US3289602A

US3289602A - Fluid pressure device

Info

Publication number: US3289602A
Application number: US484918A
Authority: US
Inventors: Bernard C Hudgens
Original assignee: TRW Inc
Current assignee: Northrop Grumman Space and Mission Systems Corp
Priority date: 1965-09-03
Filing date: 1965-09-03
Publication date: 1966-12-06
Anticipated expiration: 1983-12-06
Also published as: FR1460428A; SE315204B; DE1553238A1; DK117677B; DE1553238B2

Description

Dec. 6, 1966 B. c. HUDGENS 33 FLUID PRESSURE DEVICE Filed Sept. 5, 1965 2 Sheets-Sheet 1 Dec. 6, 1966 B. c. HUDGENS 3,289,602

FLUID PRESSURE DEVICE Filed Sept. 5, 1965 2 Sheets-$l1eet :3

enveloping gear of the internal gear set.

United States Patent 3,289,602 FLUID PRESSURE DEVICE Bernard C. Hudgens, West Lafayette, Ind., assignor to TRW Inc., Cleveland, 0hio, a corporation of Ohio Filed Sept. 3, 1965, Ser. No. 484,918 13 Claims. (Cl. 103-130) This invention relates to a fluid pressure device, including a pump or a motor and more particularly deals with p a hydraulic pump or motor of the internal gear type wherein the outer gear has one more tooth than the inner gear and one of the gears orbits about the axis of the other gear when it is rotated about its own axis and wherein the teeth or lobes of one of the gears are individual units accommodating wide tolerance variations and automatically sealed relative to the gear body under the influence of hydraulic pressure developed between the gears.

This application is a continuation-in-part of my copending application entitled Hydraulic Device, U.S. Serial No. 352,019, filed March 16, 1964.

In my aforesaid patent application, it is pointed out that the internal gear set of a pump or motor of the type having an orbiting rotating element is costly to produce, requiring close tolerances for sealing and free turning of the parts. In order to reduce the manufacturing costs and accommodate wider tolerance variations, the hydraulic device of the aforesaid application is equipped with a vane carried by each tooth of the rotor of the internal gear set. These vanes are spring pressed against the teeth of the enveloping gear of the internal gear set, and since they can move radially relative to the rotor teeth, sealing congear set and eliminates the heretofore used spring members. tion may take the form of rollers, shoes, or the like in- The vanes or tooth segments of the present invendividual pieces freely carried in recesses in the outer or The segment receiving recesses are larger than the segments to permit movement of the segments relative to the gear body, but at least a portion of the recess walls are adapted to be "mated with the segments to provide a good sealing engagement of the segments with the gear body. The coacting lsealing surfaces of the segments and gear body can be shifted to accommodate wide tolerance variations and wear of the parts in use. The segments can be provided with hardened surfaces to resist wear while the gear body carrying the segments can be composed of a less hardened high strength metal which is easy to machine.

The invention will hereinafter be specifically described as embodied in an internal gear pump having an orbiting rotor embraced by a stator where the rotor is driven through a wobble stick connection with the drive shaft and a driven cylindrical valve surrounding the wobble stick controls fluid flow through the pump. It will be understood, however. that the principles of this invention are generally applicable to fluid pressure devices embodying internal gear sets. The illustrated device is especially useful in power steering linkages for controlling the power steering motor from a steering wheel. The invention is not limited to the hereinafter described specifically illustrated embodiment.

It is an object of this invention to provide a fluid flow device with an internal gear set having individual tooth segments in at least one of the gears of the set.

Another object of the invention is to provide a fluid pressure device with an internal gear set having the lobes lot:

of the enveloping gear formed from individual segments loosely carried by the enveloping gear body and shiftable in response to fluid pressure developed by the set into sealing engagement with the gear body.

Another object of the invention is to provide vanes on the enveloping stator of an internal gear set, which vanes will accommodate wide tolerance variations in the manufacture of the gear set and will create their own seals under the influence of pressure developed by the device.

A specific object of this invention is to provide the stator of an internal gear pump of the type having an orbiting rotor with individual lobes shiftable in the stator into proper operating positions regardless of wear developed between the gears.

Another specific object of this invention is to provide an internal gear pump with a stator having recesses carrying cylindrical rollers in loose-fit relation for engaging the teeth of an orbiting rotor.

Another specific object of the invention is to provide an internal gear pump or motor of the type having an orbiting rotor surrounded by a stator wherein the stator teeth are composed of individual vanes shiftable into proper operating positions under the action of the rotor and pressures developed between the rotor and stator.

