CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Patent Application Serial No. 63/025,577, filed on May 15, 2020, the disclosure of which is incorporated herein by reference in its entirety.

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. Some control valve assemblies are highly complex and perform numerous functions for the hydraulic system. With such complexity, certain operating efficiencies can be achieved, but the costs for such systems has increased significantly. In contrast, some work machines need simple valve control with robustness as a priority. For such applications, operating efficiencies are also desirable.

SUMMARY

[0003] A hydraulic system can include a pump having a load-sense control arrangement, a reservoir, a hydraulic actuator, and a first control valve assembly in fluid communication with the actuator, the first control valve assembly including a spool disposed in a housing. The spool can include a first spool portion forming a three- position, four-way valve with the housing, the first spool portion selectively communicating fluid between the hydraulic pump, the actuator, and the reservoir, and can include a second spool portion being a three-position, two-way valve with the housing, the second spool portion selectively communicating fluid between the load-sense control arrangement and the reservoir, the second spool portion being coupled to the first spool portion such that movement of the first spool portion causes movement of the second spool portion.

[0004] In some examples, the spool is integrally formed as a single component and includes first spool portion and the second spool portion. [0005] In some examples, the first spool portion has a first, a second, and a third position, and wherein the second spool portion has a first, a second, and a third position, wherein when the first spool portion is in the first position, the first spool portion blocks flow between the actuator, the pump, and the reservoir such that the actuator is held in a static position and holds the second spool portion in the first position in which flow between the load sense control arrangement and the reservoir is enabled.

[0006] In some examples, when the first spool portion is in the second or third position, the first spool portion enables flow between the actuator, the pump, and the reservoir such that the actuator is operated, and the first spool portion moves the second spool portion into the second or third position in which flow between the load sense control arrangement and the reservoir is blocked.

[0007] In some examples, the system further includes a relief valve having a relief pressure setting, wherein when the second spool portion is in the second or third position, fluid pressure to the load-sense control arrangement is limited by the relief pressure setting. [0008] In some examples, the system further includes an orifice upstream of the relief valve.

[0009] In some examples, the system further includes an orifice downstream of the second spool portion.

[0010] In some examples, the system further includes a second control valve assembly in fluid communication with a second actuator, the second control valve assembly including a first spool portion being a three-position, four-way valve, the first spool portion having a first spool that selectively communicates fluid between the hydraulic pump, the second actuator, and the reservoir; and a second spool portion being a three-position, two-way valve, the second spool portion having a second spool that selectively communicates fluid between the load-sense control arrangement and the reservoir, the second spool being operably coupled to the first spool such that movement of the first spool causes movement of the second spool, wherein fluid is communicated between the load-sense control arrangement and the reservoir only when both the second spool portion of the first control valve assembly and the second spool portion of the second control valve assembly are both in a first position.

[0011] In some examples, the first spool portion has a first, a second, and a third position, and wherein the second spool portion has a first, a second, and a third position, wherein: when the first spool portion is in the first position, the first spool portion: blocks flow between the actuator, the pump, and the reservoir such that the actuator is held in a static position; and holds the second spool portion in the first position in which flow between the load sense control arrangement and the reservoir is enabled.

[0012] A control valve assembly for controlling a hydraulic actuator can include a housing, a first spool portion forming a three-position, four-way valve with the housing, the first spool portion selectively communicating fluid between ports in the housing associated with a hydraulic pump, an actuator, and a fluid reservoir; and a second spool portion forming a three-position, two-way valve with the housing, the second spool portion selectively communicating fluid between ports in the housing associated with a load-sense control arrangement of the pump and the reservoir, the second spool being coupled to the first spool such that movement of the first spool causes movement of the second spool.

[0013] In some examples, the first spool portion and the second spool portion are integrally formed to define a single spool.

[0014] In some examples, the first spool portion has a first, a second, and a third position, and wherein the second spool portion has a first, a second, and a third position, wherein: when the first spool portion is in the first position, the first spool portion: blocks flow between the ports associated with the actuator, the pump, and the reservoir; and holds the second spool portion in the first position in which flow between the ports associated with the load sense control arrangement and the reservoir is enabled.

[0015] In some examples, when the first spool portion is in the second or third position: the first spool portion enables flow between the ports associated with the actuator, the pump, and the reservoir; and the first spool portion moves the second spool portion into the second or third position in which flow between the ports associated with the load sense control arrangement and the reservoir is blocked.

[0016] In some examples, the control valve assembly includes a pair of actuators for moving the spool between positions.

[0017] In some examples, the pair of actuators includes solenoid actuators.

[0018] A control valve assembly for controlling a hydraulic actuator can include a housing with a plurality of flow ports; a unitarily formed spool movable within the housing body to selectively place the plurality of flow ports in fluid communication with each other; a first spool portion forming a three-position, four-way valve with the housing, the first spool portion selectively communicating fluid between ports in the housing associated with a hydraulic pump, an actuator, and a fluid reservoir; and a second spool portion forming a three-position, two-way valve with the housing, the second spool portion selectively communicating fluid between ports in the housing associated with a load-sense control arrangement of the pump and the reservoir, the second spool being coupled to the first spool such that movement of the first spool causes movement of the second spool.

[0019] In some examples, the first spool portion has a first, a second, and a third position, and wherein the second spool portion has a first, a second, and a third position, wherein: when the first spool portion is in the first position, the first spool portion: blocks flow between the ports associated with the actuator, the pump, and the reservoir; and holds the second spool portion in the first position in which flow between the ports associated with the load sense control arrangement and the reservoir is enabled.

[0020] In some examples, the first spool portion is in the second or third position: the first spool portion enables flow between the ports associated with the actuator, the pump, and the reservoir; and the first spool portion moves the second spool portion into the second or third position in which flow between the ports associated with the load sense control arrangement and the reservoir is blocked.

[0021] In some examples, the control valve assembly includes a pair of actuators for moving the spool between positions. [0022] In some examples, the pair of actuators includes solenoid actuators.

DESCRIPTION OF THE DRAWINGS

[0023] 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.

[0024] Figure l is a schematic view of a work machine having features that are examples of aspects in accordance with the principles of the present disclosure.

[0025] Figure 2 is a schematic view of a hydraulic system including work circuits suitable for use in the work machine shown in Figure 1. [0026] Figure 3 is a schematic of a control valve assembly of the hydraulic system shown in Figure 2.

[0027] Figure 3 A is a schematic view of the control valve assembly shown in Figure 3 showing a spool within a housing having a plurality of flow ports.

[0028] Figure 4 is a schematic view of the hydraulic system shown in Figure 2, with one of the control valve assemblies in a different position from what is shown in Figure 2.

[0029] Figure 5 is a schematic view of an alternative arrangement of the hydraulic system shown in Figure 2.

[0030] Figure 6 is a schematic view of the hydraulic system shown in Figure 5, with one of the control valve assemblies in a different position from what is shown in Figure 5. DETAILED DESCRIPTION

[0031] 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

[0032] As depicted at Figure 1, a work machine 1 is shown. The work machine 1 may be any type of work machine, for example a fire truck, fork lift, wheel loader, track loader, excavator, backhoe, bull dozer, fire truck or telehandler. As depicted, 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 and stabilizers 9 for stabilizing the work machine 1 during lifting operations. In one embodiment, the work attachment 2 includes a pair of forks. However, one skilled in the art will appreciate that work attachment may be any hydraulically powered work implement.

[0033] 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 circuits, such as a work circuit 14 and a steering circuit (not shown) of the work machine 10 via at least one hydraulic pump assembly 12. In one embodiment, the hydraulic system 10 includes a pump 12 mechanically coupled to the engine 7, such as by an output shaft or a power take-off. In one embodiment, pump 12 is powered indirectly by the engine 7. The work circuit 10 actuates the work attachment 2 by operation of the pump 12 in cooperation with a number of hydraulic actuators 16 and control valves 22a, 22b (shown at Figure 2).

In one embodiment, 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 7. 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 and a pump operated with load-sense control.

Hydraulic System

[0034] Referring to Figure 2, an example of a hydraulic system 10 including a pump 12, reservoir 15, two work circuits 20a, 20b for respectively controlling actuators 16a,

16b, and other components is presented. The work circuits 20a, 20b can be provided to enable any desired work function, for example either or both work circuits 20a, 20b can be configured to activate the work attachment 2 of a work machine 1. As shown, the pump 12 is a variable displacement axial pump provided with a conventional load-sense control arrangement 12a to control the displacement of the pump 12 such that an appropriate flow can be delivered to the work circuits 20a, 20b. As shown, the load-sense arrangement 12a can include a load-sense spool 12b, a maximum pressure cut-off spool 12c, and an actuator 12d for adjusting the swash plate angle of the pump 12. Although two work circuits 20a, 20b are shown, additional work circuits can be provided in the hydraulic system without departing from the concepts presented herein.

[0035] With reference to Figures 2 and 3, each of the control valves 22a, 22b, generally referred to as valve 22, is configured as a as a sectional valve with a three- position, four way spool 24 movable within a ported housing 26. Other configurations are possible. For example, a spool and sleeve type valve could be utilized. In one aspect, the spool 24 has a first portion 24a that is movable within the housing 26 between positions A, B, and C such that various ports of the spool 24 are placed in fluid communication with ports 26A, 26B, 26C, and 26D of the housing 26. For example, in the center position A, ports 30 A, 32 A, 34 A, and 36C of the spool 24 are respectively aligned with ports 26 A, 26B, 26C, and 26D. In this position, all of the ports are blocked such that fluid flow to and from ports 26C, 26D is blocked from passing through ports 26A, 26D. In the position B, ports 30B, 32B, 34B, 36B are respectively aligned with ports 26A, 26B, 26C, 26D such that fluid flow can pass between ports 26A and 26C and between ports 26B and 26D. In the position C, ports 30C, 32C, 34C, 36C are respectively aligned with ports 26A, 26B, 34C, 34d such that fluid flow can pass between ports 26A and 26D and between 26B and 26C.

[0036] With continued reference to Figure 3, the spool 24 is provided with a second portion 24b that is movable within the housing 26 between positions A, B, and C. In the presented example, the spool 24 is formed as a singular component including the first and second portions 24a, 24b, as shown at Figure 3 A. However, the first and second portions 24a, 24b could be formed separately and later joined together. With the disclosed configuration, the second portion 24b necessarily moves with the first portion 24a as the spool 24 is moved within the housing 26. As the spool portions 24a, 24b are provided in a common housing 26, separate valve structures and related componentry can be avoided.

[0037] In one aspect, the spool second portion 24b is movable between positions A, B, C such that when the spool first portion 24 is in positions A, B, C, the spool second portion 24b is respectively also in positions A, B, C. In position A of the spool second portion 24b, ports 38A and 40A of the spool second portion 24b are in fluid communication with ports 26E, 26F of the housing 26 such that flow between ports 26E and 26F is enabled. In position B of the spool second portion 24b, ports 38B and 40B of the spool second portion 24b are in fluid communication with ports 26E, 26F of the housing 26 such that flow between ports 26E and 26F is blocked. In position C of the spool second portion 24b, ports 38C and 40C of the spool second portion 24b are in fluid communication with ports 26E, 26F of the housing 26 such that flow between ports 26E and 26F is blocked.

[0038] In one aspect, the spool 24 of the control valve assembly 22 can be centered into position A by a pair of biasing springs 42, 44. The control valve assembly 22 can be moved from position A to positions B or C a pair of variable solenoid actuators 46, 48 acting on each end of the spool 24 of the valve assembly 20. The variable solenoid actuators 46, 48 can be operated by the control system 50. The valve assemblies can also be two-stage valves in which a pilot valve is controlled by a solenoid / voice coil and the main stage valve is controlled by pressure from the pilot stage. An actuator 8 coupled to an operator interface can also be used to move the spool 24.

[0039] Referring back to Figure 2, the operation of the hydraulic system 10 can be operated such that the valve assemblies 22a, 22b are selectively operated to hold, extend, or retract the actuators 16a, 16b, which are shown as being linear actuators. In order to hold the actuators 16a, 16b, the valve assemblies 22a, 22b are positioned at position A. To extend the actuators 16a, 16b, the valve assemblies 22a, 22b are position at position C. To retract the actuators 16a, 16b, the valve assemblies 22a, 22b are position at position B.

[0040] When both of the spools portions 24a, 24b are not active and in position A, as is shown at Figure 2, the second spool portions 24b are also in position A. In this position, fluid flow through the spool second portions 24b is enabled and the load-sense spool 12b is placed in fluid communication with the reservoir 15 via branch lines 70a, 70c, 70d and orifice 60. In this position, fluid flow through the spool section portions 24a, 24b also occurs from the pump 12 via branch lines 70b, 70c, 70d and orifice 62. With the load- sense arrangement 12a exposed to the reservoir 15, the load-sense line 70a provides no pump pressure on the load-sense spool 12b. In an arrangement where additional load- sense systems are connected to the load-sense arrangement 12a, the pump 12 will be controlled to meet the pressure requirements of those systems. In the case where there are either no additional load-sense systems or where no other load-sense signal is being sent to the load-sense arrangement 12a, the pump 12 will be controlled to meet the margin pressure defined by the margin spring 12e on the load-sense spool 12b, since the load- sense spool 12b is not being exposed to pump pressure.

[0041] In one aspect, the orifice 60 is sized to limit flow from the pump 12 back to the reservoir 15 when the spools portions 24b are in position A such that parasitic losses are minimized. The orifice 60 also functions as a decompensation orifice and enables for a clean, crisp signal to be fed back to the pump load-sense arrangement 12a such that the pump pressure backs off towards the margin pressure in a controlled manner. In one example, the orifice has a diameter of about 1.0 millimeter.

[0042] When one or both of the valve assemblies 22a, 22b is in position B or C (i.e. not in position A), as is shown at Figure 4, flow through one or both of the second spool portions 24b is blocked. Accordingly, the load-sense spool 12b is placed in fluid communication with the pump 12 via branches 70a and 70b and orifice 62. In this position of the valves 22a, 22b, the load-sense arrangement 12a will increase the stroke the pump 12 until the maximum pressure cut off spool 12c limits the output of pump 12. Once in this position, the pump 12 will generally operate at a constant maximum pressure.

[0043] In one aspect, the orifice 62 is sized to limit flow from the pump 12 back to the load-sense arrangement 12a when either of the spool portions 24b are in position B or C such that a controlled response results. Orifice 62 also provides additional flow limiting in combination with orifice 60 when both of the spool portions 24b are in position A to further reduce parasitic losses. In one aspect, it is advantageous to provide the orifice 62 as small as is practically possible while maintaining a clear signal, for example an effective diameter of about 0.5 millimeter.

[0044] With reference to Figures 5 and 6, an alternative configuration is shown in which an additional relief valve 64 and check valves 66, 68 are provided. With such a configuration, operation of the load-sense arrangement 12a is the same as for the configuration shown in Figures 2 and 4 when both valve arrangements 22a, 22b are in position A, as is shown at Figure 5. However, when either of the valve arrangements 22a, 22b is out of position A and in either of positions B or C, as is shown at Figure 6, the load- sense arrangement 12a receives a signal defined by the pressure setting of the relief valve 64 via orifice 62 and check valve 66. As a result, the pump 12 is operated at a constant maximum pressure defined by the relief valve 64 rather than ramping up to the maximum pressure cut off of the pump 12. For example, where the pump 12 has a maximum pressure cut off of 200 bar, a relief valve 64 having a relief pressure of 180 bar can be provided to ensure the pump 12 operates maximally at 180 bar instead of 250 bar. The configuration shown in Figures 5 and 6 also schematically illustrates how the hydraulic system 10 can be arranged to extend to and work with additional load-sense systems 70.

[0045] With the disclosed systems, several advantages result. For example, the disclosed system represents a significant cost reduction over installations where the control valves are configured for standard load-sense control and over installations where additional valves are provided. Costs are further reduced by the elimination of additional control components associated with such approaches, such as check valves and additional orifices. In some implementations, a cost savings of 30 percent or more can be achieved. An associated advantage of the disclosed system is that the removal of these additional components inherently increases the reliability of the installation as failure points are significantly reduced. As such, the disclosed systems are ideally suited where high reliability and robustness is a priority. Yet another advantage is that load-sense type valve arrangements are not ideally suited for all applications. For example, when outriggers or stabilizers on a work machine are being activated, it is preferable desired for the actuators extending the stabilizers to move quickly until the stabilizers contact the ground and it is then preferable for the actuators to extend at a relatively slower rate as they further extend. The disclosed systems perform in this exact manner as flow to the actuators has a high flow at low loads and low flow at high loads since the pump output is not reacting to the changes in the load on the stabilizers. In contrast, pressure compensated systems will attempt to maintain the same flow rate after ground contact by increasing the pump speed which results in the operator having to manually reduce flow to the actuators rather than it automatically occurring with the disclosed system. Electronic Control System 50

[0046] In one aspect, the pump 12, control valves 22a, 22b, and other related components can be operated by an electronic controller 50 with any desired number of inputs and outputs. 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 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 22a, 22b 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.

[0047] 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.

[0048] 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.

[0049] Computer readable communication media typically embodies computer readable instructions, data structures, program modules or other data in a modulated data signal such as a carrier 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.

[0050] 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.