Abstract:
A height control valve is preferably adapted to be mounted in a trailing arm suspension and fluidly interconnected to a source of pressurized air and to an air spring. The height control valve comprises a housing having a cylindrical bore, a supply port, an exhaust port and an air spring port each of which extends through the housing and fluidly communicates with the bore. A rotor is preferably rotatably mounted in the bore and interconnected to the arm wherein pivotal movement of the arm rotates the rotor with respect to the housing between first, second and third rotational positions. A plurality of seals is preferably located between the rotor and the bore defining a flow passage between the bore and the rotor wherein in the first rotational position, the flow passage isolates the air spring port from both the supply port and the exhaust port, in the second rotational position the flow passage interconnects the air spring port with the supply port, and in the third rotational position the flow passage interconnects the air spring port with the exhaust port.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application is a continuation-in-part of International Application No. PCT/US99/19932, filed Aug. 30, 1999, which claims the benefit of U.S. Provisional Patent Application Ser. No. 60/098,491, filed on Aug. 31, 1998.  
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The invention relates to a vehicle suspension in which the height of one or more axles is controlled with a height control valve which inflates one or more air springs mounted between the vehicle frame and the axle and, more specifically, to a vehicle suspension having a rotary height control valve. The height control valve can also be used to control the height of a vehicle cab relative to the vehicle frame when air springs support the cab.  
           [0004]    2. Related Art  
           [0005]    Pneumatic vehicle suspensions often have a leveling device for controlling the height of a vehicle frame relative to a vehicle axle. This leveling device, often called a height control valve, controls the amount of air within an air spring located between the frame and the axle. The height control valve typically controls the air pressure in the air spring in response to changes in the distance between the frame and the axle by selectively interconnecting the air spring with a supply of pressurized air or an exhaust port. The height control valve has its greatest use in maintaining a constant level of a vehicle chassis or frame relative to its axles in response to the loading and unloading of the vehicle, often referred to as the “ride height” of the vehicle.  
           [0006]    [0006]FIG. 1 illustrates a typical prior art height control valve  10  mounted on a frame  12  of a vehicle by bolts  14 . The valve  10  is adapted to supply air to an air spring  22  which is mounted between the frame  12  and an axle support  24 , such as a trailing arm, so that the upward and downward movement of the frame  12  relative to the axle support  24  actuates the height control valve  10  to normally exhaust air from or deliver air to the air spring  22 .  
           [0007]    Air is typically supplied from a source of pressurized air such as a tank  26  by a supply tube  28  connected to an inlet port  30  of the height control valve  10 . The air is delivered to the air spring  22  through a delivery tube  32 , which is connected to a delivery port  34  of the height control valve  10 . Air is exhausted from the air spring by an exhaust tube  36  connected to an exhaust port  40  and is vented to the atmosphere as shown in FIG. 1. An actuator arm  42  extends from the height control valve  10  and is connected to a linkage  44  extending between the axle support  24  and the vehicle frame  12 . In operation, movements of the axle support  24  relative to the frame  12  pivot the actuator arm  42  through the linkage  44  to control the height control valve  10 .  
           [0008]    Height control valves for vehicles, though known for years, remain problematic. Problems include a large number of parts leading to high assembly and service costs. Seal wear presents a further problem with prior height control valves due to the repetitive motion intrinsic to the operation.  
         SUMMARY OF THE INVENTION  
         [0009]    The invention relates to a trailing arm suspension comprising a frame bracket adapted to be mounted to a vehicle frame, a trailing arm pivotally mounted to the frame bracket, and an air spring mounted on the trailing arm and adapted to be mounted to the underside of the vehicle frame. A height control valve is adapted to be fluidly interconnected to a source of pressurized air and to the air spring and has an arm adapted to be connected to the trailing arm to control the flow of pressurized air to the air spring and the exhaust of pressurized air therefrom in response to pivotal movement of the trailing arm with respect to the vehicle frame.  
           [0010]    According to the invention, the height control valve comprises a housing having a cylindrical bore, a supply port, an exhaust port and an air spring port each of which extends through the housing and fluidly communicates with the bore. A rotor is rotatably mounted in the bore and interconnected to the arm wherein pivotal movement of the arm rotates the rotor with respect to the housing between first, second and third rotational positions. A plurality of seals is located between the rotor and the bore defining a flow passage between the bore and the rotor wherein in the first rotational position, the flow passage isolates the air spring port from both the supply port and the exhaust port, in the second rotational position the flow passage interconnects the air spring port with the supply port, and in the third rotational position the flow passage interconnects the air spring port with the exhaust port.  
           [0011]    The flow passage is preferably defined by a pair of circumferential seals. The rotor preferably has a longitudinal axis and the flow passage is inclined at an acute angle with respect to the longitudinal axis. The seals preferably comprise a circumferential seal located at each end of the rotor. The seals are preferably o-rings. The rotor of the height control valve can have a plurality of circumferential grooves, each of which receives an o-ring seal.  
           [0012]    The seals can be configured so as to provide a dead band for the suspension, wherein small movements of the axle relative to the frame are attenuated. The configuration of the seals and the position of the ports can cooperate to define a characteristic flow rate of the valve.  
           [0013]    Other objects, features, and advantages of the invention will be apparent from the ensuing description in conjunction with the accompanying drawings.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    The invention will be described with reference to the accompanying drawings in which:  
         [0015]    [0015]FIG. 1 is a side elevational view of a prior art vehicle suspension comprising a trailing arm pivotally mounted to a vehicle frame and supported relative to the vehicle frame by an air spring pressurized by a prior art height control valve responsive to changes in the vertical distance between the vehicle frame and a trailing arm;  
         [0016]    [0016]FIG. 2 is a side elevational view of a vehicle suspension having a rotary height control valve according to the invention;  
         [0017]    [0017]FIG. 3 is an exploded perspective view of the height control valve of FIG. 2 with the remaining elements of the vehicle suspension removed for clarity;  
         [0018]    [0018]FIG. 4 is a side elevational view of the height control valve of FIGS. 2 and 3, showing a lever mounted thereto in a neutral position whereby the inflation of the air spring remains constant;  
         [0019]    [0019]FIG. 5 is a cross-sectional view of the interior of the height control valve taken along lines  5 - 5  of FIG. 4 in the neutral position showing the height control valve comprising a housing provided with a rotor which has a pair of o-rings defining chambers for selectively interconnecting an air spring with a supply port and an exhaust port therein;  
         [0020]    [0020]FIG. 6 is a side elevational view showing the lever in a first actuated position whereby the air spring port is interconnected with the exhaust port in the housing of the height control valve;  
         [0021]    [0021]FIG. 7 is a cross-sectional view taken along lines  7 - 7  of FIG. 6 showing the interior of the height control valve in the first actuated position whereby the air spring port is fluidly interconnected with the exhaust port for exhausting air from the air spring;  
         [0022]    [0022]FIG. 8 is a side elevational view showing the lever in a second actuated position whereby the air spring port is interconnected with the supply port in the housing of the height control valve; and  
         [0023]    [0023]FIG. 9 is a cross-sectional view taken along lines  9 - 9  of FIG. 8 showing the interior of the height control valve in the second actuated position whereby the air spring port is fluidly interconnected with the supply port for supplying pressurized air to the air spring.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0024]    [0024]FIG. 2 illustrates a height control valve  50 , according to the invention, mounted on a frame  54  of a vehicle by bolts  55 . The height control valve  50  is adapted to supply air to an air spring  52  which is mounted between the frame  54  and an axle support  56 , such as a trailing arm, so that upward and downward movement of the frame  54  relative to the axle support  56  actuates the height control valve  50  to either exhaust air from or deliver air to the air spring  52 .  
         [0025]    As shown in FIG. 2, pressurized air is supplied by a tank  58  via a supply tube  60 , which is connected to a supply port  62  of the height control valve  50 . The air is selectively delivered to the air spring  52  through a delivery tube  64 , which is connected to an air spring port  66  of the height control valve  50 . Air is exhausted from the air spring  52  by an exhaust port  70  of the height control valve  50 , and is vented to the atmosphere via an exhaust tube  68  as shown in FIG. 2.  
         [0026]    As shown in FIG. 2, a lever  72  extends from the height control valve  50  and is connected to a linkage  74  extending between the axle support  56  and the height control valve  50 . In operation, movement of the axle support  56  relative to the frame  54  pivots the lever  72  through the linkage  74  to actuate the height control valve  50  and thereby dispense air to or exhaust air from the air spring  52  by selectively interconnecting the air spring port  66  with the supply and exhaust ports  62  and  70 , respectively.  
         [0027]    As shown in FIG. 3, the height control valve  50  comprises a housing  61  having the three radially-spaced supply, air spring, and exhaust ports  62 ,  66 , and  70 , respectively, communicating with a common cylindrical bore  76 , which extends the length of the housing  61 . Although the housing  61  is shown as being cubic in shape, any appropriately configured three-dimensional member will suffice.  
         [0028]    Each port comprises a socket threaded to receive a conventional air hose and a coaxial conduit of smaller diameter, which communicates with the bore  76  of the housing  61  in the orientation shown in the drawings. The air spring port  66  is preferably centrally located on a right-hand face  104  of the housing  61 . The supply port  62  is located on a bottom face  106  of the housing  61  closer to a rear face  102  of the housing  61  than the air spring port  66 . The exhaust port  70  is located on a top face  108  of the housing  61  closer to a front face  100  of the housing  61  than the air spring port  66 .  
