aircraft

Abstract

The present invention provides an aircraft capable of carrying objects, comprising: an electric motor for driving a propeller; a fuel cell for supplying power to the electric motor; and a secondary battery connected in parallel with the fuel cell without a converter and passively charged or discharged according to the output voltage of the fuel cell. When the objects are loaded to a maximum load, the output voltage of the fuel cell under rated operation reaches a first voltage value. When the output voltage of the fuel cell reaches the first voltage value, the secondary battery is charged to a charge rate greater than a first charge rate. Furthermore, the secondary battery, charged to the first charge rate, stores the amount of power required for the aircraft to land from the maximum allowable altitude.

Description

Technical Field

[0001] The technology disclosed in this specification relates to an aircraft capable of loading and transporting an object. Background Art

[0002] International Patent Publication WO2017 / 030034 discloses an aircraft, which includes a battery as a power source and a generator capable of charging the battery. Summary of the Invention

[0003] In such aircraft, to charge the battery with electricity generated by the generator, the generator and the battery must be connected via a converter. Installing a converter in the aircraft unnecessarily increases the size and weight of the aircraft. This specification provides a technology that can reduce the weight and size of an aircraft.

[0004] The aircraft disclosed in this specification is capable of carrying and transporting objects, and is equipped with: an electric motor that drives a propeller; a fuel cell that supplies power to the electric motor; and a secondary battery that is connected in parallel with the fuel cell without a converter and is passively charged or discharged according to the output voltage of the fuel cell. When the transported objects are loaded to the maximum load, the output voltage of the fuel cell under rated operation becomes a first voltage value. When the output voltage of the fuel cell is the first voltage value, the secondary battery is charged to a charge rate greater than a first charge rate. Moreover, the secondary battery charged to the first charge rate stores the amount of electricity required for the aircraft to land from the maximum allowable altitude.

[0005] In the aforementioned aircraft, the fuel cell and the secondary battery that supply power to the electric motor are connected in parallel without a converter. This reduces the aircraft's weight and allows for a larger loading space for transported objects. Furthermore, when the fuel cell and secondary battery are connected without a converter, the secondary battery is passively charged or discharged based on the fuel cell's output voltage.

[0006] When the fuel cell is operating at rated capacity, its output voltage varies depending on the load of the transported objects. The greater the load (i.e., the greater the power consumption of the electric motor), the lower the fuel cell output voltage. Therefore, when the aircraft is loaded with objects to its maximum capacity, the fuel cell output voltage reaches its lowest value, and as a result, the secondary battery charge rate also reaches its lowest value. In other words, in the above configuration, the first voltage value represents the assumed minimum value for the fuel cell output voltage, and the first charge rate represents the assumed minimum value for the secondary battery charge rate.

[0007] Aircraft are required to be able to land at any time, for example, in case of unexpected situations. In this regard, in the above-mentioned aircraft, the charging rate of the secondary battery will not be lower than the first charging rate regardless of the load of the transported objects. In addition, the secondary battery that has been charged to at least the first charging rate stores the amount of electricity required for the aircraft to land from the maximum allowed height. According to such a structure, even if the charging and discharging of the secondary battery is not controlled by a converter or the like, the amount of electricity required for the landing of the aircraft can be ensured in the secondary battery regardless of the load of the transported objects and the flight altitude of the aircraft. Thus, for example, in the case where an abnormality occurs in the fuel cell and the landing action is performed using the power of the secondary battery, the aircraft can reliably continue the landing action until it reaches the ground.

[0008] Additionally or alternatively to the above, when the aircraft is not carrying an object, the output voltage of the fuel cell during rated operation may be a second voltage value greater than the first voltage value. In this case, when the output voltage of the fuel cell is at the second voltage value, the secondary battery may be charged to a charge rate less than the second charge rate. Furthermore, before being charged from the second charge rate to 100%, the secondary battery may be able to store a predetermined amount of power, which may be greater than the amount obtained by multiplying the magnitude of the assumed fluctuation in the power consumption of the electric motor by the duration of the assumed fluctuation.

