| 摘要 |
<P>PROBLEM TO BE SOLVED: To eliminate the use of an expensive clutch brake for a shutoff valve to hold an valve opening condition, and to prevent the occurrence of water hammering when closing the valve. <P>SOLUTION: The shutoff valve is configured such that a spring for biasing the valve in a direction to close the valve is provided on a transmission mechanism via which an output shaft connected with the valve is connected to a brushed motor 20, and the shutoff valve includes a constant current circuit 23 for driving the motor 20 and a constant current adjusting circuit 24. When the valve is opened with the spring being twisted, the current set by the constant current adjusting circuit 24 is supplied from the constant current circuit 23 to the motor 20 when the valve is opened to hold a valve opening condition. Thus, the set current can be supplied regardless of the voltage fluctuation, power loss and stress to the mechanism part can be reduced and there is no need to use an expensive clutch brake. A short circuit 36 is arranged parallel to the motor 20 via a switcher 40 and the motor 20 is used as a brake by shortening when an emergency arises (when the valve is closed). Thereby, the abrupt closing operation of the valve 5 is prevented and water hammering is prevented. <P>COPYRIGHT: (C)2012,JPO&INPIT |
