Patent Application
20160003267
The disclosure relates generally to a hydraulic control system having high-pressure and force control, and, more particularly, to a hydraulic control system having an independent metering valve with electronic pressure and force control.
Machines, such as excavators, loaders, dozers, motor graders, and other types of heavy equipment use one or more actuators supplied with hydraulic fluid from a hydraulic source to accomplish a variety of tasks. These actuators are typically controlled based on an actuation of an operator interface device. For example, an operator interface device such as a joystick, a pedal, or another suitable operator interface device may be movable to generate a desired movement of an associated hydraulic actuator. When an operator moves the interface device, the machine operates the hydraulic actuator to move.
In some situations, it may be possible for a pressure of the fluid supplied to the actuator(s) to exceed a desired level during the above described actuation. This over-pressure situation can occur, for example, when work tool movement becomes stalled (e.g., when the work tool strikes against an immovable object). In these situations, the actuator or other components of the associated system can malfunction or be damaged.
Conventionally, over-pressure situations are dealt with by a mechanical relief valve associated with the system that can open when system pressure exceeds a desired pressure. High-pressure fluid from the system is then directed through the open mechanical relief valve and dumped into a low-pressure tank, thereby reducing the pressure of the system. Although effective, this strategy can be inefficient, as the dumped fluid contains significant energy that is wasted. Further, some hydraulic systems may experience frequent pressure spikes or high flows, such as when a load is applied to the implement. Frequent use of the mechanical relief valve can ultimately cause the mechanical relief valve to break or fail.
U.S. Pat. No. 5,813,226 describes a hydraulic system in which over-pressure situations are handled with an arrangement of metering valves. The hydraulic system described in U.S. Pat. No. 5,813,226 accomplishes pressure control without separate line reliefs. In particular, U.S. Pat. No. 5,813,226 describes a hydraulic system 10 that includes a source of pressurized fluid 12, such as a variable displacement pump 14, first and second hydraulic circuits 16, 18, an electrically controlled bypass valve 19, an electronic controller 20, and a reservoir 22. Thus, mechanical relief valves do not fail, but the system may be susceptible to extreme overpressure situations. Such overpressure situations may include situations that are caused by various external forces on a cylinder.
Accordingly, there is a need for a device and process to reduce use of mechanical relief valves in overpressure situations, which may be caused by various external forces.
In one aspect, the disclosure describes a hydraulic system that includes a cylinder having a first end and a second end opposite the first end. The hydraulic system further includes a hydraulic pump hydraulically connected to at least the first end of the cylinder to facilitate movement of the cylinder. The hydraulic system further includes a first mechanical relief valve hydraulically connected to the first end of the cylinder, a first valve hydraulically connected to the first end of the cylinder and a tank, and a first sensor configured to measure a pressure at the first end of the cylinder. A control module can be operatively coupled to the first sensor and the first valve. The control module can be configured to selectively open the first valve when the pressure at the first end of the cylinder reaches a first pressure threshold, to permit fluid to flow from the first end of the cylinder to the tank.
In another aspect, the disclosure describes a work machine, such as a mining shovel for example, that includes a boom assembly, a dipper movably connected to the boom assembly, and a cylinder operably connected to the dipper. The cylinder has a first end and a second end opposite the first end. The work machine further includes a hydraulic pump hydraulically connected to at least the first end of the first cylinder to facilitate movement of the cylinder, a first mechanical relief valve hydraulically connected to the first end of the cylinder, a first valve hydraulically connected to the first end of the cylinder and a tank, and a first sensor configured to measure a pressure at the first end of the cylinder. A control module can be operatively coupled to the first sensor and the first valve. The control module can be configured to selectively open the first valve when the pressure at the first end of the cylinder reaches a first pressure threshold, to permit fluid to flow from the first end of the cylinder to the tank.
