JPH05126255A - Piston pin for internal combustion engine - Google Patents

Abstract

PURPOSE:To properly hold a clearance between a piston pin body and a piston pin hole part while realizing facilitation of manufacture and lightness of weight by forming the piston pin body made of Ti-Al intermetallic compound. CONSTITUTION:A column-shaped piston pin body 1 used for connecting a piston 2 to a connecting rod 5 is made of Ti-Al intermetallic compound. That is, titanium Ti and aluminum Al are quenched and solidified at a synthetic reaction temperature or less to use technique of solidifying and molding alloy powder utilized in aluminum powder metallurgy, and a fine mixed material of the titanium in the aluminum is manufactured. After a piston pin shape is given to this mixed material, a reaction sintering method, that is, reaction synthesizing of the mixed material generates the Ti-Al intermetallic compound to obtain the piston pin body 1 made of Ti-Al intermetallic compound. A coating 6 of wearing resistance is formed as necessary on a surface of this piston pin body 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a piston pin which connects a piston and a connecting rod in an internal combustion engine.

[0002]

2. Description of the Related Art Generally, in an internal combustion engine, a piston is slidably accommodated in a cylinder of a cylinder block, and a crankshaft is connected to a piston pin attached to a piston pin hole of the piston through a connecting rod. The piston receives combustion pressure at its crown surface and slides in the cylinder, so that power is transmitted to the crankshaft via the connecting rod.

In such an internal combustion engine, if the weight of the piston and the piston pin can be reduced, the overall weight of the main motion system components including the connecting rod and the crankshaft can be reduced, and the friction loss can be reduced. Therefore, there is an advantage that the acceleration response and output of the internal combustion engine can be improved and the fuel consumption can be improved.

Conventionally, it has been proposed to use ceramics as a base material in order to reduce the weight of the piston pin. However, since ceramics is extremely hard and its workability is extremely poor, the piston pin is formed in the piston pin hole of the piston. However, it took time to work the surface with high accuracy so that they could be fitted with proper clearance, and it was difficult to obtain the processing accuracy.

Therefore, as disclosed in, for example, Japanese Patent Application Laid-Open No. 61-59065, in order to secure the same workability and processing accuracy as a steel material, a metal that is easily processed on the surface of the ceramic piston pin body. It has been proposed to form a facing layer.

[0006]

However, in the conventional piston pin for an internal combustion engine described above, since the purpose is to reduce the weight thereof, the metal surface layer provided on the surface of the piston pin main body is considered to be a thin wall corresponding to the processing amount. Therefore, the thermal expansion amount of the piston pin during engine operation is largely related to the thermal expansion amount of the piston pin body itself, not the metal surface layer, and as a result, the ceramics forming the piston pin body have a linear expansion coefficient. Since it is small, the clearance between the piston pin hole and the piston pin becomes large due to the difference with the linear expansion coefficient of the piston. For this reason, in combination with the extremely hard ceramics, when the piston reciprocates, the piston pin body hits the wall surface of the piston pin hole and a pin knocking sound is generated, which adversely affects the sound vibration performance and the piston pin hole. The degree of wear of the wall surface of the portion is increased, and the degree of wear of the bush in the end portion due to the impact transmitted to the fitting portion between the piston pin body and the small end portion of the connecting rod is inevitable.

The present invention has been made to solve the above-mentioned problems of the prior art, and can be manufactured easily and accurately from the viewpoint of the material and can be made lightweight, and the clearance between the piston pin body and the piston pin hole portion during engine operation. It is an object of the present invention to provide a piston pin for an internal combustion engine that can properly hold the above.

[0008]

In order to achieve the above object, the present invention uses a Ti-Al intermetallic compound as the piston pin body, and if necessary, wear resistance to the surface of the piston pin body. The coating film is formed.

[0009]

With this structure, since the piston pin body can be accurately shaped during the manufacturing process of the Ti-Al intermetallic compound, the piston pin body can be easily processed, and the quality and precision after manufacturing can be secured. .. In addition, since the Ti-Al intermetallic compound forming the piston pin body has a linear expansion coefficient similar to that of steel, the clearance between the piston pin body made of the Ti-Al intermetallic compound and the piston pin hole portion of the piston during engine operation is Since the clearance between the conventional ceramic piston pin body and the piston pin hole of the piston is much smaller, it becomes possible to set the clearance within an appropriate range.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS.
Will be described.

FIG. 1 is a front view showing a cylindrical piston pin main body with its right half being a vertical cross section, and FIG. 2 is a sectional view showing a state in which a piston and a connecting rod are connected by a cylindrical piston pin main body. ..

A cylindrical piston pin body 1A shown in FIG.
Also, the cylindrical piston pin body 1B shown in FIG. 2 is also formed of a Ti-Al intermetallic compound described later.

That is, first, titanium (Ti) and aluminum (Al) are rapidly solidified at a temperature lower than the synthesis reaction temperature to solidify a powder alloy used in aluminum powder metallurgy,
A compact mixed material of titanium and aluminum is produced by using a molding technique.

This mixed material has a ductility similar to that of an aluminum alloy, and is subjected to plastic working in cold or hot, for example, conventionally known extrusion, forging or rolling technology used for working of aluminum alloy. It is possible to do.

Next, after the shape of the piston pin is given to the mixed material, the piston pin made of Ti-Al intermetallic compound is used as the Ti-Al intermetallic compound by the reaction sintering method, that is, the reaction synthesis of the mixed material. The main body 1 (1A, 1B) is manufactured. At that time, since the melting point and the diffusion coefficient to each of titanium and aluminum are greatly different, a large amount of aluminum outflow holes or pores due to the Kakendall effect are generated after the reaction synthesis. ,
Fill the container with a mixture of titanium and aluminum, and
(Hot isostatic pressing) or pseudo H
The IP method and the non-sealed can HIP method are effective.

Ti-Al is produced by the self-propagating high temperature synthesis method.
A powder of an intermetallic compound is prepared and Ti-A is formed by powder molding.
l Piston pin bodies made of intermetallic compounds may be manufactured, or by precision casting, isothermal forging, etc.
A piston pin body made of -Al intermetallic compound can be manufactured.

As shown for the piston pin body 1B, both ends of the piston pin body 1 are respectively inserted into the piston pin hole portions 2a, 2a of the piston 2 and fixed by snap rings 3, 3. A small end portion 5a of a connecting rod 5 is rotatably connected to a central portion of the piston pin body 1 via a bush 4.

The piston 2 is slidably accommodated in a cylinder of a cylinder block (not shown), and a crankshaft (not shown) is connected via a piston pin 1 and a connecting rod 5, and the piston 2 has a crown portion 2b. At the same time, the combustion pressure is received to slide in the cylinder, and the power is transmitted to the crankshaft via the connecting rod 5.

In the above structure, the piston pin body 1
Since the Ti-Al intermetallic compound that constitutes the element has a linear expansion coefficient similar to that of conventional steel, the clearance between the piston pin body and the piston pin hole portions 2a, 2a of the piston 2 during engine operation is conventionally This is an appropriate range equivalent to the case of using the steel piston pin of 1), which is much smaller than the clearance between the conventional ceramic piston pin body and the piston pin hole portions 2a, 2a. Moreover, the piston pin body 1 as well as the piston 2 can be lightened in terms of the material (Ti-Al intermetallic compound).

Further, the shape can be accurately imparted to the piston pin body 1 in the manufacturing process of the Ti-Al intermetallic compound.

