GB2119967A - Drive units - Google Patents

Abstract

A drive unit suitable for operating aircraft flight control surfaces comprises a hydraulic multi-piston rotary motor 90. The displacement of the motor 90 is varied through a wobbler 98 whose position is adjusted by a piston unit 73 and a valve 51 responsive to an input command from a valve 11. A feedback link 69 pivotted at 70 contacts a member 53 of the valve 51. A governor valve 50 containing flyweights 55 mechanically coupled to the motor 90 contains a valve member 64 and operates a direction control valve 81. <IMAGE>

Description

SPECIFICATION Drive units The invention relates to drive units suitable for operating aircraft flight control surfaces, for example an aircraft rudder or flap, which can be used in parallel with other such units.

The invention provides a drive unit comprising a hydraulic wobbler controlled multi-piston rotary motor, means for varying the displacement of the motor in response to an input command, feedback mechanism for making the varying means responsive to the position of the wobbler, and a speed governor of the drive unit for making the varying means responsive to the output speed of the drive unit whereby the motor displacement caused to match its load as a combined function of input command, wobbler position and output speed.

In such an arrangement, the presence of an aiding load on the output drives the motor as a pump, and releases hydraulic power for use elsewhere. The direction of hydraulic flow need not be changed, and so parasitic loss and operational slack or backlash are avoided.

Drawings: Figure 1 is a schematic illustration of a drive unit according to the invention.

At the left hand side there is a input pressure command control valve 11. Centrally there is depicted a wobbler control valve 51. To the right at the top is a wobbler control piston unit 73, beneath which is a variable displacement reversible multipiston rotary hydraulic motor/pump 90. The hydraulic motor has an output shaft 93 which has a splined end 94 for connection to a mechanism (not shown) to be actuated by the unit. Directly beneath the hydraulic motor 90 there is a governor valve 50, and to its left a motor directional control valve 81.

These control elements cause the displacement of the hydraulic motor 90 to match a bi-directional load on the output shaft 93. This matching of hydraulic motor displacement is the result of a combination of an input command function translated into a force, the position a wobbler 98 of the hydraulic motor 90, and the velocity of the output shaft 93.

At the left hand side is a bi-directional input position command arrow 12 which conveys the idea that from a remote point by means not shown, a command force is delivered to the left hand end of a command position force generator 13. Disposed therein is a pair of helical springs 14, 16 positioned on either side of a spring seat collar 20, which is integrally secured to a valve member 17. The valve member 17 extends into a valve body 15 of the input pressure control valve 11. The valve member 17 carries integrally therewith a central valve land 19 and a pair of outer valve lands 18 and 21.

When an input command position force is delivered to the command position force generator 13, the entire generator unit is moved a discrete distance, and one of the springs 14, 16 experiences compression depending on the direction of the input force command 12. Accordingly, the spring seat collar 20 and the associated valve member 17 experience a resiliently applied force which is directly proportional to the position commanded by the input command 12.

The input pressure control valve 11 has a supply port 30 connected by supply 31 to the valve body 15.

Disposed, as shown, on either side of the central land 19 are supply branch lines 32,37. Supply branch line 32 provides a fluid connection to the right side of outer valve land 21 via branch supply line 33. The branch supply line 32 provides a fluid connection to one side of a centrally located force summing valve land 58 within the wobbler control valve 51. The branch supply line 32 is additionally connected to the directional control valve 81 via supply branch line 34.

The branch supply line 37 noted above is similarly in fluid communication with the left hand end of the outer valve land 18 via branch conduit 36. The branch supply line 36 provides a fluid connection to the other side of the centrally located force summing valve land 58 within the wobbler control valve 51.

The branch supply line 36 is additionally connected to the directional control valve 81 via the supply branch line 38.

A return port 40 is shown connected to the valve body 15 by a pair of return lines 41,42.

The wobbler control valve 51 is coupled to a wobbler 98 of the hydraulic motor in a manner to be described. The wobbler control valve 51 causes the wobbler 98 to move responsively to the bidirectional input command 12. The wobbler control valve 51 has a valve body 52 that carries a moveable valve member 53. A spring 62 is positioned between the valve body 52 and a side face of a first valve land 57 of the force summing valve land arrangement 60.

