Patent Publication Number: US-6701822-B2

Title: Independent and regenerative mode fluid control system

Description:
This application claims the benefit of U.S. Provisional Application Ser. No. 60/328,430 entitled “Independent and Regenerative Mode Fluid Control System,” filed Oct. 12, 2001. 
    
    
     TECHNICAL FIELD 
     This invention relates to a fluid control system for operating actuators. More particularly, the invention is directed to a fluid control system for operating multiple actuators in independent and regenerative function modes. 
     BACKGROUND 
     Some fluid control systems operate a double-acting actuator with a regeneration capability. The fluid control systems with this regeneration capability direct some of the fluid exhausted from a contracting chamber of a double-acting actuator to an expanding chamber of the actuator. 
     In the past, a regeneration valve is disposed between a main directional control valve and an actuator to provide a quick drop capability to the actuator driven in one direction by gravity loads. In such a configuration, however, an operator has little or no control over the amount of regenerated fluid recirculated from the contracting chamber to the expanding chamber. 
     A fluid control system with a relatively simple regeneration capability has been provided in association with a pump, a tank, and a double-acting actuator having a pair of actuating chambers. For example, U.S. Pat. No. 6,161,467 discloses a fluid control system having a regeneration capability. The system includes a pump, a tank, two double-acting actuators having actuating chambers, and a control valve. The control valve moves from a first position to a second position in a regeneration mode. This fluid control system, however, does not allow operation of the multiple actuators both regeneratively and independently. It is desirable to provide a fluid control system that provides accurate control of the actuators and is compact in size. 
     Accordingly, the present invention is directed to overcoming one or more of the problems as set forth above. 
     SUMMARY OF THE INVENTION 
     In one aspect of the invention, a fluid control system includes a first double-acting actuator and a second double-acting actuator. A first independent metering valve has a first control port connected to the first double-acting actuator, a second control port connected to the second double-acting actuator, first and second independently operable valves disposed between the inlet port and the first and second control ports, and a first check control mechanism having a main check valve between the inlet port and the first and second independently operable valves. The first check control mechanism controls the main check valve to allow the first and second actuators to operate in either an independent function mode or a regenerative function mode. A second independent metering valve has a first control port connected to the first double-acting actuator, a second control port connected to the second double-acting actuator, first and second independently operable valves disposed between the inlet port and the first and second control ports, and a main check valve disposed between the inlet port and the first and second independently operable valves. 
     In another aspect of the invention, a method is provided to control fluid flow to and from first and second double-acting actuators in an independent function mode and a regenerative function mode. The method includes providing a first independent metering valve having a first check control mechanism in fluid communication with the first and second double-acting actuators, providing a second independent metering valve having a main check valve in fluid communication with the first and second double-acting actuator, and operating the first control check control mechanism to allow the first and second actuators to selectively operate in independent and regenerative function modes. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description, serve to explain the principles of the invention. 
     FIG. 1 is a schematic and diagrammatic representation of a fluid control system according to one embodiment of the present invention; 
     FIG. 2 is a schematic and diagrammatic representation of an embodiment of a check mechanism for the fluid control system of FIG. 1; and 
     FIG. 3 is a schematic and diagrammatic representation of another embodiment of a check mechanism for the fluid control system of FIG.  1 . 
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
     FIG. 1 illustrates one embodiment of the fluid control system of the present invention having regenerative and independent function modes. The fluid control system  10  has a pump  12  and a reservoir  14  in fluid communication with the pump  12 . The pump  12  is typically driven by a motor (not shown in the figure), such as an engine, and receives fluid from the reservoir  14 . The pump  12  has a pump outlet port  16  connected to a supply conduit  18 . 
     In one exemplary embodiment, the fluid control system  10  includes a first double-acting actuator  20 . The first double-acting actuator  20  has a pair of actuating chambers, namely a head end actuating chamber  22  and a rod end actuating chamber  24 . The head end chamber  22  and the rod end chamber  24  are separated by a piston  26  having a piston rod  28 . The double-acting actuator  20  may be a hydraulic cylinder or any other suitable implement device used for raising, lowering, or tilting parts of a machine, such as an excavator or a track loader. 
