Control device for fuel cell vehicle

Abstract

To reduce the time required before a fuel cell vehicle can start driving prior to completion of warm-up of a fuel cell stack and / or to enable the drive force requested by a user to be obtained.SOLUTION: When a start request is issued for a fuel cell vehicle (YES at ST1), and it is determined that warm-up of a fuel cell stack is required (YES at ST2), and under such a condition that a power storage amount of a drive battery is at a prescribed amount or greater (YES at ST5), the upper limit output of the drive battery is set to be higher than the normal time (ST7) during a prescribed period until completion of the warm-up of the fuel cell stack. As a result, the power stored in the drive battery can be effectively utilized, making it possible to reduce the time required before a fuel cell vehicle can start driving prior to completion of the warm-up of the fuel cell stack and / or to enable the drive force requested by a user to be obtained.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a control device for a fuel cell vehicle.

Background Art

[0002] Conventionally, in a fuel cell system mounted on a fuel cell vehicle, when the temperature of the fuel cell (hereinafter sometimes referred to as a fuel cell stack), for example, a temperature determined based on the outside air temperature or the stack cooling water temperature, is low, a warm-up operation for raising the temperature of the fuel cell stack is executed. Then, when the temperature of the fuel cell stack reaches a predetermined startable temperature by this warm-up operation, the fuel cell system can be started. However, even after the start, until the fuel cell stack reaches a predetermined temperature (for example, until the temperature of the fuel cell stack monitored by the water temperature reaches a temperature at which efficient power generation can be performed and the warm-up is completed), the output of the fuel cell system is restricted, which may give the user a sense of discomfort. In particular, in a vehicle usage situation where stopping and restarting are repeated in a short period of time, each time the system is started, time required for the warm-up operation is necessary, and there has been a problem that the time loss is large.

[0003] Patent Document 1 discloses that when starting a fuel cell system, if the temperature of the fuel cell stack is below the freezing point and the output state of the fuel cell stack continues to be in a low output state for a predetermined reference time or more, the power generation of the fuel cell stack is stopped and only the power storage device is used as a power source to drive the drive motor, and the drive motor is set to a first driving state in which the output of the drive motor is suppressed to be equal to or less than a first upper limit output.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, even in the technology disclosed in Patent Document 1, since the output of the drive motor is restricted at the start of the fuel cell system, there is room for improvement in shortening the time until the vehicle can start running and / or obtaining the driving force required by the user before the warm-up of the fuel cell stack is completed.

[0006] The present invention has been made in view of such a point, and an object thereof is to shorten the time until the vehicle can start running before the warm-up of the fuel cell stack is completed and / or to provide a control device for a fuel cell vehicle capable of obtaining the driving force required by the user before the warm-up of the fuel cell stack is completed.

Means for Solving the Problems

[0007] The solution means of the present invention for achieving the above object is premised on a control device for a fuel cell vehicle equipped with a fuel cell and a driving battery. Then, when a start request for the vehicle is made to this control device for the fuel cell vehicle, on the condition that it is determined that the warm-up of the fuel cell is necessary and the power storage amount of the driving battery is equal to or more than a predetermined amount, the upper limit output of the driving battery is set higher than normal during a predetermined period until the warm-up of the fuel cell is completed.

[0008] By this specific matter, it becomes possible to effectively utilize the electric power stored in the driving battery, shorten the time until the vehicle can start running before the warm-up of the fuel cell is completed, and / or obtain the driving force required by the user before the warm-up of the fuel cell is completed.

Effects of the Invention

[0009] In the present invention, when a start request for the vehicle is made, on the condition that it is determined that warm-up of the fuel cell is necessary and the power storage amount of the drive battery is equal to or more than a predetermined amount, during a predetermined period until the warm-up of the fuel cell is completed, the upper limit output of the drive battery is set higher than normal, thereby shortening the time until the vehicle can start running before the warm-up of the fuel cell is completed, and / or enabling the driving force required by the user to be obtained before the warm-up of the fuel cell is completed.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0012] -Drive System of Fuel Cell Vehicle- FIG. 1 is a diagram showing a schematic configuration of a drive system of a fuel cell vehicle according to the present embodiment. As shown in this FIG. 1, the drive system of the fuel cell vehicle according to the present embodiment includes a drive motor 10 that generates a driving force (travel driving force) of the vehicle, a fuel cell system 20 including a fuel cell stack (fuel cell) 21, a drive battery (secondary battery, drive battery) 30 that can supply electric power for driving the fuel cell vehicle, and a control device 100. Note that the configuration of the drive system of the fuel cell vehicle to which the present invention is applicable is not limited to that shown in FIG. 1.