Other and further objects of this invention will be apparent to those skilled in this art from the following detailed description of the annexed sheets of drawings, which by way of preferred examples only illustrate tw embodiments of the invention. t

On the drawings:

FIGURE 1 is a longitudinal cross-sectional view with parts in elevation of a fluid pressure device especially adapted for power steering usage and incorporating the features of this invention; 7

FIGURE 2 is a transverse sectional view taken generally along the line II-II of FIGURE 1;

FIGURE 3 is a transverse sectional view taken generally along the broken line III-III of FIGURE 1;

FIGURE 4 is a View similar to FIGURE 2, but illustrating the direction of rotor force on the individual shiftable stator lobes; t i

FIGURE 5 is an enlarged fragmentary view of a portion of FIGURE 4 illustrating the manner in which the pressure differential across the vane or tooth segment creates the seal; and

FIGURE 6 is a View similar to FIGURE 5, but illustrating a modified vane construction.

As shown on the drawings:

The present invention as mentioned hereinabove relates to the new and improved means for sealing between the rot-or element and stator gear element of the internal gear set which is utilized in a hydraulic device. In order to properly describe the environment within which the present invention resides, it is necessary to discuss to some length the construction of the hydraulic device. To this end, the device illustrated, particularly in FIGURES 1, 2 and 3, will be described as a pump with those skilled in the art readily recognizing the interchangeability of the device to function as a motor.

The pump which has been shown comprises a housing 10 which receives a drive shaft 11 through a bore therein which shaft can be driven by any appropriate means. The pump elements are located in the housing opposite the shaft 11 or at the left end of FIGURE 1, and'these elements comprise an outer fixed stator gear element 12 and an inner rotatable rotor element 13 together forming the internal gear set. These two elements are located between a wear plate 14 on the left end of the housing 10 and a cover 15 suitably held in position by screws 16 threaded into the left end of the housing.

A commutating valve spool 20 is rotatably located in the bore of the housing between the shaft 11 and the pump elements and through this valve spool extends a shaft or wobble stick 21 which transmits the rotation of shaft 11 to the rotor element 13. It will be apparent from reviewing FIGURES l and 2 that the connection between the one end of shaft 21 and the end of shaft 11 amounts to a universal joint connection as well as the connection of the other end of shaft 21 to the rotor element. The purpose of these connections is to permit the rotor element 13 to partake of its rotational and orbiting movement which will be discussed in more detail hereinafter. In the specific device shown herein, the rotor element is formed with teeth 23, in this embodiment specifically six in number, and the stator gear element carries one more tooth, sometimes referred to as lobes 25, in this embodiment specifically seven in number. The rotor element has an axis indicated by the point 26 in FIGURE 2 and the stator element has an axis indicated by the point 28.

Rotation of the shaft 11 in an appropriate direction will cause the rotor to rotate about its own axis 26 in the direction of arrow 29 (FIGURE 2). However, the rotor axis 26 will orbit about the stator axis 28 in the opposite direction or in the direction of arrow 30. The result of this action is to cause the pockets 32 formed between the stator lobes 25 to pass through alternately contracting pressure cycles or strokes and expanding intake or suction strokes. In the specific pump shown, namely -a rotor element with six teeth and a stator element with seven teeth or lobes, the rotor axis will orbit about the stator axis six times for each complete rotation of shaft 11, and each orbit will produce seven pressure pulses or strokes. At any one instant of time there are 3+ pockets undergoing an exhaust or pressure stage and 3+ pockets in the intake or suction stage. One revolution of the drive shaft will therefore produce six orbits or 42 pump or pressure pulses.

To facilitate connection of the alternately expanding and contracting pockets 32 with a source of fluid supply .and exhaust, the shaft 11 has been connected to the commutating valve sleeve 20 by way of a drive pin 33 which projects from the valve sleeve into one end of a slot 34 in the left end 35 of the drive shaft. This causes the commutating valve spool 20, the rotor element 13, and the drive shaft 11 to travel at substantially the same rotational speed.

