Valve assembly including multiple gain states

Abstract

A valve assembly is provided. The valve assembly includes a valve body defining a bore. The valve assembly further includes a linear actuator adjacent to the valve body. The valve assembly further includes a valve spool disposed in the bore and operably coupled to the linear actuator. The linear actuator is configured to move the valve spool between a neutral position and an energized position. The valve spool defines a recess. The valve assembly further includes a piston disposed in the recess and configured to move between a first piston position and a second piston position within the recess.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and all advantages of U.S. Patent Application No. 62 / 942,051, filed November 29, 2019, the disclosure of which is incorporated herein by reference. Technical Field

[0003] The present disclosure generally relates to valve assemblies including first and second gain states and systems including the valve assemblies for use in workcells and other applications. Background Art

[0004] As the weight of vehicles such as off-highway vehicles increases, the braking energy required to stop these vehicles also increases. To address these increases, modern off-highway vehicles include large and robust wheel brakes designed to be prepared for worst-case scenarios, including the ability to apply the maximum brake pressure required to bring the vehicle to a quickest possible stop in an emergency. While these wheel brakes are effective in worst-case scenarios, high-fidelity control of the wheel brakes in lower-pressure braking scenarios is difficult.

[0005] A variety of electrohydraulic proportional pressure control valves are used to provide controlled pressure to working units, such as wheel brakes. Typical valves are designed for linear actuators, such as proportional electric solenoids, which generate thrust proportional to the current fed into the solenoid. These pressure control valves provide a linear output characteristic between pressure and current applied to the solenoid.

[0006] While this linear output characteristic allows braking at both lower and higher percentages of the brake pressure range, the majority of braking occurs in the lower percentages of the brake pressure range. Consequently, most braking occurs without high-fidelity control of the wheel brakes, resulting in sudden or aggressive braking of the vehicle, which impacts vehicle control and operator comfort.

[0007] Therefore, it is desirable to provide an improved valve assembly and a system including the same.Furthermore, other desirable features and characteristics will become apparent from the subsequent summary and detailed description and the appended claims, taken in conjunction with the foregoing technical field and background. Summary of the Invention

[0008] In one embodiment, a valve assembly is provided. The valve assembly includes a valve body defining a bore. The valve assembly further includes a linear actuator adjacent to the valve body. The valve assembly further includes a valve spool disposed in the bore and operably coupled to the linear actuator. The linear actuator is configured to move the valve spool between a neutral position and an energized position. The valve spool defines a recess. The valve assembly further includes a piston disposed in the recess and configured to move between a first piston position and a second piston position within the recess.

[0009] In these and other embodiments, by moving the piston from the first piston position to the second piston position, the fluid within the recess is limited to a predefined force and thus no longer acts to resist further movement of the valve spool by the linear actuator. As a result, the force required by the linear actuator to move the valve spool toward the energized position when the piston is in the second piston position is reduced relative to the force required when the piston is in the first piston position.

[0010] In these and other embodiments, the valve assembly has a first gain state and a second gain state. The valve assembly is in the first gain state when the piston is in the first piston position, and in the second gain state when the piston is in the second piston position. The valve assembly having the first gain state and the second gain state provides the user with improved fidelity at lower pressures while still allowing the working unit to reach higher pressures. For working units, such as the wheel brakes of a vehicle, lower pressures are typically utilized during the majority of the vehicle's braking. Thus, improving the fidelity of the wheel brakes at lower pressures can improve the overall usability of the vehicle. However, higher pressures may be required in emergency situations. Therefore, multiple gain states are important to allow the working units to reach higher pressures while still exhibiting improved fidelity at lower pressures.

[0011] In another embodiment, a system having a first gain state and a second gain state is also provided. The system includes, but is not limited to, a fluid source configured to provide a fluid force (e.g., hydraulic fluid pressure). The system further includes, but is not limited to, a valve assembly in fluid communication with the fluid source. The valve assembly includes, but is not limited to, a linear actuator. The valve assembly further includes, but is not limited to, a valve core. The valve core is operably coupled to the linear actuator. The linear actuator is configured to move the valve core between a neutral position and an energized position. The valve assembly further includes, but is not limited to, a piston. The piston is in fluid communication with the fluid source. The piston is configured to move between a first piston position and a second piston position. The system further includes, but is not limited to, a working unit in fluid communication with the valve assembly and configured to be activated in response to the fluid force. When the piston is in the first piston position, the system is in a first gain state, and when the piston is in the second piston position, the system is in a second gain state. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Other advantages of the disclosed subject matter will be readily appreciated as they become better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings, in which:

[0013] Figure 1A and Figure 1B is a cross-sectional plan view illustrating a non-limiting embodiment of a valve assembly;

[0014] Figure 2 is another cross-sectional plan view illustrating a non-limiting embodiment of a valve assembly;

[0015] Figure 3 is another cross-sectional plan view illustrating a non-limiting embodiment of a valve assembly; and

[0016] Figure 4 is a graph illustrating the gain behavior of a non-limiting embodiment of a valve assembly compared to the prior art. DETAILED DESCRIPTION

[0017] Except in the examples, or where otherwise expressly indicated, all numerical quantities in this specification indicating the amount of material or reaction and / or use conditions should be understood as being modified by the word "about" when describing the broadest scope of the invention. It is generally preferred to practice within the numerical ranges specified. In addition, unless expressly stated to the contrary: percentages, "parts" and ratio values are all by weight; describing a group or class of materials as suitable or preferred for a given purpose associated with the present invention means that mixtures of any two or more of the members of the group or class are also suitable or preferred; descriptions of ingredients in chemical terms refer to the ingredients when added to any combination specified in the specification and do not necessarily exclude chemical interactions between the ingredients of the mixture once mixed; the original definition of an acronym or other abbreviation applies to all subsequent uses of the same abbreviation herein and applies mutatis mutandis to normal grammatical variations of the originally defined abbreviation; and, unless expressly stated to the contrary, measurements of properties are determined by the same techniques as previously or later cited for the same properties.

[0018] It must also be noted that, as used in the specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. For example, reference to a component in the singular is intended to include a plurality of components.

[0019] The following detailed description is merely illustrative in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background or the following detailed description.

[0020] A valve assembly is provided herein. In various embodiments, the valve assembly is suitable for controlling a working unit of a vehicle. A system for controlling a working unit of a vehicle is also provided herein.

[0021] Figure 1 to Figure 3 is a cross-sectional plan view illustrating a non-limiting embodiment of a valve assembly 10. The valve assembly 10 includes a valve body 12 and a linear actuator 14 adjacent to the valve body 12. In various embodiments, the valve assembly 10 is used with a fluid source 16 (e.g., a hydraulic unit or a hydraulic pump), a tank 18 (e.g., a hydraulic oil tank), and a working unit 20 (e.g., a hydraulic cylinder or a wheel brake). In various embodiments, the fluid source 16 is configured to provide a fluid force (e.g., hydraulic fluid pressure) to the valve assembly 10. For clarity, the valve body 12 will be described as having a first body end 22 and a second body end 24.

[0022] The valve body 12 of the valve assembly 10 defines a bore 26. The bore 26 can be formed as a through-hole extending through the valve body 12. It is also contemplated that the bore 26 can be configured as a blind bore. The valve body 12 further defines a pressure port 28, a work port 30, and a tank port 32. The bore 26 generally extends through the valve body 12 between the first body end 22 and the second body end 24. Each of the ports 28, 30, and 32 can be in fluid communication with the bore 26. As shown in the non-limiting embodiment of FIG. 1 , the pressure port 28 is positioned proximate to the first body end 22, while the tank port 32 is positioned proximate to the second body end 24. The work port 30 is positioned intermediate the pressure port 28 and the tank port 32. In certain embodiments, the ports 28, 30, and 32 provide connection locations for establishing fluid communication between the valve body 12 and the hydraulic pump 16, the work unit 20, and the tank 18. Typical port connections include standard SAE straight threads or other configurations to allow hoses or other conduits to be connected between the components. However, it should be understood that other port configurations are contemplated; for example, the pressure port 28 may be disposed proximate the second body end 24 , while the tank port 32 may be disposed proximate the first body end 22 .

[0023] The bore 26 may include a first annular surface 34 and a second annular surface 36. These surfaces 34, 36 may be used to provide fluid communication between the ports 28, 30, and 32. The bore 26 may also include a countersunk area 38. In various embodiments, the countersunk area 38 is proximate to the first body end 22.

