Patent Grant
8469826
The present disclosure relates generally to torsional couplings, and more particularly to a torsional coupling with radially oriented piston and barrel combinations for transmitting torques while damping torsional vibrations.
Torsional couplings are often encountered between two rotating components that need the ability to provide some relative rotation to accommodate torsional vibrations. For instance, an engine may be utilized to drive a hydraulic piston pump in a fracture rig pumping application. A torsional coupling may be necessary to accommodate torsional vibrations resulting from engine harmonic excitations due to sequential engine cylinder firings, and torsional vibrations may also originate from the pump with each pump stroke of each cylinder. In addition, natural torsional frequencies of various components in the drive line may also be excited and in need of being absorbed and damped.
Co-owned U.S. Pat. No. 7,335,107 teaches a torsional coupling in which torques are transmitted from a first coupling element to a second coupling element by way of an interaction between radially oriented pistons of the first coupling element that are biased into contact with circular arc surfaces on the second coupling element. Torsional vibrations are accommodated by the piston contact surface moving back and forth on the circular arc. This relative rotation between the first and second coupling elements results in movement of the piston into and out of its respective barrel. Some damping occurs due to the presence of lubricating fluid and friction at the piston contact with the second coupling element as well as with its respective barrel. While the '107 patent taught an innovative new type of torsional coupling, there remains room for improvement with respect to damping, wear and design variability to address the torsional demands of different applications.
The present disclosure is directed toward improvements to torsional couplings that utilize radially oriented piston and barrel combinations.
In one aspect, a radial piston damped torsional coupling includes a second coupler oriented to rotate with respect to a first coupler about an axis through a continuum of negative, neutral and positive torque orientations. One of the first and second couplers defines a fluted perimeter surface with a number of flutes, which is at least three, distributed with radial symmetry about the axis. The other of the first and second couplers includes the number of pistons reciprocally received in respective barrels to define a variable volume chamber fluidly connected to a damping passage. A spring biases the pistons and barrels to extend toward a position where a contact end is in contact with one of the flutes. The contact end is an edge of a roller that rolls on the fluted perimeter surface in one of the flutes.
In another aspect, a machine includes an engine with a drive shaft, and a hydraulic piston pump with a pump shaft. The drive shaft is torsionally coupled to the pump shaft by a radial piston damped torsional coupling. A damping liquid source is fluidly connected to a variable volume chamber of the radial piston damped torsional coupling. The radial piston damped torsional coupling includes a first coupler linked to the drive shaft, a second coupler linked to the pump shaft, and one of the first coupler and second coupler includes a plurality of radially oriented pistons and barrel combinations with contact ends in contact with respective non-circular flutes on a fluted perimeter surface of an other of the first coupler and the second coupler. A torsional stiffness adjuster includes a damping liquid pressure regulator.
In still another aspect, a method of driving rotation of a work shaft about an axis includes applying a torque from a drive shaft to the work shaft through a radial piston damped torsional coupling. The step of applying a torque includes rotating a first coupler relative to a second coupler away from a neutral torque orientation. A roller of one of the first coupler and the second coupler rolls back and forth in a non-circular flute of a fluted perimeter surface of an other of the first coupler and the second coupler responsive to a torsional vibration. Relative rotation of the first coupler relative to the second coupler is damped by displacing damping liquid by moving a piston relative to a barrel along a radius line from the axis.
Referring to
Machine 10 also includes a torsional stiffness adjuster 20 that includes a source of damping liquid 21 fluidly connected to a pump 22, which supplies damping liquid to torsional coupling 30 via supply passage 25. A return passage 26 may include a valve 24. Depending upon the individual components, pump 22 and valve 24 may be considered a damping liquid pressure regulator 27 with the ability to set a desired pressure of damping liquid within torsional coupling 30. Those skilled in the art will appreciate that although pump 22 and valve 24 are illustrated for regulating damping liquid pressure, many other known mechanisms and plumbing connections are known for controlling the pressure in a damping liquid. In the illustrated embodiment, the damping liquid might be lubricating oil or hydraulic fluid. In one variation, torsional coupling 30 could be configured in a way to be supplied with hydraulic transmission liquid from transmission 14, and have the supply being liquid pressure regulated in any manner known in the art without departing from the present disclosure.
Referring now to
One or more springs 63 may be positioned in variable volume chamber 60, or elsewhere, to bias the pistons and barrels to extend toward a position where a contact end 55 is in contact with one of the flutes 42. In the illustrated embodiment, the barrels 53 are fixed with regard to second coupler 50, and the pistons 52 are biased responsive to two coil springs 63 to maintain contact between contact end 55 and fluted perimeter surface 41. Nevertheless, those skilled in the art will appreciate that the pistons could be fixed and the barrels could be biased to move on fixed pistons without departing from the present disclosure. In other words, the rollers may be attached to moving components (“barrels”) that are in sliding contact on their ID with fixed components (“pistons”) in contact on their OD. The contact end 55 may be an edge 57 of a roller 56 that is attached to one end of each respective piston 52.
