X-ray apparatus having a control device for preventing damaging X-ray emissions

• US 5,809,106 A
• Filed: 02/28/1997
• Issued: 09/15/1998
• Est. Priority Date: 02/29/1996
• Status: Expired due to Term

• Current Assignee: Toshiba Electron Tubes & Devices Co. Ltd. (Canon Inc.)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Ono, Katsuhiro, Kitade, Koichi
• Primary Examiner(s): Porta, David P.
• Application Number:
  US08/808,857
• Time in Patent Office: 564 Days
• Field of Search: 378/114, 378/117, 378/118, 378/132, 378/133, 378/125, 378/207
• US Class Current: 378/132
• CPC Class Codes: H01J 2235/106 Dynamic pressure bearings, e.g. helical groove type
• CPC Class Codes: H01J 35/104 Fluid bearings
• CPC Class Codes: H05G 1/26 Measuring, controlling or protecting measuring X-ray radiation G01T
• CPC Class Codes: H05G 1/36 Temperature of anode; Brightness of image power electrical temperature regulating in general G05D23/19
• CPC Class Codes: H05G 1/66 Circuit arrangements for X-ray tubes with target movable relatively to the anode

Abstract

In an X-ray tube with a hydrodynamic slide bearing, an electron beam is caused to strike the focal point track area F on its rotary anode, which then emits X rays. An X-ray emission control device that sets the conditions for emitting the X rays stores as data the rises and drops in the temperature at the electron beam incident point and the other part on the focal point track surface of the anode. On the basis of the data, the input permission or inhibition conditions for the X-ray tube at every moment are calculated and the resulting conditions are displayed on a display unit. As a result, it is possible to perform a computing process in advance to determine whether or not X rays can be emitted under specific conditions without a permitting the rotary anode in the X-ray tube with a hydrodynamic slide bearing to melt and then display the results, thereby enabling a safe, efficient photographing control.

Claims

1. An X-ray apparatus comprising:

an X-ray tube including;

a rotary anode having an X-ray emitting target;

a cathode that emits an electron beam toward said target of the rotary anode

a rotary structure to which the anode is secured;

a stationary structure that engages concentrically with the rotary structure; and

a hydrodynamic slide bearing which has helical grooves in an engaging section of the rotary structure and stationary structure and to which a liquid-metal lubricant with a specific melting point is applied;

a stator arranged around an outside periphery of the X-ray tube;

a rotational driving power supply device that supplies a rotational driving electric power to the stator;

a X-ray tube power supply device that causes an electron beam to strike an focal point track area on the rotary anode in the X-ray tube; and

an X-ray emission control device that controls an operation of the X-ray tube power supply device and sets conditions of X-ray emission, wherein

said X-ray emission control device includes;

first prediction means that predicts how a temperature at an electron beam incident point on said focal point track area and an average temperature of said focal point track area rise with time for the anode voltage, electron beam current and the electron beam incidence duration in a case where an electron beam is caused to strike the focal point track area on the rotary anode in the X-ray tube;

second prediction means that predicts how the average temperature of the focal point track area falls with time from the reached average temperature of the focal point track area by heat dissipation in a case where the electron beam incidence is stopped; and

notifying means for notifying at every moment input permission conditions to the X-ray tube obtained on the basis of prediction results from said first and second prediction means.

2. An X-ray apparatus according to claim 1, wherein the rotary anode in the X-ray tube is composed of a base section made of a high melting-point metal and a target section formed on said base section.

3. An X-ray apparatus according to claim 2, wherein said base section and target section are made of the same high melting-point metal.

4. An X-ray apparatus according to claim 1, wherein the notifying means has a touching switch that notifying input permission conditions and when said touching switch that notifies said input permission conditions is selected, the control device is driven so that X rays may be emitted from the X-ray tube under the input conditions.

5. An X-ray apparatus according to claim 1, further comprising a sensing unit that senses the rotational rate of the anode, wherein the control device includes means that calculates input permission conditions, taking into account the data corresponding to the rotational rate of the anode sensed by the sensing unit.

6. An X-ray apparatus according to claim 1, further comprising control means that controls the rotational rate of the anode, when a condition of X-ray emission is changed.

7. An X-ray apparatus according to claim 1, wherein the rotational rate of the anode in the X-ray tube at the time of X-ray emission is set in the range from 40 to 100 revolutions per second.

8. An X-ray apparatus according to claim 1, wherein the X-ray tube and an X-ray sensor are provided on a gantry rotating section arranged around the place in which a subject to be photographed is positioned, and the gantry rotating section rotates around the subject in taking X-ray photographs, thereby taking photographing tomographic images.