Abstract:
A method of shifting a transmission of a vehicle. The method includes the steps of: initiating a shift from a first gear to a second gear in the transmission; disengaging a first clutch associated with the first gear; engaging a second clutch associated with the second gear; and actively modifying a pump displacement and/or a motor displacement while the disengaging step or the engaging step are carried out. The motor is drivingly coupled to the transmission.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a hydro-mechanical transmission of a vehicle, and, more particularly, to the controlling of the shifting process of a hydro-mechanical transmission in a vehicle such as a combine. 
         [0003]    2. Description of the Related Art 
         [0004]    Agricultural vehicles utilize transmissions to change gear ratios to drive the vehicle over the ground at various speeds. The transmission of a heavy piece of equipment such as an agricultural harvester, also known as a “combine”, has to be effectively shifted in order to achieve a required ground speed and torque to perform required harvesting operations without any operator discomfort. A combine is historically termed such because it combines multiple harvesting functions with a single harvesting unit, such as picking, threshing, separating and cleaning A combine includes a header which removes the crop from a field, and a feeder housing which transports the crop matter into a threshing rotor. The threshing rotor rotates within a perforated housing, which may be in the form of adjustable concaves and performs a threshing operation on the crop to remove the grain. Once the grain is threshed it falls through perforations in the concaves onto a grain pan. From the grain pan the grain is cleaned using a cleaning system, and is then transported to a grain tank onboard the combine. A cleaning fan blows air through the sieves to discharge chaff and other debris toward the rear of the combine. Non-grain crop material, such as straw, from the threshing section proceeds through a residue system, which may utilize a straw chopper to process the non-grain material and direct it out the rear of the combine. When the grain tank becomes full, the combine is positioned adjacent a vehicle into which the grain is to be unloaded, such as a semi-trailer, gravity box, straight truck, or the like; and an unloading system on the combine is actuated to transfer the grain into the vehicle. 
         [0005]    More particularly, the engine, by way of the transmission provides power to the drive wheels or tracks of the vehicle. In order to achieve required speed and torque during machine operation, up and down shifting of the transmission is carried out by swapping clutch engagements. In order to achieve a large speed range, the difference of output to input gear ratios for first and second gear is generally significantly large (usually the output to input gear ratio for second gear is more than twice the gear ratio of the first gear). Due to this large difference in the gear ratios, the task of shifting gears without interruption in vehicle speed felt by the operator driving the vehicle becomes very critical. Such shifting can lead to a jerk of the vehicle, which can impact the comfort of the operator and other systems of the vehicle. 
         [0006]    What is needed in the art is a shifting algorithm that shifts the transmission in a smooth and efficient manner. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention provides a system and method of controlling the shifts of an electronically controlled hydro-mechanical transmission by swapping clutches, as well as actively altering the displacements of a pump and motor of the transmission at the same time. 
         [0008]    The invention in one form is directed to a method of shifting a transmission of a vehicle. The method includes the steps of: initiating a shift from a first gear to a second gear in the transmission; disengaging a first clutch associated with the first gear; engaging a second clutch associated with the second gear; and actively modifying a pump displacement and/or a motor displacement while the disengaging step or the engaging step are carried out. The motor is drivingly coupled to the transmission. 
         [0009]    The invention in another form is directed to an agricultural vehicle including a chassis, an engine carried by the chassis, a pump driven by the engine, a motor driven by the pump, a transmission shift control system that controls the displacement of the pump and the motor, and a transmission driven by the motor. The transmission has a first gear, a second gear, a first clutch arrangement associated with the first gear, and a second clutch arrangement associated with the second gear. The transmission shift control system is configured to execute the steps of: initiating a shift from the first gear to the second gear in the transmission; disengaging the first clutch associated with the first gear; engaging the second clutch associated with the second gear; and actively modifying the displacement of the pump and/or the displacement of the motor while the disengaging step and the engaging step are being carried out. 
         [0010]    The invention in yet another form is directed to a transmission shift control system for an agricultural vehicle having a chassis, an engine carried by the chassis, a pump driven by the engine, a motor driven by the pump, the transmission shift control system that controls the displacement of the pump and the motor, the transmission shift control system including a transmission driven by the motor, the transmission having a first gear, a second gear, a first clutch arrangement associated with the first gear, and a second clutch arrangement associated with the second gear. The transmission shift control system is configured to execute the steps of: initiating a shift from the first gear to the second gear in the transmission; disengaging the first clutch associated with the first gear; engaging the second clutch associated with the second gear; and actively modifying the displacement of the pump and/or the displacement of the motor while the disengaging step and the engaging step are being carried out. 
         [0011]    The present invention advantageously provides a smooth and efficient shift between gears having a substantial difference in gear ratios. 
