JPS6217315A - Two-cycle internal combustion engine and scavenging method thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention comprises a crankcase attached to a cylinder housing a piston, an exhaust passage having an exhaust port facing the cylinder, and an exhaust passage on each side of the exhaust passage. Two or more scavenging air passages are arranged and have suction ports facing the cylinder, and opening and closing of the exhaust air passages and the scavenging air passages are controlled by the piston to perform a pumping action through the scavenging air passages. The present invention relates to a scavenging method for a two-stroke internal combustion engine using an inverted scavenging method in which fresh air is supplied from the crankcase to the cylinder, and a two-stroke internal combustion engine suitable for carrying out this method.

[Conventional technology]

A two-stroke internal combustion engine (hereinafter referred to as the engine) of this type of construction is described in U.S. Pat. No. 4,253,433. This engine has two groups of scavenging air passages communicating between the crankcase and the cylinders, which act as pumps (for fresh air).

The (first) inlet leading the fuel/air mixture to the engine is connected directly to the (first) scavenging air passage located opposite the exhaust gas discharge port, the connection location being the opening of the scavenging air passage into the cylinder. and the opening to the crankcase. The other inlet for supplying air to the engine opens into the crankcase. including the cylinder centerline, the exhaust passage and the first
There are also two further scavenging air passages located on each side of the plane passing through the scavenging air passages. During engine operation, the air in the crankcase is compressed by the descending piston and pushed into the cylinder through all the scavenging passages, so the air-fuel mixture that was previously taken into the first scavenging passage is also pumped into the cylinder at the same time. Enter. Air entering from the other scavenging passage (into the cylinder) then prevents the mixed gas from escaping from the exhaust port, thus preventing fresh air from escaping from the exhaust port. This known structure attempts to reduce fuel consumption and improve combustion conditions by mixing fresh air with air. However, this advantage is offset by the complexity of the two valved inlets and two mechanically actuated throttles.

In the two-stroke engine disclosed in DE 2 650 834 A1, the (first) suction port from the scavenging passage supplying the lean gas mixture is connected to the other scavenging passage formed as a reservoir and leading to the rich gas mixture. The thin gas mixture acts as a barrier gas. As the piston descends during the combustion stroke, the lean gas mixture is precompressed and enters the scavenging channel and the storage chamber, which has previously been injected with the rich mixture. When the piston opens the suction port, a thin gas mixture flows from the scavenging passage and a rich gas mixture from the storage chamber immediately flows into the cylinder. The thin mixed gas then drives out the residual exhaust gas in the cylinder, and the rich mixed gas mixes with the thin mixed gas to form a combustible mixed gas.

Since the suction port from the scavenging air passage is located between the storage chamber and the exhaust port, there is no risk of the rich mixed gas flowing out from the exhaust port.

However, a disadvantage of this design is the complexity of requiring an auxiliary vaporizer or at least one additional air inlet.

Austrian Patent No. 138,547 discloses a two-stroke engine with cross-flow scavenging in which the cylinders are scavenged first with exhaust gas and then with fresh air, so that fresh air flows out from the exhaust port during the scavenging process. It prevents Specifically, during the piston combustion stroke (expansion stroke of the cylinder), before reaching the bottom dead center, a chamber is communicated with the cylinder, and a portion of the combustion exhaust gas enters the chamber. After this, the exhaust port is opened and the cylinder is pre-scavenged by the exhaust gas in the chamber, followed by fresh air entering the cylinder through the suction port. The upper edge of the exhaust port is lower than the upper edge of the suction port of any scavenging passage. In this way, loss of fresh air during scavenging is prevented. However, a drawback of this method is that the loss of fresh air after the initial stage of scavenging (that is, from the middle to the final stage) cannot be prevented by the above-mentioned means.

The design and manufacturing costs are also higher than that of a normal two-stroke engine of this type.

[Means for solving problems]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a cycle engine and a scavenging method therefor that have a simple structure, low production cost, good scavenging efficiency, and low emission of environmental pollutants and low operating costs.

