JPH07158472A - Exhaust gas controller of two-cycle engine - Google Patents

Abstract

PURPOSE:To provide an exhaust gas controller of a two-cycle engine capable of decreasing quantities of CO and HC caused by blowby of exhaust gas, and more surely purifying the exhaust gas. CONSTITUTION:The exhaust port 41 of each cylinder 21 is connected to an exhaust gas confluent passage 40 extending in the crank shaft direction, via an exhaust gas branched passage 42 slantly extending to the exhaust downstream side, when an exhaust gas controller of a two-cycle engine 6 having a plural number of cylinder 22 arranged in the shaft direction. An exhaust control valve 43 for variably controlling an exhaust passage area is arranged in an exhaust guide 13 connected to the downstream side of the confluent point (a) between an exhaust gas branched passage 42 and the exhaust gas confluence passage 40 for the cylinder 21' most downstream side of the exhaust gas confluent passage 40.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust control device for a two-cycle engine which can reduce the amounts of CO and HC due to blow-by of exhaust gas.

[0002]

2. Description of the Related Art For example, as an exhaust system of a two-cycle engine mounted on an outboard motor, exhaust ports of a plurality of cylinders arranged in parallel in a vertical crankshaft direction are joined together through exhaust branch passages. There is a structure that is connected to a passage, extends the merging passage downward, and opens downward.

In the above-mentioned two-cycle engine, purification of exhaust gas is required from the viewpoint of preventing air pollution due to exhaust gas. As a method for purifying such exhaust gas, it is general to dispose a catalyst in the exhaust passage.
As such a catalyst arrangement structure, conventionally, the catalyst is arranged along the inner wall of the exhaust passage in the vicinity of the exhaust port, the bent portion or the like, or the catalyst is arranged in the confluent exhaust passage formed in the cylinder block. Those provided are proposed (see Japanese Patent Laid-Open No. 61-283713).

[0004]

However, in the case of the above-mentioned conventional method for purifying exhaust gas with a catalyst, the CO and HC amounts in the exhaust gas increase in an operating region where there is a large amount of fuel blow-through, and the purifying ability of the catalyst, etc. In some cases, it may not be possible to respond sufficiently, and improvement in this respect is requested.

An object of the present invention is to provide an exhaust control device for a two-cycle engine, which is designed to improve the exhaust gas purifying ability by reducing the amount of exhaust gas blown through itself.

The present inventors have studied a method of suppressing blow-through of exhaust gas. As a result, the blow-through can be suppressed by changing the area of the exhaust passage according to the engine operating state, which reduces the amount of CO and HC. The present invention has been made paying attention to its effectiveness.

Therefore, the present invention is an exhaust control system for a two-cycle engine having a plurality of cylinders arranged in parallel in the crankshaft direction. The exhaust port of each cylinder is provided with an exhaust branch passage in an exhaust merging passage extending in the crankshaft direction. An exhaust control valve for variably controlling the exhaust passage area is disposed in the vicinity of the downstream side of the confluence point of the exhaust merging passage and the exhaust branch passage for the cylinder for the most downstream side, which is connected via the exhaust control valve. The invention of No. 2 is characterized in that the exhaust branch passage extends obliquely toward the exhaust downstream side.

According to a third aspect of the present invention, the exhaust control valve is provided in an exhaust guide which supports the engine and constitutes a part of an exhaust passage. Further, in the fourth aspect, the exhaust control valve is cooled in the exhaust guide. It is characterized in that a jacket is formed, and the exhaust jacket is surrounded by the cooling jacket.

According to a fifth aspect of the present invention, the engine is a V-type engine in which the exhaust merging passages provided for each bank are arranged in parallel, and the exhaust control valves for the exhaust merging passages are coaxial. It is characterized by being arranged.

Here, in a four-cycle engine, an exhaust control valve for variably controlling the passage area may be provided in the exhaust passage for the purpose of improving the output. However, in the case of a two-cycle engine, even if the exhaust passage area is changed by the exhaust control valve, it does not contribute to the improvement of the engine output. Therefore, it has not been conventionally considered to employ the exhaust control valve in the two-cycle engine. Therefore, the exhaust control valve of the present invention is not intended to improve the engine output but to suppress the above-mentioned blow-through, and has a purpose different from that of the above-described four-cycle engine.

