Patent Application
20130343914
This invention relates generally to radial fluid devices, and more particularly, to a variable radial fluid device with differential piston control.
The subject matter discussed in the background section herein should not be assumed to be prior art merely as a result of its mention in the background section. Similarly, a problem mentioned in the background section or associated with the subject matter of the background section should not be assumed to have been previously recognized in the prior art. The background section may rely on hindsight understanding and may describe subject matter in a manner not previously recognized in the prior art, and it should not be assumed that such descriptions represent the understanding or motivations of those skilled in the art before the filing of this application. The subject matter in the background section merely represents different approaches, which in and of themselves may also be inventions.
A fluid device may include any device that moves fluids or uses moving fluids. Two examples of a fluid device include a pump and a motor. A pump is a device that moves fluids (e.g., liquids, gases, slurries) using mechanical action. A motor is a device that converts energy received from fluids into mechanical action.
Pumps and motors may both use pistons to control fluid movement. A piston is a reciprocating component that allows fluid to expand in a chamber during an up stroke and compresses and/or ejects the fluid during a down stroke. In a pump, force may be transferred from the crankshaft to the piston for purposes of compressing or ejecting the fluid. In a motor, force may be transferred from the fluid to the piston for purposes of rotating the crankshaft. In some fluid devices, a piston may also act as a valve by covering and uncovering ports in a chamber wall.
In one example, a piston is a cylindrical component that utilizes a close tolerance cylindrical fit between the piston and a cylinder bore chamber to minimize efficiency loses from internal leakage. The term “cylinder” and its variants may refer to a general cylindrical shape represented by points at a fixed distance from a given line segment, although in practice cylinders may not be perfectly cylindrical (e.g., due to manufacturing constraints) and may include non-cylindrical cavities, passageways, and other areas.
Some fluid devices may be classified as fixed displacement or variable displacement. In a fixed-displacement fluid device, displacement distance of each piston stroke remains constant, and fluid flow through the fluid device per rotation cannot be adjusted. In a variable displacement fluid device, fluid flow through the fluid device per rotation may be adjusted by varying the displacement distance of each piston stroke.
In some fluid devices, pistons are arranged axially such that their piston stroke centerlines are configured in a circle parallel to the rotational axis of the cylinder block centerline.
In a fixed-displacement fluid device, the angle of swashplate 130 is fixed. In a variable-displacement fluid device, pressure compensator 150 may vary the angle of swashplate 130 to change displacement and direction. To minimize the load required to change the angle of swashplate 130 in variable-displacement fluid devices, the diameters of pistons 110 may be kept small, and the pivot axis of swashplate 130 may be offset from the rotation axis of cylinder block 120 to allow forces from pistons 110 to counterbalance the load.
In other fluid devices, pistons are arranged radially such that their piston stroke centerlines are configured radially outward from the rotation axis of the cylinder block.
In the example of radial fluid device 200, cam 230 is circular. In this example, circular cam 230 may be referred to as a single-lobed cam because it causes pistons 240 to complete only one sinusoidal stroke per rotation of cylinder block 220. Cams having more than one lobe, such as an elliptical (two-lobed) cam, do not typically lend themselves to being offset to vary displacement because of their unique shape.
In the example of
Particular embodiments of the present disclosure may provide one or more technical advantages. A technical advantage of one embodiment may include the capability to fully reverse fluid flow in a fluid device. A technical advantage of one embodiment may include the capability to adjust fluid flow through a fluid device without varying the displacement distance of each piston. A technical advantage of one embodiment may also include the capability to adjust fluid flow with a minimal amount of force. A technical advantage of one embodiment may also include the capability to effectively lower the volume within a fluid chamber by varying when pistons in the chamber begin their stroke. A technical advantage of one embodiment may also include the capability to increase shaft speed by balancing piston forces. A technical advantage of one embodiment may also include reduced vibration and hydraulic pressure pulse levels. A technical advantage of one embodiment may also include the capability to connect multiple fluid devices along a common drive shaft.
Certain embodiments of the present disclosure may include some, all, or none of the above advantages. One or more other technical advantages may be readily apparent to those skilled in the art from the figures, descriptions, and claims included herein.
To provide a more complete understanding of the present invention and the features and advantages thereof, reference is made to the following description taken in conjunction with the accompanying drawings, in which:
As explained above, fluid flow may be varied in a fluid device by varying piston stroke displacement distance or varying valve timing. Varying piston stroke displacement distance, however, may require a substantial amount of energy to move the cam in order to vary displacement distance. Likewise, varying valve timing may require a substantial amount of energy to open and close valves when hydraulic flow is at a maximum.
Teachings of certain embodiments recognize the capability to adjust fluid flow in a fluid device without varying piston stroke displacement distance or varying valve timing. Teachings of certain embodiments also recognize the capability to adjust fluid flow using a minimal amount of energy as compared to varying piston stroke displacement distance or varying valve timing.
