JPH10266860A - Two-cycle engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a two-cycle engine which avoids blow by of a fuel more certainly. SOLUTION: A crank room compression-style two-cycle engine has an exhaust passage 9 which has an exhaust port 9a which opens at the internal circumference of a cylinder bore 3a, a pair of main scavenging passages 29, 30 having main scavenging ports 29a, 30a which open on the both sides of the exhaust port, a facing scavenging passage 28 having a facing scavenging port 28a which opens so that new air blows out on the part facing the exhaust port 9a toward the upside of it. A vertical vortex generating sub-scavenging port 31a which blows out new air in direction almost crossing to the exhaust direction to generate vertical vortex which flows axially in the cylinder is placed between the facing scavenging port 28a and one of the main scavenging ports 29a, 30a, and the opening location of the sub-scavenging port 31a is set so that opening starting timing of the sub-scavenging port 31a in piston descending process lags behind opening starting timing of the facing scavenging port 28a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-stroke engine provided with a pair of main scavenging ports on both sides of an exhaust port and an opposing scavenging port at a portion facing the exhaust port. Improving the scavenging port.

[0002]

2. Description of the Related Art In a two-stroke engine, exhaust gas in a cylinder bore is introduced by introducing air or a mixture of air and fuel (hereinafter referred to as fresh air unless otherwise specified) into a cylinder bore through a scavenging port. A scavenging process for discharging gas from the exhaust port into the exhaust passage is provided.

However, as described above, in the scavenging process, since the exhaust gas is pushed out to the exhaust passage by the fresh air, there is a blow-by phenomenon in which a part of the fresh air is exhausted from the exhaust passage. In order to improve the properties of the gas, it is necessary to reduce the blow-through as much as possible.

In order to reduce the blow-by, the applicant of the present application forms a sub-scavenging port on the inner peripheral surface of the cylinder bore for generating a vertical vortex (tumble) of fresh air flowing in the cylinder axis direction along the inner surface of the cylinder bore. Has developed a two-stroke engine that injects fuel into the tumble and has already filed an application (Japanese Patent Application No. Hei 7-2384).
No. 27).

[0005]

However, according to the above proposal, the opening start timing of the vertical vortex generating sub-scavenging port and the opening start timing of the opposed scavenging port during the stroke of the piston descending from the top dead center to the bottom dead center. And the closing start timing of the vertical vortex generation sub-scavenging port and the closing scavenging port of the opposed scavenging port in the stroke of the piston rising from the bottom dead center to the top dead center.

For this reason, most of the scavenging flow for generating vertical vortices interferes with the opposed scavenging flow, the vertical vortex is not sufficiently generated, and the fuel in the scavenging flow for generating vertical vortex is exhausted together with the opposed scavenging flow or the main scavenging flow. There is a problem in that blow-by exhausted from the port occurs, resulting in deterioration of fuel efficiency and exhaust gas properties.

The present invention has been made in view of the above-mentioned conventional problems, and can more reliably prevent fuel from flowing through.
It aims to provide a cycle engine.

[0008]

According to a first aspect of the present invention, there is provided an exhaust passage having an exhaust port opening on an inner peripheral surface of a cylinder bore, and a pair of main scavenging ports opening on both sides of the exhaust port on the inner peripheral surface of the cylinder bore. And a counter scavenging passage having an opposing scavenging port in a portion of the inner peripheral surface of the cylinder bore facing the exhaust port and opening so as to blow fresh air upwardly from the exhaust port. In a two-cycle type engine, fresh air is blown into a portion of the inner peripheral surface of the cylinder bore between the opposed scavenging port and the one main scavenging port in a direction substantially intersecting with the exhaust direction to thereby extend the cylinder shaft along the inner surface of the cylinder bore. A vertical vortex generating sub-scavenging port that generates a vertical vortex flowing in the direction is arranged, and the opening position of the sub-scavenging port is set so that the piston moves downward from the top dead center. Opening start timing of the sub scavenging port in stroke descends point is characterized in that set to lag the opening start timing of the counter scavenging port.

According to a second aspect of the present invention, in the first aspect, a rising wall that partitions the piston top region into a sub-scavenging port side region and an exhaust port side region located on an extension of the sub-scavenging port at the top of the piston. Is provided.

According to a third aspect of the present invention, in the first or second aspect, the exhaust port, the main scavenging port, the sub-scavenging port, and the opposed scavenging port are connected to the exhaust port as the piston descends.
The scavenging port, the main scavenging port, and the sub-scavenging port are opened in this order, and the exhaust port, the main scavenging port, the sub-scavenging port, and the opposing scavenging port are arranged to close in order with the rise of the piston. And

According to a fourth aspect of the present invention, in any one of the first to third aspects, the shape of the main scavenging port is such that the inner circumferential width of the cylinder bore on the cylinder head side is smaller than the inner circumferential width of the cylinder bore on the crank chamber side. At least one of the sub-scavenging ports is characterized in that the shape of the auxiliary scavenging port is such that the inner circumferential width of the cylinder bore on the cylinder head side is larger than the inner circumferential width of the cylinder bore on the crank chamber side.