This problem is solved in an engine of the first type, in which at least two of the scavenging air passages are located on each side of the exhaust port.
By opening the suction ports of the two first scavenging passages when the piston is descending and the pressure inside the cylinder is higher than the pressure inside the crankcase, the exhaust gas inside the cylinder is prevented from flowing into the crankcase. 1 scavenging air passage and returning the fresh air present in said passage towards the crankcase; following this, also on each side of said exhaust port, said first scavenging air passage; By opening the suction ports of at least two second scavenging air passages that are located further away from the exhaust port than the piston, the exhaust gas that had flowed into the first scavenging air passage in the first step is transferred to the cylinder. The pressure is reversed to form a barrier that prevents fresh air from the cylinder and the second scavenging passage from escaping from the exhaust port, and then fresh air also flows from the first scavenging passage into the cylinder. The problem is solved by a method characterized in that a second step of scavenging air in the cylinder and filling it with fresh air in the inflowing state is performed.

As an engine suitable for carrying out this method, in the engine mentioned at the beginning, at least two of the scavenging passage groups are
two first scavenging air passages are arranged adjacent to the exhaust passage on both sides of a plane passing through the center line of the cylinder and the exhaust passage, and at least two second scavenging air passages in the exhaust passage group are disposed adjacent to the exhaust passage. The upper edge of the suction port of the first scavenging passage is higher than the upper edge of the suction port of the second scavenging passage, and the exhaust gas in the cylinder is disposed away from the exhaust passage and near the first scavenging passage. A part of the engine is configured to allow a portion of the gas to flow into the first scavenging air passage, and is provided with means for preventing the exhaust gas that has flowed into the first scavenging air passage from entering the crankcase. is provided.

In another structure of the engine suitable for carrying out the method of the present invention, at least two first scavenging passages in the group of scavenging passages are arranged on both sides of a plane passing through the center line of the cylinder and the exhaust passage. at least two second scavenging passages of the group of scavenging passages are respectively disposed adjacent to the first scavenging passage away from the exhaust passage, and a control edge of the upper surface of the piston is arranged adjacent to the first scavenging passage. The upper end region of the first scavenging passage corresponding to the suction port is stepped and lower than the part corresponding to the second scavenging passage, so that part of the exhaust gas in the cylinder flows into the first scavenging passage during the scavenging process. According to another aspect of the present invention, there is provided a device characterized in that the exhaust gas having flowed into the first scavenging passage is provided with means for preventing the exhaust gas from entering the crankcase.

[For production]

According to the method of the invention described above, the exchange of exhaust gas and fresh air, that is, scavenging, is performed in a laminar flow state.

Specifically, since the first scavenging air passage adjacent to the exhaust port is opened while the exhaust port is open and the pressure inside the cylinder is still higher than the pressure inside the crankcase, a barrier is created to prevent fresh air from flowing out. A portion of the exhaust gas that is to become flows into the first scavenging passage. Then, when the piston passes the bottom dead center and begins to rise again, and the above pressure relationship is reversed, the exhaust gas in the first scavenging passage returns to the cylinder and exits from the exhaust passage (but at that time, the exhaust gas in the first scavenging passage is Opens later (a barrier is formed to prevent fresh air from the second scavenging passage from going directly to the exhaust passage).

Since the exhaust gas that has entered the first scavenging air passage is also prevented from entering the crankcase, the exhaust gas is contained in the fresh air that is led from the carburetor to the cylinder via the crankcase and the second scavenging air passage. There is no risk of contamination. This blocking means is a state in which the cross-sectional area and length of the first scavenging passage are determined to match the volume of the cough passage to the cylinder volume;
Alternatively, the web of the crank connected to the crankshaft has a recess on its circumferential surface, and the first scavenging passage has an opening that faces the crankcase and cooperates with the recess. This is a controlled mechanism.

