Landing gear shock absorber with variable viscosity fluid

A method of absorbing shock for a landing gear of an aircraft, the method comprising the steps of:

• (a) providing a cylinder, a piston in the cylinder, a variable viscosity magneto-rheological hydraulic fluid between the cylinder and the piston, and an orifice through which the hydraulic fluid moves;
• (b) applying shock to the piston;
• (c) measuring the initial velocity of the piston due to the shock;
• then
• (d) computing a deceleration pressure of the fluid within the cylinder for decelerating the piston uniformly;
• then
• (e) continuously altering a viscosity of the hydraulic fluid by generating and varying a magnetic field in the orifice as the piston decelerates to maintain the deceleration pressure constant;
• and
• (f) wherein if the initial velocity of the piston measured in step (c) is sufficiently high, in step (d) the deceleration pressure is computed to hold the stress of the material of the cylinder during deceleration of the piston at a level that would cause permanent deformation without immediate failure.

A suspension and shock absorber for a retractable landing gear of an aircraft, comprising:

• a cylinder having a first end and a second end;
• a piston located in the cylinder, the piston having a rod extending outward from the second end of the cylinder, the piston dividing the cylinder into first and second chambers;
• a magneto-rheological hydraulic fluid located within the first chamber of the cylinder and in contact with a first side of the piston;
• a pressurized gas mixed with the hydraulic fluid in the first chamber;
• a pressurized gas in the second chamber in contact with a second side of the piston;
• an orifice stationarily mounted in the first chamber of the cylinder, through which the hydraulic fluid flows as the piston moves relative to the cylinder;
• an electromagnetic coil mounted to the orifice for generating an electromagnetic field in the orifice to vary viscosity of the hydraulic fluid flowing through the orifice;
• means for measuring a velocity of the piston upon receiving an impact;
• means including a microcomputer for computing a deceleration pressure of the fluid within the cylinder to decelerate the piston uniformly based upon the velocity measured, and for varying power supplied to the coil as the piston decelerates to maintain the deceleration pressure constant, and if an initial velocity of the piston is sufficiently high, for setting the deceleration pressure to hold the stress of the material of the cylinder during deceleration of the piston at a level that would cause permanent deformation without immediate failure;
• and
• a pressure sensor in the first chamber for continuously monitoring the deceleration pressure within the first chamber and providing a signal to the microcomputer so as to maintain the deceleration pressure constant as the piston decelerates.