Vane for vane compressor

Abstract: A vane (14) for a vane compressor comprises an aluminium-based metal core (14 a ) and a cladding (14 b ) of ferrous metal provided on the surface of the core (14 a ). The vane (14) may be formed by joining a tube (14b) of ferrous metal onto the surface of the aluminium-based metal core (14a), by drawing or pressing.

Description: BACKGROUND OF THE INVENTION Field of the Invention This invention relates to a vane for use in a vane compressor and more particularly to a vane of this kind which is reduced in weight and at the same time has improved sliding characteristics, as well as to a method of manufacturing the same. Description of the Prior Art A vane compressor comprises a cam ring, a front side block and a rear side block closing respective opposite ends of the cam ring, and a rotor rotatably received within the cam ring. The cam ring is formed with vane slots having respective vanes slidably received therein. As the rotor rotates, the vanes move out radially ofthe respective vane slots by centrifugal force and back pressure acting on the back of each vane, so that the tip of each vane urgingly slides along the inner peripheral surface of the cam ring, thereby compressing refrigerant gas trapped in compression chambers each defined between adjacent vanes. Aluminium or aluminium alloy (hereinafter both referred to as "aluminium-based metal") is conventionally employed as the material of the cam ring, the rotor, and the vanes, for the sake of light weight, as disclosed e.g. in Japanese Laid-Open Patent Publication (Kokai) No. 1-182592 or Patent Abstracts of Japan, vol. 15 no. 138 (M-1100) and JP-A-03 0186 83. When the cam ring and the vanes are both formed of an aluminium-based metal, as disclosed in Japanese Laid-Open Patent Publication (Kokai) No. 1-182592, the vanes are often subjected to surface treatment by the use of a nickel-phosphorous based (Ni-P based) material to prevent adhesion of the vanes to the cam ring, which can be caused by sliding ofthe vanes on the cam ring. Vanes with a cladding of ferrous material for improved seizure characteristics are known from Patent Abstracts of Japan, vol. 7 no. 37 (M-193) and JP-A-57 188791, US-A-5090882 and DE-A-3937197. Essentially, the prior art vanes can, therefore, be defined in general terms as comprising an aluminium-based metal core and a ferrous metal cladding on all but the opposed tips of the core. In a conventional method of manufacturing vanes, as will be described in more detail hereinbelow, powdered aluminium is extruded into an intermediate shape and then the aluminium extrudate is machined into the required shape of the vane. Finally, this machined form of aluminium is plated with a nickel-phosphorus based coating. However, the provision of the nickel-phosphorus based coating increases manufacturing cost, whilst the coating itself is liable to flaking under certain conditions, resulting in adhesion of vanes to the cam ring or seizure of the former by the latter. If the whole of a vane is formed of a ferrous metal to overcome the above problem, it is possible to obtain excellent sliding characteristics but the weight of each vane is increased, which can cause large chattering noises of vanes during use of the compressor. Further, the vanes apply large impacts on the cam ring, causing wear of the contacting portions of the associated components. SUMMARY OF THE INVENTION It is a first object of the present invention to provide a vane for use in a vane compressor which is free from seizure, can be manufactured without increasing the weight and manufacturing cost thereof, and is substantially free from deformation. It is a second object of the invention to provide a method of manufacturing a vane for use in a vane compressor which is free from seizure, without increasing the weight and manufacturing cost thereof. To attain the first object and according to a first aspect of the invention, there is provided a vane for a vane compressor including a cam ring and a rotor received rotatably in the cam ring and formed therein with a vane slot, wherein the vane is inserted slidably in the vane slot for outward movement with respect thereto when the rotor rotates such that the tip of the vane slides urgingly along an inner peripheral surface of the cam ring, which vane is characterised from the prior art, in that the aluminium-based metal core is generally solid but has a cavity therein. Since the aluminium-based metal core of the vane in accordance with the first aspect of the invention is generally solid but is formed with a cavity, the cavity absorbs any difference in thermal expansion between the core and cladding, which prevents the vane from being deformed. Further, the invention can be distinguished from the conventional type of vane which is formed by providing an Ni-P based coating on the surface of the aluminium-based metal core, in that there does not arise any seizure due to flaking of the plated coating, and in that the manufacturing cost is reduced since the cladding of ferrous metal is employed in place of the Ni-P based coating, while preserving excellent sliding characteristics of the vane. Further, and compared with vanes of which the whole is formed of a ferrous metal, the vane of the present invention is light in weight and is capable of suppressing noise produced by chattering of the vanes. To attain the second object of the invention, a second aspect of the invention provides a method of manufacturing a vane for a vane compressor, comprising the step of joining a tube of a ferrous metal on to the surface of an aluminium-based metal core, which method is distinguished from the prior art by effecting the joining step by drawing or pressing. According to this method of the second aspect of the invention, the tube of ferrous metal is joined on to the surface of the aluminium-based metal core by drawing or pressing, which makes it possible to provide the easily formed cladding of ferrous metal, such as soft iron, and to use for the core an ordinary material, such as an aluminium alloy having an alloy number of the order of 6000 (Al-Mg-Si based alloy) or 2000 (Al-Cu based alloy), instead of, say, powdered aluminium, which contributes to a reduction in the manufacturing costs. Further, the above inventive method makes it possible to obtain a shape very close to that of the vane as a final product, which helps to reduce largely the manufacturing costs. Preferably, the tube of ferrous metal is heated to approximately 200° to 300°C when the drawing or pressing is carried out. According to this preferred method, the iron tube is heated to a temperature of approximately 200° to 300°C and then drawn or pressed, so that it is firmly joined to the surface of the aluminium-based metal core, which prevents the core and cladding from being separated from each other during and under actual use conditions. Also, to attain the second object of the invention, according to a third aspect of the invention, there is provided a method of manufacturing a vane for a vane compressor, comprising the steps of inserting an aluminium-based metal core in the form of a bar into a tube of ferrous metal, heating the ferrous metal tube to approximately 200° to 300°C, inserting the ferrous metal tube and the aluminium-based metal core bar into a hole of a die, and drawing the ferrous metal tube while blowing cold air thereon. According to a method in accordance with a third aspect of the invention, the ferrous tube is heated to a temperature of approximately 200° to 300°C, and then drawn out, so that the tube is firmly joined to the surface of the aluminium-based metal core, while preventing the so-formed core and cladding from being separated from each other during and under actual use conditions. Preferably, the aluminium-based metal core or bar is cooled before it is inserted into the ferrous metal tube. Also, to attain the second object of the invention and according to a fourth aspect thereof, there is provided a method of manufacturing a vane for a vane compressor, comprising the steps of inserting a tube of a ferrous metal into a hole of a die, heating the ferrous metal tube to approximately 200° to 300°C, and pressing an aluminium-based metal core into the heated ferrous metal tube by means of a punch. According to the method of the fourth aspect of the invention, the tube of ferrous metal may be heated to a temperature of approximately 200° to 300°C, and then the aluminium-based metal core is pressed therein, so that the ferrous metal tube is joined firmly to the surface of the core, which prevents the so-formed core and cladding from being separated from each other during and under actual use conditions. Preferably, before the aluminium-based metal core is inserted into the tube of ferrous metal, the core is cooled. The above and other objects, features and advantages of the present invention will become more apparent from the following description of preferred embodiments thereof, when take in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of a vane for use in a vane compressor made by a method according to the invention; FIG. 2 is a longitudinal cross-sectional view showing the whole arrangement of the vane compressor; FIG. 3 is a cross-sectional view of the FIG. 2 vane compressor taken on line III-III of FIG. 2; FIG. 4 is a diagram useful in explaining a method of manufacturing the vane shown in FIG. 1; FIG. 5 is a diagram useful in describing another method of manufacturing the vane shown in FIG. 1; FIG. 6 is a cross-sectional view of a vane for use in a vane compressor according to an embodiment of the invention; and FIGS. 7A to 7C are diagrams useful in explaining a conventional method of manufacturing a vane. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Now, the invention will be described in detail with reference to the drawings showing preferred embodiments thereof. Referring firstly to FIGS. 2 and 3 of the drawings, a vane compressor comprises a cam ring 1, a cylindrical rotor 2 received rotatably within the cam ring 1, a front side block 3 and a rear side block 4 closing open opposite ends of the cam ring 1, a front head 5 and a rear head 6 secured to outer ends of the respective front and rear side blocks 3 and 4, and a drive shaft 7 on which is mounted and secured the rotor 2. The drive shaft 7 is rotatably supported by a pair of radial bearings 8 and 9 provided in respective front and rear side blocks 3 and 4. A discharge port 5 a is formed in an upper wall of the front head 5, through which a refrigerant gas is to be discharged as a thermal medium, while a suction port 6 a is formed in an upper wall of the rear head 