JPS59692Y2 - rotating anode x-ray tube - Google Patents

Description

[Detailed description of the invention] This invention relates to a rotating anode X-ray tube, and aims to extend the life of the bearing by suppressing the temperature rise of the bearing of the rotating shaft of the rotating anode as low as possible.

Generally, in a rotating anode X-ray tube, a bearing is provided in the shaft box fixed to the tube, and the anticathode (
A rotary shaft (hereinafter referred to as a target) and a rotor are supported, and the target and rotor continue to rotate during operation of the X-ray tube.

In this case, the temperature of the target rises to about 1200° C., and the heat is transmitted to the rotating shaft via the rotor and the support shaft that connects the target and the rotor.

Metals with high mechanical strength, such as stainless steel, are used for these support shafts and rotating shafts so that they can withstand deformation and bending, but their thermal conductivity is relatively low, and heat is transmitted to these rotating shafts. Some of the heat is also transferred to the bearings.

For this reason, lubricants that can withstand high vacuum and high temperatures are used in bearings, but from the perspective of longevity, the lower the operating temperature, the better.

This is because the higher the operating temperature, the more easily the lubricant will peel off and scatter.

Therefore, in order to make it difficult for the heat generated by the target to be transmitted to these rotating shafts, measures have been taken to increase the thermal resistance by making the target support shaft as long as possible, or in some cases making it a hollow cylinder. There is.

However, the methods of lengthening the target support shaft or making it a hollow cylinder have their own limits in terms of mechanical strength.

This idea solves the various problems mentioned above. By providing a shaft core made of a metal with high thermal conductivity at the center of the rotating shaft, most of the heat transferred to the rotating shaft from the target side is transferred to the target. The heat is guided to the tip of the rotating shaft on the opposite side of I-, and the heat is radiated from the blackened surface of the tip to prevent the temperature of the bearings on the way from rising.

The drawings will be explained below.

In FIG. 1, reference numeral 1 denotes a target blade I, which is attached to the shoulder of a rotor 3 via a target support shaft 2.

Reference numeral 4 denotes a bearing on the side of Targetera 1. Reference numeral 5 denotes a rotating shaft, which is made of a metal with low thermal conductivity such as stainless steel and has a hollow hole in the center that opens at the end of the shaft opposite to Targetera I.
', and a shaft core 5'' made of a metal with high thermal conductivity such as copper or silver inserted into the hollow hole.

6 is a sealing side bearing, 7 is a pipe that serves as a spacer between both bearings 4 and 6, 8 is a bearing holding nut, 9 is a screw for fixing the rotor 3 to the rotating shaft 5, and 10 is an axle box. fixed to the tube.

11 is a target holding nut, and 12 is a blackened surface painted on the tip of the shaft core 5'' and the hollow rotary ring 5'.

FIG. 2 is a cross-sectional view of a conventional rotating anode X-ray tube, and there are no differences from FIG. 1 except that the rotating shaft 5 is made of a single metal with low thermal conductivity such as stainless steel. do not have.

Next, regarding the device of this invention shown in FIG.
The operation of the rotary shaft 5, which is composed of a rotary shaft 5'' and a shaft core 5'' inserted into the hollow thereof, will be explained.

In the conventional device shown in Fig. 2, the total amount of heat transmitted from the target 1 to the rotating shaft 5 is Q, the amount of heat that diffuses from the rotating shaft 5 toward the bearing holding nut 8 is Q2, and the amount of heat transmitted to the target side bearing 4 is If Ql, then Q = Ql
+ Q2 (IJ is established.

On the other hand, the length of the rotating shaft 5 is l, the cross-sectional area is S, and the thermal conductivity is λ1.
Then, the thermal resistance η of the rotating shaft 5 is as follows: η=l/λ18 (21 holds true).

Next, the apparatus of the present invention shown in FIG. 1 uses a rotating shaft 5 having a structure in which a shaft core 5 made of a material with high thermal conductivity is embedded in the hollow portion of the hollow rotating shaft 5'.

The total amount of heat from the target 1 transferred to the rotating shaft 5 is Q,
If the amount of heat diffused from the rotating shaft 5 toward the bearing holding nut 8 is 02', and the amount of heat transmitted to the target side bearing 4 is Q1', then Q = Q1 + Q2 (3) holds true.

If the cross-sectional area and thermal conductivity of the hollow rotating shaft 5' are S1, λ1, and the shaft core 5'' are S2.λ2, then S = 81
+ 82 (4), η1=l/λ181, η2=l/λ282 (
5) holds true.

However, η1. η2 is the thermal resistance of the hollow rotating shaft 5' and the shaft core 5'', respectively.

From equation (5), the following holds true for the overall thermal resistance η' of the rotating shaft 5 in FIG. 1: 1/η'=1/η1+l/η2 (6).

However, from equations (5) and (6)? '=l/
It becomes λ181+λ282.

(7) (2) (4) (From formula 71 holds true.

η-η'〉O is established by λ2>λ1.

Therefore η〉η (9)
That is, the rotating shaft 5 having the structure of the present invention shown in FIG. 1 has a lower thermal resistance.

Therefore, naturally, Ql) Ql, Q2-? Q2 (1
0), the temperature of the target side bearing 4 can be kept low and its lifespan will be extended.

Note that if the blackened surface 12 is formed at the end of the rotating shaft, the heat dissipation effect at the end of the rotating shaft will be increased, and the temperature of the bearing can be lowered.

With this idea, it is possible to keep the bearing temperature low and extend its life.In addition, as the bearing temperature decreases, the degassing temperature of the anode part can be raised during exhaust, resulting in a stable high temperature. Since it becomes possible to obtain a vacuum, the effect of improving the withstand voltage of the X-ray tube is also obtained, which is a practically useful effect.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a rotating anode X-ray tube of this invention, and FIG. 2 is a sectional view of a conventional rotating anode X-ray tube. Explanation of symbols: 1: Anticathode (target), 2: Target support shaft, 3: Rotor, 4: Target side bearing, 5: Rotating shaft, 5': Hollow rotating shaft, 5'' shaft core, 8: Bearing holding nut , 10: Axle box, 12: Blackened surface.

Claims (1)

[Scope of utility model registration request] In an X-ray tube in which a rotating shaft having an anticathode at one end is rotatably supported via a bearing in an axle box fixed to a tube,
A rotary anode X-ray tube characterized in that the rotary shaft is hollow, and a shaft core made of a metal with high thermal conductivity is provided in the hollow to lower the thermal resistance of the rotary bearing.