In yet another aspect, a method of operating a hydraulic system is disclosed. The hydraulic system may include: 1) a cylinder having a first end and a second end opposite the first end, the cylinder being movable between a retracted position and an extended position; 2) a hydraulic pump selectively hydraulically connected to at least the first end of the first cylinder to facilitate movement of the cylinder; 3) a first mechanical relief valve hydraulically connected to the first end of the cylinder; 4) a first valve hydraulically connected to the first end of the cylinder and a tank; 5) a first sensor configured to measure a pressure at the first end of the cylinder; and 6) a control module operatively coupled to the first sensor and the first valve. The method may include determining that the pressure at the first end of the cylinder exceeds a first pressure threshold. The method may further include opening the first valve such that fluid flows from the first end of the cylinder to the tank, and opening the first mechanical relief valve when the pressure at the first end of the cylinder reaches a second pressure threshold such that fluid flows from the first end of the cylinder to the tank, wherein the second pressure threshold is greater than the first pressure threshold.
In yet another aspect, the disclosure describes a hydraulic system that includes a hydraulic actuation device having a first input and a second input. The hydraulic actuation device may be movable in response to fluid being applied to the first input or the second input. The hydraulic actuation device may include a motor, a cylinder, or the like. The hydraulic system further includes a hydraulic pump hydraulically connected to at least the first input of the hydraulic actuation device to facilitate movement of the hydraulic actuation device. The hydraulic system further includes a first mechanical relief valve hydraulically connected to the first input of the hydraulic actuation device, a first valve hydraulically connected to the first input of the hydraulic actuation device and a tank, and a first sensor configured to measure a pressure at the first input of the hydraulic actuation device. A control module can be operatively coupled to the first sensor and the first valve. The control module can be configured to selectively open the first valve when the pressure at the first input of the hydraulic actuation device reaches a first pressure threshold, to permit fluid to flow from the first end of the hydraulic actuation device to the tank.
Referring to the drawings, wherein like reference numbers refer to like elements,
Referring to
While aspects are described herein with reference to the mining shovel 100, it will be appreciated that any machine, vehicle, device or the like can use one or more hydraulic cylinders or hydraulic actuated motors with a high-pressure and force control according to aspects of the disclosure.
The dipper arm 106, and thus the dipper 108, can move in response to an operator input device 110 that is part of the mining shovel 100. For instance, an operator of the mining shovel 100 may provide an input by pressing a button, moving a joystick, or otherwise interacting with the operator input device 110. In an exemplary aspect, the operator input device 110 is coupled to a control module 112 such that the control module 112 can receive inputs from the operator input device 110. The control module 112, which can also be referred to as an electronic controller 112, can be further coupled to one or more components within the mining shovel 100, as described below.
With continuing reference to
The head-end chamber 136 and the rod-end chamber 140 of the hydraulic cylinder 99 may be selectively supplied with pressurized fluid or selectively drained of fluid. The head-end chamber 136 can be selectively supplied with pressurized fluid or selectively drained of fluid via a head-end port 146 that can be coupled to the IMV assembly 116. The rod-end chamber 140 can be selectively supplied with pressurized fluid or selectively drained of fluid via a rod-end port 148 that can be coupled to the IMV assembly 116. The IMV assembly 116 can further be fluidly connected to one or more hydraulic pumps 196 and one or more hydraulic tanks 156. In an exemplary aspect, the IMV assembly 116 receives fluid from the hydraulic pump 196 and routes the fluid to the rod-end chamber 140 or the head-end chamber 136 of the cylinder 99 through one or more fluid paths, as necessary. The IMV assembly 116 can also return fluid from the hydraulic cylinder 99 and route the fluid to the hydraulic tank 156 for re-use. As further described below, the IMV assembly 116 can include one or valves that route fluid through the IMV assembly 116. In various exemplary aspects, the hydraulic system 114 includes the cylinder 99 and the IMV assembly 116 that is coupled to at least one end of the cylinder 99 such that the IMV system 116 can route fluid for powering the cylinder 99. In an exemplary aspect, the IMV assembly 116 can be mounted directly to the cylinder 99, though it will be appreciated that the IMV assembly 116 may be alternatively part of the mining shovel 100 as desired, such that the IMV assembly 116 can route fluid to the hydraulic cylinder 99.
