EP1384887B1 - Reciprocating compressor - Google Patents
Reciprocating compressor Download PDFInfo
- Publication number
- EP1384887B1 EP1384887B1 EP03024463A EP03024463A EP1384887B1 EP 1384887 B1 EP1384887 B1 EP 1384887B1 EP 03024463 A EP03024463 A EP 03024463A EP 03024463 A EP03024463 A EP 03024463A EP 1384887 B1 EP1384887 B1 EP 1384887B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- coating layer
- piston
- shoe
- tin
- cam
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B27/00—Multi-cylinder pumps specially adapted for elastic fluids and characterised by number or arrangement of cylinders
- F04B27/08—Multi-cylinder pumps specially adapted for elastic fluids and characterised by number or arrangement of cylinders having cylinders coaxial with, or parallel or inclined to, main shaft axis
- F04B27/0873—Component parts, e.g. sealings; Manufacturing or assembly thereof
- F04B27/0878—Pistons
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B27/00—Multi-cylinder pumps specially adapted for elastic fluids and characterised by number or arrangement of cylinders
- F04B27/08—Multi-cylinder pumps specially adapted for elastic fluids and characterised by number or arrangement of cylinders having cylinders coaxial with, or parallel or inclined to, main shaft axis
- F04B27/0873—Component parts, e.g. sealings; Manufacturing or assembly thereof
- F04B27/0878—Pistons
- F04B27/0886—Piston shoes
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
- F05C—INDEXING SCHEME RELATING TO MATERIALS, MATERIAL PROPERTIES OR MATERIAL CHARACTERISTICS FOR MACHINES, ENGINES OR PUMPS OTHER THAN NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES
- F05C2201/00—Metals
- F05C2201/02—Light metals
- F05C2201/021—Aluminium
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
- F05C—INDEXING SCHEME RELATING TO MATERIALS, MATERIAL PROPERTIES OR MATERIAL CHARACTERISTICS FOR MACHINES, ENGINES OR PUMPS OTHER THAN NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES
- F05C2201/00—Metals
- F05C2201/02—Light metals
- F05C2201/025—Boron
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
- F05C—INDEXING SCHEME RELATING TO MATERIALS, MATERIAL PROPERTIES OR MATERIAL CHARACTERISTICS FOR MACHINES, ENGINES OR PUMPS OTHER THAN NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES
- F05C2201/00—Metals
- F05C2201/04—Heavy metals
- F05C2201/0433—Iron group; Ferrous alloys, e.g. steel
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
- F05C—INDEXING SCHEME RELATING TO MATERIALS, MATERIAL PROPERTIES OR MATERIAL CHARACTERISTICS FOR MACHINES, ENGINES OR PUMPS OTHER THAN NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES
- F05C2201/00—Metals
- F05C2201/04—Heavy metals
- F05C2201/0433—Iron group; Ferrous alloys, e.g. steel
- F05C2201/0466—Nickel
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
- F05C—INDEXING SCHEME RELATING TO MATERIALS, MATERIAL PROPERTIES OR MATERIAL CHARACTERISTICS FOR MACHINES, ENGINES OR PUMPS OTHER THAN NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES
- F05C2201/00—Metals
- F05C2201/04—Heavy metals
- F05C2201/0469—Other heavy metals
- F05C2201/0475—Copper or alloys thereof
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
- F05C—INDEXING SCHEME RELATING TO MATERIALS, MATERIAL PROPERTIES OR MATERIAL CHARACTERISTICS FOR MACHINES, ENGINES OR PUMPS OTHER THAN NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES
- F05C2201/00—Metals
- F05C2201/04—Heavy metals
- F05C2201/0469—Other heavy metals
- F05C2201/049—Lead
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
- F05C—INDEXING SCHEME RELATING TO MATERIALS, MATERIAL PROPERTIES OR MATERIAL CHARACTERISTICS FOR MACHINES, ENGINES OR PUMPS OTHER THAN NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES
- F05C2201/00—Metals
- F05C2201/04—Heavy metals
- F05C2201/0469—Other heavy metals
- F05C2201/0493—Tin
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
- F05C—INDEXING SCHEME RELATING TO MATERIALS, MATERIAL PROPERTIES OR MATERIAL CHARACTERISTICS FOR MACHINES, ENGINES OR PUMPS OTHER THAN NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES
- F05C2201/00—Metals
- F05C2201/04—Heavy metals
- F05C2201/0469—Other heavy metals
- F05C2201/0496—Zinc
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
- F05C—INDEXING SCHEME RELATING TO MATERIALS, MATERIAL PROPERTIES OR MATERIAL CHARACTERISTICS FOR MACHINES, ENGINES OR PUMPS OTHER THAN NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES
- F05C2253/00—Other material characteristics; Treatment of material
- F05C2253/12—Coating
Definitions
- the present invention relates generally to a compressor (eg US-A-5056417) according to the preamble of claim 1.
- a reciprocating compressor for example, as shown in Figure 10, is typically employed in air conditioners for automobiles and the like.
- This compressor has a pair of cylinder blocks 30 and 31 combined with each other.
- a swash plate chamber 32 is defined between these cylinder blocks 30 and 31.
- Housings 35 and 36 are attached to the outer end faces of the cylinder blocks 30 and 31 via valve plates 33 and 34, respectively.
- An intake chamber 36 and a discharge chamber 37 are defined between the valve plate 33 and the housing 35 and also between the valve plate 34 and the housing 36.
- the drive shaft 39 is rotatably supported in these cylinder blocks 30 and 31.
- a swash plate 40 serving as a cam is fixed, in the swash plate chamber 32, to the drive shaft 39.
- a plural pairs of cylinder bores 41 and 42 are defined in the cylinder blocks 30 and 31 around the drive shaft 39.
- a double-headed piston 43 is housed in each pair of cylinder bores 41 and 42.
- Shoes 44 which serve as cam followers, are located between the swash plate 40 and each piston 43.
- Each shoe 44 has a sliding surface 45 that makes sliding contact with the front face or rear face of the swash plate 40 and a spherical surface 47 that makes sliding contact with a receiving recess 46 of the piston 43.
- each piston 43 is reciprocated in the cylinder bores 41, 42 via the shoes 44 under the action of the swash plate 40.
- a refrigerant gas is introduced from the intake chamber 37 to the cylinder bores 41 and 42 as each piston 43 moves from the top dead center to the bottom dead center.
- the refrigerant gas introduced into the cylinder bores 41 and 42 is compressed as the piston 43 moves from the bottom dead center to the top dead center and is discharged to the discharge chamber 38.
- the size of the cylinder bores 41 and 42 and increasing the sizes of the pistons 43, swash plate 40 and shoes 44 is contemplated.
- the pistons 43 and the swash plate 40 are generally made of a light aluminum alloy or the like. However, these members, which are made of the same metallic material, may seize. Accordingly, shoes 44 made of a ferrous metal are located between the pistons 43 and the swash plate 40 to prevent seizure between the pistons 43 and the swash plate 40. However, since ferrous metals have high specific gravity, the increase in the size of the shoes 44 increases the total weight of the compressor.
- a refrigerant gas is introduced from an external refrigerant circuit via the swash plate chamber 32 into the intake chamber 37.
- the refrigerant gas introduced into the swash plate chamber 32 cools each part in the swash plate chamber 32 and also prevents pulsation caused by the introduction of the refrigerant into the cylinder bores 41 and 42.
- R134a CF3CH2F
- Chlorine is used as an extreme-pressure additive.
- An "extreme-pressure additive” is a substance that reacts with the surface of a metal and forms a metallic compound film to reduce frictional resistance.
- the refrigerant gas introduced into the swash plate chamber 32 washes off, by its own action, lubricant located on the surfaces of the swash plate 40 and other parts, so that lubrication between the shoes 44 and the pistons 43 and swash plate 40 is not easily achieved.
- chlorine serving as the extreme-pressure additive, is not present in the refrigerant gas molecules, a great sliding resistance exists.
- the compressor according to the present invention has cylinder blocks containing cylinder bores.
- a drive shaft is rotatably supported in the cylinder blocks.
- a cam is attached to the drive shaft to be rotatable integrally therewith.
- a piston is slidably housed in the cylinder bores.
- a cam follower is slidably held between the piston and the cam. As the cam rotates, the piston is reciprocated via the cam follower.
- the piston is made of an aluminum or aluminum alloy matrix.
- the piston contains a receiving portion for slidably receiving the cam follower therein.
- a coating layer containing tin as a major component is formed at the receiving portion of the piston.
- the coating layers formed at the receiving portions of the pistons reduce sliding resistance between the receiving portions of the pistons and the cam followers. Accordingly, even if a shortage of a lubricant occurs in the compressor, the cam followers can slide smoothly in the receiving portions of the pistons. Thus, the cam can move the cam followers with a small force. Consequently, the load acting between the cam followers and the cam can be reduced to decrease sliding resistance between them.
- the compressor comprises: a cylinder block containing a cylinder bore; a drive shaft rotatably supported in the cylinder block; a cam attached to the drive shaft to be rotatable integrally therewith; a piston slidably housed in the cylinder bore; and a cam follower slidably interposed between the piston and the cam; the piston being reciprocated via the cam follower as the cam is rotated; the piston being made of an aluminum or aluminum alloy matrix and having a receiving portion for slidably receiving the cam follower therein, with a coating layer containing tin as a major component being formed at the receiving portion of the piston.
- the cam follower may made of a ferrous metal matrix and have a first sliding portion slidably retained in the piston and a second sliding portion to be brought into slide contact with the cam; at least one of the first sliding portion and the second sliding portion having a coating layer containing tin as a major component.
- the compressor may comprise a piston having an outer circumference to be brought into slide contact with the inner circumference of the cylinder bore and the coating layer is also formed on the outer circumference of the piston.
- the cam may have a sliding portion to be brought into slide contact with the cam follower, with a coating layer containing tin as a major component being formed at the sliding portion.
- the cam further may have to be brought into slide contact with the second sliding portion of the cam follower, with a coating layer containing tin as a major component being formed at the sliding portion.
- the mentioned coating layer may contain at least one metal selected from the group consisting of copper, nickel, zinc, lead and indium.
- the cam follower may be a shoe having a spherical surface and the receiving portion of the piston is a recess which slidably receives the spherical surface of the shoe therein.
- the coating layer may contain one kind of solid lubricant selected from the group consisting of a fluororesin powder, a molybdenum disulfide powder, a carbon powder and a boron nitride powder.
- a swash plate type compressor according to a first embodiment of the present invention will be described below referring to Figure 1 to Figure 4.
- the mechanical construction of the compressor of the first embodiment is substantially the same as that of the compressor shown in Figure 10, which was described with reference to the prior art. Therefore, like or the same components as those in the compressor shown in Figure 10 are affixed with the same reference numbers, respectively, and a description of them will be omitted. Therefore, only differences from the compressor shown in Figure 10 will be described.
- each piston 1 has a coating layer 6 containing tin as a major component formed over its entire surface.
- Each piston 1 has a pair of receiving recesses 2 which slidably receive spherical surfaces of shoes 44.
- the piston 1 consists of a main body 5 made of an aluminum or aluminum alloy matrix and a coating layer 6 formed over the entire surface of the main body 5.
- the aluminum alloy for example, an Al-Si alloy or an Al-Si-Cu alloy can be suitably employed.
- the main body 5 is preferably an aluminum alloy matrix containing hard particles.
- Such aluminum alloy is typified by an aluminum-high silicon alloy.
- the aluminum-high silicon alloy contains about 10 to 30 % by weight of silicon. If the aluminum-high silicon alloy has a silicon content not exceeding the level at which a eutectic mixture is formed, the silicon can be present in the form of eutectic silicon (i.e., the hard particles).
- the main body 5 of the piston 1 is made of a matrix of aluminum-high silicon alloy 4 containing 12 % by weight of silicon 3.
- materials containing hard particles include, an Al-Mn intermetallic compound, an Al-Si-Mn intermetallic compound, an Al-Fe-Mn intermetallic compound and an Al-Cr intermetallic compound, and these materials may be used as the matrix of the main body 5.
- the shoes 44 are made of SUJ2 material (a steel material for a high carbon content chromium bearing) specified by JIS, while the swash plate 40 is made of an aluminum-high silicon alloy.
- the pistons 1 to be employed in the compressor of the first embodiment may be suitably selected, for example, from Examples 1 to 9 having various type of coating layers 6, respectively, as described below. Pistons 1 of Examples 1 to 9 will be described one by one. In Examples 1 to 9, the main bodies 5 of the pistons 1 are of the same structure, and the coating layers 6 have different compositions.
- the piston 1 of Example 1 has a tin-copper eutectoid plating layer as the coating layer 6.
- This coating layer 6 is formed as follows. The entire main body 5 is immersed in an aqueous solution containing 6 % by weight of potassium stannate and 0.012 % by weight of copper gluconate maintained at 60 to 80 DEG C is to effect electroless plating on the surface of the main body 5. Subsequently, the main body 5 is taken out of the aqueous solution and rinsed. Thus, a eutectoid plating layer of tin and copper is formed as the coating layer 6 over the entire surface of the piston 1, including the receiving recesses 2, which contact the shoes 44.
- the coating layer 6 contains 97 % by weight of tin and 3 % by weight of copper and has a thickness of 1.2 ⁇ m.
- the piston 1 of Example 2 has a tin-nickel eutectoid plating layer as the coating layer 6.
- a eutectoid plating layer of tin and nickel is formed as the coating layer 6 over the entire surface of the piston 1 including the receiving recesses 2 by employing an aqueous solution containing 6 % by weight of potassium stannate and 0.005 % by weight of nickel chloride in the same manner as in Example 1.
- the coating layer 6 contains 98 % by weight of tin and 2 % by weight of nickel and has a thickness of 1 ⁇ m.
- the piston 1 of Example 3 has a tin-zinc eutectoid plating layer as the coating layer 6.
- a eutectoid plating layer of tin and zinc is formed as the coating layer 6 over the entire surface of the piston 1 including the receiving recesses 2 by employing an aqueous solution containing 6 % by weight of potassium stannate and 0.005 % by weight of zinc sulfate in the same manner as in Example 1.
- the coating layer 6 contains 97 % by weight of tin and 3 % by weight of zinc and has a thickness of 1 ⁇ m.
- the piston 1 of Example 4 has a tin-lead eutectoid plating layer as the coating layer 6.
- a eutectoid plating layer of tin and lead is formed as the coating layer 6 over the entire surface of the piston 1 including the receiving recesses 2 by employing an aqueous solution containing 6 % by weight of potassium stannate and 0.007 % by weight of lead sulfate in the same manner as in Example 1.
- the coating layer 6 contains 95 % by weight of tin and 5 % by weight of lead and has a thickness of 2 ⁇ m.
- the piston 1 of Example 5 has a tin-indium eutectoid plating layer as the coating layer 6.
- a eutectoid plating layer of tin and indium is formed as the coating layer 6 over the entire surface of the piston 1 including the receiving recesses 2 by employing an aqueous solution containing 6 % by weight of potassium stannate and 0.005 % by weight of indium sulfate in the same manner as in Example 1.
- the coating layer 6 contains 97 % by weight of tin and 3 % by weight of indium and has a thickness of 1 ⁇ m.
- the piston 1 of Example 6 has a plating layer containing only tin as the coating layer 6. Specifically, a plating layer of only tin is formed as the coating layer 6 over the entire surface of the piston 1 including the receiving recesses 2 by employing an aqueous solution containing 6 % by weight of potassium stannate in the same manner as in Example 1.
- the coating layer 6 has a thickness of 1.5 ⁇ m.
- the piston 1 of Example 7 has, as the coating layer 6, a tin-copper eutectoid plating layer containing a fluororesin powder as a solid lubricant.
- a eutectoid plating layer of tin and copper containing a fluororesin powder is formed as the coating layer 6 over the entire surface of the piston 1 including the receiving recesses 2 by employing an aqueous solution containing 6 % by weight of potassium stannate, 0.003 % by weight of copper gluconate and 1.0 % by weight of a fluororesin powder in the same manner as in Example 1.
