Three-air-valve engine for small-displacement motorcycle

Abstract

The invention discloses a three-air-valve engine for a small-displacement motorcycle. The top face of a piston head part (14a) is bumped upwards so as to form a flat-roofed boss (14c); the inner top wall of a combustion chamber (5) has a structure with two inclined surfaces; a first inclined surface (5a) and a second inclined surface (5b) are smoothly transitioned through a curved surface; the length (L4) of an air inlet (7) of a cooling air channel is 32.5 to 39.5 millimeters and the width (L5) of the air inlet (7) is 30 to 36 millimeters; and a cam angle a between an air inlet cam (12) and an air exhaust cam (13) is more than or equal to 108.5 degrees and less than or equal to 128.8 degrees. By optimally designing a piston, an air inlet channel, an air exhaust channel, the combustion chamber, the cooling air channel and a cam shaft, the air inflation efficiency of the engine at middle and high rotational speed is guaranteed, the power and the torque of the engine are improved, and the operating requirements for high durability, high reliability and high comfortableness of the three-air-valve engine are met.

Description

technical field [0001] The invention belongs to the technical field of engines, and in particular relates to a three-valve engine of a small-displacement motorcycle. Background technique [0002] At present, small-displacement motorcycle engines all adopt a two-valve structure. This is because small-displacement motorcycle engines have relatively low performance requirements for medium and high speeds. Although the conventional two-valve engine is relatively noisy, it can meet the operating requirements. Require. With the continuous improvement of performance requirements, it has become a development trend to use three-valve engines on small-displacement motorcycles. Domestic motorcycle manufacturers have stepped up the pace of developing three-valve engines for small-displacement motorcycles. How to design the gas distribution and combustion systems of three-valve engines to meet the medium-speed and high-speed performance requirements of three-valve engines is an importan...

AI Technical Summary

Problems solved by technology

Because the space between the top and the valve is too large when the piston is compressed, the squeeze effect will be bad, the thermal efficiency of the engine will be low, and the combustion of the fuel mixture will not be sufficient

The width of the piston ring groove set on the piston skirt is usually 1mm, and the width of the oil ring combination ring groove is usually 2mm. The tension of the piston ring in this design is relatively large, so that the friction between the piston ring and the cylinder block is also large. The mechanical efficiency of the engine cannot be fully utilized, and at the same time, the wear between the engine cylinder and the piston ring and piston is relatively large, which increases the frequency of maintenance and replacement

In addition, during the operation of the engine, the friction of the piston skirt is also relatively large, which will cause excessive wear and tear, thereby reducing the normal service life of the piston.

[0004] The shape of the combustion chamber of the conventional three-valve engine is irregular, there are many steps in the combustion chamber, the air flow resistance is large, the flame propagation speed is low, and the heat transfer area is large, the heat loss is large, resulting in low thermal efficiency

At the same time, the unreasonable design of the intake and exhaust passages of the three-valve engine will lead to low intake flow coefficient, small intake tumble flow, and insufficient intake air, so that the movement speed of the mixed gas flow is slow; similarly, the exhaust flow coefficient Smaller, insufficient exhaust so the engine can't draw in as much fuel mixture

The above factors will affect the greater power output of the engine on the one hand, and on the other hand, will increase the energy consumption of the engine

Chinese patent ZL02113222.4 disclosed a three-valve engine combustion chamber on July 21, 2004. The combustion chamber is composed of a canopy and a spherical surface. Although it has the characteristics of simple manufacture, the power and torque are small, and the power is 5.6kw / 8500r / min, the torque is 7.2N.m / 6500r / min, and the noise of the valve is relatively large

[0005] The cylinder head of a conventional three-valve engine is generally equipped with a cooling air duct. The design of the cooling air duct is unreasonable, and there is a corner near the inlet of the cooling air duct, which may easily cause the air flow in the cooling air duct to be unsmooth; at the same time, the cooling air duct There is a strong vortex flow group at the outlet, which leads to a large airflow resistance there, so that the air with a small flow in the cooling air duct cannot flow out, so the heat on the back of the combustion chamber cannot be taken away by the cooling airflow, resulting in a very high temperature of the cylinder head. high

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