Variable rate bound stoppers and variable rate suspension systems containing variable rate bound stoppers

A variable rate bound stopper includes a bound stopper in the form of an elastomer member. The elastomer member has an aperture such that the bound stopper is configured to be positioned over and disposed around a piston rod of a shock absorber. A shape memory alloy (SMA) coil formed from an SMA wire extends around at least a portion of the elastomer member. The SMA coil has a relaxed state and an activated state. The SMA coil constrains the elastomer member from deforming radially outward and alters an intrinsic spring rate of the bound stopper when in the activated state.

TECHNICAL FIELD

The present specification generally relates to bound stoppers for vehicle suspension systems and, more specifically, to bound stoppers with variable spring rates for vehicle suspension systems.

BACKGROUND

A suspension system for a vehicle typically includes various components such as shock absorbers, springs, stabilizer bars and the like. Such components are typically arranged between the vehicle wheel and a vehicle body, have a set of fixed (non-variable) properties and thereby provide a set of fixed handling characteristics for the vehicle. However, variable handling characteristics may be desirable, e.g. for a vehicle traveling under different road conditions, carrying loads of different weights, or the like.

Accordingly, a need exists for alternative suspension system components that provide a variable suspension system and variable handling characteristics.

SUMMARY

In one embodiment, a variable rate bound stopper includes an elastomer member. The elastomer member has an aperture such that the variable rate bound stopper is configured to be positioned over and disposed around a piston rod of a shock absorber. A shape memory alloy (SMA) coil formed from an SMA wire extends around at least a portion of the elastomer member. The SMA coil has a relaxed state and an activated state, and the SMA coil constrains the elastomer member from deforming radially outward and alters an intrinsic spring rate of the variable rate bound stopper when in the activated state. In embodiments, the SMA coil is at least two SMA coils formed from at least two SMA wires. Each of the at least two SMA coils have a relaxed state and an activated state, extend around at least a portion of the elastomer member, and constrain the elastomer member from deforming radially outward thereby altering an intrinsic spring rate of the bound stopper when in the activated state. The bound stopper may have a first spring rate when one of the at least two SMA coils is in the activated state and constrains the elastomer member, and a second spring rate when another of the at least two SMA coils is in the activated state and constrains the elastomer member. Also, the bound stopper may have a third spring rate when two of the at least two coils are in the activated state and constrain the elastomer member.

In another embodiment, a shock absorber includes a cylinder, a piston rod extending from the cylinder and a variable rate bound stopper with an elastomer member positioned over and disposed around the piston rod of the shock absorber. A shape memory alloy (SMA) coil formed from an SMA wire extends around at least a portion of the elastomer member. The SMA coil has a relaxed state and an activated state, and the SMA coil constrains the elastomer member from deforming radially outward thereby altering an intrinsic spring rate of the bound stopper when in the activated state. In embodiments, the SMA coil is at least two SMA coils formed from at least two SMA wires. Each of the at least two SMA coils have a relaxed state and an activated state, extend around at least a portion of the elastomer member, and constrain the elastomer member from deforming radially outward thereby altering an intrinsic spring rate of the bound stopper when in the activated state. The variable rate bound stopper may have a first spring rate when one of the at least two SMA coils is in the activated state and constrains the elastomer member, and a second spring rate when another of the at least two SMA coils is in the activated state and constrains the elastomer member. Also, the bound stopper may have a third spring rate when two of the at least two coils are in the activated state and constrain the elastomer member.

In embodiments, an electrical power source may be included and be in communication with the at least two SMA coils. The electrical power source is configured to provide an activation electric current to the at least two SMA coils. Each of the at least two SMA coils is in the relaxed state when the activation electric current is not passing through a given SMA coil(s) and in the activated state when the activation electric current is passing through a given SMA coil(s). A vehicle stability control (VSC) electronic control unit (ECU) in communication with the electrical power source and the at least two SMA coils may be included. The VSC ECU is configured to activate the electrical power source such that the electrical power source provides the activation electric current to the at least two SMA coils. In embodiments, at least one of a wheel speed sensor and a roll/yaw sensor is included and is in communication with the VSC ECU. The at least one speed sensor and roll/yaw sensor is configured to provide sensor feedback to the VSC ECU and the VSC ECU is configured to automatically activate the electrical power source as a function of the sensor feedback provided by the at least one speed sensor and roll/yaw sensor. The electrical power source provides the activation electrical current to at least one of the at least two SMA coils when activated by the VSC ECU.

