JPH02238112A - Two-cycle engine - Google Patents

Abstract

PURPOSE:To prevent the counterflow of exhaust gas without using an expansion pipe and improve output by installing an accelerating suction device with the exhaust system pipe in each cylinder and connecting the part between the suction part and the exhaust system pipe of each cylinder in which combustion arises next through a suction passage. CONSTITUTION:Each accelerating suction device 70 which is integrally connected on the downstream of mufflers 60 is connected with an exhaust system pipe connected at the exhaust port of each cylinder of a multicylinder two-cycle engine, and the whole of the muffler 60 and the accelerating suction device 70 are covered by a casing 50. The accelerating suction device 70 accelerate the exhaust gas stream which is discharged from a cylinder and introduced into a connection part 51 by the passing in an accelerating part 76 including an accelerating throttle pipe 17 and a throat 72, and a negative pressure is generated in an expansion chamber 73. Then, the negative pressure is allowed to act into the exhaust system pipe of a cylinder in which combustion is carried out next, through a suction passage (not shown on the figure) connected with a connecting part 52, and the exhaust gas in the cylinder is sucked.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a two-stroke engine.

(Prior art) For one cylinder, combustion occurs once per two revolutions of the crankshaft in a four-stroke engine, whereas combustion occurs once per one revolution of the crankshaft in a two-stroke engine. The engine's detonation cycle is twice that of a four-stroke engine. Therefore, although the output is large, the amount of heat generated is also large, which causes problems such as overheating and metal fatigue, making it unsuitable for long-term, high-speed continuous operation.

On the other hand, two-stroke engines do not require intake or exhaust valve devices, so they are not mechanically complex and are suitable for high-speed operation, but on the other hand, at low speeds, the effect of pulsation due to backflow of exhaust gas becomes stronger. , the exhaust gas ratio tends to increase and the output decreases, which is a drawback of this type of engine.

(Technical Issues) The only countermeasures to the heat generation problem described above include increasing the size of heat dissipation fins and radiators, and how to efficiently guide air around the cylinders. Regarding the latter problem during low-speed operation, there is still a limit to the provision of a reversal valve such as a reed valve.

The present invention aims to solve the above-mentioned problems by constantly generating a flow of gas that enters the combustion chamber from the intake port and exits from the exhaust port, thereby increasing the engine output, cooling the engine body, and The present invention provides a two-stroke engine that improves stability during low-speed operation.

(Technical means) The above purpose is to have a plurality of cylinders, the air-fuel mixture is introduced into each cylinder from the intake port through the crankcase, and combustion is repeated alternately during the compression stroke of the piston. It is a two-stroke engine, and an acceleration suction device is installed in the exhaust system pipe of each cylinder to accelerate the exhaust gas flow by narrowing the exhaust cross-sectional area, and to suck gas by the negative pressure generated in the accelerated flow. This can be achieved by connecting suction passages for sucking exhaust gas from the next cylinder in the combustion order between the suction part of the accelerating suction device and the exhaust system pipe of the next cylinder to be burned. .

(Example) The following description will be made with reference to the drawings. The illustrated two-stroke engine 10 has second cylinders 1 and 2.

11 and 12 are pistons that reciprocate within each cylinder, 13 and 1
A connecting rod 4 connects the crankshaft 4 provided in the crankcase 3 and the pistons 11 and 12. 21, 22 are cab brakes, 23, 24
25 and 26 are air-fuel mixture intake ports that connect the inside of the crankcase and each cylinder, and 25 and 26 are exhaust ports that discharge combustion gas to the outside of the cylinders.
27 indicates a water jacket, and 28 indicates a radiator.

31 and 32 are exhaust system pipes connected to each exhaust port 25 and 26, 33 and 34 are mufflers provided to each exhaust system pipe, and 35
, 36 are accelerated suction devices provided downstream of each muffler, each consisting of an acceleration section and a suction section. The suction section 38 and one exhaust system pipe 31 are connected through suction passages 41 and 42, respectively. This suction passage sucks exhaust gas from the next cylinder in the combustion order using the negative pressure generated after combustion in a certain cylinder.
For cylinders 1-2, 2→3,...n-1-on, n→
1.

The suction paths 4l, 42 are connected to the respective exhaust system pipes 31, 32 at positions not too far from the exhaust ports 25, 26, so that the gas in the exhaust ports 25, 26 is constantly sucked in the exhaust direction by this suction action. become.

The specific configuration of the accelerating suction device is illustrated in FIG. 2, and has a structure integrated with a muffler. In the figure, 50 is a casing that covers the entire muffler 60 and the accelerated suction device 70 connected downstream thereof, 51 is a connection to the exhaust system pipes 31 and 32, and 52 is a connection to the suction paths 41 and 42. Show part.

Reference numeral 61 indicates a perforated throttle pipe which is arranged before the muffler and initially accelerates the exhaust gas flow, 62 indicates a perforated throat pipe connected to the downstream end of the perforated throttle pipe 6l, and 63 represents a perforated throttle pipe. 6
1 to a perforated tapered pipe surrounding a perforated throat 62, and each of these pipes 61 to 63 has a large number of small holes 64, 65, 66 through which the exhaust gas flow passes. Each small hole 64
The pore diameter of ~66 can be chosen arbitrarily and can vary in size. 67 is a central tube which similarly has a large number of small holes 68, and is connected to the downstream end of the Taber tube 63;
A filler 69 serving as a heat insulating material and a sound deadening material is filled between the outer periphery and the casing at an appropriate density.

The accelerating suction device 70 is connected to an accelerating throttle pipe 7l which narrows the exhaust cross-sectional area at the rear end of the central pipe 67, and to the rear end thereof,
It has a throat 72 and an expansion chamber 73 that maintain the aperture diameter, and is separated from the silencing section by a partition wall 74. The expansion chamber 73 at the rear end of the throat 72 is formed in the shape of an enlarged Taber tube, and has a plurality of suction ports 75 opened therein. It communicates with the suction port 75. The acceleration section 76
is throttled to the point where the flow velocity of the exhaust gas flow exceeds the sound velocity in that section.

The suction part 77 is connected to the suction passages 41 and 42 through the aforementioned connection part 52, but in the illustrated example, a small muffler 78 is interposed between the suction passages 4l and 42, and the small muffler 78 is connected to the suction passages 41 and 42 at the center. It has a vertically extending perforated suction pipe 79, and at the inlet of the perforated suction pipe 79 is a pre-accelerator 80 consisting of a small tapered pipe 81 and a long throat 82 integrated into the small diameter portion thereof. 83,
84 and 85 indicate small holes formed therein. Reference numeral 86 indicates a filler similar to that described above. Further, 87 indicates a partition plate between large and small mufflers, and 88 indicates a large diameter tail tube connected to the expansion chamber 73. This tail tube 88 is a part where the exhaust gas flow from the next cylinder in the order of explosion is sucked in and discharged from the suction port 75, and it is not preferable to provide resistance downstream of the expansion chamber 73. , has a sufficiently large caliber.

(Function) When the engine is started with the above configuration, fuel mixed with lubricating oil flows into each cylinder through the intake ports 23 and 24, explodes in the order of ignition, and exhaust gas flows through the exhaust ports 25 and 26 into the exhaust system. It is discharged into pipes 31 and 32.

Here, the exhaust gas flow passes through the long exhaust system pipe and the muffler 33.
, 34, it is decelerated while receiving a silencing effect, but it is significantly accelerated by passing through the acceleration section 76, and its flow velocity is restored to the same level as when it exits the exhaust ports 25, 26 due to combustion. , the exhaust gas becomes a flow exceeding the speed of sound, that is, a high-speed airflow.As a result, a significant negative pressure is generated in the expansion chamber 73,
A high-speed negative pressure flow is constantly formed from the suction passages 41 and 42 toward the suction port 75, and therefore the cylinders 1 and 2 always have the suction port 2.
A fast flow is formed from the exhaust ports 3 and 24 toward the exhaust ports 25 and 26.

Under such circumstances, the air-fuel mixture flows through the carburetors 2l and 22.
The inside of the crankcase is always at a low temperature because it is sucked into the crankcase 3 under the influence of the negative pressure and expands at the same time. Furthermore, the air-fuel mixture is transferred to cylinder 1 from each intake port 23, 24.
, 2, and is forcibly discharged from the exhaust ports 25 and 26 through explosive combustion by ignition with the pistons 11 and 12,
Since this flow is fast as mentioned above, the intake and exhaust efficiency is significantly increased. The temperature drop due to expansion when flowing into the crankcase was very significant, and did not exceed 60°C in experiments.

