JPH03242427A - Supercharger in two-cycle engine - Google Patents

Abstract

PURPOSE:To attain a high output of a 2-cycle engine with a simple constitution by constituting the engine such that a pump chamber performs pumping action such as pressing in a mixture or air into a combustion chamber by a change of exhaust pressure in an exhaust passage. CONSTITUTION:When exhaust gas, discharged from an engine, is allowed to flow into an expansion chamber 12, most of the exhaust gas is not immediately discharged from the chamber 12 and reversed for returning an unburnt mixture, discharged with the exhaust gas from a combustion chamber 8, again into it. By the exhaust gas thus reciprocated, an up and down change of exhaust pressure is generated in an exhaust passage. According to the above, pumping action is performed in a pump chamber 13, and a mixture or the outside air is forcedly pressed into the combustion chamber 8 directly or indirectly through a crankcase 4 in an intake stroke of the engine. Thus, supercharge action is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a supercharging device for a two-stroke engine.

(Conventional technology and its problems) Conventionally, turbochargers and superchargers have been extremely effective means of achieving high engine output. There are already motorcycles such as Baits that have turbochargers installed. As is well known, a turbocharger applies exhaust gas to a turbine wheel and rotates a compressor wheel on the same axis to pressurize the air and force it into the combustion chamber. A turbo unit is placed in front of the engine, and the air flowing in from the air cleaner is pressurized by the above-mentioned compressor while being guided to the surge tank, and then forced to flow into the combustion chamber via the intake manifold.

In this way, the turbo system incorporates a relatively large device called a turbocharger into the engine's intake system, so in addition to the problem of increased weight, it is difficult to set the layout for vehicles with limited foot space such as motorcycles. I worry about it. Further, both conventional turbo systems and other supercharging systems have complex structures, and therefore their costs are high.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a supercharging device that can increase the output of a two-stroke engine with a simple configuration.

(Means for Achieving the Object) In order to achieve the above object, the present invention provides a two-stroke engine in which an expansion chamber is interposed in the exhaust path, the inlet side of which communicates with the crankcase or the outside air, and the outlet side of which communicates with the crankcase or the outside air. A pump chamber that can communicate with the combustion chamber is provided, and this pump chamber performs a pumping action to push the mixture or air into the combustion chamber by changing the exhaust pressure in the exhaust path.

(Function) Therefore, according to the above configuration, when exhaust gas discharged from the engine flows into the expansion chamber, most of it is not immediately released from the chamber, but the remaining part is reversed and exhausted from the combustion chamber together with the exhaust gas. It plays the role of returning the combustion mixture back into the combustion chamber. Due to this reciprocation of exhaust gas, the exhaust pressure in the exhaust path changes vertically (
pulsation). Accordingly, a pumping action is performed in the pump chamber, and the air-fuel mixture or outside air is forcibly forced into the combustion chamber directly or indirectly through the crank chamber during the intake stroke of the engine. In other words, a supercharging effect is performed.

(Example) Hereinafter, an example embodying the present invention will be described in detail with reference to the drawings.

1 to 4 each show an operating cycle of a two-stroke engine. In the figure, 1 is a cylinder,
2 is a piston, and 3 is a crankshaft housed in a crankcase 4. An intake port 5 opens on the side of the crankcase 4, and an intake manifold 6
It communicates with a vaporizer (not shown) via. A reedle valve 7 as a check valve is attached to the intake port 5 so that it can be opened and closed during the suction/compression process (first
Figure, 4th figure! Open it to drain the mixture into the crankcase 4.
On the other hand, in the event of an explosion or scavenging, it closes to prevent the air-fuel mixture from flowing back into the carburetor.

On the other hand, a scavenging port 9 for communicating between the crankcase 4 and the combustion chamber 8 is opened at the lower part of the side surface of the combustion chamber 8, and is opened and closed by the piston 2 itself as the piston 2 moves up and down. It opens diagonally upward to allow for gas exchange. Furthermore, although an exhaust port 10 opens on the side of the combustion chamber 8, the upper edge of the exhaust port 1o is set higher than the upper edge of the scavenging port 9, so that exhaust from the combustion chamber 8 has priority. ing. An exhaust pipe 11 is connected to this exhaust port 10, and the diameter of the pipe 11 is expanded at a portion relatively close to the engine to form an expansion chamber 12 (hereinafter simply referred to as chamber 12). The outlet of this chamber 12 is narrowed in order to invert much of the exhaust gas.

A pump chamber 13 is provided outside the cylinder 1 for supercharging the engine.

This pump chamber 13 has an inlet side that communicates with the inside of the crankcase 4 via an introduction pipe 14 , a discharge side that is connected to a discharge pipe 15 , and communicates with the inside of the combustion chamber 8 via a supercharging port 16 . Although the upper edge of this supercharging port 16 is shown above the scavenging port 9 due to convenience in the drawing, it is actually set at approximately the same level as this, that is, slightly lower than the upper edge of the exhaust port 10. It is set.

Furthermore, on-off valves 17 and 18 are provided on the inflow side and the discharge side of the pump chamber 13, respectively. Furthermore, the pump chamber 13
communicates with the exhaust pipe 11 on the upstream side of the chamber 12, and a separator that partitions the pump chamber 13 side and the exhaust pipe 11 side is provided inside so as to be movable up and down. The movement of the separator 19 up and down is caused by the pulsation of the exhaust pressure within the pipe 11. Therefore, in conjunction with this movement, the on-off valves 17 and 18 open and close, allowing the air-fuel mixture from the crankcase 4 to flow in through the pumping action.・Can be discharged.

However, the vertical stroke of one separator plate is regulated by stopper means (not shown) provided at the raised position and the lowered position, respectively.

Subsequently, the effects of this example configured as described above will be specifically explained.

FIG. 1 shows the state of the ignition timing during the explosion/intake stroke. At this time, since the piston 2 is at the top dead center position, the reed valve 7 is opened and the air-fuel mixture flows into the crankcase 4. In this state, as will be described later, the separator plate 19 is held in the raised position due to the pressure difference between the pump chamber 13 side and the extreme vibe 11 side. Open/close valve 17
It flows into the pump chamber 13 through the pump chamber 13, and the capacity inside the pump chamber 13 is expanded.

When the piston 2 descends from the state shown in FIG. 1 to the state shown in FIG. The descent begins. As a result, the on-off valve 17 on the inflow side of the pump chamber 13 is closed, and conversely, the on-off valve 18 on the discharge side is opened. Also, during this period, the piston 2 further descends, and the supercharging boat 16 and the scavenging boat 9
will be held.

As shown in FIG. 3, when the supercharging port 16 and the scavenging port 9 are completely open, the air-fuel mixture from the crankcase 4 flows into the combustion chamber 8 via the scavenging port 9, and the separator When one of them descends, the pressurized air-fuel mixture is forced into the supercharging port 16, thereby increasing the filling efficiency into the combustion chamber 8. Further, in this state, the air-fuel mixture flowing in from the scavenging port 9 is jetted obliquely into the combustion chamber 8, so that the flow reverses at the upper surface and the exhaust gas remaining in the chamber is almost completely expelled.

By the way, in the case of Fig. 3, most of the exhaust gas is flowing into the chamber 12, but since the exit is narrow and the exhaust is regulated, the exhaust gas is reversed here. The unburned gas leaking from the combustion chamber 8 is returned to the combustion chamber 8.
(state in Figure 4). In this way, when most of the exhaust gas is reversed and passes through the opening for communication with the pump chamber 13, a pressure drop occurs near this opening. As a result, the separator 19 is lifted and raised to expand the volume of the pump chamber 13. Accordingly, the discharge side on-off valve 18 is closed, and the inflow side on-off valve 17 is opened. On the other hand, at this time, the piston 2 has started to move upward, and the air-fuel mixture has started to flow into the crankcase 4, so the air-fuel mixture flows into the pump chamber 13. Therefore, the separator 1 is held in the raised position by the pressure in the pump chamber 13 and thus returns again to the condition shown in FIG.

