1. A fuel cell system comprising:
a fuel cell;
a circulating pump;
an ion exchange resin filter;
an electric conductivity meter;
a circulating flow path including the fuel cell, the circulating pump, the ion exchange resin filter and the electric conductivity meter; and
a judgment part judging whether replacement of the ion exchange resin filter is needed based on a comparison between a predetermined reference electric conductivity and an electric conductivity of water circulating in the circulating flow path that is measured by the electric conductivity meter,
wherein the measurement of the electric conductivity of water circulating in the circulating flow path is scheduled at a predetermined time after a start of water circulation according to an initial electric conductivity of water circulating in the circulating flow path and an estimated time as the electric conductivity of water circulating in the circulating flow path asymptotically approaches a steady state value.
2. The fuel cell system according to claim 1 wherein the circulating flow path is a flow path through which coolant water is circulated to cool the fuel cell.
3. The fuel cell system according to claim 1 wherein the circulation in the flow path is a flow path through which pure water is circulated to humidify a fuel gas and an oxidizing agent which are supplied to the fuel cell.
4. The fuel cell system according to claim 1 wherein the predetermined time is set shorter than a period in which the electric conductivity of water circulating in the circulating flow path reaches a steady-state value.
5. The fuel cell system according to claim 1 wherein the predetermined time is set to be shorter, when the initial electric conductivity is smaller.
6. The fuel cell system according to claim 1 wherein the predetermined reference electric conductivity is an electric conductivity estimated as being measured in a case where ion-exchange efficiency has a normal ion-exchange capacity.
7. The fuel cell system according to claim 1 wherein the predetermined time is set to a period in which the water circulating in the circulating flow path circulates through the circulating flow path for a predetermined number of times.
8. The fuel cell system according to claim 1 further comprising a circulation time calculating part for determining the predetermined time after the start of the water circulation for measuring the electric conductivity of the water circulating in the circulating flow path.
9. A method of controlling a circulating flow path of a fuel cell system having a fuel cell, a circulating water pump, an ion exchange resin filter and an electric conductivity meter in the circulating flow path, comprising:
starting a water circulation;
determining a predetermined time for measuring the electric conductivity of water according to an initial electric conductivity of water circulating in the circulating flow path and an estimated time as the electric conductivity of water circulating in the circulating flow path asymptotically approaches a steady state value; and
judging whether the ion exchange resin filter needs replacement based on a comparison between a predetermined reference and an electric conductivity of water circulating in the circulating flow path as measured by the electric conductivity meter at the predetermined time after the start of water circulation.
10. A fuel cell system comprising:
a circulating means for circulating water in a fuel cell;
an ion-exchange means for exchanging ions in the circulating water;
a circulating flow path including an electric conductivity measuring means, the fuel cell, the circulating means, and the ion-exchange means; and
a judging means judging whether the ion exchange means needs replacement based on a comparison between a predetermined reference and an electric conductivity of water circulating in the circulating flow path as measured by the electric conductivity measuring means,
wherein the measurement of the electric conductivity of water circulating in the circulating flow path is scheduled at a predetermined time after a start of water circulation according to an initial electric conductivity of water circulating in the circulating flow path and an estimated time as the electric conductivity of water circulating in the circulating flow path asymptotically approaches a steady state value.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A lens system, comprising:
a lens unit;
a drive unit for driving the lens unit in an optical axis direction, any of a first maximum current value and a second maximum current value larger than the first maximum current value being capable of being set as a maximum current value for driving in the drive unit;
a detector for detecting a position of the lens unit in the optical axis direction;
a lens operation unit that operates driving of the lens unit in the optical axis direction; and
a computing unit that computes a positional command value for controlling driving of the lens unit based on a signal input from the lens operation unit, and controls the driving of the lens unit,
wherein in the case where a difference between the positional command value and a lens position is larger than a predetermined positional difference threshold and the time during which the second maximum current value is continuously set as the maximum current value for the drive unit has not exceeded a predetermined high-current maximum time, the computing unit sets the second maximum current value as the maximum current value in the drive unit, and, in the case where the time during which the second maximum current value is continuously set as the maximum current value for the drive unit has exceeded the high-current maximum time or the difference between the positional command value and the lens position is not larger than the positional difference threshold, the computing unit sets the first maximum current value as the maximum current value in the drive unit.
2. The lens system according to claim 1, further comprising:
a time setting unit for setting the predetermined high-current maximum time; and
a threshold setting unit for setting the predetermined positional difference threshold.
3. The lens system according to claim 2,
wherein the computing unit computes a speed command value for controlling driving of the lens unit based on the signal input from the lens operation unit,
the threshold setting unit sets a speed difference threshold that is a threshold for switching between the first maximum current value and the second maximum current value set in the drive unit, and
in the case where the difference between the positional command value and the lens position is larger than the positional difference threshold, or a difference between the speed command value and the drive speed is larger than the speed difference threshold, the computing unit sets the second maximum current value as the maximum current value in the drive unit, and, in the case where a time having elapsed since the first maximum current value is set as the maximum current value for the drive unit exceeds the high-current maximum time, or the difference between the positional command value and the lens position is not larger than the positional difference threshold, or the difference between the speed command value and the drive speed is not larger than the speed difference threshold, the computing unit sets the first maximum current value as the maximum current value in the drive unit.
4. The lens system according to claim 2, wherein the high-current maximum time set in the time setting unit is changed in the lens system according to a camera system connected to the lens system.
5. The lens system according to claim 2,
wherein the time setting unit sets an interval time that is a minimum time necessary to elapse since the maximum current value for the drive unit is set from the second maximum current value to the first maximum current value in order to set the maximum current value for the drive unit to the second maximum current value again, and
in the case where the maximum current value of the drive unit is changed from the second maximum current value to the first maximum current value, the value is changeable to the second maximum current value only after the interval time elapses since the change.
6. The lens system according to claim 5, wherein the interval time set in the time setting unit is changeable in the lens system according to a camera system connected to the lens system.
7. The lens system according to claim 2,
wherein the lens unit includes a zoom lens unit and a focus lens unit,
the drive unit includes a zoom drive unit that drives the zoom lens unit in the optical axis direction during zooming and, in the zoom drive unit, any of the first maximum current value and the second maximum current value larger than the first maximum current value is settable as a maximum current value for the driving of the zoom lens unit, and the drive unit further includes a focus drive unit that drives the focus lens unit in the optical axis direction during focusing and, in the focus drive unit, any of a third maximum current value and a fourth maximum current value larger than the third maximum current value is settable as the maximum current value for the driving of the focus lens unit,
the detector includes a zoom position detector that detects a position of the zoom lens unit in the optical axis direction, and a focus position detector that detects a position of the focus lens unit in the optical axis direction,
the lens operation unit includes a zoom operation unit that operates driving of the zoom lens unit in the optical axis direction, and a focus operation unit that operates driving of the focus lens unit in the optical axis direction, and
in the case where the second maximum current value is set as the maximum current value for the zoom drive unit, the fourth maximum current value is not set as the maximum current value for the focus drive unit, and, in the case where the fourth maximum current value is set as a maximum current value for the focus drive unit, the second maximum current value is not set as the maximum current value for the zoom drive unit.
8. The lens system according to claim 7, wherein, in the case where the second maximum current value is set as the maximum current value for the zoom drive unit, the maximum current value for the focus drive unit is changed to the third maximum current value and subsequently the maximum current value for the zoom drive unit is changed to the second maximum current value.
9. An image pickup system, comprising: the lens system according to claim 1; and a camera system that is connected to the lens system and takes a subject image formed by the lens system.