Patent Application
20050063851
I. Field of the Invention
The present invention relates generally to gerotor pumps, and more particularly to improved gerotor pumps wherein outer rotors are enabled for finding their own eccentricity offset axes, and furthermore, to improved methods of manufacture for preferred gerotor gear sets to be utilized therein.
II. Description of the Prior Art
Gerotor pumps are most conveniently designed around commercially available gerotor gear sets (hereinafter simply “gerotor sets”) such as those manufactured by Nichols Portland of Portland, Me. Such gerotor sets comprise an inner rotor having N outwardly extending lobes with N approximately circularly shaped grooves therebetween (i.e., with N typically having values of 4, 6, 8 or 10) in mesh with an eccentrically disposed outer rotor comprising N+1 inwardly extending circularly shaped elements. Generally, the inner rotor is mounted upon and driven by a shaft drivingly coupled to the drive shaft of a prime mover such as an electric motor. The eccentrically disposed outer rotor is then driven by the inner rotor via meshing of the outwardly and inwardly extending lobes instantly located nearest an “in-mesh” position. This meshing contact occurs with near zero relative velocity between inner and outer rotors in the region of the in-mesh position while a maximum relative velocity between tips of the outwardly extending lobes of the inner rotor and the inwardly extending lobes of the outer rotor occurs at the opposite or out-of-mesh position along an eccentricity axis.
Present art gerotor pumps comprise a fixedly positioned eccentric gerotor pocket within which the outer rotor is supported by a hydrodynamic bearing. In most gerotor pumps the gerotor pocket is simply formed as part of the pump housing and then completed by a cover plate wherein inner surfaces of the gerotor pocket and cover plate serve as first and second sides of a gerotor cavity. In high pressure gerotor pumps however, the eccentric gerotor pocket is generally formed in a center plate with first and second sides of the eccentric gerotor cavity being provided by the facing surfaces of the housing and cover plate. This is done in order to more adequately control axially directed tolerances and resulting part clearances between the gerotor set and the facing surfaces of the housing and cover plate. In either case, the bore of the eccentric gerotor cavity is formed about a preferred eccentricity offset rotation axis located along a preferred eccentricity axis at a distance nominally equal to a gear addendum. Axially oriented symmetrical fluid commutation ports are formed in either or both of the first and second sides of the gerotor cavity to either side of the preferred eccentricity axis and are fluidly coupled to housing ports.
In operation, fluid is conveyed from the inlet fluid commutation port to inlet side ones of N+1 pumping chambers formed between the outwardly and inwardly extending lobes and elements as they move out of mesh on the inlet side, and then out the outlet fluid commutation port via outlet side ones of the N+1 pumping chambers as they move back toward mesh on the outlet side. The pumping chambers are formed between N nominal line seals provided by the mesh of the outwardly and inwardly extending lobes and elements and an additional nominal line seal between one inwardly extending element and a juxtaposed one of the grooves of the inner rotor nearest the “in-mesh” position. Thus, fluid entering via the inlet fluid commutation port is conveyed to the outlet fluid commutation port at a pressure value determined by the system load via each of the sequentially moving ones of the N+1 pumping chambers. Interestingly, the shaft must rotate (N+1)/N revolutions for a complete cycle of any of the N+1 pumping chambers.
Transverse loading between the inner rotor and outer rotor is nominally generated by the product of the difference between the output and input pressures, and the net transverse plan area between instant ones of the sealing lines formed nearest to the “in” and “out” of mesh positions. Normally, the outer rotor is directly supported by the hydrodynamic bearing formed between it and the eccentric housing bore as described above. Alternately, a needle bearing could be used to support the outer rotor for a gerotor pump that rotates at too low a speed to generate sufficient hydrodynamic bearing support.
Shaft support bearings are often utilized on either side of the inner rotor to support oppositely directed equal transverse loading of the inner rotor in present art gerotor pumps subject to relatively high pressure system loads. Because such shaft support bearings are mounted in both of the housing and cover plate, this in turn requires that the housing and cover plate be positioned in line with one another in a precision manner.
Because the axes of rotation of the gerotor pump and prime mover drive shafts are each fixedly located, the rotational axis of the gerotor pump shaft cannot in general be truly co-axial with the prime mover drive shaft. This requires separate shafts drivingly coupled one-to-another by a compliant coupling. In addition, such gerotor pumps are generally provided with a shaft seal in order to retain the fluid within the pump itself thus tending to make a long and rather complex assembly of the resulting prime mover/coupling/gerotor pump assembly. In addition, the housing, center plate and cover plate must all have precision alignment features for aligning the two gerotor pump bearings along the preferred shaft rotation axis. Further, the gerotor pocket formed in the center plate must be precisely located about the preferred eccentricity offset rotation axis in order to allow proper meshing of the gerotor set.
In general, it would be desirable to provide gerotor pumps having an additional degree of freedom whereby the outer rotor could find its own optimum center of rotation under all conditions of loading and shaft deflection. This would allow significant simplification whereby the resulting gerotor pump could be directly driven by a drive motor output shaft without any of the above described bearings, shaft coupling and additional extreme precision location features.
In addition to all of the above, it is difficult to form and maintain proper clearance values between the gerotor set and the first and second sides of the gerotor cavity of a gerotor pump configured for high pressure system loads (i.e., as determined by the difference in gerotor set thickness and effective center plate thickness). This is due to such practical details as difficulties in maintaining adequate dimensional control of the thickness of the center plate as well as associated contamination resulting from utilization of required interfacing surface sealing means (i.e., such as compliant shims or O-rings). It would be desirable to provide inherently simpler internal means for determining an appropriate minimal axial clearance between the gerotor set and the first and second sides of the gerotor cavity.
Finally, although the Nichols Portland catalog states “all gerotor sets share the basic principle of having conjugately-generated tooth profiles which provide continuous fluid-tight sealing during operation”, the “tooth” (and groove) profiles of the inner rotor are not “conjugately-generated” with respect to the “tooth” profiles of the outer rotor. Rather, the inner and outer rotors of all present art gerotor sets are separately manufactured. Most are economically formed in high volume via utilization of powdered metal technology. Such gerotor sets commonly attain diametral lobe-to-lobe and lobe-to-groove clearances of perhaps 0.003 inch. Although the attainment of such diametral clearance values is in fact an outstanding example of the use of powdered metal technology, those clearances are simply too large for efficient utilization in pumps generating pressure values beyond a few hundreds of pounds per square inch. This is because of “tip leakage” across critical differential pressure bearing nominal contact points (hereinafter “contact points”).
Because of the factors presented above, present art gerotor sets used in pumps intended for higher pressures such as 2,000 PSI are generally formed of case hardening alloy steels. They are hardened and precision ground in order to attain diametral clearance between the critical lobe-to-lobe and lobe-to-groove contact points in the range of perhaps 0.0005 to 0.001 inch. Although this method of manufacture has proven successful in attaining the required accuracy for gerotor sets intended for high-pressure utilization, it is expensive and therefore deemed unsuitable for high volume applications. It would be desirable to provide methods whereby tip portions of lobes of gerotor sets that actually define the critical in- and out-of-mesh position contact points can be re-contoured so as to economically achieve the preferred diametral clearance values of 0.0005 to 0.001 inch between the critical out-of-mesh and lobe-to-groove contact points.
