Abstract:
A distributed hydraulic system locates a control assembly, that has electrohydraulic valves and a electronic controller, adjacent the respective hydraulically powered actuator controlled by that assembly. The control assembly includes a manifold block with ports to that the pump, tank return and actuator fluid conduits connect. One or more pressure ports are provided on the manifold block at which to sense pressure at different locations therein. A controller housing, in addition to containing an electronic function controller, also contains a separate pressure sensor for each pressure port, and is mounted against the manifold block so that each pressure sensor connects to a pressure port. The manifold block also has a pair of exterior walls that extend on opposites sides of the controller housing to protect the electronic controller. Other features that facilitate distributing the hydraulic control adjacent the actuators are provided.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not Applicable 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a hydraulic system having valves that are operated to control the flow of fluid to hydraulic actuators that move components on a machine, and more particularly to distributed control systems in which the valves are located adjacent the associated hydraulic actuator being controlled. 
     2. Description of the Related Art 
     A wide variety of machines are operated by hydraulic systems. For example, a backhoe is a common type of earth moving equipment that has a bucket rotatably attached to the end of an arm that in turn is pivotally coupled by a boom to a tractor. A hydraulic boom cylinder raises and lowers the boom with respect to the tractor and a hydraulic arm cylinder pivots the arm about the end of the boom. The bucket is rotated at the remote end of the arm by a hydraulic bucket cylinder. 
     Traditionally, the boom assembly was controlled by valves located near the cab of the tractor and mechanically connected to levers which the operator manipulated to independently move the boom, arm and bucket. A separate valve assembly was provided for each cylinder on the boom assembly. Operating one of the valve assemblies permitted pressurized hydraulic fluid to flow from a pump on the tractor to the associated cylinder and other fluid to return from that cylinder back to the tank on the tractor. A separate pair of hydraulic conduits ran from each valve assembly adjacent the operator cab along the boom assembly to the associated cylinder. 
     There has been a recent trend away from mechanically operated valves to electrohydraulic valves that are operated by electrical signals. Initially, all of the electrohydraulic valves were mounted on a single manifold block, such as the one described in U.S. Pat. No. 6,505,645, that was centrally located on the machine. Pairs of hydraulic conduits ran from that common manifold block to each hydraulic actuator on the machine. The use of electrohydraulic valves eventually evolved to the development of a distributed hydraulic system in which the valve assembly is collocated with the associated hydraulic actuator, such as a cylinder. With this type of system, the operator in the tractor cab manipulates joysticks or other input devices to generate electrical control signals for operating the valve assemblies. Because each valve assembly is adjacent the respective hydraulic actuator, the amount of plumbing on the machine is reduced. Now only a pair of conduits, a supply conduit and a tank return conduit, extends along the boom assembly to power the cylinders for the boom, arm and bucket on a backhoe, for example. Electrical cables run from a central electronic controller for the machine to the valves on the assemblies near the hydraulic actuators. 
     Other types of equipment also incorporate such distributed hydraulic systems. 
     SUMMARY OF THE INVENTION 
     A distributed control assembly for operating a hydraulically powered actuator includes a manifold block on which a housing for an electronic controller is mounted. The manifold block has a first supply port for connection to a source of pressurized fluid such as a pump, a first return port for connection to a fluid reservoir, and first and second workports for connection to the hydraulically powered actuator. The manifold block also has a plurality of bores each for receiving a valve to control flow of fluid among the first and second workports, the first supply port and the first return port. A separate one of a plurality of electrohydraulic valves is received in one of the plurality of bores of the manifold block and is electrically controlled by the electronic controller. 
     One aspect of the distributed control assembly relates to providing one or more pressure ports at which to sense pressure at different locations within the manifold block. The controller housing, in addition to containing an electronic function controller, also contains a separate pressure sensor for each pressure port of the manifold block. The controller housing is mounted against the manifold block so that each pressure sensor is connected to one of the pressure ports. 
     Another aspect of the distributed control assembly relates to the manifold block including a pair of exterior walls that extend on opposites sides of the controller housing. The wall protect the controller housing and its contents from damage that could result from objects striking the machine on which the distributed control assembly is mounted. 
