JPH0522941U - Light alloy connectein rods for internal combustion engines - Google Patents

Abstract

(57) [Abstract] [Purpose] To prevent fretting on the inner peripheral surface of the small end 3 in a connecting rod made of a light alloy in which a steel bush 8 is press-fitted and fixed to the small end 3. [Structure] A rod body 1 including a small end portion 3 is formed of a light alloy, and a steel bush 8 is press-fitted and fixed to the small end portion 3. An oil groove 11 is formed on the outer peripheral surface of the bush 8 up to about 105 ° to the left and right where a strong stress acts, and a part of the lubricating oil that lubricates between the piston pin and the oil holes 9 and 10 is small. It is adapted to be supplied to the end portion 3.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an improvement of a connecting rod for connecting a crankshaft and a piston of an internal combustion engine, in particular, to a connecting rod made of a light alloy such as an aluminum alloy or a titanium alloy for forming a rod body including a small end. .

[0002]

[Prior Art]

 In recent years, connecting rods made of light alloys such as aluminum alloys and titanium alloys are being used to reduce the weight of internal combustion engines.However, because these light alloy materials have relatively low wear resistance and strength, they fit with piston pins. A structure in which a steel bush is press-fitted and fixed to the matching small end is generally adopted (see, for example, Japanese Utility Model Laid-Open No. 60-110712). The inner peripheral fitting surface of the light alloy small end into which this bush is press-fitted is machined into a cylindrical surface of appropriate surface accuracy by honing or fine boring.

[0003]

[Problems to be solved by the device]

 The small end of the connecting rod as described above is repeatedly subjected to explosive pressure and inertial force from the piston pin, but due to the relationship with the turning radius of the crank pin, the small end top (the center of the small end and the center of the large end are A strong stress acts on each of the left and right sides centering on the part (intersecting the line connecting the lines) about 105 °. Therefore, in the configuration where the steel bush is press-fitted into the small end of the light alloy as described above, a microscopic deviation occurs repeatedly between the two at around 105 ° and the fitting surface, especially the surface of the light alloy side. Fretting is likely to occur. When this fretting occurs, the fatigue strength of the small end portion is sharply reduced, which causes the durability of the connecting rod to be reduced.

[0004]

[Means for Solving the Problems]

 Therefore, the present invention relates to a connecting rod made of a light alloy for an internal combustion engine in which a rod body including a small end is formed of a light alloy, and a steel bush is press-fitted and fixed to the inner circumference of the small end. An oil hole is formed through the small end and the bush, and an oil groove extending in the circumferential direction from the oil hole is formed on at least one of the outer peripheral surface of the bush and the inner peripheral fitting surface on the small end side. It is characterized by having done.

[0005]

[Action]

 In the above configuration, a part of the lubricating oil supplied to the sliding contact surface between the bush and the piston pin through the oil hole is supplied to the fitting surface between the light alloy small end portion and the steel bush by the oil groove. Due to the presence of the lubricating oil, fretting due to microscopic deviation is suppressed.

[0006]

【Example】

 1 and 2 show a first embodiment of a connecting rod according to the present invention. This connecting rod is roughly composed of a small end portion 3 into which a piston pin fits, a large end portion 4 into which a crank pin fits, and a rod portion 5 that connects the two. A rod body 1 including a small end portion 3 and a cap portion 2 forming a part of the large end portion 4 are divided into two along a plane passing through the center of the rod 4. The rod body 1 and the cap portion 2 are configured to be integrally coupled with each other by holding a bearing metal (not shown) and then using a pair of bolts 6 and nuts 7.

Further, in this connecting rod, both the rod body 1 and the cap portion 2 are formed of an aluminum alloy or a titanium alloy, and a steel end is formed on the inner periphery of the small end portion 3 formed in a cylindrical shape. The bush 8 is fitted and fixed.

An oil hole 9 is formed through the top of the small end 3, that is, at a position intersecting with a line L connecting the center of the large end 4 and the center of the small end 3. An oil hole 10 is also formed through the bush 8 so as to match the oil hole 9. However, as is apparent from FIG. 1, in order to positively diffuse a part of the lubricating oil to the outer peripheral surface of the bush 8, the oil hole 10 on the bush 8 side is larger than the oil hole 9 on the small end 3. Is formed with a small diameter.

