Patent ID: 7163379

Claim:
A gradient liquid feed pump system capable of feeding liquid while varying a mixing ratio of a plurality of eluants by use of a plurality of pumps, said pumps each comprising: a first plunger pump for sucking and delivering the eluant; a second plunger pump for receiving the eluant fed from the first plunger pump, and executing the suction and delivery thereof; a motor for driving the first and second plunger pumps through a cam; a first pressure sensor for measuring pressure in the flow path of the second plunger pump; a second pressure sensor for measuring pressure in the first plunger pump; a cam position detecting sensor for detecting a cam position; and a control means for issuing a control instruction to the motor, wherein the control means increases the rotational speed of the motor when the cam position falls in a delivery interval, and determines a period for decreasing the rotational speed of the motor on the basis of a difference between pressure values obtained from the first and second pressure sensors, respectively.