Abstract:
A modulator valve for use with the auxiliary axle anti-lock braking system of a truck, configured and constructed such that no braking application pressure signal is permitted to be delivered to the auxiliary axle anti-lock braking system when the auxiliary axle is in the lifted position, and a modulated braking application pressure signal is delivered to the auxiliary axle anti-lock braking system when the auxiliary axle is not in the lifted position. The modulated braking application pressure depends upon the pressure sensed from ride springs of the suspension system of the truck.

Description:
[0001]    This application claims the benefit of provisional application No. 61/946,386 filed Feb. 28, 2014, the entire content of which is expressly incorporated herein by reference thereto. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a modulator valve for use with the auxiliary axle anti-lock brake system of a truck. 
       BACKGROUND OF THE INVENTION 
       [0003]    In the truck-tractor industry, the number of axles required on the ground is determined by the load carried by the vehicle. When lighter weight tractors are towed, often only one rear axle is required to accommodate the load (the “primary axle”). As the load weight increases, however, an additional axle may be required to carry the added weight (the “auxiliary axle”). The primary axle is connected to the engine to provide the driving force. The auxiliary axle, when in use, only provides load distribution to the rolling surface and does not provide any driving force. 
         [0004]    On trucks with two rear axles, it has been demonstrated that if the load can be carried by one axle, fuel consumption is significantly reduced if the auxiliary axle is lifted so as to not contact the rolling surface. This lifting is typically accomplished through the use of air springs (referred to herein as “lift springs”) and leverage to pivot the auxiliary axle off of the rolling surface. Trucks with this configuration are commonly referred to as 6×2 systems (six wheel-ends with two drive wheel-ends) Systems designed to lift the auxiliary axle off of the rolling surface are well known in the prior art. 
         [0005]    Tractors are commonly fitted with a suspension system that adjusts to the weight being carried through the use of air springs (referred to herein as “ride springs”). 
         [0006]    These springs are filled with pressurized air from the truck&#39;s compressor. As the trailer load increases, the air pressure in the ride springs is increased to maintain the proper position of the frame relative to the vehicle&#39;s axles. The adjustment of the pressure in the ride springs is accomplished by automatic systems. Through the function of the suspension system, the auxiliary axle and primary axle may not carry the same amount of load. 
         [0007]    Federal vehicle safety standards require that all wheels on these trucks be provided with anti-lock brake systems. These brake systems monitor wheel motion during braking to limit wheel lock-up and improve control and stopping distance. The system has a relay valve which receives a braking signal from the driver as a low volume pneumatic pressure and then relays that signal pressure to the service brake chamber with a high volume flow to fill the chamber quickly at the requested pressure. When anti-lock brake system braking systems are used with an auxiliary axle, certain problems can occur. 
         [0008]    Specifically, when the auxiliary axle is lifted, undesirable “false events” may be recorded as lock-up by the anti-lock brake system if the system detects that the lifted wheels are not turning during a brake application. To avoid this, separate anti-lock brake system controllers can be used with the lift axle, but the application signal pressure from the vehicle&#39;s primary service brake system must be turned off when the auxiliary axle is in the lifted position. When the auxiliary axle is lowered to carry the load, the service application signal must be turned back on to enable the brakes on the wheels attached to the auxiliary axle. Inversion valves, which can be used to shut off pneumatic output based on pneumatic pressure at another location, are known in the art for use to disable the anti-lock brake system in the auxiliary axle when it is in the lifted position, but these are separate devices that are applied to each line. 
         [0009]    Additionally, when the auxiliary axle is not lifted, the auxiliary axle and the primary axle may not carry the same amount of load. This causes the contact pressure between the tires and the rolling surface to be different on the primary and auxiliary axles. Because the driver of the truck only has the ability to apply one control pressure, both the axles receive the same braking signal. If the load on the auxiliary axle is lower than that on the primary axle, the wheels on the auxiliary axle may lock-up, generating an anti-lock brake system event. This locking of the wheels can result in the tires being dragged along the road surface, causing wear and flat spots which ruin the tires, which results in added replacement and disposal expense. 