As seen in
Shaft 310 is coupled to cylinder block 320. In some embodiments, shaft 310 is removably coupled to cylinder block 320. For example, different shafts 310 may have different gear splines, and an installer may choose from among different shafts 310 for use with radial fluid device 300. If radial fluid device 300 is operating as a pump, for example, the installer may choose a shaft 310 splined to match a driving motor to be coupled to shaft 310 opposite cylinder 320.
Cylinder block 320 rotates within radial fluid device 300. In the example of
Cylinder block 320 includes a plurality of cylinders for receiving pistons 340a-340f and pistons 340a′-340f′. In the example of
The example of
Cam 330 is disposed about pistons 340, and cam 330′ is disposed about pistons 340′. During operation, pistons 340 and 340′ stroke inwards and outwards depending on the distance between cam 330 and the axis of rotation of cylinder block 320 and the distance between cam 330′ and the axis of rotation of cylinder block 320. For example, cam 330 in
Rotating cams 330 and 330′ may change when pistons 340 and 340′ begin their strokes. For example, rotating cam 330 changes the location of the transverse diameter of cam 330 and thus changes where piston 340a begins a down stroke. Similarly, rotating cam 330′ changes the location of the transverse diameter of cam 330′ and thus changes where piston 340a′ begins a down stroke. Thus, moving cam 330 and/or cam 330′ relative to one another changes the amount of time between when cam 330 and cam 330′ begin their downstrokes. Teachings of certain embodiments recognize that changing the amount of time between the downstrokes of cams 340a and 340a′ may change the maximum accessible cylinder volume of chamber 345a and therefore change how fluid flows in and out of radial fluid device 300.
In the example of
Ports 360 and 365 provide fluid into and out of radial fluid device 300. Ports 360 and 365 may each operate as either an inlet or an exhaust. Teachings of certain embodiments recognize the capability to reverse the flow within radial fluid device 300. Reversing the flow may convert a port from an inlet to an exhaust or from an exhaust to an inlet. Flow reversing will be described in greater detail with regard to
Cam gears 335 and 335′, drive gears 370 and 370, reverse rotation gear 375, and cam adjuster 380 in combination adjust the position of cams 330 and 330′. Cam gears 335 and 335′ are coupled to cams 330 and 330′, respectively. Drive gears 370 and 370′ interact with the teeth of cam gears 335 and 335′. Reverse drive gear 375 interacts with drive gears 370 and/or 370′, either directly or indirectly. In particular, reverse drive gear 375 mechanically couples drive gears 370 and 370′ together such that rotation in one direction by drive gear 370 results in rotation in the opposite direction by drive gear 370′. Cam adjuster 380 rotates at least one of drive gear 370, drive gear 370′, and reverse rotation gear 375 such that drive gear 370 and drive gear 370′ rotates cam gears 33 and 335′.
As stated above, moving cams 330 and 330′ changes when pistons 340 and 340′ begin their strokes, and changing when pistons 340 and 340′ begin their strokes can change how fluid flows in and out of radial fluid device 300. Teachings of certain embodiments recognize that mechanically coupling cam 330 to cam 330′ may reduce the energy needed to vary fluid flow through radial fluid device 300 by reducing the energy needed to rotate cams 330 and 330′.
In particular, cams 330 and 330′ are mechanically linked such that rotation in one direction by cam 330 results in rotation in the opposite direction by cam 330′. When cylinder block 320 is rotating, one of cams 330 and 330′ may move in the same direction of cylinder block 320, and the other cam may move in the opposite direction of cylinder block 320. If cams 330 and 330′ were not linked, inertial and other forces could make rotating a cam with the direction of rotating of cylinder block 320 extremely easy but rotating a cam against the direction of rotating of cylinder block 320 extremely difficult. By mechanically linking cam 330 to cam 330′, however, the overall energy required to move both cams is reduced. Mechanically linking cam 330 to cam 330′ effectively cancels out the inertial forces acting on both cams. Thus, teachings of certain embodiments recognize that moving both cam 330 and cam 330′ may require less force than moving one cam alone against the rotation of cylinder block 320.
In some embodiments, cams 330 and 330′ are mechanically linked to rotate in equal distances as well as rotate in opposite directions. For example, ten degrees of separation may be created between cams 330 and 330′ by rotating each cam five degrees in either direction.
As explained above, rotating cams 330 and 330′ may change how fluid flows through radial fluid device 300. In particular, rotating cams 330 and 330′ may change when pistons 340 and 340′ begin their strokes, and changing when pistons 340 and 340′ begin their strokes may change the maximum accessible cylinder volume within each piston chamber 345. Changing the maximum accessible cylinder volume within each piston chamber 345 changes the volume of fluid flowing through radial fluid device 300.
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In each of the examples shown in
For example,
Similar to radial fluid device 300, radial fluid device 500 features a shaft 510, bearings 515, a cylinder block 520, cams 530 and 530′, pistons 540a-540f, pistons 540a′-540f′, piston chambers 545a-545f, and ports 560 and 565. In operation, cylinder block 520 rotates within radial fluid device 500, and pistons 540a-540f and 540a′-540f′ reciprocate within piston chambers 545a-545f depending on the relative positions of cam gears 535 and 535′.
