JPH01162199A - Electron beam irradiation equipment - Google Patents

Abstract

PURPOSE:To get a unified electron beam irradiation for a unit area, by arranging a control electrode between a filament and an accelerating electrode, and supplying a control voltage to the control electrode to change an intensity of the electron beam. CONSTITUTION:A control electrode 13 is arranged between a filament 12 and accelerating electrodes 14a-14n. In case that a transporting speed of a matter to be irradiated is changed, a deviation between an actual electric current of a detecting tube from a detecting pass of a tube current 27 and a directing tube current from a directing pass of tube current 26 which is to be determined by the transporting speed of the irradiated matter, is detected by a current controlling circuit 23 to feed a voltage controlling circuit 18. A voltage of an electrode 13 is feedback-controlled so as to coincide the detecting tube current with the directing tube current. Therewith, the actual tube current is precisely followed by the tube current decided by the transporting speed. With this procedure, an electron irradiation for a unit area is unified.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an electron beam irradiation device for irradiating electron beams onto, for example, raw rubber, electric wire sheathing, etc. This invention relates to an electron beam irradiation device that irradiates according to the conditions.

(Prior Art) This type of conventional electron beam irradiation device includes, for example, a filament for electron emission and an acceleration electrode for accelerating electrons provided at the neck of a vacuum container, and a metal foil film provided on the front surface of a cone. an electron beam irradiation tube having a deflection coil provided outside the neck portion of the vacuum container between the accelerating electrode and the metal foil film; a filament power source and a DC high voltage power source for operating the electron beam irradiation tube; In order to correct the influence of the moving speed of the irradiated object, a control circuit is added to the electron beam irradiation device comprising a circuit, which controls the voltage of the filament power source according to the conveyance speed of a conveyance device that moves the irradiated object. There is something.

This electron beam irradiation device operates as follows.

That is, when a predetermined voltage is applied to the filament from a filament power supply circuit, thermoelectrons are emitted toward the accelerating electrode. These thermoelectrons are accelerated when a predetermined voltage is applied from a DC high-voltage power supply circuit to multiple accelerating electrodes via a voltage dividing resistor, and are further deflected by a deflection coil to irradiate the metal foil film of the electron beam irradiation tube. The object to be irradiated is irradiated with an electron beam through the window.

In this case, if the accelerating voltage (DC high voltage) is constant, the current flowing through the electron beam irradiation tube (hereinafter referred to as tube current) is also constant. Here, in order to change the tube current, there are two methods: changing the high voltage applied to the filament and changing the filament temperature, but the former is generally not used because the equipment is expensive because it controls the high voltage. The latter has been adopted.

By this method, the tube current can be changed to a desired value by changing the filament heating voltage. This filament heating voltage is applied when the object to be irradiated is transported by a transport device such as a belt conveyor.
It was changed according to changes in conveyance speed. That is, the filament heating voltage was set to increase as the transport speed increased.

(Problems to be Solved by the Invention) However, in this type of conventional electron beam irradiation device, the filament temperature is changed by changing the filament heating voltage and the tube current is changed, so the filament heating voltage is changed. Even if a sudden change is made in a stepwise manner, the thermal constant determined by the physical factors of the filament causes a delay, which is determined by the thermal time constant due to the physical factors of the filament, before the tube current changes correspondingly. There was a problem with putting it away. This time delay means that, for example, when the filament heating voltage is changed from IOV to 15V, it takes about 1 to 2 minutes for the tube current to change from 100mA to 300mA, and in reality, it is almost impossible to follow the change. . Therefore, in such cases, the amount of electron beam irradiation on the irradiated object becomes uneven, and in extreme cases such as an emergency stop of the transport device, the irradiated object becomes a defective product due to the excessive irradiation amount and must be discarded after removal. It had the disadvantage of being

Specific examples of such drawbacks will be described below.

