Abstract:
To dissipate hydraulic shock created by the bouncing of an implement mounted on a wheeled vehicle, such as a towed tillage implement or the bucket of a vehicle, such as a wheel loader, an electronic control valve, which supplies hydraulic fluid to the hydraulic actuator that raises and lowers the implement, is actively controlled by an electronic controller. As the vehicle with an implement is transported at higher speeds, the implement tends to bounce creating pressure spikes in the hydraulic system that raises and lowers the implement. The pressure spikes are dissipated by actively generating random or cancelling hydraulic pulses in the hydraulic system.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a towed work vehicle having an implement that is operated with a hydraulic actuator, such as a tillage implement or soil working device, including a seed planter, plow, harrow and dibble, that is towed by a tractor, or a work vehicle, such as a wheeled loader or a backhoe having an implement that is operated with a hydraulic actuator. In particular, the present invention relates to controlling implement bounce during travel of the vehicle at higher speeds. 
     BACKGROUND OF THE INVENTION 
     Various types of farm, off-road of construction vehicles are used to perform tillage and excavation functions such as plowing, planting, harvesting, leveling, digging, material handling, trenching etc. These operations are typically accomplished with the use of a hydraulically operated implement. These implements include implements towed vehicle and implements translationally supported and rotationally supported on a vehicle by a plurality of linkages. The implements are moved relative to the supports by hydraulic cylinders or motors. These vehicles are often required to travel on roads between job sites. Accordingly, it is important that the vehicle travel at reasonably high speeds, greater than 15 mph. However, due to the suspension, or lack thereof, the implements supported on the vehicle, bounce, pitch or oscillate at speeds satisfactory for road travel. This implement movement can result in the vehicle bouncing, pitching or oscillating. 
     In an attempt to improve roadability, various systems have been developed for interacting with the implements and their associated linkages and hydraulics to control bouncing and oscillation of the vehicles while operating at road speeds. One such system includes circuitry for lifting and tilting an implement combined with a shock absorbing mechanism. This system permits relative movement between the implement and the vehicle to reduce pitching of the vehicle during road travel. To inhibit inadvertent vertical displacement of the implement, the shock absorbing mechanism is responsive to lifting action of the implement. The shock absorbing mechanism is responsive to hydraulic conditions indicative of imminent tilting movement of the implement, thereby eliminating inadvertent vertical displacement of the implement. 
     Other systems for improving the performance of excavators have included accumulators that are connected and disconnected to the hydraulic system depending upon the speed of the vehicle. More specifically, the accumulators are connected to the hydraulic system when the vehicle is at speeds indicative of a driving speed and disconnected at speeds indicative of a loading or dumping. 
     Other systems include controllers that determine the acceleration of the vehicle based upon the pressure of the hydraulic actuator that lifts the implement and that generate an acceleration signal representative of the acceleration of the vehicle. The controller applies control signals to an electronic control valve to cause the electronic control valve to control the flow of hydraulic fluid applied to the actuator to maintain the pressure signal substantially constant based upon the acceleration signal. 
     These systems may have provided improvements in roadability, but it would be desirable to provide an improved system to actively dissipate the bounce in an implement with hydraulic lift. Accordingly, the present invention provides a control system which controls the pressure in the hydraulic lift cylinders of the implement or implements associated with the vehicle. The control system dissipates or disrupts the hydraulic pressure fluctuations and consequently reduces the implement bounce. 
