MXPA00009158A - Swash plate with cobalt-tin alloy coating - Google Patents

Abstract

A swash plate type compressor (10) having a cylinder block (12, 14) with cylinder bores (18) disposed parallel to the axis of the cylinder block. A rotary shaft (22) rotatably mounted within the cylinder block carries an aluminium swash plate (20). The swash plate (20) is fixed in the rotary shaft (22) and has two facial surfaces (26) and an end surface (28). The swash plate (20) has a coating layer of at least 0.2 wt.%cobalt and the balance being tin. A piston (16) reciprocally fitted within the cylinder bore (18) contains shoes (24) which slideably intervene between the piston (16) and the swash plate facial surfaces (26). The shoes (24) transfer the rotational motion of the swash plate (20) to the linear motion of the piston (16). The coated surfaces (26) of the swash plate (20) are in slidable contact with the shoes (24). The coating on the swash plate (20) permits the use of low silicon alloy aluminium without the need of metal plating or high finish polishing.

Description

"COVERING ALLOY OF COBALT-TIN IN ALUMINUM THROUGH CHEMICAL CONVERSION" ^ - BACKGROUND OF THE INVENTION FIELD OF THE INVENTION ' The present invention relates to a drive plate type compressor for compressing a refrigerant gas, by rotating a drive plate. More particularly, the present invention relates to an improvement to the drive plate compressors by applying a surface coating of tin and cobalt on the face surfaces of the drive plate to reduce frictional wear on the components. The body of the drive plate is produced from aluminum or an aluminum alloy. 2. INFORMATION FOR PUBLICIZATION Conventionally, a plate type compressor is used in systems such as an automobile air conditioning system. In accordance with a known motor-plate type compressor, the transmission of motor power is carried out as a motor plate as they are made to reciprocate a motor plate and a piston, in order to suck, compress and discharge the gas. The drive plate is usually composed of aluminum or aluminum alloy and shoes, which makes sliding contact with the drive plate when it rotates, which are composed of light weight ceramic or such as alumina. The metal in metal contact in the shoe and the interface of the drive plate requires that special precautions be taken in order to prevent undue wear and possible capture of the shoe with the drive plate. In a conventional drive plate compressor, the following problems tend to occur. 1) The amount of oil contained in the coolant gas is reduced if the coolant escapes from the drive plate type compressor. When the drive plate type compressor is operated under this condition, the lubrication on the sliding surface of the drive plate is decreased. In an extreme case, the capture of the shoe on the sliding surface of the drive plate occurs due to the generation of high temperature friction heat. 2) In the case where the compression of the liquid refrigerant is effected, the lubrication on the sliding surface of the drive plate is reduced. As a result, the capture of the shoe with the surface of the drive plate may occur.

Several methods have been developed to improve lubrication at the shoe / drive plate interface and to decrease wear on the compressor drive plates. Conventional drive plates are treated with a tin coating to improve surface wear. U.S. Patent No. 5,655,432 treated the drive plate with a crosslinked polyfluoro elastomer bonded directly to aluminum, a lubricant additive and a charge carrying additive. The material is applied as a viscous fluid and partially masked in order to coat the component only in certain areas. The coating is also applied within the range of 13 to 50 microns and since the maximum allowed variation is only 10 microns, the parts require machining after coating. The coating process itself adds to the complexity of manufacturing, and makes it more difficult to maintain manufacturing tolerances than with a conventional tin conversion coating. U.S. Patent No. 5,056,417 treated with a drive plate body with a surface coating layer made of tin and at least one metal selected from the group consisting of copper, nickel, zinc, lead and indium. Even when any of these five materials are mixed or bound with tin to improve their wear resistance, none of them is described as also acting to bind the coating to the drive plate. The present invention discloses a tin / cobalt coating with improved wear resistance and also excellent adhesion to the drive plate, in order to retain the high lubricity of the tin in the aluminum drive plate. Thus, in the present invention, the added cobalt provides a tin / cobalt surface coating with improved adhesion through a conventional adhesion coating, a tin conversion coating, which improves the wear resistance of the aluminum drive plate. .

COMPENDIUM OF THE INVENTION To avoid the aforementioned problems, the interface associated with the piston / drive plate is to pde a novel drive plate type compressor with impd capture resistance. A drive plate compressor having a cylinder block having a cylinder bore placed parallel to the axis of the cylinder block- A rotary shaft mounted rotatably within the cylinder block and a piston reciprocally adjusted in the bore of the cylinder. The shoes slide between the piston and the drive plate. The drive plate comprises a matrix composed of aluminum or aluminum alloy and in at least a portion of the surface of the drive plate a coating layer comprising at least 0.2 percent err cobalt weight, the remainder being tin. The coated part of the surface of the drive plate is that which remains in sliding contact with the shoes during the operation of the compressor.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a detailed view of a drive plate compressor in accordance with one embodiment of the present invention. Figure 2a (front face surface) is a graph of a 2 hour compressor adhesion performance test carried out in one embodiment of the present invention and a conventional tin drive plate. Figure 2b (back face surface) is a graph of a 2 hour compressor adhesion performance test carried out in a modality of the - - present invention and a conventional tin matrix plate.

DETAILED DESCRIPTION OF THE PREFERRED MODALITIES Illustrated in Figure 1, there is a detailed perspective view of an automotive plate type compressor 10 for driving the refrigerant gas through a cooling circuit. The compressor 10 comprises a two-piece cylinder block 12, 14 which is pded with a plurality of reciprocating pistons 16. For reasons of clarity, Figure 1 illustrates only one of these reciprocating pistons 16. In practice, each piston 16 is made to reciprocate within the bore of the cylinder 18. Each piston 16 is in communication with the drive plate 20 that is fixedly mounted on a rotary arrow 22 extending axially. The reciprocation movement of each piston 16 within its associated cylinder bore, is successively released by siphons, compresses and discharges the refrigerant gas. A pair of pivot shoes 24 are placed between each piston 16 and the driver plate 20. The shoe 24 transfers the rotational movement of the driver plate 20 to the linear movement of the piston 16. The driver plate 20 has two facial surfaces 26 ( only one shown for reasons of clarity) that come into contact with the shoe 24. The rotation of the arrow 22 causes the drive plate 20 to rotate between the cylinder blocks 12 and 14. The facial surfaces 26 come into contact with the shoes 24 and are subjected to a shear type friction contact with the shoe 24. An end surface 28 can be brought into contact with the piston 16 and the piston 16 is slightly inclined or bent. The end surface 28 and the facial surfaces 26 are brought into contact to prevent wear of the contact with the piston 16 and the shoes 24. The surface coating 30 must also have a low coefficient of friction to increase the efficiency of the compressor. The shape of the drive plate 20 according to the present invention can be the same as those of the conventional drive plates. The material that composes the matrix of the body of the drive plate 20 must be aluminum or aluminum alloy. The aluminum alloy, for example, can be an aluminum-type high-silicon alloy, an aluminum-silicon-magnesium-type alloy, an aluminum-silicon-copper-magnesium-type alloy, and aluminum alloys - that do not contain silicon.

The drive plate 20 is usually made of an aluminum or aluminum alloy material to make it lightweight and strong. Aluminum and aluminum alloys contain hypereutectic silico, that is, more silicon than is required to form a eutectic crystalline structure, they are frequently used. Although the surface coating 30 of the present invention can be used with hypereutectic aluminum, it is primarily intended to use aluminum and non-hypereutectic aluminum alloys having less than 12.5 weight percent silicon. Hard grains, as used herein, mean grains having average particle diameters of 20 to 100 microns and a hardness greater than 300 on the Vic ers hardness scale or, more preferably having a hardness greater than 600 on the hardness scale. Vickers hardness scale, such as a primary crystal silicon. For example, the aluminum-type, high silicon content alloy can be considered as one of the appropriate materials for the body of the drive plate 20. Because the alsyl alloy contains approximately 13 percent to 30 percent by weight of the silicon implying that the alsil alloy contains more silicon than is required to form a eutectic crystal structure, the alsil alloy has primary crystal silicon - dispersed in the structure of the matrix. Also, the alsil has superior characteristics and could resist very serious sliding operations in the drive plate. Other materials having hard grains and possibly applicable to the body of the driving plate 20 are the intermetallic compounds of: aluminum-manganese; aluminum-silicon-manganese; aluminum-iron-manganese; aluminum-chromium and the like. Conventionally, the body of the drive plate 20 is made of aluminum or aluminum alloy which is brought into direct contact with the shoes 24. However, in accordance with the present invention during the operation with the surface coating layer 30, in the The body of the driving plate 20 is brought into contact with the shoes 24 so that the frictional resistance with the shoes is greatly reduced. Although it is only necessary to coat the facial surface 26 that has contact with the shoes 24, for ease of manufacture, the entire body of the motor plate 20 is coated. According to the present invention, the body of the motor plate 20 has a surface coating layer 30. The surface coating layer 30 is formed on the body surface of the motor plate 20 at least on the part of the surface having sliding contact with the shoes 24. The surface coating layer 30, without However, it can be formed across the entire surface of the body of the drive plate 20. The surface coating plate 30 acts to reduce the frictional resistance with the shoes 24 and prevents the capture from occurring on the sliding face surface 26 of the driving plate 20. "" The surface coating layer 30 of the present invention is composed mainly of tin, modified with cobalt. If the surface coating layer 30 is composed only of tin, the coefficient of friction will be decreased but at the same time, the surface coating layer becomes rather smooth due to the characteristics of the tin and, as a result, the coating layer. surface 30 will be susceptible to abrasion. In particular, by weight percentage based on the total weight of the tin / cobalt surface coating it comprises 0.2 to 2.1 weight percent cobalt with the remainder being tin, most preferably being 98.9 percent to 99.7 percent by weight. tin weight and from 0.3 percent to 1.1 percent by weight of cobalt and more preferably from 0.5 percent to 0.9 percent by weight cobalt with the remainder tin.

It has been found by the inventors of the present invention that the coexistence of tin and cobalt in the matrix structure of the surface coating layer 30 provides a low coefficient of friction as well as improved hardness, ~~ so that high abrasion resistance is obtained. In addition, the adhesion of the coating to the driving plate 20 is improved by the addition of cobalt. The surface coating 30 can be applied to the drive plate 20 by means of a conversion coating. An aqueous tin bath is prepared in accordance with the convention and then cobalt chloride is dissolved in the bath and the aqueous solution is heated to a temperature higher than 49 ° C. The concentration of cobalt in the bath is that necessary to provide a coating on the drive plate from 0.2 percent to 2.1 percent by weight of cobalt with the remainder being tin. Preferably, the bath is at a temperature between 49 ° C and 66 ° C. To provide that amount of cobalt / tin in the mill scale 20, the bath generally comprises from 0.003 percent to 0.03 percent by weight of cobalt chloride and from 6 percent to 7.2 percent by weight of potassium stearate. Most preferably, the same amount of potassium stearate is maintained, from 0.005 percent to 0.015 percent by weight of cobalt chloride and most preferably 0.007 percent to 0.013 percent by weight of cobalt chloride. In addition, the bath comprises conventional materials such as chelates and pH stabilizers. Preferably, the source of the cobalt ion is cobalt chloride, compounds such as cobalt nitrate do not show the same results. Before applying the surface coating 30, the motor plate 20 is exposed to a cleaning solution that removes the surface oils and prepares the part for the application of the coating. The cleaning methods typically include a solvent, an acid or washed with an alkaline material. The pieces are then exposed to the solution for 5 to 6 minutes to be coated. The thickness of the surface coating 30 is preferably 0.8 to 2.5 microns. Applicants have found that if the surface coating layer 30 has a thickness of less than 0.8 micron, the coefficient of friction will not be sufficiently decreased. On the other hand, if the surface coating layer 30 has a thickness of more than 2.5 microns, the surface coating layer 30 will be susceptible to problems related to its strength as to resist detachment. In accordance with the present invention, the coefficient of friction, between the drive plate 20 and the shoe 24 is small so as to secure a uniform sliding of the shoe 24 in the driving plate 20. The surface coating layer 30 is superior in strength thereby reducing the amount of abrasion that occurs therein. Still additionally, the capture of the shoe 24 on the surface of the drive plate 20 is prevented even when a liquid refrigerant is compressed or the compressor is operated under unforeseeable circumstances such as insufficient lubrication of the sliding parts caused by leakages of the liquid. refrigerant gas to the outside of the compressor. Consequently, by the effects described above, the drive plate compressor according to the present invention can successfully withstand very serious use and achieve long service life.

Experimental Results: Example 1: In accordance with the drive plate type compressor as shown in Figure 1, the drive plate 20 is composed of a drive plate body 20 made of an aluminum alloy containing 10 percent a 12.5 weight percent silicon, and surface coating layer 30 (the number will have to be added to the figure) formed over the entire surface of the body of the drive plate 20. The surface coating layer 30 consists of tin and cobalt ~ as will be described below. The surface coating layer 30 was formed by the following process: The motor plate 20 was cleaned with an alkaline cleaner at 60 ° C for 5 minutes. The body of the drive plate 20 was immersed for 5 minutes in an aqueous bath solution containing 6.6 weight percent potassium stannate and 0.007 weight percent cobalt chloride by weight, and which was maintained at room temperature. 54 ° C to 64 ° C. Then it was taken out of the Sn / Co bath and washed with water. As a result, a surface coating layer 30 consisting of tin and cobalt was formed over the entire surface of the body of the drive plate 20. The resulting surface coating layer 30 had a thickness of 1.0 micrometer and was composed of 99.5 percent by weight. tin weight, and 0.5 percent cobalt weight.

Example 2: The motor plate body 20 as in Example 1, wherein the surface coating layer 30 was formed by the following process: The motor plate 20 was cleaned with an alkaline cleaner at 60 ° C for 5 minutes. The body of the drive plate 20 was immersed for 5 minutes in an aqueous bath solution containing 6.6 weight percent potassium stannate and 0.005 weight percent cobalt chloride by weight, and which was maintained at a temperature of 54 minutes. ° C to 64 ° C. Then it was taken out of the Sn / Co bath and washed with water. As a result, the surface coating layer 30 consisting of tin and cobalt was formed over the entire surface of the body of the drive plate 20. The resulting surface coating layer 30 had a thickness of 1.0 micrometer and was composed of 0.36 per cent. one hundred weight cobalt and the remainder tin.

Example 3: (a comparison example): The body of the drive plate as in Example 1 and Example 2 was coated with an Sn coating composition, which is not in accordance with the present invention, as follows The body of the motor plate 20 was immersed for 5 minutes in an aqueous solution containing 6.6 weight percent potassium stannate, and which was maintained at a temperature of 54 ° C to 64 ° C. It was coated, it was taken out of the solution and washed with water. As a result, a surface coating layer 30 having a thickness of 1.0 micrometer and consisting of 100 weight percent of tin was formed across the entire surface of the body of the drive plate 20.

Figures 2a and 2b illustrate the comparison of the two-hour calorimeter test administered to three different coatings prepared as above. The calorimeter test measures the accelerated wear and loss of adhesion of a typical tin coating. The samples of the test are subjected to the same conditions and then the wear of the coating is compared. The assembled compressor is subjected to both high and low speed use. A test compressor pump was operated for 1 hour at point 19, that simulates the use at low speed, and 1 hour in conditions of point 26, that simulates the use at high speed. At points 19 and 26 the compressor is subjected to 1000 and 3000 revolutions per minute, respectively. The data comparing the three coatings prepared in Examples 1 to 3 are summarized in Table 1. The wear of both facial surfaces 26 of the motor plate 20 of the motor plate was compared. - % in Weight of Co Loss of Adhesion in solution Frontal Surface Posterior Surface (mm) (mm) 150 10.4 56.8 2 .76 4.15 39.93 20.46 43.8 40.2 194.94 0. 005 0 0 0 0 38 0 0 0 0 6.3 170.4 0 0. 007 0 0 0 0 18 0 16.8 0 0 70 0 0 36 0 0 0 0 0 0 0 As indicated in Figures 2a, 2b and Table 1, the adhesion measured for the drive plates 20 which - have the surface coating layer 30 in accordance with the embodiments of the present invention are much higher than that for the conventional type coating that is described in Comparative Example 3. Also, a comparison between the different levels of cobalt of the present invention shows that the addition to higher levels of cobalt in the composition of the surface coating layer is effective to improve the adhesion and wear resistance of the motor plate 20. In this way the surface coating layer 30 of comparison example 3 contains only tin, and is more susceptible to rapid abrasion than a tin and cobalt coating according to the present invention. As will be evident from the results of the test shown in Figures 2a and 2b, in accordance with the present invention, the fact that loss of adhesion of the coating occurs is greatly reduced due to the effect of the surface coating layer 30 even when The plate type compressor is operated under serious conditions. The motor plates 20 coated with the tin / cobalt coating do not exhibit the poor adhesion caused by wear resistance - deficient of a pure tin coating due to added cobalt.

