| 摘要 |
PURPOSE:To make it unnecessary to adjust opening of a damper in accordance with the kind of gas by automatically changing the ratio of increase of air volume to that of electric current supplied to an electromagnetic proportional control valve when the kind of gas has changed. CONSTITUTION:When the kind of gas that is supplied is changed from, for instance, LPG to 4C, a resistor connected in series to the coil of an electromagnetic proportional control valve 13 is made larger in its resistance value by a gas kind changeover circuit 16 and the control range of the current through the coil is changed, for instance, from 15-230mA to 15-45mA. In this case, since the air volume of a fan 7 is directly controlled by a proportional control circuit 15 independently of a gas kind changeover circuit 16, the control range of blast stays the same as with LPG. In this way the ratio of air volume increase of the fan 7 to that current flowing through the electromagnetic proportional control valve 13 changes according to the change in the kind of gas; in other words the ratio of air supply to the gas supply amount is changed properly according to the kind of gas. |