         [0012]    Another advantage is that the shift is carried out while ignoring input from the operator that could otherwise compromise the effectiveness of the shift. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    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 embodiments of the invention taken in conjunction with the accompanying drawings, wherein: 
           [0014]      FIG. 1  is a side view of an embodiment of an agricultural harvester in the form of a combine which includes an embodiment of a transmission configured to shift by way of a transmission shift control system according to the present invention; 
           [0015]      FIG. 2  is a schematic illustration of an electronically controlled hydro-mechanical transmission along with a transmission control system contained in the combine of  FIG. 1 ; 
           [0016]      FIG. 3  is a flowchart describing a transmission shift decision making process for the transmission shift control logic that is part of the transmission control system of  FIG. 2 ; and 
           [0017]      FIG. 4  is a schematical representation of the transmission shift control logic that is part of the transmission control system of  FIG. 2 . 
           [0018]    Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates embodiments of the invention, and such exemplifications are not to be construed as limiting the scope of the invention in any manner. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]    Referring now to the drawings, and more particularly to  FIG. 1 , there is shown an agricultural vehicle  10  in the form of a combine  10 , which generally includes a chassis  12 , ground engaging wheels  14  and  16 , a header  18 , a feeder housing  20 , an operator cab  22 , a threshing and separating system  24 , a cleaning system  26 , a grain tank  28 , and an unloading auger  30 . 
         [0020]    Front wheels  14  are larger flotation type wheels, and rear wheels  16  are smaller steerable wheels. Motive force is selectively applied to front wheels  14  through a power plant in the form of a diesel engine  32  and an electronically controlled mechanical transmission  80 . Although combine  10  is shown as including wheels, is also to be understood that combine  10  may include tracks, such as full tracks or half tracks. 
         [0021]    Header  18  is mounted to the front of combine  10  and includes a cutter bar  34  for severing crops from a field during forward motion of combine  10 . A rotatable reel  36  feeds the crop into header  18 , and a double auger  38  feeds the severed crop laterally inwardly from each side toward feeder housing  20 . Feeder housing  20  conveys the cut crop to threshing and separating system  24 , and is selectively vertically movable using appropriate actuators, such as hydraulic cylinders (not shown). 
         [0022]    Threshing and separating system  24  is of the axial-flow type, and generally includes a rotor  40  at least partially enclosed by and rotatable within a corresponding perforated concave  42 . The cut crops are threshed and separated by the rotation of rotor  40  within concave  42 , and larger elements, such as stalks, leaves and the like are discharged from the rear of combine  10 . Smaller elements of crop material including grain and non-grain crop material, including particles lighter than grain, such as chaff, dust and straw, are discharged through perforations of concave  42 . 
         [0023]    Grain which has been separated by the threshing and separating assembly  24  falls onto a grain pan  44  and is conveyed toward cleaning system  26 . Cleaning system  26  may include an optional pre-cleaning sieve  46 , an upper sieve  48  (also known as a chaffer sieve), a lower sieve  50  (also known as a cleaning sieve), and a cleaning fan  52 . Grain on sieves  46 ,  48  and  50  is subjected to a cleaning action by fan  52  which provides an airflow through the sieves to remove chaff and other impurities such as dust from the grain by making this material airborne for discharge from straw hood  54  of combine  10 . Grain pan  44  and pre-cleaning sieve  46  oscillate in a fore-to-aft manner to transport the grain and finer non-grain crop material to the upper surface of upper sieve  48 . Upper sieve  48  and lower sieve  50  are vertically arranged relative to each other, and likewise oscillate in a fore-to-aft manner to spread the grain across sieves  48 ,  50 , while permitting the passage of cleaned grain by gravity through the openings of sieves  48 ,  50 . 
         [0024]    Clean grain falls to a clean grain auger  56  positioned crosswise below and in front of lower sieve  50 . Clean grain auger  56  receives clean grain from each sieve  48 ,  50  and from bottom pan  58  of cleaning system  26 . Clean grain auger  56  conveys the clean grain laterally to a generally vertically arranged grain elevator  60  for transport to grain tank  28 . Tailings from cleaning system  26  fall to a tailings auger trough  62 . The tailings are transported via tailings auger  64  and return auger  66  to the upstream end of cleaning system  26  for repeated cleaning action. A pair of grain tank augers  68  at the bottom of grain tank  28  convey the clean grain laterally within grain tank  28  to unloading auger  30  for discharge from combine  10 . The non-grain crop material proceeds through a residue handling system  70 . 
         [0025]    Now, additionally referring to  FIGS. 2-4 , there are shown more details of electronically controlled mechanical transmission  80  and transmission control system  96 , together broadly understood to be a shifting system  82 . Shifting system  82  includes electronically controlled mechanical transmission  80 , an electronically controlled variable displacement pump  84 , solenoids that control the displacement of pump  84 , an electronically controlled variable displacement motor  86 , solenoids that control the displacement of motor  86 . Electronically controlled mechanical transmission  80  includes a clutch  88 , a clutch  90 , a gear  92  and a gear  94 . There are solenoids associated with clutches  88  and  90  that control the engagement of clutches  88  and  90 . Although referred to as gears  92  and  94  this is used to refer to gear ratios  92  and  94  with more than one gear likely being involved with each gear ratio. It is also to be understood that other drive mechanisms are also contemplated, yet are herein referred to as gears although pulleys or other devices may be employed. Additionally, even though referred to as a first gear and a second gear in the claims, this it just to differentiate the gears and not to refer to a numbered gear in transmission  80 . 
