Magnetorheological damper and method of operating the same

Abstract

The present disclosure provides a magneto-rheological damper and a method of operating the same. A magneto-rheological (MR) damper includes a main tube defining a MR chamber containing a MR fluid having a viscosity that changes in response to an application of a magnetic field. A piston rod is disposed at least partially within the main tube. A MR piston is connected to the piston rod and divides the MR chamber into a MR rebound chamber and a MR compression chamber. The MR piston includes a MR rebound valve that regulates a flow of the MR fluid from the MR rebound chamber into the MR compression chamber during a rebound stroke, thereby generating a rebound damping force. A base valve assembly regulates a flow of a standard fluid. The rebound damping force is substantially entirely generated by the MR rebound valve of the MR piston. The MR compression valve of the MR piston generates a compression damping force with the base valve assembly.

Description

TECHNICAL FIELD

[0001] The present invention relates generally to a suspension damper for a vehicle. More particularly, the present invention relates to a suspension damper including a magnetorheological (MR) fluid. BACKGROUND

[0002] Damper assemblies are well known in the art for use in vehicles. One such MR damper is disclosed in patent publication US5706920A, which discloses a single tube MR damper including a main tube disposed on a central axis and extending between a first end and a second end. The damper defines a fluid compartment for containing a working fluid between the first end and the second end. A main piston is slidably disposed in the fluid compartment dividing the fluid compartment into a rebound compartment and a compression compartment. A piston rod is disposed on the central axis extending to a distal end along the central axis and attached to the main piston for moving the main piston between compression and rebound strokes.

[0003] Magnetorheological (MR) dampers are increasingly used on vehicles to continuously control the damping characteristics in order to drive and handle correctly in all driving situations. A magnetorheological fluid typically consists of a clear carrier or base fluid (e.g. polyalphaolefin) with suspended particles. When the particles are charged by a magnetic field, they line up and change the viscosity of the fluid, which in turn can be used to control the damping force. SUMMARY

[0004] The present invention provides a magnetorheological (MR) damper. The MR damper includes a main tube defining a MR chamber containing a MR fluid. The MR fluid has a viscosity that changes in response to an application of a magnetic field. The MR damper further includes a piston rod disposed at least partially within the main tube, a MR piston connected to the piston rod and dividing the MR chamber into a MR rebound chamber and a MR compression chamber. The MR piston includes a MR rebound valve configured to regulate a flow of the MR fluid from the MR rebound chamber into the MR compression chamber during a rebound stroke, thereby generating a rebound damping force. The MR damper further includes a standard fluid chamber containing a standard fluid. The standard fluid has a viscosity that does not change with an application of a magnetic field. The MR damper further includes a base valve assembly configured to regulate a flow of the standard fluid. The rebound damping force is substantially entirely generated by the MR rebound valve of the MR piston.

[0005] The present invention also provides a method for operating a magneto-rheological (MR) damper. The method includes the steps of moving an MR piston through an MR chamber containing an MR fluid having a viscosity that changes in response to the application of a magnetic field by a piston rod, the MR piston dividing the MR chamber into an MR rebound chamber and an MR compression chamber; regulating the flow of the MR fluid from the MR rebound chamber into the MR compression chamber by an MR rebound valve of the MR piston during a rebound stroke, thereby generating a rebound damping force; and regulating the flow of a standard fluid having a viscosity that does not change in response to the application of a magnetic field by a base valve assembly. The rebound damping force is substantially entirely generated by the MR rebound valve of the MR piston. BRIEF DESCRIPTION OF DRAWINGS

[0006] Other advantages of the present invention will be readily appreciated, as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

[0007] Figure 1 A partial view of a vehicle suspension including a MR damper according to the present invention is shown;

[0008] Figure 2 A cross-sectional schematic view of a first MR damper according to aspects of the present disclosure is shown;

[0009] Figure 3 A cross-sectional schematic view of a second MR damper according to aspects of the present disclosure is shown; and

[0010] Figure 4 A flowchart illustrating steps in a method for operating a MR damper according to aspects of the present disclosure is shown. DETAILED DESCRIPTION

[0011] Referring to the drawings wherein like reference numerals refer to corresponding parts throughout the several views, one aspect of the present invention is to provide a magneto-rheological (MR) damper 20, 120 for a vehicle 10. As generally illustrated in Figure 1 The MR damper 20, 120 is attached to a chassis 11 of the vehicle 10 by a top mount 12. A plurality of screws 13 extend through an upper surface of the top mount 12 to fasten the top mount 12 to a body of the vehicle 10. The top mount 12 is connected to a coil spring 14 and a piston rod 32, 132 of the MR damper 20, 120. The MR damper 20, 120 is also connected to a knuckle 15 that supports a wheel 16 of the vehicle 10.

[0012] Figure 2A first MR damper 20 of MR dampers 20, 120 that can be used for vehicle 10 is generally shown. First MR damper 20 has a dual tube configuration including a first main tube 22 and an outer tube 24 disposed coaxially around first main tube 22, and annularly defining a compensation chamber 26 between first main tube 22 and outer tube 24. First MR damper 20 includes a closed end 28 and a first rod cap 30 opposite closed end 28 and enclosing an end of each of first main tube 22 and outer tube 24. A first piston rod 32 is disposed at least partially within first main tube 22. First piston rod 32 extends through first rod cap 30 and into first main tube 22. First main tube 22 defines a first MR chamber 36, 38 containing MR fluid. The MR fluid has a viscosity that changes in response to an application of a magnetic field.

[0013] A first MR piston 40 is disposed in first main tube 22 and attached to an end of first piston rod 32. First MR piston 40 is slidable in an axial direction within first main tube 22 and seals against an inner surface of first main tube 22 to divide first MR chamber 36, 38 into a first MR rebound chamber 36 and a first MR compression chamber 38. First MR piston 40 includes a first MR coil 42 configured to generate a magnetic field to change the viscosity of the MR fluid to dynamically adjust a damping characteristic of first MR damper 20 in either or both of a compression direction and / or a rebound direction. First MR coil 42 can be connected to a power source via wires through first piston rod 32 (not shown).

[0014] First MR piston 40 includes a first piston body 44 defining a first MR compression fluid passage 46 providing a flow path for MR fluid between first MR compression chamber 38 and first MR rebound chamber 36 during a compression stroke. First MR piston 40 also includes a first MR compression valve 47 configured to regulate the flow of MR fluid from first MR compression chamber 38 through first MR compression fluid passage 46 into first MR rebound chamber 36 during a compression stroke. First MR compression valve 47 can also function as a check valve to block fluid flow through first MR compression fluid passage 46 during a rebound stroke. First MR compression valve 47 can include one or more variable orifices, which can include a deflector disc to regulate fluid flow.

[0015] The first MR piston 40 further defines a first MR rebound fluid passage 48 that provides a flow path for MR fluid between the first MR compression chamber 38 and the first MR rebound chamber 36 during a rebound stroke. The first MR piston 40 further includes a first MR rebound valve 49 configured to regulate the flow of MR fluid from the first MR rebound chamber 36 through the first MR rebound fluid passage 48 into the first MR compression chamber 38 during a rebound stroke. The first MR rebound valve 49 can also function as a check valve, thereby preventing fluid flow through the first MR rebound fluid passage 48 during a compression stroke. The first MR rebound valve 49 can include one or more variable orifices, which can include a deflector disc to regulate fluid flow.

[0016] The first MR damper 20 further includes a first fluid separator 50 that separates the first MR compression chamber 38 from a first standard fluid chamber 52 that contains a standard (i.e., non-MR) fluid, such as oil, and has a viscosity that does not vary with the application of a magnetic field. In some embodiments, and as shown, the first fluid separator 50 can include a floating piston disposed in and slidable in an axial direction within the first main tube 22. The floating piston of the first fluid separator 50 seals against an inner surface of the first main tube 22 to separate the first MR compression chamber 38 from the first standard fluid chamber 52 and prevent MR fluid from contacting the standard fluid. Figure 2

[0017] The first MR damper 20 further includes a first bottom valve assembly 60 disposed adjacent the closed end 28 and configured to regulate the flow of standard fluid between the first standard fluid chamber 52 and a compensation chamber 26, which can contain a combination of standard fluid and gas. The gas can be compressed during a rebound stroke to take-up the volume in the first MR damper 20 occupied by the first piston rod 32 when the first piston rod 32 enters through the first rod cap 30.

[0018] ​The first bottom valve assembly 60 includes a first valve body 64 that defines a first bottom compression fluid passage 66 that provides a flow path for the normal fluid between the first normal fluid chamber 52 and the compensation chamber 26. The first bottom valve assembly 60 also includes a first bottom compression valve 67 that is configured to regulate the flow of normal fluid from the first normal fluid chamber 52 through the first bottom compression fluid passage 66 into the compensation chamber 26 during the compression stroke. The first bottom compression valve 67 can also function as a check valve to block fluid flow through the first bottom compression fluid passage 66 in the opposite direction during the rebound stroke. The first bottom compression valve 67 can include one or more variable orifices, which can include a deflector disc to regulate fluid flow.

[0019] The first valve body 64 of the first bottom valve assembly 60 also defines a first bottom rebound fluid passage 68 that provides a flow path for the normal fluid between the compensation chamber 26 and the first normal fluid chamber 52. The first bottom valve assembly 60 also includes a first bottom check valve 69 that is configured to allow fluid to flow from the compensation chamber 26 through the first bottom rebound fluid passage 68 and into the first normal fluid chamber 52 while blocking fluid flow through the first bottom compression fluid passage 66 in the opposite direction. The first bottom check valve 69 is schematically shown in Figure 2 and it can include various structures, such as a ball and seat and / or one or more deflector discs, to provide the one-way flow regulation function. The first bottom check valve 69 can provide a relatively small flow restriction in the rebound direction, so that it does not create a significant damping force in the rebound direction.

[0020] The dual tube design of the first MR damper 20 includes low pressure gas in the compensation chamber 26 to act as a volume compensation. It includes passively mixed oil and gas in the reservoir tube (no physical separation). Compression forces are generated by both the first MR piston 40 and the first bottom valve assembly 60. Rebound forces are generated entirely or substantially entirely by the first MR piston 40. The first bottom valve assembly 60 can be referred to as a passive bottom valve because it acts on the normal fluid rather than the MR fluid, and it can be used to define a minimum compression force (secondary ride). The first MR piston 40 can be used for all rebound damping (secondary + primary ride) and compression body damping (primary ride). The first MR piston 40 can have an asymmetric force profile that generates less force in the compression direction than the rebound damping force in the rebound direction.

[0021] The combination of the first MR piston 40 with the first MR compression valve 47 and the first MR rebound valve 49 and the first base valve assembly 60 with the first base check valve 69 and the first base compression valve 67 causes the first MR damper 20 to generate compression forces through both the first MR piston 40 and the first base valve assembly 60, while rebound forces are generated substantially entirely by the first MR piston 40. This provides advantages over alternative damper designs, including better comfort and isolation, lower gas charge, wider tuning range in compression stroke due to shorter response times and lower temperature sensitivity.

[0022] Figure 3 A second MR damper 120, which can be used for the MR dampers 20, 120 of the vehicle 10, is generally shown. The second MR damper 120 has a single tube configuration including a second main tube 122 having a closed end 128. The second MR damper 120 includes a second rod cap 130 that closes an end of the second main tube 122 opposite the closed end 128.

[0023] A second piston rod 132 extends through the second rod cap 130 and into the second main tube 122. The second main tube 122 defines second MR chambers 136, 138 containing MR fluid. The MR fluid has a viscosity that changes in response to the application of a magnetic field.

[0024] A second MR piston 140 is disposed in the second main tube 122 and is attached to an end of the second piston rod 132. The second MR piston 140 is slidable in an axial direction within the second main tube 122 and seals against an inner surface of the second main tube 122 to divide the second MR chambers 136, 138 into a second MR rebound chamber 136 and a second MR compression chamber 138. The second MR piston 140 includes a second MR coil 142 configured to generate a magnetic field to change the viscosity of the MR fluid to dynamically adjust a damping characteristic of the second MR damper 120 in either or both of a compression direction and a rebound direction. The second MR coil 142 can be connected to a power source via wires through the second piston rod 132 (not shown in the figures).

