Direct-pilot servo-cylinder

Abstract

Servo-cylinder comprising a fluidic cylinder (100) and a servovalve (200) for supplying fluid to the cylinder (100). The cylinder (100) comprises a cylinder (101) and a piston (102) defining two chambers (103.1, 103.2) of variable volumes within the cylinder. The servovalve (200) comprises a sleeve (201) with a plurality of channels (U1, U1', U2, U2', P, P', R, R'), including at least one pressure channel (P), one exhaust channel (R), and a first connecting channel (U1) to one of the chambers (103.1), and a movable distribution element relative to the sleeve (201) between at least one first communication position of the first connecting channel (U1) with the pressure channel (P) and a second communication position of the first connecting channel (U1) with the exhaust channel (R). FIGURE IN ABRIDGED DIAGRAM: Fig. 1

Description

Title of the invention: Direct-pilot servo-actuator

[0001] The present invention relates to the field of fluidic actuators and more particularly to cylinders associated with a servovalve.

[0002] BACKGROUND OF THE INVENTION

[0003] Devices commonly referred to as "servo-cylinders" are known, combining a cylinder, such as a hydraulic cylinder, and a servovalve supplying the cylinder. Servo-cylinders are commonly used in aircraft propulsion, particularly for moving moving parts of turbojet engines, for example, the blades of a variable-pitch stator vane such as the rectifier of a high-pressure compressor.

[0004] A conventional servovalve generally comprises a pilot stage and a power stage. The pilot stage includes two hydraulic elements, namely a hydraulic emitter (nozzle or ejector) and a hydraulic receiver (vane, deflector, or fixed receiver), and a torque motor having a pivoting output shaft that moves one of the hydraulic elements of the pilot stage relative to the other to generate pressure differentials. These differentials are used to finely move a spool valve that forms part of the servovalve's power stage. The power stage includes a cylindrical sleeve that is mounted in the servovalve body and receives the spool valve, which slides in a direction perpendicular to the motor's output shaft.The movement of the mobile distribution spool within its sleeve then connects a set of drilled channels and openings whose arrangement allows the cylinder to be supplied with a pressure and flow rate that are proportional to the movement of said mobile distribution spool.

[0005] These servovalves include a mechanical link between the torque motor rotor and the power distribution spool, achieved by means of a feedback element. The feedback element is generally connected to the distribution spool at its midpoint and is also connected to the hydraulic element associated with the rotor via the latter. The feedback element controls the position of the distribution spool to the servovalve rotor and generates a torque on the torque motor that counteracts the control action. Such a servovalve is known, for example, from document WO-A-2013 / 053668.

[0006] It is also known to incorporate into the cylinder two linear sensors of the LVDT type (Linear Variable Differential Transformer) to measure the position of the cylinder rod and control the rod in position.

[0007] These servo cylinders are relatively bulky and have a complex structure, with a large number of small parts, which requires machining with tolerances of a few microns and particularly long and complicated assembly, fitting and adjustment operations.

[0008] SUBJECT OF THE INVENTION

[0009] The invention aims in particular to provide a servo-cylinder which at least partially remedies the aforementioned disadvantages. Summary of the invention

[0010] To this end, the invention provides a servo-cylinder comprising a fluidic cylinder and a servo-valve for supplying the cylinder with fluid. The cylinder comprises a cylinder and a piston which slides within the cylinder and defines a first chamber and a second chamber of variable volumes. The servo-valve comprises a sleeve with a plurality of channels, including at least one pressure channel, one exhaust channel, and a first channel connecting to the first chamber, and a distribution element movable relative to the sleeve between at least a first position for connecting the first connecting channel to the pressure channel and a second position for connecting the first connecting channel to the exhaust channel.The distribution element is a barrel mounted to pivot relative to the sleeve, the barrel having peripheral grooves to connect the relevant channels in each of the positions, and the servovalve includes a rotary electric motor to rotate the barrel and the sleeve relative to each other between the two positions.

