JPH0641788B2 - Connection structure of piston and connecting rod - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention is a cylinder main body (cylinder block) of an internal combustion engine or an air compressor having a limited height, and can make a stroke of a piston longer than a conventional one. The present invention relates to a connecting structure of a piston and a connecting rod.

[Prior Art] As shown in FIG. 3, a cylinder body 2 of a conventional internal combustion engine.
The height of 1 is the dimension p between the piston crown surface 2a of the piston 2 fitted in the cylinder 21a and the axis of the piston pin 33, and the arm of the piston 2 and the crankshaft 16 (represented by the axis). And the length r of the arm of the crankshaft 16 and the length of the connecting rod 13 (the distance between the axis a of the piston pin 33 and the axis b of the arm of the crankshaft 16). .

Therefore, in order to increase the displacement of the conventional (off-the-shelf) multi-cylinder internal combustion engine, the inner diameter of the cylinder 21a is increased or the stroke 2r of the piston 2 is increased, but the former means are adjacent to each other. There is a limit because the wall thickness between the cylinders 21a becomes thin.

In the latter means, the position of the piston pin 33 with respect to the piston 2 is moved upward to shorten the dimension p, and the arm of the crankshaft 16 is lengthened accordingly. However, in general, there is almost no margin in the dimension p between the piston crown surface 2a and the piston pin 33 (see, for example, Japanese Utility Model Laid-Open No. 64-47958).
When the dimension p is shortened, the combustion chamber 3 becomes shallower, the degree of freedom regarding the shape of the combustion chamber 3 is limited, it becomes difficult to obtain a good combustion state, the temperature of the piston ring becomes high, and cooling failure occurs. , Durability problems occur.

If only the arm length r of the crankshaft 16 is increased, the crankshaft 16 must be arranged downward correspondingly, and the height h of the cylinder body 21 increases. Cylinder body 21
Changing the height h of the is accompanied by a major modification of the processing line,
Equipment costs are high.

Therefore, in reality, the height h of the cylinder body 21 and the dimension p of the piston 2 are not changed, but the connecting rod 13 is shortened, and the arm of the crankshaft 16 is lengthened accordingly. However, the length l of the connecting rod 13 is shortened and the arm length r of the crankshaft 16 is reduced.
When (1 / r) is made longer, the piston slap becomes noticeable, and the piston ring wears, the slap noise increases, and the fuel consumption decreases.

In particular, in order to meet strict exhaust gas regulations in the future, it is required to increase the displacement of each cylinder of a conventional engine. However, due to the above-mentioned circumstances, how to achieve exhaust without changing the height of the cylinder body. The issue is how to increase the quantity.

[Problems to be Solved by the Invention] In order to solve the above-mentioned problems, an object of the present invention is to increase the stroke of the piston without changing the height of the cylinder body. It is to provide a connection structure.

[Means for Solving the Problem] In order to achieve the above object, the structure of the present invention has a semi-circular cross-section formed on the back surface of the piston crown and a semi-circular cross-section formed at the end of the connecting rod. The depressions of the receiving plate are slidably engaged, and the presser supported by the skirt is brought into contact with the back surface of the receiving plate.

[Operation] According to the present invention, since the concave portion of the connecting rod is swingably coupled to the convex portion having a semicircular cross section provided on the back surface of the piston crown portion, the connecting portion is connected as compared with the conventional pin coupling structure. The center of swing of the rod greatly approaches the piston crown surface. That is, the crankshaft arm can be lengthened by the amount that the swing center of the connecting rod approaches the piston crown surface, the cylinder body height remains the same as before, and the piston stroke lengthens and the displacement increases. .

Embodiment of the Invention FIG. 1 is a front sectional view of a connecting structure of a piston and a connecting rod according to the present invention, and FIG. 2 is a side sectional view of the same. The piston 2 shown as an example of a diesel engine has a piston crown surface 2a.
It is almost the same as that of the conventional one in which a well-known piston ring is mounted on the outer peripheral wall and the inside of the skirt portion 7 is hollow while the combustion chamber 3 is formed by forming a hollow.

According to the present invention, the convex portion 4 having the spherical surface 5 protruding downward is formed on the back surface of the crown portion of the piston. The circumference of the convex portion 4 is partitioned by an annular space 6, and the annular space 6 is filled with lubricating oil for cooling or supplied from the outside. Indentation 5a for holding oil for cooling and lubrication on the spherical surface 5 of the convex portion 4
Is provided. A bowl-shaped receiving plate 12 is integrally formed at the tip of the connecting rod 13. The concave portion 12a forming the spherical surface of the receiving plate 12 is slidably engaged with the spherical surface 5.

In order to maintain the engagement between the convex portion 4 and the receiving plate 12, the receiving plate 12
An annular presser 8 having a spherical concave portion 8a is brought into contact with the back surface of the. The presser foot 8 is supported by a tubular nut 9 screwed onto the skirt portion 7. The nut 9 can be prevented from being loosened by the retaining ring 10 engaged with the skirt portion 7.

Between the semicircular recess 14a of the base end 14 of the connecting rod 13 and the semicircular recess 15a of the bearing cap 15, the shaft of the tip end of the arm of the crankshaft 16 is connected. Connecting rod 1
The configuration of the base end portion of 3 is the same as the conventional one.

According to the present invention, the tip portion of the connecting rod 13 supports the convex portion 4 on the back surface of the piston crown portion and can swing when the crankshaft 16 rotates. Compared with the conventional structure in which the tip of the connecting rod is connected to the piston by a piston pin, the swing center a of the connecting rod 13 is arranged much closer to the piston crown surface 2a. That is, the swing center a and the piston crown surface 2
Since the dimension p with respect to a is reduced, if the arm (length r) of the crankshaft 16 is lengthened by this reduction, the piston 2
The stroke is increased, and the displacement is greatly increased without changing the height h of the cylinder body 21.

In addition, if necessary, the reduction of the dimension p between the piston crown surface 2a and the swing center a can be expressed as the arm length r of the crankshaft 16,
By allocating to the extension of the length l of the connecting rod 13, the value of 1 / r can be maintained as usual, and the inclination (maximum inclination angle) of the connecting rod 13 when the crankshaft 16 is rotated 1/4 of the piston top dead center Can be done as before, and piston sludge can be suppressed.

In the above embodiment, the presser foot 8 and the nut 9 may be integrally formed.

In the above-mentioned embodiment, the spherical convex portion of the piston is supported by the spherical concave portion of the receiving plate at the tip portion of the connecting rod, but the present invention is not limited to this, and the receiving plate at the tip portion of the connecting rod is not limited to this. The shaft portion (convex portion having a semicircular cross section) of the piston may be supported by the concave portion having a semicircular cross section (a groove having a semicircular cross section parallel to the crankshaft).

[Advantages of the Invention] As described above, the present invention enables the concave portion of the semicircular receiving plate formed at the end portion of the connecting rod to slide on the convex portion having the semicircular sectional surface formed on the back surface of the piston crown portion. Since the presser supported by the skirt is brought into contact with the back surface of the receiving plate, the swing center of the connecting rod is more biased toward the piston crown surface than in the conventional pin connection structure, and the crankshaft is displaced by that amount. Increasing the arm and connecting rod increases the stroke of the piston without increasing the maximum tilt of the connecting rod.

Since the height of the cylinder body may be the same as the conventional one, the burden on the machining of the cylinder body is not increased.

The displacement of the piston is increased by increasing the stroke of the piston, the ratio of the dead volume at the top dead center of the piston is reduced, and exhaust gas countermeasures are facilitated.

Even if the stroke of the piston increases, the maximum tilt angle of the connecting rod does not increase, so that problems such as piston slip, friction loss associated therewith, wear of the piston ring, and slap noise can be avoided.

Since the inertial mass of the piston is small, the slap noise is reduced,
It contributes to extending the durable life of piston rings and cylinder liners, reducing friction loss, and improving fuel efficiency.

Since the contact pressure at the tip of the connecting rod against the explosive load is low, it is advantageous for high supercharging.

Since the center of swing of the piston is close to the crown surface of the piston that receives the explosive load, the impact due to the swing of the piston is mitigated and the operating noise is reduced.

[Brief description of drawings]

FIG. 1 is a front sectional view of a piston-connecting rod connecting structure according to the present invention, FIG. 2 is a side sectional view of the same, and FIG. 3 is a front sectional view of a conventional piston-connecting rod pin connecting structure. 4: convex portion, 8: presser foot, 12: receiving plate, 12a: concave portion, 1
3: Connecting rod

Claims (3)

[Claims] 1. A convex portion having a semicircular cross section formed on the back surface of a piston crown portion is slidably engaged with a concave portion of a receiving plate having a semicircular cross section formed at the end of a connecting rod, and is supported by a skirt portion. The connecting structure of the piston and the connecting rod is characterized in that the above-mentioned presser is brought into contact with the back surface of the receiving plate. 2. A structure for connecting a piston and a connecting rod according to claim 1, wherein a piston ring is mounted on a piston peripheral wall below a swing center of the connecting rod with respect to the piston. 3. A piston is connected with a piston, wherein the center of swing of the connecting rod by sliding the recess of the receiving plate of the connecting rod with respect to the convex portion of the piston crown is arranged at a height near the piston crown surface. Connection structure of rods.