Therefore, it is a general object of the present invention to provide improved gerotor pumps having an additional degree of freedom whereby outer rotors thereof can find their own optimum centers of rotation, and further, wherein fewer precision parts and precision location features are required. It is a further object of the present invention to provide internal means for setting required minimal axial clearance between the gerotor set and the first and second sides of the gerotor cavities of such gerotor pumps. It is still another object of the present invention to provide re-contouring methods whereby the tip portions of lobes of resulting preferred gerotor sets can be re-contoured in order to economically achieve the preferred diametral clearance values of 0.0005 to 0.001 inch between the critical lobe-to-lobe and lobe-to-groove contact points thus enabling utilization of such preferred gerotor sets in high-pressure gerotor pumps. Furthermore, additional objects of the present invention include implementing reduced friction between inner and outer rotor elements of the improved gerotor pumps as well as providing improved porting configurations and improved port timing in and for the improved gerotor pumps.
These and other objects are achieved in improved gerotor pumps according to preferred embodiments of the present invention. Similarly to present art gerotor pumps, an inner rotor of a gerotor set having N outwardly extending lobes with N approximately circularly shaped grooves therebetween is directly driven from a drive motor's output shaft (hereinafter “the drive shaft”). The inner rotor then drives an outer rotor of the gerotor set having N+1 inwardly extending circularly shaped elements about a preferred eccentricity offset rotation axis located generally along a preferred eccentricity axis. However, in each of the improved gerotor pump embodiments of the present invention, the outer rotor is located laterally within the gerotor pocket by lateral constraining means but allowed to float in the orthogonal direction whereby the distance to an actual eccentricity offset rotation axis is determined by the mesh of the gerotor set itself. The lateral constraining means support transverse loading between the inner and outer rotor as nominally generated by the product of the difference between the output and input pressures, and the net transverse plan area between instant ones of the sealing lines formed nearest to the “in” and “out” of mesh positions (hereinafter more simply referred to as “transverse loading”). Then either the drive shaft, or alternately an axle utilized in a universal gerotor pump described below in a seventh alternate preferred embodiment, support equal and oppositely directed transverse loading.
In a preferred embodiment of the present invention, the outer rotor is located laterally by directly rolling on a cam follower disposed laterally outside the outer rotor on the same side of the preferred eccentricity offset rotation axis as the higher-pressure one of the axially oriented fluid commutation ports. In the event that a gerotor pump configured according to the preferred embodiment is to be subjected to bi-directional delivery pressure, first and second cam followers are provided and are disposed laterally in both directions from the preferred eccentricity offset rotation axis. In a slightly modified version of the preferred embodiment of the present invention suitable for use in unidirectional gerotor pumps, the cam follower is replaced by an adjustable eccentric cam follower whereby the operative lateral position of the outer rotor can be adjusted. This version of the improved gerotor pump can be mounted on a drive motor, run under desired output delivery conditions and then adjusted for smoothest running and minimum pump noise.
Thus, a first improved method of supporting a gerotor set comprised in a gerotor pump has been enabled by the preferred embodiment of the present invention. This method comprises the steps of locating the outer rotor of a gerotor set laterally with reference to a preferred eccentricity axis of a gerotor pump, and allowing the outer rotor to find its own eccentricity offset rotation axis location via the mesh of the gerotor set itself.
In alternate preferred embodiments of the present invention, the outer rotor is located within a floating ring that is in turn located laterally with respect to the preferred eccentricity axis but allowed to float nominally along the preferred eccentricity axis. Thus, the position of the floating ring in the orthogonal direction is determined via allowing the mesh of the outer rotor of the gerotor set to determine its own orthogonal location via meshing action, and therefore, the orthogonal location of the floating ring as well.
In a first alternate preferred embodiment of the present invention, the floating ring is located laterally via minimal clearance between the floating ring and laterally disposed flat surfaces formed within a modified gerotor pocket. The laterally disposed flat surfaces are formed in a precision manner in order to effect the required minimal lateral clearance.
In a second alternate preferred embodiment of the present invention, first and second lateral housing mounted positioning means are positioned within the gerotor pocket along the preferred eccentricity axis. Then the floating ring is positioned laterally with respect to the preferred eccentricity axis via the first and second lateral housing mounted positioning means engaging slots formed in opposite sides of the periphery of the floating ring.
In a third alternate preferred embodiment of the present invention, the floating ring is located laterally by a single pin fixedly mounted in the housing and engaging a hole formed in the floating ring in a laterally protruding portion thereof. Transverse loading causes the floating ring to bear against the pin and thence the housing. In a modified version of the third alternate preferred embodiment of the present invention, the pin is replaced by an adjustable eccentric pin whereby the lateral position of the floating ring can be adjusted in a manner similar to that described above with reference to the preferred embodiment.
Thus, a second improved method of supporting a gerotor set comprised in a gerotor pump has been enabled by the first, second and third alternate preferred embodiments of the present invention. This method comprises the steps of locating the outer rotor of a gerotor set within a floating ring, locating the floating ring laterally with reference to a preferred eccentricity axis of a gerotor pump, and allowing the outer rotor located within the floating ring to find its own eccentricity offset rotation axis location via the mesh of the gerotor set itself.
It is believed herein that Geroler technology similar in nature to that utilized in Char-Lynn Orbit Geroler motors manufactured by the Eaton Corporation (e.g., wherein rolls are incorporated in the outer rotor in place of the fixedly formed inwardly extending circularly shaped elements) has never been utilized in a standard gerotor pump wherein the outer rotor is rotationally driven by the inner rotor. However, such Geroler technology would generally be of benefit in gerotor pumps. Therefore, in a fourth alternate preferred embodiment of the present invention, another improved gerotor pump is provided wherein the inwardly extending circularly shaped elements are rolls specifically incorporated into the outer rotor thereof in place of more normally encountered inwardly extending circularly shaped lobes.
In a fifth alternate preferred embodiment of the present invention, modifications in porting are presented whereby relatively viscous fluid and/or high operational speeds can be used and/or obtained without bulk cavitation occurring in pumping chambers of gerotor pumps. In general, the modified porting comprises utilization of radial passages formed in outer rotors whereby fluid directly flows between individual pumping chambers and appropriate ones of inlet and outlet fluid commutation ports.
In a further teaching of the fifth alternate preferred embodiment, fluid commutation ports formed in a floating ring interdict the radial passages of the outer rotor. Fluid enters and leaves the fluid commutation ports via either side of the gerotor pocket and housing ports juxtaposed thereto. Sealing between sides is accomplished via pins freely moving within orthogonally positioned slots that act similarly to bi-directional check valves.
Thus, an improved method for conveying fluid into and out of pumping chambers of a gerotor pump has been enabled by the fifth alternate preferred embodiment of the present invention. This method comprises the steps of implementing radial passages in the outer rotor of a gerotor set, implementing fluid commutation ports interdicting only the radial passages, and utilizing movement of the radial passages over the ends of the fluid commutation ports for switching pumping chamber fluid connection from one fluid commutation port to the other.
It is important to maintain proper axial operating clearance in any of the improved gerotor pumps. If the clearance is too large, excessive leakage will occur thus reducing volumetric efficiency at higher pressures. If the clearance is too small, slight differential thermal expansion between the depth of the gerotor pocket and the thickness of the gerotor set could result in seizure at extreme temperature values. For instance, the housing might be fabricated of aluminum and the gerotor set fabricated of steel. In this case, differential thermal expansion could easily reduce axial clearance to zero and cause seizure at startup under very cold conditions.
This problem is obviated in a sixth alternate preferred embodiment of the present invention, wherein a pressure balancing plate is inserted in a pocket or pockets formed in either or both of the housing and/or cover plate, or alternately within the gerotor pocket itself. Pressure balancing plates are formed with at least the same plan view size as the outer rotor, and thus serve as one or both sides of the gerotor cavity. Each pressure balancing plate is located with reference to the preferred eccentricity axis and the preferred eccentricity offset rotation axis by registration of aligning pins in blind holes formed in the pressure balancing plate.
