JPS6376905A - Connecting rod for engine made of light alloy - Google Patents

Abstract

PURPOSE:To reduce thermal expansion quantity in axial direction of a rod body by forming a cast core hole in the rod body between the small end and the big end and casting, in the cast core hole, a strut member, by which opening stress is acted in the direction rectangular to the axis that connects respective ends of the rod to each other. CONSTITUTION:A rod body 1 is provided with a fitting hole 3 for a piston pin 13 formed on the small end 2 side and a fitting hole 5 for a crank shaft 9 formed on the big end 4 side respectively together with being made of a light alloy such as aluminum and so on. On this constitution, a cast core hole 14 with a sectional form of a trapezoid or the like is formed in the center(A) of an end portion 6 which is the most massive part of the rod body 1 between the small end 2 and the big end 4. And a strut member 15 is fitted to the cast core hole 14 previously when casting is performed. On this occasion, the strut member 15 is made of a material whose thermal expansion coefficient is smaller than that of light alloy that forms the rod body 1, for instance, a steel group material, for making said member maintain residual stress that acts in the rectangular direction to the axis against contraction of the rod body 1 on casting.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a light alloy connecting rod for an engine.

(Prior Art) Many rods are made of steel such as carbon steel. However, recently, connecting rods are increasingly being made of light alloys in order to reduce the weight of the engine itself, reduce the weight and moment of inertia of the rotating system, and improve fuel efficiency.

However, such connecting rods made of light alloy generally have a larger coefficient of thermal expansion than those made of steel, and have the disadvantage of being inferior in mechanical strength and wear resistance.

Therefore, as an example of solving these drawbacks, as described in Japanese Utility Model Application Publication No. 60-7323, the large end of the connecting rod, particularly on the side of the fitting part with the crankshaft, has a split surface. (big end)
By casting a pipe-shaped reinforcing member with a smaller coefficient of thermal expansion and higher mechanical strength than the light alloy into the fastening bolt insertion holes at both ends, it is possible to improve the strength of the fastening parts, which bear particularly high loads. The words ``$1'' and ``Fure 11'' were used on the bolt seat surface and the split mating surface.

(Problems to be Solved by the Invention) The connecting rod has a small end portion having a piston pin fitting hole on one end side and a large end portion having a crankshaft fitting hole on the other end side. It consists of a long-sleeved member.

Therefore, when the connecting rod thermally expands, the length in the axial direction of the connecting rod itself increases, and the length changes from the center of the small end (piston pin fitting center) to the large end center (crankshaft fitting center). ) will also be longer.

As a result, the top dead center of the piston located on the cylinder side becomes higher and the engine compression ratio increases, which may exceed the knock limit and cause knocking.

(Means for Solving the Problems) The present invention was made with the aim of solving the above problems. In a light alloy connecting rod each having a large end to be fitted, a cast hole is formed between the small end and the large end, and a cast hole is formed between the small end and the large end. A strut member is cast and fitted to apply a predetermined expansion stress in a direction perpendicular to the axis connecting the large end.

(Function) According to the above means, a cast hole is formed between the small end and the large end of the connecting rod, and the small end and the large end are connected to the cast hole. Because the strut member that applies expansion stress in the direction perpendicular to the line is cast-in, the mass of the connecting rod body is reduced by the majority of the above-mentioned casting, and the amount of thermal expansion in the axial direction is effectively reduced. In addition, due to the expansion stress of the strut member, the thermal expansion stress that acts in the axial direction during the thermal expansion can be replaced as much as possible in the direction orthogonal to the axis, thereby preventing the expansion in the axial direction.

(Example) First, FIGS. 1 and 2 show a connecting rod made of a light alloy for an engine according to a first embodiment of the present invention. In FIG. A connecting rod for an automobile engine having a small end portion (
A piston pin fitting hole 3 is formed on the small end 2 side, and a crankshaft fitting hole 5 is formed on the big end 4 side. The large end portion 4 is composed of an upper connecting rod main body end portion 6 that can be divided into two in the vertical direction at approximately the center thereof, and a lower side cap 7, and the dividing surface is used as an abutment surface F. It is collated integrally. On the other hand, the connecting rod main body end 6 and the cap 7 have semicircular recesses 6 a and 7 facing each other on the abutment surface F, respectively.
The crankshaft fitting hole 5 is formed by each of the recesses 6a and 7a.

