Abstract:
An apparatus for and method of controlling forces transmitted to wheels/tracks of a vehicle. The method includes receiving an electrical indication that a first brake is engaged, such as by a user pressing his foot to a service brake. The method further includes electrically transmitting an instruction to apply force restricting movement of the wheels, such as force exerted from a brake, in an amount above a first threshold, such as an amount necessary to unilaterally prevent movement. The method also includes electrically transmitting an instruction to reduce force being applied to the wheels from a transmission while the (brake) force above the first threshold is applied.

Description:
FIELD 
       [0001]    The present disclosure relates to disengagement of engine force and, more particularly, to the automatic application of brake pressure during disengagement of engine force. 
       BACKGROUND 
       [0002]    When vehicles are stopped, force exerted by an engine and propagated via a transmission or drivetrain generally can be working against braking forces that are applied. When the drivetrain forces are working against the braking forces, the energy being applied can be converted into heat. Some of this heat is generated at the transmission. Excess heat in the drivetrain can result in part wear. Additionally, while at odds, the competing forces from the drivetrain and brake are not producing useful outcomes. Accordingly, the resources expended in creating the force from the drivetrain, such as the fuel consumed by the engine, is wasted. 
         [0003]    In other instances, such as when the vehicle is stopped and facing uphill, the forces exerted by the engine and propogated via the transmission aid in keeping the vehicle stationary. Accordingly, braking forces applied that when added to the force being applied via the drivetrain are satisfactory to keep a vehicle stationary, may not be satisfactory to keep the vehicle stationary if such drivetrain forces were not present. 
       SUMMARY 
       [0004]    The present disclosure provides a method of controlling forces transmitted to wheels/tracks of a vehicle. The method includes receiving an electrical indication that a first brake is engaged, such as by a user pressing his foot to a service brake. The method further includes electrically transmitting an instruction to apply force restricting movement of the wheels, such as force exerted from a brake, in an amount above a first threshold, such as an amount necessary to unilaterally prevent movement. The method also includes electrically transmitting an instruction to reduce force being applied to the wheels from a drivetrain while the (brake) force above the first threshold is applied. 
         [0005]    According to an embodiment of the present disclosure, a work machine is provided including an engine; a transmission coupled to the engine; at least one ground engaging member selectively driven by the transmission; a first brake operable to restrict motion of the at least one ground engaging member; a brake operation detector operable transmit a first brake operation signal indicative the operational status of the first brake; a brake engagement device operable to selectively engage and disengage the first brake; a engine engagement controller operable to selectively engage and disengage the engine to and from the at least one ground engaging member; and a controller operable to transmit a signal to the engine engagement controller to cause disengagement of the engine from the at least one ground engaging member upon receiving an indication that the first brake is being applied and upon the brake engagement device applying the first brake to supply force above a first threshold. 
         [0006]    According to another embodiment of the present disclosure, a method of controlling force transmitted to a ground engaging member of a vehicle is provided. The method including receiving an electrical indication of conditions indicative of heat buildup in a transmission above a first threshold amount; and electrically transmitting an instruction to engage a first brake to apply force above a second threshold amount. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The above-mentioned and other features and advantages of this disclosure, and the manner of attaining them, will become more apparent and the disclosure itself will be better understood by reference to the following description of embodiments of the disclosure taken in conjunction with the accompanying drawings, wherein: 
           [0008]      FIG. 1  is a plan view of a work vehicle according to an exemplary embodiment of the present disclosure; 
           [0009]      FIG. 2  is diagrammatic view showing components of the exemplary embodiment work machine of  FIG. 1 ; 
           [0010]      FIG. 3  is a flowchart showing exemplary operation of the work machine of  FIG. 1 ; 
           [0011]      FIG. 4  is a flowchart showing another embodiment of exemplary operation of the work machine of  FIG. 1 ; 
           [0012]      FIG. 5  is a flowchart showing yet another embodiment of exemplary operation of the work machine of  FIG. 1 ; 
           [0013]      FIG. 6  is a flowchart showing yet another embodiment of exemplary operation of the work machine of  FIG. 1 ; and 
           [0014]      FIG. 7  is a flowchart showing yet another embodiment of exemplary operation of the work machine of  FIG. 1 . 
       
    
    
       [0015]    Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate exemplary embodiments of the disclosure and such exemplifications are not to be construed as limiting the scope of the invention in any manner. 
       DETAILED DESCRIPTION 
       [0016]    For the purposes of promoting an understanding of the principals of the invention, reference will now be made to the embodiments illustrated in the drawings, which are described below. The embodiments disclosed below are not intended to be exhaustive or limit the invention to the precise form disclosed in the following detailed description. Rather, the embodiments are chosen and described so that others skilled in the art may utilize their teachings. It will be understood that no limitation of the scope of the invention is thereby intended. The invention includes any alterations and further modifications in the illustrative devices and described methods and further applications of the principles of the invention which would normally occur to one skilled in the art to which the invention relates. 
         [0017]    Referring to  FIG. 1 , a construction or engineering vehicle  10  is provided in the form of an articulated bulldozer. Although the vehicle is illustrated and described herein as a bulldozer, the vehicle may be in the form of a tractor, a dump truck, a motor grader, an excavator, a crawler, or another agricultural or utility vehicle, for example. Vehicle  10  includes a chassis  12 , an engine  14 , and a ground-engaging mechanism, illustratively, front tracks  16  and rear tracks  18 . It is also within the scope of the present disclosure that the ground-engaging mechanism of vehicle  10  may include wheels, for example. In use, engine  14 , in cooperation with a transmission  30 , drives front tracks  16  and rear tracks  18 , causing vehicle  10  to propel across the ground. Engine  14  may be a combustion engine or an electric engine including an electric generator and at least one electric motor. For example, the electric generator and electric motor may cooperate with engine  14  and the ground-engaging mechanism to move vehicle  10 . 
         [0018]    Vehicle  10  of  FIG. 1  also includes an operator cab  20  coupled to chassis  12  to house and protect the operator of vehicle  10 . Operator cab  20  may include foot pedals, a steering wheel, joysticks, monitors, and other controls (not shown). 
         [0019]    The illustrative embodiment of vehicle  10  of  FIG. 1  further includes a work tool in the form of an articulating blade  22 . Other vehicles contemplated in this disclosure may include suitable work tools, such as a dump or haul body, forks, tillers, and mowers. Articulating blade  22  is moveably coupled to chassis  12  for pushing and/or clearing dirt and other materials. At least one hydraulic cylinder  23  may be provided to operate articulating blade  22 . The operator may control the movement of articulating blade  22  using joysticks or other controls located within operator cab  20 . 
         [0020]      FIG. 1  further shows a front end  24  and back end  25  of vehicle  10 . Front end  24  includes operator cab  20  and front tracks  16 . Back end  25  includes an engine compartment  26  and rear tracks  18 . Alternative embodiments of the vehicle may be configured to support engine compartment  26  forward of operator cab  20 . Engine compartment  26  may be supported by chassis  12  and comprised of a plurality of support members forming a frame (not shown). Engine compartment  26  houses at least part of transmission  30  and engine  14 . 
         [0021]    As shown in  FIG. 2 , vehicle  10  includes vehicle control unit (VCU)  32 , engine control unit (ECU)  34 , drivetrain  36 , brake actuator  38 , inclinometer  40 , transmission control unit  42  (TCU) and brake  44 . VCU  32  is an electronic control module that controls various vehicle systems, including other electronic control modules for various subsystems (such as ECU  34  and TCU  42 ). 
         [0022]    Drivetrain  36  includes engine  14 , clutch  46 , transmission  30 , torque converter  48 , and shaft speed sensor  50 . Clutch  46  selectively allows or prevents for power from engine  14  to be applied to transmission  30 . It should be appreciated that drivetrain  36  includes multiple clutches. Clutch  46  is discussed as being a “master clutch” that controls all transfer of engine output. However, the concepts described herein can be utilized with any clutch in drivetrain  36 . More specifically, the concepts described herein can be utilized with any clutch operationally positioned between engine  14  and ground engaging members  16 ,  18 . Engine  14  outputs rotational motion on a shaft that is coupled to torque converter  48 . Torque converter  48  sends power to transmission  30  via clutch  36 . Clutch  36  is illustratively internal to transmission  30 . Transmission  30  applies various gearing to allow customization in the application of the rotational motion to output shaft  52  that powers ground engaging members  16 ,  18 . Shaft speed sensor  50  detects rotation of output shaft  52  and supplies a signal to TCU  42  indicative thereof. The signal from shaft speed sensor  50  is then communicated from TCU  42  to VCU  32 . 
         [0023]    Brake actuator  38  is illustratively a brake pedal operative to apply service brake  44 . Brake actuator  38  further supplies a signal to VCU  32  that indicates an operational status of brake actuator  38 . Such a signal can be used to activate brake lights (not shown) or for other uses, such as those described herein. 
