Patent Description:
Valve actuators are utilized in any number of applications. In general, a piston is moved by fluid pressure to move an actuator member that controls the position of a valve. As one example, a butterfly valve is connected to be moved by an actuator member between open and closed positions within a fluid duct.

Generally, control systems that need accurate feedback on the position of the valve require some sort of transducer such as linear variable differential transducers or rotary variable differential transducers. The inclusion of such members raises the cost and complexity of the valving system.

<CIT> relates to improvements in a servoactuator or power control unit.

The invention provides a valving system according to claim <NUM> and a method of operating a valving system according to claim <NUM>.

These and other features will be best understood from the following drawings and specification, the following is a brief description.

<FIG> shows a valving system <NUM> utilized as a positioning valve. System <NUM> includes a fluid duct <NUM> having an inlet <NUM> communicating with a source of pressurized air <NUM>, such as a main compressor in a gas turbine engine. An outlet <NUM> of the duct <NUM> communicates with a use <NUM>. As examples of uses, starter air valves with the below invention will allow control of the starter speed so that engine rotors can be cooled at a controlled rate to avoid distorting and damaging the rotor. Also, fan air valves with this invention will eliminate need for a separate position feedback device. Any valve that would typically require position control or feedback for stability would benefit from this technology.

The position of a butterfly valve disc <NUM> within the duct <NUM> controls the communication of air from the inlet <NUM> to the outlet <NUM>. Butterfly valve <NUM> is shown in a closed position in <FIG>. An actuator member <NUM> is driven by a piston rod <NUM> which moves within a piston housing <NUM> defining a first fluid chamber <NUM>. Piston rod <NUM> is connected to an actuator piston <NUM>.

The actuator piston includes a smaller face piston <NUM> having a first smaller area seeing the pressure in chamber <NUM>. A larger face piston <NUM> sees the pressure in chamber <NUM>. In one embodiment, the face area of piston <NUM> might be half that of piston <NUM>, of course other ratios may be used. At any rate the pressure in chamber <NUM> acts on a larger surface area on face <NUM> than the area over which the pressure in chamber <NUM> acts on piston <NUM>. The larger face piston <NUM> has a cylindrical dome spring guide <NUM> extending away from a forward face <NUM> of the piston <NUM> on an opposed side of the rod <NUM>. A torque motor <NUM> contains an armature <NUM> receiving current <NUM> from a controller <NUM>, that may be a Full Authority Digital Electronic Controller <NUM> ("FADEC"). Alternatively, a dedicated control may be used.

As known, a torque motor flapper <NUM> includes an arm <NUM> which selectively blocks or opens ports <NUM> and <NUM>. As shown in this Figure, the flapper <NUM> closes the port <NUM> and opens the port <NUM>. Port <NUM> is connected to the source of air downstream of the butterfly valve <NUM> through line <NUM>, and port <NUM> is connected to an ambient pressure. Torque motors are known, and are utilized to control the pressure of fluids delivered into chamber <NUM> to move an actuator piston, such as piston <NUM>. However, torque motor <NUM> is unique in that the flapper <NUM> extends to a positioning extension <NUM> having a positioning piston <NUM>. A typical torque motor flapper would end at line X, however, torque motor <NUM> has extension <NUM>. Note line X is included only for reference; it is not found on the actual flapper. Spring <NUM> is positioned between the forward face <NUM> of the piston <NUM> and received within the dome <NUM>. Spring <NUM> is also received outwardly of a cylindrical portion <NUM> of positioning piston <NUM>. Spring <NUM> provides feedback on the position of piston <NUM>. Spring <NUM> provides a feedback force Ffb.

A second spring <NUM> is positioned against the positioning extension <NUM> on a remote side of the flapper extension <NUM> from the spring <NUM>. Second spring provides a force F1. As shown in this position, spring <NUM> and pressure forces in chamber <NUM> act on piston <NUM> such that it is moved to the right, compressing spring <NUM>. The force from chamber <NUM> acts against the forces from spring <NUM> and chamber <NUM>.

