JPH05290769A - Rotary anode x-ray tube - Google Patents

Abstract

PURPOSE:To prevent the sudden increase of the friction torque and the rattling of an outer wheel to be generated at the time of moving adhesion of the solid lubricant in a pre-load structure, which has been conventionally used for reducing the vibration and the noise due to the rotation of a ball bearing of a rotary anode X-ray tube. CONSTITUTION:An inside pre-load spring 10 as a load from the inside of a pair of ball bearings and an outside pre-load spring 13 for pushing the outer wheel from the outside are located, and the inside pre-load spring 10 is set stronger than the outside pre-load spring 13 by 10-30N (1-3kg), and a ball bearing 5 is loaded with this difference as a pre-load. The pre-load force at 10-30N (1-3kg) is equal to that of the usual pre-load structure, but the pushing restraint to the outer wheel in the axial direction is raised by several times of the conventional one. Even in the case where the friction torque is increased suddenly, since the restraint of the outer wheel is higher by several times, the rotation of the outer wheel with a ball is prevented, and the rattling vibration (chattering vibration) due to the inclination of the outer wheel is also prevented to flatten and smoothen the irregularity of the solid lubricant quickly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary anode X-ray tube,
Particularly, it relates to improvement of the rotating mechanism.

[0002]

2. Description of the Related Art Generally, the life of a rotary anode X-ray tube is determined by defects due to bearings, that is, increase in vibration and noise, increase in friction torque, and poor withstand voltage due to abrasion powder. In a rotating anode X-ray tube, the rotating anode rotates at a high speed (for example, 9,000 rpm) in a high vacuum atmosphere. In addition, the temperature of the bearing that rotatably supports the rotating anode portion reaches a maximum temperature of 500 ° C. because the heat generated when the X-rays are generated by the anode target is transferred through the rotating shaft.
Moreover, since the bearing part has a large thermal resistance, a temperature difference occurs between the rotating side and the stationary side of the bearing, and the maximum temperature is 250 ° C during the transition.
The rotation side becomes higher.

Since the bearing of the rotary anode X-ray tube is used in a high vacuum and high temperature environment as described above, oil lubrication as used in general rotary machines cannot be adopted, and the inner ring, outer ring or ball of the bearing cannot be adopted. Solid lubrication bearings are used whose surface is plated or evaporated with a material such as silver or lead. Further, in consideration of the temperature difference of 100 to 200 ° C. between the rotating side and the stationary side as described above, the clearance of the bearing must be set to be several times larger than that of a general rotating machine.

If the clearance of the bearing is large, vibration due to so-called looseness occurs, which causes abnormal vibration and increase in noise. Therefore, preload is applied to eliminate the clearance of the bearing as in a general rotary machine, and the above vibration and noise are eliminated. Attempts have been made to prevent it. For example, in Japanese Unexamined Patent Publication (Kokai) No. 57-38547, attention is paid to the precision of the structure in the preload structure of the rotary anode X-ray tube, particularly the eccentricity of the rotating shaft and the mounting play of the bearing. We have proposed a mechanism to prevent the inclination of the leaf spring. In addition to these, a great many inventions and ideas have been made regarding preloading of bearings of rotary anode X-ray tubes.

[0005]

The bearing preload has a proper range, and in the case of a rotary anode X-ray tube, it has a range of 10 to 30 N.
It is {1 to 3 kg}. This is because the life of the solid lubricant film is determined by the adhesion force of the solid lubricant film on the friction surface, or more precisely the adhesion force.If the preload is excessively large, the lubricant film is pushed out from the friction surface composed of the ball surface and the inner and outer ring raceways. This is because the life is shortened accordingly. That is, in oil lubrication, a large amount of surrounding oil intervenes on the friction surface due to the action of fluid to perform a lubrication action, but in solid lubrication, only the solid film attached to the friction surface contributes to lubrication.

On the other hand, the solid lubrication has a more unstable friction torque than the oil lubrication, and it may increase or decrease in the range of 10 to 100 times. That is, since it has no viscosity like oil, when a thin and uniform solid lubricating film is present on the friction surface, the friction torque is smaller than that of oil lubrication. However, the solid lubricant film of silver, lead, etc. sometimes causes the phenomenon of transfer. This is because the solid lubricating film that was attached to the ball moved to the inner and outer ring raceways of the opponent, or the solid lubricating film that was evenly attached to the ball was
It is a phenomenon that it locally attaches in the form of protrusions like sucrose. Then, when transfer occurs, or immediately after transfer, the friction torque rapidly increases and the inner and outer rings vibrate violently. The restraint force of the outer ring of the preload structure is only the force pressed by the spring, and the outer ring was rotated or vibrated at the preload of 10 to 30 N during the transfer described above, and the effect of the preload was insufficient.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and it presses the outer ring of the bearing to be preloaded from both sides with relatively strong spring force, and the inner spring force is applied to the outer side. 10 to 30N {1 to 3kg} stronger than that. A coil-shaped spring, a disc spring or the like is suitable as the spring, but a coil-shaped spring whose spring constant can be made small and whose spring force can be adjusted relatively easily is optimal, and a coil-shaped spring is particularly preferable on the inside. Further, the coil spring is easily available. When pushing with a coiled spring, a guide ring is provided so that the preload acts evenly on the outer ring. A stepped sleeve accommodating and arranging the inner spring is provided, and the stepped sleeve is fixed to the anode fixing portion of the rotating anode X-ray tube in both the axial direction and the rotating direction.
In addition, the stepped sleeve is set so that the length of the stepped sleeve is 0.1 to 0.4 mm from the inner guide ring of the spring, and it rotates even if the anode target is in a vertically downward position. A stopper that prevents the anode from falling downward due to gravity.

[0008]

Considering the force balance of the outer ring of the bearing on which the preload acts, the inner spring exerts the preload FI on the surface facing the inner side of the outer ring, and the other outer spring acts on the opposite side of this outer ring. A preload FO acts on the surface. FI and FO are stronger than FI in the range of 10 to 30 N {1 to 3 kg}, and the difference of 10 to 30 N acts between the inner and outer races of the bearing on which the preload acts and the ball to provide the preload. On the other hand, a force FI acts from the inside and a force FO acts from the outside to this outer ring, and the restraining force on the outer ring is large. Therefore, even when the solid lubricating film is transferred or when the friction torque after transfer is large, Keep stable.

Further, since the outer ring is pressed by being sandwiched by the springs from both sides, the outer ring is unlikely to incline or vibrate, and stable high-speed rotation can be maintained for a long time. Conventionally, proper preload of 10 to 30 N and restraint of the outer ring could not be achieved at the same time, but it was achieved by the above action.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments will be described in detail below with reference to the drawings. FIG. 1 is a sectional view of a rotary anode X-ray tube showing an embodiment of the present invention. An anode target 1 is fixed to one end of a rotary cylinder 3 that serves as a drive motor rotor, and a rotary shaft 4 is coupled inside the rotary cylinder 3 on the opposite side of the anode target 1. The rotary shaft 4 is provided with a predetermined interval. It is housed in the anode fixing portion 6 via the two ball bearings 5 arranged and is rotatably supported. The entire rotating body is held in vacuum by a part of the anode fixing portion 6 and the glass envelope 7 serving as a tube container. A cathode 2 serving as a cathode member is provided on the opposite surface of the anode target 1, and the cathode 2 is fixed in the glass envelope 7. The space between the anode fixing portion 6 and the glass envelope 7 is sealed with an alloy called Kovar, which is called a sealing body 8.

FIG. 2 is a partially enlarged sectional view of the vicinity of the bearing far from the anode target of FIG. 1. The embodiment of FIG. 1 will be described in more detail with reference to FIG. The bearing 5 far from the anode target is a coiled spring 10 inside a pair of ball bearings, and 40N to the right side in the figure through the slider 11 inside.
It is pressed with a force of {4 kg}. The inner coil spring 10 is housed in a stepped fixing sleeve 9, and the stepped fixing sleeve 9 is fixed to the anode fixing portion 6 by screws (not shown) at three places on the circumference. The outer ring of the ball bearing 5 close to the anode target is fixed from both sides by the stepped fixing sleeve 9 and the outer ring retainer (not shown) to position the rotor in the axial direction.

On the other hand, the ball bearing 5 far from the anode target is pressed by the outer coil spring 13 through the outer slider 12 to the left side in the drawing with a force of 20 N {2 kg}.
The inner sleeve 4a is arranged on the outer circumference of the rotary shaft 4 and defines the distance between the pair of ball bearings 5, and the nut 4b fixes the ball bearing 5 to the rotary shaft 4.
Fixed to.

Further, in FIG. 2, it is necessary to provide a gap 1 between the stepped fixing sleeve 9 and the inner slider 11 in consideration of thermal expansion. The gap l is 0.1 to 0.
4mm is suitable. If the gap 1 is expanded too much, the anode may be excessively dropped to the lower side when the X-ray tube is supported in a posture in which the anode is on the upper side because the anode is heavy. That is, in FIG. 2, the rotary shaft 4 may move excessively to the left. In order to prevent this, the gap l should be as narrow as possible. Further, if the rotary shaft moves excessively to the left, the X-ray focal point may shift or the ball bearing 5 may be damaged, which is not preferable.