In the illustrated embodiment, each of the flutes 42 is symmetrical about a radius from axis 80, at a center 44 corresponding to an extended piston and barrel configuration, as shown. A pair of off center locations 45 correspond to a bottomed out piston and barrel configuration. Thus,
Although not necessary, each of the flutes 42 may follow a non-circular contour, such as an ellipse or maybe even a superellipse. Those skilled in the art will appreciate that the equation (x/a)n+(y/b)n=1 represents a family of closed curves. When the exponent n is between zero and one, the superellipse that looks like a four-armed star with concave (inwardly curved) sides. When n is equal to 1, the curve becomes a diamond shape. When n is between one and two, the superellipse looks like a diamond with convex sides, and curvature that increases as one approaches the corners. When n is equal to 2, the curve is an ordinary ellipse, and becomes a circle if a=b. When n is greater than 2, the superellipse shape begins to look more like a rectangle with sharper corners. In the illustrated embodiment, superellipses with an exponent may be between 1.8 and 2 provide more torsional resistance (relative to a circle or ellipse) since the roller will almost immediately encounter a slope when moving off of the neutral torque orientation corresponding to center 44. Those skilled in the art will appreciate that a wide variety of different torque relationships may be obtained by choosing an appropriate contour for the individual flutes 42. As used in the present disclosure, and in reference to the above equation, a superellipse does not include a circle where a=b, nor does a superellipse correspond to a situation when the exponent n=2.
Due to the radially symmetric distribution of piston and barrel combinations 51, along with the respective spring biasing 63, the first coupler 40 and the second coupler 50 are biased toward concentricity with respect to axis 80. However, they may be off center displaceable to an eccentric distance 34 that is limited by a radial stop 46. In other words, the eccentric distance corresponds to a radial clearance between first coupler 40 and second coupler 50, and the limitation corresponds to the situation when second coupler 50 contacts one or more of the radial stops 46. Thus, the structure of the present disclosure does permit some misalignment between the respective shafts that are attached to the first and second couplers. This aspect of the disclosure also permits the two components (e.g., engine and pump) that are respectively linked to the first and second couplers 40, 50 some lateral movement, such as due to linear vibrations and the like without overstressing the coupling arrangement. In the illustrated embodiment, spring 63 is a pair of nested mechanical coil springs. However, those skilled in the art will appreciate that spring(s) 63 could be any type of suitable spring known in the art, such as a stack of bellville washers, a pneumatic spring, a single mechanical coil spring, or any combination there of without departing from the scope of the present disclosure.
Although the torsional coupling 30 is illustrated with the fluted perimeter surface 41 being located on the outer component, namely first coupler 40, the fluted perimeter surface could instead be on the inner component and be an outwardly oriented fluted perimeter surface (resembling a Greek column) without departing from the present disclosure. In such a case, the piston and barrel combinations 51 would extend radially inward, instead of radially outward as in the illustrated embodiment. Referring to
Those skilled in the art will appreciate that engineers may design a variety of torsional coupling properties by adjusting the pressure of the damping liquid, by setting the preload on the biasing spring(s) 63, and also by taking into account the mass properties of the rotating components to account for torsional stiffness changes that may be attributable to the centrifugal force on the piston and barrel combinations 51 caused by rotational speed. In addition, the natural frequencies of machine 10 may also be adjusted by changing these parameters to change the torsional stiffness of coupling 30, which may inherently change in response to rotational speed. Other design considerations include the radius of rollers 56, the contour of the individual flutes 42, which would be irregular, as well as the number of piston and barrel combinations 51 and the associated number of flutes 42.
Industrial Applicability
The present disclosure finds potential application in any machine in which one rotating component drives rotation of a second rotating component. These two rotating components could be two shafts, as in the illustrated embodiment, a gear and a shaft, two gears, or any other similar structure known in the art without departing from the present disclosure. For instance, the outer surface of the outer coupler could include gear teeth for meshing with an adjacent gear that is driven to rotate by the outer coupler from a shaft linked to the inner coupler. In the illustrated embodiment, the drive and driven shafts are co-linear. The torsional coupling of the present disclosure finds particular application in heavy machinery, such as fracture rig applications, and maybe marine applications.
When in operation, a torque is applied from a drive shaft 12 to a work shaft 16 through the radial piston damped torsional coupling 30. When the torque is applied, the first coupler 40 rotates relative to the second coupler 50 away from neutral torque orientation, as shown. After settling in at a point on the fluted surface 41, a roller 56 of the second coupler 50 may roll back and forth in a non-circular flute 42 of a fluted perimeter surface 41 responsive to a torsional vibration. Thus, when the drive shaft is driving rotation of the work shaft with some average torque, the first coupler and second coupler will seek out a relative orientation that is stable at a specific point on the contour of the flute 42 corresponding to that average torque. When a torsional vibration is encountered, one could expect the first and second couplers to oscillate rotationally with respect to each other about that stable average torque point on the flute contour. This relative rotation may be damped by displacing damping liquid through orifice 66 into and out of variable volume chamber 60 responsive to the back and forth movement of the roller, and hence the in and out movement of the pistons 52 with regard to their respective barrels 53. The piston and barrel combinations 51 may bottom out at a maximum design torque position corresponding to off center locations 45 shown in
In some applications, the non-circular flute 42 may follow the contour of a superellipse as described earlier. In the illustrated embodiment, each of the flutes 42 occupies about 30-40% of an associated superellipse closed contour. The torsional stiffness of the radial piston damped torsional coupling 30 may be changed by changing a supply pressure of the liquid damping fluid. For instance, in the illustrated embodiment, the flow area through valve 24 could be adjusted to control the pressure of the damping liquid in torsional coupling 30 generally, and in the individual variable volume chambers 60 in particular. Those skilled in the art will appreciate that any known strategy for controlling pressure of the damping liquid in the variable volume chambers would fall within the scope of the present disclosure. Finally, an eccentric off center relationship between the drive shaft 12 and the work shaft 16 may be limited by radial stops 46.
It should be understood that the above description is intended for illustrative purposes only, and is not intended to limit the scope of the present disclosure in any way. Thus, those skilled in the art will appreciate that other aspects of the disclosure can be obtained from a study of the drawings, the disclosure and the appended claims.
| Number | Name | Date | Kind |
|---|---|---|---|
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| Number | Date | Country | |
|---|---|---|---|
| 20130079159 A1 | Mar 2013 | US |
