Abstract:
The present invention relates to a vehicle brake system, which has a brake reservoir, and utilizes a tire management system that is in communication with the brake reservoir and a vehicle operator. As a result of this configuration, the tire management system communicates brake reservoir pressure signals to the vehicle operator, so-that the operator is made aware of any low pressure conditions, in the trailer, before trying to move the trailer.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to a system for monitoring the pressure in a vehicle brake system, while utilizing a tire management system. More particularly, the present invention relates to a system and a method for monitoring the pressure in a vehicle brake reservoir, where a vehicle has an attached trailer that utilizes an existing tire management system.  
       BACKGROUND OF THE INVENTION  
       [0002]     Those skilled in the art know that vehicles have a brake system (VBS), which, typically, has a brake reservoir for providing proper pressure levels of fluid (such as, air or a hydraulic fluid) within the brake system. It is further known that some vehicles (for example, trucks and tractors that pull trailers) have a tire management system (TMS), which uses pressurized air from a VBS reservoir to maintain pneumatic pressure in the vehicle tires. Often, the TMS is associated with a trailer attached to the vehicle.  
         [0003]     Unfortunately, current vehicle air brake systems, with “spring brake priority,” allow a vehicle operator to move the trailer, regardless of the pressure level in the VBS reservoir. Consequently, it is possible to operate the trailer without adequate VBS reservoir pressure to stop the trailer. Low VBS reservoir pressure may be caused by a number of factors, for example, a faulty spring brake valve or a significant, though not gross, leak in the reservoir itself. In other circumstances (such as in a multiple trailer application), VBS reservoir pressure may be too low to hold off the spring brakes, resulting in overheated brakes.  
         [0004]     Examples of relevant art involving a brake air pressure supply or VBS reservoir pressure are as follows. U.S. Pat. No. 4,593,954 to Campanini describes an air brake valve system. The air brake valve system has a valve cluster on the trailer responsible for filling and protecting the pressure in the air reservoir tank. The valve cluster has a low pressure warning means in the tractor to warn the operator of low air reservoir tank pressure. The valve cluster comprises a mechanical system that determines when the air reservoir tank pressure is too low.  
         [0005]     U.S. Pat. No. 4,763,959 to Vandermotter provides for an electronic control for a vehicle braking system. The system includes a supply reservoir connected to the compressor of the vehicle. A pressure sensor is directly connected to the supply reservoir, which is connected to a front and a rear service reservoir. The front and rear service reservoir each have individual pressure sensors. These pressure sensors are connected to an electronic control unit, which monitors these pressure sensors.  
         [0006]     U.S. Pat. No. 4,877,294 to Kuhn et al. teaches a tractor-trailer braking system having an electric pressure transducer disposed to sense the pressure of compressed air in the pneumatic power supply. The pressure transducer is mounted on the supply tank to sense the pressure inside of the tank. Kuhn also indicates that the transducer acts via electronics to operate an alarm in the operator&#39;s compartment, should the sensed pressure increase above, or decrease below, a predetermined amount.  
         [0007]     U.S. Pat. No. 5,172,958 to Sell discloses a similar air brake valve system to that in Campanini, discussed above, however, the disclosure in Sell indicates three valve clusters can be used. A first valve cluster controls the passage of compressed air from the emergency gladhand supply line to the spring air brakes. A second valve cluster controls the filling and protection of the air reservoir tank. The third valve cluster eliminates compounding of the braking forces by the service brakes when the spring brakes have been applied.  
         [0008]     U.S. Pat. No. 5,533,866 to Malecha teaches a pressurized air brake system for a vehicle comprising a first reservoir and a second reservoir connected to an air compressor. The first and second reservoirs are connected to a control system. The control system is also connected to the compressor for actuating and disengaging the compressor in response to air pressure levels in the first and second reservoirs. Malecha indicates that the reservoirs are connected to service brakes of the tandem and trailer, parking brakes, and wipers, however, other components can also be connected to the reservoirs. Each reservoir has a switch containing a pressure diaphragm. The diaphragms toggle between activated positions and deactivated positions in response to air pressure changes in the reservoirs. Malecha also states that microprocessors and air pressure sensors can be used to monitor reservoir air pressure and control the compression of air by the air compressor.  
         [0009]     U.S. Pat. No. 5,592,754 to Krieder et al. provides for a pressure transducer connected to a reservoir to sense the pressure in the reservoir. The transducer provides an electrical signal indicative of the pressure in the reservoir to an electronic controller. The controller uses the signal to control three different outputs: a low pressure warning lamp, a compressor control solenoid and a purge control solenoid. Krieder teaches that the controller is designed to control these items in lieu of three separate mechanical units.  
         [0010]     U.S. Pat. No. 6,079,436 to Delfs et al. discloses a pressure sensor connected to an air supply line between a check valve and the compressed air container. The sensor communicates the sensed pressure to control electronics. The control electronics signal one of two pressure regulating valves. The valve is connected to an outlet valve that allows air from a compressor to at least one compressed air consumer.  
