JP7555891B2 - Multicopter - Google Patents

Description

The technology disclosed in this specification relates to a multicopter that has multiple rotors, a motor that drives each rotor, and a battery that supplies power to the motor, and flies by rotating each rotor with the motor.

A conventional example of this type of technology is the multicopter described in Patent Document 1 below. In addition to multiple rotors, multiple motors, and a battery, this multicopter also includes a generator that generates electricity, an engine that drives the generator, and a control unit that controls the multicopter. In order to fly the multicopter, the control unit supplies the electricity generated by the generator to each motor and charges the battery with that electricity.

JP 2020-138594 A

The multicopter described in Patent Document 1 is required to be lightweight in order to extend its flight range and flight time, and the engine used for generating electricity is also required to be lightweight. For this reason, it is desirable to adopt an air-cooled system for cooling the engine, which does not require any additional equipment. However, if the multicopter continues to operate the engine under high load, for example, at a low flight speed, the cooling of the air-cooled engine will be insufficient, and the temperature will rise, which may cause thermal damage such as a deterioration in heat resistance due to high temperatures (such as a decrease in material strength).

This disclosed technology was made in consideration of the above circumstances, and its purpose is to provide a multicopter that makes it possible to suppress an increase in engine temperature before heat damage occurs to an air-cooled engine.

In order to achieve the above object, the technology described in claim 1 provides a multicopter that has a plurality of rotors, a motor for rotating and driving each rotor, and a battery configured to be capable of charging and discharging the power supplied to the motor, and that flies by rotating each rotor with the motor. The technology also includes a generator for generating power, an air-cooled engine for driving the generator, a control means for controlling the supply of electricity to the motor, the operation of the engine, and the charging and discharging of the battery to control the flight of the multicopter, and an output adjustment means for adjusting the output of the engine. The purpose of the control means is to execute output reduction control that controls the output adjustment means to reduce the output of the engine in accordance with the time during which the engine temperature exceeds the allowable temperature when the engine is operating under high load and the engine temperature becomes higher than a predetermined allowable temperature.

According to the configuration of the above technology, for example, when the engine continues to operate at high load under conditions of a low flight speed of the multicopter, the cooling of the air-cooled engine becomes insufficient, and the temperature rises, which may cause thermal damage due to high temperature. However, when the engine is operated at high load and the temperature of the engine becomes higher than a predetermined allowable temperature, the control means executes output reduction control to control the output adjustment means to reduce the engine output according to the time during which the engine temperature exceeds the allowable temperature . Therefore, the engine output is reduced before thermal damage occurs to the air-cooled engine.

In order to achieve the above object, the technology described in claim 2 is a multicopter that has a plurality of rotors, a motor for rotating and driving each rotor, and a battery configured to be able to charge and discharge the power supplied to the motor, and flies by rotating each rotor with the motor. The multicopter is provided with a generator for generating power, an air-cooled engine for driving the generator, a control means for controlling the supply of electricity to the motor, the operation of the engine, and the charging and discharging of the battery to control the flight of the multicopter, and an output adjustment means for adjusting the output of the engine, and the control means executes output reduction control to control the output adjustment means to reduce the output of the engine when the temperature of the engine becomes higher than a predetermined allowable temperature while the engine is being operated under high load, and further includes an airframe equipped with each rotor, a motor, an engine, and a generator, an airspeed detection means for detecting the airspeed between the airframe and the atmosphere, and an outside air temperature detection means for detecting the temperature of the outside air, and the control means executes output reduction control by determining that the temperature of the engine is higher than the allowable temperature when at least one of the following is true: the slower the detected airspeed is, or the higher the detected outside air temperature is.

According to the configuration of the above technology, for example, when the engine continues to operate at high load under conditions of a low flight speed of the multicopter, the cooling of the air-cooled engine becomes insufficient, the temperature rises, and there is a risk of heat damage due to high temperature. However, when the engine is operated at high load, the control means executes output reduction control to control the output adjustment means to reduce the output of the engine when the temperature of the engine becomes higher than a predetermined allowable temperature. Therefore, the output of the engine is reduced before heat damage occurs to the air-cooled engine. Also, when the airspeed becomes slower or the outside air temperature becomes higher during flight of the multicopter, the air-cooling conditions of the engine become worse. However, when at least one of the detected airspeed becomes slower and the detected outside air temperature becomes higher, the control means determines that the temperature of the engine will be higher than the allowable temperature and executes output reduction control. Therefore, even when the temperature of the engine becomes higher than the predetermined allowable temperature due to the flight conditions of the multicopter, the output of the engine is reduced, thereby reducing the output of the engine before heat damage occurs to the air-cooled engine.

In order to achieve the above object, the technology described in claim 3 is the technology described in claim 1 or 2, in which the control means executes current compensation control to compensate for the current supplied to the motor with the amount of stored electricity remaining in the battery when a request to increase the motor output arises while output reduction control is being executed.

According to the configuration of the above technology, in addition to the action of the technology described in claim 1 or 2, when a request to increase the motor output occurs while the output reduction control is being executed, for example, when a request to raise the multicopter occurs, the control means executes current compensation control to compensate for the amount of stored electricity remaining in the battery by the current supplied to the motor. Therefore, even if the engine output is reduced by executing the output reduction control and the amount of electricity generated by the generator is insufficient, the amount of stored electricity remaining in the battery is compensated for by the current supplied to the motor by the current compensation control, and the shortage of electricity generated by the generator is compensated for.

In order to achieve the above object, the technology described in claim 4 is the technology described in any one of claims 1 to 3 , wherein the output adjustment means includes a fuel supply means for supplying fuel to the engine and an ignition means for igniting a mixture of the fuel supplied to the engine and the intake air drawn into the engine, and the control means executes a fuel cut control for cutting the supply of fuel from the fuel supply means to the engine, or an ignition cut control for cutting the ignition of the mixture by the ignition means, in order to execute output reduction control.

According to the configuration of the above technology, in addition to the function of the technology described in any one of claims 1 to 3, the control means executes fuel cut control to cut off the supply of fuel from the fuel supply means to the engine, or ignition cut control to cut off the ignition of the mixture by the ignition means, in order to execute the output reduction control. Therefore, by executing the fuel cut control, the number of times the fuel is burned is reduced, and the output of the engine is reduced. Also, by executing the ignition cut control, the fuel supplied to the engine is vaporized without being burned, and the engine is cooled by the latent heat of vaporization.

In order to achieve the above object, the technology described in claim 5 is the technology described in claim 2 , wherein the output adjustment means includes a fuel supply means for supplying fuel to the engine, and the control means executes fuel cut control to cut the supply of fuel from the fuel supply means to the engine in order to execute output reduction control, and the control means increases the frequency of execution of the fuel cut control when at least one of the following conditions is met: the slower the detected airspeed becomes and the higher the detected outside air temperature becomes.

According to the configuration of the above technology, the slower the airspeed or the higher the outside air temperature during flight of the multicopter, the worse the air-cooling conditions of the engine become. However, the control means increases the frequency of execution of fuel cut control when at least one of the following conditions is met: the slower the detected airspeed or the higher the detected outside air temperature. Therefore, the more severe the air-cooling conditions of the engine become due to the flight conditions of the multicopter (airspeed, outside air temperature), the more the number of fuel combustions is reduced, and the more the engine output is reduced.

In order to achieve the above object, the technology described in claim 6 is the technology described in claim 4 or 5, in which the control means executes current compensation control to compensate for the current supplied to the motor with the amount of stored electricity remaining in the battery when a request to increase the motor output arises while output reduction control is being executed.

According to the configuration of the above technology, in addition to the action of the technology described in claim 4 or 5, when a request to increase the motor output arises while the output reduction control is being executed, for example, when flying the multicopter upward, the control means executes current compensation control to compensate for the amount of stored electricity remaining in the battery by the current supplied to the motor. Therefore, even if the engine output is reduced by executing the output reduction control and the amount of electricity generated by the generator is insufficient, the amount of stored electricity remaining in the battery is compensated for by the current supplied to the motor by the current compensation control, and the shortage of electricity generated by the generator is compensated for.