     A further aspect of the distributed control assembly relates to providing additional ports on the manifold block. In one embodiment, a second supply port is connected to the first supply port, and a second return port is connected to the first return port, thereby facilitating the connection of a plurality of distributed control assemblies in a daisy chain manner. Another embodiment provides ports for various pressure relief valves, an inlet check valve, and an optional manual emergency valve. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a telehandler incorporating the present invention; 
         FIG. 2  is a schematic diagram of a hydraulic system for moving a boom, and tilting a workhead of the telehandler; 
         FIG. 3  is a detailed schematic diagram of one of the hydraulic functions in  FIG. 2 ; 
         FIG. 4  is an exploded view of a distributed control assembly that operates each cylinder and piston arrangement in the hydraulic system; 
         FIG. 5  is an elevational view of the far end of the distributed control assembly in  FIG. 4  with the related valves removed; and 
         FIG. 6  is a bottom view of the controller housing of the distributed control assembly. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With initial reference to  FIG. 1 , the present invention is incorporated on a telehandler  10  that comprises a tractor  12  on which a boom  13  is pivotally mounted, however, the novel concept of the invention can be used on other types of hydraulically operated equipment. A first hydraulic actuator, such as a lift cylinder  21 , raises and lowers the boom  13  in an arc about a pivot shaft  16  of the tractor  12 . The boom  13  comprises first and second sections  14  and  15  that can be extended and retracted telescopically in response to operation of another hydraulic actuator, such as a length cylinder  22  connected between the first and second sections within the boom. The telescopic action changes the overall length of the boom. 
     A workhead  18 , such a pair of pallet forks  20  or a platform for lifting items, is attached at pivot point  24  to the remote end of the first boom section  14 . Other types of workheads may be attached to the first boom section  14 . A third hydraulic cylinder  23  rotates the workhead  18  vertically at the end of the boom  13 . Extension of a piston rod from the third, or workhead, hydraulic cylinder  23  tilts the tips of the pallet forks  20  upward, and retraction of that piston rod lowers the fork tips. 
     Referring to  FIG. 2 , a hydraulic system  30 , for controlling operation of the telehandler boom  13 , includes a fluid source  31  that has a fixed displacement pump  32  which draws fluid from a tank  33  and forces that fluid under pressure into a supply conduit  34 . The supply conduit  34  furnishes pressurized fluid to a boom lift hydraulic function  41 , an boom length hydraulic function  42 , and a workhead hydraulic function  43 , which respectively operate the boom lift cylinder  21 , the boom length cylinder  22  and the workhead cylinder  23 . Fluid returns from these three functions  41 - 43  to the tank  33  via a return conduit  40 . The supply conduit  34  and the return conduit  40  extend from the pump and tank  32  and  33  located in the tractor  12  of the telehandler  10  along the boom  13 . Other hydraulic functions also can be connected to the supply and return conduits  34  and  40 . 
     The outlet pressure from the pump  32  is measured by a first sensor  35 , which provides a signal indicating that pressure to a system controller  50 . An unloader valve  36  is operated by the system controller  50  to regulate pressure in the supply conduit  34  by releasing some of the fluid into the tank  33 . Other hydraulic systems utilize a variable displacement pump, which is be operated by the system controller  50 . The system controller  50  also receives a signal from a second pressure sensor  38  that measures the pressure in the tank return conduit  40 . In the preferred embodiment of the distributed hydraulic system, the system controller  50  is located in or near the operator cab  49  of the tractor  12  and receives control signals via a conventional communication network  56  from joysticks  54  that are manipulated by the telehandler operator. 
     Each hydraulic function  41 - 43  includes one of the hydraulic cylinders, a valve assembly, and an electronic function controller adjacent each other at various locations on the telehandler  10 . Specifically, the boom lift function  41  has a first valve assembly  44  that selectively applies the pressurized fluid from the supply conduit  34  to one of the chambers of the boom lift cylinder  21  and drains fluid from the other cylinder chamber to the return conduit  40 . A second valve assembly  45  in the boom length hydraulic function  42  controls the flow of hydraulic fluid to and from the boom length cylinder  22  and the supply and return conduits  34  and  40 . The workhead hydraulic function  43  has a third valve assembly  46  that couples the chambers of the workhead cylinder  23  to the supply and tank conduits  34  and  40 . The valve assemblies  44 ,  45  and  46  are respectively operated by electrical signals from a function controller  51 ,  52  and  53  for the hydraulic function. The system controller  50 , function controllers  51 - 53 , and the joysticks  54  exchange operational commands, control signals and data over a communication network  56 , such as the Controller Area Network serial bus that uses the communication protocol defined by ISO 11898 promulgated by the International Organization for Standardization in Geneva, Switzerland, for example. The communication network  56  also carries other messages between the engine, transmission, and other components and computers on the vehicle 
       FIG. 3  illustrates details of the boom lift function  41  with the other hydraulic functions having an identical or substantially identical configuration. The valve assembly  44  comprises four electrohydraulic pilot operated, proportional valves  61 ,  62 ,  63  and  64 , such as the one described in U.S. Pat. No. 6,745,992. The four electrohydraulic valves  61 - 64  are connected in a Wheatstone bridge configuration in which valves in opposite legs of the bridge (e.g. valves  61  and  64  or valves  62  and  63 ) are opened to extend or retract the piston rod with respect to the boom lift cylinder  21 . Specifically, the supply conduit  34  is coupled by an inlet check valve  65  to the first electrohydraulic valve  61  coupled to a first workport  66  connected to the head chamber  67  of the cylinder  21 . The second electrohydraulic valve  62  controls the flow of fluid from inlet check valve  65  to a second workport  68  that is connected to the rod chamber  69  of the cylinder  21 . The third and fourth electrohydraulic valves  63  and  64  respectively control the fluid flow between the two workports  66  and  68  and the tank return conduit  40 . 