         [0029]    The height control valve  50  further comprises a cylindrical rotor  78  having a diameter slightly less than that of the cylindrical bore  76  of the housing  61 . The rotor  78  further comprises, circumferentially and in the following axial sequence from a first end  75  to a second end  77  of the rotor  78 , a first normal circumferential groove  80 , a first inclined circumferential groove  82 , a second inclined circumferential groove  84 , a second normal circumferential groove  86 , and a third normal circumferential groove  87 . O-rings  88  and  94  are provided to fit into the first and second normal grooves  80  and  86 , respectively. O-rings  90  and  92  are provided to fit into the first and second inclined grooves  82  and  84 , respectively. A circular retaining ring  96  is provided which fits into the third normal groove  87  after the rotor  78  has been inserted within the cylindrical bore  76  of the housing  61  and has a diameter larger than the bore  76  to prevent the withdrawal of the rotor  78  therefrom.  
         [0030]    The height control valve rotor  78  has a flange section  98  that interfaces with surface  100  of valve body  61 . When installed, flange  98  and retaining ring  96  prevent rotor  78  from axial motion in bore  76  of valve body  61 .  
         [0031]    The grooves  80 - 86  of the rotor  78  are preferably provided with a depth less than that of a cross-sectional height of their corresponding o-rings  88 - 94  so that, when the o-rings  88 - 94  are positioned in their respective grooves  88 - 94 , the o-rings  88 - 94  extend slightly beyond an outer surface  99  of the rotor  78 . The portion of the o-rings  88 - 94  extending beyond the outer surface of the rotor  78  define a first annular gap  112  between the o-ring  88  in the first normal groove  80  and the o-ring  90  in the first inclined groove  82 , a second annular gap  114  between the o-ring  90  in the first inclined groove  82  and the o-ring  92  in the second inclined groove  84 , and a third annular gap  116  between the o-ring  92  in the second inclined groove  84  and the o-ring  94  in the second normal groove  86 . Each of the first, second, and third annular gaps  112 ,  114 , and  116 , respectively, are bordered on an inner and outer radial limit by the outer surface of the rotor  78  and the inner surface of the bore  76 , respectively.  
         [0032]    To assemble the height control valve  50 , o-rings  88  and  94  are secured within the first and second normal grooves  80  and  86 , respectively, of the rotor  78 , and o-rings  90  and  92  are secured within the first and second inclined grooves  82  and  84 , respectively, of the rotor  78 . The rotor  78  is then inserted within the cylindrical bore  76  of the housing  61  and the retaining ring  96  is secured within the third normal groove  87  at the second end  77  of the rotor  78  such that the ring  96  abuts the rear face  102  of the housing  61 . The aperture  73  of the lever  72  is aligned with the projection  97  of the rotor  78  and secured thereto by fastener  110 . The aperture  73  of the lever  72  and the projection  97  of the rotor  78  preferably have discontinuities, i.e., a non-circular geometry, to prevent inadvertent rotation of the rotor  78  relative to the lever  72 . The rotor  78  is thereby journalled within the bore  76  of the housing  61  between the retaining ring  96  and the rotor flange  98  and is rotatable therein by the lever  72 .  
         [0033]    The height control valve  50  is secured to the frame  54  of the vehicle in any conventional manner, such as bolts  55  as shown in FIG. 2. The lever  72  is pivotally secured to the linkage  74 , which is, in turn, pivotally secured to the axle support  56 . The height control valve  50  is connected to the air supply  58  and the air spring  52  as described above. In operation, the height control valve  50  has three distinct positions referred to as neutral (off), exhaust, and supply positions as will be further described herein.  
         [0034]    The operation of the height control valve  50  is described in FIGS.  4 - 9 , wherein FIGS.  4 - 5 ,  6 - 7  and  8 - 9  show the height control valve  50  in the neutral, exhaust and supply position, respectively. It should be noted that a projection of the location of the exhaust port  70  is illustrated in phantom lines in FIGS. 5, 7 and  9  though it would normally not be seen in a view having the cross-sectional arrangement of these figures. The location of the exhaust port  70  is important to show in these figures to illustrate the relative movement of the o-rings  90 ,  92  with respect to the supply, air spring and exhaust ports  62 ,  66  and  70 , respectively, in a manner according to the invention.  
