JPH08246839A - Crankcase ventilation passage - Google Patents

Abstract

(57) [Summary] [Purpose] In an engine to which high vibration acceleration is applied,
Provided is an improved crankcase ventilation passage to prevent lubricant from entering. A crankcase ventilation passage opening 19a is provided at the bottom of a recess 20 formed in the side surface of a cam gear 16 for interlocking the camshaft 9 with the crankshaft 4. In particular, the wall 25 may be provided upright at a position adjacent to the advancing side of the opening in the rotation direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crankcase ventilation passage, and more particularly to a crankcase ventilation passage for an engine suitable for powering equipment having high vibration acceleration.

[0002]

2. Description of the Related Art Conventionally, a two-cycle engine has been widely used as a power source for portable equipment because it is small and lightweight and can obtain a relatively high output. The 4-cycle engine tends to be used because it is relatively easy. In this four-cycle engine, for example, the inside of the crankcase is communicated with an air cleaner through a ventilation passage formed in a camshaft, so that fluctuations in the crankcase internal pressure due to movement of the piston are alleviated.

[0003]

By the way, in a rammer engine that pressurizes the ground, the lubricating oil splashes violently in the crankcase due to high vibration acceleration, so that the lubricating oil easily enters the crankcase ventilation passage. As a result of mixing the lubricating oil in the mixture, there is a tendency that white smoke is ejected from the exhaust pipe.

The present invention has been devised in order to eliminate such disadvantages of the prior art, and its main purpose is to:
It is an object of the present invention to provide an improved crankcase ventilation passage so that lubricating oil is less likely to enter in an engine to which high vibration acceleration is applied.

[0005]

According to the present invention, such an object is such that the opening of the crankcase ventilation passage is at the bottom of a recess formed in the side surface of the cam gear for interlocking the camshaft with the crankshaft. It is achieved by providing. In particular, it is preferable to erect the wall at a position adjacent to the advancing side of the opening in the rotation direction.

[0006]

According to this structure, the lubricating oil scattered in the crankcase and adhering to the cam gear is splashed by the centrifugal force, and therefore is unlikely to enter the crankcase ventilation passage opened at the side surface of the cam gear. Further, by arranging a wall on the leading side of the opening of the ventilation passage in the direction of rotation, the flow of the lubricating oil transmitted on the side surface of the cam gear is blocked, so that the effect of preventing the lubricating oil from entering is further enhanced.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the present invention will be described in detail below with reference to specific embodiments shown in the accompanying drawings.

FIG. 1 is a schematic vertical sectional view of a 4-cycle single cylinder engine to which the present invention is applied. In the cylinder 2 defined by the cylinder block of the engine 1,
The piston 3 is in sliding contact with the crank pin portion 5 of the crank shaft 4 and the connecting rod 6 is attached to the piston 3.
Are connected via

An intake valve and an exhaust valve 8 which are biased by a valve spring 7 to close the valve are provided on the side of the cylinder 2. These valves 8 extend in parallel with the crankshaft 4 and are formed on a camshaft 9 gear-coupled to the crankshaft 4 at a speed ratio of 1: 2, for intake valve driving cam 9a and exhaust valve driving cam 9a. It is connected to the cam 9b via a push rod 10.

As a result, the intake valve and the exhaust valve 8 are opened and closed in synchronization with the rotation of the crankshaft 4, and the intake of the air-fuel mixture and the exhaust of the combustion gas are conducted to the combustion chamber 11 defined by the cylinder head. Is performed at a predetermined timing.

The counterweight portion 12 of the crankshaft 4 has an oil pan 1 integrally formed with the crankcase 13.
An oil slinger 15 is provided for scraping up the lubricating oil in 4 to splash the lubricating oil toward the sliding contact portion between the cams 9a and 9b and the push rod 10 and the sliding contact portion between the cylinder 2 and the piston 3 respectively. Has been.

A governor mechanism 17 is gear-coupled to a cam gear 16 provided at the shaft end of the cam shaft 9 so as to interlock the cam shaft 9 with the crank shaft 4. The governor arm 18 connected to the governor mechanism 17 is provided with a throttle valve (not shown).
It is connected to and keeps a constant rotation speed according to the load.

The camshaft 9 is formed with a ventilation passage 19 for alleviating fluctuations in the internal pressure of the crankcase 13 due to the reciprocating motion of the piston 3. This ventilation passage 19 is shown in FIG.
As shown in, the opening is formed near the bottom surface of the recess 20 formed on the outer side surface of the cam gear 16, and is provided along the axial center of the cam shaft 9 up to the shaft end opposite to the cam gear 16. The gas-liquid separation chamber 2 provided in the cylinder block is provided with passages 22 and 23 communicating with the bearing portion 21 on this side.
4 and is connected to an air cleaner (not shown) through the gas-liquid separation chamber 24 (see FIG. 3).

A portion 19 of the ventilation passage 19 on the cam gear 16 side
“A” is formed obliquely outward from the axial center in the radial direction. Then, at a position adjacent to the advance side in the rotation direction when viewed from the opening 19b of the ventilation passage 19 on the outer surface of the cam gear 16,
The radial ribs 25 are provided upright (see FIG. 4). In this way, the lubricating oil attached to the side surface of the cam gear 16 and flowing with the rotation is blocked by the ribs 25. Further, since the opening 19b of the ventilation passage 19 is provided radially outward at a position separated from the axial center portion in the radial direction, even if lubricating oil enters, it will be discharged by centrifugal force.

[0015]

As described above, according to the present invention, the lubricating oil scattered in the crankcase and adhering to the cam gear is splashed off by the centrifugal force due to the rotation of the camshaft, and the lubricating oil transmitted to the side surface of the cam gear is The flow is interrupted by a rib standing at a position adjacent to the advancing side of the opening of the ventilation passage in the rotation direction. For this reason, it is difficult for the lubricating oil scattered in the oil pan to enter the crankcase ventilation passage in the power engine of equipment that generates high vibration acceleration such as a rammer. Therefore, it is possible to avoid the inconvenience that white smoke is generated during the exhaust.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view of a 4-cycle single-cylinder engine to which the present invention is applied.

FIG. 2 is a cross-sectional view taken along the line II-II in FIG.

FIG. 3 is a partial cross-sectional view along the line III-III in FIG. 2;

FIG. 4 is an outside view of the cam gear.

[Explanation of symbols]

 1 Engine 2 Cylinder 3 Piston 4 Crankshaft 5 Crankpin 6 Connecting Rod 7 Valve Spring 8 Valve 9 Camshaft 10 Pushrod 11 Combustion Chamber 12 Counterweight 13 Crankcase 14 Oil Pan 15 Oil Slinger 16 Camgear 17 Governor Mechanism 18 Governor Lever 19 Ventilation passage 20 Recess 21 Bearing 22/23 Passage 24 Gas-liquid separation chamber 25 Rib

Claims (2)

[Claims] 1. A crankcase ventilation passage formed in a camshaft provided in a crankcase, the opening of the passage being a recess formed on a side surface of a cam gear for interlocking the camshaft with the crankshaft. A crankcase ventilation passage provided at the bottom of the crankcase. 2. The crankcase ventilation passage according to claim 1, wherein a wall is erected at a position adjacent to the advancing side of the opening in the rotation direction.