JP2001152860A - Cylinder fuel injection type two-cycle engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cylinder fuel injection type two-cycle engine capable of preventing seize of a piston, without making excessive the clearance between an inner face of a cylinder or a liner and a peripheral surface of the piston. SOLUTION: A top portion 2a of a piston 2 includes a convex portion 2A, having inclined faces 2aa gradually inclined from peripheral sides to the center side of the piston, so that the inclined faces 2aa are toward a top portion of the cylinder 1. A scavenging passage is disposed at least a position near an exhaust port. The inclined face 2aa is a linearly inclined face of which contour of a longitudinal section is linear, in order that scavenging air 16 from the scavenging passage blows directly against the inclined faces 2aa. An angle θis formed by the ceiling wall of an outlet of the scavenging passage disposed at least the position near the exhaust port, and an orthogonal face orthogonal to an axial line of the cylinder 1. An angle α is formed by the linear inclined face 2aa on the top portion 2a of the piston 1, and a orthogonal face which is orthogonal to the axis line of the piston 2. The angle θ is smaller than the angle α.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct injection two-cycle engine in which fuel is directly injected into a combustion chamber.

[0002]

2. Description of the Related Art FIG. 6 is a longitudinal sectional view showing the structure of a conventional in-cylinder injection two-cycle engine, FIG. 7 is a sectional view taken along line AA of FIG. 6, and FIG. FIG. 9 is a longitudinal sectional view of a main part showing a state of scavenging in a conventional in-cylinder injection two-cycle engine.

A conventional in-cylinder injection two-cycle engine is:
A cylinder 1 divided into a cylinder body 1a and a cylinder head 1b, and a recess 3
Formed between the top 2a of the piston 2 and the inner surface 1bb of the cylinder head 1b of the cylinder 1 which is provided on the cylinder head 1b of the cylinder 1 A fuel injector 5 for directly injecting fuel into a combustion chamber 4 to be cooled and a spark plug 6 for igniting a mixture of injected fuel and air
And the exhaust port 7 provided in the cylinder 1 so as to exhaust when the piston 2 descends and the circumferential position of the combustion chamber 4 to scavenge into the combustion chamber when the piston 2 descends. A plurality of scavenging passages 8a, 8a ', 8b, 8
b ', 8c, and a crankshaft 10 that rotates by being transmitted through the connecting rod 9 to move up and down the piston 2. In this case, the cylinder body 1a of the cylinder 1 and the cylinder head 1b are overlapped via a gasket 11 and connected by bolts 12. Cylinder body 1a
And a cooling passage 13 is provided in the cylinder head 1b.
The cooling water is cooled by the cooling water flowing through the cooling passage 13. In this example, a liner 14 is provided on the inner surface of the cylinder body 1a. Inlet 7a of exhaust port 7
Are opened in the liner 14. Each scavenging passage 8
a, 8a ', 8b, 8b', 8c are cylinder body 1a
Outlets 8a of the scavenging passages 8a, 8a ', 8b, 8b', 8c.
a, 8aa ', 8bb, 8bb', and 8cc are also opened in the liner 14. Each scavenging passage 8a, 8a ', 8
The inlets of b, 8b ', and 8c are open to the crank chamber 15, respectively.

In such a conventional in-cylinder injection type two-cycle engine, the top 2a of the piston 2 is connected to the scavenging passage 8a,
When scavenging from 8a ', 8b, 8b', 8c, the scavenging air 16 was substantially horizontal so that it could be easily injected into the cylinder 1.

The recess 3 at the top 2a of the piston 2 is provided at or near the position where the fuel from the fuel injector 5 directly hits, and the fuel injected from the fuel injector 5 is directed toward the inner surface 1bb of the cylinder head 1b. It is for reflecting.

In some cases, the cylinder 1 does not have the liner 14 on the inner surface.

[0007]

However, in the conventional in-cylinder injection type two-stroke engine, the top 2a of the piston 2 is almost flat, so that the scavenging gas 1 is removed as shown in FIG.
6 only flows along the top 2a of the flat piston 2, which causes insufficient cooling of the piston 2 during scavenging, and the temperature of the top 2a of the piston 2 becomes high,
Occasionally, piston 2 is cylinder 1 or liner 1
4 had the problem of burning inside.

In order to prevent the seizure of the piston 2, the inner surface of the cylinder 1 or the liner 14 and the piston 2
There is a method to ensure the gap between the outer peripheral surface of the
In this case, there is a problem that disadvantages such as a decrease in engine output and an increase in piston tapping sound are generated.

