Abstract:
The present invention relates to an X-ray apparatus comprising an electron radiation source which generates an electron to an anode, a shaft which rotatably supports the anode, a stator which generates a force to rotate a rotor shaft, an enclosure which maintains at least the anode, electron radiation source and rotor shaft in vacuum, and a housing which contains a cooling medium around the enclosure. The X-ray apparatus is characterized in that an electric wire material to supply power to the electron radiation source and stator, or a connector used for connection with the electric wire material is molded by a material having an electrical insulating property.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This is a Continuation Application of PCT Application No. PCT/JP2004/015385, filed Oct. 18, 2004, which was published under PCT Article 21(2) in Japanese.  
         [0002]     This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2003-358273, filed Oct. 17, 2003, the entire contents of which are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0003]     1. Field of the Invention  
         [0004]     The present invention relates to an X-ray apparatus, and a rotary anode X-ray tube applied to an X-ray apparatus.  
         [0005]     2. Description of the Related Art  
         [0006]     An X-ray apparatus using a rotary anode X-ray tube is composed of a rotary anode X-ray tube main body which contains a rotatably supported anode target in a vacuum enclosure, a stator coil which supplies a driving magnetic field from the outside of the X-ray tube main body to a rotor connected to the anode target, and a housing which contains the X-ray tube main body and stator coil.  
         [0007]     The space between the housing and rotary anode X-ray tube main body is filled with a cooling medium to radiate the heat generated from the anode target, for example, insulating oil and non-oil/fat cooling liquid including water as a main component. Namely, the heat from the anode target is radiated to the cooling medium, and the cooling medium is cooled by convection, and the heat is exhausted. As a result, a heating element such as an anode target is cooled. In this time, the heat generated from the stator coil is also exhausted, and the stator coil is cooled as a result. Cooling by using this kind of enclosed cooling medium is often adopted for a relatively small X-ray tube having sufficient heat capacity. (Refer to Jpn. UM Appln. KOKAI Publication No. 58-164171, for example.)  
         [0008]     An example of using antifreeze solution having a high thermal conductivity among non-oil/fat cooling liquid as a cooling medium for the stator coil and rotary anode X-ray tube has been proposed. (Refer to PCT National Publication No. 2001-502473, for example.)  
         [0009]     However, when oil/fat-based cooling liquid is used as a cooling medium, impregnant varnish used widely as an insulation coating material of a stator coil is eluted to the cooling medium, and the insulation of the stator and insulating oil themselves is lowered, and the life of an X-ray apparatus is reduced.  
         [0010]     Further, when using non-oil/fat cooling liquid is used as a cooling medium, another problem arises. As the electrical conductivity of non-oil/fat cooling liquid is higher than that of oil/fat-based cooling liquid, the insulation of the stator coil must be ensured.  
       BRIEF SUMMARY OF THE INVENTION  
       [0011]     It is an object of the present invention to maintain the characteristics of an X-ray apparatus which cools a rotary anode X-ray tube by using a cooling medium, stable for a long period.  
         [0012]     The present invention thereis provided an X-ray apparatus comprising:  
         [0013]     an anode target which generates X-rays;  
         [0014]     an electron radiation source which generates an electron to the anode target;  
         [0015]     a rotor which is connected to the anode target;  
         [0016]     a stator coil which generates a driving force to rotate the rotor;  
         [0017]     an enclosure which maintains at least the anode target, electron radiation source and rotor in a specified vacuum;  
         [0018]     a housing which is configured to contain a cooling medium around the enclosure; and  
         [0019]     an electric wire material which supplies power to the electron radiation source and stator coil,  
         [0020]     wherein a molding material is provided at a specified position to prevent the cooling medium contacting the electric wire material.  
         [0021]     Also, the present invention thereis provided an X-ray apparatus characterized by comprising:  
         [0022]     a rotary anode target;  
         [0023]     an electron radiation source which generates an electron to the rotary anode target;  
         [0024]     a rotor which is connected to the rotary anode target;  
         [0025]     a stator coil which generates a driving force to rotate the rotor;  
         [0026]     an enclosure which maintains at least the rotary anode target, electron radiation source and rotor in specified vacuum;  
         [0027]     a housing which is configured to contain a cooling medium around the enclosure;  
         [0028]     an electric wire material which supplies power to the electron radiation source and stator coil, or a connector used for connection with the electric wire material; and  
         [0029]     a molding material which prevents the cooling medium contacting the electric wire material, connector or any area of the stator coil.  
         [0030]     Further, the present invention thereis provided an X-ray apparatus characterized by comprising a rotary anode target; an electron radiation source which generates an electron to the rotary anode target; a rotor which is connected to the rotary anode target; a stator coil which generates a driving force to rotate the rotor; an enclosure which maintains at least the anode target, electron radiation source and rotor in specified vacuum; a housing which is configured to contain a cooling medium around the enclosure; and an electric wire material which supplies power to the electron radiation source and stator coil, or a connector used for connection with the electric wire material,  
         [0031]     wherein the electric wire material and connector or any area of the stator coil are molded by a material having electrical insulating property. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       [0032]      FIG. 1  is a schematic diagram explaining an example of an X-ray apparatus, to which an embodiment of the present invention is applicable;  
         [0033]      FIG. 2  is a schematic diagram explaining another example of an X-ray apparatus, to which an embodiment of the present invention is applicable;  
         [0034]      FIG. 3  is a schematic diagram explaining a further example of an X-ray apparatus, to which an embodiment of the present invention is applicable;  
         [0035]      FIG. 4  is a schematic diagram explaining an example of a cooling system (using a non-oil/fat cooling medium only) applicable to the X-ray apparatus explained in  FIG. 1  to  FIG. 3 ; and  
         [0036]      FIG. 5  is a schematic diagram of the X-ray apparatus shown in  FIG. 4 , in the state that a part of a housing is removed for explaining the internal structure. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0037]     Hereinafter, an embodiment of the present invention will be explained in detail with reference to the accompanying drawings.  
         [0038]     As shown in  FIG. 1 , an X-ray apparatus  1 , which is incorporated in an X-ray image diagnostic apparatus or a non-destructive inspection apparatus, for example, and radiates X-rays to be applied to an object or an inspection object, has a housing  3 , and an X-ray tube main body (rotary anode X-ray tube)  5  capable of radiating X-rays with specified intensity to a specified direction.  
         [0039]     The X-ray tube main body  5  is housed at a specified position in the housing  3  through non-oil/fat cooling liquid  7  which includes water as a main component and has an electrical conductivity controlled to lower than a specified value. Well-known insulating oil is usable as the cooling liquid  7 .  
         [0040]     The X-ray tube main body  5  has an enclosure  9  to maintain the interior vacuum, a cathode electron gun (a thermion radiation source)  17  provided at a specified position in the enclosure  9 , a rotary anode (anode target)  11  to radiate X-rays with a specified wavelength when an electron from the electron gun  17  impinges, a rotor  15  connected to the anode target  11  (also called a rotary unit  13  including the rotor  15  and target  11 ), a stator coil  19  to supply a driving force or a magnetic field to rotate the rotor  15 , and a getter  31  to capture the gas (hydrogen gas) generated inside in order to maintain the enclosure  9  in specified vacuum. At a specified position of the enclosure  9 , a window  9   a  made of beryllium for example is provided to emit the X-rays radiated from the rotary anode  11  to the outside.  
         [0041]     In the X-ray tube main body  5 , power supply lines or electric wire materials  17 I,  19 I and  31 I for supplying power to the cathode electron gun  17 , stator coil  19  and getter  31  are used for electrical connection between a terminal (also indicated as a connector or contact) provided in each electric wire material and a corresponding terminal provided in the housing  3 . Each electric wire material may be extended to the outside of the housing  3  without using a terminal.  
         [0042]     A part of the electric wire material  17 I,  19 I or  31 I to be connected to a corresponding terminal, that is, a part of the electric wire material where a conductor is exposed or a part of a terminal of each electric wire material where a base material is exposed, is molded (coated) by resin (hereinafter, called a molded part, and denoted by adding 100 and m to a reference numeral). As the resin material used for each molded part, materials with high heat resistance and chemical resistance, such as epoxy resin and fluorine resin are preferable.  