According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the extension line inside the cylinder bore of the top wall surface of the sub scavenging passage connected to the cylinder head side edge of the sub scavenging port is the main scavenging port. The top wall surface of the sub-scavenging passage and the top wall surface of the main scavenging passage are set so that the top wall surface of the sub-scavenging passage and the top wall surface of the main scavenging passage are directed from the cylinder bore inner extension of the top wall surface of the main scavenging passage connected to the cylinder head side edge. It is characterized by.

According to a sixth aspect of the present invention, in any one of the first to fifth aspects, the extension line inside the cylinder bore of the top wall surface of the sub-scavenging passage connected to the cylinder head side edge of the sub-scavenging port is the opposed scavenging port. The top wall surface of the sub-scavenging passage and the top wall surface of the opposing scavenging passage are set so as to be directed toward the cylinder head side from the cylinder bore inner extension of the top wall surface of the opposing scavenging passage connected to the cylinder head side edge. It is characterized by.

[0014]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 to 7 are views for explaining a two-stroke engine according to a first embodiment of the present invention. FIG. 1 is a cross-sectional side view of the two-stroke engine (FIG. 2).
2 is a sectional view taken along the line II-II of FIG. 1, FIG. 3 is a sectional view taken along the line III-III of FIG. 2, and FIG. 4 is a schematic view showing a scavenging state in a cylinder of the two-cycle engine. FIG. 5 is a diagram for explaining the fuel injection timing in the two-cycle engine, and FIGS. 6 and 7 are schematic cross-sectional views for explaining the position, shape, etc. of each port of the two-cycle engine. FIGS. 6 and 7 correspond to the sectional view taken along the line III-III and the sectional view taken along the line II of FIG. 2, respectively.

In FIG. 1, reference numeral 1 denotes a crankcase compression type two-stroke engine. The engine 1 includes a crankcase 2, a cylinder block 3 located above the crankcase 2, and a cylinder head 4.

The cylinder bore 3 of the cylinder block 3
A piston 5 is slidably inserted into a, and the piston 5 is connected to a crankshaft 7 via a connecting rod 6. 7a is a flywheel attached to the outer end of the crankshaft 7. Further, an ignition plug 26a is attached to the cylinder head 4, and the ignition timing of the ignition plug 26a is controlled by a control device (not shown).

A crank chamber 2b in the crank case 2
An intake pipe (intake passage) 14 is connected to the intake port 2a that opens to the outside. A reed valve 15 is provided at a connection port of the intake passage 14, and a throttle valve 16 is provided at an upstream side of the reed valve 15.

The throttle valve 16 is connected to a throttle grip (not shown) via a throttle cable. The throttle opening is adjusted by turning the grip, and the throttle opening is adjusted by a throttle opening sensor (not shown). ) Is input to the control device as engine load information.

The cylinder block 3 has an exhaust passage 9 for discharging combustion gas, and a main scavenging passage for communicating fresh air compressed primarily in the crank chamber 2b into the cylinder bore 3a by connecting the cylinder bore 3a to the crank chamber 2b. 29,3
0, opposed scavenging passage 28, and sub-scavenging passage 31 for longitudinal vortex generation
Are formed.

Main scavenging ports 29a and 30a, which are openings to the cylinder bores 3a of the main scavenging passages 29 and 30, are located on the left and right sides of the exhaust port 9a of the exhaust passage 9, and scavenging the opposing scavenging passage 28. The port 28a is located so as to face the exhaust port 9a, and these scavenging ports 28a, 29a, 30a are directed to the combustion chamber 4a recessed on the lower surface of the cylinder head 4, thereby forming a scavenging stroke. The air compressed in the crank chamber 2b is blown out from the scavenging ports 28a, 29a, 30a toward the combustion chamber 4a.

A sub-scavenging port 31a, which is an opening of the sub-scavenging passage 31 to the cylinder bore 3a, is located at a portion of the cylinder bore 3a close to the opposed scavenging port 28a facing the exhaust port 9a, and has an exhaust direction a. A portion that opens in the intersecting direction b and that is connected to the sub-scavenging port 31a of the sub-scavenging passage 31 is a straight line extending tangentially to the inner peripheral surface of the cylinder bore 3a, that is, linearly extending in the intersecting direction b. It is a part 31b.

The straight portion 31 of the sub-scavenging passage 31
A fuel injection valve 32 is attached to b so as to inject fuel in the cross direction b. The fuel injection valve 32
The fuel injection timing and injection time are controlled by the control device.

The fuel injection valve 32 is provided in the cylinder block 3 and the cylinder head 4 in the direction of flow of the vertical vortex K of fresh air generated in the cylinder bore 3a, as shown by a two-dot chain line in FIG. Further, it may be mounted so as to directly inject into the vertical vortex K. Further, fuel may be injected and supplied also in the crank chamber 2b or the intake passage 14 upstream of the crank chamber 2b in order to sufficiently secure required fuel in a high-speed operation and a high-load operation range.

