Patent Application
20140174063
The present disclosure relates generally to a hydraulic system for controlling a work implement. Specifically, the disclosure relates to a hydraulic system and method of eliminating boom cylinder head end void and/or for improving excavator efficiency.
Machines with work implement systems actuated with hydraulic circuits and hydraulic cylinder assemblies sometimes include at least one boom cylinder, a stick cylinder, and a bucket cylinder. During some dig applications, an operator gives “full bucket close” and “stick in” commands at the same time. Consequently, the hydraulic cylinders are operable such that the bucket is urged to a fully closed position and the stick is urged in. In such situations, the bucket may interact with the soil, causing a moment on the linkage between the boom, stick, and bucket. As a result of the moment, the linkage tries to extend the boom cylinder(s) while the boom cylinder is being operably maintained in a neutral position. Any resultant movement of the boom cylinder while being controlled in a neutral operating position creates a void (e.g., entrained air in oil) in the boom cylinder head end because the hydraulic circuit associated with the boom cylinder cannot provide enough fluid flow to fill the boom cylinder head end.
United States Patent Application Publication US 20110175005 A1 discloses a hydraulic system for a machine. The hydraulic system includes a dump cylinder including a rod, a head end, and a rod end. The system includes a controllable selector valve for controlling oil pressure to the head end and the rod end of the dump cylinder. The hydraulic system also includes an anti-void release valve provided in the oil path of the dump cylinder.
In one aspect, the disclosure includes a hydraulic system including a hydraulic cylinder assembly, a pressurized fluid source, a fluid tank, a metering control valve, a line relief and first makeup valve, and a second makeup valve. The hydraulic cylinder assembly includes a cylinder, a rod, a head end including a head pressure, and a rod end including a rod pressure. The metering control valve includes a rod extension position, a rod retraction position, and a neutral position. The metering control valve is fluidly connected to the head end, the rod end, the fluid source, and the fluid tank, and includes a valve opening configured to direct fluid from the pressurized fluid source when the metering control valve is in the rod extension position. The valve opening has opening area less than about 3% of a maximum opening area of the valve opening over about the first 50% of full spool displacement. The line relief and first makeup valve are fluidly connected to the head end of the cylinder assembly. The second makeup valve is fluidly connected to the head end of the cylinder assembly, and is configured to provide fluid flow to the head end of the cylinder assembly when the rod is urged toward an extended position at a time when the metering control valve is in the neutral position.
In another aspect, the disclosure includes a machine including a power source, a work implement, and a hydraulic system. The hydraulic system includes a hydraulic cylinder assembly including a cylinder, a rod, a head end including a head pressure, and a rod end including a rod pressure. The hydraulic system further includes a fluid source, a fluid tank, and a metering control valve including a rod extension position, a rod retraction position, and a neutral position. The control valve is fluidly connected to the head end, the rod end, the fluid source, and the fluid tank, and includes a valve opening configured to direct fluid from the pressurized fluid source when the metering control valve is in the rod extension position. The valve opening is less than about 10 mm2 over about the first 6.5 mm of spool displacement. The hydraulic system also includes a line relief and makeup valve fluidly connected to the head end of the cylinder assembly, and a second makeup valve fluidly connected to the head end of the cylinder assembly. The second makeup valve is configured to provide an additional fluid flow to the first makeup valve fluid flow to the head end of the cylinder assembly when the rod is urged toward an extended position at a time when the metering control valve is in the neutral position or close to the neutral position.
In another aspect, the disclosure includes a method for operating a machine that includes a bucket, a stick, and a boom. The method includes selectively operating a boom metering control valve in a neutral position or close to the neutral position to maintain the boom in desired position and selectively operating a stick and a bucket of the machine to close the bucket and retract the stick while the boom metering control valve is in the neutral position or close to the neutral position. The method further includes, at times when said selective operation of the stick and bucket causes extension of the boom while the boom metering control valve is in the neutral position, providing fluid flow to the head end of the boom cylinder assembly via a first makeup valve fluidly connected to the head end of the cylinder assembly and a second makeup valve fluidly connected to the head end of the cylinder assembly. The method also includes selectively operating the metering control valve in a rod extension position to raise the boom to a desired position. The boom metering control valve includes a valve opening configured to direct fluid from the pressurized fluid source when the metering control valve is in the rod extension position, wherein the valve opening is less than about 10 mm2 over about the first 6.5 mm of spool displacement.
Reference will now be made in detail to specific embodiments or features, examples of which are illustrated in the accompanying drawings. Generally, corresponding or similar reference numbers will be used, when possible, throughout the drawings to refer to the same or corresponding parts.