In the rotating anode X-ray tube having the above structure, when the rotating cylinder 3 is rotated by a magnetic field generator (not shown) arranged near the rotating cylinder 3 on the outer circumference of the glass envelope 7,
A high voltage of 120 KV is applied between the anode target 1 and the cathode 2, and thermoelectrons collide with the anode target 1 at high speed from the cathode 2. When the thermoelectrons collide with the anode target 1 at high speed, X-rays are generated in the direction of the arrow in the figure.

The operation and effect of the present invention will be described in detail with reference to FIGS. 3, 4 and 5. In FIG. 3, the left side view (a) shows the axial force balance of the conventional preload structure, and the right side view.
(b) shows the axial balance of the present invention. In the conventional example of FIG. 3A, when a preload acts on the outer ring 5c of the ball bearing 5 from the left to the right, the outer ring 5c causes the balls 5b to move to the inner ring 5c.
As a result, a bearing reaction force that balances the preload is generated in the direction of the arrow. That is, the product of the bearing reaction force and sin α is equal to the preload. The preload is 5 for the outer ring.
The bearing reaction force that acts evenly over the entire side surface of c and that is generated inside the bearing is the individual balls, here 9 balls 5
It occurs in b. When a bearing reaction force is generated in the direction of the arrow in the figure, a force obtained by multiplying it by cosα is generated in the vertical direction of the outer circumference of the ball bearing 5, but this force cancels each other out over the entire circumference of the bearing and becomes zero. ..

In the present invention shown in FIG. 3 (b), the inner pre-load is twice as high as that of the conventional one, and the outer ring 5c is pressed in the right direction, and at the same time, the outer pre-load of half the inner pre-load is applied from the right side to the left side. The outer ring 5c is pressed. After all, the preload acting on the inside of the ball bearing 5 becomes the same force as the conventional one, and the bearing reaction force is also equal to the conventional one.

FIG. 4 schematically shows a state of the solid lubricant 5d coated on the surface of the ball 5a. In the present invention, the solid lubricant 5d is lead (Pb), but it may be silver (Ag). A film of lead solid lubricant 5d has a thickness of 0.5 μm and uniformly coats the surface of the ball 5b (one-dot chain line in the figure). The coating method may be plating, ion plating or vapor deposition.
The uniform dash-dotted lead film starts to wear gradually but slightly. However, after a certain period of time, the lead film is transferred from the ball to the ball, or to the inner ring and the outer ring (sometimes referred to as transfer), and the unevenness as if it is a sweet sugar is formed as shown by the solid line in the figure. The unevenness is low when present and becomes relatively uniform over the entire surface, but sometimes it becomes a locally high protrusion as shown in the figure and the height becomes 5 to 10 μm. Such irregularities are gradually smoothed while rotating for a while, and even if it is long, even low protrusions of lead having a height of several μm or less are formed on the entire surface of the ball 5b in several tens of hours. However, in rare cases, a projection having a high height may be repeatedly formed a plurality of times from a low height of several μm or less. Such a behavior of the lead film occurs in silver as well, and it is difficult to control so that this phenomenon does not occur.

In FIG. 5, the ball 5b shown in FIG.
It shows the state of rotating inside. Just height 10μ
The protrusion of m faces the outer raceway surface. When the ball 5b as shown in FIG. 4 rotates inside the ball bearing 5, the friction torque of the ball bearing 5 rapidly increases. This is a phenomenon that can be easily understood, and may increase 10 to 100 times as much as that in smoothing.
In the conventional preload structure, only the outer ring 5c is pressed from the outside with a weak force, and the rotating force due to the friction with the ball 5b can be stopped only by the force obtained by multiplying the pressing force by the friction coefficient. Since the coefficient of friction is usually 0.3 to 0.5, only a binding force less than half the pressing force works. Therefore, when the friction torque rapidly increases, the outer ring 5c also rotates together with the ball 5b, and the outer ring 5c and the ball 5b are damaged.
This is because when the outer ring 5c rotates together with the balls 5b, the outer peripheral surface of the outer ring 5c and the inner diameter surface of the anode fixing portion 6 make a strong sliding friction, causing scratch-like wear damage to the sliding surface. Then, the friction coefficient of this surface increases next, and the outer ring 5c
Is fixed to the inner diameter surface of the anode fixing portion 6, and the suspension of the balls 5b and the outer ring 5c is released. However, when the swinging motion is released, the ball 5b cannot actually make a rolling motion instantaneously, and the ball 5b slides on the raceways of the inner ring 5a and the outer ring 5c in a short time. At this time, the two are severely damaged. In order to prevent this whirling,
In Japanese Patent Laid-Open No. 60-112233, a means for processing a groove on a slider for fixing and housing an outer ring and inserting a pin in the groove is adopted. However, this invention also involves a risk that the friction between the pin and the groove may become a frictional resistance force against axial sliding due to preload.

