WO2023006237A1

WO2023006237A1 - Gravity lower control for work machines

Info

Publication number: WO2023006237A1
Application number: PCT/EP2022/025024
Authority: WO
Inventors: Roger D. Lowman; Chad Anthony LARISH; Sam Newbauer
Original assignee: Danfoss Power Solutions Ii Technology As
Priority date: 2021-07-26
Filing date: 2022-01-26
Publication date: 2023-02-02

Abstract

A hydraulic system can include a hydraulic actuator including a first port and a second port.; a hydraulic pump; a hydraulic reservoir; a first control valve operable to selectively control flow from the hydraulic pump to the first port; a first control valve operable to selectively control flow from, the hydraulic pump and the hydraulic reservoir to one or both of the first port and the second port; a load-holding valve positioned between the first control valve and the first port in a first fluid pathway; a first counterbalance valve located between the hydraulic reservoir and the first port in a second fluid pathway that is parallel to the first fluid pathway; and a controller for operating the hydraulic system, and including a lowering mode and/or an. actuation mode.

Description

GRAVITY LOWER CONTROL FOR WORK MACHINES

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of PCT Application No.

PCT/EP2021/025286, filed on July 26, 2021, the disclosure of which is incorporated herein by reference to the extent appropriate.

BACKGROUND

[0002] Work machines, such as fork lifts, wheel loaders, track loaders, excavators, backhoes, bull dozers, fire trucks, and telehandlers are known. Work machines can be used to move material, such as pallets, dirt, and/or debris. The work machines typically include a work implement (e.g,, a fork) connected to the work machine. The work implements attached to the work machines are typically powered by a hydraulic system. The hydraulic system can include a hydraulic pump that is powered by a prime mover, such as a diesel engine. The hydraulic system typically includes a number of work sections for operating actuators via control valve assemblies. It some circumstances, it is necessary to lower a load supported by the work implement through the use of gravity, for example when a system fault or failure occurs. Although some approaches for accomplishing such a function are known, improvements are desired.

SUMMARY

[0003] A hydraulic system can include a linear hydraulic actuator including a piston rod slidably disposed within a housing having a base-side port and a rod-side port, a hydraulic pump, a hydraulic reservoir, an accumulator, a first control valve operable to selectively control flow from the pump to the base-side port and from the base-side port to the reservoir, a second control valve operable to selectively control flow from the pump to the rod-side port and from the rod-side port to the reservoir, a load-holding valve positioned between the first control valve and the base-side port, a first counterbalance valve located between the reservoir and the base-side port, and a controller for operating the hydraulic system and including a lowering mode in which: the load-holding valve is held in an open position, the first control valve is metered to allow hydraulic oil to exit the base-side port via the first control valve to meet a commanded lowering speed associated with the actuator, and fluid from the reservoir can flow into the rod-side port via the second control valve or through the first counterbalance valve.

[0004] In some examples, the lowering mode is a gravity lowering mode, wherein the pressurized fluid from the pump is not utilized to lower the load.

[0005] In some examples, the system further includes a first check valve located between the reservoir and the rod-side port, wherein fluid flows through the first check valve to the rod-side port during the lowering mode.

[0006] In some examples, the first check valve is a spring check valve with a pressure setting of about 0.3 bar.

[0007] In some examples, the system further includes a second check valve located between the reservoir and the base-side port, wherein fluid flows from the base-side port through the second check valve, and to the reservoir.

[0008] In some examples, the second check valve is a spring check valve with a pressure setting of about 3 to 5 bar.

[0009] In some examples, the system further includes an accumulator in selective communication with the base-side port.

[0010] In some examples, the lowering mode farther includes the second control valve in a fully open position to allow fluid to pass through the second control valve from the reservoir to the rod-side port.

[0011] In some examples, the lowering mode further includes the second control valve in a fully closed position to block fluid from passing through the second control valve from the reservoir to the rod-side port. [0012] In some examples, the lowering mode farther includes the second control valve metering to selectively provide flow from the pump to the rod-side port via the second control valve.

[0013] In some examples, the system farther includes a second counterbalance valve operable to bypass flow around the load-holding valve, the second counterbalance valve being piloted by fluid associated with the rod-side port.

[0014] In some examples, the first and second control valves are configured to be manually positioned to allow hydraulic fluid to flow from the base-side port to the reservoir via the first control valve and from the reservoir to the rod-side port via the second control valve.

[0015] A hydraulic system can include a linear hydraulic actuator including a piston rod slidably disposed within a housing having a base-side port and a rod-side port, a hydraulic pump, a hydraulic reservoir, an accumulator, a first control valve operable to selectively control flow from the pump to the base-side port and from the base-side port to the reservoir, a second control valve operable to selectively control flow from the pump to the rod-side port and from the rod-side port to the reservoir, a load-holding valve positioned between the first control valve and the base-side port, a first counterbalance valve located between the reservoir and the base-side port, and a second counterbalance valve arranged to bypass flow around the load-holding valve, the second counterbalance valve being piloted with fluid associated with the rod-side port, and a controller for operating the hydraulic system and including a lowering mode in which: the load-holding valve is held in a closed position, fluid flows from the base-side port and through the second counterbalance valve, and the first control valve receives fluid from the second counterbalance valve and is metered to allow hydraulic oil to exit the base-side port via the first control valve to meet a commanded lowering speed associated with the actuator, and fluid from the reservoir can flow into the rod-side port via the second control valve or through the first counterbalance valve.

[0016] In some examples, the system farther includes a first check valve located between the reservoir and the rod-side port, wherein fluid flows through the first check valve to the rod-side port during the lowering mode. [0017] In some examples, the first cheek valve is a spring cheek valve with a pressure setting of about 0.3 bar.

[0018] In some examples, the system further includes a second check valve located between the reservoir and the base-side port, wherein fluid flows from the base-side port through the second check valve, and to the reservoir.

[0019] In some examples, the second check valve is a spring check valve with a pressure seting of about 3 to 5 bar.

[0020] In some examples, the system further includes an accumulator in selective communication with the base-side port.

[0021] In some examples, the lowering mode further includes the second control valve metering to selectively provide flow from the pump to the rod-side port via the second control valve.

[0022] In some examples, the first and second control valves are configured to be manually positioned to allow hydraulic fluid to flow from the base-side port to the reservoir via the first control valve and from the reservoir to the rod-side port via the second control valve.

[0023] A hydraulic system can include a linear hydraulic actuator including a piston rod slidably disposed within a housing having a base-side port and a rod-side port, a hydraulic pump, a hydraulic reservoir, an accumulator, a first control valve operable to selectively control flow from the pump to the base-side port and from the base-side port to the reservoir, a second control valve operable to selectively control flow from the pump to the rod-side port and from the rod-side port to the reservoir, a load-holding valve positioned between the first control valve and the base-side port, a first counterbalance valve located between the reservoir and the base-side port, an accumulator, a third control valve to selectively place the accumulator in fluid communication with the base-side port, and a controller for operating the hydraulic system and including a lowering mode in which: the load-holding valve is held in an open position, the third control valve is held in the closed position, the first control valve is metered to allow hydraulic oil to exit the base-side port via the first control valve to meet a commanded lowering speed associated with the actuator, and fluid from the reservoir can flow into the rod-side port via the second control valve or through the first counterbalance valve.

[0024] In some examples, the lowering mode is a gravity lowering mode, wherein the pressurized fluid from the pump is not utilized to lower the load.

[0025] In some examples, the system further includes a first check valve located between the reservoir and the rod-side port, wherein fluid flows through the first check valve to the rod-side port during the lowering mode.

[0026) In some examples, the first check valve is a spring check valve with a pressure setting of about 0.3 bar.

[0027] In some examples, further includes a second check valve located between the reservoir and the base-side port, wherein fluid flows from the base-side port through the second check valve, and to the reservoir.

[0028] In some examples, the second check valve is a spring check valve with a pressure setting of about 3 to 5 bar.

[0029] In some examples, the lowering mode further includes the second control valve in a fully open position to allow fluid to pass through the second control valve from the reservoir to the rod-side port.

[0030[ In some examples, the lowering mode further includes the second control valve in a fully closed position to block fluid from passing through the second control valve from the reservoir to the rod-side port.

[0031] In some examples, the lowering mode further includes the second control valve metering to selectively provide flow from the pump to the rod-side port via the second control valve.

[0032] In some examples, the system further includes a second counterbalance valve operable to bypass flow around the load-holding valve, the second counterbalance valve being piloted by fluid associated with the rod-side port.

[0033] In some examples, the hydraulic actuator is a linear hydraulic actuator. [0034] In some examples, the first and second control valves are configured to be manually positioned to allow hydraulic fluid to flow from the base-side port to the reservoir via the first control valve and from the reservoir to the rod-side port via the second control valve.

[0035] A hydraulic system can include a hydraulic actuator including a first port and a second port; a hydraulic pump; a hydraulic reservoir; a first control valve operable to selectively control flow from the hydraulic pump to the first port; a first control valve operable to selectively control flow from the hydraulic pump and the hydraulic reservoir to one or both of the first port and the second port; a load-holding valve positioned between the first control valve and the first port in a first fluid pathway; a first counterbalance valve located between the hydraulic reservoir and the first port in a second fluid pathway that is parallel to the first fluid pathway; and a controller for operating the hydraulic system and including a lowering mode in which: the load-holding valve is held in an open position; the first control valve is metered to allow hydraulic oil to exit the first port via the first control valve to meet a commanded lowering speed associated with the hydraulic actuator; and fluid from the hydraulic reservoir can flow into the second port.

[0036] In some examples, the lowering mode is a gravity lowering mode, wherein the pressurized fluid from the hydraulic pump is not utilized to lower a load.

[0037] In some examples, the system includes a first check valve located between the hydraulic reservoir and the second port, wherein fluid flows through the first check valve to the second port during the lowering mode.

[0038] In some examples, the first check valve is a spring check valve with a pressure setting of about 0.3 bar.

[0039] In some examples, the system includes a second check valve located between the hydraulic reservoir and the first port, wherein fluid flows from the first port through the second check valve, and to the hydraulic reservoir.

[0040] In some examples, the second check valve is a spring check valve with a pressure setting of about 3 to 5 bar. [0041] In some examples, the system includes an accumulator in selective communication with the first port.

[0042] In some examples, the system includes a second control valve and wherein the lowering mode further includes the second control valve in a fully open position to allow fluid to pass through the second control valve from the hydraulic reservoir to the second port.

[0043] In some examples, the lowering mode further includes the second control valve in a fully closed position to block fluid from passing through the second control valve from the hydraulic reservoir to the rod-side port.

[0044] In some examples, the lowering mode further includes the second control valve metering to selectively provide flow from the hydraulic pump to the second port via the second control valve.

[0045] In some examples, the first and second control valves are configured to be manually positioned to allow hydraulic fluid to flow from the first port to the hydraulic reservoir via the first control valve and from the hydraulic reservoir to the second port via the second control valve.

[0046] In some examples, the hydraulic actuator is a linear hydraulic actuator, and wherein the first port is a base-side port and the second port is a rod-side port.

[0047] In some examples, the controller includes an actuating mode in which the first control valve places the hydraulic pump and the hydraulic actuator in fluid communication with each other, wherein the load-holding valve is in an open position to allow fluid to flow from the first control valve to the first port through the load- holding valve and around the first counterbalance valve.

[0048] A hydraulic system comprising a hydraulic actuator including a first port and a second port; a hydraulic pump; a hydraulic reservoir; a first control valve operable to selectively control flow from the pump to the first port; a first counterbalance valve located between the first control valve and the first port; a first bypass valve positioned between the first control valve and the first port, the first bypass valve providing a flow path around the first counterbalance valve; and a controller for operating the hydraulic system and including: an actuating mode in which the first control valve places the hydraulic pump and the hydraulic actuator in fluid communication with each other, wherein the first bypass valve is in an open position to allow fluid to flow from the first control valve to the first port through the bypass valve and around the first counterbalance valve; and a holding mode in which the first control valve is in a neutral or closed position to substantially block flow between the hydraulic pump and the hydraulic actuator, wherein the first bypass valve is in a closed position such that fluid flow through the first bypass valve is blocked such that any fluid flow between the first port and the first control valve flows through the first counterbalance valve,

[0049] In some examples, the first control valve is in fluid communication with both the first and second ports.

[0050] In some examples, the system includes a second counterbalance valve located between the first control valve and the second port and a second bypass valve positioned between the first control valve and the second port, the second bypass valve providing a flow path around the second counterbalance valve.

[0051] In some examples, the system includes a second control valve operable to selectively control flow from the pump to the second port; a second counterbalance valve located between the second control valve and the second port; and a second bypass valve positioned between the second control valve and the second port, the second bypass valve providing a flow path around the second counterbalance valve.

[0052] In some examples, the controller includes a second actuating mode, in which the second control valve places the hydraulic pump and the hydraulic actuator in fluid communication with each other, wherein the second bypass valve is in an open position to allow fluid to flow from the second control valve to the second port through the second bypass valve and around the second counterbalance valve.

DESCRIPTION OF THE DRAWINGS

[0053] Non-limiting and non-exhaustive embodiments are described with reference to the following figures, which are not necessarily drawn to scale, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified.

[0054] Figure 1 is a schematic view of a work machine having features that are examples of aspects in accordance with the principles of the present disclosure.

[0055] Figure 2 is a schematic view of a hydraulic system including work circuits suitable for use in the work machine shown in Figure 1.

[0056] Figure 3 is a schematic of a portion of the hydraulic system shown in Figure 2 including a first example of a work section operable in gravity lower mode in an operational phase.

[0057] Figure 3 A is a schematic of the work section shown in Figure 3, wherein an actuator of the work section is alternatively shown as being a hydraulic motor.

[0058] Figure 4 is a schematic of a portion of the hydraulic system work section of Figure 3 in an operational phase.

[0059] Figure 5 is a schematic of a portion of the hydraulic system work section of Figure 3 in an operational phase.

[0060] Figure 6 is a schematic of a portion of the hydraulic system work section of Figure 3 in an operational phase.

[0061] Figure 7 is a schematic of a portion of the hydraulic system work section of Figure 3 in an operational phase.

[0062] Figure 8 is a schematic of a portion of the hydraulic system shown in Figure 3 including an accumulator and being in the operational phase shown in Figure 3.

[0063] Figure 9 is a schematic of a portion of the hydraulic system work section of Figure 8 and being in the operational phase shown in Figure 4.

[0064] Figure 10 is a schematic of a portion of the hydraulic system work section of Figure 8 and being in the operational phase shown in Figure 5. [0065] Figure 11 is a schematic of a portion of the hydraulic system work section of Figure 8 and being in the operational phase shown in Figure 6.

[0066] Figure 12 is a schematic of a portion of the hydraulic system work section of Figure 8 and being in the operational phase shown in Figure 7.

[0067] Figure 13 is a schematic of a portion of the hydraulic system work section of Figure 3 in an operational phase,

[0068] Figure 14 is a schematic of a portion of the hydraulic system shown in Figure 2 including an example of a bypass load-holding valve arrangement.

[0069] Figure 15 is a schematic of a portion of the hydraulic system shown in Figure 2 including an example of a bypass load-holding valve arrangement.

[0070] Figure 16 is a schematic of a portion of the hydraulic system shown in Figure 2 including an example of a bypass load-holding valve arrangement.

[0071] Figure 17 is a schematic of a portion of the hydraulic system shown in Figure 2 including an example of a bypass load-holding valve arrangement.

[0072] Figure 18 is a schematic of a portion of the hydraulic system shown in Figure 2 including an example of a bypass load-holding valve arrangement.

DETAILED DESCRIPTION

[0073] Various embodiments will be described in detail with reference to the drawings, wherein like reference numerals represent like parts and assemblies throughout the several views. Reference to various embodiments does not limit the scope of the claims attached hereto. Additionally, any examples set forth in this specification are not intended to be limiting and merely set forth some of the many possible embodiments for the appended claims.

General Description

[0074] As depicted at Figures 1 and 2, a work machine 1 and hydraulic system 10 are shown. The work machine 1 may be any type of work machine, for example a telehandler, fork lift, wheel loader, track loader, excavator, backhoe, bull dozer, or fire truck. As depicted, the work machine 1 includes a work attachment 2 for performing a variety of lifting tasks associated with a load 3. In one embodiment, work machine 1 is a telehandler having a telescoping boom 4 that supports the work attachment 2. In one embodiment, the work attachment 2 includes a pair of forks. However, one skilled in the art will appreciate that the work attachment may be any hydraulically powered work implement. The hydraulic system 10 can also be configured to perform a wide variety of applications such as steering, load/work holding, stabilizing, swing, and jib applications.

[0075] Work machine 1 is also shown as including at least one drive wheel 5 and at least one steer wheel 6. In certain embodiments, one or more drive wheels 5 may be combined with one or more steer wheels 6, The drive wheels 5 are powered by an engine 7. Engine 7 is also configured to power a hydraulic system 10 including various work circuits 11. As illustrated at Figure 2, example work circuits 11 are a tilt work circuit 1 la, an extension work circuit 11b, and a lift work circuit 11c. The work circuits 11 can be powered by a hydraulic pump 12 and placed in fluid communication with a common reservoir 14. In some examples, the work machine 1 includes hydraulic actuators and valves for effectuating steering and propulsion, stabilizing, and for lifting, extending, tilting, and sideways motions of the work attachment 2. In one embodiment, pump 12 is powered indirectly by the engine 7. In one embodiment, the pump 12 is mechanically coupled to the engine 7, such as by an output shaft or a power take-off 9. In operation, the work circuit 11 actuates the work attachment 2 by operation of the pump 12 in cooperation with a number of hydraulic actuators 102 and control valves 110, 120. As shown, the pump 12 is a variable displacement axial pump provided with a conventional load-sense control arrangement to control the displacement of the pump 12 such that an appropriate flow can be delivered to the work circuits 11. In one aspect, the load-sense arrangement can include a load-sense spool, a maximum pressure cut-off spool, and an actuator for adjusting the swash plate angle of the pump 12. Although three work circuits are shown, additional work circuits can be provided in the hydraulic system without departing from the concepts presented herein. Although an example work machine 1 is shown and described, the disclosure is not limited to any particular work machine and is broadly applicable to any hydraulic system including actuators operated via control valves and a pump. Hydraulic System 100

[0076] Referring to Figures 3 and 3A, an example work circuit or section 11 for operating an actuator 102 is presented. In the example shown at Figure 3, the actuator 102 is associated with a lift function of a boom and is configured as a linear actuator. Other types of actuators may be used in various applications. For example, a rotary type hydraulic actuator may be used in a winch application. Figure 3 A shows an example configuration including a hydraulic actuator 102’. Although a single actuator 102, 102’ is shown, it should be understood that the depicted work circuit section could include multiple actuators 102, 102’ operated by the same depicted control valves 110, 120 as is shown, for example, at Figure 2.

[0077] In one aspect, the actuator 102 has a housing 104 with a base-side port 104a and a rod-side port 104b and piston rod 106 slidably disposed within the housing 104. As fluid enters the base-side port 104a and exits the rod-side port 104b, the piston rod 106 extends. Likewise, as fluid enters the rod-side port 104b and exits the base-side port 104a, the piston rod 106 contracts. In the case of a hydraulic motor 102’, a housing 104’ can be provided with the ports 104a, 104b wherein fluid passing between the ports causes a shaft 106’ to rotate. Similarly, when a torque T is applied to the shaft, fluid is caused to flow between the ports 104a, 104b.

[0078] As shown, the work circuit 11 includes a first control valve 110 and a second control valve 120 for controlling the position and function of the actuator(s) 102. Each of the control valves 110, 120 is configured as a three-position, three-way valve with ports 110a, 110b, 110c and 120a, 120b, 120c, respectively. The control valves 110, 120 are also operable between positions A, B, and C. Each control valve 110, 120 is also shown as being provided with oppositely acting centering springs 112, 114 and 122, 124 for biasing the control valves 110, 120 into the position C. Oppositely acting actuators 214, 216 are provided for moving the control valve into either position B or C via a control system 50. The actuators 214, 216 can be any type of actuators for selectively controlling the position of the control valves 110, 120, for example, the actuators 214, 216 can be electric, hydraulic, electro-hydraulic, mechanical, and/or any other type of actuator capable of performing the operations described herein. Position sensors 210, 212, which may be configured as LVDT (Linear Variable Differential Transformer) sensors, are also shown as being provided with each control valve 110, 120. The work circuit 11 is also shown as being provided with pressure sensors 202, 204, 206, and 208, with counterbalance valves 170, 172, and oppositely acting check valves 174, 176. The check valves 174 and/or 176 may be utilized where the reservoir is pressurized to avoid cavitation, for example during a load bounce-down, depending on the system. In some examples, the check valve 174 is a spring check valve configured with a pressure of about 0.3 bar and the check valve 176 is a spring check valve configured with a pressure of about 3 to 5 bar.

[0079] As configured, the first control valve 110 is in fluid communication with the base-side port 104a via port 110c while the second control valve 120 is in fluid communication with the rod-side port 104b via port 120c. When the first control valve 110 is in the first position A and the second control valve 120 is in the second position B, the port 104a is placed in fluid communication with the reservoir 14 via ports 110a, 110c and the port 104b is placed in fluid communication with the pump 12 via ports 120b, 120c such that the piston rod 106 contracts. When the first control valve 110 is in the second position B and the second control valve 120 is in the first position A, the port 104a is placed in fluid communication with the pump 12 via ports 110b, 110c and the port 104b is placed in fluid communication with the reservoir 14 via ports 120a, 120c such that the piston rod 106 extends. Generally, when either or both of the control valves 110, 120 are in the third position C, at least one of the ports 104a, 104b is blocked such that fluid flow via the pump 12 and/or reservoir 14 is blocked through the actuator 102.

[0080] In one aspect, the work circuit 11 is shown as further including an arrangement 180 having a load-holding valve 150, shown herein as a poppet valve.

As configured, the load-holding valve 150 is a two-position, two-port control valve with ports 150a, 150b and being movable between first and second positions A, B. As shown, the port 150a is in fluid communication with the base-side port 104a and the port 150b is in fluid communication with the port 110c of the valve 110. The control valve 150 is provided with a biasing spring 152 that biases the control valve 150 towards the position B and with an actuator 224 for actuating the control valve 150 towards the position A. The actuator 224 can be any type of actuator for selectively controlling the position of the control valve 150, for example, the actuator 224 can be an electric, hydraulic, electro-hydraulic, mechanical, and/or any other type of actuator capable of performing the operations described herein. In the position A, the ports 150a and 150b are placed in fluid communication such that fluid can flow between the valve 110 and the base-side port 104a. In the position B, the ports 150a and 150b are isolated from each other, in this case by a double-check valve arrangement, such that fluid flow between the valve 110 and the base-side port 104a is blocked.

Accordingly, the valve 150 can act as a load-holding valve to prevent retraction of the actuator 102 when the valve 150 is in the second position B. In the example shown, the valve 150 is configured as a double poppet valve. However, a single poppet configuration may also be used in which flow is blocked in the direction from the actuator port 104a towards the control valve 110. Other types of valves that selectively block the path between the actuator 102 and the control valve 110 can also be used.

[0081] The work circuit 11 and arrangement 180 are also further shown as including a counterbalance/relief valve 160 with ports 160a, 160b that provides a flow path around the load-holding valve 150 and is piloted by fluid from the rod-side port 104b and/or the control valve 120. The counterbalance valve is biased in a closed position by a spring 162 such that the ports 160a, 160b are normally isolated from each other. The valve 160 can also be provided with a port 160c for receiving a pilot fluid. When sufficient pressure exists, for example when thermal relief is required, fluid flow is allowed to pass out of port 104a via ports 160a, 160b to bypass the closed valve 150. This thermal relief function protects the cylinder and fluid conveyance against over pressurization.

[0082] With reference to Figures 8 to 12, the work circuit 11 is shown as additionally including an accumulator arrangement including an accumulator 140 and a control valve 130. In one aspect, the accumulator 140 has a port 140a while the control valve 130 has ports 130a, 130b, wherein the ports 140a, 130a are in fluid communication with each other and the port 130b is in fluid communication with the base-side port 104a. As configured, the control valve 130 is a two-position, two-port control valve movable between first and second positions A, B. The control valve 130 is provided with a biasing spring 132 that biases the control valve 130 towards the position B and an actuator 222 for actuating the control valve 130 towards the position A. The actuator 222 can be any type of actuator for selectively controlling the position of the control valve 130, for example, the actuator 222 can be electric, hydraulic, electro-hydraulic, mechanical, and/or any other type of actuator capable of performing the operations described herein. In the position A, the ports 130a and 130b are placed in fluid communication such that the accumulator port 140b is placed in fluid communication with the actuator base-side port 104a. In the position B, the ports 130a and 130b are isolated from each other such that fluid flow into or out of the accumulator 140 is blocked.

[0083] It is noted that the any of the actuators associated with operating the control valves of the present disclosure may be configured as proportional actuators.

Gravity Lower Operation

[0084] In general, the configurations shown at Figures 3 to 12 may be referred to as lowering modes, phases, or operational states. Through the use of the controller 50, described in more detail below, the above-described control valves and sensors can be used in conjunction to effectuate gravity or powered lowering of a boom or other similar component of a work machine having one or more associated actuators 102. By use of the term gravity lowering, it is meant that a load ultimately supported by the actuator(s) can be lowered without the use of a pump by allowing the force F (or torque T in the case of a hydraulic motor) on the actuator to force hydraulic oil out of the base-side port of the actuator 102 in a controlled manner. By use of the term powered lowering, it is meant that the pump is additionally used in conjunction with the gravity force to lower a load. In some examples, the system can be configured with an interface to allow an operator to select between gravity and power down modes.

[0085] In the examples shown at Figures 3 and 8, a gravity lowering mode is effectuated in which the load-holding valve 150 is actuated into the open position A such that hydraulic oil can flow from the base-side port 104a to the control valve 110. The control valve 110 is metered in position A to allow fluid from the base-side port 104a to flow to the reservoir 14 in a controlled manner. In one example, the control valve 110 is metered to maintain a commanded lowering speed which can be sensed with a position sensor at the actuator 102 or via other means. In one example, the control valve 110 is also metered with reference to the pressure sensor 206. In some examples, the system can transition to a powered down operation, described below with respect to Figure 5, where the gravity load is insufficient to meet the commanded lowering speed. During gravity lowering in this mode, the control valve 120 is operated to the open position C whereby oil from the reservoir 14 flows into the rod- side port 104b via control valve 120 and the check valve 174 to maintain cylinder fill. The anti-cavitation valve 172 can also function to maintain cylinder fill in the actuator 102. In this mode, no pump flow is required to lower the load. Where other simultaneous functions of the system are operating that require pump power, this gravity lower mode thus frees up pump capacity for those functions, thereby increasing performance of the system. Where an accumulator 140 is present, as is the case with Figure 8, the control valve 130 can be placed in the closed position B during this gravity lowering mode such that the condition of the accumulator 140 does not impact the lowering function.

[0086] In the example shown at Figures 4 and 9, a gravity lowering mode is effectuated in which the load-holding valve 150 is actuated into the open position A such that hydraulic oil can flow from the base-side port 104a to the control valve 110. The control valve 110 is metered in position A to allow fluid from the base-side port 104a to flow to the reservoir 14 in a controlled manner. In one example, the control valve 110 is metered to maintain a commanded lowering speed which can be sensed with a position sensor at the actuator 102 or via other means. In one example, the control valve 110 is also metered with reference to the pressure sensor 206. In some examples, the system can transition to a powered down operation, described below with respect to Figure 5, where the gravity load is insufficient to meet the commanded lowering speed. During gravity lowering in this mode, the control valve 120 is operated or held in the closed position C whereby oil from the reservoir 14 flows into the rod-side port 104b via the anti-cavitation check valve 172 and the check valve 174. The anti -cavitation valve maintains the cylinder fill in the actuator 102 and also supports a smooth transition to a powered down operation, if implemented. In this mode, no pump flow is required to lower the load. Where other simultaneous functions of the system are operating that require pump power, this gravity lower mode thus frees up pump capacity for those functions, thereby increasing performance of the system. Where an accumulator 140 is present, as is the case with Figure 9, the control valve 130 can be placed in the closed position B during this gravity lowering mode such that the condition of the accumulator 140 does not impact the lowering function.

[0087] In the example shown at Figures 5 and 10, a transition phase to a powered down mode is illustrated. In this phase, the pump 12 is activated and control valve 120 is metered to position B to direct hydraulic oil into the rod-side port 104b. In this phase, the pressure sensor 206 is used by the control system as an input variable to enable smooth transition from the gravity lower mode shown in Figure 3 or 4 into the powered down mode. The counterbalance valve 160 is piloted open by fluid from the control valve 120 and provides a lowering path. It is noted that this valve does not need to be sized for full lowering flow since the solenoid load holding valve 150 is open. Where an accumulator 140 is present, as is the case with Figure 10, the control valve 130 can be placed in the closed position B during this gravity lowering mode such that the condition of the accumulator 140 does not impact the lowering function.

[0088] With reference to Figures 6 and 11 , the powered down mode of Figure 4 can also be implemented with the load-holding valve 150 in the closed position B such that all flow from the base-side port 104b flows through the counterbalance valve 160, which provides a pathway for the fluid to the control valve 110. In some cases, the load-holding valve 150 may be stuck, failed, or closed for some other reason, and the approach of Figure 6 illustrates how lowering can still be accomplished with the valve 150 in the closed position. In one aspect, the pressure sensors 202, 204, 206, 208 can be used to identify any issues with the operation of the load-holding valve 150. Where an accumulator 140 is present, as is the case with Figure 11 , the control valve 130 can be placed in the closed position B during this gravity lowering mode such that the condition of the accumulator 140 does not impact the lowering function.

[0089] With reference to Figures 7 and 12, it is illustrated that the mode illustrated at Figure 6 can also be implemented by manually positioning the control valve 110 to the position A and the control valve 120 to the position B, whereby the lowering flow is controlled through the counterbalance valve 160 and the check valve 176. Where an accumulator 140 is present, as is the case with Figure 12, the control valve 130 can be placed in the closed position B during this gravity lowering mode such that the condition of the accumulator 140 does not impact the lowering function. [0090] With reference to Figure 13, a configuration is shown in which the control valves 110 and 120 are in their neutral positions and the load holding valve 150 is closed in position B. In this position, the counterbalance valve 160 relieving function can provide for thermal relief to protect the actuator and fluid conveyance against over-pressurization. In the configuration shown, it is noted that the control valve 110 can be provided with a spring offset or software control to functionally form an orifice to allow fluid flow to achieve equilibrium with the reservoir 14. The orifice may also be provided as a notch or other opening that allows for fluid flow when the valve is in the neutral position. In some examples, the pump can be operating at a standby pressure, for example 20-25 bar. Although the accumulator 140 is shown in this configuration, the same operation is possible without the presence of the accumulator 140. This configuration can be provided for any of the examples presented herein.

Counterbalance Bypass Configuration and Operation

[0091] In one aspect, the load-holding valve 150 can provide an additional bypass function, during operation of the actuator 102 via control valve 110, wherein fluid is bypassed around the valve 160 via the valve 150. During a lifting operation, for example when fluid is delivered to the actuator base-side port 104a via control valve 110, actuating the valve 150 into the open position A allows fluid to be delivered to port 104a without requiring additional pressure that would be otherwise required to actuate the hydro-mechanical counterbalance valve 160. As a result, bypassing the valve 160 with valve 150 results in a lower required pressure to move the actuator 102 which saves energy. Such an approach may also increase stability in comparison to using a traditional counterbalance solution in situations where the load condition dynamic. Bypass could be single poppet, double poppet, or other means of selectively blocking the path between the cylinder and the control valve.

[0092] Referring to Figures 14-18, additional configurations are shown in which a load-holding valve 150 can be used in certain operational modes to bypass a counterbalance valve 160 to accomplish the above-mentioned advantages. As shown at Figure 14, a generally similar configuration to Figure 4 is shown, but with the provision of a counterbalance valve 160’ and bypass valve 150’ controlling flow to and from port 104b of the actuator 102 and with orifices provided in the neutral position C of the control valves 110, 120. With such a configuration, valves 150 and 150’ can be selectively placed in an open position to bypass the valves 160, 160’ when the control valves 110 and 120 are actively moving the load via ports 104a,

104b to reduce energy consumption. For example, valve 150 can be open when valve 110 is in the position A or B, while valve 150’ can be open when the valve 120 is in the position A or B, Nonlimiting example applications for the configuration of Figure 14 are steering, swing, jibs, vehicle drive, stabilizers, and work-holding. Figure 15 shows a simpler control valve design in which only a single control valve 110’ is provided, configured as a three-position, four-way valve, that controls flow to both ports of the actuator 102 and in which the valves 150, 160 are only provided at one of the actuator ports. Accordingly, the valve 150 can be operated to the open position to bypass the valve 160 when the control valve 110’ is moved to the position A or B to move the actuator 102 via ports 104a, 104b. Nonlimiting example applications for the configuration of Figure 15 are booms, telescoping booms, lifts, stabilizers, and work- holding. Figure 16 shows a configuration with a valve 110’ of the type shown in Figure 15 provided with two bypass valves 150, 150’ and counterbalance valves 160, 160’. With such a configuration, the valve 150 can be moved to the open position to bypass valve 160 when the valve 110’ is moved to position A to deliver flow to the actuator 102 via port 104a while the valve 150’ can be moved to the open position to bypass valve 160’ when the valve 110’ is moved to position B to deliver flow to the actuator 102 via port 104b. Nonlimiting example applications for the configuration of Figure 16 are steering, swing, jibs, vehicle drive, stabilizers, and work-holding.

Figure 17 shows a configuration similar to that provided at Figure 15, but with a load- sense controlled pump and a control valve 110” provided with a load-sense port in fluid communication with the pump 12 to further illustrate that the concepts described herein are applicable to such a configuration. Nonlimiting example applications for the configuration of Figure 17 are booms, telescoping booms, lifts, stabilizers, and work-holding. Figure 18 shows a configuration similar to that provided at Figure 16, but with a load-sense controlled pump and a control valve 110” provided with a load- sense port in fluid communication with the pump 12 to further illustrate that the concepts described herein are applicable to such a configuration. Nonlimiting example applications for the configuration of Figure 18 are steering, swing, jibs, vehicle drive, stabilizers, and work-holding. Although linear actuators 102 are depicted, actuators 102 may be configured as motors or other types of actuators. Electronic Control System 50

[0093] In one aspect, the above-described pump, control valves, pressure sensors, position sensors, and other related components can be operated by an electronic control system 50 with any desired number of inputs and outputs to achieve the above-described methods of operation. The electronic control system 50 can include multiple controllers. For example, the control system 50 can include a system-level HFX programmable controller manufactured by Eaton Corporation of Cleveland, Ohio, USA; and an Eaton VSM controller which serves as an interface module and acts as a CAN (controller area network) bus gateway, a DC to DC power supply, and a supervisory controller for the hydraulic valve system. In one aspect, the control system 50 can also include valve assemblies that are configured within an Eaton CMA valve which includes a CAN-Enabled electrohydraulic sectional mobile valve that utilizes pressure and position sensors, on board electronics, and advanced software control algorithms.

[0094] The control system 50 can include a processor and a non-transient storage medium or memory, such as RAM, flash drive or a hard drive. Memory is for storing executable code, the operating parameters, and the input from the operator user interface while processor is for executing the code. The control system 50 can also include transmitting/receiving ports, such as a CAN bus connection or an Ethernet port for two-way communication with a WAN/LAN related to an automation system and to interrelated controllers. A user interface may be provided to activate and deactivate the system, allow a user to manipulate certain settings or Inputs to the control system 50, and to view information about the system operation.

[0095] The control system 50 typically includes at least some form of memory. Examples of memory include computer readable media. Computer readable media includes any available media that can be accessed by the processor. By way of example, computer readable media include computer readable storage media and computer readable communication media. Computer readable storage media includes volatile and nonvolatile, removable and non-removable media implemented in any device configured to store information such as computer readable instructions, data structures, program modules or other data. Computer readable storage media includes, but is not limited to, random access memory, read only memory, electrically erasable programmable read only memory, flash memory or other memory technology, compact disc read only memory, digital versatile disks or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store the desired information and that can be accessed by the processor,

[0096] Computer readable communication media typically embodies computer readable instructions, data structures, program modules or other data in a modulated data signal such as a earner wave or other transport mechanism and includes any information delivery media. The term “modulated data signal” refers to a signal that has one or more of its characteristics set or changed in such a manner as to encode information in the signal. By way of example, computer readable communication media includes wired media such as a wired network or direct- wired connection, and wireless media such as acoustic, radio frequency, infrared, and other wireless media. Combinations of any of the above are also included within the scope of computer readable media.

[0097] The various embodiments described above are provided by way of illustration only and should not be construed to limit the claims attached hereto.

Those skilled in the art will readily recognize various modifications and changes that may be made without following the example embodiments and applications illustrated and described herein, and without departing from the true spirit and scope of the disclosure.

Claims

What is claimed is:

1. A hydraulic system comprising: a hydraulic actuator including a piston rod slidably disposed within a housing having a base-side port and a rod-side port; a hydraulic pump; a hydraulic reservoir; a first control valve operable to selectively control flow from the hydraulic pump to the base-side port and from the base-side port to the hydraulic reservoir; a second control valve operable to selectively control flow from the hydraulic pump to the rod-side port and from the rod-side port to the hydraulic reservoir; a load-holding valve positioned between the first control valve and the base- side port; a first counterbalance valve located between the hydraulic reservoir and the base-side port; and a controller for operating the hydraulic system and including a lowering mode in which: the load-holding valve is held in an open position; the first control valve is metered to allow hydraulic oil to exit the base- side port via the first control valve to meet a commanded lowering speed associated with the hydraulic actuator; and fluid from the hydraulic reservoir can flow into the rod-side port via the second control valve or through the first counterbalance valve,

2. The hydraulic system of claim 1_» wherein the lowering mode is a gravity lowering mode, wherein the pressurized fluid from the hydraulic pump is not utilized to lower a load,

3. The hydraulic system of claim 1, further including a first check valve located between the hydraulic reservoir and the rod-side port, wherein fluid flows through the first check valve to the rod-side port during the lowering mode.

4. The hydraulic system of claim 3, wherein the first check valve is a spring check valve with a pressure setting of about 0.3 bar.

5. The hydraulic system of claim 1 or 3, farther including a second check valve located between the hydraulic reservoir and the base-side port, wherein fluid flows from the base-side port through the second check valve, and to the hydraulic reservoir.

6. The hydraulic system of claim 5, wherein the second check valve is a spring check valve with a pressure setting of about 3 to 5 bar.

7. The hydraulic system of claim 1, further comprising an accumulator in selective communication with the base-side port.

8. The hydraulic system of claim 1, wherein the lowering mode farther includes the second control valve in a fully open position to allow fluid to pass through the second control valve from the hydraulic reservoir to the rod-side port.

9. The hydraulic system of claim 1, wherein the lowering mode farther includes the second control valve in a fully closed position to block fluid from passing through the second control valve from the hydraulic reservoir to the rod-side port.

10. The hydraulic system of claim 1, wherein the lowering mode farther includes the second control valve metering to selectively provide flow from the hydraulic pump to the rod-side port via the second control valve,

11. The hydraulic system of claim 1, wherein the first and second control valves are configured to be manually positioned to allow hydraulic fluid to flow from the base-side port to the hydraulic reservoir via the first control valve and from the hydraulic reservoir to the rod-side port via the second control valve.

12. A hydraulic system comprising: a hydraulic actuator including a piston rod slidably disposed within a housing having a base-side port and a rod-side port; a hydraulic pump; a hydraulic reservoir; a first control valve operable to selectively control flow from the hydraulic pump to the base-side port and from the base-side port to the hydraulic reservoir; a second control valve operable to selectively control flow from the hydraulic pump to the rod-side port and from the rod-side port to the hydraulic reservoir; a load-holding valve positioned between the first control valve and the base- side port; a first counterbalance valve located between the hydraulic reservoir and the base-side port; a second counterbalance valve arranged to bypass flow around the load- holding valve, the second counterbalance valve being piloted with fluid associated with the rod-side port; and a controller for operating the hydraulic system and including a lowering mode in which: the load-holding valve is held in a closed position; fluid flows from the base-side port and through the second counterbalance valve; the first control valve receives fluid from the second counterbalance valve and is metered to allow hydraulic oil to exit the base-side port via the first control valve to meet a commanded lowering speed associated with the hydraulic actuator; and fluid from the hydraulic reservoir can flow into the rod-side port via the second control valve or through the first counterbalance valve.

13. The hydraulic system of claim 12, further including a first check valve located between the hydraulic reservoir and the rod-side port, wherein fluid flows through the first check valve to the rod-side port during the lowering mode.

14. The hydraulic system of claim 13, wherein the first check valve is a spring check valve with a pressure setting of about 0.3 bar.

15. The hydraulic system of claim 13 or 14, further including a second check valve located between the hydraulic reservoir and the base-side port, wherein fluid fiow¾ from the base-side port through the second check valve, and to the hydraulic reservoir.

16. The hydraulic system of claim 15, wherein the second check valve is a spring check valve with a pressure setting of about 3 to 5 bar.

17. The hydraulic system of claim 12, further comprising an accumulator in selective communication with the base-side port.

18. The hydraulic system of claim 12, wherein the lowering mode further includes the second control valve metering to selectively provide flow from the hydraulic pump to the rod-side port via the second control valve.

19. The hydraulic system of claim 12, wherein the first and second control valves are configured to be manually positioned to allow hydraulic fluid to flow from the base-side port to the hydraulic reservoir via the first control valve and from the hydraulic reservoir to the rod-side port via the second control valve.

20. A hydraulic system comprising; a hydraulic actuator including a piston rod slidably disposed within a housing having a base-side port and a rod-side port; a hydraulic pump; a hydraulic reservoir; an accumulator; a first control valve operable to selectively control flow from the pump to the base-side port and from the base-side port to the hydraulic reservoir; a second control valve operable to selectively control flow from the pump to the rod-side port and from the rod-side port to the hydraulic reservoir; a load-holding valve positioned between the first control valve and the base- side port; a first counterbalance valve located between the reservoir and the base-side port; a third control valve to selectively place the accumulator in fluid communication with the base-side port; and a controller for operating the hydraulic system and including a lowering mode in which; the load-holding valve is held in an open position; the third control valve is held in the dosed position; the first control valve is metered to allow hydraulic oil to exit the base- side port via the first control valve to meet a commanded lowering speed associated with the hydraulic actuator; and fluid from the hydraulic reservoir can flow into the rod-side port via the second control valve or through the first counterbalance valve,

21. The hydraulic system of claim 20, wherein the lowering mode is a gravity lowering mode, wherein the pressurized fluid from the hydraulic pump is not utilized to lower a load,

22. The hydraulic system of claim 20, further including a first check valve located between the hydraulic reservoir and the rod-side port, wherein fluid flows through the first check valve to the rod-side port during the lowering mode,

23. The hydraulic system of claim 22, wherein the first check valve is a spring check valve with a pressure setting of about 0.3 bar.

24. The hydraulic system of claim 20 or 22, further including a second check valve located between the hydraulic reservoir and the base-side port, wherein fluid flows from the base-side port through the second check valve, and to the hydraulic reservoir.

25. The hydraulic system of claim 24, wherein the second check valve is a spring check valve with a pressure setting of about 3 to 5 bar,

26. The hydraulic system of claim 20, wherein the lowering mode further includes the second control valve in a fully open position to allow fluid to pass through the second control valve from the hydraulic reservoir to the rod-side port.

27. The hydraulic system of claim 20, wherein the lowering mode further includes the second control valve in a fully closed position to block fluid from passing through the second control valve from the hydraulic reservoir to the rod-side port.

28. The hydraulic system of claim 20, wherein the lowering mode further includes the second control valve metering to selectively provide flow from the hydraulic pump to the rod-side port via the second control valve.

29. The hydraulic system of claim 20, wherein the first and second control valves are configured to be manually positioned to allow hydraulic fluid to flow from the base-side port to the hydraulic reservoir via the first control valve and from the hydraulic reservoir to the rod-side port via the second control valve.

30. A hydraulic system comprising: a hydraulic actuator including a first port and a second port; a hydraulic pump; a hydraulic reservoir; a first control valve operable to selectively control flow from the hydraulic pump to the first port; a first control valve operable to selectively control flow from the hydraulic pump and the hydraulic reservoir to one or both of the first port and the second port; a load-holding valve positioned between the first control valve and the first port in a first fluid pathway; a first counterbalance valve located between the hydraulic reservoir and the first port in a second fluid pathway that is parallel to the first fluid pathway; and a controller for operating the hydraulic system and including a lowering mode in which: the load-holding valve is held in an open position; the first control valve is metered to allow hydraulic oil to exit the first port via the first control valve to meet a commanded lowering speed associated with the hydraulic actuator; and fluid from the hydraulic reservoir can flow into the second port.

31. The hydraulic system of claim 30, wherein the lowering mode is a gravity lowering mode, wherein the pressurized fluid from the hydraulic pump is not utilized to lower a load.

32. The hydraulic system of claim 30, farther including a first check valve located between the hydraulic reservoir and the second port, wherein fluid flows through the first check valve to the second port during the lowering mode.

33. The hydraulic system of claim 32, wherein the first check valve is a spring check valve with a pressure setting of about 0.3 bar.

34. The hydraulic system of claim 32 or 33, farther including a second check valve located between the hydraulic reservoir and the first port, wherein fluid flows from the first port through the second check valve, and to the hydraulic reservoir.

35. The hydraulic system of claim 34, wherein the second check valve is a spring check valve with a pressure setting of about 3 to 5 bar.

36. The hydraulic system of claim 30, further comprising an accumulator in selective communication with the first port.

37. The hydraulic system of claim 30, wherein the system further includes a second control valve and wherein the lowering mode farther includes the second control valve in a fully open position to allow fluid to pass through the second control valve from the hydraulic reservoir to the second port.

38. The hydraulic system of claim 37, wherein the lowering mode farther includes the second control valve in a fully closed position to block fluid from passing through the second control valve from the hydraulic reservoir to the rod-side port.

39. The hydraulic system of claim 37, wherein the lowering mode further includes the second control valve metering to selectively provide flow from the hydraulic pump to the second port via the second control valve.

40. The hydraulic system of claim 37, wherein the first and second control valves are configured to be manually positioned to allow hydraulic fluid to flow from the first port to the hydraulic reservoir via the first control valve and from the hydraulic reservoir to the second port via the second control valve.

41. The hydraulic system of claim 30, wherein the hydraulic actuator is a linear hydraulic actuator, and wherein the first port is a base-side port and the second port is a rod-side port.

42. The hydraulic system of claim 30, wherein the controller includes an actuating mode in which the first control valve places the hydraulic pump and the hydraulic actuator in fluid communication with each other, wherein the load-holding valve is in an open position to allow fluid to flow from the first control valve to the first port through the load-holding valve and around the first counterbalance valve.

43. A hydraulic system comprising: a hydraulic actuator including a first port and a second port; a hydraulic pump; a hydraulic reservoir; a first control valve operable to selectively control flow from the hydraulic pump to the first port; a first counterbalance valve located between the first control valve and the first port; a first bypass valve positioned between the first control valve and the first port, the first bypass valve providing a flow path around the first counterbalance valve; and a controller for operating the hydraulic system and including: an actuating mode in which the first control valve places the hydraulic pump and the hydraulic actuator in fluid communication with each other, wherein the first bypass valve is in an open position to allow fluid to flow from the first control valve to the first port through the bypass valve and around the first counterbalance valve; and a holding mode in which the first control valve is in a neutral or closed position to substantially block flow between the hydraulic pump and the hydraulic actuator, wherein the first bypass valve is in a closed position such that fluid flow through the first bypass valve is blocked such that any fluid flow between the first port and the first control valve flows through the first counterbalance valve.

44. The hydraulic system of claim 43, wherein the first control valve is in fluid communication with both the first and second ports.

45. The hydraulic system of claim 43 or 44, farther comprising: a second counterbalance valve located between the first control valve and the second port; and a second bypass valve positioned between the first control valve and the second port, the second bypass valve providing a flow path around the second counterbalance valve.

46. The hydraulic system of claim 43, farther comprising: a second control valve operable to selectively control flow from the hydraulic pump to the second port; a second counterbalance valve located between the second control valve and the second port; and a second bypass valve positioned between the second control valve and the second port, the second bypass valve providing a flow path around the second counterbalance valve.

47. The hydraulic system of claim 46, wherein the controller includes a second actuating mode, in which the second control valve places the hydraulic pump and the hydraulic actuator in fluid communication with each other, wherein the second bypass valve is in an open position to allow fluid to flow from the second control valve to the second port through the second bypass valve and around the second counterbalance valve.