Power unit

Abstract

Provided is a power unit in which a stator and a rotor of an axial magnetic flux generator constituting the power unit can be brought close to each other with a simple configuration. An engine (11) of a power unit (10) has an engine-side shaft (15) that outputs driving force by rotating about a rotating shaft (14). An axial magnetic flux generator (12) is provided with: a stator (16); a first rotor (17) rotatably disposed on one side of the stator (16); a second rotor (18) rotatably disposed on the other side of the stator (16); and a generator-side shaft (19) connected to the rotation centers of the first rotor (17) and the second rotor (18) and connected to the engine-side shaft (15). The engine-side shaft (15) is in contact with the thrust fixing section (131) along the rotating shaft (14).

Description

Technical Field

[0001] The present invention relates to a power unit. Background Art

[0002] Conventionally, there is a power unit in which an engine and a generator are integrated. Generators used in power units include radial generators and axial generators. Axial generators are called axial flux generators. Axial flux generators are easier to miniaturize than radial generators, so they are often installed in small devices.

[0003] An example of an axial flux generator is described in Patent Document 1. In the generator described in Patent Document 1, a substantially disc-shaped rotor and a stator are arranged to face each other in the axial direction. Then, the rotor rotates to generate an induced current by electromagnetic induction, thereby generating electricity.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2012-125021 Summary of the invention

[0007] Technical problem to be solved by the invention

[0008] However, when an attempt is made to construct a power unit using the invention described in Patent Document 1 or the like, it is not easy to improve the output efficiency of the generator incorporated in the engine.

[0009] Specifically, in the power unit, in order to transmit the driving force of the engine side to the generator side, the crankshaft of the engine is connected to the rotating shaft of the axial flux generator. Here, in order to improve the power generation efficiency of the axial flux generator, it is important to make the stator and the rotor as close as possible in the direction along the rotating shaft. On the other hand, the crankshaft of the engine is assembled to the engine body with a certain tolerance in the axial direction for the assembly of the components. Therefore, when the crankshaft of the engine is connected to the shaft of the axial flux generator, the position of the rotor of the axial flux generator is not fixed in the axial direction. Therefore, it is not a simple issue to make the stator and the rotor of the axial flux generator close to each other.

[0010] The present invention has been made in view of such a problem, and an object of the present invention is to provide a power unit capable of bringing a stator and a rotor of an axial flux generator constituting the power unit close to each other with a simple structure.

[0011] Technical solutions for solving technical problems

[0012] The power unit of the present invention is characterized in that it includes an engine, an axial flux generator driven by the engine, and a thrust fixing portion, wherein the engine has an engine-side shaft that outputs a driving force by rotating around a rotating shaft, and the axial flux generator has: a stator; a first rotor rotatably arranged on one side of the stator; a second rotor rotatably arranged on the other side of the stator; and a generator-side shaft connected to the rotation center of the first rotor and the second rotor and continuous with the engine-side shaft, and the engine-side shaft abuts against the thrust fixing portion along the rotating shaft. According to the power unit of the present invention, the engine-side shaft abuts against the thrust fixing portion.

[0013] Moreover, the power unit of the present invention is characterized in that it includes an engine, an axial flux generator driven by the engine, and a thrust fixing part, the engine having an engine-side shaft that outputs a driving force by rotating around a rotating shaft, the axial flux generator having a stator, a rotor arranged near the stator, and a generator-side shaft connected to the rotation center of the rotor and continuous with the engine-side shaft, the engine-side shaft abuts against the thrust fixing part along the rotating shaft, the engine-side shaft is urged by a force applying part so as to abut against the thrust fixing part, the engine-side shaft having: a first thrust abutting part arranged at a position close to the axial flux generator; and a second thrust abutting part arranged at a position farther from the axial flux generator than the first thrust abutting part, the force applying part abuts against the first thrust abutting part and applies force so that the second thrust abutting part abuts against the thrust fixing part.

[0014] Effects of the Invention

[0015] According to the power unit of the present invention, the engine side shaft abuts against the thrust fixing portion. As a result, the positions of the first rotor and the second rotor along the axial direction via the generator side shaft continuous with the engine side shaft also become predetermined positions. Therefore, the gaps between the first rotor and the second rotor and the stator can be made into predetermined lengths, and the power generation efficiency of the axial flux generator can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1A It is a cross-sectional view showing a power unit according to an embodiment of the present invention.

[0017] Figure 1B This is a rear view showing a power unit according to an embodiment of the present invention.

[0018] Figure 2A It is a cross-sectional view showing a power unit according to an embodiment of the present invention.

[0019] Figure 2B It is a cross-sectional view showing a power unit according to an embodiment of the present invention.

[0020] Figure 3A It is a cross-sectional view showing a power unit according to another embodiment of the present invention.

[0021] Figure 3B It is a perspective view showing a piston portion and the like according to an embodiment of the present invention.

[0022] Figure 4 It is an enlarged cross-sectional view showing a power unit according to still another embodiment of the present invention. DETAILED DESCRIPTION

[0023] Hereinafter, the power unit 10 according to the embodiment of the present invention will be described in detail based on the drawings. In the following description, the same reference numerals are attached to the same components in principle, and duplicate descriptions are omitted.

[0024] Figure 1A It is a cross-sectional view showing the power unit 10 . Figure 1B It is a rear view showing the power unit 10 .

[0025] The power unit 10 includes an engine 11, an axial flux generator 12 driven by the engine 11, and a thrust fixing portion 132. When the power unit 10 is operated, the engine 11 rotates and drives the axial flux generator 12, and the axial flux generator 12 outputs AC power. The power unit 10 is used as a power source for flying devices, vehicles, etc. Compared with radial generators, the axial flux generator 12 can achieve both miniaturization and high output at a high level. Therefore, by applying the axial flux generator 12 to flying devices such as drones, the flying device can be made lighter, and the continuous flight distance of the flying device can be extended.

[0026] The engine 11 here exemplifies a single-cylinder engine. The engine 11 mainly includes a housing 25, a piston 26, an engine side shaft 15, and a connecting rod 27. When the engine 11 is running, the piston 26 reciprocates by repeatedly performing a compression stroke, an explosion stroke, an exhaust stroke, and an intake stroke at high speed. The engine side shaft 15 connected to the piston 26 by the connecting rod 27 converts the reciprocating motion into a rotational motion. The engine side shaft 15 outputs a driving force by rotating around the rotating shaft 14. In addition, the engine side shaft 15 has a first thrust abutment portion 23 and a second thrust abutment portion 24. The specific structure of the engine side shaft 15 will be referred to. Figure 2A This will be described later.

[0027] The thrust fixing portion 131 and the thrust fixing portion 132 are disposed inside the housing 25 and are portions for fixing the engine-side shaft 15 in the axial direction. The portion extending toward the rear of the engine-side shaft 15 is inserted into the thrust fixing portion 131. A bearing not shown is interposed between the thrust fixing portion 131 and the engine-side shaft 15. The portion extending toward the front of the engine-side shaft 15 is inserted into the thrust fixing portion 132. A bearing not shown is interposed between the thrust fixing portion 132 and the engine-side shaft 15.

[0028] The urging portion 20 is disposed on the thrust fixing portion 131. The urging portion 20 is disposed on the front side of the thrust fixing portion 131 and is a portion that urges the first thrust contact portion 23 of the engine-side shaft 15 forward. As the urging portion 20, for example, a piston portion 21 or a spring 22 described later can be used.

[0029] The piston portion 21 is a portion that applies force to the first thrust abutment portion 23 using the pressure of an auxiliary machine of the engine 11, that is, an oil pump, which is not shown here. The oil pump forms an oil supply path for supplying oil to the main journal of the engine side shaft 15. The piston portion 21 receives pressure from a branch path branching from the oil supply path, and applies force to the first thrust abutment portion 23. By using the piston portion 21 as the force applying portion 20, a large force can be obtained without a dedicated device for generating the force. The force applying portion 20 will refer to Figure 3B This will be described later.

[0030] The spring 22 is, for example, a coil spring having an axis in the front-rear direction. The first thrust contact portion 23 is urged forward by the restoring force of the coil spring. As the spring 22, an elastic body other than the coil spring, for example, a synthetic resin having elasticity such as rubber, etc., can be used. By using the spring 22 as the force applying portion 20, an urging force can be obtained with a simple structure.

[0031] The axial flux generator 12 includes a stator 16, a first rotor 17, a second rotor 18, and a generator-side shaft 19. The axial flux generator 12 is disposed immediately behind the engine 11 and fixed to a housing 25 of the engine 11.

[0032] The stator 16 is connected to the housing 25 of the engine 11 via the stator fixing portion 28, thereby fixing its position. The stator 16 has a plurality of coils arranged in the circumferential direction.

[0033] The first rotor 17 is rotatably disposed on one side, that is, the front side, of the stator 16. The first rotor 17 has a plurality of permanent magnets disposed in the circumferential direction.

[0034] The second rotor 18 is rotatably disposed on the other side, that is, the rear side, of the stator 16. The second rotor 18 has a plurality of permanent magnets disposed in the circumferential direction.

[0035] Here, the gap between the first rotor 17 and the stator 16 is extremely short in order to improve the power generation efficiency of the axial flux generator 12. Similarly, the gap between the second rotor 18 and the stator 16 is also extremely short. In this embodiment, in order to stably shorten the length of these gaps, the engine side shaft 15 is positioned in the axial direction. For related matters, please refer to Figure 2A as well as Figure 2B Provide explanation.

[0036] The generator shaft 19 is a substantially rod-shaped member that is relatively non-rotatably connected to the rotation centers of the first rotor 17 and the second rotor 18. The generator shaft 19 is continuous with the engine shaft 15 and forms an integral linear rod-shaped rotating member.

[0037] Figure 2A 20 is a cross-sectional view showing a state before the force applying unit 20 applies force. Figure 2A , the structure of the engine side shaft 15 is described in detail.

[0038] The engine side shaft 15 has a pin portion 151, an arm portion 152, a front extension portion 153, and a rear extension portion 154. The pin portion 151 is rotatably connected to the lower portion of the connecting rod 27. The arm portions 152 are arranged on both sides of the pin portion 151, and connect the pin portion 151 to the front extension portion 153 and the rear extension portion 154. The front extension portion 153 penetrates the thrust fixing portion 132 and extends forward. The rear extension portion 154 penetrates the thrust fixing portion 131 and is connected to the generator side shaft 19.

[0039] The first thrust contact portion 23 is a portion where the rear extension portion 154 of the engine-side shaft 15 is partially expanded in diameter in the axial direction. The first thrust contact portion 23 is formed by expanding the diameter of the rear extension portion 154, which is substantially cylindrical, over the entire circumference. When the force application portion 20 is the piston portion 21 described later, the force application portion 20 does not apply force to the first thrust contact portion 23 when the power unit 10 is not in operation.

[0040] The second thrust contact portion 24 is a portion where the front extension portion 153 of the housing 25 is partially enlarged in diameter in the axial direction. The second thrust contact portion 24 is formed by enlarging the diameter of the front extension portion 153, which is substantially cylindrical, over the entire circumference. When the power unit 10 is not in operation, as described above, the force applying portion 20 does not apply the first thrust contact portion 23 forward, so the front face of the second thrust contact portion 24 does not contact the rear face of the thrust fixing portion 132.

[0041] Figure 2B It is a cross-sectional view showing a state where the urging unit 20 is urging.

[0042] By operating the engine 11, the pressure from the hydraulic circuit acts on the force applying part 20, and the force applying part 20 applies the rear surface of the first thrust contact part 23 of the engine side shaft 15 toward the front. Then, the engine side shaft 15 and the generator side shaft 19 are displaced forward, and the front surface of the second thrust contact part 24 contacts the rear surface of the thrust fixing part 132. In this way, the generator side shaft 19 continuous with the engine side shaft 15, and further the first rotor 17 and the second rotor 18 are set to a predetermined position. Thus, the gap between the first rotor 17 and the stator 16 and the gap between the second rotor 18 and the stator 16 are also set to a predetermined length.

[0043] That is, the first rotor 17, the stator 16, and the second rotor 18 of the axial flux generator 12 are arranged so as to form Figure 2B In the state shown, the gap between them becomes the design value.

[0044] Therefore, when the first rotor 17 and the second rotor 18 rotate in this state, AC power can be efficiently generated by the electromagnetic action of the second rotor 18 and the second rotor 18 and the stator 16 .

[0045] Figure 3A 1 is a cross-sectional view showing another type of power unit 10. The engine 11 of the power unit 10 shown in the figure is a two-cylinder engine having two pistons. That is, two pistons 26 and a connecting rod 27 are installed on one engine side shaft 15. Other structures are similar to Figure 2A Even with such a structure, when the power unit 10 is in operation, the force applying portion 20 applies the first thrust abutting portion 23 forward so that the second thrust abutting portion 24 abuts against the thrust fixing portion 132. In this way, in the axial flux generator 12, the gap between the first rotor 17 and the stator 16 and the gap between the second rotor 18 and the stator 16 become a predetermined distance. Thus, the axial flux generator 12 can generate electricity more efficiently.

[0046] Figure 3B 1 is a perspective view showing another embodiment of the piston portion 21 of the power unit 10. Here, only the upper portion of the thrust fixing portion 131 is shown.

[0047] The thrust fixing portion 131 is formed with an insertion hole 31 and a piston housing portion 29. The insertion hole 31 is a through hole through which the rear extension portion 154, which is a part of the aforementioned engine-side shaft 15, is inserted. The piston housing portion 29 is a hollow formed by digging the thrust fixing portion 131 at the outer portion of the insertion hole 31 into a substantially arched shape. The piston portion 21 is a substantially arched component similar to the piston housing portion 29, and is housed in the piston housing portion 29. On paper, the frontward surface of the piston portion 21 abuts against the aforementioned first thrust abutting portion 23 to apply force.

[0048] The piston portion 21 is applied with pressure from a hydraulic circuit 30. The hydraulic circuit 30 is a circuit for supplying oil from the aforementioned oil pump to the engine-side shaft 15. The piston portion 21 has an arched shape, so that it can apply force to the aforementioned engine-side shaft 15 more stably.

[0049] Figure 4 It is an enlarged cross-sectional view showing another embodiment of the power unit 10 . Figure 4 The basic structure of the power unit 10 shown is the same as that shown in FIG. 1 , but the structure of the engine 39 is different.

[0050] The engine 39 includes a first engine section 40 and a second engine section 41. The first engine section 40 and the second engine section 41 are disposed opposite to each other. In addition, an axial flux generator 12 is disposed corresponding to each of the first engine section 40 and the second engine section 41. With this configuration, the power generation amount of the power unit 10 as a whole can be increased.

[0051] The first engine unit 40 includes a first piston 43 that reciprocates, a first crankshaft 42 that converts the reciprocating motion of the first piston 43 into a rotational motion, and a first connecting rod 44 that rotatably couples the first piston 43 and the first crankshaft 42 .

[0052] The second engine section 41 includes a second piston 46 that reciprocates, a second crankshaft 45 that converts the reciprocating motion of the second piston 46 into a rotational motion, and a second connecting rod 47 that rotatably couples the second piston 46 and the second crankshaft 45 .

[0053] The first piston 43 of the first engine section 40 and the second piston 46 of the second engine section 41 share the combustion chamber 48. In other words, the first piston 43 and the second piston 46 reciprocate inside a connected cylinder 49. Thus, by the first engine section 40 and the first piston 43 moving toward the center at the same time, a high expansion ratio of the mixed gas in the combustion chamber 48 can be obtained while reducing the stroke amount.

[0054] Although not shown here, a volume space connected from the combustion chamber 48 is formed in the engine 39, and a spark plug is arranged in the volume space. In addition, an intake port and an exhaust port (not shown here) are formed in the combustion chamber 48, and a mixed gas containing a fuel such as gasoline is introduced into the combustion chamber 48 from the intake port, and the exhaust gas after combustion is exhausted from the combustion chamber 48 to the outside through the exhaust port.

[0055] Here, the first crankshaft 42 of the first engine section 40 is integrally connected to the generator-side shaft 19 of the axial flux generator 12 . On the other hand, the second crankshaft 45 of the second engine section 41 is integrally connected to the generator-side shaft 19 of another axial flux generator 12 .

[0056] The engine 39 of the above-mentioned structure operates as follows. First, in the intake stroke, the first piston 43 and the second piston 46 move from the center to the outside inside the cylinder 49, and introduce the mixed gas, which is a mixture of fuel and air, into the inside of the cylinder 49. Next, in the compression stroke, the first piston 43 and the second piston 46 are pushed toward the center by the inertia of the rotating first crankshaft 42 and the second crankshaft 45, and the mixed gas is compressed inside the cylinder 49. Next, in the combustion stroke, the spark plug (not shown) ignites in the combustion chamber 48, so that the mixed gas is burned inside the cylinder 49, and thus the first piston 43 and the second piston 46 are pushed out to the outer end as the bottom dead center. Thereafter, in the exhaust stroke, the first piston 43 and the second piston 46 are pushed inward by the inertia of the rotating first crankshaft 42 and the second crankshaft 45, and the burned gas existing inside the cylinder 49 is discharged to the outside.

[0057] In the engine 39, the stroke can be divided by using two first pistons 43 and second pistons 46 that reciprocate inside a cylinder 49. Thus, the compression ratio of the mixed gas can be increased compared to a normal gasoline engine. In addition, since the first piston 43 and the second piston 46 are opposed to each other inside the cylinder 49, the cylinder head required in a general engine is not required, and the structure of the engine 39 is simple and lightweight. In addition, the components constituting the engine 39, namely the first piston 43 and the second piston 46, the first crankshaft 42 and the second crankshaft 45, etc., are arranged opposite to each other and operate opposite to each other. Therefore, the vibration generated from the components of the engine 39 can be offset, and the vibration generated from the entire engine 39 to the outside can be reduced. Therefore, by mounting the engine 39 of such a structure on the flying device, the flying device can be miniaturized, lightweight and low-vibration. In particular, by reducing the vibration, it is possible to prevent adverse effects on precision equipment such as the calculation control device for posture control, motor output control, and GPS sensor. In addition, it is possible to prevent the delivery goods transported by the flying device from being damaged by vibration.

[0058] Hereinafter, the invention that can be grasped from the above-mentioned present embodiment will be described in conjunction with its effects.

[0059] The power unit of the present invention is characterized in that it is provided with an engine, an axial flux generator driven by the engine, and a thrust fixing part, wherein the engine has an engine-side shaft that outputs a driving force by rotating around a rotating shaft, and the axial flux generator has: a stator; a first rotor rotatably arranged on one side of the stator; a second rotor rotatably arranged on the other side of the stator; and a generator-side shaft connected to the rotation center of the first rotor and the second rotor and continuous with the engine-side shaft, and the engine-side shaft abuts against the thrust fixing part along the rotating shaft. According to the power unit of the present invention, the engine-side shaft abuts against the thrust fixing part. As a result, the positions of the first rotor and the second rotor along the axial direction via the generator-side shaft continuous with the engine-side shaft also become predetermined positions. Therefore, the gap between the first rotor and the second rotor and the stator can be made into a predetermined length, and the power generation efficiency of the axial flux generator can be improved.

[0060] In addition, in the power unit of the present invention, it is characterized in that the engine side shaft is urged by the urging portion so as to abut against the thrust fixing portion. According to the power unit of the present invention, the engine side shaft is brought into a predetermined position by using the urging portion to urging the engine side shaft, so that the first rotor and the second rotor can be brought into predetermined positions in the axial direction under the operating condition of the power unit.

[0061] In addition, in the power unit of the present invention, the force applying part is a piston part using the hydraulic circuit of the engine. According to the power unit of the present invention, the force applying part is a piston part using the hydraulic circuit of the engine, so that the first rotor and the second rotor can be arranged at a predetermined position using the driving force of the engine.

[0062] In addition, in the power unit of the present invention, the piston portion is substantially arched in shape. According to the power unit of the present invention, the piston portion is arched in shape, so that a force can be applied to the rotating engine-side shaft more stably.

[0063] In the power unit of the present invention, the biasing part is a spring. According to the power unit of the present invention, the biasing part is a spring, so that the first rotor and the second rotor can be easily arranged at predetermined positions.

[0064] In addition, in the power unit of the present invention, it is characterized in that the engine side shaft has: a first thrust abutment portion, which is arranged at a position close to the axial flux generator; and a second thrust abutment portion, which is arranged at a position farther from the axial flux generator than the first thrust abutment portion, and the force application portion applies force to the first thrust abutment portion so that the second thrust abutment portion abuts against the thrust fixing portion. According to the power unit of the present invention, the second thrust abutment portion of the engine side shaft abuts against the thrust fixing portion, so that the engine side shaft can be fixed at a specified position when the engine is running. Thereby, the first rotor and the second rotor connected to the engine side shaft can be at a specified position in the axial direction.

[0065] In addition, in the power unit of the present invention, it is characterized in that the first thrust abutment portion and the second thrust abutment portion are portions where the engine side shaft is partially enlarged in diameter. According to the power unit of the present invention, the first thrust abutment portion and the second thrust abutment portion are enlarged diameter portions, so that the rotating engine side shaft can be effectively pressed in the axial direction when the power unit is running.

[0066] Furthermore, the power unit of the present invention is characterized in that it comprises an engine, an axial flux generator driven by the engine, and a thrust fixing portion, wherein the engine has an engine-side shaft that outputs a driving force by rotating around a rotating shaft, the axial flux generator has a stator, a rotor arranged near the stator, and a generator-side shaft connected to the rotation center of the rotor and continuous with the engine-side shaft, the engine-side shaft abuts against the thrust fixing portion along the rotating shaft, the engine-side shaft is urged by a force applying portion so as to abut against the thrust fixing portion, the engine-side shaft has: a first thrust abutting portion arranged at a position close to the axial flux generator; and a second thrust abutting portion arranged at a position farther from the axial flux generator than the first thrust abutting portion, the force applying portion abuts against the first thrust abutting portion and applies force so that the second thrust abutting portion abuts against the thrust fixing portion. According to the power unit of the present invention, the engine-side shaft abuts against the thrust fixing portion. Thus, the positions of the first rotor and the second rotor along the axial direction are also predetermined via the generator side shaft continuous with the engine side shaft. Therefore, the gaps between the first rotor and the second rotor and the stator can be made into predetermined lengths, and the power generation efficiency of the axial flux generator can be improved.

[0067] Although the embodiments of the present invention have been described above, the present invention is not limited thereto and can be modified without departing from the gist of the present invention. In addition, the above-mentioned embodiments can be combined with each other.

[0068] The power unit 10 can be applied to a flying device. Specifically, the power unit 10 drives the motor, and the thrust generated by the rotational force of the motor rotates the rotor, so that the body floats. The flying device of this structure is also called a series hybrid drone.

[0069] Description of Reference Numerals

[0070] 10 Power Unit

[0071] 11 Engine

[0072] 12 Axial Flux Generator

[0073] 131 Thrust fixing part

[0074] 132 Thrust fixing part

[0075] 14 Rotation axis

[0076] 15 Engine side shaft

[0077] 151 Sales Department

[0078] 152 Arm

[0079] 153 Front extension

[0080] 154 Rear extension

[0081] 16 Stator

[0082] 17 First rotor

[0083] 18 Second rotor

[0084] 19 Generator side shaft

[0085] 20 Force application part

[0086] 21 Piston

[0087] 22 Spring

[0088] 23 First thrust contact portion

[0089] 24 Second thrust contact portion

[0090] 25 Shell

[0091] 26 Piston

[0092] 27 Connecting rod

[0093] 28 Stator fixing part

[0094] 29 Piston storage unit

[0095] 30 Hydraulic circuit

[0096] 31 Insert hole

[0097] 39 Engine

[0098] 40 First Engine Division

[0099] 41 Second Engine Unit

[0100] 42 First crankshaft

[0101] 43 First Piston

[0102] 44 First connecting rod

[0103] 45 Second crankshaft

[0104] 46 Second piston

[0105] 47 Second connecting rod

[0106] 48 Combustion Chamber

[0107] 49 Cylinder

Claims

1. A power unit, characterized in that: An engine, an axial flux generator driven by the engine, and a thrust fixing portion are provided. The engine has an engine-side shaft that outputs driving force by rotating around a rotation shaft. The axial flux generator comprises: a stator; a first rotor rotatably disposed on one side of the stator; a second rotor rotatably disposed on the other side of the stator; and a generator-side shaft connected to the rotation centers of the first rotor and the second rotor and continuous with the engine-side shaft. The engine-side shaft abuts against the thrust fixing portion along the rotation axis.

2. The power unit according to claim 1, characterized in that: The engine-side shaft is urged by the urging portion to come into contact with the thrust fixing portion.

3. The power unit according to claim 2, characterized in that: The urging portion is a piston portion using a hydraulic circuit of the engine.

4. The power unit according to claim 3, characterized in that: The piston portion has a generally dome-like shape.

5. The power unit according to claim 2, characterized in that: The force applying part is a spring.

6. The power unit according to claim 2, characterized in that: The engine-side shaft includes: a first thrust abutment portion disposed at a position close to the axial flux generator; and a second thrust abutment portion disposed at a position farther from the axial flux generator than the first thrust abutment portion. The urging portion urges the first thrust abutting portion so that the second thrust abutting portion abuts against the thrust fixing portion.

7. The power unit according to claim 6, characterized in that: The first thrust abutment portion and the second thrust abutment portion are portions where the diameter of the engine-side shaft is partially enlarged.

8. A power unit, characterized in that: An engine, an axial flux generator driven by the engine, and a thrust fixing portion are provided. The engine has an engine-side shaft that outputs driving force by rotating around a rotation shaft. The axial flux generator includes a stator, a rotor disposed near the stator, and a generator-side shaft connected to the rotation center of the rotor and continuous with the engine-side shaft. The engine side shaft abuts against the thrust fixing portion along the rotation axis, The engine side shaft is urged by the urging portion so as to abut against the thrust fixing portion. The engine-side shaft has: a first thrust abutment portion disposed at a position close to the axial flux generator; and a second thrust abutment portion disposed at a position farther from the axial flux generator than the first thrust abutment portion. The force applying portion abuts against the first thrust abutting portion to apply force, so that the second thrust abutting portion abuts against the thrust fixing portion.

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