Patent Description:
Existing applications that use magneto-rheological (MR) fluid to manipulate the fluid pressure relationship in a hydraulic fluid system are typically limited to applications compatible with certain MR fluid properties. MR fluid has a high weight/density and includes ferromagnetic particles. Various aerospace applications prefers recirculation of hydraulic fluid that is void of any contaminants and provides the relatively low fluid weight. <CIT> and <CIT> each respectively discloses a hydraulic fluid system according to the preamble of claim <NUM>.

According to the invention, there is provided a hydraulic fluid system according to claim <NUM>. Various preferred embodiments are defined in the dependent claims. Both the configuration of such a hydraulic fluid system and the operational characteristics of such a hydraulic fluid system are within the scope of this Summary.

[deleted]A hydraulic fluid circuit may be fluidly connected with the hydraulic motor. The magneto-rheological fluid (e.g., including ferromagnetic particles) of the MRF brake may be fluidly isolated from this hydraulic fluid circuit. A static or fixed quantity of the magneto-rheological fluid may be contained within the MRF brake. The MRF brake may be configured such that magneto-rheological fluid is not recirculated from outside the MRF brake, into/through the MRF brake, out of the MFB brake, and then back into the MRF brake (e.g., no exiting and re-entering of magneto-rheological fluid from and back into the MRF brake).

The MRF brake may include a rotor (e.g., rotatable) that is disposed within the magneto-rheological fluid, whereby this rotor may be interconnected with the output of the hydraulic motor. An electrical control signal to the MRF brake (e.g., to a coil) may be used to control the viscosity of the magneto-rheological fluid, which in turn may control a braking torque exerted by the MRF brake on the output of the hydraulic motor.

The hydraulic motor and MRF brake may be of an integrated configuration. A common housing assembly may contain the hydraulic motor and the MRF brake. The hydraulic motor may be disposed within a motor housing, the MRF brake may be disposed in a brake housing, and a housing may be disposed between and engage each of the motor housing and the brake housing.

A hydraulic fluid system is illustrated in <FIG> and is identified by reference numeral <NUM>. The hydraulic fluid system <NUM> includes a hydraulic motor <NUM> (e.g., a gear pump), an MRF brake <NUM>, and a controller <NUM>. The hydraulic motor <NUM> and MRF brake <NUM> are separate components in the case of the hydraulic fluid system <NUM>, and may be disposed in spaced relation to one another. Generally, the MRF brake <NUM> may be operated to control a magnitude of a braking torque exerted on the hydraulic motor <NUM>, and the magnitude of this braking torque is adjustable. In the case of the hydraulic fluid system <NUM>, the hydraulic motor <NUM> may be characterized as an adjustable orifice for the hydraulic fluid system <NUM> (e.g., fluid pressure from one or more devices fluidly connected with the hydraulic motor <NUM> drive the hydraulic motor <NUM> (e.g., a gear pump <NUM>), and the MRF brake <NUM> would in tum be used to control how the hydraulic motor <NUM> resists the fluid pressure from each such device). The hydraulic motor <NUM>, MRF brake <NUM>, and controller <NUM> collectively control the flow of the hydraulic fluid <NUM> within the hydraulic fluid system <NUM> and the pressure of the hydraulic fluid <NUM> within the hydraulic fluid system <NUM>. Representative applications of the hydraulic fluid system <NUM> include a hydraulic damper (e.g., a shimmy damper for nose wheel steering on an aircraft, as an adjustable orifice to control the "free fall" characteristics of hydraulically-actuated landing gear for aircraft, or any other application that would benefit from having a hydraulic fluid restriction (the combination of the hydraulic motor <NUM> and MRF brake <NUM>) that can be controlled quickly and in real time.

A hydraulic fluid <NUM> of any appropriate type is directed through a hydraulic fluid input line <NUM> and into an input port <NUM> of a motor housing <NUM> of the hydraulic motor <NUM>. A hydraulic fluid output line <NUM> extends from an output port <NUM> of the motor housing <NUM>. The hydraulic fluid input line <NUM>, the hydraulic fluid output line <NUM>, or both, may be interconnected with a hydraulic fluid source, such as an accumulator, and one or more other devices. At least one pressure transducer/sensor <NUM> may be associated with the hydraulic fluid input line <NUM>, at least one pressure transducer/sensor <NUM> may be associated with the hydraulic fluid output line <NUM>, or both.

The hydraulic motor <NUM> may include an output gear <NUM> and an idler gear <NUM>. Hydraulic fluid <NUM> that enters the motor housing <NUM> simultaneously rotates the output gear <NUM> and idler gear <NUM>. An output shaft <NUM> may be interconnected and rotate with the output gear <NUM>. The output shaft <NUM> may also extend to the MRF brake <NUM>.

The MRF brake <NUM> is illustrated in <FIG> and <FIG>. The MRF brake <NUM> includes a brake housing <NUM>. The brake housing <NUM> may be spaced from the motor housing <NUM>. The hydraulic fluid system <NUM> may also be configured such that the motor housing <NUM> and brake housing <NUM> do not share any common housing section.

The MRF brake <NUM> includes a magnetic coil <NUM>, a rotor <NUM>, and a rotor shaft <NUM>. The output shaft <NUM> of the hydraulic motor <NUM> may be coupled with the rotor shaft <NUM> of the MRF brake <NUM> such that the output shaft <NUM>, rotor shaft <NUM>, and rotor <NUM> collectively rotate at a common rotational speed (with rotor <NUM> and rotor shaft <NUM> being rotatable relative to the brake housing <NUM>). A speed transducer/sensor <NUM> may be associated with the rotor shaft <NUM> (e.g., to monitor a rotational speed of the rotor shaft <NUM>).

At least a portion of at least one of the rotor <NUM> and rotor shaft <NUM> may be exposed to a magneto-rheological fluid <NUM>, including with the rotor <NUM> is disposed in the magneto-rheological fluid <NUM>. A fixed quantity of the magneto-rheological fluid <NUM> may be contained/retained within the brake housing <NUM>. Stated another way, the magneto-rheological fluid <NUM> may be incorporated so as to not be recirculated through the brake housing <NUM> (e.g., the magneto-rheological <NUM> does not flow from a fluid source (e.g., an accumulator) through one or more input ports of the brake housing <NUM>, and then exit the brake housing <NUM> through one or more output ports and then back to the fluid source during operation of the MRF brake <NUM>).

The controller <NUM> may be operatively interconnected with the MRF brake <NUM> by an electrical signal control line <NUM> that extends from the controller <NUM> to the magnetic coil <NUM> of the MRF brake <NUM>. Generally, an electrical control signal is sent from the controller <NUM> to the magnetic coil <NUM> via the signal line <NUM>. Increasing the current of this electrical control signal increases the viscosity of the magneto-rheological fluid <NUM> in the MRF brake <NUM>, which increases the braking torque applied by the MRF brake <NUM> to the output shaft <NUM> of the hydraulic motor <NUM>. Similarly, decreasing the current of this electrical control signal decreases the viscosity of the magneto-rheological fluid <NUM> in the MRF brake <NUM>, which decreases the braking torque applied by the MRF brake <NUM> to the output shaft <NUM> of the hydraulic motor <NUM>.

A high pressure signal line <NUM> may extend from the pressure transducer <NUM> of the hydraulic motor <NUM> to the controller <NUM> (an input to the controller <NUM>). A low pressure signal line <NUM> may extend from the pressure transducer <NUM> of the hydraulic motor <NUM> to the controller <NUM> (an input to the controller <NUM>). A rotational speed signal line <NUM> may extend from the speed transducer/sensor <NUM> to the controller <NUM>.

The controller <NUM> may be configured to utilize a pressure control logic. The monitored pressure on the input side of the hydraulic motor <NUM> (via pressure transducer <NUM>) and the monitored pressure on the output side of the hydraulic motor <NUM> (via pressure transducer <NUM>) may be used to determine a corresponding differential pressure between the input side and output side of the hydraulic motor <NUM>, and this differential pressure may be used to generate an electrical control signal that provides a corresponding braking torque. A data structure <NUM> (e.g., a look-up table) in memory <NUM> (e.g., computer-readable) may correlate a certain differential pressure to a braking torque and an associated current for the electrical control signal. An MRF brake driver <NUM> of the controller <NUM> may generate and send an electrical control signal to the coil <NUM> of the MRF brake <NUM> (via the electrical control signal line <NUM>) that yields the desired differential pressure (between the input side and output side of the hydraulic motor <NUM>) and a corresponding desired braking torque (via producing a certain viscosity of the magneto-rheological fluid <NUM> via the current of the electrical control signal).

The controller <NUM> could also be configured to utilize a flow control logic. The flow rate through the hydraulic motor <NUM> may be correlated to a differential pressure between the input side of the hydraulic motor <NUM> (via pressure transducer <NUM>) and the output side of the hydraulic motor <NUM> (via pressure transducer <NUM>). The data structure <NUM> (e.g., a look-up table) in memory <NUM> may correlate a certain rotational speed of the rotor shaft <NUM> to a braking torque and an associated current for the electrical control signal. The MRF brake driver <NUM> of the controller <NUM> may generate and send an electrical control signal to the coil <NUM> of the MRF brake <NUM> (via the control signal line <NUM>) that yields a desired rotational speed of the rotor shaft <NUM> and a corresponding desired braking torque (via producing a certain viscosity of the magneto-rheological fluid <NUM> via the current of the electrical control signal).

A hydraulic fluid system in accordance with various embodiments is illustrated in <FIG> and is identified by reference numeral <NUM>. The hydraulic fluid system <NUM> includes four motor/brake sets 92a, 92b, 92c, and 92d. The configuration of each of these motor/brake sets 92a, 92b, 92c, and 92d is at least generally in accordance with the discussion presented above regarding <FIG> and <FIG>. The motor/brake sets 92a and 92b are disposed in series with one another, the motor/brake sets 92c and 92d are disposed in series with one another, and the motor/brake sets 92a, 92b are collectively disposed in parallel to the motor/brake sets 92c, 92d. The motor/brake sets 92a, 92b, 92c, and 92d in effect define a hydraulic bridge circuit. The output pressure and flow (magnitude and direction) may be controlled by adjusting the individual currents in the coil <NUM> of the four MRF brakes <NUM>.

The hydraulic fluid input line <NUM>' extends to the input port <NUM> of the hydraulic motor <NUM> of the motor/brake sets 92a, 92c, while the hydraulic fluid output line <NUM>' extends from the output port <NUM> of the hydraulic motor <NUM> of the motor/brake sets 92b, 92d. A hydraulic line 94a extends from the output port <NUM> of the hydraulic motor <NUM> for the motor/brake set 92a to the input port <NUM> of the hydraulic motor <NUM> for the motor/brake set 92b, and also extends to a hydraulic load <NUM>. A hydraulic line 94b extends from the output port <NUM> of the hydraulic motor <NUM> for the motor/brake set 92c to the input port <NUM> of the hydraulic motor <NUM> for the motor/brake set 92d, and also extends to the hydraulic load <NUM> (via an electrical control signal via the corresponding signal line <NUM>).

In the case of the hydraulic fluid system <NUM>, the pressure in the hydraulic fluid input line <NUM>' may be constant, and the pressure in the hydraulic fluid output line <NUM>' may be constant. The motor/brake sets 92a, 92b, 92c, and 92d in the case of the hydraulic fluid system <NUM> may be used to control the hydraulic load <NUM>. Representative hydraulic loads <NUM> include without limitation an aircraft component. The hydraulic load <NUM> may be a hydraulic actuator (e.g., a wheel brake actuator of an aircraft to control brake torque), a hydraulic (rotary) motor that drives an actuator, a vehicle, or any other device that requires the conversion of hydraulic power (the product of flow and pressure) into another form of mechanical (motive) energy.

