Fail-safe electro-hydraulic servo valve

Abstract

The subject matter of this specification can be particularly implemented as a fluid valve assembly, the fluid valve assembly including a first fluid port, a second fluid port, a third fluid port, and a valve spool, the valve spool being configured to be positioned in a first position, a second position remote from the first position, and a third position opposite the second valve position remote from the first position, the valve spool defining a first fluid conduit, a second fluid conduit, and a third fluid conduit, the first fluid conduit being configured to fluidly connect the first fluid port to the second fluid port in the first valve position, the second fluid conduit being configured to fluidly connect the first fluid port to the third fluid port in the second valve position, and the third fluid conduit being configured to fluidly connect the first fluid port to the second fluid port in the third valve position.

Description

[0001] Priority Claim

[0002] This application claims priority to U.S. Patent Application No. 16 / 664,571, filed on October 25, 2019, the entire content of which is incorporated herein by reference. Technical Field

[0003] This specification relates to an electro - hydraulic servo valve having fail - safe features. Background Art

[0004] Electro - hydraulic servo valves (EHSVs) are used for electro - hydraulic control of components such as fuel valves, actuators, or switching valves. In some applications, an EHSV can be configured to provide hydraulic power to translate the position of a linear or rotary control valve. Through position feedback, an EHSV can be configured to drive the position of a control valve.

[0005] In previous systems, electrical or hydromechanical failures could drive the second stage of the servo to either end of its respective stroke. Due to the integral nature of the actuator, depending on the failure state, the resulting control pressure could drive the actuator in either direction. If the previous device retracts below zero position, a failure in that direction will retract the actuator. Conversely, if the device extends above zero position, a failure in that direction will extend the actuator. Some examples of EHSV failure modes include servo over - current, feedback spring failure, nozzle and supply orifice contamination. When blocked, the second stage of the EHSV is driven to one of its physical limits (e.g., a hard stop). Zero bias can allow for a power - off situation that can bias the control pressure of the EHSV so that the actuator moves in a desired direction (e.g., extend or retract in the case of an actuator). Thus, in the case of a zero - current failure, the control valve will move to a known stop. This is only a protection against the power - off situation. Summary of the Invention

[0006] Generally speaking, this document describes an electro - hydraulic servo valve having fail - safe features.

[0007] In a first aspect, a fluid valve assembly includes a first fluid port, a second fluid port, a third fluid port, and a valve spool. The valve spool is configured to be positioned in a first position, a second position away from the first position, and a third position opposite the second valve position away from the first position. The valve spool defines a first fluid conduit, a second fluid conduit, and a third fluid conduit. Wherein the first fluid conduit is configured to fluidly connect the first fluid port to the second fluid port in the first valve position, the second fluid conduit is configured to fluidly connect the first fluid port to the third fluid port in the second valve position, and the third fluid conduit is configured to fluidly connect the first fluid port to the second fluid port in the third valve position.

[0008] In a second aspect according to aspect 1, the valve spool is further configured to be positioned in a fourth position, in which the valve spool is configured to prevent fluid flow between the first fluid port, the second fluid port, and the third fluid port.

[0009] In a third aspect according to aspect 1 or aspect 2, the fluid valve assembly further includes an electro-hydraulic valve configured to push the valve spool into at least the first position, the second position, and the third position.

[0010] In a fourth aspect according to aspect 3, the electro-hydraulic valve is configured to position the valve spool in the first position and the second position under nominal operating conditions.

[0011] In a fifth aspect according to any one of aspects 1 to 4, the valve spool is a linear valve spool configured to move linearly, and the first position, the second position, and the third position are linear positions of the linear valve spool.

[0012] In a sixth aspect according to any one of aspects 1 to 5, the second port and the third port are in fluid communication with a fluid actuator configured to actuate in a first direction based on fluid flow in the first direction through the second port and to actuate in a second direction opposite to the first direction based on fluid flow in the first direction through the third port.

[0013] In a seventh aspect, a method of actuating a fluid valve assembly includes actuating a valve spool of a servo valve to a first position, fluidly connecting a first fluid port to a second fluid port based on the first valve position, actuating the valve body to a second position away from the first position, fluidly connecting a third fluid port to the first fluid port based on the second valve position, actuating the valve body to a third position opposite to the second position and away from the first position, and fluidly connecting the first fluid port to the second fluid port based on the third valve position.

[0014] In an eighth aspect according to aspect 7, the method further includes actuating the valve spool to a fourth position away from the first position, the second position, and the third position, and preventing fluid flow between the first fluid port, the second fluid port, and the third fluid port by the valve spool in the fourth position.

[0015] In a ninth aspect according to aspect 7 or 8, actuating the valve spool to the first position further includes actuating an electro-hydraulic valve configured to push the valve spool into the first position, and actuating the valve spool to the second position further includes actuating the electro-hydraulic valve, wherein the electro-hydraulic valve is further configured to push the valve spool into the second position.

