JPH03199609A - Breather device for four cycle engine - Google Patents

Abstract

PURPOSE:To make an engine compact and reduce the number of components by forming a breather port directed upward and opposite via a gap to a chain guide on the upper surface of a chain passage. CONSTITUTION:A slender chain guide 92 to be in sliding contact with part of a timing chain 89 between a crankshaft 24 and cam shaft 73 is arranged in a chain passage 83 communicating via communication holes 87 with a crank chamber formed within a crankcase 20. A specified gap 92 is provided between the chain guide 92 and the top surface of the chain passage 83. A breather port 97 directed upward and opposite to the chain guide 92 with the intervening gap 96 is provided on the upper surface of the chain passage 83. Since the oil content in the blowby gas is separated with the existing chain passage 83, a cylinder head 60 is made compact and the number of components is reduced as the chain guide 92 functions as a baffle plate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a four-stroke engine for a motorcycle in which the cylinder block is tilted forward, and particularly to a breather device that separates oil from blow-by gas. Ru.

[Prior Art] In four-cycle engines for motorcycles, blow-by gas blown into the crankcase is returned to the intake system as part of exhaust gas countermeasures. Since this blow-by gas contains oil in the form of a mist, it is necessary to remove this oil from the blow-by gas. No. 52-36110.

This conventional breather device has a breather chamber in the cylinder head into which blow-by gas is introduced, a partition plate with many small holes is arranged inside this breather chamber, and the downstream end of the breather chamber is communicated with the intake pipe. The structure is as follows.

For this reason, the blow-by gas that has flowed into the breather chamber is constricted when it collides with the partition plate or passes through the small holes, so the flow rate gradually decreases, and as the flow rate decreases, the oil in the blow-by gas increases. is separated and removed.

[Problems to be Solved by the Invention] However, according to this conventional configuration, it is necessary to provide a special breather chamber in the cylinder head, and this breather chamber protrudes largely to the side of the cylinder head.

For this reason, there is a problem in that the cylinder head becomes large and a large space is required for installation around the cylinder head.

In addition, in the conventional breather device, the blow-by gas flow path in the breather chamber is formed into a complex labyrinth-like shape by separate partition plates, and the number of parts increases by the number of partition plates. For this reason, there are problems in that assembly of the breather device requires time and effort, resulting in high costs.

The present invention was made based on these circumstances, and
There is no need to secure a large space around the cylinder head, making it possible to make the engine more compact.
The purpose of the present invention is to provide a breather device for a four-stroke engine that eliminates the need for a special partition plate for separating oil and requires fewer parts in a structural part 111.

[Means for Solving the Problems] Therefore, in the present invention, a cylinder block that extends forward is provided upright in a crankcase housing a crankshaft, and a cylinder head that is connected to the front end of this cylinder block extends into the crankcase. form a chain passage,
In a 4-cycle engine in which a timing chain that interlocks the crankshaft and camshaft is inserted into the chain passage, the chain passage is communicated with the crank chamber in the crankcase through a communication hole, and the chain passage is connected to the crank chamber in the crankcase through a communication hole. A slender chain guide is provided in sliding contact with a portion of the timing chain that straddles between the crankshaft and the camshaft,
A predetermined gap is formed between the chain guide and the upper surface of the chain passage, and a breather opening is formed upward on the upper surface of the chain passage, facing the chain guide with the gap in between. .

[Function] According to this configuration, the chain passages in the cylinder block and cylinder head are connected only through the communication hole without directly opening into the crank chamber, so that the oil in the crank chamber flows into the chain passage. It becomes difficult to enter.

On the other hand, the blow-by gas that has blown into the crank chamber flows into the chain passage through the communication hole and is guided toward the cylinder head along the chain passage. After this blow-by gas is reversed at the end on the cylinder head side, a part of it enters the narrow gap between the upper surface of the chain passage and the chain guide, and is led to the breather port that opens upward.