〔Effect of the invention〕

As described above, the present invention provides laminar scavenging of upper air without requiring any additional vaporizer, additional fresh air inlet, or additional suction control means. In other words, a good scavenging condition is achieved with an extremely simple configuration, and since fresh air from the scavenging passage does not escape directly to the exhaust passage, fuel consumption is improved and harmful substances (such as hydrocarbons, In other words, the emission of HC) is reduced, contributing to environmental conservation.

This effect can be achieved by at least one at least one port opening into the cylinder on the opposite side of the exhaust port at approximately the same height as the intake port of the second scavenging air passage, and opened and closed by a piston at approximately the same time as the second scavenging air passage. Even better results can be obtained in a configuration in which three third scavenging passages are included in the scavenging passage group. By optimally selecting the opening angle of each of the first to third scavenging passages into the cylinder, it becomes easier to optimize the gas flow condition within the cylinder during scavenging.

〔Example〕

The two-stroke engine shown in Figures 1-12 has a cylinder (1) with a cylinder head (2) and a crankcase (3) with a crankshaft (4). A piston (6) connected to a crankshaft (4) via a connecting rod (5) is housed in the cylinder (1). A hole (7) for a spark plug (not shown) is formed in the cylinder head (2). The cylinder (1) and the crankcase (3) are composed of a plurality of first
A scavenging passage (8), a plurality of second scavenging passages (9), and a plurality of third scavenging passages
The scavenging air passage (10) communicates with the first scavenging air passage (8) as an intake port into the cylinder.
), the second scavenging passage (9) connects the suction port (13), and the third
The scavenging passages (10) each include an intake port (14).

The first and second scavenging passages (13) and (9) are both 2
One each is arranged on each side of a plane (E) passing through the center of the cylinder axis (15) and the exhaust passage (16). The first and second scavenging passages (8) and (9) are 2
It is better to have more than one. The piston (6
) is lowered in a stepped manner. There are also two third scavenging air passages (10), and these suction ports (
14) is diametrically opposite to the exhaust port (17) of the exhaust passage (16). The number of third scavenging passages (10) is 1
There may be one or more than two. The two first scavenging passages (8) feed one inlet (18) to the crankcase. The entrance to the crankcase of the second scavenging passage (9) is indicated by the number (19). Since the volume of the first scavenging air passage (8) is made to match the volume of the cylinder (1), exhaust gas does not enter the crankcase (3) from the cylinder (1) during engine operation. Fresh air indicated by the halftone dot area (area in which many small dots are densely arranged) is introduced from the carburetor (23) through an intake passage (24) with a check valve (25).

The exchange of exhaust gas and fresh air in this two-stroke engine proceeds as shown in FIGS. 1 to 12.

In the first stage (Figs. 1-3), the piston (6) is descending, but the control edge of the screw, which is stepped lower in the upper end region (11"), is still connected to the suction port (12).

(13), (14) and the exhaust port (17) are not exposed, and the cylinder (1) is still filled with exhaust gas. At this time, the crankshaft (4) is indicated by the arrow (18)
is rotating in the direction of On the other hand, at this time the crankcase (
3) The fresh air inside is being compressed by the piston (6),
The scavenging passages (8), (9), and (10) are in a state of being blocked by the piston.

In the second stage (Figs. 4 to 6), the piston further descends to connect the exhaust port (17) of the exhaust passage (16) and the first scavenging passage (8).
) and the suction port (12) of the upper end area (11) as described above.
”) are exposed by the action of the stepped control edge. Therefore, these exhaust channels and scavenging channels are connected to the second scavenging channel (9).
At this time, the pressure inside the cylinder is still higher than the scavenging pressure in the crankcase (3) and the first scavenging air passage (8), so the exhaust gas flows to the upper part of the first scavenging air passage (8). 21), pushing the fresh air down to the lower part (22) of the track (8). Since the first scavenging air passage (8) is sufficiently long, there is no risk of exhaust gas entering into the crankcase. The flow of exhaust gas is indicated by the arrow (29) in Figure 4.5.
, as clearly shown in (30). Figure 6 shows that the upper part (21) of the line (8) is filled with exhaust gas.