The opening and closing of the exhaust control valve is controlled according to the operating state of the engine.
For example, a method of connecting an exhaust control valve and a throttle valve via a link mechanism and controlling the opening / closing of the exhaust control valve according to the throttle opening can be adopted. Will be narrowed down. Also, a method of detecting the throttle opening and the engine speed and controlling the opening / closing of the exhaust control valve by a servomotor or the like according to the detected values can be adopted.

[0012]

According to the exhaust control system for a two-cycle engine of the present invention, the exhaust control valve for variably controlling the passage area of each cylinder is disposed in the vicinity of the downstream side of the exhaust merging passage. By changing the exhaust passage area with the exhaust control valve, for example, during low load operation with a large blow-through amount, the blow-through of fuel can be suppressed by narrowing down the exhaust passage area, and the CO and HC amounts can be reduced accordingly. In this case, according to the second aspect of the invention, since the exhaust branch passage is formed so as to extend obliquely to the downstream side, the volume of the exhaust passage up to the exhaust control valve is reduced, and the control response of the exhaust control valve is improved. As a result, the blow-through amount can be further suppressed.

According to the third aspect of the present invention, since the exhaust control valve is provided on the exhaust guide as a strength member having high rigidity, deformation due to external force and seizure due to exhaust heat can be prevented.

Further, in the invention of claim 4, since the periphery of the exhaust control valve is surrounded by the cooling jacket formed in the exhaust guide, seizure due to exhaust heat of the control valve can be more reliably prevented.

Further, according to the fifth aspect of the present invention, since the exhaust control valves for the respective exhaust merging passages are coaxially arranged, the opening / closing control of the respective passages can be performed by a common drive mechanism, and the individual exhaust passages for the respective passages can be controlled. It is not necessary to tune each drive mechanism as in the case of disposing the control valve, the increase in the number of parts can be avoided, and the structure can be simplified.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 5 are views for explaining an exhaust control device for a two-cycle engine according to an embodiment of the present invention. In the present embodiment, a case where the present invention is applied to a two-cycle engine for an outboard motor will be described as an example. .

In FIG. 5, reference numeral 1 is an outboard motor in which the apparatus of this embodiment is adopted. The outboard motor 1 is arranged at the stern 2a of the hull 2. The outboard motor 1 is connected to the upper case 5 on the lower case 4 on which the propeller propeller 3 is arranged, and the engine 6 is housed on the upper case. It is configured by connecting the top cowl 7. The outboard motor 1 is elastically supported by a swivel arm 9 via a damper member (not shown), and the swivel arm 9 is attached to a clamp bracket 8 fixed to the hull 2 around a rotary shaft extending in the left-right direction. It is swingably supported in the vertical direction.

A propulsion shaft 11 is axially supported in the lower case 4, and the propulsion propeller 3 is spline-coupled to the rear end of the propulsion shaft 11. An upper end of a drive shaft 12 extending in the vertical direction is connected to the output shaft 6a of the engine 6, and a bevel gear 10 meshing with the propulsion shaft 11 is connected to the lower end of the shaft 12.

Between the upper case 5 and the top cowl 7, an exhaust guide 13 made of aluminum die-casting which constitutes a part of the exhaust passage is arranged, and the engine 6 is mounted on the upper surface of the exhaust guide 13. It is installed. The exhaust guide 13 is fixed to the swivel arm 9 via the damper member.

The exhaust guide 13 has a pair of exhaust holes 13 communicating with the exhaust ports 6b for banks of the engine 6.
a is formed, and an exhaust pipe 14 that communicates with each exhaust hole 13 a and extends downward is connected to the lower surface of the exhaust guide 13. Further, a muffler 16 surrounding the exhaust pipe 14 is connected to the lower surface of the exhaust guide 13. The lower end of the muffler 16 is open in the lower case 4 and communicates with the rear end of the propulsion unit 3 through the case 4 to the outside.

