JP3198557B2 - Exhaust control device for two-stroke engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to an exhaust control device for a two-stroke engine.

2. Description of the Related Art Conventionally, in a two-cycle engine mounted on a vehicle such as a motorcycle, various types of exhaust control are required to improve the output of the engine in a wide rotation speed range from a low rotation speed range to a high rotation speed range. An apparatus is provided. For example, in a variable exhaust timing device, a timing valve is movably disposed on a peripheral portion of a cylinder side opening in an exhaust passage, and the timing valve is moved forward and backward in the exhaust passage as appropriate according to the engine speed range. The exhaust timing is changed. According to the two-stroke engine provided with the exhaust control device as described above, the upper edge position of the cylinder-side opening in the exhaust passage is substantially changed by the amount of movement of the timing valve into and out of the exhaust passage. The opening timing of the exhaust passage due to the reciprocating movement of the motor can be optimized in each rotation speed range. In the exhaust passage variable device, an auxiliary exhaust passage is opened in the cylinder, and an opening / closing valve is provided in the auxiliary exhaust passage, and the opening / closing valve is appropriately operated according to the engine speed range. The auxiliary exhaust passage is interrupted. According to the two-stroke engine equipped with the exhaust control device as described above, the intermittent connection of the auxiliary exhaust passage changes the cross-sectional area of the passage through which the exhaust gas passes. It can be optimal for the area.

By the way, the above-mentioned 2
When two exhaust control devices are simultaneously used in the engine, both the exhaust timing and the exhaust efficiency can be optimized in each rotation speed range, so that the output of the engine can be further improved. However, in order to simultaneously employ the above two emission control devices, it is necessary for the engine to have mechanisms and actuators required for the individual emission control devices, that is, a timing valve, an opening / closing valve, a drive actuator for operating each valve, and these valves. It is necessary to provide a link mechanism or the like that connects the actuator and the drive actuator, which leads to an increase in the size of the device and a significant complication of the structure. Incidentally, in order to solve such a problem, conventionally, Japanese Patent Application Laid-Open No. 63-2591
As disclosed in Japanese Patent Application Laid-Open No. 18-182, an exhaust valve 16 that advances into the exhaust port 14 by rotation about an exhaust valve drive shaft 17 is used. The side exhaust passage 22
The opening 23 on the exhaust passage 15 side can be directly opened and closed. However, the one disclosed in Japanese Patent Application Laid-Open No. 63-259118 uses an exhaust valve 16 that extends into the exhaust port 14. Therefore, the volume of the exhaust halves occupying the exhaust passage increases, and the resistance of the exhaust gas flow during the operation of the exhaust halves increases, which may lead to a decrease in the engine output. 2
Since the opening 23 on the exhaust passage 15 side is directly opened and closed, it is necessary to control the clearance dimension between the rotating exhaust valve and the opening 23 of the sub-exhaust passage with high precision. There is a possibility that the clearance changes due to the accumulation and the engine output characteristics deteriorate. The present invention has been made in consideration of the above-described circumstances, and it has been proposed to provide a two-stroke engine capable of minimizing an increase in the size and complexity of the structure, further improving the output, and maintaining good engine output characteristics for a long period of time. It is intended to provide an emission control device.