In this position, the flapper is exerting a spring force Ffm. While prior torque motors have a high spring rate, in this embodiment the spring rate is lower.

In <FIG> the flapper <NUM> opens part <NUM> so lower pressure air is connected to chamber <NUM>. Thus, the piston is in the closed position.

<FIG> shows valving system <NUM> with the valve piston <NUM> having moved to the left from the <FIG> position such that the butterfly valve <NUM> is now open. In this position flapper <NUM> now opens part <NUM> so higher pressure air is delivered into the chamber to cause piston <NUM> to move. While a butterfly valve in particular is disclosed, the teachings of this invention would extend to other types of valves moved by linear actuators.

As can be seen, the flapper <NUM> has now pivoted to the left, closing port <NUM> and opening port <NUM>. Positions intermediate fully open and fully closed for each port may be achieved.

The force balance equation that positions the valve shown in the <FIG> & <FIG> is: <MAT> where:.

Applicant has recognized some control features that can be utilized with such a valving system <NUM> due to the positioning extension <NUM> on the torque motor <NUM>.

First, as shown in <FIG>, there is a relationship X between the torque motor force Ffm and current which is linear.

Applicant has also recognized as shown in <FIG> that the feedback force of spring Ffb has a linear relationship Y to actuator stroke.

By associating the feedback force Ffb with the torque motor force Ffm, one can associate the feedback force Ffb with current.

Thus, as shown in <FIG>, the valve position has a linear relationship Z relative to the current.

<FIG> is a flow chart of operating the valving system <NUM> as disclosed in this application. As shown at step <NUM>, in a first step a control for the valving system <NUM> is programmed to associate current with valve positioning.

At step <NUM>, current is sent, and that current is then associated with a valve position.

The system operates as follows:
A helical compression spring <NUM> and pressure (in <NUM>) act on small piston <NUM> to move the valve in the close direction (<FIG>).

To open: An electrical signal is sent to the torque motor <NUM>, which provides a force (Ftm) proportional to the current.

Ftm applies a load to the armature, which pivots the armature <NUM> thereby lifting the flapper <NUM> off the nozzle <NUM> and provides servo pressure (from <NUM>) to the servo cavity <NUM>, this pressure provide the opening force on the valve <NUM>.

Without feedback there is only one position of the armature which will create the servo pressure that will balance the loads on the piston. Note: The helical compression spring <NUM> rate is not high enough to provide controllable proportionality to the valve (this is due to the high range of pressure valve needs to operate at).

The flapper extension <NUM> adds feedback between the valve position and the torque motor.

The torque motor <NUM> force due to current application (I) is Ftm, as I increases the force Ftm increase and opens the nozzle <NUM> to provide servo pressure. As the valve <NUM> opens, the feedback force, Ffb on the armature decreases. As Ffb decreases F<NUM> has more authority and counteracts some of the force Ftm causing the nozzle <NUM> to close and reduce servo pressure. This integrates until at a fixed current the actuator system is in balance. For any given current this balance point will be different as Ftm is directly proportional to the current. Also since the feedback is proportional to the valve position, the net effect is that the actuator is proportional to the current applied to the torque motor.

Ftm is function of Current, F1 and Ffb, nozzle area is function of Ftm, F<NUM> and Ffb, servo pressure is function of nozzle area, valve position is function of servo pressure, Ffb and F<NUM> are function of valve position. From this it is known that valve position has a linear relationship to current.

Stated slightly differently, we know Ftm is proportional to current. The actuator continues to change position of the valve until Fnet balances with Ftm. Fnet equals F<NUM> minus Ffb. The position of the valve is proportional to Fnet since at that point Fmet is qual to Ftm and position is proportional to Fnet, then the position of the valve is proportional to Ftm. Since Ftm is proportional to current, position is also proportional to current. A worker designing a system under this invention could simply calibrate the control such that it associates a particular torque motor current with the exact position of the valve, then can rely upon knowing the position of the valve to a high degree of accuracy simply by knowing the current. In this manner the need for any position transducer is eliminated.

