JPH06264759A - 4-cycle engine for motorcycle - Google Patents

Abstract

PURPOSE:To provide such a 4-cycle engine for a motorcycle that a balancer device can be easily installed, an engine case is downsized, capacity of a breather chamber can be enlarged, separativeness of blowby gas from oil content is improved, and a breather device by which blowby gas is efficiently exhausted with a simple structure is mounted. CONSTITUTION:An opening part 27 is provided on the rear face of an engine case which is divided into the lower and the upper parts and while a balancer device 23 is laid from the opening part 27 to the rear upper part of a crankshaft 18, a breather device 28 is mounted in the opening 27.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motorcycle 4-cycle engine, and more particularly to a motorcycle 4-cycle engine equipped with a balancer device.

[0002]

2. Description of the Related Art For example, in an engine of a motorcycle, an internal combustion engine section and a transmission mechanism are generally housed in the same engine case in order to make the entire engine compact. The engine case contains a crankshaft, a counter shaft of a transmission mechanism, and a drive shaft.

Some engine cases are divided into upper and lower parts or left and right parts. In the engine case which is divided into upper and lower parts, the crankshaft, the counter shaft and the drive shafts are the same as those of the engine case because of the bearing structure. It is generally arranged along the dividing plane.

For example, a single-cylinder or two-cylinder (especially narrow-angle V-type two-cylinder) four-cycle engine used for a motorcycle is apt to generate a primary vibration based on a reciprocating motion of a piston. Therefore, some engines have a balancer device for removing the primary vibration. The balancer device is
For example, a fan-shaped balancer weight corresponding to the total mass of the piston, connecting rod, etc. is fixed to the balancer shaft, and this balancer shaft is rotated in conjunction with the crankshaft, gears, chains, etc. to reduce vibration during engine operation. Had been removed.

In an engine that employs an engine case that is divided into upper and lower parts, the balancer shaft of the balancer device is also arranged along the dividing surface of the engine case for the reason described above.

On the other hand, in a four-cycle engine, it is a well-known fact that a small amount of gas with pressure generated in the combustion chamber leaks into the engine case through the gap of the piston ring.

The pressure of the gas in the engine case is
Since the piston fluctuates constantly as it moves up and down, the pressure of the gas in the engine case hinders the movement of the piston when the engine case is sealed. Therefore, it is necessary to provide a means for letting the gas in the engine case escape to the outside.

Conventionally, this gas (hereinafter referred to as blow-by gas) has been released into the atmosphere through a breather hole provided in the engine case. However, since the blow-by gas is one of the sources of air pollution, the blow-by gas is returned to the air cleaner. Then, a breather device, which is a mechanism for sending it again to the combustion chamber and re-burning it, is provided.

In many four-cycle engines, a breather chamber is provided inside the cylinder head cover of the engine. In this breather chamber, a blow-by hose communicating with the upstream side of an intake device such as a carburetor and a throttle valve,
The PCV hose leading to the downstream side of the intake device is connected,
The breather device was configured.

During operation of the engine, the blow-by gas leaked into the engine case is mixed with lubricating oil and introduced into the breather chamber through an oil return passage or the like, and after the oil component is separated in the breather chamber, the PCV hose is separated. It was re-inhaled into the combustion chamber through. At the same time, fresh air was introduced from the blow-by hose and replaced with blow-by gas in the engine case, promoting the discharge of blow-by gas.

Further, when the amount of blow-by gas leaked increases, the pressure inside the engine case increases, and blow-by gas is discharged from both the PCV hose and the blow-by hose and re-inhaled into the combustion chamber.

[0012]

However, when the balancer shaft is arranged along the dividing surface of the engine case, the total length of the engine case in the front-rear direction becomes long and the wheel base of the vehicle becomes long. If, for example, the balancer shaft is arranged above and behind the crankshaft, the overall length of the engine case in the front-rear direction does not become long, but when installing the balancer shaft and the crankshaft, it is difficult to align the respective positions.

On the other hand, in the engine in which the breather chamber is provided in the cylinder head cover as in the conventional case, the blow-by hose and the PCV hose are arranged close to each other at a distance from the engine case, so that they are introduced from the blow-by hose during the operation of the engine. There is a tendency that the fresh air that has been discharged falls out of the PCV hose as it is, and it is difficult to efficiently replace the blow-by gas with fresh air in the engine case.

Further, it is necessary to introduce fresh air to guide the blow-by gas in the engine case to the breather chamber,
The structure becomes complicated.

