The lifting system balance valve signal is cut off

Abstract

A lifting valve assembly for a working machine cylinder includes a main control valve, a balancing valve and a balancing shut-off valve. The main control valve raising position connects the head end of the cylinder having a pressurized fluid source and the rod end of the cylinder to a low-pressure reservoir to extend the cylinder. The balancing valve is between the rod end and the main control valve, biased to a closed position and having an open position connecting the rod end to the low-pressure reservoir. The rod end and head end pressure signals apply force to the balancing valve toward the open position. The balancing shut-off valve is positioned between the head end and the balancing valve, and has a normal position for applying a head end pressure signal to the balancing valve and a shut-off position for blocking the head end pressure signal from the balancing valve.

Description

Technical Field

[0001] The present disclosure relates generally to dump trucks and, more particularly, to counterbalance valve cutout in a dump body lift system of a dump truck during unstable operating conditions. Background Art

[0002] Dump trucks are used to transport materials from one location to another. One such use may include transporting mined material from an extraction site to a processing site. Dump trucks typically include a load container, such as a dump body, that holds the material. Dump trucks can discharge material by extending a lift cylinder to tilt the load container and allow the material to slide off the load container under the influence of gravity.

[0003] In some environments, the nature of the transported material may prevent it from sliding off the carrying container until the container is raised to the extreme position. For example, large mining dump trucks operating in the oil sands region of Alberta, Canada dump high-grade oil sands ore into open hoppers for processing. During the body raising event, the sticky ore payload can stick together and adhere to the surface of the dump body, staying in the dump body for more than 70% of the maximum dump body angle of the dump body. When the payload is finally released from the dump body as a sticky "block" between 85% and 90% of the entire dump body angle, the combined dump body weight and the payload center of gravity of the block can produce an over-center effect on the lifting cylinder. The over-center effect can convert the lifting cylinder load from a compression push load with high head end pressure and low rod end pressure to a tension pull load with high rod end pressure and low head end pressure. The lifting hydraulic system absorbs the over-center load energy by increasing the rod end pressure to prevent the over-center effect. One method currently used to increase rod-end pressure is through the use of a counterbalance valve, which closes when the head-end signal pressure decreases to near zero and allows the rod-end pressure to increase, much like a pressure reducing valve. However, under cold oil or other external problems, the head-end signal pressure acting on the counterbalance valve may not decrease to zero, but may swing, causing the counterbalance valve to become unstable and unable to provide enough rod-end pressure to absorb the block load. As a result, the operator may feel a potentially severe shock effect after a block event.

[0004] An example of a hydraulic circuit for controlling a lifting cylinder or a hoisting cylinder is provided in U.S. Pat. No. 8,752,372 to Ramler et al., which discloses an articulated dump truck provided with an electro-hydraulic bunker control system including a proportional control valve for a bunker hoisting cylinder and including an electromagnetically operated regeneration valve assembly mounted adjacent the hoisting cylinder and actuated during raising the bunker to dump a load of material from the bunker to generate a regeneration flow when the force required by the bunker hoisting cylinder to continue raising the bunker drops to a predetermined force. The force required to tilt the bunker is continuously calculated by an electronic control unit taking into account a sensed bunker load, a sensed bunker tip amount, and a sensed left-right tilt of the bunker. Summary of the invention

[0005] In one aspect of the present disclosure, a lift valve assembly for a cylinder of a working machine having a head end and a rod end is disclosed. The lift valve assembly may include a main control valve having a raised position, wherein the head end of the cylinder is in fluid communication with a pressurized fluid source and in fluid communication with a balanced pilot pressure channel to send a head end pressure pilot signal, wherein the rod end of the cylinder is in fluid communication with a low pressure reservoir. The lift valve assembly may also include a balancing valve positioned in a fluid flow path between the rod end of the cylinder and the main control valve, wherein the balancing valve is biased to a closed position to prevent fluid from flowing from the rod end to the low pressure reservoir and has an open position in which the rod end of the cylinder is in fluid communication with the low pressure reservoir, and wherein the rod end pressure pilot signal from the rod end and the head end pressure pilot signal from the head end apply a force to the balancing valve in the direction of the open position. The lift valve assembly may also include a balanced shut-off valve positioned along the balanced pilot pressure channel between the main control valve and the balancing valve, wherein the balanced shut-off valve has a normal position in which the head end pressure pilot signal applies a force to the balancing valve and a shut-off position in which the head end pressure pilot signal is blocked from the balancing valve.

[0006] In another aspect of the present disclosure, a work machine is disclosed. The work machine may include a main frame, a dump body pivotally connected to the main frame by a dump body shaft, and a lift cylinder having a head end and a rod end, the lift cylinder being pivotally connected to the main frame and the dump body so that the lift cylinder is extended during a load dumping cycle to rotate the dump body about the dump body shaft to raise the dump body and retracted to lower the dump body. The work machine may also include a lift valve assembly having a main control valve, a balance valve, and a balance shut-off valve. The main control valve may have a raised position, wherein the head end of the lift cylinder is in fluid communication with a pressurized fluid source and in fluid communication with a balance pilot pressure channel to send a head end pressure pilot signal, and wherein the rod end of the lift cylinder is in fluid communication with a low pressure reservoir. The counterbalance valve may be positioned in a fluid flow path between a rod end of a lift cylinder and a main control valve, may be biased to a closed position preventing fluid from flowing from the rod end to a low pressure reservoir and having an open position in which the rod end of the lift cylinder is in fluid communication with the low pressure reservoir, and a rod end pressure pilot signal from the rod end and a head end pressure pilot signal from the head end may apply a force to the counterbalance valve in the direction of the open position. The counterbalance shut-off valve may be positioned along a counterbalance pilot pressure passage between the main control valve and the counterbalance valve, may have a normal position in which the head end pressure pilot signal applies a force to the counterbalance valve and a shut-off position in which the head end pressure pilot signal is blocked from the counterbalance valve, and may include an actuator that is actuated to move the counterbalance shut-off valve from a normal position to a shut-off position. The work machine may also include a controller operably connected to the actuator of the counterbalance shut-off valve, the controller being programmed to determine whether the work machine is operating under unstable operating conditions, and actuating the actuator of the counterbalance shut-off valve in response to determining that the work machine is operating under unstable operating conditions to move the counterbalance shut-off valve to the shut-off position.

[0007] In yet another aspect of the present disclosure, a method for cutting off balance during extension of a hydraulic cylinder of a working machine is disclosed. The working machine may include a lift valve assembly having a main control valve having a raised position, wherein a head end of the hydraulic cylinder is fluidly connected to a pressurized fluid source and is fluidly connected to a balance pilot pressure channel to send a head end pressure pilot signal, and wherein a rod end of the hydraulic cylinder is fluidly connected to a low pressure reservoir. The lift valve assembly may also include a balance valve positioned in a fluid flow path between the rod end of the hydraulic cylinder and the main control valve, wherein the balance valve is biased to a closed position preventing fluid from flowing from the rod end to the low pressure reservoir and has an open position in which the rod end of the hydraulic cylinder is fluidly connected to the low pressure reservoir, and wherein a rod end pressure pilot signal from the rod end and a head end pressure pilot signal from the head end apply a force to the balance valve in the direction of the open position. The poppet valve assembly may also include a balanced shut-off valve positioned along a balanced pilot pressure passage between the main control valve and the counterbalance valve, wherein the balanced shut-off valve has a normal position in which a head end pressure pilot signal applies a force to the counterbalance valve and a shut-off position in which the head end pressure pilot signal is blocked from the counterbalance valve, and wherein the balanced shut-off valve includes an actuator that is actuated to move the balanced shut-off valve from the normal position to the shut-off position. The method for shut-off balancing may include determining whether the work machine is commanded to move the main control valve to a raised position, determining whether the work machine is operating under an unstable operating condition in response to determining that the work machine is commanded to move to the raised position, and actuating the actuator of the balanced shut-off valve in response to determining that the work machine is operating under an unstable operating condition to move the balanced shut-off valve to the shut-off position.

[0008] Additional aspects are defined by the patent claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is a side view of a work machine that can implement the hoist system balancing valve cutoff according to the present disclosure;

[0010] Figure 2 According to the present disclosure Figure 1 A schematic diagram of a lift valve assembly that can be implemented in a working machine;

[0011] Figure 3 is Figure 1 A schematic diagram of an exemplary controller and control components that may be implemented in a work machine of;

[0012] Figure 4 yes Figure 1 a graph of various operating parameters of the work machine during a load dump cycle of a dump body of the work machine, at a temperature greater than a threshold instability temperature, and with balancing in effect;

[0013] Figure 5 yes Figure 4a graph during a load dump cycle of a dump body of a work machine, at a temperature less than a threshold instability temperature, and with balancing in effect;

[0014] Figure 6 According to the present disclosure Figure 1 A flow chart of an exemplary balancing valve cut-off routine that may be implemented in a work machine of;

[0015] Figure 7 yes Figure 6 A flowchart of an implementation of an unstable operating condition box of a balancing valve cut-off routine;

[0016] Figure 8 yes Figure 6 A flow chart of an alternative implementation of an unstable operating condition box of a balancing valve cut-off routine;

[0017] Fig. 9 yes Figure 6 A flow chart of another alternative implementation of the unstable operating condition box of the balancing valve cut-off routine of FIG.

[0018] Fig.10 yes Figure 6 Flow chart of yet another alternative implementation of the unstable operating condition box of the balancing valve cut-off routine. DETAILED DESCRIPTION

[0019] Figure 1 An example of a work machine 10 that can incorporate a lift system counterbalance valve cutout according to the present disclosure is shown. The work machine 10 can be autonomous, i.e., remotely controlled or with programmed motion, can be semi-autonomous (with partial remote control or programmed functionality), or can be manually operated. The work machine 10 generally includes a main frame 12, a dump body 14 pivotally mounted to the main frame 12 by a dump body axle 16 to rotate about a dump body axis defined by the dump body axle 16, and a cab 18 mounted above a hood 20 at the front of the main frame 12. The work machine 10 is supported on the ground by front tires 22 (one shown) and rear tires 26 (one shown), each front tire mounted on one of two front wheel assemblies 24, and each rear tire mounted on one of two rear drive wheel assemblies 28. One or more engines (not shown) can be housed within the hood 20 to supply power to the drive wheel assemblies 28 via a mechanical drive train or an electric drive train, and to power the electrical, hydraulic, and other systems of the work machine 10.

[0020] As described above, the dump body 14 can rotate about the dump body axis 16. The dump body 14 can be rotated about the dump body axis 16. Figure 1The dump body 14 is rotated between a normal downward position shown and a raised position (not shown) to dump a load of material deposited in the dump body 14 by another work machine (not shown). The dump body 14 can be moved between the downward position and the raised position by one or more lift cylinders 30 (one shown), each lift cylinder having a rod end 32 pivotally connected to the main frame 12 and a head end 34 pivotally connected to the dump body 14. In other implementations, the rod end 32 can be pivotally connected to the dump body 14 and the head end 34 can be pivotally connected to the main frame 12. When the dump body 14 is in the downward position, the lift cylinders 30 are retracted and extended by providing pressurized hydraulic fluid to the head end 34 to extend a piston rod (not shown) from the rod end 32 and rotate the dump body 14 about the dump body axis 16 toward the raised position.

[0021] Figure 2 A lift valve assembly 40 is shown that is configured and operative to control the extension and retraction of the lift cylinder 30, thereby raising and lowering the dump body 14, respectively. The lift valve assembly 40 may include a housing that encloses various valve stems, springs, passages, and other control components for controlling the flow of hydraulic fluid into and out of the lift cylinder 30. The lift valve assembly 40 may include one or more high pressure (HP) fluid supply ports 42 that are fluidly connected to an HP fluid source 44 via an HP fluid supply line 46. An HP fluid supply passage 48 may extend from the HP fluid supply port 42 to a main control valve 50 and terminate at a first HP supply port 52 and a second HP supply port 54. The HP fluid supply passage 48 may also be fluidly connected to a dump valve 56 via a dump fluid passage 58. The main control valve 50 may be an 8-way, 5-position spool valve that is solenoid-actuated via a lower position control valve 60 and a raise position control valve 62. The main control valve 50 also includes a valve drain port 64 that is fluidly connected to a drain port 68 via a drain passage 66, which in turn is fluidly connected to a low pressure (LP) tank or reservoir 70 via a drain line 72. The rod-end fluid port 80 of the main control valve 50 can be connected to the stem port 82 of the lift valve assembly 40 through a rod-end fluid passage 84, and a rod-end fluid line 86 can fluidly connect the stem port 82 to the rod end 32 of the lift cylinder 30. Similarly, the head-end fluid port 90 can be connected to the head port 92 through a head-end fluid passage 94, and a head-end fluid line 96 can fluidly connect the head port 92 to the head end 34 of the lift cylinder 30.