[0011] Thus, the control and power stages of older servovalves are replaced by a rotary motor / barrel assembly arranged on the same axis, which reduces the size and number of parts of the servovalve and therefore of the servo cylinder as a whole. The reduction in the number of parts also allows for easier and less demanding assembly, which improves the reliability of the servovalve and reduces manufacturing costs.

[0012] According to optional features, used individually or in whole or in combination: - the servo-cylinder includes at least one first position sensor, the first position sensor being a rotary sensor having an input shaft mechanically connected to the piston by a device for transforming a sliding movement of the piston into a rotational movement of the input shaft; - the position sensor is connected to an electronic control unit linked to the rotary electric motor and arranged to send a command to the rotary electric motor aimed at controlling the piston in position; - the control unit includes a memory to record a response of the servo-cylinder according to the command of the electronic control unit; - the control unit is arranged to compare responses recorded in memory and determine a drift in the response of the cylinder; - the control unit is arranged to correct the control of the rotary electric motor according to the determined drift; - the servo-cylinder includes at least one second position sensor, the second position sensor being a rotary sensor having an input shaft mechanically connected in rotation to a rotor of the rotary electric motor or to the barrel; - the rotary electric motor is coaxial with the barrel.

[0013] Other features and advantages of the invention will become apparent from the following description of a particular, non-limiting embodiment of the invention. Brief description of the drawings

[0014] Reference will be made to the attached drawings, among which:

[0015] [Fig-1] is a schematic longitudinal cross-sectional view of a servo-cylinder according to the invention;

[0016] [Fig.2] is a schematic detail perspective view showing the coupling of the position sensors with the cylinder rod;

[0017] [Fig.3] is a schematic top view showing the coupling of the sensors position with the cylinder rod;

[0018] [Fig.4] is a partial schematic perspective view of the servovalve barrel;

[0019] [Fig.5] is a partial schematic perspective view of the servovalve;

[0020] [Fig.6] is a partial schematic perspective and longitudinal section view of the servovalve. DETAILED DESCRIPTION OF THE INVENTION

[0021] With reference to the figures, the servo-cylinder according to the invention comprises a main body 1 having a first housing 2 in which is housed a fluidic cylinder generally designated as 100 and a second housing 3 in which is housed a servovalve generally designated as 200 for supplying the cylinder 100 with fluid.

[0022] The cylinder 100 comprises a cylinder 101 and a piston 102 which slides within the cylinder 101 and which defines therein, in a sealed manner, a first chamber 103.1 and a second chamber 103.2 of variable volumes. The piston 102 is provided with a through rod 104, having a first end 104.1, or actuating end, extending outward from the cylinder 101 and the main body 1 to be connected to the element to be actuated and, at the opposite end, a second end 104.2, or copy end, extending projecting from cylinder 101 into a third housing 4 of the main body 1. Static and dynamic seals are arranged in a manner known in itself to ensure the sealing of cylinder 100.

[0023] The piston 102 slides in the cylinder 101 between two extreme positions, namely a position extended from the rod 104 and a position retracted from the rod 104. A helical spring 105 is arranged around a portion of the rod 104 to be interposed between the piston 102 and the cylinder 101 in order to return the piston 102 to an intermediate position in the absence of pressure in the chambers 104.1, 104.2.

[0024] The servovalve 200 comprises a sleeve 201 receiving a pivoting barrel 202 around an axis of rotation X.

[0025] The sleeve 201 is pierced with a plurality of channels, here eight (symbolized by arrows in figures 5 and 6), namely: - a first pressure channel P and a first connecting channel U1 to the first chamber 103.1 each having a first outlet opposite the barrel 202, these first two outlets being aligned on a first line L1 parallel to the axis of rotation X; - a first escapement channel R and a first connecting channel U2 to the second chamber 103.2 each having a first outlet opposite the barrel 202, these first two outlets being aligned on a second line L2 parallel to the axis of rotation X; - a first pressure channel P', a second connecting channel U2' to the second chamber 103.2, a second connecting channel U1' to the first chamber 103.1 and a second exhaust channel R', each having a first outlet opposite the barrel 202, these first four outlets being aligned on a third line L3 parallel to the axis of rotation X, the outlet of the first pressure channel P' adjoining the outlet of the second connecting channel U2' and the outlet of the second connecting channel U1' adjoining the outlet of the second exhaust channel R'.

