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US-12624666-B2 - Power unit

US12624666B2US 12624666 B2US12624666 B2US 12624666B2US-12624666-B2

Abstract

A power unit includes an engine and a transmission mechanism, which is integrated with the engine, for transfer of power from the engine. The engine includes a crankshaft which converts a reciprocal motion of a piston to produce a rotary motion, a crankcase supporting the crankshaft, a cylinder extending from the crankcase so as to protrude in a reciprocating direction of the piston, and a cylinder head coupled to a protruding end of the cylinder. The transmission mechanism includes an output shaft arranged at one side of the crankshaft in an axial direction of the crankshaft to provide, as an output, rotational power from the crankshaft. The output shaft is positioned to a side of the crankshaft that faces the cylinder head with respect to the reciprocating direction and is positioned so as to overlap with the cylinder or the cylinder head when viewed in the axial direction.

Inventors

  • Kyohei IZUMI
  • Yuji Hida
  • Jun Takagi

Assignees

  • KAWASAKI MOTORS, LTD.

Dates

Publication Date
20260512
Application Date
20240313
Priority Date
20230314

Claims (16)

  1. 1 . A power unit comprising: an engine including a piston, a crankshaft which converts a reciprocal motion of the piston to produce a rotary motion, a crankcase supporting the crankshaft, a cylinder extending from the crankcase so as to protrude in a reciprocating direction of the piston, and a cylinder head coupled to a protruding end of the cylinder; a transmission mechanism integrated with the engine for transfer of power from the engine, the transmission mechanism including an output shaft arranged at one side of the crankshaft in an axial direction of the crankshaft to provide, as an output, rotational power from the crankshaft; and a gear casing cover coupled to the cylinder at one end portion thereof in the axial direction of the crankshaft, wherein the output shaft is positioned to a side of the crankshaft that faces the cylinder head with respect to the reciprocating direction of the piston and is positioned so as to overlap with the cylinder or the cylinder head when viewed in the axial direction of the crankshaft, a gear housing space is defined by the gear casing cover and the one end portion of the cylinder in the axial direction of the crankshaft, and the transmission mechanism is arranged within the gear housing space.
  2. 2 . The power unit as claimed in claim 1 , wherein the output shaft is positioned to be situated within a dimension defined by the cylinder in a perpendicular direction that is a direction perpendicular to both the axial direction of the crankshaft and the reciprocating direction of the piston.
  3. 3 . The power unit as claimed in claim 2 , wherein the engine includes an air intake valve, an air intake valve operation control mechanism which operates the air intake valve, an exhaust valve, and an exhaust valve operation control mechanism which operates the exhaust valve, wherein the air intake valve operation control mechanism includes an air intake-side cam shaft and a cam provided on the air intake-side cam shaft to open and close the air intake valve, the exhaust valve operation control mechanism includes an exhaust-side cam shaft and a cam provided on the exhaust-side cam shaft to open and close the exhaust valve, and the output shaft defining an axis which is situated intermediate between an axis of the air intake-side cam shaft and an axis of the exhaust-side cam shaft in the perpendicular direction.
  4. 4 . The power unit as claimed in claim 3 wherein at least a portion of the output shaft is situated centrally within the dimension defined by the cylinder in the perpendicular direction.
  5. 5 . The power unit as claimed in claim 1 , wherein the transmission mechanism transfers power from the engine to the output shaft with a changed speed.
  6. 6 . The power unit as claimed in claim 5 , wherein the transmission mechanism comprises a speed reducer which reduces a speed of power from the engine.
  7. 7 . The power unit as claimed in claim 1 , wherein the transmission mechanism includes: a power transmission rotational member which rotates in an interlocking manner with the crankshaft; and a casing fixed to the cylinder and enclosing the power transmission rotational member, and the output shaft partially forming the power transmission rotational member.
  8. 8 . The power unit as claimed in claim 7 , further comprising: casing-side bearing rotatably supporting the power transmission rotational member on the casing; and cylinder-side bearings rotatably supporting the power transmission rotational member on the cylinder.
  9. 9 . The power unit as claimed in claim 8 , wherein the casing includes a rib formed thereon, which reinforces the casing.
  10. 10 . The power unit as claimed in claim 9 , wherein the rib extends in a radial direction of the power transmission rotational member and comprises a plurality of ribs spaced apart in a circumferential direction of the power transmission rotational member.
  11. 11 . The power unit as claimed in claim 7 , wherein the cylinder includes a casing mount to which the casing is coupled, and a portion of the casing mount protrudes towards the cylinder head in the reciprocating direction of the piston beyond a mating interface between the cylinder and the cylinder head.
  12. 12 . The power unit as claimed in claim 1 , wherein the output shaft coaxially couples to a rotary element.
  13. 13 . A propeller aircraft comprising the power unit as claimed in claim 12 , wherein the power unit is disposed in an airframe of the propeller aircraft, the crankshaft is disposed along with a propeller shaft in a direction aligned with a centerline, in a widthwise direction of a fuselage, of the propeller aircraft, and the power unit is disposed such that the reciprocating direction for the piston is aligned with a vertical direction and an axis defined by the cylinder is located on the centerline, in the widthwise direction of the fuselage, of the propeller aircraft, when wings of the propeller aircraft are positioned horizontally.
  14. 14 . The power unit as claimed in claim 1 , wherein the output shaft is supported by the cylinder through a bearing.
  15. 15 . The power unit as claimed in claim 1 , wherein the transmission mechanism includes an input-side gear provided on the crankshaft, and the crankshaft is supported by the gear casing cover through a first bearing at one end portion thereof in the axial direction of the crankshaft.
  16. 16 . The power unit as claimed in claim 1 , wherein the transmission mechanism includes an input-side gear provided on the crankshaft, the crankshaft is supported by the gear casing cover through a first bearing at one end portion thereof in the axial direction of the crankshaft, and the output shaft is supported by the cylinder through a second bearing.

Description

CROSS REFERENCE TO THE RELATED APPLICATION This application is based on and claims Convention priority to Japanese patent applications No. 2023-039656, filed Mar. 14, 2023 and No. 2023-199262, filed Nov. 24, 2023, the entire disclosures of which are herein incorporated by reference as a part of this application. BACKGROUND OF THE INVENTION Field of the Invention The present disclosure relates to a power unit including an engine and a transmission mechanism, which is integrated with the engine, for transfer of power from the engine. Description of Related Art Some vehicles employ, as a power source therefor, a power unit including an engine and a transmission mechanism, which is integrated with the engine, for transfer of power from the engine (for example, JP H03-009027 A). A principal shaft of the transmission mechanism in this power unit is coupled to, for example, a propeller, an impeller, or a wheel. Reduction in size is crucial for a power unit like the one in JP H03-009027 A because it involves integration of the transmission mechanism into the engine. SUMMARY OF THE INVENTION The present disclosure provides a power unit with a reduced size. A power unit, according to a first aspect of the present disclosure, comprises an engine and a transmission mechanism which is integrated with the engine for transfer of power from the engine. The engine includes a piston, a crankshaft which converts a reciprocal motion of the piston to produce a rotary motion, a crankcase supporting the crankshaft, a cylinder extending from the crankcase so as to protrude in a reciprocating direction of the piston, and a cylinder head coupled to a protruding end of the cylinder. The transmission mechanism includes an output shaft arranged at one side of the crankshaft in an axial direction of the crankshaft to provide, as an output, rotational power from the crankshaft. The output shaft is positioned to a side of the crankshaft that faces the cylinder head with respect to the reciprocating direction of the piston and is positioned so as to overlap with the cylinder or the cylinder head when viewed in the axial direction of the crankshaft. A power unit according to the present disclosure can minimize protrusion of a transmission mechanism and an output shaft thereof from an engine in a direction which is perpendicular to both an axial direction of a crankshaft and a reciprocating direction for a piston. As a result, a power unit having a reduced size can be provided for. Any combinations of at least two features disclosed in the claims and/or the specification and/or the drawings should also be construed as encompassed by the present disclosure. Especially, any combinations of two or more of the claims should also be construed as encompassed by the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS The present disclosure will be more clearly understood from the following description of preferred embodiments made by referring to the accompanying drawings. However, the embodiments and the drawings are given merely for the purpose of illustration and explanation, and should not be used to delimit the scope of the present disclosure, which scope is to be delimited by the appended claims. In the accompanying drawings, alike numerals are assigned to and indicate alike parts throughout the different figures, and: FIG. 1 shows a side view of the right of a power unit in accordance with a first embodiment of the present disclosure; FIG. 2 shows a side view of the left of the power unit; FIG. 3 shows a front elevational view of the power unit; FIG. 4 shows a rear view of the power unit; FIG. 5 shows a side view of the left of the power unit with a gear cover removed; FIG. 6 shows a horizontal cross-sectional view of the power unit; and FIG. 7 shows a cross-sectional view of the power unit, illustrating a crankshaft and a transmission mechanism. DESCRIPTION OF EMBODIMENTS What follows is a description of preferred embodiments of the present disclosure made with reference to FIGS. 1 to 7. An engine E in the instant embodiment is a reciprocating engine and is used, for example, in an aircraft having a fuselage and a propeller disposed on a leading end of the fuselage. The engine E in this case is received within the fuselage and produces power to be transferred to the propeller. This is merely one of the non-limiting examples of the use of the engine E; for instance, the engine E can also be used as a power source for a ship. The engine E can also be used as a power source for wheeled vehicles including two-wheeled and four-wheeled vehicles. In the discussions that follow, the term “widthwise direction WD” refers to a direction in or along which a crankshaft 2 of the engine E extends. Thus, the widthwise direction WD coincides with an “axial direction of a crankshaft.” With respect to the widthwise direction WD, a “widthwise inside” refers to a side facing towards a center of the engine E in the widthwise direction, whereas a “widthwise out