[0022] The brake cooling fluid port 100 of the main control valve 50 can be connected to the brake cooling port 102 through the brake cooling fluid passage 104 to provide fluid to the brake cooling system (not shown) via the brake cooling fluid line 106. The rod end pressure relief port 110 can be fluidly connected to the brake cooling fluid passage 104 through the restriction passage 112 to provide fluid to the brake cooling fluid passage 104 when the main control valve 50 is in a state such as Figure 2The intermediate position N shown provides exhaust from the rod end 32. The metered pilot pressure port 114 can be arranged to be in fluid communication with the selector spool 116 associated with the pilot pressure reducing valves 118, 120 through the selector pilot pressure passage 122, and in fluid communication with the counterbalance valve 124 through the balanced pilot pressure passage 128 via the solenoid-operated balanced shut-off valve 126. The counterbalance valve 124 can provide a return flow path for hydraulic fluid from the rod end 32 to the rod end fluid port 80, and is controlled by the head end and rod end pressure pilot signals to perform balancing when the dump body 14 is raised as further described below. The rod end restricted exhaust passage 129 can allow some flow of hydraulic fluid around the counterbalance valve 124.

[0023] Although the poppet valve assembly 40 as shown and described herein provides hydraulic fluid to the brake cooling system under certain conditions, the hydraulic fluid would otherwise be exhausted from the poppet valve assembly 40, those skilled in the art will appreciate that the hydraulic fluid may be exhausted to any suitable low-pressure reservoir. For example, in other implementations, the hydraulic fluid may be exhausted to a tank 70. In yet another alternative, the hydraulic fluid may be exhausted to a low-pressure reservoir of another hydraulic system of the work machine 10. Such implementations and corresponding modifications to the elements and passages of the poppet valve assembly 40 to direct the hydraulic fluid are apparent to those skilled in the art and are contemplated by the inventors.

[0024] Figure 3 An exemplary arrangement of electrical and control components of a work machine 10 is shown that can implement lift cylinder operation and counterbalance valve shutoff in a lift valve assembly 40 according to the present disclosure. A controller 130 can process information received from monitoring and control devices using software stored in the controller 130, and output command and control signals to devices of the work machine 10. The controller 130 can include a processor 132 for executing specific programs that control and monitor various functions associated with the work machine 10. The processor 132 can be operably connected to a memory 134, which can have a read-only memory (ROM) 136 for storing programs and a random access memory (RAM) 138 used as a working memory area for executing programs stored in the ROM 136. Although a processor 132 is shown, other electronic components such as a microcontroller, an application specific integrated circuit (ASIC) chip, or any other integrated circuit device can also be used and are contemplated.

[0025] Although the discussion provided herein relates to the functionality of the lift valve assembly 40 including the counterbalance valve cut-off, the controller 130 may be configured to control other aspects of the operation of other systems of the work machine 10, including other hydraulic cylinders, propulsion, steering, braking, etc. In addition, the controller 130 may collectively refer to a plurality of control and processing devices over which the functionality of the work machine 10 may be distributed. Portions of the functionality of the work machine 10 may be performed at a controller of a remote computing device (not shown) operably connected to the controller 130 via a communication link, such as in an autonomous vehicle with functional control at a central command station. The controllers may be operably connected to exchange information as needed to control the operation of the work machine 10. Other variations in the processing of integrating and distributing the controller 130 as described herein are contemplated for use in a work machine 10 that implements lift valve operation and counterbalance valve cut-off according to the present disclosure.

[0026] The controller 130 may be operably connected to various input devices that provide control signals to the controller 130 for operating the lift valve assembly 40 to extend and retract the lift cylinder 30 and correspondingly raise and lower the dump body 14. The lever sensor 140 may detect displacement of a manual lever, joystick, or other input device (not shown) manipulated by an operator to respectively operate the lift cylinder 30 to raise and lower the dump body 14. The lever sensor 140 may respond to the displacement by sending a lever sensor signal to the controller 130, the lever sensor signal having a value corresponding to the displacement of the input device. In an autonomous operation implementation, for example, a signal similar to the lever sensor signal may be generated by an autonomous operation controller, generated by autonomous control software of the controller 130, or sent from a remote operation control center. The controller 130 may respond to the lever sensor signal by sending a valve control signal to a solenoid or other actuating device of the valve 60, 62, 126 to operate the lift valve assembly 40 to extend or retract the lift cylinder 30 on command.

[0027] As previously discussed, the characteristics of the material, such as oil sands ore, being handled by the work machine 10 may result in unstable operating conditions when the dump body 14 is raised to dump the material. Therefore, it may be advantageous to provide an indication to the controller 103 as to whether the material may affect the operation of the lift valve assembly 40. The cab 18 may have a material switch (not shown) with an attached material switch position sensor 142 that may detect operator displacement of the material switch. The material switch position sensor 142 may respond to the displacement by sending a material switch position sensor signal having a value corresponding to the material switch position to the controller 130. In an alternative embodiment, the work machine 10 may be provided with a material sensor that may detect the characteristics of the material in the dump body 14 to indicate whether instability will be a problem. The controller 130 may respond to the machine switch position signal by storing the current position of the material switch as an indication of whether the material being handled may result in unstable operating conditions.

[0028] As described below, some configurations of the counterbalance valve cut-off strategy may depend on the position of the dump body 14, the ambient temperature of the operating environment, the oil temperature at the relevant locations in the lift valve assembly 40 and the lift cylinder 30, or a combination thereof. Thus, the dump body position sensor 144 may be operably connected to the controller 130 and operable to sense a parameter representing the angle of the dump body relative to the normal lowered position of the dump body 14, such as Figure 1 As shown, and a dump body position sensor signal representing the sensed dump body angle is directed to the controller 130. An ambient temperature sensor 146 may be mounted on an outer surface of the main frame, dump body 14, cab 18, or other suitable location to sense the ambient temperature of the working environment in which the work machine 10 is operating, and to send an ambient temperature sensor signal representing the sensed ambient temperature to the controller 130. An oil temperature sensor 148 may be mounted at a suitable location to sense the temperature of the oil used as a hydraulic fluid to operate the lift cylinder 30. In one implementation, the oil temperature sensor 148 may be mounted at the rod end 32 of one of the lift cylinders 30 to sense the temperature of the fluid that may flow from the rod end 32 to the counterbalance valve 124. In other implementations, the oil temperature sensor 148 may be mounted at a suitable location within the lift valve assembly 40. Other alternative locations are also contemplated. In any suitable location, the oil temperature sensor 148 is operably connected to the controller 130 to direct an oil temperature sensor signal representing the sensed oil temperature to the controller 130.

[0029] Return to Figure 2, the controller 130 can send position control valve control signals to actuate the solenoids of the position control valves 60, 62 to move the spool of the main control valve 50 to various positions, thereby extending and retracting the lift cylinder 30 and raising and lowering the dump body 14. The lowering position control valve 60 receives a pilot supply fluid from a lowering pilot supply port 150 via a lowering pilot supply passage 152, while the lifting position control valve 62 receives a pilot supply fluid from a raising pilot supply port 154 via a raising pilot supply passage 156. The pilot supply ports 150, 154 are in fluid communication with a pilot fluid source (not shown) via a pilot fluid supply line 158. The position control valves 60, 62 have a configuration similar to the normally open position, wherein the pilot fluid passes through the position control valves 60, 62 to the main valve pilot passages 160, 162 to act on the corresponding ends of the spool of the main control valve 50. When both position control valves 60, 62 are in the open position, the main control valve 50 is in a state such as Figure 2 The intermediate position N is shown. In the intermediate position N, the first HP supply port 52 and the head end fluid port 90 are blocked to retain fluid within the head end 34 of the lift cylinder 30 and to maintain the dump body 14 in a substantially stationary position. The rod end fluid port 80 is provided in fluid communication with the brake cooling fluid passage 104 via the restricted passage 112 to allow some of the fluid to drain from the rod end 32. The second HP supply port 54 is also fluidly connected to the brake cooling fluid passage 104, and the selector pilot pressure passage 122 is fluidly connected to the drain passage 66 to reduce the pilot pressure on the selector spool 116.

[0030] In order to move the main control valve 50 to one of the three available dump body lowering positions L1, L2, L3 in response to the control rod sensor signal from the control rod sensor 140, the controller 130 sends a proportional control signal to move the solenoid of the lowering position control valve 60 toward the second position, in which the main valve pilot passage 160 is fluidly connected to the exhaust passage 66. The reduced fluid pressure in the main valve pilot passage 160 allows the fluid pressure of the main valve pilot passage 162 to force the valve core of the main control valve 50 to the corresponding dump body lowering position L1, L2, L3. In the same manner, in response to the control rod sensor signal from the control rod sensor 140 to raise the dump body 14, the controller 130 sends a control signal to move the solenoid of the raising position control valve 62 toward its second position to fluidly connect the main valve pilot passage 162 to the exhaust passage 66 and reduce the fluid pressure in the main valve pilot passage 162 to allow the fluid pressure of the main valve pilot passage 160 to force the valve core of the main control valve 50 to the dump body raising position R.

[0031] The dump body lowering positions L1, L2, L3 control the rate at which the lift cylinder 30 is retracted and the dump body 14 is lowered. The first dump body lowering position L1 may be a powered lowering position having a maximum dump body 14 lowering rate. In this position, the rod end fluid passage 84 is provided in fluid communication with the fluid supply passage 48 to deliver pressurized fluid to the rod end 32 of the lift cylinder 30, and the head end fluid passage 94 is provided in fluid communication with the drain passage 66 to drain fluid from the head end 34 of the lift cylinder 30 to the tank 70. The selector pilot pressure passage 122 is also fluidly connected to the drain passage 66 so that the selector spool 116 is spring biased to a position that distributes metered fluid from the dump fluid passage 58 to the two pilot pressure reducing valves 118, 120. At the same time, the head end pressure pilot signal to the counterbalance valve 124 via the counterbalance pilot pressure passage 128 is reduced. The second HP supply port 54, the brake cooling fluid port 100, and the rod end pressure relief port 110 are blocked to prevent fluid from flowing to the brake cooling fluid passage 104. The second dump body lowering position L2 may be a floating position in which the dump body 14 is lowered at a slower rate. The rod end and head end connections are similar to position L1, but the brake cooling fluid passage 104 is fluidly connected to the fluid supply passage 48 to divert a portion of the hydraulic fluid away from the rod end 32 and to the brake cooling system, thereby slowing the retraction of the lift cylinder 30. The third dump body lowering position L3 may be a braking position in which a larger portion of the hydraulic fluid is diverted away from the rod end 32 to further reduce the rate of descent of the dump body 14 and to reduce the rate of descent of the dump body 14 when the dump body 14 reaches the brake. Figure 1 Control the shock in the fully lowered position.

[0032] The main control valve 50 in the illustrated embodiment has a single dump body raised position R, but in a particular implementation of the lift valve assembly 40, additional raised positions are contemplated if more control of the extension of the lift cylinder 30 is desired to raise the dump body 14. In the dump body raised position R as shown, the head end fluid passage 94 is provided in fluid communication with the fluid supply passage 48 to deliver pressurized fluid to the head end 34 and extend the lift cylinder 30, and the rod end fluid passage 84 is provided in fluid communication with the brake cooling fluid passage 104 to discharge fluid from the rod end 32 of the lift cylinder 30 to the brake cooling system. The second HP supply port 54, the valve drain port 64, and the restricted passage 112 are blocked. The first HP supply port 52 is fluidly connected to the metered pilot pressure port 114 to provide a pilot signal corresponding to the head end pressure in the head end fluid passage 94 to the selector spool 116 via the selector pilot pressure passage 122, and to the balance valve 124 via the balance pilot pressure passage 128. The pilot signal to the selector spool 116 moves the selector spool 116 to the raise position, wherein the dump fluid passage 58 is fluidly connected only to the raise pilot pressure relief valve 120 .

[0033] When the balancing cut-off valve 126 is in Figure 2 In the open position shown, the head end pressure pilot signal from the balance pilot pressure passage 128 acts on the balance valve 124 in the same direction as the rod end pressure pilot signal. The balance valve outlet pressure pilot signal and a biasing member such as a spring can act in the opposite direction of the head end and rod end pressure pilot signals. In this configuration, a pressure spike in the head end 34 or rod end 32 of the lift cylinder 30 while raising the dump body 14 will cause the balance valve 124 to open and discharge fluid from the rod end 32 to the brake cooling system. Under certain operating conditions, such as those discussed further below, it may be desirable to remove the head end pressure pilot signal from the balance valve 124 and allow the balance valve 124 to function as a rod end pressure relief valve that is only affected by the rod end pressure pilot signal from the rod end 32. During these conditions, the controller 130 may send a solenoid valve control signal to the balanced shut-off valve 126 to move the balanced shut-off valve 126 to the shut-off position where the balanced pilot pressure passage 128 is blocked and the portion of the pilot pressure passage 128 between the balanced valve 124 and the balanced shut-off valve 126 is fluidly connected to the drain passage 66 via the shut-off drain passage 164 to drain the head end pressure pilot fluid to the tank 70. When the balanced shut-off valve 126 is in the shut-off position, the balanced valve 124 will only open during the raising of the dump body 14 with pressure supplied from the rod end 32.

[0034] Industrial Applicability

[0035] Figure 4 A graphical representation of various parameters during operation of the lift valve assembly 40 dumping a load from the dump body 14 when the counterbalance shut-off valve 126 is in its normally open position to transmit a head end pressure pilot signal to the counterbalance valve 124 is provided. In this example, the work machine 10 dumps a viscous payload of material such as oil sands ore at ambient temperature with pressurized fluid flowing freely through the lift cylinder 30 and the lift valve assembly 40. The x-axis represents the time for the dump body 14 to be raised, dump the load, and be lowered back to its normal position by the lift cylinder 30. The dump body angle curve 170 shows the dump body angle indicated by the dump body position sensor 144 during the load dumping cycle, the head end pressure curve 172 and the rod end pressure curve 174 show the pressures in the head end 34 and the rod end 32 of the lift cylinder 30, respectively, and the vertical acceleration curve 176 and the longitudinal acceleration curve 178 indicate the acceleration of the main frame 12 in the respective directions.

[0036] When the main control valve 50 moves to the raised position R and pressurized fluid flows to the head end 34 of the lift cylinder 30, the lift cylinder 30 extends and increases the dump body angle. During the initial stage, when the hydraulic fluid fills the head end 34 to raise the dump body 14 and the counterbalance valve 124 opens to discharge fluid from the rod end 32 to the brake cooling system, the head end pressure is greater than the rod end pressure. As the dump body angle approaches the over-center load angle 180, some pressure oscillations occur, but the counterbalance valve 124 controls the rod end pressure to minimize the vertical and longitudinal accelerations of the main frame 12. In one implementation, the over-center load angle 180 occurs at about 70% of the maximum dump body raising angle of the dump body 14 and can be in the range of 38° to 40°. When the dump body 14 reaches the over-center load angle 180, the combined center of mass of the dump body 14 and the material load exceed the dump body axis 16 and the moment direction about the dump body axis 16 is converted. The load on the lift cylinder 30 is converted from a compressive load to a tensile load that must be resisted by the rod end 32. The rod end pressure increases while the head end pressure decreases, causing the counterbalance valve 124 to move toward the throttling position to restrict fluid flow out of the rod end 32 and prevent the dump body 14 from rapidly rotating about the dump body axis 16. Eventually, the material load slides off the surface of the dump body 14 at the load breakaway angle 182. The load on the lift cylinder 30 is converted back to a compressive load that increases the head end pressure and decreases the rod end pressure.

[0037] The operation of the poppet valve assembly 40 , and in particular the counterbalance valve 124 , may be adversely affected at low temperatures that inhibit the flow of hydraulic fluid. Figure 5 Shows something like Figure 4 , where the work machine 10 is operating at an ambient temperature of approximately -14°C. Due to flow resistance, there is a lag in the pressure change in the head end 34 that is transmitted to the counterbalance valve 124 in the head end pressure pilot signal, and a corresponding lag in the response of the counterbalance valve 124. Therefore, the pressure oscillations and main frame accelerations before the over-center load angle 180 are large because the counterbalance valve 124 responds slowly. After the dump body 14 exceeds the over-center load angle 180, further larger pressure oscillations occur and accelerations of the main frame 12 are generated, which potentially cause a shock effect to the work machine 10 and the operator.

[0038] In the poppet valve assembly 40 according to the present disclosure, the balanced cut-off valve 126 is controlled during low temperature or other unstable operating conditions to remove the head end pressure pilot signal from the balanced valve 124 so that only the rod end pressure pilot signal acts on the balanced valve 124, thereby regulating the fluid pressure in the rod end 32. As described above, the solenoid of the balanced cut-off valve 126 is actuated to move the balanced cut-off valve 126 to the cut-off position where the balanced pilot pressure passage 128 is blocked, and the portion of the pilot pressure passage 128 between the balanced valve 124 and the balanced cut-off valve 126 is fluidly connected to the drain passage 66 to drain the pilot fluid to the tank 70. Under low rod end pressure, the balanced cut-off valve 126 will remain closed, and a small amount of hydraulic fluid can flow through the rod end restricted drain passage 129 to the brake cooling system. Under higher rod end pressure, the rod end pressure pilot signal opens the balanced valve 124 to drain the hydraulic fluid from the rod end 32 to the brake cooling system through the balanced valve 124. After the unstable operating condition no longer exists (e.g., the ambient temperature rises above a threshold unstable temperature), the solenoid of the balancing shut-off valve 126 can be deactivated to return the balancing shut-off valve 126 to its normal position so that the head end pressure pilot signal can act on the balancing valve 124 together with the rod end pressure pilot signal.