In the third stage of cylinder scavenging (Figs. 7 to 9), the piston (
6) is at the bottom dead center, and the second scavenging air passage (9) opens almost simultaneously with the third scavenging air passage (10) to improve scavenging efficiency, scavenging the inside of the cylinder (1) with fresh air. do. At the same time, the pressure inside the cylinder decreases, and as a result, the flow direction in the first scavenging passage is reversed (arrow (31) in Figure 7 and arrow (31) in Figure 8).
32)), and the exhaust gas flowing into the cylinder from the line (8) acts as an air curtain-like barrier against the flow of fresh air from the second and third scavenging passages (9), (10). In this way fresh air is prevented from escaping directly into the exhaust channel (16). Near the end of the scavenging process, fresh air also comes out from the first scavenging passage (8).

In the fourth stage (FIGS. 10 to 12), when the scavenging ends, the cylinder (1) is filled with fresh air, with no loss of fresh air from the exhaust channel (16). After this, the fresh air that has completely filled the cylinder (see Figures 11-12) is compressed by the rising piston (6) again.

[Another example]

The difference in the opening timing of the first scavenging air passage (8) and the second scavenging air passage (9) is that the upper edge (12') of the suction port (12) of the scavenging air passage (Fig. 1) is Higher than the upper edge (13°) of the suction port (13) of the passage (9),
This can be achieved by not providing the step of the control edge (11) in the upper end region (11°) of the piston, or by using both the height difference and the step.

13 to 17 differ from the previous embodiments in that a control mechanism (20) is provided for the first scavenging passage (8). This control mechanism (20) is connected to a line (8) to the crankcase (3).
) are provided at a distance from each other, and a recess (27) is provided on the circumferential surface of each web (26) of the crank that cooperates with these openings, thereby allowing exhaust gas to flow through the crankcase ( 3) is prevented from entering.

The first stage of the scavenging process in this example (Figures 13-14)
Now, all inhalation ports) (12), (13),
(14) and the exhaust port (17) as well as the opening (33) to the crankcase are closed, and the cylinder (1) is filled with exhaust gas.

Figure 15.16.17 shows the third and fourth stages, which appear when the crankshaft (4) rotates in the direction of the arrow (28), and the piston position and exhaust gas - In terms of fresh air exchange, each corresponds to the above-mentioned Figure 5.8.11.

First, in Fig. 15, the crankcase (
The opening (33) to 3) still remains closed by the web (26), and during this period the exhaust gases flowing from the cylinder (1) into the line (8) according to the arrow (30) cannot enter the crankcase. There is no.

As the crankshaft (4) continues to rotate as shown by the arrow (28) toward the bottom dead center of the piston (Fig. 16), the second scavenging air passage (9) begins to open, allowing fresh air to flow into the cylinder. It begins. With the reversal of pressure and the opening of the opening (33), the exhaust gas returns to the cylinder (1) as shown by the arrow (32), and this exhaust gas acts as a barrier to prevent fresh air from escaping through the exhaust passage (16). When this scavenging air comes to an end, fresh air also enters the cylinder from the first scavenging passage (8).

In the fourth stage (FIG. 17), scavenging is completed. As described above, the control mechanism (20) completely prevents the front end of exhaust gas from entering the crankcase (3), thereby relaxing the restrictions on the dimensions of the first scavenging passage (8).

FIG. 18 shows each scavenging passage (8) in the first embodiment.

(9) +' (10) and the timing for the exhaust path (16) and the timing in the second embodiment with the control mechanism (20) are shown. Top dead center and bottom dead center are indicated by (OT) and (UT), respectively. Control mechanism (
20) has all ports open with the sign (So
) and (SS). The meanings of other symbols are as follows.

α. ...Angle α of the crank when the exhaust passage opens,
...Crank angle α22 when the first scavenging passage (8) opens. ...Second and third scavenging passages (9), (10
) Crank angle α4 when the control mechanism (20) opens...Crank angle α when the control mechanism (20) opens...Crank angle Do when the control mechanism (20) closes...The exhaust path is open Crank angle range between... Crank angle range D while the first scavenging passage (8) is open! +1”・Second and third scavenging passages (9), (10)
Crank angle range during which is open (all angles from α to α above are angles from top dead center) The order of opening/closing timing of each scavenging passage, etc. is as follows.

That is, after the exhaust passage passes the opening angle (α), the first scavenging passage (8) opens at an angle (α1), and then the second and third scavenging passages (9) and (10) open at this angle. (α2.3
), but the time or angular range (D z, 3) in which these scavenging passages (9) and (10) are open is the shortest, and they close before the other scavenging passages and exhaust passages. The first scavenging channel (8) then closes after a time or angular range (D,) and finally the exhaust channel (16) closes after a time or angular range (D,).

The angle (α4) at which the control mechanism (20) opens is determined by the angle at which the control mechanism (20) opens.
) lies between the opening angle (α.) and the bottom dead center (UT) of the piston, and the closing angle (α, ) of the mechanism lies between the closing angle of the exhaust passage and the bottom dead center.

[Brief explanation of drawings]

The figures show embodiments of the present invention, FIGS. 1 to 12 are cross-sectional views of the first embodiment, and FIGS. 13 to 17 are cross-sectional views of the second embodiment.
FIG. 18 is a graph showing the timing of both embodiments,
Of these, Fig. 1.4.7.10 is a longitudinal sectional view at each stage of the scavenging process in the first embodiment, and Fig. 2.5.8.11 is a longitudinal cross-sectional view at each stage along line nn in Fig. 1. Longitudinal section at 3.6.9
．． Figure 12 is the same cross-sectional view, and Figures 13-
Figure 17 shows each stage of the scavenging process in the second embodiment.
．． 8. It is a longitudinal cross-sectional view shown corresponding to FIG. 11. (1)...Cylinder, (3)...Crankcase, (8)...First scavenging passage, (9)...
...Second scavenging passage, (10)...Third scavenging passage, (12), (13)...Suction port,
(12'), (13')... Upper edge of the intake port, (16)... Exhaust path.

Claims (1)