Therefore, according to the first embodiment, when the piston 2 reciprocates, a pin hammering sound is generated when the piston pin body 1 hits the wall surfaces of the piston pin hole portions 2a, 2a. Therefore, the sound and vibration performance is not adversely affected, and the degree of wear of the wall surfaces of the piston pin hole portions 2a, 2a and the bush 4 can be reduced. Further, the weight reduction of the piston pin body 1 can contribute to weight reduction of the main motion system parts including the connecting rod 5 and the crankshaft, and the friction loss can be reduced (particularly when the piston 2 is also reduced in weight, Great effect),
As a result, acceleration response and output of the internal combustion engine can be improved, and fuel consumption can be improved. Furthermore, the piston pin body 1 can be manufactured easily and accurately.

Next, a second embodiment of the present invention will be described with reference to FIGS.

FIG. 3 is a front view showing a cylindrical piston pin main body with its right half being a vertical cross section, and FIG. 4 is a sectional view showing a state in which the piston and the connecting rod are connected by the cylindrical piston pin main body. ..

The second embodiment differs from the first embodiment in that a metal coating 6 is formed as a wear resistant coating on the surface of the piston pin body 1 (1A, 1B).

Generally, the piston 2 is often made of an aluminum alloy for the purpose of reducing its weight.
When a Ti-Al intermetallic compound is used as the base material of the piston pin body 1, a frictional force is generated when the wall surface of the piston pin hole portion 2a is pressed against the piston pin body 1 under the combustion pressure during engine operation. The frictional force generated by the rotational movement of the piston pin body 1 during the reciprocating movement of the piston 2 causes seizure between the piston pin body 1 and the piston pin hole portion 2a, and the piston pin body 1 and the piston pin The wear of the wall surface of the hole 2a may increase, and the friction loss may increase.

In order to eliminate such inconvenience, as shown in FIGS. 3 and 4, nickel (Ni), cobalt (Co), chromium (C) is formed on the surface of the piston pin body 1.
The metal coating 6 such as r) is formed by electroplating. Instead of the metal coating 6, a metal coating of cobalt (Co), tin (Sn), nickel (Ni) or the like may be formed by electroless plating. As a method of forming the metal coating, other than the above, vacuum deposition or thermal spraying may be used. Also,
The metal material forming the metal coating may be a material other than those exemplified above, and if a material having high hardness and excellent wear resistance is used, a further effect can be obtained.

It should be noted that forming a molybdenum coating film as the abrasion resistant film is disclosed in JP-A-62-292963.
As described in Japanese Patent Laid-Open Publication No. JP-A No. 2003-187, in order to secure wear resistance with a molybdenum coating film, it is necessary to increase the film thickness, and if the film thickness is increased, the film becomes non-uniform in nature. In particular, problems such as solvent dripping tend to occur during manufacturing, which is not suitable for mass production, and it is very difficult to secure a clearance between the piston pin hole and the piston pin. On the other hand, if the wear resistant coating is a metal coating, the film thickness for ensuring the necessary wear resistance can be reduced. Moreover, regarding the uniformity of the coating, not only the properties of thermal spraying and electroless plating, but also the electrolytic plating makes it possible to obtain a very uniform coating on the shape of the piston pin, which is suitable for mass production. In addition, the clearance between the piston pin hole and the piston pin can ensure the same accuracy as when using a steel piston pin without surface treatment which is usually used.

In the above construction, the metal coating 6 is formed on the surface of the piston pin body 1 made of the Ti-Al intermetallic compound. Therefore, when the engine is operating, the combustion pressure is applied to the wall surface of the piston pin hole 2a. No seizure occurs between the piston pin body 1 and the piston pin hole portion 2a due to a frictional force generated between the piston pin body 1 and a frictional force generated by the rotational movement of the piston pin body 1, and Wear on the wall surfaces of the piston pin body 1 and the piston pin hole 2a is reduced.

Therefore, according to the second embodiment, friction loss due to seizure or wear can be reduced as compared with the first embodiment, so that the acceleration response and output of the internal combustion engine are improved and the fuel consumption is improved. Further improvements can be achieved.

Next, a third embodiment of the present invention will be described with reference to FIGS.

