Fuel cell vehicle

Abstract

To provide a fuel cell vehicle capable of suppressing a decrease in vehicle speed when traveling uphill.SOLUTION: An FC vehicle 10 includes: a driving motor 12; an FC unit 16 that outputs electric power to the driving motor 12; a battery 18 that outputs electric power to the driving motor 12; and a controller 30. The controller 30 at least temporarily executes FC protection control to operate the battery 18 at a higher output than a rated output PB* during uphill travel.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] This specification discloses a fuel cell vehicle equipped with a fuel cell and a battery.

Background Art

[0002] Conventionally, fuel cell vehicles having a fuel cell and a battery have been known. A controller mounted on a fuel cell vehicle controls the ratio of the output power of the fuel cell, the output power of the battery, and the regenerative power of the driving motor according to the vehicle situation.

[0003] Patent Document 1 discloses such a fuel cell vehicle. When the fuel cell vehicle of Patent Document 1 detects a long uphill slope, it controls so that the output distribution amount of the fuel cell becomes larger than before the detection of the long uphill slope.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, in the prior art including Patent Document 1, when driving uphill, the output distribution of the fuel cell was made the same as or larger than the output distribution of the battery. In this case, the power generation amount of the fuel cell during uphill driving increases. Then, when the power generation amount of the fuel cell increases, the temperature of the fuel cell rises accordingly. When the temperature of the fuel cell exceeds a preset allowable value, the output of the fuel cell is forcibly restricted. As a result, in the prior art, during uphill driving, the power supplied to the driving motor may be insufficient and the vehicle speed may decrease.

[0006] Therefore, this specification discloses a fuel cell vehicle capable of suppressing a decrease in vehicle speed during uphill driving.

Means for Solving the Problem

[0007] The fuel cell vehicle disclosed in this specification includes a driving motor, a fuel cell that outputs power to the driving motor, a battery that outputs power to the driving motor, and a controller. The controller is configured to at least temporarily execute FC protection control for operating the battery at an output higher than the rated output during uphill driving.

[0008] By temporarily increasing the output of the battery, the temperature rise of the fuel cell can be suppressed accordingly. As a result, the output limit of the fuel cell can be avoided, and the decrease in vehicle speed due to power shortage can be effectively suppressed.

[0009] In this case, when the controller detects the start of uphill driving, it may execute the FC protection control, and after a predetermined period, decrease the output of the battery and increase the output of the fuel cell in conjunction with the decrease in the output of the battery.

[0010] By increasing and decreasing the output of the battery and the output of the fuel cell in conjunction with each other, the output value of the entire vehicle can be stabilized.

[0011] Also, the controller is configured to output from the battery within the range of a specified battery output upper limit value and output the insufficient output from the fuel cell. The controller may be configured to set the battery output upper limit value higher than the rated output of the battery in the FC protection control.

[0012] By setting the battery output upper limit value of the battery, it is possible to prevent the battery from becoming overly high-output.

[0013] Also, the controller may be configured to start the FC protection control when the temperature of the cooling water of the fuel cell reaches a specified threshold temperature during the uphill driving.

[0014] By adopting such a configuration, it is possible to effectively avoid the forced output limitation of the fuel cell and effectively suppress the decrease in vehicle speed due to power shortage.

[0015] Further, the controller may be configured to terminate the FC protection control when a specified relaxation time has elapsed after the start of the FC protection control, or when the temperature of the battery exceeds a specified threshold value, or when the SOC of the battery falls below a specified threshold value.

[0016] By adopting such a configuration, it is possible to effectively prevent the deterioration of the battery.

Advantages of the Invention

[0017] According to the fuel cell vehicle disclosed in this specification, it is possible to effectively suppress the decrease in vehicle speed during uphill driving.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0019] Hereinafter, with reference to the drawings, the configuration of the fuel cell vehicle 10 will be described with reference to the drawings. In the following, "fuel cell" is abbreviated as "FC". FIG. 1 is a block diagram showing the configuration of the FC vehicle 10. As shown in FIG. 1, the FC vehicle 10 includes, as a drive system, a traveling motor 12, an FC unit 16, a battery 18, a transmission 22, and wheels 24 as main components.

[0020] The traveling motor 12 is a motor generator that generates traveling power based on the supplied electric power and regeneratively generates power by the braking force of the vehicle. The power of the traveling motor 12 is transmitted to the wheels 24 via the transmission 22. When the wheels 24 rotate by this power, the FC vehicle 10 travels. The inverter 14 converts DC power into AC power and supplies it to the traveling motor 12. Further, the inverter 14 converts the regenerative power output from the traveling motor 12 into DC power and outputs it to the battery 18.

[0021] The FC unit 16 is a device that generates electricity using the electrochemical reaction between hydrogen and oxygen. The FC unit 16 has an FC stack, and the FC stack is configured by stacking a plurality of FC cells. The FC cell is formed, for example, by sandwiching a solid polymer electrolyte membrane between an anode electrode and a cathode electrode. The generated power of the FC unit 16 is supplied to the traveling motor 12 and the battery 18.

[0022] Here, the FC unit 16 generates heat during power generation. If the FC unit 16 becomes excessively hot, it will cause deterioration or damage of the FC unit 16. Therefore, a cooling circuit (not shown) through which cooling water flows is provided in the FC unit 16, and the FC unit 16 is cooled by the cooling water. A temperature sensor 26 for detecting the temperature of this cooling water is provided in the FC unit 16. Hereinafter, the temperature of the cooling water detected by the temperature sensor 26 is referred to as "FC water temperature Tf".

[0023] The battery 18 is an energy storage capable of charging and discharging electric power. Such a battery 18 is, for example, a lithium-ion secondary battery, a nickel-metal hydride battery, a capacitor, or a combination thereof. The voltage and current of the battery 18 are detected by a sensor (not shown). The controller 30 calculates the remaining capacity of the battery 18, so-called SOC, based on the detected voltage and current.

[0024] The power distribution device 20 controls the supply destinations of the output power of the FC unit 16, the output power of the battery 18, and the regenerative power of the traveling motor 12. Such a power distribution device 20 is, for example, a DC / DC converter.

[0025] The controller 30 controls the traveling motor 12, the inverter 14, the FC unit 16, the battery 18, and the power distribution device 20. Such a controller 30 is physically a computer having a processor 32 and a memory 34. In FIG. 1, the controller 30 is illustrated as a single computer, but the controller 30 may be physically configured by combining a plurality of separate computers.

[0026] Furthermore, the FC vehicle 10 has a plurality of sensors. The throttle sensor 42 detects the opening of the accelerator pedal, that is, the accelerator opening θ. The gradient sensor 40 detects the gradient A of the road surface (that is, the inclination in the longitudinal direction of the vehicle 10). Such a gradient sensor 40 is, for example, a gravity sensor. The vehicle speed sensor 44 detects the vehicle speed V. The controller 30 calculates the required output for driving the vehicle, as the required output PR, based on the detection values of these sensors. Then, the controller 30 controls the driving of the FC unit 16 and the battery 18 so that the required output PR is supplied to the traveling motor 12.

[0027] Here, the battery 18 is preset with an upper limit value of its output, that is, a battery output upper limit value PBmx. The controller 30 controls the driving of the battery 18 so that the battery output PB does not exceed this battery output upper limit value PBmx. The battery output upper limit value PBmx is usually a power value at which the battery 18 can be continuously and stably operated, that is, the rated output PB*. Also, in this example, when the FC vehicle 10 is climbing a slope, this battery output upper limit value PBmx is temporarily set to a value higher than the rated output PB*, which will be described later.

[0028] Here, when the FC vehicle 10 is climbing a slope, the required output PR increases compared to when it is driving on a flat surface. In order to satisfy this required output PR, if the outputs of both the battery 18 and the FC unit 16 are increased, there is a possibility that the power generation capacity of the FC unit 16 will be limited during the slope climbing. This will be described with reference to FIG. 5.

[0029] FIG. 5 is a diagram showing changes in altitude E, battery output PB, FC output PF, FC water temperature Tf, and vehicle speed V when a comparative example FC vehicle climbs a slope. In the example of FIG. 5, the FC vehicle starts entering the uphill slope at time t1.

[0030] By entering the uphill slope, the required output PR increases. The comparative example FC vehicle drives the battery 18 within the range of the battery output upper limit value PBmx (that is, the rated output PB*) to obtain this required output PR, and outputs the insufficient power from the FC unit 16. In this case, although it also varies depending on the vehicle speed V and the gradient A, the output of the FC unit 16 often exceeds the rated output PF* of the FC unit 16. As a result, during the slope climbing, the temperature of the cooling water for cooling the FC unit 16, that is, the FC water temperature Tf, may reach the FC water temperature allowable value Tf_mx. In the case of FIG. 5, at time t2, the FC water temperature Tf has reached the FC water temperature allowable value Tf_mx.

[0031] When Tf ≥ Tf_mx, the controller 30 reduces the FC output PF in order to lower the FC water temperature Tf. Then, as the FC output PF decreases, the electric power available for the entire vehicle decreases, leading to a decrease in the vehicle speed V.

