JPS5827076Y2 - 2 cycle engine - Google Patents

Description

[Detailed description of the invention] This invention is a two-cycle engine started by a recoil starter, etc. In order to improve the startability of this engine, the starting torque is reduced, and the reverse shock during the starting operation is prevented. It was designed to do so.

In recent years, relatively large displacement two-stroke engines have been adopted, and like other engines, high-speed rotation and high compression ratios have been adopted to improve engine thermal efficiency and make the engine smaller and lighter. The engine is ready for use.

An engine with high output like this has a large starting torque, so it is best to have a starter motor as a starting device so that it can be started using battery power, but it can be used in cold climates such as snowmobiles. Engines used in Since it is disadvantageous to employ a device, manual or kick starting methods such as a rope winding type, a kick type, or a coil starter are generally used.

However, as mentioned above, high-output engines require a considerable amount of starting torque, and at the same time, these two-stroke engines use a flywheel, whose ignition method uses a flywheel whose ignition spark strength is proportional to the rotation speed. It uses a magneto, and if the rotation speed during the starting operation is low, the ignition spark required to ignite the air-fuel mixture will be weak and the engine will not be able to start, so a fairly high starting rotation speed is required. 2
It is difficult to give a proper starting rotation speed by inputting a cycle engine, and it requires a lot of effort, especially for elderly people and women.Additionally, there is a problem in that the reversing shock at the time of starting operation can cause accidents that may cause injury to the human body. was there.

As a means to solve the above problem, a method has been proposed in which the starting torque is reduced by leaking compressed gas in the combustion chamber during the upward stroke of the piston.

As an example, as shown in Fig. 3, a bypass passage e is provided above the exhaust port on the inner wall of the cylinder a or from the combustion chamber C to the atmosphere or to the exhaust passage d. Only an on-off valve f that can be opened manually is provided.

In another example, as shown in FIGS. 4 and 5, the inner wall of cylinder a is a portion opened and closed by piston g, one end of which opens above the exhaust port, and the other end of which opens into exhaust passage d. Some engines are equipped with a bypass passage with small holes to allow compressed gas to leak, thereby reducing the compression pressure during startup.

However, in the above system, a problem unique to two-stroke engines is that carbon generated by incomplete combustion of lubricating oil mixed in the fuel accumulates intensively in the bypass passages e and h, clogging the passages. However, there was a problem in that the compression pressure reduction effect at startup was not sustainable and was inferior in practicality.

In addition, the former type with valve f (see Fig. 3) requires cumbersome operations to open and close valve f each time the engine is started, and there is a risk of forgetting to close valve f after starting the engine. The valve mechanism is complex and must be manufactured with high precision, and it is also difficult to secure a location for installing the valve operating lever i.

In addition, in the case of the latter small hole only (see Figure 4), during the compression stroke during engine operation, from the time the exhaust port closes until the opening of the bypass passage is closed by the piston g. Leakage of the effective air-fuel mixture continues, and in the exhaust stroke, the bypass passage is fully opened at an early stage, so there is a lot of leakage of effective combustion gas, which reduces the thermal efficiency (engine efficiency).
There were drawbacks such as a decrease in

Therefore, the present invention has been devised to eliminate such conventional drawbacks, and consists of a pair of two cylinders in which when the piston of one cylinder is in the downward stroke, the piston of the other cylinder is in the upward stroke. A communication port is provided in the cylinder wall surface of each of the cylinders to open the combustion chamber by the head of the piston earlier than the opening timing of the exhaust port during the downward stroke of the piston, and means for connecting the two speed ports of the pair of cylinders. The exhaust port is configured to open at a predetermined time while the double-speed vent opens to communicate with the firing chamber, and the compressed gas during the upward stroke of the piston at startup is communicated with the above-mentioned vent. To provide a two-stroke engine that reduces starting torque by causing leakage from the mouth.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below with reference to the drawings.

The two-stroke engine shown in FIG. 1 has a first cylinder 1 and a second cylinder 2, and in each cylinder 1 and 2, 3a
, 3b is a cylinder, 4a, 4b are pistons, 5a, 5
b is the cylinder head, 6a.

6b is the combustion chamber, 7a, 7b are exhaust ports, 8a, sb
is a scavenging port, 9a and 9b are suction ports, and the piston 4
a, 4b are slidably housed in cylinders 3a, 3b, and the pistons 4a, 4b are connected to their piston pins 11a by connecting rods 10a, 1ob.

11b is a crank pin 13a of the crankshaft 12.

13b for reciprocating movement, the cylinders 3a,
Exhaust lower a, 7b and scavenging port 8a provided in 3b
, sb are opened and closed by the pistons 4a and 4b, and the scavenging ports 8a and 8b are connected to the crank chambers 14a and 1.
4b, while the crank chambers 14a, 14b
The suction port 9a opens to.

9b is connected to the carburetor 16 via check valves 15a, 15b, and the crank chamber 14a,
The air-fuel mixture supplied to the crank chamber 14a,
The scavenging air is precompressed at 14b and flows into the combustion chamber 6 from the scavenging ports 8a and 8b.
A, sent into 6b, compressed, exploded and exhausted? a
, 7b.

Further, although the first cylinder 1 and the second cylinder 2 are shown separately in the drawings, their respective connecting rods 10a are connected to the same crankshaft 12.

10b are connected, and the relationship between the cylinders 1°2 of both systems is that when the piston 4a of the first cylinder 1 is in the downward stroke, the piston 4b of the second cylinder 2 is in the upward stroke, and the piston 4b of the second cylinder 2 is in the upward stroke. The first cylinder 1 is provided so as to reciprocate symmetrically so that when the piston 4b of the first cylinder 1 is on the downward stroke, the piston 4a of the first cylinder 1 is on the upward stroke.

On the walls of the cylinders 3a and 3b of both the cylinders 1 and 2,
Communication ports 17a and 17b are provided, respectively, which are opened by the heads of the pistons earlier than when the exhaust lowers a and 7b are opened during the downward stroke of the pistons 4a and 4b.

That is, this communication port 17a. The upper end of the opening of 17b is located closer to the top dead center than the upper end of the opening of exhaust lowers a and 7b, and conversely, during the upward stroke of pistons 4a and 4b, exhaust lowers a and 7b are closed. Then, the communication port 17a.

17b is provided so that it is closed.

Furthermore, the dual-speed ports 17a and 17b are provided so that their opening times overlap so that there is a period in which both of them are open at the same time.

Furthermore, while the combustion chambers 6a and 6b are in communication, the exhaust lowers a and 7b are opened for a certain period of time (see FIG. 2) to actively reduce the compression pressure.

Further, the communication port 17a of the first cylinder 1 and the communication port 17b of the second cylinder 2 are communicated by a connecting means 18.

The connecting means 18 includes a communication pipe 19 that communicates the two-speed communication ports 17a and 17b, a branch pipe 21 that connects one end to the approximate center of the communication pipe 19 and has an atmosphere opening port 20 at the other end, and A check valve 22 is provided at the open port 20 so as to allow the outside air to flow in the direction of the communication pipe 19 .

Although not shown, the two-cycle engine is equipped with a starting device such as a recoil starter for its crankshaft 12, and the starting device is manually operated to rotate the crankshaft 12 to start the engine. This engine is mounted on the snowmobile and drives its traveling gear.

FIG. 2 shows an example of the opening/closing timing of the communicating ports 17a and 17b, each of which corresponds to the piston 4a.

4b from the top dead center to the bottom dead center (in this downward stroke, the communication ports 17a, 17b open first, then the exhaust lower a,
7b, scavenging port 8a, and sb are opened in this order, and in the upward stroke after passing the bottom dead center, the scavenging port 8a opens.

8b1 exhaust port? A, 7b1 communication port 17a, 17b is closed in this order, and is a double-speed communication port 17a.

17b has an overlap period A that is simultaneously open at the intermediate point between the top dead center and the bottom dead center.

Next, to explain the function and effect of the above two-stroke engine, at the time of starting, the first cylinder 1 enters an upward stroke from the bottom dead center, and when the exhaust lower a is closed by the piston 4a, the air-fuel mixture is compressed. However, while the communication port 17a is open, the compressed gas leaks from the communication port 17a to the connecting means 18, and the compressed gas pressure is reduced.

Also, during the upward stroke of the first cylinder 1, the second cylinder 2 is in the downward stroke, and since the gas explosion mocha is not acting on the second cylinder 2 at the time of startup, the pressure in the combustion chamber 6b of the second cylinder 2 is low. is lower than the pressure in the combustion chamber 6a of the first cylinder 1,
If the opening timings of both speed ports 17a and 17b are set to overlap, the pressure in the second cylinder 2 will affect the first cylinder 10 during this overlap period A, and the compressed gas pressure in the first cylinder 1 will be reduced. By synergistically increasing the effects, it is possible to significantly reduce the starting torque, and the compressed gas pressure is similarly reduced during the upward stroke of the second cylinder 2.