[0016] In a tenth aspect according to aspect 9, the electro-hydraulic valve is configured to position the valve spool in the first position and the second position under nominal operating conditions.

[0017] In an eleventh aspect according to any one of aspects 7 to 10, the servo valve includes a linear spool configured to move linearly, and the first position, the second position, and the third position are linear positions of the linear spool.

[0018] In a twelfth aspect according to any one of aspects 7 to 11, the method further includes flowing a first fluid through a second port, actuating a fluid actuator in a first direction based on the first fluid flow, flowing a second fluid through a third port, and actuating the fluid actuator in a second direction opposite to the first direction based on the second fluid flow.

[0019] In a thirteenth aspect, a fluid actuator device includes a first fluid port, a second fluid port, a third fluid port, a spool, and a fluid actuator. The spool is configured to be positioned at a first position, a second position away from the first position, and a third position opposite to the first and second positions and away from the first position. The spool defines a first fluid conduit, a second fluid conduit, and a third fluid conduit. The first fluid conduit is configured to fluidly connect the first fluid port to the second fluid port at the first position. The second fluid conduit is configured to fluidly connect the first fluid port to the third fluid port at the second position. The third fluid conduit is configured to fluidly connect the first fluid port to the second fluid port at the valve position. And the fluid actuator is configured to be actuated in a first direction based on fluid flow through the second port in the first direction and to be actuated in a second direction opposite to the first direction based on fluid flow through the third port in the first direction, wherein the second port and the third port are in fluid communication with the fluid actuator.

[0020] In a fourteenth aspect according to aspect 13, the spool is further configured to be positioned at a fourth position, at which the spool is configured to prevent fluid from flowing between the first fluid port, the second fluid port, and the third fluid port.

[0021] In a fifteenth aspect according to aspect 13 or 14, the fluid actuator device further includes an electrohydraulic valve configured to push the spool to at least the first position, the second position, and the third position.

[0022] In a sixteenth aspect according to aspect 15, the electrohydraulic valve is configured to position the spool at the first position and the second position under nominal operating conditions.

[0023] In a seventeenth aspect according to any one of aspects 13 to 16, the servo valve includes a linear spool configured to move linearly, and the first position, the second position, and the third position are linear positions of the linear spool.

[0024] In a general embodiment, a fluid valve assembly includes a first fluid port, a second fluid port, a third fluid port, and a valve spool. The valve spool is configured to be positioned at a first position, a second position remote from the first position, and a third position opposite the first and second valve positions. The valve spool defines a first fluid conduit, a second fluid conduit, and a third fluid conduit. The first fluid conduit is configured to fluidly connect the first fluid port to the second fluid port in the first valve position, the second fluid conduit is configured to fluidly connect the first fluid port to the third fluid port in the second valve position, and the third fluid conduit is configured to fluidly connect the first fluid port to the second fluid port in the third valve position.

[0025] Various embodiments may include some, all, or none of the following features. The valve spool may be further configured to be positioned at a fourth position where the valve spool is configured to prevent fluid flow between the first fluid port, the second fluid port, and the third fluid port. The fluid valve assembly may further include an electrohydraulic valve configured to push the valve spool to at least the first, second, and third positions. The electrohydraulic valve may be configured to position the valve spool at the first and second positions under nominal operating conditions. The valve spool may be a linear valve spool configured to move linearly, and the first, second, and third positions may be linear positions of the linear valve spool. The second and third ports may be in fluid communication with a fluid actuator, and the fluid actuator may be configured to actuate in a first direction based on fluid flow through the second port in the first direction and to actuate in a second direction opposite the first direction based on fluid flow through the third port in the first direction.

[0026] In another general aspect, a method of actuating a fluid valve assembly includes actuating a valve spool of a servo valve to a first position, fluidly connecting a first fluid port to a second fluid port based on the first valve position, actuating the valve body to a second position remote from the first position, fluidly connecting a third fluid port to the first fluid port based on the second valve position, actuating the valve body to a third position opposite the second position and relative to the first position, and fluidly connecting the first fluid port to the second fluid port based on the third valve position.

[0027] Various embodiments may include some, all, or none of the following features. The method may further include actuating the valve spool to a fourth position away from the first, second, and third positions, and preventing fluid flow between the first fluid port, the second fluid port, and the third fluid port by the valve spool in the fourth position. Actuating the valve spool to the first position may further include actuating an electrohydraulic valve configured to push the valve spool to the first position, and actuating the valve spool to the second position may further include actuating the electrohydraulic valve, wherein the electrohydraulic valve is further configured to push the valve spool to the second position. The electrohydraulic valve may be configured to position the valve spool to the first and second positions under nominal operating conditions. The servo valve may include a linear valve spool configured to move linearly, and the first, second, and third positions are linear positions of the linear valve spool. The method may further include flowing a first fluid through the second port, actuating a fluid actuator in a first direction based on the first fluid flow, flowing a second fluid through the third port, and actuating the fluid actuator in a second direction opposite to the first direction based on the second fluid flow.

[0028] In another general aspect, a fluid actuator device includes a first fluid port, a second fluid port, a third fluid port, a valve spool, and a fluid actuator. The valve spool is configured to be positioned at a first position, a second position away from the first position, and a third position opposite to the first and second positions. The valve spool defines a first fluid conduit, a second fluid conduit, and a third fluid conduit. The first fluid conduit is configured to fluidly connect the first fluid port to the second fluid port at the first position, the second fluid conduit is configured to fluidly connect the first fluid port to the third fluid port at the second position, and the third fluid conduit is configured to fluidly connect the first fluid port to the second fluid port at the valve position. The fluid actuator is configured to be actuated in a first direction based on fluid flow through the second port in the first direction and to be actuated in a second direction opposite to the first direction based on fluid flow through the third port in the first direction, wherein the second port and the third port are in fluid communication with the fluid actuator.

[0029] Various embodiments may include some, all, or none of the following features. The spool valve may further be configured to be positioned in a fourth position, in which the spool valve is configured to prevent fluid flow between the first fluid port, the second fluid port, and the third fluid port. The device also includes an electrohydraulic valve configured to push the spool valve to at least the first position, the second position, and the third position. The electrohydraulic valve may be configured to position the spool valve in the first position and the second position under nominal operating conditions. The servo valve may include a linear spool configured to move linearly, and the first position, the second position, and the third position are linear positions of the linear spool. The systems and techniques described herein may provide one or more of the following advantages. First, a system may provide fail-safe operation of an actuator. Second, the system may provide a known actuator state for system failures of the servo valve. Third, the failure mode state may be selected for application-specific requirements (e.g., extend, retract, known flow direction).

[0030] Details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a schematic diagram of a prior art four-way servo valve.

[0032] Figure 2 is a schematic diagram of an exemplary fail-safe servo valve.

[0033] Figure 3 is a schematic diagram of another exemplary fail-safe servo valve.

[0034] Figure 4 is a schematic diagram of another exemplary fail-safe servo valve.

[0035] Figure 5 is a schematic diagram of an exemplary actuator controlled by a two-stage fail-safe electrohydraulic servo valve.

[0036] Figures 6A-6D is a cross-sectional view of an exemplary fail-safe servo valve in various control configurations.

[0037] Figure 7 is a flowchart of an exemplary process for fail-safe electrohydraulic servo valve control. DETAILED DESCRIPTION

[0038] This document describes a fail-safe electro-hydraulic servo valve (EHSV) system. Failures in prior EHSV configurations could drive the actuator in either of two physical directions depending on the state of the EHSV at the time of failure, causing the connected actuator to be driven to either of its physical limits (e.g., fully extended or retracted) depending on the nature of the failure. In general, the EHSVs described herein are configured to always drive the control valve (and the connected actuator) in the same predetermined direction regardless of the direction of failure in the EHSV (e.g., configured to always fail towards extension, or always fail towards retraction).

[0039] Figure 1 is a schematic diagram of a prior art four-way three-position servo valve 100. In prior systems, an electrical or electro-hydraulic mechanical failure could drive the second stage of the servo to either end of its respective stroke, and depending on the state of the failure, the resulting control pressure could drive the actuator in either direction. If the valve 100 retracts below the neutral position, a failure in that direction will retract the actuator. Conversely, if the valve 100 extends above the neutral position, a failure in that direction will extend the actuator.

[0040] Some examples of EHSV failure modes include the servo exceeding the operating current range, nozzle contamination biasing the servo nozzle such that the second stage of the servo is driven to one of its physical limits (e.g., hard stops), and bridge hole contamination biasing the servo nozzle such that the second stage is driven to one of its internal stops. Zero bias can allow a zero current condition that can bias the control pressure of the EHSV such that the actuator moves in a desired direction (e.g., extend or retract in the case of an actuator). Thus, in the case of a zero current failure, the actuator will move to a known stop. This is only protection against a power loss condition.

[0041] Figure 2 is a schematic diagram of an example fail-safe servo valve 200. For an EHSV that fails outside of the operating region, it may be desirable in some cases to move the actuator in a common direction. Some examples include but are not limited to, a servo current failure exceeding the operating current, nozzle contamination biasing the valve in a particular direction and driving the second stage to one of its physical stops, and bridge hole contamination biasing the pressure and driving the second stage to one of its physical stops.

[0042] For these and other examples, a conventional servo valve (e.g., valve 100) would drive the actuator to extend or retract depending on the direction of the failure. However, if so, it is desirable to always fail to a known stop and additional features can be incorporated to drive the actuator in the same direction regardless of the direction of the failure.

[0043] In the illustrated example, valve 200 is a three-way, three-position valve. Under normal operation, valve 200 moves to modulate inlet 201 between a first position 210 and a second position 220. In use, the first position 210 can direct fluid from inlet 201 to a fluid actuator (not shown) to move the actuator in a first direction (e.g., extend), and the second position 220 can direct fluid from inlet 201 to a fluid actuator to move the actuator in a second direction (e.g., retract). In some examples, normal operation is to use a servo device in its rated current and the associated spool stroke of the allowed rated current. Therefore, normal operation can be performed between positions 210 and 220. Servo performance parameters including control port size, rated stroke and rated current can be sized to be suitable for combined actuator operation. Open-loop or closed-loop operation can be in these states or positions unless a fault occurs.

[0044] Under abnormal operation, valve 200 may be pushed in either direction. In some fault scenarios, valve 200 may fail toward position 210 and cause the controlled actuator to move in a first direction during the fault (eg, extend during this fault mode).

[0045] The valve 200 also includes a third position 230 beyond the position 220. The third position 230 is configured to direct fluid from the inlet 201 to the fluid actuator to move the actuator in a first direction. In some failure scenarios, the valve 200 may fail toward the position 220. The movement will continue past the position 220 (e.g., retract) to the position 230 and cause the controlled actuator to move in the first direction during the failure (e.g., extend during this failure mode). The configuration of the valve 200 will cause the controlled actuator to fail in the same predetermined direction (e.g., extend or retract) regardless of the direction in which the valve 200 may be moved during the failure.

[0046] In some embodiments, the example valve can be configured so that the preselected fault directions are opposite to those in the illustrated example. For example, the valve 200 can exclude the third position 230 and instead have a third position of a different configuration beyond the first position (e.g., adjacent to the left of the position 210 in the illustrated example), which is configured to direct fluid from the inlet 201 to move the controlled actuator in the second direction. During a fault, this configuration of the valve 200 can be driven toward the position 220 during the fault, causing the actuator to retract during this fault mode, or the valve 200 can be driven past the position 210 to the third position of a different configuration, also causing the actuator to retract during this fault mode.

[0047] Figure 3 is a schematic diagram of another example fail-safe servo valve 300. Valve 300 is a three-way, four-position valve. Valve 300 is similar to Figure 2Example valve 200. A zero position 340 is added between the first position 310 and the second position 320.

[0048] Under normal operation, valve 300 moves to switch the inlet 301 between a first position 310 (e.g., extended), a second position 320 (e.g., retracted), and a zero position 340. At the zero position 340, fluid from the inlet 301 is not provided (e.g., blocked) to the actuator.

[0049] Under abnormal operation, valve 300 can be pushed in either direction. In some fault scenarios, valve 300 may fail towards position 310 and cause the controlled actuator to move in a first direction (e.g., extend during this fault mode) during the fault. In some other fault scenarios, valve 300 may fail towards position 320. This movement will continue past position 320 (e.g., retract) to position 330 and cause the controlled actuator to move in a first direction (e.g., extend during this fault mode) during the fault without having to first return through the zero position 340. The configuration of valve 300 will cause the controlled actuator to fail in the same predetermined direction (e.g., extend or retract) regardless of the direction in which valve 300 may be moved during failure.

[0050] Figure 4 Is a schematic diagram of another example fail - safe servo valve 400. Valve 400 is a four - way four - position valve. Under normal operation, valve 400 moves from a zero position 440 to a first position 410 and a second position 420. At the zero position 40, fluid is not provided (e.g., blocked) from inlets 401 and 402 to the actuator. In use, the first position 410 can direct fluid from inlets 401 - 402 in a first flow direction (e.g., forward) through a fluid actuator (not shown) and cause the actuator to move in a first actuation direction (e.g., extend), while the second position 420 can direct fluid from inlets 401 - 402 in a second flow direction (e.g., reverse) to the fluid actuator to cause the actuator to move in a second actuation direction (e.g., retract).

[0051] Under abnormal operation, valve 400 can be pushed in either direction. In some fault scenarios, valve 400 may fail towards position 410 and cause the controlled actuator to move in a first direction (e.g., extend during this fault mode) during the fault.

[0052] The valve 400 also includes a third position 430 beyond the over position 420. The third position 430 is configured to direct fluid from the inlets 401 - 402 in a first flow direction to the fluid actuator to move the actuator in a first actuation direction. In some fault scenarios, the valve 400 may fail towards the position 420. This movement will continue past the position 420 (e.g., retract) to the position 430 and cause flow in the first flow direction and cause the controlled actuator to move in the first actuation direction during the fault (e.g., extend during this fault mode). The configuration of the valve 400 will cause the controlled actuator to fail in the same predetermined direction (e.g., extend or retract), regardless of the direction in which the valve 400 may be moved during the failure.

[0053] Although the previous examples have been described in terms of extension and retraction and fail - safe fault modes using the first direction as the fail - safe direction, there are other configurations. The actuators driven by the example valves 200, 300, and 400 can be linear (e.g., extend and retract), rotary (e.g., clockwise and counter - clockwise rotation), or any other suitable fluid actuator configuration. In some embodiments, the example valves 200, 300, and 400 can be configured to drive other actuators or outputs, such as fluid jets, pressure supplies, flow supplies, and any other suitable output that can be controlled by an EHSV. Many of the above examples are described in terms of fail - safe in a first (e.g., "extended") configuration, but in some examples, the valves 200, 300, and 400 can be modified to be fail - safe in a second (e.g., retracted) configuration, returning the actuator to a predetermined safe position. In some examples, the safe position can be configured to provide safe engine shutdown, surge protection, engine relight, or any other suitable operation.

[0054] Figure 5 is a schematic diagram of an actuator 500 controlled by an example secondary fail - safe EHSV. The actuator 500 includes a secondary EHSV 518 and an actuator 550.

[0055] The first stage 510 includes an electro - actuator 512 (e.g., torque motor) that is configured to actuate in response to current and proportionally allow fluid to flow through nozzles 514a and 514b or prevent fluid from flowing through nozzles 514a - 514b. The nozzles are in fluid communication with conduits 516a and 516b.

[0056] The secondary EHSV 518 also includes a fail - safe piston assembly 520. The piston assembly 520 includes a valve spool 522. In some embodiments, the piston assembly 520 can be configured to Figures 2-4 any of the example fail - safe servo valves 200, 300, or 400 shown.

[0057] The first stage 510 is configured to receive fluid pressure from the fluid passage 530 through the supply holes 523a, 523b, and nozzles 514a, 514b and return the pressure through the fluid passage 532. When current is supplied to the electro - actuator 512, the armature 513 rocks to open the nozzle 514a to the fluid passage 532 and block the nozzle 514b, or open the nozzle 514b to the fluid passage 532 and block the nozzle 514a, depending on how the current is applied.

[0058] The fluid passage 530 is in fluid communication with the pipes 516a, 516b. When the nozzle 514a is open and the nozzle 514b is blocked, the fluid pressure in the pipe 516a drops and the pressure in the pipe 516b increases. When the nozzle 514a is blocked and the nozzle 514b is open, the fluid pressure in the pipe 516b drops and the pressure in the pipe 516a increases. These pressures are applied to opposite ends of the valve spool 522, and the pressure pushes the valve spool 522 to move axially.

[0059] The piston assembly 520 is in fluid communication with the fluid pipe 530. The valve spool 522 is also in fluid communication with the fluid pipes 536 and 538. The piston assembly 520 is configured to selectively pressurize and depressurize the fluids in the fluid pipes 536 and 538 based on the position of the valve spool 522.

[0060] The actuator 550 of the actuator 500 for the exemplary secondary fail - safe EHSV control includes a fluid actuator 552. The fluid actuator 552 includes an actuator piston 554 actuated based on the fluid pressures in the fluid chamber 556a and the fluid chamber 556b disposed opposite to the fluid chamber 556a. In the illustrated example, the fluid actuator 552 is a linear fluid actuator (e.g., a hydraulic cylinder), but in other examples, the fluid actuator 552 can be a rotary actuator, or some fluid nozzle, jet, or any other suitable form of actuator.

[0061] Generally, the electro - mechanical actuation of the electro - actuator 512 causes the mechanical actuation of the piston assembly 520, and the actuation of the piston assembly 520 causes the actuation of the actuator piston 554. Under normal operation, the actuation of the electro - actuator 512 in one direction will cause the actuator piston 554 to actuate in the first direction (e.g., extend), while the actuation of the electro - actuator 512 in the other direction will cause the actuator piston 554 to actuate in the opposite direction (e.g., retract).

[0062] Under abnormal operation, the electro - actuator 512 and / or the piston assembly 520 may fail. Some of the faults that drive the first stage 510 to this situation may be the contamination of the nozzles 514a, 514b that drive the fluid chambers 556a, 556b to rise and fall respectively, the contamination of the orifices 523a or 523b that drive the fluid chambers 516a, 516b to rise and fall respectively, the feedback spring failure, and the unexpected current fault of higher - than - rated current from the control system to the electro - actuator 512, which drives the second stage 520 beyond its operating stroke.

[0063] In these fault situations, the control system may lose control of the servo device, which means that the fluid actuator 552 cannot be positioned according to the command. The design of the secondary EHSV 518 allows the supply of control pressures 536 and 538 to the actuator 550 to reverse the polarity and position the actuator piston 554 to a desired "safe" position (e.g., it can make the actuator piston 554 always retract or always extend during such a failure).

[0064] For example, the piston assembly 520 can be configured with Figure 4 the fluid circuit of the exemplary fail - safe servo valve 400. Under normal operation, the electro - actuator 512 can operate the valve 400 between positions 410, 420, and 440 (e.g., extend, retract, and zero). Under abnormal operation, the valve 400 can be positioned to one of two hard stops at the opposite ends within the movement range of the valve 400. At one end is position 410, and in some fault modes, the valve 400 can be moved to position 410. At the opposite end is position 430, which is beyond position 420, and in other fault modes, the valve can be moved past position 420 to position 430. Positions 410 and 430 are configured to supply fluid to the actuator 550 in the same configuration (e.g., both are configured such that the actuator piston 554 extends, or both are configured to retract the actuator piston 554).

[0065] Similar embodiments exist for linear or rotary actuation systems. For example, the position 330 of the exemplary fail-safe servo valve 300 may allow the pressure acting on the actuator piston 554 to be switched, causing the actuator piston 554 to return to a predetermined safe position. This safe position may be predetermined to allow for safe engine shutdown, surge protection, engine re-ignition, or any other suitable fail-safe configuration or operational application. Generally, the exemplary fail-safe servo valves 200, 300, 400 and the exemplary actuator 500 may be implemented in substantially any system to provide a fail mode in which the actuator or other fluid or mechanical output is configured to be substantially the same as the opposite fail mode. For example, the EHSV may be configured to allow zero current failures and second stage hard over failures (e.g., in either direction) to cause the actuator to fail to the same position (e.g., retract during a failure, extend during a failure, cause low flow during a failure, cause high flow during a failure, or any other predetermined fail-safe configuration).

[0066] Figures 6A-6D is a cross-sectional view of an exemplary fail-safe valve assembly 600 under various control configurations. Assembly 600 shows Figure 5 an exemplary port of the piston assembly 520 of the exemplary second stage EHSV 518. Assembly 600 includes a housing 610, a spool 620 configured to linearly move within the housing 610, and a fluid-actuated actuator 630 configured to be controlled by the spool 620.

[0067] Figure 6A Assembly 600 is shown in a first exemplary configuration. In the illustrated example, the spool 620 is in a first position at or near the first end 601 of the housing 610. In some embodiments, the first position may allow fluid to flow downstream to cause a predetermined action, such as one of the extension or retraction of the actuator 630, one of the clockwise or counterclockwise rotation of the actuator, one of the opening or closing of the flow, or any other suitable actuation. In some embodiments, Figure 6A the configuration shown in Figure 4 may be a representation of the exemplary valve 400 configured in the first position 410.

[0068] Figure 6B Assembly 600 is shown in a second exemplary configuration. In the illustrated example, the spool 620 is in a second position at or near a zero or neutral position within the housing 610 (e.g., fluid is not provided downstream). In some embodiments, Figure 6B the configuration shown in Figure 4 may be a representation of the exemplary valve 400 configured in the first position 440.

[0069] Figure 6CShows the components 600 in a third example configuration. In the illustrated example, the valve spool 620 is in a third position within the housing 610. In the illustrated example, the actuator 630 is fully retracted, and the position of the valve spool 620 allows fluid to flow downstream to the actuator 630, thereby causing a predetermined action opposite to the action caused by the first position (e.g., in the illustrated example, the retraction of the actuator 630). In some embodiments, Figure 6C The configuration shown in Figure 4 may be a representation of the example valve 400 configured in the second position 420.

[0070] Figure 6D Shows the components 600 in a fourth configuration. In the illustrated example, the valve spool 620 is located at or near the second end 602 of the housing 610. The fourth position is configured to allow fluid to flow downstream to the actuator 630, thereby causing an action the same as or similar to the action caused by the first position (e.g., in the illustrated example, the extension of the actuator 630). In some embodiments, Figure 6D The configuration shown in Figure 4 may be a representation of the example valve 400 configured in the third position 430.

[0071] Figure 7 Is a flowchart of an example process 700 for fail-safe electrohydraulic servo valve control. In some embodiments, the process 700 may be used with the example fail-safe servo valves 200, 300, 400, and 600 and Figures 2-6D the example actuator 500 shown.

[0072] In 710, actuate the valve body of the servo valve to a first position. For example, the components 600 may be actuated to Figure 6A the configuration shown, or Figure 4 the example position 410.

[0073] In 720, fluidly connect the first fluid port to the second fluid port based on the first valve position. For example, in Figure 4 the configuration shown. The inlet 401 is connected to Ps at the position 410.

