X-ray or gamma ray systems or devices – Source – Electron tube
Reexamination Certificate
1999-06-18
2001-07-31
Kim, Robert H. (Department: 2882)
X-ray or gamma ray systems or devices
Source
Electron tube
C378S132000, C378S133000, C277S300000
Reexamination Certificate
active
06269146
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a rotating anode X-ray tube capable of discharging intense heat generated when X-rays are generated.
Conventionally, there has been a rotating anode X-ray tube as shown in FIG.
4
. In this rotating anode X-ray tube
50
, X-rays
53
are generated from a target
52
when an electron beam
51
is applied from a cathode (not shown) to the target
52
in a vacuum. At the same time, most of the kinetic energy of the electron beam
51
is transformed into heat, causing an intense heat in the target
52
. The heat of this target
52
is directly discharged outwardly of a vacuum tube
55
by radiation from the target
52
and a rotor
54
and is also discharged to the outside by heat conduction via a shaft
56
, bearings
57
and a bearing housing
58
.
However, in the above prior art rotating anode X-ray tube
50
, the heat of the shaft
56
is conducted from the shaft
56
to the bearing housing
58
through only very small surfaces of contact between a race and balls
59
of the bearings
57
, and this has led to the problem that the heat of the shaft
56
does not efficiently escape.
As described above, the inefficient escape of the heat of the shaft
56
has led to the problem that the cooling of the target
52
connected to the shaft
56
becomes insufficient to enable the increase in output power of the X-rays
53
and the continuous operation of the X-ray tube.
Furthermore, the inefficient escape of the heat of the shaft
56
has also led to the problem that the shaft
56
and the bearings
57
put in contact with the shaft
56
come to have an elevated temperature to impair the capability of the solid lubricant in the bearings
57
and extremely reduce the operating life of the bearings
57
.
SUMMARY OF THE INVENTION
Accordingly, the object of the present invention is to provide a rotating anode X-ray tube capable of efficiently discharging intense heat generated when X-rays are generated and achieving a high output power, a long-time continuous operation and a long operating life of the bearings.
In order to achieve the above object, the present invention provides a rotating anode X-ray tube comprising:
a supported member connected to a target;
a supporting member for supporting the supported member via rolling bearings;
an accommodating section formed between the supported member and the supporting member; and
a liquid metal that is accommodated in the accommodating section and does not substantially evaporate even in a vacuum.
According to the rotating anode X-ray tube of the present invention, the liquid metal is accommodated in the accommodating section formed between the supported member and the supporting member. Therefore, heat conducted from the target to the supported member is efficiently conducted via the liquid metal to the supporting member and discharged to the outside. Further, the liquid metal also operates as a coolant. Therefore, the target, the supported member and the bearing are prevented from having an increased temperature, so that a high output power, a long-time continuous operation and a long operating life of the bearing can be achieved.
In one embodiment, the liquid metal is comprised of Ga or Ga alloy and the accommodating section put in contact with the Ga or Ga alloy is made of an anti-corrosion metal having a corrosion resistance to the-Ga or Ga alloy or of an anti-corrosion ceramic.
In the above embodiment, the liquid metal is comprised of Ga (gallium) or Ga alloy, and the accommodating section is formed of an anti-corrosion metal having a corrosion resistance to the Ga or Ga alloy or of an anti-corrosion ceramic. Therefore, the accommodating section is not corroded by the Ga or Ga alloy.
In one embodiment, the liquid metal is comprised of Ga or Ga alloy and the accommodating section put in contact with the Ga or Ga alloy is formed of stainless steel or tool steel coated with TiN.
In the above embodiment, the accommodating section is formed of stainless steel or tool steel coated with TiN. Therefore, the accommodating section is not corroded by the Ga or Ga alloy. The accommodating section, which is formed of stainless steel or tool steel coated with TiN, can be manufactured at lower cost than when entirely made of the anti-corrosion material having a corrosion resistance to Ga or Ga alloy.
One embodiment further comprises an infusion hole for infusing the liquid metal into the accommodating section.
The above embodiment, which is provided with the infusion hole for infusing the liquid metal into the accommodating section, facilitates the infusion of the liquid metal into the accommodating section, allowing the liquid metal to be easily replenished even when the liquid metal is wasted during use.
In one embodiment, the infusion hole is threaded and plugged with a screw plug.
In the above embodiment, the infusion hole is threaded and plugged with the screw plug. Therefore, the liquid metal does not leak out of the infusion hole.
In one embodiment, the accommodating section is provided substantially in an axial center portion between a plurality of the rolling bearings and the accommodating section has tapered surfaces of which the diameter is maximized at the axial center and reduces toward axial ends.
In the above embodiment, the accommodating section has the tapered surfaces of which the diameter is maximized at the axial center and reduces toward axial ends. Therefore, the accommodating section is easily closely filled with the liquid metal. While the shaft is rotating, the liquid metal is gathered into the axial center portion where the diameter of the accommodating section is maximized due to a centrifugal force exerted on the liquid metal, so that the liquid metal can be prevented from leaking out of the accommodating section.
In one embodiment, a gap between the supported member and the supporting member is not greater than 0.2 mm axially outside the accommodating section.
In the above embodiment, the gap between the supported member and the supporting member is not greater than 0.2 mm axially outside the accommodating section. Therefore, the liquid metal is prevented from leaking out of the accommodating section. This was confirmed through experiment.
In one embodiment, a pumping groove for forcing the liquid metal located in the gap between the supported member and the supporting member back into the accommodating section is provided on the supported member or the supporting member.
In the above embodiment, the pumping groove formed on the supported member or the supporting member forces the liquid metal, which is located in the gap between the supported member and the supporting member, back into the accommodating section. Therefore, the liquid metal is prevented from leaking out of the accommodating section.
In one embodiment, a labyrinth groove for reserving the liquid metal is formed adjacently outside the pumping groove.
In the above embodiment, if the liquid metal should leak out of the accommodating section and further to the outside of the pumping groove, then the labyrinth groove formed adjacently outside the pumping groove catches the liquid metal.
In one embodiment, the pumping groove has a groove angle of 10 to 20 degrees with respect to a flat plane perpendicular to the axial direction of the supported member.
In the above embodiment, the pumping groove has the groove angle of 10 to 20 degrees with respect to the flat plane perpendicular to the axial direction of the supported member. With this arrangement, the pumping groove ensures the pumping force for forcing the liquid metal back into the accommodating section while the supported member is rotating, and the leakage of the liquid metal from the pumping groove when the supported member is in a state of rest is suppressed. If the groove angle of the pumping groove exceeds 20 degrees, then the pumping force increases in operation to force the liquid metal back into the accommodating section, while the groove length becomes short to let the liquid metal leak to the outside through this pumping groove in the st
Hayashida Kazunori
Hiraoka Daiji
Ohnishi Masayoshi
Ho Allen C.
Kim Robert H.
Koyo Seiko Co. Ltd.
Wenderoth , Lind & Ponack, L.L.P.
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