[0013] In the fuel cell vehicle according to this embodiment, each of the fuel cell stack 21 and the drive battery 30 can supply power to a load including the drive motor 10 alone or simultaneously from both the fuel cell stack 21 and the drive battery 30. The fuel cell stack 21 and the load including the drive motor 10 are connected via a DC / DC converter 23 and a wiring 24, and the drive battery 30 and the load including the drive motor 10 are connected via a DC / DC converter 25 and the wiring 24. Each of the DC / DC converters 23 and 25 is connected in parallel to the wiring 24.

[0014] Further, the fuel cell system 20 includes a hydrogen gas supply unit 40 including a hydrogen tank 41 and an air supply unit 50 including a compressor 51 in addition to the fuel cell stack 21. The fuel cell system 20 further includes a refrigerant circulation unit (not shown) that circulates a refrigerant for keeping the temperature of the fuel cell stack 21 within a predetermined range into the fuel cell stack 21.

[0015] The fuel cell stack 21 has a stack structure in which a plurality of single cells are stacked. The fuel cell stack 21 of this embodiment is a polymer electrolyte fuel cell, but other types of fuel cells may be used. In each single cell constituting the fuel cell stack 21, an anode-side flow path through which hydrogen, which is a fuel gas, flows is formed on the anode side with an electrolyte membrane interposed therebetween, and a cathode-side flow path through which air, which is an oxidizing gas, flows is formed on the cathode side.

[0016] The fuel cell stack 21 is provided with a temperature sensor 22 capable of measuring the temperature of the fuel cell stack 21. The temperature sensor 22 can be, for example, a temperature sensor provided in the refrigerant flow path described above to detect the temperature of the refrigerant discharged from the fuel cell stack 21 after circulating inside the fuel cell stack 21. Alternatively, as the temperature sensor 22, a sensor that directly detects the internal temperature of the fuel cell stack 21 may be used. The detection signal of this temperature sensor 22 is output to the control device 100. In the fuel cell system 20, when the temperature detected by the temperature sensor 22 is equal to or lower than a predetermined value, warm-up of the fuel cell stack 21 is performed. The operation for this warm-up is not particularly limited. For example, setting the inflow amount of air from the air supply unit 50 to be small and generating power with the fuel cell at a low power generation efficiency can be mentioned.

[0017] The hydrogen tank 41 can be, for example, a tank that stores high-pressure hydrogen gas. The hydrogen gas supply unit 40 includes a hydrogen supply flow path 42 from the hydrogen tank 41 to the fuel cell stack 21, a circulation flow path 43 that circulates unconsumed hydrogen gas (anode off-gas) through the hydrogen supply flow path 42, and a hydrogen release flow path 44 for releasing the anode off-gas to the atmosphere. In the hydrogen gas supply unit 40, the hydrogen gas stored in the hydrogen tank 41 passes through the opening and closing of the on-off valve 42a provided in the hydrogen supply flow path 42 and the pressure reduction by the pressure reducing valve 42b also provided in the hydrogen supply flow path 42, and is supplied from the hydrogen supply device 42c (for example, an injector) downstream of the pressure reducing valve 42b to the anode-side flow path of the fuel cell stack 21. The pressure of the hydrogen circulating through the circulation flow path 43 is adjusted by the circulation pump 43a. The driving amounts of the hydrogen supply device 42c and the circulation pump 43a are adjusted by the control device 100 according to the target power that the fuel cell stack 21 should output while referring to the pressure of the circulating hydrogen detected by the pressure sensor 43b provided in the circulation flow path 43.

[0018] Some of the hydrogen gas flowing through the circulation channel 43 is discharged into the atmosphere at a predetermined timing through the opening and closing adjustment of the on-off valve 44a provided in the hydrogen discharge channel 44 branched from the circulation channel 43. The opening and closing timing of each of the on-off valves 42a and 44a is adjusted by the control device 100.

[0019] The air supply unit 50 includes, in addition to the compressor 51, a first air channel 52, a second air channel 53, a third air channel 54, a flow dividing valve 55, an air discharge channel 56, a back pressure valve 57, and a flow rate sensor 58. The first air channel 52 is a channel through which the entire amount of air taken in by the compressor 51 flows. The second air channel 53 and the third air channel 54 are provided branching from the first air channel 52. The flow dividing valve 55 is provided at a portion where the first air channel 52 branches into the second air channel 53 and the third air channel 54, and by changing the valve opening state of the flow dividing valve 55, the distribution ratio of the air flowing from the first air channel 52 to the second air channel 53 and the third air channel 54 can be changed. A part of the second air channel 53 forms a cathode-side channel in the fuel cell stack 21. The third air channel 54 is a bypass channel that guides air without passing through the fuel cell stack 21. The second air channel 53 and the third air channel 54 merge to form the air discharge channel 56. The back pressure valve 57 is a throttle valve provided in the second air channel 53, downstream of the cathode-side channel and upstream of the merging point with the third air channel 54. By adjusting the opening degree of the back pressure valve 57, the back pressure of the cathode-side channel in the fuel cell stack 21 can be changed. The air discharge channel 56 is a channel for discharging the air (cathode off-gas) that has passed through the second air channel 53 together with the air that has passed through the third air channel 54 into the atmosphere. The hydrogen discharge channel 44 described above is connected to the air discharge channel 56, and the hydrogen discharged through the hydrogen discharge channel 44 is diluted by the air flowing through the air discharge channel 56 prior to being discharged into the atmosphere. The flow rate sensor 58 is provided in the first air channel 52 and detects the total flow rate of the air taken in through the first air channel 52.

[0020] In the air supply unit 50, by changing at least one condition selected from the driving amount of the compressor 51, the valve opening state of the flow dividing valve 55, and the opening degree of the back pressure valve 57, the flow rate (oxygen flow rate) of the air supplied to the cathode side flow path of the fuel cell stack 21 can be adjusted. The driving amount of the compressor 51, the valve opening state of the flow dividing valve 55, and the opening degree of the back pressure valve 57 are adjusted by the control device 100.

[0021] The driving battery 30 can be composed of, for example, a lithium ion battery or a nickel hydrogen battery. The driving battery 30 may be any rechargeable power storage device. Such a power storage device may be composed of a secondary battery, or may be a capacitor, for example. The driving battery 30 is provided with a remaining capacity monitor 31. The remaining capacity monitor 31 detects the operating state such as the remaining capacity (power storage amount) of the driving battery 30. Further, the control device 100 may be configured to calculate the state of charge (SOC) of the driving battery 30 based on this remaining capacity. The remaining capacity of the driving battery 30 is an index indicating how much the driving battery 30 is charged. The remaining capacity monitor 31 may detect the remaining capacity, for example, by integrating the current value and time of charging and discharging in the driving battery 30. Alternatively, the remaining capacity may be obtained using the voltage of the driving battery 30. The detected remaining capacity of the driving battery 30 is output to the control device 100.

[0022] The DC / DC converter 23 has a function of changing the output state of the fuel cell stack 21 in response to a control signal from the control device 100. Specifically, when taking out current and voltage from the fuel cell stack 21 toward the load, the DC / DC converter 23 controls the current and voltage taken out from the fuel cell stack 21 by switching control in the DC / DC converter 23. Further, when supplying the power generated by the fuel cell stack 21 to a load such as the drive motor 10, the DC / DC converter 23 boosts the output voltage of the fuel cell stack 21 to a voltage that can be used by the above load.

[0023] The DC / DC converter 25 has a charge / discharge control function for controlling the charge and discharge of the drive battery 30, and controls the charge and discharge of the drive battery 30 in response to a control signal from the control device 100. In addition, the DC / DC converter 25 sets the target voltage on the output side under the control of the control device 100, thereby extracting the stored power of the drive battery 30 and applying a voltage to the drive motor 10, and variably adjusts the power extraction state and the voltage level applied to the drive motor 10.

[0024] The control device 100 includes a processor such as a CPU (Central Processing Unit), a ROM (Read-Only Memory) for storing a control program, a RAM (Random-Access Memory) for temporarily storing data, and input / output ports and the like. This control device 100 obtains detection signals from various sensors such as an accelerator opening sensor, a shift position sensor, a vehicle speed sensor, and an outside air temperature sensor (not shown), in addition to the aforementioned sensors provided in the hydrogen gas supply unit 40 and the air supply unit 50, and performs various controls related to the fuel cell vehicle. For example, the control device 100 obtains the magnitude of the required output required for the drive motor 10 based on the detection signal of the accelerator opening sensor and the like, and outputs a drive signal to each part so that the power corresponding to the required output can be obtained from at least one of the fuel cell stack 21 and the drive battery 30. Specifically, when obtaining power from the fuel cell stack 21, the gas supply amounts from the hydrogen gas supply unit 40 and the air supply unit 50 are controlled so that the desired power can be obtained from the fuel cell stack 21. In addition, the control device 100 controls the DC / DC converters 23 and 25 so that the desired power is supplied from at least one of the fuel cell stack 21 and the drive battery 30 to loads such as the drive motor 10.