The engine 6 is a water-cooled two-cycle V type 6
It is a cylinder engine, and is mounted vertically such that the crankshaft 20 is substantially vertical when traveling. The engine 6 has a crankcase 22 accommodating the crankshaft 20 and a cylinder body 23 in which three pairs of cylinders 21 are arranged so as to form V banks, and a cylinder head 24 is mounted on the cylinder body 23. It has a structure.

A piston 25 slidably inserted into the cylinder 21 of the cylinder body 23 is connected to the crankshaft 20 via a connecting rod 26.

The crankcase 22 is formed with an opening 22b which communicates with the inside of the crank chamber 22a.
An intake passage 30 is connected to 2b via a reed valve 32 that opens and closes it. A throttle body 33 having a built-in throttle valve 31 is connected to the upstream side of the intake passage 30. Reference numeral 34 is a silencer that reduces intake noise.

Here, the crank chamber 2 is provided on the right side in FIG. 3 of the mating surface of the crankcase 22 with the cylinder body 23.
An outward bulging portion 22c forming a part of 2a is formed. As a result, the volume of the crank chamber 22a is expanded, the intake air amount is increased correspondingly, and the engine output is improved.

As shown in FIG. 1, the cylinder body 2
In FIG. 3, one opposed scavenging passage 35a and two main scavenging passages 35b, 35 for communicating the crank chamber 22a with each cylinder 21 are provided.
c are formed respectively.

Further, each cylinder 21 of the cylinder body 23
Is constituted by a cylindrical sleeve 36 with which the piston 25 is in sliding contact, and each scavenging passage 35 a of the sleeve 36.
A tapered portion 36a is formed at the edge of the opening that faces ~ 35c. The tapered portion 36a and the scavenging passages 35a to 35c
It forms a continuous surface with no steps from the opening edge. Further, the tapered portion 36a of the opposed scavenging passage 35a extends in a funnel shape toward the center of the cylinder 21. As a result, the scavenging passage resistance into the cylinder 21 is reduced, and thus the intake air amount can be increased.

In the V-bank of the cylinder body 23, two exhaust merging passages 40, 40 extending vertically along the crankshaft 20 and opening downward are arranged and formed. Each exhaust merging passage is formed. The lower end exhaust port 6b of 40 is opened on the lower surface of the cylinder body 23.

An exhaust branch passage 42 extending obliquely toward the exhaust merging passage 40 is connected to the exhaust port 41 of each cylinder 21. The exhaust branch passages 42 join the exhaust merging passage 40. ing.

Since the exhaust branch passage 42 is formed obliquely, the total passage length from each exhaust port 41 to the exhaust control valve described later is shortened and the exhaust passage volume is reduced. As a result, the control response is improved, and as a result, the blow-through amount is further suppressed.

Further, the length from the center of each cylinder 21 to the axis of the exhaust merging passage 40 is set longer than in the conventional case. As a result, by properly utilizing the 120-degree crank, the exhaust pulse of the adjacent cylinder is propagated to the cylinder between the scavenging close and the exhaust close.
The amount of blow-through is suppressed accordingly.

Further, by setting the length from the center of each of the cylinders 21 to the axis of the exhaust merging passage 40 to be long, the two cylinders 21 'and 21' located at the lowermost part can be separated from the exhaust merging passage 40 by that much. Become. This suppresses the thermal influence on the cylinder in the downstream side where exhaust heat is concentrated.
The exhaust merging passage 40 and the exhaust branch passages 42 are formed in a circular cross section, and the passages 40, 42 are formed.
The cross-sectional area in the longitudinal direction is substantially uniform, and from this point also, the intake air amount is improved by reducing the passage resistance.

A notch recess 25a, which is deeper from the center of the piston toward the outer peripheral side and has a substantially trapezoidal shape when viewed in the piston axial direction, is provided in the portion of the upper surface of the head of each piston 25 facing the exhaust port 41. As a result, the exhaust timing can be changed with a simple structure in which the piston is replaced.