     The fluid control system  10  has a second double-acting actuator  30 . Similar to the first actuator  20 , the second double-acting actuator  30  has a head end chamber  32  and a rod end chamber  34  separated by a piston  36 . A piston rod  38  is connected to the piston  36 . The second double-acting actuator  30  may also be a hydraulic cylinder or any other suitable implement device. 
     The fluid control system  10  includes a first independent metering valve (IMV)  40 . As shown in FIG. 1, the first IMV  40  has an inlet port  42  and two outlet ports  44 . The inlet port  42  is connected to the pump  12  via the supply conduit  18  and receives the pressurized fluid from the pump. The outlet ports  44  may be connected to a reservoir (the connection is not shown in the figure) to discharge fluid out of the first IMV  40 . In one embodiment, this reservoir may be the reservoir  14  connected to the pump  12 . 
     The first IMV  40  also has first and second control ports  46 ,  48 , respectively. The first control port  46  is connected to the rod end chamber  24  of the first double-acting actuator  20  by a conduit  50 . The second control port  48  is connected to the head end chamber  32  of the second double-acting actuator  30  by a conduit  52 . 
     The first IMV  40  has four independently operable valves. A first independently operable valve  54  is disposed between the inlet port  42  and the first control port  46 , and a second independently operable valve  56  is disposed between the inlet port  42  and the second control port  48 . A third independently operable valve  58  is disposed between the outlet port  44  and the first control port  46 , and a fourth independently operable valve  60  is disposed between the outlet port  44  and the second control port  48 . In one exemplary embodiment, these independently operable valves are proportional valves that can vary fluid flow through the valves based on load requirements. Each of the valves may be equipped with a spring (not shown) to keep the valves in a closed position when the valves are not activated. 
     The first IMV  40  has solenoid  62  coupled to the first independently operable valve  54  to operate the valve when the solenoid is energized. A second solenoid  64 , a third solenoid  66 , and a fourth solenoid  68  are coupled to the second, third, and fourth independently operable valves  56 ,  58 ,  60 , respectively, to operate the valves in a similar fashion. These solenoids are energized by a control unit (not shown) to selectively open and close the independently operable valves. 
     The first IMV  40  includes a main check valve  70  between the inlet port  42  and the first and second independently operable valves  54 ,  56 . The main check valve  70  may be located near the inlet port  42  and may be biased toward a closed position by a spring (not shown in FIG.  1 ). When the pump  14  supplies the main check valve with sufficient fluid pressure via the supply conduit  18  and the inlet port  42 , the main check valve  70  is pushed open by the fluid pressure and the fluid from the pump  12  flows through the check valve  70  to the first and second valves  54 ,  56  of the first IMV  40 . 
     The fluid control system  10  also includes a second independent metering valve (IMV)  72 . In an exemplary embodiment, the second IMV  72  is located parallel to the first IMV  40  so that the overall size of the fluid control system  10  can be minimized. The structure of the second IMV  72  may be similar to the first IMV  40 . As shown in FIG. 1, the second IMV  40  has an inlet port  74  and two outlet ports  76 . The inlet port  74  is connected to the pump  12  via the supply conduit  18  and receives the pressurized fluid from the pump. FIG. 1 illustrates the supply conduit  18  branched into two conduits to supply the pressurized fluid to the inlet port  74  of the second IMV  72  and the inlet port  42  of the first IMV  40 . The outlet ports  76  may be connected to a reservoir (the connection is not shown in the figure) to discharge the fluid out of the second IMV  72 . This reservoir may be the same reservoir  14  that is connected to the pump  12 . 
     The second IMV  72  also has first and second control ports  78 ,  80 , respectively. The first control port  78  is connected to the head end chamber  22  of the first double-acting actuator  20  by a conduit  82 . The second control port  80  is connected to the rod end chamber  34  of the second double-acting actuator  30  by a conduit  84 . 