That is, since the breather port opens into the chain passage across the chain guide, this chain guide becomes a baffle plate interposed in the blow-by gas flow path, and the end of the chain passage on the cylinder head side forms a so-called labyrinth structure. becomes. Therefore, since resistance is applied to the flow of the blow-by gas, the flow velocity of the blow-by gas decreases near the breather port, and the oil contained in this gas is separated and removed.

Therefore, in addition to making it difficult for the oil to flow into the crank chamber, the oil in the blow-by gas can be reliably removed using the existing chain passage, and the special breather chamber used in the past can be removed. It can be made unnecessary.

Furthermore, since the chain guide functions as a baffle plate that provides resistance to the flow of blow-by gas, there is no need for a dedicated baffle plate or partition plate to separate oil, and the number of parts can be reduced accordingly.

[Embodiment] An embodiment of the present invention will be described below based on drawings in which the present invention is applied to a scooter-type motorcycle.

The frame indicated by reference numeral l in FIG. 5 is provided with a steering head pipe 2 at its front end. A front wheel 4 is supported by the steering head pipe 2 via a front fork 3.

Moreover, one down tube 5 extending downward is connected to the steering head vibe 2. The lower end portion of the down tube 5 extends rearward substantially horizontally, and a pair of left and right main vibrators are connected to the rear portion of this horizontal portion 5a. The main vibro is raised immediately after the horizontal portion 5a, and the upper end of this raised portion 7 forms an extension portion 8 extending rearward.

An engine bracket 9 is attached to the front end of the main vibro extension 8. Further, a fuel tank 10 and a storage box 11 for storing a helmet, for example, are installed on the upper surface of this extension part 8, and a seat I is provided on the upper surface of these fuel tank 10 and the storage box It.
2 is placed.

Therefore, the frame l is bent downward between the front fork 3 and the seat 12 to secure a space 13 for footrest between them, and the down tube 5 is located below this space 13. A flat footrest board 14 is installed on the horizontal portion 5a.

Note that the front end of the footrest board I4 is connected to a leg shield 15, and this leg shield 15 covers the steering head vibe 2, front fork 3, and down tube 5.

By the way, below the extension part 8 of the main vibro,
A unit swing type engine unit 18 is arranged. As shown in FIG. 2, this engine unit 18 includes a four-stroke single cylinder engine 19 and an engine 1.
The transmission case 21 extends rearward from the left side of the crankcase 20 of No. 9, and a support protrusion 20c protruding from the upper surface of the crankcase 20 is pivotally supported by the engine bracket 9 via a link plate 22. ing.

The crankcase 20 has a left case 20a and a right case 20b.
It is divided into. Both cases 20a.

A crank chamber 23 is formed between the two parts 20b, and a crankshaft 24 is accommodated in the crank chamber 23. A left case 20a of the crankcase 20 and a left side surface of a transmission case 21 connected thereto are covered by a case cover 25. Both cases 20a.

A transmission chamber 26 is formed between the transmission chamber 21 and the case cover 25, and one end of the crankshaft 24 is introduced into the front end of the transmission chamber 26.

The transmission chamber 26 is separated from the crank chamber 23 by a partition wall 27, and one end of the crankshaft 24 passes through the partition wall 27 via an oil seal 28.

A driven shaft 29 parallel to the crankshaft 24 is supported at the rear of the transmission chamber 26, and a V-belt 11 dynamic transmission 30 that interlocks the driven shaft 29 and the crankshaft 24 is housed within this transmission chamber 26. has been done.

■The belt automatic transmission 30 has a structure similar to that of a conventionally known one, and as shown in FIG.
The secondary sheave 32 is attached to the outer periphery of the sheave via a centrifugal clutch 35, and the V of both these sheaves 31 and 32 is
It is equipped with a V-belt 33 wrapped around 3fa and 32a. When the rotational speed of the crankshaft 24 increases, the flyweight 34 of the primary sheave 31 receives centrifugal force and moves radially outward, forming a V-shape? The circumferential width of i'1731a is reduced.

