JPH108974A - Connecting rod supercharge device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain more improvement of an engine output by more enhancing charging efficiency without making enlargement of a diameter in a cylinder bore. SOLUTION: A supercharger is constituted by forming a suction chamber and a compression chamber partitioned by a connecting rod 5 in a crank chamber at a crank angle except in the vicinity of the top dead center, sucking new air or a mixture to the suction chamber increasing a capacity according to a swivel motion of the connecting rod 5, compressing new air or mixture in the compression chamber decreasing a capacity so as to be supplied to a cylinder. Here, thickness t2 of a part 5b except a small end part 5a of the connecting rod 5 is formed thicker than thickness t1 of the small end part 5a (t2 >t1 ). In this invention, the thickness t1 of the small end part 5a is left as it is, that is, without changing an external diameter of a piston, a crank chamber capacity pushed away by swiveling the connecting rod 5 can be increased, larger new air ratio is ensured, supercharge performance of a connecting rod supercharger can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a supercharger for an internal combustion engine which compresses fresh air or air-fuel mixture by oscillating movement of a connecting rod in a crank chamber and supplies the compressed air or air-fuel mixture to a cylinder.

[0002]

2. Description of the Related Art The applicant of the present invention has proposed a connecting rod supercharging device as one of crankcase supercharging devices for improving the output of an internal combustion engine (for example, see Japanese Patent Application Laid-Open No. Hei 6-93869). This connecting rod supercharging device forms a suction chamber and a compression chamber defined by a connecting rod in the crank chamber at a crank angle excluding the vicinity of the top dead center, and a fresh air is supplied to the suction chamber whose volume increases with the swinging motion of the connecting rod. Alternatively, the air-fuel mixture is sucked in, the fresh air or the air-fuel mixture in the compression chamber having a reduced volume is compressed and supplied to the cylinder (supercharging) to increase the charging efficiency, thereby improving the engine output. is there.

[0003]

By the way, the applicant of the present application considered that it is necessary to further increase the charging efficiency in the connecting rod supercharging device and to further improve the engine output. In other words, in order to further improve the output of an engine equipped with a connecting rod supercharging device capable of improving the charging efficiency, it is conceivable to increase the cylinder bore diameter to increase the displacement. As a result, the weight increases, and the engine vibration increases due to the increase in the inertial force. Further, the size of the cylinder block and the cylinder head is increased, and the weight of the engine is increased.

The present invention has been made in view of the above circumstances, and an object thereof is to further improve the engine output by increasing the charging efficiency without increasing the diameter of the cylinder bore. It is an object of the present invention to provide a connecting rod supercharging device for an internal combustion engine, which can achieve the above.

[0005]

In order to achieve the above object, according to the first aspect of the present invention, a suction chamber and a compression chamber defined by a connecting rod are formed in a crank chamber at a crank angle excluding near a top dead center, A connecting rod of an internal combustion engine that sucks fresh air or air-fuel mixture into a suction chamber whose volume increases due to the swinging motion of the connecting rod, compresses fresh air or air-fuel mixture in a compression chamber whose volume decreases, and supplies it to a cylinder. In the supercharging device, a thickness of a portion excluding the small end of the connecting rod is thicker than that of the small end.

According to a second aspect of the present invention, in the first aspect of the present invention, the bottom surface of the piston is a convex arcuate curved surface along the swinging direction of the connecting rod, and a step of a portion excluding a small end of the connecting rod is provided. The convex portion is formed into a concave arc-shaped curved surface facing the piston bottom surface with a minute gap.

Further, according to a third aspect of the present invention, in the first aspect of the present invention, a stepped concave portion having a convex arc-shaped curved surface along the swinging direction of the connecting rod is formed inside the piston, and the connecting rod is provided in the stepped concave portion. A part of the portion excluding the small end portion is exposed, and the step convex portion is formed into a concave arc curved surface opposed to the arc curved surface of the step concave portion formed inside the piston with a small gap. .

Therefore, according to the present invention, since the thickness of the connecting rod is made different between the small end portion and the other portion, the thickness of the small end portion remains unchanged, that is, without changing the outer diameter of the piston. As a result, the volume of the crank chamber that is pushed away by the swinging of the connecting rod can be increased, and a larger air supply ratio can be secured to improve the supercharging performance of the connecting rod supercharging device.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

<First Embodiment> FIG. 1 is a longitudinal sectional view of an internal combustion engine provided with a connecting rod supercharging device according to a first embodiment of the present invention. FIG. 3 is an enlarged sectional view taken along line X-X of FIG. 1, FIG. 4 is a perspective view of a piston, FIG. 5 is a perspective view of a connecting rod, and FIG. 6 is a perspective view of a crankshaft.