Both exhaust holes 1 of the exhaust guide 13
A valve hole 13b is formed in the portion facing 3a in a direction orthogonal to this. The valve hole 13b is provided in the lowermost cylinder 21.
The exhaust branch passage 42 and the exhaust merging passage 40 are located in the vicinity of the downstream of the confluence point a.

An exhaust control valve 43, which characterizes this embodiment, is inserted and arranged in the valve hole 13b. As shown in FIG. 4, the exhaust control valve 43 has a structure in which valve portions 43b and 43b for opening and closing the exhaust holes 13a are formed by cutting out a round bar made of stainless steel. Both valve portions 43b are coaxial. A drive shaft 43a is provided at one end of the valve portion 43b, and a support shaft 43a is provided at the other end.
c is integrally formed.

The exhaust control valve 43 has a valve portion 43.
It is configured to rotate between a fully open position in which b is flush with the inner surface of the exhaust hole 13a and a fully closed position in which the valve portion 43b stands upright and narrows down the exhaust hole 13a.

A valve hole 13b of the exhaust guide 13
A cooling jacket 13c is formed in the periphery of the exhaust control valve 40 by the jacket 13c. A lid member 45 that rotatably supports the exhaust control valve 40 and closes the opening of the valve hole 13b is inserted into the opening of the valve hole 13b.

The drive shaft 43a of the exhaust control valve 43 is projected from the exhaust guide 13 to the outside, and a plate 46 is bolted and fixed to the projected portion. As shown in FIG. 2, one end of a connecting rod 47 is connected to the plate 46, and the other end of the connecting rod 47 is connected to a drive rod 48. An arm member 49 connected to the throttle shaft 31a of the throttle valve 31 is connected to the drive rod 48. The drive rod 48
Is moved in the direction of arrow a by the lever of the operation handle located at the front end of the outboard motor.

By moving the drive rod 48 in the direction of arrow a in FIG. 2, the throttle valve 31 and the exhaust control valve 43 rotate in the directions of arrows b and c, so that the opening of the throttle valve 31 is adjusted. Accordingly, the exhaust control valve 43 is opened and closed. Specifically, the exhaust control valve 43 is set to open in proportion to the throttle opening and the exhaust control valve 43 is fully opened when the throttle opening is 70 to 80%.

Next, the function and effect of this embodiment will be described. The outboard motor 1 of the present embodiment transmits engine power to a propulsion shaft 11 via a drive shaft 12, and the propulsion shaft 11 rotationally drives the propulsion propeller 3. Then, the exhaust gas from each cylinder 21 joins from the exhaust branch passage 42 in the exhaust merging passage 40, expands in the muffler 16 through the exhaust pipe 14, and is then discharged into the lower case 4.
From here, it is discharged to the outside through the propeller propeller 3.

In the exhaust control system of this embodiment, the exhaust control valve 43 is rotated to the substantially fully closed position in an operating region where the opening of the throttle valve 31 is small, such as when the engine is idle and the load is low. As a result, the valve portion 43b of the exhaust control valve 43 narrows the passage area of the exhaust hole 13a and suppresses the exhaust gas from blowing through. Further, when the opening degree of the throttle valve 31 increases, the exhaust control valve 43 opens substantially in proportion to the opening degree, and fully opens when the throttle opening degree is 70 to 80%.

As described above, according to this embodiment, each cylinder 21
Since the exhaust control valves 43 whose passage areas are changed are arranged in both exhaust holes 13a of the exhaust guide 13 located on the downstream side of the confluence point a of the exhaust merging passage 40, the engine operating state is changed as described above. Accordingly, blow-through of exhaust gas can be suppressed, CO and HC amounts can be reduced, and exhaust gas can be purified more reliably.

Further, in this embodiment, the exhaust control valve 43 described above is used.
Is disposed in the exhaust guide 13 configured to have high rigidity because it supports the engine 6, so that the exhaust control valve 43 can be prevented from being deformed by an external force and can be prevented from being deformed by exhaust heat or the like. .