As described above, when the fuel is injected into the longitudinal vortex K by using the injection valve 32 for directly injecting the fuel into the combustion chamber 4a or the cylinder bore 3a, the fuel supply to the combustion chamber 4a is performed. Responsibility can be improved, rapid acceleration and rapid deceleration can be improved, and the effect of maintaining the longitudinal vortex K by the injected fuel flow can be obtained.

When fuel is mixed with fresh air in the crank chamber 2 or the intake passage 14 upstream thereof,
Since the fuel supply unit is separated from the combustion chamber, generation of vapor in the fuel supply system can be avoided.

The fuel injection valve 32 injects fuel toward the top of the piston 5 located at the bottom dead center through the sub-scavenging port 31a of the sub-scavenging passage 31, as indicated by the two-dot chain line in FIG. You may arrange so that it may be. in this case,
At least at the time of low load, a part of fuel can be injected during a period in which the piston 5 opens the sub scavenging port 31a.

When fuel is injected through the sub-scavenging port 31a during the opening period of the sub-scavenging port 31a, the fuel injection flow acts to accelerate the vertical vortex K. K increases and the amount of fuel blow-through decreases.

Further, as shown by a two-dot chain line in FIG.
1b may be mounted in a direction orthogonal to the air flow. In such a case, the fuel and fresh air can be more reliably mixed.

Here, the shapes, arrangement positions (positions in the cylinder axial direction) of the opposed scavenging port 28a, the main scavenging port 29a, and the sub-scavenging port 31a will be described in more detail with reference to FIGS. The shape and arrangement of the main scavenging port 30a are the same as those of the main scavenging port 29a.

As shown in FIG. 6, the main scavenging port 29
The shape of a is such that the inner circumferential width L1 of the cylinder bore on the cylinder head 4 side is equal to the inner circumferential width L1 of the cylinder bore on the crank chamber side.
'Is set to a smaller trapezoidal shape. The shape of the sub-scavenging port 31a is set to a substantially inverted triangular shape in which the inner circumferential width L2 of the cylinder bore on the cylinder head 4 side is larger than the inner circumferential width L2 'of the cylinder bore on the crank chamber side. Note that only one of the trapezoidal shape of the main scavenging port and the inverted triangular shape of the sub scavenging port may be adopted.

The positions of the exhaust port 9a, the opposed scavenging port 28a, the main scavenging port 29a, and the sub-scavenging port 31a in the cylinder axial direction are determined as the piston 5 descends from the top dead center. Scavenging port 28a, main scavenging port 29a, sub scavenging port 31a
And the exhaust port 9a, the main and sub scavenging ports 29a, 3
It is set so as to start closing in the order of 1a and the opposed scavenging port 28a. After the closing of the sub-scavenging port 31a, the closing of the opposed scavenging port 28a and the main scavenging port 29a ends.

In order to realize the opening start timing and closing start timing of each port, in FIG. 6, the upper edge 29a of the main scavenging port 29a is moved from the cylinder head side edge (upper edge) 9a 'of the exhaust port 9a. , The distance to the upper edge 31a 'of the auxiliary scavenging port 31a is h2, the distance to the upper edge 28a' of the opposing scavenging port 28a is h3, and the crank chamber side edge (lower edge) of the exhaust port 9a. Part) 9a '',
The distance to the lower edge 29a '' of the main scavenging port 29a is h
4. If the distance to the lower edge 31a '' of the sub scavenging port 31a is h5 and the distance to the lower edge 28a '' of the opposing scavenging port 28a is h6, the relationship h3 = h1 <h2 h6> h5 = h4 holds. Is set. It should be noted that h3 <h1 = h2 or h> h5 = h4 = 0.

As shown in FIG. 3, the upper end of the opposed scavenging passage 28 is formed such that the cylinder bore inner extension surface T3 of the top wall surface 28b at the upper end forms an angle θ3 with the cylinder bore 3a. The cylinder head 4 is directed above the extension line inside the cylinder bore of the sub scavenging port 31a. The angle θ3 is set to 15 ° to 70 °.

That is, the opposing scavenging port 28a of the opposing scavenging passage 28 directs fresh air from the crank chamber 2b to above the sub-scavenging port side region R1 while the piston 5 opens the sub-scavenging port 31a. It is formed so that it blows out with a certain direction. In other words, fresh air (scavenging air flow) blown out from the sub-scavenging port 31a and passing through the sub-scavenging port side region R1 flows into the opposed scavenging port 28a.
It is formed so as to blow out the fresh air upward from this so as not to collide with the air.

As shown in FIG. 7, the upper end of the sub-scavenging passage 31 is connected to the upper edge 31a 'of the sub-scavenging port 31a.
The extension surface T2 of the top wall surface 31d of the portion connected to the main scavenging passage 29 is directed more toward the cylinder head side than the extension surface T1 of the top wall surface 29d of the portion connected to the upper edge 29a 'of the main scavenging port 29a. Is formed. In other words, the angle θ1 between the extension surface T1 and the cylinder bore 3a is 3
While the angle θ2 is set to 0 ° to 80 °, the angle θ2 between the extension surface T2 and the cylinder bore 3a is 75 ° to 115 °.
Is set to In addition, the relationship is set as θ2> θ1 and θ2> θ3.

Further, a deflector 8 is provided on the top of the piston 5. The deflector 8 has a rising wall 8a that divides a piston top region into a sub-scavenging port side region R1 located on an extension of the sub-scavenging port 31a and an exhaust port side region R2 located on the exhaust port 9a side. doing. The rising wall 8a is formed by raising the top surface of the piston 5 so as to form a ridge extending in the cross direction b. The scavenging air blown out from the sub-scavenging port 31a is directed to the exhaust port 9a side. The purpose of this is to suppress diffusion to the surface. The rising wall 8
The height of a is set higher than the upper edge 31a 'of the sub-scavenging port 31a, and is set so that the scavenging flow from the opposed scavenging port 28a does not collide.

Next, the control of the fuel injection timing and period will be described with reference to FIG. FIG. 5 is a characteristic diagram showing the opening / closing timing of each port, the fuel injection timing, and the period as crank angles with the clockwise direction as the rotation direction of the engine 1. In FIG. 5, Eo and Ec denote the opening and closing timings of the exhaust port 9a, So and Sc denote the opening and closing timings of the main and opposed scavenging ports 29a and 28a, and S and Sc.
o ′ and Sc ′ indicate opening start and closing end timings of the sub scavenging port 31a.

In the case of the injection pattern A of FIG. 5, the exhaust port 9a is in the range from the upper crank angle Ec to Sc.
The main scavenging ports 29a, 23
0a and the closing end timing of the opposed scavenging port 28a, and in the case of the injection pattern B, in the range from the crank angle So to Sc, that is, from the opening start timing to the closing end timing of the main and opposed scavenging ports. Is injected from the fuel injection valve 32 during the period.

Specifically, the fuel is injected in the pattern A when the engine speed is high and the load is large, that is, when the injection time is short and the required injection amount is large. When the engine speed is high and the load is small, that is, when the injection time is short and the required injection amount is small, the fuel is injected in either the pattern A or the pattern B or in the middle thereof.

When the rotation speed of the engine is low and the load is large, that is, when the injection time is long and the required injection amount is large, the fuel is injected in either the pattern A or the pattern B or in the middle thereof. Furthermore, when the rotation speed of the engine is low and the load is small, that is, when the injection time is long and the required injection amount is small, the injection is performed in the pattern B.

In the engine 1 according to the present embodiment, as the piston 5 descends, the pressure in the crank chamber 2b increases, and at the same time, the exhaust port 9a starts to open, and the discharge of the combustion gas from the exhaust port 9a starts. When the piston 5 further descends, the main scavenging ports 29a, 30a and the opposed scavenging port 28a start opening, and the crank chamber 2b
As shown in FIG. 4, the fresh air which has been pressurized inside blows out from the main scavenging ports 29a, 30a and the opposing scavenging port 28a toward the combustion chamber 4a, and reverses at the combustion chamber 4a portion toward the exhaust port 9a. Scavenging flows I and J are formed.

When the piston 5 further descends, the sub-scavenging port 31a starts to open, and the sub-scavenging port 31a starts to open.
The fresh air is directed by the linear portion 31b in the tangential direction of the cylinder bore 3a (the direction b orthogonal to the exhaust direction a) and is blown out along the top surface of the piston, and further along the inner surface of the cylinder bore 3a in the cylinder bore axial direction. A vertical vortex K flows through the vortex. In addition, since the fuel from the fuel injection valve 32 is injected into the straight portion 31b of the sub-scavenging passage 31 in the direction in which fresh air is blown out, the injected fuel flows along the vertical vortex K. .

Since the fuel is injected in the middle of the sub-scavenging passage 31, the injected fuel is surely mixed with fresh air.
Further, it is not necessary to make the discharge pressure necessary for mixing fuel into fresh air so high.

In this embodiment, since the deflector 8 having the rising wall 8a is provided at the top of the piston, the fresh air blown out from the auxiliary scavenging port 31a is diffused toward the exhaust port even at a low load with a low flow velocity. This can be prevented by the rising wall 8a, the vertical vortex K can be reliably formed, and the fuel flowing with the vertical vortex K can be prevented from blowing through the exhaust port 9a.

As described above, the direction in which fresh air flows from the auxiliary scavenging port 31a to the exhaust direction a (cylinder bore tangential direction)
b, the main scavenging port 29a,
While the scavenging flows J and I from the counter scavenging port 28a toward the exhaust port 9a, a vertical vortex K is generated in the cylinder axial direction, and fuel is injected along the vertical vortex K. Since the deflector 8 for preventing the air and fuel from the auxiliary scavenging port 31a from diffusing to the exhaust port 9a side is provided, the amount of fuel discharged by the scavenging flows I and J can be reduced, and the fuel blow-through can be suppressed. .

