Hydraulic machine with oil dams

A hydraulic machine includes a support structure and a rotating group rotatably mounted relative to the support structure. The rotating group includes a shaft and a cylinder barrel with a plurality of circumferentially spaced cylinder bores. Reciprocal pistons extend from the shaft with each one of the pistons extending into an associated one of the cylinder bores. A joining assembly joins the shaft and the cylinder barrel so that the shaft and the cylinder barrel rotate together. The hydraulic machine further includes at least one oil dam associated with the rotating group and adapted to trap hydraulic fluid used for lubricating portions of the joining assembly.

TECHNICAL FIELD

The present invention relates to a hydraulic machine. More particularly, the present invention relates to a hydraulic machine having a rotating group and at least one oil dam associated with the rotating group.

BACKGROUND OF THE INVENTION

Hydraulic machines having a rotating group are generally known. One such machine is disclosed in U.S. Pat. No. 4,991,492. The rotating group of the hydraulic machine includes a shaft and a cylinder barrel that is connected to the shaft with a joint (or tripod) assembly. Pistons attached to the shaft extend into cylinder bores located in the cylinder barrel. When the cylinder barrel is angled relative to the shaft, the pistons move reciprocally within the cylinder bores. The cylinder barrel is tiltable relative to the shaft so that the hydraulic machine is capable of operating as both a hydraulic pump and a hydraulic motor.

In known hydraulic machines, like the one described above, the rotating group is submerged in hydraulic fluid for lubrication and cooling of the rotating group. Typically, the rotating group rotates at high speeds, at times up to 5,000 revolutions per minute. The rotation of the rotating group in the hydraulic fluid results in losses due to, amongst other things, flow resistance of the hydraulic fluid.

In order to reduce these losses, it is desirable to provide a hydraulic machine in which the rotating group is not submerged in hydraulic fluid. To accomplish this, some lubrication should be provided to locations of relative movement of the joint assembly with the shaft and cylinder barrel. The high speed of rotation of the rotating group makes such lubrication difficult as centrifugal force tends to force any lubricating fluid to the exterior of the rotating group.

SUMMARY OF THE INVENTION

At least one embodiment of the invention provides a hydraulic machine that includes a support structure and a rotating group rotatably mounted relative to the support structure. The rotating group includes a shaft and a cylinder barrel with a plurality of circumferentially spaced cylinder bores. Reciprocal pistons extend from the shaft with each one of the pistons extending into an associated one of the cylinder bores. A joining assembly joins the shaft and the cylinder barrel so that the shaft and the cylinder barrel rotate together. The hydraulic machine further includes at least one oil dam associated with the rotating group and adapted to trap hydraulic fluid used for lubricating portions of the joining assembly.

According to one embodiment, the hydraulic machine further includes a lubrication assembly for providing lubrication from a pressure passage within the hydraulic machine to a cavity at least partially closed by the oil dam. The hydraulic machine may have an oil dam that is associated with the shaft, may have an oil dam that is associated with the cylinder barrel, or may have both shaft and cylinder barrel oil dams.

According to an embodiment, the lubrication assembly may include a valve assembly having a shuttle portion that is movable within a stepped valve bore in response to a pressure differential between first and second pressure passages for opening fluid flow to a lowest pressure one of the first and second pressure passages.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1is a cross-sectional view of a hydraulic machine10constructed in accordance with an embodiment of the present invention. As will be discussed in greater detail below, in one embodiment of the present invention, the hydraulic machine10ofFIG. 1is capable of operating as both a hydraulic pump and a hydraulic motor. Alternatively, the hydraulic machine10may operate as only one of a hydraulic pump or a hydraulic motor.