     As illustrated in FIG. 1, the second IMV  72  has four independently operable valves, namely first, second, third and fourth independently operable valves  86 ,  88 ,  90 ,  92 , respectively. The first independently operable valve  86  is disposed between the inlet port  74  and the first control port  78 , and the second independently operable valve  88  is disposed between the inlet port  74  and the second control port  80 . The third independently operable valve  90  is disposed between the outlet port  76  and the first control port  78 . The fourth independently operable valve  92  is disposed between the outlet port  76  and the second control port  80 . In one exemplary embodiment, these independently operable valves are proportional valves that can vary fluid flow through the valves based on load requirements. Each of the valves may be equipped with a spring (not shown) to keep the valves in a closed position when the valves are not activated. 
     Similar to the first IMV  40 , the second IMV  72  also has a first solenoid  94  coupled to the first independently operable valve  86  to operate the valve when the solenoid is energized. A second solenoid  96 , a third solenoid  98 , and a fourth solenoid  100  are coupled to the second, third, and fourth independently operable valves  88 ,  90 ,  92 , respectively, to operate the valves. 
     These solenoids are energized by a control unit (not shown) to selectively open and close the independently operable valves. 
     The second IMV  72  includes a main check valve  102  between the inlet port  74  and the first and second independently operable valves  86 ,  88 . The main check valve  102  may be located near the inlet port  74  and may be biased toward a closed position by a spring (not shown in FIG.  1 ). When the pump  14  supplies the main check valve  102  with sufficient fluid pressure via the supply conduit  18  and the inlet port  74 , the main check valve  102  is opened by the fluid pressure and the fluid flows through the main check valve  102  to the first and second valves  86 ,  88  of the second IMV  72 . 
     As shown in FIG. 1, the first IMV  40  has a first check control mechanism  104  to control the main check valve  70 . FIG. 2 illustrates one embodiment of the first check control mechanism  104 . As shown in FIG. 2, the first check control mechanism  104  has a proportional valve  106  coupled to the main check valve  70  via a conduit  108 . The proportional valve  106  can be either normally opened or closed and can be actuated to close or open by energizing a solenoid  110  associated with the proportional valve  106 . A normally opened proportional valve is illustrated in FIG.  2 . The proportional valve  106  is connected to the first and second independently operable valves  54 ,  56  via a conduit  116 . 
     The main check valve  70  includes a body  112  having an inlet port  114  and two outlet ports, namely a first outlet port  117  and a second outlet port  119 . The inlet port  114  is in communication with the pump  12  via the supply conduit  18  and the inlet port  42 . The first outlet port  117  is connected to the first and second independently operable valves  54 ,  56  via a conduit  118 , and the second outlet port  119  is connected to the proportional valve  106  via the conduit  108 . The main check valve  70  also has a valve element  120  slidably positioned within the body  112 . A pump side chamber  122  is formed at the pump side of the valve element  120  and a proportional valve side chamber  124  is formed at proportional valve side. The pump side chamber  122  is in fluid communication with the inlet port  42  of the first IMV  40 . The valve element  120  is movable between a closed position where the inlet port  114  is blocked from communication with the first outlet port  117  (See FIG. 2) and an open position where the first outlet port  117  is in communication with the inlet port  114 . A spring  126  is provided within the proportional valve side chamber  124  and biases the valve element  120  to the closed position. The valve element  120  can be moved to the open position when the fluid pressure in the pump side chamber  122  overcomes the fluid pressure in the proportional valve side chamber  124  and the force of the spring  126 . The valve element  120  is moved to the closed position when the spring bias force and the force due to the fluid pressure in the proportional valve side chamber  124  become greater than the force due to the fluid pressure in the pump side chamber  122 . 
     As shown in FIG. 2, the valve element  120  has a first check valve  128  and a control orifice  130  disposed in communication with the pump side chamber  122  and the proportional valve side chamber  124 . The valve element  120  also has a second check valve  132  that connects the proportional valve side chamber  124  and the first outlet port  117 . In this configuration, the fluid pressure in the proportional valve side chamber  124  is equal to the higher of the fluid pressure in the pump side chamber  122  or at the first outlet  117 . 
