JPH0364689B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement of a two-stroke engine configured with a V-type multi-cylinder system.

(Prior art) Conventionally, for example, a V engine was used as a motorcycle engine.
A two-stroke engine configured with a multi-cylinder type is known. This V-type system accommodates the multiple cylinders necessary to obtain large horsepower in a compact volume.
Furthermore, it has the advantage that by adjusting the angle of V, the primary vibration due to the up and down movement of the piston can be canceled out by each cylinder, and is suitable for high-speed engines. By the way, in the case of such a V-shaped cylinder engine, conventionally, the intake system equipment is generally arranged in the V-shaped bank.

(Problem to be solved by the invention) However, in the conventional method of arranging intake system equipment in a V-shaped bank, not only does the gap between cylinders increase, but also the degree of freedom in setting the V angle is restricted. Furthermore, if the angle of the V-bank is set narrowly, it becomes necessary to open an intake passage in the center of the cylinder wall for communication with the intake system, resulting in a problem of lowering the rigidity of the cylinder.
Therefore, it was necessary to take new measures such as reinforcing the periphery in order to maintain a certain level of rigidity.

On the other hand, if the intake system equipment is placed outside the V bank, it will easily interfere with the exhaust system equipment, and if the intake system is placed close to the exhaust system, the intake system equipment will absorb heat from the exhaust system. There was also a risk that engine performance would be reduced due to the influence of

(Means for Solving the Problems) The present invention has been made to effectively eliminate such inconveniences, and its purpose is to miniaturize the entire engine and make it compact, and furthermore, to reduce the size of the entire engine. It is an object of the present invention to provide an engine that can be arranged at a distance from each other.

In other words, in a two-stroke engine in which the front and rear cylinders are V-shaped and the rear cylinder is tilted forward from the crankshaft, an exhaust passage is provided in front of the rear cylinder, and a crankcase is installed behind the rear cylinder. A transmission case is provided that extends integrally from the transmission case, and intake system equipment is disposed above the transmission case, and an intake passage that communicates the intake system equipment with the inside of the crankcase is provided on the upper wall of the crankcase.

(Function) By tilting the rear cylinder forward to widen the space above the transmission case and assembling the intake system equipment in this space, the space between the cylinders can be adjusted, making the whole machine more compact. . Furthermore, by separating the equipment in the exhaust system and the intake system, the degree of freedom in configuring each passage, etc. can be increased, and adverse effects due to mutual interference such as heat can be avoided.

Furthermore, since the intake passage can be directly communicated with the inside of the crankcase, the rigidity of the cylinder can be ensured more easily than in the conventional case where an opening is provided in the center of the cylinder wall.

(Embodiment) A preferred embodiment of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a longitudinal sectional side view of the two-stroke engine, and FIG. 2 is a view taken in the two directions of the arrow in FIG. 1 with the valve cover removed.

The illustrated two-stroke engine 1 is a V-type four-cylinder engine, which includes two cylinders facing each other in a V-shape.
The base cylinders 2, 2 are arranged in two rows in the direction perpendicular to the plane of the first drawing.

The upper part of each cylinder 2 is closed by a cylinder head 3, and a spark plug 4 is attached to the center of the cylinder head 3 as shown. A piston 5 is slidably fitted into each cylinder 2, and the piston 5 is connected via a connecting rod 6 to a crankshaft 7 having a length perpendicular to the plane of the drawing.

In this way, a combustion chamber S is formed inside the cylinder 2, which is partitioned by the inner circumferential wall of the cylinder 2, the cylinder head 3, and the piston 5, and a scavenging hole 8 and an exhaust hole are provided at opposing positions on the inner circumferential wall of the cylinder 2. 9 are open, and these sweeping and exhaust holes 8 and 9 are opened and closed by sliding of the piston 5. Note that 10 in Figure 1,
11 are a scavenging passage and an exhaust passage, respectively; the scavenging passage 10 is a passage for intermittently communicating between the crank chamber 12 and the combustion chamber S, and the exhaust passage 11 is a passage for intermittent communication between the combustion chamber S and the atmosphere, and The exhaust passage 11 opens toward the front side of the rear cylinder 2 and the lower side of the front cylinder 2, respectively.

On the other hand, a transmission case 13 is attached to the right side of the crank chamber 12 in FIG. It is stored.

By the way, a primary shaft 16 is disposed in the transmission case 13 in parallel with the crankshaft 7, and a primary driven gear 17 and a valve drive gear 18 are fitted to the shaft 16. Primary drive gear 1 fitted to the crankshaft 7
It meshes with 9.

Although not shown, the primary shaft 16 is gear-engaged with the transmission main shaft 14 and transmits driving force from the crankshaft 7 to the transmission main shaft 14.

A valve shaft 20 is rotatably supported in the transmission case 13 at right angles to the crankshaft 7, that is, in a vertical direction, and a valve that meshes with the valve drive gear 18 is mounted at the lower end of the valve shaft 20. A driven gear 21 is provided. On the other hand, at the upper end of the valve shaft 20, as shown in FIG.
2 are fixed to rotate together. and,
The upper surface side of this valve 22 is covered with a valve cover 23, and the valve cover 23 covers the intake passage 24.
constitutes part of. Note that this intake passage 24 is opened and closed by the rotary valve 22.

Incidentally, an intake port 25 is opened at the lower end of the intake passage 24, that is, at the upper part of the crank chamber 12, and a carburetor 26 as an intake system device is connected to the upper end of the intake passage 24. That is, this carburetor 26 is assembled in a space above the transmission case 13 whose rear side is wide open by tilting the rear cylinder 2 forward, and communicates with the intake passage 24.