[0024] The valve assembly 10 further includes a spool 40 disposed in the bore 26 and operably coupled to the linear actuator 14. The linear actuator 14 is configured to position the spool 40 in a neutral position (see Figure 1A ) and energized position (see Figure 3In various embodiments, the linear actuator 14 is configured to move the spool 40 to an intermediate position between the neutral position and the energized position (see Figure 2 In certain embodiments, the linear actuator 14 includes a stem 42 (also commonly referred to in the art as an armature) coupled to a spool 40 to move the spool 40 between a neutral position and an energized position. In various embodiments, the spool 40 includes a first spool end 44 and a second spool end 46, with the stem 42 coupled to the first spool end 44.

[0025] In certain embodiments, the spool 40 includes a first annular portion 48 and a second annular portion 50. The first annular portion 48 and the second annular portion 50 can be configured to mate with the first annular surface 34 and the second annular surface 36 of the bore 26 to respectively operate fluid communication between the ports 28, 30, and 32. The spool 40 can further include a flow portion 52 having a reduced diameter relative to the first annular portion 48 and the second annular portion 50 to provide fluid communication to the workport 30. The spool 40 can also include a shoulder 54 proximate the first spool end 44 and configured to mate with the countersunk area 38 of the valve body 12.

[0026] refer to Figure 1A and Figure 1B When the spool 40 is in the neutral position, fluid communication can be provided between the workport 30 and the tank port 32. In addition, when the spool 40 is in the neutral position, fluid communication can be prevented between the pressure port 28 and the workport 30. In particular, when the spool 40 is in the neutral position, the first annular portion 48 can engage the first annular surface 34, thereby preventing fluid from flowing between the pressure port 28 and the workport 30.

[0027] refer to Figure 2 and Figure 3 , fluid communication can be provided between the pressure port 28 and the workport 30 when the spool 40 is in the neutral position or the energized position, respectively. In addition, fluid communication can be prevented between the workport 30 and the tank port 32 when the spool 40 is in the neutral position or the energized position. In particular, when the spool 40 is in the neutral position or the energized position, the second annular portion 50 can engage the second annular surface 36, thereby preventing fluid from flowing between the workport 30 and the tank port 32.

[0028] It should be understood that the valve assembly 10 can be operated in different ways. For example, the energized position of the valve core can provide fluid communication between the work port and the tank port, and the neutral position of the valve core can provide fluid communication between the pressure port and the work port.

[0029] Continue to refer to Figures 1 to Figure 3, the spool 40 can define a cavity 56 between the first annular portion 48 and the second annular portion 50. In certain embodiments, when the spool 40 is in the neutral position, the cavity 56 is in fluid communication with the workport 30 and the tank port 32. Furthermore, in these embodiments, when the spool 40 is in the energized position, the cavity 56 is in fluid communication with the pressure port 28 and the workport 30. The spool 40 can have a first spool face 58 and a second spool face 60 located on either side of the cavity 56. The first spool face 58 can have a first spool surface area and the second spool face 60 can have a second spool surface area. In various embodiments, the second spool surface area of the second spool face 60 is less than the first spool surface area of the first spool face 58. As the spool 40 moves from the neutral position to the energized position, fluid provided between the pressure port 28 and the workport 30 acts on the first spool face 58 and the second spool face 60.

[0030] In certain embodiments, the spool 40 defines a recess 62 between the second spool end 46 and the cavity 56. The recess 62 can extend through the second spool end 46. The spool 40 can have a recess face 65 opposite the second spool end 46 and within the recess 62. The spool 40 can define a passage 64 extending between the recess 62 and the cavity 56, placing the recess 62 in fluid communication with the cavity 56. In various embodiments, when the spool 40 is in the center position, fluid provided between the workport 30 and the tank port 32 is also provided to the recess 62 through the passage 64. Similarly, when the spool 40 is in the energized position, fluid provided between the pressure port 28 and the workport 30 is also provided to the recess 62 through the passage 64.

[0031] The valve assembly 10 further includes a piston 66 disposed in the recess 62. The piston 66 is configured to be responsive to the fluid in a first piston position (see Figure 1A and Figure 2 ) and the second piston position (see Figure 3 In some embodiments, the first piston position and the second piston position are relative to the valve core 40. The piston 66 includes a first piston end 68 and a second piston end 70 spaced apart from the first piston end 68 with a gap 72 defined therebetween.

