JPS60231010A - Connecting rod - Google Patents

Abstract

PURPOSE:To eliminate the need of a bush member and lighten a connecting rod by plating the friction surface of the small-end portion thereof against a piston rod with copper and forming a layer of plating metal including tin to a thickness between 0.5-5mu on the surface of said plated surface. CONSTITUTION:The cylindrical part of the small-end portion of a connecting rod 10 is made of S55C or similar materials. The friction surface 16 of the small-end portion 14 against a piston pin is subjected to the plating treatment 17. The plating 17 is performed throughout the periphery of the friction surface 16, using copper 18. The plating thickness is between 3-10mu. Additional plating 19 is performed thereon to a thickness between 0.5-5mu, using tin-contained metal.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to the structure of a connecting rod for a reciprocating engine, and more particularly to the structure of a sliding portion of the small end of the connecting rod with a piston pin.

BACKGROUND ART FIG. 7 shows the structure of a reciprocating engine that has been generally well known. That is, the large end portion 2 of the connecting rod 1 is assembled to the crankshaft 4 via the connecting rod bearing 3. The small end 5 of the connecting rod 1 is attached to a piston pin 7 attached to a piston 6 via a bushing 8. The piston 6 and the piston pin 7 are fixed, and the connecting rod 1 is rotatable with respect to the piston pin 7. Therefore, when the piston 6 reciprocates in the combustion chamber 9 by repeating the suction-compression-explosion-exhaust process, the piston pin 7 and the small end 5 of the connecting rod 1
It has a structure that swings between the bushing 8 and the bushing 8 fixed to the bushing 8.

This bushing 8 is usually a copper-based bimetallic bushing, such as a sintered alloy of copper-10% tin-10% lead on low carbon steel. is press-fitted into the Since the copper-based bushing 8 is press-fitted in this way, in order to ensure the strength of the connecting rod small end 5, the small end 5 becomes larger and heavier. If the small end portion 5 is large, the weight of the entire connecting rod 1 will also be large, which is one of the obstacles to reducing the weight of the entire engine. Better: If the weight of the connecting rod 1 is large, the inertia load applied to the crankshaft 4 will also be large, so the diameter of the crankshaft 4 must be able to withstand it, which increases engine weight and friction. This leads to an increase in loss.

Furthermore, if the small end 5 is made smaller and the bushing 8 is simply eliminated, seizure will occur between the small end 5 and the piston pin 7.

Purpose of the Invention In order to solve the above problems, the present invention eliminates the bushing material between the small end of the connecting rod and the piston pin while ensuring smooth sliding performance between the small end of the connecting rod and the piston pin.
The purpose is to reduce the weight of the connecting rod, reduce the load on the crankshaft, reduce the weight of the crankshaft, and reduce friction loss.

Structure of the Invention In order to achieve this object, the connecting rod of the present invention has a small end portion on the sliding surface with the piston pin.
3μ to 10μ copper plating is applied, and 0.5μ
Tin-based plating of μ to 5μ is applied. The tin-based plating includes plating of tin, tin-copper, lead-tin, lead-tin-copper, lead-tin-indium, and the like.

Further, after plating, it is desirable to perform a heat treatment to diffuse the tin-based plating layer into the copper metal layer. moreover,
A large number of grooves extending in the circumferential direction may be provided on the sliding surface to be plated.

Effect of the Invention In such a connecting rod, the first plating layer, which is copper plating, improves the wear resistance of the small end sliding surface, and the second plating layer, which is tin-based plating, improves the wear resistance. Seizure resistance is improved while ensuring the same. Although this plating layer is thin with a thickness on the order of microns, it provides sliding surface wear resistance and seizure resistance that are equivalent to or better than conventional copper bushings. Therefore, the bushing that has been used in the past can be abolished, and the small end of the connecting rod can be made smaller due to the abolishment of the bushing.

Furthermore, if a diffusion treatment by heat treatment is performed after plating, tin in the tin-based plating will diffuse into the copper plating, hardening the copper plating layer and further improving wear resistance.

Effects of the Invention Therefore, according to the present invention, it is possible to eliminate the bushing while ensuring wear resistance and seizure resistance equivalent to or better than that of conventional bushings, and to reduce the size of the small end of the connecting rod. The effect is that the weight of the rod can be reduced. By reducing the weight of the connecting rod, the overall weight of the engine can be reduced, and the inertial load on the crankshaft can also be reduced, so by making the diameter of the crankshaft smaller, the engine can be made smaller and lighter, and friction can be reduced. It is also possible to reduce loss.

EXAMPLES Below, preferred examples of the connecting rod of the present invention will be described with reference to the drawings.

FIG. 1 shows a connecting rod according to a first embodiment of the invention. In the figure, 10 indicates the entire connecting rod, and the large end 11 is assembled to the crankshaft 13 via the connecting rod bearing 12.

The small end portion 14 is directly assembled to the piston pin 15 without using a bushing as in the conventional case.

The cylindrical portion of the small end portion 14 is made of a material such as 855C.

Plating 17 is applied to the sliding surface 16 of the small end 14 against the piston pin 15. The plating 17 is applied over the entire circumference of the sliding surface 16, as shown enlarged in FIGS.
8 is carried out, and then a 1μ thick tin plating 19 is applied on top of it.
is applied. After that, a heat treatment is performed for 30 minutes at a temperature of 180°C.

Note that the first plating layer 18 is most preferably copper plating, but the second plating layer 19 may be tin-based plating. For example, in addition to tin, tin-copper, lead-tin, lead-tin copper, lead-tin indium, etc. may be used.

