Method for Driving a Pump Device
During switchover from a suctioning step to a discharging step, a mixing pump ( 1 ) carries out a correcting step for displacing a displacing member ( 17 ) in the direction for reducing an internal volume of a pump chamber ( 2 ); and during switchover from the discharging step to the suctioning step, the pump carries out a correcting step for displacing a displacing member ( 17 ) in the direction for increasing the internal volume of the pump chamber ( 2 ). In the correcting step, intake ports ( 30 a, 30 b ), and discharging ports ( 40 a, 40 b ) of the pump chamber ( 2 ) are closed, and the displacing member ( 17 ) undergoes displacement for increasing or reducing the internal volume of the pump chamber ( 2 ) in a hermetic state. Instability caused by backlash of the displacing member ( 17 ) drive system can be eliminated, and a pressure difference between the pump chamber ( 2 ) interior and the fluid intake end or the fluid discharge end can be eliminated. It is therefore possible to eliminate or reduce variability in the amount of fluid intake or amount of fluid discharge when switching between the suctioning step and the discharging step.
1 . A method for driving a pump device, comprising:
a suctioning step for suctioning a fluid into a pump chamber from an intake port by inducing displacement of a displacing member that defines part of an inside peripheral surface of the pump chamber in the direction of increasing internal volume of the pump chamber, with the discharge port of the pump chamber closed and the intake port open;
a discharging step for discharging the fluid from the pump chamber by inducing displacement of the displacing member in the direction of decreasing internal volume of the pump chamber, with the discharge port open and the intake port closed; and
a correcting step for inducing displacement of the displacing member with both the intake port and the discharge port of the pump chamber closed;
wherein the steps are carried out in the order of suctioning, correcting, and discharging; or in the order of discharging, correcting, and suctioning.
2 . The method for driving a pump device of claim 1 wherein the suctioning and discharging steps are performed alternatingly, with the correcting step therebetween.
3 . The method for driving a pump device of claim 1 wherein
the displacing member is subjected to a displacing movement in the direction for reducing the internal volume of the pump chamber in the correcting step executed between the suctioning and discharging steps; and
the displacing member is subjected to a displacing movement in the direction for increasing the internal volume of the pump chamber in the correcting step executed between the discharging and suctioning steps.
4 . The method for driving a pump device of claim 1 wherein
the displacing member is subjected to a displacing movement so as to eliminate the difference between an internal pressure of the pump chamber and a pressure on the fluid discharge flow passage communicating with the discharge port in the correcting step executed between the suctioning and discharging steps; and
the displacing member is subjected to a displacing movement so as to eliminate the difference between the internal pressure of the pump chamber and the pressure on the fluid intake flow passage communicating with the intake port in the correcting step executed between the discharging and suctioning steps.
5 . The method for driving a pump device of claim 4 wherein
the difference between the internal pressure of the pump chamber and the pressure in the fluid discharge flow passage communicating with the discharge port is monitored, and the displacing member is displaced on the basis of the results of the monitoring in the correcting step executed between the suctioning and discharging steps; and
the difference between the internal pressure of the pump chamber and the pressure on the fluid intake flow passage communicating with the intake port is monitored, and the displacing member is displaced on the basis of the results of the monitoring in the correcting step executed between the discharging and suctioning steps.
6 . The method for driving a pump device of claim 4 wherein
during the correcting step, the displacing member is displaced in accordance with a predetermined condition.
7 . The method for driving a pump device of claim 1 wherein
a plurality of the intake ports are formed in the pump chamber; and
during the suctioning step, a suctioning operation involving sequentially opening the closed plurality of intake ports and drawing in fluid is performed repeatedly, forming a mixed fluid in which the different types of fluids are mixed in predetermined proportions.
8 . The method for driving a pump device of claim 7 wherein
before the fluid with the smallest mixture ratio is taken into the pump chamber, at least some fluid having a larger mixture proportion than the aforementioned fluid is taken into the pump chamber.
9 . The method for driving a pump device of claim 1 wherein
a plurality of the discharge ports are formed in the pump chamber; and
the closed plurality of discharge ports are opened sequentially and the fluid is discharged during the discharging step.
10 . The method for driving a pump device of claim 1 wherein
the displacing member is a diaphragm.