First, in electron beam irradiation to improve the heat resistance of electric wires and the mechanical abrasion resistance of vinyl sheets, the irradiated object is a continuous object, so the conveyance speed on the production line tends to fluctuate (although it must be kept constant at all times). For example, in the case of vinyl-based materials used as insulation coatings for electric wires, the outer diameter of the base material of the insulation material applied to the core wire decreases as the length of the wire increases. Because it is necessary to constantly change the conveyance speed of the production line based on the nature of the manufacturing method, the outer diameter of the base material of the insulation material is continuously measured, and the wire take-up speed, that is, the conveyance speed, is adjusted according to the measured value. Feedback control is used to keep the finished outer diameter of the wire constant.For this reason, there was a problem that conventional electron beam irradiation equipment could not achieve the intended purpose.Furthermore, it was used as a tire component. In the case of coachite cord, a device called a calendar is used to form a coachite cord by laminating rubber sheets on both sides of organic fibers, and when the coachite cord is wound up with a winding device, If an electron beam irradiation device is installed in the front stage of the conveyor, for example, if an abnormality occurs in the calendar due to a problem with the rubber sheet supply device and the conveyance device suddenly decelerates or comes to an emergency stop, the electron beam will be irradiated when the conveyance device is stopped. There was a problem in that the parts that were exposed to radiation became defective due to excessive irradiation and were disposed of.

Furthermore, the above-mentioned problems occur not only due to fluctuations in conveyance speed, but also when irradiation with electron beams is carried out while conveying objects to be irradiated that require various irradiation doses on a belt. .

The purpose of the present invention is to control the amount of electron beam irradiation per unit area to a constant value by changing the tube current of the electron beam irradiation tube according to the transport speed of the object to be irradiated, and to adjust the amount of irradiation according to the object to be irradiated. An object of the present invention is to provide an electron beam irradiation device that eliminates the drawbacks of conventional devices by changing the electron beam intensity at an extremely fast response speed in order to change the electron beam intensity.

(Means and effects for solving the problem) The electron beam irradiation device of the present invention includes a filament that emits electrons and an accelerating electrode that accelerates the electrons in the neck of a vacuum container.
In an electron beam irradiation device in which a metal foil film is provided on the front surface of the cone part, and a deflection coil for deflecting the electron beam is provided on the outside of the vacuum container between the accelerating electrode and the metal foil film, between the filament and the accelerating electrode. A control electrode is placed at the top of the electron beam, and a control voltage is applied to the control electrode to change the intensity of the electron beam. This electron beam irradiation device controls the voltage applied to the control electrode so that the tube current follows changes in the speed of the object to be irradiated, such as the transport device, with very high precision with almost no time delay. Despite fluctuations, the amount of electron beam irradiation per unit area can be maintained at a constant value, and therefore uniform products can be manufactured. Furthermore, since there is almost no occurrence of defective products as described above, manufacturing costs can also be reduced.

(Example) FIG. 1 is a diagrammatic cross-sectional view showing the configuration of an example of an electron beam irradiation apparatus according to the present invention. A filament 12 is provided at the rear end of the neck portion of the vacuum vessel 11, and a control electrode 13 is provided in front of the filament 12.
, a plurality of accelerating electrodes 14a.

14b, ----, 14n are provided. Usually, the number of accelerating electrodes is 7 to 8. The front opening of the cone portion of the vacuum container 11 is closed with a metal foil film 15 having a thickness of 20 μm, for example. Furthermore, a deflection coil 16 is wound around the outside of the vacuum container 11 between the acceleration electrodes 14a to 14n and the metal foil film 15. 1st
In the figure, the one in which the control electrode 13 between the filament 12 and the accelerating electrode 14a is removed is the same as the conventional electron beam irradiation device.

The filament 12 is connected to a filament power supply circuit 17 that applies, for example, AClooV, the control electrode 13 is connected to a voltage control circuit 18, the voltage control circuit 18 is connected to a current control circuit 23, and the deflection coil 16 is normally 2 to 5 KHz. is connected to a deflection circuit 19 having a deflection frequency of . Further, a DC high voltage power supply circuit 20 is provided, and a voltage obtained by dividing a high voltage of 300 to 750 kV by a resistor 21 is applied to the accelerating electrodes 14a to 14n.
to be applied. The vacuum container 11 is grounded as usual. The current control circuit 23 is connected to the DC high voltage power supply circuit 2o and the grounding resistor 24.
Tube current detection path 27 and conveyance device 2 to the junction point with
It is connected to the tube current command path 26 to the output end of No. 5. Further, in FIG. 1, reference numeral 22 is a member to which the electron flow is irradiated, and in this example, it is a rubber sheet for Isina liner that is continuously supplied from a calender roll.

Now, for example, AClooV is applied to the filament from the filament power supply circuit 17, and the accelerating electrodes 14a, 14b
, ----, resistor 2 from the DC high voltage power supply circuit 20 to 14n.
When a high voltage of, for example, 300 to 750 kV is applied as a partial voltage through the filament 1, the thermionic electrons emitted from the filament are accelerated and further deflected by the deflection coil 16, and are sent from the irradiation window of the metal foil film onto the rubber sheet. is irradiated as an electron beam. The tube current value at this time ■. is expressed by the following formula (I).

Here, W: Scanning width of the irradiated object (cm) V: Transport speed of the irradiated object (m/sec) M: Electron beam irradiation amount (Mrad) K: Constant determined by the electron beam acceleration voltage For example, in the case of 500 kV (7) , K=0.34.

Since W and M are constants that are determined once the object to be irradiated is specified, the tube current value I0 is directly proportional to the transport speed of the object to be irradiated. Here, when the control electrode voltage vc is set to a negative potential with respect to the filament voltage vf, the tube current decreases. This relationship is shown in FIG. 2, when the control electrode voltage is vc-vf, the tube current is .

= 300 (mA), VC = V, -500 (V)
When ■. The relationship is such that =0.

Here, the thermoelectrons heated to a high temperature by the filament have a positive potential with respect to the filament voltage f.The first accelerating electrode 1
The number of electrons given kinetic energy and ejected by the negative high voltage applied to 4a is continuously reduced by making the filament surface electric field negative by the control electrode voltage vc, which has a negative potential with respect to the filament voltage vf. Suppression control can be performed to any tube current value. Therefore, when the transport speed of the irradiated object changes, the deviation between the actual detected tube current from the tube current detection path 27 and the command tube current from the tube current command path 26 determined by the transport speed of the irradiated object is determined by the current. It is detected by the control circuit 23 and inputted to the voltage control circuit 18, and the control electrode voltage v is adjusted so that the detection tube current matches the command tube current.
By feedback controlling o, the tube current ■ is determined by the actual tube current and conveyance speed. , and can be tracked with extremely high precision (response speed of several millimeters 5 ec) because the time delay (maximum 1 to 2 minutes) caused by the thermal time constant of the filament, which is the case with conventional devices, can be removed. The amount of electron beam irradiation can be made uniform.

It goes without saying that the present invention is not limited to the above-mentioned examples, but can be modified in many ways.

For example, in the above example, the control electrode voltage was changed according to the transport speed, but it is also possible to change the control electrode voltage in a pulsed manner to selectively irradiate only a predetermined range in the width direction of the irradiated object. You can also. Further, the present invention allows continuous electron beam irradiation by inputting a desired electron beam irradiation amount corresponding to each object, even when different types of objects to be irradiated coexist on the transport device.

(Effects of the Invention) As explained above, according to the present invention, it is possible to make the tube current follow the speed change of the conveying device with extremely high precision and to make the electron beam irradiation amount per unit area uniform, thereby making it possible to make the electron beam irradiation amount per unit area uniform. It is possible to improve the quality of products and reduce costs by eliminating the occurrence of defective products.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an embodiment of the electron beam irradiation device according to the present invention, and FIG. 2 is a diagram showing the tube current. and the filament voltage ■. 3 is a graph showing the relationship between the potential difference of the control electrode voltage vc and the control electrode voltage vc. 11... Vacuum container 12... Filament 1
3... Control electrodes 14a to 14n... Accelerating electrode 15... Metal foil film 16... Deflection coil Patent applicant Brideston Co., Ltd. Figure 1 Figure 2 υ 500 Vf (V)

Claims (1)

[Claims] 1. A filament that emits electrons and an accelerating electrode that accelerates the electrons are provided at the neck of the vacuum container, a metal foil film is provided on the front surface of the cone, and the space between the accelerating electrode and the metal foil film is In an electron beam irradiation device provided with a deflection coil for deflecting an electron beam on the outside, a control electrode is disposed between the filament and the accelerating electrode, and a control voltage is applied to the control electrode to change the electron beam intensity. An electron beam irradiation device characterized by comprising: