JPS6193536A - Cathode structure of x-ray tube - Google Patents

Abstract

PURPOSE:To prevent generation of poor withstand voltage, with an ignition-at- exhaust filament not separated in case of being broken, by preparing a cover having an opening, at the outlet of a focusing slot in which the ignition-at- exhaust filament is housed. CONSTITUTION:While a focusing electrode 1 with a V-shaped top surface is provided with focusing slots 2 and 3, with a coiled ignition-at-exhaust filament 4 being housed in the slot 2 with a coiled operation filament 4 in the slot 3, to form a cathode body of a X-ray tube, a cover 13 having an opening 12 smaller than a filament coil in diameter is prepared to cover the outlet of the focusing slot 2. Therefore, when the anode target is heated to high temperature by electron impact for degassing, the ignition-at-exhaust filament 4 can be prevented from separating even in case of being carbonized and partly broken, and then the resultant poorness of withstand voltage can be prevented beforehand.

Description

[Detailed description of the invention] [Technical field of invention] This invention relates to a cathode structure for an X-ray tube.

[Background technology and its problems]

Conventionally, in a cathode structure in a rotating anode-type X-ray tube, the top surface of a cylindrical focusing electrode is formed in a V-shape, and focusing grooves are formed on both slopes, respectively. A coiled exhaust ignition filament is provided in one of the focusing grooves, and a coiled operating filament is provided in the other focusing groove.

By the way, for example, in a rotating anode X-ray tube where the anode target is made of graphite, harmful substances such as CO1CO2 generated from the graphite are generated during exhaust, especially during the process of heating the target to high temperature by electron bombardment to emit gas. The exhaust ignition filament made of tungsten is significantly carbonized and becomes brittle due to the gas. If carbonization is severe, part of the ignition filament at the exhaust point may break due to shock during movement or handling after exhaustion, and the filament may become loose inside the X-ray tube, causing a voltage withstand failure and rendering the product unusable. There may be cases where this happens. This carbonization occurs due to the relationship between gas partial pressure and filament temperature, if ignition continues during exhaust gas.
It is especially noticeable at both ends of the filament. Therefore, the filament is likely to break at both ends. In particular, in a rotating anode type X-ray tube, there is a limit to the extent to which the partial pressure of gases such as CO1CO□ can be lowered by extending the exhaust time due to limitations in the heat resistance of the rotating mechanism, so this phenomenon becomes a problem.

[Purpose of the invention]

The purpose of this invention is to provide a deviation prevention member to prevent the broken filament from deviating from the focusing groove even if the exhaust ignition filament breaks, thereby preventing voltage withstand failure due to filament breakage. An object of the present invention is to provide a cathode structure for a wire tube.

[Summary of the invention]

The present invention is a cathode structure for an X-ray tube in which a deviation prevention member is provided, such as a cover having an opening at the outlet of a focusing groove that accommodates an ignition filament at the exhaust point.

[Embodiments of the invention]

The cathode structure of the X-ray tube according to the present invention is constructed as shown in FIG. 1, in which the top surface of a cylindrical focusing electrode 1 is formed in a V-shape, and focusing grooves 2 are formed on both slopes, respectively. 3 is formed. A coiled exhaust ignition filament 4 is provided in one of the focusing grooves 2, and both end legs of the filament 4 are fixed to a support rod 5. This support opening 5 is fixed to the focusing electrode 1 via a cylindrical body 6 and a ceramic body 7. A coiled operating filament 8 is provided in the other focusing groove 3, and both end legs of the filament 8 are fixed to a support rod 9.

This support rod 9 is fixed to the focusing electrode 1 via a cylindrical body 10 and a ceramic body 11.

Further, in the present invention, the focusing groove 2 in which the exhaust ignition filament 4 is accommodated is provided with a cover 13 having an opening 12 as shown in FIG. 2, for example, as a filament deviation prevention member so as to close the outlet. ing. The opening 12 in each of these holes 13 is formed to have a size smaller than the size of the exhaust ignition filament 4, that is, the coil diameter. In short, it is sufficient that the exhaust ignition filament 4 does not deviate from the focusing groove 2 in which it is accommodated.

〔Effect of the invention〕

According to this invention, since the focusing groove 2 in which the exhaust point ignition filament 4 is housed is provided with a filament deviation prevention member, for example, a cover 13 having an opening 12 so as to block the outlet, even if the exhaust point ignition Even if the filament 4 becomes brittle due to carbonization and its ends are broken, it will not come loose from the focusing groove into the X-ray tube, so the withstand voltage of the X-ray tube will not be adversely affected and it can be used without any abnormality. I can do it.

[Modified example of the invention]

In the case of FIGS. 3 and 4, a grid line 17 with an interval smaller than the filament size is provided in the opening 16 of the cover 15 to prevent the ignition filament 4 from slipping out at the exhaust point. In this case, the size of the opening 16 may be larger than that of the filament 4 for ignition at the exhaust point, and the grid lines 17 are formed in the cover 15 at a coarse pitch within the range that the filament 4 for ignition at the exhaust point does not come off.
It is welded on the back side.

In the case of FIG. 5, the first operating filament 18 is placed in the focusing grooves 2 and 3 provided on the side slopes of the V-shaped top surface of the focusing electrode 1, respectively.
and a second operating filament 19, a focusing groove 20 is further provided in the center of the top surface, and an exhaust ignition filament 4 is provided within this focusing groove 20. As is clear from FIG. 6, a rod-shaped body 21 constituting a filament deviation prevention member is inserted inside the exhaust ignition filament 4.

The rod-shaped body 21 has leg portions at both ends fixed to support rods, but is cut out near the center and is electrically isolated.

In this case as well, the same effects as in the above embodiment can be obtained. That is, even if the exhaust point ignition filament 4 breaks, the exhaust point ignition filament 4 is substantially supported by the support rod 5, so it will not deviate from the focusing groove, and abnormal noises caused by the broken filament will not occur. It will not occur or be broken and fragmented again.

Further, in FIG. 7, an insulating pipe 22 made of ceramic is fitted around the outer periphery of the rod-shaped body 2, so that it is safe even if a part of it comes into contact with the ignition filament 4 at the exhaust stage.

FIG. 8 shows a modification of the rod-shaped body 23, in which both ends are welded to the legs 4a of the exhaust ignition filament 4, respectively. If the filament is integrally connected as a component, it can be easily assembled by simply welding the filament leg to the support rod.

Note that this invention can be applied to the SEIZO type, in which a plurality of sets of filaments and focusing grooves are provided, and at least one set of them is ignited for target electron impact during exhaust.

Further, the groove in which the exhaust-point ignition filament is provided is not necessarily intended for focusing the electron beam, but may simply be a groove for accommodating the filament, and is considered to be one of the focusing grooves in this application.

[Brief explanation of drawings]

1 is a sectional view showing a cathode structure of an X-ray tube according to the present invention, FIG. 2 is an enlarged perspective view of the cover in FIG. 1, and FIG. 3 is a sectional view showing a modification of the invention. FIG. 4 is an enlarged perspective view of the vicinity of the cover in FIG. 3, FIG. 5 is a cross-sectional view of another modification, and FIG. 6 is a partially enlarged view of the vicinity of the rod-shaped body in FIG. front view including cross section;
FIGS. 7 and 8 are cross-sectional views showing modified examples of the rod-shaped body. DESCRIPTION OF SYMBOLS 1... Focusing electrode, 2, 3... Focusing groove, 4... Exhaust ignition filament, 8... Operating filament. DESCRIPTION OF SYMBOLS 12... Opening, 13... Cover, 17... Grid wire, 21... Rod-shaped body, 22... Insulating pipe. Representative Patent Attorney Takehiko Suzue Figure 1 Figure 2

Claims (5)

[Claims] (1) Cathode structure of an X-ray tube in which a plurality of focusing grooves are formed in the focusing electrode, an exhaust ignition filament is provided in at least one focusing groove, and an operating filament is provided in the other focusing groove. A cathode structure for an X-ray tube, characterized in that a deviation prevention member is provided to prevent the filament from deviating from the focusing groove when the exhaust ignition filament is broken. (2) The deviation prevention member comprises a cover having an opening provided at the outlet of the focusing groove in which the exhaust point ignition filament is housed, and the opening has an opening size smaller than the size of the exhaust point ignition filament. A cathode structure for an X-ray tube according to claim 1. (3) The deviation prevention member comprises a cover having an opening provided at the outlet of the focusing groove in which the exhaust point ignition filament is housed, and a grid line is attached to the opening. The cathode structure of the X-ray tube according to item 1. (4) The cathode assembly for an X-ray tube according to claim 1, wherein the deviation prevention member is a rod-shaped body inserted inside the exhaust ignition filament. (5) The cathode structure for an X-ray tube according to claim 4, wherein the rod-shaped body has an insulating pipe fitted around its outer periphery.