X-ray or gamma ray systems or devices – Source – Target
Reexamination Certificate
2000-10-18
2002-11-05
Kim, Robert H. (Department: 2882)
X-ray or gamma ray systems or devices
Source
Target
C378S127000, C378S130000
Reexamination Certificate
active
06477236
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 11-295357, filed Oct. 18, 1999; No. 11-295358, filed Oct. 18, 1999; and No. 2000-130911, filed Apr. 28, 2000, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to an X-ray tube of a rotary anode type, particularly, to an X-ray tube of a rotary anode type equipped with a slide bearing of a dynamic pressure type lubricated by a liquid metal.
FIG. 1
is a cross sectional view showing a gist portion of a conventional X-ray tube of a rotary anode type equipped with a slide bearing of a dynamic pressure type and an X-ray tube apparatus having the X-ray tube housed in a housing. Reference numeral
141
shown in
FIG. 1
represents a vacuum vessel of an X-ray tube of a rotary anode type. A cathode
140
for emitting an electron beam, a disc-like rotary anode target
142
, etc. are arranged within the vacuum vessel
141
. Also, an X-ray emissive layer
143
for emitting an X-ray is arranged in that region of the disc-like rotary anode target
142
which faces the cathode
140
.
The disc-like rotary anode target
142
is fixed to a support shaft
145
by a fixing nut
144
. The support shaft
145
is joined to a rotor
146
formed cylindrical as a whole. The rotor
146
is of a three-layer structure consisting of an outer cylinder
146
a
, an intermediate cylinder
146
b
and an inner cylinder
146
c
having a bottom. The support shaft
145
is joined to the intermediate cylinder
146
b.
A columnar stationary structure
147
is inserted into the inside of the inner cylinder
146
c
. A spiral groove
148
having a herringbone pattern is formed on the surface of the stationary structure
147
, and a metal lubricant such as a Ga—In—Sn alloy, which is in the form of a liquid at least during the operation of the X-ray tube, is supplied into a gap including the slide bearing section of a dynamic pressure type formed between the stationary structure
147
and the rotor
146
and into the spiral groove
148
.
A lubricant storage chamber (not shown) for receiving the liquid metal lubricant is arranged in a central portion of the stationary structure
147
. A plurality of lateral lubricant passageways or ducts are arranged in radial directions between the lubricant storage chamber and the slide bearing of the dynamic pressure type. The liquid metal lubricant housed in the lubricant storage chamber is supplied through the lubricant passageways into the slide bearing section of the dynamic pressure type.
The inner cylinder
146
c
of the rotor and the stationary structure
147
, which collectively constitute the slide bearing of the dynamic pressure type, are arranged such that about 20 &mgr;m of the bearing clearance can be maintained during the operation of the X-ray tube. Each of the inner cylinder
146
c
and the stationary structure
147
, which collectively form the bearing surface, is made of a metal material such as an iron alloy tool steel, e.g., SKD-11 (JIS standards). The heat conductivity of SKD-11 is relatively small, i.e., 24 W/m·K at room temperature.
Two stepped portions
149
,
150
are annularly arranged a certain distance apart from each other in the vertical direction in the outer circumferential portion of the stationary structure
147
. The outer diameter of the stationary structure
147
is changed in each of the stepped portions
149
and
150
such that the diameter of the stationary structure
147
in the lower end portion positioned on the opposite side of the disc-like rotary anode target
142
is made smaller. A projecting portion
151
is annularly formed in the outer circumferential portion of the stepped portion
150
positioned in the lower portion. Also, a metal ring
152
is arranged on the outside of the projecting portion
151
in a manner to surround the stationary structure
147
. Annular projecting portions
153
and
154
are arranged on the inner circumferential portion and the outer circumferential portion, respectively, of the metal ring
152
. An outer edge portion
147
a
of the stationary structure
147
positioned in the lower portion in
FIG. 1
extends to the outside of the vacuum vessel
141
so as to be utilized as a portion at which the X-ray tube of the rotary anode type is fixed to a housing
155
.
The vacuum vessel
141
comprises a large diameter portion
141
a
made of a metal and surrounding the main portion of the disc-like rotary anode target
142
and a small diameter portion
141
b
surrounding the main portions of the rotor
146
and the stationary structure
147
. The small diameter portion
141
b
is made of, for example, glass, and a seal ring
156
made of a thin metal body is bonded to the edge portion of the small diameter portion
141
b
. The tip portion of the seal ring
156
is hermetically welded to the tip portion of the projecting portion
154
on the outer circumferential portion of the sealing metal ring
152
. Also, the tip portion of the projecting portion
153
in the inner circumferential portion of the sealing metal ring
152
is hermetically welded to the tip portion of the projecting portion
151
formed in the stepped portion
150
of the stationary structure
147
. In this fashion, the stationary structure
147
is hermetically sealed to the vacuum vessel
141
. A stator
157
serving to impart a rotating force to the rotary structure
146
is arranged on the outside of the small diameter portion
141
b
of the vacuum vessel
141
. The stator
157
comprises an iron core and a coil wound about the iron core.
In the X-ray tube of the rotary anode type constructed as described above, the edge portion
147
a
of the stationary structure
147
is fixed to the bottom in the central portion of a pot-like holding member
158
made of an insulating material. In the holding member
158
, the open edge portion of the cylindrical portion
158
b
is fixed to the housing
155
by a plurality of bolts
160
. Also, a through-hole is formed in the central portion of the bottom of the holding member
158
, and a top-shaped metal ring
158
a
having a central through-hole
159
is fixed to the bottom portion of the holding member
158
by a plurality of bolts
161
. The outer edge portion
147
a
of the stationary structure
147
extends through the central through-hole
159
of the metal ring
158
a.
The outer diameter of the metal ring
158
a
is inwardly tapered toward the inside of the vacuum vessel
141
and an annular projecting portion
162
is formed in the inner circumferential portion in contact with the outer edge portion
147
a
of the stationary structure
147
. Where the outer edge portion
147
a
of the stationary structure
147
is fixed to the metal ring
158
a
, the tip surface of the projecting portion
162
of the metal ring
158
a
is brought into contact with the stepped portion
150
of the stationary structure
147
.
The outer edge portion
147
a
of the stationary structure
147
is fastened and fixed to the metal ring
158
a
by a nut
163
engaged with a male screw formed on the outer circumferential wall of the outer edge portion
147
a
of the stationary structure
147
. In fastening the nut
163
, the stationary structure outer edge portion
147
a
, which is to be fixed, is pulled downward in
FIG. 1
so as to strengthen the contact between the tip surface of the projecting portion
162
and the stepped portion
160
of the stationary structure
147
, with the result that the X-ray tube of the rotary anode type is fixed to the holding member
158
.
A shielding member
164
shielding the X-ray and made of lead is arranged inside the housing
155
housing the X-ray tube of the rotary anode type. An insulating cooling oil is loaded in and circulated through the shielding member
164
. Also, an X-ray radiation window
165
for taking out the X-ray to the outside is arranged in a region positioned sideward of the X-ray emissive layer
143
. A circulating hole for circulating the
Anno Hidero
Nakamuta Hironori
Yoshida Yukinari
Kabushiki Kaisha Toshiba
Kim Robert H.
Pillsbury & Winthrop LLP
Wang George
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