Abstract:
A control system for an off-highway vehicle including a foot operated drive pedal, a foot operated retard pedal, and a hand operated auxiliary drive/retard control. The auxiliary drive/retard control is operable in a first state to signal a request for drive torque and a second state to signal a request for retard torque.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority to U.S. Provisional Application No. 62/052,204, filed Sep. 18, 2014, the entirety of which is incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to off-highway machinery and, more particularly, to an auxiliary drive and retard control that can be manipulated by an operator&#39;s hands. 
       BACKGROUND OF THE INVENTION 
       [0003]    In order to maintain a high level of efficiency at a worksite it is often desirable to operate an off-highway vehicle at the vehicle&#39;s maximum safe speed. The maximum safe speed at which an off-highway vehicle can be operated is dependent on many variables including, but not limited to, load and road conditions. To maintain the off-highway vehicle at or near the maximum safe speed an operator must continuously control the throttle and brake via conventional foot operated pedals. Operators of off-highway vehicles often work long shifts, and continuous throttle and brake control throughout the course of the shift can lead to undesirable driver fatigue. 
         [0004]    Currently, an off-highway vehicle may be equipped with a conventional cruise control system that may be used to maintain a speed set by the operator. However, under certain conditions, this set speed may not be achievable. For example, when a fully loaded off-highway vehicle ascends a 25% gradient hill, the vehicle nay be unable to attain 20% of its rated maximum speed. As a further example, when a fully loaded off-highway vehicle descends a 25% gradient hill, setting the vehicle speed at 50% of the maximum rated speed may create a situation where the brakes will be unable to maintain the set speed. 
         [0005]    Additionally, there exists a conventional retard lever which may be manipulated by the hands of an operator. However, the conventional retard lever only provides vehicle descent speed control. Therefore, an operator must still manipulate the conventional foot operated throttle when encountering a flat road or ascending a hill. 
       SUMMARY 
       [0006]    One aspect of the present disclosure is a control system for an off-highway vehicle having a foot operated drive pedal, a foot operated retard pedal, and a hand operated auxiliary drive/retard control. The auxiliary drive/retard control is operable in a first state to signal a request for drive torque and a second state to signal a request for retard torque. The hand operated auxiliary drive/retard control can be a lever, a joystick, a rotary knob, programmable push-buttons, and/or a touchscreen. Drive/retard request signals from the foot operated drive pedal and/or the foot operated retard pedal override torque/retard request signals from the hand operated auxiliary drive/retard control. The drive torque and retard torque requests can be step increased and/or step decreased by the hand operated auxiliary drive/retard control. In a preferred embodiment, the torque/retard request from the foot operated pedals overrides a torque/retard request from the hand operated auxiliary drive/retard control. In another preferred embodiment, a predetermined default drive torque or retard torque request can be step increased or step decreased by the hand operated auxiliary drive/retard control. 
         [0007]    Another aspect of the present disclosure is a method of controlling an engine and brakes of an off-highway vehicle. The method includes the steps of providing a foot operated drive pedal, a foot operated retard pedal, and a hand operated auxiliary drive/retard control. The auxiliary drive/retard control is operated to request drive or retard torque. It is determined if one of the foot operated pedals is requested drive torque or retard torque. The auxiliary drive/retard control drive or retard torque request is compared to the foot operated pedal drive or retard torque request. The auxiliary drive/retard control drive torque or retard torque request is sent if it is greater than the respective foot operated pedal drive torque or retard torque request. In a preferred embodiment, the method further includes the step of sending the foot operated pedal drive torque or retard torque request if the auxiliary drive/retard control drive torque or retard torque request is less than the foot operated pedal drive torque or retard torque request. In another preferred embodiment, the method further includes the step of determining if the foot operated pedals are requesting drive torque or retard torque and canceling to retard torque or drive torque request of the auxiliary drive/retard control. In yet another preferred embodiment, the method further includes the step of determining it the auxiliary drive/retard control has a requested a drive or retard torque step increase or step increase and sending a step increase or step increase drive torque or retard torque request. 