In order to solve the above-mentioned problems, according to the present invention, the cylinder block is provided above the exhaust passage in the cylinder block, and from the upper side of the side surface of the cylinder block downward in the axial direction of the cylinder. A receiving hole that is penetrated in an inclined manner and that opens in the vicinity of the upper edge of the exhaust port in the exhaust passage, and is accommodated in the receiving hole via a guide member provided in the receiving hole, and is directed toward the exhaust passage. A two-stroke engine having a timing valve that moves forward and backward and an auxiliary exhaust passage that connects the cylinder and the exhaust passage to each other, wherein the timing valve moves forward and backward to the exhaust passage according to an engine speed range. By changing the exhaust timing, and by interrupting the communication of the auxiliary exhaust passage, the cross-sectional area of the exhaust gas passage In the exhaust control device for a two-stroke engine, the opening on the exhaust passage side of the auxiliary exhaust passage is set to a timing halve in which the timing valve most protrudes into the exhaust passage, a lower end surface of the guide member, and It is arranged in a space surrounded by the upper edge of the exhaust port, and the communication of the auxiliary exhaust passage is interrupted by a timing halve that moves forward and backward to the exhaust passage.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 conceptually shows a two-stroke engine to which the exhaust control device according to the present invention is applied, and is applied to a motorcycle, particularly a motorcycle mainly for running off-road, such as a motocross or enduro. 2 illustrates a two-cycle engine to be mounted. FIG.
As shown in FIG. 6 to FIG. 6, in this two-cycle engine,
A base end portion of the exhaust passage 2 formed in the cylinder block 1 and located on the cylinder 3 side is branched into two branches, and the cylinder 3 has a pair of exhaust ports 4 and 4 formed therein. These exhaust ports 4 and 4 have mutually symmetrical shapes, and the height positions of the upper edges 4a and 4a (the edges on the top dead center side and the upper edges in FIGS. 5 and 6). Are set so that the exhaust timing is optimal in the high engine speed range, and the sum of the cross-sectional areas is set so that the exhaust efficiency is optimal in the low engine speed range. As shown in FIG. 1, the two-stroke engine includes a pair of housing holes 5, 5 in an upper portion (top dead center side portion in FIG. 1) of the exhaust passage 2 in the cylinder block 1. have. These accommodation holes 5, 5 penetrate in parallel with each other in such a manner as to incline downward (toward the bottom dead center, downward in FIG. 1) from the upper side of the cylinder block 1 toward the axis of the cylinder 3. And are opened near the upper edges of the pair of exhaust ports 4 in the exhaust passage 2. As shown in the drawing, timing valves 7, 7 are accommodated in these accommodation holes 5, 5 via guide members 6, 6, respectively. Timing valve 7,
Although not explicitly shown in the drawing, each of 7 has a semi-cylindrical shape, and each tip is formed in an arc shape along the cylinder 3, and is disposed so as to be able to advance and retreat into the exhaust passage 2. ing. The timing valves 7, 7 have their base ends connected to each other by an engagement pin 8, and are further fixed to a drive shaft 9 of a drive actuator (not shown) via the engagement pin 8. It is linked to the moving arm 10. Further, the two-stroke engine described in FIG.
As shown in FIG. 3, auxiliary exhaust passages 1 are respectively provided at portions of the cylinder block 1 located on both sides of the exhaust passage 2.
It has 0,10. These auxiliary exhaust passages 10, 10
As shown in FIGS. 1 and 4, one end of each of the cylinders 3 is opened in the cylinder 3 and the other end thereof is opened in the exhaust passage 2. The cylinder 3 and the exhaust passage 2 communicate with each other. ing. As clearly shown in FIG.
The openings 11, 11 on the side of the exhaust passage 2 in the auxiliary exhaust passages 10, 10 are arranged at positions extremely near the cylinder 3 and above the timing valves 7, 7 projecting into the exhaust passage 2. And openings 12, 12 on the cylinder 3 side in the auxiliary exhaust passages 10, 10.
The height positions of the upper edges 12a are slightly lower than the upper edges 4a of the exhaust ports 4 in the exhaust passage 2. That is, as shown in FIG. 1, the opening 1 on the side of the exhaust passage 2 in the auxiliary exhaust passages 10,
The timing valves 7 are connected to the exhaust passage 2.
The timing halves 7, 7 projecting most from the lower end surface of the guide member 6 and the upper edge 4 of the exhaust ports 4, 4
a, 4a. In the two-stroke engine configured as described above, when the swing arm 10 of the drive actuator (not shown) is swung, the pair of timing valves 7, 7 are interlocked via the engagement pins 8, respectively. Is moved into and out of the exhaust passage 2. At this time, as shown in FIG. 3, the pair of timing valves 7, 7 are immersed in the guide members 6, 6 in a state in which they are most retracted in the exhaust passage 2, and their bottom surfaces 7 a, 7 a Is matched with the inner peripheral surface.
In the state in which the pair of the timing valves 7 and 7 is most protruded from the exhaust passage 2, the respective tips are occupied in the vicinity of the extended upper pole of the inner peripheral surface of the cylinder 3 as shown in FIG. 2. Now, this two-stroke engine is running,
When the number of rotations is in a predetermined low number range, the above-described drive actuator (not shown) is operated, and the pair of timing valves 7, 7 are maintained in the state where they are most protruded from the exhaust passage 2. . In this state,
As shown in FIG. 2A, the upper edge of the descending piston P passes through the upper edges 4a, 4a of the exhaust ports 4, 4 in the exhaust passage 2 by the action of the protruding timing valves 7, 7. No evacuation is performed, and as shown in FIG.
Exhaust gas in the cylinder 3 is discharged to the exhaust passage 2 only when the upper edge of the piston P passes the tip of the timing valve 7,7. In this state, the upper edge of the descending piston P is located at the auxiliary exhaust passage 10,
10, the upper edge 12 of the opening 3 on the cylinder 3 side
a, 12a, and when the cylinder 3 and the exhaust passage 2 are communicated with each other, the auxiliary exhaust passages 10, 1 are also operated by the timing valves 7, 7 projecting into the exhaust passage 2.
Since the vicinity of the openings 11 on the side of the exhaust passage 2 at 0 is maintained at the same pressure state as that of the cylinder 3, gas is hardly circulated in the auxiliary exhaust passages 10 and 10. Eventually, in the above-described state, the exhaust gas in the cylinder 3 is discharged to the exhaust passage 2 at a late time and through only the pair of exhaust ports 4 and 4, and the low exhaust gas is generated due to a synergistic effect of the two. Significant improvement in engine output in the score range can be achieved. On the other hand, when the rotational speed of the engine increases from the above state and reaches a predetermined high rotational speed range, the above-described drive actuator (not shown) is operated in the opposite direction to the previous direction, as shown in FIG. At the same time, the pair of timing valves 7, 7 are maintained in a state where they are completely withdrawn from the exhaust passage 2. In this state, FIG.
As shown in (a), the exhaust gas in the cylinder 3 is immediately discharged to the exhaust passage 2 when the upper edge of the descending piston P passes through the upper edges 4a, 4a of the exhaust ports 4, 4 in the exhaust passage 2. Will be done. In this state, the upper edge of the descending piston P is the upper edge 12a of the cylinder 3 side opening 12, 12 in the auxiliary exhaust passage 10, 10.
When the cylinder 3 and the exhaust passage 2 communicate with each other, the exhaust passage 2 in the auxiliary exhaust passages 10
The vicinity of the openings 11, 11 is maintained at a pressure equivalent to the atmosphere, so that the exhaust gas in the cylinder 3 is discharged to the exhaust passage 2 through the auxiliary exhaust passages 10, 10. As a result, in the above-described state, a large amount of exhaust gas in the cylinder 3 is discharged to the exhaust passage 2 at an early stage through the pair of exhaust ports 4, 4 and the pair of auxiliary exhaust passages 10, 10. Thus, the synergistic effect of the two makes it possible to significantly improve the engine output in a high rotation speed range. Further, when the engine speed drops from the above state and reaches a predetermined low number point range again, the pair of timing valves 7, 7 are held in a state where they are most protruded into the exhaust passage 2, respectively. The exhaust gas is discharged to the exhaust passage 2 at a late time and through only the pair of exhaust ports 4 and 4. As described above, in the two-cycle engine, both the exhaust timing and the exhaust efficiency can be optimized in each of the rotational speed ranges in accordance with the rotational speed range of the engine, thereby further improving the output of the engine. be able to. Moreover, a mechanism and an actuator necessary for controlling the exhaust timing, that is, a timing valve, a drive actuator (not shown) for operating the timing valves 7, 7 and the timing valves 7, 7 and the drive actuator (FIG. Not shown)
Since both the exhaust timing and the exhaust efficiency are controlled only by the swing arm 10 that links the apparatus and the apparatus, the apparatus is not increased in size and the structure is not complicated. Note that, in the above-described embodiment, the exhaust control apparatus applied to a two-cycle engine mounted on a motorcycle, particularly a motorcycle for traveling off-road, is exemplified.
The present invention is not limited to this, and can of course be applied to a two-stroke engine for other uses. The cylinder 3 of the exhaust passage 2 formed in the cylinder block 1
The base portion located on the side is branched into two branches, and the cylinder 3
1 illustrates an exhaust control device applied to a two-stroke engine having a pair of exhaust ports 4 and 4. However, the exhaust passage may have another shape such as one having a single opening in the cylinder 3. Absent. In this case, the timing valves need not always be paired. Further, in the above-described embodiment, two types of rotation speed ranges of a low rotation speed range and a high rotation speed range of the engine are set as conditions for controlling the position of the timing valve 7, and the state in which the timing valve 7 is most protruded is set. Although it occupies the most degenerated state, it is also possible to set three or more rotation speed ranges as the position control conditions of the timing valve and occupy the timing valve at an intermediate position in the exhaust passage. . In this case, the timing valve may be a multi-stage type, that is, a timing valve composed of a plurality of valve components. When three or more rotation speed ranges are set as the position control conditions of the timing valve as described above, the exhaust gas in the cylinder is caused by the exhaust timing in the low rotation speed range and the exhaust timing in the high rotation speed range. In the middle,
It is discharged to the exhaust passage through a part of the auxiliary exhaust passage and the exhaust passage through the cylinder-side opening, and in addition to the low rotation speed region and the high rotation speed region,
It is possible to significantly improve the engine output in the middle rotation speed range.