An internal combustion engine 1 shown in FIG. 1 is a water-cooled four-cycle single-cylinder engine (hereinafter simply referred to as an engine). A piston 4 slides up and down in a cylinder bore 3 formed in a cylinder body 2 of the engine. It is fitted freely. The piston 4 is connected to a crankshaft 6 via a connecting rod 5, and the crankshaft 6 is rotatably housed in a crankcase 8 formed in a crankcase 7. Incidentally, a water jacket 9 is formed around the cylinder bore 3 of the cylinder body 2.

The engine 1 according to the present embodiment has a connecting rod supercharging device according to the present invention in the crank chamber 8. Here, the configuration of the connecting rod supercharging device will be described with reference to FIGS.

As shown in FIG. 3, the connecting rod 5 has a small end 5a at its small end 5a by a piston pin 10.
Is linked to a, the piston 4, as shown in FIG. 4, recess 4a of thickness T ₁ that accommodates the small end 5a of the connecting rod 5 to permit swinging of the connecting rod 5 is formed In addition, a piston pin hole 4b for inserting and holding the piston 10 is provided therethrough. The bottom surface 4c of the piston 4 forms a convex arcuate curved surface along the swinging direction of the connecting rod 5. That is, the bottom surface 4c is formed into an arcuate curved surface having a radius r around the piston pin hole 4b.

By the way, as shown in FIG. 5, the small end portion 4a of the connecting rod 5 (more precisely, the portion that enters the concave portion 4a of the piston 4) has the thickness of the concave portion 4a formed in the piston 4. is T ₁ minute clearance c ₁ value smaller t ₁ than (= T ₁ -c ₁₎ is set to, the portion 5b except for the small end portion 5a has a thickness t ₂ is the small end 5a
(T ₂ > t ₁ ). Therefore, as shown in FIG. 5, a stepped portion 5c is formed on the front and back surfaces at the boundary between the small end portion 5a of the connecting rod 5 and the other portion 5b.
A small clearance C ₃ (see FIG. 3)
) To form opposing concave arcuate curved surfaces. In addition, as shown in FIG.
a radius R about the piston pin hole 5d formed in
(= R + c ₃ ).

On the other hand, as shown in FIG. 5, a crank pin hole 5e is formed at the large end of the connecting rod 5 having a thickness t ₂ (> t ₁ ). 6 is connected between two opposed disk-shaped crank webs 6a of the crankshaft 6 shown in FIG. here,
Both the crank webs 6a distance T ₂ of the between is set small clearance c by ₂ minutes greater than the thickness t ₂ of the portion 5b comprising big end of the connecting rod 5 (T ₂ = t ₂ + c
₂ ). In the crankshaft 6 shown in FIG. 6, reference numeral 6b denotes a crank journal portion.

As shown in FIG. 2, the crankcase 7 has a cylindrical inner wall 7a formed along the outer periphery of the crank web 6a of the crankshaft 6, and the connecting rod 5 is formed on the cylinder body 2. A notch surface 2a is formed to avoid interference with the connecting rod 5, and the large end of the connecting rod 5 moves with a small clearance along the inner peripheral wall 7a to perform a required pumping action as described later.

Incidentally, the cylinder body 2 has a concave side wall 2b (FIG. 2) which is flush with the crank web 6a.
Is formed only on one side), and the recessed side wall 2b is formed.
And the crank web 6a are connected to one side of the connecting rod 5 (FIG. 2).
In the figure) with a small clearance.
Accordingly, in the crankcase 7, the crank web 6a and the concave side wall 2b (each formed in a pair in the vertical direction in FIG. 2), the inner peripheral wall 7a, the notch surface 2a are formed in the same plane.
And a variable-volume crank chamber 8 (see FIG. 1) defined by the piston 4.

Thus, in the connecting rod supercharging device according to the present invention, the large end of the connecting rod 5 moves along the inner peripheral wall 7a as shown in FIG. 1 at the crank angle excluding the vicinity of the top dead center. Sometimes, the crank chamber 8 is divided into a suction chamber A and a compression chamber B by the connecting rod 5, and the air-fuel mixture is absorbed in the suction chamber A whose volume increases with the swinging motion of the connecting rod 5, and the compression chamber B whose volume decreases. And constitutes a kind of positive displacement compressor for compressing the air-fuel mixture in the crankcase.
A suction passage 12 that opens to the suction chamber A and a discharge passage 13 that opens to the compression chamber B are formed at the bottom. A reed valve 14 is provided in the discharge passage 13 of the crankcase 7 for permitting only the discharge of the air-fuel mixture compressed in the compression chamber B to the outside of the compression chamber B.

