The present invention is directed to a magnetic drive vane pump.
Vane pumps are widely known in the art, for example, as disclosed in Japanese patent publication No. 53-2704 A. Generally, the vane pump includes a casing with a pump cavity and a rotor rotatable about an eccentric axis within the pump cavity. The rotor carries a plurality of vanes which moves radially so as to have their outer ends kept in sealed contact with an interior wall of the pump cavity as the rotor rotates, thereby drawing a fluid into the pump cavity, compressing and expelling it out of the pump cavity. The rotor is coupled to an external motor to be driven thereby to rotate. For this purpose, the rotor is provided with a shaft which extends outwardly of the casing for coupling with the motor. Therefore, a sealing is between the shaft and the casing. However, as the shaft is a constantly moving part, there is always a problem that the sealing may become deteriorated during an extended period of use to result in an unintended lead of the fluid.
In view of the above problem, the present invention has been achieved to provide a magnetic drive vane pump with a leakage free structure. The vane pump in accordance with the present invention includes a casing with a pump cavity, an inlet for introducing a fluid into the pump cavity, and an outlet for discharging the fluid out of the pump cavity. A rotor is disposed within the pump cavity to be rotatable about an eccentric axis with respect to the pump cavity. A plurality of vanes are carried on the rotor and are radially movable so as to be kept into sealed contact with an interior wall of the pump cavity as the rotor is driven to rotate for drawing the fluid into the pump cavity and expelling it out of the pump cavity. The rotor is configured to have a rotor magnet which is magnetically coupled to a stator magnet mounted on the casing outwardly of the pump cavity for driving the rotor. The feature of the present invention resides in that the rotor magnet is configured to have its major portion disposed in an overlapping relation with the stator magnet. Thus, the rotor magnet can be mechanically isolated from the stator magnet disposed outside of the casing to establish a sealless coupling therebetween for making the pump leakage free, yet requiring only a minimum thickness of the pump in the axial direction thereof.
Preferably, the rotor magnet is disposed radially outwardly of the stator magnet so that the stator magnet can be arranged within a radial dimension of the stator, which assures to give a compact structure to the pump with respect to the radial direction.
Also, it is preferred that the stator magnet is configured to have its axial center offset from an axial center of the rotor magnet so as to be disposed further away from the rotor than said rotor magnet with respect to the eccentric axis. With this arrangement, the rotor is attracted towards the stator magnet in an axial direction such that the rotor can rotate at a constant level with regard to its axial direction, causing no substantial axial fluctuation.
Further, the rotor magnet is preferred to be fitted around a shaft extending axially from a center of the casing with a vibration absorbing member interposed therebetween. The vibration absorbing member can well absorb radial vibrations possibly caused by an eccentric rotary motion of the rotor, thereby assuring a smooth and silent rotary motion.
Besides, each of the vanes, which are slidable fitted respectively in radial grooves in the rotor, is configured to be movable only radially without being caused to fluctuate in the axial direction. For this purpose, each vane is formed on its opposite sides respectively with ribs which engage into guide grooves formed in opposite faces of the rotor defining the radial groove therebetween.
These and still other advantageous features of the present invention will become more apparent from the following description of preferred embodiments of the present invention when taken in conjunction with the attached drawings.
Referring now to
The rotor 40 is shaped into a disc disposed within the upper recess 21 and carries a plurality of vanes 50 which are slidably received respectively in circumferentially spaced radial slits 42. As the rotor 40 is driven to rotate, each of the vanes 50 is shifted radially outwardly by a centrifugal force to have its outer end in sealing contact with the inside of the ring 32, thereby forming a displacement chamber confined between the adjacent vanes and between the ring 32 and the rotor. The displacement chamber undergoes expansion and contraction while the rotor 40 rotates about the eccentric axis, thereby drawing the fluid into and expelling it out of the pump cavity 12.
The rotor 40 carries a rotor magnet 60 which is magnetically coupled to a stator magnet 70 disposed outside of the casing 10 so as to be driven thereby to rotate. The rotor magnet 60 is a permanent magnet which is integrated with the rotor 40 to form a unitary structure. The rotor magnet 60 is shaped to have a thin base 62 secured on one axial end face of the rotor 40, a hub 64 projecting axially from the center of the base 62, and an outer ring 67 projecting axially from the periphery of the base 62. The hub 64 is received into the center concavity 29 in an overlapping relation with the stator magnet 70 with respect to the radial direction about the eccentric axis. The hub 64 is formed with a bearing hole 65 into which the shaft 23 extends together with the bearing sleeve 24 so that the rotor magnet 60 is freely rotatable about the shaft 23 together with the rotor 40. The outer ring 67 projects into an annular groove 27 formed between the annular projection 26 and the peripheral wall 28 of the lower half 20 also in an overlapping relation with the stator magnet 70 with respect to the radial direction. The outer ring 67 and the hub 64 constitute a major portion of the rotor magnet 60 which are disposed radially outwardly of the stator magnet 70 in the overlapping relation therewith, which contributes to minimize the axial dimension as well as the radial dimension of the pump.
In order to reduce radial vibrations of the rotor 40 which may occur during its rotation about the eccentric axis, a vibration absorbing member 25 is interposed between the bearing hole 65 and the bearing sleeve 24 of the shaft 23.
The stator magnet 70 is composed of a plurality of electro magnets which are mounted within an open space formed underside of the annular projection 26 and extend around the center stud 22. As shown in
As shown in
Although the present invention is explained specifically with reference to the above embodiments, it should not be delimited to the embodiments and can encompass any combination of the individual features disclosed in the above embodiments.
Number | Date | Country | Kind |
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2007-056122 | Mar 2007 | JP | national |