DETAILED DESCRIPTION

A variable rate bound stopper is provided. As used herein, the term “variable bound stopper” refers to a bound stopper having an intrinsic spring rate that may be externally altered via activation of a shape memory alloy (SMA) coil extending at least partially around the bound stopper. As used herein the term “intrinsic spring rate” refers to a spring rate or plurality of spring rates a bound stopper has without at least one SMA coil constraining the elastomer member from deforming radially when subjected to a compressive force. The variable rate bound stopper may include an elastomer member with an aperture dimensioned for the elastomer member to be positioned onto and disposed around a piston rod of a shock absorber. At least one coil formed from an SMA wire (hereafter referred to as an SMA coil) extends and winds around at least a portion of the elastomer member. The at least one SMA coil has a relaxed state and an activated state. In the activated state, the at least one SMA coil constrains the elastomer member from deforming when subjected to a compressive force and alters an intrinsic spring rate of the variable rate bound stopper. The at least one SMA coil may be activated by passing an electrical current through the SMA wire thereby heating the SMA wire and transforming the SMA wire from a first SMA phase to a second SMA phase. In embodiments, the first SMA phase is a low temperature SMA phase and the second SMA phase is a high temperature SMA phase. Various embodiments of variable bound stoppers and variable rate shock absorbers containing variable rate bound stoppers will be described in further detail herein with specific reference to the appended drawings.

FIG. 2Agenerally depicts one embodiment of a variable rate bound stopper. The variable rate bound stopper includes an elastomer member with an aperture dimensioned for the elastomer member to be positioned over and disposed around a piston rod of a shock absorber. The variable rate bound stopper has at least one SMA coil extending around at least a portion of the elastomer member. The SMA coil may be activated by passing an activation electrical current through the SMA coil thereby heating the SMA wire of the SMA coil above a transformation temperature such that the SMA transforms from a first SMA phase to a second SMA phase. Upon transforming from the first SMA phase to the second SMA phase, the SMA coil contracts around the elastomer member and constrains the elastomer member from deforming radially outward (+/−X direction in the figures) when subjected to a compressive force. Constraining the elastomer member from radial displacement when subjected to a compressive force alters the intrinsic spring rate of the elastomer member. That is, when the elastomer member is subjected to a given compressive force and the SMA coil is in its activated state, the elastomer member is restrained from deforming radially outward and has a higher spring rate (i.e., is “stiffer”) in comparison to when the elastomer member is subjected to the given compression force and the SMA coil is in its relaxed state. In embodiments, at least two SMA coils extend around at least a portion of the elastomer member and each of the at least two SMA coils may be independently activated so as to provide the elastomer member with a first spring rate when one of the at least two SMA coils is activated and a second spring rate when another of the at least two SMA coils is activated. In the alternative, or in addition to, two or more of the at least two SMA coils may be activated and provide the elastomer member with a third spring rate. It is understood that more than two SMA coils, e.g. three or more, four or more, or five or more SMA coils, may be wrapped or wound around at least a portion of an elastomer member and independently activated such that the variable bond stopper has a plurality of spring rates, e.g., four or more spring rates, five or more spring rates, etc.