An object of the present invention is to provide an in-cylinder injection type two-cycle engine which can prevent the seizure of the piston without making the gap between the inner surface of the cylinder or the liner and the outer peripheral surface of the piston excessive.

Another object of the present invention is to provide a direct injection two-stroke engine capable of efficiently cooling a piston at least near an exhaust port where the seizure of the piston is liable to occur.

[0011]

SUMMARY OF THE INVENTION The present invention comprises a cylinder,
A piston having a recess at a part of the top and moving up and down in the cylinder, a fuel injector provided in a cylinder head of the cylinder and directly injecting fuel into a combustion chamber in the cylinder, and a fuel injector and a fuel injector. An ignition plug for igniting an air-fuel mixture, an exhaust port provided in a cylinder to exhaust when the piston descends, and a plurality of scavenging passages for scavenging air into the combustion chamber when the piston descends. This is to improve the in-cylinder injection two-cycle engine.

In one in-cylinder injection two-cycle engine according to the present invention, the top of the piston has a convex portion having an inclined surface inclined toward the top of the cylinder from the outer periphery toward the center. The inclined surface is provided as a linear inclined surface having a profile of a vertical section that is linear so that scavenging gas from a scavenging passage provided at least near the exhaust port is directly blown onto the inclined surface. The angle θ formed by the ceiling wall at the outlet of the scavenging passage on the side close to the mouth with respect to an orthogonal plane orthogonal to the cylinder axis
Is characterized in that a straight inclined surface at the top of the piston is formed to be smaller than an angle α formed with an orthogonal surface orthogonal to the axis of the piston.

[0013] In another one of the in-cylinder injection two-cycle engines according to the present invention, the top of the piston has a sloping surface inclined toward the top of the cylinder from the outer periphery toward the center. Having a shaped part,
The inclined surface is provided as a curved inclined surface having a contour of a vertical cross section so that scavenging air from a scavenging passage provided at least at a position close to the exhaust port is directly blown onto the inclined surface, and at least close to the exhaust port. The angle θ between the ceiling wall at the outlet of the scavenging passage on the side and the orthogonal plane orthogonal to the axis of the cylinder is defined by the tangent drawn from the outer periphery of the top toward the center with respect to the curved inclined surface of the top of the piston and the piston. Is formed smaller than an angle β formed between the axis and an orthogonal plane perpendicular to the axis.

As described above, the top of the piston is provided with a convex portion having an inclined surface inclined toward the top of the cylinder from the outer peripheral side toward the center of the piston, and the inclined surface is provided at least at a position close to the exhaust port. If the profile of the vertical cross section is a straight slope or the profile of the vertical cross section is a curve so that the scavenging air from the scavenging passage is blown directly to the slope, Scavenging air is directly blown onto these inclined surfaces, so that the top of the piston is efficiently cooled by the scavenging air, and seizure due to excessive thermal expansion of the piston can be prevented.

In particular, the angle .theta. Formed by the ceiling wall at least at the outlet of the scavenging passage near the exhaust port with respect to an orthogonal plane orthogonal to the axis of the cylinder, and the linear inclined surface at the top of the piston is orthogonal to the axis of the piston. The tangent drawn from the outer periphery of the top toward the center with respect to the curved inclined surface of the top of the piston and the orthogonal plane perpendicular to the axis of the piston. When the angle is smaller than the angle β, the scavenging air from at least the scavenging passage on the side closer to the exhaust port can surely hit the inclined surface at the top of the piston.

As described above, if a convex portion is provided at the top of the piston so that the scavenging air from the scavenging passage is directly blown onto the inclined surface, the resistance during scavenging increases, and the necessary scavenging air in the combustion chamber is increased. There is a possibility that the amount is not ensured, but this can be solved by increasing the opening cross-sectional area of the scavenging passage.

In the present invention, the top of the piston means a portion facing the combustion chamber at the tip of the piston.

In the in-cylinder injection type two-cycle engine of the present invention, the upper part means the cylinder head side or the top side of the piston, and the lower part means the opposite side. In the present invention, the upper part and the lower part have the same name even when they are installed horizontally.

[0019]

1 to 3 show a first embodiment of an in-cylinder injection two-cycle engine according to the present invention. FIG. 1 shows an in-cylinder injection two-cycle engine of this embodiment. FIG. 2 is an enlarged view of a main part of FIG. 1, and FIG. 3 is a longitudinal sectional view of a piston for in-cylinder injection two-cycle engine used in the present embodiment. Parts corresponding to those in FIGS. 6 to 9 are denoted by the same reference numerals.