In order to achieve the above object, the technology described in claim 7 is a technology described in any one of claims 1 to 6 , in which, when the control means determines that the operating time of the engine while operating at high load has exceeded a predetermined allowable time, it executes output reduction control on the basis that the engine temperature has become higher than a predetermined allowable temperature.

According to the configuration of the above technology, in addition to the function of the technology described in any one of claims 1 to 7, when the control means determines that the operation time of the engine has exceeded a predetermined allowable time while the engine is operating under high load, it determines that the temperature of the engine has exceeded the predetermined allowable temperature and executes output reduction control to reduce the output of the engine. Therefore, by measuring the time that the engine has been operated under high load, it is possible to execute output reduction control without directly detecting the temperature of the engine.

The technology described in claim 1 makes it possible to suppress engine temperature rise before heat damage occurs to an air-cooled engine.

According to the technology described in claim 2, it is possible to suppress an increase in engine temperature before heat damage occurs to the air-cooled engine. Also, even if the engine temperature becomes higher than a predetermined allowable temperature due to the flight conditions of the multicopter, it is possible to suppress an increase in engine temperature before heat damage occurs to the air-cooled engine.

According to the technology described in claim 3, in addition to the effect of the technology described in claim 1 or 2, the motor output can be increased as required, and the multicopter can fly stably as required.

According to the technique recited in claim 4, it is possible to obtain an effect equivalent to that of the technique recited in any one of claims 1 to 3.

According to the technology described in claim 5, in addition to the effect of the technology described in claim 2 , the temperature rise of the engine can be suppressed even if the air-cooling conditions of the engine become severe due to the airspeed and outside air temperature during flight of the multicopter.

According to the technology described in claim 6, in addition to the effect of the technology described in claim 4 or 5, the motor output can be increased as required, and the multicopter can fly stably as required.

According to the seventh aspect of the present invention, in addition to the effect of the first to sixth aspects of the present invention, the configuration for executing the output reduction control can be simplified.

FIG. 1 is a perspective view showing an external appearance of a multicopter in a first embodiment. FIG. 2 is a block diagram showing the configuration of a multicopter in the first embodiment. 1 is a schematic configuration diagram showing a generator engine system and some of its associated devices in a first embodiment; 4 is a flowchart showing the content of a first engine output control in the first embodiment. 4 is a correction value map that is referred to in order to obtain a closing correction value according to a time period during which the temperature exceeds the allowable temperature in the first embodiment; 5 is a graph showing the relationship between the time period during which the temperature exceeds the allowable temperature and the amount of power generated by the generator in the first embodiment. 5 is a graph showing the relationship between the time period during which the temperature exceeds the allowable temperature and the amount of intake air in the first embodiment. 5 is a time chart showing changes in various parameters related to the first engine output control in the first embodiment; 10 is a flowchart showing the content of a second engine output control in the second embodiment. 11 is an outside air temperature correction coefficient map that is referred to in order to obtain an outside air temperature correction coefficient according to the second embodiment; 13 is an airspeed correction coefficient map that is referred to in order to obtain an airspeed correction coefficient according to an airspeed in the second embodiment; 13 is a flowchart showing the contents of multicopter flight control according to the third embodiment. 13 is a flowchart showing the contents of multicopter flight control according to the third embodiment. 13 is a power generation amount map that is referred to in order to obtain the power generation amount of the generator according to the target throttle opening degree in the third embodiment. 13 is a time chart showing changes in various parameters related to the first or second engine output control and the multicopter flight control in the third embodiment. 13 is a flowchart showing the content of a third engine output control according to the fourth embodiment. 13 is a time chart showing changes in various parameters related to the third engine output control in the fourth embodiment; 13 is a flowchart showing the content of a fourth engine output control in the fifth embodiment.

Below, we will explain several embodiments of the multicopter.

<First embodiment>

First, the first embodiment will be described in detail with reference to the drawings.

[About the multicopter configuration]
Fig. 1 is a perspective view showing the appearance of a multicopter 1 according to this embodiment. Fig. 2 is a block diagram showing the configuration of the multicopter 1. The configuration of the multicopter 1 will be described in detail below with reference to Figs. 1 and 2.

A multicopter is a type of helicopter, a rotary wing aircraft equipped with three or more rotors. The multicopter 1 of this embodiment includes an airframe 11 and an engine generator unit 12. The airframe 11 includes a plurality of arms 21 (four in this embodiment) with bifurcated tips, an arm base 22 that radially supports the plurality of arms 21 in a cantilevered manner, an airframe base 23 that supports the arm base 22, a plurality of motors 24 (eight in this embodiment) provided at the tip of each arm 21, and a plurality of rotors 25 (eight in this embodiment) that are rotated by each motor 24. This multicopter 1 is designed to fly by simultaneously rotating the plurality of rotors 25 by the corresponding motors 24.

The arm base 22 is provided on the aircraft base 23. Inside the arm base 22, a battery 31, a fuel tank 32, a main controller 33, a flight controller 34, a power control unit 35, an electric speed controller 36, etc. are provided. The arm base 22 also has an imaging unit 37 that captures or records images of the outside world. The imaging unit 37 includes a camera, a recording memory, etc.

The engine generator unit 12 is suspended below the aircraft base 23. The engine generator unit 12 includes a power generation engine system 15 (including an engine 41) described below, and a generator 42 that is driven by the engine 41 to generate electricity.

Each motor 24 is electrically connected to the generator 42 via an electric speed controller 36 (including an inverter (not shown)) and a power control unit 35. This connection allows the power generated by the generator 42 to be supplied to the motor 24 via the power control unit 35 and the electric speed controller 36.

The battery 31 is composed of a secondary battery capable of charging and discharging power. The battery 31 is electrically connected to the generator 42 via the power control unit 35, and is configured to charge the battery 31 with power generated by the generator 42. The battery 31 is electrically connected to each motor 24 via the power control unit 35 and the electric speed controller 36, and is configured to supply the power discharged from the battery 31 to each motor 24. The battery 31 is provided with various sensors (not shown) that detect the current, voltage, and temperature of the battery 31, and these sensors send electrical signals related to the detection results to the main controller 33.

The fuel tank 32 stores fuel (e.g., gasoline). This fuel is used to drive the engine 41. A level sensor (not shown) provided in the fuel tank 32 sends an electrical signal regarding the remaining amount of fuel to the main controller 33.

The main controller 33 is configured as a small computer and controls all operations related to the multicopter 1. The main controller 33 includes a wind direction acquisition unit 45, a rotation control unit 46, a wind power acquisition unit 47, a machine control unit 48, and an engine control unit 50. Here, for example, the engine control unit 50 controls the operation of the engine 41 in order to control the power generation in the generator 42. The main controller 33 including the engine control unit 50 corresponds to an example of a control means in this disclosed technology that controls the supply of electricity to each motor 24, the operation of the engine 41, and the charging and discharging of the battery 31 in order to control the flight of the multicopter 1.

The flight controller 34 is a device that controls the flight of the multicopter 1. This flight controller 34 sends electrical signals to the main controller 33 and the electric speed controller 36 to instruct the thrust related to the flight of the multicopter 1, while receiving electrical signals related to the charge state of the battery 31 from the main controller 33. The flight controller 34 receives electrical signals related to the pilot's operation commands from the remote control 30, which will be described later, and electrical signals related to the detection results from the various sensors 28, which will be described later.

The power control unit 35 is a device that controls the power supplied to each motor 24. This power control unit 35 receives power generated by the generator 42, supplies and receives power to and from the battery 31, and supplies power to the electric speed controller 36. The power control unit 35 receives an electrical signal related to a charge/discharge switching command from the main controller 33.

The electric speed controller 36 is a device that controls the rotation speed of each motor 24. This electric speed controller 36 supplies the power supplied via the power control unit 35 to each motor 24 as drive power. The electric speed controller 36 receives an electrical signal related to a thrust command from the flight controller 34.