     Each of these electrohydraulic valves  61 - 64  has a pilot valve  70  that is controlled by solenoid operator  71  which is activated by a signal from the function controller  51 . The pilot valve  70  controls the pressure in a control chamber  72  of the respective electrohydraulic valve which pressure in turn controls movement of the main valve element  73  that governs the fluid flow through the electrohydraulic valve. 
     A first pressure relief valve  74  responds to pressure at the first workport  66  exceeding a predefined level by opening a path from the control chamber  72  of the third electrohydraulic valve  63  to the tank return conduit  40 . This action releases the pressure in that control chamber, thereby allowing the workport pressure acting on the third electrohydraulic valve&#39;s main valve element  73  to open that valve. This combined action of a pressure relief valve and a main valve element creates a path from the first workport  66  to the tank return conduit  40  while releasing the excessive workport pressure. Because the first pressure relief valve  74  handles only minimal fluid flow from the control chamber  72 , it can be smaller that a conventional relief valve through which fluid from the workport would flow due to an excessive pressure condition. 
     A second pressure relief valve  78  responds to pressure at the second workport  68  exceeding a predefined level by opening a path from the control chamber  72  of the fourth electrohydraulic valve  64  to the tank return conduit  40 . That action provides a path through the fourth electrohydraulic valve  64  that releases the pressure at the second workport  68  into the tank return conduit  40 . Here too, the combination of a relatively small pressure relief valve and a main valve element provide the workport pressure relief function. 
     A manually operated emergency valve  75  provides a controllable path between the first workport  66  and the tank return conduit  40 . The emergency valve  75  is operated by turning a screwdriver that engages a threaded valve element  76 . In the event that power driving the pump  32  is lost, opening the emergency valve  75  releases fluid from the head chamber  67  of the boom lift cylinder  21  which lowers the boom  13 . 
     Referring again to  FIG. 2 , operation of the three valve assemblies  44 ,  45  and  46  is controlled by a separate function controller  51 ,  52  and  53 , respectively, which is collocated with the associated valve assembly along the boom  13 . The combination of a valve assembly  44 ,  45  or  46  with a function controller  51 ,  52  or  53  forms a distributed control assembly  81 ,  82  and  83  for the associated hydraulic function  41 ,  42  or  43 . The three distributed control assemblies have identical construction with the one  81  for the boom lift function  41  being shown in  FIGS. 4 and 5 . 
     The first distributed control assembly  81  has a manifold block  80  with a first end face  84  and an opposite second end face  86 . The first end face  84  has a first supply port  87  and a first return port  88  therein, and the second end face  86  has a second supply port  90  and a second return port  91 . A supply passage  92  directly connects the first and second supply ports  87  and  90 . Similarly, a return passage  94  directly connects the first and second return ports  88  and  91  through the manifold block  80 . The terms “directly connects” and “directly connected ”, as used herein, mean that the associated components are connected together by a conduit without any intervening element, such as a valve, an orifice or other device, which restricts or controls the flow of fluid beyond the inherent restriction of any conduit. As seen in  FIG. 2 , the pump supply conduit  34  has segments in which hoses connect each distributed control assembly  81 - 82  in a daisy chain manner. A similar daisy chain connection occurs for the return conduit  40  in which hoses are connected to the first and second return ports  88  and  91 . 
     A first workport  66  also is located on the first end face  84 , while the second workport  68  is on the second end face  86 . The first end face  84  of the manifold block  80  has a first valve bore  95 , within which the first electrohydraulic valve  61  is received. The manifold block  80  has internal passages that connect the first valve bore  95  with the supply passage  92  and the first workport  66  so that the first electrohydraulic valve  61  can control the fluid flow there between as depicted in  FIG. 3 . A second valve bore  96  is provided in the first end face  84  to receive the third electrohydraulic valve  93  and additional passages extend in the manifold block  80  between the second valve bore and both the return passage  94  and the first workport  66 . 
