Patent ID: 7705330

Claim:
An electron beam irradiation device, comprising: an electron beam to irradiate an irradiated object passing through an irradiation chamber while introducing an inert gas into the irradiation chamber; an oxygen concentration detection device to detect oxygen concentration in the irradiation chamber; a flow regulating valve to regulating flow rate of the inert gas introducing in the irradiation chamber; and a valve travel control device to control valve travel of the flow regulating valve on the basis of the oxygen concentration detected by the oxygen concentration detection device so that the flow rate of the inert gas decreases when the oxygen concentration becomes low, wherein the valve travel control device changes the relation between the oxygen concentration and the valve travel of the flow regulating valve corresponding to the speed of the irradiated object so that flow rate of the inert gas for the same oxygen concentration when the speed of the irradiated object is high becomes relatively bigger than the flow rate when the speed of the irradiated object is low, and, the valve travel control device is configured to control the flow regulating valve such that the valve travel is set to a fully-opened state when the speed of the irradiated object exceeds a predetermined value irrespective of the oxygen concentration, that the valve travel is set to a basic valve travel, which is determined according to the oxygen concentration, when the speed of the irradiated object is zero, and that the valve travel is set to an opening degree smaller than that of the fully-opening state and larger than that of the basic valve travel at the same oxygen concentration when the speed of the irradiated object is larger than zero and smaller than the predetermined value.