         [0026]    Pump  84  is drivingly connected to engine  32 . Pump  84  drives motor  86 , which in turn drives an input shaft of electronically controlled mechanical transmission  80 . The displacements of pump  84  and motor  86  are controlled by changing the swash plate angle, by altering the current to the solenoids associated with pump  84  and motor  86 , as illustrated in  FIG. 2 . The solenoids are control by the transmission shift control logic, which is part of transmission shift control system  96 , which may be considered a controller  96 . Transmission shift control logic, which is part of controller  96  controls the engagement of clutches  88  and  90  by way of controlling current to the solenoids of the proportional control valves. The transmission shift control logic receives input from sensors that determine the velocity and acceleration commands from the operator, the speed of engine  32  and other various input signals. The transmission shift control logic also receives feedback signals, such as vehicle velocity and/or vehicle acceleration from the components of vehicle  10  including transmission  80 . 
         [0027]    A method  100  for determining if a shift is to be made is illustrated in  FIG. 3 . In method  100 , at step  102  a decision is made as to whether a shift is in progress, if the answer is “No”, then it determines if transmission  80  of vehicle  10  is in one gear or another at steps  104  and  114 . If transmission  80  is in the 1 st  gear, then a further evaluation is made at step  106  as to whether the transmission output speed (TOS)/Engine speed ratio is greater than a predetermined up-shift point, if so, and all other shift conditions are met at step  108 , then an upshift is initiated at step  110 . 
         [0028]    In a similar manner if transmission  80  of vehicle  10  is in 2 nd  gear and the TOS/Engine speed ratio is less than the down-shift point (step  116 ) and all other down-shift conditions are satisfied at step  118 , then a down-shift is initiated at step  120 . At the beginning of method  100  if a shift is in progress then method  100  transitions to step  112  until the shift is complete, hence ignoring inputs, such as those from steps  106 ,  108 ,  116 , and  118 , as well as operator inputs until the shift has been completed. 
         [0029]    The present invention uses a combination of feed-forward and feedback control methods to achieve minimum transmission output speed interruption felt by the operator driving vehicle  10  while gear shifting progresses in electronically controlled 2-speed electronically controlled mechanical transmission  80 . The displacements of pump  84  and motor  86  and the engagement-disengagement of gear clutches  88  and  90  are controlled by the transmission shift control logic in electronic control unit  96  based on various inputs, such as operator commands, measured torque going through the transmission, measured vehicle speed and/or acceleration, measured pressure between pump and motor in the hydraulic circuit, engine speed etc. 
         [0030]    As shown in  FIG. 3 , a shift is commanded based on the value of the transmission output speed (TOS) to engine speed ratio. At the initiation of a shift, the actuator associated with the oncoming clutch  88  or  90  is actuated until a (kiss) point occurs, in that the clutch starts transmitting torque without any further increase in current to the solenoid, which activates the actuator associated with that particular clutch. The increase-decrease rate, magnitude and crossover point of on-coming and off-going clutch current to the solenoids during shifts is determined based on the required output torque of transmission  80 . During the shift, pump and motor displacements are purely calculated based on vehicle velocity and/or acceleration feedback and engine speed independent of vehicle velocity or acceleration commands from the operator driving vehicle  10 . 
         [0031]    The pump and motor displacements are increased or decreased during the shift using vehicle velocity and/or acceleration feedback in order to maintain the desired acceleration or deceleration and/or velocity of vehicle  10 . Additionally, pump and motor commands compensate for a detected or anticipated increase in vehicle velocity during up-shift and conversely a decrease in vehicle velocity during down-shifts. 
         [0032]    Once a target transmission output speed to motor speed ratio is achieved, the shift is considered to be completed. The shift-in-progress flag goes low, which then transfers control back to the machine operator. Pump and motor displacements are now again a function of velocity or acceleration commands given by the machine operator apart from the present invention, since the shift is completed. 
         [0033]    The present invention advantageously incorporates a combined open and closed loop control method for controlling the shifting of a hydro-mechanical transmission, which has a variable displacement pump and a variable displacement motor in series with electronically controlled mechanical transmission of a vehicle. The control method includes controlling the clutches based on estimation or measurement of required transmission output torque and controlling the pump and/or motor displacements based on a difference of gear ratio associated with on-coming and off-going clutches, measured vehicle velocity and/or acceleration feedback and engine speed during the up or down shift of the transmission. 
         [0034]    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.