[0039] Figure 6 An exemplary balancing valve cut-off routine 200 is shown that may be executed by the controller 130 to identify unstable operating conditions and actuate the balancing cut-off valve 126 in response. The balancing valve cut-off routine 200 may begin at box 202, where the controller 130 detects a lever sensor signal from the lever sensor 140 or other source that indicates displacement of an input device by an operator of the work machine 10. After detecting the lever sensor signal, control may be passed to box 204, where the controller 130 determines whether the work machine 10 is commanded to raise the dump body 14 based on the lever sensor signal. If the lever sensor signal is not a signal to raise the dump body 14, control may be passed to box 206, where the controller 130 may control the solenoid of the balancing cut-off valve 126 to deactivate and allow the balancing cut-off valve 126 to move to its normal position, or if the balancing cut-off valve 126 is already set in the normal position, to maintain it in the normal position. After ensuring that the balancing cut-off valve 126 is in the correct position, control may be passed back to box 202 to monitor subsequent lever sensor signals.

[0040] If at box 204, the control lever sensor signal is a signal to raise the dump body 14, control may be passed to box 208, where the controller 130 may determine whether the work machine 10 is operating under unstable operating conditions. As described above, unstable operating conditions may include operating the work machine 10 at an ambient temperature or oil temperature below a threshold unstable temperature and where fluid flow is affected, raising the dump body 14 beyond the over-center load angle 180, or a combination of temperature, dump body angle, and other operating parameters. If at box 208, the controller 130 determines that the work machine 10 is not operating under unstable conditions, control may be passed to box 206 to ensure that the balancing shut-off valve 126 is in a normal position, and then passed to box 202 to monitor the subsequent control lever sensor signal. If at block 208, the controller 130 determines that the work machine 10 is operating under unstable conditions, control may pass to block 210, where the controller 130 may actuate the solenoid of the balanced shut-off valve 126 to move the balanced shut-off valve 126 to the shut-off position, disconnect the head end pressure pilot signal from the balanced valve 124, and exhaust the pilot passage to the tank 70. After moving the balanced shut-off valve 126 to the shut-off position, control may pass back to block 202 to monitor subsequent control lever sensor signals.

[0041] Figure 7-10 Several alternative strategies are shown in accordance with the present disclosure for controller 130 to determine when work machine 10 is experiencing unstable operating conditions that may require a balanced shutoff. Figure 7 1 shows an implementation in which the work machine 10 can dump viscous materials such as oil sands ore, where the properties of the material can cause vibrations in the work machine 10 regardless of the current ambient temperature or oil temperature. In this embodiment, the process at box 204 can start at box 220, where the controller 130 detects a dump body position sensor signal from the dump body position sensor 144. After detecting the signal, control can be passed to box 222, where the controller 130 determines whether the current dump body angle indicated by the signal is greater than a threshold unstable angle, which can be less than but close to the over-center load angle 180. If it is desired to perform a balanced cutoff before reaching the over-center load angle 180, the threshold unstable angle can be used as a cutoff reference. If the dump body angle is less than the threshold unstable angle, the work machine 10 has not yet reached an unstable operating condition, and control can be passed back to box 206 to be executed as described above. If the dump body angle is greater than the threshold unstable angle, the work machine 10 has reached an unstable operating condition, and control can be passed to box 210 to actuate the balanced cutoff valve 126 to the cutoff position.

[0042] Figure 8An implementation is shown in which the work machine 10 may operate in a cold environment, where instability may occur at low temperatures regardless of the nature of the work material loaded in the dump body 14. Processing at box 204 may begin at box 230, where the controller 130 detects a temperature sensor signal from an associated temperature sensor, such as the ambient temperature sensor 146 or the oil temperature sensor 148. The sensed temperature for a given implementation may be the temperature that most accurately correlates to an unstable operating condition of the work machine 10. After detecting the temperature sensor signal, control may be passed to box 232, where the controller 130 determines whether the current sensed temperature indicated by the signal is greater than a threshold instability temperature. If the sensed temperature is greater than the threshold instability temperature, the flow of the hydraulic fluid will not be adversely affected, and control may be passed back to box 206. If the sensed temperature is less than the threshold instability temperature, the work machine 10 is operating in an unstable operating condition, and control may be passed to box 210 to actuate the balanced shut-off valve 126 to the shut-off position.

[0043] Fig. 9 Provides can be Figure 7 and Figure 8 An implementation of a combination of embodiments of the present invention, wherein an unstable operating condition may occur when the work machine 10 is operating at low temperatures and the dump body 14 is raised and approaches or exceeds the over-center load angle 180. In this embodiment, the controller 130 may initially execute blocks 230, 232 to determine whether the current sensed temperature is less than a threshold unstable temperature, and if the sensed temperature is greater, control passes back to block 206. If the sensed temperature is less than the threshold unstable temperature, control may pass to blocks 220, 222 to determine whether the dump body angle is greater than a threshold unstable angle. If the dump body angle is less than the threshold unstable angle, control will pass back to block 206, and if the dump body angle is greater than the threshold unstable angle, control will pass back to block 210.

[0044] Fig.10An implementation of an unstable operating condition that may occur when the work machine 10 is processing materials such as oil sands ore, which may produce a mass that adheres to the surface of the dump body 14 beyond the over-center load angle 180, or may cause a transition from a compressive push load to a tensile pull load to occur before the dump body 14 reaches the over-center load angle 180. In this embodiment, at block 240, the controller 130 detects a material transition position sensor signal from the material transition position sensor 142. Block 240 may be performed in real time, or the controller 130 may retrieve from the memory 134 the value of the material transition position sensor signal received from the material transition position sensor 142 the last time the material transition position sensor 142 detected a change in the material transition position. Control then passes to block 242, where the controller 130 determines whether the material or material characteristic corresponding to the material transition position corresponds to a potentially unstable material. If the material indicated by the material transition position is not an unstable material, control may pass back to block 206. If the controller 130 determines that the material transition position indicates an unstable material, control may be passed to blocks 220, 222 to determine whether the dump body angle is greater than a threshold unstable angle. If the dump body angle is less than the threshold unstable angle, control may be passed back to block 206, and if the dump body angle is greater than the threshold unstable angle, control may be passed back to block 210. In some implementations of evaluating material properties, ambient temperature or oil temperature may also be considered when determining when to actuate the balancing shut-off valve 126.

[0045] The lift valve assembly 40 and the balancing valve cut-off routine 200 of the working machine 10 according to the present disclosure provide an effective solution to the instability that occurs in the balancing valve under certain operating conditions. The balancing cut-off valve 126 constitutes a single control element that is actuated by the controller 130 to release the balance in the lift valve assembly 40, which is in contrast to systems such as the regenerative hydraulic circuit of the Ramler et al. patent, which implements many controlled elements in addition to the main control valve that must be controlled by the controller to control the operation of the circuit. At the same time, the balancing valve cut-off routine 200 can be configured according to the needs of the specific implementation in the working machine 10 to determine when the working machine 10 is operating under unstable operating conditions. In most implementations, the controller 130 can utilize sensor information that is already available based on the operation and control of other systems of the working machine 10. In this way, the potential adverse vibration of the working machine 10 can be reduced, thereby reducing the maintenance of the working machine 10 and extending its service life.

[0046] The lift valve assembly 40 is shown and described herein as being implemented to control the operation of the lift cylinder 30. However, those skilled in the art will appreciate that the lift valve assembly 40 and the counterbalance valve cut-off routine 200 may be implemented to control the operation of any hydraulic cylinder in a work machine where counterbalance during extension or retraction of the hydraulic cylinder provides a benefit and counterbalance cut-off is desired during unstable operating conditions. Such implementations may include boom cylinders, stick cylinders, and / or implement cylinders in excavators, lift cylinders in loaders and bulldozers, and the like. The inventors contemplate such implementations.

[0047] Although the preceding text sets forth detailed descriptions of many different embodiments, it should be understood that the legal scope of protection is defined by the words of the claims set forth at the end of this patent. The detailed description should be construed as merely exemplary and does not describe every possible embodiment, as describing every possible embodiment would be impractical, if not impossible. Many alternative embodiments may be implemented using current technology or technology developed after the filing date of this patent, which still fall within the scope of the claims defining the scope of protection.

[0048] It should also be understood that unless a term is expressly defined herein, no limitation, either express or implied, of the meaning of that term beyond its ordinary or customary meaning is intended, and that the term should not be construed as limiting the scope of any statement made in any part of this patent (except in the language of the claims). To the extent that any term recited in the claims at the end of this patent is referred to herein in a manner consistent with a single meaning, this is done solely for clarity so as not to confuse the reader, and is not intended to limit such claim term, by implication or otherwise, to that single meaning.

Claims

1. A lift valve assembly (40) for a lift cylinder (30) of a work machine (10) having a head end (34) and a rod end (32), the lift valve assembly (40) comprising: a main control valve (50) having a raised position, wherein the head end (34) of the lift cylinder (30) is in fluid communication with a pressurized fluid source (44) and with a balanced pilot pressure passage (128) to send a head end pressure pilot signal, and wherein the rod end (32) of the lift cylinder (30) is in fluid communication with a low pressure reservoir (70); a counterbalance valve (124) positioned in a fluid flow path between the rod end (32) of the lift cylinder (30) and the main control valve (50), wherein the counterbalance valve (124) is biased to a closed position preventing fluid from flowing from the rod end (32) to the low pressure reservoir (70) and to an open position having the rod end (32) of the lift cylinder (30) in fluid communication with the low pressure reservoir (70), and wherein a rod end pressure pilot signal from the rod end (32) and the head end pressure pilot signal from the head end (34) apply a force to the counterbalance valve (124) in the direction of the open position; and A balancing shut-off valve (126) is positioned along the balancing pilot pressure passage (128) between the main control valve (50) and the balancing valve (124), wherein the balancing shut-off valve (126) has a normal position in which the head end pressure pilot signal applies the force to the balancing valve (124) and a shut-off position in which the head end pressure pilot signal is blocked from the balancing valve (124).

2. The poppet valve assembly (40) of claim 1, wherein a portion of the balanced pilot pressure passage (128) between the balanced valve (124) and the balanced shut-off valve (126) is fluidly connected to the low-pressure reservoir (70) when the balanced shut-off valve (126) is in the shut-off position.

3. The poppet valve assembly (40) of claim 1, wherein the balanced shut-off valve (126) includes an actuator that is actuated to move the balanced shut-off valve (126) from the normal position to the shut-off position.

4. The lift valve assembly (40) according to claim 1, wherein the main control valve (50) has a main control valve normal position, in which the head end (34) of the lift cylinder (30) is not fluidly connected to the pressurized fluid source (44), the rod end (32) of the lift cylinder (30) is fluidly connected to the low-pressure reservoir (70) via a restricted passage (112), and the balanced pilot pressure passage (128) is fluidly connected to the low-pressure reservoir (70).

5. The lift valve assembly (40) according to claim 1 includes a balancing valve (124) outlet pilot pressure channel (128) at the outlet of the balancing valve (124) to send a balancing valve outlet pressure pilot signal to apply a force to the balancing valve (124) in the direction of the normal position.

6. A working machine (10), comprising: Main frame (12); a dump body (14) pivotally connected to the main frame (12) via a dump body axle (16); a lift cylinder (30) having a head end (34) and a rod end (32), the lift cylinder being pivotally connected to the main frame (12) and the dump body (14) such that the lift cylinder (30) is extended to rotate the dump body (14) about the dump body axis (16) to raise the dump body (14) and retracted to lower the dump body (14) during a load dumping cycle; The poppet valve assembly (40) of claim 1, wherein the balanced shut-off valve (126) includes an actuator that is actuated to move the balanced shut-off valve (126) from the normal position to the shut-off position; and a controller (103) operably connected to the actuator of the balanced shut-off valve (126), the controller (103) being programmed to: determining whether the work machine (10) is operating under unstable operating conditions, and The actuator of the balanced shut-off valve (126) is actuated in response to determining that the work machine (10) is operating under the unstable operating condition to move the balanced shut-off valve (126) to the shut-off position.

