JPH0318621A - Two cycle engine - Google Patents

Abstract

PURPOSE:To effectively supply a large quantity of air-fuel mixture to a combustion chamber, being free from the volume of a crank chamber by providing a bypass passage, on the upstream side of a check valve, which introduces inertia air-fuel mixture from an intake pipe directly to the combustion chamber. CONSTITUTION:In a 2-cycle engine, a piston 5 connected to a crankshaft 4 is arranged in a combustion chamber A above a crankcase 1. An intake pipe 6 for introducing air-fuel mixture via a check valve 9 is communicated to the lower portion of the crankcase 1 and a crank chamber 7 is communicated via a communicating passage 110 with the combustion chamber A. Hereupon, a bypass passage 12 which introduces inertia air-fuel mixture directly to the combustion chamber A is provided on the upstream side of the check valve 9. It becomes possible thereby to supply a quantity of air-fuel mixture more than that of the air-fuel mixture determined by the volume of the crank chamber 7 to the combustion chamber A via the bypass passage 12. Consequently, horse power and torque can be remarkably improved in cooperation with the improvement of scavenging performance.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a two-stroke engine. [Conventional technology and its technical issues] Two-stroke cycle gasoline engines have a simple mechanism among reciprocating engines, and are lightweight and compact, so they are widely used as engines for motorcycles and light vehicles. As shown in FIG. 5(a), this type of conventional two-stroke engine sucks the air-fuel mixture into the crank chamber from the lower suction boat 61 due to the low pressure generated at the bottom of the piston during the compression stroke (intake/compression). Piston 5' finishes compression and (b
), the mixture is ignited and the piston 5' is pushed down by the combustion gas. During this time, intake continues as usual in the crank chamber, but eventually the piston 5' blocks the intake hole 61, so compression occurs in the crank chamber, and at the same time, as shown in (c), the upper part of the exhaust gas that was blocked by the piston is A hole 10' is opened, and the gas that has finished combustion is ejected from this hole. When the piston 5' further descends, the scavenging hole 11' on the opposite side of the exhaust hole 10' is opened, and as shown in (d), the air-fuel mixture compressed in the crank chamber is blown out from the scavenging hole and inside the cylinder. The remaining combustion gas is expelled from the exhaust hole 10', after which the air-fuel mixture is filled. When this scavenging is finished, the piston 5' moves up and compresses the new air-fuel mixture, which is ignited when the piston reaches top dead center. This is one cycle, and we move on to the next cycle.

Intake control in the above two-stroke engine is performed by raising and lowering the piston, so when the piston lowers, the intake port is forcibly closed, even though there is negative pressure inside the crankcase. It is difficult to supply sufficient mixture. Therefore, as shown in FIG. 6, conventionally, a check valve 9' called a reed valve is provided at the port of the intake pipe 6' facing the crank chamber 2.
' falls and the pressure of the air-fuel mixture in the crank chamber increases, the check valve 9' closes, and the air-fuel mixture in the crank chamber flows into the scavenging passage 11.
It was designed to be fed into combustion chamber A from ''. However, with this structure, the amount of mixture that can be sent to combustion chamber A is limited to the volume of crank chamber 2, and a larger amount of mixture can not be sent to the combustion chamber, which puts a big limit on improving horsepower and torque. was there. The present invention was devised to solve the above-mentioned problems, and its purpose is to effectively feed a large amount of air-fuel mixture to the combustion chamber without being restricted by the volume of the crank chamber. Our objective is to provide a two-stroke engine that can significantly improve torque and torque. [Means for Solving the Problems] In order to achieve the above object, the present invention changes the concept of conventional two-stroke engines, which assumes that all the air-fuel mixture is filled into the combustion chamber via the crank chamber. However, the air-fuel mixture is filled not only from the crank chamber but also from outside the crank chamber using inertial force.

That is, the basic feature of the present invention is that a piston connected to the crank is disposed in the combustion chamber at the upper part of the crankcase, and an intake pipe for introducing the air-fuel mixture through the check valve connects to the lower part of the crankcase. In an engine in which the combustion chamber is connected to the combustion chamber by a scavenging passage, a bypass passage is provided upstream of the check valve to directly guide the inertial mixture from the intake pipe to the combustion chamber.

Another feature of the present invention is that, in addition to providing the bypass passage for guiding the inertial mixture from the intake pipe to the combustion chamber on the upstream side of the check valve as described above, the piston is provided in the upper part of the piston. The purpose is to drill a pore at the end of the passage at or near the point to allow the air-fuel mixture to flow from the crank chamber as an airflow. According to this structure, the air-fuel mixture in the crankcase flows from the pores into the passage as a jet stream,
The ejector effect allows a larger amount of inertial mixture to be reliably supplied to the combustion chamber. [Examples] Examples of the present invention will be explained below based on the attached drawings. Figures 1, 1a and 2 show an embodiment of a two-stroke engine according to the invention. 1 is a crankcase, and 2 is a cylinder block that is connected to the upper part of the crankcase 1 and defines a combustion chamber (cylinder) A with a piston to be described later. 3 is a spark plug attached to the upper part of the combustion chamber 8; 4 is a crankshaft rotatably disposed in the crankcase 1; 5 is a piston slidably inserted into the cylinder 2; and connected with connecting rod 50.