On the other hand, as shown in FIG. 1, a cylinder head 15 attached to the cylinder body 2
6 and an exhaust passage 17 are formed. An intake port and an exhaust port, which are openings of the intake passage 16 and the exhaust passage 17 to the combustion chamber S, are opened and closed at appropriate timing by an intake valve 18 and an exhaust valve 19, respectively. As a result, required gas exchange is performed in the cylinder bore 3.
The intake valve 18 and the exhaust valve 19 are connected to a tappet 21, which is driven by a cam formed integrally with a camshaft 20,
The opening / closing operation is performed by the respective switches 22.

Incidentally, one end of a suction pipe 23 is connected to the suction passage 12 formed in the crankcase 7, and the other end of the suction pipe 23 is connected to an air cleaner (not shown). A carburetor (not shown) is provided on the way. Further, the discharge passage 13 formed in the crankcase 7 and the intake passage 16 formed in the cylinder head 15 are connected by a pressurized suction pipe 24 also serving as a pressure accumulation chamber. An exhaust pipe (not shown) is connected to an exhaust passage 17 formed in the cylinder head 15.

Next, the operation of the connecting rod supercharging device according to the present invention will be described.

When the engine 1 is driven, the connecting rod 5 swings in the crank chamber 8, and as described above, the connecting rod 5 is moved to the crankcase 7 at a crank angle other than near the top dead center.
When moving along the inner peripheral wall 7a, the crank chamber 8 is partitioned into a suction chamber A and a compression chamber B as shown in FIG.
The air-fuel mixture is drawn into the suction chamber A in the crank chamber 8 through the suction pipe 23 and the suction passage 12 due to the negative pressure generated in the crank chamber 8.

On the other hand, the air-fuel mixture is compressed in the compression chamber B, the volume of which decreases with the swinging movement of the connecting rod 5, and the air-fuel mixture pressurized in the compression chamber B and the pressure is increased increases the reed valve 14. It passes through and is stored in the pressurized suction pipe 24.
When the intake valve 18 is opened during the intake stroke, a high-pressure mixture in the pressurized intake pipe 24 is supplied (supercharged) from the intake passage 16 into the cylinder bore 3.

Thus, the air-fuel mixture supplied (supercharged) into the cylinder bore 3 as described above is compressed in a subsequent compression stroke, and then is supplied to combustion in the combustion chamber S, and is generated by this combustion. Part of the heat energy is taken out as rotational power of the crankshaft 6. The exhaust gas generated in the cylinder bore 3 by the combustion of the air-fuel mixture is discharged to the atmosphere through the exhaust passage 17 and an exhaust pipe (not shown) when the exhaust valve 19 is opened in the exhaust stroke.

As described above, in the engine 1 according to the present embodiment, the air-fuel mixture is compressed in the crank chamber 8 by the connecting rod supercharging device according to the present invention and supercharged into the cylinder bore 3, so that the air-fuel mixture is However, in the connecting rod supercharging device, the thickness of the connecting rod 5 is made different between the small end portion 5a and the other portion 5b as described above. 5a can increase the thickness t ₂ of the portion 5b except the connecting rod 5 it is possible to increase the volume of the crank chamber 8 displace by swing accordingly. As a result, the supercharging performance of the connecting rod supercharging device can be improved by securing a large air supply ratio, and thereby the output of the engine 1 can be further increased.

Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 7 is a front view of a connecting portion between a piston and a small end portion of a connecting rod showing a connecting rod supercharging device according to a second embodiment of the present invention.
7 is a sectional view taken along the line Y-Y of FIG. 7, and FIG. 9 is an exploded perspective view of the piston and the small end of the connecting rod. In these figures, the same elements as those shown in FIGS. ing.

[0027] Also in this embodiment, it is thicker (t ₂ <t ₁₎ than the thickness t ₁ of the thickness t ₂ of the portion 5b of the small end 5a except for the small end 5a of the connecting rod 5 However, a part of the portion 5 b having the thickness t ₂ faces the inside of the piston 4.

That is, the recess 4a formed in the piston 4
A substantially fan-shaped stepped recess 4d is formed in a part of both side walls of the connecting rod 5, and the stepped recess 4d has a radius r along the swinging direction of the connecting rod 5 (FIG. 9).
) Is formed.

[0029] On the other hand, to face a portion of the thickness t ₂ of the portion 5b except for the small end 5a of the connecting rod 5 to the stage recess 4d formed on the piston 4, as shown in FIGS. 7 and 8, partial and molding the Dantotsu portion 5c of 5b with a small clearance c ₃ a concave arc curved surface facing the arc curved surface 4e stage recess 4d of the piston 4. The step projection 5c is formed into an arc-shaped curved surface having a radius R (= r + c ₃ ) centered on the piston pin hole 5d formed in the small end 5a of the connecting rod 5.