On the other hand, when the communication port 17b of the second cylinder 2 opens, the fresh air that flows into the connecting means 18 through the communication port 17a during the ascending stroke of the first cylinder 1 during engine operation after startup is As shown in the acupressure diagram, the pressure P2 of the second cylinder 2 is higher than the royal power P1 of the first cylinder 1, and the fresh air flowing into the connecting means 18 due to the pressure difference is transferred to the first cylinder 1. After being pushed through the opening 17a, the communication opening 17a closes.

This supercharging action compensates for the output drop due to the reduction in compression ratio that occurs during installation of the communication ports 17a and 17b, and reduces the starting torque without causing a significant drop in output.

At that time, the high temperature combustion gas flows from the other communication port 17b or 17a against the fresh air flowing in from one communication port 17a or 17b (thereby, the fresh air may be ignited, so this connecting means 18 Check valve 2 from the atmosphere opening 20 inside
2, the fresh air in the connecting means 18 is diluted, the air-fuel ratio is increased, and ignition is prevented.

Furthermore, since gas flows in the communication ports 17a, 17b and the connecting means 18 every cycle, there is no carbon buildup.

For example, if a two-cylinder two-stroke engine with an output of about 53 horsepower is provided with the communication ports 17a and 17b and connected to the connecting means 18 (trowel), the operating pulling force of the manual starting device is initially required to be about 50 kg. However, by installing it, the weight was reduced by 40 kg, a factor of 20, and when you actually start the engine, you can feel that this reduction is more than half of the reduction effect.

On the other hand, the decrease in output due to the installation of the communication ports 17a and 17b was about 1.2φ at 0.5 horsepower.

Note that the connecting means 18 in the above embodiment has a communication port 17a.
, 17b, as well as the atmosphere opening 20
, a branch pipe 21 and a check valve 22 are provided to make it possible to introduce outside air.
Even if only the communication pipe 19 is formed, the effect of reducing the starting torque at the time of starting can be obtained.

Also, a communication port 17a. The opening position of 17b is exhaust lower a,
7b, above the suction port 9a, above sb, and other cylinders 3a.

It can be installed at any position on the circumference of 3b.

Furthermore, when the communication port of one cylinder 1 or 2 is closed, the scavenging port of the other cylinder 2 or 1 may already be open.

Therefore, according to the two-stroke engine of the present invention as described above, the communication port reduces the compression pressure and reduces the starting torque at the time of starting, thereby improving the startability of the engine and preventing reverse shock during the starting operation. In addition, by forming a pair of two cylinders in which one cylinder is in a downward stroke and the other cylinder is in an upward stroke, and by communicating the both speed ports of this pair of cylinders with a connecting means, It has various excellent advantages, such as almost no reduction in output loss, prevention of carbon adhesion, simple structure, and can be manufactured at low cost.

[Brief explanation of drawings]

The drawings illustrate the embodiment of the present invention, and FIG. 1 is a schematic configuration diagram, and FIG. 2 is a line showing the opening/closing timing of the communication port with respect to the crank angle, together with a finger pressure diagram and the opening/closing timing of the exhaust port and the scavenging port. 3 is a longitudinal sectional view showing one example of the conventional art, FIG. 4 is a longitudinal sectional view showing another example of the conventional art, and FIG. 5 is a view taken along the line 1--1 in FIG. 4. 1...First cylinder, 2...Second cylinder, 3
a, 3b...Cylinder, 4a, 4b...
・Piston N5a15b...Cylinder head,
6a, 6b... Combustion chamber, 7a, 7b...
・Exhaust port, 17a, 17b...Communication port, 18・
...Connection means, 19...Communication pipe, 20.
... Atmosphere opening port, 21 ... Branch pipe, 22
······non-return valve.

Claims (2)

[Scope of utility model registration request] (1) A pair of cylinders that are started by a recoil starter or the like and have a plurality of cylinders, such that when the piston of one cylinder is in the downward stroke, the piston of the other cylinder is in the upward stroke; A communication port is provided in the cylinder wall surface of the pair of cylinders so that the combustion chamber is opened by the head of the piston earlier than the opening timing of the exhaust port during the downward stroke of the piston, and both speed ports of the pair of cylinders are connected to each other. The exhaust port is configured to open at a predetermined time while the two-speed vent opens to communicate the two combustion chambers through a connecting means, and the compressed gas in the upward stroke of the piston at startup is A two-stroke engine characterized by reducing starting torque by leaking through a communication port. (2) The communication means has an atmosphere opening in the intermediate portion, and is equipped with a check valve that allows conduction from the outside air toward the communication opening. cycle engine.