JP6423637B2 - Natural lubrication structure of OHV engine - Google Patents

Description

  The present invention relates to a natural oil supply structure for an OHV engine.

  FIG. 2 shows an outline of a conventional OHV engine (an engine that opens and closes a valve by an overhead valve system). Reference numeral 1 in FIG. 3 is a piston that slidably moves up and down in the cylinder liner 2, 4 is a cylinder head, 5 is an engine valve mounted in the cylinder head 4, 6 is a port, and 7 is the cylinder. A cam disposed at a position lower than the head 4 and rotated by driving the engine, 8 is a push rod that periodically slides up and down with the lower end of the cam 7, and 9 is a rocker shaft whose base end is pushed up by the push rod 8. A rocker arm 11 that tilts about 10 is drilled on the cylinder head 4 side to pass the push rod 8. An upper push rod hole 12 indicates a lower push rod hole formed on the cylinder block 1 side for passing the push rod 8, and a base end of the rocker arm 9 is pushed by the cam 7 via the push rod 8. When pushed up, both engine valves 5 are pushed down at the same time via the valve bridge 13 by the tip of the rocker arm 9 tilted about the rocker shaft 10 and opened, and the port 6 is opened in the cylinder liner 2. Intake air is taken in and exhaust air is sent out.

  Many of these types of OHV engines continue to follow the design of more than 20 years ago. As shown in the figure, an annular oil passage is formed in the outer peripheral portion on the upper side of the cylinder liner 2 having a large heat load. 14 is formed, and oil is guided from another oil passage 15 having a higher pressure to the oil passage 14 and extracted to the outlet pipe 16 so that the upper side of the cylinder liner 2 is actively cooled by forced oil supply. However, the necessity of cooling the upper side of the cylinder liner 2 with forced oiling is decreasing due to the improvement of the cooling performance accompanying the increase in the flow rate of the water cooling system (the capacity increase of the water pump) in recent years.

  In addition, as the prior art document information that has been disclosed about the structure of a general OHV engine and the lubrication of a valve operating system, there is the following Patent Document 1.

JP-A-10-259706

  However, even though the necessity of cooling the upper side of the cylinder liner 2 with forced oiling is diminished, if the cylinder block 1 and the cylinder liner 2 are fitted with a gap, the outer peripheral portion on the upper side of the cylinder liner 2 is moved to. Fretting wear occurs between the cylinder liner 2 and the cylinder block 1 (surface wear caused by repeated reciprocation of minute reciprocating slips between two contacting objects). There was a problem.

  That is, the oil supply to the upper side of the cylinder liner 2 plays a role not only in the cooling of this part but also in the lubrication aspect. If the conventional forced oil supply is completely abolished, the fretting wear as described above occurs. For this reason, the conventional design has been followed as it is, but the structure for carrying out unnecessary forced oiling is not preferable due to high cost.

  The present invention has been made in view of the above circumstances, and forcibly lubricates the upper side of the cylinder liner by providing a natural lubrication structure for an OHV engine that can perform natural lubrication on the upper side of the cylinder liner at a low cost by simple processing. It is an object of the present invention to prevent fretting wear between a cylinder liner and a cylinder block while reducing costs by eliminating the necessary structure.

The present invention is a natural oiling structure for an OHV engine in which an engine valve is opened through a push rod and a rocker arm by a cam disposed at a position lower than a cylinder head, and the push rod is passed through the structure. Therefore, the lower push rod hole drilled on the cylinder block side is inclined so as to be separated from the cylinder liner as it goes downward, and obliquely downward from the cylinder side on the inner peripheral surface of the upper portion of the lower push rod hole. An oil passage is bored toward the outer circumferential surface of the cylinder liner, and the outer circumferential surface of the cylinder liner that is above the position of the piston pin at the top dead center is made the oil supply position by the oil passage, and is bored on the cylinder head side. Flowed down from the upper surface of the cylinder head to the lower push rod hole through the upper push rod hole It is characterized in that the part of yl is configured to naturally flows down to the oil passage.

  That is, in the OHV engine, there is a system in which oil used for lubricating the valve train in the cylinder head flows from the upper surface of the cylinder head to the lower push rod hole through the upper push rod hole and returns to the oil pan. Since it already exists, if a part of the oil that has flowed down to the lower push rod hole is distributed to the oil passage and allowed to flow naturally toward the outer peripheral surface of the cylinder liner, the space between the cylinder liner and the cylinder block is reduced. Lubricating can greatly suppress fretting wear.

  As a result, for OHV engines with sufficiently high water cooling performance, it is possible to abolish the structure required to forcibly lubricate the upper side of the cylinder liner as in the past, greatly reducing processing costs and components. On the other hand, the oil passage can be processed at low cost by a simple process using the existing lower push rod hole in the cylinder block of the OHV engine.

Also, since the outer peripheral surface of the cylinder liner to be above the position of the piston pin at the top dead center is set to the oil supply position, fretting act largely side thrust of the piston between the cylinder liner and the cylinder block Lubrication can be performed to cover most of the range in which wear is likely to occur , and fretting wear between the cylinder liner and the cylinder block can be more effectively prevented.

  According to the natural oil supply structure of the OHV engine of the present invention described above, various excellent effects as described below can be obtained.