The force summing valve land arrangement 60 also has a central force summing valve land 58 and a second valve land 59 as shown. The spring 62 functions to keep the valve member 53 in a neutral condition absent any forces experienced by the valve member 53.

The wobbler control valve is hydraulically coupled to the wobbler 98 through a wobbler position control piston unit 73 via the pair of lines 63, 64, the piston 75, piston rod 76, balljoint 77 and wobbler control arm 99.

Returning to the description of the moveable valve member 53, there are in addition to, respectively, a first, second and force summing central valve land 57, 58 and 59, a central land 54, as well as an outer land 56. At the right hand end of valve member 53 there is shown secured thereto a valve member spring seat 66, a spring 66 and slideably mounted spring seat collar 68. To the right of this just described arrangement is shown a wobbler feedback link 69 mounted for pivotal movement on a pivot pin 70. The wobbler feedback link 69 has at one end a wobbler feedback link contact 71, and at the other end a balljoint arrangement 72 which mechanically couples the feedback link 69 to the piston rod 76.

This just described arrangement allows the feedback link 69 to transmit reciprocating movement of the piston rod 76 through the ball joint 72 to feedback link contact 71 which engages an end face of the slideable spring seat collar 68, which in turn communicates the force representative of the reciprocating motion of the piston 76 to the moveable valve member 53 via the spring 67 and spring seat 66.

The wobbler control valve 51 in addition to being hydraulically coupled to the input pressure control valve 11 and hydromechanically coupled to the hydraulic motor wobbler 98, is coupled hydraulically to hydraulic motor 90, governor valve 50 and the direction control valve 81 in a manner now to be described.

The hydraulic coupling from the wobbler control valve 51 to the hydraulic motor 90 includes a single supply line 38 which is connected to the supply port 30 and branch return lines 54a, 45b and 45c con necked via return line 45 to return port 40.

The governor valve 50 is hydraulically coupled to the wobbler control valve 51 through the directional valve 81 via a pair of lines 87, 88 which respectively provide fluid under pressure to the side face of valve land 57 at the left hand end of moveable valve member and to the side face of outer valve land 56 at the right hand end of moveable valve member 53.

The pressure differential between lines 87, 88 provide velocity control in a manner to be described more fully hereinafter.

The variable displacement hydraulic motor, indicated generally at 90, and which in the form shown is an axial piston motor. As is well known in the art, an axial piston motor has a series of pistons 91 carried within a series of longitudinal bores in a cylinder block 95 which connects to an output shaft 93. A valve block 100, forming part of the motor, has a pair of ports 96,97 one of which 97 receives fluid under pressure from supply port 30, and the other port 96 is connected to return port 40.

The power drive unit disclosed herein provides for infinitely variable positioning of the wobbler 98 to have the wobbler angle change to vary the displace ment of piston 91 to thereby cause the hydraulic motor output to match the bi-directional load experienced by output shaft 93.

In contradistinction to earlier approaches that provided reversible motor action by alternately directing the fluid under pressure between the ports of the valve block, the invention herein being described maintains the use of the same supply and return pressure ports throughout the full range of the power drive units operation.

In the instant invention reversal of the hydraulic motor 90 is accomplished by movement of the wobbler from, for example, the vertical or zero angle position to the right or left.

The output shaft 93 of hydraulic motor 90 is mechanically coupled to the governor valve 50 by schematically indicated broken line 61. The governor valve 50 has a valve body 49 which terminates at its right hand end with flyweight housing 63 which carriesflyweights 55 pivotally secured to the hous ing 63. Rotation of the housing 63 in either direction causes the flyweights to move conventionally and cause valve member 64 to move to the left.

The valve member 64 has a plurality of valve lands 105, 106, 107, 108, 109 and 110 which cooperate with the hydraulic lines connected to the valve body 49 in a mannerto be described more fully hereinafter.

