Temperature compensating means for a hydraulic shock absorber

Claim 1

A hydraulic shock absorber adapted to be connected between the sprung and unsprung masses of a vehicle comprising a tubu ar structure having an end wall at one end thereof provided with means on the exterior thereof for connecting the shock absorber to one of the vehicle masses, said tubular structure defining a hydraulic fluid containing reservoir and a hydraulic fluid containing cylindrical chamber, a piston disposed within said chamber dividing the same into a compression portion and a rebound portion, said piston being axially movable within said chamber toward said end wall in a compression stroke and away from said end wall in a rebound stroke, a metallic piston rod extending through said rebound chamber portion having an inner end portion connected with said piston and an outer end portion provided with means for connecting the shock absorber with the other of the vehicle masses, said tubular structure having means at the end thereof opposite from said one end forming a fluidtight seal about the exterior periphery of said piston rod intermediate the ends thereof, and means for controlling the flow of hydraulic fluid (1) from said compression chamber portion to said rebound chamber portion and said reservoir in response to the compression stroke of said piston and (2) from said rebound chamber portion and said reservoir to said compression chamber portion in response to the rebound stroke of said piston, said flow controlling means including interior surface means in said piston rod provided as an integral part of the metal thereof defining an axial opening extending axially inwardly from the inner end of said piston rod and terminating in a substantially spaced relation to the outer end thereof, and radial opening means in said piston rod communicating exteriorly with said rebound chamber portion and interiorly with said axial opening intermediate the ends thereof, and an elongated element formed of a material having a coefficient of thermal expansion that is greater than that of the material of said piston rod, said element being disposed by an axially inward mounting movement within said axial opening with one end portion thereof mounted in fixed relation to the surface means defining the terminal end of said axial opening and with the opposite end portion thereof being free of spring bias and disposed in a flow-restricting relation to said radial opening means which varies in response to changes in the temperature thereof due to the aforesaid variation in coefficient of expansion so as to provide a control of the flow of hydraulic fluid from said rebound chamber portion to said compression chamber portion during the rebound stroke of said piston which compensates for changes in temperature of the hydraulic fluid.