Patent ID: 7784494

Claim:
A flow divider for distributing fluid supplied from a pump to a priority flow circuit and a surplus flow circuit, the flow divider comprising: a housing including a pump port connectable to the pump, a priority flow port connectable to the priority flow circuit, a surplus flow port connectable to the surplus flow circuit, a supply flow path communicated with the pump port, a priority flow path communicated with the priority flow port, a surplus flow path communicated with the surplus flow port, and a spool hole defined by a wall surface and communicated with the supply flow path, the priority flow path, and the surplus flow path; a spool, arranged in the spool hole in an axially movable manner, for distributing fluid from the supply flow path to the priority flow path and the surplus flow path; a surplus restriction, defined by the spool and the wall surface of the spool hole, for restricting flow rate of the fluid from the supply flow path to the surplus flow path, wherein the supply flow path includes a first supply passage and a second supply passage branched from each other and communicated with the spool hole; the surplus restriction is a variable restriction, for varying the flow rate in accordance with the movement of the spool, and includes a first surplus restriction, for restricting the flow rate from the first supply passage to the surplus flow path, and a second surplus restriction, for restricting the flow rate from the second supply passage to the surplus flow path, the second surplus restriction being formed to restrict the flow rate in at least two steps; and the spool including a cross-sectional area changing portion located at a position corresponding to the second surplus restriction; wherein the cross-sectional area changing portion has a diameter that is reduced from the second supply passage toward the surplus flow path, wherein the spool has a cross-sectional area that changes in a stepped manner at the cross-sectional area changing portion, wherein the second surplus restriction includes a first step and a second step arranged closer to the surplus flow path than the first step, and the cross-sectional area of the spool at a portion corresponding to the second step is less than the cross-sectional area of the spool at a portion corresponding to the first step, wherein the first step and the second step restrict the flow rate of the fluid from the second supply flow path to the surplus flow path, respectively; and wherein the second step restricts the flow rate of the fluid from the second supply passage to the surplus flow path when the flow path between the second step and a wall of the spool hole is narrower than the flow path between the first step and the wall of the spool hole, wherein when the open amount of the second surplus restriction is sufficiently wide, the open amount of the second step is narrower than the open amount of the first step.