[0025] The control device 100 includes a battery upper limit output control unit 110 as a functional unit realized by the control program. When a start request for the fuel cell vehicle (when the ignition is ON), and it is determined that warm-up of the fuel cell stack 21 is necessary and the power storage amount (remaining capacity) of the drive battery 30 is equal to or greater than a predetermined amount (hereinafter, this condition will be referred to as the upper limit output UP condition), during a predetermined period until the warm-up of the fuel cell stack 21 is completed, the battery upper limit output control unit 110 has a function of setting the upper limit output of the drive battery 30 higher than that in the normal state (when the upper limit output UP condition is not satisfied).

[0026] Specifically, when the temperature of the fuel cell stack 21 received from the temperature sensor 22 is equal to or lower than a predetermined temperature (for example, below the freezing point), it is determined that warm-up of the fuel cell stack 21 is necessary. The threshold temperature for this warm-up can be arbitrarily set. Also, it is determined whether the power storage amount of the drive battery 30 detected by the remaining capacity monitor 31 is equal to or greater than a predetermined amount (for example, the SOC is 40% or more). The threshold value for this power storage amount can also be arbitrarily set. And when it is determined that warm-up of the fuel cell stack 21 is necessary and the power storage amount of the drive battery 30 is equal to or greater than the predetermined amount, the upper limit output of the drive battery 30 is set higher than normal, and at substantially the same time as the above-described start request, by controlling the DC / DC converter 25, the stored power of the drive battery 30 is drawn and a voltage is applied to the drive motor 10, and the power draw state and the voltage level applied to the drive motor 10 are set higher than in the case of normal control. More specifically, the control device 100 stores a normal output map and an upper limit output UP map as maps for controlling the output of the drive motor 10. The normal output map is used when the upper limit output UP condition is not satisfied, while the upper limit output UP map is used when the upper limit output UP condition is satisfied. The upper limit output of the drive battery 30 set in this upper limit output UP map is set higher by a predetermined amount than the upper limit output of the drive battery 30 set in the normal output map. The upper limit output of the drive battery 30 set in this normal output map and the upper limit output of the drive battery 30 set in the upper limit output UP map are determined by experiments and simulations.

[0027] -Control at Startup- Next, the control at startup of the fuel cell vehicle by the fuel cell system 20 configured as described above will be explained. FIG. 2 is a flowchart showing the procedure of this control at startup.

[0028] First, in step ST1, it is determined whether a start request (IG OFF → IG ON) of the fuel cell vehicle has been made. If the start request of the fuel cell vehicle has not been made and the determination in step ST1 is NO, the process simply returns.

[0029] On the other hand, if the start request of the fuel cell vehicle has been made and the determination in step ST1 is YES, the process proceeds to step ST2, and it is determined whether warm-up of the fuel cell stack 21 is necessary. If warm-up of the fuel cell stack 21 is not necessary and the determination in step ST2 is NO, it is assumed that power generation by the fuel cell stack 21 can be sufficiently performed, and the process proceeds to step ST3 to shift to the "READY ON" state, and in step ST4, output control of the drive battery 30 using the normal output map is performed.

[0030] On the other hand, if warm-up of the fuel cell stack 21 is necessary and the determination in step ST2 is YES, the process proceeds to step ST5, and it is determined whether the power storage amount (or SOC) of the drive battery 30 is equal to or greater than a predetermined value α. If the power storage amount (or SOC) of the drive battery 30 is less than the predetermined value α and the determination in step ST5 is NO, it is considered that the situation where the upper limit output of the drive battery 30 can be set high (the upper limit output UP map cannot be used), and the process proceeds to step ST4, and output control of the drive battery 30 using the normal output map is performed.