[0026] In contrast to these initial opportunities: - the first pressure channel P and the second pressure channel P' have a second outlet connected to a pressurized fluid channel connected to a fluid reservoir; - the first exhaust channel R and the second exhaust channel R' have a second outlet connected to a fluid return channel to the fluid reservoir; - the first connecting channel U1 and the second connecting channel Ul' have a second outlet connected to the first chamber 103.1; - the first connecting channel U2 and the second connecting channel U2' have a second outlet connected to the second chamber 103.2.

[0027] The barrel 202 is movable relative to the sleeve 201 between two positions, namely an exit position of the rod 104, in which the first chamber 103.1 is supplied and the second chamber 103.2 is at the escape, and a retraction position of the rod 104 in which the first chamber 103.1 is at the escape and the second chamber 103.2 is supplied.

[0028] The barrel 202 has peripheral grooves to connect the relevant channels in each of these two positions, namely: - a first longitudinal groove 203 extending parallel to the axis of rotation X opposite the first line L1 and the first outlets of the first pressure channel P and the first connecting channel U1 when the barrel 202 is in the exit position of the rod 104; - a second longitudinal groove 204 extending parallel to the axis of rotation X opposite the second line L2 and the first outlets of the first escape channel R and the first connecting channel U2 when the barrel 202 is in the exit position of the rod 104; - a first third longitudinal groove 205.1 extending parallel to the axis of rotation X opposite the third line L3 and the first outlets of the second escape channel R' and the second connecting channel Ul' when the barrel 202 is in the retraction position of the rod 104; - a second third longitudinal groove 205.2 extending parallel to the axis of rotation X opposite the third line L3 and the first outlets of the second pressure channel P' and the second connecting channel U2' when the barrel 202 is in the retraction position of the rod 104.

[0029] The barrel 202 further includes on its periphery a first neutral zone 206.1 between grooves 203 and 204, a second neutral zone 206.2 between grooves 204 and 205.1, 205.2 and a third neutral zone 206.3 between grooves 205.1, 205.2 and 203. The neutral zones 206.1, 206.2, 206.3 have dimensions such that, when the outlets of the channels P, P', Ul, Ul', U2, U2', R, R' are located opposite the neutral zones 206.1, 206.2, 206.3, the neutral zones 206.1, 206.2, 206.3 block said outlets.

[0030] It is understood that, when the barrel 202 is in the exit position of the rod 104: - the first longitudinal groove 203 connects the first pressure channel P and the first connecting channel U1 to supply the first chamber 103.1; - the second longitudinal groove 204 connects the first exhaust channel R and the first connecting channel U2 to exhaust the second chamber 103.2; - the third neutral zone 206.3 closes the first outlets of the second exhaust channel R', the second connecting channel Ul', the second pressure channel P' and the second connecting channel U2'.

[0031] It is understood that, when the barrel 202 is in the retraction position of the rod 104: - the first third longitudinal groove 205.1 connects the second exhaust channel R' and the second connecting channel U1' to exhaust the first chamber 103.1; - the second third longitudinal groove 205.2 connects the second pressure channel P' and the second connecting channel U2' to supply the second chamber 103.2; - the third neutral zone 206.3 seals the first outlets of the first exhaust channel R, the first connecting channel Ul, the first pressure channel P and the first connecting channel U2.

[0032] Preferably, the barrel 202 is arranged to also include a third position forming a locking position of the rod 104 in position, third position in which the neutral zones 206.1, 206.2, 206.3 block the outlets of the channels U1,U1',U2, U2'.