The mining shovel 100 may include the hydraulic system 114 that, among other features, can monitor and control pressure within the hydraulic cylinder 99. For example, the control module 112 may cause an actuator 198 of the hydraulic cylinder 99 to retract or extend. For example, the control module may be coupled to one or more pressure sensors, such as sensors 158, 159, and 204. The control module 112 may receive pressure readings from the sensors 158, and 159, and 204. Based on the pressure readings, the control module 112 can control the flow of fluid in the hydraulic system 114 by opening or closing one or more metering valves, such as metering valves 188, 164, 184, 194, and 302. As shown and described further below, the metering valve 302 may be configured as a pump bypass valve 302. Each of the metering valves 188, 164, 184, 194, and 302 may include a solenoid element. In accordance with the illustrated aspect, the metering valve 188 includes a solenoid element 189, the metering valve 164 includes a solenoid element 165, the metering valve 184 includes a solenoid element 185, and the bypass valve 302 includes a solenoid element 303. Each solenoid element may be coupled to the control module 112. An electronic signal from the control module 112 may be received by one or more of the solenoid elements, which may cause the one or more solenoid elements to energize. When solenoid elements are energized, the respective valves may be caused to open (or close), allowing (or preventing) fluid to pass through. Signals from the control module 112 to the various solenoid elements, and thus to various metering valves, may be generated in response to operator input or in response to various pressures within the hydraulic system 114 being above various thresholds, as determined by the control module 112.
The hydraulic system 114 may include pilot conduits and drain conduits (not shown) connecting to one or more of the metering valves and/or one or more of the solenoid elements. The pilot conduits and drain conduits may assist in the operation of the one or more of the metering valves and/or one or more of the solenoid elements. For example, upon actuation of a solenoid element, the pilot valve mechanism associated with the metering valve may be magnetically repelled from the solenoid element, allowing the metering valve to one of open or close.
In a first exemplary configuration, the cylinder 99 can be moved, for instance extended, by opening metering valves 164 and 194 and keeping metering valves 188 and 184 closed. In the first configuration, the pump 196 can supply pressurized fluid to conduit 161. In an exemplary aspect, the pump 196 is electronically controlled by the control module 112, although it will be understood that the pump 196 may be alternatively controlled as desired. In one exemplary aspect, the system 114 may include a warm-up valve 304. In the first configuration, the warm-up valve 304 may be closed such that the fluid flows to a check valve 168 via fluid conduits 161 and 162. The fluid can flow from the pump 196 through fluid conduits 161 and 162, and up to one or more check valves, such as the check valves 168. Once the fluid pressure builds to a predetermined level, the check valve 168 may be pushed open such that fluid flows through the open metering valve 164 to fluid conduit 170 to fill the head-end chamber 136. The metering valve 164 may be caused to open by the control module 112, via the operator input device 110 for example. The fluid in the head-end chamber 136 can cause the cylinder 99 to extend. Further, in the first configuration, the control module 112 can cause the independent metering valve 194 to open such that fluid flows from the rod-end chamber 140, over fluid conduit 180, and through the open metering valve 194. The fluid may flow through the open metering valve 194 to fluid conduit 205, to fluid conduit 206, and thus to the tank 156. Thus, in the first exemplary configuration, fluid in the rod-end chamber 140 may be decreased and fluid in the head-end chamber 136 may be increased to extend the cylinder 99.
In a second exemplary configuration, the cylinder 99 can be moved, for instance retracted, by opening metering valves 184 and 188 and keeping metering valves 164 and 194 closed. In the second configuration, the pump 196 can supply pressurized fluid to fluid conduit 161. In the second configuration, the warm-up valve 304 may be closed such that the fluid flows to the check valve 168 via fluid conduits 161 and 162. The warm-up valve 304 may include a solenoid element 305 that is coupled to the control module 112 such that the control module 112 can electronically control the warm-up valve 304. The fluid can flow from the pump 196 through fluid conduits 161 and 162, and up to one or more check valves, such as the check valves 168. Once the fluid pressure builds to a predetermined level, the check valve 168 may be pushed open such that fluid flows through the open metering valve 184 to fluid conduit 180 to fill the rod-end chamber 140. The metering valve 184 may be caused to open by the control module 112, via the operator input device 110 for example. The fluid in the rod-end chamber 140 can cause the cylinder 99 to retract. Further, in the second exemplary configuration, the control module 112 can cause the metering valve 188 to open such that fluid flows from the head-end chamber 136, over fluid conduit 170, and through the open metering valve 188. The fluid may flow through the open metering valve 188 to fluid conduit 171, to fluid conduit 206, and thus to the tank 156. Thus, in the second exemplary configuration, fluid in the head-end chamber 136 may be decreased and fluid in the rod-end chamber 140 may be increased to retract the cylinder 99.