The bore of the housing is provided with two annular grooves 38 and 39 which communicate respectively with

radial passages

40 and 41 opening in the sides of the housing 10 and adapted for connection to conduits through which the fluid enters and leaves the pump. The groove 38 is located in the plane of the slot 34 and therefore is in constant communication with the interior of the com-mutating valve spool 20 while the groove 39 is located within the axial limits of the valve spool 20. A circumferential series of ports 43 extend at one end to the :bore of the housing and at the other end through holes 45 in the wear plate 14 to the pockets 32 between the lobes of the stator gear element 12. The commutating valve spool is provided with a plurality of circumferentially spaced radial passages 47, (further identified by letters a, b, c, a, e, and j) which extend from the outer surface thereof to the hollow inside, and located between these radial passages 47 are provided corresponding numbers of axially extending grooves 49 (further identified by letters a, b, c, d, e and 7). These grooves 49 extend axially a length suflicient to provide a fluid bridge between the ports 43 and the annular groove 39 when the grooves 49 and ports 43 are in axial alignment with each other.

In order to give an understanding of the mode of operation of the pump and cooperation of the stator gear element 12 and the rotor element 13 with the commutating valve spool, reference is best had to FIGURES 1, 2 and 3 of the drawings. The sectional views shown 4 in FIGURES 2 and 3 show the rotor element and the commutating valve spool in the same angular position they occupy relative to each other because of their mechanical connection with the drive shaft 11. Assuming that the drive shaft 11 is being rotated in a clockwise direction 29 as viewed in FIGURE 2, it will be seen that pockets A, B and C are on an intake stroke, pockets D, E and F are on a pressure stroke, and pocket G is at the point of completing a pressure stroke and just prior to starting an intake stroke. The pockets A, B and C are being connected in FIGURE 3 to the fluid input side of the pump through radial passages a, b and 0, whereas pockets D, E and F communicate with the pressure or output side of the pump by way of axial grooves d, e and f, whereas pocket G is in what may be referred to as a transition position being neither connected to the radial passage 1 or axial groove a. From this description it will be apparent how the rotating and orbiting rotor element produces successively alternating pump and intake strokes in the various pockets 32 and how the action of the commutating valve spool appropriately connects the pockets undergoing pump strokes to the pressure side of the pump and at the same time connects the expanding pockets undergoing an intake stroke to the intake side of the pump. It will thus be seen that as a given tooth on the rotor element moves along a curved surface 25 into a pocket 32 to produce a pump stroke, that a givenpocket rotationally behind the referred to tooth is producing an intake stroke. Referring to FIGURE 2, it will be seen that the tooth which is undergoing the intake stroke may be immediately behind the tooth producing the pump stroke or it may be the second or third tooth behind depending upon which tooth is taken as the reference tooth, because as described hereinabove, at least three pump pulses are being produced and at least three intake pulses.

If the shaft 11 is rotated in a reverse direction it will be obvious that the condition of the pockets will be reversed and passages a, b and 0 will be connected to the output side of the pump and grooves a, e and f will be connected to the input side of the pump. The general overall construction of this hydraulic device is shown in US. Patent, No. 3,087,436, issued April 30, 1963.

The improvement of the present invention comprises a vane or individual tooth for each of the seven lobes of the stator 12. In the embodiment of the invention illustrated in FIGURES 1 through 5, these vanes or tooth segments 50 take the form of hollow cylindrical metal tubes each receiving a screw 16 therethrough and each fitting in a somewhat oversized fragmental cylindrical recess 51 in the stator body. The recesses 51 open inwardly to accommodate projection of the tubes 50 to form the lobes 25. As shown in FIGURE 1, the tubes 50 extend the full distance between the wear plate 14 and the end cover 15, but they have a sliding fit with the cover and wear plate at their ends so that they can rotate and shift radially in the recesses 51. The sliding fit between the ends of the tubes or rollers and the wear plate and end cover is such that leakage will be minimized.

The stator 12, therefore, comprises, as shown in FIGURE 4, a metal ring or apertured disk 52 with a ring of fragmental cylindrical recesses 51 spaced equally around the inner periphery thereof and loosely receiving the rollers or tubes 50 therein. This ring or disk 52 has finger-like portions 53 between each of the recesses 51 providing gaps between the rollers 50 for receiving the stator teeth 23. About one-third of the periphery of each roller 50 extends inwardly from the recesses 51 to provide the active lobe surfaces 25 for the stator.

As also shown in FIGURE 4, as the rotor 13 rotates and orbits within the stator 12, its teeth 23 exert forces on the rollers 50 generally indicated by the

arrows

55, 56, 57, 58 and 59. This causes the rollers to shift into tight seating engagement with the oversized recesses 51 in the vicinity of the arrow heads. Looseness and noisy operation even under unloaded conditions will, therefore,

be avoided. However, as shown in FIGURE 5, the main or controlling force vector on the rollers is created by the pressure differential between the successive pockets of the pump.