[Claims] [1] A crankcase is attached to a cylinder housing a piston, and an exhaust passage has an exhaust port facing the cylinder, and an intake port is arranged on each side of the exhaust passage and has an exhaust port facing the cylinder. Two or more scavenging air passages are provided, and opening and closing of these exhaust passages and scavenging air passages are controlled by the piston, so that fresh air is transferred from the crankcase acting as a pump to the cylinder through the scavenging air passages. In a scavenging method for an internal combustion engine, the suction ports of at least two first scavenging passages of the scavenging passages located on each side of the exhaust port are closed when the piston is descending and the pressure in the cylinder is By opening when the pressure in the crankcase is higher than the pressure in the crankcase,
a first step in which the exhaust gas in the cylinder is allowed to flow into the first scavenging passage without flowing into the crankcase, and the fresh air present in this passage is returned towards the crankcase; In the first step, at least two second scavenging air passage suction ports are opened on each side of the exhaust port by the piston, the suction ports of at least two second scavenging air passages being located further from the exhaust port than the first scavenging air passage. The exhaust gas that had flowed into the first scavenging air passage is returned to the cylinder by pressure reversal to form a barrier that prevents fresh air from the cylinder and the second scavenging air passage from escaping from the exhaust port, and then A scavenging method for a two-stroke internal combustion engine, characterized in that a second step of scavenging the cylinder and filling the cylinder with fresh air while fresh air also flows into the cylinder from the first scavenging passage. . [2] At least one third scavenging air passage, which opens into the cylinder on the opposite side of the exhaust port and is opened and closed almost simultaneously with the second scavenging air passage, is used together with the second scavenging air passage to provide the second scavenging air passage. Claim No. [1] which executes the process of
Scavenging method described in section. [3] A cylinder (1) housing a piston, a crankcase (2) connected to the cylinder housing a crankshaft, and an exhaust path having an exhaust port open to the cylinder and leading to the outside. (16), a group of scavenging air passages (8) having an intake port open to the cylinder and communicating with the crankcase;
9), (10), and at least two first scavenging passages (8) of the scavenging passage group passing through the center line of the cylinder and the exhaust passage (16). At least two second scavenging passages (9) of the scavenging passage group are arranged adjacent to the exhaust passage on both sides of the plane, and at least two second scavenging passages (9) of the scavenging passage group are located apart from the exhaust passage (16) and in the vicinity of the first scavenging passage. The upper end (12) of the suction port (12) of the first scavenging passage (8)
') is made higher than the upper edge (13') of the suction port (13) of the second scavenging air passage (9), and a part of the exhaust gas in the cylinder flows into the first scavenging air passage (8) during the scavenging process. A two-cycle internal combustion engine characterized in that the exhaust gas is configured to allow the exhaust gas to flow into the first scavenging passage (8), and is provided with means (A) for preventing the exhaust gas that has flowed into the first scavenging passage (8) from entering the crankcase (3). institution. [4] The two-cycle internal combustion engine according to claim 3, wherein the means (A) is configured such that the volume of the first scavenging air passage (8) is sufficiently large compared to the volume of the cylinder. institution. [5] The means (A) includes a recess (27) that the web (26) of the crank connected to the crankshaft has on its circumferential surface, and a recess (27) in which the first scavenging passage faces the crankcase. an opening (33) provided for cooperating with the recess;
A two-stroke internal combustion engine according to claim 3, which is a control mechanism (20) comprising: [6] Opening to the cylinder on the opposite side of the exhaust port (17) at approximately the same height as the suction port (13) of the second scavenging air passage (9), and approximately at the same time as the second scavenging air passage (9). At least one third scavenging passage (1
0) is included in the scavenging passage group (8), (9), (10). cycle internal combustion engine. [7] A cylinder (1) that houses a piston, a crankcase (3) that houses a crankshaft and is connected to the cylinder, and an exhaust path that has an exhaust port that opens into the cylinder and is led to the outside. (16), a group of scavenging air passages (8) having an intake port open to the cylinder and communicating with the crankcase;
9), (10), and at least two first scavenging passages (8) of the scavenging passage group passing through the center line of the cylinder and the exhaust passage (16). At least two second scavenging passages (9) of the scavenging passage group are arranged adjacent to the exhaust passage on both sides of the plane, and at least two second scavenging passages (9) of the scavenging passage group are located apart from the exhaust passage (16) and in the vicinity of the first scavenging passage. The control edge (11) on the upper surface of the piston (6) is connected to the second scavenging passage (9) in a stepped manner at an upper end region (11') corresponding to the suction port (12) of the first scavenging passage. It is lower than the corresponding part, and is configured so that a part of the exhaust gas in the cylinder can flow into the first scavenging passage (8) during the scavenging process, and the exhaust gas that has flowed into the first scavenging passage (8) is Two-stroke internal combustion engine, characterized in that it is provided with means (A) for preventing entry into the crankcase (3). [8] The two-cycle internal combustion engine according to claim [7], wherein the means (A) is configured such that the volume of the first scavenging air passage (8) is sufficiently large compared to the volume of the cylinder. institution. [9] The means (A) includes a recess (27) that the web (26) of the crank connected to the crankshaft has on its peripheral surface, and a recess (27) in which the first scavenging passage faces the crankcase. 2, which is a control mechanism (20) consisting of an opening (33), and
cycle internal combustion engine. [10] Opening to the cylinder on the opposite side of the exhaust port (17) at approximately the same height as the suction port (13) of the second scavenging air passage (9), and approximately at the same time as the second scavenging air passage (9). at least one third scavenging air passage (
10) is included in the scavenging passage group (8), (9), (10). cycle internal combustion engine. [11] The upper edge (12') of the suction port (12) of the first scavenging passage (8) is connected to the suction port (12) of the second scavenging passage (9).
3) The two-stroke internal combustion engine according to any one of claims [7] to [10], which is higher than the upper end edge (13') of the engine.