Abstract:
Cold planers work in a variety of conditions where different rotor speeds can be beneficial. The rotor is connected directly to the engine via a clutch so the speed cannot be changed independent of the engine speed. The control system disclosed herein enables the operator to quickly select from a plurality of different engine/rotor speeds. The engine/rotor speeds correspond to different machine applications. Each speed corresponds to a point on the torque map for the particular cold planer that will offer acceptable machine performance for the particular application. If the operator inputs one of the plurality of different commands, a timer is activated and movement of the cold planer must take place within a predetermined time period or the engine speed is reduced to the elevated idle speed where the clutch is able to engage the rotor.

Description:
TECHNICAL FIELD 
       [0001]    This disclosure relates generally to a system and method for controlling the engine and rotor speeds of cold planers for optimizing performance and fuel efficiency. 
       BACKGROUND 
       [0002]    Cold planers, also known as pavement profilers, road milling machines or roadway planers, are machines designed for scarifying, removing, mixing or reclaiming material from the surface of bituminous or concrete roadways and similar surfaces. Cold planers typically have a plurality of tracks or wheels which adjustably support and horizontally transport the machine along the surface of the road to be planed. Cold planers also have a rotatable planing rotor or cutter that may be mechanically or hydraulically driven. Vertical adjustment of a cold planer with respect to the road surface may be provided by hydraulically adjustable rods that support the cold planer above its tracks or wheels. 
         [0003]    While the rotor may be driven hydraulically, such hydraulically powered motor systems are typically less efficient at transmitting power to the rotor than mechanical drive arrangements which directly connect the rotor to the engine through a clutch. Mechanical drive arrangements are also particularly suited for mounting the rotor directly on the frame of the cold planer. Mounting of the rotor, or more specifically the rotor bearing housings, directly on the vehicle frame provides rigidity between the rotor and the machine suspension system thereby minimizing undesirable deflection of the rotor during the surface milling or planing operation. For these reasons, it may be desirable to mount the rotor and the engine driving the rotor directly on the cold planer frame and provide a direct mechanical drive between the engine and the rotor. 
         [0004]    This disclosure is directed to cold planers that work on a variety of conditions that may require different rotor speeds or where different rotor speeds could be beneficial. In cold planers where the rotor is connected directly to the engine via a clutch and belt system, the speed of the rotor cannot be changed independently of the engine speed. 
         [0005]    Two problems are associated with this type of cold planer. First, frequent changing of the rotor speed and therefore the planing operation at hand, may cause substantial wear and tear on the clutch. Second, while a direct mechanical connection between the engine and rotor is more efficient, cold planers still consume large quantities of fuel, which can substantially affect operating costs. 
         [0006]    Therefore, a control system is needed for cold planers that work on a variety of conditions thereby requiring a variety of different rotor speeds. Such a control system may be designed to help protect clutch life and/or reduced fuel consumption. 
       SUMMARY OF THE DISCLOSURE 
       [0007]    A cold planer is disclosed which includes an engine coupled to a clutch. The clutch is detachably engaged with a rotor. The engine and clutch are linked to a controller. The controller is also linked to a control console. The control console includes a plurality of operator inputs. The plurality of operator inputs includes a rotor speed control switch and a propel enable switch. The rotor speed control switch has at least an off position, an on position and a plurality of different engine speed positions. The propel enable switch sends a signal to the controller to allow the cold planar to move. 
         [0008]    The controller is programmed to adjust the engine speed to a first speed when (1) the engine is running, (2) the rotor speed control switch is switched to the on position and (3) the clutch is not engaged with the rotor. In an embodiment, the first speed can range from about 800 to about 1100 rpm. 
         [0009]    The controller is also programmed to send a signal to the clutch to engage the rotor when the engine reaches the first speed. The controller is also programmed to adjust the engine speed from the first speed to a second speed that is greater than or equal to the first speed when the engine is running at the first speed and after the controller has sent a signal to the clutch causing the clutch to engage the rotor. In an embodiment, the second speed may range from about 1100 rpm to about 1300 rpm. 
         [0010]    The rotor speed control switch may be a toggle switch or similar device with two active positions. The rotor speed control switch changes what the desired setting is and an LED display above or near the switch indicates the desired setting. The engine does no elevate to the desired speed until either the propel enable switch is pressed, the machine is manually lowered or automatically lowered with the grade/slope adjustment mechanism. 
         [0011]    And, upon activation of the propel enable switch, the timer is activated and, if a predetermined time period has elapsed without movement of the cold planer, the controller is programmed to return the engine to the second speed. 
         [0012]    A method for controlling the speed of an engine and a rotor of a cold planer is also disclosed. The method includes providing the cold planer with an engine coupled to a clutch. The clutch is detachably engaged with a rotor. The engine and clutch are linked to a controller. The controller is also linked to a control console and a timer. The control console includes a plurality of operator inputs that include a rotor speed control switch and a propel enable switch. The rotor speed control switch has at least an off position and an on position. 
         [0013]    The method also includes adjusting the engine speed to a first speed when the engine is running and the rotor speed control switch is switched to an on position and the clutch is not engaged with the rotor. 
         [0014]    The method also includes engaging the rotor with the clutch when the engine reaches the first speed. The method also includes adjusting the engine speed from the first speed to a second speed after the clutch has engaged the rotor. 
         [0015]    The method also includes adjusting the engine speed from the second speed to a third speed that is higher than the second speed when the rotor speed control switch is switched to a third speed position. And, the method also includes activating the timer upon activation of the propel enable switch and, if a predetermined time period elapses without movement of the cold planer, returning the engine speed to the second speed. 
         [0016]    Another cold planer is disclosed which comprises an engine coupled to a clutch. The clutch is attachably engaged with a rotor. The engine and clutch are linked to a controller. The controller is also linked to a control console. The control console includes a plurality of operator inputs including a rotor speed control switch and a propel enable switch. The cold planer also includes a timer. The rotor speed control switch is a toggle switch having an off position, an on position and a neutral position. The rotor speed control switch is able to access a plurality of different engine speeds by toggling the rotor speed control switch repeatedly to the on position. 
         [0017]    The controller is programmed to adjust the engine speed to a first speed when the engine is running and the rotor speed control switch is switched to the on position and the clutch is not engaged with the rotor. The controller is also programmed to send a signal to the clutch to engage the rotor when the engine reaches the first speed. 
         [0018]    The controller is also programmed to adjust the engine speed from the first speed to the second speed that is higher than the first speed when the engine is running at the first speed and after the controller has sent a signal to the clutch causing the clutch to engage the rotor. 
         [0019]    The controller is also programmed to adjust the engine speed from the second speed to a third speed that is higher than the second speed when the rotor speed control switch is toggled to the on position when the engine is running at the second speed. 
         [0020]    The first speed is a low idle speed for engaging the clutch. The second speed is a elevated idle speed while the clutch is engaged. The third speed is a low cutting speed. The rotor speed control switch also providing access to higher cutting speeds than the third speed, such as a fourth speed and optionally, a fifth speed. Higher speeds are also possible. In an embodiment, the third speed may range from about 1500 to about 1800 rpm; the fourth speed may range from about 1650 to about 1950 rpm; and the fifth speed may range from about 1800 to about 2100 rpm. 
         [0021]    Upon activation of one or more operator inputs selected from the group consisting of activating propel enable switch, changing a height of a cold planer above a work surface, changing a setting of a grade/slope system, stopping the cold planer and combinations thereof, the timer is activated. If a predetermined time period has elapsed without movement of the cold planer after the timer is activated, the controller is programmed to return the engine to the second speed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]      FIG. 1  is a side view of a cold planer having a disclosed control system. 
           [0023]      FIG. 2  schematically illustrates the communication between the controller, the control console, the rotor, clutch, engine and various sensors. 
           [0024]      FIGS. 3-5  are flow diagrams illustrating a disclosed control scheme for reducing fuel consumption and clutch wear. 
           [0025]      FIG. 6  is a torque map that graphically illustrates the relationship between engine speed, torque and horsepower of a cold planer. 
       
    
    
     DETAILED DESCRIPTION 
       [0026]    A cold planer  10  is illustrated in  FIG. 1  and includes a frame  12  that is carried for movement along a road surface by a pair of front track assemblies  14  and a pair of rear track assemblies  16 . The frame  12  is supported on the track assemblies  14 ,  16  (only two of four track assemblies are shown in  FIG. 1 ) by hydraulically actuated adjustable struts  18 ,  20  that extend respectively between each of the pair of track assemblies  14 ,  16  and the frame  12 . The hydraulic cylinders  19 ,  23  are used to raise and lower the cold planer  10 . 
