Patent ID: 8123496

Claim:
A liquid chromatograph apparatus comprising: two pump units for feeding a mobile phase; introduction means for introducing an object to be measured into the mobile phase fed by the pump units; a separation column for separating components to be measured from the object to be measured, which is introduced by the introduction means; detection means for detecting the components to be measured, which are separated by the separation column; and a data processor programmed to control operation of the two pump units, the introduction means, the separation column, and the detection means, wherein each pump unit includes: a first piston which moves back and forth in a first pump chamber having an inlet port and an outlet port, a second piston which moves back and forth in a second pump chamber having an inlet port and an outlet port, piston driving means for moving the first and second pistons back and forth, a position detection sensor for detecting a back-and-forth movement position of the first piston, a connecting pipe for connecting the outlet port of the first pump chamber to the inlet port of the second pump chamber, an inlet side valve, connected to the inlet port of the first pump chamber, for allowing a fluid to flow into the first pump chamber, and for checking the fluid from flowing into and out of the first pump chamber, an outlet side valve, that is a check valve comprising a magnetic ball and an electromagnetic induction sensor, connected to the connecting pipe, for allowing the fluid to flow into the second pump chamber from the first pump chamber through the connecting pipe, and for checking the fluid from flowing into the second pump chamber and flowing out of the first pump chamber, wherein, the electromagnetic induction sensor is connected in between the inlet port of the second pump chamber and the outlet port of the first pump chamber and detects opening and closing states of the check valve, a flow sensor, disposed at the outlet port of the second pump chamber, for detecting a flow rate of the fluid flowing out of the outlet port, and a controller programmed to control a speed of driving the first and second pistons by the piston driving means, based on the back-and-forth movement position of the first piston, which is detected by the position detection sensor, the flow rate of the fluid flowing out of the outlet port of the second pump chamber, which is detected by the flow sensor, and the opening and closing states of the check valve detected by the electromagnetic induction sensor.