MULTICOPTER

Abstract

A multicopter is provided which includes an engine configured to generate rotation by burning fuel in the engine, a plurality of propellers configured to generate a lift by rotating, a rotation transmission path configured to distribute and transmit the rotation generated by the engine to the propellers.

Claims

1. A multicopter comprising: an engine configured to generate rotation by burning fuel in the engine; a plurality of propellers configured to generate a lift by rotating; and a rotation transmission path configured to distribute and transmit the rotation generated by the engine to the propellers.

2. The multicopter of claim 1, wherein the rotation transmission path comprises: a first shaft mechanically coupled to a first propeller of the plurality of propellers; a second shaft mechanically coupled to a second propeller of the plurality of propellers; and a differential configured to distribute the rotation generated by the engine to the first and second shafts such that the first and second shafts rotate, respectively, at speeds corresponding to rotational resistances applied to the first and second shafts.

3. The multicopter of claim 2, wherein the rotation transmission path further comprises: a first brake device configured to apply a braking force to the first shaft; and a second brake device configured to apply a braking force to the second shaft.

4. The multicopter of claim 3, wherein each of the first and second brake devices is a non-contact type brake device comprising a brake disk configured to rotate together with a corresponding one of the first and second shafts, and a stator configured to apply a braking force to the brake disk while being kept out of contact with the brake disk.

5. The multicopter of claim 3, wherein the first and second brake devices are regenerative braking devices configured to apply braking forces to the first and second shafts, respectively, by converting torque of the first and second shafts to electric power.

6. The multicopter of claim 2, wherein the rotation transmission path further comprises: a first auxiliary motor configured to apply torque to the first shaft; and a second auxiliary motor configured to apply torque to the second shaft.

7. The multicopter of claim 2, wherein the plurality of propellers comprises at least four propellers, and the rotation transmission path further comprises: a third shaft mechanically coupled to a third propeller of the plurality of propellers; a fourth shaft mechanically coupled to a fourth propeller of the plurality of propellers; and a second differential configured to distribute the rotation generated by the engine to the third and fourth shafts such that the third and fourth shafts rotate, respectively, at speeds corresponding to rotational resistances applied to the third and fourth shafts.

8. The multicopter of claim 3, wherein the plurality of propellers comprises at least four propellers, and the rotation transmission path further comprises: a third shaft mechanically coupled to a third propeller of the plurality of propellers; a fourth shaft mechanically coupled to a fourth propeller of the plurality of propellers; and a second differential configured to distribute the rotation generated by the engine to the third and fourth shafts such that the third and fourth shafts rotate, respectively, at speeds corresponding to rotational resistances applied to the third and fourth shafts.

9. The multicopter of claim 4, wherein the plurality of propellers comprises at least four propellers, and the rotation transmission path further comprises: a third shaft mechanically coupled to a third propeller of the plurality of propellers; a fourth shaft mechanically coupled to a fourth propeller of the plurality of propellers; and a second differential configured to distribute the rotation generated by the engine to the third and fourth shafts such that the third and fourth shafts rotate, respectively, at speeds corresponding to rotational resistances applied to the third and fourth shafts.

10. The multicopter of claim 5, wherein the plurality of propellers comprises at least four propellers, and the rotation transmission path further comprises: a third shaft mechanically coupled to a third propeller of the plurality of propellers; a fourth shaft mechanically coupled to a fourth propeller of the plurality of propellers; and a second differential configured to distribute the rotation generated by the engine to the third and fourth shafts such that the third and fourth shafts rotate, respectively, at speeds corresponding to rotational resistances applied to the third and fourth shafts.

11. The multicopter of claim 6, wherein the plurality of propellers comprises at least four propellers, and the rotation transmission path further comprises: a third shaft mechanically coupled to a third propeller of the plurality of propellers; a fourth shaft mechanically coupled to a fourth propeller of the plurality of propellers; and a second differential configured to distribute the rotation generated by the engine to the third and fourth shafts such that the third and fourth shafts rotate, respectively, at speeds corresponding to rotational resistances applied to the third and fourth shafts.

12. The multicopter of claim 7, wherein the rotation transmission path further comprises a center differential configured to distribute rotation to the differential configured to distribute rotation to the first and second shafts, and to the second differential.

13. The multicopter of claim 1, further comprising an alternator configured to generate electric power utilizing rotation of the engine, and a battery configured to store the electric power generated by the alternator.

14. The multicopter of claim 2, wherein the differential includes: a ring gear arranged such that the rotation generated by the engine is applied to the ring gear; a differential case fixed to the ring gear so as to rotate together with the ring gear; a pinion provided in the differential case, and supported so as to be rotatable about an axis perpendicular to an axis of the ring gear; and a pair of side gears each supported so as to be rotatable about an axis parallel to the axis of the ring gear, and meshing with the pinion, wherein the first shaft is connected to one of the side gears, and the second shaft is connected to the other of the side gears.

15. The multicopter of claim 3, wherein the differential includes: a ring gear arranged such that the rotation generated by the engine is applied to the ring gear; a differential case fixed to the ring gear so as to rotate together with the ring gear; a pinion provided in the differential case, and supported so as to be rotatable about an axis perpendicular to an axis of the ring gear; and a pair of side gears each supported so as to be rotatable about an axis parallel to the axis of the ring gear, and meshing with the pinion, wherein the first shaft is connected to one of the side gears, and the second shaft is connected to the other of the side gears.

16. The multicopter of claim 4, wherein the differential includes: a ring gear arranged such that the rotation generated by the engine is applied to the ring gear; a differential case fixed to the ring gear so as to rotate together with the ring gear; a pinion provided in the differential case, and supported so as to be rotatable about an axis perpendicular to an axis of the ring gear; and a pair of side gears each supported so as to be rotatable about an axis parallel to the axis of the ring gear, and meshing with the pinion, wherein the first shaft is connected to one of the side gears, and the second shaft is connected to the other of the side gears.

17. The multicopter of claim 5, wherein the differential includes: a ring gear arranged such that the rotation generated by the engine is applied to the ring gear; a differential case fixed to the ring gear so as to rotate together with the ring gear; a pinion provided in the differential case, and supported so as to be rotatable about an axis perpendicular to an axis of the ring gear; and a pair of side gears each supported so as to be rotatable about an axis parallel to the axis of the ring gear, and meshing with the pinion, wherein the first shaft is connected to one of the side gears, and the second shaft is connected to the other of the side gears.

18. The multicopter of claim 6, wherein the differential includes: a ring gear arranged such that the rotation generated by the engine is applied to the ring gear; a differential case fixed to the ring gear so as to rotate together with the ring gear; a pinion provided in the differential case, and supported so as to be rotatable about an axis perpendicular to an axis of the ring gear; and a pair of side gears each supported so as to be rotatable about an axis parallel to the axis of the ring gear, and meshing with the pinion, wherein the first shaft is connected to one of the side gears, and the second shaft is connected to the other of the side gears.

19. The multicopter of claim 7, wherein the differential configured to distribute rotation to the first and second shafts includes: a ring gear arranged such that the rotation generated by the engine is applied to the ring gear; a differential case fixed to the ring gear so as to rotate together with the ring gear; a pinion provided in the differential case, and supported so as to be rotatable about an axis perpendicular to an axis of the ring gear; and a pair of side gears each supported so as to be rotatable about an axis parallel to the axis of the ring gear, and meshing with the pinion, wherein the first shaft is connected to one of the side gears, and the second shaft is connected to the other of the side gears.

20. The multicopter of claim 8, wherein the differential configured to distribute rotation to the first and second shafts includes: a ring gear arranged such that the rotation generated by the engine is applied to the ring gear; a differential case fixed to the ring gear so as to rotate together with the ring gear; a pinion provided in the differential case, and supported so as to be rotatable about an axis perpendicular to an axis of the ring gear; and a pair of side gears each supported so as to be rotatable about an axis parallel to the axis of the ring gear, and meshing with the pinion, wherein the first shaft is connected to one of the side gears, and the second shaft is connected to the other of the side gears.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0045] FIG. 1 schematically shows a multicopter according to a first embodiment of the present invention;

[0046] FIG. 2 is an enlarged sectional view of a differential shown in FIG. 1;

[0047] FIG. 3 schematically shows a multicopter according to a second embodiment of the present invention;

[0048] FIG. 4 schematically shows a multicopter according to a third embodiment of the present invention;

[0049] FIG. 5 schematically shows a multicopter according to a fourth embodiment of the present invention;

[0050] FIG. 6 shows a modification of the first embodiment in which two of the engines as shown in FIG. 1 are arranged such that the rotations generated by the respective engines are transmitted to a common center differential;

[0051] FIG. 7 schematically shows another modification of the first embodiment in which a greater number of the propellers shown in FIG. 1 are used; and

[0052] FIG. 8 schematically shows a further modification of the first embodiment in which universal joints are mounted in portions of the rotation transmission path extending from the engine shown in FIG. 7 to the respective propellers.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0053] FIG. 1 shows a multicopter according to the first embodiment of the present invention. The multicopter is an unmanned rotorcraft capable of flying in the air to perform measurements and observations with an onboard camera, transport various articles, and spray pesticides. The multicopter includes a single engine 1, first to fourth propellers 2.sub.1, 2.sub.2, 2.sub.3 and 2.sub.4 which generate a lift when rotated, a rotation transmission path 3 which distributes and transmits rotation generated by the engine 1 to the four propellers 2.sub.1, 2.sub.2, 2.sub.3 and 2.sub.4, a fuel tank 4, and a battery 5.

[0054] The engine 1 is a driving unit that generates rotation by burning fuel inside the engine 1. The displacement of the engine 1 is determined e.g., within the range of 10-200 cm.sup.3. Fuel for the engine 1 is a petroleum-based fuel (such as gasoline). The fuel tank 4 stores fuel to be supplied to the engine 1, and is connected to the engine 1 via a fuel tube 6. The battery 5 is a secondary battery for controlling the engine, and for supplying electric power to e.g. a gyro sensor, not shown. An alternator 7 is fixedly attached to the engine to generate electric power utilizing the rotation of the engine 1. The electric power generated by the alternator 7 is stored in the battery 5.

[0055] Each of the first to fourth propellers 2.sub.1, 2.sub.2, 2.sub.3 and 2.sub.4 includes a plurality of blades 8 each extending in a radial direction from the center of rotation of the propeller. Each blade 8 has such a blade angle as to generate a lift when the propeller rotates.

[0056] The rotation transmission path 3 includes a center differential 10 which distributes the rotation transmitted from the engine 1 to first and second center shafts 9.sub.1 and 9.sub.2; a differential 12 which distributes the rotation transmitted from the engine 1 via the first center shaft 9.sub.1 to first and second shafts 11.sub.1 and 11.sub.2; and a second differential 13 which distributes the rotation transmitted from the engine 1 via the second center shaft 9.sub.2 to third and fourth shafts 11.sub.3 and 11.sub.4.

[0057] The first shaft 11.sub.1 is mechanically coupled to the first propeller 2.sub.1 so that when the first shaft 11.sub.1 rotates, the first propeller 2.sub.1 rotates together with the first shaft 11.sub.1. In the same manner as the first shaft 11.sub.1 is mechanically coupled to the first propeller 2.sub.1, the second shaft 11.sub.2 is mechanically coupled to the second propeller 2.sub.2; the third shaft 11.sub.3 is mechanically coupled to the third propeller 2.sub.3; and the fourth shaft 11.sub.4 is mechanically coupled to the fourth propeller 2.sub.4.

[0058] As shown in FIG. 2, the differential 12 includes a ring gear 14 which receives the rotation transmitted from the engine 1 (shown in FIG. 1) via the first center shaft 9.sub.1; a differential case 15 fixed to the ring gear 14 so as to rotate together with the ring gear 14; a pinion shaft 18 fixed to the differential case 15 to extend perpendicular to the center axis of the ring gear 14; pinions 16 located in the differential case 15, and supported by the pinion shaft 18 so as to be rotatable about the pinion shaft 18; and a pair of side gears 17 meshing with the pinions 16. Each side gear 17 is supported by the differential case 15 so as to be rotatable about an axis parallel to the center axis of the ring gear 14. The first shaft 11.sub.1 is connected to one of the side gears 17, while the second shaft 11.sub.2 is connected to the other side gear 17.

