Vane type gas compressor

Abstract: In relation to a vane type gas compressor in which a cylinder block, a front side block, a rear side block, a rotor and vanes are made of aluminum alloys, and a rotor shaft which is supported between bearing portions of the both side blocks in a manner freely capable of rotation is made of an iron series metal. It is intended that a refrigerant which does not destroy the ozone layer is used, and no cohesion is caused at the bearing portions even when the bearing portions are in a no-lubrication state. HFC-134a (1,1,1,2-tetrafluoroethane; CH₂FCF₃) containing no chlorine in its component is used as the refrigerant. Bushes and which are made of cast iron subjected to the phosphate coating treatment are provided at boss portions of the both side blocks.

Description: BACKGROUND OF THE INVENTION The present invention relates to a vane type gas compressor, and in particular relates to a vane type gas compressor used for air conditioners for automobiles. As conventional vane type gas compressors, for example, there are those in which a front side block, a rear side block, a cylinder, a rotor and vanes which constitute the compressor main body are made of aluminum alloys, while a rotor shaft is made of a hardened steel material such as an SCM material or the like, and CFC-12 (dichlorodifluoromethane; CCl 2 F 2 ) is used as a refrigerant. In such a vane type gas compressor, the rotor shaft resides in the plain bearing type, namely both ends of the rotor shaft are supported in a manner freely capable of rotation by means of bearing portions provided at boss portions at the centers of the front side block and the rear side block, respectively. And the lubrication at the bearing portions has been usually performed by blowing lubricating oil under a high pressure from an oil reservoir in the rear space of a casing, or by using lubricating oil dissolved in CFC-12 as the refrigerant. In addition, it has been also performed by the lubricating action of CFC-12 itself. However, CFC-12, which is used for the conventional vane type gas compressor, contains chlorine as a component, and this chlorine destroys the ozone layer, so that the use thereof will be prohibited in the future. Therefore, an alternative refrigerant thereof is necessary, and for this purpose, it is considered that a refrigerant containing no chlorine is used. However, the chlorine itself is an element having the lubricating action, so that on the contrary, when the refrigerant containing no chlorine is used, its lubricating property is inferior to that of CFC-12. For example, when the compressor is stopped under an operating condition in which the amount of lubricating oil is relatively less in the oil reservoir in the rear space of the casing, and it is left for a long time, such a state occurs that the lubricating oil is diluted by the liquid refrigerant, and the lubricating oil at the bearing portion is washed out by the liquid refrigerant. When the compressor is started from this state, the bearing portion temporarily is in a no-oil feeding state, however, when the refrigerant containing no chlorine is used, the lubricating action of the refrigerant itself cannot be expected at all, so that there is a fear to cause a new problem that cohesion takes place due to the mutual sliding contact between metals of the rotor shaft of the iron series metal and the bearing surface of the aluminum alloy, resulting in seizure. In order to overcome this problem EP-A-438922 has disclosed a vane type refrigerant gas compressor according to the preamble of claim 1 in which bearing surfaces are used which consist of compound layers mainly made of iron sulphide. From EP-A-399425 it is known that bearings in general can also be formed with surfaces consisting of compound layers formed by phosphatizing solutions containing Zinc, Sodium, P 2 O 5 , NO 3 , BF 4 , B(OH) 3 and NaF in varying proportions. SUMMARY OF THE INVENTION Thus the present invention has been made taking the above-mentioned problem into consideration, an object of which is to provide and additional vane type gas compressor wherein a refrigerant which does not destroy the ozone layer is used, and no cohesion takes place at the bearing portions of both side blocks. In order to solve the above-mentioned task, the present invention lies in a vane type gas compressor provided with a cylinder which has its inner circumference of a substantially oval cylinder shape, a front and a rear side blocks which are attached to both sides of the cylinder, a rotor which is accommodated in a cylinder chamber formed by the side blocks and said cylinder in a manner freely capable of rotation, a rotor shaft which transmits rotational force to the rotor, and a plurality of vanes which are inserted into a plurality of vane grooves provided in the radial direction of the rotor in a manner freely capable of frontward and rearward movement, wherein said front and rear side blocks are provided with plain bearings for supporting the rotor shaft in a manner freely capable of rotation respectively, while said cylinder, front side block, rear side block, rotor and vanes are made of aluminum alloys, and the rotor shaft is made of an iron series metal, wherein a refrigerant HFC-134a (1,1,1,2-tetrafluoroethane; CH 2 FCF 3 ) is used as the gas, and said plain bearings are such that bushes, which are made of cast iron and have their bearing surfaces at least to which the phosphate coating treatment