Further, in order to improve the separability of the blow-by gas and the oil in the breather chamber, it is desirable to increase the capacity of the breather chamber and make the breather chamber a maze structure. However, in the cylinder head cover of the engine. Has a small space for accommodating the valve mechanism,
It is difficult to increase the capacity of the breather chamber, and if measures such as partially bulging the head cover are taken, the engine cannot be made compact. When the capacity of the breather chamber is small, the lubricating oil may blow up due to the pressure difference between the inside of the engine case and the inside.

Further, if the breather chamber has a maze structure, the cylinder head cover becomes complicated and the cost increases.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a four-cycle engine for a motorcycle in which the balancer device can be easily installed and the engine case can be made compact.

Another object of the present invention is to provide a breather device capable of increasing the capacity of the breather chamber, improving the separability of the blow-by gas and the oil component, and efficiently discharging the blow-by gas with a simple structure. It is to provide a 4-cycle engine for a motorcycle equipped with.

[0019]

In order to solve the above-mentioned problems, a four-cycle engine for a motorcycle according to the present invention has an opening on the back surface of an engine case which is divided into upper and lower parts as described in claim 1. The balancer device is inserted into the rear upper part of the crankshaft through this opening.

In order to solve the above-mentioned problems, a breather device is installed in the opening as described in claim 2.

[0021]

According to the present invention having the above-described structure, the balancer device is easily installed because the balancer device is attached to the rear upper part of the crankshaft through the opening part provided on the back surface of the engine case which is vertically divided. While it can be installed,
The engine case can be made compact.

Further, since the breather device is installed in the opening, the capacity of the breather chamber can be increased and the separability between the blow-by gas and the oil component is improved, while the blow-by gas can be efficiently discharged with a simple structure. A breather device can be provided.

[0023]

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

FIG. 1 is a schematic vertical sectional view showing an example of a four-cycle two-cylinder engine for a motorcycle to which the present invention is applied.

In FIG. 1, the engine 1 has an outer shape mainly composed of a cylinder head cover 2, a cylinder head 3, a cylinder block 4, and an engine case 5.

The cylinder head 3 is provided with a bubble mechanism 8 including a camshaft 6 and an intake / exhaust valve 7. Further, the cylinder head 3 is provided with an intake passage 9 and an exhaust passage 10. The downstream side of a carburetor 11a, which is an engine intake system 11, is connected to the intake passage 9, and the engine intake system 1 is provided upstream of the carburetor 11a.
The air cleaner 11b which is 1 is connected. On the other hand, an exhaust pipe which is an engine exhaust system (not shown) is connected to the exhaust passage 10. The upper portion of the cylinder head 3 is closed by the cylinder head cover 2.

A cylinder liner 12 is fitted inside the cylinder block 4, and this cylinder liner 1
A piston 15 provided with two piston rings 13 and 13 and one oil ring 14 slides in 2 in the vertical direction. A combustion chamber 16 is formed in the space between the cylinder head 3 and the piston 15 in the cylinder liner 12. The piston 15 is connected to the crankshaft 18 via a connecting rod 17.

The reciprocating stroke of the piston 15 is converted into rotational movement by the crankshaft 18, and a counter drive shaft 20 of the transmission mechanism 19 is transferred from a primary drive gear (not shown) provided at the right end of the crankshaft 18 via a clutch mechanism (not shown). It is transmitted to the drive shaft 21.

The engine case 5 is divided into an upper engine case 5a and a lower engine case 5 which are divided into upper and lower parts.
b. Bearings (not shown) for the crankshaft 18, the counter shaft 20, and the drive shaft 21 are provided vertically inside the split surface 22 between the upper engine case 5a and the lower engine case 5b. The shafts 18 are provided by these bearings. , 2
It supports 0 and 21.

A balancer device 23 is disposed above and rearward of the crankshaft 18. The balancer device 23 includes a balancer shaft 23a and, for example, two balancer weights 23b, 23 fixed to the balancer shaft 23a.
c and a balancer driven gear 23d fixed to the balancer shaft 23a. Both ends of the balancer shaft 23a are axially supported in parallel with the crankshaft 18 by lower bearings 24a and 24b formed in the upper engine case 5a and upper bearings 25a and 25b separately formed.

