fluctuate, and a solution was required. [Means for solving the problem]

[0005] The fuel cell system for solving the above problem comprises a fuel cell stack, a power storage device that is charged with power generated by the fuel cell stack, a load that is driven by the power of the power storage device, and an electronic control unit for driving the load, wherein the electronic control unit has a drive circuit that inputs power from the power storage device to drive the load, and a control unit that is connected to the power storage device together with the drive circuit and detects the voltage of the power storage device upstream of the drive circuit, and the control unit comprises sampling means that samples the voltage of the power storage device at a period that is a division of the drive period of the load, and averaging means that averages the voltage of the power storage device sampled by the sampling means.

[0006] According to this, the control unit of the electronic control unit is connected to the power storage device together with the drive circuit, and when detecting the voltage of the power storage device upstream of the drive circuit, the sampling means samples the voltage of the power storage device at a period obtained by dividing the drive period of the load. The averaging means averages the voltage of the power storage device sampled by the sampling means. Thus, it is possible to detect the voltage of the power storage device with high accuracy while being less susceptible to the influence of voltage fluctuations caused by driving the load.

[0007] In addition, in the fuel cell system, the averaging means may arrange the voltages of the power storage device sampled by the sampling means in descending or ascending order, extract voltages of the power storage devices within a certain continuous range from the voltages of the power storage devices arranged in descending or ascending order, and average the extracted voltages of the power storage devices.

[0008] In the fuel cell system, the power storage device may be a capacitor. In this case, since the power storage device is a capacitor with large voltage fluctuations, the estimated value of the SOC is affected by the voltage detection result, but the accuracy of the SOC can be improved by applying the present invention. Effect of the Invention

[0009] According to the present invention, the voltage of the power storage device can be detected with high accuracy. [Brief description of the drawings]

[0010] [Figure 1] 1 is a schematic side view of a fuel cell forklift according to an embodiment. [Diagram 2] FIG. 1 is a schematic diagram of a fuel cell system. [Diagram 3] FIG. [Figure 4] An enlarged view of a portion of the voltage waveform. [Diagram 5] 11A and 11B are diagrams for explaining the storage order, descending order, extraction, and averaging of sampled values. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. As shown in Fig. 1, driving wheels (front wheels) 12a are provided on the front lower part of a body 11 of a fuel cell forklift 10, and steering wheels (rear wheels) 12b are provided on the rear lower part of the body 11. A mast 13 is erected at the front of the body 11. The mast 13 is made up of a pair of left and right outer masts 13a supported on the body 11 so as to be tiltable forward and backward, and an inner mast 13b that slides on the outer masts to rise and fall. A lift cylinder 14 is disposed at the rear of each outer mast 13a. A lift bracket 16 equipped with forks 15 is supported on the inside of the inner mast 13b so as to be able to rise and fall. The forks 15 are raised and lowered together with the lift bracket 16 by the extension and retraction of the lift cylinder 14.

[0012] The pair of left and right tilt cylinders 17 have their base ends rotatably connected to the vehicle body 11, and their tip ends rotatably connected to the side surfaces of the outer masts 13a. The masts 13 tilt forward and backward as the tilt cylinders 17 are driven to extend and retract.

[0013] A lift lever 19 and a tilt lever 20 are provided in front of the operator's cab 18. The lift lever 19 is a lever for raising and lowering the fork 15, and the tilt lever 20 is a lever for tilting the mast 13 in the forward and backward directions. An accelerator pedal 21 is provided below the operator's cab 18, and the vehicle speed is adjusted according to the amount of operation of the accelerator pedal 21.

[0014] The vehicle body 11 is equipped with a fuel cell system 22, a travel motor 23, and a loading motor 24. The travel motor 23 is driven by the fuel cell system 22 to drive the drive wheels 12a. In detail, the output shaft of the travel motor 23 is connected to the rotating shaft of the drive wheels 12a via a reduction gear (not shown), and when the output shaft rotates due to the drive of the travel motor 23, the rotating shaft of the drive wheels 12a rotates in accordance with the rotation, thereby driving the drive wheels 12a.

[0015] In addition, a cargo handling motor 24 is driven by the fuel cell system 22, and a cargo handling pump (not shown) is driven by the driving of the cargo handling motor 24. Based on the driving of the cargo handling pump, the lift cylinder 14 and the tilt cylinder 17 are extended and retracted, so that the fork 15 can be moved up and down and tilted.

[0016] In this manner, the fuel cell system 22 is used as a power source for the cargo motor 24 and the travel motor 23, which serve as the hydraulic source for the lift cylinder 14 and the tilt cylinder 17. Next, the fuel cell system 22 will be described with reference to FIG.

[0017] 2, the fuel cell system 22 includes a fuel cell stack 31, a hydrogen tank 32, a solenoid valve 33, an injector 34, a compressor 35, a hydrogen circulation pump 36, a DC / DC converter 37, an electricity storage device 38, a main contactor 39, an inverter 40, and an electronic control unit (ECU) 41. A capacitor is used as the electricity storage device 38.

[0018] The fuel cell stack 31 in the fuel cell system 22 is configured by stacking multiple cells, with each cell being electrically connected in series. A hydrogen tank 32 is capable of supplying hydrogen gas to the fuel cell stack 31 via a solenoid valve 33 and an injector 34. A compressor 35 is capable of supplying air containing oxygen to the fuel cell stack 31. Then, a chemical reaction occurs within the fuel cell stack 31 between the hydrogen supplied from the hydrogen tank 32 and the oxygen in the air supplied from the compressor 35, generating electrical energy.

[0019] A solenoid valve 33 and an injector 34 are provided in the pipe connecting the fuel cell stack 31 and the hydrogen tank 32. The amount of hydrogen gas supplied to the fuel cell stack 31 is adjusted by the solenoid valve 33. The solenoid valve 33 and the compressor 35 are controlled by an electronic control unit 41.

[0020] A hydrogen circulation pump 36 is provided in the hydrogen circulation path in the fuel cell stack 31. The gas discharged from the fuel cell stack 31 contains unreacted hydrogen. In order to supply this unreacted hydrogen again to the fuel cell stack 31, the hydrogen circulation pump 36 returns the gas discharged from the fuel cell stack 31 to the fuel cell stack 31. The hydrogen circulation pump 36 also boosts the hydrogen pressure to the hydrogen supply pressure of the fuel cell stack 31.

[0021] An electromagnetic diaphragm pump is used as the hydrogen circulation pump 36. In an electromagnetic diaphragm pump, an electromagnetic solenoid coil is energized and cut off at, for example, 50 Hz, to periodically flow an electric current through an oscillator, causing the oscillator to reciprocate. As a result of this reciprocating motion, hydrogen gas is drawn into the pump chamber, and the gas is pressurized and discharged. The hydrogen circulation pump 36 is driven by the electric power of the power storage device 38.

[0022] As shown in FIG. 2, a positive output terminal of the fuel cell stack 31 is connected to an electric storage device (capacitor) 38 via a DC / DC converter 37 and a main contactor 39. The main contactor 39 is closed when the vehicle is started by turning on the key switch of the vehicle, and is opened when the vehicle is stopped by turning off the key switch. A vehicle load is connected to the electric storage device (capacitor) 38. That is, the fuel cell stack 31 is electrically connected to the vehicle load via the DC / DC converter 37 and the electric storage device 38. The direct current power generated by the fuel cell stack 31 is stepped down to a predetermined voltage by the DC / DC converter 37, and then output to the vehicle load via the electric storage device (capacitor) 38. The vehicle load includes a traveling motor 23 and a loading motor 24 that are driven based on the operation of an accelerator pedal 21, a lift lever 19, and a tilt lever 20 as operating members. That is, the vehicle load includes a loading motor 24 and a traveling motor 23 for driving the axles, and the loading motor 24 and the traveling motor 23 are driven by power supplied from the fuel cell system 22 to perform loading and traveling operations of the vehicle.