     Similarly, the second end face  86 , as shown in  FIG. 5 , has a third valve bore  97  therein within which the second electrohydraulic valve  62  is received in the completed assembly. Internal passages from the supply passage  92  and the second workport  68  open into the third valve bore  97 . A fourth valve bore  98  also is located in the second end face  86  with passages opening into that bore that provide paths from the tank return passage  94  and the second workport  68 . 
     Referring again to both  FIGS. 4 and 5 , the manifold block  80  has opposite first and second side faces  100  and  102  which extend between the two end faces  84  and  86 . The first side face  100  has an aperture  104  which communicates with the supply passage  92  and the first and third valve bores  95  and  97 . The aperture  104  in the first side face  100  receives the inlet check valve  65 . The second side face  102  has first and second apertures  106  and  108  that are respectively connected to the first and second workports  66  and the bores for the third and fourth electrohydraulic valves  63  and  64 . This pair of apertures  106  and  108  respectively receive the first and second pressure relief valves  74  and  78 . A third aperture  110  is located within the second side face  102  and has passages opening therein which lead to the first workport  66  and the return passage  94 . The manually operated emergency valve  75  is received within that third aperture  110 . 
     The first and second side faces  100  and  102  each include an upstanding wall  112  and  114 , respectively, that are spaced apart forming a cavity  116  on the exterior of the manifold block  80 . The cavity  116  has a flat bottom surface  118  through which a pair of pressure ports  120  and  122  extends. As shown in  FIG. 3 , the first pressure port  120  communicates with the first workport  66 , while the second pressure port  122  communicates with the second workport  68 . The figure also shows that a first function pressure sensor  124  is connected to the first pressure port  120  and a second function pressure sensor  126  is connected to the second pressure port  122 . 
     The first and second function pressure sensors  124  and  126  and the function controller  51  are enclosed within a controller housing  128 , thereby forming a controller assembly  55  that is illustrated in  FIGS. 4 and 5 . The controller housing  128  has an electrical connector  136  which receives a mating connector that is connected to the communication link  58  and to conductors leading to the solenoid operators  71  of the four electrohydraulic valves  61 - 64 . The controller housing  128  fits between the two walls  112  and  114  of the manifold block  80  and is bolted against the surface  118  of the cavity  116 . The two exterior walls  112  and  114  of the manifold block  80  extend above the upper surface of the controller housing  128 . Thus, the two walls  112  and  114  protect the function controller  51  from being struck by objects in the vicinity of the hydraulic actuator on the machine. 
     A printed circuit board within the housing  128  contains the electronic circuitry of the function controller  51  and the two pressure sensors  124  and  126 . With additional reference to  FIG. 6 , the bottom surface  134  of the controller housing  128  has apertures  130  and  132  which respectively align with the first and second pressure ports  120  and  122  on the manifold block  80 . That alignment applies the pressure from the two workports  66  and  68  to the first and second pressure sensors  124  and  126  within the controller housing  128 . O-rings or other seals are located around the first and second pressure ports  120  and  122  to provide a fluid tight seal between the manifold block  80  and the controller housing  128  of the controller assembly  55 . 
     U.S. Pat. No. 6,718,759 describes a velocity based system for controlling a hydraulic system, such as that shown in  FIG. 2 . The system controller  50  and the function controllers  51 - 53  incorporate microcomputers that execute software programs which perform specific tasks assigned to the respective controller. The system controller  50  supervises the overall operation of the hydraulic system  30 . To produce movement of a given hydraulic cylinder  21 - 23  on the boom  13 , the telehandler operator manipulates the corresponding joystick  54  to produce a signal that indicates the movement desired. Each joystick  54  has circuitry that transmits signals via the communication network  56  to the function controller  51 ,  52  or  53  that operates the respective hydraulic cylinder  21 ,  22  or  23 . The joystick signals also are received by the system controller  50 . 
     Each function controller  51 ,  52  and  53  converts a joystick signal intended for it in to a velocity command specifying the desired direction and speed that the associated hydrolic cylinder is to move. That velocity command and pressures sensed at the workport ports of the associated valve assembly  44 - 46  are used to determine which of the four electrohydraulic valves  61 - 64  to open in order to produce the desired motion of hydraulic cylinder. Then drive signals for operating the designated valves are generated and applied to the solenoid operators of those valves. 
     The foregoing description was primarily directed to a preferred embodiment of the invention. Although some attention was given to various alternatives within the scope of the invention, it is anticipated that one skilled in the art will likely realize additional alternatives that are now apparent from disclosure of embodiments of the invention. Accordingly, the scope of the invention should be determined from the following claims and not limited by the above disclosure.