Caterpillar Inc.

J. Otto Byers & Associates

J Otto Byers, Jr

Lambert Haner

A valve positioning system according to the present invention includes a force motor which responds to a command signal corresponding to a desired valve flow rate by energizing magnetic coils with a current to produce a flux force which moves the valve. Preferably two Hall effect sensors sense the actual position and provide a feedback signal to a control loop which compares the sensed position with the commanded position. The valve is positioned by adjusting the energizing current provided to the magnetic coils. The system optionally includes circuitry to compensate for the error in the actual position relative to the commanded position produced by changes in current in the magnetic coils.

Servo positioning system

A force motor having a cylindrical armature of ferromagnetic material is provided. An electromagnetic coil is disposed coaxially around the armature. First and second cylindrical plates are disposed on opposite ends of the armature in spaced proximity from the armature forming a respective gap having a predetermined length. A substantially tubular permanent magnet is disposed coaxially around the armature. The magnet is magnetized radially with respect to the longitudinal axis and provides a pair of oppositely directed magnetic flux paths. A current source energizes the electromagnetic coil, which produces an electromagnetic flux path directed through the gaps and the armature to cause the armature to move. Advantageously, temperature compensators are provided to differentially expand and contract, with respect to the cylindrical plates, in response to a varying temperature of the force motor. The differential expansion of the temperature compensators urges the cylindrical plates toward one another to reduce the predetermined length of the gaps.

Force motor having temperature compensation characteristics

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.

Growing community of inventors

Kalamazoo, MI, United States of America

J Otto Byers, Jr