US 5,249,603 AGranted

Proportional electro-hydraulic pressure control device

AssigneeCaterpillar Inc.

InventorJ. Otto Byers, Jr.

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Abstract

A proportional electrohydraulic pressure control device is disclosed. The device includes a linear motor having a permanent magnet. The magnet is radially magnetized providing first and second oppositely directed magnetic flux paths. A valve body is included which has a fluid supply port, first and second fluid control ports, and a central bore. The central bore defines first and second chambers at opposite ends of the bore. A linearly shiftable spool having first and second ends is disposed in the central bore. The first and second control ports define an annulus communicable with the central bore. A fluid source is communicable with the annulus of the control ports and supplies pressurized fluid to one of the first and second chambers. The fluid pressure in an associated chamber applies an axial force on a respective end of the spool. The spool is positional to a first neutral position causing a minimum fluid pressure at the first control port. Advantageously, the permanent magnetic flux forces are equal and opposite to the pressurized fluid force applied to the first end of the spool, thereby latching the spool at the first neutral position.

A proportional electrohydraulic pressure control device having a longitudinal axis, comprising:

an armature bounded by a pair of ends, a shaft having first and second ends extending axially from the ends of said armature, said armature being rectilinearly translatable along the longitudinal axis;
a substantially tubular permanent magnet having radial magnetization and being disposed coaxially around said armature, said permanent magnet providing first and second oppositely directed magnetic flux paths;
an electromagnetic coil being disposed coaxially about said armature and adjacent to said permanent magnet;
a current source being connected to said electromagnetic coil and adapted to energize said electromagnetic coil, said energized coil producing an electromagnetic flux path which causes said armature to move;
a valve body having a fluid supply port, a fluid exhaust port, first and second fluid control ports, and a central bore being axially aligned with the longitudinal axis and a linearly shiftable spool having first and second ends, said central bore defining first and second chambers at opposite ends of said central bore, said first and second control ports defining an annulus being communicable with said central bore, said spool being disposed in said central bore with the first end of said spool being connected to the first end of said shaft;
a first adjustable spring having a retainer and an adjusting assembly, the second end of said shaft being engageable with the first spring retainer and the first adjusting assembly being adapted to adjust said first adjustable spring to position said spool to a first neutral position that causes a minimum fluid pressure at the first control port, the first permanent magnetic flux path producing a predetermined force counter to the first adjustable spring force for biasing said spool at the first neutral position;
and
a second adjustable spring having a retainer and an adjusting assembly, the second end of said spool being engageable with the second spring retainer and the second adjusting assembly being adapted to adjust said second adjustable spring to position said spool to a second neutral position that causes a minimum fluid pressure at the second control port, the second permanent magnetic flux path producing a predetermined force counter to the second adjustable spring force for biasing said spool at the second neutral position.

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Abstract

Claims14