| 摘要 |
PURPOSE:To prevent a noise from generating and the quantity of air flow from abruptly varying without increasing the number of pieces of parts by setting the rotational speed of a convection blower at a value so that it may not become more than a set value or less than the same. CONSTITUTION:An electronic control unit 4 comprises a convection blower changeover circuit 46 for carrying out setting of the lowest rotational speed of a convection blower 303 in accordance with the output of a thermocouple amplifier circuit 42, and carrying out the control of a high rotation zone. The changeover circuit 46 consists of first and second output discriminating circuits 46A and 46B. The convection blower 303 is continuously varied of its power feed quantity in a stepless manner in accordance with the outputs from the thermocouple amplifier circuit 42, a rotational speed indicating circuit 43, and a rotational speed compensating circuit 44, and thus is continuously varied of its rotational speed. Further, since the output of the amplifier circuit 42 is made more than a second set value A2, a relay switch RS2 is connected to a power feed circuit via a resistor R50. Hence, the quantity of power supply is made constant irrespective of the output of the amplifier circuit 42, and the rotational speed is made constant. As a result, the rotational speed can be continuously varied in accordance with the output signal of a thermocouple 402. |