         [0011]     U.S. Pat. No. 6,682,459 to Knight teaches a vehicle brake compressed air supply system having an electronic air charge controller (EAC) and a first and a second pressure sensor. The first pressure sensor measures the pressure within a line connected to a supply reservoir. The pressure in the line is indicative of the pressure in the reservoir. The sensed pressure is sent to the EAC so that it can determine if the pressure in the reservoir is below a pre-determined amount. If the pressure is below the pre-determined amount, a signal is sent to the engine to increase RPM.  
         [0012]     It would, however, be safer and economically advantageous for a vehicle to utilize a vehicle brake systems in conjunction with an existing tire management system, to detect and warn the vehicle operator of low brake pressure conditions.  
       SUMMARY OF THE INVENTION  
       [0013]     The present invention relates to a vehicle brake system, which has a brake reservoir that is in communication with a vehicle tire management system, which has a transducer that is in communication with a vehicle operator. As a result of this arrangement, the transducer communicates brake reservoir pressure signals to the vehicle operator so that the vehicle operator is aware of low brake pressure conditions in the vehicle.  
         [0014]     Further advantages of the present invention will be apparent from the following description and appended claims, reference being made to the accompanying drawings forming a part of a specification, wherein like reference characters designate corresponding parts of several views. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]      FIG. 1  is a diagrammatical illustration of a vehicle in accordance with the present invention;  
         [0016]      FIG. 2  is a schematic circuit in accordance with the vehicle of  FIG. 1 ; and  
         [0017]      FIG. 3  is a flow chart of the logic in accordance with the present invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0018]     It is to be understood that the invention may assume various alternative orientations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions, directions or other physical characteristics relating to the embodiments disclosed are not to be considered as limiting, unless the claims expressly state otherwise.  
         [0019]      FIG. 1  is a diagrammatical illustration of a vehicle  10 , which may be, for example, a truck or a tractor, with a vehicle brake pressure monitor system (VPM)  20  disposed therewith. As illustrated, the vehicle  10  has an attached trailer  25 . The vehicle  10  comprises a vehicle electronic control unit  12  (ECU), which may be a part of an engine, and a compartment  15 , where a vehicle operator would be located. The vehicle  10  also-comprises a warning device  16 , which is in electrical communication with the ECU  12  by way of a first electrical line  17 .  
         [0020]     The VPM  20  comprises a brake reservoir  30  (provided on heavy duty truck trailers) that is part of a vehicle brake system  35  (VBS), a pressure protection valve  28 , and a tire management system  40  (TMS). The TMS  40  may be a tire management system already installed on the vehicle  10 . The TMS  40  is utilized to maintain a certain level of air pressure in the vehicle tires (not shown). The VBS  35  utilizes the brake reservoir  30  to assure that a level of air pressure is sustained and is available to the VBS  35  for proper braking of the vehicle  10 . The pressure protection valve  28  is utilized in the VPM  20  to only allow air flow through the TMS  40  and then onto the tires, if the air pressure in the reservoir  30  is above a pre-set pressure limit. This design prevents the TMS  40  from depleting pressurized air from the brake reservoir  30  at the expense of the safety critical vehicle brake system  35 .  
         [0021]     It should be appreciated that in the present invention the trailer  25  is not required. In this embodiment, the truck or tractor, itself, would comprise the VPM  20 , the TMS  40 , and the VBS  35  with the brake reservoir  30 . This embodiment, however, would function much the same as that described above for the embodiment with the trailer  25 .  
         [0022]     Again referring to  FIG. 1 , the TMS  40  comprises a first air line  27  that provides pressurized air from the brake reservoir  30  to a supply solenoid  46 . The supply solenoid passes the pressurized air to a second air line  49 . The air line  49  provides the pressurized air to, for example, the tires for maintaining air pressure within the tires. In turn, the air line  49  is connected to a pressure transducer  44 , which already exists in the TMS  40 .  
         [0023]     It is a discovery of the present invention that an additional transducer is not required for communicating the pressure within the brake reservoir  30  to the ECU  12 , since the existing transducer  44  may be utilized. In the present invention, the communicating of the pressure within the brake reservoir  30  is provided via a second electrical line  47 . The second electrical line  47  electrically communications between the pressure transducer  44  and a controller  45  (a.k.a., tire management electronic control unit). The controller  45  would be disposed on the trailer  25  (or truck/tractor) and then electrically communicate brake pressure signals and/or various warning signals to the vehicle ECU  12  via a third electrical line  18 .  
         [0024]     It should be appreciated that the electronic control function provided by the controller  45  could be provided by a different controller (not shown) that might be disposed elsewhere on the trailer  25  (or truck/tractor), or by the vehicle ECU  12  itself, and still remain within the spirit and scope of the present invention.  
         [0025]      FIG. 2  illustrates a schematic circuit of the TMS  40 , which comprises the first air line  27 , a supply solenoid  46 , a bleed air line  41 , the pressure transducer  44 , an exhaust valve  43 , and a control solenoid  42 . The first air line  27  has the supply solenoid  46  connected thereto. The bleed air line  41  is connected to the first air line  27  but bypasses the supply solenoid  46 . The pressure transducer  44  is connected to the second air line  49  downstream of the supply solenoid  46 , and the exhaust valve  43  is downstream of the pressure transducer  44  on the second air line  49 . The exhaust valve  43  is controlled by the control solenoid  42  via control line  48 , and the control solenoid  42  is connected to the first air line  27 .  