In the in-cylinder injection two-cycle engine of the present embodiment, the top 2a of the piston 2 has a convex portion having an inclined surface 2aa inclined toward the top of the cylinder 1 from the outer periphery toward the center. 2A. The inclined surface 2aa is connected to each of the scavenging passages 8a, 8a ',
Outlets 8aa, 8aa ', 8bb of 8b, 8b', 8c,
It is provided as a linear inclined surface having a vertical cross-sectional profile so that scavenging air from 8bb 'and 8cc is directly blown onto the inclined surface 2aa. In this example, the profile of the longitudinal section of the convex portion 2A of the top 2a is formed in a truncated cone shape, and the inclined surface 2aa is a linear inclined surface.

The scavenging passages 8a, 8a ', 8b, 8b', 8
Exits 8aa, 8aa ', 8bb, 8bb', 8cc of c
Walls 8aat, 8aat ', 8bbt, 8b in
bt 'and 8 cct make an angle θ with respect to an orthogonal plane orthogonal to the axis of the cylinder 1 by an angle α formed by a linear inclined surface 2aa at the top 2a of the piston 2 with respect to an orthogonal plane orthogonal to the axis of the piston 2. It is formed small.

As described above, three or more scavenging passages 8a, 8
In the case of having the a ′, 8b, 8b ′, and 8c, it is preferable that the relationship of θ <α also be established in the scavenging passage 8c as described above. Is not concentrated, the relationship of θ <α may not be established. That is, the ceiling wall 8cct may not be inclined so that the scavenging air 16 from the outlet 8cc of the scavenging passage 8c blows directly to the linear inclined surface 2aa.

As described above, the shape of the piston 2 toward the center from the outer peripheral side of the top 2a is changed to the scavenging passages 8a, 8a ', 8
When the convex portion 2A is formed so that the scavenging air 16 from the b, 8b ', 8c is directly blown onto the inclined surface 2aa, the scavenging air 16 is directly blown onto the linear inclined surface 2aa as shown in FIG. 2 is efficiently cooled by the scavenging air 16, and seizure of the piston 2 can be prevented.

Also, three or more scavenging passages 8a, 8a
, 8b, 8b ', 8c, at least the outlets 8aa, 8aa, 8a, 8b, 8b, 8b' of the scavenging passages 8a, 8a ', 8b, 8b'.
8aa ′, 8bb, 8bb ′, ceiling wall 8aat,
8aat ', 8bbt, 8bbt' make an angle θ with respect to an orthogonal plane orthogonal to the axis of the cylinder 1 and a linear inclined surface 2aa at the top 2a of the piston 2 with respect to an orthogonal plane orthogonal to the axis of the piston 2. When the angle is smaller than the angle α, the scavenging air 16 from the scavenging passages 8 a, 8 a ′, 8 b, 8 b ′ at least close to the portion where heat is concentrated on the exhaust port 7 side
Is sprayed directly onto the inclined surface 2aa, and a portion of the top 2a of the piston 2 near the side where heat is concentrated is efficiently cooled by the scavenging air 16 to prevent seizure of the piston 2.

When two scavenging passages 8a, 8a ', 8b, 8b' are provided on the opposing surface of the cylinder 1, the ceiling walls 8bbt at the outlets 8bb, 8bb 'of the scavenging passages 8b, 8b'. 8 bbt ′ is only the angle θ formed by the piston 2 with respect to the orthogonal plane orthogonal to the axis of the cylinder 1.
May be formed to be smaller than the angle α formed by a linear inclined surface 2aa at the top 2a of the top surface 2a with respect to an orthogonal surface orthogonal to the axis of the piston 2.

FIG. 4 is a longitudinal sectional view showing a second embodiment of the in-cylinder injection type two-cycle engine piston according to the present invention, and FIG. 5 is an embodiment of the in-cylinder injection type two-cycle engine according to the present invention. It is a longitudinal section showing the important section composition in the 2nd example of form.

Also in the in-cylinder injection two-cycle engine of this example, the top 2a of the piston 2 has a convex shape having an inclined surface 2aa 'inclined toward the top of the cylinder 1 from the outer periphery toward the center. It has a portion 2A.
However, the inclined surface 2aa 'of this example is provided with the outlet 8a of each of the scavenging passages 8a, 8a', 8b, 8b ', 8c shown in FIG.
a, 8aa ', 8bb, 8bb', and 8cc are provided as curved inclined surfaces whose vertical cross-sections are curved so that scavenging air is directly blown onto the inclined surface 2aa '. In this example, the contour of the longitudinal section of the convex portion 2A of the top 2a is formed by a convex spherical surface.