[0031] On the other hand, when the power storage amount (or SOC) of the drive battery 30 is equal to or greater than a predetermined value α and a YES determination is made in step ST5, it is in a situation where the upper limit output of the drive battery 30 can be set high (the upper limit output UP map can be used). Then, the process proceeds to step ST6 and shifts to the "READY ON" state, and in step ST7, output control of the drive battery 30 using the upper limit output UP map is performed. After the output control of the drive battery 30 using this upper limit output UP map is started, the process returns to step ST2, and it is determined whether or not the situation where warm-up of the fuel cell stack 21 is necessary continues. While the situation where warm-up of the fuel cell stack 21 is necessary continues, the operations of steps ST2, ST5, ST6, and ST7 described above are repeated. When the warm-up of the fuel cell stack 21 is completed, a NO determination is made in step ST2, and the process shifts to the operations of steps ST3 and ST4 described above, and output control of the drive battery 30 using the normal output map is performed.

[0032] FIG. 3 is a timing chart at the start of the fuel cell vehicle described above (when the upper limit output UP condition is satisfied). In this FIG. 3, the states of the ignition switch (IG), the warm-up state of the fuel cell stack 21, the READY state, the transition of the upper limit output of the fuel cell stack 21, and the transition of the upper limit output of the drive battery 30 are respectively shown. Further, this FIG. 3 shows the transition in the prior art by a dashed-dotted line and the transition in the present embodiment by a solid line.

[0033] First, an ON operation of the ignition switch (IG) is performed at timing t1. At this time, since the upper limit output UP condition is satisfied, the upper limit output of the drive battery 30 is set high (see output UO1 in FIG. 3), and accordingly, the "READY ON" state (a state where running is possible) is entered. In the prior art, since the upper limit output of the drive battery 30 is restricted (the output is zero), the "READY ON" state is not entered, and it is in a state where running is impossible (see the transition shown by the dashed-dotted line in FIG. 3).

[0034] After that, when the temperature of the fuel cell stack 21 reaches a predetermined temperature at timing t2 (when it becomes in a state where startup is possible), the upper limit output of the fuel cell stack 21 gradually increases. In the prior art, at this timing, the upper limit output of the drive battery 30 is set slightly higher, but it is still output-limited, and the user cannot obtain the driving force required. That is, until the warm-up of the fuel cell stack 21 is completed at timing t3 and the limit on the upper limit output of the fuel cell stack 21 is released, the user cannot obtain the driving force required. On the other hand, in the present embodiment, due to the upper limit output of the drive battery 30 being set high, a situation is achieved where the user can obtain the driving force required. And in the present embodiment, when the warm-up of the fuel cell stack 21 is completed at timing t3, since an efficient power generation can be performed by the fuel cell stack 21, the upper limit output of the drive battery 30 becomes the normal upper limit value (the upper limit value equivalent to the upper limit value set in the normal output map: refer to the output UO2 in FIG. 3).

[0035] -Effect of the embodiment- As described above, in the present embodiment, when a startup request of the fuel cell vehicle is made, on the condition that it is determined that warm-up of the fuel cell stack 21 is necessary and the power storage amount of the drive battery 30 is equal to or more than a predetermined amount, the upper limit output of the drive battery 30 is set higher than normal during a predetermined period until the warm-up of the fuel cell stack 21 is completed. Thereby, the electric power stored in the drive battery 30 is effectively utilized, the time until it becomes possible to start running before the warm-up of the fuel cell stack 21 is completed is shortened, and the user can obtain the driving force required.

[0036] -Other embodiments- Note that the present invention is not limited to the above-described embodiment, and all modifications and applications included in the scope of the claims and the scope equivalent thereto are possible.

[0037] For example, in the above-described embodiment, output control of the drive battery 30 using the upper limit output UP map is performed from when a start request for the fuel cell vehicle is made (timing t1 in FIG. 3) until warm-up of the fuel cell stack 21 is completed (timing t3 in FIG. 3). The present invention is not limited to this, and output control of the drive battery 30 using the upper limit output UP map may be performed only between timing t1 and timing t2 in FIG. 3, or output control of the drive battery 30 using the upper limit output UP map may be performed only between timing t2 and timing t3 in FIG. 3.

Industrial Applicability

[0038] The present invention is applicable to a control device for a fuel cell vehicle equipped with a fuel cell stack and a drive battery.

Explanation of Signs

[0039] 21... fuel cell stack (fuel cell) 30... drive battery (drive battery) 100... control unit 110... battery upper limit output control unit

Claims

【Claim 1】 A control device for a fuel cell vehicle equipped with a fuel cell and a drive battery, when a start request for the vehicle is made, on the condition that it is determined that warm-up of the fuel cell is necessary and the power storage amount of the drive battery is equal to or more than a predetermined amount, during a predetermined period until the warm-up of the fuel cell is completed, the upper limit output of the drive battery is set higher than normal. A control device for a fuel cell vehicle characterized by this.

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