Abstract:
A ground engaging vehicle including a movable member, a hydraulically driven actuator, a hydraulic pump, a plurality of valves and at least one hydraulic conduit. The hydraulically driven actuator is coupled to the movable member and the actuator has a first chamber and a second chamber. The plurality of non-proportional valves include a first valve, a second valve, a third valve and a fourth valve. The at least one hydraulic conduit couples the pump with the first valve and the second valve. The first valve is in direct fluid communication with the first chamber. The second valve is in direct fluid communication with the second chamber. The third valve is in direct fluid communication with the first chamber and the fourth valve is in direct fluid communication with the second chamber. The first valve and the second valve each include an open position and a closed position.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a hydraulic system, and more particularly, to a ground engaging vehicle utilizing a hydraulic control system. 
       BACKGROUND OF THE INVENTION 
       [0002]    Hydraulics has a history practically as old as civilization itself. Hydraulics, more generally, fluid power, has evolved continuously and been refined countless times into the present day state in which it provides a power and finesse required by the most demanding industrial and mobile applications. Implementations of hydraulic systems are driven by the need for high power density, dynamic performance and maximum flexibility in system architecture. The touch of an operator can control hundreds of horsepower that can be delivered to any location where a pipe can be routed. The positioning tolerances can be held within thousandths of an inch and output force can be continuously varied in real time with a hydraulic system. Hydraulics today is a controlled, flexible muscle that provides power smoothly and precisely to accomplish useful work in millions of unique applications throughout the world. 
         [0003]    Most basic systems involve fluid drawn from a reservoir by a pump and forced through a shifted valve into an expandable chamber of a cylinder, which communicates with the work piece, ultimately performing a useful task. After the work is performed, the valve is shifted so the fluid is allowed back to the reservoir. The fluid cycles through this loop again and again. This is a simple on/off operation resulting in only two output force possibilities, zero or maximum. In many industrial and mobile hydraulic applications a dynamic variable force or variable displacement is required. This is accomplished with the use of throttling, a process whereby some of the high-pressure fluid is diverted, depressurized and returned to the reservoir. The use of such a diversion results in an output force at some intermediate point between zero and maximum. If a greater amount of fluid is allowed back to low pressure, the output force is lower. Conversely, if the amount of fluid allowed back to the low pressure portion of the system is less, then the output force is higher. Throttling, while being somewhat inefficient is highly effective. 
         [0004]    Another widely implemented form of hydraulics is hydrostatics. A hydrostatic power transmission system consists of a hydraulic pump, a hydraulic motor and an appropriate control. This system can produce a variable speed and torque in either direction. Hydrostatic systems result in an increase in efficiency over the throttling method, but at a high initial expense. An extended control effort is required and response of a hydrostatic system is not as fast as with servo or proportional valves that may be used in a throttling operation. 
         [0005]    What is needed in the art is a more efficient hydraulic system for use with mobile equipment. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention provides a hydraulic system control for use with a ground engaging vehicle. 
         [0007]    The invention in one form is directed to a ground engaging vehicle including a movable member, a hydraulically driven actuator, a hydraulic pump, a plurality of valves and at least one hydraulic conduit. The hydraulically driven actuator is coupled to the movable member and the actuator has a first chamber and a second chamber. The plurality of non-proportional valves include a first valve, a second valve, a third valve and a fourth valve. The at least one hydraulic conduit couples the pump with the first valve and the second valve. The first valve is in direct fluid communication with the first chamber. The second valve is in direct fluid communication with the second chamber. The third valve is in direct fluid communication with the first chamber and the fourth valve is in direct fluid communication with the second chamber. The first valve and the second valve each include an open position and a closed position. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  illustrates a ground engaging vehicle in the form of a loader/backhoe utilizing an embodiment of the hydraulic control system of the present invention; 
           [0009]      FIG. 2  is a schematical representation of one embodiment of the hydraulic control system used by the loader/backhoe of  FIG. 1 ; 
           [0010]      FIG. 3  is a schematical representation of another embodiment of a hydraulic control system used in the loader/backhoe of  FIG. 1 ; 
           [0011]      FIG. 4  is a schematical representation of yet another embodiment of a hydraulic control system used in the loader/backhoe of  FIG. 1 ; 
           [0012]      FIG. 5  is a schematical representation of still another embodiment of a hydraulic control system used in the loader/backhoe of  FIG. 1 ; and 
           [0013]      FIG. 6  is a schematic block diagram illustrating a connection of a controller which uses a method of the present invention to thereby show the controlling interconnections of the various components with systems utilize the vehicle of  FIG. 1  and the embodiments of  FIGS. 2-5 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0014]    Referring now to the drawings, and more particularly to  FIG. 1 , there is shown a ground engaging vehicle  10 , more particularly illustrated as a backhoe/loader  10  having an engine  12 , a movable arm  14 , a moveable arm  16 , a hydraulic cylinder  18 , a hydraulic cylinder  20  and control levers  22 . Vehicle  10  includes a hydraulic system control that is more precisely described in the following discussion that is driven by engine  12 . The hydraulic system providing power to move movable arms  14  and  16  by way power provided to hydraulic cylinders  18  and  20  and under the control of an operator by way of control levers  22 . 
