X-ray or gamma ray systems or devices – Source – Electron tube
Reexamination Certificate
2002-01-18
2003-07-15
Dunn, Drew A. (Department: 2882)
X-ray or gamma ray systems or devices
Source
Electron tube
C378S141000
Reexamination Certificate
active
06594340
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2001-012698 filed Jan. 22, 2001, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a rotary anode type X-ray tube apparatus, and more particularly to a rotary anode type X-ray tube apparatus having a cooling structure, which can improve a cooling efficiency of a rotary anode type X-ray tube received in a housing.
2. Description of the Related Art
In a rotary anode type X-ray tube apparatus, a rotary anode type X-ray tube is received in a housing, and the rotary anode type X-ray tube comprises a cathode for generating an electron beam, an anode target for emitting X-rays upon irradiation of the electron beam, a rotating mechanism for rotatably supporting the anode target, and a vacuum envelope for enclosing the cathode, the anode target, and the rotating mechanism.
FIG. 1
shows a conventional rotary anode type X-ray tube apparatus. In
FIG. 1
, numeral
41
denotes a housing, and a rotary anode type X-ray tube is enclosed in the housing
41
. A coolant such as insulating oil is filled in a space between the housing and the rotary anode type X-ray tube.
In the rotary anode type X-ray tube
41
shown in
FIG. 1
, there are enclosed a cathode
44
for generating an electron beam, an anode target
45
for emitting X-rays upon irradiation of the electron beam, a rotating mechanism
46
for rotatably supporting the anode target
45
. The rotating mechanism
46
comprises a rotary cylinder
47
to which the anode target
45
is fixed, a stationary shaft
48
for rotatably supporting the rotary cylinder
47
, and dynamic pressure type bearings.
In the dynamic pressure type bearings, helical grooves of herringbone patterns are formed on the surface or surfaces of the stationary shaft
48
and/or the rotational structure
47
, and a liquid metal lubricant such as gallium or gallium alloy is applied to the helical grooves and a gap space between the stationary shaft
48
and the rotational structure
47
. A stator coil
49
for generating a rotating magnetic field is provided outside the vacuum envelope
43
and disposed around the rotary cylinder
47
.
A cooler device
50
is located outside of the housing
41
and comprises a heat exchange unit, a pump unit and so on. A coolant outlet path such as an outlet pipe P
0
couples the cooler device
50
to the housing
41
to supply a coolant from the cooler device
50
to the housing, and a coolant inlet pipe such as an inlet pipe Pi also couples the housing
41
to the cooler device
50
to return the coolant from the housing
41
to the cooler device
50
.
In the apparatus shown in
FIG. 1
, the insulating oil as the coolant which is heated by the rotary anode type X-ray tube
42
is supplied from the housing
41
to the cooler device
50
via the outlet pipe P
0
and the insulating oil which has been cooled in the cooler device
50
is also supplied to housing
41
from the cooler device
50
via the inlet pipe Pi so that the insulating oil is circulated in a circulating path as shown by arrow Y.
In an operating mode, the stator coils
49
applies the rotating magnetic field to the rotary cylinder
47
of the rotating mechanism
46
to rotate the rotary cylinder
47
so that the anode target
45
is rotated. The electron beam generated from the cathode
44
is accelerated by a high voltage between the cathode
44
and the anode target
45
and is impinged on the rotated anode target
45
so that X-rays are emitted from the rotated anode target
45
. The X-rays pass through a radiation window W
1
provided on the vacuum envelope
43
and a radiation window W
2
provided on the housing
41
and are guided outside of the housing
41
.
Heat is generated from the anode target
45
, stator coils
49
, the dynamic pressure type slide bearing between the stationary shaft
48
and the rotary cylinder
47
, and so on, and is transmitted to the insulating oil circulated between the cooler device
50
and the housing
41
. Thus, the insulating oil absorbing the heat cools the X-ray tube.
The dynamic pressure type bearing has advantages of low noise, low vibrations, and long life due to small rotational friction. However, a shearing force is applied to the liquid metal lubricant in rotation of the rotary cylinder and a shearing energy is transferred to the liquid metal lubricant so that the liquid metal lubricant is heated due to the shearing energy and a temperature of the dynamic pressure type bearing is increased. Thus, a diffusion reaction is prompted between the liquid metal lubricant and a bearing material of the rotary cylinder and the stationary shaft. As a result, it may be impossible to constantly maintain a stable rotation of the rotary cylinder. Accordingly, a method of cooling the bearing is employed in the conventional X-ray apparatus, in which a coolant space is provide in the stationary shaft constituting the rotating structure and the insulating oil is supplied to the coolant space to cool the bearing section of the stationary shaft.
There will be described a conventional rotary anode type X-ray tube apparatus having a stationary shaft of a bearing with reference to
FIG. 2
, in which a coolant space is formed. In
FIG. 2
, same numerals denote same parts or members in
FIG. 1
, and a detailed description thereof will be omitted.
A hollow space
51
for circulating a coolant such as an insulating oil to cool a stationary shaft
48
is formed in the stationary shaft
48
in an axial direction and a pipe
52
is so arranged to extend in the hollow space
51
in the axial direction. The pipe
52
is coupled to the inlet pipe Pi at a bottom end
52
A thereof and is extended along the hollow space
51
, and a top end
52
B of the pipe Pi is closely faced to the inner bottom of the pipe Pi.
In the configuration shown in
FIG. 2
, the insulating oil passing through the inlet pipe Pi is guided in the pipe
51
and flows in the pipe
51
as shown by arrow Y
1
. The insulating oil is supplied from the opening of the top end
52
B to the flow space and path between the pipe
51
and the stationary shaft
52
. Then, the insulating oil flows in the flow path and outlets in the space of the housing
41
, as shown in FIG.
2
. The inlet pipe Pi, the pipe
51
, and the flow path between the pipe
51
and the stationary shaft
52
constitutes a part of the circulating coolant path for guiding the insulating oil, which cools the bearing to maintain the temperature of the bearing in a predetermine temperature range.
Thereafter, the insulating oil flowed from the flow path in the stationary shaft
52
into the space in the housing
41
flows to the stator coils
49
and the vacuum envelope
43
to absorb heat generated from the stator coils
49
and the vacuum envelope
43
and is supplied to the cooler device
50
through the outlet pipe P
0
.
In the conventional rotary anode type X-ray tube apparatus, the coolant hollow space is provided in the stationary shaft constituting the rotating mechanism to absorb heat generated from the bearing, and so on. In this construction, an inner diameter of the stationary shaft in the coolant hollow space can not be set to be relatively large, because the stationary shaft has a relatively small outer diameter and the stationary shaft must have a sufficient mechanical strength. If the stationary shaft has a small inner diameter to have a sufficient mechanical strength, a pressure loss is produced in the coolant flow space or path in the stationary shaft, and a flow rate of the coolant circulating in the apparatus is lowered and the circulating amount of the coolant is decreased in the apparatus. Thus, a cooling efficiency of cooling the stator coils, the vacuum envelop and so on is lowered due to the lowering of the circulating amount of the coolant.
There is an improved method of increasing a cooling efficiency, in which a pumping ability of pumping the coolant is increa
Dunn Drew A.
Kabushiki Kaisha Toshiba
Kiknadze Irakli
Pillsbury & Winthrop LLP
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