Abstract:
A ground engaging vehicle having an engine, a transmission driven by the engine, a controller, and a braking system. The controller is communicatively coupled to the engine and the transmission. The braking system is communicatively coupled to the controller. The controller is configured to execute testing steps to evaluate the braking system. The braking system includes a service brake and/or a parking brake. The testing steps executed by the controller include applying either the service brake or the parking brake; engaging the transmission to drive the vehicle; significantly increasing power output from the engine to the transmission, and sensing whether the transmission has an output movement that is above a predetermined amount.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a brake testing method for a vehicle, and, more particularly, to a vehicle brake testing method for a wheeled or high-speed rubber tracked vehicle. 
       BACKGROUND OF THE INVENTION 
       [0002]    A brake is a device designed to inhibit motion, and most commonly uses a friction element to convert kinetic energy into heat. Brakes are generally applied to rotating axles or wheels. Almost all wheeled vehicles have a brake of some sort. The effective applying of a brake typically causes a piston to push a frictional pad toward a surface, such as a brake disc, causing the rotating wheel to slow down. 
         [0003]    It is generally accepted that brake system defects are responsible for a high number of vehicle accidents. An analysis by the Indiana University Institute for Research and Public Safety of the accidents reported for a five-year period covered by the report (1972-1977) indicates that the vehicles&#39; braking system was definitely at fault in nearly 3% of the accidents, probably at fault in over 5% of the accidents, and possibly at fault in close to 20% of the reported accidents. Brake inspection and testing is given a high priority in the states that have motor vehicle inspection programs. A typical brake test includes measuring the vehicle&#39;s stopping power. Typically, the vehicle&#39;s wheels are placed on a constant speed, torque motor driven pair of rollers. The brakes are applied and the magnitude of the torque drive required to rotate the rollers with the brakes applied is used as an indication of the vehicle braking force. 
         [0004]    What is needed in the art is repeatable, efficient brake test that can be performed apart from a test station on a vehicle that is in service. 
       SUMMARY 
       [0005]    The present invention provides a brake test system and method for a ground-engaging vehicle and, more particularly, a brake test system for an articulated dump truck. 
         [0006]    The invention in one form is directed to a ground-engaging vehicle having an engine, a transmission driven by the engine, a controller, and a braking system. The controller is communicatively coupled to the engine and the transmission. The braking system is communicatively coupled to the controller. The controller is configured to execute testing steps to evaluate the braking system. The braking system includes a service brake and/or a parking brake. The testing steps executed by the controller include applying either the service brake or the parking brake; engaging the transmission to drive the vehicle; significantly increasing power output from the engine to the transmission, and sensing whether the transmission has an output movement that is above a predetermined amount. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein: 
           [0008]      FIG. 1  is a schematical illustration of a vehicle incorporating an embodiment of the brake system testing method of the present invention; and 
           [0009]      FIG. 2A-C  are a schematical flowchart illustrating the steps of the invention utilized with the vehicle of  FIG. 1 . 
       
    
    
       [0010]    Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates one embodiment of the invention and such exemplification is not to be construed as limiting the scope of the invention in any manner. 
       DETAILED DESCRIPTION 
       [0011]    Referring now to the drawings, and, more particularly, to  FIG. 1 , there is illustrated, in a schematical fashion a vehicle  10  having ground engaging devices  12 , a differential  14 , a transmission  16 , an engine  18 , a controller  20 , a braking system  22  that includes a service brake  24 , a parking brake  26 , and brake pads  28 . Vehicle  10  may be in the form of an articulated dump truck or other ground engaging vehicle utilized for construction, agriculture, forestry, mining and other related vehicles. Ground engaging devices  12  are in the form of wheels  12 , as illustrated, but may be in the form of a track, such as a high-speed rubber track on vehicle  10 . A differential  14  may be utilized to transfer the rotational power provided from engine  18 , the power being directed to ground engaging devices  12 . Transmission  16  converts the rotational speed of engine  18  into a different output speed and power, directing the rotational power to differential  14 . Engine  18  can be an internal combustion diesel engine that provides an output torque to transmission  16 , which directs rotary power to ground engaging devices  12 . Alternatively, engine  18  may provide power that is then directed in a fluid manner to ground engaging devices  12 , such as utilizing a hydraulically driven system. For the purposes of clarity, only two wheels  12  are shown being driven, although it is also anticipated that the present invention relates to vehicles having another number of wheels or tracks being driven by engine  18 . 
         [0012]    Controller  20  may be integral with engine  18  and may be in the form of an engine control device or as illustrated controller  20  may be a chassis control unit (CCU), here generically referred to as controller  20 . Controller  20  is interconnected with transmission  16 , engine  18 , service brake  24 , and parking brake  26 . Controller  20  can alter the speed and power output of engine  18 , engage transmission  16  into a selected gear, and apply service brake  24  and/or parking brake  26 . 
         [0013]    Now, additionally referring to  FIG. 2A-C , there is illustrated a method  100  carried out by controller  20  of vehicle  10 . The operator can initiate a periodic verification of the functioning of brake system  22  by initiating method  100  at step  102 . At step  102 , the operator may start the testing mode upon being prompted by controller  20 , indicating that such a test may be needed before complete control of vehicle  10  is available to the operator. Upon initiation of the test at step  102 , method  100  tests to ensure that the transmission temperature is at a proper operating range between, in this case, 80° C. to 100° C. This occurs at steps  104  and  108  although other temperatures are contemplated. If the temperature is below 80° C., then method  100  proceeds to step  106  where a message is displayed to the operator, indicating that the transmission needs to be warmed up before testing of the brakes can occur and indicates that the brake testing should be restarted when this condition exists. In a like manner, if the transmission temperature is above 100° C., a message is provided at step  110  indicating that the transmission needs to be cooled down before the running of the brake test. 