         [0015]    Referring additionally now to  FIG. 2 , there is shown a schematic illustration of system  50  that includes an electrical hydraulic control of a typical hydraulic actuator such as a hydraulic cylinder  18  or  20 . For ease of illustration, the hydraulic cylinder utilized in the schematics generically refer to any hydraulic cylinder utilized on vehicle  10 , not just to cylinders  18  and  20 , which simply exemplify motive power for moving arms  14  and  16  respectively. Electro-hydraulic system  50  includes an electric motor  52 , a pump/motor  54 , an inverter/charger  56 , a storage element  58 , which provide power to system  50  to ultimately drive load  60  by way of actuator  62 . Actuator  62  may be thought of as a generic hydraulic cylinder and it includes a piston  64  having a chamber  66  on one side of piston  64  and a chamber  68  on the other side of piston  64 . Electro-hydraulic system  50  further includes valves  70 ,  72 ,  74 ,  76 ,  78  and  80  that are interconnected within system  50  by way of hydraulic lines  82 . System  50  further includes check valve  84  and a reservoir  86 . 
         [0016]    Electric motor  52  is electrically controlled to supply a specific amount of rotating velocity to the shaft that interconnects motor  52  with pump/motor  54 . A control  22  is moved, thereby instructing the controller to send a signal to cause inverter  56  to supply power to electric motor  52 . The speed of electric motor  52  is effectively regulated by a control  22  causing a production of hydraulic flow of fluid from reservoir  86  through valve  80  depending upon the selection of the position of valves  70 - 80 . System  50  operates by utilizing digital on/off valves  70 - 80  and these valves are not proportional valves as are utilized in prior art systems. Proportional valves, or throttling valves restrict or meter the fluid flow therethrough and are not used in the present invention, where the metering of the fluid flow is accomplished by the controlled driving of pump  54 . 
         [0017]    The combination of motor  52  and pump  54  provide the metering of flow of the hydraulic fluid by controlling the speed of pump/motor  54  to correspond to the desired action as selected by the operator&#39;s movement of a control lever  22 . If it is desired to move load  60  upward by providing pressurized fluid to chamber  66  then valves  70  and  78  may be energized to thereby allow hydraulic fluid to be pumped from chamber  68  into chamber  66  thereby moving load  60  in the desired direction. Additionally, valve  80  may be energized thereby placing a check valve in the flow of fluid from reservoir  86  to pump  54  thereby allowing only any needed makeup of fluid to be drawn into the system. Additionally, valves  74  and  76  may be positioned to prevent cavitation of the system during its operation. Once load  60  is in a desired position as indicated by a return of a control  22  to a neutral position, then valves  70  and  78  may be returned to their normally closed position to prevent hydraulic fluid flow through lines  82  thereby holding load  60  and its desired position. For purposes of illustration, load  60  will be assumed to having been moved to a higher energy potential, which can be understood in light of  FIG. 1  as the raising of load  60  along with the weight of a movable member, for example, moving moveable arm  16  into a higher position relative to the ground. When it is desirable to lower load  60 , this can be accomplished in different manners including one in which energy is recovered from the lowering of the potential energy of load  60 , which is undertaken by allowing pump/motor  54  to reverse drive electric motor  53  causing electric motor  52  to function as a generator or alternator  52  causing the circuitry of inverter/charger  56  to charge energy storage  58 , which may be an electrical energy storage device  58  in the form of a battery  58 , thereby converting energy from the loss of potential mechanical positioning of load  60 . This is accomplished by energizing valve  70  and  78  while electrically not energizing motor  52  to thereby allow the hydraulic pressure coming from chamber  66  to pass through valve  70  through pump/motor  54  driving the shaft that is connected to motor  52  to allow the recovery of energy. Alternatively, if the speed of load  60  is inadequate then valve selections can be undertaken to cause load  60  to be driven down by energizing electric motor  52  in an opposite direction driving pump  54  in the opposite direction as well. In another alternate configuration, if pump  54  is driven in the same direction then valve  72  can be activated thereby supplying pressure to chamber  68  then valve  74  is energized allowing the flow to go through check valve  84  back to the reservoir. 
         [0018]    By electronically controlling and reversing motor  52  this allows for the driving of pump  54 , which is a fixed displacement pump causing the movement of piston  64  thus load  60 . This advantageously eliminates the proportional control valve that meters the flow and eliminates pressure losses through such valves. In this embodiment, each hydraulic cylinder of vehicle  10  has its own pump to thereby minimize the losses due to valve metering. Furthermore, pump  54  is turned into motor  54  to capture energy from over-running loads such as if load  60  is the lowering of moveable arm  16  or lowering of any other portion wherein potential energy can be recovered. The retraction speed can be faster as the pump can spin faster when in the motor mode and since the retraction is almost always due to gravity and its affect on the movement of load  60  and the rod side makeup fluid can be done by appropriate activation of valves  74  and/or  76 . Additionally, powering down the load can be further supplemented by appropriate positioning of valves  74 ,  78  and/or  80  without reversing direction of the motor. If the reservoir is pressurized it may enable faster pump rotation more flow or reduced displacement. If the reservoir is pressurized potentially the return check valve can be eliminated. 
