AIRCRAFT

In an aircraft, a cooling target having a different amount of heat depending on a situation is sufficiently cooled. An aircraft (10) is provided with a cooling facility (40a) having a first cooling circuit (42a) and a second cooling circuit (42b) that are independent of each other. The first cooling circuit (42a) includes a first circulation flow path (44a) that allows a first cooling medium to sequentially and repeatedly pass through a cooling target (34a, 34b). Similarly, the second cooling circuit (42b) includes a second circulation flow path (44b) that allows a second cooling medium to sequentially and repeatedly pass through the cooling target. Here, the first circulation flow path (44a) and the second circulation flow path (44b) do not communicate with each other. Therefore, the first cooling medium and the second cooling medium do not merge or split.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefits of Japanese application no. 2021-055983, filed on Mar. 29, 2021. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.

BACKGROUND

Technical Field

The disclosure relates to an aircraft provided with a cooling facility for cooling a device (cooling target) that requires cooling.

Description of Related Art

An electric multicopter equipped with a battery pack is known as a kind of aircraft. In this case, the multicopter is provided with a plurality of ducted fans or propellers which are lift generators. Further, the airframe is equipped with a motor for rotating the lift generator, and a battery serving as a power supply that supplies electric power to the motor. In some cases, an additional generator may be installed to supply electric power to the battery pack and the motor. The battery is discharged or charged according to the flight state of the multicopter.

During the flight of the multicopter, it is necessary to continuously supply electric power from the battery to the motor and continuously rotate the lift generator. Therefore, the temperature of the battery is managed to be within an appropriate range. Specifically, a cooling facility that circulates and supplies a cooling medium to the battery is attached. By taking the heat of the battery with the cooling medium, it is possible to prevent the battery from becoming excessively hot.

In the multicopter, electric power needs to be reliably obtained from the battery which is the power supply. Therefore, it is necessary to reliably cool the battery. Thus, it is conceivable that the cooling facility has a redundant configuration. That is, for example, two systems of cooling circuits are provided for the battery. The configurations described in Patent Documents 1 and 2 are known as configurations in which two systems of cooling circuits are provided for the same power supply. The power supply is a battery in Patent Document 1 and a fuel cell in Patent Document 2.

RELATED ART

Patent Documents

For example, when the multicopter makes an emergency landing due to an unforeseen situation, a large load is applied to the battery. In this case, the temperature of the battery tends to rise significantly. Accordingly, it is considered necessary to sufficiently cool the battery.

In the configuration described in Patent Document 1, the cooling medium is supplied in only one of two systems of cooling circuits. Accordingly, the supply amount of the cooling medium is limited. Therefore, it is not easy to cope with the situation where a large load is applied to the battery pack (when the temperature of the battery pack is expected to rise significantly).

Furthermore, in the configuration described in Patent Document 2, when the conductivity of the cooling water of one system increases, in order to reduce the ion concentration in the cooling water, the cooling water is merged with the cooling water of the remaining one system, which passes through an ion exchange membrane in advance and has a low ion concentration. That is to say, it is not a configuration for changing the supply amount of the cooling water according to the load of the power feeder.

As described above, although the cooling facility having a redundant configuration is known, a cooling facility capable of appropriately changing the supply amount of the cooling medium to the device that requires cooling, such as a power feeder, has not been proposed.

SUMMARY

According to an embodiment of the disclosure, an aircraft is provided, including a cooling facility for cooling a cooling target. The cooling facility has a first cooling circuit and a second cooling circuit that are independent of each other. The first cooling circuit includes a first circulation flow path that allows a first cooling medium to sequentially and repeatedly pass through the cooling target, a first pressure applying part provided in the first circulation flow path to apply an extrusion pressure to the first cooling medium, and a first cooling heat exchanger provided on a downstream side of the first circulation flow path with respect to the cooling target to take heat from the first cooling medium. The second cooling circuit includes a second circulation flow path that allows a second cooling medium to sequentially and repeatedly pass through the cooling target, a second pressure applying part provided in the second circulation flow path to apply an extrusion pressure to the second cooling medium, and a second cooling heat exchanger provided on a downstream side of the second circulation flow path with respect to the cooling target to take heat from the second cooling medium. The first circulation flow path and the second circulation flow path do not communicate with each other.

DESCRIPTION OF THE EMBODIMENTS

The disclosure provides an aircraft provided with a cooling facility which is capable of sufficiently cooling a device (cooling target) that requires cooling even if the device has a different amount of heat depending on the situation.

According to an embodiment of the disclosure, an aircraft is provided, including a cooling facility for cooling a cooling target. The cooling facility has a first cooling circuit and a second cooling circuit that are independent of each other. The first cooling circuit includes a first circulation flow path that allows a first cooling medium to sequentially and repeatedly pass through the cooling target, a first pressure applying part provided in the first circulation flow path to apply an extrusion pressure to the first cooling medium, and a first cooling heat exchanger provided on a downstream side of the first circulation flow path with respect to the cooling target to take heat from the first cooling medium. The second cooling circuit includes a second circulation flow path that allows a second cooling medium to sequentially and repeatedly pass through the cooling target, a second pressure applying part provided in the second circulation flow path to apply an extrusion pressure to the second cooling medium, and a second cooling heat exchanger provided on a downstream side of the second circulation flow path with respect to the cooling target to take heat from the second cooling medium. The first circulation flow path and the second circulation flow path do not communicate with each other.

