Patent Application
20080314706
The present invention relates generally to piston dampers, and more particularly to a damper having a gas cup assembly and to a gas cup assembly for a damper.
Conventional piston dampers include dampers having a tube, a piston assembly (such as a piston assembly including a piston core and a piston ring positioned outward of the piston core to define a through passageway between the piston core and the piston ring), and a piston rod. The tube contains a damping fluid. The piston assembly slideably engages the tube between the closed and open end portions of the tube. The piston rod has a first end portion attached to the piston assembly and a second end portion extending outside the open end portion of the tube. A rod guide assembly is attached to the open end portion of the tube to guide the piston rod and to seal the damping fluid within the tube. A floating, hermetically-sealing gas cup (such as one made of impermeable aluminum) slidingly engages the tube to separate the damping fluid from a gas and slides (floats) to adjust for the volume change caused by the moving piston rod, thermal expansion of the damping fluid, and normal loss of damping fluid, as is known to those skilled in the art. The gas cup has a single seal disposed in fully-circumferential surface groove on the outwardly-facing circumferential surface of the gas cup.
Conventional piston dampers include magnetorheological (MR) dampers having MR damping fluid and non-MR dampers having non-MR damping fluid (such as hydraulic fluid). The MR fluid, which typically is hydraulic fluid containing iron particles, passes through an MR passageway (i.e., a magnetically energizable passageway) of the MR piston assembly. Exposing the MR fluid in the MR passageway to a varying magnetic field, generated by providing a varying electric current to an electric coil of the MR piston assembly, varies the damping effect of the MR fluid in the MR passageway providing variably-controlled damping of relative motion between the MR piston assembly and the tube. The electric current is varied (including turning off the electric current) to accommodate varying operating conditions, as is known to those skilled in the art. The seal for the gas cup of a monotube MR damper comes down to a choice of seal materials such as a polyurethane seal (for better abrasion resistance to the typically iron particles in the MR fluid) or an HNBR (Hydrogenated Nitrile Butadiene Rubber) seal (for better high temperature and gas sealing properties).
What is needed is an improved gas cup assembly and an improved damper having a gas cup assembly.
A first expression of an embodiment of the invention is for a damper including a damper cylinder, a floating damper gas cup assembly, a damping fluid, a gas, a damper piston assembly, a piston rod, and a rod guide assembly. The damper cylinder has a closed end portion and an open end portion. The damper gas cup assembly is disposed in, and is slidingly engagable with, the damper cylinder to create a first chamber extending from the damper gas cup assembly toward the open end portion and a second chamber extending from the damper gas cup assembly toward the closed end portion. The damper gas cup assembly includes a gas-and-liquid-impermeable damper gas cup and a liquid-permeable member. The damper gas cup has a central longitudinal axis and has an outwardly-facing first circumferential surface with a fully-circumferential first surface groove. The first surface groove is adapted to receive a first seal. The member is disposed outside, and is attached to, the damper gas cup and has an outwardly-facing second circumferential surface with a fully-circumferential second surface groove. The second surface groove is adapted to receive a second seal. The damping fluid is disposed within the first chamber and is in contact with the member. The gas is disposed within the second chamber and is in contact with the damper gas cup. The damper piston assembly is disposed within the first chamber and is slidingly engagable with the damper cylinder. The piston rod has a first end portion which is attached to the damper piston assembly and has a second end portion which extends outside the open end portion of the damper cylinder. The rod guide assembly is attached to the open end portion of the damper cylinder and is adapted to guide the piston rod and to seal the damping fluid within the first chamber.
A second expression of an embodiment of the invention is for a damper gas cup assembly including a gas-and-liquid-impermeable damper gas cup and a liquid-permeable member. The damper gas cup has a central longitudinal axis and has an outwardly-facing first circumferential surface with a fully-circumferential first surface groove. The first surface groove is adapted to receive a first seal. The member is disposed outside, and is attached to, the damper gas cup and has an outwardly-facing second circumferential surface with a fully-circumferential second surface groove. The second surface groove is adapted to receive a second seal.
A third expression of an embodiment of the invention is for a damper gas cup assembly including a gas-and-liquid-impermeable damper gas cup, a liquid-permeable member, a first seal, and a second seal. The damper gas cup has a central longitudinal axis and has an outwardly-facing first circumferential surface with a fully-circumferential first surface groove. The member is disposed outside, and is attached to, the damper gas cup and has an outwardly-facing second circumferential surface with a fully-circumferential second surface groove. The first seal is disposed in the first surface groove. The second seal is disposed in the second surface groove.