[0009] As described above, the output voltage of the fuel cell varies depending on the load of the transported objects. Therefore, when the aircraft is unloaded, the output voltage of the fuel cell is highest, and as a result, the charge rate of the secondary battery is also highest. In other words, in the above configuration, the second voltage value represents the maximum value assumed for the output voltage of the fuel cell, and the second charge rate represents the maximum value assumed for the charge rate of the secondary battery.

[0010] In aircraft, the power consumption of the electric motor fluctuates not only with the amount of objects being transported, but also with external disturbances such as wind direction and speed. In this case, the secondary battery's charge rate may exceed the second charge rate, potentially causing the secondary battery to overcharge, depending on the extent of the external disturbance. In this regard, in the aforementioned aircraft, the secondary battery is configured to store a predetermined amount of power, which is greater than the assumed magnitude of the fluctuation in the electric motor's power consumption multiplied by the duration of the assumed fluctuation, before being charged from the second charge rate to 100%. This configuration prevents overcharging of the secondary battery even when the electric motor's power consumption fluctuates while the aircraft is unloaded. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, in which like numerals represent like elements, and in which:

[0012] Figure 1 It is a block diagram showing the structure of the aircraft according to the embodiment.

[0013] Figure 2 Shows the current-voltage curves of secondary batteries and fuel cells. DETAILED DESCRIPTION

[0014] In one embodiment of the present technology, the amount of power required for landing the aircraft can be calculated by multiplying the output power of the fuel cell at rated operation with the transported objects loaded to their maximum capacity by the time required for landing. This configuration allows the aircraft to reliably continue landing even when the secondary battery is used to land the aircraft with the objects loaded to their maximum capacity.

[0015] In one embodiment of the present technology, the time required for landing can be a value obtained by dividing the maximum allowable altitude by the maximum allowable descent speed of the aircraft. With this structure, a landing operation using a secondary battery can be performed at a maximum descent speed less than or equal to the maximum allowable descent speed of the aircraft.

[0016] The aircraft 10 of this embodiment will be described with reference to the accompanying drawings. Aircraft 10 can carry objects and fly while loaded with them. Aircraft 10 is a so-called multirotor. However, aircraft 10 is not limited to a multirotor; any helicopter that generates lift through propellers may be used. Furthermore, aircraft 10 may be an unmanned aircraft or a manned aircraft.

[0017] like Figure 1 As shown, the aircraft 10 includes a fuel cell 12 , a secondary battery 14 , a propeller 16 , an electric motor 18 , and a power controller 20 .

[0018] The propeller 16 is connected to the electric motor 18 and driven by the electric motor 18. The propeller 16 rotates in accordance with the operation of the electric motor 18, thereby generating lift in the aircraft 10. The number of propellers 16 is not limited.

[0019] The fuel cell 12 generates electricity using fuel gas supplied from a fuel tank (not shown). The fuel cell 12 is connected to the motor 18 via a power line 24. The electricity generated by the fuel cell 12 is supplied to the motor 18 via the power line 24.

[0020] The secondary battery 14 is connected to a power line 24. The secondary battery 14 is connected in parallel with the fuel cell 12 via the power line 24, and is connected to the motor 18 along with the fuel cell 12. A diode 22 is inserted between the fuel cell 12 and the secondary battery 14 to block the current flowing to the fuel cell 12. The current generated by the secondary battery 14 is prevented from flowing to the fuel cell 12 by the diode 22 and is supplied to the motor 18 via the power line 24. The secondary battery 14 can also be charged with the electricity generated by the fuel cell 12.

[0021] The power controller 20 is electrically connected to the fuel cell 12. The power controller 20 can control the output power of the fuel cell 12 by controlling the amount of fuel gas supplied to the fuel cell 12. The power controller 20 is configured to be driven by the power supplied from the fuel cell 12.

[0022] As described above, the fuel cell 12 and the secondary battery 14, which supply power to the electric motor 18, are connected in parallel without a converter. This allows the aircraft 10 to be lightweight and a larger loading space for transported objects to be secured. On the other hand, when the fuel cell 12 and the secondary battery 14 are connected without a converter, the secondary battery 14 is passively charged or discharged based on the output voltage of the fuel cell 12.

[0023] Here, in Figure 2 The following diagram shows a current-voltage curve (hereinafter sometimes referred to as an "IV curve") L1 of the fuel cell 12 and an IV curve L2 of the secondary battery 14. As shown in the IV curve L1, the output voltage of the fuel cell 12 varies depending on the output current of the fuel cell 12. The smaller the output current, the larger the output voltage.

[0024] When the fuel cell 12 is in rated operation, the output voltage of the fuel cell 12 changes according to the load of the transported objects. The greater the load (that is, the greater the power consumption of the motor 18), the lower the output voltage of the fuel cell 12. Therefore, when the transported objects are loaded to the maximum load in the aircraft 10, as shown in FIG. Figure 2 As shown at point a1, the output voltage of the fuel cell 12 reaches a voltage value V1, which is the minimum value. Hereinafter, this voltage value is referred to as the first voltage value V1. As a result, the charging rate of the secondary battery 14, which is passively charged or discharged according to the output voltage of the fuel cell 12 (i.e., the first voltage value V1), also becomes the lowest. The charging rate of the secondary battery 14 in this case is referred to as the first charging rate CR1. That is, the first voltage value V1 means the minimum value assumed for the output voltage of the fuel cell 12, and the first charging rate CR1 means the minimum value assumed for the charging rate of the secondary battery 14.

[0025] The aircraft 10 is required to be able to land at any time in case of an unexpected situation. In this regard, in the aircraft 10 described above, the charging rate of the secondary battery 14 will not be lower than the first charging rate CR1 regardless of the load of the transported objects. In addition, the secondary battery 14 is designed to store the amount of electricity required for the aircraft 10 to land from the maximum allowable altitude when it is charged to at least the first charging rate CR1. According to such a structure, even if the charging and discharging of the secondary battery 14 is not controlled by a converter or the like, the amount of electricity required for the landing of the aircraft 10 can be ensured in the secondary battery 14 regardless of the load of the transported objects and the flight altitude of the aircraft 10. As a result, for example, in the case where an abnormality occurs in the fuel cell 12 and the landing action is performed using the power of the secondary battery 14, the aircraft 10 can reliably continue the landing action until it reaches the ground.

[0026] Therefore, the first charge rate CR1 of the secondary battery 14 is determined based on the amount of power required for the landing of the aircraft 10. The amount of power required for landing of the aircraft 10 can be a value obtained by multiplying the output power V1 of the fuel cell 12 at rated operation when the aircraft 10 is loaded to its maximum capacity by the time required for the landing operation. With this configuration, even if, for example, a malfunction occurs in the fuel cell 12 and the aircraft 10 is forced to use power from the secondary battery 14 while the aircraft 10 is loaded to its maximum capacity, the landing operation can be reliably continued until the aircraft touches the ground.

[0027] The required time [s] required for the aforementioned landing maneuver may be a value obtained by dividing the maximum altitude [m] permitted by the aircraft 10 by the maximum descent speed [m / s] permitted by the aircraft 10. With this configuration, the aircraft 10 can perform a landing maneuver at a speed equal to or less than the maximum descent speed permitted by the aircraft 10. The maximum descent speed permitted by the aircraft 10 may be appropriately determined based on the configuration of the aircraft 10, the object being transported, and the like.