According to the disclosure, the cooling facility provided in the aircraft has the first cooling circuit and the second cooling circuit that are independent of each other. That is, the first circulation flow path included in the first cooling circuit for the first cooling medium to sequentially and repeatedly flow through, and the second circulation flow path included in the second cooling circuit for the second cooling medium to sequentially and repeatedly flow through do not communicate with each other. Therefore, the first cooling medium and the second cooling medium do not merge or split.

Then, when the amount of heat of the cooling target is low (when the temperature is low), for example, the cooling target can be cooled by the first cooling circuit while the cooling performed by the second cooling circuit is stopped. Furthermore, when the amount of heat of the cooling target is high (when the temperature is high), for example, cooling may be performed by both the first cooling circuit and the second cooling circuit. By configuring the first cooling circuit and the second cooling circuit independently of each other in this way, it is possible to change the degree of cooling according to the amount of heat generated by the cooling target.

In addition, since the first circulation flow path and the second circulation flow path do not communicate with each other, it is not required to provide a merging point or a branching point. Therefore, the first circulation flow path and the second circulation flow path are simplified and the weight of the cooling facility is reduced. Accordingly, the flexibility in the layout of the cooling facility in the aircraft is improved, and the weight of the aircraft can be reduced.

Suitable embodiments of an aircraft according to the disclosure are provided hereinafter and will be described in detail with reference to the accompanying drawings. In the following, “upstream” and “downstream” represent an upstream side in a flow direction and a downstream side in the flow direction of a first cooling medium to a fourth cooling medium.

Further, in order to facilitate understanding, the following description illustrates a case where a first cooling circuit42a(and a third cooling circuit42c) is set to a flow state with priority, but a second cooling circuit42b(and a fourth cooling circuit42d) may be set to the flow state with priority instead. In the latter case, the second cooling circuit42b(and the fourth cooling circuit42d) corresponds to the “first cooling circuit” in the claims. Then, the first cooling circuit42a(and the third cooling circuit42c) corresponds to the “second cooling circuit” in the claims.

FIG. 1is a schematic perspective view of a multicopter10as an aircraft according to the present embodiment. The multicopter10includes an airframe12, a right main wing14R and a left main wing14L that project from the front side of the airframe12and extend in the width direction, and a right horizontal stabilizer16R and a left horizontal stabilizer16L that project from the rear side of the airframe12and extend in the width direction. Further, a right support bar18R is bridged from the right main wing14R to the right horizontal stabilizer16R, and a left support bar18L is bridged from the left main wing14L to the left horizontal stabilizer16L.

Propellers20ato20care provided on the right main wing14R, the right support bar18R, and the right horizontal stabilizer16R, respectively. Propellers20dto20fare provided on the left main wing14L, the left support bar18L, and the left horizontal stabilizer16L, respectively. The six propellers20ato20fare lift generators. That is, the multicopter10can take off or fly in the air under the action of the six propellers20ato20f.

In the present embodiment, the multicopter10is a so-called hybrid type multicopter. That is, as shown inFIG. 2, the airframe12is equipped with a first engine30a, a second engine30b, a first battery32a, and a second battery32bfor driving the propellers20ato20f. The first engine30ais controlled by a first power control unit (PCU)34a, and the second engine30bis controlled by a second PCU34b. Both the first PCU34aand the second PCU34bfunction as inverters. First and second generators35aand35bare provided between the first engine30aand the first PCU34a, and between the second engine30band the second PCU34b, respectively.

The first PCU34a, the second PCU34b, the first battery32a, and the second battery32bare all electrically connected to both a first junction box36aand a second junction box36b. Further, both the first junction box36aand the second junction box36bare electrically connected to motors37ato37fthat are for driving the propellers20ato20f. As the motors37ato37fare energized, the rotor blades of the propellers20ato20frotate. As a result, the multicopter10can take off or fly in the air.

The first generator35aand the second generator35b(both are rotary electric machines) for supplying electric power to the first battery32aand the second battery32bare electrically connected to the first battery32aand the second battery32bvia the first junction box36aand the second junction box36b. When the multicopter10is in a steady operation and the loads on the first battery32aand the second battery32bare low, electric power is supplied to the first battery32aand the second battery32bvia the first junction box36aand the second junction box36b. That is, the first battery32aand the second battery32bare charged.

The multicopter10is provided with a first cooling facility40ashown inFIG. 3and a second cooling facility40bshown inFIG. 4. The first cooling facility40ais for cooling the first PCU34aand the second PCU34b, and the second cooling facility40bis for cooling the first battery32aand the second battery32b. That is, in the present embodiment, the first PCU34a, the second PCU34b, the first battery32a, and the second battery32bare the devices (cooling target) that require cooling. Nevertheless, a generator, a DC-DC converter, a current converter such as a DC-AC inverter, and the like can also be the cooling target.

Hereinafter, the first cooling facility40aand the second cooling facility40bwill be described. As shown inFIG. 3, the first cooling facility40aincludes the first cooling circuit42aand the second cooling circuit42b. That is, the first cooling facility40ahas two systems of cooling paths. First, the first cooling circuit42ahas a first circulation flow path44afor circulating and supplying the first cooling medium to the first PCU34aand the second PCU34b. In the first circulation flow path44a, the first PCU34ais arranged on the upstream side and the second PCU34bis arranged on the downstream side. In other words, the first cooling medium flows in the order of the first PCU34aand the second PCU34b.

In the middle of the first circulation flow path44a, a first cooling jacket46ais provided at a portion passing in the vicinity of the first PCU34aand the second PCU34b. That is, the first cooling jacket46aconstitutes a part of the first circulation flow path44a. Further, a first temperature sensor48ais provided slightly upstream of the first cooling jacket46a. The first temperature sensor48adetects the temperature of the first cooling medium flowing slightly upstream of the first cooling jacket46ain the first circulation flow path44a.

In the first circulation flow path44a, a first storage container50afor storing the first cooling medium and a first pump52aserving as the first pressure applying part are provided upstream of the first cooling jacket46a. When the first pump52ais energized, a discharge pressure (extrusion pressure) is applied from the first pump52ato the first cooling medium in the first storage container50a. As a result, the first cooling medium flows in the first circulation flow path44a.

Further, a first cooling heat exchanger54ais arranged downstream of the second PCU34bin the first circulation flow path44a. When the first cooling medium whose temperature rises by cooling the first PCU34aand the second PCU34bpasses through the first cooling heat exchanger54a, the first cooling medium is, for example, cooled by cooling air from a cooling fan (not shown) provided in the vicinity of the first cooling heat exchanger54a, or air in contact with the first cooling heat exchanger54a. The cooled first cooling medium is temporarily stored in the first storage container50a, and then sent out to the first circulation flow path44aunder the action of the first pump52a. By repeating the above, the first cooling medium circulates and flows in the first circulation flow path44a.

On the other hand, the second cooling circuit42bhas a second circulation flow path44bfor circulating and supplying the second cooling medium to the first PCU34aand the second PCU34b. Also, in the second circulation flow path44b, the first PCU34ais located on the upstream side and the second PCU34bis located on the downstream side. That is, when the second cooling medium flows, the second cooling medium passes through the first PCU34aand the second PCU34bin this order.

In the middle of the second circulation flow path44b, a second cooling jacket46bis provided at a portion passing in the vicinity of the first PCU34aand the second PCU34b. That is, the second cooling jacket46bconstitutes a part of the second circulation flow path44b. Further, a second temperature sensor48bis provided slightly upstream of the second cooling jacket46b. The second temperature sensor48bdetects the temperature of the second cooling medium flowing slightly upstream of the second cooling jacket46bin the second circulation flow path44b. In this case, the second cooling jacket46bfaces the first cooling jacket46a, which facilitates the layout settings of the first PCU34aand the second PCU34bfor the first cooling jacket46aand the second cooling jacket46b.

In the second circulation flow path44b, a second storage container50bfor storing the second cooling medium and a second pump52bserving as the second pressure applying part are provided upstream of the second cooling jacket46b. When the second pump52bis energized, a discharge pressure (pushing pressure) is applied from the second pump52bto the second cooling medium in the second storage container50b. As a result, the second cooling medium flows in the second circulation flow path44b.

In addition, a second cooling heat exchanger54bis arranged on the downstream side of the second PCU34bin the second circulation flow path44b. When the second cooling medium whose temperature rises by cooling the first PCU34aand the second PCU34bpasses through the second cooling heat exchanger54b, the second cooling medium is, for example, cooled by cooling air from a cooling fan (not shown) provided in the vicinity of the second cooling heat exchanger54b, or air in contact with the second cooling heat exchanger54b. The cooled second cooling medium is temporarily stored in the second storage container50b, and then sent out to the second circulation flow path44bunder the action of the second pump52b. By repeating the above, the second cooling medium can circulate and flow in the second circulation flow path44b.

As can be seen fromFIG. 3, the first circulation flow path44aand the second circulation flow path44bdo not communicate with each other. Accordingly, the first cooling medium and the second cooling medium do not merge or split. As described above, the first cooling circuit42aand the second cooling circuit42bare independent circuits (systems). Therefore, it is possible to set the second cooling circuit42bto either the flow state or the flow stopped state while the first cooling circuit42ais in the flow state.

In the above configuration, the first temperature sensor48aand the second temperature sensor48bare electrically connected to a central processing unit (CPU)56, which is the determination part. The temperatures detected by the first temperature sensor48aand the second temperature sensor48bare transmitted to the CPU56as information signals. The first pump52aand the second pump52bare also electrically connected to the CPU56. The CPU56transmits a command signal of energization or stop to the first pump52aand the second pump52b.

On the other hand, the second cooling facility40bincludes two systems of cooling paths, the third cooling circuit42cand the fourth cooling circuit42d, as shown inFIG. 4. Here, the third cooling circuit42cis configured in the same manner as the first cooling circuit42a, and the fourth cooling circuit42dis configured in the same manner as the second cooling circuit42b. That is, the third cooling circuit42cand the fourth cooling circuit42dcorrespond to the “first cooling circuit” and the “second cooling circuit” in the claims, respectively. However, in the present specification, in order to clearly distinguish the components of the first cooling facility40aand the components of the second cooling facility40b, the same or corresponding components in the first cooling facility40aand the second cooling facility40bare assigned with different names and reference numerals.