A hydraulic fluid system in accordance with various embodiments is illustrated in <FIG> and is identified by reference numeral <NUM>. Generally, a hydraulic motor or gear pump (e.g., hydraulic motor <NUM>) and an MRF brake (e.g., MRF brake <NUM>) are integrated into a common housing assembly <NUM>. This housing assembly <NUM> includes a gear pump housing <NUM>, a brake housing <NUM>, and a cover plate <NUM>. The brake housing <NUM> includes components for an MRF brake, and furthermore closes an open end of the gear pump housing <NUM>. The cover plate <NUM> seals an open end of the brake housing <NUM>. The gear pump includes an output gear <NUM> and an idler gear <NUM>. An idler gear shaft <NUM> is associated and rotates with the idler gear <NUM>. A shaft <NUM> is associated and rotates with each of the output gear <NUM> (gear pump) and a rotor <NUM> (MRF brake). Bearings <NUM> may rotatably support the shaft <NUM> and the idler gear shaft <NUM>. A seal <NUM> may be mounted on the shaft <NUM> adjacent to the brake housing <NUM> and into which the shaft <NUM> extends. A magnetic coil <NUM> may be disposed within the brake housing <NUM>, along with a magneto-rheological fluid <NUM> in which the rotor <NUM> is disposed. An electrical control signal to the magnetic coil <NUM> may be used to control the braking torque exerted by the magneto-rheological fluid <NUM> on the rotor <NUM> (and any portion of the shaft <NUM> that also interfaces with this magneto-rheological fluid <NUM>. Increasing the current of the electrical control signal to the magnetic coil <NUM> increases the viscosity of the magneto-rheological fluid <NUM>, and thereby the increases the magnitude of the braking torque exerted by the magneto-rheological fluid <NUM> on the rotor <NUM>. Decreasing the current of the electrical control signal to the magnetic coil <NUM> decreases the viscosity of the magneto-rheological fluid <NUM>, and thereby decreases the magnitude of the braking torque exerted by the magneto-rheological fluid <NUM> on the rotor <NUM>.

Any feature of any other various aspects addressed in this disclosure that is intended to be limited to a "singular" context or the like will be clearly set forth herein by terms such as "only," "single," "limited to," or the like. Merely introducing a feature in accordance with commonly accepted antecedent basis practice does not limit the corresponding feature to the singular. Moreover, any failure to use phrases such as "at least one" also does not limit the corresponding feature to the singular. Use of the phrase "at least substantially", "at least generally," or the like in relation to a particular feature encompasses the corresponding characteristic and insubstantial variations thereof (e.g., indicating that a surface is at least substantially or at least generally flat encompasses the surface actually being flat and insubstantial variations thereof). Finally, a reference of a feature in conjunction with the phrase "in one embodiment" does not limit the use of the feature to a single embodiment.

Claim 1:
A hydraulic fluid system (<NUM>), comprising:
a hydraulic motor (<NUM>) comprising an output;
a magneto-rheological fluid "MRF" brake (<NUM>) interconnected with said output of said hydraulic motor (<NUM>), said MRF brake (<NUM>) comprising a magneto-rheological fluid; wherein said hydraulic motor and said MRF brake define a first set; the system characterized by
a second hydraulic motor and a second MRF brake operatively interconnected with said second hydraulic motor and that defines a second set, and wherein said first set and said second set are connected in series;
a third hydraulic motor and a third MRF brake operatively interconnected with said third hydraulic motor and that defines a third set; and
a fourth hydraulic motor and a fourth MRF brake operatively interconnected with said fourth hydraulic motor and that defines a fourth set, wherein said third set and said fourth set are connected in series, and wherein said first set and said second set are collectively connected in parallel with said third set and said fourth set.