JPH0439409A - Connecting rod for internal combustion engine - Google Patents

Abstract

PURPOSE:To improve the load bearing ability of the small end part of a connecting rod by press-fitting a ring-shaped member made of light alloy between the inner periphery of a small end part having a press-fitted bush and the above bush to reduce initial stress caused by press-fitting the small end part. CONSTITUTION:A ring-shaped member 5 made of light alloy is press-fitted into the inner periphery of the small end part 3 of a connecting rod 1, and a bush 7 to rotatably accommodate a piston pin is press-fitted into the inner periphery of the small end part 3. Thus initial strees caused by press-fitting in the small end part 3 can be reduced to improve the load bearing ability of the small end part.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a connecting rod for an internal combustion engine, and particularly to a technique for improving the strength of a small end portion to which a piston side is connected.

(Prior art) The small end of the connecting rod is connected to the piston via a piston pin, and the connection method is a full float type in which the piston pin can rotate relative to both the piston and the connecting rod. A connecting rod used in this type is shown in FIG. In this type, a bushing 55 is usually press-fitted into the small end 53 of the connecting rod 51, and the inner peripheral surface of the bushing 55 is coated with a bearing alloy layer 57.

Furthermore, in Japanese Utility Model Application Publication No. 56-4021, a bushing made of an iron-based metal having a coefficient of thermal expansion that is the same as or close to that of aluminum or an aluminum-based alloy is press-fitted into the small end of a connecting rod made of aluminum or an aluminum-based alloy, It is described that the small end is reinforced by securing the press-fit allowance during operation.

(Problems to be Solved by the Invention) In the conventional connecting rod as described above, for example, the bushing 55 is press-fitted into the connecting rod 51 (with a press-fitting allowance of 60 μm), so that the small end portion 53 is , a circumferential stress σ1 is generated as an initial stress at the cross section I-■ as shown in FIG.
It is minimum at the outer circumferential surface. On the other hand, during operation of an internal combustion engine in which the connecting rod 51 is used, a piston tensile inertia force acts on the connecting rod 51, and the circumferential stress σ2 at the cross section 1-I due to this tensile inertia force is As shown in the figure, the maximum value is on the inner circumferential surface A of the bushing 55, and the negative value is on the outer circumferential surface side.

Therefore, in reality, a composite stress obtained by adding the inertial stress σ2 to the press-fit stress σ1 acts on the cross section I-1 of the small end portion 53 during operation of the internal combustion engine. In this case, both the initial stress and the inertial stress at the inner peripheral surface B of the press-fit hole 59 are 10.3
kg/-2, and the combined stress value here is the maximum, and the connecting rod 51 is made of a light alloy with low material strength.
In particular, the load carrying capacity on the inner circumferential surface B of the press-fit hole 59 is significantly reduced.

Therefore, an object of the present invention is to improve the strength of the small end of the connecting rod.

[Structure of the Invention (Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides a connecting device for an internal combustion engine in which a bushing is press-fitted into the inner peripheral surface of a ring-shaped small end that connects the piston side. In the rod, a light alloy ring member is press-fitted between the inner circumferential surface of the small end and the bush.

(Function) By press-fitting a light alloy ring member into the inner peripheral surface of the small end of the connecting rod and further press-fitting a bushing into the inner peripheral surface of the ring member, the initial stress at the small end generated by this press-fitting is reduced. is reduced, and the load carrying capacity of the small end is improved.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

A connecting rod 1 according to a first embodiment of the present invention shown in FIG. A bushing 7 for rotatably housing a piston pin (not shown) is press-fitted into the surface, and the inner peripheral surface of the bushing 7 is coated with a bearing alloy layer 9.

FIGS. 2(a) and 2(b) show the processing procedure for the connecting rod 1. FIG.