The third cooling circuit42chas a third circulation flow path44cfor circulating and supplying the third cooling medium to the first battery32aand the second battery32b. In the third circulation flow path44c, the first battery32ais located on the upstream side and the second battery32bis located on the downstream side. That is, the third cooling medium flows in the order of the first battery32aand the second battery32b.

In the middle of the third circulation flow path44c, a third cooling jacket46cis provided at a portion passing in the vicinity of the first battery32aand the second battery32b. That is, the third cooling jacket46cconstitutes a part of the third circulation flow path44c. Further, the first battery32ais provided with a third temperature sensor48c. The third temperature sensor48cdetects the temperature of the first battery32ato be cooled prior to the second battery32b.

In the third circulation flow path44c, a third storage container50cfor storing the third cooling medium and a third pump52cwhich is the third pressure applying part are provided upstream of the third cooling jacket46c. When the third pump52cis energized, a discharge pressure (extrusion pressure) is applied from the third pump52cto the third cooling medium in the third storage container50c. As a result, the third cooling medium flows in the third circulation flow path44c.

Further, a third cooling heat exchanger54cis arranged downstream of the second battery32bin the third circulation flow path44c. When the third cooling medium whose temperature rises by cooling the first battery32aand the second battery32bpasses through the third cooling heat exchanger54c, the third cooling medium is, for example, cooled by cooling air from a cooling fan (not shown) provided in the vicinity of the third cooling heat exchanger54c, or air in contact with the third cooling heat exchanger54c. The cooled third cooling medium is temporarily stored in the third storage container50c, and then sent out to the third circulation flow path44cunder the action of the third pump52c. By repeating the above, the third cooling medium circulates and flows in the third circulation flow path44c.

On the other hand, the fourth cooling circuit42dhas a fourth circulation flow path44dfor circulating and supplying the fourth cooling medium to the first battery32aand the second battery32b. Also, in the fourth circulation flow path44d, the first battery32ais located on the upstream side and the second battery32bis located on the downstream side. That is, when the fourth cooling medium flows, the fourth cooling medium passes through the first battery32aand the second battery32bin this order.

In the middle of the fourth circulation flow path44d, a fourth cooling jacket46dis provided at a portion passing in the vicinity of the first battery32aand the second battery32b. That is, the fourth cooling jacket46dconstitutes a part of the fourth circulation flow path44d. Further, the second battery32bis provided with a fourth temperature sensor48d. The fourth temperature sensor48dreliably detects the temperature of the second battery32b. In this case, the fourth cooling jacket46dfaces the third cooling jacket46c, which facilitates the layout settings of the first battery32aand the second battery32bfor the third cooling jacket46cand the fourth cooling jacket46d.

In the fourth circulation flow path44d, a fourth storage container50dfor storing the fourth cooling medium and a fourth pump52dserving as the fourth pressure applying part are provided upstream of the fourth cooling jacket46d. When the fourth pump52dis energized, a discharge pressure (extrusion pressure) is applied from the fourth pump52dto the fourth cooling medium in the fourth storage container50d. As a result, the fourth cooling medium flows in the fourth circulation flow path44d.

Further, a fourth cooling heat exchanger54dis arranged on the downstream side of the second battery32bin the fourth circulation flow path44d. When the fourth cooling medium whose temperature rises by cooling the first battery32aand the second battery32bpasses through the fourth cooling heat exchanger54d, the fourth cooling medium is, for example, cooled by cooling air from a cooling fan (not shown) provided in the vicinity of the fourth cooling heat exchanger54d, or air in contact with the fourth cooling heat exchanger54d. The cooled fourth cooling medium is temporarily stored in the fourth storage container50d, and then sent out to the fourth circulation flow path44dunder the action of the fourth pump52d. By repeating the above, the fourth cooling medium can circulate and flow in the fourth circulation flow path44d.

As shown inFIG. 4, the third circulation flow path44cand the fourth circulation flow path44ddo not communicate with each other. Accordingly, the third cooling medium and the fourth cooling medium do not merge or split. That is, the third cooling circuit42cand the fourth cooling circuit42dare also independent circuits (systems). Therefore, it is possible to set the fourth cooling circuit42dto either the flow state or the flow stopped state while the third cooling circuit42cis in the flow state.

The third pump52c, the fourth pump52d, the third temperature sensor48c, and the fourth temperature sensor48dare electrically connected to the CPU56. That is, the CPU56receives the temperatures detected by the third temperature sensor48cand the fourth temperature sensor48das information signals, and transmits a command signal of energization or stop to the third pump52cand the fourth pump52d. Further, the first generator35aand the second generator35bare also electrically connected to the CPU56. Information regarding whether the first generator35aand the second generator35bare operating is sent to the CPU56.

The first pump52a, the second pump52b, the third pump52c, and the fourth pump52dare all variable displacement pumps. That is, the CPU56can control the circulation flow rates (supply flow rates) of the first cooling medium, the second cooling medium, the third cooling medium, and the fourth cooling medium by appropriately adjusting the discharge pressures of the first pump52a, the second pump52b, the third pump52c, and the fourth pump52d. Suitable specific examples of the first cooling medium to the fourth cooling medium include water, oil, ethylene glycol, etc.

The multicopter10according to the present embodiment is basically equipped with the first cooling facility40aand the second cooling facility40bconfigured as described above. Next, the functions and effects thereof will be described in relation to the operations of the first cooling facility40aand the second cooling facility40b.

The multicopter10shown inFIG. 1can take off and fly by energizing the motors37ato37f(seeFIG. 2). That is, the rotation shafts of the motors37ato37frotate, and the rotor blades of the propellers20ato20frotate following the rotation shafts, which creates lift that raises or flies the multicopter10. The multicopter10that has risen in the air flies horizontally in the air at a substantially constant predetermined speed. At this time, the multicopter10is in the steady operation state. Then, the multicopter10that has flown a predetermined distance lands by reducing the lift created by the propellers20ato20f.

In the above process from takeoff to landing, the loads carried by the first engine30a, the second engine30b, the first battery32a, and the second battery32bchange. The load is large during takeoff, landing, and acceleration, and small during the steady operation. Then, when the loads on the first engine30aand the second engine30bare large, the first PCU34aand the second PCU34bhave high temperatures; and when the loads on the first battery32aand the second battery32bare large, the first battery32aand the second battery32bhave high temperatures.

The operation of the first cooling circuit42awhen cooling the first PCU34aand the second PCU34bwill be described.FIG. 5is a schematic flowchart regarding the operation of the first cooling circuit42a. “Lo” inFIG. 5indicates that the first pump52aand the second pump52bare operated at low output. Further, “Hi” means that the first pump52aand the second pump52bare operated at high output.

A temperature threshold value for determining whether to energize the first pump52aand the second pump52band what kind of discharge pressure is applied during energization is input to the CPU56. In the present embodiment, regarding the temperature of the first cooling medium detected by the first temperature sensor48a(hereinafter, also referred to as “detected temperature TR1”), Ta which is the temperature of a % of the maximum allowable temperature Tmax, Tb which is the temperature of b % of the maximum allowable temperature Tmax, and Tc which is the temperature of c % of the maximum allowable temperature Tmax are input as temperature threshold values. Of course, a, b, and c are positive, and satisfy the relationship of a<b<c. In addition, the maximum allowable temperature Tmax is a temperature at which the first PCU34aand the second PCU34bcan be kept at or below the heat resistant temperature.

First, the first pump52ais energized to operate at low output. In this state, in step S1, it is determined whether the information signal from the first temperature sensor48ais received by the CPU56, and whether the received value is normal. If “YES”, the process proceeds to step S2, and it is determined whether some abnormality has occurred, such as whether the first cooling medium is flowing in the first circulation flow path44aand whether the cooling fan is rotating. When it is determined as “normal (YES)”, it enters a normal operation mode in step S3.

As described above, information regarding the detected temperature TR1of the first cooling medium is transmitted to the CPU56. In step S4, the CPU56determines whether the detected temperature TR1is lower than Ta. If “YES”, the process proceeds to step S5, and the first pump52aoperates at low output. On the other hand, the second pump52bis stopped. Accordingly, at this time, only the first cooling medium flowing through the first cooling jacket46acools the first PCU34aand the second PCU34b. When step S5is completed, the process returns to step S4.

When the load on the first engine30aor the second engine30bis large, the temperature of either the first PCU34aor the second PCU34bbecomes high. In this case, it is determined as “NO” in step S4, and the process proceeds to step S6. In step S6, it is determined whether the detected temperature TR1is lower than Tb. When the detected temperature TR1is lower than Tb, it is determined as “YES.”

At this time, the temperature of the first cooling medium is equal to or higher than Ta and lower than Tb, and is a relatively high temperature. Therefore, the CPU56transmits a command signal to the first pump52a, and in step S7, operates the first pump52aat high output. Along with this, the circulation supply amount of the first cooling medium increases. That is, the circulation amount of the first cooling medium in the first cooling jacket46ais larger than that when the detected temperature TR1is lower than Ta, which makes it possible to sufficiently cool the first PCU34aand the second PCU34b. When step S7is completed, the process returns to step S4.

On the other hand, when it is determined as “NO” in step S6, that is, when the detected temperature TR1is equal to or higher than Tb, the process proceeds to step S8to determine whether the detected temperature TR1is lower than Tc. When the detected temperature TR1is lower than Tc, it is determined as “YES.”

At this time, the temperature of the first cooling medium is equal to or higher than Tb and lower than Tc, and is a higher temperature. Therefore, the CPU56transmits a command signal to the first pump52aand the second pump52b, and in step S9, operates the first pump52aat high output, and energizes the second pump52bto operate at low output. Along with this, the circulation supply amount of the first cooling medium increases, and the second cooling medium starts to circulate in the second circulation flow path44b. That is, in addition to that the circulation amount of the first cooling medium in the first cooling jacket46ais larger than that when the detected temperature TR1is lower than Tb, the second cooling medium flows in the second cooling jacket46b.