As shown in FIGURE 5, the pocket C is the last intake pocket before the pressure cycle starts with the successive pocket D. Pocket D is thus under greater pressure than pocket C and this pressure differential across the vane roller 50 urges the vane into sealing contact with the tooth 23 at point 60 and with the recess 51 at point 61. The general direction of the loading force on the roller vane 50 is indicated by the arrow 62. leakage from the high pressure pocket D back to the lower pressure pocket C is thus effectively prevented even thoughthe roller vane 50 is loosely fitted in its recess 51 of the stator body 52.

It will also be evident from FIGURE 5 that the sealing efficiency of the assembly is insured even though wide tolerance variations occur between the roller vanes 50 and the vane body 52 of the stator 12. On the intake side of the pump, the roller vanes 50 need not be in the tight sealing engagement with their recesses 51, but, as pointed out in connection with FIGURE 4, the rotor reaction on the vanes on the intake side of the pump is such that the vanes will not rattle or vibrate in the body ring 52 of the stator because the force vectors as shown by the arrows 55 through 59 insure seating of the roller vane at some area of the recess even when the vanes are not subjected to the pressure differential occurring on the pressure side of the pump. Thus, the loose tooth segments or roller vanes are automatically positioned in their free-fitting recesses under the forces developed within the pump and the assembly in effect is self-compensating. If wear develop-s on the rollers or on the teeth of the rotor, this self-compensating action will still maintain the efliciency of the pump and leakage paths will not be opened up. In addition, friction of operation can be somewhat reduced because the rollers 50 can shift and rotate to some degree under the influence of the rotor.

The tightness of the screws 16 controls too, to a certain extent, the degree of looseness of the rollers 50 relative to the stator body 52.

In the embodiment shown in FIGURE 6, the modified stator 12 has a ring body 52, provided with rectangular recesses 51' around its inner periphery receiving gear segments or vanes 50' of generally rectangular configuration, but having rounded lobe defining inner faces 25'. The segments 50' can be solid or hollow as desired, and as shown in FIGURE 6, the screws 16' are relocated to pass through the ring body 52' between the recesses 51 thereof.

The vanes 50 function in the same manner as the roller vanes 50 and are sealed under influence of the pressure differential between pockets C and D at points 60' and 61 with the general direction of the sealing force being indicated by the arrow 62'. The segments or vanes 50' do not rotate in the recesses or pockets 51' as do the rollers 50, but otherwise function in the same manner as the rollers 50.

From the above descriptions, it will, therefore, be understood that this invention provides an internal gear pump or motor with an internal gear set having vanes, lobes, or tooth segments loosely carried by the enveloping gear of the set to greatly increase permissible tolerances in the set and to provide a self-compensating, self-sealing assembly. The invention materially decreases the manufacturing costs of pumps and motors of the internal gear type especially where one of the gear elements orbits as it rotates.

Although minor modifications might be suggested by those versed in the art, it should be understood that I wish to embody within the scope of the patent granted hereon, all such modifications as reasonably and properly come within the scope of my contribution to the art.

I claim as my invention:

1. In an internal gear type fluid pressure device includ ing a first gear surrounded by and meshed with a second gear, one of said gears having one less tooth than the other gear, said gears being relatively rotatable, one of said gears being mounted for orbital movement relative to the other gear, said second gear having circumferentially spaced fragmental cylindrical recesses around the inner periphery thereof opening through said inner periphery, cylindrical rollers mounted in said recesses and free to rotate therein, said rollers projecting beyond said openings through the inner periphery of the second gear to provide the teeth for said second gear, said first gear and a portion of the second gear between the rollers cooperating with the rollers to form expanding and contracting chambers therebetween, said first gear simultaneously contacting at least two rollers in all positions of the gears to form seals, two of said seals separating the expanding chambers from the contracting chambers, .and passages communicating with the chambers for flow of fluid into the expanding chambers and out of the contracting chambers.