[0059] The differential 12 is configured to distribute the rotation transmitted from the engine 1 to the first and second shafts 11.sub.1 and 11.sub.2 such that the respective shafts 11.sub.1 and 11.sub.2 rotate at speeds corresponding to the rotational resistances to the respective shafts 11.sub.1 and 11.sub.2. In particular, if the rotational resistance to the first shaft 11.sub.1 is larger than the rotational resistance to the second shaft 11.sub.2, the differential 12 distributes and transmits the rotation of the first center shaft 9.sub.1 to the first and second shafts 11.sub.1 and 11.sub.2 such that the first shaft 11.sub.1 rotates at a lower speed than the second shaft 11.sub.2, and if the rotational resistance to the first shaft 11.sub.1 is smaller than the rotational resistance to the second shaft 11.sub.2, the differential 12 distributes and transmits the rotation of the first center shaft 9.sub.1 to the first and second shafts 11.sub.1 and 11.sub.2 such that the first shaft 11.sub.1 rotates at a higher speed than the second shaft 11.sub.2.

[0060] The differential 13 between the third shaft 11.sub.3 and the fourth shaft 11.sub.4, shown in FIG. 1, is of the same structure as the differential 12 between the first shaft 11.sub.1 and the second shaft 11.sub.2. The center differential 10 is also of the same structure as the differential 12.

[0061] Since this multicopter uses the engine 1 as the power source of the first to fourth propellers 2.sub.1, 2.sub.2, 2.sub.3 and 2.sub.4, and fuel for the engine 1 has a far higher energy density than a battery used for an electric motor, this multicopter is capable of staying in the air for a prolonged period of time, and/or has a larger weight capacity. Since the output of the single engine 1 is distributed to the plurality of propellers 2.sub.1, 2.sub.2, 2.sub.3 and 2.sub.4 to drive them, it is not necessary to synchronously drive a plurality of engines as in the case when the first to fourth propellers 2.sub.1, 2.sub.2, 2.sub.3 and 2.sub.4 are driven by separate engines. This makes easier to stabilize the attitude of the multicopter.

[0062] Since this multicopter has an alternator 7 configured to generate electric power utilizing the rotation of the engine 1, and a battery 5 which is capable of store electric power generated by the alternator 7, it is possible to use a lightweight battery 5 while ensuring available power of the battery 5 during the flight of the multicopter. This serves to effectively increase the flight duration and/or the weight capacity of the multicopter.

[0063] FIG. 3 shows a multicopter of the second embodiment according to the present invention. Here, elements corresponding to those of the first embodiment are denoted by identical numerals and their description is omitted.

[0064] The rotation transmission path 3 of the second embodiment includes first to fourth brake devices 20.sub.1, 20.sub.2, 20.sub.3 and 20.sub.4 which apply braking forces to the first to fourth shafts 11.sub.1, 11.sub.2, 11.sub.3 and 11.sub.4, respectively. The first to fourth brake devices 20.sub.1, 20.sub.2, 20.sub.3 and 20.sub.4 are non-contact type brake devices each comprising a brake disk 21 that rotates together with the corresponding one of the first to fourth shafts 11.sub.1, 11.sub.2, 11.sub.3 and 11.sub.4, and a stator 22 configured to apply a braking force to the brake disk 21, while being kept out of contact with the brake disk 21. For example, the brake devices may be eddy current disk brakes.

[0065] With the multicopter of the second embodiment, it is possible to apply different rotational resistances to the first to fourth shafts 11.sub.1, 11.sub.2, 11.sub.3 and 11.sub.4, respectively, which are connected together via the differentials 10, 12 and 13, by selectively and individually actuating the first to fourth brake devices 20.sub.1, 20.sub.2, 20.sub.3 and 20.sub.4, thereby rotating the first to fourth propellers 2.sub.1, 2.sub.2, 2.sub.3 and 2.sub.4 at different speeds from each other. Thus in this embodiment, by controlling the braking forces applied to the first to fourth shafts 11.sub.1, 11.sub.2, 11.sub.3 and 11.sub.4, it is possible to control the attitude of the multicopter.

[0066] Since the multicopter of the second embodiment uses non-contact type brake devices 20.sub.1, 20.sub.2, 20.sub.3 and 20.sub.4, there is no friction loss between the brake disk 21 and the stator 22 of each brake device, and thus, there will be no energy loss while the first to fourth brake devices 20.sub.1, 20.sub.2, 20.sub.3 and 20.sub.4 are not actuated. This serves to effectively increase the flight duration and the weight capacity of the multicopter.

[0067] FIG. 4 shows a multicopter of the third embodiment according to the present invention. Here, elements corresponding to those of the first embodiment are denoted by identical numerals, and their description is omitted.

[0068] The rotation transmission path 3 of this embodiment includes first to fourth brake devices 25.sub.1, 25.sub.2, 25.sub.3 and 25.sub.4 which apply braking forces to the first to fourth shafts 11.sub.1, 11.sub.2, 11.sub.3 and 11.sub.4, respectively. The first to fourth brake devices 25.sub.1, 25.sub.2, 25.sub.3 and 25.sub.4 are regenerative braking devices configured to apply braking forces to the first to fourth shafts 11.sub.1, 11.sub.2, 11.sub.3 and 11.sub.4 by converting the torques of the first to fourth shafts 11.sub.1, 11.sub.2, 11.sub.3 and 11.sub.4 to electric power. The first to fourth brake devices 25.sub.1, 25.sub.2, 25.sub.3 and 25.sub.4 are electrically connected to the battery 5 so that the electric power generated during regenerative braking is stored in the battery 5.

[0069] The first to fourth brake devices 25.sub.1, 25.sub.2, 25.sub.3 and 25.sub.4 also serve as auxiliary motors capable of selectively and individually applying torques to the first to fourth shafts 11.sub.1, 11.sub.2, 11.sub.3 and 11.sub.4 by receiving electric power from the battery 5.

[0070] Thus, the first to fourth propellers 2.sub.1, 2.sub.2, 2.sub.3 and 2.sub.4 of the multicopter of the third embodiment can be rotated at different speeds from each other by selectively actuating the first to fourth brake devices 25.sub.1, 25.sub.2, 25.sub.3 and 25.sub.4 to individually apply braking forces to the first to fourth shafts 11.sub.1, 11.sub.2, 11.sub.3 and 11.sub.4. Alternatively, the first to fourth propellers 2.sub.1, 2.sub.2, 2.sub.3 and 2.sub.4 of the multicopter of the third embodiment can also be rotated at different speeds from each other by selectively actuating the first to fourth brake devices 25.sub.1, 25.sub.2, 25.sub.3 and 25.sub.4 as auxiliary motors to individually apply torques to the first to fourth shafts 11.sub.1, 11.sub.2, 11.sub.3 and 11.sub.4. Thus, in the third embodiment, by controlling the braking forces or torques applied to the first to fourth shafts 11.sub.1, 11.sub.2, 11.sub.3 and 11.sub.4, it is possible to control the attitude of the multicopter.

[0071] Since the multicopter of the third embodiment uses regenerative braking devices as the first to fourth brake devices 25.sub.1, 25.sub.2, 25.sub.3 and 25.sub.4, the electric power generated by the brake devices 25.sub.1, 25.sub.2, 25.sub.3 and 25.sub.4 is recyclable, which minimizes energy loss, thus effectively prolonging the flight duration of the multicopter.

[0072] FIG. 5 shows a multicopter of the fourth embodiment according to the present invention. Here, elements corresponding to those of the second embodiment are denoted by identical numerals, and their description is omitted.

[0073] The rotation transmission path 3 of this embodiment includes first to fourth auxiliary motors 23.sub.1, 23.sub.2, 23.sub.3 and 23.sub.4 which apply torques to the first to fourth shafts 11.sub.1, 11.sub.2, 11.sub.3 and 11.sub.4, respectively. The rotation transmission path 3 further includes a one-way clutch 24 disposed between the first auxiliary motor 23.sub.1 and the first shaft 11.sub.1 such that the one-way clutch 24 allows transmission of torque that tends to accelerate the rotation of the first shaft 11.sub.1, but prohibits transmission of torque that tends to decelerate the rotation of the first shaft 11.sub.1, from the first auxiliary motor 23.sub.1 to the first shaft 11.sub.1. That is, the one-way clutch 24 is configured and arranged in such a manner that when the first auxiliary motor 23.sub.1 is activated, the one-way clutch 24 engages, thus allowing transmission of torque from the first auxiliary motor 23.sub.1 to the first shaft 11.sub.1, and when the first auxiliary motor 23.sub.1 is deactivated, the one-way clutch 24 disengages, thereby allowing the first shaft 11.sub.1 to rotate independently of the first auxiliary motor 23.sub.1. This prevents the inertia moment of the first auxiliary motor 23.sub.1 from acting on the first shaft 11.sub.1 as rotational resistance when the first auxiliary motor 23.sub.1 stops. One-way clutches 24 identical in structure to, and arranged in the same manner as, the above one-way clutch 24 are provided between the second to fourth auxiliary motors 23.sub.2, 23.sub.3 and 23.sub.4 and the second to fourth shafts 11.sub.2, 11.sub.3 and 11.sub.4, respectively.

[0074] Electric power from the battery 5 is used to drive the first to fourth auxiliary motors 23.sub.1, 23.sub.2, 23.sub.3 and 23.sub.4. Alternatively, however, electric power generated by the alternator 7 may be used to drive the first to fourth auxiliary motors 23.sub.1, 23.sub.2, 23.sub.3 and 23.sub.4. In particular, electric power generated by the alternator 7 while the engine 1 is running may be stored in the battery 5, while simultaneously, electric power from the battery 5 may be used to drive the first to fourth auxiliary motors 23.sub.1, 23.sub.2, 23.sub.3 and 23.sub.4.

[0075] Thus, in the fourth embodiment, rotational resistances applied to the first to fourth shafts 11.sub.1, 11.sub.2, 11.sub.3 and 11.sub.4 can be altered individually by selectively actuating the first to fourth auxiliary motors 23.sub.1, 23.sub.2, 23.sub.3 and 23.sub.4, thereby individually applying torques to the first to fourth shafts 11.sub.1, 11.sub.2, 11.sub.3 and 11.sub.4. Thus, the attitude of the multicopter of the fourth embodiment can be controlled by controlling the torques applied to the first to fourth shafts 11.sub.1, 11.sub.2, 11.sub.3 and 11.sub.4. It is also possible to individually decelerate the rotations of the first to fourth propellers 2.sub.1, 2.sub.2, 2.sub.3 and 2.sub.4 by selectively actuating the first to fourth brake devices 20.sub.1, 20.sub.2, 20.sub.3 and 20.sub.4.

[0076] Since the multicopter of the fourth embodiment is configured such that the first to fourth shafts 11.sub.1, 11.sub.2, 11.sub.3 and 11.sub.4 are rotated at different speeds by applying torques to the first to fourth shafts 11.sub.1, 11.sub.2, 11.sub.3 and 11.sub.4, energy loss is small compared to the arrangement in which the rotational speeds of the first to fourth shafts 11.sub.1, 11.sub.2, 11.sub.3 and 11.sub.4 are controlled by applying braking forces thereto, so that it is possible to effectively prolong the flight duration of the multicopter.

[0077] While the multicopter of each of the above-described embodiments uses a single engine 1, two engines 1 may be used, as shown in FIG. 6, so that the rotations of the two engines 1 are applied simultaneously to the (single) center differential 10. With this arrangement, redundancy of the multicopter improves because even if one of the two engines 1 unexpectedly stops, the propellers 2.sub.1, 2.sub.2, 2.sub.3 and 2.sub.4 can still be driven by the other engine.

[0078] While the multicopter of each of the above-described embodiments uses four propellers 2, the present invention is applicable to a multicopter including more than four propellers. For example, as shown in FIGS. 7 and 8, the present invention is applicable to multicopters including eight propellers 2.sub.1-2.sub.8. The multicopter shown in FIG. 8 includes universal joints 26 mounted in the rotation transmission path 3, which extends from the engine 1 to the propellers 2.sub.1-2.sub.8. The universal joints 26 allow a large number of propellers, such as the eight propellers 2.sub.1-2.sub.8, to be arranged on a common circle (or on a common oval as shown).

[0079] It is to be understood that the embodiments shown are mere examples and do not restrict the invention in every respect. The scope of the present invention should be construed based on the appended claims and not based on the description. It is further to be understood that the present invention covers every modification within the range equivalent in meaning to what is recited in the claims.