Next, the operation of the engine 1 will be described. The rotation of the crankshaft 7 is transmitted to the primary shaft 16 via both gears 19, 18, and the rotation of this primary shaft 16 is further transmitted to the valve shaft 20 by both gears 18, 21, and the valve shaft 20 is rotated during engine operation. It is constantly driven to rotate. As the valve shaft 20 rotates, the intake rotary valve 22 fixed thereto also constantly rotates.
2, the intake passage 24 is opened and closed at appropriate timing.

FIG. 1 shows a state in which the piston 5 is at the top dead center position, and at this time, the sweep and exhaust holes 8 and 9 are both closed by the piston 5 as shown in the figure.
Since the intake passage 24 is kept open by the rotary valve 22, the crank chamber 12 is maintained at negative pressure by the compression movement of the piston 5, and therefore the carburetor 2
The air-fuel mixture formed in step 6 flows into the crank chamber 12 through the intake port 25. At the same time, the air-fuel mixture filled in the combustion chamber S in the previous cycle is compressed, and when the piston 5 reaches the top dead center as shown in Figure 1, a spark flies from the spark plug 4, which causes the air-fuel mixture to explodes and burns. Due to this explosive force, the piston 5
When the engine moves downward, the rotary valve 22 closes the intake passage 24, and the air-fuel mixture sucked into the crank chamber 12 is compressed. When the piston 5 comes close to the bottom dead center, the exhaust hole 9 first opens and the combustion gas is discharged into the atmosphere through the exhaust passage 11. Subsequently, the scavenging hole 8 is also opened, so the air-fuel mixture compressed in the crank chamber 12 flows into the combustion chamber S through the scavenging hole 8 and expels the combustion gas. Then piston 5
When the exhaust gas rises past the bottom dead center and the scavenging and exhaust holes 8 and 9 close, the air-fuel mixture is compressed again and the same cycle as described above is repeated.

As described above, since the exhaust passage 11 and the intake passage 24 are separated from each other during operation of the engine, there is no problem in which heat from the exhaust system is transmitted to the intake system, and adverse effects due to heat propagation can be avoided.

Next, a modified embodiment of the present invention will be described based on FIGS. 3 and 4. 3 is a longitudinal sectional side view of the engine, and FIG. 4 is a view taken in the direction of arrow 4 in FIG. 3 with the valve cover removed.

This engine 101 is also a V-type four-cylinder engine, and this valve shaft 120 is installed at a slight inclination from the vertical, and a pulley 130 is fixed to the upper end of the valve shaft 120 as shown.

Another valve shaft 131 is provided parallel to the valve shaft 120. An intake rotary valve 122 is fixed to the middle of the valve shaft 131, and a pulley 132 is fixed to the upper end of the valve shaft 131. A belt 133 is stretched as shown.

By the way, three rotary valves 122 are provided as shown in FIG. In addition, in this modified embodiment, a pair A of opposite cylinders forming a V shape,
Each of the crank chambers 112 and 112' of B has a fourth
As shown in the figure, intake ports 125, 125, 125',
125' are open, two each, and the intake ports 12
5,125 is rotary valve 122-1,12
2-2, the other intake ports 12 are opened and closed synchronously.
5', 125' are rotary valves 122-2, 1
They are opened and closed synchronously at 22-3.

In this way, each crank chamber 112, 112' has two intake ports 125, 125 and 125', 12'.
Since 5' is open, it is possible to expand the effective opening area, increase the amount of intake air, suppress the deterioration of low-speed performance in the engine, and improve high-speed output. However, since the opening area of each intake port is small, the intake inertia effect can also be fully utilized.

According to this modified embodiment, it goes without saying that in addition to the above-mentioned effects, the effects listed in the first embodiment can also be obtained.

(Effect of the invention) As described above, the two-stroke engine of the present invention has
When assembling the intake system equipment, the rear cylinder of the V-type engine is tilted forward to create a wider space above the transmission case, and the intake system equipment can be assembled into this space, which was previously a constraint. The degree of freedom in adjusting the V-shape angle is increased, and the entire engine can be made more compact.

Furthermore, since there is no need to provide an opening for the intake passage in the center of the cylinder, the rigidity of the cylinder can be easily ensured.

Furthermore, since the equipment in the exhaust system and the intake system are separated, the degree of freedom in configuring each exhaust and intake passage increases, and there is also the effect that heat from the exhaust system can be prevented from being transmitted to the intake system.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, and FIG. 1 is a longitudinal cross-sectional side view of a two-stroke engine, FIG. 2 is a view in two directions as viewed from the arrow in FIG. 1 with the valve cover removed, and FIG. 4 is a vertical sectional side view of a two-stroke engine according to a modified embodiment of the present invention, and FIG. 4 is a view taken from arrow 4 in FIG. 3 with the valve cover removed.
FIG. In the drawing, 2 is a cylinder, 5 is a piston, 7 is a crankshaft, 8 is a scavenging hole, 9 is an exhaust hole, 10 is a scavenging passage, 11 is an exhaust passage, 12 is a crank chamber, 1
3 is the transmission case, 14 is the transmission main shaft,
16 is a primary shaft, 20 and 120 are valve shafts, 22 and 122 are intake rotary valves, 2
4 is an intake passage, 25, 125, 125' are intake ports,
26 is a vaporizer.

Claims (1)

[Claims] 1. In a two-stroke engine in which the front cylinder and the rear cylinder are V-shaped and the rear cylinder is inclined forward from the crankshaft, an exhaust passage is provided in the front side of the rear cylinder, and the rear cylinder is A transmission case is provided that extends integrally from the crankcase at the rear, and intake system equipment is arranged above this transmission case, and an intake passage that communicates the intake system equipment with the inside of the crankcase is provided above the crankcase. A two-stroke engine that is characterized by being mounted on the wall.