[0032] Second piston end 70 includes an extension 76 configured to cooperate with second spool end 46 to prevent fluid communication between recess 62 and tank port 32 when piston 66 is in the first piston position. As spool 40 moves from the neutral position to the energized position, when piston 66 is in the first piston position, fluid provided between pressure port 28 and workport 30 via passage 64 acts on piston face 74. When piston 66 is in the second piston position, piston 66 and spool 40 cooperate to define a relief passage 78, thereby limiting the force of the fluid acting on piston face 74 and preventing piston 66 from absorbing the additive force of the fluid. To this end, by moving piston 66 from the first piston position to the second piston position, the force acting on piston face 74 due to the fluid within recess 66 is limited to the pressure at which relief passage 78 begins to meter flow out of recess 62. The pressure within recess 62 acts on recess face 65 to prevent linear actuator 14 from moving spool 40. In various embodiments, as the extension 76 is disengaged from the second spool end 46, the release passage 78 is in fluid communication with the tank port 32. Thus, when the piston 66 is in the second position, the passage 64 is in fluid communication with the tank port 32 via the passage 78, such that the fluid pressure in the passage 64 is limited to the pressure at which the passage 78 is initially in fluid communication with the tank port 32. Thus, when the piston 66 is in the second position, fluid can flow from the passage 64, through the recess 62, around the piston 66, through the release passage 78, and to the tank port 32.

[0033] The valve assembly 10 can further include a first biasing member 80 that applies a first force on the valve spool 40 to bias the valve spool 40 to the first body end 22 (e.g., toward the neutral position). The valve assembly 10 can further include a second biasing member 82 that applies a second force on the piston 66 to bias the piston 66 to the first piston position. The first biasing member 80 and the second biasing member 82 can independently include any standard spring or any other feedback device commonly used and known to those skilled in the art, such as a pneumatic strut, an electromagnet, or an elastic force feedback device. Alternatively, in applications where only unbalanced workport pressure is used to return the valve spool to the neutral position and / or return the piston 66 to the first piston position, the first biasing member 80 and / or the second biasing member 82 can be omitted.

[0034] Continue to refer to Figures 1 to Figure 3, the valve assembly 10 can further include a pin 84 extending through the valve core 40 and the piston 66. In various embodiments, the pin 84 extends through the void 72 of the piston 66, the recess 62 of the valve core 40, and the passage 64 of the valve core. The valve assembly 10 can further include a plug 86 disposed within the bore 26 proximate to the second body end 24 of the valve body 12. The pin 84 can be adapted to abut the plug 86 to prevent the pin 84 from moving beyond the plug 86 toward the second body end 24.

[0035] The spool 40 can be operably arranged with the pin 84 so as to slide relative to the pin 84. In various embodiments, the presence of the pin 84 causes the second spool surface area of the second spool face 60 to be smaller than the first spool surface area of the first spool face 58. These surface areas of the first spool face 58 and the second spool face 60, in the presence of fluid forces, create an unbalanced pressure load on the spool 40. In various embodiments, this unbalanced pressure load biases the spool 40 toward the first body end 22 (e.g., toward a neutral position).

[0036] The piston 66 may also be operably arranged with the pin 84 so as to slide relative to the pin 84. In various embodiments, the presence of the pin 84 causes the piston surface area of the piston face 74 to be equal to the second spool surface area of the second spool face 60. The force from the first biasing member 80, combined with the force due to pressure acting on the difference in area of the spool faces 58 and 60, and due to pressure acting on the recessed face 65, causes a force to be applied against the linear actuator 14.

[0037] Figure 4 is a graph illustrating gain states of a non-limiting embodiment of the valve assembly 10 compared to the prior art. The valve assembly 10 has a first gain state 88 and a second gain state 90. When the piston 66 is in the first piston position, the valve assembly 10 can be in the first gain state 88. When the piston 66 is in the second piston position, the valve assembly 10 can be in the second gain state 90. It should be understood that the valve assembly 10 can be configured to have more than two gain states. When the valve assembly 10 is in the first gain state 88, a greater force is required on the spool 40 by the linear actuator 14 to move the spool 40 toward the second body end 24 than when the valve assembly 10 is in the second gain state 90. When the valve assembly 10 is in the second gain state 90, a reduced force is required on the spool 40 by the linear actuator 14 to move the spool 40 toward the second body end 24 than when the valve assembly 10 is in the first gain state 88.