[0023] The power storage device (capacitor) 38 is electrically connected to the fuel cell stack 31 in parallel with the vehicle load (travel motor 23, cargo handling motor 24, etc.). In the power storage device (capacitor) 38, when the generated power of the fuel cell stack 31 exceeds the power required by the vehicle load (travel motor 23, cargo handling motor 24, etc.), the surplus power is charged to the power storage device (capacitor) 38. On the other hand, when the generated power falls short of the required power, the shortage of power is discharged from the power storage device (capacitor) 38.

[0024] An inverter 40 is connected to a positive line between the DC / DC converter 37 and the power storage device (capacitor) 38. The inverter 40 converts DC power into AC power and supplies it to an AC motor in the compressor 35. The compressor 35 is driven by this AC power. The hydrogen circulation pump 36 is driven by an electronic control unit 41.

[0025] The electronic control unit 41 has a microcomputer 42, an actuator drive circuit 43, and voltage dividing resistors 44, 45, and voltage dividing resistors 46, 47. The microcomputer 42 has a CPU (Central Processing Unit) 48 that decodes commands and executes data processing, and a memory 49 that holds programs and data. The memory 49 is composed of a ROM (Read Only Memory) 50 and a RAM (Random Access Memory) 51. The RAM 51 has a buffer that temporarily stores data.

[0026] An input terminal of the actuator drive circuit 43 is connected to the positive terminal of the power storage device 38. An output terminal of the actuator drive circuit 43 is connected to the hydrogen circulation pump 36. The actuator drive circuit 43 receives power from the power storage device 38 to drive the hydrogen circulation pump 36.

[0027] The microcomputer 42 has a first voltage detection port P1 and a second voltage detection port P2. A connection point α1 on the DC / DC converter 37 side of the main contactor 39 in a positive electrode line between the DC / DC converter 37 and the power storage device 38 is connected to ground via a series circuit made up of voltage dividing resistors 44 and 45. The first voltage detection port P1 is electrically connected to a connection point α2 between the voltage dividing resistors 44 and 45 in the series circuit. As a result, the first voltage detection port P1 is connected to the DC / DC converter 37 side of the main contactor 39 via the voltage dividing resistors 44, 45.

[0028] In this manner, the voltage at connection point α1 on the DC / DC converter 37 side of the main contactor 39 is input to the electronic control unit (ECU) 41. After the voltage at connection point α1 on the DC / DC converter 37 side of the main contactor 39 is input to the electronic control unit (ECU) 41, it is divided by resistors 44, 45 and converted into a voltage detectable by the microcomputer 42. After the voltage at connection point α1 on the DC / DC converter 37 side of the main contactor 39 is divided (converted), it can be detected by the microcomputer 42 at the first voltage detection port P1.

[0029] A connection point β1 on the power storage device 38 side of the main contactor 39 in the positive line between the DC / DC converter 37 and the power storage device 38 is connected to ground via a series circuit made up of voltage dividing resistors 46 and 47. A second voltage detection port P2 is electrically connected to a connection point β2 between the voltage dividing resistors 46 and 47 in the series circuit. As a result, the second voltage detection port P2 is connected to the power storage device 38 side of the main contactor 39 via the voltage dividing resistors 46 and 47. The microcomputer 42 is connected to the power storage device 38 together with the actuator drive circuit 43, and can detect the voltage of the power storage device 38 on the upstream side of the actuator drive circuit 43 using the second voltage detection port P2.

[0030] In this way, the voltage of the power storage device 38, which is the voltage at the connection point β1 on the power storage device 38 side of the main contactor 39, is used as a power supply voltage in the actuator drive circuit 43, while the voltage of the power storage device 38 is input to the electronic control unit (ECU) 41. After the voltage of the power storage device 38 is input to the electronic control unit (ECU) 41, it is divided by resistors 46 and 47 and converted into a voltage detectable by the microcomputer 42. After the voltage of the power storage device 38 is divided (converted), it can be detected by the microcomputer 42 at the second voltage detection port P2.