[0025] The second MR piston 140 includes a second piston body 144 defining a second MR compression fluid passage 146 that provides a flow path for MR fluid between a second MR compression chamber 138 and a second MR springback chamber 136 during the compression stroke. The second MR piston 140 also includes a second MR compression valve 147 configured to regulate the flow rate of MR fluid from the second MR compression chamber 138 through the second MR compression fluid passage 146 and into the second MR springback chamber 136 during the compression stroke. The second MR compression valve 147 can also function as a check valve to prevent fluid flow through the second MR compression fluid passage 146 during the springback stroke. The second MR compression valve 147 may include one or more variable orifices and may include deflector plates to regulate fluid flow.

[0026] The second piston body 144 of the second MR piston 140 further defines a second MR springback fluid passage 148, which provides a flow path for MR fluid between the second MR compression chamber 138 and the second MR springback chamber 136 during the springback stroke. The second MR piston 140 also includes a second MR springback valve 149 configured to regulate the flow rate of MR fluid from the second MR springback chamber 136 through the second MR springback fluid passage 148 into the second MR compression chamber 138 during the springback stroke. The second MR springback valve 149 can also function as a check valve to prevent fluid flow through the second MR springback fluid passage 148 during the compression stroke. The second MR springback valve 149 may include one or more variable orifices and may include deflector plates to regulate fluid flow.

[0027] The second MR damper 120 also includes a second fluid separator 150 that separates the second MR compression chamber 138 from the second standard fluid chambers 152 and 162, which contain standard (i.e., non-MR) fluids, such as oil, and have a viscosity that does not change with the application of a magnetic field. In some embodiments, and as... Figure 3 As shown, the second fluid separator 150 may include a floating piston disposed in the second main pipe 122 and slidable axially within the second main pipe 122. The floating piston of the second fluid separator 150 seals against the inner surface of the second main pipe 122 to separate the second MR compression chamber 138 from the second standard fluid chambers 152, 162 and to prevent the MR fluid from contacting the standard fluid.

[0028] The second MR damper 120 also includes a second base valve assembly 160 disposed within the second standard fluid chamber 152, 162, dividing the second standard fluid chamber 152, 162 into an upper chamber 152 and a lower chamber 162. The second base valve assembly 160 is configured to regulate the flow of standard fluid between the upper chamber 152 and the lower chamber 162 of the second standard fluid chamber 152, 162. In some embodiments, and as shown, the second base valve assembly 160 can include a floating piston disposed in the second main tube 122 and slidable in an axial direction within the second main tube 122. Figure 3

[0029] The second base valve assembly 160 includes a second valve body 164 defining a second base compression fluid passage 166 providing a flow path for standard fluid between the upper chamber 152 and the lower chamber 162. The second base valve assembly 160 also includes a second base compression valve 167 configured to regulate the flow of standard fluid from the upper chamber 152 through the second base compression fluid passage 166 and into the lower chamber 162 during a compression stroke. The second base compression valve 167 can also function as a check valve, thereby preventing fluid flow through the second base compression fluid passage 166 in the opposite direction during a rebound stroke. The second base compression valve 167 can include one or more variable orifices, which can include a deflector disc to regulate fluid flow.

[0030] The second valve body 164 of the second base valve assembly 160 also defines a second base rebound fluid passage 168 providing a flow path for standard fluid between the lower chamber 162 and the upper chamber 152. The second base valve assembly 160 also includes a second base check valve 169 configured to allow fluid flow from the lower chamber 162 through the second base rebound fluid passage 168 and into the upper chamber 152, while preventing fluid flow through the second base compression fluid passage 166 in the opposite direction. The second base check valve 169 is shown schematically above, and it can include various structures, such as a ball and valve seat and / or one or more deflector discs, to provide the one-way flow regulation function. The first base check valve 69 can provide a relatively small flow restriction in the rebound direction, thus not creating a significant damping force in the rebound direction. Figure 3

[0031] ​​The second MR damper 120 also includes a gas cup 170 disposed within the second main pipe 122 and separating the lower chamber 162 of the second standard fluid chambers 152, 162 from the gas-containing gas compartment 172. When the second piston rod 132 enters through the second rod cap 130, the gas can be compressed during the rebound stroke to absorb the volume occupied by the second piston rod 132 in the second MR damper 120. In some embodiments, the gas cup 170 may be configured as a floating piston that can slide axially within the second main pipe 122.

[0032] The single-tube design of the second MR damper 120 includes low-pressure gas in the gas compartment 172 for volume compensation. Compression force is generated by both the second MR piston 140 and the second bottom valve assembly 160. Rebound force is generated entirely or substantially entirely by the second MR piston 140. The second bottom valve assembly 160 can be referred to as a passive bottom valve because it acts on a standard fluid rather than an MR fluid; the second bottom valve assembly 160 can be used to define a minimum compression force (secondary ride comfort). The second MR piston 140 can be used for all rebound damping (secondary + primary ride comfort) and compression body damping (primary ride comfort). The second MR piston 140 can have an asymmetrical force distribution, generating a smaller force in the compression direction than the rebound damping force in the rebound direction.

[0033] The combination of the second MR piston 140 with the second MR compression valve 147 and the second MR rebound valve 149, and the second bottom valve assembly 160 with the second bottom check valve 169 and the second bottom compression valve 167, allows the second MR damper 120 to generate compressive force through both the second MR piston 140 and the second bottom valve assembly 160, while the rebound force is generated almost entirely by the second MR piston 140. This provides advantages over alternative damper designs, including better comfort and isolation, lower gas charge, and a wider tuning range during the compression stroke due to shorter response time and lower temperature sensitivity.

[0034] exist Figure 4 The flowchart illustrates a method 200 for operating an MR damper. As will be understood from this disclosure, the sequence of operations within the method is not limited to the one described above. Figure 4 The executable sequence may be performed in one or more varying sequences as applicable and in accordance with this disclosure.

[0035] Method 200 includes: in step 202, moving the MR piston through an MR chamber containing MR fluid via a piston rod.

[0036] The method 200 further includes, at step 204, regulating a flow of MR fluid from the MR rebound chamber into the MR compression chamber during a rebound stroke by the MR rebound valve of the MR piston, thereby generating a rebound damping force. The rebound damping force can be generated substantially entirely by the MR rebound valve of the MR piston.

[0037] The method 200 further includes, at step 206, regulating a flow of a standard fluid having a viscosity that does not vary with application of a magnetic field by the base valve assembly.

[0038] In some embodiments, regulating the flow of the standard fluid at step 206 further includes, at step 208a, regulating a flow of the standard fluid between the standard fluid chamber and the compensation chamber during a compression stroke by the base compression valve of the base valve assembly, thereby generating a compression damping force; and at step 208b, passing fluid flow from the compensation chamber into the standard fluid chamber while preventing fluid flow in the opposite direction by the base check valve.

[0039] In some embodiments, the MR damper has a dual tube configuration including an outer tube disposed coaxially around a main tube, and defining an annular compensation chamber between the main tube and the outer tube.

[0040] In some embodiments, the MR damper has a single tube configuration including a main tube defining a standard fluid chamber containing a standard fluid, and wherein the base valve assembly divides the standard fluid chamber into an upper chamber and a lower chamber.

[0041] In some embodiments, regulating the flow of the standard fluid at step 206 further includes, at step 210a, regulating a flow of the standard fluid between the upper chamber and the lower chamber during a compression stroke by the base compression valve of the base valve assembly, thereby generating a compression damping force; and at step 210b, passing fluid flow from the lower chamber into the upper chamber while preventing fluid flow in the opposite direction by the base check valve.

[0042] In some embodiments, the method 200 further includes, at step 212, generating a magnetic field by the MR coil disposed within the MR piston, thereby adjusting at least one of the rebound damping force and the compression damping force in a compression direction.

[0043] In some embodiments, the MR coil is configured to adjust both the rebound damping force and the compression damping force.

[0044] It is clear that many modifications and variations of the application are possible in light of the above teachings and can be practiced otherwise than as specifically described. These prior statements should be construed in breadth in accordance with the scope of the appended claims. These prior statements should be construed to cover any combination of the practicality of novelty practice of the application.

Claims

1. A magneto-rheological (MR) damper, the MR damper comprising: a main tube defining an MR chamber containing an MR fluid having a viscosity that changes in response to an application of a magnetic field; a piston rod disposed at least partially within the main tube; an MR piston connected to the piston rod and dividing the MR chamber into an MR rebound chamber and an MR compression chamber, the MR piston including an MR rebound valve configured to regulate a flow of the MR fluid from the MR rebound chamber into the MR compression chamber during a rebound stroke, thereby generating a rebound damping force; a standard fluid chamber containing a standard fluid having a viscosity that does not change in response to an application of a magnetic field; and a base valve assembly configured to regulate a flow of the standard fluid, and wherein the rebound damping force is generated substantially entirely by the MR rebound valve of the MR piston; wherein the MR damper further includes a fluid separator disposed within the main tube and separating the MR chamber from the standard fluid chamber for isolating the MR fluid from the standard fluid; wherein the fluid separator includes a floating piston slidable in an axial direction within the main tube.