The large end portion 4 is fitted with bolts 11 and 11 into bolt insertion holes 6b and 7b provided in opposite ends of the connecting rod main body end portion 6 and the cap 7, respectively.
The crankshaft 9 is inserted through the crankshaft 9 and these two are fastened to each other via the crankshaft 9, thereby being integrated. Further, a piston pin 13 is fitted into the piston pin fitting hole 3 of the small end portion 2 . In addition, the code|symbol 10 is white metal.

On the other hand, at the center A of the connecting rod main body end 6 near the large end, which has the largest mass between the small end 2 and the large end 4 of the connecting rod 1, the cross section has a substantially trapezoidal shape, for example. A cast hole 14 is formed, and a strut member 15 as shown in FIG. 2, for example, is fitted into the cast hole 14 in advance during the casting stage.

As is clear from FIG. 2, the strut member 15 is
The bottom portion 14a of the cast hole 14 having a substantially trapezoidal cross section and the bottom portion 15a corresponding to each of the side wall portions 14b, 14b.
, and side portions 15b, 15b, and is made of, for example, a steel material having a much smaller coefficient of thermal expansion than the light alloy forming the connecting rod 1. Therefore, in the above-mentioned cast state, the connecting rod main body made of a light alloy having a large coefficient of thermal expansion is fitted in a state in which residual stress acting in a direction perpendicular to the axis is maintained against contraction of the connecting rod main body.

That is, in the above configuration, the cast hole 14 is formed between the small end 2 and the large end 4 of the connecting rod l, and the small end 2 and the large end 4 are formed with respect to the cast hole 14. Since the strut member 15 that applies expansion stress in the direction orthogonal to the line connecting the two is cast-fitted, the mass mass of the connecting rod body end 6 is reduced in the cast hole 14 portion, and the shaft is substantially In addition to reducing the amount of thermal expansion in the direction, the expanding stress of the strut member 5 allows the thermal expansion stress that acts in the axial direction of the connecting rod during the thermal expansion to be replaced as much as possible in the direction perpendicular to the axis.

As a result, the amount of thermal expansion in the axial direction of the connecting rod 1 can be reduced as much as possible, and an increase in the engine compression ratio can also be prevented, thereby eliminating the possibility of knocking.

Next, FIGS. 3 to 5 show a light alloy connecting rod for an engine according to a second embodiment of the present invention.

In this embodiment, the strut member 15 in the first embodiment described above has a two-sided structure as shown in FIGS.
For example, the two support plate portions 16 and 16 at the center are integrally joined by spot welding or the like to form an I-shaped cross section.

According to the strut member 15' having such a configuration, the rigidity of the strut member 15' itself can be further improved, so that the expansion action due to the above-mentioned residual stress at the time of thermal expansion of the connecting rod can also be made more effective. This makes it possible to more effectively reduce the amount of thermal expansion in the axial direction.

(Effects of the Invention) As explained above, the present invention provides a light alloy having a small end portion to which a piston pin is fitted at one end, and a large end portion to which a crankshaft is fitted to the other end. In the connecting rod made of The structure is characterized by a strut member that is cast-fitted to apply the expansion stress of .

Therefore, according to the present invention, a cast hole is formed between the small end and the large end of the connecting rod, and the cast hole is perpendicular to the line connecting the small end and the large end. Since the strut member is cast-fitted to apply expansion stress in the direction of Due to the expansion stress of the strut member, the thermal expansion stress acting in the axial direction during the thermal expansion can be replaced as much as possible in the direction perpendicular to the axis.

As a result, an increase in the engine compression ratio in the axial direction of the connecting rod can also be prevented, so that there is no possibility of knocking occurring.

[Brief explanation of the drawing]

FIG. 1 is a front view of a light alloy connecting rod for an engine according to a first embodiment of the present invention, FIG. 2 is a perspective view of a strut member in the same connecting rod, and FIG.
4 is a perspective view of a strut member in the connecting rod, and FIG. 5 is a center view of the strut member. FIG. 1... Connecting rod 2... Small end 3... Piston pin fitting hole 4... Large end 5... Crankshaft fitting hole 6. ...Connecting rod body end 14...
・Cast hole 15.15' ・・Strut member l: Connecting rod 2 = Small end 3: Piston pin fitting hole l: Large end j: Crankshaft fitting hole B: Connecting rod body end/ 4Z
:vJ hole is, is' Ni strut member Fig. 3

Claims (1)

[Claims] 1. A connecting rod made of light alloy that has a small end on one end into which a piston pin is fitted, and a large end on the other end into which a crankshaft is fitted. A cast hole is formed in between, and a strut member is cast-fitted to apply a predetermined expansion stress to the cast hole in a direction perpendicular to the axis connecting the small end and the large end. Light alloy connecting rod for engines.