Referring now to
The vehicle 104 may include but is not limited to vehicles that perform some type of operation associated with a particular industry such as mining, construction, farming, transportation, etc. and operate between or within work environments (e.g. construction site, mine site, power plants, on-highway applications, marine applications, etc.). Non-limiting examples of vehicle 104 include cranes, earthmoving vehicles, mining vehicles, backhoes, loaders, material handling equipment, and farming equipment.
Machine 100 is equipped with systems that facilitate the operation of the machine 100 at worksite 110. In the depicted embodiment, these systems include the work implement control system 108, a drive system 112, and a power system 114 that provides power to the work implement control system 108 and the drive system 112. In the depicted embodiment, the power system 114 includes an engine 136, for example an internal combustion engine. In alternative embodiments the power system 114 may include other power sources such as electric motors (not shown), fuel cells (not shown), batteries (not shown), ultra-capacitors (not shown), electric generators (not shown), and/or any power source which would be known by an ordinary person skilled in the art.
The drive system 112 may include a transmission (not shown), and ground engaging devices 115. The transmission may include any device or group of devices that may transfer force between the power system 114 and the ground engaging devices 115. The transmission may include one or more of a mechanical transmission, variator, gearing, belts, pulleys, discs, chains, pumps, motors, clutches, brakes, torque converters, fluid couplings and any transmission which would be known by an ordinary person skilled in the art.
The work implement control system 108 includes a work implement 116, which may perform work at worksite 110. In the depicted embodiment, the work implement 116 is a bucket 126. In alternative embodiments the work implement may include other types of work implements 116 such as (but not limited to) blades, lift groups, material handling arms, multi-processors, rakes, shears, snow plows and snow wings.
The work implement control system 108 may include any members, and linkages; as well as any systems and controls to actuate the members and linkages as a function of operator, autonomous system, or other inputs, to maneuver the work implement 116 to perform work at worksite 110, which would be known by an ordinary person skilled in the art.
In the depicted embodiment of a excavator 106, the work implement control system 108 includes a boom 122, a stick 124, the bucket 126, at least one boom cylinder assembly 128, a stick cylinder assembly 130, a work implement cylinder assembly 102, a work implement linkage 134, a controller 182, and an operator interface 188. The boom cylinder assembly 128 includes a boom cylinder 133 and a boom rod 132.
In the depicted embodiment, machine 100 includes a cab 118 including the operator interface 188. The operator interface 188 may include devices with which an operator communicates with, interacts with, or controls the machine 100. In one embodiment, the operator interface 188 may include devices with which the operator interacts physically. In another embodiment, the devices may operate with voice activation. In still other embodiments, the operator may interact with the operator interface 188 in any way a person skilled in the art would contemplate. In the depicted embodiment, the operator interface includes a joystick 120.
The operator interface 188 may be operable to generate commands to the work implement control system 108 to move the work implement 116 to perform work at the worksite 110. The operator interface 188 may be operable to generate work implement control system 108 control commands as a function of predetermined movement from an operator. In alternative embodiments, machine controls encoded in the controller 182 onboard the machine 100, or an autonomous control system located remotely from the machine 100 may communicate work implement control system 108 commands.
In the depicted embodiment, an operator may enter commands to maneuver the work implement 116 through moving the joystick 120. These commands may be transmitted via sensors and communication links to the controller 182. The controller 182 may transmit signals via communication links to actuate hydraulic fluid valves to allow pressurized fluid flow to and from the cylinder assemblies 128, 130, 102 as is well known in the art. As pressurized fluid flows to and from the cylinder assemblies 128, 130, 102, rods (such as boom rod 132) may extend from and retract into cylinders (such as boom cylinder 133) to move the work implement 116. In other embodiments hydro-mechanical control systems may transmit operator commands to actuate the work implement 116.
In the depicted embodiment, a work implement linkage assembly 134 is operably connected to the work implement cylinder assembly 102 and the work implement 116 to actuate work implement 116 in a desired way.
The controller 182 may include a processor (not shown) and a memory component (not shown). The processor may include microprocessors or other processors as known in the art. In some embodiments the processor may include multiple processors. The processor may execute instructions transmitted through the operator interface 188 or other means such as remote or autonomous controls to perform work at the worksite 110 with work implement 116. The memory component may include any form of computer-readable media which would be known to an ordinary person skilled in the art now or in the future. The memory component may include multiple memory components.
The controller 182 may be enclosed in a single housing. In alternative embodiments, the controller 182 may include a plurality of components operably connected and enclosed in a plurality of housings. The controller 182 may be located on-board the machine, or may be located off-board or remotely.