[0028] Next, the case where no transport object is loaded on the aircraft 10 will be described. As described above, the output voltage of the fuel cell 12 changes according to the amount of the transport object loaded. Figure 2 As shown at point a2, the output voltage of the fuel cell 12 when the aircraft 10 is not loaded with a transport object becomes the voltage V2, which is the highest value. Hereinafter, this voltage value is referred to as the second voltage value V2. As a result, the charging rate of the secondary battery 14, which is passively charged or discharged according to the output voltage of the fuel cell 12 (i.e., the second voltage value V2), also becomes the highest. The charging rate of the secondary battery 14 in this case is referred to as the second charging rate CR2. That is, the second voltage value V2 means the maximum value assumed for the output voltage of the fuel cell 12, and the second charging rate CR2 means the maximum value assumed for the charging rate of the secondary battery 14.

[0029] In aircraft 10, the power consumption of electric motor 18 fluctuates not only with the load of the transported objects but also with external disturbances such as wind direction and speed. In such situations, the charge rate of secondary battery 14 may exceed the second charge rate CR2, potentially causing overcharge of secondary battery 14 depending on the severity of the external disturbance. Regarding this, in aircraft 10 of this embodiment, secondary battery 14 is configured to store a predetermined amount of power before being charged from the second charge rate CR2 to 100%. This predetermined amount of power is greater than the amount obtained by multiplying the assumed fluctuation range of electric motor 18 power consumption by the assumed duration of the fluctuation.

[0030] That is, the second charge rate CR2 is set to allow a certain margin (i.e., a allowance) relative to 100% in consideration of the assumed fluctuations in the power consumption of the electric motor 18. The minimum value of this margin is calculated by multiplying the magnitude of the assumed fluctuation in the power consumption of the electric motor 18 (kW) by the duration of this assumed fluctuation (h), divided by the energy per 1% charge rate of the secondary battery 14 (kWh / %). Therefore, the second charge rate CR2 is less than the value obtained by subtracting this margin from 100%. With this configuration, even if the power consumption of the electric motor 18 fluctuates when the aircraft 10 is not carrying any objects, overcharging of the secondary battery 14 can be avoided.

[0031] The above describes the embodiments of the present technology in detail, but these are merely examples and do not limit the scope of the invention. The technology described in the scope of the invention includes various modifications and changes to the specific examples illustrated above. The technical elements described in this specification or drawings have technical practicality alone or in various combinations, and are not limited to the combinations described in the claims at the time of application. In addition, the technology illustrated in this specification or drawings can achieve multiple objectives simultaneously, and achieving one of the objectives itself has technical practicality.

Claims

1. An aircraft capable of carrying an object, wherein: have: an electric motor, driving the propeller; a fuel cell for supplying electric power to the electric motor; and A secondary battery is connected in parallel with the fuel cell without a converter and is passively charged or discharged according to the output voltage of the fuel cell. When the transported object is loaded to a maximum load, the output voltage of the fuel cell in rated operation becomes a first voltage value. When the output voltage of the fuel cell is the first voltage value, the secondary battery is charged to a charge rate that is greater than a first charge rate. The secondary battery charged to the first charge rate stores an amount of electric power required for the aircraft to land from the maximum allowable altitude. When the transport object is not loaded, the output voltage of the fuel cell in rated operation becomes a second voltage value greater than the first voltage value. When the output voltage of the fuel cell is the second voltage value, the secondary battery is charged to a charge rate lower than a second charge rate. The second charge rate is equal to or greater than the first charge rate and less than 100%.

2. The aircraft according to claim 1, wherein: The amount of electric power required for landing of the aircraft is a value obtained by multiplying the output power of the fuel cell when operating at a rated level with the transported object loaded to a maximum load by the time required for landing.

3. The aircraft according to claim 2, wherein: The time required for landing is a value obtained by dividing the maximum allowable altitude by the maximum allowable descent speed of the aircraft.

4. The aircraft according to any one of claims 1 to 3, wherein: The secondary battery can further store a predetermined amount of power before being charged from the second charge rate to 100%. The predetermined amount of electric power is larger than an amount of electric power obtained by multiplying a range of fluctuation assumed in the power consumption of the electric motor by a duration of the assumed fluctuation.

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