         [0043]     Each molded part  117   m ,  119   m  or  131   m  is formed close to at least the holes of the housing  3  and enclosure  9  or around a not-shown connector, to prevent penetration of the cooling liquid into the enclosure  9 . Namely, all areas of the electric wire materials to come in contact with the cooling liquid  7  may be molded.  
         [0044]     Particularly, when the electric wire material for the stator coil  19  is impregnant varnish, for example, having the possibility of penetrating the cooling liquid  7 , a molding material may be used in all areas around the stator coil  19  (The stator coil  19  may be completely coated with a molding material.) Molding the stator coil  19  decreases the noise (electromagnetic noise) generated when a current flows in the stator coil  19 .  
         [0045]     As a stator coil molding material, it is preferable to have the above-mentioned resin dispersed with powder of a material having an electrical insulation and thermal conductivity higher than resin, for example, alumina (aluminum oxide), aluminum nitride and boron nitride.  
         [0046]     By coating the electric wire material (power supply line) immersed in the cooling liquid or around the connector with a molding material having high electrical insulation as described above, the degree of freedom of the material of the medium usable as cooling liquid can be increased. In this case, glycol, such as ethylene glycol and propylene glycol, and mixture of water and glycol, are usable as a cooling medium.  
         [0047]      FIG. 2  and  FIG. 3  are schematic diagrams explaining another embodiment of an X-ray apparatus including a rotary anode X-ray tube shown in  FIG. 1 . The same components as those explained in  FIG. 1  are given the same reference numerals, and a detailed explanation will be omitted.  
         [0048]     As shown in  FIG. 2 , the X-ray tube main body  5  is housed at a specified position in the housing  3  through non-oil/fat cooling liquid  7  which includes water as a main component and has an electrical conductivity controlled to be lower than a specified value. Well-known insulating oil is usable as the cooling liquid  7 .  
         [0049]     The cooling liquid  7  filled in the housing  3  is cooled by a cooling unit  21  which is provided at a specified position on the outside of the housing  3  and forcibly cools the cooling liquid  7 , through first and second connectors C 01  and C 02  provided at specified positions of the housing. At the same time, the cooling liquid  7  is circulated at a specified flow rate between the housing  3  and the cooling unit  21 , by a pump  21   a  which is incorporated integrally with the cooling unit  21  or provided at any position in the route of flowing the cooling liquid  7 . The pump  21   a  is preferably a gear pump.  
         [0050]     Therefore, the heat generated in the stator coil  19  or enclosure  9 , particularly in the vicinity of the anode target  11  is exhausted to the cooling unit  21  through the cooling liquid  7 . Even if an X-ray tube with a large X-ray output is incorporated, the X-ray tube can be efficiently cooled. This can provide the X-ray apparatus  1  with stable characteristics and the capability of maintaining stable characteristics for a long period.  
         [0051]     As shown in  FIG. 3 , the cooling liquid  7  circulated by the cooling unit  21  and pump  21   a  may also be circulated in the anode target  11  having the highest heating value, electron gun  17 , recoil electron capture trap (shielding structure)  23  and rotor  15  provided around the electron gun  17 , through a cooling liquid flow path C 11  or C 12 , for example.  
         [0052]     In this time, the cooling liquid circulated in the enclosure  9  and the cooling liquid circulated between the enclosure  9  and housing  3  may be the same cooling liquid.  
         [0053]      FIG. 4  shows an example of a cooling system, which efficiently cools the anode target in the X-ray tube main body of the X-ray apparatus shown in  FIG. 3 , and the shaft of a rotary unit consisting of the anode target and rotor.  
         [0054]     As shown in  FIG. 4 , the cooling liquid  7  fed from the pump  21   a  of the cooling unit  21  is cooled by a heat exchanger  21   b , and guided to a pipe  13   h  of a fixed shaft  13   a  of the rotary unit  13  of the anode target  11  through a pipe P 101 , via a connection point T 4  and a connection point T 1  of the housing  3 . A cooling medium flow path is provided close to at least a part of the X-ray tube main body  5 , and composed of a first cooling path C 101  including the pipe P 101 , a second cooling path C 102 , and a third cooling path C 103 .  