First, as shown in FIG. 2(a), the ring member 5 is press-fitted into the inner circumferential surface of the small end portion 3 with a press-fitting allowance of 50 μm, and the inner circumferential surface of the ring member 5 is processed to a predetermined shape. Next, the bushing 7 coated with the bearing base metal layer 9 is press-fitted into the inner peripheral surface of the ring member 5 with a press-fitting allowance of 60 μm as shown in FIG. 2(b), and the inner peripheral surface of the bearing base metal layer 9 is Finish processing.

Next, the operation of the above configuration will be explained.

FIG. 3 shows the circumferential stress σ4 due to the press-fitting of the ring member 5 and bushing 7 at the cross section I-1 of the small end 3 in FIG.
is shown by a solid line, and the dotted line in the figure shows the circumferential stress σ when only the ring member 5 is press-fitted into the small end portion 3.

Comparing the above-mentioned FIG. 3 with FIG. 7 showing the circumferential stress at cross section I-1 according to the conventional example, regarding point B, the conventional example is located at the inner circumferential surface position of the press-fit hole 59 and 10. 3kg/m
ad2, and on the other hand, in the first embodiment, the inner circumferential surface position of the ring member 5 is -2°9kg/ms', so the circumferential stress generated as the initial stress at point B is significantly This will improve the load carrying capacity here.

In addition, regarding the point C in the cross section 1-1, the stress in the first embodiment is increased to 13.4 kg/mm2, compared to the stress of 8.3 kg/mm2 in the conventional example, or as shown in Fig. 8 above. As shown, since the piston tensile inertia force at point C is smaller than that at point B, there is no particular problem, and therefore the strength of the small end portion 3 as a whole is improved.

Figure 4 shows the fatigue limits at points B and C in the conventional example and the first embodiment.
The point C has changed from 01 in the prior art to 02 in this embodiment. According to this, at point B, the margin for the fatigue limit decreases from b2, which is approximately 80% of the fatigue limit, to b2, which is less than 60% of the fatigue limit, and at point 0, the margin for the fatigue limit increases significantly.
From C0 below 0% to C slightly above 60% of the fatigue limit
2, the allowance for the fatigue limit is slightly reduced, but the fatigue strength of the entire small end 3 including the ring member 5 is improved.

FIG. 5 shows a second embodiment of the present invention, in which a ring member 15 made of fiber-reinforced substantially alloy or particle-reinforced light alloy is used in place of the ring member 5 made of light alloy in the first embodiment. This is what I used.

The connecting rod 11 of this second embodiment also
Similar to the connecting rod 1 of the embodiment, the ring member 1
In addition to improving the fatigue strength of the small end 13 by press-fitting 5, the strength of the ring member 15 itself is improved by reinforcing it with fibers or particles, and the durability is improved. Therefore, the weight is reduced compared to the first embodiment, and the load carrying capacity of the small end portion 13 is further improved.

[Effects of the Invention] As described above, according to the present invention, a light alloy ring member is further press-fitted between the small end of the connecting rod and the bushing press-fitted into the small end. The initial stress due to press-fitting at the small end is reduced, and the load bearing capacity of the small end can be significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a front view of the main parts of a connecting rod showing a first embodiment of the present invention, FIGS. 2(a) and (b) are explanatory views showing the processing steps of the first embodiment, and FIG. The initial stress characteristic diagram at the small end in the example, FIG. 4 is the durability limit characteristic diagram,
FIG. 5 is a front view of main parts of a connecting rod showing a second embodiment of the present invention, FIG. 6 is a front view of main parts of a connecting rod showing a conventional example, and FIG. 7 is a front view of main parts of a connecting rod showing a conventional example. The initial stress characteristic diagram, FIG. 8, is a stress characteristic diagram showing the piston tensile inertia force acting on the small end. 1.11...Connecting rod 3.13...Small end 5,15...Ring member 7
...butshu

Claims (1)

[Claims] In a connecting rod for an internal combustion engine in which a bush is press-fitted into the inner peripheral surface of a ring-shaped small end that connects the piston side, a light alloy ring member is press-fitted between the inner peripheral surface of the small end and the bush. A connecting rod characterized by: