JPS60153428A - Stratified scavenging two-cycle internal-combustion engine - Google Patents

Abstract

PURPOSE:To make such a scaverging as being stratified in thick and thin parts performable, by dividing a scavenging passage into plural parts in a cylinder radial direction, while installing plural scavenging holes separately interconnected each, in each of these divided scavenging passages. CONSTITUTION:An air-fuel mixture flows in a scavenging passage 12 at the crankcase side by way of an opening 10 at the crank chamber side of a scavenging passage formed in a crankcase 13 in the scavenging process. Since the air-fuel mixture flowing in the scavenging passage 12 is of heterogeneous fluid in type inclusive of fuel vapor and/or liquefied fuel, such a fluid of the liquefied fuel as being relatively large in specific gravity is one-sided to the outer side of a flow at a bent part. On the other hand, a thick air-fuel mixture much inclusive of a fuel component such as the liquefied fuel flows in a scavenging passage at the outside formed in a cylinder 1, while a thin air- fuel mixture being small in the fuel component flows in another scavenging passage 4 at the inside, respectively. The thick air-fuel mixture is fed to an empty space 3 inside the cylinder by way of a scavenging hole 7 formed in position away from an exhaust port 2 while the thin mixture to the said cylinder space 3 by way of a scavenging hole 6 nearer to the exhaust port in a separate manner, respectively, whereby such a scavenging as being stratified in thick and thin parts is performable.

Description

Detailed Description of the Invention 21 The present invention relates to a stratified scavenging crank chamber compression two-stroke internal combustion engine. In a small two-stroke internal combustion engine equipped with a carburetor, the scavenging air contains liquid fuel even at the moment it flows into the cylinder through the scavenging hole. Contains particles and liquid films. The inventors have discovered that by utilizing these properties of scavenging air, it is possible to create rich and lean air-fuel mixtures in the intake pipe or crank chamber with basically the same structure as conventional engines with carburetors, thereby realizing stratified scavenging. (For example, patent application dated May 19, 1982, patent application No. 58-08807)
No. 9 Title of the invention: stratified scavenging two-stroke internal combustion engine,
Patent application dated December 30, 1982 (1)'Application number notification not received Title of invention...Scavenging air hole for two-stroke internal combustion engine)
.

The present invention focuses on the behavior of the air-fuel mixture when it is pressure-fed from the crank chamber to the scavenging passage, separates the air-fuel mixture with different fuel concentrations, and supplies the mixture into the cylinder through different scavenging passages and scavenging holes, thereby achieving stratified scavenging. By achieving this, fresh air ventilation makes it possible to reduce losses.

An object of the present invention is to reduce the fuel consumption of the engine and the amount of unburned hydrocarbons in the exhaust gas by reducing the fresh air blowout.

Application examples of the invention will be described in detail below with reference to the drawings.

Figure 1 is a part of a cross-sectional view in the cylinder radial direction of a Schnurre scavenged two-stroke gasoline engine with a carburetor to which the present invention is applied. FIG. 3 is a three-dimensional view of the scavenging passage and the scavenging hole.

In this application example, the scavenging passage formed in the cylinder (1) is divided into two pairs in the cylinder radial direction by the scavenging passage partition Jl (11), and the divided scavenging passage (4)
, and (5) individually communicating with each other <6)
, (7) are formed.

During operation of this engine, a mixture of air and gasoline adjusted to an appropriate amount by the carburetor flows into the crank chamber (9) through the intake pipe, and as shown in Figure 2, during the scavenging process, the air and gasoline mixture flows from the crank case (13) through the crank chamber during the scavenging process. ) flows into the crankcase side scavenging passage (12) through the crank chamber side opening (10) of the scavenging passage. Since the scavenging passage (12) is usually an open passage, the scavenging air flows in a curved manner.

Mixture flowing in the scavenging passage JP-A-153428 (2) Since air is a heterogeneous fluid that includes fuel vapor and liquid fuel, fluids with relatively high specific gravity such as liquid fuel flow outside the flow at curved parts. It depends on the bias. Therefore, by dividing the scavenging passage in the cylinder radial direction as in this application example, two types of air-fuel mixtures having different specific gravities can be separated. That is, a rich air-fuel mixture containing a large amount of fuel components such as liquid fuel flows into the outer scavenging passage (5) formed in the cylinder, and flows through the inner scavenging passage (4).
A lean air-fuel mixture with few fuel components flows through. The rich air-fuel mixture flows through the scavenging hole (
7) and the lean mixture is separately supplied into the cylinder (3) via the N6 hole (6) near the IP hole, thereby making it possible to scavenge the air stratified into rich and thin layers.

As described above, the present invention utilizes the properties of the air-fuel mixture flowing through the scavenging passage and the shape of the scavenging passage to easily generate rich and lean air-fuel mixtures and obtain stratified scavenging. Therefore, when applying the present invention, stratified scavenging can be achieved without complicating the engine structure and without any difficult manufacturing problems, and the fuel consumption and unburned hydrocarbons in the exhaust gas can be significantly reduced. It is possible to reduce this by 5-.

Note that the scavenging air flow can be precisely controlled by not only dividing the scavenging passage into two in the radial direction of the cylinder as in the example of the present invention, but also dividing it in the circumferential direction of the cylinder so that the scavenging holes and the scavenging passage are divided into three or more. It is natural that the effect of stratified scavenging can be further enhanced by

[Brief explanation of the drawing]

Figure 1 is a partial cross-sectional view in the cylinder radial direction of a Schnuler scavenged two-stroke gasoline engine with a carburetor to which the present invention is applied, Figure 2 is a cross-sectional view of the scavenging passage of the engine shown in Figure 1', and Figure 3 is a cross-sectional view of the scavenging passage of the engine shown in Figure 1'. FIG. 3 is a three-dimensional view of a scavenging passage and a scavenging hole of the engine. In these figures, (1)... cylinder, (2)...
Exhaust hole, (3)...Inner cylinder space, (4)...Inner scavenging passage, (5)...Outer scavenging passage, (6)''...
Lean mixture scavenging hole, (7) Rich mixture scavenging hole, (8
)... Piston, (9)... Crank chamber, (to)
-... Crank chamber side opening of m air passage, (11)...
Partition wall of scavenging passage, (12)...Crankcase side scavenging passage, (15)...Crankcase, (14)...
- Crank web, (15)...Conrid. Figure 2

Claims (2)

[Claims] (1) A scavenging passage that communicates between the crank chamber adjacent to the cylinder and a scavenging hole opened in the inner wall of the cylinder is divided into a plurality of scavenging passages in the cylinder radial direction, and a plurality of scavenging passages that communicate with each of the divided scavenging passages separately are formed. Crank chamber compression two-stroke internal combustion engine with scavenging holes. (2) In the above "Claims" (1), the mixture of fuel and air that is force-fed from the crank chamber to the scavenging passage is mixed with a relatively high fuel concentration by using inertia, gravity, centrifugal force, etc. This is a two-stroke internal combustion engine with a crank chamber pressure network Schöhle scavenging system, in which the air and relatively thin air-fuel mixture are separated and supplied into the cylinders through separate scavenging passages and scavenging holes.