Here, the rising wall 8a constituting the deflector 8 is desirably provided to be inclined toward the side opposite to the exhaust side in FIG. When the rising wall 8a is inclined in this manner, the scavenging flow composed of the air and fuel blown out from the auxiliary scavenging port 31a flows through the auxiliary scavenging port side region R1 along the rising wall 8a. , Since it receives a reaction force directed toward the anti-exhaust side, it is difficult to diffuse to the exhaust port side even after passing through the region R1, which is particularly effective when the scavenging flow rate at low load and low speed rotation is small and the flow velocity is low. It is a target.

When the fuel injection valve 32 is arranged so that its injection flow is directed from the auxiliary scavenging port to the top of the piston 5, fuel can be accumulated on the top of the piston 5 at low speed or at low load. Since the ignition plug 26a is arranged above the R1 region at the top of the piston 4, even when the vertical vortex K is at a low speed, or when the vertical vortex K does not occur at a low load, a rich mixture is provided in the vicinity of the ignition plug 26a. It can be formed to improve ignitability.

In this embodiment, h3 <h2, h3
6> h5, θ3 <θ2, the opposing scavenging port 28a can be used to supply fresh air from the crank chamber to the auxiliary scavenging port side area when the piston 5 is located at the bottom dead center. Since it is formed so as to blow upward from R1, the scavenging flow from the opposite scavenging port 28a can be prevented from colliding with the scavenging flow forming the longitudinal vortex K from the auxiliary scavenging port 31a, or the collision can be suppressed. Therefore, the exhaust efficiency of the exhaust gas from the combustion chamber 4a can be improved in the scavenging exhaust stroke while suppressing the blow-through of the fuel, the exhaust residue can be reduced, and illegal combustion at low load and low speed rotation can be reduced. it can.

In the present embodiment, the shape of the main scavenging ports 29a and 30a, which start opening later than the exhaust port 9a, is such that the inner circumferential width L1 of the cylinder head side is larger than the width L1 'of the crank chamber 3a. Since the size is reduced, the flow rate of the scavenging gas at the initial stage, which easily reaches the exhaust port 9a, is reduced. Therefore, even if the scavenging flow I interferes with the vertical vortex K, the amount of fresh air in the vertical vortex K reaching the exhaust port 9a can be reduced.

On the other hand, regarding the shape of the sub-scavenging port 31a, the width L2 on the cylinder head side is changed to the width L2 'on the crank chamber side.
Since it is set wider, the blow-out direction b portion of the vertical vortex K is hardly bent toward the exhaust port 9a, and in the initial stage of the scavenging which is easy to reach the exhaust port 9a, the vertical vortex K causes interference with the scavenging flow. Also, the amount of fresh air of the vertical vortex K reaching the exhaust port 9a can be reduced. Also, θ1 <θ2, h
Since at least one of 1 <h2 is adopted, the scavenging flow I and the longitudinal vortex K are less likely to cause interference.

That is, the main scavenging passage 2 extending from the crank chamber 2b to the cylinder head 4 side substantially in parallel with the cylinder axis.
Fresh air flowing through the upper and lower scavenging passages 29 and 30 is bent toward the inside of the cylinder bore 3a by the upper and lower ceiling walls 29d and 30d.
Of the cylinder bore 3a and the angle θ1 (30 ° to
80 °), the blowing direction m into the cylinder bore 3a has a velocity component in the direction of the cylinder head 4. Therefore, the main scavenging flow I occupies the position shown as Ix in FIG. 7 in the section II where the vertical vortex K is generated.

The upper end of the opposed scavenging passage 28 is formed such that the cylinder bore inner extension surface T3 of the top wall surface 28b forms an angle θ3 with the cylinder bore 3a, and is located above the cylinder bore inner extension of the auxiliary scavenging port 31a. Through the cylinder head 4. Therefore, fresh air from the crank chamber 2b blows out in a direction upward above the sub-scavenging port side region R1 while the piston 5 opens the sub-scavenging port 31a. This opposed scavenging flow J occupies the position shown as Jx in FIG. 7 in the section II.

On the other hand, fresh air flowing from the crank chamber 2b straight through the sub-scavenging passage 31 extending in the direction of the cylinder head 4 substantially in parallel with the cylinder axis is supplied to the top wall 31d of the sub-scavenging passage 31.
Is bent toward the inside of the cylinder bore 3a, but the extension surface T2 of the top wall surface 31d is
And the angle θ2. The angle θ2 is set to 75 ° to 115 °, θ2>θ1> 0 and θ2>θ3> 0, and the blowout b from the sub-scavenging port 31a is
At the Ix portion of the main scavenging flow I and the Jx portion of the opposing scavenging flow J, a reliable vertical vortex K does not occur at any position below, beside, or above.

The Ix portion of the main scavenging flow I and the Jx portion of the opposing scavenging flow J cause interference, and the main scavenging flow I is pushed by the opposing scavenging flow J to be surely reversed in the direction of the exhaust port 9a. While heading toward the cylinder head 4.

FIGS. 8 to 10 are views for explaining a V-type two-stroke engine for an outboard motor according to a second embodiment of the present invention, in which the same reference numerals as those in FIGS. The corresponding parts are shown.