The hydraulic machine10includes a support structure12. In one example, the support structure12may be a housing. The support structure12rotatably supports a rotating group14of the hydraulic machine10. The rotating group14includes a shaft16, a portion of which is shown inFIG. 1. The shaft16includes an end18into which a hole20extends. The hole20terminates at an end wall22and has an outer periphery defined by cylindrical surface24. The end18of the shaft16also includes a radially outwardly extending flange portion that defines a drive disk26of the shaft16. A plurality of semi-spherical holes extends into the drive disk26.FIG. 1illustrates one of the semi-spherical holes at28. The semi-spherical holes are spaced equally about the circumference of the drive disk26. Bearing34extends between the support structure12and an exterior surface of the shaft16adjacent the drive disk26for supporting rotation of the shaft relative to the support structure.

The rotating group14also includes a cylinder barrel36. A cross-section of the cylinder barrel36is illustrated inFIG. 2. The cylinder barrel36includes opposite first and second ends38and40, respectively. A blind hole42extends into a first end38of the cylinder barrel36. The blind hole42terminates at an end wall44and has an outer periphery defined by cylindrical surface46that is centered on a centerline50of the cylinder barrel36. A boss52extends outwardly of the second end40of the cylinder barrel36. The boss52has a cylindrical outer surface54and defines an internal lobed cavity56that extends into the cylinder barrel36beyond the second end40.FIG. 9illustrates an end view of the lobed cavity56. The boss52includes both thick wall portions and thin wall portions for defining the lobed cavity56. Two through-holes connect the blind hole42and the lobed cavity56. A stepped through-hole58is located near the centerline50of the cylinder barrel36and another through-hole60is spaced radially away from the centerline50. The cylinder barrel36also includes a plurality of circumferentially spaced cylinder bores62, one of which is shown inFIG. 2.

The cylinder barrel36is supported in a yoke66of the hydraulic machine10. The yoke66illustrated inFIG. 1is a two-piece yoke having an upper yoke piece68and a lower yoke piece70fastened together by fasteners72. The yoke66supports an annular plate74having ports, one of which is shown at76inFIG. 1. The cylinder barrel36rotates upon the plate74such that the cylinder bores62of the cylinder barrel36rotate into and out of fluid communication with the ports. The yoke66includes first and second pressure passages80and82, respectively, through which hydraulic fluid passes when flowing to and from the ports of the plate74.FIG. 7illustrates portions of each of the pressure passages80and82of the yoke.66During operation of the hydraulic machine10, one of the pressure passages80or82is a high pressure passage and the other of the pressure passages82or80is a low pressure passage. The yoke66is tiltable relative to the support structure12for tilting the cylinder barrel36relative to the shaft16. Any known means for tilting the yoke66relative to the support structure12may be used with the hydraulic machine10of the present invention, including but not limited to one or more setting pistons, linear motors, or rotary motors.

The rotating group14also includes a plurality of pistons, one of which is illustrated at88inFIG. 1. Each piston88includes base90defined by a toroidal outer surface92and a flat bottom surface94. A stem96extends outwardly from the base in a direction opposite the bottom surface94. The stem96is tapered so that it widens as it extends away from the base90. Each piston88terminates at a head portion98having a flat upper surface100and an annular outer surface102adapted to support a piston ring.

The number of pistons88equals the number of cylinder bores62in the cylinder barrel36. In one embodiment, the hydraulic machine10includes nine pistons88. Each one of the pistons88extends into an associated one of the cylinder bores62of the cylinder barrel36. The base90of each piston88is received in and is movable within an associated one of the semi-spherical holes28in the end surface of the drive disk26. When the cylinder barrel36is angled relative to a centerline106of the shaft16, the pistons88reciprocate within their associated cylinder bores62during rotation of the rotating group14. The greater the angle of the cylinder barrel36relative to the shaft12, the greater the displacement resulting from the reciprocation of the piston88within the cylinder bore62.

A joining assembly112is interposed between and mechanically connects the shaft16and the cylinder barrel36. The joining assembly112includes a joint coupling114that is received in the hole20of the shaft16and is fixed for rotation with the shaft.FIG. 1illustrates a fastener116fixing the joint coupling114relative to the shaft16. Those skilled in the art will recognize that in addition to, or as an alternative to, the fastener116, other means for fixing the joint coupling114to the shaft16may be used. The joint coupling114includes an internal lobed cavity118. In one embodiment, the lobed cavity118has three circumferentially spaced lobes and is similar to the lobed cavity56illustrated inFIG. 9. A central through-hole extends through the joint coupling and connects to the lobed cavity118. A compression spring122and a spring guide123are received in the central through-hole and support a portion of a support pin124. The support pin124supports an end of a joint shaft130relative to the shaft16. Another support pin126, located in the stepped through-hole58of the cylinder barrel36, supports an opposite end of the joint shaft130relative to the cylinder barrel36. Spherical grooves132(FIG. 8) extend into each end of the joint shaft130for receiving an end of the associated support pin124or126. Three, spaced apart legs extend radially outwardly of the joint shaft130at each end.FIG. 8illustrates a perspective view of the joint shaft130with the legs located at the shaft end being indicated by136and, the legs located at the cylinder barrel end being indicated by138. The joint shaft130is elongated between its ends. Each of the legs136and138of the joint shaft130receives an associated roller for enabling a tilting of the joint shaft relative to the shaft16and the cylinder barrel36.FIG. 1illustrates roller140received on leg136and, roller142received on leg138.

The rotating group14of the hydraulic machine10is not submerged in hydraulic fluid. Thus, the area150of the hydraulic machine10located between the shaft16and the cylinder barrel36is generally free of hydraulic fluid. The hydraulic machine10includes a lubrication assembly for providing lubrication to the rollers140and142located on the joint shaft130of the joining assembly112during operation of the hydraulic machine10. The lubrication assembly includes a shaft lubrication portion for providing lubrication to the rollers140located on legs136of the joint shaft130and positioned within the shaft16and a barrel lubrication portion for providing lubrication to the rollers142located on legs138of the joint shaft130and positioned within the cylinder block36.

The shaft lubrication portion includes a plurality of fluid paths for providing fluid to the lobed cavity118of the joint coupling114. One of the paths is illustrated inFIG. 1. The other paths are constructed in a similar manner. The path illustrated inFIG. 1includes a through-hole154that extends longitudinally through the piston88. As shown inFIG. 1, the through-hole154extends between the flat upper surface100of the head portion98of the piston88and the flat bottom surface94of the base90of the piston. Hydraulic fluid entering the cylinder bore62from port76flows through the through-hole154in the piston88to a pool located beneath the base90of the piston88in the semi-spherical hole28of the drive disk26. A flow path portion156extends from the pool of the semi-spherical hole28in the drive disk26and through the drive disk in a direction parallel to the centerline106. The flow path portion156then extends along the outer surface of the shaft16. The flow path portion156may include, in part, a groove machined into the outer surface of the shaft16and closed by the close contact of the bearing34. The flow path portion156connects with radially extending flow path portions158and160. Flow path portion158extends radially through the shaft16and, flow path portion160extends radially through the joint coupling114to the lobed cavity118.

The barrel lubrication portion of the lubrication assembly includes a valve assembly166that is fixed within a through-hole of the yoke66and extends into the blind hole42on the first end38of the cylinder barrel36. Bearings168, such as needle bearings, are interposed between the valve assembly166and the cylinder barrel36for enabling rotation of the cylinder barrel about the valve assembly. The valve assembly166includes a cylindrical body portion170(FIG. 7) having a stepped valve bore172that is angled relative to centerline50passing through the cylindrical body portion, as shown inFIG. 1. As best shown inFIG. 7, first and second ends174and176, respectively, of the valve bore172are larger in diameter than a central portion178of the valve bore. Shoulder180defines the transition between the first end174of the valve bore172and the central portion178of the valve bore and, shoulder182defines the transition between the second end174and the central portion178of the bore. As shown inFIG. 7, the first end174of the valve bore172is in communication with the first pressure passage80of the yoke66via a first cross-port186and, the second end176of the valve bore172is in fluid communication with the second pressure passage82of the yoke66via a second cross-port188. A main lubrication passage190extends downwardly, as viewed inFIG. 7, from the central portion178of the valve bore172along the centerline50and terminates at a lower end wall of the cylindrical body portion170of the valve assembly166. Radial passages192extend outwardly from the main lubrication passage190to an outer wall of the cylindrical body portion170at a location near the plate74. Flow through the radial passages192provides lubrication to the bearings168.

A shuttle portion200of the valve assembly166is located in the valve bore172. The shuttle portion200controls the flow of lubricating fluid from the first and second pressure passages80and82of the yoke66to the main lubrication passage190of the valve assembly166. The shuttle portion200is generally bone-shaped having larger diameter first and second end sections202and204that are connected by a narrow central section206. The central section206of the shuttle portion200is longer than the central portion178of the valve bore172such that when one of the first and second end sections202or204abuts its associated shoulder180or182, the other of the first and second end sections204or202is spaced away from the other shoulder182or180. For example, with reference toFIG. 7, when the first end section202of the shuttle portion200abuts shoulder180, the second end section204is spaced away from shoulder182. In this illustrated condition, fluid may flow from the second pressure passage82into the second end176of the valve bore172, about the second end section204of the shuttle portion200and into the main lubrication passage190of the valve assembly166. The shuttle portion200is adapted to move based upon a differential pressure between the first and second pressure passages80and82of the yoke66and thus, the differential pressure between the first and second ends174and176of the valve bore172. High pressure fluid acts upon the associated end section of the shuttle portion200to force the end section into engagement with its associated shoulder for opening fluid communication between the low pressure passage of the yoke66and the main lubrication passage190of the valve assembly166.

Fluid passing through the main lubrication passage190of the valve assembly166collects in a small chamber located in the blind hole42of the cylinder barrel36between the lower end wall of the cylindrical body portion170of the valve assembly and the end wall44of the cylinder barrel. Fluid passing through the radial passages192for lubricating the bearings168also collects in the chamber. The fluid in the chamber is in fluid communication with the lobed cavity56of the boss52of the cylinder barrel36via the stepped through-hole58and through-hole60.

The hydraulic machine10illustrated inFIG. 1also includes oil dams212and214, respectively, associated with the shaft16and the cylinder barrel36for at least partially closing the lobed cavities118and56for trapping fluid to lubricate movement of the joining assembly112relative to the shaft16and cylinder barrel36, respectively.FIG. 5illustrates a top view of the shaft oil dam212and,FIG. 6illustrates a cross-sectional view of the shaft oil dam212. The shaft oil dam212is annular and includes a cylindrical sidewall220that extends downwardly from flat top wall222. The top wall222is adapted to cover a peripheral portion of the opening to the lobed cavity118and includes a tapered edge224that defines a central opening226. The outer diameter of the sidewall220of the shaft oil dam212is approximately equal to the diameter of the cylindrical surface24defining hole20of the shaft16so that the shaft oil dam212fits tightly into the hole20. When assembled into the hole20illustrated inFIG. 1, the shaft oil dam212is located atop the joint coupling114and is interposed between an o-ring230and a retaining ring232. The retaining ring232snaps into a groove located in the cylindrical surface24and is adapted to engage the top wall222of the shaft oil dam212to secure the shaft oil dam in the hole20of the shaft16and fix the shaft oil dam212for rotation with the shaft. As an alternative to a retaining ring232, other means for securing the shaft oil dam212in the hole20and fixing the shaft oil dam212for rotation with the shaft16may be used. Other example means for securing the shaft oil dam212relative to the shaft16include press fitting the shaft oil dam212into the hole20, using an adhesive, one or more fasteners or a combination of an adhesive and fasteners to hold the shaft oil dam212relative to the shaft16, or providing a threaded interconnection between the shaft oil dam212and the cylindrical surface24of the shaft16or a surface of the joint coupling114. As yet another alternative, the shaft oil dam212may be formed integrally with the shaft16or the joint coupling114as long as provisions are provided for enabling insertion of the joint shaft130with associated rollers140. Such provisions may include a large central opening or cutouts, such as will be described with reference toFIG. 8.

FIG. 3illustrates a bottom view of the cylinder barrel oil dam214and,FIG. 4illustrates a cross-sectional view of the cylinder barrel oil dam214. The cylinder barrel oil dam214is annular and includes a generally cylindrical sidewall238that extends downwardly from an annular and generally flat top wall240. A number of arched cutouts242extend into the sidewall238at spaced intervals about its circumference. The number of cutouts242equals the number of cylinder bores62in the cylinder barrel36. The internal diameter of the sidewall238is sized to receive the boss52on the second end40of the cylinder barrel36. The length of the sidewall238may be varied for completely covering the cylindrical outer surface54of the boss52. The top wall240defines a central opening244through which the joint shaft230extends. In the embodiment illustrated inFIG. 3, three holes246for receiving spring pins extend through the top wall240.FIG. 4illustrates a cross-section of one of the holes246and,FIG. 1illustrates a spring pin extending through one of the holes for fixing the cylinder barrel oil dam214to the boss52. In an alternative embodiment illustrated inFIG. 9, three holes250for receiving spring pins extend through the sidewall238of the cylinder barrel oil dam214. Other structures inFIG. 9have the same reference numbers as used previously. In addition to, or as an alternative to, the use of spring pins for securing the cylinder barrel oil dam to the boss for rotation with the cylinder barrel, adhesives or other fasteners or a combination of both may be used. As a further alternative, the cylinder barrel oil dam may be press fit on or snap fit on the boss. As yet another alternative, the cylinder barrel oil dam214may be formed integrally with the cylinder barrel36or the boss52of the cylinder barrel as long as provisions are provided for enabling insertion of the joint shaft130with associated rollers142. Such provisions may include a large central opening or cutouts, such as will be described with reference toFIG. 8.

The oil dams212and214function to trap lubricating fluid for lubricating the rollers140and142of the joining assembly112. Fluid provided to the shaft lubrication portion of the lubrication assembly is trapped in the lobed cavity118of the joint coupling114by shaft oil dam212. Similarly, fluid provided to the barrel lubrication portion of the lubrication assembly is trapped in the lobed cavity56of the boss52by cylinder barrel oil dam214. The top walls222and240of the oil dams212and214, respectively, overhang peripheral portions of the openings to the lobed cavities118and56, respectively. Due to the high rate of rotation of the rotating group14, the fluid located in the lobed cavities56and118is forced outwardly by centrifugal force. The overhanging portions of the oil dams212and214trap the fluid in the lobed cavities118and56for lubricating the rollers140and142during operation of the hydraulic machine10.

FIG. 8is a perspective, partially exploded view illustrating a joint shaft130and alternative embodiments of the shaft and cylinder barrel oil dams260and262, respectively. InFIG. 8, structures that are similar to those described previously are labeled with the same reference numbers as previously used. InFIG. 8, the top wall264of the shaft oil dam260extends inwardly a greater distance than the top wall224described with reference toFIGS. 5 and 6. As a result, the opening266in the top wall264is too small for receiving the legs136of the joint shaft130. To enable the oil dam260to receive the legs136, three cutouts268(two of which are shown) are formed in the top wall264for receiving the legs136. The cutouts268may be sized for receiving the legs136only, when the rollers140are assembled onto the legs136after insertion of the joint shaft130through the shaft oil dam260, or may be sized for receiving both the legs136and the rollers140. Similarly, the opening270in the top wall272of the cylinder barrel oil dam262is too small to receive the legs138of joint shaft130. Thus, the cylinder barrel oil dam262also includes three cutouts,274(one of which is completely shown) sized for receiving legs138. The cutouts274may be sized for receiving the legs138only, when the rollers142are assembled onto the legs138after insertion of the joint shaft130through the cylinder barrel oil dam262, or may be sized for receiving both the legs138and the rollers142. When assembled into a hydraulic machine10, the cutouts268and274are positioned over thick walled portions between lobes of the respective lobed cavities118and56and the legs136and138are received in indented portions, like those indicated at276inFIG. 8, of the oil dams260and262.

According to one method of assembling the hydraulic machine10, spring pins for attaching the cylinder barrel oil dam214to the boss52are inserted into holes in the boss. The joint shaft130is inserted through the central opening244of the cylinder barrel oil dam214and, rollers142are assembled onto the legs138of the joint shaft. Grease is placed in the stepped through-hole58for temporarily supporting the support pin126and, the support pin126is positioned in the grease. The joint shaft130then is inserted into the lobed cavity56of the boss52such that the end of the joint shaft130is supported by the support pin126. Adhesive is applied to internal surfaces of the oil dam214and, the oil dam214is secured to the cylinder barrel36by pressing the oil dam toward the boss52such that the spring pins are received in the holes246of the oil dam.

Next, the joint coupling114is inserted into the hole20of the shaft16and is fixed relative to the shaft. The spring122and the spring guide123are positioned relative to the joint coupling114and, the support pin124is placed in the spring guide123. The o-ring230is assembled atop the joint coupling114. Next, the pistons88are attached to the shaft16by inserting each piston into its associated semi-spherical hole28. The joint shaft130then is inserted through the central openings of the retaining ring232and the shaft oil dam212. Next, the rollers140are assembled onto the legs136of the joint shaft130and, the joint shaft130is inserted into the lobed cavity118of the joint coupling114such that it is supported by the support pin124. The shaft oil dam212is positioned atop the o-ring230and the joint coupling114and fixed in place by the retaining ring232. Lastly, the rotating group14is assembled relative to the support structure12and yoke66.

FIG. 10is a cross-sectional view of a hydraulic machine10A constructed in accordance with an alternative embodiment of the present invention. Components inFIG. 10that are the same as or similar to those shown inFIG. 1are identified by the same reference number as used inFIG. 1. In the hydraulic machine10A ofFIG. 10, the shaft lubrication portion of the lubrication assembly differs from that illustrated inFIG. 1. In the hydraulic machine10A ofFIG. 10, the through-holes154that extend longitudinally through the pistons88merely provide lubrication to the semi-spherical hole28of the drive disk26for lubricating movement of the piston. The shaft lubrication portion is located downstream of the valve assembly166and is provided fluid from the barrel lubrication portion. The shaft lubrication portion includes flow paths that extend through the support pins124and126and through the joint shaft130for providing lubrication to the internal lobed cavity118. InFIG. 10, a longitudinal flow path302extends through support pin124. Support pin126also includes a longitudinal flow path304. Joint shaft130includes a longitudinal flow path306that extends between opposite ends and a plurality of flow paths, generally indicated by308, for providing fluid to the surfaces of the legs136and138near the respective rollers140and142. Radially paths that form a portion of the flow paths308are closed by a plug to force lubricating fluid to the rollers140and142. Also, through-hole60in the cylinder barrel36is closed by an orifice plug to force lubricating fluid to pass through the stepped through-hole58and into the longitudinal flow path302of support pin124.

Although the principles, embodiments and operation of the present invention have been described in detail herein, this is not to be construed as being limited to the particular illustrative forms disclosed. They will thus become apparent to those skilled in the art that various modifications of the embodiments herein can be made without departing from the spirit or scope of the invention.