[0074] In 730, actuate the valve body to a second position away from the first position. For example, the components 600 may be actuated to Figure 6C the configuration shown or Figure 4 the position 420.

[0075] In 740, fluidly connect the third fluid port to the first fluid port based on the second valve position. For example, in Figure 4 the configuration shown, the inlet 401 is connected to Pb at the position 420.

[0076] In some embodiments, process 700 may further include flowing a first fluid through a second port, actuating a fluid actuator in a first direction based on the first fluid flow, flowing a second fluid through a third port, and actuating the fluid actuator in a second direction opposite the first direction based on the second fluid flow. For example, the piston assembly 520 of the secondary EHSV 518 is configured to provide flow to actuate the actuator 550 in a first direction and provide a different flow to actuate the actuator 550 in the opposite direction. In another example, the assembly 600 is configured to retract the actuator 630 in the configuration shown in Figure 6C and extend the actuator in the configurations shown in Figure 6A and 6D .

[0077] In 750, the valve body is actuated to a third position opposite the second position and away from it. For example, the assembly 600 can be actuated to the configuration shown in Figure 6D or the position 430 of Figure 4 .

[0078] In 760, the first fluid port is fluidly connected to the second fluid port based on the third valve position. For example, in the configuration shown in Figure 4 , the inlet 401 is connected to Ps in the position 430.

[0079] In some embodiments, process 700 may further include actuating the valve body to a fourth position away from the first, second, and third positions, and preventing fluid flow between the first fluid port, the second fluid port, and the third fluid port by the valve body in the fourth position. For example, the assembly 600 can be actuated to the configuration shown in Figure 6B (e.g., the zero position).

[0080] In some embodiments, actuating the valve body to the first position may further include actuating an electrohydraulic valve configured to push the valve body to the first position, and actuating the valve body to the second position may further include actuating an electrohydraulic valve, where the electrohydraulic valve is also configured to push the valve body to the second position. For example, the electroactuator 512 is configured to actuate in response to an electric current and controllably and alternately allow fluid to flow through one of the nozzles 514a or 514b and block fluid from flowing through the other of the nozzles 514a - 514b to actuate the movement of the fail-safe servo valve piston assembly 520.

[0081] In some embodiments, the electrohydraulic valve may be configured to position the valve body to the first and second positions under nominal operating conditions. For example, the first stage 510 may be configured to position the piston assembly 520 to the configurations shown in Figure 6A and Figure 6C under normal circumstances. During a failure in which the spool 620 is driven to the left or right hard stop, this corresponds toFigure 6A the configuration shown in Figure 6D the configuration shown in, which causes the actuator 550 to be driven in the same direction as Figure 6A the configuration shown.

[0082] In some embodiments, the servo valve can be a linear valve configured to move between a first position, a second position, and a third position. For example, the exemplary fail-safe servo valves 200, 300, 400, 520, and 600 are illustrated and described as linear valves.

[0083] Although some implementations have been described in detail above, there may be other modifications. For example, the logical flow depicted in the figures does not require the particular order or sequential order shown to achieve the desired result. Additionally, other steps may be provided from the described flow, or steps may be eliminated from the described flow, and other components may be added to the described system, or components may be removed from the described system. Accordingly, other implementations are within the scope of the following claims.

Claims

1. A fluid valve assembly, comprising: A first fluid port; A second fluid port; A third fluid port; A valve spool configured to be in a first position, a second position away from the first position, and a third position opposite to and away from the first and second positions, the valve spool defining: A first fluid conduit configured to fluidly connect the first fluid port to the second fluid port in the first position; A second fluid conduit configured to fluidly connect the first fluid port to the third fluid port in the second position; And A third fluid conduit configured to fluidly connect the first fluid port to the second fluid port in the third position; Wherein the second fluid port and the third fluid port are in fluid communication with a fluid actuator; Wherein the fluid valve assembly causes the fluid actuator to fail in the same predetermined direction regardless of the direction in which the fluid valve assembly is moved during failure.

2. The fluid valve assembly according to claim 1, wherein the valve spool is further configured to be positioned in a fourth position, in which the valve spool is configured to prevent fluid from flowing between the first fluid port, the second fluid port, and the third fluid port.

3. The fluid valve assembly according to claim 1, further comprising an electrohydraulic valve configured to push the valve spool into at least the first position, the second position, and the third position.

4. The fluid valve assembly according to claim 3, wherein the electrohydraulic valve is configured to position the valve spool in the first position and the second position under nominal operating conditions.

5. The fluid valve assembly according to any one of claims 1 to 4, wherein the valve spool is a linear valve spool configured to move linearly, and the first position, the second position, and the third position are linear positions of the linear valve spool.

6. The fluid valve assembly according to any one of claims 1 to 4, wherein the fluid actuator is configured to actuate in a first direction based on fluid flow in a first direction through the second fluid port, and to actuate in a second direction opposite to the first direction based on fluid flow in the first direction through the third fluid port.

7. The fluid valve assembly according to claim 2, further comprising an electrohydraulic valve configured to push the valve spool into at least the first position, the second position, and the third position.

8. The fluid valve assembly according to claim 7, wherein the electrohydraulic valve is configured to position the valve spool in the first position and the second position under nominal operating conditions.

9. The fluid valve assembly according to claim 6, wherein the valve spool is a linear valve spool configured to move linearly, and the first position, the second position, and the third position are linear positions of the linear valve spool.

10. A method of actuating a fluid valve assembly, comprising: Actuating the valve spool of a servo valve to a first position; Fluidly connecting the first fluid port to the second fluid port based on the first position; Actuating the valve spool to a second position away from the first position; Fluidly connect a third fluid port to a first fluid port based on a second position; Actuate a valve body to a third position away from the second position and opposite the first position; And Fluidly connect the first fluid port to a second fluid port based on the third position; Wherein the second fluid port and the third fluid port are in fluid communication with a fluid actuator; Wherein the fluid valve assembly causes the fluid actuator to fail in the same predetermined direction regardless of the direction that causes the fluid valve assembly to move during failure.

11. The method according to claim 10, further comprising: Actuate a valve spool to a fourth position away from the first position, the second position, and the third position; And Prevent fluid from flowing between the first fluid port, the second fluid port, and the third fluid port by the valve spool located at the fourth position.

12. The method according to claim 10, wherein: Actuating the valve spool to the first position further includes actuating an electrohydraulic valve configured to push the valve spool to the first position; and Actuating the valve spool to the second position further includes actuating the electrohydraulic valve, wherein the electrohydraulic valve is further configured to push the valve spool to the second position.

13. The method according to claim 12, wherein the electrohydraulic valve is configured to position the valve spool to the first position and the second position under nominal operating conditions.

14. The method according to any one of claims 10 to 13, wherein the servo valve includes a linear valve spool configured to move linearly, and the first position, the second position, and the third position are linear positions of the linear valve spool.

15. The method according to any one of claims 10 to 13, further comprising: Cause a first fluid to flow through the second port; Actuate the fluid actuator in a first direction based on the first fluid flow; Cause a second fluid to flow through the third port; And Actuate the fluid actuator in a second direction opposite to the first direction based on the second fluid flow.

16. The method according to claim 11, further comprising: Actuating the valve spool to the first position further includes actuating an electrohydraulic valve configured to push the valve spool to the first position; And Actuating the valve spool to the second position further includes actuating the electrohydraulic valve, wherein the electrohydraulic valve is further configured to push the valve spool to the second position.

17. The method according to claim 16, wherein the electrohydraulic valve is configured to position the valve spool to the first position and the second position under nominal operating conditions.

18. The method according to claim 17, wherein the valve spool includes a linear valve spool configured to move linearly, and the first position, the second position, and the third position are linear positions of the linear valve spool.

19. A fluid actuator device, comprising: A first fluid port; A second fluid port; A third fluid port; A valve spool configured to be positioned at a first position, a second position away from the first position, and a third position away from the first position and opposite the second position, the valve spool defining: A first fluid conduit configured to fluidly connect a first fluid port to the second fluid port at the first location; A second fluid conduit configured to fluidly connect the first fluid port to the third fluid port at the second location; And A third fluid conduit configured to fluidly connect the first fluid port to the second fluid port at a third location; And A fluid actuator configured to actuate in a first direction based on fluid flow through the second port in the first direction and to actuate in a second direction opposite the first direction based on fluid flow through the third port in the first direction, wherein the second port and the third port are in fluid communication with the fluid actuator; Wherein the fluid actuator device causes the fluid actuator to fail in the same predetermined direction regardless of the direction that causes the fluid actuator device to move during failure.

20. The device according to claim 19, wherein the spool is further configured to be positioned in a fourth position, in which the spool is configured to prevent fluid flow between the first fluid port, the second fluid port, and the third fluid port.

21. The device according to claim 19 or 20, further comprising an electrohydraulic valve configured to push the spool into at least the first position, the second position, and the third position.

22. The device according to claim 21, wherein the electrohydraulic valve is configured to position the spool in the first position and the second position under nominal operating conditions.

23. The device according to claim 19 or 20, wherein the spool comprises a linear spool configured to move linearly, and the first position, the second position, and the third position are linear positions of the linear spool.

24. The device according to claim 22, wherein the spool comprises a linear spool configured to move linearly, and the first position, the second position, and the third position are linear positions of the linear spool.

25. The device according to claim 21, wherein the spool comprises a linear spool configured to move linearly, and the first position, the second position, and the third position are linear positions of the linear spool.

Images