         [0027]    A rotor  21  is rotatably mounted to the frame  12  and has a housing  22  surrounding all but the body of the rotor  21 , which is necessarily exposed to the road surface  24 . The depth of the cut or penetration of the cutting teeth (not shown) of the rotor  12  is controlled by appropriate extension or retraction of the adjustable struts  18 ,  20  and cylinders  19 ,  23 . The cold planer  10  also includes an engine  26  as a source of power that may drive the rotor  21  via a mechanical drive arrangement that includes pulleys  28 ,  30 , a belt  32  and a belt tensioner  34 . Of course, as will be apparent to those skilled in the art, other arrangements can be employed besides the mechanical arrangement shown in  FIG. 1 , such as a gear train, hydraulic system or others. 
         [0028]    The cold planer  10  also includes a pickup conveyor belt  36  which delivers debris to the discharge conveyor belt  38 . The discharge conveyor belt  38  and its associated framing and pulleys (not shown) is supported by the telescoping arm  40 . Finally, the cold planer  10  also includes a control console  42 . 
         [0029]    A control console  42  is partially illustrated in  FIG. 2  which schematically illustrates the relationship between the controller or ECM  44  and the remaining components relevant to this disclosure. Of course, the control console  42  may also include gauges for a water pump, compressor, etc. Specifically, the controller  44  includes a memory  46  and may also include a timer  48 . The controller  44  is linked to the engine  26  and, a clutch  50 , which may be a hydraulically actuated clutch  50  that is coupled to the engine  26 . The clutch  50  may also be detachably engaged to the rotor  21 , which may also be linked to the controller  44 . The controller  44  may also be linked to a variety of sensors, such as grade sensors, one of which is shown at  52  in  FIG. 1 , height position sensors  54 , which may be linked, coupled or associated with the struts  18 ,  20  (see  FIG. 1 ) and a movement sensor  56  which may be linked, coupled or associated with the front and/or rear track assemblies  14 ,  16  or the rotor  21 . 
         [0030]    Still referring to  FIG. 2 , the control console  42  may include a variety of operator inputs, such as a rotor speed control switch  58 , a propel enable switch  60 , a grade/slope auto/manual switch  62 , a manual adjustment mechanism  64  for the grade/slope system and a height adjustment mechanism  66  for manually adjusting the struts  18 ,  20  and cylinders  19 ,  23  (see  FIG. 1 ). The grade/slope auto/manual switch or button  62  may be disposed elsewhere, such as on a grade/slope controller (not shown), which may be disposed elsewhere on the cold planer  10  or near the top of the operator console (not shown). 
         [0031]    The rotor speed control switch  58  may be a two position rocker or toggle switch that the operator may use to select from a plurality of different engine/rotor speeds. In one embodiment, the rotor speed control switch  58  enables the operator to choose between three different cutting speeds S 3 , S 4  and S 5  and the controller  44  will automatically cause the engine  26  to run at one of the idle speeds S 1  and S 2 , which will be explained in detail below. The selected or desired speed is shown on the display  59 , which may be an LED display or other suitable display or indicator. 
         [0032]    The propel enable switch  60  may be in the form of a simple push button (see  FIG. 2 ), and includes two positions: an on position (with the button depressed); and an off position (with the button released, which may activate a timer as explained below). When the operator presses the propel enable switch  60  (or button  60 ), the machine may be propelled in either the forward or reverse directions. If the operator presses and releases the propel enable switch  60 , he/she has a predetermined time period such as 6 or 10 seconds to initiate movement of the cold planer  10 . While the predetermined time period is indicated as 10 seconds in  FIGS. 3-4 , the predetermined time period can vary from about 5 to about 25 seconds or more. In one embodiment, the predetermined time period is 6 seconds; in another embodiment, the predetermined time period is 10 seconds. In other embodiments, the predetermined time period may vary. Alternatively, the operator can press and hold the propel enable switch  60  until the cold planer  10  is moved before releasing the propel enable switch  60 . 
