FIELD OF THE INVENTION

[0001] The invention relates to dampers for clutches, and more particularly to variable hysteresis dampers. BACKGROUND OF THE INVENTION

[0002] Vehicles may include hysteresis packages as part of clutch assemblies. A traditional hysteresis package clutch pack has a near constant hysteresis. It would be desirable to have a variable hysteresis to introduce a higher damping in a high load condition and reduce the hysteresis in a transient state to minimize potential NVH such as a creeping rattle. SUMMARY OF THE INVENTION

[0003] In one aspect, there is disclosed a damper hysteresis assembly that includes a first frictional spacer positioned adjacent a stack plate. A first hysteresis adjustment plate is attached to the stack plate. A hub is provided. A second hysteresis adjustment plate is disposed adjacent the first hysteresis adjustment plate and about the hub. A second frictional spacer is disposed between the second hysteresis adjustment plate and a Belleville spring disposed about the hub. The first and second hysteresis adjustment plates are axially adjustable relative to each other when toque is applied to the hub applying a variable load to the Belleville spring varying a hysteresis value of the damper hysteresis assembly.

[0004] In one aspect, there is disclosed a damper hysteresis assembly that includes a first frictional spacer positioned adjacent a stack plate. The first hysteresis adjustment plate includes ramps formed thereon. A hub is provided. A second hysteresis adjustment plate is disposed adjacent the first hysteresis adjustment plate and about the hub. The second hysteresis adjustment plate includes ramps formed thereon. A second frictional spacer is disposed between the second hysteresis adjustment plate and a Belleville spring disposed about the hub. The ramps axially adjust the first and second hysteresis plates relative to each other when torque is applied to the hub applying a variable load to the Belleville spring varying a hysteresis value of the damper hysteresis assembly.

[0005] In a further aspect, there is disclosed a damper hysteresis assembly that includes first and second spring cover plates fastened to each other. A first frictional spacer is positioned between the first spring cover plate and a stack plate. The first hysteresis adjustment plate includes ramps formed thereon. A hub is provided. A second hysteresis adjustment plate is disposed adjacent the first hysteresis adjustment plate and about the hub. The second hysteresis adjustment plate includes ramps formed thereon. A second frictional spacer is disposed between the second hysteresis adjustment plate and a Belleville spring disposed about the hub. The ramps axially adjust the first and second hysteresis plates relative to each other when torque is applied to the hub applying a variable load to the Belleville spring varying a hysteresis value of the damper hysteresis assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 is an exploded perspective view of a hysteresis damper assembly;

[0007] Figure 2 is a perspective view of a hysteresis adjustment plate;

[0008] Figure 3 is section view of the hysteresis damper assembly with no applied torque;

[0009] Figure 4 is section view of the hysteresis damper assembly with applied torque;

[0010] Figure 5 is section view of the hysteresis damper assembly with no applied torque and applied torque with a graphical representation of a load-deflection curve of a Belleville spring; [0011] Figure 6 is a graphical representation of a hysteresis curve in drive and coast conditions;

[0012] Figure 7 is a graphical representation of ramps having a curved profile;

[0013] Figure 8 is a graphical representation of ramps having a curved profile;

[0014] Figure 9 is a graphical representation of ramps having a graduated profile. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Automobiles and other vehicles commonly have a clutch assembly as part of a powertrain system. The clutch assembly, which may include a damper assembly, can be located between an engine and a transmission assembly. The engine produces torque, which can be transferred to a clutch assembly by a flywheel. [0016] Friction discs can receive torque from a flywheel and a pressure plate of a clutch cover which is bolted to the flywheel. Friction discs can transfer torque to torsional springs. Torque then travels from torsional springs to cover plates which transfers torque to a hub. The hub can include an outer hub and an inner hub.

[0017] Referring to Figure 1, there is shown a damper hysteresis assembly 10. The damper hysteresis assembly 10 includes spring cover plates 12, 14 that are fastened together such as by rivets 15. A first frictional spacer 16 is positioned between the first spring cover plate 12 and a stack plate 18. A first hysteresis adjustment plate 20 is attached to the stack plate 18 such as by rivets or tabs. A hub 22 is disposed between spring cover plates 12, 14 and can include outer splines and grooves to engage with the stack plate 18 when the torque is applied. [0018] Hub 22 can include inner splines and grooves to engage a shaft (not shown), for example, a shaft leading to a transmission assembly. Torque can travel from hub 22 to a transmission assembly and then to wheels, thereby rotating the wheels and accelerating an affiliated vehicle - drive side. Torque can also travel in the reverse direction from the wheels to the transmission assembly and then to the engine, thereby slowing down the engine and decelerating the vehicle - coast side.

[0019] A second hysteresis adjustment plate 24 is disposed adjacent the first hysteresis adjustment plate 20 about the hub 22. A second frictional spacer 26 is disposed between the second hysteresis adjustment plate 24 and a Belleville spring 28 about the hub 22. The second hysteresis plate 24 and the second frictional spacer 26 are engaged with the hub 22 such as by splines or grooves and can slide axially on the hub 22. The number of friction spacers can vary depending on needs. [0020] Referring to Figure 2, the first and second hysteresis adjustment plates 20, 24 include ramps 30 formed thereon. The ramps 30 include coast ramps 32 and drive ramps 34. The coast and drive ramps 32, 34 may have inclines that increase in opposing directions. The drive ramps 34 in the depicted embodiment include two drive ramps 34 that are spaced about 90 degrees from each other about the diameter of the hysteresis adjustment plates 20, 24. The drive ramps 34 have an increasing incline in a clockwise direction in the figure. The number of coast and drive ramps 32, 34 can vary depending on needs. For example, a plurality of ramps 30 may be formed on the first and second hysteresis adjustment plates 20, 24.

[0021] The coast ramps 32 in the depicted embodiment include two coast ramps 32 that are spaced about 90 degrees from each other about the diameter of the hysteresis adjustment plates 20, 24. The coast ramps 32 have an increasing incline in a counter-clockwise direction in the figure. The ramps 30 of the first and second hysteresis adjustment plates 20, 24 face each other when installed. [0022] Referring to Figure 3-5, during operation of the damper hysteresis assembly 10, as torque is applied to the assembly the axial spacing (X) of the first and second hysteresis adjustment plates 20, 24 is varied as the ramps 30 slide on each other.

[0023] In figure 3, no torque is applied and the first and second hysteresis adjustment plates 20, 24 are adjacent each other axially. When a torque is applied as shown in Figure 4, the ramps 30 slide on each other and the first and second hysteresis adjustment plates 20, 24 are spaced axially from each other as indicated by the arrow. The axial movement compresses the Belleville spring 28 which generates a variable force in this case higher which acts on friction surfaces of the frictional spacers 16, 26 and increases the hysteresis.

[0024] Referring to Figure 5, the first and second hysteresis adjustment plates 20, 24 are shown with torque applied and with no torque applied. The load-deflection curve of the Belleville spring 28 of these conditions is also shown. As can be seen in the load-deflection plot, by adjusting the axial position X, the load from the Belleville spring 28 may be controlled which can adjust or control the hysteresis value. The coast and drive ramps 32, 34 can have steeper or gentler inclines that increases or decreases the axial position X when the torque is applied. To freely determine the differing hysteresis values on the full hysteresis curve, as shown in Figure 6, the shape of the coast and drive ramps 32, 34 may have various shapes. For example, the coast and drive ramps 32, 34 may include a constant angle 36 as shown in Figure 2. Alternatively, the coast and drive ramps 32, 34 may include a curved shape. For example, the coast and drive ramps 32, 34 may include a convex or concave curve 38, 40, as shown in Figures 7 and 8. As can be seen, the axial position X may increase or decrease as described above. In another aspect, the coast and drive ramps 32, 34 may include a graduated shape 42, as shown in Figure 9. The graduated shape 42 may have different profiles along the coast and drive ramps 32, 34. As shown in the Figure the coast and drive ramps 32, 34 may have a first angle 44 that transitions to a flat 46. The flat 46 may transition to a second angle 48. In this manner, the coast and drive ramps 32, 34 have varied heights along the coast and drive ramps 32, 34.

[0025] The load-deflection curve of the Belleville Spring 28 may be also adjusted or controlled such that there is a steep slope on the curve or there is a gentler slope on the curve. Additionally, two or more Belleville springs 28 may be included in the damper hysteresis assembly 10 to again modify the shape of the hysteresis curve.

[0026] Referring to Figure 6, there is shown a plot showing the variable hysteresis for both drive and coast conditions. The first and second hysteresis adjustment plates 20, 24 include both coast and drive ramps 32, 34 such that a variable hysteresis may be applied to have more damping in high load conditions, such as a high power level from an engine and also reduce hysteresis in a transient state to avoid noise, vibration and harshness (NVH) such as creeping rattle.

[0027] We claim: