Abstract:
A vehicle ride-height and automatic suspension control system for a vehicle having an air suspension system. The automatic suspension control system provides the vehicle operator with selectable ride-heights and controls vehicle level as it rounds curves or corners. The system utilizes a series of photoelectric sensors that are linked between the vehicle chassis and axles and are combined with the vehicle steering system. Continuously sampling of the photoelectric sensors by a controller increments or decrements a digital register. When the counter reaches either the upper or lower selected threshold values the appropriate air bag is inflated or deflated for a duration of time. System sensitivity is adjustable by selecting different counter thresholds and by selecting the duration of air bag inflation or deflation.

Description:
BACKGROUND OF INVENTION 
     This invention relates to automatic suspension control systems for motor vehicles, and more particularly to a computer controlled air suspension system for motor homes and recreational vehicles. 
     Ride-height control systems for motor homes and recreational vehicles are well known in the art. These systems typically utilize air suspension systems which permit the distance between the axles and chassis to be adjusted according to the amount of pressure within the air bags. The ride-height of the vehicle may therefore be adjusted for varying loading conditions, road conditions, wind, and rough terrain. Systems for maintaining a particular ride-height for varying conditions generally utilize a vehicle pneumatic system, comprised of an air compressor and air tank, and a pneumatic valve connected to each of the vehicle air bags. Each of the valves is secured to the vehicle chassis and connected to the vehicle axle by means of a mechanical linkage. As the distance between the chassis and axle fluctuates, air is supplied to, or vented from, each air bag through its respective valve. These systems are unsatisfactory for a number of reasons. First is the requirement for manually adjusting each valve linkage to select a new ride height as environmental conditions change. Second, these systems utilize a great deal of air, and therefore put a constant drain on the vehicle pneumatic system, due to the constant transfer of air into and out of the bags as the chassis and axle oscillate and the system “hunts” for the proper setting. Further, with known systems, adjusting the sensitivity of the system for different quality of ride requires changing the pneumatic valves. 
     SUMMARY OF INVENTION 
     The present invention discloses a vehicle ride-height and automatic suspension control system with selectable ride-heights and sensitivity. The invention also provides for automatic control of the suspension system as the vehicle rounds curves or corners by means of a gear tooth counter and direction sensor that is combined with the vehicle steering system. 
     The system of the invention utilizes a series of photoelectric cells activated by shutters on a shaft that are placed offset to each other and are mechanically linked between the vehicle chassis and axle. The offset provides for more than one ride-height setting. 
     Sampling a photoelectric cell by a controller every millisecond increments or decrements a counter or register. When the counter reaches either the upper or lower threshold value the appropriate solenoid valve is energized to inflate or deflate a particular air bag for a duration of time that is selected by the user. 
     System sensitivity is adjustable by selecting different counter thresholds and by selecting the duration of solenoid actuation. 
     In addition, a gear tooth counter and direction sensor are utilized to detect direction and degrees of rotation of the steering wheel. This allows the controller to select one of two modes (economy or active) of suspension control. Surpassing set limits of movement of the steering system determines the appropriate selection of modes to minimize roll of the vehicle when rounding curves or corners or when abrupt turns are made. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     These and other advantages and features of the invention will become apparent upon an understanding of the best mode for carrying out the invention as described hereinafter in conjunction with the following drawings: 
     FIG. 1 is a perspective view of the forward end of a typical vehicle suspension system utilizing the present invention; 
     FIG. 2 is a perspective view of the rear end of a typical vehicle suspension system utilizing the present invention; 
     FIG. 3 is an exploded view of a sensing unit utilizing photocells and shutter; 
     FIG. 4 is an end view of the sensing unit of FIG. 3; 
     FIG. 5 is a cross-sectional view of the sensing unit taken along line  5 — 5  in FIG. 4; 
     FIG. 6 is a block diagram of a the pneumatic and control system by which the invention is accomplished; 
     FIG. 7 is a schematic block diagram illustrating the steps of the controller that is a part of the system and method; 
     FIG. 8 is diagram illustrating the threshold register values and interval time values for actuating the solenoids that control the air to the suspension air bags; 
     FIG. 9 is a schematic view of a vehicle steering wheel and gear to illustrate the gear tooth counter and direction sensor; and 
     FIG. 10 is a schematic side view of the steering system and counter-sensor of FIG.  9 . 
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, FIGS. 1 and 2 show the forward and rear ends of a typical vehicle air suspension system that utilizes air bags mounted adjacent each wheel of the vehicle. The air suspension system typically comprises a vehicle chassis  12 , forward axle  14 , rear axle  16 , and air bags  18 , supporting the axles  14  and  16  from the chassis  12 . The depicted system utilizes a single sensing unit, indicated generally by the reference numeral  20 , in the forward end which unit  20  controls both forward air bags  18 , and two sensing units  20  in the rear end each controlling a single air bag  18 . All the sensing units  20  are substantially identical in construction and operation and therefore only one such unit will be described in detail. 
     The sensing units  20  are secured to the vehicle chassis  12  and are mechanically linked to the vehicle axles  14  and  16  of air suspension system  22  by means of a pair of connecting arms  24  and  25 . Arm  24  is pivotally connected to the respective one of the axles  14  or  16  and is adjustably and pivotally connected to the other connecting arm  25  by connector  27  that adjustably receives the arm  24 . Connecting arm  25  has its other end connected to the shaft  32  of sensing unit  20 . As best seen in FIG. 5, shaft  32  is rotated by means of the connecting arm  25 . This arrangement allows the sensing units  20  to continuously monitor the distance between the chassis  12  and the axles  14  and  16  through action of the arms  24  and  25  as more fully described hereinafter. 
     A sensing unit  20  is shown in detail in FIGS. 3,  4  and  5  and is comprised of a housing  30  having a key-shaped hollow interior  31  that receives an elongated shaft  32  which carries a plurality of shutter disks  34 . The shutter disks  34  each have a clear section  36  and an opaque section  38  and are mounted on the shaft  32  in a spaced-apart relationship sandwiched between a plurality of spacer disks  40 , as best seen in FIG.  3 . The spacer disks  40  are keyed to the shaft  32  by key balls  42  and are thereby prevented from rotating relative to the shaft  32 . However, the shutter disks  34  are mounted on the shaft  32  between the spacer disks  40  in a manner to provide for manual rotation and thus adjustment of the shutter disks  34  relative to the shaft  32 , albeit with considerable force. This allows the shutter disks  34  to be positioned with the clear/opaque interfaces in the desired position relative to the shutter&#39;s respective photoelectric cells  44 . Manual repositioning of the shutter disks  34  may be accomplished, for example, via access opening  46 , which is normally sealed by means of cover  48 . This repositioning has the effect of selecting a new ride-height to be maintained by that particular shutter disk  34  since the clear/opaque interface line has been moved with respect to its respective photocell  44 . Preferably, the air bags  18  use tapered pistons providing for varying the vehicle ride from soft to stiff. 
     With the sensing units  20  in place, as the distance between the vehicle axle  14  or  16  and the vehicle chassis  12  varies, connecting arms  24  and  25  will cause the shaft  32  of a sensing unit  20  to rotate. This in turn causes the shutter disks  34  to rotate. In a preferred embodiment, each sensing unit  20  contains three shutter disks  34 , each which determines a different vehicle ride-height (distance between the chassis and axle), as for example high, medium, and low. The interface line between the clear section  36  and opaque section  38  on each of the disks  34  is rotationally offset from the interface line of the other disks to provide for these different ride heights. A block diagram of the basic pneumatic control system is shown in FIG. 6. A standard vehicle pneumatic system typically includes an air compressor  50  and an air tank  52  connected to four solenoid valves  54 , two of which valves  54  control the air bags  18  the rear of the vehicle, and two of which valves  54  control the bags  18  in the front of the vehicle. Each of the four solenoid valves  54  may add air to, or vent air from, its respective air bag(s)  18  under the direction of a controller  56 . The function of the controller  56  is schematically shown in FIG. 7, with each functional block being designated by a “step” number. FIG.  7  and the appropriate step will be referred to in the description hereinafter. 
     Selection of one of the three ride-heights (low, medium, high) is typically made by the vehicle operator by operating the appropriate height select switch  58  on the vehicle control panel. Actuation of the ride height switch  58  by the operator (FIG. 7, step  2 ) to select the desired ride height instructs the controller  56  to monitor a particular shutter disk  34  and photoelectric cell  44  in each sensing unit  20  (FIG. 7, step  3 ). The selected photoelectric cell  44  is sampled every millisecond to determine the position of the clear/opaque interface line on its respective shutter disk  34 , which is continually being rotated due to vehicle oscillations. If the clear portion  36  of the shutter disk  34  is positioned within the photoelectric cell  44 , indicating that the selected ride height is too low, the photoelectric cell  44  will conduct and a “low” signal will be sent to the controller  56 . Similarly, if the opaque portion  38  of the shutter disk  34  is positioned within the photoelectric cell  44 , indicating that the selected ride-height is too high, the photoelectric cell  44  will not conduct and a “high” signal will be sent to the controller  56 . 
     The ride height selector  58  allows the user to select sensitivity of three different variables. First, the counter threshold value at which a command is sent by the controller  56  to a solenoid valve  54  may be increased or decreased. Secondly, the duration of the solenoid valve  54  operation may be increased or decreased, thereby increasing or decreasing the amount of air in the air bags  18  during a particular command. The height selector  58  also allows the user to select one of three shutter disks  34  to vary the distance between the frame and the axle. For example, this selection allows the vehicle operator to make corrections to compensate the vehicle level while driving along a crowned road. 
     A signal is sent by the controller  56  to all solenoid valves  54  appropriately inflating or deflating the air bag(s)  18  until a state change of the photoelectric cell  20  has been detected, i.e., if power is initially applied to the controller  56 , or a different shutter disk  34  is selected, or the steering mode has changed, as described hereinafter. 
     The basic system of the invention is also useful for stabilizing vehicle roll when cornering or rounding curves. When the vehicle is traveling at or below a predetermined speed, approximately 15 mph or less, the controller  56  maintains an “economy” mode regardless of the amount of rotation of the steering system. As illustrated in FIGS. 9 and 10, a fixed gear tooth counter and direction sensor  60  along with a gear  62  having teeth  63  are combined with the steering wheel  64  of the vehicle and used to detect direction and degrees of rotation of the steering system to determine which mode, the economy mode or the “active” mode, will be selected by the controller  56 . A steering system counter in controller  56  (FIG. 7, step  3 ) is decremented each time the sensor  60  detects a gear tooth  63  passing the face of sensor  60  moving counter clockwise, which indicates the vehicle is turning left. Similarly, the steering system counter in controller  56  is incremented each time the sensor  60  detects a gear tooth  63  passing the face of sensor  60  moving clockwise, thus indicating the vehicle is turning right. 
     The controller  56  will maintain the active mode until such time that the steering system counter returns to a value within the selected threshold values (see FIG.  8 ). An additional 6 seconds of active mode is performed to assist the air bags  18  to return to a balanced pressure relative to each other. The steering system counter is then reinitialized to zero in relationship with a gear tooth  63 , or absence of a gear tooth, present to the sensor  60  at that instant. The reinitializing method used allows the system to adjust to the physical relation of the steering wheel  64  to the path the vehicle is on. This permits the system to remain in economy mode even if driving in a strong side wind. 
     The system also provides the user the ability to completely deflate all air bags  18  or inflate all air bags  18  to system pressure to enhance low speed maneuvering, e.g., passing under a structure or driving over a street curb. However, when the vehicle is traveling at a speed above the predetermined speed, the system is able to select the modes automatically (see FIG.  7 ). 
     As previously indicated, the ride-height counter in controller  56  (FIG. 7, step  3 ) is decremented each time the sensor  20  is sampled and light passes through the shutter  34  indicating the vehicle ride height is low. The ride-height counter is incremented each time the sensor  20  is sampled and light is blocked by the shutter  34  indicating the vehicle ride-height is high. When the steering system (FIG. 9) prompts the controller  56  to operate in economy mode, the upper or lower threshold counter values are determined by the height selector inputs (FIG. 7, step  2 ). When the ride height counter reaches either the upper or lower threshold, the appropriate solenoid valve  54  for that sensing unit  20  is energized to inflate or deflate the corresponding air bag  18  for the selected duration of time (FIG. 7, step  7 ). After the selected duration of time has elapsed (FIG. 7, step  8 ), the counter is reinitialized to the reference level that counting can be reinitiated (FIG. 7, step  9 ). 
     When the steering system (FIGS. 9 and 10) prompts the controller  56  to operate in active mode, the upper or lower threshold counter values are set at 0.75 seconds. When the counter reaches either the upper or lower threshold (FIG. 7, step  5 ), the appropriate solenoid valve  54  for that sensing unit  20  is energized to inflate or deflate the corresponding air bag  18  until a state change of the sensing unit  20  has been detected (FIG. 7, step  11 ). After a state change has been detected, the corresponding solenoids  54  are turned off and the counter is reinitialized to the reference level so that counting can be reinitiated (FIG. 7, step  9 ). While in active mode and a rear air bag  18  is being inflated, the corresponding front air bag  18  is also inflated to assist in maintaining the proper distance between the chassis  12  and axle  14  of the vehicle. 
     While this specification has described preferred embodiments of the invention utilizing a photoelectric cell and shutter arrangement to pass discreet high/low signals to a digital counter, it is clear that other switching and indicating devices may also be utilized. For instance, a simple mechanical switch, if sufficiently durable, could be used to pass the high/low signals. It is therefore to be understood that the invention is not limited to the specific components set forth herein for purposes of exemplification, but is to be limited only by the scope of the appended claims including the full range of equivalency to which each element thereof is entitled.