As mentioned above, in this example, the air-fuel mixture is supercharged by a pumping action that utilizes the pulsation of exhaust gas generated in the exhaust vibe 11, so the turbocharger has a complicated structure with a conventional turbine. It is possible to achieve high engine output without having to Therefore, the device as a whole is miniaturized, and is particularly suitable for two-wheeled vehicles where legroom is often restricted. Further, in this example, since the air-fuel mixture is supercharged instead of air supercharging, high output can be directly achieved.

FIG. 5 shows a second embodiment of the present invention.
This embodiment differs from the embodiment in that the inflow side of the pump chamber 13 is communicated with the outside air. That is, the second embodiment is configured to perform air supercharging, and the other configurations and effects are substantially the same as those of the first embodiment.

However, unlike the first embodiment, since air is supercharged, it is possible to achieve the effect of realizing high engine output with low fuel consumption.

Note that the inflow side of the pump chamber 13 may be connected to the upstream side of the reed valve 7 in the intake manifold 6.

FIG. 6 shows a third embodiment of the present invention, in which the connection point of the discharge pipe 15 in the pump chamber 13 is changed from the combustion chamber 8 to the crankcase 4 in the first embodiment.
It has been changed to . As a result, the crankcase 4
The air-fuel mixture that has flowed into the pump chamber 13 through the introduction pipe 14 is returned to the crankcase 4 through the discharge pipe 15 during the intake and exhaust processes, and is then returned to the combustion chamber 8 via the scavenging port 9. flows into. In other words, in the first embodiment, the compressed air-fuel mixture was directly supplied to the combustion chamber 8, but in the third embodiment, it was indirectly supplied via the crankcase 4. It turns out.

Furthermore, in the third embodiment, the pump chamber 13 and the exhaust pipe 11 are connected diagonally (connected at an obtuse angle with the upstream side of the exhaust pipe 11). This is different from the second embodiment. By connecting diagonally in this manner, the exhaust gas can be taken in smoothly to the separator plate 19 side, and the effect that fluctuations in exhaust pressure can be easily applied to the separator plate 19 can be obtained.

Note that the other configurations are the same as those of the first embodiment, and the same effects are exhibited.

FIG. 7 shows a fourth embodiment of the present invention, in which the on-off valves 17 and 18 on the inflow side and discharge side of the pump chamber 13 in the third embodiment are omitted. That is,
In the fourth embodiment, the entire inlet pipe 14 is likened to the pump chamber 13, and the air-fuel mixture is moved in and out of the crankcase 4 by raising and lowering one separator plate as the exhaust pressure fluctuates, thereby producing a supercharging effect. be.

In addition to the effects of the third embodiment, the fourth embodiment configured as described above has the advantage of simplifying the configuration.

(Effect of the invention) The effects of the present invention are as follows.

■Does not require large equipment like conventional turbo systems,
Since it is only necessary to provide a simple pump chamber, the entire device can be made smaller and lighter, the degree of freedom in layout around the engine can be increased, and it can also be easily applied to conventional engines.

■Since supercharging is performed by a pump action that utilizes the pulsation of exhaust gas, it is possible to achieve high engine output with a simple structure and at low cost.

[Brief explanation of drawings]

1 to 4 are sectional views for explaining the operation of the apparatus according to the first embodiment of the present invention, FIG. 5 is a sectional view of the apparatus according to the second embodiment, and FIG. 6 is a sectional view of the apparatus according to the second embodiment. FIG. 7 is a sectional view of the device according to the fourth embodiment. 8... Combustion chamber 12... Chamber 13... Pump chamber 17.18... One on-off valve... Separation plate

Claims (1)

[Claims] In a two-stroke engine in which an expansion chamber is interposed in the exhaust path, a pump chamber is provided whose inlet side communicates with the crankcase or the outside air and whose discharge side communicates with the combustion chamber. A supercharging device for a two-stroke engine, characterized in that it is configured to perform a pumping action to push air-fuel mixture or air into the combustion chamber by changes in air pressure.