Swash-plate of swash-plate type compressor

Details Swash-plate of swash-plate type compressor Swash-plate of swash-plate type compressor

1999-12-16

2002-01-08

Copenheaver, Blaine (Department: 1775)

Stock material or miscellaneous articles

All metal or with adjacent metals

Having metal particles

C428S564000, C428S568000, C428S569000, C428S652000, C428S653000, C428S654000, C428S937000, C075S231000, C075S249000, C092S071000

Reexamination Certificate

active

06337141

ABSTRACT:

BACKGROUND OF INVENTION
1. Field of Invention
The present invention relates to a swash plate of a swash-plate type compressor, more particularly a swash plate having a surface sliding layer, for which a high Si aluminum alloy with improved sliding properties is used.
2. Background Technique
In the swash-plate type compressor, the swash plate
2
is rigidly secured obliquely to a rotary shaft as shown in FIG.
1
. Alternatively, the swash plate is secured obliquely to a rotary shaft in such a manner that its slanting angle is variable. The compression and expansion are carried out by means of rotating the swash-plate which increases or decreases the volume of partition space within a compressor, depending upon the rotation of the rotary shaft. Such swash plate
2
is caused to slide on a shielding member referred to as a shoe
3
. Gas-tight sealing between the swash plate
2
and the shoe
3
enables the compression and expansion of the cooling medium in the stated space.
4
is a ball.
A noteworthy point in the sliding conditions of a swash-plate is that, during the initial operational period of a compressor, the cooling medium reaches the sliding part prior to the lubricating oil reaching the sliding part between the swash plate and the shoe; thus the cooling medium has a rinsing effect on the lubricating oil which remains on the sliding part, with the result that the sliding condition is a dry condition free of lubricating oil. The sliding condition requirements of the swash plate are therefore very severe.
The sliding properties, which are required for a swash-plate used under the conditions described above, are seizure resistance, wear resistance, and the like. Proposals have thus been made to add hard matters into the aluminum material for enhancing the wear resistance, to improve the material of the swash plate, and to subject an iron-based swash-plate to heat treatment for enhancing the hardness and hence wear-resistance. In addition, the following surface treating methods are also proposed.
One of the present applicants proposed in Japanese Unexamined Patent Publication No. Sho51-36611 to bond sintered Cu material on the shoe in the case of an iron-based swash plate. That is, an iron-based swash plate was heretofore subjected to hardening treatment. However, when the material of the opposed member, i.e., the shoe, is an iron-based material, the sliding takes place between identical kinds of materials thereby incurring a problem of possible seizure. Sintered copper alloy is used for the opposing material (shoe) opposed to an iron-based swash plate, so as to avoid the above-mentioned problem.
In addition, it was also proposed to apply tin plating on the iron-based swash-plate so as to avoid the sliding between identical kinds of materials and hence to enhance the seizure resistance. Since the tin plating applied on an iron-based swash-plate is soft, a problem that arises is insufficient wear-resistance.
In bronze-based material lead realizes compatiblity and lubrication effects. Improved sliding performance can, therefore, be attained by means of flame-spraying the lead-added bronze (c.f., European Publication No. EP 0713972A1). However, the trend toward using lead-free materials has recently intensified, and, therefore, it is urgently needed to develop sliding material, which can replace the lead-added bronze.
Prior proposals of the surface-treating methods of a swash plate of the swash-plate type compressor cannot attain the properties superior to those attained by the lead-added bronze. From such a point of view, the present inventors turned their attention to flame-spraying of aluminum materials, particularly Al—Si alloy. The Si of the Al—Si alloy crystallizes as the primary crystal or eutectic, with the result that the wear resistance can easily be enhanced. It is, however, difficult to find in the aluminum materials, any component(s), which can outstandingly enhance the seizure resistance.
SUMMARY OF INVENTION
It is, therefore, an object of the present invention to provide a swash plate of a swash-plate type compressor, which can solve the problems involved in the prior art.
No considerations have been given, as far as the present inventors are aware, to flame-spray simultaneously the Al—Si alloy in the eutectic or hyper-eutectic region and a tribological material such as graphite or MoS
2
. Spraying temperature of 700° C. or higher is necessary for flame-spraying the aluminum-alloys, while active reaction between the graphite and oxygen occurs at a temperature of 500° C. or higher. There is, therefore, a danger that the graphite cannot be incorporated in the flame-sprayed layer, when even a small amount of oxygen is present in the spraying flame. The present inventors recognized, therefore, concern regarding for the combustion and loss of graphite in the flame-spraying gas under the presence of oxygen in such gas. Unexpectedly, the present inventors discovered that tribological materials can be dispersed in the aluminum materials.
In accordance with the objects of the present invention, there is provided a swash plate of a swash-plate type compressor, characterized in that a flame-sprayed layer deposited on the substrate consists of (a) aluminum alloy containing from 12 to 60% by weight of Si and granular Si particles dispersed in the matrix thereof and (b) at least one dispersing phase of graphite carbon, amorphous carbon and carbon, carbon, the crystallizing degree of which is between that of the graphite carbon and amorphous carbon, and MoS
2
.
The present invention is explained hereinafter in detail. The percentage is weight % unless otherwise specified.
DESCRIPTION OF PREFERRED EMBODIMENTS
The present inventors energetically carried out experiments and discovered that the flame-sprayed Al—Si based aluminum alloys in a eutectic region or a hyper-eutectic region exhibits improved adhesiveness with a substrate; and, the Si particles are refined.
In the flame-sprayed Al—Si based alloy of the present invention, Si in granular form is dispersed in the aluminum matrix finely and in a large amount. Thus, a large amount of granular Si despersed finely in the aluminum matrix enhances the hardness and hence wear-resistance of the alloy. In addition, the granular Si particles disperse finely in a large amount and suppress the adhesion between the aluminum matrix and a shoe and hence seizure due to such adhesion.
EP 0713972A1 filed by the present applicants provides a detailed explanation of the flame-sprayed copper alloy by referring to an example of Cu—Pb alloy. The rapid cooling and solidification of molten particles is common in the Al-alloy example. One feature of the flame-sprayed Al—Si alloy is that an additive element (Si) has a higher melting point than that of the matrix element (Al). As a result, Si in granular form is finely dispersed in the aluminum matrix in a large amount. Thus, the effect is obtained such that Si enhances the hardness and hence wear-resistance of the alloy.
In the present invention, the granular Si particles do not have the same shape as seen in the primary Si of the conventional melted alloy or the Si particles of the rolled alloy. They have a one-directional, lengthwise property. On the other hand, the granular Si particles of the present invention have spheroidal, nodular, polygonal, island-form having concavities or irregular shapes, which are not classified as the former shapes, and have almost the same size in any direction. More specifcally, the ratio of the longest and shortest diameter is 3:1 or less, in average. Furthermore, the marked noteworthy distinction between the primary Si and eutectic Si seen in the conventional melted alloys disappears in the case of the present invention.
When the Si content of the aluminum-alloy according to the present invention is less than 12%, the enhancement effects of wear resistance and are slight. On the other hand, when the Si content exceeds 60%, it is difficult to produce the alloy powder to be flame-sprayed. A preferable Si content is from 15 to 50%. When the size of Si particles exceeds

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