X-ray generating apparatus

Abstract

 An X-ray generating apparatus includes a rotatable anti-cathode having a main portion arranged to generate an X-ray upon impingement thereon of thermoelectrons, a casing having a hermetically sealed chamber for maintaining the surroundings of the main portion of anti-cathode in a vacuum atmosphere, and an electric motor for rotatively driving the anti-cathode. The electric motor comprises a rotor functioning as a rotating force output portion and a stator for rotating the rotor, the rotor being fixed to a portion of the anti-cathode within the chamber and being housed within the chamber.

Description

[0001] The present invention relates to an X-ray generating apparatus and, more particularly, to an X-ray generating apparatus of the type which includes a rotatable anti-cathode. Description of the Prior Art:

[0002] An X-ray generating apparatus of this type typically comprises a rotatable anti-cathode housed in a sealed casing, an electric motor for rotating the anti-cathode and an electron gun for emitting thermoelectrons toward the anti-cathode which generates the X-ray upon impingement of the thermoelectrons. Fig. 1 illustrates a conventional rotatable anti-cathode type X-ray generating apparatus, in which reference numeral 1 denotes a rotatable anti-cathode, numeral 2 is a casing and numeral 3 is an electric motor. The rotatable anti-cathode 1 has a hollow larger-diametered main portion 1a which is adapted to generate X-ray 5 upon impingement thereon of thermoelectrons e emitted from an electron gun 4, and a hollow cylindrical shaft portion 1b which is contiguous to the main portion 1a. Defined within the anti-cathode 1 is a refrigerant circulating path 7 by a partition member 6 which is substantially analogous to and concentric with the anti-cathode 1. The refrigerant circulating path 7 comprises a refrigerant supply path 7a defined between the partition member 6 and the anti-cathode 1, and a refrigerant discharge path 7b formed inside the partition member 6. Refrigerant flows through the path 7 as indicated by arrows .

[0003] The casing 2 includes a hermetically sealed portion 2a which maintains the surroundings of the main portion 1a and the electron gun 4 in a vacuum atmosphere, and a support portion 2b for rotatably supporting the anti-cathode 1 through bearings 8 which is fitted on the shaft portion 1b. A window 2c is formed in the wall of the hermetically sealed portion 2a for allowing the X-ray 5 emitted from the main portion 1a to penetrate the casing 2. A rear end (the right end in the figure) of the support portion 2b is connected to an end portion of the partition member 7 in a liquid-tight manner. Further, formed in a position close to the rear end of the support portion 2b is an inlet 2d which is in communication with the refrigerant supply path 7a as shown in the figure.

[0004] The electric motor 3 drives the anti-cathode 1 rotatively and includes a rotor 3a which functions as a rotational force output portion and is fixed to the shaft portion 1b, and a stator 3b fixed to the support portion 2b of the casing so as to surround the rotor 3a. An air-tight seal 9a is provided around the shaft portion 1b in order to maintain the vacuum of the sealed portion 2a, while a liquid-tight seal 9b is fitted on the rear end of shaft portion 1b to prevent the refrigerant from flowing into the annular space outside of the shaft portion 1b where the bearings 8 and motor 3 are located.

[0005] In the conventional X-ray generating apparatus as discussed above, however, the shaft portion 1b of anti-cathode 1 must have a length sufficient to permit the mount of the motor 3 therearound, thus making it difficult to reduce an overall size and weight of the cathode 1. Moreover, the mounting space for the motor 3 around the shaft 1b is limited. This practically prevents an increase of torque of the motor 3 by enlarging a diameter of the rotor 3a which is positioned inside of the stator 3b, though a higher torque is often desired for improving the cooling efficiency or for using the anti-cathode 1 of large size and/or heavy weight.

[0006] The present invention has been accomplished in view of the above, and it is an object of the present invention to provide an X-ray generating apparatus which may reduce a size and weight of an anti-cathode.

[0007] Another object of the invention is to provide an X-ray generating apparatus which enables to increase a torque of electric motor for driving.

[0008] According to the present invention, an X-ray generating apparatus includes a rotatable anti-cathode having a main portion adapted to generate an X-ray upon impingement thereon of thermoelectrons, a casing having a hermetically sealed chamber for maintaining the surroundings of the main portion of anti-cathode in a vacuum atmosphere, and an electric motor for rotatively driving the anti-cathode. The electric motor comprises a rotor functioning as a rotating force output portion and a stator for rotating the rotor, the rotor being fixed to a portion of the anti-cathode within the hermetically sealed chamber of the casing and being housed within the hermetically sealed chamber.

[0009] The arrangement of the invention makes it possible to reduce a size and weight of the anti-cathode by shortening a shaft portion thereof because it is no longer necessary to provide a mounting space for the electric motor around the shaft portion.

[0010] In an embodiment of the invention, the stator of the electric motor is disposed outside the hermetically sealed chamber of the casing. It may be understood that this facilitates a maintenance work of the motor.

[0011] Preferably, the rotor of the electric motor is positioned outside the stator. Such an arrangement increases a diameter and moment of inertia of the rotor, thus enabling a stable rotation of the anti-cathode as well as a resultant increase of torque of the motor without enlargement of stator.

[0012] Other objects, features and advantages of the invention will be apparent from the following description of preferred embodiments thereof when taken in conjunction with accompanying drawings.

Fig. 1 is a longitudinally sectional view schematically illustrating a prior art X-ray generating apparatus;

Fig. 2 is also a longitudinally sectional view schematically illustrating an X-ray generating apparatus according to an embodiment of the present invention;

Fig. 3 is a view similar to Fig. 2 showing an X-ray generating apparatus according to another embodiment of the present invention; and

Fig. 4 is also a similar view of an X-ray generating apparatus according to a further embodiment of the present invention.

[0013] Referring first to Fig. 2 of the drawings, there is illustrated a principal portion of an X-ray generating apparatus according to an embodiment of the present invention, which generally comprises a rotatable anti-cathode 11, a casing 12 for the anti-cathode, an electric motor 13 and a lead wire 14 for supply of electric power to the motor 13.

[0014] The anti-cathode 11 has a hollow larger-diametered main portion 11a which is adapted to generate X-ray upon impingement thereon of thermoelectrons emitted from an electron gun (not shown). A hollow cylindrical shaft portion 11b of the anti-cathode 11 extends rearwardly, i.e. to the right in the figure, from the main portion 11a. As in the prior art, a partition member (not shown) is inserted into the anti-cathode 11 to define a circulating path of refrigerant for cooling the main portion 11a.

[0015] The casing 12 includes a hermetically sealed chamber 12a for maintaining the surroundings of the main portion 11a and electron gun (not shown) in a vacuum atmosphere, and a support portion 12b connected to the main portion 12a to rotatably support the anti-cathode 11. Though not shown, the support portion 12b supports the shaft portion 11b of anti-cathode 11 through a bearing fitted on the shaft portion 11b. An air-tight seal 15 is provided between the support portion 12b and the hermetically sealed chamber 12a in order to maintain the vacuum of sealed chamber 12a. Further, as in the prior art, the support portion 12b is formed with a refrigerant inlet and a discharge port which are in communication with the circulating path formed in the anti-cathode 11.

[0016] The electric motor 13 in the illustrated embodiment is a brushless DC motor for rotatively driving the anti-cathode 11, and comprises a rotor 13a which functions as a rotating force output portion and a stator 13b for rotating the rotor 13a, the rotor being positioned outside the stator so as to surround the latter. The rotor 13a is fixed to the main portion 11a of the anti-cathode 11, while the stator 13b is mounted on the outer surface of the hermetically sealed chamber 12a of the casing 12. A wall, indicated at 12c, of the chamber 12a is recessed to accommodate the stator 13b in a matched relation with the rotor 13a.