As described above, according to the exhaust control apparatus of the present invention, the auxiliary exhaust passage is interrupted by the advance / retreat movement of the timing valve for changing the exhaust timing to the exhaust passage. It is not necessary to provide a dedicated mechanism for intermittently switching the power supply, and it is possible to suppress the enlargement of the apparatus and the complexity of the structure as much as possible, and to further improve the output of the engine. Further, in the present invention, the timing valve is slidably provided in an upper portion of the cylinder block and inclined downward from the upper portion of the side surface of the cylinder block toward the direction of the cylinder axis. The exhaust timing and the cross-sectional area of exhaust gas change by moving back and forth (sliding) into the exhaust passage, so that the volume of the exhaust halve occupied in the exhaust passage is small.
Thus, the resistance of the exhaust gas flow can be reduced to prevent the engine output from decreasing as much as possible. Further, since the timing valve of the present invention is a slide type, when the timing valve enters the accommodation hole and the guide member, the attached carbon and tar are scraped off, so that the timing valve (exhaust valve) does not accumulate. The reliable operability of the exhaust valve can be favorably maintained over a long period of time. Further, in the present invention, the exhaust passage side opening of the auxiliary exhaust passage is arranged in a space surrounded by the timing valve in a state where the timing valve projects most into the exhaust passage, the lower end surface of the guide member, and the upper edge of the exhaust opening. , Because the auxiliary exhaust passage is not directly interrupted by the exhaust valve,
It is not necessary to control the clearance dimension between the timing valve and the opening of the sub-exhaust passage with high accuracy, and furthermore, the above-mentioned clearance does not change due to carbon deposition due to long-term use, so that a good engine for a long period of time Output characteristics can be maintained.

