JPH0968215A - Connecting rod - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a connecting rod whose strength can be enhanced by reducing bending stresses due to inertial forces, without increasing its weight. SOLUTION: At the right and left junctions 5a, 5b of a connecting rod part 4, which connects the small 2 and large 3 ends of a connecting rod 10 together, and the large end 3, right and left openings 7a, 7b are formed in symmetry with respect to the centerline L of a rod shaft. The right junction 5a is therefore separated into inside and outside junctions 8i, 8o and the left junction 5b into inside and outside junctions 9i, 9o. The outside corner 6a of the outside junctions 8o, 9o is formed by a rounded surface which projects outward with a point 11 as its center, and the outside junctions 8o, 9o are formed on a tangent 14 connecting the outer edge of the small end 2 to the end point 12 of the axis of a bolt hole 12 an the large end 3. Therefore an increase in the weight of each junction is avoided, and an increase in cross-sectional secondary moments which is achieved by the separation into the outside and inside junctions can result in a structure that resists bending deflections due to inertial forces.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a connecting rod for connecting a piston and a crankshaft, and more particularly to a connecting rod structure for weighing the connecting rod and improving its strength.

[0002]

2. Description of the Related Art FIGS. 3 and 4 are views for explaining the structure of a conventional connecting rod and its drawbacks.
First, as shown in FIG. 3, in the conventional connecting rod 1, the left and right connecting portions 5a of the connecting rod portion 4 connecting the small end portion 2 (see FIG. 1) and the large end portion 3 and the large end portion 3, and 5b
(See FIG. 1) are solid, respectively, and the connecting portions 5a and 5b
The outer corner portion 6 in the plan view is formed by a concave R surface centering on the outer point 7 toward the inner side of the radius R2. JP-A-5-240236 and JP-A-6-50
Japanese Patent No. 322 discloses such a connecting rod. An inertial force Fk proportional to the square of the engine speed acts on the connecting rod 1. Due to this inertial force, the connecting portion 5a of the large end portion 3 is
A half of the inertial force Fk as shown in FIG. 4 acts on 5 and 5b, which may cause a crack as shown in the figure. In order to prevent this destruction, the connecting portions 5a, 5
It is effective to increase the cross-sectional area of b or increase R2 to prevent stress concentration.

[0003]

However, simply increasing the cross-sectional area of the connecting portion as described above increases the weight of the connecting rod, which in turn causes an increase in inertial force, and causes vibration and noise. It becomes a cause that deteriorates the engine performance. Furthermore, the above R2
There is a limit to the increase of B, and the bending moment generated by inertial force is not fundamentally reduced. Therefore,
An object of the present invention is to provide a connecting rod capable of reducing bending stress due to inertial force and increasing strength without increasing the weight of the connecting rod.

[0004]

In order to achieve the above object, the main means adopted by the present invention is the gist of the invention, namely, a connecting rod portion and a large end portion for connecting a small end portion and a large end portion. Left and right openings or thin left and right portions that are eccentric from the rod axis center line in plan view are formed in the left and right joints with and, respectively, and the left and right joints are separated into inner joints and outer joints. Is formed by an R surface projecting outward, and the outer joint portion is formed on a tangent line connecting the outer edge of the small end portion and the bolt hole center axis end point of the large end portion. It is a connecting rod that is a point that becomes. As described above, the cross-sectional area of the connecting portion is increased by making the outer edge of the connecting portion into the R surface projecting outward, but the weight increase is avoided by forming the opening or the thin portion by that amount, and By increasing the second moment of area by dividing the joint portion into the outer joint portion and the inner joint portion, a structure resistant to bending due to inertial force can be obtained. Further, it is known that the dynamic tensile force due to the rotation of the crankshaft acts on the tangent line connecting the outer edge of the small end and the central end of the bolt hole of the large end, but in the connecting rod of the present invention, Since the outer joint portion is formed on the tangent line connecting the outer edge of the small end portion and the center end of the bolt hole of the large end portion, the outer joint portion directly receives the tensile force and generates a bending moment. Since this is not done, the breaking force due to bending will be extremely small.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments embodying the present invention will be described below with reference to the accompanying drawings to provide an understanding of the present invention. It should be noted that the following embodiments are examples embodying the present invention, and do not limit the technical scope of the present invention. 1 is a plan view of the entire connecting rod according to an embodiment of the present invention, and FIG. 2 is an enlarged view of a connecting portion of the connecting rod shown in FIG. The same elements as those of the conventional connecting rod shown in FIGS. 3 and 4 are designated by the same reference numerals, and the description thereof will be omitted. One of the differences between the connecting rod 1 according to this embodiment and the conventional structure shown in FIGS. 3 and 4 is that the connecting rod 10 has a small end portion 2 and a large end portion 3 as shown in FIGS. Left and right connecting portions 5a and 5b of the connecting rod portion 4 and the large end portion 3 for connecting the and are respectively formed with left and right openings 7a and 7b symmetrical with respect to the rod axis center line L in a plan view shown in FIG. That is what is being done. As a result, the left and right connecting portions 5 are
Of the a and 5b, the right joint 5a is the inner joint 8i and the outer joint 8o, and the left joint 5b is the inner joint 9a.
i and the outer coupling portion 9o are separated from each other. In addition, the outer corner portion 6 of the outer joint portions 8o and 9o in plan view.
The point that a is formed by an R surface (see FIG. 2) protruding outward with a radius R1 about the point 11 is new. Further, it is also unprecedented that the outer coupling portions 8o and 9o are formed on a tangent line 14 connecting the outer edge of the small end portion 2 and the central axis end point 13 of the bolt hole 12 of the large end portion 3. As described above, in order to relieve the bending stress applied to the joint, it is effective to increase the sectional area of the joint, but it is more effective to increase the bending rigidity of the joint, that is, the second moment of area. Target. In the above-described embodiment, for example, the connecting portion 5
The outer edge of a is an R surface projecting outward like a circular arc of radius R1 centered on the point 11 and the opening 7a is provided inside the joint to avoid an increase in the cross-sectional area. While avoiding an increase in weight), the second moment of area is increased. As a result, even if bending occurs due to inertial force, the bending stress due to it is suppressed, and a structure that is strong against dynamic bending due to rotation of the crankshaft is obtained. Furthermore, the dynamic tensile force due to the rotation of the crankshaft is
It is known to work on a tangent line 14 that connects the outer edge of the and the central axis end point 13 of the bolt hole 12 of the large end portion 3. According to this, the distance between the member that receives the tensile force and the tangent line is Although the larger the bending moment due to the tensile force becomes, the outer connecting portions 8o and 9o of the connecting rod 10 of this embodiment have the outer edge of the small end 2 and the center of the bolt hole of the large end 3 at the center. Since it is formed on the tangent line connecting the shaft end point 13, the outer connecting portion 8o
Since 9 and 9o directly receive the tensile force and the bending moment can be suppressed to a small value, the breaking force due to bending can be extremely small.

[0006]

EXAMPLE In the above embodiment, the left and right openings 7a and 7a
Although b is formed symmetrically with respect to the central axis L of the connecting rod 10, it does not necessarily have to be symmetrical, and the left and right may be slightly different in shape. This is because one side receives a tensile force, while the other side receives a compressive force, so that the appropriate shape of the opening may be different between the left and right. Also, the openings 7a and 7b are
It is not always necessary to form a complete opening, and it is possible to form only that portion in a thin portion. By reducing the thickness in this way, it is possible to further increase the rigidity while reducing the weight of the joint.

[0007]

As described above, according to the present invention, the left and right connecting portions of the connecting rod portion and the large end portion for connecting the small end portion and the large end portion,
Left and right openings or thin left and right portions, which are eccentric from the rod axis center line in plan view, are formed to separate the left and right joint portions into an inner joint portion and an outer joint portion, respectively, and an outer corner portion of the outer joint portion in plan view. Is formed by an R surface projecting outward, and further, the outer coupling portion is formed on a tangent line connecting an outer edge of the small end portion and a bolt hole central axis end point of the large end portion. It is a connecting rod. Therefore, since the outer edge of the joint is an R surface protruding outward and the opening or the thin portion is formed inside, an increase in the weight of the joint is avoided, and the outer joint and the inner joint are substantially separated. The splitting increases the moment of inertia of area, resulting in a structure that is resistant to bending due to inertial force. Further, since the outer joint portion is formed on the tangent line connecting the outer edge of the small end portion and the central end portion of the bolt hole of the large end portion, the outer joint portion directly receives the tensile force and receives the bending moment. Since it does not occur, the breaking force due to bending can be extremely small.

[0008]

[Brief description of drawings]

FIG. 1 is a plan view of an entire connecting rod according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a connecting portion of the connecting rod shown in FIG.

FIG. 3 is a plan view of a connecting portion of a conventional connecting rod.

FIG. 4 is a plan view of a connecting portion of a conventional connecting rod.

[Explanation of symbols]

 2 ... Small end part 3 ... Large end part 4 ... Coupling part 5a, 5b ... Coupling part 6a ... Outer corner part 7a, 7b ... Opening 8i, 9i ... Inner connecting part 8o, 8o ... Outer connecting part 10 ... Connecting rod

Claims (1)

[Claims] 1. Left and right openings or left and right thin-walled portions that are eccentric from the rod axis center line in plan view are formed in the left and right connecting portions of the connecting rod portion and the large end portion that connect the small end portion and the large end portion, respectively. The left and right joints are separated into an inner joint and an outer joint, and outer corners of the outer joint in plan view are formed by R surfaces projecting outward, and the outer joint is A connecting rod formed on a tangent line connecting an outer edge of a small end portion and a bolt hole central axis end point of a large end portion.