Servo valve with linear actuator and mechanical feedback

Abstract

The invention relates to a servo valve (100) with a pilot stage (20), comprising two hydraulic elements (30, 6) movable relative to each other to displace a power distribution member (2), the pilot stage (30) comprising a linear actuator (40) having a main plunger (41) arranged to change the relative position of the hydraulic elements (30, 6). The pilot stage (20) also comprises a feedback lever (50) in position.

Description

Technical Field

[0001] The present invention relates to the field of hydraulic servo valves, and in particular to a servo valve having a pilot stage including a linear actuator. Background Art

[0002] A conventional servo valve is composed of a pilot stage that controls a movable power-directing member of a power stage. The function of the power stage is to provide a pressure or flow rate that is proportional to the command applied to the pilot stage.

[0003] The pilot stage consists of two hydraulic elements, a hydraulic transmitter (nozzle or injector) and a hydraulic receiver (flapper, deflector, or fixed receiver), such that changing their relative position generates a pressure differential that is used to finely control the movement of a movable power guiding member of the servo valve's power stage. The movable power guiding member slides within a cylindrical sleeve located in the servo valve body. Typically, the position of the hydraulic transmitter or receiver is controlled by a torque motor that moves one of the hydraulic elements of the pilot stage toward the other. Movement of the movable power guiding member within its sleeve subsequently establishes communication between a set of openings and a drilled channel arranged to transmit a pressure or flow rate proportional to the movement of the movable power guiding member. A mechanical guide member is connected to a mechanical feedback rod that is rigidly fixed to the movable one of the hydraulic transmitter and receiver.

[0004] There are servo valves in which a hydraulic transmitter or receiver is moved by a linear actuator. A position sensor measures the position of the powered member and controls the linear actuator via power electronics, which provide electronic feedback similar to the mechanical feedback provided by a feedback rod in a servo valve. This electronics is expensive and negatively impacts the size, weight, and reliability of the servo valve. Summary of the Invention

[0005] The object of the present invention is to improve the reliability of a servo valve.

[0006] To this end, a servo valve with a pilot stage is provided, which includes a hydraulic element for ejecting a fluid jet and a hydraulic element for receiving the fluid jet, the hydraulic elements being movable relative to each other to change their relative positions and thereby generate a pressure difference that can be used to move a power guide member of the servo valve, one of the two elements being mounted in a fixed position on the servo valve body and the other of the elements being mounted at a movable end of a support connected to the servo valve body, the pilot stage including a linear actuator including a main pusher, the main pusher being arranged to selectively apply a force to the support, the force tending to change the relative position of the hydraulic elements, the pilot stage also including a lever provided with a force transmission interface, the force transmission interface including a first application point for applying an output force to the lever and the transmission device and a second transmission point for transmitting the output force from the lever toward the support, the lever also being connected to the power guide member at a third connection point, the first application point and the second transmission point being located on opposite sides of a first plane extending parallel to the output direction of the main pusher and perpendicular to the neutral axis of the lever.

[0007] This enables a servo valve to be provided with a position feedback arrangement which enables the use of a linear actuator without resorting to a motion sensor to sense the movement of the power guiding component.Having a purely mechanical feedback greatly increases the reliability of the servo valve of the present invention.

[0008] Advantageously, the connection interface is arranged such that the connection at the first application point or at the second transfer point is a point connection or a ball joint connection or a linear connection or a pivot connection.

[0009] The vibration behavior of the servo valve is improved when the force transmission interface comprises a cam and indeed when the cam is arranged to provide a pivot connection at the second transmission point and / or when the bearing is connected to the body of the servo valve by a fixed connection.

[0010] In a specific embodiment, the force transmission interface simultaneously includes a first portion extending along a first direction intersecting the neutral axis of the lever and a second portion extending along a second direction intersecting the first direction, and / or the force transmission interface simultaneously includes a third portion extending along a third direction intersecting the neutral axis of the lever and a fourth portion extending along a fourth direction intersecting the third direction.

[0011] Advantageously, the transmission device, at a second point, acts on an auxiliary pusher which comes into contact with the rod in order to push it.

[0012] The fixed position hydraulic element may be the fluid receiver and the hydraulic element carried by the rod may be the fluid ejector; or the fixed position hydraulic element may be the fluid ejector and the movable element may be the fluid receiver.

