Internal combustion engine of saddle riding vehicle

Patent metadata

Field	Value
Publication number	US-10655512-B2
Application number	US-201815914681-A
Country	US
Kind code	B2
Filing date	Mar 7, 2018
Priority date	Mar 30, 2017
Publication date	May 19, 2020
Grant date	May 19, 2020

Abstract

In a valve train of an internal combustion engine, an input sprocket mounting portion is provided on one end of an exhaust camshaft, and a valve operating cam portion is formed on the other end of the camshaft. A decompression shaft of a decompression device is inserted in a decompression shaft hole, which is formed from the input sprocket mounting portion toward the valve operating cam portion. The decompression shaft hole is formed at a position offset from an axis of the camshaft. A camshaft inner oil passage is formed in the camshaft to extend from one end toward the other end of the camshaft in parallel arrangement to the decompression shaft hole to supply lubricant from the bearing journal portion to the bearing journal portion. The above arrangement makes it possible to supply a sufficient amount of lubricant oil to slide portions of the valve train of a saddle riding vehicle.

First claim

The invention claimed is:

1. An internal combustion engine of a saddle riding vehicle, wherein the engine has a valve train in which an exhaust camshaft rotatably mounted on a cylinder head forms a portion of an oil supply passage to the valve train, the exhaust camshaft having a bearing journal portion on one side thereof and another bearing journal portion on another side, and the valve train includes a centrifugal decompression device making use of rotation of the exhaust camshaft, wherein:
the valve train includes one bearing journal portion formed on one end of the exhaust camshaft and supported by the cylinder head, and another bearing journal portion on another end of the camshaft;
an input sprocket mounting portion for mounting thereon an input sprocket for driving the camshaft is formed on the one end of the camshaft, while a valve operating cam portion is formed on the other end of the camshaft;
a decompression shaft hole receiving rotatably therein a decompression shaft of the decompression device is formed in the camshaft from the input sprocket mounting portion toward the valve operating cam portion;
the decompression shaft hole is formed at a position offset from an axis of the camshaft;
a camshaft inner oil passage is formed in the camshaft to supply a lubricant to the bearing journal portion on the one side and to the bearing journal portion on the other side, the camshaft inner oil passage extending from the one end to the other end of the camshaft in parallel arrangement to the decompression shaft hole;
a decompression weight swing restricting portion for restricting rotation of a decompression weight integrally provided on the decompression shaft is disposed on one end of the camshaft at a position offset from the axis of the camshaft; and
a decompression shaft removal preventing threaded portion is formed in the decompression weight swing restricting portion at a position parallel to the decompression shaft hole and offset from the axis of the camshaft, the decompression shaft removal preventing threaded portion being threadedly engaged with a bolt for preventing removal of the decompression shaft.

2. The internal combustion engine of a saddle riding vehicle according to claim 1 , wherein:
the camshaft has a first exhaust cam between the bearing journal portion on the one side and the bearing journal portion on the other side, and a second exhaust cam axially outside the bearing journal portion on the other side;
the decompression device includes a decompression pin for movements to project from and retract into the second exhaust cam on the camshaft in connection with rotation of the decompression shaft;
the decompression shaft hole extends axially to an area between the bearing journal portion on the one side and the bearing journal portion on the other side; and
the camshaft inner oil passage is arranged on a side opposite to the decompression shaft removal preventing threaded portion with respect to the decompression pin, as viewed along the axis of the camshaft.

3. The internal combustion engine of a saddle riding vehicle according to claim 2 , wherein:
the bearing journal portion on the one side has a diameter greater than a diameter of the bearing journal portion on the other side; and
the decompression shaft removal preventing threaded portion is formed as a hole axially extending in the region of the bearing journal portion on the one side.

4. The internal combustion engine of a saddle riding vehicle according to claim 3 , wherein a center hole portion is formed in the decompression weight swing restricting portion of the camshaft, the center hole portion being a reference portion in machining the camshaft.

5. The internal combustion engine of a saddle riding vehicle according to claim 4 , wherein:
a tightening member accommodating hole is formed in a surface of the cylinder head, facing a cylinder head cover, the tightening member accommodating hole being for insertion and accommodation of a tightening member for fastening a crankcase and a cylinder body of the engine to each other;
the bearing journal portion on the one side is rotatably supported by a head-side journal receiving portion disposed above the tightening member accommodating hole of the cylinder head and by a holder-side journal receiving portion formed on a camshaft holder-positioned above the camshaft; and
the camshaft inner oil passage is in communication with the tightening member accommodating hole of the cylinder head.

6. The internal combustion engine of a saddle riding vehicle according to claim 5 , wherein:
the camshaft has thereon a flange portion for restricting an axial thrust; and
an oil passage leading into the camshaft is provided adjacent to the flange portion.

Assignees

• Honda Motor Co Ltd

Inventors

• Okada Nozomi
• Hoi Yosuke
• Kisaichi Toru

Classifications

• F01M2001/064

  Camshaft with passageways · CPC title

• F01M9/103

  of valve stem and guide · CPC title

• F01M9/102

  of camshaft bearings · CPC title

• F01M9/105 Primary

  using distribution conduits · CPC title