Therefore, on the secondary sheave 32 side, the V-belt 33
is pulled inward in the radial direction, the circumferential width of the V-shaped groove 32a is expanded, and as a result, the V-groove 32a is
The winding diameter of the belt 33 is changed.

The driven shaft 29 is interlocked with an axle 37 of a rear wheel 36 via a gear transmission (not shown), and this axle 37 is supported by the rear end of the transmission case 21.

On the other hand, the engine 19 has a cylinder block 40 extending substantially horizontally forward from the front end of the crankcase 20.
It is equipped with Cylinder 40 in cylinder block 40
A piston 41 is housed in a, and this piston 4
1 is connected to the crankshaft 24 via a connecting rod 42.

The cylinder block 4o is surrounded by an air shroud 43. At the right end of the air shroud 43,
A fan cover 44 is provided continuously. This fan cover 44 also serves as a crankcase cover that continuously covers the right case 20b.
An axial fan 45 is disposed inside. The fan 45 is located on the right side of the cylinder block 40 and is provided facing a continuous portion of the air shroud 43 with the fan cover 44. A rotating shaft 46 of the fan 45 is supported via a bearing 49 on a boss portion 48 of a support stay 47 extending from the right case 20b, and a driven pulley 50 is mounted on the rotating shaft 4c. .

The fan cover 44 also integrally covers the flywheel magnet 5I fixed to the right end of the crankshaft 24. A drive pulley 5 is attached to the rotor 52 of the flywheel magneto 51.
3 is attached, and a belt 54 is wound between the driving pulley 53 and the driven pulley 50.

Therefore, the fan 45 is driven to increase its speed by power transmission from the crankshaft 24, and when the fan 45 is driven to rotate, outside air is drawn in from the suction port 55 on the right side of the air shroud 43. is blown around the cylinder block 40, and the area around the cylinder is forcibly air-cooled.

Furthermore, a cylinder head 60 is attached to the front end of the cylinder block 40. The cylinder head 60 is connected to the rising part 7 of the main vibro, as shown in FIG.
The cylinder head 60 is formed with an intake port 62 and an exhaust port 63 that open into the combustion chamber 61.

The intake port 62 extends above the cylinder head 60 and is opened toward the rear, and a carburetor 65 is connected to this open end via a joint 64.

The carburetor 65 is arranged above the crankcase 20, and an air cleaner 67 is connected to the carburetor 65 via an intake pipe 6B. The air cleaner 67 is arranged above the transmission case 21 and the case cover 25.

The cylinder head 60 also includes an intake valve 68 that opens and closes the intake port 62 and an exhaust valve 69 that opens and closes the exhaust port 63.
is provided. These intake valves 68 and exhaust valves 69 are arranged vertically with respect to the cylinder 40a, and their valve stems 68a and 139a are introduced into the valve operating chamber 70 at the front end of the cylinder head 60.

One cam $11173 is rotatably supported in the valve operating chamber 70. An intake cam 73a and an exhaust cam 73b are formed on the camshaft 73, and these cams 73a, 73
b is the valve stem 68 via the rocker arm 74.
a, in contact with B9a. The facing parts of the rocker arm 74 and the valve stems G8a, 69a are located at the upper and lower ends of the valve operating chamber 70, and tappet clearance adjustment is provided on the upper and lower surfaces of the front end of the cylinder head 60 corresponding to these facing parts. Openings 75 and 76 are formed. These openings 75 and 76 have tabezoto covers 77.
, 78 are removably screwed.

Further, an oil pipe 79 from an oil pump (not shown) is connected to the cylinder head 60. The lubricating oil from this oil pipe 79 passes through the oil passage 73c inside the camshaft 73 to the suction/exhaust cams 73a, 7
The lubricating oil that is supplied to the contact portion between the rocker arm 3b and the rocker arm 74 and lubricates the area around this contact portion is collected on the bottom surface of the valve operating chamber 70.