Referring now toFIG. 1, embodiments of a variable rate vehicle suspension system10include a variable rate bound stopper100, a shock absorber120, and a spring130. The shock absorber120includes a cylinder122and a piston rod124slidably engaged with and extending from the cylinder122. The cylinder122of the shock absorber120is mechanically connected to a knuckle170which is mechanically connected to a tire T. The piston rod124includes an upper rod end126mechanically connected to a vehicle body (not shown). The shock absorber120is configured to dampen vibrations transmitted from the tire T toward the vehicle body and maintain a height control distance HC between a body component B and a road surface RS on which the tire T and vehicle are located. The variable rate bound stopper100may be generally cylindrically shaped and be positioned on and disposed around the piston rod124. An SMA coil assembly140formed from a SMA wire extends around at least a portion of the variable rate bound stopper100and is sized to be received within an inner diameter of the spring130. The SMA coil assembly140is in communication with an electrical power source. It is understood that whileFIG. 1depicts the variable rate bound stopper100in combination with the shock absorber120and spring130, e.g., as part of a strut assembly, the variable rate bound stopper100may be used with the shock absorber120without the spring130.

Referring now toFIG. 2A, an expanded side cross-sectional view of the variable rate bound stopper100is depicted. The variable rate bound stopper100includes an elastomer member102with a lower end104and an upper end106. Extending between the lower end104and the upper end106is a side wall105. The side wall105has an inner surface107and an outer surface108. In embodiments, a lower portion (−Y direction) of the elastomer member102has a first diameter D1and an upper portion (+Y direction) of the elastomer member has a second diameter D2. The second diameter D2is dimensioned for the elastomer member102to slide over and have an interference fit with the piston rod124of the shock absorber120. The piston rod124may have a tab128extending radially (+/−X direction) from the piston rod124and the elastomer member102may have a notch110that is complimentary with the tab128such that the elastomer member102fits and is secured onto the piston rod124at a desired position. An upper flange129positioned proximate to the upper rod end126of the piston rod124may be included to ensure the upper end106of the elastomer member102does not slide past or off of the piston rod124during compression of the elastomer member102. Extending around, e.g., wound around in a corkscrew manner, at least a portion of the elastomer member102is the SMA coil assembly140including a first SMA coil142formed from an SMA wire. In embodiments depicted inFIG. 2A, the first SMA coil142extends around the outer surface108of the elastomer member102. In other embodiments, the first SMA coil142is embedded within the elastomer member102as described in greater detail below. In some embodiments, more than one SMA coil may be wound around at least a portion of the elastomer member102as part of the SMA coil assembly140. For example,FIG. 2Adepicts a second SMA coil144and a third SMA coil146wound around at least a portion of the elastomer member102. It is understood that the second SMA coil144and the third SMA coil146are also formed from SMA wires and may be separate from each other, i.e., the first SMA coil142, the second SMA coil144and the third SMA coil146may be three separate and distinct SMA coils. It is also understood one or more of the SMA coils142,144,146may be formed from different shape memory alloys with different properties such that one or more of the SMA coils142,144,146have different properties and can operate independently.

Referring toFIGS. 2A-2B, activation of one or more of the SMA coils142,144,146with a corresponding radial contraction (+/−X direction) of the elastomer member102is depicted inFIG. 2B. Not being bound by theory, the SMA wire forming the SMA coils142,144,146has a transformation temperature below which the SMA exists in a first SMA phase (e.g., a low temperature SMA phase) and above which the SMA exists in a second SMA phase (e.g., a high temperature SMA phase). Transformation from the first SMA phase to the second SMA phase, and vice-versa, typically results in a change of yield strength of the SMA wire and a reversible strain of the SMA wire. For example and without limitation, a nickel-titanium (Ni—Ti) alloy with generally equal proportions of Ni and Ti (commercially known as Nitinol) has or exists in a low temperature martensite phase below a transformation temperature and has or exists in a high temperature austenite phase above the transformation temperature. The low temperature martensite phase for the shape memory Ni—Ti alloys has a typical yield strength of about 100 megapascal (MPa) and the high temperature austenite phase has a typical yield strength of about 560 MPa, i.e. about a five-fold increase in strength. Also, transformation from the low temperature martensite phase to a high temperature austenite phase, and vice-versa, results in a reversible strain of up to 8% for shape memory Ni—Ti alloys. Accordingly, when one or more of the SMA coils142,144,146transform from the first SMA phase to the second SMA phase, the respective one or more SMA coils142,144,146exhibit an increase in yield strength and/or a change in physical dimension (e.g., length).

Still referring toFIGS. 2A-2B, activation of the one or more of the SMA coils142,144,146, e.g., by flowing an activation electrical current through and increasing the temperature of one or more of the SMA coils142,144,146such that one or more of the SMA coils transforms from a low temperature SMA phase to a high temperature SMA phase, may increase the yield strength of the one or more SMA coils142,144,146that is activated. As used herein the term “activation electrical current” refers to an electrical current sufficient to increase the temperature of an SMA coil via electrical resistance heating above a transformation temperature for the SMA from which the SMA coil is formed. Increasing the yield strength of the SMA wire that forms the SMA coils142,144,146increases resistance of radial displacement of the elastomer member102when subjected to a compression force. In the alternative, or in addition to, activation of the one or more of the SMA coils142,144,146may result in a reversible strain of the one or more SMA coils142,144,146that is activated. The reversible strain may decrease a length of the SMA wire that forms the SMA coils142,144,146thereby resulting in an SMA coil with a reduced diameter. That is, each of the SMA coils142,144,146have a first coil diameter when the SMA coils142,144,146are in a relaxed state and a second coil diameter when the SMA coils142,144,146are in an activated state. In embodiments, the first coil diameter is greater than the second coil diameter. In other embodiments, the first coil diameter is less than the second coil diameter. Reducing the coil diameter of the SMA coils142,144,146provides an inward force ‘2’ on the elastomer member102as depicted inFIG. 2B. The inward force2applied to the elastomer member102by the one or more SMA coils142,144,146in the activated state reduces or attempts to reduce (constrains) the diameter D1of the elastomer member102shown inFIG. 2Ato the diameter D1′ shown inFIG. 2B. It is understood that reducing or attempting to reduce the diameter D1of the elastomer member102constrains the elastomer member102from deforming in a radial direction (+/−X direction) when a compression force is applied to the elastomer member102as described below.

Referring toFIGS. 3A-3C, a series of spring rates for the variable rate bound stopper100subjected to a given vibration compression force ‘6’ is depicted. Particularly,FIGS. 3A-3Cdepict compression of the variable rate bound stopper100due to the piston rod124sliding within the cylinder122due to the vibration compression force6. For example and without limitation, the vibration compression force6may be due vibration from the tire T (FIG. 1) impacting an object (e.g., a pot hole) on a road or the tire T traveling on a rough road surface with bumps, holes, etc. Upon compression of the shock absorber120, a lower flange123moves in a direction towards the variable rate bound stopper100(+Y direction) and comes into contact with the lower end104of the elastomer member102. InFIG. 3A, the elastomer member102is compressed to a height H1when the variable rate bound stopper100is subjected to the vibration compression force6. InFIG. 3B, the elastomer member102is compressed to a height H2which is greater than the height H1when the variable rate bound stopper100is subjected to the vibration compression force6. InFIG. 3C, the elastomer member102is compressed to a height H3which is greater than the height H2when the variable rate bound stopper100is subjected to the vibration compression force6. In embodiments, compression of the elastomer member102to the height H1depicted inFIG. 3Ais due to the activation of the first SMA coil142, compression of the elastomer member102to the height H2depicted inFIG. 3Bis due to the activation of SMA coils142and144, and compression of the elastomer member102to the height H3depicted inFIG. 3Cis due to the activation of SMA coils142,144and146. In other embodiments, compression of the elastomer member102to the height H1depicted inFIG. 3Ais due to the activation of the first SMA coil142, compression of the elastomer member102to the height H2depicted inFIG. 3Bis due to the activation of the second SMA coil144, and compression of the elastomer member102to the height H3depicted inFIG. 3Cis due to the activation of the third SMA coil146. In still other embodiments, compression of the elastomer member102to the height H1depicted inFIG. 3Ais due to the activation of the first SMA coil142, compression of the elastomer member102to the height H2depicted inFIG. 3Bis due to the activation of SMA coils142and144, and compression of the elastomer member102to the height H3depicted inFIG. 3Cis due to the activation of SMA coils142and146. Accordingly, it is understood that compression of the elastomer member102to a given height when subjected to a vibration compression force may be provided by any number or combination of SMA coils being activated.

The compression of the elastomer member102to the different heights when subjected to the same vibration compression force6is the result of the variable rate bound stopper100depicted inFIGS. 3A-3Chaving different springs. For example and without limitation, the variable rate bound stopper100depicted inFIG. 3Ahas a first spring rate, the variable rate bound stopper100depicted inFIG. 3Bhas a second spring rate greater than the first spring rate, and the variable rate bound stopper100depicted inFIG. 3Chas a third spring rate, greater than the second spring rate. It is also understood that other SMA coil activation arrangements or scenarios than discussed above in reference toFIGS. 3A-3Cmay be used to provide the variable rate bound stopper with a desired spring rate.

WhileFIGS. 3A-3Cdepict the variable rate bound stopper100having different spring rates in response to a vibration compression force, the variable rate bound stopper100may have different spring rates in response to a constant load applied to the shock absorber120. For example and without limitation, a constant load in a bed of a pickup truck may reduce the height of the bed and/or rear bumper of the pickup truck relative to a road surface the pickup truck is traveling on. Also, it may be desirable to offset or counter the reduced height of the bed, fender, rear bumper or other body component of the pickup truck (referred to herein as “height control”) as described below.

Referring now toFIGS. 4A-4C, a series of spring rates for the variable rate bound stopper100subjected to a given load force ‘F1’ is depicted. Particularly,FIGS. 4A-4Cdepict compression of the shock absorber120and the variable rate bound stopper100due to a generally constant load that results in the force F1being transferred or applied to the variable rate bound stopper100. For example and without limitation, the force F1on the variable rate bound stopper100may be due to a load in a bed of pickup truck (not shown) exerting a force on the shock absorber120such that the shock absorber120is compressed, i.e., the piston rod124slides within the cylinder122(−Y direction). Upon compression of the shock absorber120, the variable rate bound stopper100moves in a direction towards the cylinder122(−Y direction) and the lower end104of the elastomer member102comes into contact with the lower flange123and is compressed. InFIG. 4A, the elastomer member102is compressed to a height H1and provides a control height distance HC1when the variable rate bound stopper100is subjected to the load force F1. InFIG. 4B, the elastomer member102is compressed to a height H2and a control height distance HC2which is greater than the height H1and control height distance HC1, respectively, when the variable rate bound stopper100is subjected to the load force F1. InFIG. 4C, the elastomer member102is compressed to a height H3and control height distance HC3which is greater than the height H2and control height distance HC2, respectively, when the variable rate bound stopper100is subjected to the load force F1. In embodiments, compression of the elastomer member102to the height H1depicted inFIG. 4Ais due to the activation of the first SMA coil142, compression of the elastomer member102to the height H2depicted inFIG. 4Bis due to the activation of SMA coils142and144, and compression of the elastomer member102to the height H3depicted inFIG. 4Cis due to the activation of SMA coils142,144,146. In other embodiments, compression of the elastomer member102to the height H1depicted inFIG. 4Ais due to the activation of the first SMA coil142, compression of the elastomer member102to the height H2depicted inFIG. 4Bis due to the activation of the second SMA coil144, and compression of the elastomer member102to the height H3depicted inFIG. 4Cis due to the activation of the third SMA coil146. In still other embodiments, compression of the elastomer member102to the height H1depicted inFIG. 4Ais due to the activation of the first SMA coil142, compression of the elastomer member102to the height H2depicted inFIG. 4Bis due to the activation of SMA coils142and144, and compression of the elastomer member102to the height H3depicted inFIG. 4Cis due to the activation of SMA coils142and146. Accordingly, it is understood that compression of the elastomer member102to a given height when subjected to a load force may be provided by any number or combination of SMA coils being activated.

