Bellows pump device
A bellows pump device includes first and second bellows mounted on a pump head so as to be expandable/contractible independently of each other and configured to suck a fluid from a suction passage thereinto by expansion thereof and discharge the fluid therefrom to a discharge passage by contraction thereof. First and second air cylinder portions are configured to respectively cause the first and second bellows to perform expansion/contraction operation. First and second detection devices are configured to detect expanded/contracted states of the first and second bellows, respectively. A control unit is configured to control drive of the first and second air cylinder portions on the basis of each of detection signals of the first and second detection devices such that, before one bellows comes into a most contracted state, the other bellows is caused to contract from a most expanded state.
1. A bellows pump device comprising:
a pump head in which a suction passage and a discharge passage for a fluid are formed;
a suction check valve configured to permit flow of the fluid in one direction in the suction passage and block flow of the fluid in another direction in the suction passage;
a discharge check valve configured to permit flow of the fluid in one direction in the discharge passage and block flow of the fluid in another direction in the discharge passage;
first and second bellows mounted on the pump head so as to be expandable/contractible independently of each other and configured to suck the fluid from the suction passage thereinto by expansion thereof and discharge the fluid therefrom to the discharge passage by contraction thereof;
a first driving device configured to cause the first bellows to perform expansion/contraction operation continuously between a most expanded state and a most contracted state;
a second driving device configured to cause the second bellows to perform expansion/contraction operation continuously between a most expanded state and a most contracted state;
a first detection device configured to detect an expanded/contracted state of the first bellows;
a second detection device configured to detect an expanded/contracted state of the second bellows; and
a control unit programmed to control drive of the first and second driving devices on the basis of each of detection signals of the first and second detection devices such that the second bellows is caused to contract from the most expanded state before the first bellows comes into the most contracted state, and the first bellows is caused to contract from the most expanded state before the second bellows comes into the most contracted state, wherein the control unit includes:
a first calculation section configured to calculate a first expansion time from the most contracted state of the first bellows to the most expanded state of the first bellows and a first contraction time from the most expanded state of the first bellows to the most contracted state of the first bellows on the basis of the detection signal of the first detection device;
a second calculation section configured to calculate a second expansion time from the most contracted state of the second bellows to the most expanded state of the second bellows and a second contraction time from the most expanded state of the second bellows to the most contracted state of the second bellows on the basis of the detection signal of the second detection device;
a first determination section configured to determine, on the basis of the calculated first expansion time and the first contraction time, a first time difference from a time point at which the first bellows in the most expanded state starts contraction operation to a time point at which the second bellows in the most expanded state starts contraction operation before the first bellows comes into the most contracted state through the contraction operation;
a second determination section configured to determine, on the basis of the calculated second expansion time and second contraction time, a second time difference from a time point at which the second bellows in the most expanded state starts contraction operation to a time point at which the first bellows in the most expanded state starts contraction operation before the second bellows comes into the most contracted state through the contraction operation; and
a drive control section configured to control drive of the first and second driving devices such that contraction operation of the second bellows in the most expanded state is started at a time point at which the first time difference elapses from a time point at which the first bellows in the most expanded state starts contraction operation, and contraction operation of the first bellows in the most expanded state is started at a time point at which the second time difference elapses from a time point at which the second bellows in the most expanded state starts contraction operation.
2. The bellows pump device according to claim 1 , wherein
the first determination section determines the first time difference on the basis of the first expansion time and first contraction time calculated immediately before,
the second determination section determines the second time difference on the basis of the second expansion time and second contraction time calculated immediately before, and
the drive control section controls drive of the first and second driving devices on the basis of the first and second time differences determined immediately before.
3. The bellows pump device according to claim 1 , wherein the first determination section calculates the first time difference using the following equation:
first time difference=(first expansion time+first contraction time)/2; and
the second determination section calculates the second time difference using the following equation:
the second time difference=(second expansion time+second contraction time)/2.