JPS6220620A - 2-cycle engine - Google Patents

Abstract

PURPOSE:To improve the efficiency of suction, exhaust, and scavenging, by a method wherein a pair of pistons are coupled to a common crank shaft with a phase difference, suction and exhaust ports are formed in a cylinder part on the piston side having rapid phase and a scavenging port is provided in the cylinder part on the piston side having delay phase. CONSTITUTION:Since, when a crank shaft 26 is rotated, upper and lower pistons 5 and 4 are approached to each other to decrease the volume of a combustion chamber 6, fuel-air mixture is compressed, and ignition explosion is conducted by means of an ignition plug 2. When the upper and lower pistons 5 and 4 are separated from each other by dint of an explosion force, a rotation force is exerted on the crank shaft 26. With the lower piston 4 lowered, fuel-air mixture, pressurized in the crank chamber, and fuel-air mixture, pressurized in the back chamber of the piston resulting from raising of the upper piston 5, incomes to a combustion chamber 6 through a scavenging port 14. In which case, since the lower piston 4 is set to a rapid phase and the upper piston 5 to a delay phase, suction and exhaust ports 8 and 7 and a scavenging port 14 are asymmetrical to each other in relation to a displacement in the volume of a combustion chamber.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a uniflow type two-stroke engine.

(Prior Art) Conventional two-stroke engines generally have one piston in one cylinder, and the piston is connected to the crankshaft via one connecting rod, and the piston connects the intake port, exhaust port, Since the scavenging port was structured to be Ilm 11 II Jall, there were the following drawbacks. That is, (1) intake/exhaust and scavenging port opening/closing are at top dead center (T])C)
, are symmetrical about the bottom dead center (B 1' C), so the blow-by and blow-back of unburned gas are large, the suction efficiency and charging efficiency are low, and the fuel consumption rate is high. Also, the output is low.

(2) The inertia of the reciprocating part is large and vibrations are large.

(3) Most of the components are cooled by an external cooling method, which not only requires a cooling capacity comparable to that of humans, but also causes large cooling losses because a large amount of heat is carried away to the outside air.

(4) Since the scavenging is not completely performed (that is, the combustion gas and the scavenging gas are mixed), the output is low, and irregular combustion is likely to occur at low speed rotation.

(Purpose of the invention) The present invention makes the opening of the intake/exhaust and scavenging ports asymmetrical with respect to the first dead center and bottom dead center so that the intake/exhaust can be carried out completely, and also uses a uniflow type to improve the scavenging efficiency and improve the output. The purpose is to achieve this goal.

(Structure of the Invention) The present invention connects a pair of pistons facing each other in a common cylinder with a phase difference to a common crankshaft via a connecting rod, and connects an exhaust port and an intake port to the cylinder part on the side of the piston that has an earlier phase. This is a two-stroke engine characterized by air ports arranged in the cylinder portion on the slower piston side.

(Example) Fig. 1 is a vertical front view taken perpendicular to the crankshaft during the scavenging stroke, and Fig. 2 is a longitudinal side view taken along the line ■-■ in Fig. 1 during the explosion stroke. The cylinder head 2 is integrated into the cylinder head 2, and the lower end is connected to the crankcase 3.
Fixed.

In the common cylinder 1, a lower phase piston 4 and a slower phase upper piston 5 are slidably fitted, and both pistons 4
．． The combustion chambers 6 and 5 are concentrically opposed to each other. An exhaust port 7 and an intake port 8 are provided in a portion of the cylinder 1 within the range in which the lower piston 4 moves up and down, the exhaust port 7 is connected to a muffler 9, and the muffler 9 communicates with the atmosphere via an exhaust outlet 10. are doing. Intake port 8 is insulator 1
1 to the t1r bulleta 12, and the population of the bulletas 1-11 is connected to the atmosphere through the air-free --) 13. A scavenging port 14 is provided in the cylinder portion within the range in which the upper piston 5 moves up and down, and this scavenging port 1
4 is connected to the crankcase 3 via the scavenging passage 15 (Fig. 2).
When the upper piston 5 descends as shown in FIG. 2, the scavenging port 14 opens toward the piston back chamber 17 between the upper piston 5 and the cylinder head 2. Cooling fins 18 to 21 are integrally provided on the upper surface of the upper piston 5, the lower surface and upper surface of the cylinder head 2, and the outer peripheral surface of the common cylinder 1, respectively. 22 is a spark plug.

The upper piston 5 has a rod 2 whose upper end is fixed at its center.
4 and a connecting rod 25 to a crank arm 27 of a crankshaft 26.

28 is a connecting bin, and 29 is a crank bin. The lower piston 4 has two parallel connecting rods 30 (
2) to the crank arm 31.

32 is a recoil starter, 33 is a handle, and 34 is a flywheel.

