Hydraulic accumulator charging circuit

Abstract

A hydraulic circuit and charging valve arrangement is disclosed for charging an accumulator where the accumulator is used to power an additional function such as a brake valve. The accumulator charging circuit is connected to a load sensing power steering circuit including a flow divider that controls the flow of a fixed displacement pump to selectively effect actuation of a power steering motor and an auxiliary device such as a bucket loader or backhoe control valve. The charging circuit includes a pilot operated charging valve which controls the flow divider of the load sensing steering circuit for the purpose of recharging the accumulator. The charging valve includes a valve member that is biased against a coil spring to a neutral position when the accumulator is charged. When the accumulator pressure drops below a preset level, the valve member is shifted thereby permitting fluid flow through the charging valve to the flow divider in the load sensing steering circuit. This results in the buildup of pressure in the hydraulic circuit which recharges the accumulator and shifts the charging valve member back to its neutral position. The charging valve is constructed to effectively raise the reset pressure required to shift the charging valve member back to its neutral position, thereby creating a controlled hysteresis in the operation of the charging valve.