Patent Application
20100084234
The subject invention relates to dampers such as shock absorbers and struts for example, and more particularly to a damper with a dual constraint disc valve to provide a digressive damping force.
Dampers, such as shock absorbers and struts for example, are used to dissipate energy from road load inputs, providing a desired vehicle ride and handling characteristic. A typical damper includes a piston that moves axially through a cylinder that contains hydraulic fluid and valves, and which often contains a plurality of discs positioned on one or both sides of the piston. The piston includes a center opening to receive a rod and the discs include disc openings that are aligned with the center opening. The piston also includes fluid passages that are spaced from the center opening. The discs are positioned to at least partially overlap the fluid passages.
Fluid flows through the fluid passages as the rod moves the piston back and forth within the cylinder. This movement dissipates the energy, i.e. the road load inputs, to provide a more comfortable ride and appropriate handling. The discs, which at least partially block the fluid passages regulate fluid flow rate through the passages during compression and rebound strokes experienced by the damper.
Traditionally, the piston and discs are secured together by the rod and a nut. The nut is tightened against the discs and pistons to provide a desired preload for the disc stack. If the preload is not properly set, or if this load degrades during vehicle operation, the damping characteristics of the damper can be adversely affected. Further, it is difficult to provide a properly preloaded damper that will generate a desired digressive damping force characteristic.
Traditional solutions have modified the piston to provide a more complex piston architecture that is used in combination with other components to achieve a desired preload and damping characteristic combination. These additional components have included sintered or machined rings between pistons, tapered piston ports, coil springs, Belleville washers, multi-finger discs, etc. These solutions are expensive and do not always operate effectively as fluid flow control can be inconsistent.
A valve assembly for a damper includes a piston with a central hole to receive a rod and at least one fluid passage spaced form the central hole. At least one deflecting disc is positioned on one side of the piston to at least partially overlap the fluid passage. The deflecting disc includes a center opening that is aligned with the central hole of the piston and is defined by an inner peripheral surface. At least one translating disc is positioned in an overlapping relationship with the at least one deflecting disc and is defined by an outer peripheral surface. A cage is positioned over the deflecting and translating discs and includes an abutment feature that constrains the translating disc at the outer peripheral surface while the deflecting is constrained at the rod disc by the inner peripheral surface.
In one example, the cage comprises a single piece structure. In one example, the cage includes a base portion with a center aperture that is aligned with the central hole of the piston and a wall portion that transitions from the base portion and extends toward the piston to form the abutment feature.
In one example, the inner peripheral surface of the deflecting disc abuts directly against the rod and the outer peripheral surface of the translating disc abuts directly against the abutment feature of the cage to provide radial constraint.
In one example, a backing washer is positioned axially between the cage and the piston. The backing washer acts to control a maximum deflection of the at least one deflecting disc.
These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.
The shock absorber 10 includes an inner cylinder 14 and an outer cylinder 16 separated by an outer chamber 18. A cylinder head 20 is mounted within the inner cylinder 14 at one end and a base valve 22 is mounted within the inner cylinder 14 at an opposite end. The valve assembly 12 is positioned within the inner cylinder 14 between the cylinder head 20 and the base valve 22. A rod 24 is secured to the valve assembly 12 with a nut 26, for example. Other attachment structures such as rivets or welding could also be used to secure the rod 24 to the valve assembly 12.
A first mounting structure S1 is associated with the outer cylinder 16 and a second mounting structure S2 is associated with the rod 24. One of the first S1 and second S2 mounting structures is coupled to a vehicle structure, such as a frame for example. The other of the first S1 and second S2 mounting structures is coupled to a component that receives road load inputs, such as a wheel or track for example.
The inner cylinder 14 defines an inner chamber 28 that is separated into a compression side 30 and a rebound side 32 by the valve assembly 12. During a compression stroke, the valve assembly 12 moves towards the base valve 22 to regulate fluid flow from the inner chamber 28 to the outer chamber 18 as known. During compression and rebound strokes, fluid flows through the valve assembly 12 between the compression 30 and rebound 32 sides of the inner chamber 28.
The valve assembly 12 is shown in greater detail in
The piston 40 comprises a single plane castled piston configuration with the first side 42 providing a generally flat single plane surface that is defined by a plurality of land areas 48. A plurality of fluid passages 50 are also formed in the piston 40 which extend from the first side 42 to the second side 44. The fluid passages 50 are axial passages that are spaced radially outwardly apart from the central hole 46. Any number of fluid passages can be formed depending upon the vehicle application and desired flow rate. Axial ports 52 are formed in the first side 42 at locations of the fluid passages 50. The axial ports 52 are located on the land areas 48 in castle sections.
The second side 44 has an inner portion 54 that forms a generally flat planar surface, and consists of a plurality of land areas 56. Circular grooves 58 are formed in the second side 44 and are aligned with the fluid passages 50.
The second side 44 also includes an outer portion 60 that extends outwardly away from the inner portion 54 about an outer periphery of the inner portion 54. The outer portion 60 defines an outer peripheral surface 62 that is slidingly received within the inner cylinder 14. This outer portion 60 extends up to the first side 42 and transitions into one of the land areas 48 of the first side. This configuration forms a cup-shaped recess at the second side 44 of the piston with the first side 42 having an uppermost surface that is defined by a single plane.
A plurality of discs 66 are positioned on the first side 42 of the piston 40. It should be understood that discs 66 could also be used on both sides of the piston 40, or could be located only on the second side 44. As shown in
As shown in
The deflecting discs 300 are defined by an outermost peripheral surface 302 and an innermost peripheral surface 304. The innermost peripheral surface 304 defines a central opening 306 that overlaps the central hole 46 of the piston 40. The deflecting discs 300 have a sufficient diameter to at least partially overlap the fluid passage 50. The deflecting discs 300 are clamped to the piston 40 at the center, and are constrained at the innermost peripheral surface 304 by the rod 24. This aligns the deflecting discs 300 radially with the rod 24.
In the example shown in
In the example shown, the translating discs 200 have central openings 206 that are defined by varying inner diameters with the outermost peripheral surfaces 202 being defined by a constant/common outer diameter. It should be understood that while the example discloses translating discs with varying inner diameters, the inner diameters could also be sized to have a common inner diameter. The deflecting discs 300 have a constant/common diameter defined by the innermost peripheral surface 304 at the center opening 306 and have varying outer diameters at the outermost peripheral surfaces 302. It should be understood that while varying outer diameters are shown for the deflecting discs 300, the outer diameters could be the same or different from each other.
In the example shown in
In the example shown, a deflecting disc 300a is having with the largest outer diameter is positioned immediately adjacent the first side 42 of the piston. The translating discs 200 are then stacked on top of this deflecting disc 300a in an order of increasing inner diameter at the innermost peripheral surface 204. Thus, a translating disc 200a with the smallest inner diameter is positioned closest to the piston 40, the next translating disc 200b with a larger inner diameter is positioned next to translating disc 200a, and a translating disc 200c with the largest inner diameter is positioned furthest from the piston 40.
Next, the deflecting discs 300b-f are positioned on top of translating disc 200c in order of decreasing outer diameter. The deflecting disc 300b with the largest outer diameter is placed on top of translating disc 200c and the deflecting disc 300f with the smallest outer diameter is furthest away from the piston 40. The translating discs 200 are located between the deflecting discs 300 and the piston 40 to provide a preload on the deflecting discs 300 of the shock absorber 10.
A cage 74 is positioned in an overlapping relationship with the translating 200 and deflecting 300 discs. The cage 74, in one example, is formed from a single piece stamped metal structure. The cage could also be cold formed, sintered, etc., and could be made from other suitable materials.
The cage 74 includes a base portion 76 with a center aperture 78 that is aligned with the central hole 46 of the piston 40 and the central openings 206, 306 of the translating 200 and deflecting 300 discs. The center aperture 78 defines a surface that abuts directly against the rod 24. The base portion 76 transitions into a wall portion 80 that extends toward the first side 42 of the piston 40. The wall portion 80 has an outer peripheral surface 82 and an inner peripheral surface 83 that forms an abutment feature. As shown, the abutment feature radially constrains the outermost peripheral surfaces 204 of the translating discs 200. The innermost peripheral surfaces 304 of all of the deflecting discs 300 are radially constrained by direct abutment against the rod 24. The cage 74 is constrained by the rod 24 at the center aperture 78. Thus, a dual constraint disc configuration is provided by cooperation of the cage 74 and rod 24.
The outer peripheral surface 82 of the cage 74 is spaced radially inward relative to the outer peripheral surface 62 of the piston 40. As such, the outer peripheral surface 82 of the cage does not contact the inner cylinder 14. A transition surface 84 extends from the outer peripheral surface 62 of the piston 40 to a land area 48 on the first side 42 of the piston 40. The transition surface 84 is tapered and the distal end of the wall portion 80 of the cage 74 includes a corresponding tapered surface 86 that rests on the transition surface 84.
In the example shown in
It should be understood that while a multi-fingered configuration is shown in the example of
A backing washer 100 is positioned axially between the cage 74 and the first side 42 of the piston 40. In the example shown, the backing washer 100 is placed on the disc stack such that the backing washer 100 is sandwiched between the base portion 76 of the cage 74 and the disc stack. The cage 74 and backing washer 100 cooperate to preload the discs 66 against the piston 40. Further, the backing washer 100 acts to control the maximum deflection of the deflecting discs 300.
In the example shown, the backing washer 100 includes a boss portion 102 that abuts against the disc stack and an enlarged portion 104 that abuts against the cage 74. The backing washer 100 includes a center opening 106, aligned with the central hole 46 of the piston 40 and through which the rod 24 extends. An outermost peripheral surface 108 of the backing washer 100 is spaced radially inward of the wall portion 80 of the cage 74. It should be understood that the configuration of the backing washer 100 in
Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.