- the coating layer 6 contains 99 % by weight of tin, 0.9 % by weight of copper and 0.1 % by weight of the fluororesin powder and has a thickness of 1.4 ⁇ m.
- Example 8 While the piston 1 of Example 8 has a tin-copper eutectoid plating layer like the coating layer 6 in Example I, the coating layer 6, which is formed by chemical plating treatment in the same manner as in Example 1, is subjected to heat treatment at a temperature of 150° C for one hour.
- the piston 1 of Example 9 has a tin-copper-zinc eutectoid plating layer as the coating layer 6.
- a eutectoid plating layer of tin, copper and zinc is formed as the coating layer 6 over the entire surface of the piston 1, including the receiving recesses 2, by employing an aqueous solution containing 6 % by weight of potassium stannate, 0.003 % by weight of copper gluconate and 0.003 % by weight of zinc sulfate in the same manner as in Example 1.
- the coating layer 6 contains 97 % by weight of tin, 1.5 % by weight of copper and 1.5 % by weight of zinc and has a thickness of 1.2 ⁇ m.
- Figure 4 is a graph showing the results of this test.
- the test results shown in Figure 4 demonstrate that seizure between the shoes 44 and the swash plates 40 takes much longer under severe use conditions in the compressors employing the pistons 1 of Examples 1 to 9 having the coating layers 6 compared with the compressor of the comparative example.
- a coating layer 6 containing tin as a major component is formed on the surface of each piston 1.
- Tin is a self-lubricating substance. Accordingly, sliding resistance between the receiving recesses 2 of the piston 1 and the spherical surfaces 47 of the shoes 44 is reduced, and even when there is a shortage of lubricant in the compressor, the shoes 44 can move smoothly along the inner surfaces of the receiving recesses 2. Accordingly, the swash plate 40 can move the shoes 44 within the receiving recesses 2 with a small force. As a result, the load acting between the sliding surface 45 of each shoe 44 and the swash plate 40 is moderated to reduce sliding resistance between the sliding surface 45 and the swash plate 40. Therefore, when the discharge capacity of a compressor is to be increased, even if the sizes of the pistons 1 and of the swash plate 40 are increased without increasing the size of the shoes 44, no problems arise due to an increase in the sliding resistance.
- the coating layer 6 is formed over the entire surface of each piston 1. Accordingly, the sliding resistance between the outer circumference of the piston 1 and the inner circumferences of the cylinder bores 41 and 42 is reduced to allow smooth movement of the piston in the cylinder bores 41 and 42.
- the coating layer 6 By incorporating at least one metal selected from copper, nickel, zinc, lead and indium in the coating layer 6 that contains tin as the major component, not only can the coating layer 6 be densified, but a hard metallic compound can be dispersed throughout the coating layer 6 to reinforce it. This reduces the coefficient of friction and abrasion resistance.
- a hard tin-copper compound Cu 6 Sn 5
- the coating layer 6 is formed by means of chemical plating. With this chemical plating method, a eutectic mixture of tin and other metals, such as copper, can be easily deposited, and a solid lubricant, such as a fluororesin powder, can be easily incorporated into the coating layer 6.
- the compressor according to the second embodiment unlike the compressor shown in Figure 10, has shoes 7, each having a coating layer 11, containing tin as a major component, formed over its entire surface.
- the main body 12 of each shoe 7 is made of SUJ2 material as specified in JIS.
- the shoe 7 has a spherical surface 8 that slidably engages a receiving recess 46 of the piston 43 and a sliding surface 10, which makes sliding contact with the front face or rear face of the swash plate 40.
- the spherical surface 8 of the shoe 7 has a spherical portion 9 having a radius of curvature greater than that of the rest of the surface 8.
- An oil reservoir for storing a lubricant therein is defined between this spherical portion 9 and each receiving recess 46 of the piston 43.
- the sliding surface 10 of the shoe 7 is slightly tapered toward the periphery to have a convex-like shape to permit easy entry of lubricant into the clearance between the sliding surface 10 and the swash plate 40.
- both the swash plate 40 and the pistons 43 are made of an aluminum-high silicon alloy.
- suitable shoes 7 can be selected from those having various coating layers 11 as shown in the following Examples 1 to 9.
- the shoes 7 of Examples 1 to 9 will be described one by one.
- the main bodies 12 of the shoes 7 of Examples 1 to 9 are all the same, and only the coating layers 11 are different from one another.
- the shoe 7 of Example 1 has a tin-copper eutectoid plating layer as the coating layer 11.
- This coating layer 11 is formed as follows.
- the main body 12 of the shoe 7 is immersed in an aqueous solution containing 6 % by weight of potassium stannate and 0.012 % by weight of copper gluconate. In this state, the main body 12 is connected to a cathode, and a metal bar having a high ionization tendency is used as an anode.
- a predetermined voltage is applied between these electrodes using the thus prepared aqueous solution as an electrolyte, tin and copper are separated out under electrolytic action to adhere intimately to the surface of the main body 12.
- the main body 12 is taken out of the aqueous solution and rinsed.
- a eutectoid plating layer of tin and copper is formed as the coating layer 11 over the entire surface of the shoe 7.
- the shoe 7 thus plated is then surface polished while taking the clearance between the swash plate 40, with which the shoe 7 is used, and the piston 43 into consideration to have a uniform coating layer 11.
- the coating layer 11 contains 97 % by weight of tin and 3 % by weight of copper and has a thickness of 1.2 ⁇ m.
- the shoe 7 of Example 2 has a tin-nickel eutectoid plating layer as the coating layer 11.
- a eutectoid plating layer of tin and nickel is formed as the coating layer 11 over the entire surface of the shoe 7 by employing an aqueous solution containing 6 % by weight of potassium stannate and 0.005 % by weight of nickel chloride in the same manner as in Example 1.
- the coating layer 11 contains 98 % by weight of tin and 2 % by weight of nickel, and the thickness of the coating layer 11 is adjusted to 1 ⁇ m by surface polishing.
- the shoe 7 of Example 3 has a tin-zinc eutectoid plating layer as the coating layer 11.
- a eutectoid plating layer of tin and zinc is formed as the coating layer 11 over the entire surface of the shoe 7 by employing an aqueous solution containing 6 % by weight of potassium stannate and 0.005 % by weight of zinc sulfate in the same manner as in Example 1.
- the coating layer 11 contains 97 % by weight of tin and 3 % by weight of zinc, and the thickness of the coating layer 11 is adjusted to 1 ⁇ m by surface polishing.
- the shoe 7 of Example 4 has a tin-lead eutectoid plating layer as the coating layer 11.
- a eutectoid plating layer of tin and lead is formed as the coating layer 11 over the entire surface of the shoe 7 by employing an aqueous solution containing 6 % by weight of potassium stannate and 0.007 % by weight of lead sulfate in the same manner as in Example 1.
- the coating layer 11 contains 95 % by weight of tin and 5 % by weight of lead, and the thickness of the coating layer 11 is adjusted to 2 ⁇ m by surface polishing.
- the shoe 7 of Example 5 has a tin-indium eutectoid plating layer as the coating layer 11.
- a eutectoid plating layer of tin and indium is formed as the coating layer 11 over the entire surface of the shoe 7 by employing an aqueous solution containing 6 % by weight of potassium stannate and 0.005 % by weight of indium sulfate in the same manner as in Example 1.
- the coating layer 11 contains 97 % by weight of tin and 3 % by weight of indium, and the thickness of the coating layer 11 is adjusted to 1 ⁇ m by surface polishing.
- the shoe 7 of Example 6 has a plating layer containing tin only as the coating layer 11. Specifically, a plating layer of tin only is formed as the coating layer 11 over the entire surface of the shoe 7 by employing an aqueous solution containing 6 % by weight of potassium stannate in the same manner as in Example 1. The thickness of the coating layer 11 is adjusted to 1.5 ⁇ m by surface polishing.
- the shoe 7 of Example 7 has a tin-copper eutectoid plating layer containing a molybdenum disulfide powder as a solid lubricant as the coating layer 11.
- a eutectoid plating layer of tin and zinc containing the molybdenum disulfide powder is formed as the coating layer 11 over the entire surface of the shoe 7 by employing an aqueous solution containing 6 % by weight of potassium stannate, 0.003 % by weight of copper gluconate and 1.0 % by weight of the molybdenum disulfide powder in the same manner as in Example 1.