     SUMMARY OF THE INVENTION 
     In a preferred form of the invention, a control system for a vehicle having an implement moveable relative to the vehicle includes a pressurized fluid source, a hydraulic actuator, an electronic control valve, a transducer or a switch, and an electronic controller. The hydraulic actuator is mechanically coupled between the vehicle and the implement or between the implement frame and the implement transport wheels to lift the implement. The electronic control valve is fluidly coupled to the pressurized fluid source and the hydraulic actuator to control the flow of pressurized fluid that is applied to the hydraulic actuator by the pressurized fluid source. The electronic control valve has raise, neutral and lower positions. The pressurized fluid is applied to the hydraulic actuator by the pressurized fluid source to raise the implement relative to the vehicle when the electronic control valve is in the raise position and pressurized fluid is applied to the hydraulic actuator by the pressurized fluid source to lower the implement relative to the vehicle when the electronic control valve is in the lower position. The transducer generates an activation signal related to the pressure in the hydraulic actuator or the speed of the vehicle. The electronic controller is electrically coupled to the electronic control valve and the transducer or the switch. The electronic controller is programmed to generate valve command signals based upon the activation signal or position of the switch and apply the command signals to the electronic control valve to cause the electronic control valve to control the flow of pressurized fluid applied to the hydraulic actuator to actively dissipate implement bounce. The electronic controller is programmed to compare the activation signal to a predetermined threshold value or determine the position of the switch, and when the predetermined threshold value is exceeded or the switch is in the activation position, to activate the electronic control valve to cycle the electronic control valve from the neutral position to the raise position and back to the neutral position, and from the neutral position to the lower position and back to the neutral position, creating hydraulic pulses in the hydraulic actuator and dissipating implement bounce. The frequency of the hydraulic pulses is either random or out of phase with the implement bounce if the electronic control valve is activated by the predetermined threshold value being exceeded and random if the electronic control valve is activated by positioning the switch in the activation position. 
     The invention also includes a vehicle in which the control system is installed. Further, the invention includes a method of dissipating implement bounce in a vehicle using the control system by comparing the activation signal generated by a transducer to a predetermined threshold value or determining the position of a switch, and if the activation signal exceeds the predetermined threshold value or the switch is in the activation position, activating the electronic control valve to cycle from the neutral position to the raise position and back to the neutral position, and from the neutral position to the lower position and back to the neutral, creating hydraulic pulses in the hydraulic actuator and dissipating implement bounce. The frequency of the hydraulic pulses is either random or out of phase with the implement bounce if the electronic control valve is activated by the predetermined threshold value being exceeded and random if the electronic control valve is activated by positioning the switch in the activation position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic side elevation view of a tractor and tillage implement with the tillage implement shown in transport position with portions broken away. 
         FIG. 2  is a schematic side elevation view of a wheel loader equipped with a bucket shown in various elevational and tilted positions. 
         FIG. 3  is a diagrammatic view of a control system used with the tractor and tillage implement illustrated in  FIG. 1  and the wheel loader illustrated in  FIG. 2  and including a hydraulic system according to the present invention. 
         FIGS. 4A and 4B  are graphic representations of the pressure of a hydraulic actuator versus time showing the position of an electronic control valve in accordance with the disruptive embodiment of the present invention. 
         FIGS. 5A and 5B  are graphic representations of the pressure of a hydraulic actuator versus time showing the position of an electronic control valve in accordance with the cancellation embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     While the present invention is susceptible of embodiment in various forms, there is shown in the drawings and will hereinafter be described preferred embodiments of the present invention with the understanding that the present disclosure is to be considered as an exemplification of the invention that is not intended to limit the invention to the specific embodiment illustrated. 
     Referring now to  FIG. 1 , a tractor  104  tows a soil-working vehicle  106 . The vehicle  106  includes a frame  108 , to which one or more agricultural implements or tools  110  are movably mounted. The implement shown in  FIG. 1  being a plow. The frame  108  is connected to a draw bar  172  of the tractor  104  or other agricultural vehicle, and is moved through the fields or over roads on wheels  174 . Hydraulic actuators  164  that are supported by frame  108  and control the position of implements  110 . The implements  110  are shown in the transport position. To till the soil, the implements  110  are lowered by the hydraulic actuators into the ground. 
     Referring now to  FIG. 2 , a vehicle  10 , such as a wheel loader, includes a frame  12 ; air filled tires  14  and  16 ; a suitable implement  20 , such as a bucket; a pair of lift arms  22 ; and a pair of hydraulic actuators  24  including hydraulic actuator columns  23  and hydraulic actuator cylinders  25 . The frame  12  of vehicle  10  is carried by the tires  14  and  16 . The frame  12  includes an operator cab  18 . The pair of lift arms  22  is connected to the frame  12  by a pair of arm pivots  26 . The lift arms  22  are also connected to the frame by the hydraulic actuators  24  which include the hydraulic actuator columns  23  which translate relative to the hydraulic actuator cylinders  25 . The hydraulic actuator columns  23  extend and retract relative to hydraulic actuator cylinders  25 , forcing lift arms  22  to pivot about arm pivots  26  causing bucket or implement  20  to be raised or lowered, or rotated, as shown by phantom lines in  FIG. 2 . The hydraulic actuators  24  raise, lower, and hold the implement  20  relative to the frame  12  to carry out construction tasks such as moving and unloading the contents thereof. 
     The implement  20  is pivotally connected to the end of the lift arms  22 . Extending and retracting hydraulic actuators  31  causes the implement  20  to rotate, as shown in  FIG. 2 . 
     A control system including a hydraulic system  50  and an electronic controller  58 , shown in  FIG. 3 , is mounted on the tractor  104  or implement frame  108  in  FIG. 1  or frame  12  in  FIG. 2 . The hydraulic system  50  includes a hydraulic fluid source or reservoir  30 ; a hydraulic return conduit  32 ; a hydraulic supply conduit  34 ; a hydraulic pump  36 , which is the source of pressurized hydraulic fluid; hydraulic conduits  38 ,  42 , and  44 ; an electronic control valve  40 ; and a transducer  46 . The control system includes the hydraulic system  50 , a signal data bus  56 , an electronic controller  58  and a control signal bus  64 . By way of example, electronic control valve  40  may be a Danfoss electro-hydraulic valve with spool position feedback. 
     The reservoir  30  is fluidly connected to the hydraulic pump  36  by the hydraulic supply conduit  34 . The hydraulic pump  36  is fluidly connected to the electronic control valve  40  by the hydraulic conduit  38 . The electronic control valve  40  is fluidly connected to the hydraulic actuator  24  by hydraulic conduits  42  and  44 . The pressure transducer  46  is also in fluid communication with hydraulic conduit  42 . The electronic control valve  40  is also fluidly connected to the reservoir  30  by the hydraulic return conduit  32 , thereby completing the hydraulic circuit of the hydraulic system  50 . The transducer  46  is connected to the electronic controller  58  by signal data bus  56 . The electronic controller  58  is connected to the electronic control valve  40  by the control signal bus  64 . 
     The electronic controller  58  operates to dissipate hydraulic shock in the hydraulic actuators  24 , thereby dampening vertical motions of the vehicle. In operation, the transducer  46 , which is in fluid communication with the hydraulic fluid, measures the pressure in the hydraulic conduit  42 , which is substantially the same as that in the hydraulic actuator  24 . A signal from the transducer  46  is electrically communicated to the electronic controller  58  over the signal data bus  56 . Using the sampled pressure information, the electronic controller  58  calculates a digital control signal. The digital control signal is passed over the control signal bus  64  to the electronic control valve  40 . 
     By way of example, the electronic controller  58  could be a digital processing circuit, such as an Intel 87C196CA. Alternatively, the electronic controller  58  can be programmed to generate a pulse-width-modulated (PWM) signal. The electronic control valve  40  would in turn be a PWM valve controllable with a PWM signal. 
     The electronic control valve  40  controls the flow of hydraulic fluid into and out of the hydraulic actuator  24  thereby causing the hydraulic actuator column  23  to move in or out of the hydraulic actuator cylinder  25 . Hydraulic fluid is supplied to the electronic control valve  40  from the reservoir  30 , through the hydraulic supply conduit  34 , to the hydraulic pump  36 , which forces the hydraulic fluid through the hydraulic conduit  38  and into the electronic control valve  40 . The electronic control valve  40  controls the ingress and egress of hydraulic fluid to the hydraulic actuator  24 . The electronic control valve  40  controls both the path of flow for the hydraulic fluid and the volumetric flow of hydraulic fluid. The electronic control valve  40  directs hydraulic fluid either into the hydraulic conduit  42  and out of the hydraulic conduit  44  or into the hydraulic conduit  44  and out of the hydraulic conduit  42 , depending on the intended direction of travel of the hydraulic actuator column  23 . The control signal received from the control signal bus  64  commands the electronic control valve  40  to control both the direction of hydraulic fluid flow and the volumetric flow of the fluid. Excess hydraulic fluid is directed by the electronic control valve  40  through the hydraulic return conduit  32  and back to the reservoir  30 . 
     The type of vehicles to which the described control can be applied includes, but is not limited to towed implements such as plows, seed planters, harrows and dibbles, excavators, backhoes, snowplows, cranes, skid-steer loaders and wheel loaders (see  FIGS. 1 and 2 ), and other construction or utility vehicles having an implement  20 , arm, or boom moveable relative to the vehicle frame  12 ,  108 . The control system is not limited to vehicles with a pair of lift arms  22  such as the vehicle  10 , but may also be applied to vehicles with a multiplicity of lift arms or a single lift arm such as on a backhoe or a crane. 
     The hydraulic actuator  24 ,  164 , used to move the implement  20 ,  110 , is used to dampen bouncing and pitching of the vehicle by actively dissipating the bounce in the implement  20 ,  110  with a hydraulic lift. The control system may be applied to vehicles using various types of hydraulic actuation systems including hydraulic cylinders and hydraulic motors. 
     The electronic controller  58 , shown in  FIG. 3 , is programmed to actively dissipate the bounce in the implement  20 ,  110 . As the implement  20 ,  110  bounces, the pressure of the hydraulic fluid in the hydraulic cylinder or actuator  25 ,  164  fluctuates. By actively controlling the electronic control valve  40 , the hydraulic pressure fluctuations are dissipated or disrupted, causing the bounce of implement  20 ,  110  to be reduced. 
     Two methods of controlling the electronic control valve  40  to reduce implement bounce are described, disruptive valve control and cancellation valve control. Both methods are initiated when the hydraulic pressure in the hydraulic actuator spikes beyond a predetermined threshold value  72  or the vehicle is traveling at a speed greater than a predetermined threshold speed. The disruptive valve control method may be initiated manually by positioning a switch in an activation position. In one preferred embodiment the predetermined threshold value  72  is about 1.2 times the pressure required to hold the implement  20 ,  110  in the raised position. 
     The pressure spikes  74  can also be determined by measuring the variation in tire  16  deflections, the vertical accelerations of the implement  20 ,  110  with an accelerometer mounted to the implement  20 ,  110  or deflections of the frame  12  on which the implement  20 ,  110  is mounted with a strain gauge and comparing the deflections or accelerations to a predetermined threshold value. The disruptive valve control method can also be initiated when the speed of the vehicle exceeds a predetermined threshold value. 
     To insure that the pressure spikes  74  are caused by implement bounce while transporting the vehicle and not by pressure spikes caused by using the implement  20 ,  110  as it digs or lifts a load, the speed of the vehicle may be measured and transmitted to the electronic controller  58 . Once the speed of the vehicle exceeds a predetermined threshold speed, such as 15 mph, the electronic controller  58  may initiate the disruptive valve control method or allow the disruptive or cancellation methods to be initiated. If the speed of the vehicle drops below the predetermined threshold speed, the electronic controller  58  may terminate the disruptive or cancellation methods. 
     When the predetermined threshold value  72  is met and/or the predetermined threshold speed value is met, the electronic controller  58  cycles the electronic control valve  40  from the neutral position to the raise position and back to the neutral position, and from the neutral position to the lower position and back to the neutral position. The flow of hydraulic fluid through the electronic control valve  40  during the raise and lower cycles is small and substantially equal, so that the implement  20 ,  110  does not move substantially and will maintain its desired transport height when the implement bounce has been dissipated. 
     The disruptive valve control method is shown graphically in the  FIGS. 4A and 4B . When the activation signal  70  related to the pressure in the hydraulic actuator  24 ,  164  exceeds a predetermined threshold value  72 , the electronic controller  58  calculates a random digital control signal. The digital control signal is passed over the control signal bus  64  to the electronic control valve  40 , which is alternately cycled from the neutral position to the raise position and back to the neutral position, and from the neutral position to the lower position and back to the neutral position. That is, the electronic control valve  40  is alternatively moved from its neutral position to its raise position to its neutral position (see time periods A in  FIG. 4A ) and then from its neutral position to its lower position to its neutral position (see time periods B in  FIG. 4A ), in repetitive cycles at randomly spaced intervals of time. The length of the time interval between the raise cycles and lower cycles (see time periods C in  FIG. 4A ) varies randomly. 
     The hydraulic fluid flow through electronic control valve  40  during the raise cycles and lower cycles is small and substantially equal, so that the implement  20 ,  110  does not move substantially, i.e., the time intervals A and B are equal. Preferably, each raise cycle follows a lower cycle and each lower cycle follows a raise cycle. However, the raise cycles and lower cycles can be activated randomly, as long is the total number of raise cycles and total number of lower cycles are substantially the same, so that the implement  20 ,  110  does not move substantially. 
     Retracting the hydraulic actuator cylinder  25  requires less oil than extending it. Consequently, if intervals A and B are small and equal, the implement  20 ,  110  could actually lower through the dissipation cycle. To insure the implement  20 ,  110  is in the fully raised position when the bounce has been dissipated, the electronic control valve  40  cycles can end with the electronic control valve  40  in a prolonged raise position. 
     In a second embodiment of the disruptive valve control method shown in  FIG. 4B , the time interval C between the raise cycles and the lower cycles is substantially zero. In this embodiment, the length of time intervals A and B vary. However, preferably, the total of the length of time of intervals A substantially equals the total of the length of time of intervals B, so that the implement  20  does not move substantially. Again, the electronic control valve  40  cycles can end with the electronic control valve  40  in a prolonged raise position to insure that the implement  20 ,  110  is in the fully raised position when the bounce has been dissipated. 
     By generating the random hydraulic pulses in the hydraulic actuator  24 ,  164 , the hydraulic pulses created by the implement bounce will dissipate faster than if the electronic control valve  40  were continuously closed in the neutral position. The random pattern of the raise and lower cycles during the disruptive valve control method prevents the electronic control valve  40  from exciting the implement bounce. 
     In the cancellation method, shown in  FIGS. 5A and 5B , the electronic controller  58  determines the frequency and period at which the implement  20 ,  110  is bouncing. Assuming that the dampening forces and mass of the implement remain constant, the frequency of the bounce will remain constant. The frequency of the implement bounce is determined by measuring the pressure in the hydraulic actuator  24 , 110 . 
     The electronic controller  58  then controls the electronic control valve  40  movement from its neutral position to its raise position to its neutral position (see time interval A in  FIG. 5A ) and then from its neutral position to its lower position to its neutral position (see time interval B in  FIG. 5A ) in repetitive cycles out of phase with the bouncing of implement  20 ,  110  to create a cancelling effect. The frequency of the bouncing is determined by the length of time between the pressure spikes  74 , as measured by the transducer  46  or by other means. 
     When the activation signal  70  related to the pressure in the hydraulic actuator  24 ,  164  as measured by the transducer  46  is greater than steady state  76 , the electronic control valve  40  would be positioned in the lower position (shown as time interval B in  FIG. 5A ), absorbing some of the energy by allowing the implement  20 ,  110  to lower slightly. When the activation signal  70  related to the pressure in the hydraulic actuator  24 ,  164  as measured by the transducer  46  is less than steady state  76 , the electronic control valve  40  would be positioned in the raise position (shown as time interval A in  FIG. 5A ), raising the implement  20 ,  110  slightly. 
     Similar to the disruptive control method, the flow of hydraulic fluid through the electronic control valve  40  during raising and lowering of the implement  20 ,  110  is small and substantially equal, so that the implement  20 ,  110  does not move substantially. Preferably, each raise cycle follows a lower cycle and each lower cycle follows a raise cycle. However, the raise cycles and lower cycles can be activated randomly, as long is the total number of raise cycles and total number of lower cycles are substantially the same, so that the implement  20  does not move substantially. Again, the electronic control valve  40  cycles can end with the electronic control valve  40  in a prolonged raise position to insure that the implement  20 ,  110  is in the fully raised position when the bounce has been dissipated. 
     Also, as shown in  FIG. 5B , the length of time of the intervals A and B may be less than on half the period at which the implement  20 ,  110  is bouncing. Therefore, the electronic control valve  40  is in the neutral position during the time interval C. 
     In both disruptive and cancellation methods, when the pressure spikes  74  have been reduced below the predetermined threshold value  72  or a predetermined time has passed, the electronic control valve  40  is returned to its neutral position. If the pressure spikes  74  exceed the threshold value again, the process is repeated until the pressure spikes  74  have been reduced below the predetermined threshold value  72  or a predetermined time has passed. 
     While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.