JPH0510214A - Two-cycle engine device - Google Patents

Abstract

PURPOSE:To construct a two-cycle engine device which is embodied in a simple structure and which cart suck part of the exhaust gas certainly. CONSTITUTION:A two-cycle engine device concerned includes a crank case 1 for two-cycle engine, a piston 2 accommodated in this crank case 1, and an exhaust and a draft system which are coupled with the crank case 1. A notch 7 for draft in a specified dimension is furnished at the skirt formed at that part of piston 2 which is confronting the exhaust system. Thereby it is practicable to construct an EGR using a simple configuration, and to drop greatly the HC concentration in the combustion gas, which should allow eliminating any reed valve or bypass pipe and also provision of any extra assembly line for it and which should improve the producibility and aconomy to a great extent from the conventional techniques.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-cycle engine system, and more particularly to a two-cycle engine system in consideration of exhaust gas regulation.

[0002]

2. Description of the Related Art As a method for reducing nitrogen oxides (NOx), there are conventionally known methods such as delaying the ignition timing and using a reducing catalyst. On the other hand, in recent years, a part (5 to 20%) of the exhaust gas is returned to the intake gas EG
The R (Ex. Gas Recirculation) method is relatively often taken up as an effective method.
FIG. 5 shows an example thereof.

In the conventional example shown in FIG. 5, a part of the exhaust gas is returned from the exhaust system 61 into the crankcase 50 through the bypass pipe 62. In the figure, reference numeral 63 indicates a reed valve. Reference numeral 51 indicates a piston, and reference numeral 70 indicates an ignition plug.

[0004]

However, in the above-mentioned conventional example, it takes a lot of time and labor to equip the bypass pipe 62 and the reed valve 63 or to adjust them. Further, there is a defect that the structure is complicated and the productivity is poor.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a two-cycle engine device which improves the inconveniences of the conventional example and has a particularly simple structure and can surely intake a part of the exhaust gas. And

[0006]

According to the present invention, a two-cycle engine having a crankcase for a two-cycle engine, a piston housed in the crankcase, and an exhaust system and a ventilation system connected to the crankcase. In the apparatus, the skirt portion of the piston facing the exhaust port of the exhaust system is provided with a ventilation cutting portion of a predetermined size. This aims to achieve the above-mentioned object.

[0007]

[Operation] Due to the action of the ventilation cutting portion provided on the skirt of the piston, the combustion gas of high HC concentration in the vicinity of TDC of the piston during the intake process is changed depending on the timing before and after the piston is located at TDC. It was captured for a moment and introduced into the crankcase 1 to establish exhaust gas recirculation.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. First, in FIG. 1, reference numeral 1 is a crankcase, reference numeral 2 is a piston, and reference numeral 3 is a cylinder in which a combustion chamber 3A is arranged at an upper portion. The intake pipe 11 of the intake system is provided on the crankcase 1 side of the cylinder 3.
The exhaust pipe 21 of the exhaust system is installed below the combustion chamber 3A of the cylinder 3.
An air filter 12 and a carburetor 13 are attached to the intake system. A muffler 22 is also provided in the exhaust system. Further, a ventilation cutout portion 7 having a predetermined size is provided on a skirt portion of the piston 2 facing the exhaust pipe 21. Other configurations are the same as those of the above-mentioned conventional example.

Now, the transient HC concentration in the exhaust pipe 21 in FIG. 3 will be considered. In this 2-cycle engine, the HC concentration is high from the EC portion to the EO portion in FIG. Further, since the emission of combustion gas starts from the EO portion, the HC concentration drops sharply. In the figure, the HC concentration increases due to the scavenging of the scavenging air again before the BDC point. In the embodiment of FIG. 1, the combustion gas under the high HC concentration is recirculated.

That is, the piston 2 is in the state shown in FIG.
In the prior art, the exhaust port 21A of the exhaust pipe 21 is sealed by the piston skirt in the prior art. However, under the same condition, in the present embodiment, the ventilation cutting portion 7 having a predetermined size is used.
As shown in FIG. 2, the exhaust port 21A of the exhaust pipe 21
The feature is that the partial space is set so as to communicate with the crankcase 1 as it is. That is, in the diagram shown in FIG. 3, combustion gas having a high HC concentration near TDC is captured for a moment during the intake stroke of the piston 2 and is introduced into the crankcase 1 for recirculation. The experimental results are shown in FIG. In the experiment, the engine rotation was 3500 [RPM]
Set to. The load is unified to 75%. In the experimental results shown in FIG. 4, shows the case of using a conventional catalyst,
Shows the case according to the prior art of FIG. 5, and shows the case according to the present embodiment. Despite the simple structure, the HC concentration of the combustion gas could be reduced to a level almost equal to that of the complicated structure of FIG.

[0011]

Since the present invention is constructed and functions as described above, according to the present invention, a ventilation cutting portion of a predetermined size is provided in the skirt portion of the piston facing the exhaust port portion. It is possible to significantly reduce the HC concentration of the combustion gas,
Since the reed valve and bypass pipe are unnecessary, and the assembly line is completely unnecessary, it is only necessary to increase the cutting process for the piston production process by one.
It is possible to provide an unprecedented, excellent two-cycle engine device capable of significantly improving its productivity and economic efficiency as compared with the prior art.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of the present invention.

FIG. 2 is an enlarged explanatory view showing a ventilation cutting portion in FIG.

FIG. 3 is a diagram showing a change in HC concentration at an exhaust port when an exhaust gas recirculation system is not adopted.

FIG. 4 is an explanatory diagram showing a case where the experimental result of FIG. 1 is compared with a conventional one.

FIG. 5 is a schematic configuration diagram showing a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Crankcase 2 Piston 3A Combustion chamber 3 Cylinder 7 Cutting part for ventilation 11 Intake pipe 21 Exhaust pipe

Claims (1)

Claim: What is claimed is: 1. A two-cycle engine device having a crankcase for a two-cycle engine, a piston housed in the crankcase, and an exhaust system and a ventilation system connected to the crankcase. In the above, the ventilation cutting portion of a predetermined size is provided in the skirt portion of the piston facing the exhaust port of the exhaust system.
Cycle engine equipment.