is applied, are fitted and fastened by insertion under pressure or the like into each of holes opened at boss portions of the front and the rear side blocks. In accordance with the above-mentioned constitution, HFC-134a which contains no chlorine in its component is used as the refrigerant, so that the destruction of the ozone layer is prevented. In addition, each of the bearing portions of the front and the rear side blocks are subjected to insertion under pressure of the bushes (bearing metals) which are made of cast iron and have their bearing surfaces to which the phosphate coating treatment is applied, so that even when the lubricating oil is not supplied temporarily to the spaces between the bushes and the rotor shaft to provide a no-lubrication state, the cohesion and the seizure are not caused. BRIEF DESCRIPTION OF DRAWINGS Fig. 1 is a cross-sectional view showing the whole constitution of a vane type gas compressor according to the present invention. Fig. 2 is a cross-sectional view showing a bearing portion of the vane type compressor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of the vane type gas compressor according to the present invention will be explained hereinafter on the basis of the drawings. Fig. 1 is a cross-sectional view showing the whole constitution of the vane type gas compressor according to the present invention, and Fig. 2 is a cross-sectional view showing a bearing portion of the vane type compressor. As shown in Fig. 1, this vane type gas compressor is constituted by an electromagnetic clutch M, a compressor main body 10, a casing 11 of a shape having an opening at one end for surrounding this compressor main body 10 in an air-tight manner, and a front head 12 attached to the opening end face of this casing 11. The compressor main body 10 has a cylinder 13 which has its inner circumference of a substantially oval cylinder shape, and a front side block 14 and a rear side block 15 which are attached to both sides of this cylinder 13, thereby a cylinder chamber 16 having a substantially oval cylinder shape is formed, and in this cylinder chamber 16 is accommodated a rotor 19 which is integrated with a rotor shaft 17 and installed with a plurality of vanes 18 at the circumference in a manner freely capable of frontward and rearward movement into a plurality of vane grooves provided in the radial direction thereof. At the center of the front side block 14, a boss portion 14a is formed as shown in Fig. 2. In addition, also at the rear side block 15, a boss portion 15a is formed in the same manner as the front side block 14. Further, the compressor main body 10, the rotor 19 and the vanes 18 are formed, for example, with aluminum alloys such as hyper-eutectic Al-Si alloy casting materials or the like, while the rotor shaft is formed with a hardened steel material such as SCM, SCr or the like. And in the present example, as the refrigerant gas, HFC-134a (1,1,1,2-tetrafluoroethane; CH 2 FCF 3 ) containing no chlorine is used. Further, in the present example, bushes 14b and 15b, which are made of cast iron and have their bearing surfaces at least to which the phosphate coating treatment is applied, are fitted and fastened into the boss portions 14a and 15a by means of a method of insertion under pressure or the like, and both end portions of the rotor shaft 17 are inserted into the bushes 14b and 15b so as to support the rotor 19 in a manner freely capable of rotation. The bushes 14b and 15b are cast iron corresponding to FC 25, which are casted into a column shape or a cylinder shape and then finished into a predetermined size and accuracy for the outer diameter, inner diameter and length by means of mechanical processing, respectively. And then, the bushes are introduced into a chemical conversion treatment tank for iron, and by means of known treatment steps, a chemical conversion treatment coating of phosphate is formed on the entire surfaces of the bushes, or at least on bearing surfaces thereof. As the phosphate coating, a manganese phosphate coating is most preferable. This coating is extremely hard as compared with coatings usually used for plastic working such as zinc phosphate, calcium zinc phosphate and the like, so that it is excellent in abrasion resistance. Incidentally, in Fig. 1, 21 is an oil reservoir for storing lubricating oil, 22 is an oil separator for separating lubricating oil from the refrigerant gas, 23 is an oil communication passage for supplying lubricating oil to bearing surfaces 14c and 15c of the both side blocks 14 and 15, 24 is a suction port for sucking the refrigerant gas, 25 is a suction passage and 26 is a discharge port from which the refrigerant gas is discharged. Next, the function of the vane type gas compressor thus constituted will be explained, wherein it is assumed that the rotor shaft 17 rotates on the bearing surfaces 14c and 15c of the both side blocks 14 and 15 in the no-lubrication state in which there is no lubricating oil. In this case, in the present example, HFC-134a containing no chlorine in its component is used as the refrigerant, so that the lubricating property is inferior as compared with the case in which CFC-12 is used. However, when the bearing surfaces 14c and 15c of the both side blocks 14 and 15 are formed in accordance with such constitution, as being different from the conventional bearing surface made of a soft aluminum alloy, owing to such reasons that at first the base substrate of the bearings becomes hard, the surface of the iron base substrate is coated with the above-mentioned manganese phosphate coating and the like, the cohesion with the rotor shaft 17 made of the steel material is prevented. And the thickness of the phosphate coating can be made fairly thick to be about 10 to 15 µm including a thickness of an etching layer, so that even after severe operation or use for a long period, there is no such an event that the iron base substrate is exposed as a result of complete abrasion, and there is no such an event that the iron base substrate and the iron of the rotor shaft are subjected to direct sliding contact to cause the cohesion, further resulting in the seizure. Incidentally, as an additional discussion, it is also possible to directly apply the chemical conversion treatment onto the aluminum alloy, however, a chemical conversion treatment coating on the aluminum alloy is different from the coating on the iron steel material, which cannot have its thick coating thickness (usually about 1 to 2 µm), and is soft and weak in adhesion, so that it is easily peeled off due to the sliding contact with the rotor shaft, the base substrate of the aluminum alloy is exposed, and the effect of preventing seizure cannot be obtained. Therefore, in the present example, HFC-134a containing no chlorine in its component is used as the refrigerant, so that the lubricating property is inferior as compared with the case in which the conventional CFC-12 is used, however, even when the rotor shaft 17 rotates on the bearing portions of the both side blocks 14 and 15 in the no-lubrication state in which there is no lubricating oil, the bearing portions are provided with the above-mentioned bushes 14b and 15b which are excellent in the abrasion resistance and the seizure resistance, so that there is no such an event that the cohesion takes place resulting in the seizure. In addition, HFC-134a is different from CFC-12, which contains no chlorine in its component, so that the ozone layer is not destroyed by chlorine, and the environmental destruction can be prevented. Incidentally, the cast iron (FC material) has been used as the bush material in the present example, however, it is also available that a sintered material of the iron series is used, and the phosphate coating treatment is applied in the same manner. In addition, the bushes 14b and 15b have been fitted and fastened by the insertion under pressure into the boss portions 14a and 15a, however, for example, it is also possible to contemplate the integration of an aluminum alloy cast article or a die-cast with the bush by means of a method of the internal chill and the like. As explained above, according to the present invention, with respect to the vane type gas compressor in which the cylinder block, the front side block, the rear side block, the rotor and the vanes are made of aluminum alloys, and the rotor shaft which is supported between the bearing portions of the both side blocks in a manner freely capable of rotation, HFC-134a (1,1,1,2-tetrafluoroethane) containing no chlorine in its component is used as the refrigerant, and each of the bearing portions of the front side block and the rear side block is provided with the bush which is made of cast iron and subjected to the phosphate coating treatment, so that no chlorine is generated and the destruction of the ozone layer is prevented, and the cohesion at the bearing surface can be prevented even in the case of the no-lubrication state in which there is no lubricating oil at the bearing portion.

Claims: A vane type gas compressor comprising: a cylinder; a front and a rear side blocks attached to both sides of the cylinder for forming a cylinder chamber; a rotor rotatably provided in the cylinder chamber; a rotor shaft for transmitting rotational force to the rotor; a plurality of vanes inserted into a plurality of vane grooves provided in the radial direction of the rotor in a manner freely slidable in the grooves; a plurality of plain bearings provided respectively in the front and the rear side blocks for rotatably supporting the rotor shaft; and a refrigerant HFC-134a (1,1,1,2-tetrafluoroethane; CH 2 FCF 3 ) for compressible gas of the gas compressor; characterized in that the cylinder has an inner circumference of a substantially oval shape; wherein the cylinder, the front and the rear side block, the rotor and the vanes are made of aluminum alloys, and the rotor shaft is made of an iron series metal; and wherein the plain bearings are made of cast iron and have bearing surfaces to which a phosphate coating treatment is applied; wherein the phosphate coating applied to the bearing surfaces is manganese phosphate coating; wherein the thickness of the manganese phosphate coating is in a range from 10 µm to 15 µm. A vane type gas compressor according to claim 1, wherein the plain bearings are fitted and fastened respectively by insertion under pressure into each of holes opened at boss portions of the front and the rear side blocks.

Inventors: IJIRI MAKOTO, SHIMIZU YUTAKA, YAMAGUCHI MASARU, YAMANE SHUJI, IJIRI, MAKOTO, SHIMIZU, YUTAKA, YAMAGUCHI, MASARU, YAMANE, SHUJI, Ijiri, Makoto, c/o Seiko Seiki K.K., SHIMIZU, YUTAKA,, Yamaguchi, Masaru, c/o Seiko Seiki K.K., Yamane, Shuji, c/o Seiko Seiki K.K.
Applicants: CALSONIC CORP, SEIKO SEIKI KK, CALSONIC CORPORATION, SEIKO SEIKI KABUSHIKI KAISHA
Application year: 1993
Main classification: F04C18
IPC codes: F04C29, F04C18, F01C21