Because the exhaust gas and air-fuel mixture are always drawn in one direction, there is no backflow of exhaust gas, which was impossible in conventional 2-stroke engines even with reed valves.
Because a relatively large amount or more of the exhaust gas flowed back into the combustion chamber, the output from combustion also reached a ceiling, whereas in the two-stroke engine of the present invention, the output from combustion reached a limit of 100.
Since nearly 20% of the air-fuel mixture is filled with fresh air-fuel mixture, the output can be improved accordingly. Moreover, in the engine of the present invention, a reed valve can be eliminated by forced suction on the exhaust side. This has already been confirmed through experiments.

Because the accelerating suction device is installed in the exhaust system pipe, the exhaust gas flow is always accompanied by an exhaust pressure that corresponds to the rotation speed, but this creates a reaction on the piston side that counteracts the exhaust pressure, so the Torque is improved and stable operating conditions can be obtained. A comparative test was conducted on a motorcycle modified with the two-stroke engine of the present invention and a motorcycle equipped with a conventional engine, and the following results were obtained. According to this, it can be seen that the two-stroke engine of the present invention exhibits performance that is incomparable to the comparative cars in terms of both output and cooling performance. Note that the load 7 is the 7th stage of the total load 9, which is set on the tester, and corresponds to the case where a load of more than normal braking is applied to the drive wheels when driving on the road.

(Effects) Since the present invention is configured and operates as described above, the air-fuel mixture flowing into the cylinder from the crankcase and the exhaust gas discharged from the cylinder after combustion have a steady flow in the exhaust direction. Flow is formed, stable rotation is obtained during low speed operation, there is no backflow of exhaust gas and exhaust heat during high speed operation, and very high output is obtained due to smooth intake and exhaust characteristics. Since the entire crankcase is cooled by the expansion of the mixture air flowing inward, the heat generated by combustion is constantly removed from the cylinders installed in the crankcase, and the risk of the engine overheating is completely eliminated.

Therefore, the problems of high-speed continuous operation, heat dripping, and metal fatigue, which were problems of two-stroke engines, have been solved by the present invention, and, as confirmed in operational tests, the problems of high-speed continuous operation, heat dripping, and metal fatigue have been solved. The valve is no longer needed.

Conventional two-stroke engines have an expansion tube with an expanded cross-sectional area in the exhaust tube to reduce exhaust pressure and prevent backflow of exhaust gas, but this structure is effective at low speeds. However, when the speed exceeds the medium speed range, there is no effect on the backflow of exhaust gas and exhaust heat, and the effect of backflow reaches near the maximum reed valve, so the limit of the output output was also low. However, according to the present invention, high-speed airflow Since the flow is always directed in one direction, there is almost no backflow of exhaust gas even without an expansion tube, resulting in remarkable effects such as improved output, increased torque at low speed rotation, and prevention of overheating. was gotten.

BRIEF DESCRIPTION OF THE DRAWINGS The drawings show an embodiment of a two-stroke engine according to the present invention, and FIG. 1 is an explanatory sectional view, and FIG. 2 is a longitudinal sectional view showing an embodiment of an accelerating suction device.

Claims (4)

[Claims] (1) A two-stroke engine having a plurality of cylinders, in which the air-fuel mixture is introduced into each cylinder from the intake port through the crankcase, and combustion is repeated alternately during the compression stroke of the piston, The exhaust system pipe of each cylinder is provided with an acceleration suction device that accelerates the exhaust gas flow by narrowing the exhaust cross-sectional area and sucks gas using the negative pressure generated in the accelerated flow. A two-stroke engine characterized in that a suction passage for suctioning exhaust gas from the next cylinder in the combustion order is connected between each cylinder and the exhaust system pipe of the cylinder to be burned next. (2) The two-stroke engine according to claim 1, wherein the accelerating section of the accelerating suction device has a throat whose cross-sectional area is narrowed to the point where the passage speed of the exhaust gas flow exceeds the sound speed of that section. (3) A two-stroke engine according to claim 1 or 2, wherein the accelerating suction device is provided downstream of a resistance to exhaust gas flow that includes a muffler. (4) The two-stroke engine according to claim 1, wherein the accelerating suction device is provided with an accelerating section immediately after the muffler and is structurally integrated with the muffler.