Additional Experimental Results: A normal tape adhesion test was administered in the samples prepared in Examples 1 to 3. The test measures the amount of coating that can be removed when placed under strain or strain. A 3M 610 cellophane tape was applied to the motor plates covered in strips of 2 to 3 millimeters. The tape was rubbed with a rubber eraser to ensure adhesion of the tape and then the tape was removed with a rapid movement where a 90 degree angle was maintained between the tape and the surface of the drive plate 20. without cobalt (all of tin) showed the most deficient adhesion. The adhesion improved correspondingly by increasing the amounts of cobalt in the coatings, i.e., a cobalt / tin coating with 0.QQ5 percent by weight of Co, had improved adhesion in relation to a cobalt / tin coating of 0.005 percent by weight. weight. Also, in accordance with the present invention, still in the state where the surface coating layer 30 of the drive plate 20 is gradually reduced by abrasion, the glass silicon - dispersed primary on the surface of the body of the drive plate 20 was subjected to exposure and sticking on the surface of the drive plate 20. Since the primary glass silicon has higher hardness, additional abrasion of the coating layer is prevented surface 30. It will be apparent to those skilled in the art that various modifications may be made to the foregoing invention without departing from the spirit and scope of the claims that will be given below.

Claims (12)

1. - CLAIMS: A drive plate type compressor comprising: a cylinder block having a cylinder bore placed parallel to the axis of the cylinder block; a rotary arrow mounted rotatably inside the cylinder block; a drive plate fixed to the rotary arrow for rotation with the rotary arrow inside the cylinder block; a piston adjusted reciprocably in the cylinder bore; and shoes slidingly intervening between the piston and the drive plate wherein the drive plate comprises a matrix composed of aluminum or aluminum alloy and, at least a portion of the surface of the drive plate, a coating layer comprising at least less 0.2 weight percent cobalt being the remainder tin, the coated part of the surface of the motor plate being in sliding contact with the shoes.
2. 2. The drive plate type compressor of claim 1, wherein the matrix of the drive plate contains hard grains having an average particle diameter of 20 to 100 microns and a hardness greater than 300 on the Vickers hardness scale.
3. 3. The drive plate type compressor of claim 2, wherein the matrix of the drive plate containing hard grains and has the hardness greater than 600 on the Vickers hardness scale.
4. The drive plate compressor of claim 1, wherein the matrix of the drive plate comprises aluminum type alloy and high silico content including from 13 percent to 30 percent silicon by weight.
5. The drive plate compressor of claim 1, wherein the drive plate comprises an aluminum-silicon alloy having 13 percent or less by weight of silicon.
6. The drive plate compressor of claim 2, wherein the drive plate comprises an aluminum-silicon type alloy having from about 10 to 12.5 weight percent silicon.
7. 7. The drive plate compressor of claim 1, wherein the thickness of the surface coating layer is from 0.8 micron to 2.5 microns.
8. 8. The drive plate compressor of claim 1, wherein the thickness of the surface coating layer is 1.1 to 1.8 microns.
9. 9. The drive plate compressor of claim 1, wherein the coating "comprises of

   0. 2 percent to 2.1 percent by weight of cobalt.
10. 10. The drive plate compressor of claim 1, wherein the coating comprises from 0.3 percent to 1.1 percent by weight of cobalt.
11. A method for coating a drive plate for a drive plate type compressor comprising the steps of: providing a drive plate of an aluminum alloy and low silicon content including less than 13 weight percent silicon, drive plate has two surfaces and one end surface; exposing the drive plate to an aqueous tin bath at a temperature of 49 ° C to 66 ° C, the bath comprising tin and cobalt in amounts so as to provide a conversion coating from 0.5 percent to 0.9 percent cobalt; the rest tin on the surface of the drive plate.
12. 12. The method according to claim 12, wherein the cobalt in the bath is provided by cobalt chloride.