Patent Publication Number: US-2006017317-A1

Title: Selective actuation of secondary circuit of dual brake valve

Description:
BACKGROUND OF THE INVENTION  
      1. Technical Field  
      This invention relates to braking systems for vehicles and, in particular, to the provision of advanced braking functions by use of a dual brake valve, or brake valve actuator, of a vehicle.  
      2. Description of the Prior Art  
      Over-the-highway vehicles typically have a primary braking system and a separate secondary braking system. A dual brake valve, or brake valve actuator, has primary and secondary circuits that control the primary and secondary braking systems, respectively, of the vehicle. When the vehicle brake pedal is depressed there is a direct mechanical movement of a piston in the primary circuit, sending primary supply air to primary delivery. Some of this air is ported to the piston of the secondary circuit, moving it to cause the sending of secondary supply air to secondary delivery. The secondary piston is not driven mechanically by the brake pedal unless there is a primary air failure and the primary piston moves far enough, under pedal pressure, that it mechanically engages the secondary piston.  
      Some over-the-highway vehicles with anti-lock braking system (ABS) also have an automatic traction control (ATC) function, in which braking of the driven wheels is provided without driver demand, to control wheel slippage due to engine power and low traction surfaces. This ATC function is provided typically with an ATC valve, which is an on-off valve controlled by an electronic control unit (ECU) of the vehicle braking system. When ATC is desired, the ECU opens the ATC valve, which directs air pressure to the brakes of the driven wheels through their ABS modulators. The modulators control the on-off of the supply air that is present, thus controlling the actual brake actuation.  
      To make a roll stability program or electronic stability program for such a vehicle, it is necessary to control also the non-driven wheels of the vehicle (for example the front axle). One needs to be able to apply selectively the brakes of the non-driven wheels, without driver interaction—including the brakes of the trailer. This function is typically accomplished by copying the ATC hardware from the primary circuit for the driven wheels, for use with the non-driven wheels in the secondary braking system. The secondary braking system is, as a result, actuated without pressing the brake pedal. The resulting system is relatively complex.  
      As an example,  FIG. 1  shows one prior art hardware arrangement that is used for obtaining roll stability on a straight truck or bus (no trailer). The primary circuit of the dual brake valve provides driver control pressure to a relay valve (designated ATC) having an ATC solenoid, associated with the driven wheels. Supply air from the primary reservoir, as passed by the relay valve, goes to the vehicle&#39;s rear (to the right as viewed in  FIG. 1 ) ABS wheel end modulators. The solenoid on the relay valve, and the modulators, are all under the control of the ECU, to which also is connected vehicle condition sensors (not shown in  FIG. 1 ).  
      The secondary circuit of the dual brake valve provides driver control pressure to a relay valve having an ATC solenoid, associated with the non-driven (front) wheels. Supply air from the secondary reservoir, as passed by the relay valve, goes to the vehicle&#39;s front ABS wheel end modulators. The solenoid on the relay valve, and the modulators, are all under the control of the ECU. Because both the front and rear relay valves are controllable by ATC solenoids, they have reservoir air going to them, bypassing the dual brake valve, and so they can be actuated at any time with or without driver intervention, to brake the wheels.  
      In the prior art system shown in  FIG. 1 , the rear wheels (or driven wheels) are controllable in this manner for ABS and ATC, and also for stability functions. When a stability function is initiated, in response to a signal from a vehicle condition sensor, braking effect is provided at all wheels, and the ABS function is used simultaneously to prevent wheel lockup. The front wheels (or non-driven wheels) are controllable in this manner for ABS and roll stability and electronic stability functions only.  
      The prior art system shown in  FIG. 1  also includes a pressure sensor in the secondary delivery line and a pressure sensor in the primary delivery line. These sensors sense the pressure at the delivery of the brake valve, to indicate driver demand, and deliver that indication as input to the ECU to use in controlling the event. This also indicates the potential pressure that can be delivered to the brake chambers, so that the ECU can select between driver requested pressure and stability function requested pressure. This prior art system thus requires, on top of the ABS hardware, two pressure sensors and two ATC solenoids, plus a secondary circuit relay, in order to be able to perform the stability function.  
     SUMMARY OF THE INVENTION  
      The present invention relates to an apparatus including a dual brake valve having a primary circuit for pressurizing a primary vehicle braking system in response to application of force to a brake pedal of the vehicle, and having a secondary circuit for pressurizing a secondary vehicle braking system in response to application of the primary circuit or force to the brake pedal. The apparatus also includes an actuator for, when energized, actuating the secondary circuit independently of the primary circuit or the vehicle brake pedal.  
      The present invention also relates to a braking system including a dual brake valve having a primary circuit for pressurizing a primary vehicle braking system in response to application of force to a brake pedal of the vehicle, and having a secondary circuit for pressurizing a secondary vehicle braking system in response to application of the primary circuit or force to the brake pedal. The system includes one or more sensors for sensing a vehicle condition for which pressurizing of the secondary braking system is desired and for outputting a sensor output signal. The system also includes an electronic control unit electrically connected with the sensors to receive the sensor output signal. The electronic control unit is responsive to the sensor output signal to output an actuator control signal. The system further includes an actuator operatively connected with the sensor to receive the actuator control signal and to actuate the secondary circuit of the dual brake valve independently of the vehicle brake pedal.  
      The present invention also relates to apparatus including a dual brake valve having a primary circuit for pressurizing a primary vehicle braking system in response to application of force to a brake pedal of the vehicle, and a secondary circuit for pressurizing a secondary vehicle braking system in response to application of the primary circuit or force to the brake pedal. The apparatus also includes means for actuating the secondary circuit of the dual brake valve in response to the actuator control signal.  
      The present invention also relates to a method of pressurizing a secondary braking system of a vehicle that also has a primary braking system, the vehicle having a dual brake valve that includes a primary circuit for pressurizing the primary system in response to application of force to a brake pedal of the vehicle and a secondary circuit for pressurizing the secondary system in response to application of the primary circuit or force to the brake pedal. The method includes the steps of sensing a vehicle condition for which it is desired that pressurizing of the secondary braking system is desired independently of application of force to the brake pedal, and in response to the sensing, actuating the secondary circuit of the dual brake valve without actuating the primary circuit of the dual brake valve. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a schematic illustration of a prior art vehicle braking system;  
       FIG. 2  is a schematic illustration of a vehicle braking system in accordance with the present invention;  
       FIG. 3  is an illustration of a prior art dual brake valve;  
       FIG. 4  is a schematic illustration showing a first embodiment of the present invention;  
       FIG. 5  is a schematic illustration showing a second embodiment of the present invention;  
       FIG. 6  is a schematic illustration of dual brake valve showing a third embodiment of the present invention;  
       FIG. 7  is a schematic illustration of dual brake valve showing a fourth embodiment of the present invention; and  
       FIG. 8  is a schematic illustration of dual brake valve showing a fifth embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      This invention relates to braking systems for vehicles and, in particular, to the provision of advanced braking functions by use of a dual brake valve, or brake valve actuator, of a vehicle. The dual brake valve might be modified or might be used unmodified. As representative of the invention,  FIG. 2  shows schematically a hardware arrangement or system  10  in accordance with the present invention that is used for obtaining advanced stability on a straight truck or bus  12  (no trailer). In this regard, the system of  FIG. 2  can replace the prior art system of  FIG. 1 .  
      The system  10  includes a primary braking system  13  and a secondary braking system  14 . In the system  10  that is shown in  FIG. 2 , the ATC valve and relay for the secondary braking system  14  of the vehicle circuit is replaced with a simple quick release valve  17 , or is eliminated completely.  
      The system  10  of  FIG. 2  includes a dual brake valve, or brake valve actuator,  20 . One or more vehicle condition sensors  22  is connected with an ECU  18 , for sensing a vehicle condition for which pressurizing of the secondary braking system  14  of the vehicle  12  is desired, for example, to perform an advanced braking function. The sensor(s)  22  provides or sends an appropriate sensor output signal to the ECU  18 . The ECU  18  receives the sensor output signal and provides or sends an appropriate actuator control signal to an actuator  64 - 64   d  ( FIGS. 4-8 ) for actuating a secondary circuit of the dual brake valve  20 .  
       FIG. 3  illustrates an unmodified (prior art) dual brake valve  20  having a primary circuit  46  and a secondary circuit  58 . The dual brake valve  20  as shown in  FIG. 3  includes a housing  32 . Supported for sliding movement in the housing  32  are a first or primary piston  34 , and a second or secondary piston  36 . When the vehicle operator depresses the brake pedal  38 , a force is applied in the direction of the arrow  40 , that is, downward as viewed in  FIG. 3 . This force is mechanically transmitted to the primary piston  34 , which moves in the housing  32  in the direction  40 .  
      The movement of the primary piston  34  moves the primary piston off a seat, enabling air to flow from a supply port  44  of the primary circuit  46  to a delivery port  48  of the primary circuit. At the same time, a small amount of the primary circuit supply air is directed through an opening or passage  50  to a chamber  52  in which the secondary piston  36  is located. This supply air acts as a pilot pressure, moving the secondary piston  36  downward. The downward movement of the secondary piston  36  moves the secondary piston off a seat  54 , enabling air to flow from a supply port  56  of the secondary circuit  58  to a delivery port  60  of the secondary circuit.  
      With the prior art dual brake valve  20  the secondary circuit  58  is actuated only in response to actuation of the primary circuit  46 . The secondary circuit  58  is never actuated alone. The secondary piston  36  is not driven mechanically by the brake pedal  38  unless in an emergency (a primary air failure) in which case the primary piston  34  moves far enough, under pedal pressure, that it engages the secondary piston.  
      In a first embodiment of the invention, shown schematically in  FIG. 4 , the system  10  includes a shuttle valve  62  that serves as an actuator  64  for the secondary circuit  58  of the dual brake valve  20 . The shuttle valve  62  has one input shown schematically at  66  that receives the pilot pressure from the primary circuit  46  of the dual brake valve  20 , shown schematically at  66 . The shuttle valve  62  has an auxiliary input shown schematically at  68  that receives an auxiliary pressure from a source (not shown) such as secondary supply and that is controlled by the ECU  18 . The output of the shuttle valve  62  is connected to the chamber  52  of the secondary circuit  58  of the dual brake valve  20 , as shown schematically at  70 .  
      The system  10  including the ECU  18  is configured so that, during normal operation of the braking system, the pressure at the auxiliary input  68  is less than the pilot pressure at the input  66 , for example, zero. In this case, a ball  72  in the shuttle valve  62  is located at the auxiliary input  68 . As a result, the pilot pressure from the primary circuit  46  of the dual brake valve  20  is delivered to the output  70  of the shuttle valve  62  and acts to control actuation of the secondary circuit  58  of the dual brake valve  20 .  
      In the event that it is desired to actuate the secondary circuit  58  of the dual brake valve  20  independently of the primary circuit  46 , for example, to provide secondary circuit braking for stability purposes, the ECU  18  acts to provide an auxiliary pressure at the auxiliary input  68  of the shuttle valve  62  that is greater than the pressure at the input  66  from the primary circuit. This action in effect energizes the shuttle valve  62 . Because the auxiliary pressure is greater than the input pressure delivered from the primary circuit  46  of the dual brake valve  20 , the auxiliary input pressure is delivered to the output  70  of the shuttle valve  62  and thence to the chamber  52  of the secondary circuit  58  of the dual brake valve  20 . As a result, the secondary piston  36  is moved to allow air to flow from the secondary supply  56  to the secondary delivery  60 . The advanced braking functions can thus be effected.  
      The shuttle valve  62  can be incorporated in the system  10  in various different ways. For example, additional porting can be provided on the dual brake valve  20  to enable the extra output from the primary circuit  46  and the extra input to the secondary chamber  52 . The shuttle valve  62  can be mounted on the side of the dual brake valve  20 . Thus, the shuttle valve  62  or in fact any of the actuators of the present invention might be considered to be part of the dual brake valve  20 .  
      In a second embodiment of the invention, shown schematically in  FIG. 5 , the system  10  includes an actuator  64   a  for the secondary circuit  58  of the dual brake valve  20 . The actuator  64   a  includes an additional control surface, or additional piston  80 , for actuating the secondary circuit  58  of the dual brake valve  20 .  
      The additional piston or secondary piston  80 , as shown schematically in  FIG. 5 , is interposed between the primary circuit  46  and the secondary circuit  58  of the dual brake valve  20 . The secondary circuit  58  remains operable by pilot pressure from the primary circuit  46 , as is indicated by the dashed line  50 . The additional piston  80  is additionally energizable by an auxiliary or control pressure  82  that is received from a source (not shown) such as secondary supply and that is controlled by the ECU  18 .  
      The ECU  18  is configured so that, during normal operation of the braking system  10 , the auxiliary pressure  82  at the auxiliary piston  80  input is less than the pilot pressure  50  at the input from the primary circuit  46 , for example, zero. As a result, the pilot pressure  50  from the primary circuit  46  of the dual brake valve  20  acts to control actuation of the secondary circuit  58 .  
      In the event that it is desired to actuate the secondary circuit  58  of the dual brake valve  20  independently of the primary circuit  46 , for example, to provide secondary circuit braking for stability purposes, the ECU  18  acts to provide an auxiliary pressure  82 , at the auxiliary piston  80 , that is greater than the pressure  50  from the primary circuit  46 . This action energizes the actuator  64   a.  Specifically, the additional piston  80  is moved and causes the secondary piston  36  of the dual brake valve  20  to be actuated. As a result, the secondary piston  36  is moved to allow air to flow from the secondary supply  56  to the secondary delivery  60 , so that advanced braking functions can be effected. The additional piston  80  can be incorporated in the vehicle braking system  10  in various different ways, for example within or attached to the housing  32  of the dual brake valve  20 , within the skill of the art.  
      In a third embodiment of the invention, shown schematically in  FIG. 6 , the system  10  includes an electric actuator  64   b  for actuating the secondary circuit  58  of the dual brake valve  20 . The electric actuator  64   b , as shown schematically in  FIG. 6 , is associated with the secondary circuit  58  of the dual brake valve  20 . The secondary circuit  58  remains operable by pilot pressure from the primary circuit  46 , as is indicated by the dashed line  50 .  
      The electric actuator  64   b  may be a solenoid  84  having a coil  86  and a movable member  88  that is connected with the secondary piston  36  of the dual brake valve  20 . The actuator  64   b  can be incorporated in various ways, for example within or attached to the housing  32  of the dual brake valve  20 , within the skill of the art. The actuator  64   b  in the embodiment of  FIG. 6  is located between the primary piston  34  and the secondary piston  36  of the dual brake valve  20  so that the movable member  88  of the actuator, when energized by a current through the coil  86 , pushes the secondary piston down away from the primary piston.  
      The electric actuator  64   b  is operable by a control signal from the ECU  18 . The ECU  18  is configured so that, during normal operation of the braking system  10 , the electric actuator  64   b  is not energized. As a result, the pilot pressure  50  from the primary circuit  46  of the dual brake valve  20  acts to control actuation of the secondary circuit  58 , in a manner as described above.  
      In the event that it is desired to actuate the secondary circuit  58  of the dual brake valve  20  independently of the primary circuit  46 , for example, to provide secondary circuit braking for stability purposes, the ECU  18  acts to energize the actuator  64   b , for example, by sending an appropriate current through the coil  86 . The actuator  64   b  is energized and the movable member  88  is moved, causing the secondary piston  36  of the dual brake valve  20  to be pushed down away from the primary piston  34 . As a result, the secondary piston  36  is moved to allow air to flow from the secondary supply  56  to the secondary delivery  60 , so that advanced braking functions can be effected.  
      In a fourth embodiment of the invention, shown schematically in  FIG. 7 , the system  10  includes an actuator  64   c  that includes an additional control surface, or additional piston  90 , for actuating the secondary circuit  58  of the dual brake valve  20 . The additional piston  90 , as shown schematically in  FIG. 7 , is disposed below the secondary circuit  58  of the dual brake valve  20 , adjacent the exhaust end of the dual brake valve, so that, when actuated, it pulls the secondary piston down  36 , away from the primary piston  34 . The secondary circuit  56  of the dual brake valve  20  remains operable by pilot pressure from the primary circuit  46 , as is indicated by the dashed line  50 . The additional piston  90  is alternatively operable through an auxiliary input  92  by an auxiliary or control pressure that is received from a source (not shown) such as the secondary supply and that is controlled by the ECU  18 .  
      The additional piston  90  is part of an additional pneumatic actuator  64   c  and can be incorporated in various ways, within or attached to the housing  32  of the dual brake valve  20 , within the skill of the art. The actuator  64   c  in the embodiment of  FIG. 7  is located below the secondary circuit  56  of the dual brake valve  20 , so that the additional piston  90 , when actuated, pulls the secondary piston  36  away from the primary piston  34 .  
      The ECU  18  is configured so that, during normal operation of the braking system  10 , the additional pneumatic actuator  64   c  is not actuated. As a result, the pilot pressure  50  from the primary circuit  46  of the dual brake valve  20  acts to control actuation of the secondary circuit  58 , in a manner as described above.  
      In the event that it is desired to actuate the secondary circuit  58  of the dual brake valve  20  independently of the primary circuit  46 , for example, to provide secondary circuit braking for stability purposes, the ECU  18  acts to provide a suitable auxiliary pressure  92  to the additional piston  90 . The pneumatic actuator  64   c  is energized and causes the secondary piston  36  of the dual brake valve  20  to be pulled away from the primary piston  34 . As a result, the secondary piston  36  is moved to allow air to flow from the secondary supply  56  to the secondary delivery  60 .  
      In a fifth embodiment of the invention, shown schematically in  FIG. 8 , the system  10  includes an electric actuator  64   d  for actuating the secondary circuit  58  of the dual brake valve  20 . The electric actuator  64   d , as shown schematically in  FIG. 8 , is associated with the secondary circuit  58  of the dual brake valve  20 . The secondary circuit  58  remains operable by pilot pressure from the primary circuit, as is indicated by the dashed line  50 .  
      The electric actuator  64   d  may be a solenoid  94  having a coil  96  and a movable member  98  that is connected with the secondary piston  36  of the dual brake valve  20 . The actuator  64   d  can be incorporated in various ways, for example within or attached to the housing  32  of the dual brake valve  20 , within the skill of the art. The actuator  64   d  in the embodiment of  FIG. 8  is located below the secondary circuit  58  of the dual brake valve  20 , adjacent the exhaust end of the valve  20 , so that the movable member  98  of the actuator, when energized, pulls the secondary piston  36  away from the primary piston  34 . The electric actuator  64   d  is operable by a control signal from the ECU  18 .  
      The ECU  18  is configured so that, during normal operation of the braking system  10 , the electric actuator  64   d  is not energized. As a result, the pilot pressure  50  from the primary circuit  46  of the dual brake valve  20  acts to control actuation of the secondary circuit  58 , in a manner as described above.  
      In the event that it is desired to actuate the secondary circuit  58  of the dual brake valve  20  independently of the primary circuit  46 , for example, to provide secondary circuit braking for stability purposes, the ECU  18  acts to energize the actuator  64   d  by, for example, sending an appropriate current through the coil  96 . The actuator  64   d  is energized and causes the secondary piston  36  of the dual brake valve  20  to be pulled away from the primary piston  34 . As a result, the secondary piston  36  is moved to allow air to flow from the secondary supply  56  to the secondary delivery  60 .