[0030] In Thus, also in this embodiment, the thickness t ₂ of the portion 5b except for the small end 5a of the connecting rod 5 larger than the thickness t ₁ of the small end portion 5a (t ₂ <t ₁₎ Therefore, the same effect as in the first embodiment can be obtained.

In the first and second embodiments,
By improving the output of the engine 1, the connecting rod 5
Since the explosive compressive force acting on the connecting rod 5 increases, it is necessary to increase the thickness of the small end 5a of the connecting rod 5 so as to increase the sectional area. However, this is only for the purpose of increasing the strength, and the cylinder bore 3 does not increase in diameter as in the case where the overall thickness of the connecting rod 5 is increased.

Although the present invention has been described above with reference to the case where the present invention is applied to a 4-cycle single-cylinder engine, the present invention is naturally applicable to a 4-cycle multi-cylinder engine and a 2-cycle engine. It is.

[0033]

As apparent from the above description, according to the present invention, the suction chamber and the compression chamber defined by the connecting rod are formed in the crank chamber at the crank angle excluding the vicinity of the top dead center, and the connecting rod swings. 2. Description of the Related Art In a connecting rod supercharging device of an internal combustion engine, fresh air or air-fuel mixture is sucked into a suction chamber whose volume increases with movement, and fresh air or air-fuel mixture in a compression chamber whose volume decreases is compressed and supplied to a cylinder. Since the thickness of the portion excluding the small end of the connecting rod is made thicker than that of the small end, it is possible to secure a large air supply ratio by increasing the exhaust volume that the connecting rod pushes away without increasing the piston diameter. As a result, the supercharging performance of the connecting rod supercharging device can be improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an internal combustion engine including a connecting rod supercharging device according to Embodiment 1 of the present invention.

FIG. 2 is a cross-sectional perspective view of a main part of an internal combustion engine showing a configuration of a connecting rod supercharging device according to Embodiment 1 of the present invention.

FIG. 3 is an enlarged sectional view taken along line XX of FIG. 1;

FIG. 4 is a perspective view of a piston of the internal combustion engine including the connecting rod supercharging device according to the first embodiment of the present invention.

FIG. 5 is a perspective view of a connecting rod of the internal combustion engine including the connecting rod supercharging device according to the first embodiment of the present invention.

FIG. 6 is a perspective view of a crankshaft of an internal combustion engine including the connecting rod supercharging device according to the first embodiment of the present invention.

FIG. 7 is a front view of a connecting portion between a piston and a small connecting rod end showing a connecting rod supercharging device according to a second embodiment of the present invention.

FIG. 8 is a sectional view taken along line YY of FIG. 7;

FIG. 9 is an exploded perspective view of a piston and a small end portion of a connecting rod showing a connecting rod supercharging device according to a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Internal combustion engine 3 Cylinder bore (cylinder) 4 Piston 4c Piston bottom surface 4d Piston step concave part 4e Piston step concave arc curved surface 5 Connecting rod 5a Connecting rod small end 5b Portion excluding connecting rod small end 5c Connecting rod step convex 8 Crank chamber A suction chamber B compression chamber

Claims (3)

[Claims] 1. A suction chamber defined by a connecting rod and a compression chamber are formed in a crank chamber at a crank angle excluding the vicinity of a top dead center, and fresh air or mixing is formed in the suction chamber whose volume increases with the swinging motion of the connecting rod. In a connecting rod supercharging device for an internal combustion engine, which sucks air and compresses fresh air or air-fuel mixture in a compression chamber having a reduced volume and supplies the compressed air or air-fuel mixture to a cylinder, a thickness of a portion excluding a small end of the connecting rod is reduced. A connecting rod supercharging device for an internal combustion engine, characterized in that it is thicker than that of an end portion. 2. A concave arcuate curved surface which has a bottom surface of a piston which is a convex arcuate curved surface along a swinging direction of a connecting rod and a step convex portion other than a small end portion of the connecting rod opposes the piston bottom surface with a small gap. The connecting rod supercharging device for an internal combustion engine according to claim 1, wherein the device is formed into a shape. 3. A stepped recess having a convex arc-shaped curved surface along the swinging direction of the connecting rod is formed inside the piston, and a part of a portion excluding a small end portion of the connecting rod is made to face the stepped concave, and the stepped recess is formed. 2. The connecting rod supercharging device for an internal combustion engine according to claim 1, wherein the convex portion is formed into a concave circular curved surface opposed to the circular curved surface of the step concave portion formed inside the piston with a small gap.