Several benefits and advantages are derived from one or more of the expressions of the embodiment of the invention. In one example, the liquid-permeable member provides an internal fluid path allowing the damping fluid to bypass the second seal which avoids the undesirable pumping action created between the two seals when two seals in series are conventionally employed on a component which is moved against a sealing surface, as can be appreciated by those skilled in the art. In the same or a different example, when the damping fluid is an MR damping fluid containing, for example, abrasive iron particles, the first seal can be a better gas seal than the second seal, and the second seal can be a better abrasion resistant seal then the first seal (rather than conventionally choosing one seal which compromises on meeting all sealing requirements). In this example, the liquid-permeable member will filter out the abrasive particles in the MR damping fluid supplying substantially particle-free damping fluid between the first and second seals providing clean lubrication without exposing the first seal to the abrasive particles, and the first seal will protect the second seal from the abrasive particles which encounter the first seal. This should, in this example, improve the durability of the gas cup assembly and may even allow the design clearance between the damper piston and the damper gas cup to be reduced (resulting in a shorter damper requiring less relatively expensive MR damping fluid), as can be appreciated by those skilled in the art.
Referring now to the drawings,
It is noted that the terminology “circumferential surface” is not limited to circular cylindrical surfaces for the purpose of describing any one or more or all of the expressions of the embodiment of
In one enablement of the first expression of the embodiment of
In one implementation of the enablement, the damping fluid 16 is a magnetorheological (MR) damping fluid, and the first seal 44 is a better gas seal than is the second seal 50. In one variation, the second seal 50 is a better abrasion resistant seal than is the first seal 44. In one choice of materials, the first seal 44 comprises nitrile-butadiene rubber (NBR), and the second seal 50 comprises polyurethane. In one modification, the damper gas cup 34 includes a longitudinally-extending closed bottom portion 56 and a longitudinally extending open top portion 58, wherein the top portion 58 extends outward of the bottom portion 56, and wherein the top portion 58 includes the first surface groove 42. In one arrangement, the member 36 is substantially coaxially aligned with the longitudinal axis 38, surrounds the bottom portion 56, and contacts the top portion 58.
In the same or a different implementation, first surface groove 42 has an outwardly-facing first entrance 60, and the first surface groove 42 completely surrounds the first seal 44 except at the first entrance 60. In the same or a different implementation, the second surface groove 48 has an outwardly-facing second entrance 62, and the second surface groove 48 completely surrounds the second seal 50 except at the second entrance 62.
In a first configuration of the first expression of the embodiment of
A second expression of the embodiment of
It is noted that the enablements, implementations, etc. of the first expression of the embodiment of
A third expression of the embodiment of
It is noted that the enablements, implementations, constructions, examples, etc. of the first and second expressions of the embodiment of
Several benefits and advantages are derived from one or more of the expressions of the embodiment of the invention. In one example, the liquid-permeable member provides an internal fluid path allowing the damping fluid to bypass the second seal which avoids the undesirable pumping action created between the two seals when two seals in series are conventionally employed on a component which is moved against a sealing surface, as can be appreciated by those skilled in the art. In the same or a different example, when the damping fluid is an MR damping fluid containing, for example, abrasive iron particles, the first seal can be a better gas seal than the second seal, and the second seal can be a better abrasion resistant seal then the first seal (rather than conventionally choosing one seal which compromises on meeting all sealing requirements). In this example, the liquid-permeable member will filter out the abrasive particles in the MR damping fluid supplying substantially particle-free damping fluid between the first and second seals providing clean lubrication without exposing the first seal to the abrasive particles, and the first seal will protect the second seal from the abrasive particles which encounter the first seal. This should, in this example, improve the durability of the gas cup assembly and may even allow the design clearance between the damper piston and the damper gas cup to be reduced (resulting in a shorter damper requiring less relatively expensive MR damping fluid), as can be appreciated by those skilled in the art.
The foregoing description of several expressions of an embodiment of the invention has been presented for purposes of illustration. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be defined by the claims appended hereto.
The present application claims priority of U.S. Provisional Application No. 60/936,550 filed Jun. 20, 2007.
| Number | Date | Country | |
|---|---|---|---|
| 60936550 | Jun 2007 | US |