The compression of the elastomer member102to the different heights when subjected to the same load force F1is the result of the variable rate bound stopper100depicted inFIGS. 4A-4Chaving different spring rates. For example and without limitation, the variable rate bound stopper100depicted inFIG. 4Ahas a first spring rate, the variable rate bound stopper100depicted inFIG. 4Bhas a second spring rate greater than the first spring rate, and the variable rate bound stopper100depicted inFIG. 4Chas a third spring rate, greater than the second spring rate. It is also understood that other SMA coil activation arrangements or scenarios than discussed above in reference toFIGS. 4A-4Cmay be used to provide the variable rate bound stopper with a desired spring rate.

Referring now toFIG. 5, a graphical depiction of a plurality of springs rates (SR1, SR2, . . . SR6) of the variable rate bound stopper100is depicted. Particularly, displacement (compression; −Y direction) of the variable rate bound stopper100as a function of force applied to the variable rate bound stopper100is shown inFIG. 5. For example and without limitation, the variable rate bound stopper100may have a first spring rate SR1when none of the SMA coils142,144,146are activated, a second spring rate SR2when only the first SMA coil142is activated and a third spring rate SR3when SMA coils142and144are activated. The variable rate bound stopper100may have a fourth spring rate SR4when SMA coils142and146are activated, a fifth spring rate SR5when SMA coils144and146are activated and a sixth spring rate SR6when SMA coils142,144,146are activated. Accordingly, the variable rate bound stopper100may have a wide range of spring rates provided by activation of two or more SMA coils and the spring rates may be provided by any number or combination of the SMA coils being activated. WhileFIG. 5illustrates a linear relationship between force and displacement, it is understood that the bound stoppers and variable rate bound stoppers described herein may have a non-linear relationship between force and displacement, for example and without limitation a parabolic relationship, a logarithmic relationship, an exponential relationship, or the like. Accordingly,FIG. 5schematically illustrates a variable rate bound stopper as described herein having a plurality of spring rates as a function of a plurality of SMA coils as described herein being activated and constraining radial deformation of the variable rate bound stopper.

Referring now toFIGS. 1 and 6, a vehicle50may include a variable rate vehicle suspension system10and a plurality of vehicle motion sensors. Particularly, a plurality of wheel speed sensors WSS#1, WSS#2, WSS#3, and WSS#4may be in communication with a VSC ECU160. At least one roll/yaw sensor may also be in communication with the VSC ECU160. The VSC ECU160may be in communication with an SMA coil controller162, an electrical power source164and SMA coils142,144,146. In embodiments, the plurality of vehicle motion sensors provide sensor feedback related to the motion of the vehicle to the VSC ECU160and the VSC ECU160provides spring rate instructions to the SMA coil controller162. The SMA coil controller162is configured to activate the electrical power source164as a function of the spring rate instructions received from the VSC ECU160. Upon activation of the electrical power source164and depending on the spring rate instructions from the SMA coil controller162, the electrical power source164provides an activation electrical current to one or more of the SMA coils142,144,146. The activation electrical current flows through the one or more SMA coils142,144,146and the temperature of the one or more SMA coils142,144,146increases from a temperature below a transformation temperature of the one or more SMA coils142,144,146to a temperature above the transformation temperature of the one or more SMA coils142,144,146. Increasing the temperature of the one or more SMA coils142,144,146from below the transformation temperature to above the transformation temperature results in the one or more SMA coils142,144,146transforming from a low temperature SMA phase to a high temperature SMA phase. The one or more SMA coils142,144,146in the low temperature SMA phase are in a relaxed state and the one or more SMA coils142,144,146in the high temperature SMA phase are in an activated state. Transformation of the one or more SMA coils142,144,146from the low temperature SMA phase to the high temperature SMA phase results in a reversible strain of the one or more SMA coils142,144,146, i.e., the one or more SMA coils142,144,146contract around the variable rate bound stopper100and constrain the variable rate bound stopper100from deforming radially outward (+/−X direction) when subjected to a compressive force.

WhileFIG. 6depicts the VSC ECU160configured to activate the electrical power source164via the SMA coil controller162, in embodiments the VSC ECU160activates the electrical power source164directly, i.e., the VSC ECU160may be configured to activate the electrical power source164without the use of the SMA coil controller162. Also, activation of the one or more SMA coils142,144,146by the electrical power source164may be referred to herein as activation of the one or more SMA coils142,144,146by the VSC ECU160.

