JPH11210865A - Al-alloy power transmission part excellent in fatigue life and wear resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an Al-alloy power transmission part which improves hard plating of the Al-alloy power transmission part, and which has both fatigue life and wear resistance. SOLUTION: In an Al-alloy power transmission part in which parts differed from each other in the requirements-characteristics such as fatigue life and wear resistance exist, a plating film with a hardness (Hv) of 250 or more is provided on the surface. With respect to the plating film hardness (Hv), the residual stress of the plating film surface of a part in which fatigue life is especially required, meets the following equations: plating film hardness (Hv) >=8 ×residual stress (kgf/mm<2> ) of plating film surface + 330, and plating film hardness (Hv) >=100 × residual stress (kgf/mm<2> ) of plating film surface -500.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power transmission part made of an aluminum alloy having a hard plating film on its surface, and particularly to a fatigue life and abrasion resistance suitable for being used as a pulley for a transportation machine such as an automobile. It relates to an excellent power transmission component made of Al alloy.

[0002]

2. Description of the Related Art In recent years, aircraft, such as automobiles, have been developed in order to promote global environmental conservation such as reduction of carbon dioxide emissions, or to enhance the performance and energy saving of machines themselves.
In transport machines such as railway vehicles and industrial machines such as robots, weight reduction of component parts is required. And
As part of this weight reduction measure, the use of components for components has been changing from steel to aluminum or aluminum alloys (hereinafter simply referred to as Al alloys). Especially,
Among the components, if the power transmission component is made of Al alloy,
Not only can the power transmission component itself be reduced in weight, but also the drive device for the power transmission component can be reduced in size.

Examples of the power transmission component include a gear, a rack, and a pulley (belt or pulley). A typical pulley will be described below as an example. Pulleys have been widely used as cam timing pulleys and rear pulleys not only for transport aircraft but also for bicycles, industrial machines, and home electric appliances. There are various types of pulley shapes depending on the application.
Figure 4 shows. As shown in the vertical sectional view of FIG. 4 (a) and the plan view of FIG. 4 (b), the cam timing pulley 1 basically includes a cylindrical fixing portion 4 having a hole 5 into which a drive shaft is fitted. The fixing part
4 comprises a disk-shaped arm portion 2 arranged on the outer periphery of the arm member 4 and a cylindrical power transmission portion 3 arranged on the outer periphery of the arm portion 2. It should be noted that such a basic configuration is basically the same for other pulleys, even if the shape and size are variously different.

However, since a relatively large torque is applied to the pulley having such a structure, particularly for a transport machine, a particularly high fatigue life and wear resistance are required. For this reason, when the pulley is changed from a steel pulley to an Al alloy pulley, there is a problem that the fatigue life and wear resistance of the Al alloy pulley are significantly inferior to those of the steel pulley. In particular, in a pulley 1 having an arm 2 and a power transmission unit 3 as shown in FIG. 4, when a large torque is applied, the relatively thin arm 2 is most susceptible to fatigue failure. The power transmission section 3 that comes into contact with the like is most easily worn.

Among them, in order to improve the wear resistance of the Al alloy pulley, especially the improvement of the Al alloy material side, which is significantly softer than steel, is limited. It is necessary to provide a hard coating on the surface of the pulley.

[0006] Because of this necessity, Japanese Unexamined Patent Publication No.
No. 10829 discloses an Al alloy pulley for a textile machine or the like, in which steel is plasma-sprayed on the surface of an Al alloy pulley and then subjected to Cr plating. In addition, Tokiko Sho 58
JP-A-35562 discloses an Al alloy high-speed cam timing pulley for automobiles in which a hard anodic oxide film is formed on the surface of an Al alloy pulley. Furthermore, JP-A-6-
No. 158264 discloses an Al alloy pulley in which a high-carbon steel material containing a large amount of Cr is sprayed at a high speed frame. Also, JP-A-9-280345 and the like,
It is disclosed that the surface of an Al alloy pulley is coated with a resin.

Japanese Patent Application Laid-Open No. 8-39432 discloses that in a power transmission component made of a metal base such as a Ti alloy provided with a hard Ni-P plating film, the plating film is damaged by external stress or impact. A technique for preventing fatigue destruction and peeling of a plating film itself due to long-term use has been disclosed.
More specifically, after a hard electric Ni-P plating film is provided on the surface of the metal base material, a heat treatment is performed to achieve higher hardness and higher adhesion of the plating film, and then fine particles are further applied to the plating film. A technique of applying shot peening or dry honing to apply residual compressive stress to the plating film, recovering the decrease in toughness of the Ni-P plating film due to the heat treatment, and improving the hardness and toughness of the plating film in a well-balanced manner. It has been disclosed.

[0008]

All of the above-mentioned prior arts for coating the surface of an Al alloy pulley involve improving the abrasion resistance of the Al alloy pulley or the adhesion of the abrasion resistant film. It is only intended to improve Therefore, the wear resistance itself is certainly improved as compared with the Al alloy pulley without the coating. But,
These conventional techniques completely improve the fatigue life of an Al alloy pulley having an arm portion and a power transmission portion, when a relatively large torque is applied, particularly against fatigue fracture of the arm portion, as shown in FIG. Not intended.

On the other hand, in an Al alloy pulley having an arm portion and a power transmission portion as shown in FIG. 4, the improvement of the fatigue life against fatigue failure is particularly improved for the arm portion to which bending stress is repeatedly applied. It is necessary to improve the wear resistance of the power transmission unit, and different characteristics are required at the pulley portion. For this reason, the coating of the surface of the Al alloy pulley, the plating film,
It is necessary to satisfy not only the abrasion resistance but also these different required characteristics. In addition, as will be described later, according to the findings of the present inventors, a plating film effective for improving the wear resistance of the power transmission portion, on the contrary, is particularly required to have a fatigue life of the arm portion and the like. The fatigue life of the part may be reduced. That is, in the field of power transmission components made of Al alloy such as pulleys, there are portions where required characteristics of fatigue life and wear resistance are different from each other, so that the wear resistance of the power transmission portion is improved and the arm portion is improved. There is a unique situation where improving fatigue life is a mutually contradictory technical problem.

Therefore, the above-mentioned prior arts, in which the surface of an Al alloy pulley is coated, are not intended to improve the fatigue life of the Al alloy pulley, particularly the arm, and therefore, rather, the Al alloy pulley is coated. In some cases, the fatigue life of the pulley is degraded, and this point reduces the reliability of the Al alloy pulley and significantly prevents the power transmission parts such as the pulley from being alloyed with Al.

[0011] For example, the technique of plasma-spraying steel on the surface of an Al alloy pulley followed by Cr plating, as disclosed in the above-mentioned JP-A-49-10829, improves the wear resistance of the Al alloy pulley. It is effective for. However, with respect to the fatigue life of one Al alloy pulley, there is a problem that the Cr plating itself becomes a starting point and fatigue fracture easily occurs, so that it cannot be put to practical use.

The technique of forming a hard anodic oxide film on the surface of an Al alloy pulley, such as the above-mentioned Japanese Patent Publication No. 58-35562, is based on the fact that the hard anodic oxide film itself is brittle. Peeling or chipping easily occurs,
It is not a technology that can be put to practical use only from the viewpoint of improving the wear resistance of the Al alloy pulley.

[0013] Next, the technique of high-speed flame spraying of a high carbon steel material containing a large amount of Cr on the surface of an Al alloy pulley, such as the above-mentioned Japanese Patent Application Laid-Open No. 6-158264, discloses an Al alloy pulley. It is effective for improving abrasion resistance. However, with respect to the fatigue life of one Al alloy pulley, there is a problem in that the Cr contained therein becomes a starting point and easily causes fatigue fracture, as in the above-mentioned conventional technology, so that it cannot be put to practical use.

[0014] Further, a technique for coating the surface of an Al alloy pulley with a resin, such as the aforementioned Japanese Patent Application Laid-Open No. 9-280345, is described in
The resin coating easily peels off, and is not a technology that can be put to practical use only from the viewpoint of improving the abrasion resistance of the Al alloy pulley, as in the above-described technology.

On the other hand, JP-A-8-39432 attempts to increase the fatigue strength of a metal power transmission component such as a Ti alloy by using a Ni-P plating film on the surface. That is,
In the same publication, the hardness of the plating film is increased, and the fatigue strength of the power transmission component made of Ti alloy is increased by the flap tightening effect of the increased hardness of the plating layer. In order to prevent deterioration of the Ni-P plating film, the toughness of the Ni-P plating film is improved by positively applying residual compressive stress to the plating film.

However, in the case of an Al alloy pulley or the like intended by the present invention, the Al alloy has a lower strength (hardness) and the like than the Ti alloy, and differs from the Ti alloy when plated with high hardness. The hardness difference between the base Al alloy and the plating film is remarkable. In addition, in the Al alloy pulley intended by the present invention, especially in the arm portion to which an external force such as bending stress is repeatedly applied, the plating film itself is conversely formed by the difference in hardness between the plating film and the Al alloy. A peculiar phenomenon that the fatigue life of the steel is reduced may occur. Therefore, in the field of Al alloy power transmission components such as pulleys, there are portions where the required characteristics of fatigue life and abrasion resistance are different from each other, as well as the improvement of the abrasion resistance of the power transmission portion and the arm portion. Improving the fatigue life is a mutually contradictory technical problem. As a result, when applying the technique of JP-A-8-39432 and applying high hardness plating and positively applying residual compressive stress to the plating film by shot peening or dry honing, as described later, In addition, there is a problem that the Ni-P plating film itself becomes a starting point, so that the fatigue breakage of the Al alloy pulley main body is apt to occur, and the fatigue life is shortened, so that there is a case where it cannot be put to practical use.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a power transmission component made of an Al alloy in which there are portions where required characteristics of fatigue life and wear resistance are different from each other. , Ni, Ni-P, Fe-P, Cr, etc., improved hard plating, combined with both contradictory required characteristics of fatigue life and wear resistance, excellent in fatigue life and wear resistance
The purpose is to provide an aluminum alloy power transmission component.

[0018]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a power transmission part made of an Al alloy in which parts having different required characteristics of fatigue life and wear resistance have a hardness (Hv). In addition to providing a plating film with a thickness of 250 or more on the surface, the residual stress on the plating film surface, especially in the area where fatigue life is required, depends on the plating film hardness (Hv), and the plating film hardness (Hv) ≥ 8 × plating Residual stress on film surface (kgf / mm ² )
+330 and hardness of plating film (Hv) ≧ 100 × residual stress (kgf / mm ² ) −500 on the plating film surface.

Among the Al alloy power transmission parts, the pulleys made of Al alloy having different characteristics of fatigue life and wear resistance between the arm portion and the power transmission portion particularly require the fatigue life. Residual stress on the plating film surface of the arm portion, which is the portion to be applied, the plating film hardness (Hv) ≧ 8 × residual stress on the plating film surface (kgf / mm ² ) in relation to the plating film hardness (Hv) +330 and plating film hardness (Hv) ≧ 10
The gist is to satisfy 0 × residual stress (kgf / mm ² ) -500 on the plating film surface.

The present inventors first investigated the fatigue fracture characteristics of the pulley main body when a large torque is applied to the Al alloy pulley including the arm portion and the power transmission portion for a vehicle such as an automobile. As a result, in such a case, there are two forms in which the Al alloy pulley becomes unusable, one is a fatigue type in which an arm portion causes fatigue failure, and the other is a power transmission for transmitting power to a belt. It has been found that this is a wear type in which the surface of the power transmission section is roughened due to wear of the section.

This means that, in the case of an Al alloy pulley including an arm portion and a power transmission portion, the pulley must have both characteristics of fatigue life and abrasion resistance. Among them, the required characteristics of fatigue life and wear resistance are different between the arm portion and the power transmission portion. In the case of Al alloy power transmission parts where there are parts where the required characteristics of fatigue life and wear resistance are different from each other, plating films corresponding to these required characteristics, and in some cases, Means that it is necessary to provide different plating films on the surface.

Among the above, the roughening of the surface of the power transmission portion due to the wear type is originally caused by insufficient hardness of the surface or the surface coating of the Al alloy pulley, as is generally known in the art.
Then, as the skin on the surface of the power transmission unit becomes more noticeable, slip and squeal of the belt occur more frequently, and eventually a situation occurs in which efficient power transmission becomes impossible.

On the other hand, the fatigue type, in which the arm portion causes fatigue failure, is of course closely related to the fatigue fracture characteristics of the Al alloy itself, which is the base material of the pulley, particularly mechanical properties such as tensile strength and proof stress. It is known. Therefore, among Al alloys, JIS 5000 series, 6000 series or 7000 series Al alloys having excellent fatigue fracture characteristics have been used. However, even when using an Al alloy having a tensile strength of 190 N / mm ² or more, which has sufficient fatigue fracture characteristics required for these pulley applications, an Al alloy pulley provided with a hard plating film does not The point of causing fatigue fracture of the arm portion during use is a unique point.

In the present invention, as a result of studying the relationship between the fatigue fracture mode and the plating characteristics of an Al alloy pulley having a plating film, Ni, Ni-P, Fe-P, Cr
Hard plating film is deeply related to the fatigue fracture of the aluminum alloy of the pulley body, and in the arm portion of the aluminum alloy pulley, especially where the external force such as bending stress is repeatedly applied, the hard plating film itself It was found that cracks and the like are a starting point of fatigue fracture of the Al alloy, and there is a peculiar phenomenon that the fatigue life is rather shorter than that of the Al alloy without the plating film. And then,
Among the various characteristics of the hard plating film, the residual stress on the plating film surface is deeply related to the fatigue failure of the pulley body,
It was found that the higher the residual stress on the plating film surface, the lower the fatigue fracture characteristics of the pulley body, and the lower the residual stress on the plating film surface, the better the fatigue fracture characteristics of the pulley body and the better the fatigue life.

Furthermore, it is also importantly found that simply reducing the residual stress on the surface of the plating film cannot reliably guarantee the fatigue fracture characteristics or the fatigue life of the pulley body. That is, in order to reliably guarantee the fatigue life of the pulley body, it is necessary to define the residual stress on the plating film surface in relation to the plating film hardness (Hv), which is one of the basic characteristics of the plating film. I also found something.

Regarding the residual stress on the plating film surface,
Usually, hard plating such as Ni, Ni-P, Fe-P, Cr, relatively soft plating such as Zn, or anodic oxide film, etc.
The fact that the residual stress on the surface of the coating provided on the surface of the Al alloy affects the cracking and peelability (adhesion) of the coating itself is, of course, known in Japanese Patent Application Laid-Open No. Hei 8-39432. However, the hard plating film provided on the surface of the Al alloy
It becomes the starting point of the fatigue fracture of the alloy, conversely reducing the fatigue life of the Al alloy itself, or the residual stress on the plating film surface provided on the surface of the Al alloy is deeply related to the fatigue fracture of the Al alloy itself There is no recognition or knowledge that it is.

Actually, in Japanese Patent Application Laid-Open No. Hei 8-39432 and the like, in order to improve the fatigue fracture characteristics or the fatigue life of a power transmission part made of a Ti alloy, the Ni-P The hardness of the plating film is increased, and the residual compressive stress of the plating film is positively applied. This is to positively increase the hardness of the plating film, which is recognized as harmful in the present invention, and impart residual compressive stress to the fatigue fracture characteristics or the fatigue life of the pulley body. It can be said that they are oriented differently from technical ideas and means. For this reason, although the technique of JP-A-8-39432 is effective when applied to a Ti alloy having a relatively high hardness, it is effective when applied to an Al alloy pulley. -P plating film itself is the starting point,
Since the fatigue breakage of the Al alloy pulley body is apt to occur, the fatigue life is shortened, and the result is that it cannot be put to practical use.

Further, in the present invention, as will be described later, even if the basic characteristics of the plating film such as the composition, film thickness, and hardness of the plating film are the same, as will be described later, even if the plating conditions are the same. Is that the residual stress on the surface of the plating film is greatly different due to the subtle difference. Therefore, even if the basic characteristics of the plating film and the basic conditions of the plating method are exactly the same, it cannot be said that the residual stress on the surface of the plating film is the same by itself. That is, in order to ensure the fatigue fracture characteristics or fatigue life of the Al alloy pulley main body and the Al alloy power transmission component main body, the residual stress itself on the plating film surface was measured. This indicates that it is necessary to evaluate whether the value falls within the range defined by the invention.

Accordingly, the fact that the fatigue life of the power transmission component made of the Al alloy can be reliably ensured also has the significance of the regulation by the residual stress on the plating film surface of the present invention. More specifically, when improving the fatigue life of Al alloy power transmission components,
Even if the fatigue life is improved experimentally or on a trial basis, in fact, we will continue to manufacture a large amount of aluminum alloy power transmission components on a continuous basis, In order to ensure continuous application, as a practical matter, it is necessary to continuously assure customers and other customers that all industrially manufactured power transmission parts made of Al alloy will not cause fatigue failure. . This point of product assurance is particularly strict and is an important issue particularly for applications such as transport equipment requiring safety.

Further, the plating conditions are not always exactly the same every time in the plating line of the power transmission component made of Al alloy, or in the prototype stage, the power transmission component made of Al alloy having excellent fatigue life is put on the actual plating line. In manufacturing, in order to continue producing Al alloy power transmission parts with good reproducibility or efficiency, accurate and quantitative evaluation results of the fatigue life of the manufactured product are fed back, and the It is important for industrial quality control to always guarantee the fatigue life. This point is the same even when the plating line process or conditions are significantly changed or a plating line is newly added for the purpose of cost reduction and improvement of the properties of the Al alloy. Therefore, guaranteeing the fatigue life, which is one of the effects of the present invention, means that the fatigue life of the power transmission component made of an Al alloy is not only excellent in terms of data, but also the quality control and the process. Including management
It has more strict industrial meaning.

It is not yet clear why the residual stress on the surface of the plating film provided on the surface of the Al alloy is deeply related to the fatigue fracture of the Al alloy itself. But,
Originally, materials having high hardness and rigidity, such as Ti alloys and steels, have very little influence or contribution to the fatigue fracture characteristics of the Ti alloys or the steels themselves, due to the properties thereof. However, in the case of an Al alloy, the hardness and rigidity are relatively lower than that of a Ti alloy or steel.
The influence and contribution to the fatigue fracture characteristics and the like of the alloy are increased. In addition, external forces such as bending stress are repeatedly applied, such as arm portions of pulleys, and in recent years, power transmission parts which have been reduced in thickness for weight reduction are particularly hard plating films provided on the surface. Properties such as residual stress
It is thought that it has a more significant effect on the fatigue fracture characteristics of the alloy.

[0032]

BEST MODE FOR CARRYING OUT THE INVENTION The basic conditions and characteristic requirements of a plating film according to the present invention and the reasons for limitation will be specifically described below.

In the present invention, the plating film on the surface of the power transmission component made of an Al alloy has a residual stress on the surface of the plating film in relation to the hardness of the plating film (Hv). Residual stress (kgf / mm ² ) + 330 and plating film hardness (Hv) ≥ 100 × residual stress on plating film surface
It is necessary to satisfy (kgf / mm ² ) −500. In particular, in an Al alloy pulley including an arm portion and a power transmission portion, at least the residual stress on the plating film surface of the arm portion needs to satisfy a relationship with the plating film hardness (Hv). is there.

Details will be described with reference to FIG. 1 which will be described later in the examples, with reference to residual stress on the plating film surface, plating film hardness (Hv),
And the relationship with the fatigue life of the Al alloy pulley will be described.
In FIG. 1, the horizontal axis shows the residual stress (kgf / mm ² ) on the plating film surface of the Al alloy pulley, and the vertical axis shows the plating film hardness (Hv). The residual stress (kgf / mm ² ) on the surface of the plating film in the present invention can be measured as an average stress from the outermost surface of the plating film to a depth at which X-rays penetrate by a known X-ray stress measuring method. In the case where the plating film is amorphous and the X-ray stress measurement method cannot be used, such as in some electroless plating, it can be measured by a known spiral stress meter. Furthermore, plating film hardness
(Hv) can be measured by a Vickers hardness tester.

In FIG. 1, the circled plots indicate Ni-P
Plating, triangular plots are Ni plating respectively, square plots are each Cr plating, ☆ plots are each electroless Ni
Indicates plating. In addition, among the plots of circles, triangles, and squares, the white ones have characteristics that are 20% or more improved than the fatigue life of the Al alloy pulley without the plating film.
Indicates an Al alloy pulley provided with a plating film. In the circle, triangle, and square plots,
This shows an Al alloy pulley provided with a plating film, which has the same characteristics as the fatigue life of an Al alloy pulley not provided with a plating film.
Further, among the plots of circles, triangles, and squares, the black-painted ones are inferior in terms of the fatigue life of the Al alloy pulley without a plating film, and are made of an Al alloy with a coating. Each pulley is represented.

As is apparent from FIG. 1, if the residual stress on the surface of the plating film of the Al alloy pulley is high, many shaded or black plots are shown, and the fatigue life of the Al alloy pulley does not improve or decreases. You can see that it is. On the other hand, Al
As the residual stress on the plating film surface of the alloy pulley becomes lower, there are many white plots, which indicates that the fatigue life of the Al alloy pulley is improved. Then, More importantly, the residual stress of the plating film surface of the Al alloy pulley 15 kgf / mm ² or less, or even a lower value of 10 kgf / mm ² or less, in this region, yet fatigue life Al alloy pulleys not improving or decreasing
(Shaded to black plots).

That is, the results of FIG. 1 show that, as described in the above findings, simply reducing the residual stress on the plating film surface results in the existence of pulleys having poor fatigue life, and ensuring the fatigue fracture characteristics or fatigue life of the pulleys. Cannot be guaranteed. To ensure the fatigue life of the pulley body, it is necessary to regulate the residual stress on the plating film surface in relation to the plating film hardness (Hv), which is one of the basic characteristics of the plating film. It indicates that there is.

However, as described above, as the residual stress on the surface of the plating film of the Al alloy pulley becomes lower, the fatigue life of the Al alloy pulley is improved. It can be seen that the necessary condition is to lower the residual stress on the plating film surface, preferably to 15 kgf / mm ² or less, more preferably to 10 kgf / mm ² or less.

More specifically, oblique lines A ₁ , A ₂ , B ₁ ,
B ₂ is the residual stress on the plating film surface and the plating film hardness (Hv)
And a critical region for ensuring the fatigue life of the pulley body. That is, the diagonal line A ₁
Y = a line of 8X + 330, the area above the hatched A ₁ is plated film hardness (Hv) ≧ 8 × plating film surface residual stress (kg
f / mm ² ) +330, which ensures the fatigue fracture characteristics or fatigue life of the pulley body. Also, the diagonal line A ₂
Y = a line of 8X + 410, the area above the hatched A ₂ is plated film hardness (Hv) ≧ 8 × plating film surface residual stress (kg
f / mm ² ) +410 is more preferable.

Further, the oblique line B ₁ is a line of Y = 100X−500,
Left area than the hatched B ₁ is, plating film hardness (Hv) ≧ 100
× This area satisfies the residual stress (kgf / mm ² ) -500 on the plating film surface and ensures the fatigue fracture characteristics or fatigue life of the pulley body. The oblique line B ₂ is a line of Y = 100X−50, and the area on the left side of the oblique line B ₂ is plating film hardness (Hv) ≧
A more preferable region satisfying 100 × residual stress (kgf / mm ² ) −50 of the plating film surface is shown. So this figure
From 1 as well, by specifying the residual stress on the plating film surface in relation to the plating film hardness (Hv) of the present invention, the fatigue life of the pulley body is improved and the fatigue life of the pulley body is reliably guaranteed. We can see that we can do it. The critical significance of the definition of the residual stress on the plating film surface of the present invention is also clear.

As the residual stress on the plating film surface of the Al alloy pulley becomes lower, the fatigue life of the Al alloy pulley increases. Therefore, in order to improve the fatigue life of the Al alloy pulley, the residual stress on the plating film surface is reduced, and further, the residual stress on the plating film surface has a specific relationship with the plating film hardness (Hv). This is done by adjusting the conditions of the plating film. However, as described above, even if the basic characteristics of the plating film are the same, the residual stress on the plating film surface greatly differs. Therefore, in order to reliably guarantee the fatigue life of the Al alloy pulley body and the Al alloy power transmission component body, finally, the residual stress itself on the plating film surface is measured and specified in the present invention. Needless to say, it is necessary to evaluate whether the value is within the range.

Typical factors of the plating film that affect the residual stress on the plating film surface are the composition and thickness of the plating film. In particular, in hard plating such as Ni-P, when the plating film is amorphous, the residual stress on the plating film surface is
This is approximately 0 kgf / mm ² , which is preferable because it easily enters the region in FIG. 2 where the improvement of the fatigue life of the Al alloy pulley is guaranteed.

The components (type) of the plating film in the present invention
The hard plating of Ni, Ni-P, Fe-P, Cr, etc. is appropriately selected according to the required properties of the pulley such as corrosion resistance and wear resistance. In order to have excellent abrasion resistance, which is one of the important characteristics of the plating film in the present invention, the plating film hardness (Hv) needs to be 250 or more, and furthermore, the plating film hardness (Hv ) Is preferably 400 or more.

In order to satisfy these hardnesses, Ni, Ni
-P, Fe-P, Cr or other hard plating, or hard plating such as SiC, alumina, BN, silica, silicon nitride, etc. dispersed in these plating films to achieve even higher hardness Preferably, it is used. In addition, the plating film is not limited to a single layer or a single layer, and may be a combination or a combination thereof to form a composite or multilayer plating film.

On the other hand, in order to keep the residual stress on the surface of the plating film within the range of the present invention, which is another important characteristic of the plating film in the present invention, it is necessary to use an alloy hard plating such as Ni-P or Fe-P. In this case, it is possible to control the residual stress even if the alloy components such as the P content are adjusted. Also, the residual stress can be controlled by the film thickness described later. Therefore, the relationship with the required properties of other plating film such as the abrasion resistance,
It is preferable to determine the component composition of the plating film in relation to other plating film conditions such as the film thickness described below.

Next, since the residual stress on the surface of the plating film tends to increase as the thickness of the plating film increases, the thickness is preferably as thin as about several μm. However, in the case of Ni-P plating containing 2 to 4 wt% of P, depending on the type and conditions of plating, the residual stress on the plating film surface is low when the film thickness is 5 μm or less or 40 μm or more. Since there are some parts that cannot be said, it is preferable to set an optimum film thickness for each type of plating and each condition.

However, the thickness of the plating film is an important factor for ensuring the abrasion resistance of the Al alloy pulley, which is one of the important characteristics in the present invention. Contrary to the residual stress on the surface of the plating film, the wear resistance improves as the film thickness of the plating film increases to about several tens μm, and the plating film hardness (Hv) is 250 or more, preferably Plating film hardness
(Hv) 400 or more can be easily secured. Therefore, the thickness of the plating film is preferably determined from both viewpoints of reducing the residual stress on the plating film surface and ensuring abrasion resistance.

In this regard, in the present invention, the Al alloy pulley for a transport machine such as an automobile including the arm portion and the power transmission portion shown in FIG. The required characteristics of the arm portion and the power transmission portion are different. That is, the fatigue fracture characteristic of the pulley when a large torque is applied is mainly a problem in the arm portion, and the power transmission portion for transmitting power to the belt is for preventing the surface from being roughened due to wear. It is abrasion resistant.

Therefore, in an Al alloy pulley for a transport machine such as an automobile including an arm portion and a power transmission portion, the plating film on the arm portion reduces the residual stress particularly on the plating film surface in order to improve the fatigue life. Must be lower. For this purpose, the thickness of the plating film on the arm portion is preferably as thin as about several μm. On the other hand, it is preferable that the thickness of the plating film of the power transmission section is as thick as about several tens of μm in order to improve abrasion resistance. In addition, the plating film on the arm
There is also a method to make the plating film amorphous to improve the fatigue life

More specifically, in an Al alloy pulley for a transport machine such as an automobile including an arm portion and a power transmission portion, N
When performing hard plating such as i, Ni-P, or Cr, or hard plating in which hard particles such as SiC are further dispersed in these plating films, the thickness of the plating film on the arm portion is about several μm of 10 μm or less, The thickness of the plating film on the power transmission section is 10μ.
m and preferably about 15 to 20 μm.

Next, how to provide a plating film in the present invention will be described. When providing hard plating of Ni, Ni-P, Cr, etc., or hard plating in which hard particles such as SiC are further dispersed in these plating films, there are plating methods such as electroless plating, displacement plating, and immersion plating. Basically, it is efficient to provide an Al alloy pulley by electroplating.

More specifically, a method of electroplating a pulley made of an Al alloy for a transport machine such as an automobile including an arm portion and a power transmission portion will be described with reference to FIG. Figure 2 shows
Al with excellent fatigue life and abrasion resistance, where the thickness of the plating film on the power transmission section is greater than the thickness of the plating film on the arm section.
1 shows an outline of an electroplating apparatus for obtaining an alloy pulley. In FIG. 2, the electroplating apparatus is a plating bath.
7 and an aluminum alloy pulley 1 to be plated
, And a rotating shaft 9 for negatively charging the pulley 1, and anodes 8, 8 arranged opposite the pulley 1.
And a power supply 10 for energizing these electrodes.

A rotating shaft 9 supporting a large number of Al alloy pulleys 1 to be plated is provided with a plating film by rotating or revolving the pulley 1 with respect to the surface of the anode 8. At this time, the rotation or revolution of the pulley 1 is changed to the power transmission units 3 of the pulley 1.
Is carried out closer to the surface of the anode 8 than the arms 2, 2, and in a plane perpendicular to the plane containing the anode 8, with the axis parallel to the anode as the center. Three
, 3 can be made thicker than the thickness of the arm portions 2, 2.

Electroplating is a method in which a plating film is grown by applying a voltage between an anode and an aluminum alloy pulley to be plated, which is a cathode, and passing an electric current. For this reason,
There is a tendency that current flows easily to the portion closest to the anode. Therefore, the plating film thickness in a portion where a large amount of current flows is thicker than that in a portion where a small amount of current flows. The above-mentioned method makes use of such characteristics of the electroplating to make the thickness of the plating film of the power transmission portions 3 and 3 larger than the thickness of the plating film of the arm portions 2 and 2.

The type of the Al alloy used for the power transmission component in the present invention is appropriately selected according to the required characteristics and mechanical properties of the power transmission component such as a pulley. However, as described above, particularly, the fatigue fracture of the arm portion of the pulley is greatly affected by the characteristics of the Al alloy as the base material. For this reason, among the power transmission components, particularly when a fatigue life is required, among the Al alloys, the alloy has the fatigue fracture characteristics particularly required for pulley applications, and preferably has a tensile strength of 190N.
It is preferable to use an Al alloy such as 5,000 series such as JIS 5052 and 5056, 6000 series such as JIS 6063, or 7000 series such as JIS 7075 with / mm ² or more. However, depending on the application,
2000 series such as JIS 2014 and 2017 and 4000 series such as JIS4032
It is also possible to use the system, AC4B, AC8C, ADC12, etc.

The production or molding of the power transmission component such as the pulley is performed by a known method. For example,
A predetermined power transmission component is manufactured by hot forming or cold forming of an Al alloy ingot by rolling, extrusion, forging, or the like, or by powder metallurgy such as sintering of an Al alloy powder.

[0057]

EXAMPLES (Example 1) Hereinafter, the present invention will be specifically described with reference to examples. JIS 5052 tensile strength is 195N / mm ²
(O material) An Al alloy is processed into a pulley including an arm part and a power transmission part with the shape shown in Fig. 4, and this pulley is used as a material to be plated, and is used for electric Ni plating, electric Ni-P plating, and electroless Ni plating. , Cr plating to form each plating film on the surface. In the Al alloy pulley including the arm portion and the power transmission portion, the thickness of the plating film of the arm portion and the power transmission portion was the same. Then, the plating film hardness and the residual stress of the plating film surface of the Al alloy pulley having the plating film formed on the surface were measured, and the fatigue life of the Al alloy pulley was evaluated. These results are shown in FIG.

In addition, among the examples shown in FIG. 1, the typical conditions of the plating film, the residual stress on the plating film surface, and the evaluation of the fatigue life of the Al alloy pulley are summarized.
The results are shown in Tables 1 and 2. Table 1 shows examples of electric Ni-P plating, and Table 2 shows examples of electric Ni plating, examples of electroless Ni plating, and examples of Cr plating. In addition, regarding the correspondence with FIG. 1 in Tables 1 and 2,
In Tables 1 and 2, only the marks (types of plating) plotted in FIG. 1 are shown, and no distinction is made between white, shaded, and black. In Tables 1 and 2, plating films were provided.
The evaluation of the fatigue life of Al alloy pulleys is indicated by circles for pulleys whose properties have been improved by at least 20% over the fatigue life of Al alloy pulleys without a plating film. Use pulleys that have the same characteristics as the pulley's fatigue life.
In addition, the pulleys having inferior characteristics to the fatigue life of the Al alloy pulley having no plating film provided thereon are represented by x marks.

The hardness of each plating film was measured by a Vickers hardness tester. In addition, the residual stress (kgf / mm ² ) of each plating film surface was determined using a Cr of 12,000 k
It was measured by a known X-ray stress measurement method using a constant of gf / mm ² and a Poisson's ratio of 0.3. At this time, for the electroless Ni plating only, the film stress was measured at the time of plating by a spiral stress meter.

Further, the fatigue life of the Al alloy pulley was determined by a rotational fatigue test in which the pulley was rotated while applying a tensile force of 300 kgf / mm ² to simulate the actual use environment of the pulley for automobile parts. And the number of rotations until fatigue fracture occurred. In addition, the comparison was made based on the fatigue life of an unplated Al alloy pulley according to the same test method and conditions.
The fatigue life of the unplated Al alloy pulley is 5 × 10
^Five times.

[0061] First, as is apparent from FIG. 1, the hatched A ₁ and A ₂
Satisfies the upper region, that is, plating film hardness (Hv) ≧ 8 × residual stress (kgf / mm ² ) +330 of the plating film surface,
More preferably, the plating film satisfies plating film hardness (Hv) ≧ 8 × residual stress (kgf / mm ² ) +410 on the plating film surface, and a region on the left side of oblique lines B ₁ and B ₂ , that is, plating Film hardness (Hv) ≥ 100 x Residual stress on the plating film surface (kgf /
mm ² ) −500, more preferably, plating film hardness (Hv) ≧ 100 × residual stress on the plating film surface (kgf / mm ² ) −
A plating film satisfying 50 can improve the fatigue fracture characteristics or fatigue life of the pulley body regardless of the type of the plating film, and can reliably guarantee it.

On the other hand, if the residual stress on the surface of the plating film of the Al alloy pulley is 15 kgf / mm ² or less or 10 kgf / mm ² or less, Regardless of the type, the fatigue life of the Al alloy pulley is not improved or rather reduced. Therefore, from this example, it is clear that in the present invention, the definition of the residual stress on the plating film surface in relation to the plating film hardness (Hv) has a critical significance to reliably guarantee the fatigue life of the pulley body. is there.

As is clear from Tables 1 and 2, FIG.
Each of the invention examples within the above-mentioned invention region can improve the fatigue fracture characteristics or the fatigue life of the pulley main body and reliably guarantee the same regardless of the type of the plating film and the difference in the basic plating conditions.

Further, a comparison between the invention examples in Tables 1 and 2 and the comparative example, that is, Invention Example No. 4 in the electric Ni-P plating shown in Table 1
As is clear from the comparison between Comparative Example No. 8 and Invention Example No. 5 and Comparative Example No. 11, even when the basic conditions of the plating film are the same or similar, the residual stress on the plating film surface is large. It can be seen that the fatigue life of the pulley body is significantly different.

This is because, in the electro-Ni plating shown in Table 2, Invention Example No. 12 and Comparative Example No. 16 and Invention Example No. 14 and Comparative Example No. 1
7, In addition, invention example No. 22 and comparative example in Cr plating
It is clear from the comparison between No. 27 and Invention Example No. 24 and Comparative Example No. 26.

And, as described above, these results
Even if the basic characteristics of the plating film and the basic conditions of the plating are exactly the same, it cannot be said that the residual stress on the surface of the plating film alone is the same, that is, Al
In order to ensure the fatigue fracture characteristics or fatigue life of the alloy pulley body and the Al alloy power transmission component body, it is necessary to measure and evaluate the residual stress itself on the plating film surface. I have. Therefore, as in the present invention, the significance of the fact that the fatigue fracture characteristics or the fatigue life can be surely guaranteed by defining the residual stress on the plating film surface is supported.

[0067]

[Table 1]

[0068]

[Table 2]

(Embodiment 2) The same pulley as in Embodiment 1
An electric Ni-P plating film containing P 2 to 4 wt% was formed on the surface by using the plating apparatus shown in (1). The thickness of the aluminum alloy pulley including the arm portion and the power transmission portion is set to about 5 μm, and the thickness of the power transmission portion is set to approximately 20 μm. -P plating film was formed on the surface.

FIG. 3 shows the film thicknesses of the arm portion and the power transmission portion of the pulley provided with the electric Ni-P plating film on the surface. Figure
The numerical value of 3 indicates the electric Ni formed on the surface of each part of pulley 1.
-P indicates the thickness of the plating film. As is clear from FIG. 3, it can be seen that by using the apparatus and method shown in FIG. 2, it is possible to manufacture an Al alloy pulley having a different thickness of the plating film in each portion.

Further, as in Example 1, the fatigue life of this Al alloy pulley was evaluated. As a result, in particular, the fatigue life of the arm portion was improved by 20% or more compared to the fatigue life of the unplated Al alloy pulley.

As is clear from the above embodiments, the present invention can combine the inconsistent characteristics of fatigue life and abrasion resistance required for a power transmission component made of an Al alloy. Not only pulleys, but also other Al alloy power transmission parts where the required characteristics of fatigue life and wear resistance are different, such as gears, racks, etc., for transport vehicles such as automobiles, for bicycles, It can be seen that it can be used for industrial machines and home appliances.