Reference numeral 6 denotes an intake pipe, which opens to the atmosphere via an air cleaner (not shown), and its tip reaches the crank chamber 7. Also,
For example, a piston-type carburetor 8 is provided in the middle, which mixes gasoline with air.

9 is a check valve provided at the tip or midway of the intake pipe 6;
In the illustrated example, a reed valve structure is used, which is provided at the tip of the intake pipe 6 and has one end of a tongue piece such as a metal piece fixed.

Reference numeral 10 is an exhaust hole provided at a position that is closed during the upward movement of the piston 5, and communicates with the muffler via an exhaust pipe. The exhaust hole 10 may be opened and closed by a variable valve. Reference numeral 11 denotes a scavenging hole which is different in height from the exhaust hole 10, and is provided in at least two locations, with one end connected to the combustion chamber A and the other end connected to the crank chamber through a communication passage 110 formed on the outside of the cylinder. 7. Although the above structure is similar to that of a conventional two-stroke engine, the present invention has a bypass passage l2 whose one end communicates with the intake passage 6 upstream of the check valve 9 and whose other end communicates with the combustion chamber A.
is specially set up. For more information. The pie bus passage 12 is
It is provided in the outer part of the cylinder and at a position out of phase with the communication passage 110 in the circumferential direction. In the one shown, one end communicates with the chamber 60 on the upstream side of the check valve 9, and the other end communicates with the chamber 60 on the upstream side of the check valve 9. A position where the piston 5 at the point position cannot be closed, in other words, the top is at a lower level than the exhaust hole 10,
Preferably, it communicates with the combustion chamber A at approximately the same level as the scavenging hole l1 at a predetermined angle. The bypass passage 12 may be formed directly into a part of the cylinder block as shown in the figure, or may be assembled as an independent pipe-shaped part and connected to the intake pipe O and the combustion chamber A by welding or the like. ．． Preferably, as shown in detail in FIG. 2, a bypass passage 12 is formed in the side wall of the piston 5, particularly in the vicinity of the groove 52 into which the piston ring is inserted, through the side wall 53 and diagonally upward, that is, at the bottom dead center position of the piston. The pores 13 are formed so as to communicate with the pores 13. For example, the pore 13 is 4■
φ and diameter are small, and at least one, preferably two or more, are arranged.

Note that the inner wall of the cylinder 2 may be provided with a diagonal groove 14, especially when it communicates with the end region 120 of the bypass passage l2. FIGS. 3(a), 3(b), and 3(c) show another embodiment of the present invention, in which the combustion chamber A and the exhaust pipe 6 upstream of the check valve are connected, S; bypass passage; 12 is equipped with a control valve l5. Fig. 3(a) shows a control valve 15 in which a small check valve such as a reed valve is arranged, and Fig. 3(b) shows a control valve in which a diaphragm type negative pressure valve is arranged. 7 and the back pressure chamber may be connected by a passage vibrator 150, but it may also be controlled by the CPU using an electromagnetic valve or the like.7 In FIG. 3(C), a throttle valve such as a butterfly type is arranged as the control valve 15. By adjusting the opening degree of the throttle valve, backflow prevention and bypass mixture flow rate are controlled. The opening degree can be adjusted by controlling the elements that move the valve stem using the CPU. [Operation of the embodiment] When the piston 5 rises from the state shown in FIG. 1, the pressure in the crank chamber 7 becomes negative, so the air-fuel mixture passes through the intake pipe 6, expands the check valve 9, and is sucked into the crank chamber 7. It will be included. On the other hand, the air-fuel mixture in the combustion chamber A is compressed by the rise of the piston 5, is ignited by the spark plug 3 near top dead center, and explodes, and the expanded gas pushes the piston 5 down. When the piston 5 descends and its movement comes to an end, the exhaust hole lO, which had been blocked by the piston 5 until then, opens into the combustion chamber A, from which the combustion gas that has finished exploding is blown out.
When the piston 5 further moves down a little further, the scavenging hole l1, which was blocked by the piston 5, looks into the combustion chamber A. As a result, the air-fuel mixture in the crank chamber, which has been compressed by the downward movement of the piston 5, is ejected from the communication passage 110 through the scavenging hole 11 into the combustion chamber A, and the residual combustion gas is pushed out from the exhaust hole 10.