[0032] In order to prevent a decrease in the vehicle speed V during such uphill driving, the FC vehicle 10 disclosed in this specification executes FC protection control at least temporarily during uphill driving. The FC protection control is a control for operating the battery 18 at an output higher than the rated output PB* while operating the FC unit 16 at an output equal to or lower than the rated output PF*. Hereinafter, the power control for uphill driving in the FC vehicle 10 disclosed in this specification will be described in detail.

[0033] FIG. 2 is a diagram showing changes in altitude E, battery output PB, FC output PF, FC water temperature Tf, and vehicle speed V when the FC vehicle 10 disclosed in this specification is driving uphill. Before the start of uphill driving, the battery output upper limit value PBmx is the same value as the rated output PB* of the battery 18. When uphill driving starts at time t1, the required output PR increases. To obtain this required output PR, the controller 30 controls the driving of the battery 18 and the FC unit 16 so as to increase the battery output PB within the range of the battery output upper limit value PBmx = PB* and supplement the shortage with the FC output PF. As a result, immediately after time t1, both the battery output PB and the FC output PF temporarily increase.

[0034] Here, if the state where the FC output PF is high continues, as described above, the FC water temperature Tf rises to the FC water temperature allowable value Tf_mx, and output limitation of the FC unit 16 occurs. Therefore, in this example, when the controller 30 detects the start of uphill driving, it executes FC protection control to temporarily increase the battery output PB above the rated output PB* and reduce the FC output PF accordingly.

[0035] For example, in the example of FIG. 2, assume that the controller 30 detects the start of uphill travel at time t2. In this case, the controller 30 starts FC protection control to temporarily change the battery output upper limit value PBmx to a battery output relaxation upper limit value PBmx_up that is higher than the rated output PB*. As a result, the battery output PB rises to the battery output relaxation upper limit value PBmx_up. Also, as the battery output PB rises, the FC output PF decreases accordingly.

[0036] Note that the controller 30 may determine that it is in uphill travel, for example, when the slope A is equal to or greater than a specified threshold value and the vehicle speed V is equal to or greater than a specified threshold value. Alternatively, in another form, the controller 30 may determine whether it is in uphill travel by comparing the current position detected by the GPS with the map information registered in the navigation system.

[0037] Here, of course, if the state where the battery output PB exceeds the rated output PB* continues for a long time, problems such as a decrease in the life of the battery 18 will occur. On the other hand, if the state where it exceeds the rated output PB* is for a short period, there is almost no adverse effect on the battery 18. In this example, paying attention to such characteristics, when starting uphill travel, the battery output upper limit value PBmx is set higher than the rated output PB* only for a previously specified relaxation time ta.

[0038] As a result, between time t2 when the start of uphill travel is detected and time t3 when the relaxation time ta has elapsed, the battery output PB becomes higher than the rated output PB*, and the FC output PF decreases. Thereby, the rise in the FC water temperature Tf is suppressed.

[0039] Thereafter, at time t3 when the relaxation time ta has elapsed, the controller 30 decreases the battery output upper limit value PBmx from the battery output relaxation upper limit value PBmx_up to the rated output PB*. As a result, the battery output PB decreases to the rated output PB*. Also, in conjunction with the decrease in the battery output PB, the FC output PF increases. And as the FC output PF increases, the FC water temperature Tf also gradually increases. However, since FC protection control for operating the battery 18 at a high output has been executed beforehand, the start timing of the increase in the FC water temperature Tf in this example is later than the start timing in FIG. 5. As a result, the probability of completing the uphill running before the FC water temperature Tf reaches the FC water temperature allowable value Tf_mx becomes high. And thereby, a decrease in the vehicle speed V due to power shortage during the uphill running can be effectively suppressed.

[0040] Note that the battery output relaxation upper limit value PBmx_up is not particularly limited as long as it is higher than the rated output PB*. For example, it is 1.2 times, or 1.5 times, or 2 times the rated output PB*. For example, the battery output relaxation upper limit value PBmx_up may be the same value as the maximum output of the battery 18. Such a battery output relaxation upper limit value PBmx_up may be a preset fixed value or a variable value that varies according to conditions. Also, the relaxation time ta is not limited as long as it is greater than 0. For example, it is several seconds, or several tens of seconds, or several minutes. The relaxation time ta may be a preset fixed value or a variable value that varies according to conditions. Also, in this example, the end timing of the FC protection control is determined by the elapsed time, but the end timing of the FC protection control may be determined based on other parameters. For example, when starting the FC protection control, the controller 30 may detect the temperature or SOC of the battery 18 and end the FC protection control when the temperature exceeds a specified threshold value or when the SOC falls below a specified threshold value.