The supply port 30 is hydraulically coupled to governor valve 50 via supply line 35 and supply branch lines 39,39a and 39b.

The return port 40 is also hydraulically coupled to the governor valve 50 via return branch lines 44,46, 46a,46b,46c and 46d.

The directional control valve 81 is hydraulically coupled to the governor valve 50 by one set of lines 48, 48a, 48b and 48c, and by a second set of lines 47, 47a, 47b and 47c.

The operation of the system will now be undertaken with a view to explaining the novel and advantageous cooperation of the variously described components set forth at length hereinbefore.

If we assume that the input command 12 is to the right, there will be present in spring 14 a force directly proportional to the input spring 14 a force directly proportional to the input command 12. The input pressure control valve 11 responds to the force as evidenced by movement of the valve member 17 to the right from the position shown. This just noted movement allows fluid under pressure from supply port 30 to be delivered to the righthand side face of the valve land 58 of the wobbler control valve 51 via the line 31 and line 32. This just noted movement of the valve member 17 also causes the right hand end of the valve member 17 to experience on the end face of valve land 21 the supply pressure from port 30 via lines 31; 32 and 33.The movement of the valve member 17 simultaneously allows the left hand side face of the valve land 58 to be connected to the return port 40, via lines 36,37,42 and 41.

It should be appreciated from the foregoing that there will be a differential present between the lines 32,36 and across the valve land 58 proportional to the input command. The differential pressure across the valve land 58 causes the valve member 53 to move against the spring force presented by the spring 62 positioned to the left of the valve land 57.

Movement of the valve member 53 to the left in the valve body 52 will allow supply port 30 to be hydraulically coupled to the right hand side of piston 75 of the wobbler control piston unit 73 via lines 35, 38 and 64. This just noted movement of the valve member 53 simultaneously allows for the hydraulic coupling of the left hand side of the piston 75 to the return port 40 via lines 63, 45b, 45,44 and 43. Note also that the left hand end of the valve member 53 is also hydraulically coupled to the return port 40 via lines 45c, 45,44 and 43. In a manner similar two that described in respect of the differential pressure experienced across the valve land 58, there appears a similar differential pressure across the piston 75 which causes the piston and its integrally connected piston rod 76 and associated balljoints 72,77 to move to the left. This movement results in the wobbler feedback link 69 pivotally moving about pivot pin 70, which in turn causes wobbler feedback link contact 71 to move in a direction away from the direction of travel of valve member, which is, as will be recalled simultaneously moving to the left under the influence of the differential pressure experienced across the central force summing valve land 58. It should be realized that this reduces the force tending to move valve member 53 to the right.

The movement to the left of the piston 75 of the wobbler controlled piston unit 73 acting through piston rod 76 and balljoint 77, and the wobbler control arm 99 causes the wobbler 98 to move from the neutral position illustrated to the position shown by dotted line 101. From the earlier description of the hydraulic motor 90, it will be recalled that the hydraulic motor 90 always has fluid under pressure aplied via port 97 in valve block 100 which results in a gradually increasing speed being experienced by the output shaft 93 as the wobbler moves toward the dotted line position 101.

As the output shaft 93 increases in speed, the mechanical coupling 61 connecting the output shaft 93 with the flyweight housing 63 causes the flyweights 55 to rotate and the flyweight to move such that valve member 64 of the governor valve 50 moves to the left. The movement of the valve member 64 is directly proportional to the speed of rotation of the output shaft 93.

The movement of the valve member 64 to the left allows fluid under supply pressure to be delivered from supply port 30 to directional valve 81 via, lines 35,39, 39b, 48, 48b and 48c. Initially, fluid under supply pressure would be delivered from the directional valve 81 to the right hand side of the wobbler control valve land 56. From the earlier description, it will be recalled that the lower end face of valve land 82 of valve member 83 of the directional control valve 81 is coupled to the return port 40 via lines 38, 36,37,42 and 31. Accordingly, there will be a downward force on valve member 83, a consequence of the supply pressure exerted on the top side of valve land 85, and the return pressure experienced by the lower end face of valve land 82.This just noted downward force causes the valve member 83 to move downwardly and allows fluid under supply pressure present on line 48b to be delivered to the left hand end face of first valve land 57.

Simultaneously with the downward movement of the valve member 83 and the delivering of supply pressure to the left hand end face ofthewobbler control valve land 57, the right hand side face of valve land 56 will be connected to return port 40 via lines 88, 47b, 47, 46b, 46, 44 and 43. The presence of the pressure differential across the valve member 53 valve land side faces of lands 57 and 56 result in a force being experienced by the valve member 53 which will move the valve member against the input command force that has been created as a consequence of the differential pressure across the central force summing valve land 58 described in detail earlier.

It will be appreciated that if there is an aiding load being experienced by the output shaft 93, the velocity of the output shaft 93 would increase at a rate proportional to the aiding load. The position of the wobbler 98 is dependent in part upon the direction of loading on the output shaft 93, such that upon the appearance of a loading on the output shaft 93 in the same direction as that commanded by the input command 12, the wobbler 98 will assume the position shown by dotted line 102 and thereby cause the hydraulic motor 90 to operate as a pump and thereby regenerate hydraulic power into the system for use by other means.

As will be recalled, the differential pressure acros lines 87 and 88 will provide velocity control in that in the operation being described, where there is an aiding load, the increased velocity of the output shaft resulted in the valve member 53 of the wobbler control valve 51 moving to the right. Movement of the valve member 53 to the right results in the reversal of supply pressure across the piston 75 of the wobbler control piston unit 73. It will be remembered that supply pressure from port 30 had initially been directed to the right hand side of piston 75 in the manner described in detail earlier.

When one envisions the valve member 53 moved to the right as a consequence of the differential pressure between lines 87,88, it is apparent that supply port 30 is connected to the left hand side of piston 75 via lines 35, 38 and 63. The right hand side of piston 75 is connected to the return port 40 via lines 64, 45a, 45,44 and 43. With supply pressure on the left hand face of piston 75 and return pressure on the right hand side of piston 75, the piston 75 and integral piston rod 76 experiences a resulant force that moves the associated rod 76 balljoints 72, 77, wobbler control arm 99, and wobbler 98 from the dotted line position 101 towards the neutral position and then on to the dotted line position 102.Once the wobbler 98 passes the neutral position and begins to move toward the dotted line position 102, the wobbler position causes the motor to reverse and commence an infinitely variable increasing pumping action. Because of the aiding load, this pumping action regenerates power back into the system for use by other hydralic actuatable units not shown.

Accordingly, the prior art parasitic loss inherent in power drive units that employed discharge flow regulating valves has been completely circumvented by the invention just described.

Some further comment is now offered in respect of the governor valve 50. A line 65 is shown terminated with an arrow and the designation "TO BRAKE". Line 65 is normally hydraulically coupled to supply port 30 via lines 39a, 39 and 35. The brake which is not shown is of the conventional disk brake type, and the brake is applied to a component connected to the drive train (not shown) between the output shaft 93 and the flight surface to be controlled. The brake is of the type that requires fluid pressure to be applied in order to maintain the brake release. The removal of fluid under pressure from the brake results in a spring biased brake application.

It will be observed that when the valve member 64 of the governor valve is moved, the maximum distance allowed by the constraints of the valve body's physical design, the line 65 to the brake which had been connected to the supply port 30 via lines 39a, 39 and 35 is now connected to the return port 40 via the passage between valve lands 107, 108 and lines 46b, 46,44 and 43. With the fluid circuit just described completed the brake will be applied and movement of the flight control surface will be halted.

In the event that the input force command 12 is to the left, the valve member 17 of input pressure control valve will move to the left and fluid under pressure from supply port 30 will be delivered to the left hand side of central force summing valve land 58 via lines 31,37 and 36. The right hand side face of central force summing valve land will be coupled to the supply port 40 via lines 32,33,42 and 41. The resultant differential pressure across the central force summing valve land 58 produces a force that moves the valve member 53 of the wobbler control valve 51 to the right which allows supply pressure from port 30 to be delivered to the left hand side of piston 75 of the wobbler control piston unit 73 via lines 63,38 and 35. The right hand side of piston 75 is connected to return port 40 via lines 64,45a,45,44 and 43.The supply versus return pressure differential across the piston 75 results in a force that moves piston 75 and integral piston rod 76, balljoints 72, 77, wobbler control arm 99 and wobbler 98 to the right.