The warm-up valve 304 may be opened, by the control module 112, during initial operation of the machine 100 with the metering valve 164 closed, the metering valve 184 closed, the metering valve 188 closed, and the metering valve 194 closed in order to move hydraulic fluid from the pumps 196 through conduit 161, through conduit 162, through conduit 205, through conduit 206, and into tanks 156 in order to increase the temperature of the hydraulic fluid within the system.
In an exemplary aspect, when a force on the cylinder 99, and in particular the rod 132, is greater than a threshold as determined by the control module 112, the control module 112 causes fluid to flow in the hydraulic system 100 such that the force on the rod 132 is decreased below the threshold. In these instances, the control module 112 might not receive an input from the operator input device 110 to fluidly fill or drain the cylinder 99, so the control module 112 can monitor the cylinder 99 to increase or decrease hydraulic fluid in the head-end chamber 136 or the rod-end chamber 140 as necessary. A given force on the cylinder 99 that is greater than a respective threshold can be a compression force in which the force is along a first direction D1 defined from the head-end 136 toward the rod-end 140, or the given force on the cylinder 99 that is greater than a respective threshold can be a tension force in which the force is defined in a second direction D2 defined from the rod-end 140 toward the head-end 136. Thus, a tension force on the rod 132 can be in a direction opposite the compression force on the rod 132. Further, the control module 112 can be configured to determine the threshold based on whether the force on the cylinder 99 is a tension force or a compression force. As further described below, the control module 112 can also be configured to determine the threshold based on a machine state of the mining shovel 100. In some instances, the threshold varies based on which activity the mining shovel 100 is performing when the force applied to the cylinder 99. Compression and tension forces may be caused by an external force, such as an external force on the dipper 108 for example.
With continuing reference to
The IMV assembly 116 may include the metering valves 164 that fluidly connect the hydraulic pump 196 to the head-end chamber 136 of the cylinder 99. When the fluid pressure in the head-end 136 is below a fluid pressure threshold, as measured by the first sensor 158, the control module 112 may route pressurized hydraulic fluid from the pump 196 to the head-end 136 by increasing the opening of the valves 164. In an exemplary aspect, the control module 112 causes the valves 164 to open and close to varying degrees, allowing a larger or smaller amount of fluid to pass through the valves 164. In this aspect, the valves 164 may have an infinite number of open positions between the fully open and fully closed. A valve being in a fully open position may refer to a valve that is open such that a maximum amount of fluid passes through it, and a valve being in a fully closed position may refer to a valve that is closed such that no fluid or a minimum amount of fluid is allowed to pass through the valve. In other aspects, the valve 164 is configured to move discretely between the fully open and the fully closed positions.
In an exemplary aspect, the control module 112 can open the valve 194 to decrease the tension force along the second direction D2. When the control module 112 opens the valve 194, fluid can be permitted to flow from the rod-end 140, through the conduit 180 and the valve 194, to conduits 205 and 206 to the tank 156. Once the fluid pressure within the rod-end 140 decreases below a fluid pressure threshold, the control module 112 may cause the opening of the valve 194 to be reduced partially or fully blocking the fluid pathway from the rod-end 140 to the tank 156.
In an exemplary aspect, the control module 112 can open the valve 188 to decrease the compression force along the first direction D1. When the control module 112 opens the valve 188, fluid can be permitted to flow from the head-end 136, through the conduit 170 and the valve 188, to conduits 171 and 206 to the tank 156. Once the fluid pressure within the head-end 136 decreases below a fluid pressure threshold, the control module 112 may cause the opening of the valve 188 to be reduced partially or fully blocking the fluid pathway from the head-end 136 to the tank 156.
The IMV assembly 116 can also include one or more makeup valves, such as first and second makeup valves 221 and 223, that are positioned within the IMV arrangement 118. The makeup valves 221 and 223 may provide hydraulic fluid to the head-end chamber 136 or the rod-end chamber 140 when pressure is below a threshold in the corresponding head-end 136 or rod-end 140. The makeup valves 221 and 223 are shown in
In accordance with an exemplary scenario in which the mining shovel 100 is in a digging state, the actuator 198 of the hydraulic cylinder 99 can be extended by the weight of the dipper 108, rather than in response to an input from the operator input device 110. Thus, an external force can be applied to the mining shovel 100 that can result in a tension force being applied to the cylinder 99. For example, the control module 112 can determine that the tension force along the second direction D2 is greater than a threshold that is determined by the control module 112 based on the state (e.g., digging) of the mining shovel 100. As the actuator 198 is extended, for example due to an external force, a volume of the head-end chamber 136 can be increased. Thus, a volume of the rod-end chamber 140 can be decreased, which can increase a pressure at the rod-end 140. The control module 112 can determine that the pressure at the rod-end 140 is greater than a threshold. In response to the determination, the control module 112 can cause metering valve 194 to open, thereby metering the flow out of the rod-end 140 of the cylinder 99 such that the pressure at the rod-end 140 returns below the threshold. In an exemplary aspect, the control module 112 causes the valve 194 to open and close to varying degrees, allowing a larger or smaller amount of fluid to pass through the valve 194. In this aspect, the valve 194 can have an infinite number open positions between the fully open position and the fully closed position. In some other aspects, the valve 194 can be configured to move discretely between the fully open and the fully closed positions. Additionally, or alternatively, the control module 112 causes the valve 164 to open, routing hydraulic fluid from the pump 196 to the head-end 136 of the cylinder 99 to decrease the tension force along the second direction D2 until pressure at the rod-end 140 is below the threshold.
Thus, in accordance with an exemplary aspect, the control module 112 may cause the metering valve 194 to open. For example, the control module 112 can determine that the pressure at the rod-end 140 is greater than a threshold. In response to this determination, the control module 112 can open the valve 194 so that fluid is routed from the rod-end chamber 140 into the IMV assembly 116. The fluid can be routed from the rod-end 140 through the open valves 194, and then through the fluid path 206, and outside of the IMV assembly 116 to the hydraulic tank 156 for re-use. Thus, the control module 112 can be operatively coupled to the sensor 159 that is configured to measure a pressure at the rod-end 140 of the cylinder 99. The control module 112 can be configured to selectively open the valve 194 when the pressure at the rod-end 140 of the cylinder 99 reaches a first pressure threshold, to permit fluid to flow from the rod-end 140 of the cylinder 99 to the tank 156.
In accordance with an exemplary scenario in which the mining shovel 100 is in a digging state, the actuator 198 of the hydraulic cylinder 99 can be retracted by the weight of the dipper 108, rather than in response to an input from the operator input device 110. Thus, an external force can be applied to the mining shovel 100 that results in a compression force being applied to the cylinder 99. For example, the control module 112 can determine that the compression force along the first direction is greater than a threshold that is determined by the control module 112 based on the state (e.g., digging) of the mining shovel 100. When the control module 112 determines that the fluid pressure in the head-end chamber 136 is above a threshold, as measured by the sensors 158, the control module 112 can cause the openings of the valve 188 to increase. Thus, fluid can be pushed from the head-end chamber 136 of the cylinder 99 to decrease the pressure at the head-end 136, and thus decrease the compression force along the first direction. The pushed fluid can flow through fluid conduit 170, and through the open valve 188. The fluid can further be permitted through fluid conduits 171 and 206, and then to the tank 156. Thus, the control module 112 can be operatively coupled to at least one sensor 158 that is configured to measure a pressure at the head-end 136 of the cylinder 99. The control module 112 can be configured to selectively open one the valve 188 when the pressure at the head-end 136 of the cylinder 99 reaches a first pressure threshold, to permit fluid to flow from the head-end 136 of the cylinder 99 to the tank 156.