A balancer drive gear 26 is provided at the left end of the crankshaft 18. The balancer drive gear 26 meshes with the balancer driven gear 23d of the balancer device 23, and the balancer shaft 2
3a is rotated in the opposite direction of the crankshaft 18. The balancer driven gear 23d and the balancer drive gear 26 are provided with alignment marks (not shown), respectively. When the balancer device 23 is installed, the alignment marks are aligned so that the crankshaft 18 and the balancer device 23 are correctly aligned. The relationship is getting.

FIG. 2 is an enlarged view of the vicinity of the balancer device 23 of FIG. 1, and FIG. 3 is a view of the vicinity of the balancer device 23 viewed from above.

2 and 3, an opening 27 is provided on the back surface of the upper engine case 5a. The size and shape of the opening 27 are such that the balancer device 23 can be inserted. A breather device 28 is provided in the opening 27.

The breather device 28 includes a breather cover 28.
a, a breather hose 28b, and a partition plate 29.

As shown in FIG. 4, the partition plate 29 has a partition plate body 29a whose central portion is curved in a convex shape upward.
And side plates 29b and 29c vertically provided upward from both longitudinal edges of the partition plate body 29a, and brackets 29d and 29e provided downwardly from the other edge of the partition plate body 29a. To be done. This partition board 2
9 is integrally manufactured by press molding a thin metal plate, for example.

This partition plate 29 includes brackets 29d,
Together with the upper bearings 25a and 25b that pivotally support the balancer shaft 23a via 29e, the lower bearings 24a and 24b are fastened and fixed together by fixing means such as bolts 30.
The blow-by passage 3 is provided between the side plates 29b and 29c of the partition plate 29 and the edge 27a of the opening 27.
1 is formed. Further, oil return passages 32 are formed at the four corners of the opening 27. On the other hand, the opening 27 is closed by a breather cover 28a. Although not shown in detail, the inside of the breather cover 28a has a maze structure and forms a breather chamber 28c together with the partition plate 29. Further, the breather chamber 28c and the air cleaner 11b are communicated with each other by a breather hose 28b.

Reference numeral 33 is a starter motor,
It is connected to the crankshaft 18 via a plurality of gears (not shown).

The engine 1 is equipped with an engine lubrication device (not shown), and the lubricating oil stored in an oil pan 34 provided at the bottom of the engine case 5 is cranked by an oil pump (not shown) such as a crankshaft 18 and a transmission mechanism 19. It is pumped to each part in the engine 1.
Lubricating oil that lubricates each part falls in the engine case 5, is stored in the oil pan 34, and is recirculated.

Next, the operation of this embodiment will be described.

To assemble the engine 1, the crankshaft 18, the counter shaft 20 of the transmission mechanism 19, the drive shaft 21 and the like are assembled in the lower engine case 5b, and the upper engine case 5a is covered and fixed by bolts or the like not shown.

Next, as shown in FIG. 5, the preassembled balancer device 23 is inserted through the opening 27 provided in the upper engine case 5a to form the balancer shaft 23a in the upper engine case 5a. It is installed on the lower bearings 24a and 24b. The partition plate 29, which is a component of the breather device 28, is fastened together with the upper bearings 25a and 25b via the brackets 29d and 29e of the partition plate 29 to the lower bearings 24a and 24b by fixing means such as bolts 30. Fix it.

Next, the breather cover 2 is provided with the opening 27.
8a, and a breather hose 28b is used to provide a breather chamber 28c in the breather cover 28a and an air cleaner 11b.
Connect and communicate with.

When the balancer device is installed by inserting the balancer device 23 from the opening 27 provided in the upper engine case 5a, the alignment mark (not shown) of the balancer driven gear 23d and the balancer drive gear 26 is provided in the opening 27. Can be easily seen from. Further, since the balancer shaft is not arranged along the dividing surface of the engine case, the overall length of the engine case in the front-rear direction does not become long, and the engine case can be made compact.

On the other hand, when the engine 1 is started, the air enters the carburetor 11a from the air cleaner 11b and is mixed with the fuel in the carburetor 11a to form a mixture, which then passes through the intake passage 9 of the cylinder head 3 and the cylinder block 4a.
It is sent to the internal combustion chamber 16.

The air-fuel mixture sent into the combustion chamber 16 is compressed by the piston 15 which slides up and down in the cylinder liner 12 and then ignited by an ignition plug (not shown) to explode, pushing down the piston 15 to generate power. It has occurred.

