JP2645294B2 - Two-cycle internal combustion engine - Google Patents

Description

The present invention relates to a two-stroke internal combustion engine, and more particularly, to a two-stroke internal combustion engine that improves torque performance in a high-speed rotation region.

2. Description of the Related Art In a two-stroke internal combustion engine, for example, the ignition timing is delayed to increase the temperature of exhaust gas, and the torque performance in a high-speed rotation region is improved.

As described above, when the temperature of the exhaust gas is increased in the high-speed rotation region, a phenomenon such as an increase in the sound speed of the exhaust gas and a reduction in the apparent length of the exhaust pipe occurs, and the torque performance in the high-speed rotation region is improved. I do.

[Problems to be Solved by the Invention] By the way, when performing such ignition retarding, if the ignition timing is delayed in the high-speed rotation region, it is affected by squish that concentrates the air-fuel mixture toward the spark plug, Blowout due to squish is likely to occur, which is a cause of misfire.

The present invention has been made in view of such circumstances,
It is an object of the present invention to provide a two-cycle internal combustion engine that raises the temperature of exhaust gas without retarding ignition and improves torque performance in a high-speed rotation region.

[Means for Solving the Problems] In order to solve the above problems, the present invention forms a combustion chamber between a piston top surface at top dead center and a cylinder head wall surface facing the piston top surface. In a two-stroke internal combustion engine in which a pair of spark plugs are provided on the cylinder head, the pair of spark plugs are provided at different distances from the center of the combustion chamber, and at least in a rotation region equal to or less than a maximum torque generating rotation speed. It is characterized in that an ignition plug close to the center of the combustion chamber is ignited, and only the ignition plug distant from the center of the combustion chamber is ignited in a rotation region equal to or higher than the maximum torque generating rotational speed.

[Operation] In the two-stroke internal combustion engine of the present invention, in a rotation region equal to or lower than the maximum torque generating rotation speed, the ignition is performed by the ignition plug at least close to the center of the combustion chamber.

On the other hand, in a rotation region at or above the maximum torque generating rotation speed, only the ignition plug is ignited away from the center of the combustion chamber, so that the combustion time of the air-fuel mixture increases and the temperature of the exhaust gas rises. For this reason, the sound speed of the exhaust gas is improved in the high-speed rotation region, and a phenomenon such as a reduction in the apparent length of the exhaust pipe occurs, and the torque performance is improved.

Next, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a side view of a motorcycle equipped with a two-stroke internal combustion engine of the present invention.

In the drawing, reference numeral 1 denotes a motorcycle body. A front pipe 4 is provided on a head pipe 2 of the vehicle body 1 via a front fork 3, and a rear wheel 6 is provided via a rear arm 5 at the rear.

A two-cycle internal combustion engine 7 is mounted in the center of the vehicle body 1, and the two-cycle internal combustion engine 7 includes a crankcase 8, a cylinder block 9, and a cylinder head 10. An exhaust pipe 11 is connected to the front of the cylinder block 9, a carburetor 13 is provided via an intake pipe 12 to the rear, and an air cleaner 14 is connected to the carburetor 13. The cylinder head 10 has a pair of spark plugs 15,1
6 are provided.

This two-cycle internal combustion engine is configured as shown in FIG.

A piston 17 is provided in the cylinder block 9 so as to be able to reciprocate, and a cylinder chamber 18 and a crank chamber 19 are defined by the piston 17. Scavenging ports 20 and 21 for communicating the cylinder chamber 18 and the crank chamber 19 are formed in the cylinder block 9, and are opened and closed by the reciprocating motion of the piston 17. An exhaust passage 2 for discharging exhaust gas is formed in the cylinder block 9, and the exhaust pipe 11 is connected to the exhaust passage 22. In addition, an intake passage for sucking an air-fuel mixture is provided in the cylinder block 9.
An intake pipe 12 is connected to the intake passage 23, and a reed valve 24 is disposed in the intake passage 23.

As shown by a two-dot chain line in FIG. 2, a combustion chamber 25 is formed between the piston top surface 17a at the top dead center and the cylinder head wall surface 10a facing the piston top surface 17a. The pair of spark plugs 15 and 16 provided are provided at different distances L1 and L2 from the center A of the combustion chamber 25.

This cylinder head 10 has a notch 10b facing the outer peripheral portion of the piston 17, and a squish zone is formed in the combustion chamber 25 so that the air-fuel mixture is concentrated in the combustion chamber 25 so that the ignition rate and the flame propagation are increased. Has become.

The ignition plug 15 is provided so that its electrode portion 15a coincides with the cylinder head wall surface 10a, and the other ignition plug 1
Numeral 6 is provided at a portion where the part 10c of the cylinder head 10 is recessed, and the electrode portion 16a is located at a position recessed from the cylinder head wall surface 10a.

The ignition of the ignition plugs 15 and 16 is performed in a rotation region equal to or lower than the maximum torque generation rotation speed, that is, from the low speed rotation region to the maximum torque generation rotation speed, the pair of ignition plugs 15 and 16 are ignited to shorten the combustion time. I have.

On the other hand, in the rotation region equal to or higher than the maximum torque generating rotation speed, only the ignition plug 16 distant from the center portion A of the combustion chamber 25 is ignited, and the combustion time is extended to increase the temperature of the exhaust gas. In this way, by extending the burning time,
Since the temperature of the exhaust gas rises in the high-speed rotation region, a phenomenon such as an increase in sound speed and a reduction in the apparent length of the exhaust pipe occurs, and the torque performance is improved.

In the rotation range below the maximum torque generating rotation speed, the ignition plug 15 close to the center portion A of the combustion chamber 25 may be ignited without igniting both the pair of ignition plugs 15 and 16.

FIG. 3 is a sectional view of a two-cycle internal combustion engine showing another embodiment.

In this embodiment, one spark plug 27 is provided at the center of the cylinder head 10, the other spark plug 28 is provided at the end, and the electrode 27a of the center spark plug 27 is
The electrode 28a of the spark plug 28 at the other end is located away from the center A of the combustion chamber 25.

In this embodiment, at least in the rotation range below the maximum torque generating rotation speed, the spark plug 27 close to the center A of the combustion chamber 25 is used.
Is ignited, and only the ignition plug 28 distant from the center portion A of the combustion chamber 25 is ignited in a rotation region equal to or higher than the maximum torque generating rotation speed. As described above, by igniting only the ignition plug 28 in the rotation region equal to or higher than the maximum torque generating rotation speed, the combustion time is extended, the exhaust gas temperature is increased, and the torque performance is improved.

[Effects of the Invention] As described above, according to the present invention, a pair of spark plugs are provided at different distances from the center of the combustion chamber, and at least in the center of the combustion chamber in a rotation region below the maximum torque generating rotation speed. In the rotation region above the maximum torque generating rotation speed, only the ignition plug distant from the center of the combustion chamber is ignited. Ki burning time increases. Therefore, the temperature of the exhaust gas becomes high, the sound speed of the exhaust gas is improved in a high-speed rotation region, and a phenomenon such as a reduction in the apparent length of the exhaust pipe occurs, and the torque performance is improved.
In addition, the temperature of the exhaust gas is raised without delaying the ignition timing, so that the squish is prevented from blowing out and the operability is excellent.

[Brief description of the drawings]

FIG. 1 is a side view of a motorcycle equipped with a two-stroke internal combustion engine of the present invention, FIG. 2 is a cross-sectional view of a two-stroke internal combustion engine, and FIG. 3 is a cross-sectional view of an internal combustion engine of another embodiment. In the figure, reference numeral 7 denotes a two-cycle internal combustion engine, 10 denotes a cylinder head, 15, 16, 27, and 28 denote spark plugs, 17 denotes a piston, 17a denotes a piston top surface, 25 denotes a combustion chamber, and A denotes a center of the combustion chamber. .

Claims (1)

(57) [Claims] 1. A two-stroke internal combustion engine having a combustion chamber formed between a piston top surface at top dead center and a cylinder head wall surface facing the piston top surface, and a pair of spark plugs provided in the cylinder head. In the above, the pair of spark plugs are provided at different distances from the center of the combustion chamber, and in a rotation region equal to or lower than the maximum torque generating rotation speed, at least a spark plug close to the center of the combustion chamber is ignited to generate the maximum torque. A two-stroke internal combustion engine characterized in that only a spark plug distant from the center of the combustion chamber is ignited in a rotation range equal to or higher than the rotation speed.