         [0026]     The air pressure (e.g., in pounds per square inch) in the brake air reservoir  30  is determined by sensing air pressure within the first air line  27  of the tire management system  40  with the pressure transducer  44 . The pressure transducer  44  provides an electronic signal based on the monitored air pressure in the first air line  27 . This electronic signal is transmitted to the tire management electronic control unit  45  of the vehicle  10 .  
         [0027]     The tire management electronic control unit  45  calculates an air pressure of the brake air reservoir  30  and then communicates a calculated air pressure signal of the brake air reservoir  30  to an operator of the vehicle  10  (for example, by way of the ECU  12  on the third electrical line  18 , and then on to the warning device  16  in the vehicle compartment  15  by way of first electrical line  13 ). When the warning is activated, it is optionally possible that a data link message is generated (see  FIG. 3  and the discussion below).  
         [0028]     The warning device  16  may take, for example, the form of a pressure read out and/or lights to indicate the pressure levels. It is also conceivable to mount a warning lamp on the nose of the trailer  25 . The warning devices  16  could be devices that are common in the art.  
         [0029]     Illustrated in  FIG. 3  is a flow chart of the logic of the present invention, where the brake reservoir  30  is in pneumatic communication with the tire management system  40 . The pressure transducer  44  is in electrical communication with the controller  45 . The controller  45  is also in electrical communication with the warning device  16  in the vehicle compartment  15 , wherein the controller  45  begins a starting logic sequence (Start). The controller  45  then determines if the pressure in the brake reservoir  30  is greater than a brake reservoir pressure limit (pounds per square inch, PSI) and, if so, the controller  45  deactivates the warning device  16  and returns to the starting logic sequence.  
         [0030]     If the pressure in the brake reservoir  30  is not greater than a brake reservoir pressure limit, the controller  45  determines if a vehicle speed (information) signal is available. If the controller  45  does not determine that the vehicle speed signal is available, then the controller  45  activates the warning device  16  and returns to the starting logic sequence.  
         [0031]     The vehicle speed signals may be provided from the data link  18  (a.k.a. a third electrical line  18 ), from an anti-lock braking system (ABS) module (not shown) disposed on or near the trailer  25 . The vehicle speed signals may also be provided other sources (truck/tractor), which may utilize a PLC4TRUCKS link (based on components available from Intellon Corporation), a radio frequency link, or an industry standard wired data bus (like Society of Automotive Engineers J1708 or J1587). In addition, the TMS controller  45  could be modified to utilize a separate hardwired speed sensor (not shown).  
         [0032]     If the controller  45  does determine that the vehicle speed signal is available, then the controller  45  determines if the vehicle speed is equal to zero and, if so, then the controller  45  returns to the starting logic sequence. If the speed is not equal to zero, then the controller  45  activates the warning device  16  and returns to the starting logic sequence.  
         [0033]     In addition to the logic sequences detailed above, the instant invention can include additional criteria that are indicated in  FIG. 3  for monitoring brake pressure, for example:  
         [0034]     a) at various steps within the logic sequence, optionally broadcast brake reservoir pressure and controller  45  decisions on the data link,  
         [0035]     b) provide a logic sequence step that would allow a movement of the trailer  25  at low speeds without providing a warning, but then communicate a warning if a certain vehicle speed threshold (for example, 10 miles per hour) were to be exceeded,  
         [0036]     c) utilize of a rate of change in a rising and/or a dropping of brake reservoir supply pressure to reduce annoyance warnings,  
         [0037]     d) determine the engine  14  revolutions per minute (RPM), in place of vehicle speed,  
         [0038]     e) determine if the air compressor (not shown) is running, in place of or in addition to determining the brake reservoir pressure,  
         [0039]     f) incorporate timers (for example, a reservoir pressure timer) into any of the logic sequence steps, before various actions or inactions would be taken, and/or  
         [0040]     g) utilize various speed and pressure sensors data to develop a Proportional Integral Derivative (PID) algorithm for warning of low air supply.  
         [0041]     As a result of any of these added criteria or a combination thereof, control between the trailer  25  and ECU  12  could then be provided.  
         [0042]     Additional efficiencies may be obtained when the TMS  40  is integrated into a controller (not shown) associated with the ABS. In such an arrangement, the electronic control unit  45 , for the TMS  40 , would actually be an ABS controller, which would control the ABS and also the TMS  40 . This would allow sharing of wheel speed information, data links, and other information that would be present on the various electrical communication lines within the truck, tractor, and/or trailer.  
         [0043]     In accordance with the provisions of the patent statutes, the principles and modes of operation of this invention have been described and illustrated in its preferred embodiments. However, it must be understood that the invention may be practiced otherwise than specifically explained and illustrated without departing from its spirit or scope.