         [0008]    Another aspect of the disclosure is a control system for an off-highway vehicle having a foot operated drive pedal, a foot operated retard pedal, and a hand operated auxiliary drive/retard lever. The lever is movable to a first position to signal a request for drive torque and a second position to signal a request for retard torque. In a preferred embodiment, the lever extends along a longitudinal axis and at least a part of the lever is rotatable about the longitudinal axis to step increase or step decrease the drive torque request or the retard torque request. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The foregoing and other features and advantages of the present disclosure will become apparent to one skilled in the art to which the present disclosure relates upon consideration of the following description of the invention with reference to the accompanying drawings, wherein like reference numerals, unless otherwise described refer to like parts throughout the drawings and in which: 
           [0010]      FIG. 1  illustrates a drive/retard control constructed in accordance with a preferred embodiment of the invention; 
           [0011]      FIG. 2  is a basic block diagram showing the interconnection between the various components of the auxiliary drive and retard control system shown in  FIG. 1 ; and 
           [0012]      FIGS. 3A and 3B  are a flow chart showing an operation of the drive and retard control system. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    With attention directed to  FIG. 2 , an off-highway vehicle system  2  is shown. The system  2  has an engine  4  controlled by an engine control unit  6 . The engine control unit  6  receives input from a drive pedal  8  and communicates directly with a central control unit  10 . As used in this document, “drive” means accelerator or throttle. The central control unit  10  communicates directly with a memory bank  12 , a vehicle speed sensor  16 , and a driver display  18 . The central control unit  10  also receives input from a retard pedal  20  and an auxiliary drive/retard control  22 . As used in this application, “retard” means brake. The central control unit  10  can actuate the left and right brakes  28 ,  30 . In one disclosed embodiment the left and right brakes  28 ,  30  are actuated by left and right retard solenoids  24 ,  26 , respectively. However, it is understood that the brakes  28 ,  30  can be actuated by any other suitable mechanism/system. The left and right retard solenoids  24 ,  26  can be controlled by pulse width modulation. As is known in the art, the duty cycle of an associated solenoid can be controlled in order to apply a desired fluid pressure to the associated brake that is related or proportional to the duty cycle parameters. Although standard disc brakes are illustrated in  FIG. 2 , it is understood that an off-highway vehicle would employ a wet braking system (or any other suitable braking system) as is known in the off-highway vehicle technical field. 
         [0014]    With attention directed to  FIG. 1 , one embodiment of an auxiliary drive/retard  22  control is shown. The auxiliary drive/retard control  22  illustrated in  FIG. 1  is a control lever. However, it will be appreciated that the auxiliary drive/retard control  22  may be any other suitable operator interface such as, but not limited to, joysticks, rotary knobs, programmable push-buttons, touchscreens, etc. The control lever  22  has a base portion  32  and a stalk portion  34 . The base portion  32  is provided with a slot  36 . The stalk portion  34  extends along a central axis  38  between a proximal end  40  and a distal end  42 . The distal end  42  is pivotally mounted within the base portion  32  such that the stalk portion  34  extends through the slot  36 . The proximal end  40  of the stalk portion  34  has a rotary switch  44  and a resume button  46 . The rotary switch  44  is oriented such that the switch  44  rotates about the central axis  38  of the stalk portion  34 . The rotary switch  44  may be provided with a raised portion  48  to facilitate rotation of the rotary switch  36  by an operator. The resume button  46  is oriented such that depression of the button  46  moves the button  46  along the central axis  38  of the stalk portion  34  toward the distal end  42 . The stalk portion  34  is shown in  FIG. 1  in a neutral position N. The stalk portion  34  may be moved out of the neutral N position by rotating the stalk portion  34  relative to the base portion  32  to a drive position D or a retard position R. 