  (I) According to the invention described in claim 1 of the present invention, natural oil supply to the upper side of the cylinder liner can be realized at a low cost by simple processing, so that the cooling performance of the water cooling system is sufficiently high. By applying this, the structure required to forcibly lubricate the upper side of the cylinder liner can be abolished, and the fretting wear between the cylinder liner and the cylinder block is reduced by the above-mentioned natural lubrication while reducing costs. It can be prevented by lubrication.

According to the invention described in claim 1, (II) the present invention, to cover most likely Scope occur fretting wear and acts largely side thrust of the piston between the cylinder liner and the cylinder block Lubrication can be performed, and fretting wear between the cylinder liner and the cylinder block can be more effectively prevented.

It is sectional drawing which shows an example of the form which implements this invention. It is sectional drawing which shows a prior art example.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows an example of an embodiment for carrying out the present invention. The parts denoted by the same reference numerals as those in FIG. 2 represent the same thing, and are arranged at a position lower than the cylinder head 4 in this embodiment. The natural oil supply structure of the OHV engine, in which the valve 7 is opened by the cam 7 via the push rod 8 and the rocker arm 9, is drilled on the cylinder block 1 side to pass the push rod 8. An oil passage 17 is bored from the upper portion of the lower push rod hole 12 toward the outer peripheral surface of the cylinder liner 2 obliquely below, and the cylinder head 4 is inserted through the upper push rod hole 11 bored on the cylinder head 4 side. A part of the oil that has flowed down from the upper surface to the lower push rod hole 12 is allowed to flow naturally into the oil passage 17.

  That is, in the OHV engine, the oil used for lubricating the valve operating system in the cylinder head 4 flows down from the upper surface of the cylinder head 4 to the lower push rod hole 12 through the upper push rod hole 11 to the oil pan. A return path already exists, and a part of the oil that has flowed down to the lower push rod hole 12 can be distributed to the oil passage 17 and allowed to flow naturally toward the outer peripheral surface of the cylinder liner 2.

  Here, the upper push rod hole 11 and the lower push rod hole 12 are slightly inclined so as to be separated from the cylinder liner 2 in the downward direction, and the oil from the upper surface of the cylinder head 4 flows into the upper push rod hole 11. The oil passage 17 is also preferably formed on the cylinder liner 2 side on the inner peripheral surface of the lower push rod hole 12 because the oil flows down along the cylinder liner 2 side on the inner peripheral surface of the lower push rod hole 12. .

  Further, when the oil passage 17 is formed, the outer peripheral surface of the cylinder liner 2 on the upper side from the position of the piston pin P at the top dead center is lubricated so as to cover a range where the side thrust of the piston 3 is large. It is good to set as a position.

  Thus, as described above, if a part of the oil that has flowed down to the lower push rod hole 12 is distributed to the oil passage 17 and allowed to flow naturally toward the outer peripheral surface of the cylinder liner 2, the cylinder liner 2 and the cylinder block It is necessary to lubricate the upper side of the conventional cylinder liner 2 with respect to an OHV engine having a sufficiently high cooling performance in a water-cooling system, since it is possible to significantly reduce fretting wear. Can be abolished (for example, the oil passages 14 and 15 and the outlet pipe 16 in FIG. 2), and the processing cost and components can be greatly reduced. On the other hand, the cylinder block of the OHV engine The oil passage 17 can be processed at low cost by simple processing using the existing lower push rod hole 12 in FIG.

  Therefore, according to the above-described embodiment, natural lubrication to the upper side of the cylinder liner 2 can be realized at low cost by simple processing. Therefore, the cylinder liner 2 can be applied to an OHV engine having a sufficiently high cooling performance of the water cooling system. The structure necessary for forcibly lubricating the upper side can be eliminated, and thereby fretting wear between the cylinder liner 2 and the cylinder block 1 can be prevented by lubrication by natural lubrication while reducing costs. be able to.

Here, particularly in the present embodiment, the oil passage 17 is formed so that the outer peripheral surface of the cylinder liner 2 above the position of the piston pin P at the top dead center is the oil supply position. 2 and the cylinder block 1 can be lubricated so as to cover most of the range in which the side thrust of the piston 3 between the cylinder block 1 and the fretting wear is likely to occur . It is possible to more effectively prevent fretting wear in the meantime.

  In addition, the natural oil supply structure of the OHV engine of the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made without departing from the gist of the present invention.

1 Cylinder Block 2 Cylinder Liner 4 Cylinder Head 7 Cam 8 Push Rod 9 Rocker Arm 11 Upper Push Rod Hole 12 Lower Push Rod Hole 17 Oil Passage P Piston Pin

Claims (1)

A natural oiling structure for an OHV engine in which an engine valve is opened via a push rod and a rocker arm by a cam disposed at a position lower than the cylinder head, and a cylinder block for passing the push rod. The lower push rod hole drilled on the side is inclined so as to be separated from the cylinder liner as it goes downward, and the outer periphery of the cylinder liner obliquely downward from the cylinder side on the inner peripheral surface of the upper portion of the lower push rod hole Upper push rod hole drilled on the cylinder head side with an oil passage drilled toward the surface and the outer circumferential surface of the cylinder liner above the position of the piston pin at the top dead center as the oil passage. The oil that has flowed down from the upper surface of the cylinder head to the lower push rod hole through the There natural lubrication structure for OHV engine, characterized in that it is configured to naturally flows down to the oil passage.

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