2. The MR damper of claim 1, wherein, the MR damper has a dual tube configuration including an outer tube disposed coaxially around the main tube and annularly defining a compensation chamber between the main tube and the outer tube.

3. The MR damper of claim 2, wherein, the base valve assembly includes: a base compression valve configured to regulate a flow of the standard fluid during a compression stroke, thereby generating a compression damping force; and a base check valve configured to allow fluid to flow from the compensation chamber into the standard fluid chamber while preventing fluid flow in the opposite direction.

4. The MR damper of claim 1, wherein, the MR damper has a single tube configuration including the main tube defining the standard fluid chamber, and wherein the base valve assembly divides the standard fluid chamber into an upper chamber and a lower chamber.

5. The MR damper of claim 4, wherein, the base valve assembly includes: a base compression valve configured to regulate a flow of the standard fluid between the upper chamber and the lower chamber during a compression stroke, thereby generating a compression damping force; and a base check valve configured to allow fluid to flow from the lower chamber into the upper chamber while preventing fluid flow in the opposite direction.

6. The MR damper of claim 1, further comprising a gas cup disposed in the main tube and separating the normal fluid chamber from a gas compartment containing a gas, wherein, the gas cup is slidable in an axial direction within the main tube.

7. The MR damper according to claim 1, wherein, the MR piston has an asymmetric force profile producing a force in a compression direction that is less than the rebound damping force produced in a rebound direction.

8. The MR damper of claim 1, further comprising an MR coil disposed within the MR piston and configured to generate a magnetic field, thereby regulating at least one of the rebound damping force and a compression damping force in a compression direction. the MR coil is configured to regulate both the rebound damping force and the compression damping force.

9. The MR damper according to claim 8, wherein, ​ 10. A method for operating a magneto-rheological (MR) damper, the MR damper being the MR damper of any one of claims 1 to 9; the method comprising the steps of: moving the MR piston through an MR chamber containing MR fluid having a viscosity that changes in response to application of a magnetic field by a piston rod, the MR piston dividing the MR chamber into an MR rebound chamber and an MR compression chamber; regulating flow of the MR fluid from the MR rebound chamber into the MR compression chamber by an MR rebound valve of the MR piston during a rebound stroke, thereby generating a rebound damping force; and regulating flow of a standard fluid having a viscosity that does not change in response to application of a magnetic field by a base valve assembly, and wherein the rebound damping force is substantially entirely generated by the MR rebound valve of the MR piston.

11. The method of claim 10, wherein, the MR damper has a dual tube configuration including an outer tube disposed coaxially around a main tube, and annularly defining a compensation chamber between the main tube and the outer tube.

12. The method of claim 11, wherein, The step of regulating flow of the standard fluid further comprises: regulating flow of the standard fluid between a standard fluid chamber and the compensation chamber by a base compression valve of the base valve assembly during a compression stroke, thereby generating a compression damping force; and communicating fluid flow from the compensation chamber into the standard fluid chamber by a base check valve while preventing fluid flow in the opposite direction.

13. The method of claim 10, wherein, the MR damper has a single tube configuration including a main tube defining a standard fluid chamber containing the standard fluid, and wherein the base valve assembly divides the standard fluid chamber into an upper chamber and a lower chamber.

14. The method of claim 13, wherein, The step of regulating flow of the standard fluid further comprises: regulating flow of the standard fluid between the upper chamber and the lower chamber by a base compression valve during a compression stroke, thereby generating a compression damping force; and communicating fluid flow from the lower chamber into the upper chamber by a base check valve while preventing fluid flow in the opposite direction.

15. The method of claim 10, further comprising generating a magnetic field by an MR coil disposed within the MR piston, thereby adjusting at least one of the rebound damping force and the compression damping force in a compression direction.

16. The method of claim 15, wherein, the MR coil is configured to adjust both the rebound damping force and the compression damping force.

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