The engine generator unit 12 includes a part of the generator engine system 15, including the engine 41, and a generator 42. The engine 41 is the driving source for the generator 42, and in this embodiment, is configured as a small reciprocating gasoline engine. That is, the engine 41 drives the generator 42 so that the generator 42 generates electricity to be supplied to each motor 24 or the battery 31. In addition, various components 57, 60, and 62 that configure the generator engine system 15, which will be described later, receive electrical signals related to engine control commands for the purpose of generating electricity from the engine control unit 50 of the main controller 33.

In this embodiment, the multicopter 1 is equipped with various sensors 28 and a remote control 30. The various sensors 28 include sensors for detecting the altitude, attitude, latitude, longitude, acceleration, and obstacles of the multicopter 1. The remote control 30 is a controller held by the pilot of the multicopter 1, and includes devices such as a transceiver that transmits electrical signals related to operations from a joystick operated by the pilot to the multicopter 1 and receives electrical signals related to operations from the multicopter 1.

In the multicopter 1 of this embodiment, each motor 24, the battery 31, and the engine 41 form a series hybrid system. That is, in this multicopter 1, the engine 41 is used only for generating electricity with the generator 42, each motor 24 is used to rotate and drive each rotor 25, and the battery 31 is used to charge and discharge the electricity generated by the generator 42. In this way, the multicopter 1 is designed to fly by operating the generator 42 with the power of the engine 41 to generate electricity, and operating each motor 24 with the generated electricity to rotate each rotor 25. In addition, in this multicopter 1, the surplus electricity that is supplied to each motor 24 out of the electricity generated by the generator 42 with the power of the engine 41 is temporarily stored in the battery 31, and is supplied from the battery 31 to each motor 24 as needed.

The multicopter 1 configured as described above is adapted to realize various flight modes by supplying power to each motor 24 and rotating each of the multiple rotors 25. That is, the multicopter 1 realizes hovering flight by balancing the lift generated by each rotor 25 with the gravity acting on the multicopter 1 by controlling the rotation speed of each rotor 25. The multicopter 1 realizes ascending flight by making the lift generated by each rotor 25 greater than the gravity acting on the multicopter 1, and realizes descending flight by making the lift generated by each rotor 25 smaller than the gravity acting on the multicopter 1. In addition, the multicopter 1 realizes forward, backward, and left/right movement flight by controlling the rotation speed of each rotor 25 and creating an imbalance in the lift generated by each rotor 25. Furthermore, the multicopter 1 realizes turning (rotational) flight by setting a difference in the rotation speed of each rotor 25 that rotates relative to each other.

Here, the main controller 33 sends an electrical signal to the power control unit 35 regarding a charge/discharge switching command, thereby controlling the supply of electricity generated by the generator 42 to each motor 24 and the charging of the battery 31, and also controlling the discharging of electricity charged in the battery 31 to each motor 24.

[About the power generation engine system]
Next, the generator engine system 15 will be described. Fig. 3 is a schematic diagram showing the generator engine system 15 of this embodiment and some of its associated devices. The configuration of the generator engine system 15 will be described in detail below with reference to Fig. 3.

This power generation engine system (hereinafter simply referred to as the "engine system") 15 includes an engine 41 consisting of a single cylinder. In this embodiment, an air-cooled engine 41 is used to reduce the weight of the multicopter 1. The engine 41 is a four-stroke reciprocating engine, and includes one cylinder 52 including a combustion chamber, a crankshaft 53, and other well-known components. The engine 41 is provided with an intake passage 54 through which intake air flows to the engine 41 to introduce intake air into the cylinder 52, and an exhaust passage 55 for leading exhaust air from the cylinder 52. An air cleaner 56 is provided at the entrance of the intake passage 54. A surge tank 54a is provided in the middle of the intake passage 54, and a throttle device 57 is provided upstream of the surge tank 54a. The throttle device 57 opens and closes to adjust the amount of intake air flowing through the intake passage 54. The throttle device 57 is composed of a poppet valve and includes a valve body (not shown) that reciprocates relative to a valve seat, and a step motor 58 for driving the valve body to change the opening degree. The engine system 15 of this embodiment is not provided with a throttle sensor for detecting the opening degree of the valve body (throttle opening degree). The throttle device 57 adjusts the amount of intake air flowing through the intake passage 54 by opening and closing the flow path with the valve body. The throttle device 57 corresponds to an example of the output adjustment means in this disclosed technology. Meanwhile, a catalyst 59 for purifying the exhaust is provided in the exhaust passage 55.

The intake passage 54 is provided with one injector 60 for injecting fuel into the passage 54. The injector 60 is configured to inject fuel (gasoline) supplied from the fuel tank 32 described above. The fuel tank 32 and the injector 60 constitute an example of a fuel supply means for supplying fuel to the engine 41 in this disclosed technology. The fuel supply means corresponds to an example of an output adjustment means in this disclosed technology. The engine 41 in this embodiment operates with an engine cycle including a series of intake strokes, compression strokes, explosion strokes, and exhaust strokes. In the intake passage 54, a combustible mixture is formed by the intake air introduced during the intake stroke of the engine cycle and the fuel injected from the injector 60 into the intake passage 54.

The engine 41 is provided with one spark plug 61 and one ignition coil 62 corresponding to each cylinder 52. The spark plug 61 sparks upon receiving an ignition signal output from the ignition coil 62. In this disclosed technology, both parts 61 and 62 constitute an example of an ignition means for igniting the mixture of fuel and intake air supplied to the cylinder 52 of the engine 41. The ignition means corresponds to an example of an output adjustment means of this disclosed technology. In the cylinder 52, the mixture explodes and burns due to the spark action of the spark plug 61 during the compression stroke of the engine cycle, and the explosion stroke progresses. The exhaust gas after combustion is discharged from the cylinder 52 to the exhaust passage 55 during the exhaust stroke. The exhaust gas flows through the catalyst 59, where it is purified, and is discharged to the outside. By periodically repeating this series of engine cycles with a crank angle of 720°CA, the crankshaft 53 of the engine 41 rotates, and the engine 41 obtains output.

Various sensors 71, 72, 73, 74 provided in correspondence with the engine 41 constitute a means for detecting the operating state of the engine 41. The engine temperature sensor 71 provided in the engine 41 detects the temperature of the cylinder block 41a of the engine 41 as the engine temperature THE, and outputs an electric signal corresponding to the detected value. The rotation speed sensor 72 provided in the engine 41 detects the rotation speed of the crankshaft 53 as the engine rotation speed NE, and outputs an electric signal corresponding to the detected value. The intake pressure sensor 73 provided in the surge tank 54a downstream of the throttle device 57 detects the intake pressure PM in the surge tank 54a (intake passage 54), and outputs an electric signal corresponding to the detected value. The outside air temperature sensor 74 provided in the air cleaner 56 detects the temperature (outside air temperature) THA of the outside air drawn into the intake passage 54, and outputs an electric signal corresponding to the detected value. The outside air temperature sensor 74 corresponds to an example of an outside air temperature detection means in this disclosed technology. An airspeed sensor 75 installed on the aircraft 11 detects the airspeed FSPD between the aircraft 11 and the atmosphere and outputs an electrical signal corresponding to the detected value. The airspeed sensor 75 corresponds to an example of an airspeed detection means in this disclosed technology.

This engine system 15 includes the aforementioned engine control unit 50 for controlling the operation of the engine 41. The various sensors 71 to 75 are each connected to the engine control unit 50. The step motor 58 of the throttle device 57, each injector 60, and an ignition coil 62 are also connected to the engine control unit 50. As is well known, the engine control unit 50 includes a central processing unit (CPU), various memories, external input circuits, external output circuits, etc.

In this embodiment, the engine control unit 50 controls the throttle device 57 (step motor 58), each injector 60, and ignition coil 62 based on electrical signals from various sensors 71 to 75 to operate the engine 41.