In FIG. 8, reference numeral 100 denotes an outboard motor. As shown in the lower part of FIG. 8, an upper case 103 is connected to an upper part of a lower case 102 provided with a propulsion unit 101, and an engine 105 is connected to the upper part. The outboard motor 100 has a clamp bracket 111 attached to a stern 110 a of a hull 110.
It is pivotally supported to swing left and right and up and down via

The engine 105 is a water-cooled two-cycle V-type four-cylinder in which the crankshaft 7 is arranged vertically so as to be substantially vertical when traveling, and four cylinders are arranged toward the rear of the hull so as to form a V bank. Engine.

The intake system A of the engine 105 has a reed valve 15, an intake pipe 11, a throttle valve 16, and an intake port 2a formed in front of a crank chamber 2b provided for each cylinder of the crankcase 2. The intake silencer 12 common to the cylinders is connected. At the upper end of the intake silencer 12, an outside air inlet 12a that opens rearward is formed, and outside air is introduced from the cowling opening of the top cowl 104.

The fuel system B supplies the fuel in the fuel tank 115 provided on the hull 110 side to the vapor separator 117 provided on the outboard motor 100 side.
6 and a second fuel pump 118 that pressurizes the fuel in the vapor separator 117 and supplies the fuel to the fuel injection valves 32 disposed for each cylinder via the fuel delivery pipe 123.

The fuel tank 115 and the first fuel pump 1
16 is the primary pump that sends fuel manually at startup
19, a hose-side connector 120, and a cowling-side connector 121, and a fuel filter 122 is interposed between the first fuel pump 116 and the vapor separator 117. Note that 123 is a fuel supply rail, 124
Is a pressure regulator, and 125 is a return pipe.

The exhaust system C supplies the exhaust gas 9a, the first exhaust passage 9, and the second exhaust passage 1 which open the combustion gas generated in the combustion chamber 4a into the V bank of the cylinder bore 3a.
26 and the third propulsion device 101 via the third exhaust passage 127.
Is discharged into the water.

In the cylinder body 3, opposed scavenging passages 28 communicating the cylinder bore 3a and the crank chamber 2b are provided.
The main scavenging passages 29 and 30 and the vertical scavenging sub-scavenging passage 31 are formed, and the basic structure is the same as that of the above-described first embodiment.

As described above, in the engine 105 of the present embodiment, the crankshaft is oriented substantially vertically and the cylinder bore axis is oriented substantially horizontal during traveling, and the sub-scavenging passage 31 of each cylinder is It is located at the highest position of the cylinder, and the sub-scavenging port 31a is formed at the end of the scavenging passage 31 on the cylinder head side (the end on the near side in FIG. 9). The sub-scavenging port 31a is open in the direction b intersecting the exhaust direction a, and the portion of the sub-scavenging passage 31 connected to the scavenging port 31a is the cylinder bore 3a.
A linear portion 31b extends linearly in the tangential direction of the inner peripheral surface of a, that is, in the cross direction b. The fuel injection valve 32 is mounted on the straight portion 31b so as to inject fuel in a direction intersecting the cross direction b.

EC for controlling the operation of the engine 105
U65 is based on detection signals from various sensors 51 to 58 for detecting various parameters indicating the engine operating state, and in substantially the same manner as the above-described control method, the fuel injection timing of the fuel injection valve 32 and the fuel injection time ( Injection amount) and the ignition timing by the ignition circuit. In addition, 128 to 131 are an atmospheric pressure sensor, a back pressure sensor, a cylinder temperature sensor, and a knock sensor, respectively. Reference numeral 132 denotes a shift sensor that detects a shift operation and a shift position of a power transmission device (not shown) that transmits engine power to the propulsion device 101. Reference numeral 133 denotes a trim angle sensor that detects a trim angle of the outboard motor 100.

According to this embodiment, since the air compressed in the crank chamber 2b is blown out from the auxiliary scavenging port 31a in the direction b intersecting the exhaust direction a, the vertical vortex K is generated in the cylinder axis direction. And the scavenging flow J from the opposing scavenging port 28a and the scavenging flow I from the main scavenging ports 29 and 30 can be prevented from interfering with the vertical vortex K.
The vertical vortex K can be maintained, and the fuel blow-through can be suppressed as in the above-described embodiment.

In this embodiment, when the crankshaft is arranged substantially vertically and the cylinder shaft is arranged substantially horizontally, the auxiliary scavenging passage 3
1 and the sub-scavenging port 31a are provided at the highest position of each cylinder, and the fuel is injected and supplied to the cylinder head side end of the sub-scavenging passage 31, so that the sub scavenging port 31a is closed by the piston 5. Is injected into the cylinder bore together with the sub-scavenging flow at the same time as the sub-scavenging port 31a is opened by the lowering of the piston 5.

As described above, injection can be performed even during the period in which the sub scavenging port 31a is closed, so that a long fuel injection period can be secured, and even if the fuel injection valve has a small capacity or the fuel injection pressure is not increased too much. The required amount of fuel for high-speed high-load operation can be supplied.