         [0014]    At step  112 , a test is undertaken to ensure that engine  18  is running by testing to see if the rpm is above 200. If the engine rpm is below 200, then a message is sent at step  114  and the display will indicate that the engine should be started and that the brake test be restarted. If the engine is running, then method  100  proceeds to step  116  in which it is tested to see if parking brake  26  has been applied. If parking brake  26  has not been applied, then method  100  proceeds to step  118  and a message is displayed indicating that the parking brake  26  should be applied and that the test  100  should be restarted. Alternatively, if vehicle  10  is configured such that parking brake  26  can be applied by controller  20 , then controller  20  will apply parking brake  26 . 
         [0015]    If parking brake  26  has been applied at step  116 , then transmission  16  is engaged into a preselected gear, such as third gear forward, and then, at step  122 , the speed of engine  18  is increased to a predetermined level for a predetermined time. For example, the engine may be increased to 100% of the top rated speed and held there for a predetermined time, such as four seconds. During the execution of the full speed engine output at step  122 , controller  20  tests to see if transmission  16  is moving at step  124 . The movement of transmission output  16  would indicate that one or more brakes  28  are allowing movement of ground engaging devices  12 . If transmission output is less than one-half of a revolution, although other amounts of rotation are also contemplated, at step  124 , method  100  proceeds to step  130 . Otherwise, if transmission  16  rotates one-half revolution or more then the test is aborted at step  126  and a message is displayed at step  128  indicating that vehicle  10  should be taken out of service and that the parking brake troubleshooting section is referred to on the display. If the transmission  16  rotated less than one-half of a revolution at step  124 , then, at step  130 , the engine  18  is reduced to an idle speed and transmission  16  is placed in neutral. 
         [0016]    Steps  132 ,  134 ,  136 ,  138 , and  140  may be identical or substantially similar to steps  120 ,  122 ,  124 ,  126 , and  128  respectively. This allows a repeat of the parking brake test carried out by the initial set of steps, except at step  134  transmission  16  is engaged in a reverse gear such as 3 rd  gear, reverse. This substantially repeated test, then, if failed at step  136 , leads to the aborting of the test at step  138  and the display of a message at step  140 , which is the same as the message at step  128 . If transmission  16  has an output of less than one-half revolution at step  136 , then method  100  proceeds to step  142  in which engine  18  is reduced to an idle speed and transmission  16  is placed in neutral. At step  144 , the parking brake indicator on the display in vehicle  10  indicates that the parking brake test has been passed. 
         [0017]    At step  146 , service brake  24  is applied and parking brake  26  is released. This may be accomplished by controller  20  or by some interaction of the operator, in which case, a message will be sent to the display telling the operator to apply the service brake and/or release the parking brake. At step  148 , transmission  16  is engaged, for example, in third gear forward. At step  150 , the engine speed of engine  18  is increased to 100% and held there for a minimum of four seconds and, again at step  152 , the transmission is checked for rotation and, if the rotation is greater than or equal to one-half of a revolution, then method  100  proceeds to step  154  where the test is aborted and a message displayed at step  156  indicating that vehicle  10  should be taken out of service and a reference to the service brake troubleshooting section in the operator&#39;s manual is displayed. If the transmission moves less than one-half of a revolution, then engine  18  is returned to idle speed and the transmission is placed in neutral at step  158 . At step  160 , the transmission is engaged into reverse third gear and then, at step  162 , engine  18  is increased in speed to 100% for a minimum of four seconds. If transmission  16  rotates for more than half of a revolution at step  164 , then method  100  proceeds to step  166  where the test is aborted and step  168  in which a message is displayed, which may be identical to the message displayed at step  156 . If transmission  16  rotates for less than one-half of a revolution at step  164 , then the engine is brought to idle and transmission  16  is placed into neutral and service brake  24  is released. At step  172 , the display indicates that the service brake has passed and it is checked off on the test mode display. At step  174 , the display indicates that the test has been successfully completed and method  100  proceeds to step  176  in which the test is completed and terminated. It should be noted that whenever the test is aborted, the engine speed is immediately reduced and steps may be taken to stop any movement of vehicle  10 . Additionally, the sensing of rotation of transmission  16  goes on while engine speed of engine  18  is being increased so that, if any movement of the transmission, even with less than full power output from engine  18 , is detected beyond the predetermined allowable movement, then method  100  proceeds to abort the test. So, while indicated in the flow chart as individual steps, controller  20  monitors the movement of transmission  16  during the increased output of engine  18  before and during the carrying out of full power output of engine  18  during the predetermined time of four seconds. 
         [0018]    Method  100  automatically applies a driving force against the service brake and the parking brake while detecting machine or transmission motion to confirm that both service brake  24  and parking brake  26  have adequate holding torque. Failure of the test, results in the operator being instructed to take vehicle  10  out of service due to the detection of inadequate brake function. 
         [0019]    Advantageously, the inventive test mode provides a verification of the service and parking brake performance. Further, the test mode may be fully automatic, only requiring the operator to engage the test mode at a desired interval since the previous testing. Further, the method of the present invention provides for daily verification of braking performance that may be required in some operating environments, such as at a mining operation. Yet still further, the present invention takes advantage of electronic brake valve to automatically apply the service brakes. 
         [0020]    While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.