The scavenging passages 8a, 8a ', 8b, 8b', 8
Exits 8aa, 8aa ', 8bb, 8bb', 8cc of c
Walls 8aat, 8aat ', 8bbt, 8b in
bt ′ and 8 cct make an angle θ between the curved surface 2 aa ′ of the top 2 a of the piston 2 and the tangent line 17 drawn from the outer periphery of the top 2 a toward the center with respect to the orthogonal surface orthogonal to the axis of the cylinder 1. Is formed smaller than an angle β formed between the piston and an orthogonal plane orthogonal to the axis of the piston 2.

It should be noted that the relationship of θ <β depends on the scavenging passages 8a,
8a ', 8b, 8b', and 8c is preferably established for the entirety of the scavenging passage 8c on the opposite side of the exhaust port 7.
Then, the relationship of θ <β may not be established.

The same effect as that of the first embodiment can be obtained by the in-cylinder injection type two-cycle engine including the cylinder 1 and the piston 2.

Further, three or more scavenging passages 8a, 8a
, 8b, 8b ', 8c, at least the outlets 8aa, 8aa, 8a, 8b, 8b, 8b' of the scavenging passages 8a, 8a ', 8b, 8b'.
8aa ′, 8bb, 8bb ′, ceiling wall 8aat,
8aat ', 8bbt, 8bbt' makes an angle θ with respect to an orthogonal plane perpendicular to the axis of the cylinder 1 from the outer periphery of the top 2a to the center with respect to the curved inclined surface 2aa 'of the top 2a of the piston 2. If the angle between the drawn tangent line 17 and the orthogonal plane perpendicular to the axis of the piston 2 is smaller than the angle β, at least the scavenging passages 8a, 8a ', 8b, 8b' close to the portion where heat is concentrated on the exhaust port 7 side. Scavenging 16
Is directly blown onto the inclined surface 2aa ′, and the portion of the top 2a of the piston 2 near the side where heat is concentrated is scavenged 16
Thus, the piston 2 can be efficiently cooled and seizure of the piston 2 can be prevented.

When two scavenging passages 8a, 8a ', 8b, 8b' are provided on opposite surfaces of the cylinder 1, the ceiling walls 8bbt at the outlets 8bb, 8bb 'of the scavenging passages 8b, 8b'. 8 bbt ′ is only the angle θ formed by the piston 2 with respect to the orthogonal plane orthogonal to the axis of the cylinder 1.
Of the top 2a with respect to the curved inclined surface 2aa 'of the top 2a
Tangent line 17 and piston 2 drawn from the outer circumference toward the center
May be formed smaller than the angle β formed between the plane and the orthogonal plane perpendicular to the axis.

In each of the above examples, the case where the inclined surfaces 2aa and 2aa 'of the convex portion 2A when the top portion 2a is cut longitudinally is a linear inclined surface or a curved inclined surface is shown. It is not limited, for example, a rising slope changes to a curved slope near the top with a linear slope, or a rising slope changes to a straight slope near the top with a curved slope. Is also good. The relationship of θ <α may be established in the case of the rising type having a linear slope, and the relationship of θ <β may be established in the case of the rising type having a curved slope.

In the present invention, each scavenging passage 8
Exits 8aa, 8aa of a, 8a ', 8b, 8b', 8c
', 8bb, 8bb', 8cc ceiling wall 8aa
The angle θ formed by t, 8aat ′, 8bbt, 8bbt ′, and 8cct with an orthogonal plane orthogonal to the axis of the cylinder 1 is an upward angle with respect to an orthogonal plane orthogonal to the axis of the cylinder 1 in the above example. As shown in the example, if the angle θ satisfies the relationship of θ <α or θ <β, the cylinder 1
May be 0 degree with respect to an orthogonal plane orthogonal to the axis of the cylinder 1, or may be a downward angle with respect to an orthogonal plane orthogonal to the axis of the cylinder 1.

Further, in the above-described example, the example in which the present invention is applied to the cylinder 1 having the liner 14 on the inner surface has been described. However, the present invention is not limited to this. The invention is equally applicable.

[0036]

In the in-cylinder injection type two-stroke engine according to the present invention, the top of the piston has a convex portion having a slope inclined toward the top of the cylinder from the outer periphery toward the center. The inclined surface has a straight inclined surface or a curved surface whose vertical cross-section has a straight line so that scavenging air from a scavenging passage provided at least near the exhaust port is directly blown onto the inclined surface. Since the inclined surfaces are provided as curved inclined surfaces, scavenging air is directly blown to these inclined surfaces, and the top of the piston is efficiently cooled by the scavenging air, so that seizure due to excessive thermal expansion of the piston can be prevented. In particular, at least the angle θ formed by the ceiling wall at the outlet of the scavenging passage on the side close to the exhaust port with respect to the orthogonal plane orthogonal to the axis of the cylinder, and the linear inclined plane at the top of the piston perpendicular to the axis of the piston. Or an angle β between a tangent drawn from the outer periphery of the top toward the center with respect to the curved inclined surface of the top of the piston and an orthogonal plane orthogonal to the axis of the piston. Since it is formed smaller, it is possible to ensure that at least scavenging air from the scavenging passage near the exhaust port hits the inclined surface of the piston top.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a first example of an embodiment of a direct injection two-stroke engine according to the present invention.

FIG. 2 is a longitudinal sectional view of a main part showing a state at the time of scavenging in the in-cylinder injection two-cycle engine shown in FIG.

FIG. 3 is a longitudinal sectional view of an example of a piston for in-cylinder injection type two-cycle engine used in the present embodiment.

FIG. 4 is a longitudinal sectional view of another example of the in-cylinder injection type two-cycle engine piston used in the present embodiment.

FIG. 5 is a vertical sectional view of a main part showing a state of scavenging in a second example of the in-cylinder injection two-cycle engine according to the present invention;

FIG. 6 is a longitudinal sectional view of a conventional in-cylinder injection two-cycle engine.

FIG. 7 is a sectional view taken along line AA of FIG. 6;

FIG. 8 is a longitudinal sectional view of a conventional in-cylinder injection type two-cycle engine piston.

FIG. 9 is a vertical sectional view of a main part showing a state during scavenging in a conventional in-cylinder injection two-cycle engine.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Cylinder 1a Cylinder main body 1b Cylinder head 1bb Inner surface 2 Piston 2a Top 2A Convex part 2aa, 2aa 'Inclined surface 3 Recess 4 Combustion chamber 5 Fuel injector 6 Spark plug 7 Exhaust port 8a, 8a', 8b, 8b ', 8c Scavenging passage 8aa, 8aa ', 8bb, 8bb', 8cc Exit of scavenging passage 8aat, 8aat ', 8bbt, 8bbt', 8cc
t Ceiling wall at outlet 9 Connecting rod 10 Crankshaft 11 Gasket 12 Bolt 13 Cooling passage 14 Liner 15 Crank chamber 16 Scavenging 17 Tangential line

Claims (2)

[Claims] 1. A cylinder, a piston having a concave portion at a top portion thereof, which moves up and down in the cylinder, and is provided on a cylinder head of the cylinder, and injects fuel directly into a combustion chamber in the cylinder. A fuel injector and an ignition plug for igniting a mixture of the injected fuel and air, an exhaust port provided in the cylinder to perform exhaust when the piston descends, and when the piston descends A plurality of scavenging passages for scavenging gas into the combustion chamber. The in-cylinder injection type two-stroke engine, wherein the top of the piston is inclined such that the top of the piston is inclined toward the top of the cylinder from the outer periphery toward the center. The inclined surface has a convex portion having a surface, and at least the scavenging air from the scavenging passage provided at a position close to the exhaust port is directly on the inclined surface. The profile of the vertical cross section is provided as a linear inclined surface that is linear so as to be sprayed, and at least the ceiling wall at the outlet of the scavenging passage on the side close to the exhaust port is orthogonal to the orthogonal surface orthogonal to the axis of the cylinder. The angle .theta. Is smaller than an angle .alpha. Formed by the linear inclined surface at the top of the piston with respect to an orthogonal surface perpendicular to the axis of the piston. 2. A cylinder, a piston having a recess at a part of a top portion thereof, which moves up and down in the cylinder, and is provided on a cylinder head of the cylinder and injects fuel directly into a combustion chamber in the cylinder. A fuel injector and an ignition plug for igniting a mixture of the injected fuel and air, an exhaust port provided in the cylinder to perform exhaust when the piston descends, and when the piston descends A plurality of scavenging passages for scavenging gas into the combustion chamber. The in-cylinder injection type two-stroke engine, wherein the top of the piston is inclined such that the top of the piston is inclined toward the top of the cylinder from the outer periphery toward the center. The inclined surface has a convex portion having a surface, and at least the scavenging air from the scavenging passage provided at a position close to the exhaust port is directly on the inclined surface. The vertical cross section is provided as a curved inclined surface having a curved shape so as to be sprayed, and at least the ceiling wall at the outlet of the scavenging passage on the side close to the exhaust port forms an orthogonal surface perpendicular to the axis of the cylinder. The angle θ is an angle β formed between a tangent drawn from the outer periphery of the top toward the center with respect to the curved inclined surface of the top of the piston and an orthogonal plane orthogonal to the axis of the piston.
An in-cylinder injection two-stroke engine characterized by being formed smaller.