A chain passage 83 that spans the crankcase 20 is continuously formed on the left side of the cylinder block 40 and the cylinder head 60. The left end of the camshaft 73 is introduced into the front end of the chain passage 83, and a timing sprocket 84 is attached to the introduction end of the camshaft 73.

Further, the front end of the chain passage 83 on the cylinder head 60 side is connected to the valve train chamber 70 through the communication hole 81 as shown in FIG.
It is communicated with. The communication hole 81 is continuous with the bottom surface of the chain passage 83, and the lubricating oil in the valve operating chamber 70 flows out into the chain passage 83 through the communication hole 81.

As shown in FIG. 1, the chain passage 83 is inclined downward as it advances toward the crankcase 20, and its rear end on the crankcase 20 side is provided with a partition wall 85 between it and the crank chamber 23. It is being

A communication hole 87 for communicating the crank chamber 23 and chain passage 83 and an oil return hole 8B are formed in the partition wall 85. The communication hole 87 is for introducing the blow-by gas that has blown into the crank chamber 23 into the chain passage 83, and the oil return hole 8 opens at the rear of the communication hole 87.
6 is provided at a continuous position on the bottom surface of the chain passage 83. A driving sprocket 88 is provided on the outer periphery of the crankshaft 24 passing through the chain passage 83, and a timing chain 89 is passed between the driving sprocket 88 and the timing sprocket 84.

In the chain passage 83 through which the timing chain 89 passes, as shown in FIG. 9
3 is accommodated. The first chain guide 92 is biased by a rod 95 of a tensioner 94 in a direction to press the timing chain 89 in the event of a disturbance, thereby applying appropriate tension to the timing chain 89.

The first chain guide 92 is connected to the chain passage 83.
is opposed to the upper surface of with a predetermined gap 96 in between,
A breather port 97 is provided on the upper surface of the front end of the chain passage 83 that faces the front end of the first chain guide 92 . This breather port 97 is connected to the air cleaner 67 via a breather pipe (not shown).

Note that an inspection window 82 for checking the oil level is provided on the left side of the front end of the crankcase 20.

Further, in the case of this embodiment, the cylinder head 60 is water-cooled, and a cooling water passage l is provided around the combustion chamber 61.
Equipped with OO. This cooling water passage 100 is connected to a radiator 101 via piping (not shown), and this radiator lot is connected to the suction port 5 of the fan cover 44.
It is installed at 5. For this reason, the radiator lot is located at the upstream end of the intake of engine cooling air, so that air is always guided during engine operation.

A cooling water pump 102 is provided in the middle of the piping that leads the cooling water from the radiator 101 to the cooling water passage 00. As shown in FIG. 2, the cooling water pump 102 is installed on the left side of the cylinder head 60, and the drive shaft 104 of the impeller 103 is coaxially connected to the camshaft 73 at the left end. So, cooling water pump 1
02 is driven by a cam 73.

The area from the engine of the engine unit 18 to below the seat 12 is covered with a cover 110 made of synthetic resin.

Next, the operation of the above configuration will be explained.

During engine operation, blow-by gas that has blown into the crank chamber 23 flows into the chain passage 83 through the communication hole 87 as shown by the arrow in FIG. This blow-by gas flows inside the chain passage 83 along the first and second chain guides 92, 93 toward the cylinder head 60, and collides with the end of the chain passage 83 on the cylinder head 60 side. The flow direction is reversed.

A portion of the blow-by gas whose flow has been reversed enters the gap 96 between the first chain guide 92 and the upper surface of the chain passage 83, and is returned to the air cleaner 67 from there through the breather port 97 that opens upward.