As the pressure balancing plates are urged toward the gerotor set, they serve generally the same purpose of limiting face leakage as pressure balancing bearing blocks do in many gear pumps. However, the disc brake like tendency of such pressure balancing bearing blocks to drag on the surfaces of the gears in such a gear pump may be obviated in any gerotor pump comprising a floating ring by forming its pressure balancing plate or plates large enough to bear axially upon the floating ring and then selectively forming the floating ring slightly thicker than the gerotor set. Then the axial force provided initially by compression of the sealing rings plus balancing forces provided by the sum of the products of pressure applied to each effective pressure balancing zone and the respective areas thereof maintains contact between the pressure balancing plate or plates and the floating ring, and the gerotor set operates without drag at the selected value of axial clearance.
Features described above in the first through sixth alternate preferred embodiments may be used singly or in combination to configure gerotor pumps having minimal part count and optimum manufacturing economy. In the case of a very high pressure gerotor pump however, it may be desirable to additionally eliminate the imposition of transverse loading on the drive shaft and yet generally maintain the self aligning capability described above.
Therefore, in a seventh alternate preferred embodiment of the present invention, universal gerotor pumps having independent pumping cartridges are provided wherein each of the independent pumping cartridges comprises a gerotor set, floating ring, and two pressure balancing plates. Transverse loading is internally supported within the independent pumping cartridges. The inner rotors are supported via inner rotor supporting axles that are alternately supported by hydrodynamic bearings operatively formed between the axles and bores of the pressure balancing plates, or by sleeve or needle bearings mounted in the pressure balancing plates. In the universal gerotor pumps, the outer rotor and the floating ring are able to float with reference to the inner rotor as previously taught. In addition, the pumping cartridges are able to float with reference to the drive shaft.
In order for any of the above described gerotor pumps to realize higher pressure output values it is of course imperative that the above noted commonly attained diametral lobe-to-lobe and lobe-to-groove clearances of perhaps 0.003 inch be significantly reduced. This is achieved in methods for re-contouring lobe tip regions of inner and/or outer rotors of gerotor sets according to any of the eighth, ninth and tenth alternate preferred embodiments of the present invention as presented below. In general, these methods entail initially forming only the tip regions of either or both of the outwardly extending lobes of the inner rotor and/or the inwardly extending lobes of the outer rotor in a slightly enlarged manner and then re-forming the tip regions as desired. In practice the tip regions are so formed during the powdered metal r manufacturing process mentioned above such that a line-to-line contact, or even an actual interference, would occur along the eccentricity axis if the inner and outer rotors were forced together.
In the method of the eighth alternate preferred embodiment of the present invention, the outer rotors are forcibly distorted by lateral compressive force (e.g., with respect to the eccentricity axes) just sufficiently for the provision of assembly clearance along the eccentricity axes for the inner rotors. This still allows for assembly of the inner rotors because the inner and outer rotors have been formed such that there is still some clearance along the lateral axis to initially form the gerotor sets. Then inward radial forces are applied to the outer rotors proximate to the lobe-to-groove contact points thus defining orthogonal orientation for the eccentricity axes. Next the gerotor sets are immersed in or by a fine lapping slurry. Then as the lateral compressive force is progressively relaxed during a sequential lapping operation, compressive force along the eccentricity axis is imposed upon the tip regions of the lobes as a function of remaining stress present in the outer rotors.
Lapping of the assembled gerotor sets is accomplished by rotationally driving them as they would be driven in a gerotor pump as the lateral compressive force is relaxed. Lapping occurs on tip regions of the N+1 inwardly extending lobes of the outer rotor and the N outwardly extending lobes of the inner rotor until both the lateral compressive force and remaining stress in the outer rotor are relaxed and working clearance values related to the size of the particles in the fine lapping slurry are obtained. Finally, the re-contoured gerotor sets are removed from the fine lapping slurry and cleaned.
In the ninth alternate preferred embodiment of the present invention, a method for “zone” size re-contouring tip regions of lobes of inner rotors for matching outer rotors formed in a standard manner is presented. This method involves lapping of only the tip regions of the outwardly extending lobes of the inner rotors whereby only they are initially formed in a slightly enlarged manner as described above. In this case, inner rotors are positioned within enlarged lapping tools that just clear the outwardly extending lobes of the inner rotors but are otherwise shaped like an outer rotor to form first lapping gerotor sets. Then inward radial forces are applied to the enlarged lapping tools to forcibly form lobe-to-groove contact points and thus determine orientation of eccentricity axes for the first lapping gerotor sets. Next the first lapping gerotor sets are immersed in or by a fine lapping slurry and rotated in order to lap the inner rotors in the manner described above until the desired inner rotor geometries are obtained.
In this case, the desired inner rotor geometries must be determined by accurate gaging methods. For instance, the radial location of the tip apexes of the inwardly extending lobes of outer rotors could be determined via utilization of plug go/no go gages whereby they could be separated into “zone” size determined batches and then the inner rotors lapped as described above until they are re-contoured into matching “zone” size determined batches as determined by ring go/no go gages.
In the tenth alternate preferred embodiment of the present invention, a method for re-contouring tip regions of inner and outer rotors in conformity with respective standardized first and second preferred sizes is presented wherein the tip regions of the outwardly extending lobes of inner rotors are lapped to the first preferred size, and the tip regions of the inwardly extending lobes of outer rotors are lapped to the second and mating preferred size. In this case, tip regions of the outwardly extending lobes of the inner rotors are lapped in exactly the same manner as described above in the ninth alternate preferred embodiment until the first preferred size is obtained. Additionally however, outer rotors are positioned around contracted lapping tools that just clear the inwardly extending lobes of the outer rotors but are otherwise shaped like an inner rotor to form second lapping gerotor sets. Then inward radial forces are applied to the outer rotors to forcibly form lobe-to-groove contact points and thus determine orientation of eccentricity axes for the second lapping sets. Next the second lapping gerotor sets are immersed in or by a lapping slurry and rotated in order to lap the outer rotors in the manner described above until the desired outer rotor geometries are obtained.
Thus, improved gerotor pumps configured according to the teachings of the preferred and alternate preferred embodiments of the present invention achieve the desired goals of achieving high pressure values and smooth performance as well as having reduced complexity and therefore reduced implementation cost relative to their performance capabilities. Preferably included are re-contoured lobe tips of comprised gerotor sets according to the teachings of the eighth, ninth or tenth alternate preferred embodiments in order to achieve the desired goal of re-contouring tip portions of lobes of gerotor sets in order to economically achieve the preferred diametral clearance values of 0.0005 to 0.001 inch between the critical lobe-to-lobe and lobe-to-groove contact points.
In a first group of aspects, then, the present invention is directed to improved gerotor pumps wherein the outer rotor is laterally constrained but allowed to float in an orthogonal direction whereby the actual eccentricity offset rotation axis location is determined by mesh of the gerotor set itself. Included are gerotor pumps wherein the N+1 inwardly extending circularly shaped elements are N+1 inwardly extending rolls. Also included are gerotor pumps wherein means are provided whereby the operative lateral position of the outer rotor can be adjusted.
In another aspect, the present invention is directed to a first improved method for supporting a gerotor set comprised in a gerotor pump, wherein the method comprises the steps of locating the outer rotor of a gerotor set laterally with reference to a preferred eccentricity axis of the gerotor pump, and allowing the outer rotor to find its own eccentricity offset rotation axis location via mesh of the gerotor set itself.
In other aspects the present invention is directed to improved gerotor pumps wherein the outer rotor is located within a floating ring and the floating ring is laterally constrained but allowed to float in the orthogonal direction whereby the actual eccentricity offset rotation axis location is determined by mesh of the gerotor set itself.