2. In an internal gear type fluid pressure device including a first gear surrounded by and meshed with a second gear, one of said gears having one less tooth than the other gear, said gears being relatively rotatable, one of said gears being mounted for orbital movement relative to the other gear, said second gear having circumferentially spaced recesses around the inner periphery thereof separated by fingers therebetween and opening through said inner periphery, individual gear teeth vane units loosely mounted in said recesses and projecting therefrom to define the tooth contact surfaces of the second gear, said first gear and the fingers of the second gear cooperating with the vane units to form expanding and contracting chambers therebetween, said first gear simultaneously contacting at least two of the vane units in all positions of the gears to form seals, two of said seals separating the expanding chambers from the contracting chambers, passages communicating with the chambers between the gears for flow of fluid into and out of the chambers, and said vane units being shiftable under the influence of pressure developed in the chambers to seek sealed engagement with the gears regardless of wide variations in fit between the gears including the vane units defining the chambers.

3. A fluid pressure device of the internal-external orbiting gear type which comprises a housing having a fluid inlet and a fluid outlet, a shaft rotatably supported in the housing, a first gear, a second gear surrounding and meshed with the first gear, one of said gears having one less tooth than the other gear, said gears being relatively rotatable, one of said gears orbiting about the axis of the other gear and coacting therewith to form expanding and contracting chambers between the gears, means coupling said shaft to a rotatable gear, said orbiting gear orbiting about the axis of the other gear at a higher speed than the shaft speed, ports communicating with the charmbers between the gears, a valve in the housing controlling flow between the ports and the fluid inlet and outlet of the housing, said second gear having circumferentially spaced recesses therearound opening through the inner periphery thereof, individual gear teeth vane units loosely positioned in said recesses and projecting beyond the openings in the inner periphery of the second gear to define the entire contact surfaces meshing with the first gear, and said units being shiftable under pressure developed in the chambers into sealing engagement with both gears to isolate the chambers, whereby wide tolerance variations may be accommodated between the gears including the vane units.

4. The device of claim 1 wherein the cylindrical rollers are loosely mounted in the recesses and are shiftable under the influence of pressure developed in the chambers into sealed engagement with the gears.

5. The device of claim 1 wherein the cylindrical rollers are hollow.

6. The device of claim 1 including a valve controlling flow through the passages.

7. The device of claim 6 including a shaft coupled to a rotatable gear.

8. The device of claim 7 wherein the valve and shaft are in coupled relation.

9. The device of claim 2 wherein the individual gear teeth vane units are rollers free to rotate in the recesses.

10. The device of claim 2 wherein the individual gear teeth vane units are generally rectangular and have rounded inner surfaces defining the gear teeth.

11. The device of claim 3 wherein the individual gear teeth vane units are hollow, the housing is composed of stacked parts and draw bolts extending through the hollow units mount the housing parts together.

12. The device of claim 3 wherein the valve is cou pled t the shaft.

13. The device of claim 3 wherein the valve is a cylindrical spool valve and a wobble stick extends through the valve to couple the shaft with the orbiting gear.

References Cited by the Examiner UNITED STATES PATENTS DONLEY J.

Nash 9156 Gallings 103-14 Lavaud 123-855 Kraissl 103-186 English 103-426 Quintilian 103-126 Charlson 9156 Henry l23-855 Wankel et a1 123-8 Rineer 1 103--136 Luck 9156 Dettlof et al. 103130 Gilreath 103126 Peras 103-430 Stormuehler 230 STOCKING, Primary Examiner. SAMUEL LEVINE, MARK NEWMAN, Examiners.

W. L. FREEH, Assistant Examiner.

Claims

1. IN AN INTERNAL GEAR TYPE FLUID PRESSURE DEVICE INCLUDING A FIRST GEAR SURROUNDED BY AND MESHED WITH A SECOND GEAR, ONE OF SAID GEARS HAVING ONE LESS TOOTH THAN THE OTHER GEAR, SAID GEARS BEING RELATIVELY ROTATABLE, ONE OF SAID GEARS BEING MOUNTED FOR ORBITAL MOVEMENT RELATIVE TO THE OTHER GEAR, SAID SECOND GEAR HAVING CIRCUMFERENTIALLY SPACED FRAGMENTAL CYLINDRICAL RECESSES AROUND THE INNER PERIPHERY THEREOF OPENING THROUGH SAID INNER PERIPHERY, CYLINDRICAL ROLLERS MOUNTED IN SAID RECESSES AND FREE TO ROTATE THEREIN, SAID ROLLERS PROJECTING BEYOND SAID OPENINGS THROUGH THE INNER PERIPHERY OF THE SECOND GEAR TO PROVIDE THE TEETH FOR SAID SECOND GEAR, SAID FIRT GEAR