         [0035]    [0035]FIGS. 4 and 5 show the height control valve  50  in the neutral position corresponding to the frame  54  at a desired or “design” height with respect to the axle support  56  and the lever  72  in a substantially horizontal position with respect to the surface supporting the travel of the vehicle. As best shown in FIG. 5, in the neutral position, the supply port  62  and the exhaust port  70  are each sealed from fluid communication with the air spring port  66 , and with each other. The exhaust port  70  is isolated within the first annular gap  112  between the o-ring  88  in the first normal groove  80  and the o-ring  90  in the first inclined groove  82 . The air spring port  66  is isolated within the second annular gap  114  between the o-rings  90  and  92  in the first and second inclined grooves  82  and  84 , respectively. The supply port  62  is isolated within the third annular gap  116  between the o-ring  92  in the second inclined groove  84  and the o-ring  94  in the second normal groove  86 . Thus, in the neutral position, no airflow occurs and the vehicle maintains the operating distance between the frame  54  and the axle support  56 .  
         [0036]    [0036]FIGS. 6 and 7 show the height control valve  50  in the exhaust position corresponding to the frame  54  above the desired or design height from the axle support  56  and the lever  72  pivoted downwardly with respect to the surface supporting the travel of the vehicle. As best shown in FIG. 7, in the exhaust position, the rotation of the rotor  78  by the pivoting of the lever  72  has shifted the second annular gap  114  relative to the ports  66  and  70  so that the air spring port  66  communicates with the exhaust port  70  therein between the o-rings  90  and  92  in the first and second inclined grooves  82  and  84 , respectively. The supply port  62  remains isolated within the third annular gap  116  between the o-ring  92  in the second inclined groove  84  and the o-ring  94  in the second normal groove  86 . Air is exhausted from the air spring  52  sufficiently to restore the frame  54  to the operating distance relative to the axle support  56  and to return the height control valve  50  to the neutral position shown in FIGS. 4 and 5.  
         [0037]    [0037]FIGS. 8 and 9 show the height control valve  50  in the supply position corresponding to the frame  54  below the desired or “design” height with respect to the axle support  56  and the lever  72  pivoted upwardly with respect to the surface supporting the travel of the vehicle. As best shown in FIG. 9, in the supply position, the rotation of the rotor  78  by the pivoting of the lever  72  has shifted the second annular gap  114  relative to the ports  66  and  62  so that the air spring port  66  communicates with the supply port  62  therein between the o-rings  90  and  92  in the first and second inclined grooves  82  and  84 , respectively. The exhaust port  70  remains isolated within the first annular gap  112  between the o-ring  88  in the first normal groove  80  and the o-ring  90  in the first inclined groove  82 . Air is supplied to the air spring  52  sufficiently to restore the frame  54  to the operating distance relative to the axle support  56  and to return the height control valve  50  to the neutral position shown in FIGS. 4 and 5.  
         [0038]    The relative distance of the frame  54  and the axle support  56  determines in which of the three positions the height control valve  50  is placed. Assuming that the initial position is the neutral position shown in FIGS. 4 and 5, the distance between the frame  54  and the axle support  56  becoming greater than the normal operating distance due to the removal of a sufficient amount of weight, for example, rotates the rotor  78  and causes the height control valve  50  to be placed in the exhaust position, as shown in FIGS.  6  and  7 . Air is exhausted from the air spring  52  until the desired operating distance is restored and the height control valve  50  returns to the neutral position of FIGS. 4 and 5. Conversely, the distance between the frame  54  and the axle support  56  becoming less than the normal operating distance due to the addition of a sufficient amount of weight, for example, rotates the rotor  78  and causes the height control valve  50  to be placed in the supply position, as shown in FIGS. 8 and 9. Air will be supplied to the air spring  52  until the operating distance is restored and the height control valve  50  returns to the neutral position of FIGS. 4 and 5.  
         [0039]    Spacing and location of the supply and exhaust ports  62  and  70 , respectively, can be selected to control the amount of rotation of the rotor  78  that can occur with no air entering or exhausting from the air spring port  66 . This degree of permissible rotation without actuating the height control valve  50  is referred to as the “dead band” for the valve  50  and is preferably optimally selected to provide smooth actuation of the valve  50  and to prevent inadvertent actuation thereof due to small movements of the axle support  56  relative to the frame  54 . The characteristic flow rate of the valve can vary from a binary on/off response to a more throttled behavior depending upon the shape and location of the supply, air spring, and exhaust ports and upon the inclination and curvature of the o-rings  90  and  92  in the first and second inclined grooves  82  and  84 , respectively.  
         [0040]    Although the height control valve  50  is shown regulating the ride height of a vehicle frame relative to its axles, the height control valve  50  can be used in any suitable application to maintain the pressure in a pneumatic spring based upon the movement of one member relative to another. For example, in a passenger cab supported on a vehicle frame by air springs, the height control valve  50  can be used in a similar fashion to control the height of the cab relative to the frame.  
         [0041]    While particular embodiments of the invention have been shown, it will be understood, of course, that the invention is not limited thereto since modifications may be made by those skilled in the art, particularly in light of the foregoing teachings. Reasonable variation and modification are possible within the scope of the foregoing disclosure of the invention without departing from the spirit of the invention.