In another aspect, the present invention is directed to a second improved method for supporting a gerotor set comprised in a gerotor pump, wherein the method comprises the steps of locating the outer rotor of a gerotor set within a floating ring, locating the floating ring laterally with reference to a preferred eccentricity axis of the gerotor pump, and allowing the outer rotor located within the floating ring to find its own eccentricity offset rotation axis location via mesh of the gerotor set itself.
In still other aspects the present invention is directed to improved gerotor pumps wherein radial passages are formed connecting each groove located between the inwardly extending circularly shaped lobes and the outside circular surface of the outer rotor. Included are aspects wherein fluid commutation ports formed in the floating ring are utilized in place of the axially oriented fluid commutation ports.
In another aspect the present invention is directed to an improved method for conveying fluid into and out of pumping chambers of a gerotor pump, wherein the method comprises the steps of implementing radial passages in the outer rotor of a gerotor set, implementing fluid commutation ports interdicting only the radial passages, and utilizing movement of the radial passages over the ends of the fluid commutation ports for switching pumping chamber fluid connection from one fluid commutation port to the other.
In other aspects the present invention is directed to the improved gerotor pumps wherein at least one pressure balancing plate large enough to substantially cover the outer rotor is urged toward the gerotor set in the axial direction thereby limiting face leakage. Included are aspects wherein a floating ring is formed selectively thicker than the gerotor set, and further wherein at least one pressure balancing plate large enough to substantially cover the floating ring is urged into axial contact with the floating ring thereby permitting the gerotor set to operate without any drag at a selected value of axial clearance.
In still other aspects the present invention is directed to universal gerotor pumps wherein gerotor set are located within a floating ring and between pressure balancing plates wherein the gerotor set, floating ring, pressure balancing plates and an axle are combined in an independent pumping cartridge and further wherein the axle is supported for rotation within the pressure balancing plates and in turn supports the inner rotor, and further wherein the entire pumping cartridge is angularly oriented but allowed to otherwise float with reference to the drive shaft.
In another aspect, the present invention is directed to a third improved method for supporting a gerotor set comprised in a gerotor pump, wherein the method comprises the steps of locating the inner rotor of a gerotor set between first and second pressure balancing plates, locating the outer rotor of the gerotor set within a floating ring, locating the floating ring between the first and second pressure balancing plates and laterally with reference to the inner rotor whereby an independent pumping cartridge is formed, providing a rotational constraint for the independent pumping cartridge, allowing the outer rotor to find its own eccentricity offset rotation axis location with reference to the axis of rotation of the inner rotor via mesh of the gerotor set itself, and allowing the independent pumping cartridge as a whole to find its own operational position within its rotational constraint via rotational driving engagement of the inner rotor with the drive shaft.
In a final group of aspects, the present invention is directed to methods for forming conjugately-generated tip regions of inner and outer rotors, zone fitted tip regions of inner and outer rotors, or absolute sized generated tip regions of inner and outer rotors, wherein the methods in general comprise the steps of: initially forming either or both of tip regions of outwardly extending lobes of the inner rotors and inwardly extending lobes of the outer rotors in a slightly enlarged manner; assembling gerotor sets whose inner and outer rotor tip regions are to be conjugately-generated by compressively distorting the outer rotors, or assembling inner or outer rotors whose tip regions are to re-generated to a selected size on or within lapping tools formed similarly to outer or inner rotors, respectively; and then lapping the tip regions as required to form closely fitting gerotor sets in order to enable gerotor pumps to achieve higher pressure values.
A better understanding of the present invention will now be had with reference to the accompanying drawing, wherein like reference characters refer to like parts throughout the several views herein, and in which:
With reference now to
N+1 pumping chambers 36 are formed between N nominal line seals 38 provided by the mesh of the outwardly and inwardly extending lobes and circularly shaped elements 16 and 20 and an additional nominal line seal 38 between one inwardly extending circularly shaped element 20 and a juxtaposed one of N grooves 40 of the inner rotor 14 nearest the “in-mesh” position. The inner rotor 14 is directly driven by the output shaft 42 of a drive motor 44 (hereinafter “the drive shaft 42”) via a feature enabling transmission of torque from one element to another such as implemented herein by Woodruff key 46.
The outer rotor 18 is rotationally driven in turn by the inner rotor 14 via mesh of the outwardly extending lobes 16 with the inwardly extending circularly shaped elements 20 via those line seals 38 instantly positioned whereat they can transmit a tangential driving force component.
In any of gerotor pumps 10, or 100, 130, 150, 180, 230, 260 and 270 yet to be described, blind insertion of the drive shaft 42 is a factor in volume production. Such blind insertion is complicated by the necessity of providing interfacing means for transmitting torque between the drive shaft 42 and inner rotor 14. Because of the concomitant necessity for supporting transverse loading, it is preferable to implement the drive shaft 42 as a round shaft with a single feature such as Woodruff key 46. Insertion of the drive shaft 42 is assisted by locating shaft seal 48 within the motor 44; configuring the drive shaft 42 with a conical shape as shown at numerical indicator 172; laterally constraining the Woodruff key 46 with temporary constraining means (not shown); and then slowly rotating the drive shaft 42 within bore 174 of the inner rotor 14 until the Woodruff key 46 engages key slot 176.
The gerotor pump 10 is intended for unidirectional use with reference to differential pressure thereacross. Thus, the cam follower 22 is located on the higher pressure side of the gerotor pump 10 in a standard manner by a bore 50 formed in the gerotor pocket 26. The bore 50 is precisely located a distance equal to the sum of the outside radius of the outer rotor 18 and the outside radius of the cam follower 22 from axis of rotation 52 of the drive shaft 42. This is done in order to locate the outer rotor 18 along a preferred eccentricity axis 54 as accurately as possible.
The gerotor pocket 26 is contoured to provide at least nominal clearance for the outer rotor 18 and the cam follower 22, and specifically so as to provide freedom of motion in the orthogonal direction for the gerotor set 12 as indicated by numerical indicators 56a and 56b. The bore 50 is actually formed in an inner surface 58 of the gerotor pocket 26, and the inner surface 58 is formed at a slightly greater depth from the shoulder 30 than the axial thickness of the gerotor set 12 whereby the inner surface 58 serves as a first side of a gerotor cavity 27. A cover plate 60 is inserted into the bore 32 against the shoulder 30 and is forcibly retained thereat by a beveled retaining ring 62 whereby its inner surface 64 serves as the second side of the gerotor cavity 27. Proper indexing for the cover plate 60 is provided via engagement of alignment pins 66 with blind holes 68 formed in either of the shoulder 30 and the cover plate 60 (the holes 68 formed in the cover plate 60 are not located within a sectional view plane and thus numerical indicator 68 only indicates their presence).
The gerotor set 12 is oriented with the outer rotor 18 nominally disposed about a preferred eccentricity offset rotation axis 70. It is shown in
As implied above, the outer rotor 18 is urged laterally outward by a force derived from fluid pressure present at the higher pressure one of the axially oriented fluid commutation ports 72a and 72b. In order to support the outer rotor 18 against that force, the cam follower 22 is located on that side of the outer rotor 18. If the gerotor pump 10 operates with clockwise rotation and is in fact being utilized as a pump, the higher pressure one of the fluid commutation ports 72a and 72b would of course be an outlet fluid commutation port 72a and that case is so depicted in
In operation, the drive shaft 42 as well as other components of the gerotor pump 10 are subject to slight deflections in response to differential pressure induced transverse loading (hereinafter “transverse loading” or “the transverse loading”). The outer rotor 18 is concomitantly subjected to an equal and oppositely directed transverse loading with reference to that applied to the drive shaft 42 whereby it flexes sufficiently to be supported laterally by the cam follower 22. The cam follower 22 suffers internal deflection as well. In some cases it may be necessary to supplement the outer rotor 18 with a hardened steel tire 78 in order to properly support such transverse loading. As the differential pressure increases and causes further deflection of the components, the outer rotor 18 or steel tire 78 (if used) is free to roll on the cam follower 22 in order to allow the instant position of an actual eccentricity offset rotation axis 70′ to be determined by the mesh of the gerotor set 12 itself.
Relative displacements of the drive shaft 42 and gerotor set 12 resulting from such transverse loading are comparatively depicted between the plan views shown
Even such small port timing error angles can have a significant effect on theoretical pump output pressure ripple as is comparatively depicted between
On the other hand, in
As a practical matter, it is difficult to achieve the ideally centered condition shown in
In passing it should be noted that a similar porting problem exists with piston pumps. Piston pumps have similar identical but phase shifted individual fluid flow delivery curves. Those curves usually have a purely sinusoidal form because the flow displacement is usually based upon a swash plate that generates a sinusoidal mechanical displacement of the pistons within their cylinders. However, the individual cylinders are ported in an exactly similar way to the axially oriented fluid commutation ports 72a and 72b described above and are thus subject to the same types of positional errors and flow discontinuities as described above.
In any case, the cam follower derived lateral constraint of the gerotor set 12 can beneficially be altered in an otherwise identical unidirectional gerotor pump 10 (not shown) via replacing the cam follower 22 with an adjustable eccentric cam follower 92 such as that shown in
With reference now to
Although gerotor pocket 26′ could have been formed with nominal clearance for the outer rotor 18 and cam followers 22 similarly to the gerotor pocket 26, it and bore 32 are depicted as being formed concentric with the axis of rotation 52. Thus, there is no requirement for the alignment pins 66 or holes in the shoulder 30 (or a cover plate 60′—not shown).
A first improved method of supporting a gerotor set comprised in a gerotor pump has been enabled by the preferred embodiment of the present invention. As depicted in
As a practical matter, optimal use of the first improved method of supporting a gerotor set 12 comprised in a gerotor pump 10 is limited to applications wherein the gerotor set 12 operates at relatively low fluid pressures and/or low speeds. In part, this is because the cam follower 22 is generally much smaller than the steel tire 78 or the outer rotor 18 and must rotate at a significantly faster speed than the gerotor set 12. This is a problem because even cam followers comprising roll separators are subject to significant load de-rating. Further, cam followers having higher load values generally comprise a full complement of rolls and are themselves limited to relatively low speed operation.
However, other methods of similarly constraining the gerotor set 12 can be used without departing from the spirit of the present invention in order to markedly increase operational speeds. For instance, shown in
As before, the inner surface 58 of the gerotor pocket 104 is formed at a minimally greater depth from the shoulder 30 than the axial thickness of the gerotor set 12 whereby the inner surface 58 serves as a first side of a gerotor cavity 105. Also as before, the cover plate 60 is inserted into the bore 32 against the shoulder 30 and is forcibly retained thereat by a beveled retaining ring 62 whereby its inner surface 64 serves as the second side of the gerotor cavity 105. Further, the cover plate 60 and bore 32 are again formed concentric with the axis of rotation 52 whereby no alignment pins 66 are required. As differential pressure increases and causes deflection of the components, the floating ring 102 is free to roll on the selected one of the flat surfaces 108a or 108b in order to allow the instant position of an actual eccentricity offset rotation axis 70′ to be determined by the mesh of the gerotor set 12 itself.
On the other hand, if floating ring rotation is deemed undesirable, an enlarged floating ring 110 having an eccentric bore with a single radially oriented slot 112 formed in the thickest portion of the ring can be used as shown in
Still other methods of similarly constraining the gerotor set 12 can be used without departing from the spirit of the present invention. For instance, shown in
Yet another method of similarly constraining the gerotor set 12 is depicted in
The floating ring 152 is again precluded from rotation. In this case however, this is accomplished via combination of the mesh of the gerotor set 12 and the engagement of the pin 154 in the hole 158.
This type of lateral constraint of the gerotor set 12 can enable adjustment of the lateral position of the floating ring 152 and the gerotor set 12 similarly to the above explained adjustment utilizing an adjustable eccentric cam follower 92. This is accomplished via replacing the pin 154 by an adjustable eccentric pin 164 such as depicted in
A second improved method of supporting gerotor sets comprised in gerotor pumps has been enabled by the first, second and third alternate preferred embodiments of the present invention. As depicted in
With reference now to
In operation, the rolls 182 accelerate from near zero relative rotational speed (e.g., with reference to the outer rotor 184) at the in-mesh position to a maximum relative rotational speed as each roll 182 moves over a juxtaposed outwardly extending lobe 16 and attains a significant relative motion component. Finally, each roll 182 decelerates back to the near zero relative rotational speed as it returns to the in-mesh position. In so doing, the rolls 182 form hydrodynamic bearings within the partial bores 188 thereby supporting forces transmitted by the line seals 38 without Coulomb friction and wear.
Generally, outwardly extending lobes 16 of the inner rotor 14 and inwardly extending circularly shaped elements 20 of the outer rotor 18 tend to largely block axially oriented fluid commutation ports 72a or 72b configured as recommended by Nichols Portland—especially near the “in-mesh” position. Therefore, in a fifth alternate preferred embodiment of the present invention, modifications in porting are presented whereby relatively viscous fluid and/or high operational speeds can be used and/or obtained without bulk cavitation occurring in gerotor pump pumping chambers. In general, the modified porting comprises utilization of radial passages 192 formed in outer rotors thereof such that each fluidly communicates with an individual pumping chamber 36 in conjunction with fluid commutation ports 190a and 190b formed for selective interdiction with the radial passages 192 so as to more effectively convey fluid from or to housing ports of such gerotor pumps. In a first type of the modified porting, the fluid commutation ports 190a and 190b are implemented as curved slot shaped fluid commutation ports of uniform radial size formed nominally concentric with the preferred eccentricity offset rotation axis 70. In a second type of the modified porting, radial porting is implemented wherein the radial passages 192 are implemented as radial face slots 200 that fluidly communicate via face fluid commutation ports 214 formed in a floating ring 212.
Depicted in
Depicted in
With reference now to
Orthogonal sealing between one side of the preferred eccentricity axis 54 and the other is accomplished via pins 218 freely moving within orthogonally positioned slots 140 formed similarly to those described above in the second alternate preferred embodiment. As shown in
In improved gerotor pumps comprising either type of modified porting arrangement, improved performance with viscous fluids and/or at high operational speeds is obtained because the rate at which either of fluid commutation ports 190 or 214 is opened or closed is significantly quicker than with axially oriented fluid commutation ports 72a or 72b configured as recommended by Nichols Portland. Thus, an improved method for conveying fluid into and out of pumping chambers of a gerotor pump has been enabled as is depicted in
In passing however, it should be noted that improved gerotor pumps comprising any version of the modified porting arrangement described above involve radial fluid flow components subject to centrifugal force. This is especially true in the cases of improved gerotor pump 210 already described, and improved gerotor pumps 270, 310, 370 and 400 to be described below. By way of example, if the improved gerotor pump 210 were to be implemented using the afore mentioned standard Nichols Portland model 6170 gerotor set, then differential pressures approaching 5 PSI could be expected at an input rotational speed of about 4,500 RPM. Unless a system reservoir utilized therewith were pressurized, this would amount to a practical limit on operational speed in order to limit input side bulk cavitation. Since the outer diameter of the Nichols Portland model 6170 gerotor set is 3 inches, this would suggest a rule of thumb limiting operational speeds for gerotor pumps utilizing radial porting to
Nmax=4,500 Sqrt[3/d]RPM
where Nmax is the maximum rotational speed inn RPM and Sqrt[3/d] is the square root of the ratio of 3 inches (e.g., the outer diameter of the 6170 gerotor set) divided by the outer diameter of the gerotor set in question.
