Abstract:
A hydraulic actuator includes a shock absorber and a control system that is separate from the shock absorber and which generates damping loads for the hydraulic actuator. The control system generates the damping load by using a pair of variable valves, a pair of check valves, an accumulator, a pump/motor and a flow controller. The forces are generated in all four quadrants of compression/rebound and active/passive. A device which recuperates the energy generated by the hydraulic actuator can be incorporated into the hydraulic actuator to generate energy in the form of electrical energy.

Description:
FIELD 
       [0001]    The present disclosure is directed to semi-active and active suspension systems. More particularly, the present disclosure is directed to semi-active and active suspension systems that recuperate the energy generated during the damping of the suspension system. 
       BACKGROUND 
       [0002]    This section provides background information related to the present disclosure which is not necessarily prior art. 
         [0003]    Suspension systems are provided to filter or isolate the vehicle&#39;s body (sprung portion) from the vehicle&#39;s wheels and axles (unsprung portion) when the vehicle travels over vertical road surface irregularities as well as to control body and wheel motion. In addition, suspension systems are also used to maintain an average vehicle attitude to promote improved stability of the vehicle during maneuvering. The typical passive suspension system includes a spring and a damping device in parallel with the spring which are located between the sprung portion and the unsprung portion of the vehicle. 
         [0004]    Hydraulic actuators, such as shock absorbers and/or struts, are used in conjunction with conventional passive suspension systems to absorb unwanted vibration which occurs during driving. To absorb this unwanted vibration, hydraulic actuators include a piston located within a pressure cylinder of the hydraulic actuator. The piston is connected to the sprung portion or body of the vehicle through a piston rod. Because the piston is able to restrict the flow of damping fluid within the working chamber of the hydraulic actuator when the piston is displaced within the pressure cylinder, the hydraulic actuator is able to produce a damping force which counteracts the vibration of the suspension. The greater the degree to which the damping fluid within the working chamber is restricted by the piston, the greater the damping forces which are generated by the hydraulic actuator. 
         [0005]    In recent years, substantial interest has grown in automotive vehicle suspension systems which can offer improved comfort and road handling over the conventional passive suspension systems. In general, such improvements are achieved by utilization of an “intelligent” suspension system capable of electronically controlling the suspension forces generated by hydraulic actuators. 
         [0006]    Different levels in achieving the ideal “intelligent” suspension system called a semi-active or a fully active suspension system are possible. Some systems control and generate damping forces based upon the dynamic forces acting against the movement of the piston. Other systems control and generate damping forces based on the static or slowly changing dynamic forces, acting on the piston independent of the velocity of the piston in the pressure tube. Other, more elaborate systems, can generate variable damping forces during rebound and compression movements of the hydraulic actuator regardless of the position and movement of the piston in the pressure tube. 
         [0007]    The movement produced in the hydraulic actuators in both the passive, semi-active and active suspension systems generates energy and this energy is dissipated into heat of the hydraulic actuator&#39;s fluid and the components of the actuator. 
       SUMMARY 
       [0008]    This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features. 
         [0009]    The present disclosure provides the art with a system which captures the energy generated in a passive, semi-active or active suspension system in a way that the energy can be reused later or the energy can be converted into another form of energy such as electrical energy. 
         [0010]    Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
     
    
     
       DRAWINGS 
         [0011]    The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. 
           [0012]      FIG. 1  is a diagrammatic illustration of a vehicle incorporating the energy harvesting suspension system in accordance with the present disclosure; 
           [0013]      FIG. 2  is a schematic view of the hydraulic actuator illustrated in  FIG. 1  illustrating the components of the hydraulic actuator; 
           [0014]      FIG. 3  is a schematic view of the hydraulic actuator illustrated in  FIG. 2  showing fluid flow during a semi-active compression mode of the hydraulic actuator; 
           [0015]      FIG. 4  is a schematic view of the hydraulic actuator illustrated in  FIG. 2  showing fluid flow during an active compression operation mode; 
           [0016]      FIG. 5  is a schematic view of the hydraulic actuator illustrated in  FIG. 2  showing fluid flow during a semi-active rebound mode of the hydraulic actuator; 
           [0017]      FIG. 6  is a schematic view of the hydraulic actuator illustrated in  FIG. 2  showing fluid flow during an active rebound operation mode; 
           [0018]      FIG. 7  is a schematic view of a hydraulic actuator in accordance with another embodiment of the present disclosure which incorporates an energy recuperating system; 
           [0019]      FIG. 8  is a schematic view of the hydraulic actuator illustrated in  FIG. 7  showing fluid flow during a semi-active compression mode of the hydraulic actuator; 
           [0020]      FIG. 9  is a schematic view of the hydraulic actuator illustrated in  FIG. 7  showing fluid flow during an active compression operation mode; 
           [0021]      FIG. 10  is a schematic view of the hydraulic actuator illustrated in  FIG. 7  showing fluid flow during a semi-active rebound mode of the hydraulic actuator; and 
           [0022]      FIG. 11  is a schematic view of the hydraulic actuator illustrated in  FIG. 7  showing fluid flow during an active rebound operation mode. 
       
    
    
       [0023]    Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
       DETAILED DESCRIPTION 
       [0024]    Example embodiments will now be described more fully with reference to the accompanying drawings. 
         [0025]    The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. There is shown in  FIG. 1 , a vehicle incorporating a suspension system in accordance with the present disclosure and which is designated generally by the reference numeral  10 . Vehicle  10  includes a rear suspension  12 , a front suspension  14  and a body  16 . Rear suspension  12  has a transversely extending rear axle assembly (not shown) adapted to operatively support a pair of rear wheels  18 . The rear axle is attached to body  16  by means of a pair of hydraulic actuators  20  and by a pair of springs  22 . Similarly, front suspension  14  includes a transversely extending front axle assembly (not shown) to operatively support a pair of front wheels  24 . The front axle assembly is attached to body  16  by means of a pair of hydraulic actuators  26  and by a pair of springs  28 . Hydraulic actuators  20  and  26  serve to dampen the relative motion of the unsprung portion (i.e., front and rear suspensions  12 ,  14 ) with respect to the sprung portion (i.e., body  16 ) of vehicle  10 . Sensors (not shown), at each wheel  18  and each wheel  24 , sense the position and/or the velocity and/or the acceleration of body  16  in relation to rear suspension  12  and front suspension  14 . While vehicle  10  has been depicted as a passenger car having front and rear axle assemblies, hydraulic actuators  20  and  26  may be used with other types of vehicles or in other types of applications including, but not limited to, vehicles incorporating non-independent front and/or non-independent rear suspensions, vehicles incorporating independent front and/or independent rear suspensions or other suspension systems known in the art. Further, the term “hydraulic damper” as used herein is meant to refer to shock absorbers and hydraulic dampers in general and thus will include McPherson struts and other hydraulic damper designs known in the art. 
         [0026]    Referring to  FIG. 2 , one of hydraulic actuators  20  is illustrated schematically. While  FIG. 2  only illustrates hydraulic actuator  20 , hydraulic actuators  26  include the same components discussed below for hydraulic actuator  20 . The only difference between hydraulic actuators  20  and  26  may be the way in which the hydraulic actuator is attached to the sprung and/or unsprung portion of the vehicle. 
         [0027]    Referring to  FIG. 2 , hydraulic actuator  20  comprises a control system  30  and a shock absorber  32 . Control system  30  comprises a pair of inlet valves  34  and  36 , a pair of valves  38  and  40  which control fluid flow and/or pressure, a motor/pump  42 , a flow controller  44  and an accumulator  46 . Flow controller  44  can be a single valve assembly, multiple valve assemblies or any other device or devices that control fluid flow. These components  30 - 46  are fluidically connected with each other as illustrated in  FIGS. 2-6  by a plurality of fluid lines  48 . 
         [0028]    Shock absorber  32  comprises a pressure tube  50  having a fluid chamber  52  that is divided into an upper working chamber  54  and a lower working chamber  56  by a piston assembly  58 . Piston assembly  58  is slidingly received within pressure tube  50  and piston assembly  58  includes a piston rod  60  that extends through upper working chamber  54  and is attached to the sprung portion of vehicle  10 . Pressure tube  50  is attached to the unsprung portion of vehicle  10 . Piston assembly  58  can also include a pair of optional blow-off valves  62  and  64 . Blow-off valves  62  and  64  define the upper limit of pressure drop over piston assembly  58  during a compression stroke and a rebound stroke, respectively, of shock absorber  32 . Blow-off valves  62  and  64  limit the maximum pressures and thus the maximum forces in shock absorber  32 . This protects the shock absorber and the vehicle from damage and it improves the comfort on potholes. During the normal operation of shock absorber  32 , blow-off valves  62  and  64  remain closed and the pressures above and below piston assembly are controlled by valves  38  and  40  as described below. 
         [0029]    The pressures above and below piston assembly generated by the rebound stroking and compression stroking of shock absorber  32  define the force that shock absorber  32  is generating. Valves  38  and  40  are fast switching adaptive valves which can generate a wide range of flow and/or pressure drops for any given flow rate. Because of motor/pump  42  and flow controller  44 , the flows through valves  38  and  40  are not dependent on the velocity of piston assembly  58  in pressure tube  50 . This allows damping forces to be generated not only in the semi-active quadrants of shock absorbers  32  force vs. velocity graphs but also in the active quadrants. 
         [0030]    Referring to  FIG. 3 , fluid flow in a semi-active compression mode for shock absorber  32  is illustrated. When piston assembly  58  moves in the compression direction (downward in  FIG. 3 ) at a given velocity, a variable semi-active compression force can be generated by creating a pressure drop over valve  38 . As piston assembly  58  is pushing damping fluid out of lower working chamber  56 , fluid flows into valve  40 . Simultaneously, damping fluid is sucked into upper working chamber  54  through inlet valve  34 . The rod volume flow of fluid flows into accumulator  46 . The pressure in upper working chamber  54  will be the same or slightly less than the pressure in accumulator  46 . In this case, damping fluid flow from motor/pump  42  can either be directed by flow controller  44  towards upper working chamber  54  where the damping pressure is low to increase the pressure in upper working chamber  54  and optimize energy consumption, or directed by flow controller  44  towards lower working chamber  56  in order to achieve even higher pressures in lower working chamber  56 . These flows are illustrated by arrows  70  in  FIG. 3 . 
         [0031]    Referring to  FIG. 4 , fluid flow in an active compression mode for shock absorber  32  is illustrated. When piston assembly  58  moves in the compression direction (downward in  FIG. 4 ) at a given velocity, a variable active rebound force can be generated. This means that shock absorber  32  and rear suspension  12  are actively pushed into compression by the system itself. To achieve this, a pressure drop must be maintained over valve  38  as piston assembly  58  is sucking damping fluid into upper working chamber  54 . This is achieved by directing damping fluid flow through flow controller  44  from motor/pump  42  into upper working chamber  54 . As long as the damping fluid flow from motor/pump  42  is higher than the flow of damping fluid sucked into upper working chamber  54 , the remaining pumped damping flow will be pushed through valve  38  which can then control the pressure in upper working chamber  54 . Simultaneously, damping fluid is pushed out of lower working chamber  56 , through valve  40  and into motor/pump  42  and accumulator  46 . In order to optimize energy consumption, valve  40  should be controlled to be fully opened such that the pressure drop across valve  40  is minimal. This will ensure that the pressure in lower working chamber  56  remains as low as possible. These flows are illustrated by arrows  72  in  FIG. 4 . 
         [0032]    If there is no movement of piston assembly  58 , either active compression forces or active rebound forces can be generated by directing damping fluid from motor/pump  42  to either upper working chamber  54  or lower working chamber  56  to compensate for static body roll while cornering for example. Also, by turning motor/pump  42  off and closing flow controller  44 , the damping forces for shock absorber  32  can be controlled by one or both of valves  38  and  40 . 