     FIG. 3 illustrates another embodiment of the check control mechanism  104 . The check control mechanism  104  in FIG. 3 has the main check valve  70  and the proportional valve  106  actuated by the solenoid  110 . Unlike the check control mechanism shown in FIG. 2, however, the check control mechanism in FIG. 3 has the first check valve  128  and the control orifice  130  externally, i.e., not in the valve element  120 . The check valve  128  and the control orifice  130  are disposed in communication with the pump side chamber  122  and the proportional valve side chamber  124 . The relative positions of the check valve  128  and the control orifice  130  may be reversed. In this embodiment, the valve element  120  has the second check valve  132  that connects the proportional valve side chamber  124  and the first outlet port  117 . 
     In FIG. 1, the second IMV  72  has a second check control mechanism  105 , which is similar to the check control mechanism  104  for the first IMV  40 . In another embodiment, however, the fluid control system  10  may not be equipped with the second check control system  105 . 
     Industrial Applicability 
     The operation of the fluid control system  10  as illustrated in FIG. 1 is described hereafter. When the pump  12  is operated, pressurized fluid flows from the pump  12  to the inlet port  42  of the first IMV  40  and the inlet port  74  of the second IMV  72  via the split conduit  18 . The pressurized fluid is applied to the pump side chamber  122  of the first check control mechanism  104  of the first IMV  40  and the second check control mechanism  105  of the second IMV  72 . 
     The valve element  120  of the check control mechanism  104  is initially in the closed position, wherein the inlet port  114  is blocked from communication with the first outlet port  117 . When the fluid pressure from the pump  12  is sufficiently small, the spring  126  maintains the valve element  120  in the closed position. When the valve element  120  is in the closed position, the fluid in the pump side chamber  122  travels through the check valve  128  and the control orifice  130  to the proportional valve side chamber  124 . 
     When the fluid control system  10  is in the independent function mode, the proportional valve  106  of the check control mechanism  104  is in the open position. Once the pressure in the pump side chamber  122  overcomes the fluid pressure in the proportional valve side chamber  124  and the bias force of the spring  126 , and the proportional valve  106  is open, the fluid pressure in the pump side chamber  122  moves the valve element  120  to the open position where the inlet port  114  is in fluid communication with the first outlet port  117 . Thus, the fluid from the pump  12  flows through the first check control mechanism  104  to the first and second independently operable valves  54 ,  56  of the first IMV  40 . Similarly, the fluid from the pump  12  flows through the second check control mechanism  105  to the first and second independently operable valves  86 ,  88  of the second IMV  72  when the valve element  120  of the second check control mechanism  105  opens. 
     To pressurize the head end chamber  22  of the first double-acting actuator  20 , the first valve  86  of the second IMV  72  is selectively opened and the third valve  90  is closed. The pressurized fluid from the pump  12  then flows through the second IMV  72  to the head end chamber  22  of the first double-acting actuator  20 , and the piston  26  and the piston rod  28  move in the upward direction according to the orientation in FIG.  1 . At the same time, the fluid in the rod end chamber  24  of the first actuator  20  flows to the first IMV  40  through the conduit  50  and the first control port  46 . The third valve  58  of the first IMV  40  is opened and the fluid from the rod end chamber  24  of actuator  20  can exit to the reservoir through the third valve  58 . In this case, the first valve  54  of the first IMV  40  should be closed so that the pressurized fluid from the pump  12  does not flow through the first valve  54 . 
     The actuation direction of the first actuator  20  may be reversed by opening the first valve  54  and closing the third valve  58  of the first IMV  40 , and opening the third valve  90  and closing the first valve  86  of the second IMV  72 . The pressurized fluid from the pump  12  will flow through the first valve  54  of the first IMV  40  to the rod end chamber  24  of the first actuator  20 , and the piston  26  and the piston rod  28  will move in the downward direction according to the orientation of FIG.  1 . The fluid in the head end chamber  22  flows to the reservoir  14  through the third valve  90  of the second IMV  72 . 