7. The work machine (10) of claim 6, comprising a control lever sensor (140) operably connected to the controller (103), and wherein the controller (103) is programmed to: detecting a lever sensor signal from the lever sensor (140), wherein the lever sensor signal indicates one of lowering the dump body (14), raising the dump body (14), and maintaining a position of the dump body (14); determining whether the control lever sensor signal indicates raising the dump body (14); and In response to determining that the control lever sensor signal indicates raising the dump body (14), it is determined whether the work machine (10) is operating in the unstable operating condition.

8. The work machine (10) of claim 6, comprising a dump body position sensor (144) operably connected to the controller (103), and wherein the controller (103) is programmed to: detecting a dump body position sensor signal from the dump body position sensor (144), wherein the dump body position sensor signal indicates a dump body angle of the dump body (14); determining the dump body angle based on the dump body position sensor signal; and When the dump body angle is greater than a threshold unstable angle, it is determined that the work machine (10) is operating under the unstable operating condition.

9. The work machine (10) of claim 6, comprising a temperature sensor (146, 148) operably connected to the controller (103), and wherein the controller (103) is programmed to: detecting a temperature sensor signal from the temperature sensor (146, 148); determining a sensed temperature based on the temperature sensor signal; and When the sensed temperature is less than a threshold unstable temperature, it is determined that the work machine (10) is operating under the unstable operating condition.

10. The work machine (10) of claim 6, comprising a dump body position sensor (144) and a temperature sensor (146, 148) operably connected to the controller (103), and wherein the controller (103) is programmed to: detecting a temperature sensor signal from the temperature sensor (146, 148); determining a sensed temperature based on the temperature sensor signal; detecting a dump body position sensor signal from the dump body position sensor (144), wherein the dump body position sensor signal indicates a dump body angle of the dump body (14); determining the dump body angle based on the dump body position sensor signal; comparing the sensed temperature to a threshold unstable temperature; comparing the dump body angle to a threshold unstable angle in response to determining that the sensed temperature is less than the threshold unstable temperature; as well as When the dump body angle is greater than the threshold unstable angle, it is determined that the work machine (10) is operating under the unstable operating condition.

11. A method for cutting off balance during an extended period of a lift cylinder (30) of a working machine (10), wherein the working machine (10) includes a lift valve assembly (40) having a main control valve (50), the main control valve having a raised position, wherein a head end (34) of the lift cylinder (30) is fluidly connected to a pressurized fluid source (44) and to a balance pilot pressure passage (128) to send a head end pressure pilot signal, and wherein a rod end (32) of the lift cylinder (30) is fluidly connected to a low pressure reservoir (70), the lift valve assembly (40) further comprising a balance valve (124) positioned in a fluid flow path between the rod end (32) of the lift cylinder (30) and the main control valve (50), wherein the balance valve (124) is biased to a closed position preventing fluid from flowing from the rod end (32) to the low pressure reservoir (70) and having the rod end (32) of the lift cylinder (30) ) is in an open position in fluid communication with the low-pressure reservoir (70), and wherein a rod end pressure pilot signal from the rod end (32) and a head end pressure pilot signal from the head end (34) apply a force to the balancing valve (124) in the direction of the open position, and wherein the poppet valve assembly (40) further comprises a balancing shut-off valve (126) positioned along the balancing pilot pressure passage (128) between the main control valve (50) and the balancing valve (124), wherein the balancing shut-off valve (126) has a normal position in which the head end pressure pilot signal applies the force to the balancing valve (124) and a shut-off position in which the head end pressure pilot signal is blocked from the balancing valve (124), and wherein the balancing shut-off valve (126) comprises an actuator, the actuator being actuated to move the balancing shut-off valve (126) from the normal position to the shut-off position, the method for shutting off balancing comprises: determining whether the work machine (10) is commanded to move the main control valve (50) to the raised position; determining whether the work machine (10) is operating in an unstable operating condition in response to determining that the work machine (10) is commanded to move to the raised position; as well as The actuator of the balanced shut-off valve (126) is actuated in response to determining that the work machine (10) is operating under the unstable operating condition to move the balanced shut-off valve (126) to the shut-off position.

12. The method for off-balancing of claim 11, wherein the work machine (10) includes a main frame (12), a dump body (14) pivotally connected to the main frame (12) by a dump body axle (16), and wherein the lift cylinder (30) is pivotally connected to the main frame (12) and the dump body (14) such that the lift cylinder (30) extends to rotate the dump body (14) about the dump body axle (16) to raise the dump body (14) and retracts to lower the dump body (14) during a load dumping cycle, wherein determining whether the work machine (10) is operating in the unstable operating condition comprises: determining a dump body angle of the dump body (14) relative to the main frame (12); as well as When the dump body angle is greater than a threshold unstable angle, it is determined that the work machine (10) is operating under the unstable operating condition.

13. The method for disconnecting balance according to claim 11, wherein determining whether the work machine (10) is operating in the unstable operating condition comprises: determining a sensed temperature of the work machine (10); as well as When the sensed temperature is less than a threshold unstable temperature, it is determined that the work machine (10) is operating under the unstable operating condition.

14. The method for cut balancing according to claim 13, wherein the sensed temperature is an ambient temperature of an environment in which the work machine (10) is operating.

15. The method for off-balancing of claim 11, wherein the work machine (10) includes a main frame (12), a dump body (14) pivotally connected to the main frame (12) by a dump body axle (16), and wherein the lift cylinder (30) is pivotally connected to the main frame (12) and the dump body (14) such that the lift cylinder (30) extends to rotate the dump body (14) about the dump body axle (16) to raise the dump body (14) and retracts to lower the dump body (14) during a load dumping cycle, wherein determining whether the work machine (10) is operating in the unstable operating condition comprises: determining a sensed temperature of the work machine (10); determining a dump body angle of the dump body (14) relative to the main frame (12); comparing the sensed temperature to a threshold unstable temperature; comparing the dump body angle to a threshold unstable angle in response to determining that the sensed temperature is less than the threshold unstable temperature; as well as When the dump body angle is greater than the threshold unstable angle, it is determined that the work machine (10) is operating under the unstable operating condition.

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