Controllable vehicle suspension system with a controllable magnetorheological fluid strut

• US 7,849,983 B2
• Filed: 05/01/2007
• Issued: 12/14/2010
• Est. Priority Date: 05/01/2006
• Status: Active Grant

• Current Assignee: Lord Corporation (Parker-Hannifin Corporation)
• Original Assignee: Lord Corporation (Parker-Hannifin Corporation)
• Inventors: St. Clair, Kenneth Alan, Jolly, Mark R., Marjoram, Robert, McMahon, William J., Kintz, K. Andrew, Carlson, J. David
• Primary Examiner(s): Williams; Melanie Torres
• Application Number:
  US11/742,911
• Publication Number:
  US 20070257408A1
• Time in Patent Office: 1,323 Days
• Field of Search: 188/267, 188/267.1, 188/269, 188/314, 188/315, 188/322.12, 188/267.2, 188/322.19, 188/322.22, 188/322.16
• US Class Current: 188/267.1
• CPC Class Codes: B60G 99/002 Suspension details of the suspension of the vehicle body on the vehicle chassis
• CPC Class Codes: B60G 99/008 Other suspension arrangements with fluid springs
• CPC Class Codes: F16F 13/002 comprising at least one fluid spring F16F13/005, F16F13/02, F16F13/04 take precedence
• CPC Class Codes: F16F 9/064 Units characterised by the location or shape of the expansion chamber F16F9/068, F16F9/08 take precedence
• CPC Class Codes: F16F 9/535 Magnetorheological [MR] fluid dampers springs comprising magnetorheological [MR] elastomers F16F1/361
• CPC Class Codes: Y10T 29/49826 Assembling or joining

Abstract

The controllable suspension system includes a strut with a magnetorheological fluid damper. The magnetorheological fluid damper includes a longitudinal damper tubular housing having a longitudinally extending axis and an inner wall for containing magnetorheological fluid. The damper includes a piston head movable within the damper tubular housing along a longitudinal length the housing, with the damper piston head providing a first upper variable volume magnetorheological fluid chamber and a second lower variable volume magnetorheological fluid chamber, with a fluid flow gap between the upper and lower fluid chambers with a piston head fluid flow interface length HL, the damper piston having a longitudinal piston rod for supporting the piston head within the housing, with the piston supported within the housing with a piston rod bearing assembly disposed between the housing and the rod, with the piston rod bearing assembly having a piston rod bearing seal interface length BL, wherein contact between the piston head and the damper tubular housing inner wall is inhibited.

Claims

1. A controllable suspension system for controlling the relative motion between a first body and a second body, said controllable suspension system comprised of a strut, said strut including a magnetorheological fluid damper, said magnetorheological fluid damper including,

a longitudinal damper tubular housing having a longitudinally extending axis, said longitudinal damper tubular housing having an inner wall for containing a magnetorheological fluid within said tubular housing,

a damper piston, said damper piston comprised of a piston head movable within the damper tubular housing along a longitudinal length of said tubular housing, with said damper piston head providing a first upper variable volume magnetorheological fluid chamber and a second lower variable volume magnetorheological fluid chamber, said damper piston head having a fluid flow gap between the first upper variable volume magnetorheological fluid chamber and the second lower variable volume magnetorheological fluid chamber with a piston head fluid flow interface length HL,

said damper piston having a longitudinal piston rod for supporting said piston head within said longitudinal damper tubular housing,

said piston supported within said longitudinal damper tubular housing with a piston rod bearing assembly disposed between said longitudinal damper tubular housing and said longitudinal piston rod, said piston rod bearing assembly having a piston rod bearing seal interface length BL, wherein contact between said piston head and said damper tubular housing inner wall is inhibited and said magnetorheological fluid damper includes a volume compensator, said volume compensator proximate said piston rod bearing assembly.

2. A controllable suspension system as claimed in claim 1 wherein BL>

HL.

3. A controllable suspension system as claimed in claim 1 wherein said strut includes a longitudinal gas spring, said longitudinal gas spring aligned with said longitudinal damper tubular housing longitudinally extending axis.

4. A controllable suspension system as claimed in claim 1 wherein said piston rod bearing assembly includes a bearing holder which receives a first upper bearing and a distal second lower bearing to provide said piston rod bearing seal interface length BL.

