Abstract:
An air suspension includes a crossover valve in fluid communication with a manifold, a first set of springs in fluid communication with the manifold through a first set of valves, and a second set of springs in fluid communication with the manifold through a second set of valves. The crossover valve is movable between an open position to allow fluid communication to each of the first and the second sets of springs and a closed position that separates the first set of springs from the second set of springs.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Application No. 60/990,935, which was filed on Nov. 29, 2008. 
     
    
     TECHNICAL FIELD 
       [0002]    This invention generally relates to a crossover valve for an air suspension. 
       BACKGROUND OF THE INVENTION 
       [0003]    Air suspensions are often utilized in off-road vehicles; however, operational performance of these off-road vehicles can be limited by roll stiffness of the suspension. Roll stiffness limits an articulation angle of the suspension and keeps some vehicle tires from contacting the ground under certain off-road conditions. For example, uneven ground can cause one wheel to have ground contact while a laterally opposite wheel remains out of contact with the ground due to the limited articulation of the suspension. 
         [0004]    One solution has been to use a crossover valve in an axle to vary stiffness as needed between laterally opposed springs in an attempt to maintain four wheel contact with the ground. The crossover valve attenuates stiffness by allowing air from one spring on one side of the vehicle to be communicated to a laterally opposite spring on the other side of the vehicle. For a typical four-wheel drive vehicle, one crossover valve is used on a front axle to allow air communication between front right and front left springs, and another crossover valve is used on a rear axle to allow air communication between rear right and rear left springs. 
         [0005]    The inclusion of the two crossover valves is disadvantageous from a cost and material perspective. Further, due to limited packaging space, it is a challenge to route and plumb the crossover valves into the suspension. 
         [0006]    Thus, there is a need for a more cost effective suspension control that provides desired stiffness attenuation in addition to overcoming other deficiencies in the prior art as outlined above. 
       SUMMARY OF THE INVENTION 
       [0007]    An air suspension system includes a crossover valve that is integrated into a suspension valve block. The suspension system has a plurality of springs including front and rear springs, and left and right springs. Each spring has an associated spring valve. The crossover valve, which is normally open, can separate left and right portions of the valve block. When the crossover valve is closed all associated spring valves can be opened to allow flow between right and left springs but not between front and rear springs. 
         [0008]    In one example, the air suspension includes a crossover valve in fluid communication with a manifold, a first set of springs in fluid communication with the manifold through a first set of valves, and a second set of springs in fluid communication with the manifold through a second set of valves. The crossover valve is movable between an open position to allow fluid communication to each of the first and the second sets of springs and a closed position that separates the first set of springs from the second set of springs. Fluid communication occurs only between springs in the first set of springs when the crossover valve is in the closed position, and fluid communication occurs only between springs in the second set of springs when the crossover valve is in the closed position. 
         [0009]    In one example, the first set of springs includes a front right spring and a front left spring for a front axle, and the first set of valves includes a front right valve controlling fluid communication between the manifold and the front right spring and a front left valve controlling fluid communication between the manifold and the front left spring. The second set of springs includes a rear right spring and a rear left spring for a rear axle, and the second set of valves includes a rear right valve controlling fluid communication between the manifold and the rear right spring and a rear left valve controlling fluid communication between the manifold and the rear left spring. 
         [0010]    In one example, the air suspension system includes a control, such as an electronic control unit, computer, microprocessor, etc., which generates control signals to open and close the valves. The crossover valve and the first and second sets of valves can only be moved between open and closed positions in response to a control signal generated by the control. 
         [0011]    These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1A  is top schematic view of a vehicle with an air suspension incorporating the subject invention. 
           [0013]      FIG. 1B  is a front schematic view of a rear axle from  FIG. 1A . 
           [0014]      FIG. 2  is a schematic diagram including a pressure manifold, crossover valve, springs, and spring valves. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0015]      FIG. 1A  shows a vehicle  10  that includes a front axle  12  and a rear axle  14 . An air suspension system  16  includes a reservoir  18  and a plurality of springs  20   a - d  that are in fluid communication with the reservoir  18 . The springs  20   a - d  are associated with the front  12  and rear  14  axles. Spring  20   a  comprises a right front spring, spring  20   b  comprises a left front spring, spring  20   c  comprises a right rear spring, and spring  20   d  comprises a left rear spring. The springs  20   a - d  absorb road load inputs to provide a comfortable ride. Air pressure within the springs  20   a - d  can be varied to improve handling when the vehicle  10  is used in an off-road application, for example. 
         [0016]      FIG. 1B  shows a front view of the rear axle  14  and air suspension system  16 . The suspension system  16  would be similarly configured for the front axle  12 . The springs  20   a - d  are typically positioned between a vehicle chassis or frame member  24  and a component that is either associated with the axles or which is another suspension component. In the example shown in  FIG. 1B , the right and left rear springs  20   c ,  20   d  are supported by an axle housing  22 . However, it should be understood that while the springs are shown as being positioned directly between the associated axle and the frame member  24 , the springs could also be positioned between a suspension component, such as a control arm for example, which would be supported by the axle and the frame member. 