[0031] The microcomputer 42 can A / D (analog / digital) convert the voltage at the first voltage detection port P1 and store the converted voltage in a buffer of the RAM 51 of the memory 49. The microcomputer 42 can A / D convert the voltage at the second voltage detection port P2 and store the converted voltage in a buffer of the RAM 51 of the memory 49.

[0032] The electronic control unit 41 estimates the SOC (state of charge) of the power storage device (capacitor) 38 based on the measured terminal voltage of the power storage device (capacitor) 38 and the internal resistance of the power storage device 38. Then, the electronic control unit 41 adjusts the amount of hydrogen and oxygen supplied to the fuel cell stack 31 by controlling the opening degree of the solenoid valve 33 and the discharge amount of the compressor 35 based on the estimated SOC of the power storage device (capacitor) 38, thereby controlling the power generated by the fuel cell stack 31.

[0033] Next, the operation of the fuel cell forklift 10 thus configured will be described. The microcomputer 42 performs a fault diagnosis of the main contactor 39. During the fault diagnosis of the main contactor 39, when the main contactor 39 is closed, the microcomputer 42 determines whether or not the difference between the voltage at the first voltage detection port P1 and the voltage at the second voltage detection port P2 is less than a threshold value while the hydrogen circulation pump (electromagnetic diaphragm pump) 36 is in operation. That is, the microcomputer 42 determines whether or not the difference between the voltage corresponding to the voltage at the connection point α1 on the DC / DC converter 37 side of the main contactor 39 and the voltage corresponding to the connection point β1 on the power storage device 38 side of the main contactor 39 is less than a threshold value. If the difference between the voltage at the first voltage detection port P1 and the voltage at the second voltage detection port P2 is less than the threshold value, the microcomputer 42 determines that the main contactor 39 is operating normally and is normal. Also, if the difference between the voltage at the first voltage detection port P1 and the voltage at the second voltage detection port P2 is equal to or greater than the threshold value, the microcomputer 42 determines that the main contactor 39 is not operating normally and is abnormal.

[0034] The electromagnetic diaphragm pump, which is the hydrogen circulation pump 36, is driven at a low frequency, for example, 50 Hz. At this time, the voltage at the second voltage detection port P2 in the microcomputer 42 fluctuates up and down, as shown by the solid line in Figure 3. In particular, at a given drive period Td, the voltage drops significantly and then returns to the original voltage level. This is repeated, resulting in a fluctuating waveform, as shown by the solid line in Figure 3.

[0035] If the drive period Td of the hydrogen circulation pump (electromagnetic diaphragm pump) 36 in the actuator drive circuit 43 is X (msec), A / D conversion of the voltage at the second voltage detection port P2 in the microcomputer 42 is performed at a speed of X / 20 or less.

[0036] As shown in Fig. 4, the microcomputer 42 samples the voltage at the second voltage detection port P2, which is obtained by dividing the voltage of the power storage device 38 on the upstream side of the actuator drive circuit 43. At this time, when the drive frequency of the hydrogen circulation pump (electromagnetic diaphragm pump) 36 is 50 Hz, sampling is performed at 1 msec, which is a period obtained by dividing the drive period Td of the hydrogen circulation pump (electromagnetic diaphragm pump) 36 as the actuator, which is 20 msec (= Td / 20). In Fig. 4, the voltage V1 is sampled at a timing of t1, the voltage V2 is sampled at a timing of t2, the voltage V3 is sampled at a timing of t3, and so on, and the voltage V20 is sampled at a timing of t20. In this way, the drive period Td is divided by 20, and the voltages V1 to V20 are sampled every Td / 20.

[0037] The results of the A / D conversion are stored in a buffer of the RAM 51 of the memory 49. This is indicated by V1, V2, V3, ..., V19, and V20 in the storage order column corresponding to the No. column in FIG.