[0013] In a preferred embodiment, the linear actuator comprises a piezoelectric actuator.

[0014] Other characteristics and advantages of the invention will emerge on reading the following description of a particular, non-limiting embodiment of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] · Figure 1 is a schematic side view of a servo valve in a first embodiment of the present invention;

[0016] · Figure 2 is a schematic side view of a lever in a first embodiment of the present invention;

[0017] · Figure 3 yes Figure 1 A schematic diagram of the servo valve in a first transient state;

[0018] · Figure 4 yes Figure 1 A schematic diagram of the servo valve in a second transient state;

[0019] · Figure 5 yes Figure 1 A schematic diagram of the servo valve in a third transient state;

[0020] · Figure 6 yes Figure 1 A schematic diagram of the servo valve in a fourth transient state;

[0021] · Figure 7 yes Figure 1 A schematic diagram of the servo valve in a fifth transient state;

[0022] · Figure 8 is a schematic side view of a lever in a second embodiment of the present invention;

[0023] · Figure 9 yes Figure 8 A schematic front view of the lever in place;

[0024] · Figure 10 yes Figure 9 Schematic plan view of the lever;

[0025] · Figure 11 is a schematic detail diagram of a lever in a third embodiment of the present invention;

[0026] · Figure 12 yes Figure 10 A schematic detail diagram of the lever in a first state;

[0027] · Figure 13 yes Figure 10 A schematic detail diagram of the lever in the second state; and

[0028] · Figure 14is a schematic detail view of a lever in a fourth embodiment of the present invention. DETAILED DESCRIPTION

[0029] refer to Figure 1 and Figure 2 In this example, the present invention is used in a servo valve for regulating air pressure flow, the servo valve having two stages, one of which is a pilot stage. Of course, the present invention is not limited to this application and can be used in other types of servo valves.

[0030] The servo valve, generally designated 100, comprises a body 1 having a power guiding member 2 mounted therein, sliding in a sealed manner in a cylindrical housing 3, thereby forming a power guiding stage. The power guiding member 2 is movable between two extreme positions and is shaped so as to define sealed chambers C1, C2, C3 and C4 in the housing 3, such that in the extreme positions of the power guiding member 2 relative to the center (or neutral) position, they communicate with:

[0031] A feed port P with a first utilization port U1 and a return port R with a second utilization port U2; or

[0032] A feed port P with a second utilization port U2 and a return port R with a first utilization port U1 .

[0033] The sliding of the power guide member 2 in the housing 3 is controlled by means of pilot chambers 4 and 5, which are fed with fluid under pressure by a pressure distribution member, specifically, in this example, a fixed receiver 6. The receiver 6 comprises a receptacle 9 with two orifices 7 and 8. The orifices 7 and 8 are in fluid flow communication with a respective one of the pilot chambers 4 and 5 via conduits 10 and 11. The receptacle 9 is connected to the circuit R via a conduit 12.

[0034] The pilot stage 20 of the servo valve 100 comprises a rod 21 pivotally mounted at its first end 22 to the body 1. The rod 21 has a free second end 23 on which a fluid ejector 30 is mounted so as to face the receiver 6. A pressure spring 24 is mounted so as to act between the body 1 and a portion 25 of the rod 21 so as to exert a restoring force on the rod 21 so that it moves about the first end 22 along the Figure 1 The lever 21 includes an internal conduit 31 for delivering fluid to the fluid ejector 30. The internal conduit 31 is in fluid flow connection with a feed port P of the servo valve 100 via a conduit 32 formed in the body 1.

[0035] The pilot stage 20 includes a piezoelectric linear actuator 40 having a main pusher 41 to selectively exert a force on the rod 21 .

[0036] The pilot stage also comprises a lever 50 placed between the main pusher 41 and a first end 61 of an auxiliary pusher 60 slidably mounted on the body 1 . A second end 62 of the auxiliary pusher 60 is in contact with the portion 25 of the rod 21 .

[0037] The lever 50 is provided with a force transmission interface 52 at its first end 51. The force transmission interface 52 includes a first ceramic hemisphere 53 having a first center 53.1 and protruding from a first face 54 of the lever 50. A second ceramic hemisphere 55 having a second center 55.1 protrudes from a second face 56 of the lever 50 opposite the first face 54. The first and second ceramic hemispheres 53, 55 are positioned such that when the first and second centers 53.1, 55.1 are orthogonally projected onto a neutral axis 57 of the lever 50, their respective first and second orthogonal projections 53.1, 57.2 are separated by a non-zero distance d. 53-55 .

[0038] The second end 58 of the lever 50 comprises a tungsten carbide ball 59 which is received in the recess 13 in the power directing member 2 .

[0039] Therefore, the output force Fs of the main pusher 41 is applied to the first application point 70 of the first ceramic hemisphere 53. Then, the output force F S The force is transmitted to the first end 61 of the auxiliary pusher 60 via the second transmission point 71 of the second ceramic hemisphere 55. The second end 62 of the auxiliary pusher 60 then acts on the rod 21, overcoming the force of the spring 24, to move the fluid injector 30 towards the first orifice 7. In a corresponding manner, the withdrawal of the main pusher 41 causes the fluid injector 30 to move towards the second orifice 8 under the action of the spring 24. Thus, depending on the voltage applied to the terminals of the actuator 40, the actuator exerts a force on the rod 21 that tends to move the fluid injector 30 mounted on the second end 23 of the rod 21, facing the receiver 6.

[0040] The first point corresponds to a first application point 70 for applying the output force. The second point corresponds to a second transmission point 71 for transmitting the output force. The ball 59 constitutes a third connection point 73 for connection to the power guiding member 2.

[0041] like Figure 1 As shown, the first application point 70 for applying the output force Fs from the main pushing member 41 to the lever 50 and the second transfer point 71 for transferring the output force Fs from the lever 50 to the rod 21 are located on opposite sides of a first plane P1, which is parallel to the output direction Oy of the main pushing member 41 and perpendicular to two-eighths of the neutral axis 57 of the lever 50.

[0042] In operation, such as Figure 1As shown, when a voltage Ue corresponding to half the nominal utilization voltage Un is applied to the terminals of the actuator 40, the main pusher 41 of the actuator 40 is then in a half-stroke state. The servo valve 100 is in its equilibrium state, and the fluid injector 30 injects a fluid jet into the receiving portion 9. No pressure difference is generated between the pilot chambers 4 and 5, and the power guiding member 2 remains in its neutral position, with the utilization ports U1 and U2 separated from the feed port P.

[0043] When an input voltage Ue corresponding to the nominal utilization voltage Un is applied to the terminals of the actuator 40, the voltage Ue causes the main pusher 41 to extend to 100% of its stroke and, by acting on the first application point 70, this causes the lever 50 to pivot about the third connection point 73 (along the axis of FIG. Figure 3 The second transfer point 71 is moved and the auxiliary pusher 60 is displaced in translation against the force of the spring 24. The fluid ejector 30 is then found facing the orifice 7 and ejects a fluid jet toward the orifice 7 ( Figure 3 The pressure difference thus generated between the pilot chambers 4 and 5 causes the power guiding member 2 to move to the right in its housing 3, as shown in FIG. Figure 1 and Figure 3 As shown (increase the volume of the pilot chamber 4). Then, the port U1 is connected to the feed port P for fluid flow ( Figure 4 As the power guide member 2 moves, the third connection point 73 moves to the right (as shown in FIG. Figure 4 As shown), the lever 50 is pivoted about the third connection point 73. This translational displacement causes the second transfer point 71 to move to the right (as shown). Figure 4 As shown), thereby reducing the force transmitted from the second transmission point 71 of the lever 50 to the auxiliary pusher 60 ( Figure 4 ) and returns the rod 21 to its initial position ( Figure 5 ). The servo valve then returns to its equilibrium state.

[0044] Figure 4 and Figure 5 The diagrams show the stages of movement of the lever 50 and the auxiliary pusher 60. For the sake of clarity, they show the second transfer point 71 of the lever moving away from the first end 61. When reading this specification, a person skilled in the art will understand that if Figure 4 and Figure 5 The pivotal movement of the lever 50 about the third connection point 73 and the leftward movement of the auxiliary pusher 60 are shown to occur simultaneously.