Next, FIGS. 4 and 5 show a small end portion of a connecting rod according to a second embodiment of the present invention. In this embodiment, the sliding surface 16 is provided with a large number of grooves 20 extending in the circumferential direction.

Copper plating 18 is applied to this sliding direction 16 as in the first embodiment, and tin-based plating 19 is applied thereon. Since the thickness of the plating layer 17 is small and is on the order of μ as in the first embodiment, grooves 20a also appear on the surface after plating. On the surface of the sliding surface after this plating, the area ratio of the surface smooth portion 21 to the entire sliding movement 16 is 40% to 80%.
It is set so that In this embodiment, it is set to 60%. Furthermore, after plating, a heat treatment similar to that of the first embodiment is performed.

In addition, in the first embodiment and the second embodiment, the copper plating 18
The reason why the thickness is set in the range of 3μ to 10μ is because if it is less than 3μ, the wear life will be insufficient, and if it is more than 10μ, the plating thickness will tend to be uneven. Further, the reason why the thickness of the tin-based plating 19 is set to 0.5 μm to 5 μm is due to the same reason.

In the connecting rod configured in this way, the copper plating 18 mainly improves the wear resistance on the sliding surface 16, and the tin plating 19 mainly improves the wear resistance and seizure resistance. That is, if the copper plating 18 is used alone, the seizure resistance may be insufficient, and by applying the tin-based plating 19 thereon, the seizure resistance is improved. The first plating layer 18 has adhesion to the connecting rod 10 and piston pin 1.
Copper plating is most preferable in terms of wear resistance.

In this way, the wear resistance and seizure resistance of the sliding surface 16 of the small end portion 14 can be improved by the plating layer 17, so that the bushing used conventionally is no longer necessary. Furthermore, since the plating layer 17 only needs to have a small thickness on the order of μ, the small end portion 14 can be made smaller in width to a greater extent than the conventional one while ensuring strength. Therefore, the weight of the entire connecting rod 10 is also reduced.

Furthermore, due to the heat treatment after plating, tin in the tin-based plating layer 19 is diffused into the copper plating layer 18.
is hardened, and wear resistance is further improved. However, since this diffusion phenomenon gradually occurs during operation due to the high temperature atmosphere, it is not necessary to carry out the process in engines with light loads.

Furthermore, since the movement between the sliding surface 16 of the small end 14 and the piston pin 15 is a rocking movement, there is a possibility that it is difficult to achieve a fluid lubrication state between them. If the grooves 20a are provided, lubricating oil is retained within the grooves 2Oa, thereby improving the lubrication performance.

By the way, when we compared this example (first example, second example) with the conventional bushing type and the one where the bushings were simply abolished, we found the following results. I got good results.

Example 1: Copper plating thickness 5 μm, tin plating thickness 1 μm Example 2:
With groove 20a, copper plating thickness 5μ, tin plating thickness 1μ Comparative example 1: Conventional bushing type, bushing material is copper-10% tin-10% lead alloy Comparative example 2: Simply eliminating the bushing, The material of the small end is 855G. Lubricating oil used: SAE 10W-30 engine oil. The results are shown in Figure 6. As is clear from the figure, Example 1
In Example 2, a seizure resistance equal to or higher than that of the conventional bush type was obtained, and in Example 2, due to the effect of providing the grooves 20a, considerably higher seizure resistance was obtained compared to the conventional one. In Comparative Example 2 in which the bushing was simply abolished, the seizure limit load was 100k (1/cnf),
Compared to the conventional bush type, it has decreased significantly.

Moreover, by applying this plating process, the connecting rod 10 can be downsized, and in this example, the weight of the connecting rod 10 can be reduced by 20 to 40 g.

As is clear from the above description, according to the present invention, it is possible to reduce the weight of the connecting rod while improving the wear resistance and seizure resistance, contributing to the weight reduction of the entire engine, and the inertia weight. By reducing this, it is possible to reduce the diameter of the crankshaft and reduce friction loss.

[Brief explanation of drawings]

1 is a side view of a connecting rod according to a first embodiment of the present invention, FIG. 2 is a partially enlarged sectional view of the device shown in FIG. 1, and FIG.
4 is a sectional view of the small end of the connecting rod according to the second embodiment of the present invention; FIG. 5 is a partially enlarged sectional view of the device shown in FIG. 4; FIG. 6 is a partially enlarged sectional view of the device shown in FIG. is a characteristic diagram of the seizure limit load, and Figure 7 is a longitudinal cross-sectional view of a conventional reciprocating engine. 10... Connecting rod 11...
・Big end 13...Crankshaft 14...Small end 15...Piston pin 16...Sliding surface 17...Plating Layer 18...Copper plating layer 19...Tin-based plating layer 20.20a...Groove 21...Smooth surface portion Fig. 1 13 Fig. 2 Figure 4 Figure 6

Claims (3)

[Claims] (1) A connecting rod characterized in that a 3μ to 10μ copper plating is applied to the sliding surface of the small end of the piston pin, and then a 0.5μ to 5μ tin-based plating is applied thereon. (2) The above-mentioned plated connecting rod,
The connecting rod according to claim 1, wherein the connecting rod is maintained at a temperature of 150'C to 200'C for a predetermined period of time, and the plated portion is subjected to a diffusion treatment. (3) A large number of grooves extending in the circumferential direction are formed in the sliding direction, and the area ratio of the smooth surface portion of the plated sliding surface is 40% to 80%. Connecting rod as described in section.