Relay Valve Control Arrangement to Provide Variable Response Timing on Full Applications

Abstract

A brake system and related components including a metering device are configured to regulate a control signal received from a brake control device such that a control valve delays the supply of a level of requested braking pressure for a prescribed amount of time. The metering device can be an inversion valve and orificed check valve in a control circuit adapted to allow relatively unrestricted flow until a threshold pressure is reached, after which pressure the inversion valve closes and the flow is metered through an orifice. This has the effect of allowing rapid brake actuation to a first level, and then slowing further application of the brake until full requested braking is achieved. An electronic control unit can also be configured to regulate a control signal to delay development of the requested brake pressure.

1 . An electronic control unit for controlling delivery pressure to an associated braking unit:
 an input for receiving a pressure signal indicative of a requested level of delivery pressure;   a controller operative to regulate a control signal such that the pressure delivered to an associated braking unit increases at a first rate until a threshold pressure value is reached and increases at a second rate between the threshold pressure value and the requested level of delivery pressure, wherein the second rate is slower than the first rate; and   an output for transmitting the control signal.   
     
     
         2 . The electronic control unit as set forth in  claim 1 , wherein the controller is further operative to determine the threshold pressure value in response to receiving the pressure signal indicative of the requested level of delivery pressure. 
     
     
         3 . The electronic control unit as set forth in  claim 2 , wherein the threshold pressure value is a percentage of the requested level of delivery pressure. 
     
     
         4 . The electronic control unit as set forth in  claim 2 , wherein the threshold pressure value is a percentage of the maximum braking power. 
     
     
         5 . The electronic control unit as set forth in  claim 1 , wherein the threshold pressure value is about sixty psi. 
     
     
         6 . The electronic control unit as set forth in  claim 1 , wherein the controller is operative to regulate the control signal at the first rate until the threshold pressure value is reached at the associated braking unit and to regulate the control signal at the second rate until the requested level of delivery pressure is reached at the associated braking unit, in response to the requested level of delivery pressure exceeding the threshold pressure value. 
     
     
         7 . The electronic control unit as set forth in  claim 1 , wherein the control signal is a pneumatic control signal. 
     
     
         8 . The electronic control unit as set forth in  claim 1 , wherein the electronic control unit transmits the control signal to an associated control valve. 
     
     
         9 . The electronic control unit as set forth in  claim 8 , wherein the electronic control unit is in a common housing with the associated control valve. 
     
     
         10 . The electronic control unit as set forth in  claim 1 , wherein the control signal is an electrical control signal. 
     
     
         11 . A method of controlling a delivery pressure comprising:
 receiving at least one pressure signal indicative of a requested level of delivery pressure;   transmitting a control signal to an associated control valve such that the associated control valve delivers pressure to an associated braking unit at a first rate until a threshold pressure value is reached; and   transmitting the control signal at a second rate to deliver pressure to the associated braking unit until the requested level of delivery pressure is reached, wherein the second rate is slower than the first rate.   
     
     
         12 . The method as set forth in  claim 11 , wherein transmitting the control signal at the second rate includes generating a pulse width modulated signal. 
     
     
         13 . The method as set forth in  claim 11 , wherein transmitting the control signal at the second rate includes slowing the supply of pressure to the associated braking unit when the delivered pressure exceeds the threshold pressure value. 
     
     
         14 . The method as set forth in  claim 11 , further comprising: determining the threshold pressure based on the requested level of delivery pressure. 
     
     
         15 . The method as set forth in  claim 14 , wherein determining the threshold pressure is based on a percentage of the requested level of delivery pressure. 
     
     
         16 . The method as set forth in  claim 14 , wherein determining the threshold pressure is based on a percentage of a maximum braking power. 
     
     
         17 . The method as set forth in  claim 11 , further comprising comparing the delivered pressure to the threshold pressure value and the requested level of delivery pressure during transmission of the control signal. 
     
     
         18 . An electronic control unit for controlling an associated control valve comprising:
 an input for receiving a pressure signal indicative of a requested level of delivery pressure;   a means for regulating a control signal to deliver pressure at a first rate until a threshold pressure; and   a means for regulating the control signal to deliver pressure at a second rate between the threshold pressure and the requested level of delivery pressure;   wherein the second rate is slower than the first rate.   
     
     
         19 . An electronic control unit a set forth in  claim 18 , further comprising:
 a means for determining the threshold pressure.