- the coating layer 11 contains 99 % by weight of tin, 0.9 % by weight of copper and 0.1 % by weight of the molybdenum disulfide powder, and the thickness of the coating layer 11 is adjusted to 1.4 ⁇ m by surface polishing.
- Example 8 While the shoe 7 of Example 8 has a tin-copper eutectoid plating layer as the coating layer 11 like in Example 1, the coating layer 11, which is formed by electrolytic plating treatment and polished in the same manner as in Example 1, is subjected to heat treatment at a temperature of 150° C for one hour.
- the shoe 7 of Example 9 has a tin-copper-zinc eutectoid plating layer as the coating layer 11.
- a eutectoid plating layer of tin, copper and zinc is formed as the coating layer 11 over the entire surface of the shoe 7 by employing an aqueous solution containing 6 % by weight of potassium stannate, 0.003 % by weight of copper gluconate and 0.003 % by weight of zinc sulfate in the same manner as in Example 1.
- the coating layer 11 contains 97 % by weight of tin, 1.5 % by weight of copper and 1.5 % by weight of zinc, and the thickness of the coating layer 11 is adjusted to 1.2 ⁇ m by surface polishing.
- the present inventors performed the following test to confirm the anti-seizure performance of compressors using the shoes 7 of Examples 1 to 9, respectively.
- the time until seizure between the swash plate 40 and the shoes 7 was measured while each compressor, which was incorporated into an automotive air conditioner, was operated under severe conditions (where no lubricant is present in the compressor).
- the compressors were operated continuously in this test under the following conditions; intake pressure: -0.5 kg/cm 2 , discharge pressure: 3 kg/cm 2 , revolutions of the drive shaft 39: 1000 rpm.
- the swash plates 40 and the pistons 43 of the compressors were made of an aluminum-high silicon alloy.Further, in carrying out this test, a compressor using shoes made of an SUJ2 material only, i.e., shoes having no coating layer 11, was provided as a comparative example and tested in the same manner as described above.
- Figure 6 is a graph showing the results of this test.
- the test results shown in Figure 6 demonstrate that seizure between the shoes 7 and the swash plates 40 takes much longer under severe use conditions in the compressors employing the shoes 7 of Examples 1 to 9 having the coating layers 11 compared with the compressor of the comparative example.
- a coating layer 11 containing tin as a major component is formed on the surface of each shoe 7. Accordingly, sliding resistance between the receiving recesses 46 of the piston 43 and the spherical surfaces 8 of the shoes 7 is reduced, and the sliding resistance between the swash plate 40 and the sliding surface 10 of the shoe 7 is reduced. Accordingly, even when there is a shortage of lubricant in the compressor, smooth sliding of the swash plate 40 and the pistons 43 can be guarantied at the joints thereof to control sliding resistance at the joints.
- the shoes 44 can move smoothly along the inner surfaces of the receiving recesses 46 under the action of the coating layer 11 formed on the spherical surfaces 8. As a result, the load acting between the sliding surface 10 of each shoe 7 and the swash plate 40 is moderated to reduce sliding resistance between the sliding surface 10 and the swash plate 40.
- the coating layer 11 is also present on the sliding surface 10 of the shoe 7, thus, the sliding resistance between the sliding surface 10 and the swash plate 40 can be further reduced. Therefore, when the discharge capacity of a compressor is to be increased, even if the sizes of the pistons 43 and the swash plate 40 are increased without changing the size of the shoes 7, no problems arise due to an increase in the sliding resistance.
- the coating layer 11 that contains tin as the major component formed on the surface of each shoe 7, which is made of a ferrous metal, can protect the shoe 7 from rusting.
Description
- The present invention relates generally to a compressor (eg US-A-5056417) according to the preamble of
claim 1. - A reciprocating compressor, for example, as shown in Figure 10, is typically employed in air conditioners for automobiles and the like. This compressor has a pair of
cylinder blocks swash plate chamber 32 is defined between thesecylinder blocks Housings cylinder blocks valve plates intake chamber 36 and adischarge chamber 37 are defined between thevalve plate 33 and thehousing 35 and also between thevalve plate 34 and thehousing 36. - The
drive shaft 39 is rotatably supported in thesecylinder blocks swash plate 40 serving as a cam is fixed, in theswash plate chamber 32, to thedrive shaft 39. A plural pairs ofcylinder bores cylinder blocks drive shaft 39. A double-headed piston 43 is housed in each pair ofcylinder bores Shoes 44, which serve as cam followers, are located between theswash plate 40 and eachpiston 43. Eachshoe 44 has a slidingsurface 45 that makes sliding contact with the front face or rear face of theswash plate 40 and aspherical surface 47 that makes sliding contact with a receivingrecess 46 of thepiston 43. - In the compressor described above, when the
swash plate 40 is rotated with the rotation of thedrive shaft 39, eachpiston 43 is reciprocated in thecylinder bores shoes 44 under the action of theswash plate 40. When thepiston 43 is reciprocated, a refrigerant gas is introduced from theintake chamber 37 to thecylinder bores piston 43 moves from the top dead center to the bottom dead center. Then, the refrigerant gas introduced into thecylinder bores piston 43 moves from the bottom dead center to the top dead center and is discharged to thedischarge chamber 38. - Generally, in order to increase the discharge capacity of a compressor, increasing the size of the
cylinder bores pistons 43,swash plate 40 andshoes 44 is contemplated. Thepistons 43 and theswash plate 40 are generally made of a light aluminum alloy or the like. However, these members, which are made of the same metallic material, may seize. Accordingly,shoes 44 made of a ferrous metal are located between thepistons 43 and theswash plate 40 to prevent seizure between thepistons 43 and theswash plate 40. However, since ferrous metals have high specific gravity, the increase in the size of theshoes 44 increases the total weight of the compressor. - Assume that only the size of the
pistons 43 and that of theswash plate 40 are increased, without changing the size of theshoes 44, in order to increase the discharge capacity. However, if the discharge capacity is increased, the load applied by thepistons 43 via theshoes 44 to theswash plate 40 is also increased. Accordingly, if the size of theshoes 44 remains unchanged, the load applied per unit area of thespherical surfaces 47 and that of thesliding surfaces 45 of theshoes 44 is increased. Consequently, the sliding resistance between thespherical surfaces 47 of theshoes 44 and thereceiving recesses 46 defined in thepistons 43 and the sliding resistance between thesliding surfaces 45 of theshoes 44 and theswash plate 40 are increased. - If the sliding resistance between the
spherical surfaces 47 of theshoes 44 and thereceiving recesses 46 of thepiston 43 is increased, theshoes 44 cannot move smoothly along the inner surfaces of the shoe retainingrecesses 46. The shoes are moved by theswash plate 40 within thereceiving recesses 46. If the shoes cannot move smoothly, the load applied between thesliding surfaces 45 of theshoes 44 and theswash plate 40 is increased, which further increase the sliding resistance between thesliding surfaces 45 of theshoes 44 and theswash plate 40. - In the compressor described above, a refrigerant gas is introduced from an external refrigerant circuit via the
swash plate chamber 32 into theintake chamber 37. The refrigerant gas introduced into theswash plate chamber 32 cools each part in theswash plate chamber 32 and also prevents pulsation caused by the introduction of the refrigerant into thecylinder bores swash plate chamber 32 washes off, by its own action, lubricant located on the surfaces of theswash plate 40 and other parts, so that lubrication between theshoes 44 and thepistons 43 andswash plate 40 is not easily achieved. In such cases, if chlorine, serving as the extreme-pressure additive, is not present in the refrigerant gas molecules, a great sliding resistance exists. - Therefore, it is an objective of the present invention to provide a reciprocating compressor that reduces the sliding resistance at the cam-piston joints.