6, through which the refrigerant gas is to be drawn in to the compressor. The discharge port 5 a and the suction port 6 a communicate, respectively, with a discharge pressure chamber 10 defined by the front head 5 and the front side block 3, and a suction chamber 11 defined by the rear head 6 and the rear side block 4. As best shown in FIG. 3, a pair of compression spaces 12 are defined at generally diametrically opposed locations between an inner peripheral surface 1 a of the cam ring 1 and an outer peripheral surface of the rotor 2 (one of the compression chambers is shown in the figure). The rotor 2 has its outer peripheral surface formed therein with a plurality of axial vane slots 13 at circumferentially equal intervals, in each of which a vane 14, described in detail hereinbelow, is received radially slidably. Each compression space 12 is divided by vanes 14 into compression chambers, the volume of each of which varies with rotation of the rotor 2. A pair of refrigerant outlet ports 16 are formed through opposite lateral side walls of the cam ring 1 at diametrically opposed locations (only one of them is shown in FIG. 2). The opposite lateral side walls of the cam ring 1 are provided with two discharge valve covers 17 each formed integrally with a valve stopper 17 a and fixed to the cam ring 1 by bolts 18. Discharge valves 19 are mounted between the respective lateral side walls of the cam ring 1 and the valve stoppers 17 a in such a manner that they are supported by the valve covers 17. When the outlet ports 16 are open, refrigerant gas compressed within the compression chambers is delivered via the ports 16, communication passages 2 a and 3 a , the discharge pressure chamber 10 and the discharge port 5 a . A pair of refrigerant inlet ports, not shown, are formed in the rear side block 4 at upper and lower locations corresponding to the two compression spaces 12 at the upper and lower locations, respectively. The suction chamber 11 communicates via the inlet ports with the compression spaces 12. As shown in FIG. 1, the vane 14 of the present embodiment comprises a metal core 14 a of an aluminium or aluminium alloy (hereinafter referred to as "an aluminium-based metal") and a cladding 14 b of a ferrous metal covering the surface of the core 14 a . FIG. 4 shows how the vane 14 is manufactured by a drawing process. A metal core 34 a in the form of a bar of an aluminium-based metal is inserted into an iron tube 34 b which is to form the cladding 14 b . Then, the iron tube 34 b and the aluminium-based metal core bar 34 a are inserted into a hole 21 a , having a cross-section identical to that of the vane, of a die 21, while the iron tube 34 b alone is heated by a heater 20 to 200°C or a higher temperature, thereby expanding the same. The iron tube 34 b is drawn out together with the aluminium-based metal core bar 34 a while blowing cold air thereon. Taking actual use conditions (-30° to +200°C) of the vane 14 into consideration, the aluminium-based metal core bar 34 a may be cooled to -30°C or a lower temperature before it is inserted into the iron tube 34 b . The aluminium-based metal core bar 34 a clad with the iron tube 34 b is then cut off into individual vanes. FIG. 5 shows another method of manufacturing vanes, which is based on a pressing process. In this manufacturing method, an iron tube 44 b is inserted into a hole 22 a of a die 22 and the tube 44 b is heated by a heater 23 up to 200°C or a higher temperature to thereby expand the same. Then, an aluminium-based metal core 44 a is pressed into the iron tube 44 b by means of a punch 24. Before pressing the metal core 44 a into the tube 44 b , the core may be cooled to -30°C or a lower temperature, similar to the first-described method. The metal core 44 a clad with the iron tube 44 b is then cut off into individual vanes. The operation of the variable capacity vane compressor constructed as above will now be explained below. As torque is transmitted from an engine, not shown, to the drive shaft 7, the rotor 2 is rotated. Refrigerant gas flowing out of an outlet port of an evaporator, not shown, is drawn into the suction chamber 11 of the compressor via the suction port 6 a thereof. The refrigerant gas is drawn into the compression spaces 12 from the suction chamber 11 via the refrigerant inlet ports. The compression spaces 12 are divided by vanes into compression chambers, each of which varies in capacity with rotation of the rotor 2, as described above, whereby refrigerant gas trapped in each compression chamber is compressed and the compressed refrigerant gas opens the discharge valve 19 to flow out via the refrigerant outlet ports 16 into the discharge pressure chamber 10, followed by being discharged via the discharge port 5 a . As the rotor rotates, the vanes 14 move radially outwardly of the respective vane slots 13 by centrifugal force and back pressure acting on the back of each vane, so that the tip of each vane urgingly slides along the inner peripheral surface 1 a of the cam ring 1. As described above, the vane 14 of the present embodiment is distinguished from the conventional type, which is formed by plating an Ni-P based coating on the surface of an aluminium-based metal core, in that there does not arise seizure due to flaking of the coating (cladding) and that the manufacturing cost is reduced since