Abstract:
A clutch device for use with a vehicle suspension system to vary the stiffness of a stabilizer bar. A plurality of dampers connected to the clutch body alternate with a plurality of dampers connected to the stabilizer bar. The dampers are coated with a friction material and surrounded by a fluid. When a load is applied on the walls of clutch body, the friction material comes into contact, dampening the rotation action of the stabilizer bar. A sensor senses the parameters of the ride and generates a signal based on these parameters. The signal activates a power source controller which applies the load to the walls.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates generally to an active clutch device utilized on a stabilizer bar of a vehicle suspension system which includes a plurality of interacting dampers which provide variable stiffness in the stabilizer bar.  
           [0002]    Vehicles are commonly equipped with suspension systems for absorbing road shock and other vibrations, while providing for a smooth and comfortable ride. Also tipping or rolling over of vehicles is undesirable. A suspension component, such as a stabilizer bar, is often used to increase roll rigidity and improve the steering stability of the vehicle. The stabilizer bar is generally attached to the lower A-arms of the suspension system and controls sway as the vehicle turns and provides a pull down force during cornering.  
           [0003]    As a vehicle turns, the body of the vehicle rolls to the outside of the turn. The suspension components on the outside of the turn are generally compressed, while the suspension components on the inside of the turn are generally extended. The stabilizer bar counters this motion by pushing up on the suspension components collapsed through torsion in the stabilizer bar.  
           [0004]    During cornering, it is desirable that the stiffness of the stabilizer bar be increased. If the stabilizer bar is too compliant, the vehicle will not respond well during cornering, increasing the likelihood of rolling over. However, if the stabilizer is too stiff, the ride and handling will be compromised during normal vehicle operation. Therefore, it is desirable that the compliance of the stabilizer bar be variable to adjust for changing driving conditions.  
           [0005]    In a proposed vehicle suspension system, a clutch device includes a chamber which houses a plurality of discs and either a magnetic-rheological or electro-rheological fluid. On the application of either a high strength magnetic or electrical field, respectively, the fluid increases in viscosity, which increases both the stiffness of the stabilizer bar and the ride of the vehicle. In this system, the discs are attached to a pair of split stabilizer bars, the discs selectively driving each other.  
         SUMMARY OF THE INVENTION  
         [0006]    This invention relates to an active clutch device for use on a stabilizer bar of a vehicle suspension system to provide variable stiffness in the stabilizer bar.  
           [0007]    A clutch device positioned in the middle of a split stabilizer bar is employed to vary the stabilizer bar stiffness. A clutch body secured to the vehicle frame includes a plurality of clutch dampers which alternate with a plurality of bar dampers which are secured to the stabilizer bar. The alternating dampers are coated with a friction material and surrounded with a fluid enclosed in the clutch body by walls. When a load is applied on the walls, the walls pressing the friction material together to dampen the rotational action of the stabilizer bar. The walls are secured to the clutch body and the stabilizer bar by a sliding component, such as an annular elastic bead, which allows for the slight movement of the walls.  
           [0008]    A sensor senses the ride parameters and generates a signal based on these parameters. When the vehicle corners and the sensor detects a need for an increase in vehicle roll stiffness, the sensor generates a signal which activates a power source controller. The controller proportionally applies the load to the walls, proportionally dampening the stabilizer bar. The load can be applied from a hydraulic, pneumatic, or electrical power source. Alternatively, the load can be applied by applying a magnetic or electrical field to magnetic-rheological or electro-rheological fluid, respectively, in the clutch body.  
           [0009]    Accordingly, the present invention provides an active clutch device for use on a stabilizer bar of a vehicle suspension system to provide variable stiffness in the stabilizer bar.  
           [0010]    These and other features of the present invention will be best understood from the following specification and drawings.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    The various features and advantages of the invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows:  
         [0012]    [0012]FIG. 1 illustrates a front schematic view of a stabilizer bar of the present invention employed in a vehicle suspension system;  
         [0013]    [0013]FIG. 2 illustrates a front cross-sectional view of the clutch device of the present invention utilizing a hydraulic or pneumatic load source;  
         [0014]    [0014]FIG. 3 illustrates a front cross-sectional view of a second embodiment of the clutch device utilizing magnetic-rheological fluid or electro-rheological fluid as the load source; and  
         [0015]    [0015]FIG. 4 illustrates a front cross-sectional view of a third embodiment of the clutch device utilizing an electrical load source. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0016]    [0016]FIG. 1 illustrates a stabilizer bar  20  of a vehicle suspension system  22 . As shown schematically, ends  24  of the stabilizer bar  20  are attached by linkages  23  to control arms  26  which are mounted to wheels  28 . As known, the stabilizer bar  20  provides a stabilizer function.  
         [0017]    As shown in FIG. 2, the stabilizer bar  20  of the present invention is equally split to form a left stabilizer bar portion  20   a  and a right stabilizer bar portion  20   b , a division  21  located between the portions  20   a  and  20   b . A clutch device  30  receives the inner portions  32  and  34 , respectively, of stabilizer bar portions  20   a  and  20   b.    
         [0018]    The clutch device  30  includes a clutch body  36  which is attached to the vehicle frame  38 , shown schematically. The clutch body  36  is split into a left compartment  40  and right compartment  42  which receive the inner portions  32  and  34 , respectively, of the stabilizer bar  20 . Each compartment  40  and  42  is formed and enclosed by an inner wall  44  and an outer wall  46 , each wall  44  and  46  including an outer periphery  48  and an inner periphery  50 . The outer peripheries  48  are substantially sized and shaped to fit the clutch body  36 , and the inner peripheries  50  are substantially sized, shaped and aligned to receive the inner portions  32  and  34  of the stabilizer bar  20   a  and  20   b , respectively.  
         [0019]    A flexible component  52  seals the outer peripheries  48  of the walls  44  and  46  to the clutch body  36  and the inner peripheries  50  to the stabilizer bar portions  20   a  and  20   b . As the components  52  are slightly flexible, the components  52  allow for slight movement of the walls  44  and  46 . In the preferred embodiment, the components  52  and  54  are a flexible elastic annular bead or a diaphragm.  
         [0020]    A plurality of clutch dampers  56  and a plurality of stabilizer bar dampers  58  are alternatingly connected to the clutch body  36  and the stabilizer bar portions  20   a  and  20   b , respectively. Although six clutch friction plate dampers  56  and four stabilizer bar friction plate dampers  58  are illustrated, any number of dampers  56  and  58  can be utilized. It is preferred that the dampers  56  and  58  are substantially perpendicular to the stabilizer bar  20 . The outer periphery  60  of each of the clutch dampers  56  is secured to the clutch body  36 , and the inner periphery  62  of each of the stabilizer bar dampers  58  is secured to the stabilizer bar portions  20   a  and  20   b . The dampers  56  and  58  are slightly flexibly secured such that slight movement is possible. The inner periphery  64  of the clutch dampers  56  and the outer periphery  66  of the stabilizer bar dampers  58  are unsecured.  
         [0021]    Friction material  68  is positioned substantially between each of the walls  44  and  46  and the dampers  56  and  58 . It is preferred that the friction material  68  be coated on the walls  44  and  46  and dampers  56  and  58 . During normal vehicle operation when the stabilizer bar  20  is in a relatively unstiffened state, a slight gap  82  exists between the friction material  68 . As the gap  82  is substantially narrow, the frictional material  68  almost engages the other friction material  68  when the stabilizer bar  20  is in the unstiffened state. However, for illustrative purposes, the gaps  82  in FIG. 2 between the friction material  68  are shown enlarged and not to scale.  
         [0022]    A fluid  70  in each compartment  40  and  42  substantially surrounds the friction material  68  to dissipate heat and increase the freedom of movement between the friction material  68 . The fluid  70  is retained in the compartments  40  and  42  by walls  44  and  46  and is sealed by the flexible components  52 .  
         [0023]    During vehicle operation, a sensor  72  detects a ride parameter, such as lateral acceleration, wheel load, wheel velocity or yaw rate. When the sensor  72  detects an increase in the rotation of the stabilizer bar  20 , the sensor  72  generates and forwards a signal  74  to a power source controller  76 . The controller  76  applies a load  78  on walls  44  and  46  which corresponds to the signal  74  generated. In this embodiment the load  78  is applied through fluid pressure. One skilled in the art would understand what ride parameters would need to be detected to determine the desired stiffness of the stabilizer bar  20 .  
         [0024]    During normal vehicle operation when the stabilizer bar  20  is in a relatively unstiffened state, a small gap  82  exists between the friction materials  68 . When the sensor  72  detects a need for an increase in stiffness, a signal  74  is sent to the power source controller  76 . The controller  76  applies the load  78  to the walls  44  and  46  which are slightly pressed inwardly towards the dampers  56  and  58 . As the dampers  54  and  56  are flexibly connected to the clutch body  36  and the stabilizer bar  20 , the friction materials  68  are brought into contact, stiffening the stabilizer bar  20 . When the sensor  72  detects a need for a decrease in the stiffness of the stabilizer bar  20 , a signal  74  is generated to slightly move the walls  44  and  46  outwardly away from the dampers  56  and  58 . The friction materials  68  disengage, reducing stiffness in the stabilizer bar  20 .  
         [0025]    As further illustrated in FIG. 2, the controller  76  activates a hydraulic or pneumatic source  83  to generate the load  78 . The source  83  injects a pressurized fluid into a middle section  84  located between the inner walls  44  and into outer sections  86  created between the outer walls  46  and sealing walls  80  fixed to the clutch body  36 . The fluid may be hydraulic or air. When the fluid or air enters the middle section  84  and the outer sections  86 , the fluid or air presses on the outer walls  46  and the inner walls  44 , creating the load  78  and pressing the friction materials  68  into contact to stiffen the stabilizer bar  20 . The valving etc. to selectively control the application of this pressurized fluid is within the skill of a worker in this art.  
         [0026]    Alternatively, as illustrated in FIG. 3, an electro-rheological or magnetic-rheological fluid  92  is contained in the middle section  84  and the outer sections  86 . An electric or magnetic field, respectively, is generated by a field source  90 . When stiffening is desired in the stabilizer bar  20 , the controller  76  activates the field source  90  which generates a field that increases the viscosity of the fluid  92 . As the fluid  92  thickens, load  78  presses on the walls  44  and  48 , pressing the friction material  68  into contact. Additionally, the fluid  70  between the friction material  68  can also either be electro-rheological or magnetic-rheological, which changes viscosity in response to an electric or magnetic field, respectively. The applied electric or magnetic field thickens the fluid, further increasing the stiffness of the stabilizer bar  20 . The structure to create and apply the field  90  may be as known, and a worker in the art would be able to develop an appropriate system.  
         [0027]    [0027]FIG. 4 illustrates a third embodiment of the present invention. The load  78  is generated by an electrical source  88 , shown schematically. The load  78  is applied to the walls  44  and  46 , pressing the friction material  68  into contact to stiffen the stabilizer bar  20 . Again, the electrical details necessary are within the level of skill in the art.  
         [0028]    The clutch device  30  dampens or locks the stabilizer bar  20  depending on the required vehicle roll stiffness to prevent roll-over and to insure adequate handling. If the friction materials  68  are positioned apart, there will be low stiffness in the stabilizer bar  20  and a small amount of relative rotation between the stabilizer bar portions  20   a  and  20   b . The ride of the vehicle will be soft and there will be relatively low suspension spring rate during bumps. If the walls  44  and  46  slide so as to cause the friction materials  68  to substantially contact, the stiffness of the stabilizer bar  20  increases and there will be no relative rotation between the stabilizer bar portions  20   a  and  20   b . The ride of the vehicle will be relatively stiff and will have a relatively high suspension spring rate.  
         [0029]    There are several advantages to utilizing the active clutched stabilizer bar  20 . For one, as the stabilizer bar  20  is active, the roll stiffness of the stabilizer bar  20  can be continually modified to increase handling and also to avoid roll-over conditions. The stabilizer bar  20  provides additional roll stabilizer during extreme maneuvers and roll over conditions. The compliance of the stabilizer bar  20  can be adjusted to the actual conditions existing. The stabilizer bar  20  could have low compliance for normal driving, and a high compliance for cornering.  
         [0030]    Accordingly, the present invention provides an active clutch device for use on a stabilizer bar of a vehicle suspension system to provide variable stiffness in the stabilizer bar.  
         [0031]    The foregoing description is only exemplary of the principles of the invention.  
         [0032]    Many modifications and variations of the present invention are possible in light of the above teachings. The preferred embodiments of this invention have been disclosed, however, so that one of ordinary skill in the art would recognize that certain modifications would come within the scope of this invention. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specially described. For that reason the following claims should be studied to determine the true scope and content of this invention.