The controller 182 may be communicatively connected to the operator interface 188 to receive operator command signals, and operatively connected to hydraulic valves to control movement of the work implement 116. The controller 182 may be communicatively connected to one or more sensors or other devices to receive signals indicative of machine 100 system operating parameters.
An operator, or an autonomous function, may desire to dig earth or other material at work site 110 with the depicted excavator 106, and then dump the material into a haul truck (not shown) or other holding vehicle. As the work implement control system 108 responds to dig commands, for example, “stick in” and “bucket close,” the stick cylinder assembly 130 may extend so that the stick 124 is urged in toward the cab 118, and the work implement cylinder assembly 102 may extend so that the bucket 126 may begin to close, moving downwards and curling inward towards the stick 124 and cab 118, digging material and then holding it as is well known by ordinary persons skilled in the art. While the bucket 126 is digging, interaction between the bucket 126 and the material the bucket 126 is digging may cause a resistive load to be applied to the work implement 116. This resistive load may create a moment on the work implement control system 108, which may cause an extension of the boom cylinder assembly 128 even though the operator is not inputting a “boom up” command. An unintended extension of the boom cylinder assembly 128 may create a void in the boom cylinder 133, which requires that the boom cylinder 133 be filled with fluid before the boom cylinder 133 would move in response to a subsequent “boom up” command by the operator. Boom cylinder 133 void is well known by ordinary persons skilled in the art.
The operator, or an autonomous function, may give a command to raise the boom 122 to position the loaded bucket 126 containing the material over the haul truck, and then begin a dump function. During the raise function, the boom cylinder void requires that the boom cylinder 133 be filled with fluid before the boom cylinder 133 would move. Filling the void takes a period of time, for example, at least about 0.5 second, which introduces a delay in the response of the boom cylinder 133 to the operator's “boom up” command. During the dump function the work implement cylinder assembly 102 may be retracted causing the bucket 126 to open, rotating outwards from the stick 124 and cab 118, and dump the material into the haul truck as is well known by ordinary persons skilled in the art.
Referring now to
The hydraulic system 200 is suitable for use in the excavator 106 of
The first hydraulic circuit 201 includes a hydraulic cylinder assembly 202, a pressurized fluid source 206, a fluid tank 210, a boom load control valve 224, and a metering control valve 204. The cylinder assembly 202 includes a head end 212 having a head pressure, a rod end 214 having a rod pressure, a cylinder 290, and a rod 292. The metering control valve 204 includes a closed position (shown in relation to
The cylinder assembly 202 may include any mechanical actuator operable to apply a substantially unidirectional force through a unidirectional stroke which would be known to an ordinary person skilled in the art. The rod 292 may include a piston which divides the cylinder 290 into two (2) chambers, one on the head end 212, and one on the rod end 214. Each chamber may include a port through which fluid may flow in and out of the chamber. The rod 292 may move back and forth in the cylinder 290 as fluid flows in and out of the chambers, as is known by ordinary persons skilled in the art. The rod 292 may be operably connected to the boom 122.
In the excavator 106 embodiment depicted in
The fluid source 206 may include any source of pressurized hydraulic fluid which would be known by an ordinary person skilled in the art. The fluid source 206 may include, but is not limited to, a fixed displacement pump (not shown), a variable displacement pump (not shown), a hydraulic fluid accumulator (not shown), or any other pressurized fluid energy storage device. In the depicted embodiment, engine 136 may drive fluid source 206 through one or more gears. In alternative embodiments, the fluid source 206 may include a pump driven in any manner which would be known by an ordinary person skilled in the art. Non-limiting examples include gear driven, belt driven, or electric motor driven pumps. The fluid tank 210 may include any reservoir for holding fluid which would be known by an ordinary person skilled in the art.
Springs hold the metering control valve 204, as shown in
The metering control valve 204 may include a rod extension pilot port 238 selectively fluidly connected to a pilot pressurized fluid source 276 through pilot fluid conduit 260. When fluid from the pilot fluid source 276, with a high enough pressure to overcome the force of the K2 spring, flows through pilot fluid conduit 260 to the rod extension pilot port 238, the metering control valve 204 may move to the rod extension position as shown in
The metering control valve 204 may include a rod retraction pilot port 240 selectively fluidly connected to a pilot pressurized fluid source 276 through pilot fluid conduit 280. When fluid from the pilot fluid source 276, with a high enough pressure to overcome the force of the K1 spring, flows through pilot fluid conduit 280 to the rod retraction pilot port 240, the metering control valve 204 may move to the rod retraction position as shown in
The pilot fluid source 276 may include the fluid source 206 or the pilot fluid source 276 may be a separate source. The pilot fluid source 276 may, for example, include a pump driven by the engine 136 through gears. Embodiments of the pilot fluid source may include a fixed displacement pump (not shown), a variable displacement pump (not shown), a hydraulic accumulator, or any other pressurized fluid source which would be known by an ordinary person skilled in the art. The pilot fluid source 276 may be driven or powered by the power system 114 through mechanical linkage, electrically, hydraulically, or by any means which would be known by an ordinary person skilled in the art.
In the depicted embodiment, the head end 212 is fluidly connected to the metering control valve 204 via a boom load control valve 224 and fluid conduits 234, 236. The rod end 214 is fluidly connected to the metering control valve 204 through fluid conduit 228. The fluid source 206 is fluidly connected to the metering control valve 204 through a check valve 220 and fluid conduit 222. The tank 210 is fluidly connected to the metering control valve 204 through a back pressure valve 232 and fluid conduits 230 and 231.
As shown in relation to
As shown in relation to
The second hydraulic circuit 208 is fluidly connected to the head end 212 and the fluid tank 210. The second hydraulic circuit 208 is configured to fluidly connect the head end 212 to the fluid tank when the head pressure falls below the back pressure. The hydraulic circuit 208 is also operable to fluidly connect the head end 212 to the fluid tank 210 when the head pressure exceeds a predetermined value.
As shown in relation to
According to various aspects, the pressure relief valve 252 may be a spring-biased and normally-closed pressure relief valve, and the makeup valve 246 may be a spring-biased and normally closed check valve. The pressure relief valve 252 is configured to open when the head pressure exceeds a predetermined value which overcomes a spring constant K3 of a spring that urges the pressure relief valve to a closed position. The second makeup valve 218 may be a spring-biased and normally closed check valve.
Referring now to
As shown in
Referring now to
In the excavator 106 of
Referring to
Further as shown in
The pressurized fluid flowing into the head end 212 may push the piston of rod 292 and begin extending the rod 292 from the cylinder 290. As the rod 292 begins extending, fluid may flow out of the rod end 214, through fluid conduit 228, through the metering control valve 204, through fluid conduit 230, and to the tank 210. The arrows marked “R” illustrate the flow of pressurized fluid from the rod end 214.
Referring now to
Further as shown in
The pressurized fluid flowing into the rod end 214 may push the piston of rod 292 and begin retracting the rod 292 into the cylinder 290. As the rod 292 begins retracting, fluid may flow out of the head end 212, through fluid conduit 228, through boom load control valve 224, through fluid conduit 236, through the metering control valve 204, through fluid conduit 231, and to the tank 210. The arrows marked “H” illustrate the flow of fluid from the head end 212.
An operator, or an autonomous function, may desire to dig earth or other material at work site 110 with the depicted excavator 106, and then dump the material into a haul truck (not shown) or other holding vehicle. As the work implement control system 108 responds to dig commands, for example, “stick in” and “bucket close,” the stick cylinder assembly 130 may extend so that the stick 124 is urged in toward the cab 118, and the work implement cylinder assembly 102 may extend so that the bucket 126 may begin to close, moving downwards and curling inward towards the stick 124 and cab 118, digging material and then holding it as is well known by ordinary persons skilled in the art. While the bucket 126 is digging, interaction between the bucket 126 and the material the bucket 126 is digging may cause a resistive load to be applied to the work implement 116. This resistive load may create a moment on the work implement control system 108, which may cause an extension of the boom cylinder assembly 128 even though the operator is not inputting a “boom up” command. An unintended extension of the boom cylinder assembly 128 may create a void in the boom cylinder 133. The combination line relief with makeup function valve 216 and the second makeup valve 218 of the second hydraulic circuit 208 may be configured to provide fluid flow to the head end 212 of the boom cylinder 133 to fill the void. Thus, the boom cylinder 133 is filled with fluid before a subsequent “boom up” command by the operator and the boom cylinder 133 can move in response to the “boom up” command without delay.
The operator, or an autonomous function, may give a command to raise the boom 122 to position the loaded bucket 126 containing the material over the haul truck, and then begin a dump function. During the raise function, since the boom cylinder void has been filled, the boom cylinder 133 can move without delay. During the dump function the work implement cylinder assembly 102 may be refracted causing the bucket 126 to open, rotating outwards from the stick 124 and cab 118, and dump the material into the haul truck as is well known by ordinary persons skilled in the art.
From the foregoing, it will be appreciated that, although specific embodiments have been described herein for purposes of illustration, various modifications or variations may be made without deviating from the spirit or scope of inventive features claimed herein. Other embodiments will be apparent to those skilled in the art from consideration of the specification and figures and practice of the arrangements disclosed herein. It is intended that the specification and disclosed examples be considered as exemplary only, with a true inventive scope and spirit being indicated by the following claims and their equivalents.