Radial fluid device 500 also features cam gears 535 and 535′, drive gears 570 and 570′, reverse rotation gears 575, and cam adjuster 580. Cam gears 535 and 335′, drive gears 570 and 570, reverse rotation gears 575, and cam adjuster 580 in combination adjust the position of cams 530 and 530′. Cam gears 535 and 535′ are coupled to cams 530 and 530′, respectively. Drive gears 570 and 570′ interact with the teeth of cam gears 535 and 535′. Reverse drive gears 375 interact with drive gears 570 and/or 570′, either directly or indirectly. In particular, reverse drive gears 575 mechanically couples drive gears 370 and 370′ together such that rotation in one direction by drive gear 570 results in rotation in the opposite direction by drive gear 570′. Cam adjuster 580 rotates at least one of drive gear 570, drive gear 570′, and reverse rotation gear 575 such that drive gear 570 and drive gear 570′ rotates cam gears 33 and 535′.
By using worm drive gears 570 and 570′ instead of the spur drive gears 370 and 370′ of radial fluid device 300, cam adjuster 380 may be moved from the front of radial fluid device 300 to the side of radial fluid device 500, as shown in
In addition, repositioning cam adjustor 580 may allow multiple fluid devices 500 to be coupled together.
Teachings of certain embodiments recognize that coupling multiple fluid devices together may eliminate the need for an additional gearbox when multiple fluid devices are used. The cams of each fluid device may operate at different phase angles. When used in applications where operating loads reverse direction, one fluid device can vary its effective displacement to act as a motor and regenerate power to a coupled fluid device. For example, in
In each of these examples, flow volume may be adjusted by changing the phase angle between adjacent cams. Teachings of certain embodiments recognize that phase angle may be changed during operation to provide a constant flow volume even as system flow demand varies.
For example,
Similar to radial fluid devices 300 and 500, radial fluid device 600 features a shaft 610, bearings 615, a cylinder block 620, cams 630 and 630′, pistons 640a-640f, pistons 640a′-640f′, piston chambers 645a-645f, and ports 660 and 665. In operation, cylinder block 620 rotates within radial fluid device 600, and pistons 640a-640f and 640a′-640f′ reciprocate within piston chambers 645a-645f depending on the relative positions of cam gears 635 and 635′.
Radial fluid device 600 also features cam lugs 635 and 635′, yokes 670 and 670′, and pressure compensators 680 and 685. Cam lugs 635 and 635′, yokes 670 and 670′, and pressure compensators 680 and 685, in combination, adjust the position of cams 630 and 630′. Cam lugs 635 and 635′ are coupled to cams 630 and 630′, respectively. Yokes 670 and 670′ interact with cam lugs 635 and 635′. Pressure compensator 680 is coupled to at least one of yoke 670 and 670′, and pressure compensator 685 is coupled to at least one of yoke 670 and 670′ opposite pressure compensator 680.
In operation, pressure compensator 680 provides linear movement that pushes or pulls at least one of yokes 670 and 670′. In this example, cams 330 and 330′ are supported by roller bearings to minimize friction induced hysteresis effects. Pressure compensator 685 reacts against the linear movement of pressure compensator 680 to balance the yokes 670 and 670′. In the example of
Radial fluid device 600, like radial fluid devices 300 and 500, features two sets of pistons, seven radial pistons per set, and two lobes per cam. Teachings of certain embodiments, however, recognize that other radial devices may have any number of piston sets, pistons per sets, and lobes per cam. In addition, embodiments may have other configuration changes as well, such as different cam followers (e.g., sliding, roller, and spherical ball).
Similar to radial fluid devices 300, 500, and 600, radial fluid device 700 features a shaft 710, bearings 715, a cylinder block 720, cams 730 and 730′, pistons 740a-740f, pistons 740a′-740f′, piston chambers 745a-745f, and ports 760 and 765. In operation, cylinder block 720 rotates within radial fluid device 700, and pistons 740a-740f and 740a′-740f′ reciprocate within piston chambers 745a-745f depending on the relative positions of cam gears 735 and 735′. Unlike radial fluid devices 300, 500, and 600, each piston in radial fluid device 700 completes three sinusoidal strokes per rotation of cylinder block 720.
Modifications, additions, or omissions may be made to the systems and apparatuses described herein without departing from the scope of the invention. The components of the systems and apparatuses may be integrated or separated. Moreover, the operations of the systems and apparatuses may be performed by more, fewer, or other components. The methods may include more, fewer, or other steps. Additionally, steps may be performed in any suitable order.
Although several embodiments have been illustrated and described in detail, it will be recognized that substitutions and alterations are possible without departing from the spirit and scope of the present invention, as defined by the appended claims.
To aid the Patent Office, and any readers of any patent issued on this application in interpreting the claims appended hereto, applicants wish to note that they do not intend any of the appended claims to invoke paragraph 6 of 35 U.S.C. §112 as it exists on the date of filing hereof unless the words “means for” or “step for” are explicitly used in the particular claim.