     Similarly, the second valve  56  of the first IMV  40  can be opened to allow fluid flow through the second valve  56  to the head end chamber  32  of the second actuator  30  to move the piston  36  and the piston rod  38 . Simultaneously, the fluid from the rod end chamber  34  of the second actuator  30  flows via the conduit  84  to the second IMV  72 . The fourth valve  92  should be open to discharge the fluid from the rod end chamber  34  to the reservoir  14 . During this operation, the fourth valve  60  of the first IMV  40  and the second valve  88  of the second IMV  72  should be closed. To reverse the direction of the second actuator  30 , the second valve  88  of the second IMV  72  and the fourth valve  60  of the first IMV  40  should be opened, and the first valve  56  and the fourth valve  92  of the second IMV  72  should be closed. The first and second double-acting actuators  20 ,  30  are operated and controlled independently as described above. 
     The operation of the fluid control system  10  in the regenerative function mode will now described. This regenerative function mode is often referred to as “Chicago Dump.” 
     In the regenerative function mode, the proportional valve  106  of either the first check control mechanism  104  for the first IMV  40  or the second check control mechanism  105  for the second IMV  72  is closed. When the proportional valve  106  of the check control mechanism  104  is closed, the main check valve  70  is held in the closed position to block the fluid from the pump  12  from reaching the first outlet port  117  despite the fluid pressure from the pump  12 . Thus, the pressurized fluid from the pump  12  does not reach any of the independently controlled valves of the first IMV  40 . 
     When the proportional valve  106  of the check control mechanism  105  for the second IMV  72  is open, the main check valve  70  allows the pressurized fluid from the pump  12  to flow to the first and second valves  94 ,  96  of the second IMV  72 . When the first valve  86  is opened, the fluid from the pump  12  flows through the first valve  86  into the head end chamber  22  of the first actuator  20  via the conduit  82 . The fluid in the rod end chamber  24  flows out to the first IMV  40  via the conduit  50 . In the regenerative function mode, the third and fourth valves  58 ,  60  of the first IMV  40  should be closed and the first and second valves  54 ,  56  should be opened so that fluid from the rod end chamber  24  of the first actuator  20  flows into the head end chamber  32  of the second actuator  30  via the first and second valves  54 ,  56 . Because the main check valve  70  is held in the closed position, the regenerative fluid flow is not disturbed by the pressured flow from the pump  12  to the first IMV  40 , and the regenerative flow passes through the first IMV  40 . This regenerative flow to the head end chamber  32  acts to extend the piston rod  38 . At the same time, the fluid in the rod end chamber  34  of the second actuator  30  flows out to the second IMV  72  via the conduit  84 . The second valve  88  should be closed and the fourth valve  92  should be open so that the fluid can be discharged to the reservoir  14  and the pressurized fluid from the pump  12  does not enter through the second valve  88 . In this configuration, the second actuator  30  is operated under lower pressure than the first actuator  20 . 
     The actuation direction of the actuators  20 ,  30  can be reversed by closing the first and fourth valves  86 ,  92  of the second IMV and opening the second and third valves  88 ,  90 . In this case, the rod end chamber  34  of the second actuator  30  is operated under higher fluid pressure than the rod end chamber  24  of the first actuator  20 . 
     Alternatively, the proportional valve  106  of the first check control mechanism  104  may be opened and the proportional valve  106  of the second check control mechanism  105  may be closed. When the proportional valve  106  of the check control mechanism  105  for the second IMV  72  is closed, the main check valve  70  is held in the closed position and the fluid from the pump  12  is prevented from reaching any one of the independently controlled valves of the second IMV  72 . This allows the rod end chamber  24  of the first actuator  20  or the head end chamber  32  of the second actuator  30  to operate under higher fluid pressure than the rod end chamber  34  of the second actuator  30  or the head end chamber  22  of the first actuator  20 , respectively. 
     Thus, the present invention provides a fluid control system to accurately control operation of multiple double-acting actuators in independent and regenerative modes. The fluid control system is advantageous in several respects, one being in that it can efficiently switch between the independent and regenerative function modes. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the electro-hydraulic pump control system of the present invention without departing from the scope or spirit of the invention. Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.