the cladding 14 b of ferrous metal is employed instead of the Ni-P based coating. Further, the vane 14 maintains excellent sliding characteristics. Further, and compared with vanes of which the whole is formed of a ferrous metal, the vane of the present invention is light in weight and is capable of suppressing noise produced by any chattering of the vanes. Further, as described hereinabove, the vanes 14 are formed by the manufacturing method based on a drawing or pressing process, which makes it possible to provide the cladding 14 b of easily-shaped ferrous metal, such as soft iron, and to employ for the metal core 14 a an ordinary metal, such as an aluminium-based metal having an alloy number of the order of 6000 (Al-Mg-Si based alloy) or 2000 (Al-Cu based alloy), instead of,say, powdered aluminium, which contributes to a reduction in the manufacturing cost. Further, the inventive methods make it possible to obtain a shape (near net shape) very close to that of a vane as a final product, which helps also to reduce significantly the manufacturing cost. Further, in both the inventive methods, the iron tubes 34 b , 44 b may be heated up to 200°C or a higher temperature for expansion, and then drawn or pressed, so that the tube 34 b or 44 b is firmly joined to the surface of the aluminium-based metal core, which prevents the core 14 a and the cladding 14 b from being separated from each other during and under actual use conditions (-30° to +200°C). FIG. 6 shows a vane 54 according to another embodiment of the invention on an enlarged scale. This embodiment is distinguished from the first-described embodiment in that an aluminium-based metal core 54 a having a cavity 25 is employed in place of the solid aluminium-based metal core 14 a . When the vane 54 of this embodiment is employed, the cavity 25 absorbs a difference in thermal expansion between the aluminium-based metal of the core 54 a and the ferrous cladding 54 b , which prevents the vane from being deformed. By way of comparison, FIGS 7A to 7C illustrate a conventional method of manufacturing compressor vanes wherein powdered aluminium is extruded into an intermediate shape, as shown in FIG 7A, and then the aluminium extrudate 114 a is machined or otherwise formed into the required general shape of the vane 1114 a . Finally, this machined form of aluminium is plated with nickel-phosphorous based coating (cladding) 114 b . However, and as discussed above, the provision of the nickel-phosphorous based coating 114 b and the machining of the aluminium extrudate core 114 a increase the manufacturing costs, whilst the coating (cladding) 114 b itself is liable to flaking under certain operating conditions, resulting in adhesion of the vane to the cam ring of the compressor or seizure of the former by the latter.

Claims: A vane (14, 54) for a vane compressor including a cam ring (1) and a rotor (2) which is received rotatably in the cam ring (1) and is formed therein with a vane slot (13), wherein the vane (14, 54) is insertable slidably in the vane slot (13) for outward movement with respect thereto when the rotor (2) rotates such that the tip of the vane (14, 54) slides urgingly along an inner peripheral surface of the cam ring (11), and wherein the vane (14, 54) comprises an aluminium-based metal core (14 a , 54 a ) and a ferrous metal cladding (14 b , 54 b ) on all but the opposed tips of the core (14 a , 54 a ), characterised in that the aluminium-based metal core (54 a ) is generally solid but has a cavity (25) therein. A method of manufacturing a vane (14, 54) for a vane compressor, comprising the step of joining a tube (34 b , 44 b ) of a ferrous metal on to the surface of an aluminium-based metal core (34 a , 44 a ), characterised in that the joining step is effected by drawing or pressing. A method according to claim 2, wherein the ferrous metal tube (34 b , 44 b ) is heated to approximately 200° to 300°C when the drawing or pressing is carried out. A method of manufacturing a vane (14, 54) for a vane compressor comprising the steps of inserting an aluminium-based metal core in the form of a bar into a tube (34 b ) of a ferrous metal, heating the ferrous metal tube (34 b ) to approximately 200° to 300°C, inserting the ferrous metal tube (34 b ) and aluminium-based metal bar (34 a ) into a hole of a die and drawing the ferrous metal tube (34 b ) while flowing cold air thereon. A method according to claim 4, wherein the aluminium-based metal bar (34 a ) is cooled before it is inserted into the ferrous metal tube (34 b ). A method of manufacturing a vane (14, 54) for a vane compressor, comprising the steps of inserting a tube (44 b ) of a ferrous metal into a hole of a die, heating the ferrous metal tube (44 b ) to approximately 200° to 300°C, and pressing an aluminium-based metal core (44 a ) into the ferrous metal tube (44 b ) by means of a punch (24). A method according to claim 6, wherein, before the aluminium-based metal core (44 a ) is inserted into the ferrous metal tube (44 b ), the core (44 a ) is cooled.

Inventors: MURAYAMA TOSHIHIRO, SAITO TADASHI, MURAYAMA, TOSHIHIRO, SAITO, TADASHI, Murayama, Toshihiro, c/o Zexel Co. Kounan-works, Saito, Tadashi, c/o Zexel Co. Kounan-works
Applicants: ZEXEL CORP, ZEXEL CORPORATION
Application year: 1995
Main classification: F04C18
IPC codes: F04C18, F04C29, F01C21