FIG. 3 is a graph showing the lower piston displacement A1, the upper piston displacement B, and the combustion chamber volume displacement C. As is clear from the upper piston displacement curve I3 to the lower piston displacement curve in Figure 3, when the lower piston reaches the top dead center T (state in Figure 2),
The upper piston is 11 points before the top dead center, that is, the upper piston is lagged in phase by Ll (approximately 90 degrees) than the lower piston, and this means that connecting rod 2 in Fig. 1
This can be seen in the fact that 5 is slightly inclined with respect to the vertical line. That is, the upper piston 5 in FIG. 2 is in a state before the top dead center. The intake port 8 and the exhaust port 7 are opened and closed by the lower piston 4, so they are opened and closed symmetrically with respect to the top dead center T1 and the bottom dead center B of the lower piston 4. On the other hand, the scavenging port 14 is opened and closed by the upper piston 5. Therefore, the displacement curve B of the upper piston 5 is symmetrical with respect to the bottom dead center B. Therefore, as is clear from the opening/closing curves of each port added to the combustion chamber volume displacement curve C, the scavenging port 14 closes later than the exhaust port 7, which improves the charging efficiency. Become. FIG. 4 shows the relationship shown in FIG. 3 in relation to the crank angle.

When the crankshaft 26 rotates during engine operation, the upper and lower pistons 5.4 approach H, and when the volume of the combustion chamber 6 decreases, the air-fuel mixture that has been supplied to the combustion chamber 6 is compressed. , an ignition explosion is performed by the ignition plug 22. During the stroke in which the upper and lower pistons 4.5 are separated from each other due to the explosion pressure in the combustion chamber 6, rotational force acts on the crankshaft 26, and the lower piston 4 descends, causing the air-fuel mixture pre-pressurized in the crank chamber 16 to be mixed with the upper piston. 5, the air-fuel mixture pre-pressurized in the piston back chamber 17 flows into the combustion chamber 6 through the scavenging port 14, and flows inside the combustion chamber 6 from above to below (in one direction) in the direction of arrow X in FIG. ,
The exhaust gas in the combustion chamber 6 is pushed out to the exhaust port 7 side in a layered manner, and the combustion chamber 6 is filled with fresh air. The upper piston 5 and the lower piston 4 are configured so that the lower piston 4 has an earlier phase and the upper piston 5 has a later phase, so that the combustion chamber volume displacement C (Fig. 3) In this case, the intake/exhaust ports 8.7 and the scavenging ports 1 and 4 are substantially asymmetrical.

(Effects of the Invention) As explained above, in the present invention, the opposed pistons 5.4 having a phase difference are rotated by the same crankshaft 26, and the intake and exhaust ports 8.7 are In the example, the scavenging port 14 is opened and closed by the lower piston 4), and the scavenging port 14 is opened and opened by the piston with a slower phase (in the example, the upper piston 5), and the back side of the piston is formed on the back side of the upper piston 5, which is slower in phase than the crank chamber 16. Connect chamber 17,
Cooling fins 18 and 19 are provided on the back side of the piston v17 at a location that is not a sliding surface, and the upper piston 5 is operated by passing the rod 24 through the lower piston 4 and connecting it to the connecting rod 25. Special advantages arise.

(1) Intake, exhaust, and scavenging ports are combustion chamber 6 and crank chamber 16
It opens and closes asymmetrically in response to changes in volume, improving output and fuel efficiency. In other words, intake and exhaust can be performed completely.

(2) Since the two pistons 4.5 having a phase difference operate substantially opposite to each other, the reciprocating inertia is small and vibrations are significantly reduced.

(3) Since the back sides of the two pistons 4.5 are cooled by intake air, internal cooling is increased and cooling loss is reduced (charge cooled method).

(4) Because the scavenging air flow flows from the upper scavenging port 14 of the combustion chamber 6 toward the lower exhaust port 7 (uniflow),
There is less mixing of fresh air and combustion gas, which stabilizes combustion and improves output.

(5) The port opened and closed by the upper piston 5 is the scavenging port 1
4, the scavenging area can be set large, and since the intake port 8 and exhaust port 7 are the only ports that are closed by the lower piston 4, the intake and exhaust area can be greatly increased. , exhaustion, and moderation are completely possible.

When the present invention is applied to an alcohol engine that uses alcohol, which has a large latent heat, as fuel, the startability is improved due to the internal cooling effect. Therefore, it is effective for practical use of alcohol engines. Further, the present invention can also be embodied as shown in FIGS. 5 and 6. In FIGS. 5 and 6, a hollow rod 24- is used, and this rod 24- is used.
4- communicates the piston back chamber 17 with the crank chamber 16, and has a structure in which the rod 24 is cooled by intake air.

[Brief explanation of the drawing]

Claims (4)

[Claims] (1) A pair of pistons facing each other in a common cylinder with a phase difference are connected to a common crankshaft via a connecting rod, and an exhaust port and an intake port are connected to the cylinder part of the piston side with the earlier phase, and the exhaust port and intake port are connected to the cylinder part of the piston side with the earlier phase. A two-stroke engine characterized by having scavenging ports arranged in each side cylinder. (2) A two-stroke engine according to claim 1, wherein a cylinder head is provided on the opposite side of the common cylinder from the crankshaft, and a piston back side chamber between the cylinder head and the piston facing the cylinder head is connected to the crank chamber. (3) A piston with a slow phase is arranged above and a piston with an early phase is arranged below, and the operation of the upper piston is performed by connecting a concentric rod passing through the lower piston with a connecting rod. 2-stroke engine as described in section. (4) A two-stroke engine according to claim 3, wherein the upper piston and cylinder head are provided with fins that protrude into the back chamber.