[0033] The servovalve 200 also includes a rotary electric motor 207 mounted in the sleeve 201 coaxially with the barrel 202 and having an output shaft connected to the barrel 202 to rotate the barrel 202 and the sleeve 201 relative to each other between two positions. A helical torsion spring 208 extends between the barrel 202 and the sleeve 201 to return the barrel 202 to a predefined safety position when the rotary electric motor 207 is not powered. Indeed, in the event of a loss of power to the motor, for example, it is desirable that the barrel can be returned to a known and fixed position. The torsion spring 208 is arranged to return the barrel 202 to one of the three aforementioned positions (stem extended, stem retracted, or stopped in position) according to the specified requirements.

[0034] The rotary electric motor 207 is controlled by an electronic control unit 300.

[0035] The control unit 300 comprises at least one processor and a memory containing a computer program executable by the processor. In the case of an application to an aircraft engine (for example, when the element to be actuated by the servo actuator is a variable-pitch blade of a high-pressure compressor's stator in a turbomachine), the control unit 300 may be the control unit motor commonly called FADEC. The program of the control unit 300 is arranged to control the rod 104 of the cylinder 100 according to a setpoint calculated with respect to the operation of the turbomachine and according to the actual position of the rod 104.

[0036] The servo cylinder thus includes two first position sensors 110, housed in the housing 4, to detect the position of the rod 104. The redundancy of the position sensors 110 is advantageous because it improves the operational reliability of the servo cylinder. The first position sensors 110 are rotary sensors having an input shaft 111 perpendicular to the sliding direction of the piston 102 and provided with a crank 112 having a crankpin 113 received by sliding in a groove 104.3 made in the second end 104.2 of the rod 104 perpendicular to the sliding direction of the piston 102. It is understood that, when the piston 102 slides in the cylinder 101, the rod 104 pulls or pushes the crankpins 113 according to the sliding direction, thus causing a rotation of the crankpins 112 and therefore of the input shafts 111 of the position sensors 110.The cranks 212 thus mechanically link the input shaft 111 to the piston 102 by transforming the translational movement of the piston 102 into a rotational movement of the input shaft 111. The position sensors 110 detect the position of the rod 104 along the sliding direction and are connected to the control unit 300 to provide it with a signal representing this position. The first position sensors 110 are of the RVDT type.

[0037] The control unit 300 is programmed to generate a control of the rotary electric motor 207 of the servovalve 200 aimed at controlling the rod 104 in position, based on a position setpoint and the position signal provided by the position sensors 110. This type of control is known in itself and will not be described in more detail here.

[0038] The control unit 300 is further programmed to store in its memory the position that follows a command and that is representative of a response of the piston 102 (and therefore of the rod 104) as a function of the command supplied to the rotary electric motor 207 of the servovalve 200 by the control unit 300. Preferably, the control unit 300 is programmed to compare responses stored in memory and determine a drift in the response of the servo cylinder. Advantageously, the control unit 300 is programmed to correct the servovalve command according to the drift thus determined. This drift may correspond to a longer reaction time to reach a given position, for example, due to an increase in fluid viscosity caused by a drop in ambient temperature or a drop in pressure in the cylinder's supply circuit (for example, due to a leak).

[0039] In a preferred embodiment of the invention, the servo-cylinder includes a second position sensor 210. The second position sensor 210 is a rotary sensor, here also of the RVDT type, having an input shaft aligned on the axis of rotation X and mechanically connected in rotation to a rotor of the rotary electric motor 207 or to the barrel 202.

[0040] The second position sensor 210 is connected to the control unit 300 and allows it to specifically monitor the response of the servovalve according to the command from the control unit 300 while the first position sensors 110 allow monitoring the performance of the servo cylinder as a whole.

[0041] The position signals emitted by the position sensors 110, 210 allow the control to be corrected according to the actual response of the servo cylinder, to monitor the health status of the servo cylinder and possibly to issue an alert to plan preventive maintenance of the servo cylinder.

[0042] Of course, the invention is not limited to the embodiment described but encompasses any variant falling within the scope of the invention as defined by the claims.

[0043] In particular, the servo-cylinder may have a different structure from that described.

[0044] The servo-cylinder can be hydraulic or pneumatic.