In this embodiment, an air-cooled engine 41 is used to reduce the weight of the multicopter 1. Therefore, if the multicopter 1 continues to operate at a high load, for example, at a low flight speed, the air-cooled engine 41 may not provide sufficient cooling, causing the temperature to rise and resulting in heat damage due to deterioration of heat resistance (reduction in material strength, etc.) caused by high temperatures. Therefore, in this embodiment, the main controller 33 (including the engine control unit 50) executes the following first engine output control to deal with this type of heat damage.

[First engine output control]
Next, a first engine output control executed by the main controller 33 (including the engine control unit 50) will be described below. The first engine output control is shown in a flow chart in FIG.

When the process transitions to this routine, in step 100, the main controller 33 retrieves the engine temperature THE, the outside air temperature THA, the air speed FSPD, the battery remaining capacity SOC%, and the operation mode based on the detection values of the various sensors 71 to 75. Here, the operation mode means a mode related to the operation of the engine 41, and includes "high mode operation" and "low mode operation". The high mode operation is a mode in which the engine 41 is operated at a high load in order to obtain the amount of power generation required for flying the multicopter 1 and charging the battery 31, or the amount of power generation required for rapidly ascending the multicopter 1. In order to operate the engine 41 at a high load, the main controller 33 controls, for example, the throttle device 57 to be fully open. The low mode operation is a mode in which the engine 41 is operated at a medium-low load in order to obtain the amount of power generation required only for flying the multicopter 1. In order to operate the engine 41 at a medium-low load, the main controller 33 controls, for example, the throttle device 57 to be at a medium-low opening.

Next, in step 110, the main controller 33 determines whether the current operation mode is high mode operation. If the result of this determination is positive, the main controller 33 proceeds to step 120, and if the result of this determination is negative, the main controller 33 proceeds to step 180.

In step 180, the main controller 33 determines the target throttle opening THRstep according to the flight mode of the multicopter 1. The main controller 33 determines the target throttle opening THRstep according to, for example, whether the multicopter 1 is in a low-speed flight mode or an idle flight mode. After that, the main controller 33 transitions the process to step 170.

On the other hand, in step 120, the main controller 33 inputs the time during which the engine 41 has been operating in high mode (high mode operation time CHF). The main controller 33 starts counting the high mode operation time CHF when the engine 41 transitions to high mode operation.

Next, in step 130, the main controller 33 determines whether the high mode operation time CHF has exceeded a predetermined allowable time A1. Here, the allowable time A1 means the predicted time until the engine 41 transitions to high mode operation, the temperature rises, and the temperature reaches the allowable upper limit temperature. If the result of this determination is positive, the main controller 33 transitions to step 140, and if the result of this determination is negative, the main controller 33 transitions to step 190.

In step 190, the main controller 33 sets the target throttle opening THRstep to "236", which corresponds to full throttle, and then proceeds to step 170. "236" is a command value for controlling the step motor 58 and is expressed as the number of steps.

On the other hand, in step 140, the main controller 33 calculates the time during which the engine 41 is considered to have exceeded the allowable temperature (time beyond the allowable temperature) CET by subtracting the allowable time A1 from the high mode operation time CHF.

Next, in step 150, the main controller 33 obtains a closing correction value THRCL for correcting the opening degree (throttle opening degree) of the throttle device 57 according to the time period during which the temperature exceeds the permissible limit CET. The main controller 33 can obtain the closing correction value THRCL (indicated by the number of steps of the step motor 58) according to the time period during which the temperature exceeds the permissible limit CET, for example, by referring to a closing correction value map as shown in FIG. 5. In the map in FIG. 5, the closing correction value THRCL increases in a curved manner as the time period during which the temperature exceeds the permissible limit CET increases from "0", and is set to a constant value.

Next, in step 160, the main controller 33 calculates the target throttle opening THRstep by subtracting the closing correction value THRCL from "236". This target throttle opening THRstep is an opening that reduces the output of the engine 41 in order to reduce the temperature of the engine 41 by the amount that the temperature of the engine 41 exceeds the allowable temperature.

Then, moving from step 160, step 180, or step 190, in step 170, the main controller 33 controls the throttle device 57 to the target throttle opening THRstep, and then returns the process to step 100.

Here, the main controller 33 controls the throttle device 57 to the target throttle opening THRstep corrected by the closing correction value THRCL, and the power generation amount of the generator 42 changes according to the time CET of exceeding the allowable temperature, as shown by the bold line in FIG. 6. That is, as shown by the bold line in FIG. 6, the power generation amount of the generator 42 decreases linearly from the high power generation amount Whi as the time CET of exceeding the allowable temperature increases, and becomes a constant value. Also, in FIG. 6, the low power generation amount Wlow shown by the dashed line indicates the maximum power generation amount required for the flight of the multicopter 1. FIG. 6 is a graph showing the relationship between the time CET of exceeding the allowable temperature and the power generation amount of the generator 42.

In addition, the main controller 33 controls the throttle device 57 to the target throttle opening THRstep corrected by the closing correction value THRCL, so that the intake air volume of the engine 41 decreases linearly from the maximum value to a constant value as the allowable temperature exceeding time CET increases, as shown by the bold line in Figure 7. Figure 7 is a graph showing the relationship between the allowable temperature exceeding time CET and the intake air volume.

According to the first engine output control described above, when the engine 41 is operated at high load (high mode operation) and the temperature of the engine 41 becomes higher than a predetermined allowable temperature, the main controller 33 executes output reduction control to control the throttle device 57 (output adjustment means) to reduce the output of the engine 41. Specifically, when the main controller 33 determines that the high mode operation time CHF has exceeded a predetermined allowable time A1 while the engine 41 is operated at high load (high mode operation), it executes output reduction control on the assumption that the temperature of the engine 41 has become higher than the predetermined allowable temperature. In this embodiment, as the output reduction control, the main controller 33 reduces the throttle opening of the throttle device 57 from full open by a required amount.

[Actions and Effects of Multicopters]
According to the configuration of the multicopter 1 of this embodiment described above, when the high mode operation (high load operation) of the engine 41 is continued under the condition that the flight speed of the multicopter 1 is low, the cooling of the air-cooled engine 41 becomes insufficient, the temperature rises, and there is a risk of thermal damage due to high temperature. However, when the engine 41 is in the high mode operation state and the temperature of the engine 41 becomes higher than a predetermined allowable temperature, the main controller 33 (control means) executes output reduction control to reduce the output of the engine 41. Here, when the main controller 33 determines that the high mode operation time CHF has exceeded the predetermined allowable time A1 while the engine 41 is in the high mode operation state, it executes output reduction control assuming that the temperature of the engine 41 has become higher than the predetermined allowable temperature. Therefore, the output of the engine 41 is reduced before thermal damage occurs to the air-cooled engine 41. Therefore, it is possible to suppress the temperature rise of the engine 41 before thermal damage occurs to the air-cooled engine 41. In addition, by measuring the time during which the engine 41 is in the high mode operation, it is possible to execute output reduction control without directly detecting the temperature of the engine 41. Therefore, the configuration for executing the output reduction control can be simplified.

Figure 8 shows the changes in various parameters related to the first engine output control in a time chart. In Figure 8, (a) shows the changes in the operation mode of the engine 41, (b) shows the changes in the throttle opening, (c) shows the changes in the engine output (≒power generation amount), (d) shows the changes in the battery charge/discharge, (e) shows the changes in the high mode operation time CHF, and (f) shows the changes in the engine temperature THE (≒oil temperature).

In FIG. 8, when the operation mode (a) becomes high mode operation (high load operation) from time t0, if the high mode operation time CHF (f) exceeds the allowable time A1 at time t1, i.e., the engine temperature THE exceeds the allowable temperature TAL, the throttle opening (b) begins to decrease from full open, the engine output (c) begins to decrease from "max output", and the battery charge/discharge (d) begins to decrease from "max charge". Here, after time t0, the operation mode becomes high mode operation as shown in (a), but between time t0 and time t1, the engine output becomes "max output", and the power generated by the generator 42 is used for flying the multicopter 1 and for charging the battery 31, in the first high mode operation H1, and after time t1, the engine output is reduced from "max output", and the power generated by the generator 42 is used for flying the multicopter 1, and the charging to the battery 31 is suppressed, in the second high mode operation H2. As a result, the engine temperature THE in (f) does not increase as shown by the two-dot chain line, and is maintained at the allowable temperature TAL as shown by the solid line, and it can be seen that the temperature rise of the engine 41 can be suppressed. Note that after time t2, by operating in the output suppression stable mode, the throttle opening in (b), the engine output in (c), and the battery charge/discharge in (d) are constant.

Furthermore, according to the configuration of the multicopter 1 of this embodiment, the engine 41 of the power generating engine system 15 drives the generator 42 to generate electricity, and the generated electricity is supplied to each motor 24 to fly the multicopter 1. The generated electricity is also charged to the battery 31 to replenish the charge. Therefore, even if the engine 41 stops and the generator 42 cannot be driven, the multicopter 1 can fly by supplying the electricity charged in the battery 31 to each motor 24. Therefore, the cruising distance and flight time of the multicopter 1 can be extended by the amount that the electricity generated by the generator 42 can be charged and replenished to the battery 31. In addition, the output reduction control can suppress the fuel consumption of the engine 41, so the cruising distance and flight time of the multicopter 1 can be extended accordingly.

<Second embodiment>

Next, the second embodiment will be described in detail with reference to the drawings. In the following description, the same components as those in the first embodiment will be given the same reference numerals and will not be described again. The following description will focus on the differences.

In this embodiment, the configuration of the second engine output control is different from that of the first engine output control of the first embodiment.

[Second engine output control]
Next, the second engine output control executed by the main controller 33 (including the engine control unit 50) will be described. The contents of the second engine output control are shown in a flowchart in Fig. 9. This flowchart differs from the flowchart in Fig. 4 in that step 135 is provided instead of step 130, step 145 is provided instead of step 140, and steps 200 to 220 are provided between step 120 and step 135.

When the process transitions to this routine, the main controller 33 executes the processes of steps 100 to 120, and then in step 200, determines the outside air temperature correction coefficient Ktha according to the outside air temperature THA. The main controller 33 can determine the outside air temperature correction coefficient Ktha according to the outside air temperature THA, for example, by referring to an outside air temperature correction coefficient map as shown in FIG. 10. In the map of FIG. 10, the higher the outside air temperature THA, the smaller the outside air temperature correction coefficient Ktha becomes between the maximum value KTmax (>1.0) and the minimum value KTmin (<1.0), and when the outside air temperature THA becomes a predetermined temperature T1 (for example, 25°C), the outside air temperature correction coefficient Ktha is set to "1.0". Therefore, the higher the outside air temperature THA is above the predetermined temperature T1, the smaller the outside air temperature correction coefficient Ktha becomes below "1.0".

Next, in step 210, the main controller 33 determines the airspeed correction coefficient Kfspd according to the airspeed FSPD. The main controller 33 can determine the airspeed correction coefficient Kfspd according to the airspeed FSPD by, for example, referring to an airspeed correction coefficient map as shown in FIG. 11. In the map in FIG. 11, the faster the airspeed FSPD, the larger the airspeed correction coefficient Kfspd becomes between the minimum value KFmin (<1.0) and the maximum value KFmax (>1.0), and the airspeed correction coefficient Kfspd is set to "1.0" when the airspeed FSPD becomes a predetermined speed F1. Therefore, the slower the airspeed FSPD becomes than the predetermined speed F1, the smaller the airspeed correction coefficient Kfspd becomes.

Next, in step 220, the main controller 33 calculates the output suppression judgment time KA by multiplying the permissible time A1 by the outside air temperature correction coefficient Ktha and the airspeed correction coefficient Kfspd. Therefore, as the outside air temperature THA increases, the outside air temperature correction coefficient Ktha becomes smaller than "1.0", and therefore the output suppression judgment time KA becomes shorter than the permissible time A1. Also, as the airspeed FSPD decreases, the airspeed correction coefficient Kfspd becomes smaller than "1.0", and therefore the output suppression judgment time KA becomes shorter than the permissible time A1. The output suppression judgment time KA is the corrected time obtained by correcting the permissible time A1 with the outside air temperature THA and the airspeed FSPD.

Next, in step 135, the main controller 33 judges whether the high mode operation time CHF has exceeded the output suppression judgment time KA. Here, the output suppression judgment time KA is the time for judging whether the output should be suppressed due to an increase in the temperature of the engine 41, and is correlated with the temperature of the engine 41. If the result of this judgment is positive, the main controller 33 shifts the process to step 145, and if the result of this judgment is negative, the process shifts to step 190. Therefore, the shorter the output suppression judgment time KA is compared to the allowable time A1, the longer the high mode operation time CHF is compared to the output suppression judgment time KA. Therefore, the main controller 33 judges that the temperature of the engine 41 has risen above a predetermined allowable temperature and executes output reduction control to reduce the output of the engine 41.

In step 145, the main controller 33 calculates the time period CET during which the temperature exceeds the allowable limit by subtracting the output suppression determination time KA from the high mode operation time CHF. The main controller 33 then executes the process from step 150 onwards.

According to the second engine output control described above, unlike the first engine output control, the main controller 33 is configured to execute output reduction control by determining that the temperature of the engine 41 is higher than the allowable temperature when at least one of the following conditions is met: the detected airspeed FSPD is slower and/or the detected outside air temperature THA is higher.

[Actions and Effects of Multicopters]
According to the configuration of this embodiment described above, in addition to the actions and effects of the first embodiment, the following actions and effects can be obtained. That is, when the multicopter 1 is flying, the slower the airspeed or the higher the outside air temperature, the worse the air-cooling conditions of the engine 41 become. However, when at least one of the following is true: the slower the detected airspeed FSPD and the higher the detected outside air temperature THA, the main controller 33 (control means) determines that the temperature of the engine 41 will be higher than the allowable temperature TAL and executes the output reduction control. Therefore, even when the temperature of the engine 41 becomes higher than the predetermined allowable temperature TAL due to the flight conditions of the multicopter 1, the output of the engine 41 is reduced, so that the output of the engine 41 is reduced before heat damage occurs to the air-cooled engine 41. Therefore, even when the temperature of the engine 41 becomes higher than the predetermined allowable temperature TAL due to the flight conditions of the multicopter 1, the temperature rise of the engine 41 can be suppressed before heat damage occurs to the air-cooled engine 41.

<Third embodiment>

Next, the third embodiment will be described in detail with reference to the drawings.

In this embodiment, we will explain the flight of the multicopter 1 and the associated multicopter flight control related to the power supply to each motor 24. This multicopter flight control is performed on the premise that the first engine output control or the second engine output control described in each of the above embodiments is performed.

[About multicopter flight control]
Next, a description will be given of the multicopter flight control executed by the main controller 33. The contents of the multicopter flight control are shown in the form of a flowchart in FIG.

When processing transitions to this routine, the main controller 33 (including the engine control unit 50) determines in step 300 whether or not there is a request for the multicopter 1 to ascend. If the result of this determination is positive, the main controller 33 transitions processing to step 310, and if the result of this determination is negative, the main controller 33 transitions processing to step 390.

In step 390, since there is no request for ascent, the main controller 33 determines whether there is a request to both fly the multicopter 1 and charge the battery 31. If the result of this determination is positive, the main controller 33 transitions the process to step 320, and if the result of this determination is negative, the main controller 33 transitions the process to step 440.

On the other hand, in step 310, since there is a request to ascend, the main controller 33 sets the ascend flag XRIS to "1".

Next, moving from step 310 or step 390 to step 320, the main controller 33 executes high mode operation of the engine 41. For example, the main controller 33 executes high mode operation by setting the target throttle opening THRstep to full open and controlling the throttle device 57 to the target throttle opening THRstep.

Next, in step 330, the main controller 33 determines the power generation amount WE of the generator 42 based on the target throttle opening THRstep. The main controller 33 can determine the power generation amount WE corresponding to the target throttle opening THRstep by, for example, referring to a power generation amount map as shown in FIG. 14. In this map, the power generation amount WE is set to increase in a curved manner as the target throttle opening THRstep increases.

Next, in step 340, the main controller 33 determines whether the rise flag XRIS is "1". If the result of this determination is positive, the main controller 33 transitions the process to step 350 since there is a rise request. If the result of this determination is negative, the main controller 33 transitions the process to step 400 since there is no rise request.

In step 400, the main controller 33 calculates the chargeable power generation amount WEBin by subtracting a predetermined low power generation amount WElow from the power generation amount WE.

Next, in step 410, the main controller 33 flies the multicopter 1 at a low power generation amount WElow and charges the battery 31 with the chargeable power generation amount WEBin, and returns the process to step 300.

On the other hand, in step 350, the main controller 33 determines whether the power generation amount WE is equal to or greater than a predetermined high power generation amount WEhi. If the result of this determination is positive, the main controller 33 shifts the process to step 360 since the output of the engine 41 is not being suppressed. If the result of this determination is negative, the main controller 33 shifts the process to step 420 since the output of the engine 41 is being suppressed.

In step 420, the main controller 33 calculates the assist discharge amount WEBout of the battery 31 by subtracting the power generation amount WE from the high power generation amount WEhi.

Next, in step 430, the main controller 33 stops charging the battery 31 and executes battery ascent assist control. Here, the battery ascent assist control executes ascending flight of the multicopter 1 by supplying both the power generation amount WE and the assist discharge amount WEBout to each motor 24. After that, the main controller 33 transitions the process to step 370.

On the other hand, in step 360, the main controller 33 stops charging the battery 31 and causes the multicopter 1 to fly upwards with the high power generation amount WEhi, which is the entire power generation amount WE generated by the generator 42. That is, the main controller 33 causes the multicopter 1 to fly upwards by supplying all of the power generation amount WE generated by the generator 42 to each motor 24.

Next, in step 370, moving from step 360 or step 430, the main controller 33 determines whether the ascending flight of the multicopter 1 has been completed. If the result of this determination is positive, the main controller 33 transitions the process to step 380, and if the result of this determination is negative, the main controller 33 returns the process to step 300.

In step 380, the main controller 33 cancels the request to ascend the multicopter, sets the ascent flag XRIS to "0", and then returns the process to step 300.

On the other hand, moving from step 390 to step 440, the main controller 33 determines whether or not there is a request to fly the multicopter 1. If the result of this determination is positive, the main controller 33 transitions the process to step 450, and if the result of this determination is negative, the main controller 33 transitions the process to step 470.

In step 450, the main controller 33 executes low mode operation of the engine 41. For example, the main controller 33 executes low mode operation by setting the target throttle opening THRstep to a medium-low opening and controlling the throttle device 57 to the target throttle opening THRstep.

Next, in step 460, the main controller 33 flies the multicopter 1 with a low power generation amount WElow and returns the process to step 300.

On the other hand, in step 470, the main controller 33 determines whether or not there is an idle request for the engine 41. If the result of this determination is positive, the main controller 33 proceeds to step 480, and if the result of this determination is negative, the main controller 33 proceeds to step 490.

In step 480, the main controller 33 causes the engine 41 to idle, and then returns the process to step 300. The main controller 33 can cause the engine 41 to idle by controlling the throttle device 57 to a predetermined idle opening.

On the other hand, in step 490, the main controller 33 stops the engine 41 and then returns the process to step 300.

According to the multicopter flight control described above, when a request arises to increase the output of each motor 24 while the main controller 33 (control means) is executing the output reduction control, for example, when it becomes necessary to fly the multicopter 1 upward, the main controller 33 executes the current compensation control to compensate for the current supplied to each motor 24 with the assist discharge amount WEBout, which is the amount of stored electricity remaining in the battery 31.

[Actions and Effects of Multicopters]
According to the configuration of the multicopter 1 of this embodiment described above, in addition to the actions and effects of the first or second embodiment, the following actions and effects are obtained. That is, when a request to increase the output of each motor 24 occurs while the output reduction control is being executed, for example, when a request to raise the multicopter 1 occurs, the main controller 33 (control means) executes current compensation control to compensate for the amount of stored electricity remaining in the battery 31 to be supplied to each motor 24. Therefore, even if the output of the engine 41 is reduced by executing the output reduction control and the amount of electricity generated by the generator 42 is insufficient, the amount of stored electricity remaining in the battery 31 is compensated for by the current supplied to each motor 24 through the current compensation control, and the shortage of the amount of electricity generated by the generator 42 is compensated for. Therefore, the output of each motor 24 can be increased as requested, and the multicopter 1 can fly stably as requested.

Figure 15 shows the changes in various parameters related to the first or second engine output control and multicopter flight control in a time chart. In Figure 15, (a) shows the presence or absence of a rapid climb request for the multicopter 1, (b) shows the change in the operation mode of the engine 41, (c) shows the change in the throttle opening, (d) shows the change in engine output (≒ power generation amount), (e) shows the change in battery charge/discharge, (f) shows the change in the high mode operation time CHF, and (g) shows the change in the engine temperature THE (≒ oil temperature).

In FIG. 15, when the operation mode (b) becomes high mode operation (high load operation) from time t0, if the high mode operation time CHF (f) exceeds the allowable time A1 at time t3, that is, if the engine temperature THE (g) exceeds the allowable temperature TAL, the throttle opening (c) begins to decrease from full open, the engine output (d) begins to decrease from "max output", and the battery charge/discharge (e) begins to decrease from "max charge". Here, after time t0, the operation mode becomes high mode operation as shown in (b), but between time t0 and time t3, the engine output becomes "max output", and the power generated by the generator 42 is used for flying the multicopter 1 and for charging the battery 31, resulting in a first high mode operation H1, and after time t3, the engine output is reduced from "max output", and the power generated by the generator 42 is used for flying the multicopter 1, resulting in a second high mode operation H2 in which charging to the battery 31 is suppressed. As a result, the engine temperature THE in (g) does not increase as shown by the two-dot chain line, and is maintained at the allowable temperature TAL as shown by the solid line, and it can be seen that the temperature rise of the engine 41 can be suppressed. Here, if a sudden increase request in (a) is received between times t1 and t2 during high mode operation (first high mode operation H1), both charging and discharging in (e) become "0". Furthermore, if a rapid increase request (a) is received between times t4 and t5 during high mode operation (second high mode operation H2), the battery charge/discharge (e) will be set to "0" and a predetermined amount shown by hatching will be discharged and supplied to each motor 24. After time t6, the throttle opening (c), engine output (d), and battery charge/discharge (e) will be constant values by operating in output suppression stable mode.

<Fourth embodiment>

Next, the fourth embodiment will be described in detail with reference to the drawings.

In this embodiment, the third engine output control is different from the first or second engine output control of each of the above embodiments.

[Third engine output control]
Next, a description will be given of the third engine output control executed by the main controller 33. The third engine output control is shown in a flow chart in FIG.

When processing transitions to this routine, in step 500, the main controller 33 acquires the engine temperature THE, outside air temperature THA, air speed FSPD, remaining battery charge SOC%, and driving mode based on the detection values of various sensors 71-75, etc.

Next, in step 510, the main controller 33 determines whether the current operation mode is high mode operation. If the result of this determination is positive, the main controller 33 proceeds to step 520, and if the result of this determination is negative, the main controller 33 proceeds to step 590.

In step 590, the main controller 33 determines the target throttle opening THRstep according to the flight mode of the multicopter 1. The main controller 33 determines the target throttle opening THRstep according to, for example, whether the multicopter 1 is in a low-speed flight mode or an idle flight mode. After that, the main controller 33 returns the process to step 500.

On the other hand, in step 520, the main controller 33 sets the target throttle opening THRstep to "236", which corresponds to full throttle.

Next, in step 530, the main controller 33 retrieves the high mode operation time CHF.

Next, in step 540, the main controller 33 determines whether the high mode operation time CHF has exceeded a predetermined allowable time A1. If the result of this determination is positive, the main controller 33 proceeds to step 550, and if the result of this determination is negative, the main controller 33 proceeds to step 600.

In step 600, the main controller 33 executes no fuel cut control for the engine 41, and returns the process to step 500. Here, fuel cut means cutting off the injection (supply) of fuel from the injector 60 to the engine 41.

On the other hand, in step 550, the main controller 33 calculates the allowable temperature exceeding time CET by subtracting the allowable time A1 from the high mode operation time CHF.

Next, in step 560, the main controller 33 determines whether the time CET exceeding the allowable temperature is equal to or greater than the sum of the predetermined allowable time A1 and the first predetermined value b1. If the result of this determination is positive, the main controller 33 proceeds to step 570, and if the result of this determination is negative, the main controller 33 proceeds to step 610.

In step 610, the main controller 33 reduces the output of the engine 41 by 5% by executing fuel cut control once every 20 revolutions of the engine 41, and returns the process to step 500.

On the other hand, in step 570, the main controller 33 determines whether the time CET exceeding the allowable temperature is equal to or greater than the sum of the predetermined allowable time A1 and a second predetermined value c1 (> b1). If the result of this determination is positive, the main controller 33 proceeds to step 580, and if the result of this determination is negative, the main controller 33 proceeds to step 620.

In step 620, the main controller 33 reduces the output of the engine 41 by 10% by executing fuel cut control once every 10 revolutions of the engine 41, and returns the process to step 500.

On the other hand, in step 580, the main controller 33 reduces the output of the engine 41 by 15% by executing fuel cut control once every seven revolutions of the engine 41, and returns the process to step 500.

According to the third engine output control described above, the main controller 33 (control means) executes fuel cut control to cut off fuel injection (supply) from the injector 60 to the engine 41 in order to execute output reduction control, unlike the above-mentioned embodiments. Here, the main controller 33 increases the frequency of execution of the fuel cut control as the allowable temperature exceeding time CET, obtained by subtracting the allowable time A1 from the high mode operation time CHF, becomes longer.

[Actions and Effects of Multicopters]
The configuration of the multicopter 1 of this embodiment described above provides the following actions and effects, which are different from the previous embodiments. That is, the main controller 33 (control means) executes fuel cut control to cut the injection of fuel from the injector 60 (fuel supply means) to the engine 41 in order to execute output reduction control. Therefore, the number of times the fuel is burned is reduced, and the output of the engine 41 is reduced. Therefore, the temperature rise of the engine 41 can be suppressed before heat damage occurs to the air-cooled engine 41.

Furthermore, according to the configuration of this embodiment, the main controller 33 increases the frequency of execution of fuel cut control as the time CET exceeding the allowable temperature becomes longer. Therefore, the more severe the air-cooling conditions of the engine 41 due to the flight conditions of the multicopter 1, the more the number of fuel combustions is reduced, and the more the output of the engine 41 is reduced. Therefore, even if the air-cooling conditions of the engine 41 become severe due to the flight conditions of the multicopter 1, the temperature rise of the engine 41 can be suppressed.

Figure 17 shows the changes in various parameters related to the third engine output control in a time chart. In Figure 17, (a) shows the change in crank angle of the engine 41 (720°CA is one engine cycle) and the associated timing of injection IJ and injection cut IJC. In Figure 17, (b) shows the change in throttle opening and the change in high mode operation time CHF, (c) shows the change in engine temperature THE (≒oil temperature), (d) shows the presence or absence of fuel cut, (e) shows the change in battery charge/discharge, and (f) shows the change in engine output (≒power generation).

In FIG. 17, when the throttle opening degree (b) is fully open (the operation mode is high mode operation (high load operation)) at time t0, if the high mode operation time CHF (b) exceeds the allowable time A1 at time t1, the fuel cut (d) is performed once every 20 revolutions of the engine 41. As a result, the battery charge/discharge (e) is reduced by 5% from full charge, and the engine output (f) is reduced by 5% from the maximum output. After that, if the high mode operation time CHF (b) exceeds the allowable time A1 + a predetermined value b1 at time t2, the fuel cut (d) is performed once every 10 revolutions of the engine 41. As a result, the battery charge/discharge (e) is reduced by 10% from full charge, and the engine output (f) is reduced by 10% from the maximum output. After that, at time t3, when the high mode operation time CHF (b) exceeds the allowable time A1 + the predetermined value c1, the fuel cut (d) is performed once every seven revolutions of the engine 41. This causes the battery charge/discharge (e) to decrease by 15% from full charge, and the engine output (f) to decrease by 15% from the maximum output. In this way, by increasing the frequency of fuel cut control as the high mode operation time CHF elapses, the charge to the battery 31 decreases, but the output of the engine 41 decreases, so that the engine temperature THE (c) does not increase as shown by the two-dot chain line, but is maintained below the allowable temperature TAL with slight increases and decreases as shown by the solid line, and it can be seen that the temperature rise of the engine 41 can be suppressed.

<Fifth embodiment>

Next, the fifth embodiment will be described in detail with reference to the drawings.

In this embodiment, the fourth engine output control is different from the third engine output control of the fourth embodiment.

[Fourth engine output control]
Next, the fourth engine output control executed by the main controller 33 (including the engine control unit 50) will be described. Fig. 18 shows the contents of the fourth engine output control in the form of a flowchart. In this flowchart, step 545 is provided instead of step 540, step 555 is provided instead of step 550, step 565 is provided instead of step 560, and step 575 is provided instead of step 570. Also, the configuration differs from that of the flowchart in Fig. 16 in that steps 700 to 720 are provided between step 530 and step 545.

When processing transitions to this routine, the main controller 33 executes the processing of steps 500 to 530, and then in step 700, determines the outside air temperature correction coefficient Ktha according to the outside air temperature THA. The main controller 33 can determine the outside air temperature correction coefficient Ktha according to the outside air temperature THA, for example, by referring to an outside air temperature correction coefficient map such as that shown in FIG. 10.

Next, in step 710, the main controller 33 determines the airspeed correction coefficient Kfspd according to the airspeed FSPD. The main controller 33 can determine the airspeed correction coefficient Kfspd according to the airspeed FSPD, for example, by referring to an airspeed correction coefficient map such as that shown in FIG. 11.

Next, in step 720, the main controller 33 calculates the output suppression judgment time KA by multiplying the allowable time A1 by the outside air temperature correction coefficient Ktha and the airspeed correction coefficient Kfspd. Therefore, as the outside air temperature THA increases, the outside air temperature correction coefficient Ktha becomes smaller than "1.0", and the output suppression judgment time KA becomes shorter than the allowable time A1. As the airspeed FSPD decreases, the airspeed correction coefficient Kfspd becomes smaller than "1.0", and the output suppression judgment time KA becomes shorter than the allowable time A1.

Next, in step 545, the main controller 33 judges whether the high mode operation time CHF has exceeded the output suppression judgment time KA. Here, the output suppression judgment time KA means the time for judging whether the output should be suppressed due to an increase in the temperature of the engine 41. If the result of this judgment is positive, the main controller 33 shifts the process to step 555, and if the result of this judgment is negative, the process shifts to step 600. Therefore, the shorter the output suppression judgment time KA is compared to the allowable time A1, the longer the high mode operation time CHF is compared to the output suppression judgment time KA, and therefore the main controller 33 will execute output reduction control to reduce the output of the engine 41.

In step 555, the main controller 33 calculates the time beyond the allowable temperature CET by subtracting the output suppression determination time KA from the high mode operation time CHF.

Next, in step 565, the main controller 33 determines whether the time CET exceeding the allowable temperature is equal to or greater than the sum of the output suppression determination time KA and the first predetermined value b1. If the result of this determination is positive, the main controller 33 assumes that the airspeed FSPD has slowed down or the outside air temperature THA has increased, and proceeds to step 575. If the result of this determination is negative, the main controller 33 proceeds to step 610.

In step 575, the main controller 33 determines whether the time CET exceeding the allowable temperature is equal to or greater than the sum of the output suppression determination time KA and a second predetermined value c1 (> b1). If the result of this determination is positive, the main controller 33 transitions the process to step 580, assuming that the airspeed FSPD has slowed or the outside air temperature THA has increased. If the result of this determination is negative, the main controller 33 transitions the process to step 620.

According to the fourth engine output control described above, unlike the third engine output control, the main controller 33 increases the frequency of execution of fuel cut control when at least one of the following conditions is met: the slower the detected airspeed FSPD becomes and/or the higher the detected outside air temperature THA becomes. In other words, the frequency is increased to once every 20 revolutions of the engine 41, once every 10 revolutions of the engine 41, and once every 7 revolutions of the engine 41.

[Actions and Effects of Multicopters]
According to the configuration of the multicopter 1 of this embodiment described above, the following actions and effects can be obtained, unlike the fourth embodiment. That is, during the flight of the multicopter 1, the slower the airspeed FSPD or the higher the outside air temperature THA, the worse the air-cooling conditions of the engine 41 become. However, the main controller 33 increases the frequency of execution of the fuel cut control when at least one of the following is true: the slower the detected airspeed FSPD or the higher the detected outside air temperature THA. Therefore, the more severe the air-cooling conditions of the engine 41 become due to the flight conditions of the multicopter 1, i.e., the airspeed FSPD and the outside air temperature THA, the more the number of fuel combustions is reduced, and the output of the engine 41 is reduced. Therefore, even if the air-cooling conditions of the engine 41 become severe due to the airspeed FSPD and the outside air temperature THA during the flight of the multicopter 1, the temperature rise of the engine 41 can be suppressed.

[About another embodiment]
The disclosed technology is not limited to the above-described embodiments, and may be implemented by modifying part of the configuration as appropriate without departing from the spirit of the disclosed technology.

(1) In the fourth and fifth embodiments, the fuel cut control is performed to cut off the injection (supply) of fuel from the injector 60 to the engine 41 in order to execute the output reduction control. However, the ignition cut control can also be performed to cut off the ignition of the air-fuel mixture by the spark plug 61 in order to execute the output reduction control. When the ignition cut control is executed in this manner, the engine 41 can be cooled by the latent heat of vaporization of the fuel supplied to the engine when the ignition is cut off.

(2) In the third embodiment, the case where multicopter flight control is executed on the premise that the first engine output control or the second engine output control is executed has been described. In contrast, the multicopter flight control described in the third embodiment can also be executed on the premise that the third engine output control or the fourth engine output control is executed. In this case, too, it is possible to obtain the same actions and effects as the third embodiment with respect to the multicopter flight control.

(3) In each of the above embodiments, when the engine 41 is operated under high load and it is determined that the operating time has exceeded a predetermined allowable time, the temperature of the engine 41 is deemed to be higher than a predetermined allowable temperature, and output reduction control is executed. In contrast, it is also possible to configure the system to execute output reduction control when the engine temperature THE detected by the engine temperature sensor 71 is higher than a predetermined allowable temperature.

(4) In the third embodiment, when the main controller 33 is executing the output reduction control and a request arises to increase the output of each motor 24, the main controller 33 is configured to execute a current compensation control to compensate for the assist discharge amount WEBout, which is the amount of stored power remaining in the battery 31, by the current supplied to each motor 24. In contrast, a charge amount detection means for detecting the charge amount of the battery may be further provided, and the main controller may be configured to execute the current compensation control when the amount of stored power remaining in the battery is equal to or greater than a predetermined amount. In this case, the battery power is not supplied to the motor when the amount of stored power remaining in the battery is less than the predetermined amount. This makes it possible to prevent the battery life from being shortened.

This disclosed technology can be applied to a multicopter equipped with a generator and battery, with the engine used as the power source for the generator.

1 Multicopter 11 Airframe 15 Power generation engine system 24 Motor 25 Rotor 31 Battery 32 Fuel tank (fuel supply means)
33 Main controller (control means)
41 Engine 42 Generator
50 Engine control unit (control means)
57 Throttle device (output adjustment means)
60 Injector (fuel supply means)
61 Spark plug (ignition means)
62 Ignition coil (ignition means)
74 Outside air temperature sensor (outside air temperature detection means)
75 Airspeed sensor (airspeed detection means)
THA Outside air temperature FSPD Air speed CHF High mode operation time A1 Allowable time TAL Allowable temperature

Claims (7)

A plurality of rotors;
a motor for rotating the rotors;
A multicopter that flies by rotating each of the rotors with the motor, comprising: a battery configured to be able to charge and discharge power supplied to the motor;
A generator for generating electricity;
an air-cooled engine for driving the generator;
A control means for controlling the power supply to the motor, the operation of the engine, and the charging and discharging of the battery in order to control the flight of the multicopter;
and an output adjustment means for adjusting the output of the engine, wherein when the temperature of the engine becomes higher than a predetermined allowable temperature while the engine is operating at high load, the control means executes output reduction control to control the output adjustment means so as to reduce the output of the engine in accordance with the time during which the temperature of the engine exceeds the allowable temperature . A plurality of rotors ;
a motor for rotating the rotors;
a battery configured to be capable of charging and discharging power supplied to the motor;
A multicopter that flies by rotating each rotor with the motor,
A generator for generating electricity;
an air-cooled engine for driving the generator;
A control means for controlling the power supply to the motor, the operation of the engine, and the charging and discharging of the battery in order to control the flight of the multicopter;
an output adjusting means for adjusting the output of the engine;
wherein the control means executes an output reduction control for controlling the output adjustment means to reduce the output of the engine when the temperature of the engine becomes higher than a predetermined allowable temperature while the engine is being operated under high load;
an airframe having the rotors, the motor, the engine, and the generator mounted thereon;
an airspeed detection means for detecting an airspeed between the aircraft and the atmosphere;
Further comprising an outside air temperature detection means for detecting the temperature of the outside air,
The control means determines that the temperature of the engine will be higher than the allowable temperature when at least one of the following conditions is true: the detected airspeed is slower; and the detected outside air temperature is higher; and executes the power reduction control. The multicopter according to claim 1 or 2,
The control means performs a current compensation control to compensate for the current supplied to the motor with the amount of stored electricity remaining in the battery when a request to increase the output of the motor occurs while the output reduction control is being performed. The multicopter according to any one of claims 1 to 3,
the output adjustment means includes a fuel supply means for supplying fuel to the engine, and an ignition means for igniting a mixture of the fuel supplied to the engine and intake air taken into the engine,
The control means performs a fuel cut control to cut off the supply of fuel from the fuel supply means to the engine, or an ignition cut control to cut off the ignition of the mixture by the ignition means, in order to perform the output reduction control. The multicopter according to claim 2 ,
the output adjustment means includes a fuel supply means for supplying fuel to the engine;
the control means executes a fuel cut control for cutting off the supply of fuel from the fuel supply means to the engine in order to execute the output reduction control;
The control means increases the frequency of execution of the fuel cut control when at least one of the following conditions is met: the detected airspeed becomes slower; and the detected outside air temperature becomes higher. The multicopter according to claim 4 or 5,
The control means performs a current compensation control to compensate for the current supplied to the motor with the amount of stored electricity remaining in the battery when a request to increase the output of the motor occurs while the output reduction control is being performed. The multicopter according to any one of claims 1 to 6,
The control means, when it determines that the operating time of the engine during high load operation has exceeded a predetermined allowable time, executes output reduction control as the temperature of the engine has exceeded a predetermined allowable temperature.

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