When it is expected that it is not easy to remove the heat from the first PCU34aand the second PCU34bonly by increasing the circulation amount of the first cooling medium, the second cooling circuit42boperates and the circulation supply of the second cooling medium is started. Thus, cooling performed by the first cooling medium flowing through the first cooling jacket46aand cooling performed by the second cooling medium flowing through the second cooling jacket46bare performed at the same time. Therefore, in this case, the first PCU34aand the second PCU34bcan still be sufficiently cooled. When step S9is completed, the process returns to step S4.

When it is determined as “NO” in step S8, that is, when the detected temperature TR1is equal to or higher than Tc, the process proceeds to step S10. In this step S10, the CPU56transmits a command signal to the second pump52b, and operates the second pump52bat high output. That is, in this case, both the first pump52aand the second pump52boperate at high output. Therefore, the circulation supply amounts of both the first cooling medium and the second cooling medium increase.

When it is expected that it is not easy to remove the heat from the first PCU34aand the second PCU34beven with the circulation amount of the first cooling medium increased and the supply of the second cooling medium started, the supply amount of the second cooling medium is increased. That is, a large amount of the first cooling medium and the second cooling medium flow to the first cooling jacket46aand the second cooling jacket46b. Therefore, in this case, the first PCU34aand the second PCU34bcan still be sufficiently cooled. When step S10is completed, the process returns to step S4.

Here, when it is determined as “NO” in steps S1and S2, the CPU56determines “enter the fail operation mode” in steps S11and S12. That is, the process proceeds to step S10, a command signal is transmitted to the first pump52aand the second pump52b, and both the first pump52aand the second pump52bare operated at high output. Thus, the circulation supply amounts of both the first cooling medium and the second cooling medium increase. In this way, a so-called fail-safe is incorporated in the operation control of the first cooling circuit42a. Therefore, even if an unexpected situation occurs, the first PCU34aand the second PCU34bcan be sufficiently cooled.

The above control regarding the first pump52aand the second pump52bis an example, and the timing of starting the energization of the second pump52b(starting the supply of the second cooling medium) and the output of the first pump52aand the second pump52bmay be appropriately set according to whether the multicopter10is small or large.FIG. 6shows the above operation pattern as the first example, and other operation patterns corresponding to the detected temperature TR1as the second example and the third example. The definitions of “Lo” and “Hi” inFIG. 6are the same as inFIG. 5. Further, the temperature of the second cooling medium may be monitored together with the temperature of the first cooling medium by the second temperature sensor48b.

Next, the operation of the second cooling circuit42bfor cooling the first battery32aand the second battery32bwill be described.FIG. 7is a schematic flowchart regarding the operation of the second cooling circuit42b. In addition, “Lo” and “Hi” inFIG. 7andFIG. 8mean that the first pump52aand the second pump52bare operated at low output and high output, respectively.

A temperature threshold value for determining whether to energize the third pump52cand the fourth pump52dand what kind of discharge pressure is applied during energization is also input to the CPU56. In the present embodiment, regarding the temperatures of the first battery32aand the second battery32bdetected by the third temperature sensor48cand the fourth temperature sensor48d(hereinafter, also referred to as “detected temperatures TR2”), To which is the optimum temperature for operating the first battery32aand the second battery32b, Tα which is α degree higher than To, Tβ which is β degree higher than To, and Tγ which is γ degree higher than To are input as temperature threshold values. Of course, α, β, and γ are positive, and have a relationship of α<β<γ. The temperatures of the third cooling medium and the fourth cooling medium may be detected by the third temperature sensor48cand the fourth temperature sensor48d, and these may be used as the temperatures of the first battery32cand the second battery32d.

First, the third pump52cis energized to operate at low output. In this state, in step S101, it is determined whether the information signals from the third temperature sensor48cand the fourth temperature sensor48dare received by the CPU56, and whether the received value is normal. If “YES”, the process proceeds to step S102, and it is determined whether some abnormality has occurred, such as whether the third cooling medium is flowing in the third circulation flow path44cand whether the cooling fan is rotating. When it is determined as “normal (YES)”, it enters a normal operation mode in step S103.

As described above, information regarding the detected temperature TR2of the third cooling medium detected by the third temperature sensor48cand the fourth temperature sensor48dis transmitted to the CPU56. In step S104, the CPU56determines whether the detected temperature TR2is lower than To. If “YES”, the process proceeds to step S105, and the third pump52cis stopped. On the other hand, the fourth pump52dis maintained in a stopped state. That is, in this case, the third cooling medium stays in the third cooling jacket46c, and the fourth cooling medium stays in the fourth cooling jacket46d. Therefore, the heat of the first battery32aand the second battery32bis suppressed from being removed by the third cooling medium or the fourth cooling medium. That is, the first battery32aand the second battery32bare prevented from being excessively cooled. Then, when step S105is completed, the process returns to step S104.

The situation where the detected temperature TR2is lower than To is typically when the multicopter10is in a steady operation. At this time, the first battery32a, the second battery32b, or both are charged by the first generator35avia the first junction box36aand the second junction box36b. Similarly, the first battery32a, the second battery32b, or both are charged by the second generator35bvia the first junction box36aand the second junction box36b.

