JPH057569B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a crankshaft for a reciprocating internal combustion engine.

The crankshaft of a reciprocating internal combustion engine usually consists of a main shaft, a crank pin eccentric to the main shaft,
It consists of a crank arm that connects the main shaft and a crank pin, and the large end of a connecting rod is fitted onto the crank pin via a bearing.
In order to balance the inertial force caused by the large end of the connecting rod, rotating parts such as the crank pin and crank arm, and reciprocating parts such as the piston and piston pin, a crank weight is installed on the opposite side of the main shaft from the crank pin. It is provided.

In relatively small internal combustion machines such as motorcycle engines, a crankshaft is often used in which the crank arm and crank weight are integrated into a disc-shaped crank web centered approximately on the axis of the main shaft. . FIG. 1 shows an example of such a crankshaft. This crankshaft 01 is divided into parts each having a crank web 02, 03.
This is an assembly type crankshaft in which a crankpin 05 is press-fitted into a crankpin boss 04 provided in the crankshaft 3 to form one crankshaft 01. Ukrank web 0
2 and 03 are disk-shaped as shown in the figure, and the main shaft 06
₁ and 06 ₂ , a crank weight 07 is provided on the opposite side from the crank pin boss 04. 08
is a connecting rod that is fitted into the crank pin 05 before the crank pin 05 is press-fitted. 09
010 is a main bearing, and 010 is a sprocket provided on the main shaft 06.

This crankshaft 01 has a crank web 02,
Since the outer shape of 03 is circular, each part can be rolled and transported during manufacturing and assembly, and the shape is relatively simple, making processing easy and high productivity.

The present invention aims to improve such a crankshaft and provide a crankshaft which is further reduced in weight and has improved material efficiency while retaining its advantages and advantages.

The present invention will be described below with reference to the embodiments shown in FIGS. 2 to 4. These drawings are perspective views showing the crankshaft portion when the present invention is applied to a prefabricated crankshaft as shown in FIG. 1, that is, the portion corresponding to the crank web 02 and the main shaft ₀₆₁ in FIG. , a front view and a side sectional view. The other crank web facing this,
That is, the crank web corresponding to the crank web 03 in FIG. 1 also has a shape similar to that shown in FIGS. 2 to 4.

1 is a main shaft, 2 is a crank web, and the crank web 2 has a substantially disk shape centered on the axis 10 of the main shaft 1. A crank pin boss 3 is formed in the upper part of the crank web 2 (the upper part in the drawings, the same applies hereinafter), and a crank pin (not shown) is press-fitted into the boss hole 4. The lower part of the crank web 2, that is, the part on the opposite side of the crank pin boss 3 with respect to the axis 10, is a thick-walled crank weight part 5, and when the crankshaft rotates, the large end of the connecting rod, the crank pin and To balance the inertial force due to the rotation of the mass near the crank pin boss 3 and the reciprocating motion of the piston, piston pin, etc. 6, 6 are through holes provided on both left and right sides of the upper part of the crank web 2, starting from the left side or right side of the crank pin boss 3, respectively, and extending almost along the outline of the crank web 2 to the vicinity of the crank weight part 5. It extends in a V-shape. As shown in FIG. 3, these through holes 6, 6 are arranged symmetrically with respect to a line connecting the center of the boss hole 4 and the center 10 of the main shaft 1, and the outline of each through hole 6 is A part that is approximately concentric with the circle that forms the outline of the web 2, a part B that is defined by the outer part of the crank pin boss 3, and a main shaft 1.
It is formed by a part C forming the outer part of the boss part, a part D connecting the part B and part C, and a part E ending the through hole 6 near the upper end of the crank weight part 5. There is. Therefore, when viewed from a different perspective, this crank web 2 includes an arcuate crank weight portion 5 and a main shaft boss portion 7 around the main shaft axis 10.
and a crank arm portion 8 that connects the crank pin boss 3 to the crank pin boss 3, and a ring-shaped portion 9 that connects the crank pin boss 3 and the left and right upper ends of the crank weight portion 5 in a ring shape. These crank weight portions, crank arm portions, and annular portions perform the various functions necessary for the crankshaft in the most efficient manner.

Similar to a conventional crankshaft, the crank weight portion 5 has a position and shape most suitable for balancing inertial force. Said B of the through hole 6
The crank arm part 8 defined by the parts D, D, and C has a crank pin boss outer diameter d that is strong enough to press-fit the crank pin, and an explosive load acting on the crank pin and the main shaft boss part 7. It has a dimension e sufficient for strength against the bending moment due to inertial load, and has no extra parts other than the parts necessary for the press-fitting and load transmission. Further, the ring-shaped portion 9 is located at the most efficient position for increasing the moment of inertia of the crank web 2.
That is, it is provided on the outer periphery. In an engine, the moment of inertia of the crankshaft plays an important role in stabilizing idling operation and smoothing out torque fluctuations. It is lighter in weight than a crankshaft with a web, and can maintain a sufficient moment of inertia. Also, due to the presence of the ring-shaped portion 9, the outer shape of the rank web 2 is circular, so that it can be manufactured and manufactured in the same way as the conventional crankshaft shown in FIG.
Each crankshaft part can be rolled and transported during assembly.

Furthermore, the through hole 6 extends below the diametrical line MM in the direction perpendicular to the diameter passing through the center of the crank pin boss hole 4 of the crank web 2, and is hollowed out at a portion that has a low contribution rate to the balance of inertial force.

In this way, the crank feb 2 according to the present invention
In order to ensure crank balance, moment of inertia, and strength, parts with a low contribution rate are made into through holes 6 to reduce the overall weight, and the structure is made up of three parts: a crank weight part 5, a crank arm part 8, and an annular part 9. Although these parts are designed to most efficiently function as a crankshaft, the annular part 9 is further made lighter and more efficient as described below.

The ring-shaped portion 9 has a cross-sectional area near the crank pin boss 3 smaller than a cross-sectional area near the crank weight portion 5. In the illustrated embodiment, the thickness of the annular portion 9 is uniform, and the cross-sectional area is changed by gradually decreasing the height H of the side surface from the vicinity of the crank weight portion 5 to the vicinity of the crank pin boss 3. There is. That is,
The annular portion 9 consists of three parts 9 ₁ , 9 ₂ , and 9 ₃ . The height H of the portion 9 ₁ near the crank weight portion 5 is relatively high, and the height H of the portion 9 ₃ near the crank pin boss 3 is relatively high. The two parts 9 ₁ , 9 ₃ are connected by an intermediate inclined part 9 ₂ . The portion ₉₁ is close to the MM line (FIG. 3), and the degree to which the mass of this portion lowers the crank balance ratio is small. Therefore, the height H of the side surface of the portion ₉₁ is increased to increase the mass, which serves to increase the moment of inertia of the crank web 2. On the other hand, the portion ₉₃ is located away from the MM line toward the crank pin and has a large effect on reducing the crank balance ratio. Therefore, the height H of this portion ₉₃ is reduced to reduce the mass.
However, since it is located at the outermost periphery of the crank web 2, it has the effect of increasing the moment of inertia of the web 2. And these parts 9 ₁ and 9 ₃ ,
By connecting at the intermediate portion 9 _{2 where} the height H gradually changes, the annular portion 9 can efficiently secure the moment of inertia of the crank web 2 without significantly affecting the crank balance, and 2 can be further reduced in weight.

Further, in this embodiment, a recess 1 is provided in the upper center of the crank weight portion 5, in a portion close to the axis 10.
1 is provided. This part has a low contribution rate to strength and crank balance, and has a small influence on the moment of inertia. Therefore, this part has been thinned out to reduce the overall weight.

As described above, the present invention provides a crankshaft having a disk-shaped crank web, in which the portions having a low contribution rate in ensuring the crank balance, moment of inertia, and strength of the crank web are formed as through holes, and the crank weight portion, the crank The structure consists of three parts, an arm part and a ring-shaped part, so that these parts can function as a crankshaft most efficiently.In addition, the cross-sectional area of the part of the ring-shaped part near the crank pin boss is By making the area of the step smaller than that of the part close to the part, further weight reduction and efficiency have been achieved. Therefore, the crankshaft of the present invention is much lighter and has lower material costs than conventional ones.
Moreover, since the crank web has a circular shape,
It is easy to transport during production and assembly, and has good productivity.

It goes without saying that the present invention can be applied to the crankshaft of a multi-cylinder engine regardless of the number of cylinders in the engine.

[Brief explanation of drawings]

Figure 1 is a perspective view showing a conventional crankshaft, Figure 2 is a perspective view showing a conventional crankshaft.
The figure is a perspective view showing one embodiment of the present invention, FIG. 3 is a front view of the same, and FIG. 4 is a sectional view of the same. 1...Main shaft, 2...Crank web, 3...Crank pin boss, 4...Boss hole, 5...Crank weight part, 6...Through hole, 7...Main shaft boss part, 8...Kunk arm part, 9 ...ring-shaped part,
10...Axis of the main shaft, 11...Recess.

Claims (1)

[Claims] 1 It has a disk shape centered around the axis of the main shaft,
In a crankshaft having a crank web that supports a crank pin and has a crank weight as an arcuate portion diametrically opposed to the crank pin, the crank web is connected to an arcuate crank weight portion, a portion surrounding the main shaft axis, and a crank web. A crank arm part that connects the pin boss,
It is composed of a ring-shaped part that connects the crank pin boss and the left and right upper ends of the crank weight part in a ring shape, and the cross-sectional area of the part of the ring-shaped part near the crank pin boss is determined by the cross-sectional area of the part near the crank weight part. A crankshaft characterized by having a cross-sectional area smaller than that of.