         [0024]    Inclinometer  40  is an instrument for measuring angles of slope. Specifically, inclinometer  40  measures the slope assumed by vehicle  10 . Inclinometer  40  produces an electronic signal indicative of the slope angle assumed by vehicle  10  and supplies that signal to VCU  32 . 
         [0025]    TCU  42  an electronic control module that controls operation of transmission  30 . TCU  42  operates at least partially at the direction of VCU  32 . 
         [0026]    Brake  44  is illustratively a service brake. Brake  44  operates upon engagement of brake actuator  38 . Brake  44  is further operable to respond to commands from VCU  32 . Although brake  44  is described herein as a service brake, embodiments are envisioned where the brake controlled by VCU  32  is a parking brake or other brake. Brake  44  operates to inhibit motion of ground engaging members  16 ,  18  and to inhibit rotation of output shaft  52 . Accordingly, while brake  44  can be monitored, the applied brake discussed below can be a brake other than brake  44 . 
         [0027]    At the outset, vehicle  10  operates in a conventional manner with drivetrain  36  providing power to ground engaging members  16 ,  18  to translate vehicle  10  across terrain. As part of this operation, clutch  46  is engaged to permit powering of ground engaging members  16 ,  18  (block  700 ). VCU  32  operates a pair of timers, Timer 1 and Timer 2. Embodiments are envisioned where the timers are operated by a different electronic control unit, provided that the inputs, described herein are provided to that electronic control unit. Timer 1 operates to keep track of time that brake actuator  38  is activated while the torque converter  48  output to output shaft  52 , as measured by shaft speed sensor  50 , is zero. Thus, timer 1 counts the time that brake actuator  38  is pressed and that ground engaging members  16 ,  18  are stationary. Timer 2, which is discussed more later, is operable to count the time that brake actuator  38  has been released. 
         [0028]    Timer 1 and Timer 2 are reset to a value of zero, block  710 . VCU  32  then proceeds to wait for signals (from brake actuator  38  and shaft speed sensor) that the conditions of brake actuator  38  being active and that output of torque converter  48  is zero, block  720 . For as long as one of these conditions is not met, VCU  32  loops to continue waiting for these conditions to be satisfied. 
         [0029]    When the conditions are satisfied, VCU  32  then inquires as to how long the conditions have been satisfied and as to whether the elapsed time is greater than or equal to a defined threshold, block  730 . If the elapsed time is not greater than or equal to the defined threshold, Timer 1 is incremented, block  740 . VCU  32  again checks to confirm that the conditions (brake applied and torque output= 0 ) are satisfied, block  720 . 
         [0030]    When the conditions are satisfied and have been for greater than or equal to the defined threshold such that Timer 1≧Timeout, VCU  32  sends a signal to activate or latch brake  44  to a threshold, block  750 . VCU  32  thereby applies brake  44  to apply a threshold amount of force. The threshold amount is illustratively an amount of force necessary to unilaterally prevent movement of vehicle  10 . To this end, the determination of the threshold may take into account the orientation of vehicle  10 , via data received from inclinometer  40  or otherwise. It should be appreciated that activation of brake actuator  38  is a binary function such that all brake application is reported equally. Thus, based on the binary signal from brake actuator  38 , the degree to which brake  44  is actuated is not known. 
         [0031]    Once brake  44  is latched to apply force at or above the defined threshold, VCU  32  sends signals to TCU  42  instructing disengagement of clutch  46 , block  755 . Prior to disengagement of clutch  46 , the output of engine  14  is being translated, via drivetrain  36 , to ground engaging members  16 ,  18  and such output is being opposed by brakes  44 . Such opposition places stress on engine  14  and other parts of drivetrain  36 . Such stress results in the creation of heat and increased wear on engine  14  and other parts of drivetrain  36 . This stress further causes engine  14  to consume an increased amount of fuel relative to an unstressed condition. Disengagement of clutch  46  reduces the stress experienced by engine  14  and drivetrain generally. Accordingly, less wear is placed on drivetrain generally, and engine  14  is able to consume less fuel than it would otherwise consume. 
         [0032]    VCU  32  then proceeds to monitor vehicle  10  to determine when brake actuator  38  is released, block  760 . For so long as brake actuator  38  remains active, VCU  32  continues to monitor brake actuator  38 . When VCU  32  receives an indication that brake actuator  38  is no longer active, VCU  32  sends signals to TCU  42  to engage clutch  46 . VCU  32  further starts to increment Timer 2, block  765 . For so long as Timer 2 is below the pre-set timeout level, block  770 , the status of brake actuator  38  continues to be monitored, block  780 . For so long as brake actuator  38  continues to be de-activated, Timer 2 is incremented, block  785 . If brake actuator  38  is re-activated before Timer 2 reaches the timeout level, Timer 2 is reset to zero, block  790 , and VCU  32  continues to monitor the status of brake actuator  38 . Once Timer 2 reaches the timeout level, VCU  32  issues a signal to release brake  44  latch, block  795 . VCU  32  then resets Timers 1 and 2, block  710 , and continues monitoring brake actuator  38  and shaft speed sensor  50 , block  720 . 
         [0033]    In another embodiment, rather than waiting a set amount of time (Timer 2) after detection of brake actuator  38  deactivation, an embodiment is envisioned where a torque output of the transmission that needed to hold vehicle  10  in place (by being able to overcome gravity in view of a received indication of incline or otherwise) is determined. A signal to disengage the brake is sent when the torque output of the engine is determined to be greater enough to produce the needed force to hold vehicle  10  in place. 
         [0034]    It should be appreciated that while the above description discusses instructions present within and executed by VCU  32 , embodiments are envisioned where various functions are carried out by other parts. Such other parts may or may not communicate their actions to VCU  32 . In one example the operation of engagement and/or disengagement of clutch  46  is controlled via a part other than VCU  32  and the engagement/disengagement status of clutch  46  is not communicated to VCU  32 . In such embodiments, VCU  32  continues to monitor the application of brake actuator  38  and signals generated by shaft speed sensor  50 . VCU  32  then engages brake  44  at the threshold force in anticipation of disengagement of clutch  46  by such other part. However, the above operation is described where disengagement of clutch  46  is dependent upon receiving permission from VCU  32  or some other part that is able to ascertain the status of brake  44  and whether brake  44  is latched at the threshold force. 
         [0035]    In reiteration of above described modes and with reference to  FIGS. 3-6  operation of the system of vehicle  10  is again described. As shown in  FIG. 3 , a signal is received that indicates that brake actuator  38  is depressed, block  300 . An instruction is then transmitted to apply brake  44  to a threshold, such as full application, block  310 . Then, an instruction is transmitted to reduce force being applied by transmission  30  to ground engaging members  16 ,  18 , such as by disengaging clutch  46 , block  320 . 
         [0036]    In another embodiment, shown in  FIG. 5 , a signal is received that indicates that brake actuator  38  is depressed, block  400 . A signal is further received that indicates vehicle orientation, such as a signal from an inclinometer, block  510 . In an optional step, a determination can be made of whether the brake force currently applied is sufficient to hold vehicle  10  in place given what is known about the orientation of vehicle  10 , block  520 . Regardless of whether the determination is made, a signal is then sent to cause engagement of brake  44  with enough force to hold vehicle  10  in place given what is known about the orientation of vehicle  10 , block  530 . Then, an instruction is transmitted to reduce force being applied by transmission  30  to ground engaging members  16 ,  18 , such as by disengaging clutch  46 , block  540 . 
         [0037]    In another embodiment, shown in  FIG. 4 , a signal is received (or a signal is stopped) so as to provide an indication that brake actuator  38  is disengaged, block  400 . A signal is then sent instructing for re-engagement of transmission  30 , such as by re-engagement of clutch  46 , block  410 . A signal is then transmitted that instructs for disengagement of brake  44 , block  420 . 
         [0038]    In still another embodiment, shown in  FIG. 6 , a signal is received that indicates conditions that are known to be conditions in which transmission  30  is disengaged, such as by disengagement of clutch  46 , block  600 . A signal is then sent that instructs for engagement of brake  44 , block  610 . 
         [0039]    The above-described apparatus and method provide that adequate brake force is being applied to prevent movement of vehicle  10  before or as force generated by engine  14  is disconnected from ground engaging members  16 ,  18 . 
         [0040]    In yet another embodiment, a temperature sensor (not shown) is provided on transmission  30  or another part of drivetrain  36 . A signal to engage brake  44  to the latch threshold is then sent once brake actuator  38  is depressed and the temperature is determined to be above a threshold. Such threshold is indicative of expected disengagement of clutch  46 . 
         [0041]    In another embodiment, activation of a throttle, such as a gas pedal, is monitored and used to determine when brake  44  can be released. In such an embodiment, brake  44  would only be release when the gas pedal is pressed above a threshold (such as 20% of its travel). 
         [0042]    While this invention has been described as having preferred designs, 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 disclosure pertains and which fall within the limits of the appended claims.