[0038] The microcomputer 42 averages the sampled voltage at the second voltage detection port P2, that is, the voltage of the power storage device 38 on the upstream side of the actuator drive circuit 43 (more specifically, the divided voltage).

[0039] In detail, first, the microcomputer 42 arranges in descending order the sampled voltages of the second voltage detection port P2, i.e., the divided voltages of the power storage device 38 on the upstream side of the actuator drive circuit 43 (sampled voltages V1 to V20), as shown in the descending order column in Fig. 5. In Fig. 5, the descending order is V5, V4, V6, V1, V2, V3, V20, V7, V8, V9, V10, V19, V11, V12, V13, V18, V14, V15, V16, and V17.

[0040] Then, the microcomputer 42 extracts the upper X / 5 to 2X / 5 from the voltage values ​​A / D converted at X / 20 for the drive period X. In Fig. 5, as shown in the extraction column, V1, V2, V3, V20, and V7 correspond to 4, 5, 6, 7, and 8 in the No. column. That is, the microcomputer 42 extracts the voltages of the second voltage detection port P2 arranged in descending order, that is, the voltages of the power storage device 38 in a certain continuous order range (V1 value, V2 value, V3 value, V20 value, and V7 value) from the voltages of the power storage device 38 on the upstream side of the actuator drive circuit 43 that have been divided.

[0041] The microcomputer 42 averages the extracted voltages (V1, V2, V3, V20, and V7) by taking the arithmetic mean value as the average value, as shown in the averaging column in Fig. 5. That is, the average value is calculated as (V1+V2+V3+V20+V7) / 5.

[0042] Therefore, when diagnosing a fault in the main contactor 39, the microcontroller 42 can prevent a false detection from occurring by judging that the difference between the voltage at the first voltage detection port P1 and the voltage at the second voltage detection port P2 is large even when the main contactor 39 is normal.

[0043] Conventionally, when the power supply voltage input to an electronic control unit (ECU) is used as the power supply for other actuators, a voltage drop occurs in the power supply voltage depending on the driving force and cycle of the actuator, making it impossible to measure the appropriate voltage.

[0044] In contrast, in this embodiment, the drive period Td of the hydrogen circulation pump 36, X (msec), is divided to sample the voltage and store it in a buffer, after which the voltage is sorted in descending order within the buffer, and the average of the top X / 5 to 2X / 5 is calculated and used as the voltage filter value. This makes it possible to measure the voltage appropriately regardless of the operation of the hydrogen circulation pump (electromagnetic diaphragm pump) 36 as an actuator. Also, it is possible to measure the voltage appropriately without adding any parts, etc.

[0045] Therefore, the voltage drop can be filtered out by passing it through a software filter that corresponds to the operation of the hydrogen circulation pump 36, which is an actuator serving as a load. As a result, the accuracy of the voltage of the power storage device 38 on the input side of the actuator drive circuit 43 can be improved.

[0046] According to the above embodiment, the following effects can be obtained. (1) The fuel cell system 22 includes a fuel cell stack 31, an electricity storage device 38 that is charged with power generated by the fuel cell stack 31, a hydrogen circulation pump 36 as a load that is driven by the power of the electricity storage device 38, and an electronic control unit 41 for driving the hydrogen circulation pump 36. The electronic control unit 41 includes an actuator drive circuit 43 as a drive circuit that receives power from the electricity storage device 38 to drive the hydrogen circulation pump 36, and a microcomputer 42 as a control unit that is connected to the electricity storage device 38 together with the actuator drive circuit 43 and detects the voltage of the electricity storage device 38 upstream of the actuator drive circuit 43. The microcomputer 42 as the control unit includes sampling means and averaging means, and the microcomputer 42 as the sampling means samples the voltage of the electricity storage device 38 at a period that is a division of the drive period of the hydrogen circulation pump 36. The microcomputer 42 as the averaging means averages the sampled voltage of the electricity storage device 38.

[0047] As a result, the microcomputer 42 of the electronic control unit 41 is connected to the electricity storage device 38 together with the actuator drive circuit 43, and detects the voltage of the electricity storage device 38 upstream of the actuator drive circuit 43. At this time, the microcomputer 42 samples the voltage of the electricity storage device 38 at a period that is a division of the drive period of the hydrogen circulation pump 36, and the sampled voltages of the electricity storage device 38 are averaged. This makes it possible to detect the voltage of the electricity storage device 38 with high accuracy, without being easily affected by voltage fluctuations caused by the drive of the hydrogen circulation pump 36.

[0048] (2) The microcomputer 42 as an averaging means sorts the sampled voltages of the power storage device 38 in descending order, extracts the voltages of the power storage device 38 in a certain continuous range from the voltages of the power storage device 38 sorted in descending order, and averages the extracted voltages of the power storage device 38. Thus, the voltage of the power storage device 38 can be detected with higher accuracy.

[0049] (3) The power storage device 38 is a capacitor. Therefore, since the power storage device is a capacitor with large voltage fluctuations, the estimated value of the SOC is affected by the voltage detection result, but the accuracy of the SOC can be improved.

[0050] The embodiment is not limited to the above, and may be embodied as follows, for example. Although the voltage of the power storage device is divided and input to the microcomputer 42, the present invention is not limited to this. The voltage of the power storage device may be input directly to the microcomputer 42.

[0051] The reason why X / 5 to 2X / 5 was extracted from the sampled voltage of the storage device 38 is because the waveform is downward. Depending on the waveform, instead of extracting X / 5 to 2X / 5, it is also possible to extract the voltage of the storage device 38 in a certain continuous sequence range.

[0052] In the above embodiment, the sampled voltages of the power storage device 38 are arranged in descending order, but the sampled voltages of the power storage device 38 may be arranged in ascending order. The averaging means arranges the voltages of the power storage devices sampled by the sampling means in ascending order, extracts voltages of the power storage devices in a certain continuous order range from the voltages of the power storage devices arranged in ascending order, and averages the extracted voltages of the power storage devices.

[0053] All sampled values ​​of the voltage of the storage device 38 may be averaged. The actuator as the load is not limited to the electromagnetic diaphragm pump 36. In the electromagnetic diaphragm pump, the driving frequency is low, for example 50 Hz, and a voltage drop appears in the voltage measurement.

[0054] Although the load was an actuator, any load that is easily affected by the operating frequency can be used. In this case, the load may be a sensor. Although the fuel cell system is applied to a fuel cell forklift, it may be applied to industrial vehicles other than forklifts, and further, it may be applied to vehicles other than industrial vehicles.

[0055] Furthermore, the fuel cell system may be applied not only to fuel cell vehicles but also to ground-mounted fuel cell devices, that is, fixed-position power generators. [Explanation of symbols]

[0056] 22... fuel cell system, 31... fuel cell stack, 36... hydrogen circulation pump, 38... power storage device, 41... electronic control unit, 42... microcomputer, 43... actuator drive circuit.

Claims

1. A fuel cell stack; a power storage device that is charged by the power generated by the fuel cell stack; A load driven by the power of the power storage device; an electronic control unit for driving the load; Equipped with The electronic control unit includes: a drive circuit that receives power from the power storage device and drives the load; a control unit that is connected to the power storage device together with the drive circuit and detects a voltage of the power storage device upstream of the drive circuit, The control unit is A sampling means for sampling the voltage of the storage device at a period obtained by dividing a drive period of the load; an averaging means for averaging the voltage of the power storage device sampled by the sampling means, The fuel cell system is characterized in that the averaging means arranges the voltages of the power storage device sampled by the sampling means in descending or ascending order, extracts voltages of the power storage device in a certain continuous order range from the voltages of the power storage device arranged in descending or ascending order in which voltage drops corresponding to the operation of the load have been removed, and averages the extracted voltages of the power storage device.

2. 2. The fuel cell system according to claim 1, wherein the power storage device is a capacitor.

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