Temperature adaptive radial shaft seal assemblies using shape memory alloy elements

Abstract

A dynamic radial shaft assembly and methods of use for rotating or reciprocating shafts include an elastic seal member having at least a portion thereof in sealing communication with the rotating or reciprocating shaft; and a shape memory alloy element in contact with the elastic seal member, wherein the shape memory alloy element is adapted to change a shape orientation and or modulus property as a function of temperature change so as to change or maintain a compressive force and / or sealing area of the seal member portion against the rotating or reciprocating shaft at temperatures from −55° C. to about 250° C.

Description

BACKGROUND[0001]The present disclosure relates to a temperature adaptive radial shaft sealing device that provides improved sealing over a wide range of temperatures while minimizing the friction and wear associated with the same.[0002]Most automotive sub-systems such as the engine, transmission, driveline, suspension dampers, pumps, brakes and other hydraulic / pneumatic actuators utilize seals to prevent ingress of extraneous materials (dust, dirt, humidity, air etc.) into the actuators and / or egress of fluids from the actuators. The seals can be used in a static or a dynamic application. Most dynamic seals have at least one part of the seal in contact with a sliding or a rotating surface. As an example, a shock absorber has a cylindrical piston rod that reciprocates axially through a sealed bearing embedded at one end of a closed cylindrical tube that encloses a hydraulic fluid. As another example, most rotating elements in the transmission require the use of rotary dynamic seals t...

AI Technical Summary

Benefits of technology

The patent describes dynamic shaft seal assemblies and methods of use. These assemblies use a shape memory alloy element that changes its shape and modulus properties as a function of temperature to maintain a compressive force and sealing area against a rotating or reciprocating shaft. The seal assembly is mounted on the shaft using an elastic seal body and a shape memory alloy element in compressive contact with the seal body. The seal assembly is designed to provide a constant sealing force over a range of temperatures and to automatically adjust to changes in the elastic seal body's modulus. The technical effects of this invention include improved sealing performance and durability in extreme temperature environments, reduced maintenance costs, and improved operational efficiency.

Problems solved by technology

While commercially available radial shaft seals satisfy most of the requirements of a given application at one temperature extreme, it is difficult to satisfy all of the requirements at both temperature extremes.

For example, it is oftentimes difficult to minimize seal friction at temperatures at the lower end of the extremes (freezing and below) while maintaining adequate seal friction / minimum leakage at the temperatures approaching the higher end of the temperature extremes (temperatures in excess of 100° C.).

However, because of thermal expansion properties inherent to the materials (e.g., spring steel, aluminum, brass, and the like) used to form the spring, uniform spring loads do not occur over the wide temperature ranges to which seals are exposed such as experienced by dynamic seals used in the automotive environment.

The disadvantages of prior art radial shaft seals include, but are not limited to, excessive friction, excessive leakage, excessive wear, reduced life / durability, and non-uniform compliance / sealing pressure over the required operating temperature range, among others.

Good compression forces holding the seal against a reciprocating or rotating member accelerate seal wear and shorten service life whereas reducing the compressive force can result in leaking, especially at the temperature extremes in which the dynamic seal device can be used.

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