         [0015]    An operator may control an off-highway vehicle equipped with the system  2  shown in  FIG. 2  in a conventional manner utilizing the drive pedal and retard pedal  8 ,  20 . The driver display  18  may provide information relating to the operation of the off-highway vehicle such as payload, vehicle speed (provided by the vehicle speed sensor  16 ), brake  28 ,  30  temperature, and/or engine  4  temperature. The system  2  may be augmented with a GPS unit  14 , which could assist in providing information about the vehicle speed as well as also providing information about the location of the vehicle in the worksite. As will be explained below, the operator may supplement control of the vehicle through manipulation of the auxiliary drive/retard control lever  22 . 
         [0016]    When the stalk portion  34  of the auxiliary drive/retard control lever  22  is moved from the neutral position to the drive position D, the central control unit  10  communicates with the engine control unit  6  to operate the engine  4  at a default percentage of the maximum drive torque. In the disclosed embodiment the default drive torque percentage is 15%, however other default percentages may be used. When the stalk portion  34  is in the drive position D, rotating the rotary switch  44  clockwise about the central axis  38  of the stalk portion  34  causes the engine control unit  6  to send a step output to increase the drive torque of the engine  4  by 5%. The rotary switch  44  can be used to increase the drive torque of the engine up to a maximum of 100% of the rated engine  4  torque. Additionally, when the stalk portion  34  is in the drive position D, the rotary switch  44  can be used to decrease the drive torque of the engine  4  down to a minimum of 0% by rotating the rotary switch  44  counterclockwise about the central axis  38  of the stalk portion  34 . When the stalk portion  34  is moved away from drive position D to the neutral position N, the auxiliary drive/retard control lever  22  sends no signal to the central control unit  10  and the off-highway vehicle system  2  operates as a standard off-highway vehicle system that may be controlled by the drive and retard pedals  8 ,  20 . 
         [0017]    When the stalk portion  34  is moved from the neutral position N to the retard position R the central control unit  10  controls the left and right retard solenoids  24 ,  26  to operate the left and right brakes  28 ,  30  at a default percentage of the maximum retard torque. In the disclosed embodiment the default retard torque percentage is 20%. Therefore, as an example, if the left and right brakes  28 ,  30  utilize a hydraulic system that operates at 700 psi, setting the retard torque percentage to 20% will result in the central control unit  10  operating the left and right retard solenoids  24 ,  26  via pulse width modulation such that the left and right brakes  28 ,  30  receive 140 psi from the hydraulic system. It is understood that other default percentages for the default retard torque may be used. When the stalk portion  34  is in the retard position R, rotating the rotary switch  44  clockwise about the central axis  38  of the stalk portion  34  causes the central control unit  6  to send a step output to increase the retard torque by 5%. The rotary switch  44  can be used to increase the retard torque up to a maximum of 100% of the rated retard torque. Additionally, when the stalk portion  34  is in the retard position R, the rotary switch  44  can be used to decrease the retard torque down to a minimum of 0% by rotating the rotary switch  44  counterclockwise about the central axis  38  of the stalk portion  34 . When the stalk portion  34  is moved away from the retard position D to the neutral position N the auxiliary drive/retard control lever  22  sends no signal to the central control unit  10 , and the off-highway vehicle system operates as a standard off-highway vehicle system that may be controlled by the drive and retard pedals  8 ,  20 . 
         [0018]    Similar to conventional cruise control systems, input from the drive and retard pedals  8 ,  20  can override input set by the auxiliary drive/retard control lever  22 . Therefore, for example, if the auxiliary drive/retard control lever  22  is set at 25% drive torque and an operator depresses the retard pedal  20 , the system  2  may cancel the drive torque set by the auxiliary drive/retard control lever  22  and apply retard torque as requested by the retard pedal  20 . The resume button  46  may be used to recall a previously set drive or retard torque. Continuing the above example, once the operator releases the retard pedal  20  and wishes to continue at the previously set drive torque, the operator may depress the resume button  46 , which can cause the system  2  to revert back to the previously set 25% drive torque set by the auxiliary drive/retard control lever  22 . 
         [0019]    With attention directed to  FIGS. 3A and 3B , operation of the drive/retard control system  2  will now be explained. At step  100  the central control unit  10  determines whether the auxiliary drive/retard control lever  22  is in the neutral position N, has been moved to the drive position D, or has been moved to the retard position R. If the central control unit  10  determines the auxiliary drive/retard control lever is in the neutral position N the system  2  proceeds to step  102  where the system  2  resets to minimum drive and retard torque values, and cancels any drive or retard request commands that may have previously been sent. The system  2  may then operate as a standard off-highway vehicle system controlled by the drive and retard foot pedals  8 ,  20 . The system then proceeds to steps  104  and  106  where the system respectively ends control and resets back to step  100 . 
         [0020]    Referring to  FIG. 3A , the drive control portion of the drive/retard control system  2  will first be discussed. At step  100 , if the central control unit  10  determines the auxiliary drive/retard control lever  22  is in the drive position D, the system  2  proceeds to step  108  where the central control unit  10  determines whether the retard pedal  20  is depressed. If the retard pedal  20  is depressed the system  2  proceeds to step  110  and the central control unit  10  cancels the drive torque set by the auxiliary drive/retard control lever  22 . Next, at step  112 , the central control unit  10  determines whether the resume button  46  is depressed. If the resume button  46  is depressed the control system  2  returns to step  108 . If the resume button  46  is not depressed the system  2  proceeds to step  114 . At step  114  the central control unit  10  determines if the auxiliary drive/retard control lever  22  is still in the drive position D. If the lever  22  is no longer in the drive position D the control system  2  returns to step  108 . If the lever  22  remains in the drive position D the control system returns to step  110 . The determination made at step  114  is the last step in the instance where the auxiliary drive/retard control lever  22  is in the drive position D and the retard pedal  20  is depressed. 
         [0021]    Returning back to step  108 , if the auxiliary drive/retard control lever  22  is in the drive position D and the retard pedal  20  is not depressed the system  2  proceeds to step  116 . At step  116  the central control unit  10  determines if the drive pedal  8  is depressed. If the drive pedal  8  is depressed the system  2  proceeds to step  118 . At step  118  the central control unit  10  measures whether the torque request of the drive pedal  8  is greater than the torque request of the auxiliary drive/retard control lever  22 . If the torque request of the drive pedal  8  is greater than the torque request of the control lever  22  the system proceeds to step  120 , and the torque request of the drive pedal  8  overrides the torque request of the control lever  22 . The system  2  then restarts at step  100 . If the torque request of the drive pedal  8  is less than the torque request of the control lever  22  the system  2  proceeds to step  122 . With attention momentarily directed back to step  116 , if the central control unit  10  determines that the drive pedal  8  is not depressed the system  2  also proceeds to step  122 . At step  122  the central control unit  10  communicates with the engine control unit  6  to operate the engine  4  at the default percentage of the maximum rated drive torque which, in the disclosed embodiment, is 15%. 
         [0022]    After step  122  the system proceeds to step  124  where the central control unit  10  determines whether the rotary switch  44  has been rotated. If the rotary switch  44  has not been rotated the system  2  resets back to step  100 . If the central control unit  10  determines that the rotary switch  44  has been rotated counterclockwise the system  2  proceeds to step  126  and the requested drive torque is decreased by 5%. The system then resets back to step  100 . If the central control unit  10  determines that the rotary switch  44  has been rotated clockwise the system  2  proceeds to step  128  and the requested drive torque is increased by 5%. The system  2  then resets back to step  100 . The discussion of step  128  completes the discussion of the drive control portion of the drive/retard control system  2 . 
         [0023]    Referring to  FIG. 3B , the retard control portion of the drive/retard control system  2  will now be discussed. Returning back to step  100 , if the central control unit  10  determines the auxiliary drive/retard control lever  22  is in the retard position R the system  2  proceeds to step  130 . At step  130  the central control unit  10  determines whether the drive pedal  8  is depressed. If the drive pedal  8  is depressed the system  2  proceeds to step  132 , and the central control unit  10  cancels the retard torque set by the auxiliary drive/retard control lever  22 . Next, at step  134  the central control unit  10  determines whether the resume button  46  is depressed. If the resume button  46  is depressed the system  2  returns to step  130 . If the resume button  46  is not depressed the system  2  proceeds to step  136 . At step  136  the central control unit  10  determines if the auxiliary drive/retard control lever  22  is still in the retard position R. If the lever  22  is no longer in the retard position R the system  2  returns to step  130 . If the lever  22  remains in the retard position R the control system  2  returns to step  132 . The determination made at step  136  is the last step in the instance where the auxiliary drive/retard control lever  22  is in the retard position R and the drive pedal  8  is depressed. 
         [0024]    Returning back to step  130 , if the auxiliary drive/retard control lever  22  is in the retard position R and the drive pedal  8  is not depressed the system proceeds to step  138 . At step  138  the central control unit  10  determines if the retard pedal  20  is depressed. If the retard pedal  20  is depressed the system  2  proceeds to step  140 . At step  140  the central control unit  10  measures whether the retard request of the retard pedal  20  is greater than the retard request of the auxiliary drive/retard control lever  22 . If the retard request of the retard pedal  20  is greater than the retard request of the control lever  22  the system proceeds to step  142 , and the retard torque request of the retard pedal  20  overrides the retard torque request of the control lever  22 . The system then restarts at step  100 . If the retard request of the retard pedal  20  is less than the retard request of the control lever  22  the system  2  proceeds to step  144 . With attention momentarily directed back to step  138 , if the central control unit  10  determines that the retard pedal  20  is not depressed the system  2  also proceeds to step  144 . At step  144  the central control unit  10  controls the left and right retard solenoids  24 ,  26  to operate the left and right brakes  28 ,  30  at the default percentage of the maximum available retard torque which, in the disclosed embodiment, is 20%. 
         [0025]    After step  144  the system  2  proceeds to step  146  where the central control unit  10  determines whether the rotary switch  44  has been rotated. If the rotary switch  44  has not been rotated the system  2  resets back to step  100 . If the central control unit  10  determines that that the switch  44  has been rotated counterclockwise the system  2  proceeds to step  148  and the requested retard torque is decreased by 5%. The system  2  then resets back to step  100 . If the central control unit  10  determines that the rotary switch  44  has been rotated clockwise the system  2  proceeds to step  150  and the requested retard torque is increased by 5%. The system  2  then resets back to step  100 . The discussion of step  150  completes the discussion of the retard control portion of the drive/retard control system  2 . 
         [0026]    If an operator traverses the same stretch of road repeatedly throughout a shift it may be beneficial to allow an operator to store a predetermined sequence of requested drive and retard torques. The memory bank  12  of the off-highway vehicle system  2  may cooperate with the central control unit  10  to provide such a feature in the following manner. First, the operator inputs to the central control unit  10  that he or she wishes to begin recording a torque request sequence. The central control unit  10  communicates with the memory bank  12  to record the exact drive or retard torque requested until the operator inputs to the central control unit  10  to end recording of the torque request sequence. During future operation of the vehicle, the central control unit  10  may display a previously recorded torque request sequence on the driver display  18 . The operator of the vehicle may choose to execute the previously recorded torque request sequence, at which point the central control unit  10  communicates with the memory bank  12  to carry out the desired torque request sequence. 
         [0027]    What has been described above are examples of the present invention. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the present invention, but one of ordinary skill in the art will recognize that many further combinations and permutations of the present invention are possible. Accordingly, the present invention is intended to embrace all such alterations, modifications, and variations that fall within the spirit and scope of the appended claims.