Also taught in the fifth alternate preferred embodiment of the present invention is a method of reducing hydrodynamic bearing loading between an outer rotor 202 and any of the floating rings 102, 110, 116, 138, 152 and 212 described above, or 274, 300, 346 and 374 yet to be described, wherein fluid pressure within each pumping chamber 36 is conveyed radially outward in an appropriately selective manner. In the case of the gerotor set 204 this happens as a matter of course because pressurized fluid is conveyed through each radial face slot 200 to the space between the outer rotor 202 and any of the floating rings 212, 274, 300 and 374. As a matter of fact, pressurized fluid is even conveyed to the flat surfaces 108a and 108b in gerotor pump 210 via passage of the pressurized fluid through the face fluid commutation ports 214.
On the other hand, similar reduced hydrodynamic bearing loading between either outer rotor 18 or 184 and any of the floating rings 102, 110, 116, 138, 152, and 346 could be implemented by simply forming radial holes 226 connecting each pumping chamber 36 to the outside circular surface 228 of either of the outer rotors 18 and 184 as respectively shown in
Yet another factor with any of the gerotor pumps 10, 100, 130, 150, 180 or 210 is face leakage between the inner and outer rotors 14, and 18 or 202, respectively, and inner surfaces 58 and 64. It is important to maintain proper operating axial clearance at all times. If the clearance is too large, excessive leakage will occur thus reducing volumetric efficiency at higher pressures. If the clearance is too small, differential thermal expansion between the depth of any of gerotor cavities 26, 104, 136, 162 or 222 and the thickness of the gerotor set 12 or 204 could result in seizure at extreme temperature values. For instance, the housing 28 might be fabricated of aluminum and the gerotor set 12 or 204 fabricated of steel. In this case, differential thermal expansion could easily reduce axial clearance to zero and cause seizure at startup under very cold conditions. It is very difficult to control the appropriate dimensional tolerances such that the actual working gaps between the inner and outer rotors 14 and 18 or 202, and either of the inner surfaces 58 and 64 are maintained as required to effect minimal face leakage.
Shown in
Again for convenience, the pressure balancing plate 232 is depicted in
In order to implement the balancing function of a pressure balancing plate 232, the shadow axially oriented fluid commutation ports 244a and 244b communicate fluidly with pressure balancing zones 250 located on the opposite side 252 of the pressure balancing plate 232 via bores 254 provided for that purpose. Areas of the pressure balancing zones 250 are determined by appropriately configured sealing rings 256 installed in grooves 258a and 258b theresurrounding. In cases where the axially oriented fluid commutation ports 72a and 72b are the ones formed in a pressure balancing plate 232, the bores 254 must additionally convey fluid between the axially oriented fluid commutation ports 72a and 72b and the housing ports 74a and 74b. In such cases, the bores 254 are enlarged and positioned in juxtaposition to the housing ports 74a and 74b in order to effectively convey the pump's delivery fluid flow.
Shown in
When urged toward a gerotor set 12 or 204, a pressure balancing plate 262 serves generally the same purpose of limiting face leakage as pressure balancing bearing blocks do in many gear pumps. However, the disc brake like tendency of such pressure balancing bearing blocks to drag on the surfaces of the gears in such a gear pump may be obviated by selectively forming the floating ring 102 slightly thicker than the gerotor set 12 or 204. Then the axial force provided initially by compression of the sealing rings 256 plus the axial force derived from pressure applied to either or both of the pressure balancing zones 250a and 250b maintains contact between the pressure balancing plate 262 and the floating ring 102, and the gerotor set 12 or 204 operates without any equivalent drag at a selected value of axial clearance therebetween.
Shown in
Fluid flowing from or to the face fluid commutation ports 276a passes through holes 286a and 286b formed in the floating ring 274. Passage of these fluid flows plus those flowing to or from the face fluid commutation ports 276b is provided by housing ports 74a and 74b.
As particularly depicted in
The teachings of the fifth and sixth embodiments can also be implemented in a modified version of the gerotor pump 270 as depicted in
However, it is apparent that there would be some difficulties in implementing this particular version of the gerotor pump 270. Firstly, since all of the fluid must pass through the holes 286a and 286b (e.g., instead of half of the fluid as in the floating ring 274), loses therein would be higher. Furthermore, the severely reduced incidence angles of edges 302 of the fluid commutation port grooves 298a and 298b render it difficult to form spacing therebetween accurately equal to the width of the holes 226. Thus, it is apparent that maintaining precise port timing would be difficult. In counterpoint, this observation also implies that similar edges 304 of the face fluid commutation ports 276a and 276b could beneficially be formed parallel to the preferred eccentricity axis 54 (not shown). This would result in the distance therebetween not changing as a function of final forming operations of the inner bore 306 of the floating ring 274.
The Nichols Portland catalog suggests that a separate center plate fabricated in a similarly slightly thicker manner (e.g., than the gerotor set 12 or 204) be utilized in the same manner to limit face leakage. This is understood herein to be standard practice for prior art high pressure gerotor pumps. However, fabricating either of the gerotor pumps 260 or 270 with a floating ring 102, 274 or 300 and a pressure balancing plate 262 or 280 as depicted respectively in
With reference now to
In this case, the drive motor 44 includes the shaft seal 48 and the motor bearing 312 with the shaft seal 48 seated against a shoulder 318 and the motor bearing 312 being forcibly retained by a beveled retaining ring 320. The gerotor set 204 and floating ring 274 are located axially by a barrier plate 322 seated against shoulder 324. A pressure balancing plate 326 is positioned against the floating ring 274 but is urged theretoward by sealing rings 256 and pressure balancing zones 328 located in a cover plate 330. As before, the cover plate 330 is forcibly retained against shoulder 30 by beveled retaining ring 62. However, in this case the cover plate 330 comprises delivery ports 332 within which are mounted delivery fittings 334.
Proper angular indexing of the barrier plate 322, floating ring 274 and pressure balancing plate 326 is achieved via engagement of housing mounted pins 284 with slots 140 in each element while proper indexing of the cover plate 330 is achieved via engagement of the end of the housing mounted pins 284 with blind holes 336. However, transverse loading derived forces are mainly transmitted to the housing 314 via flat surfaces 108 while nominal orthogonal clearance for the floating 274 is provided as again indicated by numerical indicators 56a and 56b.
Bi-directional operation is enabled by check valves 338. As before, the check valve 338 instantly in fluidic communication with the lower port pressure vents the planar regions 288 and bores 290 to the lower pressure side of the gerotor pump 310. Because of the significantly enlarged and angularly disposed bores 254 in the pressure balancing plate 326, it is most convenient to utilize commercially available check valves such as an Axial Flow Lee Check valve available from The Lee company of Westbrook, Conn. for the check valves 338.
As implied by the above description of improved gerotor pump 310, features comprised in the gerotor pumps 10, 100, 130, 150, 180, 210, 230, 260 or 270 may be used singly or in combination to configure preferred gerotor pumps having selected performance characteristics along with minimal part count and optimum manufacturing economy. In some cases however, it is desirable to eliminate the reaction force (e.g., to transverse loading) hereinabove imposed on the drive shaft 42—even at the cost of slightly increased manufacturing costs. This would eliminate the lateral deflection noted above in the case of drive shaft 42. Further, because it would contain transverse loading within the pump structure it would allow utilization with a more nearly standard drive motor through simple spline shaft coupling means.