[0045] The return spring 105 for the rod 104 in the intermediate position is optional. Another type of spring can also be used, such as Belleville washers for example.

[0046] The helical return spring of the barrel 202 in the defined safety position can be replaced by an elastomer sleeve, a spiral spring, an elastic blade, a permanent magnet or an electromagnet... This return element can act on the barrel 202 or on the rotor of the rotary electric motor 207. This return element can also be omitted.

[0047] The electronic control unit can be of the microcontroller or FPGA type. It can be dedicated to the servo actuator or perform other functions (as in the case of a FADEC). The servo actuator response monitoring function is optional.

[0048] The motor 207 for driving the barrel 202 can be of any type and for example a servomotor, a brushed or brushless motor, a stepper motor... The barrel 202 can also directly form the rotor of the motor, the barrel 202 rotating in an armature provided with electromagnetic windings to form the stator of the motor.

[0049] The sleeve 201 can be moved around the barrel 202 which is fixed to it.

[0050] The position sensors 110, 210 may be of a different type than RVDT. The position sensors 110 may be replaced by linear sensors, for example of the LVDT type.

[0051] The crank 112 can be replaced by any device for transforming a translational movement into a rotational movement, such as a pair of tapered gears or a wheel / rack.

[0052] The cylinder 100 can be a single-acting cylinder, the piston being returned to one or the other of its two extreme positions by a spring. This makes it possible to limit the number of channels to be made in the sleeve 201 and the body 1.

[0053] The invention is applicable to all fields and in particular to aeronautics, aerospace, boating, automobiles, industrial machinery...

Claims

Demands

1. Servo-cylinder comprising a fluidic cylinder (100) and a servovalve (200) for supplying the cylinder (100) with fluid; the cylinder (100) comprising a cylinder (101) and a piston (102) which is slidably received in the cylinder (101) and which defines in the latter a first chamber (103.1) and a second chamber (103.2) of variable volumes; the servovalve (200) comprising a sleeve (201) pierced with a plurality of channels (Ul, Ul', U2, U2', P, P', R, R') of which at least one pressure channel (P), one exhaust channel (R) and a first connecting channel (Ul) to the first chamber (103.1), and a movable distribution element relative to the sleeve (201) between at least a first communication position of the first connecting channel (Ul) with the pressure channel (P) and a second communication position of the first connecting channel (Ul) with the exhaust channel (R); characterized in that the distribution element is a barrel (202) mounted to pivot relative to the sleeve (201), the barrel (202) having peripheral grooves (203, 204, 205.1, 205.2) to connect the relevant channels in each of the positions and in that the servovalve (200) includes a rotary electric motor (207) to rotate the barrel (202) and the sleeve (201) relative to each other between the two positions.

2. Servo-cylinder according to claim 1, comprising at least a first position sensor (110), the first position sensor (110) being a rotary sensor having an input shaft (111) mechanically connected to the piston (102) by a transformation element of a sliding motion of the piston (102) into a rotational motion of the input shaft (111).

3. Servo-cylinder according to claim 2, wherein the first position sensor (110) is connected to an electronic control unit (300) connected to the rotary electric motor (207) and arranged to issue a command to the rotary electric motor (207) aimed at controlling the piston (102) in position.

4. Servo-cylinder according to claim 3, wherein the electronic control unit (300) includes a memory for recording a response of the servo-cylinder (100) as a function of the command from the electronic control unit (300).

5. Servo-cylinder according to claim 4, wherein the electronic control unit (300) is arranged to compare responses stored in memory and determine a drift in the response of the cylinder (100).

6. Servo-cylinder according to claim 5, wherein the electronic control unit (300) is arranged to correct the control of the rotary electric motor (207) according to the determined drift.

7. Servo-cylinder according to any one of the preceding claims, comprising at least a second position sensor (210), the second position sensor (210) being a rotary sensor having an input shaft mechanically connected in rotation to a rotor of the rotary electric motor (207) or to the barrel (202).

8. Servo-cylinder according to any one of the preceding claims, wherein the rotary electric motor (207) is coaxial with the barrel (202).

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