In the compression process of the air-fuel mixture by the piston 15, a part of the air-fuel mixture compressed to a high pressure leaks into the engine case 5 through the gaps between the piston rings 13, 13 and the oil ring 14 and the cylinder liner 12. The air-fuel mixture that flows into the engine case 5 is generally called blow-by gas. Engine 1 operating at high speed
The blow-by gas is particularly large when the rotation speed of the cylinder is suddenly reduced, the piston rings 13 and 13 and the oil ring 14 are damaged, and the cylinder liner 12 is worn and the clearance between the piston 15 and the piston 15 increases. Occur.

Since blow-by gas becomes a source of air pollution, the blow-by gas is introduced into the breather chamber 28c through the blow-by passage 31 provided in the breather device 28,
From there breather hose 28b air cleaner 1
It is refluxed to 1b and then sent again to the combustion chamber 16 for re-combustion.

As described above, according to the present invention, since the breather device 28 is provided on the engine case 5, it is not necessary to guide the blow-by gas to the cylinder head cover 2, and therefore a complicated structure such as a PCV hose and a blow-by hose is not required. .

On the other hand, the engine 1 lubricates each part in the engine 1 with a lubricating device (not shown). Lubricating oil pumped by an oil pump (not shown) drops in the engine case 5 after lubricating each part of the engine 1. At this time, a part of the lubricating oil is splashed by the crankshaft 18 and the transmission mechanism 19 which are rotating at high speed. It is raised and becomes mist-like oil mist and floats in the engine case 5.

Although a part of the oil mist is prevented from directly entering the breather chamber 28c by the partition plate 29,
A part of it is mixed with the high-pressure blow-by gas in the engine case 5 and enters the breather chamber 28c through the blow-by passage 31. However, since the blow-by gas is directly guided to the breather chamber 28c without passing through the oil return passage as in the conventional case, the mixing of oil mist is reduced. Also, since the blow-by passage 31 is large, the breather chamber 28
The internal pressure of c becomes equal to or close to the internal pressure of the engine case 4, and the lubricating oil does not blow up.

Since the breather chamber 28c is not provided inside the cylinder head cover 2 as in the conventional case, but is provided as a separate body, it is possible to increase the capacity of the breather chamber 28c and the internal maze structure. It becomes possible. Therefore, the oil component of the blow-by gas mixed with the oil mist that has entered the breather chamber 28c adheres to the maze structure and is separated from the blow-by gas. The oil mist separated from the blow-by gas then falls spontaneously, and the partition plate main body 2 in which the central portion of the partition plate 29 is curved upward in a convex shape
9a, the oil return passages 32 formed at the four corners of the opening 27 fall into the engine case 5.

As described above, the application of the present invention improves the separability of blow-by gas and oil.

In the above embodiment, an example in which the present invention is applied to an engine for a motorcycle has been shown, but the present invention can be applied to an engine for other purposes including a balancer device.

The breather device of the present invention can also be applied to a multi-cylinder engine that does not have a balancer device.

[0055]

As described above, according to the four-cycle engine for a motorcycle of the present invention, an opening is provided on the back surface of the engine case which is divided into the upper and lower parts, and the balancer device is connected to the crankshaft through the opening. The balancer device can be easily installed because it is inserted rearward and upward, and the engine case can be made compact.

Further, since the breather device is installed in the opening, the capacity of the breather chamber can be increased and the separability between the blow-by gas and the oil component is improved, while the blow-by gas can be efficiently discharged with a simple structure. A breather device can be provided.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view showing an embodiment of a four-cycle two-cylinder engine for a motorcycle according to the present invention.

FIG. 2 is an enlarged view of the vicinity of the balancer device of FIG.

FIG. 3 is a view of the vicinity of the balancer device as viewed from above.

FIG. 4 is a view showing a shape of a partition plate.

FIG. 5 is an assembly structure diagram of a balancer device and a breather device.

[Explanation of symbols]

 1 engine 5 engine case 5a upper engine case 5b lower engine case 11 engine intake system 15 piston 18 crankshaft 19 transmission mechanism 23 balancer device 23a balancer shaft 23b, 23c balancer weight 23d balancer driven gear 24a, 24b lower bearing 25a, 25b upper bearing 26 Balancer drive gear 27 Opening 28 Breather device 28a Breather cover 28b Breather hose 28c Breather chamber 29 Partition plate 31 Blow-by passage 32 Oil return passage

Claims (2)

[Claims] 1. A four-cycle engine for a motorcycle, wherein an opening is provided on a back surface of an engine case which is divided into an upper part and a lower part, and a balancer device is inserted from the opening to a rear upper part of a crankshaft. 2. The four-cycle engine for a motorcycle according to claim 1, wherein a breather device is installed in the opening.