[0045] When zero input voltage Ue is applied to the terminals of the actuator 40, the voltage Ue causes the main pusher 41 to retract and the lever 50 to pivot R1 (along the axis of the actuator 40) about the third connection point 73 by the action of the spring 24. Figure 6As shown in the clockwise direction), thereby moving the second transfer point 71 and causing the auxiliary pusher 60 to shift rightward (as shown in the clockwise direction). Figure 6 ). The fluid ejector 30 is then found facing the orifice 8, and it ejects the fluid jet toward the orifice 8 ( Figure 6 The pressure difference thus generated between the pilot chambers 4 and 5 causes the power guiding member 2 to move to the left in its housing 3, as shown in FIG. Figure 1 and Figure 6 As shown (increase the volume of the pilot chamber 5). Then, the port U2 is connected to the feed port P for fluid flow ( Figure 7 As the power guide member 2 moves, the third point 73 shifts to the left (as shown in FIG. Figure 7 As shown), the lever 50 is pivoted about the first application point 70. This translational displacement causes the second transfer point 71 to move to the left (as shown). Figure 7 As shown), the auxiliary push member 60 is shifted to the left (as shown Figure 7 ), and causes the rod 21 to return to its initial position ( Figure 7 ).

[0046] This provides the servo valve 100 with a position feedback mechanism, enabling the use of a linear actuator without resorting to a motion sensor to sense the movement of the power guide member 2. Having fully mechanical feedback greatly increases the reliability of the servo valve of the present invention. The first application point 70 and the second transfer point 71 are always located on opposite sides of the first plane P1, regardless of the position of the power guide member 2 within its housing.

[0047] In the following description of the second, third and fourth embodiments, elements that are the same as or similar to those described above are given the same reference numerals.

[0048] exist Figures 8 to 10 In the second embodiment shown, the force transmission interface 52 includes a cam 80. In this example, the cam 80 is centered at 0 80 The lower left quarter of the disk (such as Figure 8 and 9 The cam 80 is received in a slot 82 formed in the first end 61 of the auxiliary pusher 60. A pin 83 engages in a second hole 84 of the auxiliary pusher 60 and passes through the first hole 81 to provide a pivot connection 83.1 at the second transfer point 71. The first application point 70 is provided by the right quadrant (as shown). Figure 9 As shown), the second transfer point 71 is provided by the pivot connection 83.1.

[0049] In such Figures 11 to 13In the third embodiment shown, the force transmission interface 52 is made of steel and includes a first portion 90 extending in a first direction O90 intersecting the neutral axis 57 of the lever 50, and a second portion 91 extending in a second direction O91 intersecting the first direction O90. The first portion 90 has a smaller cross-section than the second portion 91 and provides a first flexure point 92 that allows the second portion 91 to pivot relative to the first portion 90. Symmetrically about a plane P57 containing the neutral axis 57, the force transmission interface 52 includes a third portion 93 extending in a third direction O93 intersecting the neutral axis 57 of the lever 50, and a fourth portion 94 extending in a fourth direction O94 intersecting the third direction O93. The third portion 93 has a smaller cross-section than the fourth portion 94 and provides a second flexure point 95 that allows the fourth portion 94 to pivot relative to the third portion 93.

[0050] The first flexure point 92 and the second flexure point 95 correspond to the first application point 70 and the second transfer point 71 , respectively. Figure 12 and 13 Two states are shown when the force transmission interface 52 and the lever 50 are subjected to the movement of the main pusher 41 and the auxiliary pusher 60 .

[0051] In a fourth embodiment of the present invention, Figure 14 As shown, the lever 50 acts directly on the rod 21 to push the rod 21 .

[0052] The first point is for applying the output force F of the actuator 40 S The second point is used to transmit the output force F from the actuator 40. S The second transfer point 71.

[0053] The invention is naturally not limited to the above description, but covers any variant coming within the ambit defined by the claims.

[0054] Specifically:

[0055] Although in this example the connection at the first application point and the second transfer point is a point connection provided by a sphere contacting a plane, the invention is equally applicable to other ways of providing a point connection or other types of connection, such as a spherical joint, a linear connection or a pivot connection;

[0056] Although the stem is pivotally mounted on the body above its first end, the present invention is equally applicable to other types of connections between the stem and the servo valve body, such as fixed connections or torsion studs attached to a weld frame machined into the servo valve body or actually pressed into the servo valve body;

[0057] Although the wand described above has an internal conduit for delivering fluid to the fluid ejector, the invention is equally applicable to other types of fluid feed, such as feeding via a flexible hose or via an external conduit attached to the wand;

[0058] Although the actuators described above are piezoelectric actuators, the present invention is equally applicable to other types of linear actuators, such as electric, pneumatic or hydraulic jacks;

[0059] Although the fixed hydraulic element described above is a fluid receiver and the element mounted at the end of the stem is a fluid transmitter, the present invention is equally applicable to a fluid transmitter located in a fixed position on the servo valve body, the fluid transmitter being associated with a fluid receiver mounted at the end of the stem, for example, a receiver such as a deflector or a flapper;

[0060] Although the pilot stage described above comprises a rod on which the fluid ejector is mounted, the invention is applicable to other types of supports, such as vanes;

[0061] Although the pilot stage described above includes a spring acting on a rod, the present invention is equally applicable to other position return means, such as a hydraulic spring or a rod with fixed ends. Furthermore, the present invention can operate without a device for restoring the position of the support, for example, when a second piezoelectric actuator is positioned facing the first end on the other side of the rod, and the control of the second actuator is coupled to the control of the first actuator.

[0062] Although the transfer interface described above is located at the first end of the lever, the present invention is equally applicable to a transfer interface located at a distance from the end of the lever; and

[0063] • Although the second end of the rod described above has a tungsten carbide ball received in a recess in the power directing member, the present invention is applicable to other connection means for providing a third connection point, such as a ball joint or a pivot.

Claims

1. A servo valve (100), the servo valve having a pilot stage (20), the pilot stage comprising a first hydraulic element (30) for ejecting a fluid jet and a second hydraulic element (6) for receiving the fluid jet, the first hydraulic element (30) and the second hydraulic element (6) being movable relative to each other to change their relative positions and thereby generating a pressure difference that can be used to move a power guide member (2) of the servo valve (100), the second hydraulic element (6) being mounted in a fixed position on a body (1) of the servo valve (100), the first hydraulic element (30) being mounted in a fixed position on a body (1) of the servo valve (100), Mounted at a movable end (23) of a support (21), the support being connected to a main body of the servo valve (100), the pilot stage (20) comprising a lever (50) provided with a force transmission interface (52), the force transmission interface comprising a first application point (70) for applying an output force (Fs) to the lever (50) and a second transmission point (71) for transmitting the output force (Fs) from the lever (50) toward the support (21), the lever (50) also being connected to a power guide member (2) at a third connection point (73), the servo valve being characterized in that: The pilot stage (20) further comprises a linear actuator (40), the linear actuator comprising a main pusher (41), the main pusher being arranged to exert the output force (Fs) on the support (21) so as to tend to change the relative position of the first hydraulic element (30) and the second hydraulic element (6); and The first application point (70) and the second transfer point (71) are located on opposite sides of a first plane (P1), which is parallel to the output direction (Oy) of the main pusher (41) and extends perpendicular to the neutral axis (57) of the lever (50).

2. The servo valve (100) according to claim 1, characterized in that The force transmission interface (52) is arranged such that the connection at the first application point (70) or at the second transmission point (71) is a point connection or a ball joint connection or a linear connection or a pivot connection.

3. The servo valve (100) according to claim 1, characterized in that The force transmission interface (52) includes a cam (80).

4. The servo valve (100) according to claim 3, characterized in that The cam (80) is arranged to provide a pivot connection at the second transfer point (71).

5. The servo valve (100) according to claim 1, characterized in that The force transmission interface (52) includes a first portion (90) extending along a first direction (O90) intersecting a neutral axis (57) of the lever (50) and a second portion (91) extending along a second direction (O91) intersecting the first direction (O90).

6. The servo valve (100) according to claim 5, characterized in that The force transmission interface (52) includes a third portion (93) extending along a third direction (O93) intersecting the neutral axis (57) of the lever (50) and a fourth portion (94) extending along a fourth direction (O94) intersecting the third direction (O93).

7. The servo valve (100) according to claim 1, characterized in that The second transfer point acts on an auxiliary pushing member (60), and the auxiliary pushing member contacts the supporting member (21) to push the supporting member.

8. The servo valve (100) according to claim 1, characterized in that The second hydraulic element (6) is a fluid receiver, and the first hydraulic element (30) carried by the support (21) is a fluid ejector.

9. The servo valve (100) according to claim 1, characterized in that The support member (21) is connected to the body of the servo valve via a fixed connection.

10. The servo valve (100) according to claim 1, characterized in that The linear actuator (40) comprises a piezoelectric actuator.

Images