FIG. 5 is a front view showing a cylindrical piston pin main body with its right half being a vertical cross section, and FIG. 6 is a sectional view showing a state in which a piston and a connecting rod are connected by a cylindrical piston pin main body. ..

The third embodiment is different from the second embodiment in that the surface of the piston pin body 1 (1A, 1B) is replaced with a metal film as a wear resistant film and molybdenum disulfide (Mo) is used.
That is, the solid lubricant film 7 made of S ₂ ), carbon (C), graphite (BN) or the like is formed.

In the above structure, since the solid lubricant film 7 is formed on the surface of the piston pin body 1 made of Ti-Al intermetallic compound, the combustion pressure is applied to the piston pin hole 2a of the piston pin hole 2a during engine operation. Wall and piston pin body 1
There is no seizure between the piston pin body 1 and the piston pin hole portion 2a due to a frictional force generated between the piston pin body 1 and the rotational force of the piston pin body 1, and the piston pin body 1 Therefore, the wear of the wall surface of the piston pin hole 2a is reduced. Further, due to the effect of the solid lubricant, friction loss between the piston pin body 1 and the piston pin hole portion 2a and friction between the piston pin body 1 and the bush 4 in the small end portion 5a of the connecting rod 5 are achieved. Loss can also be reduced.

Therefore, according to the third embodiment, the friction loss due to seizure or wear can be reduced as compared with the first embodiment, and the friction loss can be further reduced by the effect of the solid lubricant. As a result, the acceleration response and output of the internal combustion engine can be improved, and the fuel consumption can be further improved.

[0035]

As described above, according to the present invention, since the piston pin body is made of Ti-Al intermetallic compound, it can be easily and accurately manufactured from the viewpoint of the material and can be reduced in weight. By properly maintaining the clearance with the piston pin hole, it is possible to reduce the occurrence of pin hammering noise. Further, since the piston pin main body does not hit the wall surface of the piston pin hole portion, the degree of wear of the wall surface of the piston pin hole portion and the bush can be reduced. Further, the weight reduction of the piston pin body can contribute to the weight reduction of the main motion system components including the connecting rod and the crankshaft, and the friction loss can be reduced. Therefore, the sound and vibration performance can be improved, the acceleration response and output of the internal combustion engine can be improved, the fuel consumption can be improved, and the productivity can be improved.

If a wear resistant coating is formed on the surface of the piston pin body, seizure occurs between the piston pin body and the piston pin hole even if the piston is made of an aluminum alloy. Moreover, the wear of the piston pin body and the wall surface of the piston pin hole portion is reduced, and thus the friction loss can be surely reduced, so that the piston can be surely used for the aluminum alloy piston.

[Brief description of drawings]

FIG. 1 is a front view showing a cylindrical piston pin body that is a first embodiment of the present invention with its right half being a vertical cross section.

FIG. 2 is a cross-sectional view showing a state in which a piston and a connecting rod are connected by a cylindrical piston pin body that is the first embodiment of the present invention.

FIG. 3 is a front view showing a cylindrical piston pin main body according to a second embodiment of the present invention, with a right half of which is a vertical cross section.

FIG. 4 is a sectional view showing a state in which a piston and a connecting rod are connected by a cylindrical piston pin body which is a second embodiment of the present invention.

FIG. 5 is a front view showing a cylindrical piston pin main body according to a third embodiment of the present invention, with a right half portion thereof being a vertical cross section.

FIG. 6 is a sectional view showing a state in which a piston and a connecting rod are connected by a cylindrical piston pin main body which is a third embodiment of the present invention.

[Explanation of symbols]

 1A, 1B Piston pin body 2 Piston 2a Piston pin hole 4 Bush 6 Metal coating 7 Solid lubricant coating

Claims (2)

[Claims] 1. A piston pin for an internal combustion engine, wherein the piston pin body is made of a Ti-Al intermetallic compound. 2. The piston pin for an internal combustion engine according to claim 1, wherein a wear resistant coating is formed on the surface of the piston pin main body.