         [0010]    There are currently devices known as load sensing valves that adjust output relative to the input based on preset mechanical and pneumatic adjustments, but these adjustments must be made specific to the installation, require complicated calculations, and are subject to installation errors. Accordingly, there is a need in the art for improvements in such devices, and these are now provided by the present invention. 
       SUMMARY OF THE INVENTION 
       [0011]    The present invention now combines all of the functions discussed above into a single self-contained modulator valve device for better control and operation of vehicle braking when the auxiliary axle is lifted. The present device receives the driver&#39;s brake application signal from the primary air brake control system, and allows delivery to the anti-lock brake system relay valve only when the auxiliary axle is not in the lifted position. Moreover, when the auxiliary axle is not in the lifted position, the device modulates the delivery signal to the auxiliary axle braking system to a percentage of the input signal based on predetermined ride spring pressure ranges. 
         [0012]    The present invention provides a number of features that contribute to improved operation and control of vehicle braking when the auxiliary axle is lifted. One feature is the automatic shut off the driver&#39;s brake control signal to the auxiliary axle anti-lock brake system when the auxiliary axle is in the lifted position. Another feature is the determination of the relative load carried by the auxiliary axle by measuring the air pressure in the auxiliary ride springs. The present invention also modulates the application pressure sent to the auxiliary axle anti-lock brake system relay valve proportionally to the load being carried by that axle. Yet another feature is the ability to universally install the device on different vehicles without having to perform complex mechanical or pneumatic adjustments. 
         [0013]    The invention now provides a modulator valve for installation in the braking system of an auxiliary axle. The modulator valve has a valve body that includes a control port for receiving a brake application pressure signal from the driver&#39;s primary braking system; a lift port for receiving a pressure signal from an auxiliary axle lifting system; a ride port for receiving a pressure signal from a suspension system comprised of ride springs; a supply port for receiving a pressure signal from a supply reservoir; and a delivery port for delivering a pressure signal to the auxiliary axle&#39;s anti-lock brake system. 
         [0014]    Operatively connected to the control port and lift port is a first piston, spring, and valve configuration such that when the auxiliary axle is lifted, no brake application pressure signal is allowed to pass the first piston, spring, and valve configuration, and when the auxiliary axle is not lifted, a brake application pressure signal is allowed to pass the first piston, spring, and valve configuration. 
         [0015]    Operatively connected to the control port, supply port, and delivery port is a modulator piston having an upper surface and a lower surface. The upper surface is separated into distinct areas. The lower surface area of the modulator piston comprises 100% of the sum of the areas of the upper surface of the modulator piston. The lower surface area of the modulator piston is operatively connected to the delivery port. When a brake application pressure signal is received by one or more areas of the upper surface of the modulator piston, the lower surface of the modulator piston in conjunction with pressure from the supply reservoir operates to deliver a modulated pressure signal to the auxiliary axle anti-lock brake system. Also, the ride port is associated with a restricting orifice to dampen vibration effects during operation. 
         [0016]    Operatively connected to the control port, ride port, and modulator piston is a second piston, spring, and valve configuration. The second piston, spring, and valve configuration senses pressure from the ride springs that are part of the truck&#39;s suspension system. When the pressure from the ride springs is less than a certain pressure X 1 , the second piston, spring, and valve configuration operates such that the braking application pressure signal is only felt on one of the distinct areas of the upper surface of the modulator piston. When the pressure signal from the ride springs is greater than a certain threshold X 1 , the second piston, spring, and valve configuration operates such that a brake application pressure signal is delivered to more than one distinct area of the upper surface of the modulator piston. 
         [0017]    Because the force applied to the upper surface of the modulator piston is only applied to a fraction of the total surface area of the upper surface of the modulator piston, the delivery pressure signal applied to the lower surface of the modulator piston need only be a proportionate fraction of the braking application pressure signal to equalize pressure between the upper and lower surfaces of the modulator piston. In other words, if the braking application pressure signal is applied to 50% of the upper surface area of the modulator piston, then only 50% of the brake application pressure signal need be applied to the lower surface of the modulator piston to equalize pressure the two surfaces of the modulator piston, thereby delivering a pressure signal to the auxiliary axle anti-lock brake system that is 50% of the braking application pressure signal. 
         [0018]    In a particular embodiment of the invention, the upper surface of the modulator piston is separated into three distinct areas. The first area preferably comprises 25% of the total area of the upper surface of the modulator piston. The combined areas of the first and second area preferably comprise 50% of the total area of the upper surface of the modulator piston. When ride spring pressure is less than X 1 , the braking application pressure signal is delivered only to the first area of the upper surface of the modulator piston. When ride spring pressure is greater than X 1  but less than X 2 , the braking application pressure signal is delivered to the first and second areas of the upper surface of the modulator piston. When ride spring pressure is greater than X 2 , the braking application pressure signal is delivered to the entire upper surface of the modulator piston. In the above three scenarios, the preferred pressure signal delivered to the auxiliary axle anti-lock brake system will be 25%, 50%, and 100% of the brake application pressure signal, respectively. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0019]    Other features and advantages of the invention will be better understood in the light of the detailed description that follows, with reference to the appended drawings in which: 
           [0020]      FIG. 1  illustrates an external view of the invention; 
           [0021]      FIG. 2  illustrates a top view of the invention and annotates the functional regions of the various components; 
           [0022]      FIG. 3  illustrates a cross section of the invention along its centerline and shows the condition of the invention when the auxiliary axle is in the lifted position; 
           [0023]      FIG. 3S  shows that the cross-section of  FIG. 3  is taken along lines A-A of  FIG. 3S ; 
           [0024]      FIG. 4  illustrates a cross section of the invention along its centerline in normal operating condition with the auxiliary axle not lifted; 
           [0025]      FIG. 4S  shows that the cross-section of  FIG. 4  is taken along lines A-A of  FIG. 4S ; 
           [0026]      FIG. 5  illustrates a cross section of the invention with a pressure signal from the driver&#39;s primary braking system A with the auxiliary axle not lifted; 
           [0027]      FIG. 5S  shows that the cross-section of  FIG. 5  is taken along lines A-A of  FIG. 5S ; 
           [0028]      FIG. 6  illustrates a cross section of the ride pressure gaging portion of the device when ride spring pressure is less than X 1 ; 
           [0029]      FIG. 6S  shows that the cross-section of  FIG. 6  is taken along lines A-A of  FIG. 6S ; 
           [0030]      FIG. 7  illustrates a cross section of the ride pressure gaging portion of the device when ride spring pressure is greater than X 1 , but less than X 2 ; 
           [0031]      FIG. 7S  shows that the cross-section of  FIG. 7  is taken along lines A-A of  FIG. 7S ; 
           [0032]      FIG. 8  illustrates the flow of control pressure from the driver&#39;s primary breaking system through passage  70  to area  62  of modulator piston  6  when ride spring pressure is greater than X 1 , but less than X 2 ; 
           [0033]      FIG. 8S  shows that the cross-section of  FIG. 8  is taken along lines A-A of  FIG. 8S ; 
           [0034]      FIG. 9  illustrates a cross-section of the ride pressure gaging portion of the device when the ride spring pressure is greater than X 2 ; 
           [0035]      FIG. 9S  shows that the cross-section of  FIG. 9  is taken along lines A-A of  FIG. 9S ; 
           [0036]      FIG. 10  illustrates the flow of control pressure from the driver&#39;s primary breaking system through passage  71  to area  63  of modulator piston  6  when the ride spring pressure is greater than X 2 ; 
           [0037]      FIG. 10S  shows that the cross-section of  FIG. 10  is taken along lines A-A of  FIG. 10S ; 
           [0038]      FIG. 11  illustrates the exhaust phase of the invention; and 
           [0039]      FIG. 11S  shows that the cross-section of  FIG. 11  is taken along lines A-A of  FIG. 11S . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0040]    The invention applies to a modulator valve for universal installation in tractors or trucks. The modulator operates to (1) automatically shut off the driver&#39;s brake control signal to the auxiliary axle anti-lock brake system when the auxiliary axle is in the lifted position, (2) determine the relative load carried by the auxiliary axle by measuring the air pressure in the auxiliary ride springs, and (3) modulate the application pressure sent to the auxiliary axle anti-lock brake system relay valve proportionally to the load being carried by that axle. 
         [0041]    An external view of the invention is shown in  FIG. 1 . Control port  1  receives the brake application pressure signal from the driver&#39;s primary brake system A. Lift port  2  receives pressure from lift springs B 1  and B 2 . Ride port  3  receives pressure from pneumatic ride springs C 1  and C 2 . Supply port  4  receives pressure from the system supply reservoir D. Output to the auxiliary axle anti-lock brake system E is connected at delivery port  5 . 
         [0042]    Output pressure from delivery port  5  is preferably selected to be 25% of the pressure signal at control port  1  for any pressure at ride port  3  below X 1  pounds per square inch (“psi”). Output pressure from delivery port  5  is desired to be 50% of the pressure signal at control port  1  for any pressure at ride port  3  above X 1  psi, but less than X 2  psi, where X 1  is less than X 2 . Output pressure from delivery port  5  is desired to be 100% of the pressure signal at control port  1  for any pressure at ride port  3  above X 2  psi. 
         [0043]    The X 1  and X 2  pressures can be selected as desired and can vary over a wide range depending upon the vehicle to which the device is incorporated. Typically, X 2  is greater than X 1  by at least 10% to 50% or more. In preferred embodiments, X 2  may be  1 ,  2  or even  3  times greater than X 1  with X 1  being in the range of 25 to 75 psi. As noted, however, a skilled artisan can select the appropriate values for X 1  and X 2  for any particular vehicle. 
         [0044]      FIG. 2  depicts a top view of the invention and annotates the functional regions of the various components. Lift sensing region  20  houses the components that receive pressure from lift springs B 1  and B 2 . Ride pressure gaging region and control distribution region  30  houses the components that receive pressure from ride springs C 1  and C 2  and the brake application pressure from the driver&#39;s primary brake system A through control port  1 . Delivery pressure modulation region  50  houses the components that effectuate delivery of a modulated pressure to the auxiliary axle anti-lock brake system through delivery port  5 . Mounting bracket  60  allows for universal installation of the invention.  FIG. 3  depicts a cross section of the invention along its centerline and shows the condition of the invention when the auxiliary axle is in the lifted position. Pressure from lift springs B 1  and B 2  flows through lift port  2  and acts upon piston  21 . The force exerted on piston  21  overcomes the return force of springs  22 . Springs  22  therefore compress and the extension of piston  21  is held away from valve seal  23 . As such, the return force of spring  24  is allowed to act upon valve seal  23  to seat and block pressure received from driver&#39;s primary brake system A through control port  1 . The extension of piston  21  is hollow, venting any pressure to atmosphere through exhaust  25 . Accordingly there will be no delivery of pressure to the auxiliary axle&#39;s anti-lock brake system relay because no pressure is passed to the modulation section of the invention, thereby preventing an undesirable false positive anti-lock brake system event. 
         [0045]      FIG. 4  shows a cross section of the invention along its centerline in normal operating condition with the auxiliary axle not lifted. Because the auxiliary axle is not lifted, there is no positive pressure at lift port  2 . With no pressure on piston  21 , return springs  22  are permitted to expand. Such expansion is strong enough so that the extension of piston  21  is allowed to act upon valve seal  23  and overcome the spring force of spring  24 . This results in valve seal  23  being lifted off of its seat, thereby allowing flow into other functional areas of the device from the driver&#39;s primary braking system A in the event of a braking event. As shown, with no pressure applied at control port  1 , there will be no delivery to the auxiliary axle&#39;s anti-lock brake system relay. 
         [0046]      FIG. 5  shows the condition in which the auxiliary axle is not lifted, such that the positive control pressure from the driver&#39;s primary braking system A can flow though control port  1  and into pressure passage  11  into the downstream functions of the invention. Modulator piston  6  is separated by O-ring seals  8  into three separate areas, area  61 , area  62 , and area  63 . Area  61  comprises 25% of the total area of modulator piston  6 . Area  61  and area  62  combine to comprise 50% of the total area of modulator piston  6 . Area  63  makes up the remainder of the total area of modulator piston  6 , namely 25% of the total area. 
         [0047]    The force generated by the control pressure acting on area  61  of modulator piston  6  forces modulator piston  6  downward to seat against seal  64  of exhaust tube  65 . As control pressure rises, the force (area  61  x control pressure) on modulator piston  6  rises and eventually overcomes the spring force of return spring  67 , which unseats seal  66 . 
         [0048]    When seal  66  is unseated, supply pressure from supply reservoir D is permitted to flow through supply port  4 , and act upon the bottom of modulator piston  6 , area  68 . Rising supply pressure on the bottom of modulator piston  6  flows out through delivery port  5  to signal anti-lock brake system E to apply braking pressure. As supply pressure rises at delivery port  5  and against the bottom of modulator piston  6 , modulator piston  6  will rise until the force generated on the bottom of modulator piston  6  (area  68 ×delivery pressure) balances the force on the top of modulator piston  6  (area  61 ×control pressure). As the forces equalize, modulator piston  6  permits return spring  67  to move exhaust tube  65  upward until seal  66  seats and closes the supply. 
         [0049]    Because area  61  in a preferred embodiment is only 25% of area  68 , the delivery pressure at delivery port  5  need only be 25% of the control pressure from the driver&#39;s primary braking system A to equalize the forces felt on the top and bottom of modulator piston  6 . Accordingly, the signal to the auxiliary axle anti-lock brake system E will be modulated to 25% of the control pressure sent to the brake system by the driver&#39;s primary braking system A. Area  61  can be between  15  and 33% of area  68  depending upon the specific braking system of the truck. 
         [0050]      FIG. 6  shows a cross section of the ride pressure gaging portion of the device when ride spring pressure from ride springs C 1  and C 2  flowing through ride port  3  is less than trigger pressure X 1 . In general, pressure from ride springs C 1  and C 2  acts upon gaging pistons  31  and  35 . At pressures below X 1 , springs  32  and  36  have sufficient spring force to hold the extended tube section of gaging pistons  31  and  35  away from seals  33  and  37 . Seals  33  and  37  are held seated by springs  34  and  38 . Seals  33  and  37  block flow of the control pressure from the driver&#39;s primary breaking system A (as shown in  FIG. 5 ) from passages  11   a,    11   b,  and  11   c  to passages  70  and  71 , and then to the top of modulator piston  6  (as shown in  FIG. 5 ). The hollow extensions of gaging pistons  31  and  35  are open to vent to atmosphere though exhaust ports  39   a  and  39   b.  The pressure from ride springs C 1  and C 2  is lower than trigger pressure X 1 , so control pressure from the driver&#39;s primary brake system A is only at area  61  of modulator piston  6 . Areas  62  and  63  are vented to atmosphere. 
         [0051]      FIG. 7  shows a cross section of the ride pressure gaging portion of the device. In  FIG. 7 , the ride spring pressure from ride springs C 1  and C 2  is greater than trigger pressure X 1  but is less that trigger pressure X 2 . Pressure from the ride springs C 1  and C 2  acts upon gaging pistons  31  and  35 . At pressures above X 1 , spring  32  is overcome by pressure applied to piston  31  and the tubular extension of gaging piston  31  is raised to press against seal  33 . The force resulting from the extension of gaging piston  31  against seal  33  is sufficient to overcome the spring force of spring  34 , thereby opening flow into passage  70 , which allows control pressure to be felt at area  62  of modulator piston  6  (as shown in  FIG. 8 ). Springs  36  are not compressed at pressures greater than X 1  but less than X 2 . Therefore, the passage  71  remains closed at this range of ride spring pressures. 
         [0052]      FIG. 8  illustrates the flow of control pressure from the driver&#39;s primary breaking system through passage  70  to area  62  of modulator piston  6 . Area  61  and area  62  are both exposed to control pressure when the ride pressure from ride springs C 1  and C 2  is greater than X 1 . Thus, the control pressure is preferably acting on an area equal to 50% of the total area on the top of modulator piston  6 . 
         [0053]    Because the combined area  61  and area  62  in the preferred embodiment is only 50% of area  68 , the delivery pressure at delivery port  5  need only be 50% of the control pressure from the driver&#39;s primary braking system A to equalize the forces felt on the top and bottom of modulator piston  6 . Accordingly, the signal to the auxiliary axle anti-lock brake system E will be modulated to 50% of the control pressure sent to the brake system by the driver&#39;s primary braking system A when ride pressure is greater than X 1  but less than X 2 . When the combined area is a different proportion of area  68 , the signal will be adjusted accordingly. 
         [0054]      FIG. 9  shows in cross-section the ride pressure gaging portion of the device, when the ride spring pressure C 1  and C 2  is higher than the trigger pressure X 2 . Pressure from the ride springs flows through a restricting orifice  75  and then through chambers  76 ,  77  and  78  to act upon gaging pistons  35  and  31 . The restricting orifice  75  dampens vibration effects. The ride springs C 1  and C 2  compress and expand as irregularities in the rolling surface are encountered, causing transient pressure changes in the ride springs. The restricting orifice  75  limits flow rates to or away from chambers  76 ,  77  and  78 , thereby reducing transient pressure changes acting on pistons  31  and  35 . At pressures above X 2 , springs  32  and  36  are overcome, moving the extended tube section of pistons  31  and  35  into contact with seals  33  and  37 , which are held seated by springs  34  and  38 . The passages  70  and  71  leading to the modulating piston  6 , are opened to flow of the control pressure from passages  11   a,    11   b  and  11   c  to the top of piston  6 , as shown in  FIGS. 8 and 10 . The hollow extensions of pistons  31  and  35  are closed by seals  33  and  37 . 
         [0055]      FIG. 10  illustrates the flow of control pressure from the driver&#39;s primary breaking system through passage  71  to area  63  of modulator piston  6 . Areas  61 ,  62 , and  63  are all exposed to control pressure when the ride pressure from ride springs C 1  and C 2  is greater than X 2 . Thus, the control pressure is acting on an area equal to 100% of the total area on the top of modulator piston  6 . 
         [0056]    Because the combined areas of area  61 ,  62  and area  63  is 100% of area  68 , the delivery pressure at delivery port  5  must be 100% of the control pressure from the driver&#39;s primary braking system A to equalize the forces felt on the top and bottom of modulator piston  6 . Accordingly, the signal to the auxiliary axle anti-lock brake system E will be 100% of the control pressure sent to the brake system by the driver&#39;s primary braking system A when ride pressure is greater than X 2 . 
         [0057]      FIG. 11  depicts the exhaust phase of the invention. The driver has released the brake application, venting the control pressure from control port  1 , passage  11 , and the top of modulator piston  6 . Once the forces on top of modulator piston  6  are removed, the delivery pressure acting on area  68  will cause modulator piston  6  to lift off of seal  64 . This allows delivery pressure to flow through exhaust tube  65  and out to the atmosphere through exhaust  69 . Additionally, after pressure is vented from modulator piston  6 , the force of spring  67  acts to reseat seal  66 , thereby preventing pressure from supply reservoir D from acting upon area  68 . 
         [0058]    The exemplary embodiment has been described with reference to the non-limiting preferred embodiments. Obviously, modification and alterations will occur to others upon reading and understanding the preceding detailed description. As noted above, the preferred area ratios can be varied as desired for optimizing performance without departing from the invention. It is intended that the exemplary embodiment be construed as including all such modification and alterations insofar as they come within the scope of the appended claims or equivalents thereof