While a positioning valve is illustrated in <FIG> and <FIG>, any number of other valve applications can benefit from this invention.

As an example, <FIG> shows a surge bleed valve positioning system <NUM>. Here, an engine <NUM> has a compressor surge bleed <NUM>. A valving system <NUM> which may operate such as in the above invention controls the flow of the bleed line <NUM> to an outlet <NUM>. The FADEC <NUM> controls current to the valving system <NUM> to achieve a desired valve position.

<FIG> shows a system <NUM> having manual positioning. A manual control <NUM> is utilized to control the flow of current to a valving system <NUM> which may be as disclosed above to control the flow between an inlet <NUM> and an outlet <NUM>.

<FIG> shows a flow sharing application <NUM>. Here a pair of sources of air <NUM> and <NUM> lead to valves <NUM> and <NUM>, respectively. Pressure sensors <NUM> may be associated with each line <NUM> and <NUM>. A FADEC controls the flow of air from inlets <NUM> and <NUM> to an outlet <NUM> through lines <NUM> and <NUM>. Again, the valves <NUM> and <NUM> may operate as disclosed above.

<FIG> shows a bowed rotor modulation application. Here, a starter <NUM> is associated to start an engine <NUM>. A speed reference sensor <NUM> may sense the speed of the engine and provide feedback to a FADEC <NUM>. The FADEC supplies current to a valving system <NUM> which controls the flow of air from inlet <NUM> to outlet <NUM> heading to the starter <NUM> to control the engine. A rotor modulation mode may be utilized when initially starting an engine to allow the engine to speed up slowly to correct for a bowed rotor condition.

<FIG> shows a variable pressure regulator application <NUM>. A desired pressure is sent from a reference pressure schedule <NUM> to a comparison node <NUM>. Comparison node <NUM> receives signals from the pressure sensor <NUM> on an inlet line <NUM>. Feedback from the comparison is sent to a FADEC <NUM> which controls the current supply to a valve system <NUM> to control the amount of fluid reaching an outlet <NUM>.

A variable temperature control application <NUM> is illustrated in <FIG>. Here a temperature sensor <NUM> on a fluid line <NUM> is sent to a comparison member <NUM> which also receives a reference desired temperature <NUM>. Feedback from the comparison is sent to a FADEC <NUM> which controls a valving system <NUM> which may be similar to the valving systems disclosed above. The valving system <NUM> controls the amount of air to a hot air application <NUM>, and a line <NUM> receives cold air.

In sum, embodiments are disclosed which provide accurate feedback on the position of the valve member without the need of a position sensing transducer.

Claim 1:
A valving system (<NUM>) comprising:
a fluid duct (<NUM>);
a control (<NUM>);
a valve member received within the fluid duct (<NUM>) to control the flow of fluid between a duct inlet (<NUM>) to a duct outlet (<NUM>);
an actuator member (<NUM>) connected to move with an actuator piston (<NUM>) and change the position of the valve member, said actuator piston moving within a housing (<NUM>), said housing defining a smaller face fluid chamber (<NUM>) acting on a small area piston face, and there being a larger face fluid chamber (<NUM>), acting on a larger face of the actuator piston (<NUM>), said larger face being on a remote side of said actuator
piston from said small area piston face of said actuator piston;
a torque motor (<NUM>) comprising an armature (<NUM>) and a flapper (<NUM>) caused to move by current (<NUM>) received at the armature from the control (<NUM>), said flapper moving between two fluid ports (<NUM>, <NUM>) to control the opening of the two fluid ports and control the pressure in the larger face fluid chamber, said flapper further having a positioning extension (<NUM>), and said positioning extension engaging a first feedback spring (<NUM>) operable between it and the larger face of said actuator piston providing a spring force in combination with a spring force from the positioning extension; and
said control being operable to provide current to said armature to control the fluid received in said larger face fluid chamber from said first and second fluid ports, said
control being programmed to associate the current supplied to the armature to an actual position of the valve member.