5. A controllable suspension system for controlling the relative motion between the first body and the second body as claimed in claim 1, said controllable suspension system including a first strut, said first strut including a magnetorheological fluid damper, said controllable suspension system including at least a second magnetorheological fluid damper strut between said first body and the second body.

6. A controllable suspension system as claimed in claim 5, including at least a third magnetorheological fluid damper strut between said first body and the second body.

7. A controllable suspension system for controlling the relative motion between a first body and a second body, said controllable suspension system comprised of a strut, said strut including a magnetorheological fluid damper, said magnetorheological fluid damper including,

a longitudinal damper tubular housing having a longitudinally extending axis, said longitudinal damper tubular housing having an inner wall for containing a magnetorheological fluid within said tubular housing,

a damper piston, said damper piston comprised of a piston head movable within the damper tubular housing along a longitudinal length of said tubular housing, with said damper piston head providing a first upper variable volume magnetorheological fluid chamber and a second lower variable volume magnetorheological fluid chamber, said damper piston head having a fluid flow gap between the first upper variable volume magnetorheological fluid chamber and the second lower variable volume magnetorheological fluid chamber with a piston head fluid flow interface length HL,

said damper piston having a longitudinal piston rod for supporting said piston head within said longitudinal damper tubular housing,

said piston supported within said longitudinal damper tubular housing with a piston rod bearing assembly disposed between said longitudinal damper tubular housing and said longitudinal piston rod, said piston rod bearing assembly having a piston rod bearing seal interface length BL, wherein contact between said piston head and said damper tubular housing inner wall is inhibited,

and said piston rod bearing assembly includes a bearing holder which receives at least a first bearing and includes a compliance member cavity for receiving a volume compensator gas compliance member.

8. A controllable suspension system for controlling the relative motion between a first body and a second body, said controllable suspension system comprised of a strut, said strut including a magnetorheological fluid damper, said magnetorheological fluid damper including,

a longitudinal damper tubular housing having a longitudinally extending axis, said longitudinal damper tubular housing having an inner wall for containing a magnetorheological fluid within said tubular housing,

a damper piston, said damper piston comprised of a piston head movable within the damper tubular housing along a longitudinal length of said tubular housing, with said damper piston head providing a first upper variable volume magnetorheological fluid chamber and a second lower variable volume magnetorheological fluid chamber, said damper piston head having a fluid flow gap between the first upper variable volume magnetorheological fluid chamber and the second lower variable volume magnetorheological fluid chamber with a piston head fluid flow interface length HL,

said damper piston having a longitudinal piston rod for supporting said piston head within said longitudinal damper tubular housing,

said piston supported within said longitudinal damper tubular housing with a piston rod bearing assembly disposed between said longitudinal damper tubular housing and said longitudinal piston rod, said piston rod bearing assembly having a piston rod bearing seal interface length BL, wherein contact between said piston head and said damper tubular housing inner wall is inhibited,

and said piston rod bearing assembly includes a bearing holder which receives at least a first bearing and includes a sensor target magnet holder which receives a target magnet.

9. A controllable suspension system for controlling the relative motion between a first body and a second body, said controllable suspension system comprised of a strut, said strut including a magnetorheological fluid damper, said magnetorheological fluid damper including,

a longitudinal damper tubular housing having a longitudinally extending axis, said longitudinal damper tubular housing having an inner wall for containing a magnetorheological fluid within said tubular housing,

a damper piston, said damper piston comprised of a piston head movable within the damper tubular housing along a longitudinal length of said tubular housing, with said damper piston head providing a first upper variable volume magnetorheological fluid chamber and a second lower variable volume magnetorheological fluid chamber, said damper piston head having a fluid flow gap between the first upper variable volume magnetorheological fluid chamber and the second lower variable volume magnetorheological fluid chamber with a piston head fluid flow interface length HL,

said damper piston having a longitudinal piston rod for supporting said piston head within said longitudinal damper tubular housing,

said piston supported within said longitudinal damper tubular housing with a piston rod bearing assembly disposed between said longitudinal damper tubular housing and said longitudinal piston rod, said piston rod bearing assembly having a piston rod bearing seal interface length BL, wherein contact between said piston head and said damper tubular housing inner wall is inhibited,

and said magnetorheological fluid damper includes a volume compensator, said volume compensator proximate said piston rod bearing.