- The object is achieved by the features of
claim 1. The compressor according to the present invention has cylinder blocks containing cylinder bores. A drive shaft is rotatably supported in the cylinder blocks. A cam is attached to the drive shaft to be rotatable integrally therewith. A piston is slidably housed in the cylinder bores. A cam follower is slidably held between the piston and the cam. As the cam rotates, the piston is reciprocated via the cam follower. The piston is made of an aluminum or aluminum alloy matrix. The piston contains a receiving portion for slidably receiving the cam follower therein. A coating layer containing tin as a major component is formed at the receiving portion of the piston. - Therefore, according to the present invention, the coating layers formed at the receiving portions of the pistons reduce sliding resistance between the receiving portions of the pistons and the cam followers. Accordingly, even if a shortage of a lubricant occurs in the compressor, the cam followers can slide smoothly in the receiving portions of the pistons. Thus, the cam can move the cam followers with a small force. Consequently, the load acting between the cam followers and the cam can be reduced to decrease sliding resistance between them.
- The compressor comprises: a cylinder block containing a cylinder bore; a drive shaft rotatably supported in the cylinder block; a cam attached to the drive shaft to be rotatable integrally therewith; a piston slidably housed in the cylinder bore; and a cam follower slidably interposed between the piston and the cam; the piston being reciprocated via the cam follower as the cam is rotated; the piston being made of an aluminum or aluminum alloy matrix and having a receiving portion for slidably receiving the cam follower therein, with a coating layer containing tin as a major component being formed at the receiving portion of the piston.
- Further, the cam follower may made of a ferrous metal matrix and have a first sliding portion slidably retained in the piston and a second sliding portion to be brought into slide contact with the cam; at least one of the first sliding portion and the second sliding portion having a coating layer containing tin as a major component.
- The compressor may comprise a piston having an outer circumference to be brought into slide contact with the inner circumference of the cylinder bore and the coating layer is also formed on the outer circumference of the piston.
- The cam may have a sliding portion to be brought into slide contact with the cam follower, with a coating layer containing tin as a major component being formed at the sliding portion.
- The cam further may have to be brought into slide contact with the second sliding portion of the cam follower, with a coating layer containing tin as a major component being formed at the sliding portion.
- The mentioned coating layer may contain at least one metal selected from the group consisting of copper, nickel, zinc, lead and indium.
- The cam follower may be a shoe having a spherical surface and the receiving portion of the piston is a recess which slidably receives the spherical surface of the shoe therein.
- The coating layer may contain one kind of solid lubricant selected from the group consisting of a fluororesin powder, a molybdenum disulfide powder, a carbon powder and a boron nitride powder.
-
- Figure 1 is an enlarged cross-sectional view of a pertinent portion of a swash plate type compressor according to a first embodiment of the present invention;
- Figure 2 is a perspective view showing a piston in the first embodiment;
- Figure 3 is an enlarged cross-sectional view of a pertinent portion of the piston;
- Figure 4 is a graph showing measurement results of time until seizure that occurred with the first embodiment;
- Figure 5 is an enlarged cross-sectional view of a pertinent portion of a swash-plate type compressor according to a second embodiment of the invention;
- Figure 6 is a graph showing measurement results of time until seizure that occurred with the second embodiment;
- Figure 7 is a cross-sectional view showing a wave cam type compressor according to another embodiment of the invention;
- Figure 8 is an enlarged cross-sectional view of a pertinent portion of a cam follower according to another embodiment of the invention;
- Figure 9 is an enlarged cross-sectional view of a pertinent portion of a swash plate according to another embodiment of the invention; and
- Figure 10 is a cross-sectional view of a prior art swash-plate type compressor.
-
- A swash plate type compressor according to a first embodiment of the present invention will be described below referring to Figure 1 to Figure 4. It should be noted here that the mechanical construction of the compressor of the first embodiment is substantially the same as that of the compressor shown in Figure 10, which was described with reference to the prior art. Therefore, like or the same components as those in the compressor shown in Figure 10 are affixed with the same reference numbers, respectively, and a description of them will be omitted. Therefore, only differences from the compressor shown in Figure 10 will be described.
- As shown in Figures 1 to 3, the compressor according to the first embodiment, unlike the compressor shown in Figure 10, each
piston 1 has acoating layer 6 containing tin as a major component formed over its entire surface. Eachpiston 1 has a pair of receivingrecesses 2 which slidably receive spherical surfaces ofshoes 44. - The
piston 1 consists of amain body 5 made of an aluminum or aluminum alloy matrix and acoating layer 6 formed over the entire surface of themain body 5. As the aluminum alloy, for example, an Al-Si alloy or an Al-Si-Cu alloy can be suitably employed. Themain body 5 is preferably an aluminum alloy matrix containing hard particles. Such aluminum alloy is typified by an aluminum-high silicon alloy. The aluminum-high silicon alloy contains about 10 to 30 % by weight of silicon. If the aluminum-high silicon alloy has a silicon content not exceeding the level at which a eutectic mixture is formed, the silicon can be present in the form of eutectic silicon (i.e., the hard particles). In the first embodiment, themain body 5 of thepiston 1 is made of a matrix of aluminum-high silicon alloy 4 containing 12 % by weight ofsilicon 3. - Incidentally, other materials containing hard particles include, an Al-Mn intermetallic compound, an Al-Si-Mn intermetallic compound, an Al-Fe-Mn intermetallic compound and an Al-Cr intermetallic compound, and these materials may be used as the matrix of the
main body 5. - Further, in the first embodiment, the
shoes 44 are made of SUJ2 material (a steel material for a high carbon content chromium bearing) specified by JIS, while theswash plate 40 is made of an aluminum-high silicon alloy. - The
pistons 1 to be employed in the compressor of the first embodiment may be suitably selected, for example, from Examples 1 to 9 having various type ofcoating layers 6, respectively, as described below.Pistons 1 of Examples 1 to 9 will be described one by one. In Examples 1 to 9, themain bodies 5 of thepistons 1 are of the same structure, and the coating layers 6 have different compositions. - The
piston 1 of Example 1 has a tin-copper eutectoid plating layer as thecoating layer 6. Thiscoating layer 6 is formed as follows. The entiremain body 5 is immersed in an aqueous solution containing 6 % by weight of potassium stannate and 0.012 % by weight of copper gluconate maintained at 60 to 80 DEG C is to effect electroless plating on the surface of themain body 5. Subsequently, themain body 5 is taken out of the aqueous solution and rinsed. Thus, a eutectoid plating layer of tin and copper is formed as thecoating layer 6 over the entire surface of thepiston 1, including the receiving recesses 2, which contact theshoes 44. Thecoating layer 6 contains 97 % by weight of tin and 3 % by weight of copper and has a thickness of 1.2 µm. - The
piston 1 of Example 2 has a tin-nickel eutectoid plating layer as thecoating layer 6. Specifically, a eutectoid plating layer of tin and nickel is formed as thecoating layer 6 over the entire surface of thepiston 1 including the receiving recesses 2 by employing an aqueous solution containing 6 % by weight of potassium stannate and 0.005 % by weight of nickel chloride in the same manner as in Example 1. Thecoating layer 6 contains 98 % by weight of tin and 2 % by weight of nickel and has a thickness of 1 µm. - The
piston 1 of Example 3 has a tin-zinc eutectoid plating layer as thecoating layer 6. Specifically, a eutectoid plating layer of tin and zinc is formed as thecoating layer 6 over the entire surface of thepiston 1 including the receiving recesses 2 by employing an aqueous solution containing 6 % by weight of potassium stannate and 0.005 % by weight of zinc sulfate in the same manner as in Example 1. Thecoating layer 6 contains 97 % by weight of tin and 3 % by weight of zinc and has a thickness of 1 µm. - The
piston 1 of Example 4 has a tin-lead eutectoid plating layer as thecoating layer 6. Specifically, a eutectoid plating layer of tin and lead is formed as thecoating layer 6 over the entire surface of thepiston 1 including the receiving recesses 2 by employing an aqueous solution containing 6 % by weight of potassium stannate and 0.007 % by weight of lead sulfate in the same manner as in Example 1. Thecoating layer 6 contains 95 % by weight of tin and 5 % by weight of lead and has a thickness of 2 µm. - The
piston 1 of Example 5 has a tin-indium eutectoid plating layer as thecoating layer 6. Specifically, a eutectoid plating layer of tin and indium is formed as thecoating layer 6 over the entire surface of thepiston 1 including the receiving recesses 2 by employing an aqueous solution containing 6 % by weight of potassium stannate and 0.005 % by weight of indium sulfate in the same manner as in Example 1. Thecoating layer 6 contains 97 % by weight of tin and 3 % by weight of indium and has a thickness of 1µm. - The
piston 1 of Example 6 has a plating layer containing only tin as thecoating layer 6. Specifically, a plating layer of only tin is formed as thecoating layer 6 over the entire surface of thepiston 1 including the receiving recesses 2 by employing an aqueous solution containing 6 % by weight of potassium stannate in the same manner as in Example 1. Thecoating layer 6 has a thickness of 1.5 µm. - The
piston 1 of Example 7 has, as thecoating layer 6, a tin-copper eutectoid plating layer containing a fluororesin powder as a solid lubricant. Specifically, a eutectoid plating layer of tin and copper containing a fluororesin powder is formed as thecoating layer 6 over the entire surface of thepiston 1 including the receiving recesses 2 by employing an aqueous solution containing 6 % by weight of potassium stannate, 0.003 % by weight of copper gluconate and 1.0 % by weight of a fluororesin powder in the same manner as in Example 1. Thecoating layer 6 contains 99 % by weight of tin, 0.9 % by weight of copper and 0.1 % by weight of the fluororesin powder and has a thickness of 1.4 µm. - While the
piston 1 of Example 8 has a tin-copper eutectoid plating layer like thecoating layer 6 in Example I, thecoating layer 6, which is formed by chemical plating treatment in the same manner as in Example 1, is subjected to heat treatment at a temperature of 150° C for one hour. - The
piston 1 of Example 9 has a tin-copper-zinc eutectoid plating layer as thecoating layer 6. Specifically, a eutectoid plating layer of tin, copper and zinc is formed as thecoating layer 6 over the entire surface of thepiston 1, including the receiving recesses 2, by employing an aqueous solution containing 6 % by weight of potassium stannate, 0.003 % by weight of copper gluconate and 0.003 % by weight of zinc sulfate in the same manner as in Example 1. Thecoating layer 6 contains 97 % by weight of tin, 1.5 % by weight of copper and 1.5 % by weight of zinc and has a thickness of 1.2 µm. - The present inventors performed the following test so as to confirm anti-seizure performance of compressors using the
pistons 1 of Examples 1 to 9 respectively. In this test, the time until seizure between theswash plate 40 and theshoes 44 was measured while each compressor, which was incorporated into an automotive air conditioner, was operated under severe conditions (where no lubricant is present in the compressor). The compressors were operated in this test under the following conditions; intake pressure: -0.5 kg/cm2, discharge pressure: 3 kg/cm2, revolutions of the drive shaft 39: 1000 rpm. Further, theshoes 44 were made of an SUJ2 (JIS) material, and theswash plates 40 were made of an aluminum-high silicon alloy. Further, in carrying out this test, a compressor using pistons made only of an aluminum-high silicon alloy 4 containing 12 % by weight ofsilicon 3, i.e., pistons having nocoating layer 6, was provided as a comparative example and tested in the same manner as described above. - Figure 4 is a graph showing the results of this test. The test results shown in Figure 4 demonstrate that seizure between the
shoes 44 and theswash plates 40 takes much longer under severe use conditions in the compressors employing thepistons 1 of Examples 1 to 9 having the coating layers 6 compared with the compressor of the comparative example. In particular, the compressor incorporated with thepistons 1 of Example 1, each having a tin-copper eutectoid plating layer as thecoating layer 6, shows the best anti-seizure performance. - As described above, in the first embodiment, a
coating layer 6 containing tin as a major component is formed on the surface of eachpiston 1. Tin is a self-lubricating substance. Accordingly, sliding resistance between the receivingrecesses 2 of thepiston 1 and thespherical surfaces 47 of theshoes 44 is reduced, and even when there is a shortage of lubricant in the compressor, theshoes 44 can move smoothly along the inner surfaces of the receiving recesses 2. Accordingly, theswash plate 40 can move theshoes 44 within the receivingrecesses 2 with a small force. As a result, the load acting between the slidingsurface 45 of eachshoe 44 and theswash plate 40 is moderated to reduce sliding resistance between the slidingsurface 45 and theswash plate 40. Therefore, when the discharge capacity of a compressor is to be increased, even if the sizes of thepistons 1 and of theswash plate 40 are increased without increasing the size of theshoes 44, no problems arise due to an increase in the sliding resistance. - The
coating layer 6 is formed over the entire surface of eachpiston 1. Accordingly, the sliding resistance between the outer circumference of thepiston 1 and the inner circumferences of the cylinder bores 41 and 42 is reduced to allow smooth movement of the piston in the cylinder bores 41 and 42. - By incorporating at least one metal selected from copper, nickel, zinc, lead and indium in the
coating layer 6 that contains tin as the major component, not only can thecoating layer 6 be densified, but a hard metallic compound can be dispersed throughout thecoating layer 6 to reinforce it. This reduces the coefficient of friction and abrasion resistance. For example, when copper is incorporated into thecoating layer 6 that contains tin as the major component, thecoating layer 6 is densified and a hard tin-copper compound (Cu6Sn5) is dispersed throughout thecoating layer 6 to reinforce it. - The
coating layer 6 is formed by means of chemical plating. With this chemical plating method, a eutectic mixture of tin and other metals, such as copper, can be easily deposited, and a solid lubricant, such as a fluororesin powder, can be easily incorporated into thecoating layer 6. - Next, a swash plate type compressor according to a second embodiment of the invention will be described referring to Figures 5 and 6. It should be noted here that the mechanical constitution of the compressor of the second embodiment is substantially the same as that of the compressor shown in Figure 10 described referring to the prior art. Therefore, like or the same components as those in the compressor shown in Figure 10 are affixed with the same reference numbers respectively, and description of them will be omitted. Therefore, only the differences from the compressor shown in Figure 10 will be described.