Referring toFIGS. 1, 3A-3C, 4A-4C and 6, the VSC ECU160may activate one or more of the SMA coils142,144,146and thereby alter the intrinsic spring rate of the variable rate bound stopper100. Particularly, the plurality of vehicle motion sensors provide vehicle speed and roll/yaw feedback to the VSC ECU160. In embodiments, the VSC ECU160may automatically activate one or more of the SMA coils142,144,146as a function of the sensor feedback from at least one of the wheel speed sensors WSS#1, WSS#2, WSS#3, WSS#4, the roll/yaw sensor and a combination thereof. In the alternative, or in addition to, the VSC ECU160may activate one or more of the SMA coils142,144,146as a function of a load force applied to the variable rate bound stopper100, a height of a bed or rear bumper of a pickup truck from a road surface the pickup truck is traveling on, or the like. In some embodiments, the VSC ECU160may activate one or more of the SMA coils142,144,146as a function of a user selection. For example and without limitation, a user of the vehicle50may desire a “stiffer” or “softer” ride and/or the rear bumper of the vehicle50to have a higher or lower height from the road surface the vehicle50is traveling on. That is, the user of the vehicle50may desire the variable rate vehicle suspension system10of the vehicle50to have a higher or lower spring rate and/or a higher or lower vehicle height control. In such examples, the user may manually select a given spring rate and/or height control for the variable rate vehicle suspension system10. The manually selected spring rate and/or height control is transmitted to the VSC ECU160and the VSC ECU160activates one or more of the SMA coils142,144,146as a function of the user selection. Activation of the one or more SMA coils142,144,146provides the desired spring rate and/or height control.

Referring toFIG. 7, another embodiment of a variable rate bound stopper200is depicted. Particularly, the variable rate bound stopper200may be similar to the variable rate bound stopper100discussed above except the SMA coils142,144,146are embedded within the elastomer member102. The SMA coils142,144,146may be embedded in the elastomer member102during the forming of the elastomer member102and embedding the SMA coils142,144,146within the elastomer member102may protect the SMA coils142,144,146from the environment during operation of a vehicle that has a variable rate vehicle suspension system10with the variable rate bound stopper100. It is understood that the SMA coils142,144,146may be embedded within the elastomer member102with end portions of the SMA coils142,144,146extending from the elastomer member102such that the electrical power source164is in communication with the SMA coils142,144,146and the VSC ECU160in combination with the electrical power source164may activate one or more of the SMA coils142,144,146as discussed above with reference toFIGS. 3A-3C and 4A-4C.

Referring toFIG. 8, another embodiment of a variable rate bound stopper300is depicted. Particularly, the variable rate bound stopper300may be similar to the variable rate bound stopper100and/or variable rate bound stopper200discussed above except only a subset of the SMA coils142,144,146are embedded within the elastomer member302. As depicted inFIG. 8, SMA coils142,146extending around the outer surface308of the elastomer member302and the second SMA coil144is embedded within the elastomer member302. WhileFIG. 8depicts two of the SMA coils (SMA coils142,146) extending around the outer surface308of the elastomer member302and one of the SMA coils (second SMA coil144) embedded within the elastomer member302, it is understood that a subset of any number of SMA coils used to alter the intrinsic spring rate of the variable rate bound stopper300may extend around the outer surface308of the elastomer member302or be embedded within the elastomer member302.

In embodiments, the elastomer member described herein is formed from an elastomeric material such as, without limitation, polyurethane, natural rubber, or the like. The SMA coils and SMA wires described herein is formed from a shape memory material such as, without limitation, shape memory alloys, shape memory polymers, or the like.

The above-described variable rate bound stoppers can provide a bound stopper having variable spring rates due to activation/deactivation of one or more SMA coils that are used to constrain radial deflection of the bound stoppers to differing degrees. Operation of the SMA coils can be automatic, such as based on sensor feedback from one or more vehicle motion sensors or based on a detected height of the vehicle from the ground, or manual, such as based on user ride preferences.