That is, since the breather port 97 opens into the chain passage 83 across the first chain guide 92, when viewed from the breather 9 side, the front end of the first chain guide 92 is exposed to blow-by gas. It functions as a baffle plate interposed in the flow path, and the range from the end of the chain passage 83 on the cylinder head 60 side to the opening of the breather port 97 has a bent so-called labyrinth structure.

For this reason, the blow-by gas that has been guided inside the chain passage 83 to the end on the cylinder head 60 side has its flow direction changed or its flow forcedly constricted.
The flow velocity decreases as the flow moves toward the Breezolo 9F side.

Due to this decrease in flow rate, the oil contained in the blow-by gas is separated under the influence of gravity, and the chain passage 83
It attaches to the wall surface and the first chain guide 92, and also travels through the chain passage 83 to the crank chamber 23.
flows to the side. This oil is then returned to the crank chamber 23 through the oil return hole 86.

Therefore, according to the above configuration, the oil contained in the blow-by gas can be removed using the existing chain passage 83.

Moreover, this chain passage 83 and the crank chamber 23 are separated by a partition wall 85, and the chain passage 83 is separated from the crank chamber 23 by a partition wall 85.
Since the chain passage 83 is connected to the crank chamber 23 only through a communication hole 87 formed in the partition wall 85, it becomes difficult for oil in the crank chamber 23 to flow into the chain passage 83 itself.

Therefore, a special breather chamber like the conventional one can be omitted from the cylinder head 60, and the cylinder head 60 can be made more compact.

Further, as described above, since the first chain guide 92 functions as a baffle plate that provides resistance to the flow of blow-by gas, there is no need for a dedicated baffle plate or partition plate as in the past.

Therefore, the number of parts and assembly man-hours can be reduced, and there are also advantages such as lower costs.

In the above embodiment, the breather port is provided on the cylinder head, but the present invention is not limited to this, and may be provided on the cylinder block side, for example.

Further, the breather device according to the present invention is not limited to one that is used for a unit swing type engine that integrates a belt automatic transmission, and may be used, for example, for an engine fixed to a frame. Of course, two-wheeled vehicles are not limited to the scooter type.

[Starting effect] According to the present invention detailed above, the oil contained in the blow-by gas can be removed using the existing chain passage, so it is not necessary to separate the special breather chamber from the cylinder head as in the past. This can be omitted and the cylinder head can be made more compact.

Furthermore, since the chain guide functions as a baffle plate that provides resistance to the flow of blow-by gas, there is no need for a special baffle plate or partition plate to separate the oil.
It is possible to reduce costs by reducing the number of parts and assembly man-hours.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, in which Fig. 1 is a side view of the engine with the chain passage section sectioned, Fig. 2 is a sectional view of the entire engine unit, and Fig. 3 shows the positional relationship between the frame and the cylinder head. FIG. 4 is a sectional view of the cylinder head, and FIG. 5 is a side view of the scooter type motorcycle. 20... Crank case, 23... Crank chamber, 2
4...Crank f source, 40...Cylinder block, CO...Cylinder head, 73...Camshaft, 83
... Chain passage, 87 ... Communication hole, 89 ... Timing chain, 92.93 ... Chain guide,
96...luJ gap, 97...breather mouth.

Claims (1)

[Scope of Claims] A cylinder block extending forward is installed upright on a crankcase housing a crankshaft, a camshaft is provided on a cylinder head connected to the front end of the cylinder block, and a camshaft is provided on the cylinder block and cylinder head, and the cylinder block and cylinder head are connected to the crankcase. In a 4-stroke engine, a timing chain is inserted into the chain passage to interlock the crankshaft and the camshaft. An elongated chain guide that communicates with the chamber and slides into contact with a portion of the timing chain spanning between the crankshaft and the camshaft is provided in the chain passage,
A predetermined gap is formed between the chain guide and the upper surface of the chain passage, and a breather opening is formed upward on the upper surface of the chain passage, facing the chain guide across the gap. 4-stroke engine breather device.