- As shown in Figure 5, the compressor according to the second embodiment, unlike the compressor shown in Figure 10, has
shoes 7, each having acoating layer 11, containing tin as a major component, formed over its entire surface. Themain body 12 of eachshoe 7 is made of SUJ2 material as specified in JIS. Theshoe 7 has aspherical surface 8 that slidably engages a receivingrecess 46 of thepiston 43 and a slidingsurface 10, which makes sliding contact with the front face or rear face of theswash plate 40. Thespherical surface 8 of theshoe 7 has aspherical portion 9 having a radius of curvature greater than that of the rest of thesurface 8. An oil reservoir for storing a lubricant therein is defined between thisspherical portion 9 and each receivingrecess 46 of thepiston 43. The slidingsurface 10 of theshoe 7 is slightly tapered toward the periphery to have a convex-like shape to permit easy entry of lubricant into the clearance between the slidingsurface 10 and theswash plate 40. - Further, in the second embodiment, both the
swash plate 40 and thepistons 43 are made of an aluminum-high silicon alloy. - In the compressor of the second embodiment,
suitable shoes 7 can be selected from those havingvarious coating layers 11 as shown in the following Examples 1 to 9. Theshoes 7 of Examples 1 to 9 will be described one by one. Themain bodies 12 of theshoes 7 of Examples 1 to 9 are all the same, and only the coating layers 11 are different from one another. - The
shoe 7 of Example 1 has a tin-copper eutectoid plating layer as thecoating layer 11. Thiscoating layer 11 is formed as follows. Themain body 12 of theshoe 7 is immersed in an aqueous solution containing 6 % by weight of potassium stannate and 0.012 % by weight of copper gluconate. In this state, themain body 12 is connected to a cathode, and a metal bar having a high ionization tendency is used as an anode. When a predetermined voltage is applied between these electrodes using the thus prepared aqueous solution as an electrolyte, tin and copper are separated out under electrolytic action to adhere intimately to the surface of themain body 12. Subsequently, themain body 12 is taken out of the aqueous solution and rinsed. Thus, a eutectoid plating layer of tin and copper is formed as thecoating layer 11 over the entire surface of the shoe 7.Theshoe 7 thus plated is then surface polished while taking the clearance between theswash plate 40, with which theshoe 7 is used, and thepiston 43 into consideration to have auniform coating layer 11. Thecoating layer 11 contains 97 % by weight of tin and 3 % by weight of copper and has a thickness of 1.2µm. - The
shoe 7 of Example 2 has a tin-nickel eutectoid plating layer as thecoating layer 11. Specifically, a eutectoid plating layer of tin and nickel is formed as thecoating layer 11 over the entire surface of theshoe 7 by employing an aqueous solution containing 6 % by weight of potassium stannate and 0.005 % by weight of nickel chloride in the same manner as in Example 1. Thecoating layer 11 contains 98 % by weight of tin and 2 % by weight of nickel, and the thickness of thecoating layer 11 is adjusted to 1 µm by surface polishing. - The
shoe 7 of Example 3 has a tin-zinc eutectoid plating layer as thecoating layer 11. Specifically, a eutectoid plating layer of tin and zinc is formed as thecoating layer 11 over the entire surface of theshoe 7 by employing an aqueous solution containing 6 % by weight of potassium stannate and 0.005 % by weight of zinc sulfate in the same manner as in Example 1. Thecoating layer 11 contains 97 % by weight of tin and 3 % by weight of zinc, and the thickness of thecoating layer 11 is adjusted to 1 µm by surface polishing. - The
shoe 7 of Example 4 has a tin-lead eutectoid plating layer as thecoating layer 11. Specifically, a eutectoid plating layer of tin and lead is formed as thecoating layer 11 over the entire surface of theshoe 7 by employing an aqueous solution containing 6 % by weight of potassium stannate and 0.007 % by weight of lead sulfate in the same manner as in Example 1. Thecoating layer 11 contains 95 % by weight of tin and 5 % by weight of lead, and the thickness of thecoating layer 11 is adjusted to 2 µm by surface polishing. - The
shoe 7 of Example 5 has a tin-indium eutectoid plating layer as thecoating layer 11. Specifically, a eutectoid plating layer of tin and indium is formed as thecoating layer 11 over the entire surface of theshoe 7 by employing an aqueous solution containing 6 % by weight of potassium stannate and 0.005 % by weight of indium sulfate in the same manner as in Example 1. Thecoating layer 11 contains 97 % by weight of tin and 3 % by weight of indium, and the thickness of thecoating layer 11 is adjusted to 1 µm by surface polishing. - The
shoe 7 of Example 6 has a plating layer containing tin only as thecoating layer 11. Specifically, a plating layer of tin only is formed as thecoating layer 11 over the entire surface of theshoe 7 by employing an aqueous solution containing 6 % by weight of potassium stannate in the same manner as in Example 1. The thickness of thecoating layer 11 is adjusted to 1.5 µm by surface polishing. - The
shoe 7 of Example 7 has a tin-copper eutectoid plating layer containing a molybdenum disulfide powder as a solid lubricant as thecoating layer 11. Specifically, a eutectoid plating layer of tin and zinc containing the molybdenum disulfide powder is formed as thecoating layer 11 over the entire surface of theshoe 7 by employing an aqueous solution containing 6 % by weight of potassium stannate, 0.003 % by weight of copper gluconate and 1.0 % by weight of the molybdenum disulfide powder in the same manner as in Example 1. Thecoating layer 11 contains 99 % by weight of tin, 0.9 % by weight of copper and 0.1 % by weight of the molybdenum disulfide powder, and the thickness of thecoating layer 11 is adjusted to 1.4 µm by surface polishing. - While the
shoe 7 of Example 8 has a tin-copper eutectoid plating layer as thecoating layer 11 like in Example 1, thecoating layer 11, which is formed by electrolytic plating treatment and polished in the same manner as in Example 1, is subjected to heat treatment at a temperature of 150° C for one hour. - The
shoe 7 of Example 9 has a tin-copper-zinc eutectoid plating layer as thecoating layer 11. Specifically, a eutectoid plating layer of tin, copper and zinc is formed as thecoating layer 11 over the entire surface of theshoe 7 by employing an aqueous solution containing 6 % by weight of potassium stannate, 0.003 % by weight of copper gluconate and 0.003 % by weight of zinc sulfate in the same manner as in Example 1. Thecoating layer 11 contains 97 % by weight of tin, 1.5 % by weight of copper and 1.5 % by weight of zinc, and the thickness of thecoating layer 11 is adjusted to 1.2 µm by surface polishing. - The present inventors performed the following test to confirm the anti-seizure performance of compressors using the
shoes 7 of Examples 1 to 9, respectively. In this test, the time until seizure between theswash plate 40 and theshoes 7 was measured while each compressor, which was incorporated into an automotive air conditioner, was operated under severe conditions (where no lubricant is present in the compressor). The compressors were operated continuously in this test under the following conditions; intake pressure: -0.5 kg/cm2, discharge pressure: 3 kg/cm2, revolutions of the drive shaft 39: 1000 rpm. Further, theswash plates 40 and thepistons 43 of the compressors were made of an aluminum-high silicon alloy.Further, in carrying out this test, a compressor using shoes made of an SUJ2 material only, i.e., shoes having nocoating layer 11, was provided as a comparative example and tested in the same manner as described above. - Figure 6 is a graph showing the results of this test. The test results shown in Figure 6 demonstrate that seizure between the
shoes 7 and theswash plates 40 takes much longer under severe use conditions in the compressors employing theshoes 7 of Examples 1 to 9 having the coating layers 11 compared with the compressor of the comparative example. In particular, the compressor incorporated with theshoes 7 of Example 1, each having a tin-copper eutectoid plating layer as thecoating layer 11, shows the best anti-seizure performance. - As described above, in the second embodiment, a
coating layer 11 containing tin as a major component is formed on the surface of eachshoe 7. Accordingly, sliding resistance between the receivingrecesses 46 of thepiston 43 and thespherical surfaces 8 of theshoes 7 is reduced, and the sliding resistance between theswash plate 40 and the slidingsurface 10 of theshoe 7 is reduced. Accordingly, even when there is a shortage of lubricant in the compressor, smooth sliding of theswash plate 40 and thepistons 43 can be guarantied at the joints thereof to control sliding resistance at the joints. - The
shoes 44 can move smoothly along the inner surfaces of the receiving recesses 46 under the action of thecoating layer 11 formed on the spherical surfaces 8. As a result, the load acting between the slidingsurface 10 of eachshoe 7 and theswash plate 40 is moderated to reduce sliding resistance between the slidingsurface 10 and theswash plate 40. Thecoating layer 11 is also present on the slidingsurface 10 of theshoe 7, thus, the sliding resistance between the slidingsurface 10 and theswash plate 40 can be further reduced. Therefore, when the discharge capacity of a compressor is to be increased, even if the sizes of thepistons 43 and theswash plate 40 are increased without changing the size of theshoes 7, no problems arise due to an increase in the sliding resistance. - Since tin not only exhibits excellent lubrication properties but also prevents rust, the
coating layer 11 that contains tin as the major component formed on the surface of eachshoe 7, which is made of a ferrous metal, can protect theshoe 7 from rusting. - Effects brought about by incorporating at least one metal selected from the group including copper to the
coating layer 11 that contains tin as the major component are the same as in the first embodiment. - It should be understood that the present invention is not to be limited to the foregoing embodiments but may be embodied as follows by changing the make-up of the respective parts:
- (1) In any of the first and second embodiments, while the
present invention is embodied in a double-headed piston
swash plate type compressor, the present invention may be
embodied, for example, in a single-headed piston swash
plate type compressor, a variable volume type compressor,
which can adjust discharge volume by changing the tilt
angle of the swash plate, a wave cam type compressor as
shown in Figure 7, or the like. Incidentally, in the wave
cam type compressor shown in Figure 7, like or the same
components as those in the compressor shown in Figure 10
are affixed with the same reference numbers, respectively,
and description of them will be omitted.As shown in Figure
7, this wave cam type compressor has a
wave cam 48 having a wavy cam surface in place of theswash plate 40 in the compressor shown in Figure 1. The slidingsurface 45 of eachshoe 44 is designed to make sliding contact with the front cam surface or rear cam surface of thewave cam 48. In the wave cam type compressor described above, eachpiston 43 is adapted to reciprocate twice or more (twice in Figure 7) per revolution of thedrive shaft 39, and theshoes 44 are required to follow the complicated cam surfaces as the cam surfaces produce displacement. Accordingly, in wave cam type compressors, compared with the swash plate type compressors, the conditions between theshoes 44 and thepistons 43 and between theshoes 44 and thewave cam 48 are more harsh. Accordingly, a reduction in the sliding resistance occurring at the junction of thewave cam 48 and thepistons 43 is important so that the wave cam type compressor can perform stable compression.In the compressor shown in Figure 7, to reduce sliding resistance occurring at the joints between thewave cam 48 and thepistons 43, thepistons 43 may be replaced with thepistons 1 as described in the foregoing first embodiment, or theshoes 44 may be replaced with theshoes 7 as described in the foregoing second embodiment. - (2) While substantially
hemispherical shoes shoes 77 and 44 may be replaced with a structure employing rollers. Otherwise, as shown in Figure 8, each cam follower may consist of aslipper 13, which makes sliding contact with theswash plate 40, and aball 14, which engages arecess 13a of theslipper 13. Theball 14 is slidably engaged in the receivingrecess 46 of the piston 43.Incidentally, in Figure 8, like or the same components as those in the compressor shown in Figure 10 are affixed with the same reference numbers, respectively, and descriptions of them will be omitted. In the construction shown in Figure 8, thepistons 43 may be replaced with thepistons 1 as described in the foregoing first embodiment, or thecoating layer 11 as formed on theshoe 7 in the foregoing second embodiment may be formed on theslipper 13 or theball 14 or both. The construction of the cam follower shown in Figure 8 may be applied to the above-described wave cam type compressor shown in Figure 7. - (3) In the first embodiment, a
coating layer 15 that contains tin as the major component is formed on each surface of theswash plate 40, which makes sliding contact with theshoes 44, as shown in Figure 9. The composition of thecoating layer 15 may be the same as that of thecoating layer 6 of thepiston 1. Thus, the sliding resistance between theswash plate 40 and theshoes 44 can be further reduced. A coating layer containing tin as the major component may be formed on the slidingsurface 45 of eachshoe 44 instead of forming the coating layers 15 on each side of theswash plate 40. In other words, theshoe 7 in the second embodiment may be given thecoating layer 11 only at the slidingsurface 10, andsuch shoes 7 may be employed as the shoes in the first embodiment. - (4) In the first embodiment, the
coating layer 6 may be formed only at the receiving recesses 2 of thepistons 1. - (5) In the second embodiment, the
coating layer 11 may be formed on either thespherical surface 8 or the slidingsurface 10 of eachshoe 7. When thecoating layer 11 is formed only on thespherical surface 8 of theshoe 7, the coating layers 15 may be formed on each side of theswash plate 40 as described in (3).When thecoating layer 11 is formed only on the sliding surface of theshoe 7, thepiston 1 in the first embodiment, i.e., thepiston 1 having thecoating layer 6, may be employed. - (6) In the first embodiment, the surface of the
main body 5 of thepiston 1 may be subjected to pretreatment such as alumite treatment, manganese phosphate treatment, zinc phosphate treatment or zinc plating treatment prior to formation of thecoating layer 6 on themain body 5. Thus, sliding resistance of thepiston 1 with respect to theshoes 44 can further be reduced. - (7) In any of the foregoing embodiments, an alumina ceramic
(Al2O3) layer may be formed on the sliding
surface 10 of themain body 12 of eachshoe 7 and the slidingsurface 45 of each shoe 44.Thus, the sliding resistance of the shoes with theswash plate 40 can further be reduced. - (8) In any of the foregoing embodiments, the ratio of tin
to other metals also present in the
coating layer coating layer coating layer - (9) In any of the foregoing embodiments, the fluororesin
powder or the molybdenum disulfide powder incorporated in
the
coating layer - (10) In any of the foregoing embodiment, the
coating layer coating layer - (11) In any of the foregoing embodiments, the thickness of
the
coating layer coating layer coating layer coating layer -
Claims (9)
- A compressor, comprising:a cylinder block (30,31) containing a cylinder bore (41,42);a drive shaft (39) rotatably supported by the cylinder block (30,31);a cam (40,48) attached to the drive shaft (39) to be rotatable integrally therewith;a piston (1, 43) housed in the cylinder bore (41,42); anda shoe (7, 44) having a spherical and flat sliding surfaces and slidably interposed between the piston (1, 43) and the cam (40, 48);the piston (1, 43) being reciprocated via the shoe (44) as the cam (40,48) is rotated;the piston (1, 43) being made of an aluminum or aluminum alloy matrix and having a receiving recess (2, 46) for slidably receiving the spherical surface (8, 47) of the shoe (7, 44) therein, characterized in thatthe shoe (7, 44) is made of a ferrous metal matrix; anda coating layer (6) containing tin as a major component is formed at the receiving recess (2) of the piston (1).
- The compressor according to claim 1,
characterized in that
a coating layer is formed at both of spherical and flat surfaces of the shoe (7). - The compressor according to Claim 1, wherein
the piston (1) has an outer circumference to be brought into slide contact with an inner circumference of the cylinder bore (41, 42), and the coating layer (6) is also formed on the outer circumference of the piston (1). - The compressor according to Claim 1, characterized in that a coating layer (6) is formed on the cam (40, 48) that reduces a sliding resistance between the cam (40, 48) and the shoe (7).
- The compressor according to Claim 4, wherein the coating layer (6, 11) of the cam (40, 48) contains tin as its major component.
- The compressor according to Claim 1 or 2, wherein a thickness of the coating layer (6, 11) is in a range of 1 to 5µm.
- The compressor according to Claim 1 or 2, wherein the coating layer (6, 11) contains at least one component selected from a group consisting of copper, nickel, zinc, lead and indium.
- The compressor according to Claim 1 or 2, wherein the coating layer (6, 11) contains one kind of solid lubricant selected from a group consisting of a fluororesin powder, a molybdenum disulfide powder, a carbon powder and a boron nitride powder.
- The compressor according to claim 1, wherein tetrafluoroethane is used as a refrigerant gas.
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP03024463A EP1384887B1 (en) | 1996-05-08 | 1996-05-08 | Reciprocating compressor |
DE69635002T DE69635002T2 (en) | 1996-05-08 | 1996-05-08 | piston compressor |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP03024463A EP1384887B1 (en) | 1996-05-08 | 1996-05-08 | Reciprocating compressor |
EP96913701A EP0838590B1 (en) | 1996-05-08 | 1996-05-08 | Reciprocating compressor |
Related Parent Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP96913701A Division EP0838590B1 (en) | 1996-05-08 | 1996-05-08 | Reciprocating compressor |
Publications (3)
Publication Number | Publication Date |
---|---|
EP1384887A2 EP1384887A2 (en) | 2004-01-28 |
EP1384887A3 EP1384887A3 (en) | 2004-07-21 |
EP1384887B1 true EP1384887B1 (en) | 2005-07-27 |
Family
ID=29797379
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP03024463A Expired - Lifetime EP1384887B1 (en) | 1996-05-08 | 1996-05-08 | Reciprocating compressor |
Country Status (1)
Country | Link |
---|---|
EP (1) | EP1384887B1 (en) |
Family Cites Families (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS5786580A (en) * | 1980-11-19 | 1982-05-29 | Toyoda Autom Loom Works Ltd | Piston for swash plate type compressor |
JPS6241980A (en) * | 1985-08-16 | 1987-02-23 | Taiho Kogyo Co Ltd | Shoe for swash plate type compressor |
JPH0697033B2 (en) * | 1988-11-11 | 1994-11-30 | 株式会社豊田自動織機製作所 | Swash plate type compressor |
JP3007644B2 (en) * | 1989-10-26 | 2000-02-07 | 株式会社豊田自動織機製作所 | Swash plate compressor |
JP3039762B2 (en) * | 1995-03-07 | 2000-05-08 | 株式会社豊田自動織機製作所 | Reciprocating compressor |
-
1996
- 1996-05-08 EP EP03024463A patent/EP1384887B1/en not_active Expired - Lifetime
Also Published As
Publication number | Publication date |
---|---|
EP1384887A3 (en) | 2004-07-21 |
EP1384887A2 (en) | 2004-01-28 |
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