Brakes – With condition indicator – Wear
Reexamination Certificate
2000-03-01
2002-10-29
Schwartz, Christopher P. (Department: 3613)
Brakes
With condition indicator
Wear
C188S00111E
Reexamination Certificate
active
06471015
ABSTRACT:
FIELD OF THE INVENTION
The invention herein described relates generally to brake control systems, more particularly to electronic braking systems, and still more particularly to aircraft braking systems.
BACKGROUND OF THE INVENTION
Known in the prior art are aircraft wheel and brake assemblies including a on-rotatable wheel support, a wheel mounted to the wheel support for rotation, and a brake disk stack having front and rear axial ends and alternating rotor and stator disks mounted with respect to the wheel support and wheel for relative axial movement. Each rotor disk is coupled to the wheel for rotation therewith and each stator disk is coupled to the wheel support against rotation. A back plate is located at the rear end of the disk pack and a brake head is located at the front end. The brake head houses a plurality of actuator rams that extend to compress the brake disk stack against the back plate. Torque is taken out by the stator disks through a static torque tube or the like.
As the brake disks wear, the running clearance of the actuator rams correspondingly increases. To maintain an acceptable running clearance, mechanical adjustor devices have been employed. While functional, these devices add weight and complexity to the braking system, and need to be overhauled usually each time the brake disk stack is replaced. For at least these reasons, it would be desirable to provide for running clearance adjustment without the need for these mechanical adjustor devices.
Present day aircraft brake systems also have employed wear pin indicators to measure overall wear of the brake disk stack. Brake wear is indicated by the length of the pin relative to a reference plate. This arrangement requires a visual inspection of the pin to determine wear and is inherently imprecise. It would be desirable to provide for brake wear measurement without the need for a visual inspection and with greater precision.
Moreover, it would be desirable to provide for brake actuator running clearance and brake wear indication utilizing means that may be interfaced into an electro-mechanical brake system. Electro-mechanical braking systems eliminate drawbacks associated with hydraulic braking systems such as fluid leaks, high maintenance requirements, fire hazard and higher overall weight.
Electrically actuated aircraft brakes of various configurations are known, as exemplified by U.S. Pat. Nos. 4,381,049, 4,432,440, 4,542,809 and 4,567,967. The brake assemblies shown in these patents include electric motors which respond to an electrical control signal to effect rotation of a ring gear member which interacts through a plurality of balls to drive a linearly movable ram member into contacting engagement with a brake disk stack to effect compression thereof and braking of a wheel.
In U.S. Pat. No. 4,596,316, another configuration of an electrically actuated brake uses a roller screw drive wherein a ring gear member interacts through a plurality of roller screws to drive a ram member into engagement with the brake pressure plate to effect compression of the brake disk stack for braking action. A plurality of electric motors and their associated pinions drive a ring gear into rotation and the plurality of roller screws effect linear axial movement of the ram member.
In U.S. Pat. No. 4,865,162, a further electrically actuated aircraft brake employs a roller screw drive mechanism driven by an electric torque motor through a gear drive associated with either the screw or the nut of the roller screw drive mechanism. Rotation of the gear drive by the torque motor moves the other one of the screw or nut into axial engagement with a brake disk stack to compress the stack for braking. A plurality of the roller screw drive mechanisms and respective gear drives and torque motors are mounted in a balanced arrangement about the axis of the wheel to apply and release a brake pressure force on the brake disk stack in response to an electrical control signal to the torque motors.
In U.S. Pat. No. 4,995,483, there is described a motor position feedback control system for an electrically actuated aircraft brake. The system controller provides brake clamping and declamping in response to a position feedback controlled brake actuator in which an electric torque motor drives a rotating member of a reciprocating drive mechanism to axially move another member into and out of engagement with a brake pressure plate of a multi-disk brake assembly. The position feedback is obtained using a rotor position resolver which provides relative position information to the controller. Such a system requires a re-calibration of the position sensor after a power interruption which may result in loss of braking capability, long recovery time and possible uncommanded brake clamp force application.
Among other things, it would be desirable to have an electrically actuated aircraft brake that has greater durability than the prior art brakes that use roller screw drive mechanisms, thereby to minimize deterioration of components that may lead to increased friction in the mating screw components and the associated loss of efficiency and response of the brake. Also, it would be desirable to have an electrically actuated brake wherein equal force can be applied by multiple ram actuators and which optimizes brake clamping force dynamic response.
SUMMARY OF THE INVENTION
The present invention provides a brake system and method, particularly an electrically actuated aircraft brake system and method, which provides various advantages over known brake systems and methods.
According to one aspect of the invention, a brake system and method are provided to enable brake wear measurement while eliminating the need for previously used brake wear indicator pins. More particularly, brake wear measurement is obtained by analyzing the output of position sensing circuitry. In a preferred embodiment, present brake disk stack height is measured using an actuator position sensor or sensors, and the output of the sensor or sensors is compared to a reference brake disk stack height to provide an indication of the amount of brake wear. The reference brake disk stack height preferably is obtained by loading the brake disk stack by a predetermined amount and using the actuator position sensor or sensors to measure the displacement of the actuator ram or rams to the brake disk stack. In brake systems employing multiple actuator rams, the outputs of respective position sensors are averaged to provide an actuator displacement measurement for the associated brake disk stack. The actuator position sensor preferably is an absolute position encoder that outputs a signal representative of the actual position of the actuator ram relative to the brake housing.
Accordingly, a preferred embodiment of the invention provides a brake system and method characterized by a brake disk stack, at least one reciprocating ram, a motive device operatively connected to the reciprocating ram for selectively moving the reciprocating ram into and out of forceful engagement with the brake disk stack for applying and releasing braking torque on a rotatable member (e.g., a wheel), and a controller that controls the motive device for selective control of the reciprocating ram and regulation of the force applied by the reciprocating ram against the brake disk stack. In accordance with the invention, a position sensor supplies a position signal representative of the position of the reciprocating ram, and the controller includes means for effecting displacement of the reciprocating ram to load the brake disk stack by a predetermined amount to obtain from the position sensor a present displacement value of the position signal, and for comparing the present displacement value to a reference displacement value to provide a measurement of wear of the brake disk stack.
A preferred embodiment of the invention is further characterized by the use of a position sensor directly linked to the actuator ram, and preferably one that is robust. A preferred position sensor is a LVDT transducer, although other types of t
Christ Franklin C.
Ralea Mihai
Goodrich Corporation
Renner , Otto, Boisselle & Sklar, LLP
Ronyak David M.
Schwartz Christopher P.
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