Air-cooled overhead-valve engine

Abstract

An air-cooled overhead-valve engine comprises a cooling fan connecting to one end portion of crankshaft and surrounding with fan casing, a combustion air intake port provided in the direction of downstream side of cooling air, and push rods for driving a cam arranged in opposite side to said intake port with relate to a center of cylinder. The engine can be used suitable to power lawn mowers and the like.

What is claimed is: 
     
       1. In an air-cooled overhead-valve internal combustion engine, said engine being composed of a crankcase with a crankshaft, a cylinder block with a cylinder head and a combustion chamber mounted in said crankcase, at least a pair of intake and exhaust valves installed in intake and exhaust ports formed in said cylinder head, a valve drive system mounted adjacent to said cylinder block for driving said intake and exhaust valves through cam-driven push rods, an intake pipe connected at one end thereof to said intake port and at its opposite end to an air cleaner and a carburetor, an exhaust duct connected at one end thereof to said exhaust port, a flywheel joined to said crankshaft at the other end of the output side end of said crankshaft and a cooling fan mounted on said flywheel, the improvements wherein said cooling fan is housed, together with said crankcase and flywheel, in a fan casing having a pair of inlet and outlet openings bored in opposite walls thereof, said inlet opening is located at the flywheel side of said crankshaft, while said outlet opening is located at the opposite side of said crankshaft from said flywheel, and said cam-driven push rods are located in said crankcase on that side of said cylinder block far remote from wherein said intake pipe is connected to said intake port, said cooling fan being mounted in said fan casing in such a manner that the cooling air from said cooling fan is allowed to flow in a direction substantially parallel with the axis of said crankshaft, along the surface of said cylinder block and cylinder head. 
     
     
       2. An engine as set forth in claim 1, wherein said intake port is located adjacent to that side of said cylinder block nearer said cooling fan and said intake pipe is laid substantially perpendicularly with the axis of said crankshaft while said exhaust port is located adjacent to that side of said cylinder block far remote from said cooling fan, the axis of said exhaust port extending substantially parallel with the axis of said crankshaft. 
     
     
       3. An engine as set forth in 2, wherein said inlet and exhaust ports are located in said cylinder block along said crankshaft, between said inlet and outlet openings of said fan casing that that said inlet and exhaust ports are directly exposed to the streams of cooling air from said cooling fan. 
     
     
       4. An engine as set forth in claim 1, wherein said inlet and exhaust ports are located in said cylinder block along said crankshaft, between said inlet and outlet openings of said fan casing so that said inlet and exhaust ports are directly exposed to the streams of cooling air from said cooling fan. .Iadd. 
     
     
       5.  In an air-cooled overhead-valve internal combustion engine, said engine being composed of a crankcase with a crankshaft, a cylinder block with a cylinder head and a combustion chamber mounted in said crankcase, at least a pair of intake and exhaust valves installed in intake and exhaust ports formed in said cylinder head, a valve drive system mounted adjacent to said cylinder block for driving said intake and exhaust valves through cam-driven push rods, an intake pipe connected at one end thereof to said intake port and at its opposite end to an air cleaner and a carburetor, an exhaust pipe connected at one end thereof to said exhaust port, a flywheel joined to said crankshaft at the other end of the output side end of said crankshaft and a cooling fan mounted on said flywheel, the improvements wherein said cooling fan is housed, together with said crankcase and flywheel, in a fan casing having a pair of inlet and outlet openings bored in opposite walls thereof, said inlet opening is located at the flywheel side of said crankshaft, while said outlet opening is located at the opposite side of said crankshaft from said flywheel, and said cam-driven push rods are located in said crankcase on that side of said cylinder block far remote from where said intake pipe is connected to said intake port, said cooling fans being mounted in said fan casing in such a manner that the cooling air from said cooling fan is allowed to flow in a direction substantially parallel with the axis of said crankshaft, along the surface of said cylinder block and cylinder head, an air inlet port formed in said fan casing adjacent said cylinder head upstream with respect to the cooling air flow and at a position where the dynamic pressure due to said fan is low, said inlet port being connected to said air cleaner, and a spark plug mounted in said cylinder head in a space surrounded by said intake and exhaust ports and said push rods. .Iaddend. .Iadd. 
     
     
       6.  An engine as set forth in claim 5, wherein said intake port is located adjacent to that side of said cylinder block nearer said cooling fan and said intake pipe is laid substantially perpendicularly with the axis of said crankshaft while said exhaust port is located adjacent to that side of said cylinder block far remote from said cooling fan, the axis of said exhaust port extending substantially parallel with the axis of said crankshaft. .Iaddend. .Iadd. 
     
     
       7.  An engine as set forth in claim 6, wherein said intake and exhaust ports are located in said cylinder head along said crankshaft, between said inlet and outlet openings of said fan casing so that said intake and exhaust ports are directly exposed to the streams of cooling air from said cooling fan. .Iaddend. .Iadd. 
     
     
       8.  An engine as set forth in claim 5, wherein said intake and exhaust ports are located in said cylinder head along said crankshaft, between said intake and outlet openings of said fan casing so that said inlet and exhaust ports are directly exposed to the streams of cooling air from said cooling fan. .Iaddend.