The wobbler 98 and wobbler control arm 99 assume that dotted line piston 102. This movement will be recalled reverses the direction of rotation of the hydraulic motor 90.

The movement of valve member 53 to the right as just described is resisted by the pivotal movement of wobbler feedback link 69 about the pivot pin 70, which pivotal movement causes the wobbler feedback link contact 71 to bear against the sliding spring seat collar 68.

It should be understood that the movement of the valve element 64 of the governor valve 50 will always be to the left as the output velocity of the output shaft 93 increases, irrespective of the direction of rotation of output shaft 93.

The directional valve 81 responds, as will be recalled, to changes in pressure at either end of the valve member 83. The pressure at either end of the valve memer83 is determined by the pressure in lines 34 and 38 which are connected respectively via lines 32,36 and 37 to input pressure control valve 11.

It will be remembered that movement of the valve member 17 of the input pressure control valve 11 provided supply pressure on line 34 to directional valve 81, while simultaneously providing return pressure to line 38.

In the most recently described mode of operation where the input command 12 is in a direction to the left, it will be apparent that supply and return pressures present in lines 34 and 38 are reversed.

The fluid circuit that provides supply pressure to directional valve 81 is completed from supply port 32 via lines 31,37,36 and 38. The fluid circuit that establishes return pressure at the directional valve 81 is completed from return port 40 via lines 41,32 and 34. From the foregoing, it can be seen that directional valve 81 now has supply pressure at the bottom face of valve land 86 and return pressure available adjacent the top end face of valve land 84.

With the valve member 83 of directional valve 81 in the position shown, it is clear from the immediately preceding description that the presence of supply pressure at the bottom of the valve member 83 coupled with return pressure at the valve member upper end will result in valve member 83 remaining in the position shown. It will be noted that the initial movement of the valve member 64 of the governor valve 50 allows supply pressure from port 30 to be delivered to and through directional valve 81 to the right hand end of wobbler control valve land 56 via lines 35,39, 39b, 48, 48c and 88. The left hand face of wobbler control valve member 53 is connected to return port 40 via lines 45c, 45,44 and 43.Note also that the left hand side face of wobbler control valve land 57 is also connected to the return port 40 upon initial movement to the left of governor valve member 64 via the lines 87, 47c, 47, 46c, 46,44 and 43.

In the mode of operation presently being described where the input command 12 is to the left, and the wobbler control valve member 53 responds by moving to the right, it can now be seen that there will be a opposing feedback force experienced by valve member 53 and that this feedback force is proportional to velocity.

In the event that there is an aiding load experienced by the output shaft 93, the arrangement just described will cause the wobbler 98 to move past the neutral position shown in solid line towards the broken line position 101 and the hydraulic motor will be driven as a pump and regenerate power back into the hydraulic system for use by other hydraulically activated components connected to the system.

Claims (7)

1. A drive unit comprising a hydraulic wobbler controlled multi-pistion rotary motor, means for varying the displacement of the motor in response to an input command, feedback mechanism for making the varying means responsive to the position of the wobbler, and a speed governor of the drive unit for making the varying means responsive to the output speed of the drive unit whereby the motor displacement caused to match its load as a combined function of input command, wobbler position and output speed.

2. A drive unit according to claim 1 wherein the varying means is a valve.

3. A drive unit according to claim 2 wherein the feedback mechanism couples the valve to the wobbler.

4. A drive unit according to any preceding claim wherein the varying means includes a piston directly mechanically coupled to the wobbler.

5. A drive unit according to any preceding claim wherein the governor is coupled to the varying means through a direction control valve.

6. A drive unit according to any preceding claim including an input command valve hydraulically coupled to the varying means.

7. A drive unit as herein described with reference to the drawing.