         [0017]    In the example of a four-wheel drive vehicle, the front  12  and rear  14  axles are drive axles that receive driving input from a power source  26  such as an engine or an electric motor for example. The front  12  and rear  14  axles each include gear assemblies  28  that drive axle shafts  30  to rotate a pair of laterally spaced wheels  32 . 
         [0018]    As discussed above, the springs  20   a - d  are each filled with air and the pressure inside of the springs  20   a - d  is varied to provide a desired ride and handling characteristic. As shown in  FIG. 1A , the front right  20   a  and front left  20   b  springs are associated with the front axle  12 , and the rear right  20   c  and rear left  20   d  springs are associated with the rear axle  14 . 
         [0019]    The air suspension system  16  comprises a suspension valve block  40 , shown in detail in  FIG. 2 , which controls air supply to the springs  20   a - d . The valve block  40  is a six valve, cross-linked configuration and includes a manifold  42  that is connected to the reservoir  18  via a reservoir valve  44 . Also in fluid communication with the manifold  42  are a plurality of valves  46   a - d  and the plurality of springs  20   a - d . A front right valve  46   a  controls fluid communication between the manifold  42  and the front right spring  20   a , a front left valve  46   b  controls fluid communication between the manifold  42  and the front left spring  20   b , a rear right valve  46   c  controls fluid communication between the manifold  42  and the rear right spring  20   c , and a rear left valve  46   d  controls fluid communication between the manifold  42  and the rear left spring  20   d.    
         [0020]    A sensor  48  monitors pressure in the manifold  42 . The sensor  48  can be used to check pressure at each of the plurality of valves  46   a - d  and the reservoir valve  44  to make sure that over-pressurization is not occurring. 
         [0021]    A crossover valve  50  is also in fluid communication with the manifold  42 . The crossover valve  50  controls fluid communication between front  20   a ,  20   b  and rear  20   c ,  20   d  springs, and controls fluid communication between right  20   a ,  20   c  and left  20   b ,  20   d  springs to vary stiffness as needed to maintain ground contact for all wheels. This will be discussed in greater detail below. 
         [0022]    The crossover valve  50  is in fluid communication with the manifold  42  at a position that can fluidly separate the springs for front  12  and rear  14  axles from each other. Each valve from the plurality of valves  46   a - d  is in a normally closed position and the crossover valve  50  is in a normally open position. This would allow air to flow between the springs  20   a ,  20   b  on the front axle  12  and the springs  20   c ,  20   d  on the rear axle  14  once the valves  46   a - d  are opened. 
         [0023]    When the crossover valve  50  is in a closed position, the manifold  42  is essentially cut in half with fluid communication being prevented between front springs and rear springs, i.e. air cannot flow between springs  20   a ,  20   b  on the front axle  26  and springs  20   c ,  20   d  on the rear axle  14 . 
         [0024]    When the front right  46   a  and front left  46   b  valves are open and the crossover valve  50  is closed, fluid communication only occurs between the front right  20   a  and front left  20   b  springs. When the rear right  46   c  and rear left  46   d  valves are open and the crossover valve  50  is closed, fluid communication only occurs between the rear right  20   c  and rear left  20   d  springs. Air pressure within one of the springs  20   a ,  20   b  can be increased to provide a greater stiffness while air in the other of the springs  20   a ,  20   b  would be decreased to provide a softer spring. This adjustment between right and left springs on a common axle provides stiffness attenuation as needed to maintain ground contact for all for wheels. 
         [0025]    A controller  60 , such as a computer, microprocessor, or electronic control unit for example, controls opening and closing of the crossover valve  50  and the plurality of valves  46   a - d . In one example, the controller  60  generates an electronic control signal to close the crossover valve  50  when a four-wheel drive low mode is activated. In this mode, the controller  60  also generates control signals to open the plurality of valves  46   a - d , and fluid communication occurs back and forth only between the right and left front springs  20   a ,  20   b  and only back and forth between the right and left rear springs  20   c ,  20   d , i.e. fluid transfer only occurs right and left between two pairs of springs associated with the same axle. There is no fluid transfer between front  20   a ,  20   b  and rear  20   c ,  20   d  springs in this mode, i.e. fluid from the front springs  20   a ,  20   b  cannot be communicated to the rear springs  20   c ,  20   d . If a predetermined speed limit is exceeded, or if a vehicle user de-selects the four-wheel drive low mode, the controller  60  generates control signals to open the crossover valve  50  and to close the plurality of valves  46   a - d  resulting in a return to a normal operation mode. It should be understood that while a four wheel drive configuration is shown with front and rear drives axles, the subject air suspension system  16  could also be used with other types of axle configurations. 
         [0026]    As such, a single crossover valve  50  is included in the manifold  42  and is normally open to separate left and right portions of the valve block  40 . When this crossover valve  50  is closed, each valve from the plurality of valves  46   a - d  can be opened to allow flow between left and right springs but not between front and rear springs. This configuration provides significant cost savings from a material and labor perspective. 
         [0027]    Although a preferred embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.