[0017] In the above X-ray generating apparatus, since the rotor 13a is fixed to the main portion 12a of anti-cathode within the chamber 12a, it is no longer necessary to provide a mounting space for the motor 13 around the shaft portion 11b. This means that a length of the shaft portion 11b can be reduced as compared with the prior art apparatus, resulting in a miniaturization and lightening of the entire anti-cathode. Additionally, since in the illustrated example the rotor 13a is positioned outside of the stator 13b, the rotor 13a has an increased diameter and moment of inertia when compared with the prior art. Accordingly, the rotational movement of rotor 13a is stabilized and a resultant torque is increased without enlarging the stator 13b. It is however to be noted here that rotor 13a may be positioned inside the stator 13b as in the prior art, in case only the miniaturization of the apparatus is required. Further, in the illustrated example the stator 13b of the motor 13 is disposed outside the hermetically sealed chamber 12a, so that the maintenance of the stator 13b is facilitated with a possibility of improvement in the maintenance of the entire apparatus.

[0018] Although in the above embodiment the stator 13b of the motor 13 is mounted to the exterior of the hermetically sealed chamber 12a, it may be disposed within the chamber 12a as shown in Fig. 3 where the same numerals are used to indicate the same or corresponding elements in Fig. 2. The wall 12c of chamber 12a is not recessed to permit the location of stator 13b inside the rotor 13a within the chamber 12a. The lead wire 14 penetrates the wall 12c in an air-tight manner.

[0019] In an embodiment shown in Fig. 4, the stator 13a is fixed to the main portion 11a of anti-cathode 11 at the side facing the shaft portion 11b and the stator 13b is disposed between the rotor 13a and the shaft portion 11b. An annular extension 12d is provided to support the stator 13a in the chamber 12a. In Fig. 4 the same reference numerals are used to indicate the same or corresponding elements in Fig. 2.

Claims

1. An X-ray generating apparatus comprising a rotatable anti-cathode having a main portion adapted to generate an X-ray upon impingement thereon of thermoelectrons, a casing having a hermetically sealed chamber for maintaining the surroundings of said main portion of said anti-cathode in a vacuum atmosphere, and an electric motor for rotatively driving said anti-cathode, said electric motor comprising a rotor functioning as a rotating force output portion and a stator for rotating said rotor, said rotor being fixed to a portion of said anti-cathode within said chamber and being housed within said chamber.

2. An X-ray generating apparatus according to claim 1, wherein said stator of said electric motor is disposed outside said chamber of said casing.

3. An X-ray generating apparatus according to claim 1, wherein said rotor of said electric motor is positioned outside said stator.

4. An X-ray generating apparatus comprising:
   an anti-cathode having a main portion adapted to generate an X-ray upon impingement of thereon of thermoelectrons and a shaft portion integral with said main portion;
   a casing having a hermetically sealed vacuum chamber in which at least said main portion of said anti-cathode is housed, and a support portion for rotatably supporting said shaft portion of said anti-cathode; and
   an electric motor for rotatively driving said anti-cathode, said motor including a stator and a rotor fixed to said main portion of said anti-cathode, and at least said rotor being housed within said chamber.

5. An X-ray generating apparatus according to claim 4, wherein said stator is secured to said casing outside of said chamber.

6. An X-ray generating apparatus according to claim 5, wherein a wall of said casing defining said chamber is recessed to accommodate said stator in a matched relation with said rotor.

7. An X-ray generating apparatus according to claim 4, wherein said stator is disposed within said chamber.

8. An X-ray generating apparatus according to claim 4, wherein said rotor is fixed to said main portion at a side remote from said shaft portion.

9. An X-ray generating apparatus according to claim 4, wherein said rotor is fixed to said main portion at a side facing said shaft portion.

10. An X-ray generating apparatus according to claim 4, wherein said rotor is positioned outside of said stator to surround said stator.

Drawing