At this time, the air-fuel mixture filling the crank chamber 7 from the intake pipe 6 is compressed by the downward stroke of the piston. Conventionally, the above operation filled the combustion chamber A with the air-fuel mixture that filled the crank chamber 7 at the end of the scavenging stage, and the subsequent upward movement of the piston 5 compressed it only on the piston head side. In the invention, the bypass passage 12 is opened during the stroke of the piston between the top dead center and the bottom dead center, and the intake passage 6 upstream of the check valve 9 communicates with the combustion chamber A. For this reason,
Almost simultaneously with the supply of the compressed air-fuel mixture in the crank chamber 7 through the scavenging hole 11, the inertial air-fuel mixture is directly introduced into the combustion chamber A through the bypass passage 12, and is confined in the combustion chamber A by the upward movement of the piston 5.

Figures 4(a) and 4(b) show the above process. When the piston 5 is pushed down during the explosion stroke and the exhaust hole 10 opens, the combustion gas is sent to the muffler 16, but at this time, the combustion gas from the previous explosion is A strong negative pressure is applied to the exhaust hole 10 due to the exhaust gas, and therefore, when the bypass passage 12 is exposed by the subsequent descent of the piston 5, the air-fuel mixture is reliably sucked in by the action of the negative pressure. At the same time, the compressed air-fuel mixture in the crank chamber 7 is ejected from the scavenging hole 11 into the cylinder.

When the piston 5 reaches the bottom dead center and then moves upward, the bypass passage 12 is closed, and therefore the bypass passage 12 is closed.
There is almost no possibility that the air-fuel mixture will flow backwards, and of course it will end instantaneously near the top dead center of the piston, so the fire will not spread to the bypass passage 12. At this time, the exhaust hole 10 is still about half open, and in this process, the exhaust hole 1
0, the reflected wave from the previous explosion has returned, and as a result, a large amount of air-fuel mixture filled from the bypass passage 12 and the scavenging hole 11 flows into the combustion chamber A as shown by the arrow in Fig. 4(b). is pushed back. Therefore, a large amount of air-fuel mixture is compressed by the subsequent upward movement of the piston 5. From the above, according to the present invention, the amount of fuel supplied to the combustion chamber A can be increased, and the cylinder volume can be substantially increased. In addition, when the small hole 13 is bored in the upper part of the piston 5, during the exhaust or scavenge stroke of the piston 5,
The air-fuel mixture compressed in the lower crank chamber 7 becomes a jet stream from the pores 13 and is injected toward the combustion chamber A from the end of the passage. This creates a strong ejector effect,
The suction efficiency of the inertial mixture in the bypass passage 12 is increased. Therefore, a large amount of air-fuel mixture can be filled into the combustion chamber A more reliably, and torque at low and medium speeds can be significantly improved.

〔Effect of the invention〕

According to the first aspect of the present invention described above, in a two-stroke engine, it becomes possible to supply a mixture to the combustion chamber in an amount greater than the amount determined by the volume in the crank chamber, which improves scavenging performance. It has the excellent effect of dramatically increasing horsepower and torque. According to the second aspect of the present invention, the air-fuel mixture compressed in the crank chamber is passed through the passage as a jet stream, so that an excellent effect can be obtained in that the inertial air-fuel mixture can be more reliably supplied to the combustion chamber.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing an embodiment of the two-stroke engine according to the present invention at the bottom dead center position of the piston, FIG. 1a is a partial sectional view showing the piston at the top dead center position, and FIG. Partially enlarged view of Figure 1, Figure 3 (a) (b)
(c) is a partial cross-sectional view showing another embodiment of the present invention, FIGS. (a) to (d) are explanatory diagrams showing the stroke cycles of a conventional piston intake type two-stroke engine, and FIG. 6 is a sectional view of a conventional two-stroke engine using a check valve. 1...Crankcase, 2...Cylinder, 5...
Piston, 6... Intake pipe, 7... Crank chamber, 8.
...Carburetor, 9...Check valve, 10...Exhaust hole,
11...Scavenging hole, 12...Bypass passage, 13...
・Pore, A... combustion chamber.

Claims (3)

[Claims] (1) A piston connected to the crank is placed in the combustion chamber at the top of the crankcase, an intake pipe is connected to the bottom of the crankcase via a check valve, and the inside of the crankcase is connected to the combustion chamber by a scavenging passage. A two-stroke engine, characterized in that a bypass passage is provided upstream of the check valve to guide the air-fuel mixture from the intake pipe to the combustion chamber without passing through the crank chamber. (2) A type in which a piston connected to the crank is arranged in the combustion chamber at the top of the crankcase, an intake pipe is connected to the bottom of the crankcase via a check valve, and the inside of the crankcase is connected to the combustion chamber by a scavenging passage. In the engine, a bypass passage is provided upstream of the check valve to guide the air-fuel mixture from the intake pipe to the combustion chamber without passing through the crank chamber, and
A two-stroke engine, characterized in that the piston is provided with a pore in an end area of the passage for allowing the air-fuel mixture to flow from the crank chamber as an airflow. (3) 2 as set forth in either claim 1 or 2, which includes a bypass passage provided with a control valve.
cycle engine.