An oil groove 11 is formed on the outer peripheral surface of the bush 8 and extends in the circumferential direction around the oil hole 10 as shown in detail in FIGS. As shown in the development view of the bush 8 in FIG. 6, the oil groove 11 has a linear shape along the circumferential direction near the oil hole 10 and is branched into two forks from the left and right intermediate portions. And the tip is closed. As shown in FIG. 2, the tip of the oil groove 11 extends leftward and rightward around 105 ° about the line L 1 described above. The central portion of the oil groove 11, that is, the portion where the oil hole 10 is located is a recess having the same diameter as the oil hole 9 on the small end 3 side.

According to the configuration of the above-described embodiment, a part of the lubricating oil sprayed on the inside of the piston (not shown) flows into the oil hole 9, and passes through the oil hole 10 to the piston pin (not shown) and the bush. 8 is supplied to the sliding surface. A part of the lubricating oil that has flowed into the oil hole 9 flows into the oil groove 11 and diffuses through the oil groove 11 to the fitting surface between the bush 8 and the light alloy small end portion 3. At this time, the oil groove 11 extends to the vicinity of 105 ° on the left and right where stress strongly acts, and since it branches in a bifurcated shape, the lubricating oil can be diffused widely in the width direction of the bush 8. The interposition of the lubricating oil film reduces the friction coefficient on the fitting surface and suppresses fretting due to microscopic deviation. As described above, since the oil hole 9 and the oil hole 10 have a difference in diameter, a part of the lubricating oil flowing into the oil hole 9 is reliably guided to the oil groove 11.

Next, FIGS. 7 to 10 show a second embodiment of the present invention. In this embodiment, the steel bush 8 is simply provided with the oil hole 10 as shown in FIG. 10, and the oil groove 12 is formed on the inner peripheral surface side of the light alloy small end portion 3. Has been formed. As shown in FIG. 7, the oil groove 12 extends linearly in the left-right direction around the oil hole 9, and the tip end thereof extends in a T-shape. The tip portion of the oil groove 12 also extends from the center line L to the left and right up to about 105 ° as shown in FIG. Also, the oil hole 9 on the small end portion 3 side is formed larger than the oil hole 10 of the bush 8 as in the above-described embodiment. In this example, the tip of the oil groove 12 is not closed, but is open to both end surfaces of the small end portion 3.

Also in this embodiment, the lubricating oil is surely supplied to the fitting surface between the light metal small end 3 and the bush 8 in the vicinity of 105 ° where fretting is most likely to occur, and fretting is suppressed. Can be achieved.

It is to be noted that an oil groove may be formed on both the inner peripheral surface of the light alloy small end portion 3 and the outer peripheral surface of the bush 8 to introduce lubricating oil.

[0014]

[Effect of the device]

 As is clear from the above description, according to the connecting rod made of the light alloy of the internal combustion engine according to the present invention, the engagement with the small end portion of the outer circumference of the steel bush that is press-fitted and fixed to the small end portion of the light alloy is performed. Since the lubricating oil is allowed to diffuse through the oil groove on the surface, fretting of the light alloy surface due to microscopic deviation between the two is suppressed, and durability is improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of a connecting rod according to the present invention.

FIG. 2 is a front view of a partly cutaway view.

FIG. 3 is a front view showing only a bush.

FIG. 4 is a plan view of the bush.

FIG. 5 is a side view of the bush.

FIG. 6 is a development view of a bush showing the shape of an oil groove.

FIG. 7 is a sectional view showing a second embodiment of the connecting rod according to the present invention.

FIG. 8 is a partially cutaway front view of the same.

9 is a sectional view taken along the line AA of FIG.

FIG. 10 is a sectional view showing only a bush.

[Explanation of symbols]

 1 ... Rod main body 3 ... Small end 8 ... Bushing 9 ... Oil hole 10 ... Oil hole 11 ... Oil groove 12 ... Oil groove

Claims (1)

[Scope of utility model registration request] 1. A connecting rod made of a light alloy for an internal combustion engine, wherein a rod body including a small end is made of a light alloy, and a bush made of steel is press-fitted and fixed to an inner circumference of the small end. And an oil hole is formed penetrating the bush and the bush, and an oil groove extending in the circumferential direction from the oil hole is formed on at least one of the outer peripheral surface of the bush and the inner peripheral fitting surface on the small end side. A light alloy connecting rod for internal combustion engines.