Referring still to
In an exemplary aspect, the control module may be further configured to control the valves during boom jacking such that the mining shovel 100 is protected from damage. Boom jacking may refer to a situation in which the ropes 103 lose tension such that the ropes 103 are slack. For example, during operation, the cylinder 99 can be extended such that the dipper 108 applies a force to the ground or the face of mining material. In response to the force that the dipper 108 applies, an opposite force may be applied on the cylinder 99. For example, a compression force may be applied on the cylinder 99, and such a force may cause the boom 101 to rotate away from the dipper 108 such that the boom 101 is in a boom jacking position, which may cause the ropes 103 to lose tension. Thus, the tension on the ropes 103 during the boom jacking position may be less as compared to the tension on the ropes 103 when the boom 101 is in a normal position. The control module 112 can determine that the compression force along the first direction is greater than a threshold that is determined by the control module 112 based on the state (e.g., boom jacking) of the mining shovel 100. In an exemplary aspect, the control module 112 can detect the boom jacking position, and can control the forces on the cylinder 99, through the hydraulic system 114, in response to the boom jacking position such that the cylinder 99 is controlled to minimize stress on the mining shovel 100 as the boom 101 is returned to the normal position. Moreover, the extent and the effect of the boom jacking may be reduced.
In an exemplary aspect, one or more sensors may detect boom jacking by monitoring the tension on the ropes 103. The sensors may be coupled to the control module 112 so that the control module 112 may determine that the mining shovel 100 is in a boom jacking position by determining that the tension on the ropes 103 is below a predetermined threshold. In this regard, the sensors may be associated with the ropes 103 or other associated structure. The sensors may be load cells, strain gages, stress gauges, and the like to determine the boom and jacking position of the mining shovel 100. In another exemplary aspect, one or more angle sensors may detect boom jacking by monitoring an angle of the boom 101 relative to one more structures of the mining shovel 100. The one or more angle sensors may be coupled to the control module 112 so that the control module 112 may determine that the mining shovel 100 is in a boom jacking position by determining that the angle of the boom 101 relative to the one or more structures is greater or less than respective thresholds.
When the control module 112 determines that the mining shovel 100 is in the boom jacking position, the control module 112 may control a rate at which the boom 101 is lowered to the ground by monitoring the force on the rod 132. For example, the control module 112 may put the mining shovel 100 into an override mode such that the operator cannot control the dipper assembly 104 via the operator input device 110. When the mining shovel is in the boom jacking position, the control module 112 may monitor and control the valve assembly 116, and in particular the pressure at the head-end 136, so that the cylinder 99 is retracted at a controlled rate, thereby returning the boom 101 to the normal position at a controlled rate. When the boom 101 returns to the normal position, as determined by the control module 112, the control module 112 may return the mining shovel to operator control such that the operator can again control the dipper assembly 104 via the operator input device 110. In an exemplary aspect, if the control module 112 does not control the pressure at the head-end 136 at a controlled rate when the mining shovel 100 is in the boom jacking position, the boom 101 may fall back into the normal position at a free-fall rate, which may be greater than desired and may cause the structural integrity of the mining shovel 100 to decrease over time or the like.
In another exemplary aspect, the control module 112 may be further configured to control the valves during dipper propelling such that the mining shovel 100 is protected from damage. Dipper propelling may refer to a situation in which dipper assembly 104, and in particular the dipper arm 106, is parallel to the ground while the bucket 108 is propelled into a face of mining material, such as a wall or bank for example. This action may apply a compression force on the rod 132, as described above. Such a force during dipper propelling may cause the boom assembly 102 to flip backward away from the mining material or otherwise damage one of the components. The control module 112 may determine whether the compression force is greater than a predetermined threshold. For example, the control module 112 can determine that the compression force along the first direction is greater than a threshold that is determined by the control module 112 based on the state (e.g., dipper propelling) of the mining shovel 100. The predetermined threshold is based on the operation (state) of the mining shovel 100. In an exemplary aspect, the predetermined threshold associated with the mining shovel being in a dipper propelling operation may be less than the predetermined threshold associated with the mining shovel being in a boom jacking operation. In an exemplary aspect, the control module 112 can detect the dipper propelling operation, can determine that the compression force is greater than a predetermined threshold associated with the dipper propelling operation, and can control the forces on the cylinder 99, through the hydraulic system 114, in response to the determination such that the cylinder 99 is controlled to minimize stress on the boom assembly 102 as it is returned to the normal position. By way of further example, if the boom assembly 102 is pushed backward as a result of dipper propelling and the ropes 103 are slacked, the bank or wall of the mining material may collapse, and the boom assembly 102 can crash downward because the earth is no longer supporting its weight, which may result in damage. Thus, controlling the rate at which the boom assembly is returned may reduce damage that may result from dipper propelling when the compression forces exceed a threshold.
The construction and arrangements of the hydraulic system 114, as shown in the various exemplary aspects, are illustrative only. Although only a few aspects have been described in detail in this disclosure, many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter described herein. Some elements shown as integrally formed may be constructed of multiple parts or elements, the position of elements may be reversed or otherwise varied, and the nature or number of discrete elements or positions may be altered or varied. The order or sequence of any process, logical algorithm, or method steps may be varied or re-sequenced according to alternative aspects. Other substitutions, modifications, changes and omissions may also be made in the design, operating conditions and arrangement of the various exemplary aspects without departing from the scope of the present disclosure.
The present disclosure is applicable to hydraulic systems on work machines, and more specifically to hydraulic systems on mining shovels. Mining shovels are configured to load, excavate, and transport mining material. As part of the operations, compression and tension forces can be placed on the cylinder 99 within the hydraulic system 114. Such forces can create pressures within the rod-end chamber 140 or the head-end chamber 136 that are above threshold levels. The control module 112 can determine various threshold levels based on the operation of the mining shovel 100, and based on whether the pressure is at the rod-end 140 or the head-end 136. When a pressure is above a respective threshold, the control module 112 can open various configurations of valves in the IMV assembly 116 to reduce pressure levels. Valves in the IMV assembly 116 may be independently opened by the control module 112 to reduce pressures at lower pressure thresholds than a pressure threshold at which the mechanical relief valves are caused to open. Thus, mechanical relief valves in the hydraulic system 114 can be preserved because they are actuated less as compared to a system without the IMV assembly 116. Further, the mechanical relief valves still protect the hydraulic system from high pressure conditions. Further still, the control module 112 allows IMV assembly 116 to provide tailored responses based on various forces that are on induced on the cylinder 99, as it is recognized that the cylinder 99 can withstand different thresholds during different machine operations. Additionally, the control module 112 may be configured to control the IMV assembly 116 based on the cylinder that is being monitored. For instance, various cylinders may have different force thresholds that each of the cylinders can withstand, and the control module 112 may be configured to control various cylinders having various force thresholds. Thus, the control module 112 may be compatible with a variety of hydraulic systems having various configurations of cylinders.
If the head-end force is greater than the rod-end force, the control module 112 may determine that a compression force is being applied to the rod 132, at 416. At 418, the control module 112 may compare the compression force to a second limit or threshold, which may also be referred to as a compression threshold. As described above, the second limit or threshold may be based on characteristics of the cylinder 99, the state of the machine 100, or the like. If the compression force is less than or equal to the compression threshold, the process may proceed to step 420, where one or more appropriate metering valves are closed by the control module 112. If the compression force is greater than the compression threshold, the process may proceed to step 422, where the pressure at the rod-end 140 is relieved by opening one or more appropriate metering valves until the compression force decreases below the compression threshold. After and/or during 420 and 422, pressures may continue to be monitored by one or more sensors, and the control module 112 may continue to compare the head-end force to the rod-end force, at 406.
It will be appreciated that the foregoing description provides examples of the disclosed system and technique. However, it is contemplated that other implementations of the disclosure may differ in detail from the foregoing examples. All references to the disclosure or examples thereof are intended to reference the particular example being discussed at that point and are not intended to imply any limitation as to the scope of the disclosure more generally. All language of distinction and disparagement with respect to certain features is intended to indicate a lack of preference for those features, but not to exclude such from the scope of the disclosure entirely unless otherwise indicated.
Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context.
