US 4,577,509 A · Arrangement for determining the travel of a piston

Abstract

A contactlessly, measuring arrangement for determining the position of a piston in a suspension component such as a vibration damper, gas spring or hydro-pneumatic suspension. In one embodiment, the piston and/or the piston rod of the suspension component and a further electrode are mounted inside the cylinder of the suspension component to form a variable capacitor which, with the aid of other circuitry, measures the position of the piston. The further electrode preferably is in the form of a tube extending from the base of the cylinder into a hollow cylinder formed within the piston rod which receives the tube. In the capacitive embodiment, additionally, there may be provided a further tube within the first tube to form a reference, second capacitor which is sensitive to pressure and temperature in the same manner as the first capacitor. The first capacitor serves as the variable capacitor for making a position measurement of the piston and the two tubes fixed relative to one another are employed to form the reference capacitor. In an alternative embodiment, the outer surface of the cylinder has an inductive coil wound therearound for producing a magnetic field which is variable dependent upon the position of the piston within the cylinder. Both measuring arrangements when connected in a Wheatstone Bridge circuit produce an electrical signal indicative of the position of the piston.

Claims20

Dependent claims

A damping cylinder of a vibration damper, said damping cylinder having an arrangement for determining a position of piston means therewithin, said cylinder having a space therewithin with said piston means disposed in said space for axial slidable movement within said cylinder;

at least one damping medium being disposed within said cylinder for damping said axial movement of said piston means with respect to said cylinder;
said arrangement for determining the position of said piston means comprising:
means for sensing a position of said piston means within said cylinder;
said position sensing means having a first element and a second element;
said first element of said position sensing means being disposed to be movable with said piston means;
said second element of said position sensing means being disposed to be substantially stationary with respect to said cylinder;
said first element and said second element being electrical insulated one from the other;
said two elements forming a variable impedance component which is substantially electrically reactive;
and wherein said variable reactive electrical impedance varies, in operation, with said position of said piston means in said cylinder;
an electrical signal generated by at least one of said elements and being indicative of said position of said piston means;
and
electrical connecting means, connected to at least one of said elements, for sensing said electrical signal, indicative of said position of said piston means.

9 more elements

A damping cylinder of said vibration damper, said cylinder having an arrangement for determining a position of piston means therewithin, said cylinder having a space therewithin with said piston means disposed in said space for axial slidable movement within said cylinder;

at least one damping medium being disposed within said cylinder for damping said axial movement of said piston means with respect to said cylinder;
one of said at least one damping medium being hydraulic damping oil;
said arrangement for determining the position of said piston means comprising:
said piston means including a circular, hollow piston rod;
said cylinder having a base at one end thereof from which a hollow circular cylindrical, first tube extends into said space and also into said hollow piston in a telescopic relationship therewith, thereby forming, with a dielectric material, comprising said hydraulic damping oil, disposed between said first tube and said piston rod, a variable, first capacitor;
a longitudinal axis of said piston rod being substantially aligned with a longitudinal axis of said first tube;
said first tube being insulated from said cylinder and said hollow piston rod;
a first lead connected to said first tube;
and
second lead connected to said hollow piston rod.

7 more elements

Dependencies are inferred from the claim text.

Arrangement for determining the travel of a piston

Life of this patent

Arrangement for determining the travel of a piston

Life of this patent

Abstract

Claims20