[0041] Also, in FIG. 2, the FC protection control is executed only immediately after the start of uphill driving. However, when driving on a long uphill slope, the FC protection control may be executed multiple times at intervals. For example, in the example of FIG. 3, after the first FC protection control is completed at time t3, as the FC output PF increases, the water temperature of the FC water temperature Tf gradually increases. And assuming that at time t4 before the end of the uphill drive, the FC water temperature Tf reaches the specified threshold temperature Tf_th. Note that Tf_th ≦ Tf_mx. In this case, the controller 30 may start the FC protection control again to make the battery output upper limit value PBmx higher than the rated output PB*. By restarting the FC protection control, the forced output limitation of the FC unit 16 can be effectively avoided, and power shortage and thus a decrease in the vehicle speed V can be suppressed. Also, by restarting the FC protection control, the output of the FC unit 16 is suppressed and the FC water temperature Tf gradually decreases. Note that in order to protect the battery 18, after the nth FC protection control is completed, the start of the (n + 1)th FC protection control may be prohibited until a specified waiting time elapses or until the temperature of the battery 18 becomes equal to or lower than the specified threshold value.

[0042] FIG. 4 is a flowchart showing the flow of power control in the uphill driving of the FC vehicle 10 of this example. As shown in FIG. 4, when the uphill driving is started, the controller 30 starts the FC protection control (S10). That is, the controller 30 sets the battery output upper limit value PBmx to a battery output relaxation upper limit value PBmx_up higher than the rated output PB*. As a result, while the battery output PB becomes higher than the rated output PB*, the FC output PF decreases, and an increase in the FC water temperature Tf is suppressed.

[0043] This FC protection control continues until a specified relaxation time ta elapses. When the relaxation time ta has elapsed (Yes in S12), the controller 30 ends the FC protection control (S16). That is, the controller 30 lowers the battery output upper limit value PBmx to the rated output PB*. As a result, the battery output PB decreases, and accordingly, the FC output PF increases.

[0044] Thereafter, the controller 30 monitors the FC water temperature Tf (S18). When the FC water temperature Tf becomes equal to or higher than the FC water temperature allowable value Tf_mx (Yes in S18), the controller 30 returns to step S10 and resumes the FC protection control. Thereafter, the same process is repeated until the uphill driving ends.

[0045] As is clear from the above description, according to the technology disclosed in this specification, since the rise in the FC water temperature Tf can be suppressed, the output limitation of the FC unit 16 during uphill driving, and thus, the decrease in the vehicle speed V due to power shortage can be effectively suppressed. Note that the above-described configurations are all examples, and other configurations may be appropriately changed as long as the configuration described in claim 1 is provided. For example, in the previous description, the FC protection control is executed immediately after detecting the uphill driving. However, the start timing of the FC protection control may be shifted later. That is, even after detecting the uphill driving, normal control may be performed, and the FC protection control may be started after the FC water temperature Tf reaches a predetermined temperature.

Explanation of Signs

[0046] 10 Fuel cell vehicle, 12 Driving motor, 14 Inverter, 16 FC unit, 18 Battery, 20 Power distribution device, 22 Transmission, 24 Wheels, 26 Temperature sensor, 30 Controller, 32 Processor, 34 Memory, 40 Gradient sensor, 42 Throttle sensor, 44 Vehicle speed sensor.

Claims

1. A driving motor, a fuel cell that outputs power to the driving motor, a battery that outputs power to the driving motor, a controller, and is configured such that the controller at least temporarily executes FC protection control to operate the battery at an output higher than the rated output during uphill driving. A fuel cell vehicle.

2. The fuel cell vehicle according to Claim 1, wherein when the controller detects the start of uphill driving, the controller executes the FC protection control, and after a predetermined period, reduces the output of the battery and increases the output of the fuel cell in conjunction with the reduction in the output of the battery. A fuel cell vehicle.

3. The fuel cell vehicle according to Claim 1, wherein the controller is configured to output from the battery within a range of a specified battery output upper limit value and output a shortage of output from the fuel cell, and the controller is configured to set the battery output upper limit value higher than the rated output of the battery in the FC protection control. A fuel cell vehicle.

4. The fuel cell vehicle according to Claim 1, wherein the controller is configured to start the FC protection control when the temperature of the cooling water of the fuel cell reaches a specified threshold temperature during the uphill driving. A fuel cell vehicle.

5. The fuel cell vehicle according to Claim 1, wherein the controller terminates the FC protection control when a specified relaxation time has elapsed after the start of the FC protection control, or when the temperature of the battery exceeds a specified threshold, or when the SOC of the battery falls below a specified threshold. A fuel cell vehicle.

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