         [0033]    The grade/slope system is designed to raise and/or lower the struts  18 ,  20  ( FIG. 1 ) in response to obstacles on or deviations in the surface  24 . The grade/slope system may be switched between automatic and manual modes via the grade/slope auto/manual switch  62 . When the grade/slope auto/manual switch  62  is switched between the auto and manual modes or, if the switch  62  is in the manual mode and the grade/slope manual adjustment mechanism  64  is changed, the controller  44  may initiate a timer for a predetermined period of time, such as 10 seconds. Again, this predetermined time period may vary from about 5 to about 25 seconds. If the controller  44  does not detect movement of the cold planer  10  by way of the movement sensor  56  after the predetermined time period (e.g. 10 seconds) has elapsed, the controller may send a signal to the engine to reduce the engine speed to the elevated idle speed S 2 . The elevated idle speed S 2  may be greater than or equal to S 1 . 
         [0034]    Similarly, in preparing to road the cold planer  10 , if the operator lowers the cold planer  10  by changing the manual height adjustment mechanism  66 , the controller  44  may also activate the timer  48  for the predetermined time period, such as 10 seconds. If movement of the cold planer  10  is not sensed by the movement sensor  56  or the controller  44  within the predetermined time period, the controller  44  may send a signal to the engine  26  causing the engine  26  to operate at the elevated idle speed S 2 . Otherwise, the operator can press the propel enable button  60  which will cause the controller  44  to run the engine at S 3  or the last operating speed S 3 , S 4  or S 5 . There is no separate milling and travel modes. Both milling operations and travel or roading operations may be carried out using the same algorithms as shown in  FIGS. 3-5 . 
         [0035]      FIGS. 3 and 4  illustrate the control scheme programmed into the memory  46  of the controller  44  in detail. First, the engine and system are started at  100  and the controller  44  determines whether the rotor speed control switch  58  is in an on position at  101 . If the rotor speed control switch  58  is not in the on position, but is in a neutral or off position, the system may revert back to the start mode at  100  and checks whether the rotor speed control switch is on at  101  repeatedly until the operator activates the rotor speed control switch  58 . When the rotor speed control switch  58  is activated at  101  by the operator, the controller  44  may send a signal to the engine  26  to set the operating speed at the low idle speed of S 1  at  102 . The controller then checks whether the engine is operating at the low idle speed S 1  at  103  and, if a speed adjustment needs to be made, the system loops back to the step  102  and sets the engine speed to S 1 . When the engine speed is at S 1 , or the low idle speed, the controller sends a signal to the clutch  50  to engage the rotor  21  at  104 . Engagement between the rotor and clutch is confirmed at  105  and, when the rotor  21  and clutch  50  are engaged, the controller  44  sends a signal to the engine  26  to set the engine speed to the elevated idle speed S 2  at  106 . Confirmation that the engine  26  is operating at S 2  is confirmed at  107 . 
         [0036]    S 1 , the low idle speed, and S 2 , the elevated idle speed, are selected based upon the specific cold planer  10  design and the size of the engine  26 . By way of example only, one suitable engine speed for the low idle S 1  may be 1000 rpm, although S 1  may vary from about 800 to about 1100 rpm, and S 2  is greater than or equal to S 1 . S 2  may therefore vary from about 800 to about 1350 rpm. One suitable engine speed for the elevated idle S 2  may be 1150 rpm. Of course, these values may vary greatly depending upon the size of the engine  26  and the size and type of the cold planer  10 . 
         [0037]    Once the engine speed is set at S 2 , a variety of different operator inputs may cause the controller  44  to activate the timer  48  for the predetermined time period, e.g., about 10 seconds, and to set the engine speed to the last operating speed before the rotor speed control switch  58  is turned off. The purpose of the timer  48  is to ensure that the cold planer  10  begins to move after one of the operator inputs is received. Specifically, after the engine speed is raised to S 2  at  106 ,  107 , the controller will check to determine whether the propel enable switch  60  is on at  108 . Once the propel enable switch  60  is turned to the on position (see  FIG. 2 ), the controller will start the timer at  109 , set the engine speed to the last operating speed, and check to determine whether movement of the cold planer  10  has been initiated at  110 . If movement of the cold planer  10  has not been initiated at  110 , and the predetermined time period has elapsed at  111 , the system reverts back to either steps  106  or  107  and the engine speed is reduced to S 2 . Similarly, if the cold planer  10  is lowered manually at  112 , the timer is started by the controller  44  at  113  and the controller  44  checks for movement at  114  and, if no movement is detected within the predetermined time period, e.g. ten seconds,  115 , the machine may be optionally raised at  116  before the system reverts back to  106  where the speed of the engine  26  is reset to the elevated idle speed, S 2 . 