         [0055]     The second cooling path C 102  guides the cooling medium  7  to the vicinity of the electron gun  17  and the recoil electron capture trap  23 , and guides the cooling medium  7  from the recoil electron capture trap  23  to a circular space  27  formed at a position opposite to the rear side of the anode target. The cooling medium  7  is ejected from the outlet port C 132  of the circular space  27 , and returned to the cooling unit  21  through the internal space  3   b  of the housing  3 .  
         [0056]     More specifically, in the X-ray apparatus shown in  FIG. 4 , the flow path to be supplied with the cooling medium is connected from a radiator  21   b  of the cooling unit  21  directly to the pipe  13   h  of the fixed shaft  13   a  of the rotor  15  through the pipe P 101  (an inlet port C 111 , the first cooling path C 101 ).  
         [0057]     The cooling medium guided to the pipe  13   h  is guided to a pipe P 102  from the periphery of the inlet port C 111  and outlet port C 112  provided nearby, through a hollow in the fixed shaft  13 , or a space formed between the pipe  13   h  and shaft  13   a  provided in the cylindrical fixed shaft  13   a . The cooling medium is further guided to the second cooling path C 102  provided around the cathode  17  or in the vicinity of the recoil electron capture trap  23  and anode target  11 . Namely, the cooling medium circulating in the fixed shaft  13   a  is guided from the inlet port C 121  to the vicinity of the recoil electron capture trap  23 , and ejected to the outlet port C 122 .  
         [0058]     The cooling medium circulating in the recoil electron capture trap  23  is guided through the pipe P 103  to an inlet port C 131  of the third cooling path C 103  defined as the circular space  27 , which is formed by a wall  25  formed outside the vacuum enclosure  9  and close to the stator coil  19 , in a form surrounding the enclosure  9  and crossing a not-shown rotary shaft of the rotary unit  13 .  
         [0059]     The circular space  27  is connected to the outlet port C 132  formed at a position of 180° from the inlet port C 131  holding the central part therebetween.  
         [0060]     The cooling medium is led from the inlet port C 131  into the circular space  27 , and exhausted from the outlet port C 132  to the internal space of the housing  3 . Therefore, the internal space  3   b  of the housing  3  is filled with the cooling medium. The cooling medium led into the internal space  3   b  is returned from a connection point T 2  to the cooling unit  21  through a pipe P 104 .  
         [0061]     In other words, in the cooling mechanism shown in  FIG. 4 , the pipes P 101 , P 102  and P 103  respectively connect the space between the radiator (heat exchanger)  21   b  of the cooling unit  21  and inlet port C 111  (first cooling path C 101 ), the space between the outlet port C 112  (first cooling path C 101 ) and inlet port C 121  (second cooling path C 102 ), and the space between the outlet port C 122  (second cooling path C 102 ) and inlet port C 131  (third cooling path C 103 ). The pipes P 101  and P 103  are partially exposed to the outside of the housing, but can be provided within the housing. The position (of the pipes) is not limited to the example shown in the drawing. Namely, any pipe or inlet and outlet ports are connected by a hose, and at least one end is removable.  
         [0062]     With use of the cooling paths shown in  FIG. 4 , the cooling medium fed from the heat exchanger  21   b  first cools the rotary body  13   b  and fixed shaft  13   a , which serve as a bearing unit of the rotary unit  13  generating a high heating value. This certainly prevents burning of the dynamic pressure fluid bearing. The area around the getter  31  and stator coil  19  is certainly cooled.  
         [0063]     The stator  19  is immersed together with the X-ray tube main body  5  in the cooling medium in the housing  3 , and preferably molded by a resin material having high electrical insulation, waterproof and thermal conductivity.  
         [0064]     As a resin material usable for molding, there are epoxy resin, tar epoxy resin, polyimide resin, acrylic resin, fluoric resin, silicon resin and polyurethane resin. A mixed resin including one of these resins as a main component is also usable.  
         [0065]     As described above, powder of alumina, aluminum nitride and boron nitride may be dispersed in the resin in order to increase the thermal conductivity of the molding material.  
         [0066]     This prevents deterioration of electrical insulation around the stator  19  without contacting the water-based cooling medium.  
         [0067]     In the X-ray apparatus shown in  FIG. 4 , solely one kind of water-based cooling medium may be used as a cooling medium. This can decrease the cost and facilitate maintenance. A water-based cooling medium has a high heat transfer rate compared with insulating oil, and can efficiently radiate the heat of the whole apparatus.  
         [0068]     Further, a water-based cooling medium has a small viscosity coefficient compared with insulating oil (non-oil/fat cooling medium). This decreases the load of the pump  21   a . Therefore, the flow rate of circulating a cooling medium is stabilized. Further, the cooling capacity of a cooling medium is increased by the cooling mechanism. This decreases the possibility of damaging (burning) the dynamic pressure fluid bearing that is considered to have a relatively large load.  
         [0069]      FIG. 5  shows the state of the X-ray apparatus shown in  FIG. 4 , with a part of the housing removed for explaining the internal structure.  
         [0070]     As shown in  FIG. 5 , the molding material  119   m  provided at a specified position around the stator coil  19  also serves as a fixing block  19   s  to fix the stator coil  19  (X-ray tube main body  5 ) to the housing  3 . Of course, the fixing block  19   s  may be separated from the part used for molding the electric wire material  19 I.  
         [0071]     A fixing block  9   s  usable when fixing the enclosure  9  of the X-ray tube main body  5  to the housing  3  may be formed integrally with the enclosure  9  at a specified position of the enclosure  9 , in a step of supplying a molding material used for molding an optional electric wire material ( FIG. 5  shows the state that the mold is already formed.)  
         [0072]     As describe above, it is also possible to place a molding material used for molding at a specified position of the enclosure  9  or in an area different from an area indispensable for molding an electric wire material, when molding the electric wire materials for the stator coil  19  and getter  31 , and use that (molded) part as a positioning part (fixed block) for fixing the housing  3  to the enclosure  9  and stator coil  19 .  
         [0073]     By forming the positioning part (fixed block) for fixing the housing to the enclosure and stator coil as one body with a molding material, the number of man-hours for building up the X-ray apparatus can be decreased, and the X-ray tube main body (enclosure) can be precisely set (built up) in the housing. Further, by providing a fixed block in the enclosure and status coil by molding, the influence of external force acting on the X-ray tube main body can be absorbed within the housing, and damage during transportation can be decreased.  
         [0074]     The present invention is not restricted to the above-mentioned embodiments as they are and their constituent elements can be variously modified/embodied without departing from the essence of the present invention. Various embodiments of the present invention can be achieved by properly combining a plurality of constituent elements disclosed in the embodiments. For example, some constituent elements may be eliminated from all the constituent elements of the embodiments of the present invention.  
         [0075]     As explained hereinbefore, according to the present invention, a heat generated in a heating component can be efficiently exhausted (cooled) without lowering the insulation of the cooling liquid by using an oil/fat-based cooling liquid, even if an electric wire material used inside includes impregnant varnish. Therefore, the characteristics of the X-rays radiated from the X-ray tube can be maintained stable for a long period.  
         [0076]     According to the present invention, a noise (electromagnetic noise) generated by flowing a current in the stator coil can be decreased.  
         [0077]     Further, according to the present invention, a cooling medium with a high cooling efficiency can be used without considering the insulation (conductivity) of the cooling liquid, and the cooling efficiency is increased.  
         [0078]     According to the present invention, stable characteristics can be ensured for a long period in an X-ray apparatus which cools a rotary anode X-ray tube by using a cooling medium. Therefore, the life of an X-ray image diagnostic apparatus and a non-destructive inspection apparatus incorporating with the X-ray apparatus is increased. Further, as the life of the X-ray apparatus itself is increased, the running costs of an X-ray image diagnostic apparatus and a non-destructive inspection apparatus are also decreased.