[Brief description of the drawings]

FIG. 1 is a sectional side view conceptually showing a main part of a two-stroke engine to which an exhaust control device according to the present invention is applied.

FIG. 2 is an essential part cross-sectional side view showing an operation in a state where a timing valve is projected.

FIG. 3 is a sectional side view of an essential part showing an operation in a state where the timing valve is retracted.

FIG. 4 is a sectional view taken along line IV-IV in FIG. 1;

FIG. 5 is a sectional view taken along line VV in FIG. 4;

FIG. 6 is a sectional view taken along line VI-VI in FIG. 4;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Cylinder block 2 ... Exhaust passage 3 ... Cylinder 4 ... Exhaust port 4a ... Upper edge of exhaust port 5 ... Housing hole 6 ... Guide member 7 ... Timing valve 10, 10 ... Auxiliary exhaust passage 11 ... Opening on the exhaust passage side

Claims (1)

(57) [Claims] 1. An exhaust passage provided in an upper portion of an exhaust passage in a cylinder block and penetrating from an upper portion of a side surface of the cylinder block in a manner inclined downward toward an axial center of the cylinder and above an exhaust port in the exhaust passage. An accommodating hole opened near the edge, a timing valve accommodated in the accommodating hole via a guide member provided in the accommodating hole, and advanced and retracted into the exhaust passage; and communicating between the cylinder and the exhaust passage with each other A two-stroke engine provided with an auxiliary exhaust passage that changes exhaust timing by moving the timing valve into and out of the exhaust passage according to the engine speed range, and communicates with the auxiliary exhaust passage. An exhaust control device for a two-stroke engine that changes the cross-sectional area of the exhaust gas by intermittent And The opening on the exhaust passage side in the auxiliary exhaust passage is disposed in a space surrounded by a timing halb in a state where the timing valve protrudes most into the exhaust passage, a lower end surface of the guide member, and an upper edge of the exhaust port. An exhaust control device for a two-stroke engine, wherein the communication of the auxiliary exhaust passage is interrupted by a timing halve moving forward and backward to the exhaust passage.