Further, since the exhaust control valve 43 is surrounded by the cooling jacket 13c formed on the exhaust guide 13, the cooling efficiency can be improved and the deformation due to exhaust heat can be prevented from this point as well.

Further, according to this embodiment, the exhaust control valve 4
3 is integrally formed with the valve portion 43b so that
The opening and closing of each exhaust hole 13a can be controlled by one drive mechanism,
It is not necessary to perform tuning as in the case of separately disposing the exhaust control valves, and the cost can be suppressed as much as the increase in the number of parts can be avoided.

In the above embodiment, the case where the exhaust control valve 43 is provided in the exhaust guide 13 has been described as an example, but the present invention is not limited to this.

FIG. 7 is a diagram showing an exhaust control device according to a modification of the above-mentioned embodiment, in which the same reference numerals as those in FIG. 1 designate the same or corresponding parts. The exhaust control valve 43 is arranged in the exhaust pipe 50 connected to the lower surface of the exhaust guide 13.
This is an example in which the passage area of the exhaust pipe 50 is changed by rotating the control valve 43. In this example as well, the blow-through of exhaust gas can be suppressed in accordance with the engine operating state, and the same effect as in the above-described embodiment can be obtained.

[0047]

As described above, according to the exhaust control system for a two-cycle engine of the present invention, the exhaust port of each cylinder is connected to the exhaust merging passage extending in the crankshaft direction via the exhaust branch passage extending to the exhaust downstream side. An exhaust control valve for variably controlling the area of the exhaust passage is disposed near the downstream side of the confluence point of the exhaust branch passage for the most downstream cylinder and the exhaust confluence passage. There is an effect that the amount can be reduced and the exhaust gas can be reliably purified.

[Brief description of drawings]

FIG. 1 is a cross-sectional view illustrating an exhaust control device of a two-cycle engine according to an exemplary embodiment of the present invention.

FIG. 2 is a side view showing an engine equipped with the apparatus of the embodiment.

FIG. 3 is a sectional plan view showing the engine of the embodiment.

FIG. 4 is a diagram showing an exhaust control valve of the apparatus of the above embodiment.

FIG. 5 is a side view showing an outboard motor to which the apparatus of the above embodiment is applied.

FIG. 6 is a sectional view showing an exhaust control device according to a modification of the above embodiment.

FIG. 7 is an enlarged view of a scavenging port portion of the engine of the above embodiment.

[Explanation of symbols]

 6 2-cycle engine 13 Exhaust guide 13a Exhaust hole 13c Cooling jacket 20 Crankshaft 21 Cylinder 40 Exhaust confluence passage 41 Exhaust port 42 Exhaust branch passage 43 Exhaust control valve a Confluence point

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location F01P 3/12 8206-3G F02B 25/20 R

Claims (5)

[Claims] 1. In an exhaust control device of a two-cycle engine having a plurality of cylinders arranged in parallel in a crankshaft direction, an exhaust port of each cylinder is connected to an exhaust merging passage extending in the crankshaft direction via an exhaust branch passage. An exhaust control valve for variably controlling the area of the exhaust passage is disposed in the vicinity of the downstream side of the confluence point of the exhaust merging passage with the exhaust branch passage for the cylinder on the most downstream side. apparatus. 2. The exhaust gas exhaust passage according to claim 1, wherein the exhaust gas branch passage extends obliquely downstream of the exhaust gas.
Exhaust control device for cycle engine. 3. The exhaust control valve according to claim 1 or 2, wherein the exhaust control valve is provided in an exhaust guide that supports an engine and constitutes a part of an exhaust passage.
Exhaust control device for cycle engine. 4. The exhaust control device for a two-cycle engine according to claim 2, wherein a cooling jacket is formed in the exhaust guide so as to surround the exhaust control valve. 5. The engine according to claim 1, wherein the engine is a V-type engine, the exhaust merging passage is provided for each bank, and the both exhaust merging passages are arranged in parallel so as to extend in a crankshaft direction. The exhaust control device for a two-cycle engine is characterized in that the exhaust control valves for the exhaust merging passages are arranged coaxially.