         [0038]    If the grade/slope system is set to auto by way of the switch  62  on the control console  42  at  117 , the controller  44  starts the timer at  118  and checks for movement at  119 . If no movement is detected by the end of the predetermined time period at  120 , the controller  44  reverts the system back to  106  and resets the engine speed at S 2 . Similarly, if the grade/slope setting is changed by way of the controlled mechanism  64  on the control console  42  at  121 , the timer is started at  122  and the controller  44  checks for movement of the cold planer  10  at  123 . If no movement is detected by the end of the elapsed time period at  124 , the system reverts back to step  106  and the speed of the engine  26  is reset to S 2 . Also, if the operator stops the cold planer  10  or for another reason, the cold planer  10  is stopped or its motion is ceased at  125 , the timer is started at  126  and the controller  44  checks for movement at  127 . If no movement is detected after the predetermined time period has elapsed at  128 , the controller sends a signal to the engine to revert to the elevated idle speed S 2 , or the system returns to step  106  as shown. 
         [0039]    The operator is free to use the rotor speed control switch  60  to change the engine speed at any time. The speed chosen by the operator is shown on the display  60  and the engine  26  will operate at that speed after the propel enable switch is pressed at  108 , the cold planer  10  is lowered at  112 , the grade/slope auto/manual switch  62  is switched from manual to auto mode, the grade/slope value is adjusted via the grade/slope mechanism  64  while the grade/slope auto/manual switch is in auto mode, or when the cold planer  10  is manually lowered, e.g., by lowering the cold planer  10  using the height adjustment mechanism  66 . 
         [0040]    Still referring to  FIG. 3 , if movement is detected at  110  after the propel enable switch  60  is turned on at  108 , the system checks the position of the rotor speed control switch  58  to determine which operating speed (S 3 , S 4  or S 5 ) the operator has selected. Thus, after movement has been detected by the controller at  110 , the controller then determines whether the rotor speed control switch has been pressed once at step  200 . If the rotor speed control switch  58  has been pressed once, the engine speed is set to S 3  at  201  from the previous operating speed. If the rotor speed control switch  58  is pressed again at  202 , the controller  44  sends a signal to the engine  26  to set the engine speed to S 4  at  203  from the previous operating speed. If, however, at step  200 , the controller determines that the rotor speed control switch  58  has been pressed twice at  204 , the engine speed is set to S 4  at  205  from the previous operating speed and, if the operator presses the rotor speed control switch  58  another time at  206 , the controller  44  sets the speed of the engine  26  to S 5  at  207  from the previous operating speed. If the controller  44  determines that the rotor speed control switch has been pressed three times at  208 , the controller  44  sets the engine speed to S 5  at  209  from the previous operating speed. Once the max speed of S 5  has been reached, if the operator presses the rotor speed control switch  58  another time at  210 , the controller sets the engine speed back to S 3  at  211  from the previous operating speed. However, the system may be designed to set the speed of the engine to S 4  at step  211  as well. 
         [0041]    It will be noted that speed control for milling operations is the same as for roading or travel operations. That is, there is no separate travel and milling modes. To travel, the operator merely raises the cold planer  10  to a suitable height using the height adjust knob  66  followed by pressing or activating the propel enable switch  60 , which will cause the controller  44  to run the engine  26  at S 3  or the last operating speed S 3 , S 4  or S 5 . 
         [0042]      FIG. 5  illustrates, schematically, the return of the engine speed to the previous operating speed, unless the operator intervenes by toggling the rotor speed control switch  58 . When the rotor speed control switch  58  is toggled to the on/switch position (see  FIG. 3 ) at  101  and then is subsequently turned off at  1101 , the current operating speed is recorded at  1102  and when the rotor speed control switch is toggled on again at  1103 , the engine speed is set to the last operating speed at  1104 . 
         [0043]    Of course, the variables discussed above may be changed based upon machine requirements. The purpose of the described control system is two-fold. First, cold planers  10  can consume large quantities of fuel and reducing the speed of the engine  26  between movements of the cold planer  10 , especially if the delay between movements is greater than a predetermined time period, e.g. 5 seconds, 6 seconds, 10 seconds, 20 seconds, 30 seconds, etc., fuel is saved by lowering the engine speed to the elevated idle speed S 2  without substantially compromising the speed of the milling operation. S 2  is greater than or equal to S 1 , which may be the lowest operating speed of the engine  26 . The operator can then reestablish the desired operating speed, S 3 , S 4  or S 5 , by pressing the rotor speed control switch  58  the desired number of times. 
         [0044]    The second benefit provided by the disclosed control system is saving wear and tear on the clutch  50 . Specifically, the clutch  50  remains engaged with the rotor  21  while the engine  26  is operating at the elevated idle speed S 2 . The reader will note that if no movement of the cold planer  10  is detected after a predetermined time period following five different operator input actions shown at  108 ,  112 ,  117 ,  121  and  125 , the speed of the engine  26  is lower to the elevated idle speed S 2 . Thus, the clutch  50  remains engaged with the rotor  21 . Disengagement of the clutch only comes after a complete shut down, upon initiation by the operator. 
         [0045]    A third benefit is the use of a single control mode for both milling and travel operations. The operator does not need to know or remember what mode he/she is in. There is preferably only a single speed control that is used for milling and roading. 
         [0046]    Further, it will be noted that the number of operating speeds in the above example is just three, S 3 , S 4  and S 5 . However, the number of operating speed may vary greatly, depending upon the machine and working conditions. For example, anywhere from two to eight different operating speeds may also be desirable. 
         [0047]      FIG. 6  is a torque map for an exemplary cold planer  10  that illustrates the suitability of the cutting speeds S 3  (1500-1800 rpm), S 4  (1650-1950 rpm) and S 5  (1800-2100 rpm). Specifically, if the rotor  21  engages a hard object while cutting or milling, the speed of the engine  26  and rotor  21  declines. Referring to the left side of  FIG. 5 , reducing engine speeds below about 1300 rpm results in a decrease in torque. However, if operating at 1900, 1750 or 1600 rpm, or speeds between those values, a reduction in the engine speed results in an increase in torque as shown on the right side of the graph, which is desirable when the cold planer  10  is asked to cut or mill through a hard object. 
       INDUSTRIAL APPLICABILITY 
       [0048]    In operation, the operator will engage the rotor  21  by pressing the rotor speed control switch  58  on the control console  42 . The rotor speed control switch  58  may be a momentary two position switch, a rocker switch or a toggle switch, and the default position may be a center position of the switch  58  as illustrated in  FIG. 2 . One position of the rotor speed control switch  58  may be dedicated to turning the rotor  21  off while the other position may be dedicated for engaging the rotor  21  and cycling through the different operating speeds S 3 , S 4 , S 5 . 
         [0049]    The rotor  21  is engaged by pressing the rotor speed control switch  58  in the on direction as illustrated in  FIG. 2 . When the rotor  21  is engaged, the desired speed of the engine  26  will be a low idle speed  51  which, for example, may be about 1000 rpm. An initial pressing of the rotor speed control switch  58  automatically causes the controller  44  to direct the engine  26  to run at  51  regardless of any other commands being given. An initial engagement of the rotor may override all other timers, machine commands, etc. The low idle speed S 1  is preferably chosen to preserve the life of the clutch  50  and to conserve fuel. For some cold planers  10 , a low idle speed of 1000 rpm provides extended clutch life whenever the clutch  50  engages the rotor  21 . Once the engine  26  reaches the low idle speed of S 1 , the rotor  21  will engage the clutch  50 . After the rotor  21  has engaged the clutch  50 , the speed of the engine  26  will automatically proceed to the elevated idle speed of S 2 . For at least some cold planers, a elevated idle speed S 2  of 1150 rpm is satisfactory as fuel consumption is low and the transition to the higher milling speeds S 3 , S 4 , S 5  is relatively easy. 
         [0050]    The operator will be able to select between a plurality of milling speeds S 3 , S 4 , S 5 . For at least some cold planers, suitable low, medium and high milling speeds of 1500-1800 rpm (e.g., 1600 rpm), 1650-1950 rpm (e.g., 1750 rpm) and 1800-2100 rpm (e.g., 1900 rpm) will be satisfactory. The number of different cutting/milling speeds and the actual engine speeds used for the cutting/milling will vary from cold planer to cold planer as will be apparent to those skilled in the art. The speed of the engine  26  is selected by pressing the rotor speed control switch  58  in the on/cycle direction once for S 3 , twice for S 4  and three times for S 5  as generally illustrated in  FIG. 4 . If the rotor speed control switch  58  is pressed again after the high speed of S 5  is reached, the desired speed will go to S 3 . Indicators, such as the display  60 , may be placed on the control console  42  to tell the operator what the current speed setting is. The speed of the engine  26  may remain at the elevated idle speed S 2  as the operator cycles through the settings via the rotor speed control switch  58  while the cold planer  10  is stationary. 
         [0051]    The speed of the engine  26  will elevate to the desired setting once the speed of the engine  26  reaches the elevated idle speed S 2 . After the engine  26  reaches the speed S 2  or a higher speed, a plurality of operator inputs can initiate the activation of the timer  48  so the controller  44  can determine that the cold planer  10  is indeed moving within the predetermined time period. As explained above, the predetermined time period can be relatively short, such as five, six or 10 seconds long or may be extended to a longer time period such as 15 or 20 seconds or longer. Ten seconds has proven to be a satisfactory time period for at least some embodiments. However, the predetermined time period may range from about 5 to about 25 seconds, more typically, from about 5 to about 15 seconds. 
         [0052]    For example, when the propel enable switch  60  is pressed to the on position, the operator has the predetermined time period within which to start moving the cold planer  10 . If movement is not detected by the controller  44  within the predetermined time period, the speed of the engine  26  is reduced to S 2 . The operator will have to press the propel enable switch  60  again to re-enable movement of the cold planer  10 . 
         [0053]    If the operator adjusts height of the cold planer  10 , via the height adjustment mechanism  66 , the timer is started and if movement is not initiated before the end of the predetermined time period, the controller  44  sends a signal to the engine  26  to lower the engine speed to S 2 . Similarly, if the grade and slope system is set to auto mode via the switch  62 , the timer will start and the operator has the predetermined time period within which to start movement of the cold planer  10  or the controller  44  will send a signal to the engine  26  to reduce the engine speed to S 2 . Further, if a setting in the grade and slope system is changed, such as a manual adjustment via the grade/slope manual slope manual adjustment mechanism  64 , the timer  48  will be activated and the operator has the predetermined time period within which to initiate movement of the cold planer  10 . Also, if the operator stops the cold planer  10  or if the cold planer  10  stops for some other reason, the timer  48  will be activated and the controller will communicate with the engine to reduce the engine speed to S 2  if movement is not reinitiated within the predetermined time period. 
         [0054]    Essentially, any time a new command is given, the timer  48  will be activated. When the cold planer  10  is propelling forward with the rotor  21  activated, it is assumed that the cold planer  10  is milling (although in some instances it may not be) and the speed of the engine  26  will remain at the desired speed, S 3 , S 4 , S 5  . . . The timer  48  need not be activated when the cold planer  10  is moving. 
         [0055]    A benefit of automatically lowering the speed of the engine  26  is reduced fuel consumption and reduced noise levels. The timer  48  effectively limits the cycling from the elevated idle speed S 2  to the higher S 3 , S 4  or S 5  milling speeds. If the desired cutting speed is changed while the speed of the engine  26  is elevated, i.e. before the timer expires or while propelling forward with the rotor  21  activated, the actual desired speed may change to the new setting immediately. When the cold planer  10  is propelling in a reverse direction, it may be assumed that a cold planer  10  is not milling and the speed of the engine  26  will follow the desired speed based upon the propel system engine speed map, not the set S 3 , S 4  or S 5  milling speed. 
         [0056]    To turn the rotor off, the operator will press the rotor speed control switch  58  in the off direction. The clutch  50  will automatically disengage from the rotor  21  and the speed of the engine  26  may drop to the S 1  speed or a lower speed. For example, the engine speed may drop to 800 rpm or the lowest engine speed based upon the other machine commands being performed. In an embodiment, S 1  may be the lowest engine speed.