         [0033]    Referring to  FIG. 5 , fluid flow in a semi-active rebound mode for shock absorber  32  is illustrated. When piston assembly  58  moves in the rebound direction (upward in  FIG. 3 ) at a given velocity, a variable semi-active rebound force can be generated by creating a pressure drop over valve  38 . As piston assembly  58  is pushing damping fluid out of upper working chamber  54 , fluid flows into valve  38 . Simultaneously, damping fluid is sucked into lower working chamber  56  through inlet valve  36  from accumulator  46 . The pressure in lower working chamber  56  will be the same or slightly less than the pressure in accumulator  46 . In this case, damping fluid flow from motor/pump  42  can either be directed by flow controller  44  towards lower working chamber  56  where the damping pressure is low to increase the fluid pressure in lower working chamber  56  and optimize energy consumption, or directed by flow controller  44  toward upper working chamber  54  in order to achieve even higher pressures in upper working chamber  54 . These flows are illustrated by arrows  74  in  FIG. 5 . 
         [0034]    Referring to  FIG. 6 , fluid flow in an active rebound mode for shock absorber  32  is illustrated. When piston assembly  58  moves in the rebound direction (upward in  FIG. 4 ) at a given velocity, a variable active compression force can be generated. This means that shock absorber  32  and rear suspension  12  are actively pushed into rebound by the system itself. To achieve this, a pressure drop must be maintained over valve  40  as piston assembly  58  is sucking damping fluid into lower working chamber  56 . This is achieved by directing damping fluid flow through flow controller  44  from motor/pump  42  into lower working chamber  56 . As long as the damping fluid flow from motor/pump  42  is higher than the flow of damping fluid sucked into lower working chamber  56 , the remaining pumped damping flow will be pushed through valve  40  which can then control the pressure in lower working chamber  56 . Simultaneously, damping fluid is pushed out of upper working chamber  54 , through valve  38  and into motor/pump  42 . In order to optimize energy consumption, valve  38  should be controlled to be fully opened such that the pressure drop across valve  38  is minimal. This will ensure that the pressure in upper working chamber  54  remains as low as possible. Fluid flow from accumulator  46  will be directed towards motor/pump  42 . These flows are illustrated by arrows  76  in  FIG. 6 . 
         [0035]    Referring now to  FIG. 7 , a hydraulic actuator  120  in accordance with another embodiment of the present disclosure is illustrated. Hydraulic actuator  120  comprises shock absorber  32 , control system  30  which includes the pair of inlet valves  34  and  36 , the pair of valves  38  and  40 , motor/pump  42 , flow controller  44  and accumulator  46 . Thus, hydraulic actuator  120  is the same as hydraulic actuator  20  except that hydraulic actuator  120  includes an optional energy recuperation device  122 . Energy recuperation device  122  comprises a pair of intake valves  124  and  126 , and a turbine/generator  128 . Turbine/generator  128  receives damping fluid from upper working chamber  54  or lower working chamber  56  through intake valves  124  and  126 . Intake valves  124  and  126  are positioned such that damping fluid will flow from upper working chamber  54  or lower working chamber  56  depending on which working chamber  54 ,  56  is at the highest pressure. In this way, both valves  38  and  40  can be bypassed by the flow of damping fluid through energy recuperation device  122 . Thus, energy can be recuperated in the form of electric power depending on the control of energy recuperating device  122 . 
         [0036]    Referring to  FIG. 8 , fluid flow in a semi-active compression mode for shock absorber  32  is illustrated. When piston assembly  58  moves in the compression direction (downward in  FIG. 8 ) at a given velocity, a variable semi-active compression force can be generated by creating a pressure drop over turbine/generator  128 . As piston assembly  58  is pushing damping fluid out of lower working chamber  56 , fluid flows through intake valve  126  into turbine/generator  128 . Simultaneously, damping fluid is sucked into upper working chamber  54  through inlet valve  34 . The rod volume flow of fluid flows into accumulator  46 . The pressure in upper working chamber  54  will be the same or slightly less than the pressure in accumulator  46 . In this case, damping fluid flow from motor/pump  42  can either be directed by flow controller  44  towards upper working chamber  54  where the damping pressure is low to increase the pressure in upper working chamber  54  and optimize energy consumption, or directed by flow controller  44  towards lower working chamber  56  in order to achieve even higher pressures in lower working chamber  56 . These flows are illustrated by arrows  130  in  FIG. 8 . Fluid flow through turbine/generator  128  will generate electrical energy. 
         [0037]    Referring to  FIG. 9 , fluid flow in an active compression mode for shock absorber  32  is illustrated. When piston assembly  58  moves in the compression direction (downward in  FIG. 9 ) at a given velocity, a variable active rebound force can be generated. This means that shock absorber  32  and rear suspension  12  are actively pushed into compression by the system itself. To achieve this, a pressure drop must be maintained over valve  38  as piston assembly  58  is sucking damping fluid into upper working chamber  54 . This is achieved by directing damping fluid flow through flow controller  44  from motor/pump  42  into upper working chamber  54 . As long as the damping fluid flow from motor/pump  42  is higher than the flow of damping fluid sucked into upper working chamber  54 , the remaining pumped damping flow will be pushed through valve  38  which can then control the pressure in upper working chamber  54 . Simultaneously, damping fluid is pushed out of lower working chamber  56 , through valve  40  and into accumulator  46 . In order to optimize energy consumption, valve  40  should be controlled to be fully opened such that the pressure drop across valve  40  is minimal. This will ensure that the pressure in lower working chamber  56  remains as low as possible. These flows are illustrated by arrows  132  in  FIG. 9 . 
         [0038]    If there is no movement of piston assembly  58 , either active compression forces or active rebound forces can be generated by directing damping fluid from motor/pump  42  to either upper working chamber  54  or lower working chamber  56  to compensate for static body roll while cornering for example. Also, by turning motor/pump  42  off and closing flow controller  44 , the damping forces for shock absorber  32  can be controlled by one or both of valves  38  and  40 . 
         [0039]    Referring to  FIG. 10 , fluid flow in a semi-active rebound mode for shock absorber  32  is illustrated. When piston assembly  58  moves in the rebound direction (upward in  FIG. 10 ) at a given velocity, a variable semi-active rebound force can be generated by creating a pressure drop over turbine/generator  128 . As piston assembly  58  is pushing damping fluid out of upper working chamber  54 , fluid flows into turbine/generator  128 . Simultaneously, damping fluid is sucked into lower working chamber  56  through inlet valve  36  from accumulator  46  and turbine/generator  128 . The pressure in lower working chamber  56  will be the same or slightly less than the pressure in accumulator  46 . In this case, damping fluid flow from motor/pump  42  can either be directed by flow controller  44  towards lower working chamber  56  where the damping pressure is low to increase the fluid pressure in lower working chamber  56  and optimize energy consumption, or directed by flow controller  44  toward upper working chamber  54  in order to achieve even higher pressures in upper working chamber  54 . These flows are illustrated by arrows  134  in  FIG. 10 . Fluid flow through turbine/generator  128  will generate electrical energy. 
         [0040]    Referring to  FIG. 11 , fluid flow in an active rebound mode for shock absorber  32  is illustrated. When piston assembly  58  moves in the rebound direction (upward in  FIG. 11 ) at a given velocity, a variable active compression force can be generated. This means that shock absorber  32  and rear suspension  12  are actively pushed into rebound by the system itself. To achieve this, a pressure drop must be maintained over valve  40  as piston assembly  58  is sucking damping fluid into lower working chamber  56 . This is achieved by directing damping fluid flow through flow controller  44  from motor/pump  42  into lower working chamber  56 . As long as the damping fluid flow from motor/pump  42  is higher than the flow of damping fluid sucked into lower working chamber  56 , the remaining pumped damping flow will be pushed through valve  40  which can then control the pressure in lower working chamber  56 . Simultaneously, damping fluid is pushed out of upper working chamber  54 , through valve  38  and into motor/pump  42 . In order to optimize energy consumption, valve  38  should be controlled to be fully open such that the pressure drop across valve  38  is minimal. This will ensure that the pressure in upper working chamber  54  remains as low as possible. Fluid flow from accumulator  46  will be directed towards motor/pump  42 . These flows are illustrated by arrows  136  in  FIG. 11 . 
         [0041]    The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.