Therefore, in a seventh alternate preferred embodiment of the present invention, first and second types of universal gerotor pumps (e.g., as respectively embodied herein by first and second universal gerotor pumps 340 and 370 described below) are provided wherein a gerotor set, floating ring, two pressure balancing plates and an axle are combined in independent pumping cartridges. In general, the first type of universal gerotor pump comprises a two degree of freedom coupling (e.g., similar in operative nature to an Oldham coupling) for providing reaction torque (e.g., to the applied drive shaft torque) from its housing to its independent pumping cartridge while the second type of universal gerotor pump comprises an offset angular position constraint for providing the reaction torque. In either case, transverse loading is internally supported within the independent pumping cartridges. The inner rotors are supported via the axles that in turn are alternately supported by hydrodynamic bearings operatively formed between the axles and bores of the pressure balancing plates, or by sleeve or needle bearings mounted in the pressure balancing plates. Ideally, such universal gerotor pumps incorporate optimum porting as taught above in the fifth embodiment and outer rotors that are dominantly supported by pressurized fluid conveyed through radial face slots as also taught above in the fifth embodiment. However, in special cases the outer rotors could be supported within the floating ring by needle bearings instead of hydrodynamic bearings. This would be useful for implementing gerotor pumps wherein very slow and/or reversing operation is contemplated and it is desired to absolutely preclude breakaway characteristics otherwise resulting from Coulomb friction.
Specifically with reference now to
In the independent pumping cartridge 342 the floating ring 346 and pressure balancing plates 348a and 348b are formed generally according to the teachings of the first and sixth alternate preferred embodiments as described above. In this case however, external flat surfaces 356 of the floating ring 346 and pressure balancing plates 348a and 348b are slidingly mounted within an intermediate ring 358 on internal opposing flat surfaces 360 thereof. Thus, opposing transverse loading derived forces in the floating ring 346 and the pressure balancing plates 348a and 348b are resisted by and confined within the intermediate ring 358. Then, orthogonal opposing external surfaces 362 of the intermediate ring 358 are slidingly mounted within orthogonal flat surfaces 364 formed in a modified gerotor pocket 366 formed in housing 368. Utilization of the respective interfacing external flat surfaces 356 and 362 on the floating ring 346, the pressure balancing plates 348a and 348b, and on the intermediate ring 358 are required in order to provide reaction torque necessary to support applied motor torque.
With further reference now to
In the second universal gerotor pump 370 a pin 380 serves to tie the floating ring 374 and pressure balancing plates 376a and 376b together. Transverse loading is thus supported within the independent pumping cartridge 372 via the pin 380. However, the pin 380 is formed longer than the combined axial length of the assembled floating ring 374 and pressure balancing plates 376a and 376b. Then the reaction torque necessary to support the applied motor torque is provided by the ends 382 of the pin 380 extending beyond the independent pumping cartridge 372 and engaging oblong slots 384 formed in each of a housing 386 and/or a cover plate (not shown).
In the universal gerotor pumps 340 and 370, the respective independent pumping cartridges 342 and 372 are held together axially by near proximity to and between respective flat surfaces 390 and 392 of the housings 368 and 386 and an opposing internal flat surface of the cover plate by sealing rings 256 and pressure applied to the pressure balancing zones 250 as taught in the sixth embodiment. A drive shaft 394 utilized in place of the drive shaft 42 does not have to support transverse loading derived forces and therefore comprises a spline 396 in place of a second Woodruff key 46 for transmitting driving torque to a centrally disposed female spline 388 (e.g., as indicated in Pigs. 27 and 29) within the axle 350. Although the drive shaft 394 is free of transverse loading it is considered preferable herein to locate the female spline 388 centrally within the axle 350 and thus in transverse planar alignment with either of the floating rings 346 or 374.
Thus in either of the first or second universal gerotor pumps 340 or 370, the outer rotor 202, and floating ring 346 or 374 are able to float with reference to the inner rotor 14 and axle 350 as previously taught. In addition, the independent pumping cartridges 342 and 372 as a whole are able to float with reference to drive shaft 394. No transverse loading is present in the first universal gerotor pump 340 while the only transverse loading applied to drive shaft 394 by the independent pumping cartridge 372 in the second universal gerotor pump 370 is an equal and oppositely directed reaction force to that applied to the ends 382 of the pin 380 as a result of the applied motor torque.
Housing ports 74a and 74b may be located either in the housing 368 or 386, or in the cover plate and are coupled to the juxtaposed set of curved slot shaped fluid commutation ports 190a and 190b or face fluid commutation ports 276b via appropriate bores 254 as described above with reference to the sixth alternate preferred embodiment.
A third improved method of supporting gerotor sets comprised in gerotor pumps has been additionally enabled by the seventh embodiment of the present invention. As depicted in
providing a rotational constraint for the independent pumping cartridge, allowing the outer rotor located within the floating ring to find its own eccentricity offset rotation axis location with reference to the axis of rotation of the inner rotor via mesh of the gerotor set itself; and allowing the independent pumping cartridge as a whole to find its own operational position within its single tangential constraint via the rotationally driving engagement of the inner rotor with the drive shaft.
All of the improved gerotor pumps described hereinabove have either been depicted in conjunction with a fully integrated drive motor 44, or as being adapted for receiving an integrated drive motor 44. However, teachings of the preferred and various alternate preferred embodiments of the present invention can of course also be utilized to configure similarly improved stand-alone gerotor pumps. Therefore, with reference now to
In general terms, the stand-alone gerotor pump 400 is configured similarly to many known gear pumps wherein a sub-assembly 406 comprising the front and rear bearing blocks 404a and 404b, floating ring 212 and gerotor set 204 is slidingly positioned within a bore 408 formed in a housing 410. The bore 408 has laterally disposed flat surfaces 108a and 108b with respective central relief output and input passages 412a and 412b formed similarly to the manner in which housing ports 216a and 216b penetrate the nominal centers of the flat surfaces 108a and 108b in the housing 224 depicted in
As before, the floating ring 212 is formed very slightly longer than the gerotor set 204 whereby the gerotor set 204 is completely free to rotate therein even when the front and rear bearing blocks 404a and 404b are forcibly placed in contact with the floating ring 212. The housing 410, in turn, is similarly formed slightly longer than the combined axial lengths of the front bearing block 404a, floating ring 212 and rear bearing block 404b. Thus, when respective front and rear cover plates 414 and 416 are located by dowel pins 418 and forcibly retained on either end of the housing 410 by multiple bolts 420 (one shown), slight axial movement of the sub-assembly 406 is still possible.
The front cover plate 414 serves as the mounting surface for the stand-alone gerotor pump 400. A pilot boss 422 is provided and multiple bolts 424 (again—one shown) are utilized in mounting the stand-alone gerotor pump 400. Forward migration of the needle bearing 354a is precluded by retainer plate 426. In addition, a shaft seal 48 is mounted within the front cover plate 414 for sealing the input end 428 of the pump shaft 402. In this exemplary case, the stand-alone gerotor pump 400 is configured as a unidirectional pump whereby an O-ring seal 430 is used to limit high pressure fluid to the area 432 immediately surrounding the front end of the output relief passage 412a.
The rear cover plate 416 comprises respective output and input ports 434a and 434b within which are mounted delivery fittings 334. The rear bearing block 404b comprises relief slots 436a and 436b for enabling restriction free fluid passage from or to respective relief passages 412a and 412b as well as respective face fluid commutation ports 214. A sealing ring 256 is mounted in the rear cover plate 416 and defines a pressure balancing zone 328 between the rear cover plate 416 and the rear bearing block 404b. Output fluid pressure forces the sub-assembly 406 together and urges it toward the front cover plate 414. Input fluid pressure is conveyed to the bores 290 from the relief slot 436b in a standard manner by face slot 438. Finally, seepage fluid is eliminated by O-ring seals 440.
Again, the gerotor pumps 10, 130, 150, 180, 210, 230, 260, 270, 310, 340, 370 and 400, possess numerous advantages over gerotor pumps configured according to the present art. The primary advantages relate to providing gerotor pumps of simplified design having an additional degree of freedom whereby their outer rotors can find their own optimum centers of rotation, and further, wherein fewer precision parts and precision location features are required. Further advantages include providing adjustment means for enabling smooth and quite running of uni-directional gerotor pumps under load, providing improved critical part location constraints for enabling smooth and quite running of bi-directional gerotor pumps, and providing internal means for setting required minimal axial clearance between the gerotor set and the first and second sides of the gerotor cavity of gerotor pumps.
With reference now to
Operational volumetric efficiency is significantly limited by tip leakage through leakage path 466 and to a lesser extent through leakage path 468. This is because relatively large working clearance values are usually experienced as a result of limitations of prior art fabrication methods. Typically such fabrication methods involve utilization of powdered metal technology wherein diametral clearance values of perhaps 0.003 inch between contact points 452 and 460 are generally experienced. Clearly, such tip leakage would be significantly reduced via significantly reducing the diametral clearance between the contact points 452 and 460.
In order for any of the above described gerotor pumps to realize higher pressure output values it is of course imperative that this diametral lobe-to-lobe and lobe-to-groove clearances be significantly reduced. This is achieved in methods for re-contouring lobe tip regions of inner and/or outer rotors of gerotor sets according to any of the eighth, ninth and tenth alternate preferred embodiments of the present invention as presented below. In general, these methods entail initially forming only the tip regions of either or both of the outwardly extending lobes of the inner rotor and/or the inwardly extending lobes of the outer rotor in a slightly enlarged manner and then re-forming the tip regions as desired.
These methods are possible because close inspection of portions of outwardly extending lobes 470 of the inner rotor 458 and inwardly extending lobes 472 of the outer rotor 464 nearest the out-of-mesh position 454 reveal that only the respective extreme tip regions 474 and 476 thereof are involved in forming contact point 452. Reducing working clearance between the tip regions 474 and 476 alone would significantly reduce diametral clearance along the eccentricity axis 456 generally present in prior art gerotor sets 450, thereby significantly narrowing leakage paths 466 and 468, and thus significantly reducing tip leakage.
In greater detail, re-contouring methods are presented in the eighth, ninth and tenth alternate preferred embodiments wherein either or both tip regions 474 and 476 of respective modified inner and outer rotors 478 and 480 are initially formed in a slightly enlarged manner (i.e., such as during the powdered metal technology manufacturing process mentioned above) as shown in respective plan views presented in an exaggerated manner in
A method for forming conjugately-generated tip regions of inner and outer rotors utilized in gerotor sets is presented in the eighth alternate preferred embodiment of the present invention. As depicted in
In any case, an inner rotor 478 is eccentrically positioned along the eccentricity axis 456 within each stressed outer rotor 480. In addition, the cam follower 494 of a third displacement means 490c is forcibly applied in juxtaposition to the contact point 460 along the eccentricity axis 456. This force is applied through the contact point 460 and inner rotor 458 to the inner rotor drive spindle 496. The result is a continuing orthogonal relationship between eccentricity and lateral axes 456 and 488 during an ensuing lapping operation.
Finally, the gerotor sets 482 are immersed within or by a fine lapping slurry and lapping is begun. This can be effected by either rotationally driving the inner rotor spindle 496 as depicted in
For that reason, the methods described below for forming conjugately-generated tip regions of inner and outer rotors utilized in gerotor sets depicted in the flow chart of
In any case, as the lapping progresses, torque applied by the lateral compressive force by displacement means 490a and 490b is progressively relaxed whereby compressive force is imposed upon those tip regions 474 and 476 near the out-of-mesh positions 454 as a function of remaining stress present in the outer rotors 480. The lapping operation continues until both the compressive force and the remaining stress in the outer rotors 480 are totally relaxed whereupon working tip clearances at contact points 452 and 460 achieve values related to the size of particles in the fine lapping slurry. Finally, the re-contoured gerotor sets 482 are removed from the fine lapping slurry and cleaned. Then the re-contoured gerotor sets 482 are utilized as gerotor sets comprising mated inner and outer rotors 478 and 480. Thus, gerotor sets 482 are re-contoured according to the preferred embodiment of the present invention and can in fact be said to be conjugately-generated.
With reference now to
The method for forming conjugately-generated tip regions of inner and outer rotors utilized in gerotor sets then is depicted in the flow chart of
A method for “zone” size re-contouring tip regions of lobes of inner rotors for matching outer rotors formed in a standard manner is presented in the ninth alternate preferred embodiment of the present invention. As depicted in
Again, this method has been described with reference to “zone” size re-contouring tip regions of lobes of inner rotors for matching outer rotors formed in a standard manner with reference to the first lapping gerotor sets 508 as depicted in
In this case, the desired inner rotor geometries must be determined by accurate gaging methods. For instance, as depicted in
The method for “zone” size re-contouring tip regions of lobes of inner rotors for matching outer rotors formed in a standard manner is depicted in the flow chart of
A method for re-contouring tip regions of inner and outer rotors in conformity with respective standardized first and second preferred sizes is presented in the tenth alternate preferred embodiment of the present invention.
This method involves lapping of the tip regions 474 of the outwardly extending lobes 470 of inner rotors 478 to a first preferred size, and lapping the tip regions 476 of the inwardly extending lobes 472 of outer rotors 480 to a second and mating preferred size. In this case, the tip regions 474 of the outwardly extending lobes 470 of the inner rotors 478 are lapped in exactly the same manner as described above with reference to
The method for re-contouring tip regions of inner and outer rotors in conformity with respective standardized first and second preferred sizes is depicted in the flow chart of
Thus, utilizing the methods of re-contouring lobe tips of gerotor sets as presented in the teachings of the eighth, ninth and tenth alternate preferred embodiments of the present invention achieves the desired goal of providing re-contoured tip portions of lobes of gerotor sets in order to economically achieve preferred diametral clearance values of 0.0005 to 0.001 inch between the critical lobe-to-lobe and lobe-to-groove contact points and thus enable utilization thereof in high-pressure gerotor pumps.
Having described the invention, however, many modifications thereto will become immediately apparent to those skilled in the art to which it pertains, without deviation from the spirit of the invention. For instance, in the case of any gerotor pump 100, 130, 150, 180 or 230 intended for low speed operation, a needle bearing (not shown) could be utilized for supporting the outer rotor 18. Or keys located in slots could be used instead of the pins 134 in the gerotor pump 130. Or an angular position constraint comprising a housing mounted pin and pumping cartridge slot could be used instead of the ends 382 of the pins 380 for providing the reaction torque necessary to support applied motor torque in the universal gerotor pump 370. Further, the exemplary stand-gerotor gerotor pump 400 could have been implemented by simply configuring the exemplary gerotor pump 310 with needle bearings disposed on either side of its gerotor set within the housing 314 and cover plate 330. Or alternately, the exemplary gerotor pump 310 could have been implemented by utilizing a separate housing formed similarly to housing 410 utilized in the exemplary stand-alone gerotor pump 400 and affixed to the motor end bell 316 at the plane of the shoulder 324. And of course, any of the gerotor pumps described herein can also be utilized as a hydraulic motor and could have been so described. All such modifications fall within the scope of the invention.
The instant gerotor pumps preferably comprising gerotor sets with re-contouring tip regions according to the methods described above are capable of providing improved high-pressure fluid delivery at significantly reduced costs for a wide range of applications, and accordingly find industrial application in various industries both in America and abroad.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US02/39812 | 12/11/2002 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 60341510 | Dec 2001 | US | |
| 60349770 | Jan 2002 | US |