10. A controllable suspension system for controlling the relative motion between a first body and a second body, said controllable suspension system comprised of a strut, said strut including a magnetorheological fluid damper, said magnetorheological fluid damper including,

a longitudinal damper tubular housing having a longitudinally extending axis, said longitudinal damper tubular housing having an inner wall for containing a magnetorheological fluid within said tubular housing,

a damper piston, said damper piston comprised of a piston head movable within the damper tubular housing along a longitudinal length of said tubular housing, with said damper piston head providing a first upper variable volume magnetorheological fluid chamber and a second lower variable volume magnetorheological fluid chamber, said damper piston head having a fluid flow gap between the first upper variable volume magnetorheological fluid chamber and the second lower variable volume magnetorheological fluid chamber with a piston head fluid flow interface length HL,

said damper piston having a longitudinal piston rod for supporting said piston head within said longitudinal damper tubular housing,

said piston supported within said longitudinal damper tubular housing with a piston rod bearing assembly disposed between said longitudinal damper tubular housing and said longitudinal piston rod, said piston rod bearing assembly having a piston rod bearing seal interface length BL, wherein contact between said piston head and said damper tubular housing inner wall is inhibited,

and said damper piston head includes a polymer overmolded electromagnetic coil.

11. A controllable suspension system as claimed in claim 10 wherein said polymer overmolded electromagnetic coil includes a plurality of coil guides.

12. A controllable damper for controlling motion, said controllable damper including:

a longitudinal damper tubular housing having a longitudinally extending axis, said longitudinal damper tubular housing having an inner wall for containing a fluid within said tubular housing,

a damper piston, said damper piston comprised of a piston head movable within the damper tubular housing along a longitudinal length of said tubular housing, with said damper piston head providing a first upper variable volume fluid chamber and a second lower variable volume fluid chamber, said damper piston head having a fluid flow gap between the first upper variable volume fluid chamber and the second lower variable volume fluid chamber with a piston head fluid flow interface length HL,

said damper piston having a longitudinal piston rod for supporting said piston head within said longitudinal damper tubular housing,

said piston supported within said longitudinal damper tubular housing with a piston rod bearing assembly disposed between said longitudinal damper tubular housing and said longitudinal piston rod, said piston rod bearing assembly having a piston rod bearing seal interface length BL, wherein contact between said piston head and said damper tubular housing inner wall is inhibited and said damper includes a volume compensator, said volume compensator proximate said piston rod bearing assembly.

13. A controllable damper as claimed in claim 12 wherein BL>

HL.

14. A controllable damper as claimed in claim 12 wherein said damper includes an upper strut end head member with an electrical power input.

15. A controllable damper as claimed in claim 12 wherein said damper piston rod bearing assembly includes a bearing holder which receives a first upper bearing and a distal second lower bearing to provide said piston rod bearing seal interface length BL.

16. A controllable damper as claimed in claim 12 wherein said damper piston rod bearing assembly includes a bearing holder which receives at least a first bearing and a sensor target magnet holder which receives a target magnet.

17. A controllable damper for controlling motion, said controllable damper including:

a longitudinal damper tubular housing having a longitudinally extending axis, said longitudinal damper tubular housing having an inner wall for containing a fluid within said tubular housing,

a damper piston, said damper piston comprised of a piston head movable within the damper tubular housing along a longitudinal length of said tubular housing, with said damper piston head providing a first upper variable volume fluid chamber and a second lower variable volume fluid chamber, said damper piston head having a fluid flow gap between the first upper variable volume fluid chamber and the second lower variable volume fluid chamber with a piston head fluid flow interface length HL,

said damper piston having a longitudinal piston rod for supporting said piston head within said longitudinal damper tubular housing,

said piston supported within said longitudinal damper tubular housing with a piston rod bearing assembly disposed between said longitudinal damper tubular housing and said longitudinal piston rod, said piston rod bearing assembly having a piston rod bearing seal interface length BL, wherein contact between said piston head and said damper tubular housing inner wall is inhibited,

and said damper piston rod bearing assembly includes a bearing holder which receives at least a first bearing and a compliance member cavity for receiving a volume compensator gas compliance member.

18. A controllable damper for controlling motion, said controllable damper including:

a longitudinal damper tubular housing having a longitudinally extending axis, said longitudinal damper tubular housing having an inner wall for containing a fluid within said tubular housing,

a damper piston, said damper piston comprised of a piston head movable within the damper tubular housing along a longitudinal length of said tubular housing, with said damper piston head providing a first upper variable volume fluid chamber and a second lower variable volume fluid chamber, said damper piston head having a fluid flow gap between the first upper variable volume fluid chamber and the second lower variable volume fluid chamber with a piston head fluid flow interface length HL,

said damper piston having a longitudinal piston rod for supporting said piston head within said longitudinal damper tubular housing,

said piston supported within said longitudinal damper tubular housing with a piston rod bearing assembly disposed between said longitudinal damper tubular housing and said longitudinal piston rod, said piston rod bearing assembly having a piston rod bearing seal interface length BL, wherein contact between said piston head and said damper tubular housing inner wall is inhibited, and said damper includes an upper strut end head member with an electrical power input,

and said longitudinal piston rod damper piston rod bearing assembly includes a bearing holder which receives at least a first bearing and a sensor target magnet holder which receives a target magnet.

19. A controllable damper for controlling motion, said controllable damper including:

a longitudinal damper tubular housing having a longitudinally extending axis, said longitudinal damper tubular housing having an inner wall for containing a fluid within said tubular housing,

a damper piston, said damper piston comprised of a piston head movable within the damper tubular housing along a longitudinal length of said tubular housing, with said damper piston head providing a first upper variable volume fluid chamber and a second lower variable volume fluid chamber, said damper piston head having a fluid flow gap between the first upper variable volume fluid chamber and the second lower variable volume fluid chamber with a piston head fluid flow interface length HL,

said damper piston having a longitudinal piston rod for supporting said piston head within said longitudinal damper tubular housing,

said piston supported within said longitudinal damper tubular housing with a piston rod bearing assembly disposed between said longitudinal damper tubular housing and said longitudinal piston rod, said piston rod bearing assembly having a piston rod bearing seal interface length BL, wherein contact between said piston head and said damper tubular housing inner wall is inhibited, and

said damper piston head includes an injected pressurized polymer overmolded electromagnetic coil.

20. A controllable damper as claimed in claim 19 wherein said polymer overmolded electromagnetic coil includes a plurality of coil guides, said coil guides aligned with said longitudinally extending axis.

21. A method of making a controllable suspension system for controlling the relative motion between a first body and a second body,

said method comprising:

providing a longitudinal damper tubular housing having a longitudinally extending axis, said longitudinal damper tubular housing having an inner wall for containing a magnetorheological fluid within said tubular housing, said damper tubular housing inner wall having an damper tubular housing inner wall ID, said longitudinal damper tubular housing having a first upper end and a second distal lower end,

providing a piston rod bearing assembly, said piston rod bearing assembly having a piston rod bearing seal interface length BL for supporting a damper piston within said longitudinal damper tubular housing,

providing a damper piston, said damper piston including a piston head and a longitudinal piston rod for supporting said piston head within said longitudinal damper tubular housing, said piston head having a piston head OD,

disposing said piston rod bearing assembly in said longitudinal damper tubular housing proximate said first upper end,

receiving said damper piston longitudinal piston rod in said piston rod bearing assembly, wherein said piston head is movable within the damper tubular housing along the longitudinal length of said tubular housing, with said damper piston head providing a first upper variable volume magnetorheological fluid chamber and a second lower variable volume magnetorheological fluid chamber, said damper piston head having a fluid flow gap between the first upper variable volume magnetorheological fluid chamber and the second lower variable volume magnetorheological fluid chamber, and between the piston head OD and the damper tubular housing inner wall ID, with a piston head fluid flow interface length HL with contact between said piston head OD and said damper tubular housing inner wall ID inhibited,

providing a magnetorheological damper fluid and disposing said magnetorheological damper fluid in said damper tubular housing,

and providing a volume compensator, and disposing said volume compensator proximate said piston rod bearing assembly.

22. A method as claimed in claim 21, said method including providing a longitudinal gas spring, and aligning said longitudinal gas spring with said longitudinal damper tubular housing longitudinally extending axis.

23. A method as claimed in claim 21, wherein providing said piston rod bearing assembly with said piston rod bearing seal interface length BL includes providing a length BL>

HL.

24. A method as claimed in claim 21, wherein providing said piston rod bearing assembly includes providing a bearing holder which receives a first upper bearing and a distal second lower bearing to provide said piston rod bearing seal interface length BL.

25. A method as claimed in claim 21 including providing a first magnetorheological fluid damper, and at least a second magnetorheological fluid damper between said first body and the second body.

26. A method as claimed in claim 25 including providing at least a third magnetorheological fluid damper between said first body and the second body.

27. A method of making a controllable suspension system for controlling the relative motion between a first body and a second body,

said method comprising:

providing a longitudinal damper tubular housing having a longitudinally extending axis, said longitudinal damper tubular housing having an inner wall for containing a magnetorheological fluid within said tubular housing, said damper tubular housing inner wall having an damper tubular housing inner wall ID, said longitudinal damper tubular housing having a first upper end and a second distal lower end,

providing a piston rod bearing assembly, said piston rod bearing assembly having a piston rod bearing seal interface length BL for supporting a damper piston within said longitudinal damper tubular housing,

providing a damper piston, said damper piston including a piston head and a longitudinal piston rod for supporting said piston head within said longitudinal damper tubular housing, said piston head having a piston head OD,

disposing said piston rod bearing assembly in said longitudinal damper tubular housing proximate said first upper end,

receiving said damper piston longitudinal piston rod in said piston rod bearing assembly, wherein said piston head is movable within the damper tubular housing along the longitudinal length of said tubular housing, with said damper piston head providing a first upper variable volume magnetorheological fluid chamber and a second lower variable volume magnetorheological fluid chamber, said damper piston head having a fluid flow gap between the first upper variable volume magnetorheological fluid chamber and the second lower variable volume magnetorheological fluid chamber, and between the piston head OD and the damper tubular housing inner wall ID, with a piston head fluid flow interface length HL with contact between said piston head OD and said damper tubular housing inner wall ID inhibited,

providing a magnetorheological damper fluid and disposing said magnetorheological damper fluid in said damper tubular housing,

and providing said piston rod bearing assembly includes providing a bearing holder which receives at least a first bearing and includes a compliance member cavity for receiving a volume compensator gas compliance member.

28. A method of making a controllable suspension system for controlling the relative motion between a first body and a second body,

said method comprising:

providing a longitudinal damper tubular housing having a longitudinally extending axis, said longitudinal damper tubular housing having an inner wall for containing a magnetorheological fluid within said tubular housing, said damper tubular housing inner wall having an damper tubular housing inner wall ID, said longitudinal damper tubular housing having a first upper end and a second distal lower end,

providing a piston rod bearing assembly, said piston rod bearing assembly having a piston rod bearing seal interface length BL for supporting a damper piston within said longitudinal damper tubular housing,

providing a damper piston, said damper piston including a piston head and a longitudinal piston rod for supporting said piston head within said longitudinal damper tubular housing, said piston head having a piston head OD,

disposing said piston rod bearing assembly in said longitudinal damper tubular housing proximate said first upper end,

receiving said damper piston longitudinal piston rod in said piston rod bearing assembly, wherein said piston head is movable within the damper tubular housing along the longitudinal length of said tubular housing, with said damper piston head providing a first upper variable volume magnetorheological fluid chamber and a second lower variable volume magnetorheological fluid chamber, said damper piston head having a fluid flow gap between the first upper variable volume magnetorheological fluid chamber and the second lower variable volume magnetorheological fluid chamber, and between the piston head OD and the damper tubular housing inner wall ID, with a piston head fluid flow interface length HL with contact between said piston head OD and said damper tubular housing inner wall ID inhibited,

providing a magnetorheological damper fluid and disposing said magnetorheological damper fluid in said damper tubular housing, and

providing said piston rod bearing assembly includes providing a bearing holder which receives at least a first bearing and a sensor target magnet holder which receives a target magnet.

29. A method of making a controllable suspension system for controlling the relative motion between a first body and a second body,

said method comprising:

providing a longitudinal damper tubular housing having a longitudinally extending axis, said longitudinal damper tubular housing having an inner wall for containing a magnetorheological fluid within said tubular housing, said damper tubular housing inner wall having an damper tubular housing inner wall ID, said longitudinal damper tubular housing having a first upper end and a second distal lower end,

providing a piston rod bearing assembly, said piston rod bearing assembly having a piston rod bearing seal interface length BL for supporting a damper piston within said longitudinal damper tubular housing,

providing a damper piston, said damper piston including a piston head and a longitudinal piston rod for supporting said piston head within said longitudinal damper tubular housing, said piston head having a piston head OD,

disposing said piston rod bearing assembly in said longitudinal damper tubular housing proximate said first upper end,

receiving said damper piston longitudinal piston rod in said piston rod bearing assembly, wherein said piston head is movable within the damper tubular housing along the longitudinal length of said tubular housing, with said damper piston head providing a first upper variable volume magnetorheological fluid chamber and a second lower variable volume magnetorheological fluid chamber, said damper piston head having a fluid flow gap between the first upper variable volume magnetorheological fluid chamber and the second lower variable volume magnetorheological fluid chamber, and between the piston head OD and the damper tubular housing inner wall ID, with a piston head fluid flow interface length HL with contact between said piston head OD and said damper tubular housing inner wall ID inhibited,

providing a magnetorheological damper fluid and disposing said magnetorheological damper fluid in said damper tubular housing, and

said magnetorheological fluid damper includes a volume compensator, said volume compensator proximate said piston rod bearing.

30. A method of making a controllable suspension system for controlling the relative motion between a first body and a second body,

said method comprising:

providing a longitudinal damper tubular housing having a longitudinally extending axis, said longitudinal damper tubular housing having an inner wall for containing a magnetorheological fluid within said tubular housing, said damper tubular housing inner wall having an damper tubular housing inner wall ID, said longitudinal damper tubular housing having a first upper end and a second distal lower end,

providing a piston rod bearing assembly, said piston rod bearing assembly having a piston rod bearing seal interface length BL for supporting a damper piston within said longitudinal damper tubular housing,

providing a damper piston, said damper piston including a piston head and a longitudinal piston rod for supporting said piston head within said longitudinal damper tubular housing, said piston head having a piston head OD,

disposing said piston rod bearing assembly in said longitudinal damper tubular housing proximate said first upper end,

receiving said damper piston longitudinal piston rod in said piston rod bearing assembly, wherein said piston head is movable within the damper tubular housing along the longitudinal length of said tubular housing, with said damper piston head providing a first upper variable volume magnetorheological fluid chamber and a second lower variable volume magnetorheological fluid chamber, said damper piston head having a fluid flow gap between the first upper variable volume magnetorheological fluid chamber and the second lower variable volume magnetorheological fluid chamber, and between the piston head OD and the damper tubular housing inner wall ID, with a piston head fluid flow interface length HL with contact between said piston head OD and said damper tubular housing inner wall ID inhibited,

providing a magnetorheological damper fluid and disposing said magnetorheological damper fluid in said damper tubular housing, and

providing an overmolded piston head EM coil.

31. A method as claimed in claim 30, said method including providing said piston head with a plurality of longitudinally extending guides.

32. A method of making a controllable damper for controlling motion, said method comprises:

providing a longitudinal damper tubular housing having a longitudinally extending axis, said longitudinal damper tubular housing having an inner wall for containing a fluid within said tubular housing, said longitudinal damper tubular housing having a first end and a second distal end,

providing a piston rod bearing assembly, said piston rod bearing assembly having a piston rod bearing seal interface length BL for supporting a damper piston within said longitudinal damper tubular housing,

providing a damper piston, said damper piston including a piston head and a longitudinal piston rod for supporting said piston head within said longitudinal damper tubular housing,

disposing said piston rod bearing assembly in said longitudinal damper tubular housing proximate said first end,

receiving said damper piston longitudinal piston rod in said piston rod bearing assembly, wherein said piston head is movable within the damper tubular housing along the longitudinal length of said tubular housing, with said damper piston head providing a first upper variable volume fluid chamber and a second lower variable volume fluid chamber, said damper piston head having a fluid flow gap between the first upper variable volume fluid chamber and the second lower variable volume fluid chamber with a piston head fluid flow interface length HL, with HL<

BL,

and providing a volume compensator, and disposing said volume compensator proximate said piston rod bearing assembly.