[0038] Continue to refer Figure 4Multiple gain states, such as first gain state 88 and second gain state 90 of valve assembly 10, provide the user with improved fidelity at lower pressures while still allowing working unit 16 to reach higher pressures. With respect to a vehicle's wheel brakes, lower pressures are typically utilized during the majority of the vehicle's braking. Thus, improving the fidelity of the wheel brakes at lower pressures can improve the overall usability of the vehicle. However, higher pressures may be necessary in emergency situations. Therefore, multiple gain states are important for allowing working unit 16 to reach higher pressures while still exhibiting improved fidelity at lower pressures.

[0039] When the valve assembly 10 is in the first gain state 88, the force of the fluid from the workport 30 acts on the difference between the area of the spool faces 58 and 60 and the area of the recess face 65. This force biases the pin 84 against the plug 86. However, this force on the piston 66 is insufficient to overcome the second force of the second biasing member 82, thereby maintaining the piston 66 in the first piston position. To this end, the force generated by the pressure acting on the surface area of the spool faces 58 and 60 and the recess face 65, as well as the force from the first biasing member 80, biases the spool 40 toward the first body end 22 (e.g., toward the neutral position) in opposition to the force generated by the linear actuator 14. Thus, when the valve assembly 10 is in the first gain state 88, a greater force resists movement of the spool 40 toward the second body end 24, thereby reducing the force of the fluid acting on the workport 30 relative to the magnitude of the force generated by the linear actuator 14. Reference Figure 4 , the first gain state 88 exhibits a lower slope of pressure at the workport 30 with respect to input current to the linear actuator 14 than the second gain state 90 .

[0040] When the valve assembly 10 is in the second gain state 90, the fluid force from the workport 30 continues to act on the surface area of the spool faces 58 and 60 and the recess face 65. Compared to the first gain state 88, the force acting on the piston 66 is sufficient to overcome the second force of the second biasing member 82, thereby moving the piston 66 to the second piston position and defining the release passage 78. With the release passage 78 defined, the force acting on the recess face 65 is limited, and the force due to the pressure in the cavity 56 acting on the surface area of the spool faces 58 and 60 and the limited pressure in the recess 62 acting on the recess face 65, as well as the force from the biasing member 80, resists the force generated by the linear actuator 14. Thus, when the valve assembly 10 is in the second gain state 90, which is opposite to the first gain state 88, the reduced force resists movement of the spool 40 toward the second body end 24, thereby increasing the force of the fluid acting on the workport 30 relative to the magnitude of the force generated by the linear actuator 14. Figure 4, the second gain state 90 exhibits a higher slope of the pressure at the workport 30 with respect to the input current to the linear actuator 14 than the first gain state 88 .

[0041] The valve assembly 10 can further include a spring 92 and a spring retaining member 94 proximate the first body end 22. The spring retaining member 94 can be an extension of the linear actuator 14 or a separate component. The spring 92 can be positioned within the countersunk area 38 of the bore 26. The spring 92 can include a variety of compression spring configurations. Other spring types that can be used include bevel springs, torsion springs with levers, leaf springs, and the like.

[0042] The spring retainer member 94 can be configured with an internal shoulder. The spring 92 can be longitudinally positioned between the shoulder 54 of the valve core 40 and the internal shoulder of the spring retainer member 94. The spring retainer member 94 can serve as a stationary component against which the spring 92 is compressed. In various embodiments, the valve core 40 includes an extension 96 having an inner diameter suitable for guiding the spring 92. The extension 96 maintains the spring 92 in a longitudinal orientation.

[0043] In certain embodiments, a washer 98 is disposed between the shoulder 54 of the spool 40 and the spring 92. The washer 98 provides a mechanical stop for the compression of the spring 92. Additionally, the washer 98 defines a neutral position for the spool 40. As shown in FIG1 , the washer 98 contacts the countersunk area 38 due to the tension of the spring 92 acting on the washer 98. The washer 98 also contacts the shoulder 54 of the spool 40 when the spool 40 is in the neutral position due to the tension of the first biasing member 80 acting on the spool 40. When the spool 40 is in the neutral position, the tension from the first biasing member 80 may also be lower than the tension provided by the spring 92.

[0044] It will be appreciated that spring compression may be tailored to various applications by modifying the length of the spring retaining member, the thickness of the washer, the stiffness of the spring, or various other structural features apparent to those skilled in the art.

[0045] Refer again to Figure 1 to Figure 3 , which describes a non-limiting embodiment of the operation of the valve assembly 10. In certain embodiments, when fluid is desired to operate the working unit 20, the valve assembly 10 is energized. The linear actuator 14 generates an axial force starting from the neutral state shown in FIG. The linear actuator 14 moves the valve spool 40 toward the second body end 24 to Figure 2, the valve assembly 10 is shown in its first gain state 88. In the first gain state 88, fluid is allowed to flow from the pressure port 28 around the reduced diameter flow portion 52 and through the cavity 56 of the spool 40 to the workport 30 to operate the work unit 20. Simultaneously, fluid flow to the tank port 32 is blocked by the cooperation between the second annular surface 36 of the valve body 12 and the second annular portion 50 of the spool 40. As described above, when the valve assembly 10 is in the first gain state 88, a greater force resists movement of the spool 40 toward the second body end 24. This reduces the force of the fluid acting on the workport 30 relative to the force generated by the linear actuator 14 due to the force of the second biasing member 82 acting on the spool 40 via the piston 66. In other words, a greater force from the linear actuator 14 is required to move the spool 40 toward the second body end 24 than when the valve assembly 10 is in the second gain state 90.

[0046] As the linear actuator 14 continues to provide axial force during the first gain state 88, as shown Figure 2 As shown in FIG, the linear actuator 14 continues to move the spool 40 toward the second body end 24 to the second gain state 90 of the valve assembly 10, as shown in FIG. Figure 3 . In the second gain state 90, fluid is still allowed to flow from the pressure port 28 around the reduced diameter flow portion 52 and through the cavity 56 of the valve spool 40 to the workport 30 to operate the work unit 20. At the same time, fluid flow to the tank port 32 is still blocked by the cooperation between the second annular surface 36 of the valve body 12 and the second annular portion 50 of the valve spool 40. As described above, when the valve assembly 10 is in the second gain state 90, the reduced force resists movement of the valve spool 40 toward the second body end 24. As a result, the force of the fluid acting on the workport 30 is increased relative to the force generated by the linear actuator 14 when the piston 66 is in the second position due to the release passage 78 defined for the piston 66. In other words, a smaller force applied by the linear actuator 14 to the valve spool 40 is required to move the valve spool 40 toward the second body end 24 than when the valve assembly 10 is in the first gain state 88.

[0047] The force of the fluid acts on the unbalanced surface area of the first and second spool faces 58, 60 of the spool 40, as well as the surface area of the recessed face 65. As the force increases, it approaches the force generated by the linear actuator 14, and the spool 40 begins to move toward the first body end 22. Movement of the spool 40 toward the first body end 22 increases fluid communication with the tank port 32 and decreases fluid communication with the pressure port 28, thereby stabilizing or decreasing the force at the workport 30. As the force decreases, the net force of the spool 40 toward the second body end 24 exceeds the net force of the spool 40 toward the first body end 22, causing the spool 40 to move toward the second body end 24. Movement of the spool 40 toward the second body end 24 decreases fluid communication with the tank port 32 and increases fluid communication with the pressure port 28. This cycle of movement causes the spool 40 to "modulate" (i.e., move back and forth). During modulation, the linear actuator 14 remains energized. The spool 40 modulates until the pressure and force of the spring 92 balance the force of the linear actuator 14. At steady-state equilibrium, (when the kinetic force created by changes in linear actuator 14 current or force from the work unit 20 has dissipated), the spool 40 will reach a stable position where the fluid flow from the pressure port 28 to the work port 30 is equal to the fluid flow from the work port 30 to the tank port 32.

[0048] Upon desired fluid release, the linear actuator 14 is de-energized and no longer generates a force toward the second body end 24. The spool 40 moves toward the first body end 22 due to the imbalance between the force of the fluid and the force from the first biasing member 80. In the neutral position, because the spool 40 has not traveled far enough to accommodate the sufficient release fluid flow, a force generated by the residual kinetic energy of the work unit 20 is present at the workport 30. The combination of the first force of the first biasing member 80 and the force generated by the residual force at the workport 30 compresses the spring 92, allowing the spool 40 to move beyond the neutral position toward the first body end 22 to the released position. In the released position, fluid is allowed to flow rapidly from the workport 30 around the flow portion 52 of the spool 40 and toward the tank port 32. As the fluid is released, the force of the fluid compressing the spring 92 decreases. The spring 92 eventually overcomes the combined force and moves the spool 40 back to the neutral position shown in FIG.

[0049] The flow rate from workport 30 to tank port 32 is determined by the amount of flow required in the application, for example, the amount of flow necessary to decouple a hydraulic actuator or brake within an acceptable timeframe. For a given spool configuration, the opening area, or gap, required to provide fluid communication between the ports is a function of the spool stroke or travel. Greater flow rates require a larger cross-sectional flow area, or gap, and in turn, require the spool 40 to travel further to increase the area of the gap. Similarly, when linear actuator 14 is first energized, the required flow rate from pressure port 28 to workport 30 is determined by the amount of flow required in the application, for example, the amount of flow necessary to actuate a hydraulic brake within an acceptable timeframe.

[0050] As described above, this document also provides a system for controlling a working unit 20. The system has a first gain state 88 and a second gain state 90. The system includes a fluid source 16 configured to provide a fluid force. The system further includes a valve assembly 10, wherein the valve assembly 10 is in fluid communication with the fluid source 16. The valve assembly 10 includes a linear actuator 14. The valve assembly 10 further includes a valve spool 40. The valve spool 40 is operably coupled to the linear actuator 14. The linear actuator 14 is configured to move the valve spool 40 between a neutral position and an energized position. The valve assembly 10 further includes a piston 66. The piston 66 is in fluid communication with the fluid source 16. The piston 66 is configured to move between a first piston position and a second piston position. The system further includes a working unit 20, which is in fluid communication with the valve assembly 10 and configured to activate in response to the fluid force. When the piston 66 is in the first piston position, the system is in the first gain state 88, and when the piston 66 is in the second piston position, the system is in the second gain state 90.

[0051] Although the present invention has been described in conjunction with specific preferred embodiments, it should be understood that the invention as claimed should not be overly limited to these specific embodiments. Although at least one illustrative embodiment has been presented in the foregoing detailed description of the present disclosure, it should be understood that there are a large number of variations. It should also be understood that the illustrative embodiments are merely examples and are not intended to limit the scope, applicability or configuration of the present invention in any way. On the contrary, the foregoing detailed description will provide a convenient roadmap for implementing the illustrative embodiments of the present invention to those skilled in the art. It should be understood that various changes can be made to the functions and arrangements of the elements described in the illustrative embodiments without departing from the scope of the present disclosure set forth in the appended claims.

[0052] Furthermore, any ranges and subranges relied upon, both individually and collectively, when describing various embodiments of the present invention are within the scope of the appended claims and should be understood to describe and contemplate all ranges, including integer and / or fractional values therein, even if such values are not explicitly recited herein. Those skilled in the art will readily recognize that the recited ranges and subranges adequately describe and enable various embodiments of the present invention, and that these ranges and subranges can be further delineated as corresponding halves, thirds, quarters, fifths, and so forth. As just one example, a range "from 0.1 to 0.9" can be further divided into a lower third, i.e., from 0.1 to 0.3, a middle third, i.e., from 0.4 to 0.6, and an upper third, i.e., from 0.7 to 0.9, which are individually and collectively within the scope of the appended claims and can be relied upon individually and / or collectively and provide sufficient support for specific embodiments within the scope of the appended claims. Furthermore, with respect to language defining or modifying ranges, such as "at least ," "greater than ," "less than ," "not greater than ," and the like, it should be understood that such language includes subranges and / or upper or lower limits. As another example, a range of "at least 10" inherently includes a subrange from at least 10 to 35, a subrange from at least 10 to 25, a subrange from 25 to 35, etc., and each of these subranges can be relied upon individually and / or collectively and provide sufficient support for specific embodiments within the scope of the appended claims. Finally, within the scope of the appended claims, individual numbers within the disclosed ranges can be relied upon and provide sufficient support for specific embodiments. For example, the range "from 1 to 9" includes various individual integers, such as 3, and individual numbers that include decimal points (or fractions), such as 4.1, which can be relied upon and provide sufficient support for specific embodiments within the scope of the appended claims.

[0053] The present invention has been described herein in an illustrative manner, and it should be understood that the terminology used is intended to be in the nature of words of description rather than of limitation. Numerous modifications and variations of the present invention are possible in light of the above teachings. The present invention may also be practiced otherwise than as specifically described within the scope of the appended claims. The subject matter of all combinations of independent and dependent claims, whether singly or plurally dependent, is expressly contemplated herein.

[0054] Industrial Applicability

[0055] While the present invention is not limited to a particular end application, use, or industry, vehicles typically rely on a valve assembly to provide fluid to a working unit, such as a wheel brake. The valve assembly includes a valve configured to move between a first piston position and a second piston position to provide the valve assembly with multiple gain states.

Claims

1. A valve assembly comprising: a valve body defining a bore; a linear actuator adjacent to the valve body; a spool disposed in the bore and operably coupled to the linear actuator, the linear actuator configured to move the spool between a neutral position and an energized position, the spool defining a recess; and a piston disposed in the recess and configured to move between a first piston position and a second piston position within the recess, wherein the linear actuator is configured to generate a force for moving the valve spool from the neutral position to the energized position, and wherein the force required by the linear actuator to move the valve spool toward the energized position when the piston is in the second piston position is reduced relative to the force required when the piston is in the first piston position.

2. The valve assembly according to claim 1, wherein Movement of the spool from the neutral position to the energized position generates a fluid force, and wherein the piston is adapted to move to the second piston position in the presence of the fluid force.

3. The valve assembly according to claim 1 or 2, wherein: The valve assembly further includes a pin extending through the spool and the piston, wherein the spool and the piston are operatively arranged with the pin to slide relative to the pin.

4. The valve assembly according to claim 1 or 2, wherein: The valve core defines a cavity, and the valve core has a first valve core surface and a second valve core surface located on both sides of the cavity.

5. The valve assembly according to claim 4, wherein The first valve core surface has a first valve core surface area, the second valve core surface has a second valve core surface area, and the second valve core surface area of the second valve core surface is smaller than the first valve core surface area of the first valve core surface.

6. The valve assembly according to claim 5, wherein The piston has a piston face having a piston surface area, and the second spool surface area is equal to the piston surface area.

7. The valve assembly according to claim 4, wherein: The spool defines a passage extending between the recess and the cavity such that the recess is in fluid communication with the cavity.

8. The valve assembly according to claim 7, wherein: The passage is adapted to partially confine fluid moving from the cavity to the recess.

9. The valve assembly according to claim 1 or 2, wherein: The spool and the piston cooperate to define a relief passage when the piston is in the second piston position.

10. The valve assembly according to claim 1 or 2, wherein: The valve assembly further comprises: a first biasing member that applies a first force on the valve spool to bias the valve spool to the neutral position; and A second biasing member applies a second force on the piston to bias the piston to the first piston position.

11. The valve assembly according to claim 1 or 2, wherein: The valve assembly has a first gain state and a second gain state, the valve assembly being in the first gain state when the piston is in the first piston position and the valve assembly being in the second gain state when the piston is in the second piston position.

12. The valve assembly according to claim 1 or 2, wherein: The first piston position and the second piston position of the piston are relative to the valve spool.

13. A system having a first gain state and a second gain state, the system comprising: a fluid source configured to provide a fluid force; a valve assembly in fluid communication with the fluid source, the valve assembly comprising: Linear actuators, a spool operably coupled to the linear actuator, the linear actuator configured to move the spool between a neutral position and an energized position, the spool defining a recess, and a piston disposed in the recess and in fluid communication with the fluid source, the piston configured to move between a first piston position and a second piston position; and an operating unit in fluid communication with the valve assembly and configured to activate in response to the fluid force; wherein the system is in the first gain state when the piston is in the first piston position, and the system is in the second gain state when the piston is in the second piston position, wherein the linear actuator is configured to generate a force for moving the valve spool from the neutral position to the energized position, and wherein the force required by the linear actuator to move the valve spool toward the energized position when the piston is in the second piston position is reduced relative to the force required when the piston is in the first piston position.

14. The system according to claim 13, wherein: Movement of the spool from the neutral position to the energized position generates a fluid force, and wherein the piston is adapted to move to the second piston position in the presence of the fluid force.

15. The system according to claim 13 or 14, wherein: The system further includes a pin extending through the spool and the piston, wherein the spool and the piston are operatively arranged with the pin to slide relative to the pin.

16. The system according to claim 13 or 14, wherein: The valve core defines a cavity, and the valve core has a first valve core surface and a second valve core surface located on both sides of the cavity.

17. The system according to claim 16, wherein: The first valve core surface has a first valve core surface area, the second valve core surface has a second valve core surface area, and the second valve core surface area of the second valve core surface is smaller than the first valve core surface area of the first valve core surface.

18. The system according to claim 17, wherein: The piston has a piston face having a piston surface area, and the second spool surface area is equal to the piston surface area.

19. The system according to claim 16, wherein: The spool defines a passage extending between the recess and the cavity such that the recess is in fluid communication with the cavity.

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