Further, the fuel injected during the closing period of the sub-scavenging port 31a evaporates and is pushed out by the sub-scavenging flow at the same time that the sub-scavenging port 31a is opened, so that the fuel is easily miniaturized in the cylinder bore. In addition, the formation of an air-fuel mixture is easy, unburned gas is less likely to be generated, and the fuel consumption and exhaust gas properties can be further improved in combination with the reduction in blow-through.

In the above embodiment, only the case where the sub-scavenging passage for generating vertical vortex communicates with the crank chamber has been described. However, the air pump, which is provided separately through the sub-scavenging passage,
You may comprise so that the air from a blower fan etc. may be blown out into a cylinder bore.

Further, in the present invention, the blow-by is reduced by devising the arrangement position of the opposed scavenging port 28a, the blow-out direction of fresh air, and the like. However, the blow-through is reduced by a structure other than the present invention shown in FIG. Such a configuration is also possible.

In the example shown in FIG. 11, the portion of the inner peripheral surface of the cylinder bore 3a facing the exhaust port 9a is left as the cylinder wall 3a 'without providing an opposing scavenging port. The structure is the same as that of the example of FIG. 9 except that the opposed scavenging port is not provided.

In the example of FIG. 11, a vertical vortex flowing in the axial direction along the inner surface of the cylinder bore can be generated with a simple structure, and the vertical vortex flows from the portion of the inner peripheral surface of the cylinder bore facing the exhaust port 9a to the vertical vortex. Since there is no scavenging flow that blows out so as to collide, the longitudinal vortex can be reliably maintained, and fuel blow-through can be suppressed.

[0073]

As described above, according to the two-stroke engine according to the first aspect of the present invention, the sub-scavenging port for blowing fresh air in a direction substantially intersecting with the exhaust direction is provided on the inner peripheral surface of the cylinder bore. A vertical vortex that flows in the cylinder axis direction along the inner surface can be generated, and the start timing of opening the sub-scavenging port is delayed from the opening start timing of the opposed scavenging port. Interfering with the scavenging flow for generating vertical vortices from the sub-scavenging port makes it difficult to maintain vertical vortices. As a result, the amount of fuel blown through the vertical vortices can be reduced, and fuel consumption and exhaust gas properties can be improved.

According to the second aspect of the present invention, a deflector having a rising wall for partitioning the piston top region into a sub-scavenging port side region and an exhaust port side region located on an extension of the sub-scavenging port at the piston top portion. Since the flow rate of the scavenging flow for generating vertical vortices from the sub-scavenging port is low and the load is low, even during low-speed rotation, the scavenging flow can be prevented from diffusing to the exhaust port side by the rising wall, Vertical vortices can be more reliably generated, and fuel blow-through can be more reliably prevented.

According to the third aspect of the present invention, as the piston descends, the exhaust port, the opposed scavenging port, the main scavenging port, and the sub-scavenging port start opening in this order, and as the piston rises, the exhaust port, the main scavenging port, and the main scavenging port. The port, the sub-scavenging port, and the opposing scavenging port are started to close in this order, so that the scavenging flow from the main and opposing scavenging ports is less likely to interfere with the scavenging flow for vertical vortex generation from the sub-scavenging port. It is possible to surely generate the fuel, and it is possible to more reliably prevent the fuel from flowing through.

According to the fourth aspect of the present invention, the shape of the sub scavenging port is such that the shape of the main scavenging port is such that the inner circumferential width of the cylinder bore on the cylinder head side is smaller than the inner circumferential width of the cylinder bore on the crank chamber side. At least one of a shape in which the inner circumferential width of the cylinder bore on the cylinder head side is larger than the inner circumferential width of the cylinder bore on the crank chamber side. In the initial period, the scavenging flow from the main scavenging port is surely reversed to the exhaust port side,
When adopting the method, the scavenging flow for vertical vortex generation is less likely to bend to the exhaust port side, and the scavenging flow from the secondary scavenging port is more likely to reach the exhaust port. Also in the period, the interference between the scavenging flow from the opposing main scavenging port and the longitudinal vortex can be made less likely to occur, and the fuel blow-through can be more reliably prevented.

According to the fifth aspect of the present invention, an extension of the top wall surface of the sub scavenging passage connected to the cylinder head side edge of the sub scavenging port is connected to the cylinder head side edge of the main scavenging port. Since the shapes of the top wall surface of the sub-scavenging passage and the top wall surface of the main scavenging passage are set so as to be directed to the side opposite to the cylinder head from the extension of the top wall surface of the main scavenging passage inside the cylinder bore, the flow from the main scavenging passage Blows toward the cylinder head side, whereas the blow-off flow from the sub-scavenging passage blows out along the piston top surface, avoiding the interference between the scavenging flow from the main scavenging port and the vertical vortex from the sub-scavenging port. In addition, fuel blow-through can be more reliably prevented.

According to the sixth aspect of the present invention, since the top wall surface of the sub-scavenging port is directed to the side opposite to the cylinder head from the top wall surface of the opposed scavenging port, the blowout flow from the opposed scavenging port is swept for generating vertical vortices. Interference with the air flow is less likely to occur, longitudinal vortices can be more reliably generated, and fuel blow-through can be more reliably prevented.

[Brief description of the drawings]

FIG. 1 is a sectional side view (a sectional view taken along line II of FIG. 2) of a two-stroke engine according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a sectional view taken along line III-III in FIG. 2;

FIG. 4 is a view schematically showing a scavenging state in a cylinder of the two-cycle engine.

FIG. 5 is a diagram for explaining a fuel injection timing and an injection period in the two-cycle engine.

FIG. 6 is a schematic diagram for explaining the shape of each port and the like of the two-cycle engine.

FIG. 7 is a schematic diagram for explaining the shape of each port and the like of the two-cycle engine.

FIG. 8 is a configuration diagram illustrating a two-stroke V-type four-cylinder engine for an outboard motor according to a second embodiment of the present invention.

FIG. 9 is a sectional rear view of the engine according to the second embodiment.

FIG. 10 is a system diagram of an intake system, a fuel supply system, and an exhaust system of the engine according to the second embodiment.

FIG. 11 is a cross-sectional rear view showing a two-cycle engine outside the present invention.

[Explanation of symbols]

 1,105 2 cycle engine 2b Crank chamber 3a Cylinder bore 5 Piston 8 Deflector 8a Rising wall 9 Exhaust passage 9a Exhaust port 28 Opposed scavenging passage 28a Opposed scavenging port 28b Top wall surface of opposing scavenging passage 29,30 Main scavenging passage 29a, 30a Main Scavenging port 29d Top wall surface of main scavenging passage 31 Secondary scavenging passage 31a Secondary scavenging port 31d Top wall surface of sub-scavenging passage a Exhaust direction b Direction intersecting with exhaust direction K Vertical vortex L1 Width of main scavenging port on cylinder head side L1 'Main scavenging Port width on crack chamber side L2 Width of sub scavenging port on cylinder head side L2 'Width of sub scavenging port on crank chamber side

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02F 1/22 F02F 1/22 A 3/24 3/24 3/28 3/28 B

Claims (6)

[Claims] An exhaust passage having an exhaust port opening on the inner peripheral surface of a cylinder bore, a pair of main scavenging passages having main scavenging ports opening on both sides of the exhaust port on the inner peripheral surface of the cylinder bore, and a pair of main scavenging passages having an inner peripheral surface of the cylinder bore. A crank chamber compression type two-stroke engine including a facing scavenging passage having a facing scavenging port that opens toward the upper part of the exhaust port to blow out fresh air at a portion facing the exhaust port. A vertical vortex that generates a vertical vortex flowing in the cylinder axial direction along the inner surface of the cylinder bore by blowing fresh air in a direction substantially intersecting the exhaust direction at a portion between the opposed scavenging port and the one main scavenging port. A secondary scavenging port is disposed, and the opening position of the secondary scavenging port is adjusted by the secondary scavenging during the stroke of the piston descending from top dead center to bottom dead center. A two-stroke engine, wherein the port opening start timing is set to be later than the opening start timing of the opposed scavenging port. 2. The deflector according to claim 1, wherein a deflector having a rising wall for partitioning the piston top region into a sub-scavenging port side region and an exhaust port side region located on an extension of the sub-scavenging port is provided at the piston top portion. A two-stroke engine. 3. The scavenging port according to claim 1, wherein the exhaust port, the main scavenging port, the auxiliary scavenging port, and the opposed scavenging port are
As the piston descends, it starts to open in the order of the exhaust port, the opposed scavenging port, the main scavenging port, and the sub-scavenging port.
A two-stroke engine, wherein the exhaust port, the main scavenging port, the auxiliary scavenging port, and the opposed scavenging port are arranged to start closing in order with the rise of the piston. 4. The method according to claim 1, wherein
The shape of the main scavenging port is such that the inner circumferential width of the cylinder bore on the cylinder head side is smaller than the inner circumferential width of the cylinder bore on the crank chamber side. The shape of the sub scavenging port is that the inner circumferential width of the cylinder bore on the cylinder head side is the crank. The shape is larger than the inner circumferential direction width of the cylinder bore on the chamber side.
A two-stroke engine characterized by employing at least one of the following. 5. The cylinder head side edge of the main scavenging port according to any one of claims 1 to 4, wherein an extension of the top wall surface of the sub scavenging passage that is continuous with the cylinder head side edge of the sub scavenging port inside the cylinder bore. The top wall surface of the sub-scavenging passage and the top wall surface of the main scavenging passage are set so as to be directed toward the cylinder head side from the cylinder bore inner extension of the top wall surface of the main scavenging passage connected to the section. Cycle engine. 6. The cylinder head side edge of the opposed scavenging port according to any one of claims 1 to 5, wherein an extension of the top wall surface of the sub scavenging passage connected to the cylinder head side edge of the sub scavenging port is inside the cylinder bore. The top wall surface of the sub-scavenging passage and the top wall surface of the opposing scavenging passage are set so as to be directed toward the opposite side of the cylinder head from the extension of the top wall surface of the opposing scavenging passage on the inner side of the cylinder bore. Cycle engine.