         [0019]    Now, additionally referring to  FIG. 3  there is illustrated another embodiment of the present invention identified as hydraulic system  150  where elements are numbered similar to that in  FIG. 2  except that they are all increased by the number  100 . Additionally illustrated in  FIG. 3  are the movement of a load  188  by an actuator  190  schematically similar to actuator  162 , additional valves  192  and  194  along with a Load Sense (LS) pump  196 . In this embodiment an additional actuator  190  is driven from a common reservoir with the elements shown in  FIG. 2 . The two hydraulic circuits benefit each other by utilizing a common tank rail to drive the anti-cavitation flow and to minimize pump flow during a gravity extend or retract. Valve  194  is used to block pump flow in the case of a gravity induced load while valve  192  is used to control the speed of actuator  190 . The functioning of valve  192  and  194  could be combined into one valve. Pressurized fluid from actuator  162  may be routed to actuator  190  when both are commanded to move and the fluid contained in a chamber of actuator  162  is of sufficient pressure to move actuator  190 . This may occur, for example, when load  160  is being lowered. 
         [0020]    Now, additionally referring to  FIG. 4 , there is illustrated another embodiment of the present invention identified as hydraulic system  250 , that is substantially similar to that in  FIG. 3  except that motor  152  is directly linked to engine  12 . Motor  152  functions as a generator and also directly drives a pump  254  that includes a bidirectional swash plate like a hydrostatic pump. Here again a pressurized reservoir  186  can prove advantageous. Engine  12  directly drives pump  254 , with motor  152  functioning as a generator/motor to either provide additional power to pump  254  or to store energy in energy storage device  158  when pump  254  does not require as much energy as is available from engine  12 . This system approach allows a much smaller generator/motor and power electronics than those illustrated in  FIGS. 2 and 3 . 
         [0021]    Now, additionally referring to  FIG. 5 , there is shown a system  350  that is substantially similar to  FIGS. 3 and 4  except that motor  152  along with inverter  156  and energy storage  158  have been eliminated and a hydraulic accumulator  198  is added along with a hydraulic pump  252 . In this case, pump  254  is directly driven by engine  12  with hydraulic pump  252  providing supplemental power when needed by drawing on energy stored in accumulator  198 . The function is similar to that described above being undertaken this time with a hydraulic driving fluid rather than the electrical supplement of power. Pump  252  may be a proportional pump that is electrohydraulically controlled and is used to store energy in hydraulic accumulator  198  similar to the storage of energy in batteries  58  or  158 . Again as energy is removed from either loads  60 ,  160  or  188  the fluid may be routed so as to drive hydraulic motor  254 . Motor  254  may be variably coupled through a transmission system (not shown), and may be under the control of a controller, causing the driving of pump/motor  252  to store energy in hydraulic accumulator  198 . This configuration is similar to that described previously where energy is stored and removed from hydraulic accumulator  198  as a storage system. Further, pump  254  may have a fluid flow therethrough that is variable by the varying of the speed of the pump and/or the displacement of the pump. 
         [0022]    The overall advantage of the present invention is that the flow provided by the pump system is substantially unmetered or restricted except for any natural restriction which may occur in hydraulic lines  82  or  182  so that energy is not lost in the metering process as it is in the prior art control systems utilized on ground engaging vehicles. The present invention provides for the improvement of energy capture of a hydraulic system which may be by way of a dual hydrostatic pump and accumulator system while simplifying the system design. The embodiments presented allow for a reduction in fuel consumption by tying in the second cylinder into the energy saving technique of the present apparatus and method. Further, the embodiments presented above may feed back energy to the drive train for immediate use rather than storing it in the energy storage device. This is considered energy re-use so that the potential energy stored in an elevated load is directly used as the load is lowered. For example, if an operator is simultaneously lowering a loader bucket and accelerating the tractor, the energy derived from the lowering of the loader bucket is used add energy to the drive train thereby reducing a load on the engine. 
         [0023]    Now, additionally referring to  FIG. 6  there is a schematic block diagram of system  50 ,  150 ,  250  or  350  including controller  88 , sensors  90  and a display  92 . The interconnection of these elements is illustrated to show the controlling interaction between a controller  88  and engine  12 , operator inputs  22 , sensors  90 , display  92 , valves  70  et al., motor  52 ,  152 ,  252  and storage system  58 ,  158  and  198 . Controller  88  reacts to operator inputs  22  as well as information from sensors  90  to control the fluid flow in the system. Sensors  90  may include pressure sensors and positional sensors both linear and angular in nature to supply feedback signals to controller  88  of the movement of the actuators and the load that is being moved by the system. Valves  70  et al. are not metering valves but are rather digitally operated valves providing either complete fluid flow, no fluid flow or the introduction of a check valve into the line. No metering is undertaken by valves  70  et al. 
         [0024]    Having described the preferred embodiment, it will become apparent that various modifications can be made without departing from the scope of the invention as defined in the accompanying claims.