[0073]

As described above, according to the present invention, inconsistent characteristics such as fatigue life and wear resistance are obtained.
In addition, it is possible to provide an Al alloy power transmission component that guarantees these characteristics. Therefore, the present invention has excellent industrial value for expanding the use of power transmission parts made of Al alloy particularly for transport vehicles such as automobiles, and promoting Al alloying and weight reduction of transport devices and the like.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a relationship between residual stress on a plating film surface and plating film hardness (Hv) of the present invention, and fatigue life of an Al alloy pulley.

FIG. 2 is a diagram for obtaining an Al alloy pulley in which a plating film thickness of a power transmission portion is thicker than a plating film thickness of an arm portion.
It is explanatory drawing which shows the outline of an electroplating apparatus.

FIG. 3 is an explanatory view showing an example of the present invention and showing film thicknesses of an arm portion and a power transmission portion of a pulley provided with an electric Ni-P plating film on its surface.

FIGS. 4A and 4B show a typical example of an automobile pulley to which the present invention is applied. FIG. 4A is a longitudinal sectional view and FIG. 4B is a plan view.

[Explanation of symbols]

1: pulley, 2: arm (rim) part, 3: power transmission part, 4: fixed part, 5: hole into which drive shaft is fitted, 6: electrolytic layer, 7: plating bath,
8: anode, 9: rotating shaft, 10: power supply, A ₁ , A ₂ , B ₁ , B ₂ : diagonal line indicating a critical area that guarantees the fatigue life of the pulley,

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Takenori Nakayama 1-5-5 Takatsukadai, Nishi-ku, Kobe Kobe Steel Works Kobe Research Institute

Claims (15)

[Claims] 1. A power transmission part made of an Al alloy in which parts having different required characteristics of fatigue life and abrasion resistance are provided with a plating film having a hardness (Hv) of 250 or more on the surface. The residual stress on the plating film surface in the required part is the plating film hardness (Hv) ≥ 8 × the residual stress on the plating film surface (kgf / mm ² ) in relation to the plating film hardness (Hv).
+330 and Al alloy power transmission with excellent fatigue life and wear resistance characterized by satisfying plating film hardness (Hv) ≧ 100 × residual stress (kgf / mm ² ) -500 on the plating film surface parts. 2. The Al alloy power transmission component according to claim 1, wherein the power transmission component is a pulley. 3. The pulley includes a cylindrical fixed portion, a disk-shaped arm portion disposed on the outer periphery of the fixed portion, and a cylindrical power transmission portion disposed on the outer periphery of the arm portion. The residual stress on the plating film surface of the arm portion is related to the plating film hardness (Hv), and the plating film hardness (Hv) ≧ 8 × the residual stress on the plating film surface (kgf / mm ² ) +330, and the plating Film hardness (Hv) ≧ 100 × Residual stress on the surface of the plating film (kgf / mm
² ) The power transmission component made of an aluminum alloy according to claim 2, which satisfies -500. 4. The residual stress on the plating film surface is defined as: plating film hardness (Hv) ≧ 8 × residual stress on the plating film surface (kgf / m
m ²⁾ +410, and, fatigue life and resistance according to any one of claims 1 to 3 satisfying the residual stress (kgf / mm ²⁾ -50 of the plating film hardness (Hv) ≧ 100 × plating film surface Power transmission parts made of Al alloy with excellent wear properties. 5. The residual stress on the surface of the plating film is 15 kg.
The power transmission component made of an Al alloy having excellent fatigue life and abrasion resistance according to any one of claims 1 to 4, which is not more than f / mm ² . 6. The residual stress on the surface of the plating film is 10 kg.
The power transmission component made of an Al alloy excellent in fatigue life and abrasion resistance according to any one of claims 1 to 5, which is f / mm ² or less. 7. The power transmission component made of an Al alloy excellent in fatigue life and abrasion resistance according to claim 1, wherein the plating film hardness (Hv) is 400 or more. 8. The power transmission unit according to claim 1, wherein the thickness of the plating film of the arm portion is smaller than the thickness of the plating film of the power transmission unit.
The Al alloy power transmission component having excellent fatigue life and wear resistance according to any one of the above. 9. The method according to claim 9, wherein the plating film is made of Ni, Ni-P, Fe-P, Cr.
A hard plating selected from the group consisting of: excellent in fatigue life and wear resistance according to any one of claims 1 to 8;
Power transmission parts made of Al alloy. 10. The aluminum alloy having excellent fatigue life and abrasion resistance according to claim 1, wherein the plating film is provided by electroplating an aluminum alloy power transmission component. Power transmission parts. 11. The method according to claim 11, wherein the electroplating is performed on the anode surface with Al.
The Al alloy power transmission component according to claim 10, wherein the plating film is provided by rotating or revolving the alloy power transmission component. 12. The Al alloy pulley is rotated or revolved such that the power transmission portion of the Al alloy pulley is closer to the anode surface than the arm portion, and the plating film thickness of the power transmission portion is adjusted to the arm portion. 2. A plating film having a thickness greater than the thickness of the plating film.
2. A power transmission component made of an Al alloy having excellent fatigue life and wear resistance according to 1. 13. The power transmission component made of an Al alloy excellent in fatigue life and wear resistance according to claim 1, wherein the tensile strength of the Al alloy is 190 N / mm ² or more. 14. The Al alloy power transmission component according to claim 1, wherein the Al alloy power transmission component is used for a transport aircraft. 15. The Al alloy power transmission component according to any one of claims 1 to 14, wherein the Al alloy power transmission component is for an automobile.