33. A method as claimed in claim 32 said method includes providing an upper strut end head member with an electrical power input and disposing said strut end head member proximate said damper tubular housing first end.

34. A method as claimed in claim 32, wherein providing said piston rod bearing assembly includes providing a bearing holder which receives a first upper bearing and a distal second lower bearing to provide said piston rod bearing seal interface length BL.

35. A method of making a controllable damper for controlling motion, said method comprises:

providing a longitudinal damper tubular housing having a longitudinally extending axis, said longitudinal damper tubular housing having an inner wall for containing a fluid within said tubular housing, said longitudinal damper tubular housing having a first end and a second distal end,

providing a piston rod bearing assembly, said piston rod bearing assembly having a piston rod bearing seal interface length BL for supporting a damper piston within said longitudinal damper tubular housing,

providing a damper piston, said damper piston including a piston head and a longitudinal piston rod for supporting said piston head within said longitudinal damper tubular housing,

disposing said piston rod bearing assembly in said longitudinal damper tubular housing proximate said first end,

receiving said damper piston longitudinal piston rod in said piston rod bearing assembly, wherein said piston head is movable within the damper tubular housing along the longitudinal length of said tubular housing, with said damper piston head providing a first upper variable volume fluid chamber and a second lower variable volume fluid chamber, said damper piston head having a fluid flow gap between the first upper variable volume fluid chamber and the second lower variable volume fluid chamber with a piston head fluid flow interface length HL, with HL<

BL,

and providing said piston rod bearing assembly includes providing a bearing holder which receives at least a first bearing and includes a compliance member cavity for receiving a volume compensator gas compliance member.

36. A method of making a controllable damper for controlling motion, said method comprises:

providing a longitudinal damper tubular housing having a longitudinally extending axis, said longitudinal damper tubular housing having an inner wall for containing a fluid within said tubular housing, said longitudinal damper tubular housing having a first end and a second distal end,

providing a piston rod bearing assembly, said piston rod bearing assembly having a piston rod bearing seal interface length BL for supporting a damper piston within said longitudinal damper tubular housing,

providing a damper piston, said damper piston including a piston head and a longitudinal piston rod for supporting said piston head within said longitudinal damper tubular housing,

disposing said piston rod bearing assembly in said longitudinal damper tubular housing proximate said first end,

receiving said damper piston longitudinal piston rod in said piston rod bearing assembly, wherein said piston head is movable within the damper tubular housing along the longitudinal length of said tubular housing, with said damper piston head providing a first upper variable volume fluid chamber and a second lower variable volume fluid chamber, said damper piston head having a fluid flow gap between the first upper variable volume fluid chamber and the second lower variable volume fluid chamber with a piston head fluid flow interface length HL, with HL<

BL,

and providing said piston rod bearing assembly includes providing a bearing holder which receives at least a first bearing and includes a sensor target magnet holder which receives a target magnet.

37. A method of making a controllable damper for controlling motion, said method comprises:

providing a longitudinal damper tubular housing having a longitudinally extending axis, said longitudinal damper tubular housing having an inner wall for containing a fluid within said tubular housing, said longitudinal damper tubular housing having a first end and a second distal end,

providing a piston rod bearing assembly, said piston rod bearing assembly having a piston rod bearing seal interface length BL for supporting a damper piston within said longitudinal damper tubular housing,

providing a damper piston, said damper piston including a piston head and a longitudinal piston rod for supporting said piston head within said longitudinal damper tubular housing,

disposing said piston rod bearing assembly in said longitudinal damper tubular housing proximate said first end,

receiving said damper piston longitudinal piston rod in said piston rod bearing assembly, wherein said piston head is movable within the damper tubular housing along the longitudinal length of said tubular housing, with said damper piston head providing a first upper variable volume fluid chamber and a second lower variable volume fluid chamber, said damper piston head having a fluid flow gap between the first upper variable volume fluid chamber and the second lower variable volume fluid chamber with a piston head fluid flow interface length HL, with HL<

BL,

and providing said damper piston including said piston head includes providing an injected pressurized polymer overmolded electromagnetic coil.