At the time of takeoff, landing, acceleration, etc., the load on the first battery32aand the second battery32bis large, and the temperatures of the first battery32aand the second battery32brises to be equal to or higher than To. In this case, it is determined as “NO” in step S104, and the process proceeds to step S106. In step S106, it is determined whether the detected temperature TR2is lower than Ta. When the detected temperature TR2is lower than Ta, it is determined as “YES.”

At this time, the temperature of the first battery32ais equal to or higher than To and lower than Ta, and is a relatively high temperature. Therefore, the CPU56transmits a command signal to the third pump52c, and in step S107, energizes the third pump52cto operate at low output. Along with this, the circulation supply of the third cooling medium is started. That is, the third cooling medium starts to flow in the third cooling jacket46c. Therefore, the heat of the first battery32aand the second battery32bis removed by the third cooling medium. That is, the first battery32aand the second battery32bare cooled.

At this point, the fourth pump52dremains stopped. Therefore, the fourth cooling medium does not flow through the fourth circulation flow path44d. That is, only the third cooling medium cools the first battery32aand the second battery32b. Further, since the third pump52coperates at low output, the circulation amount of the third cooling medium is small. Therefore, the first battery32aand the second battery32bare prevented from being excessively cooled to set the detected temperature TR2lower than To. When step S107is completed, the process returns to step S104.

It is assumed that the load on the first battery32aand the second battery32bfurther increases, and the temperatures of the first battery32aand the second battery32bincrease to be equal to or higher than Ta. In this case, it is determined as “NO” in steps S104and S106, and the process proceeds to step S108. In step S108, it is determined whether the detected temperature TR2is lower than Tβ. When the detected temperature TR2is lower than Tβ, it is determined as “YES.”

At this time, the temperature of the first battery32ais equal to or higher than Tα and lower than Tβ, and is a higher temperature. Therefore, the CPU56transmits a command signal to the third pump52c, and in step S109, operates the third pump52cat high output. Along with this, the supply amount of the third cooling medium increases. That is, a larger amount of the third cooling medium flows in the third cooling jacket46c. Therefore, in this case, the heat of the first battery32aand the second battery32bis still sufficiently removed by the third cooling medium. That is, the first battery32aand the second battery32bare sufficiently cooled.

Even at this point, the fourth pump52dis still stopped. Therefore, the fourth cooling medium does not flow through the fourth circulation flow path44d. That is, only the third cooling medium cools the first battery32aand the second battery32b. When step S109is completed, the process returns to step S104.

It is assumed that the load on the first battery32aand the second battery32bfurther increases, and the temperatures of the first battery32aand the second battery32bincrease to be equal to or higher than Tβ. In this case, it is determined as “NO” in steps S104, S106, and S108, and the process proceeds to step S110. In step S110, it is determined whether the detected temperature TR2is lower than Tγ. When the detected temperature TR2is lower than Tγ, it is determined as “YES.”

At this time, the temperature of the first battery32ais equal to or higher than Tβ and lower than Tγ, and is a higher temperature. Therefore, the CPU56transmits a command signal to the fourth pump52d, and in step S111, energizes the fourth pump52dto operate at low output. Along with this, flow of the fourth cooling medium in the fourth cooling jacket46dis started. That is, a large amount of the third cooling medium flows in the third cooling jacket46c, while a relatively small amount of the fourth cooling medium flows in the fourth cooling jacket46d.

When it is expected that it is not easy to remove the heat from the first battery32aand the second battery32bonly by increasing the circulation amount of the third cooling medium, the fourth cooling circuit42doperates and the circulation supply of the fourth cooling medium is started. Thus, cooling performed by the third cooling medium flowing through the third cooling jacket46cand cooling performed by the fourth cooling medium flowing through the fourth cooling jacket46dare performed at the same time. Therefore, in this case, the heat of the first battery32aand the second battery32bis sufficiently removed by the third cooling medium and the fourth cooling medium. That is, the first battery32aand the second battery32bcan be sufficiently cooled. When step S111is completed, the process returns to step S104.

On the other hand, when it is determined as “NO” in steps S104, S106, S108, and S110, that is, when the detected temperature TR2is equal to or higher than Tγ, the process proceeds to step S112. At this time, the temperature of the first cooling medium is equal to or higher than Tγ, and is an even higher temperature. Therefore, the CPU56transmits a command signal to the fourth pump52d, and in step S112, operates both the first pump52aand the second pump52bat high output. Along with this, the circulation supply amount of the fourth cooling medium is further increased. That is, in addition to that the circulation amount of the third cooling medium in the third cooling jacket46cis larger than that when the detected temperature TR2is lower than Tβ, the circulation amount of the fourth cooling medium in the fourth cooling jacket46dbecomes larger than that when the detected temperature TR2is lower than Tγ.

When it is expected that it is not easy to remove the heat from the first battery32aand the second battery32beven with the circulation amount of the third cooling medium increased and the supply of the third cooling medium started, the supply amount of the fourth cooling medium is increased. That is, a large amount of the third cooling medium and the fourth cooling medium flow to the third cooling jacket46cand the fourth cooling jacket46d. Therefore, in this case, the first battery32aand the second battery32bcan still be sufficiently cooled. When step S112is completed, the process returns to step S104.

When it is determined as “NO” in steps S101and S102, the CPU56determines “enter the fail operation mode” in steps S113and S114. That is, the process proceeds to step S112, a command signal is transmitted to the third pump52cand the fourth pump52d, and both the third pump52cand the fourth pump52dare operated at high output. Thus, both the third cooling medium and the fourth cooling medium are supplied in a large amount and circulate. In this way, the fail-safe is also incorporated in the operation control of the second cooling circuit42b. Therefore, even if an unexpected situation occurs, the first battery32aand the second battery32bcan be sufficiently cooled.

The above control regarding the third pump52cand the fourth pump52dis an example, and similar to the control regarding the first pump52aand the second pump52b, the timing of starting the energization of the fourth pump52d(starting the supply of the second cooling medium) and the output of the third pump52cand the fourth pump52dmay be appropriately set according to whether the multicopter10is small or large.FIG. 8shows the above operation pattern as the first example, and other operation patterns corresponding to the detected temperature TR2as the second example and the third example.

It can be seen fromFIG. 6andFIG. 8that it is possible to control with various operation patterns by adopting variable displacement pumps as the first pump52a, the second pump52b, the third pump52c, and the fourth pump52d. AlthoughFIG. 6andFIG. 8show switching between low output operation and high output operation only in order to simplify the description and facilitate understanding, it is also possible to set an intermediate output operation between low output operation and high output operation. The low output operation, the intermediate output operation, and the high output operation may be set to, for example, 40% to 60%, 60% to 80%, and 80% to 100% of the maximum output, respectively.

Further, although not particularly shown inFIG. 5andFIG. 7, even if the first engine30aor the second engine30b, or the first generator35aor the second generator35bstops due to an unexpected situation while the rotor blades of the propellers20ato20fare rotating, the first pump52a, the second pump52b, the third pump52c, and the fourth pump52dmay operate at high output.

Here, for comparison,FIG. 9andFIG. 10show a distributed integrated type cooling facility60and a parallel type cooling facility62, respectively. The components shown inFIG. 2toFIG. 4are assigned with the same reference numerals.

In the case of the distributed integrated type cooling facility60shown inFIG. 9, the second circulation flow path44bbranches from a predetermined point of the first circulation flow path44a, and the second circulation flow path44bjoins the first circulation flow path44aat another predetermined point. That is, in this case, the first circulation flow path44aand the second circulation flow path44bcommunicate with each other at two points. In this configuration, if a problem occurs in the communication point, the cooling medium cannot flow to both the first circulation flow path44aand the second circulation flow path44b. That is, it becomes difficult to cool the first battery32aand the second battery32b.

Further, in the parallel type cooling facility62shown inFIG. 10, both the first circulation flow path44aand the second circulation flow path44bneed to be provided with branch flow paths that individually pass through the first battery32aand the second battery32b. As the number of pipes increases and the structure becomes complicated correspondingly, it becomes difficult to reduce the size.

In contrast thereto, in the first cooling facility40a(second cooling facility40b) according to the present embodiment, the first circulation flow path44aand the second circulation flow path44b(third circulation flow path44cand fourth circulation flow path44d) do not communicate with each other. Therefore, when it becomes difficult to circulate and flow the first cooling medium (third cooling medium) in the first circulation flow path44a(third circulation flow path44c), the first PCU34aand the second PCU34b(first battery32aand second battery32b) can be cooled by the second cooling medium (fourth cooling medium) flowing through the second circulation flow path44b(fourth circulation flow path44d). Further, since it is not necessary to provide branch flow paths in the first circulation flow path44aand the second circulation flow path44b(third circulation flow path44cand fourth circulation flow path44d), the number of pipes does not increase excessively. Correspondingly, the cooling facility can be downsized.

The disclosure is not particularly limited to the above-described embodiments, and various modifications can be made without departing from the gist of the disclosure.

For example, in this embodiment, the temperature of the first cooling medium immediately before flowing into the cooling jacket provided in the vicinity of the first PCU34aand the second PCU34bis detected, but the temperature of the first PCU34aitself and the temperature of the second PCU34bitself may be detected.

Further, in this embodiment, the second pump52band the fourth pump52dare energized or stopped, but an on-off valve controlled by the CPU56may be provided in each of the second circulation flow path44band the fourth circulation flow path44d, and the second pump52band the fourth pump52dmay be continuously energized. In this case, when the flow of the second cooling medium and the fourth cooling medium is started, the on-off valve may be opened with a small opening. Further, when the circulation amount is increased, the opening of the on-off valve may be increased. Similarly, in each of the first circulation flow path44aand the third circulation flow path44c, an on-off valve controlled by the CPU56may be provided so that the first pump52aand the third pump52care continuously energized.

In addition, as in the third cooling facility40cexemplified inFIG. 11, the first cooling medium and the second cooling medium may flow in one cooling heat exchanger54e. In this case, the flow path through which the first cooling medium flows and the flow path through which the second cooling medium flows may be separately provided in the cooling heat exchanger54e. Of course, the first cooling facility40acan be changed in the same manner.

In any case, the cooling target is not particularly limited to the first PCU34a, the second PCU34b, the first battery32a, and the second battery32b. For example, the cooling target may be the CPU56, the first generator35a, the second generator35b, a DC-DC converter, etc. Furthermore, the number of cooling targets may be 3 or more.