On the other hand, as is clear from the balance of the forces of the present invention shown in FIG. 3 (b), in the present invention, the axial pressing force for restraining the outer ring 5c is three times that of the conventional one. Therefore, it was possible to completely prevent the outer ring 5c from rolling around with the ball 5b.

Next, another effect of the present invention will be described with reference to FIG. FIG. 5 shows the moment when the projection of the solid lubricating film having a height of 10 μm rolls on the raceway surface of the outer ring 5c as described above.
At this time, the outer ring 5c tends to incline as indicated by the broken line in the figure. The function of suppressing this inclination is higher as the length of the arrow indicating the magnitude of the force from the left to the right in the figure, that is, the stronger the preloads 14a and 14b. The outer preloads 14c and 14b, and the arrows pointing from the right to the left in the drawing tend to decrease the force of the upper preload 14c in the drawing, and the inner preload 14a is strengthened correspondingly, and the effect of suppressing the inclination is enhanced. As the upper force 14c decreases, the preload 14d from the right to the left in the lower part of the figure increases, and the lower part of the outer ring 5c tends to move to the left. As a result of the above, it has the effect of making the intersection angle θ of the vertical planes of the outer ring 5c and the inner ring 5a approach zero. Suppressing the inclination has an effect of reducing backlash vibration of the outer ring 5c and preventing damage due to chatter vibration between the ball 5b and the raceways of the inner ring 5a and the outer ring 5c. Further, the outer ring 5c has a strong force to press the ball 5b, and when the inclination is suppressed, the protrusion of the solid lubricating film formed on the surface of the ball 5b is pressed with a stronger force,
It can be smoothed more quickly.

FIG. 6 is a partial cross-sectional view of a rotary anode X-ray tube showing another embodiment of the present invention, and has the same structure as that of FIG. In this embodiment, a disc spring is used for both the inner preload spring 10 and the outer preload spring 13, and the volume occupied by the preload spring is smaller than that of the coil spring. The spring constant of the inner preload spring 10 is 2 times that of the outer preload spring.
Doubled. There is also a combination in which the inner preload spring 10 is a coil spring and the outer preload spring 13 is a disc spring.
Since the ambient temperature exceeds 200 ° C., a high temperature spring material such as Inconel or tungsten is suitable as the spring material.

[0022]

As described above, according to the present invention, the preload is pressed from both sides to the outer ring of the ball bearing which applies the preload,
The inner preload is 10 to 30 N {1 from the outer pressing force.
~ 3kg} Strengthen this difference and apply this difference to the ball bearing as a preload, so the axial restraining force of the outer ring can be increased, and even if the friction torque suddenly increases during transfer of the solid lubricant, the outer ring will move with the ball. It is possible to prevent rolling around and prevent damage caused by rolling around of the outer ring and balls. Further, since the outer ring is prevented from tilting and the backlash vibration of the outer ring is suppressed, damage to the ball bearing due to the backlash vibration can be prevented. Furthermore, since the projections of the solid lubricating film are smoothed quickly, as a result, the rotating anode X
It reduces vibration and noise of the wire tube.

[Brief description of drawings]

FIG. 1 is a sectional view of a rotary anode X-ray tube showing an embodiment of the present invention.

FIG. 2 is a partial cross-sectional view of a portion of FIG. 1 according to the present invention.

FIG. 3 is a force balance diagram showing a difference between the present invention and a conventional example.

FIG. 4 is a schematic diagram showing the behavior of a solid lubricating film on the surface of a ball.

FIG. 5 is a schematic diagram illustrating an operation effect.

FIG. 6 is a partial sectional view of a rotary anode X-ray tube showing another embodiment of the present invention.

[Explanation of symbols]

 1 Anode Target 2 Cathode 3 Rotating Cylinder 4 Rotating Shaft 5 Ball Bearing 6 Anode Fixing Part 7 Glass Envelope 8 Sealing Body 9 Fixing Sleeve 10 Inner Preload Spring 11 Inner Slider 12 Outer Slider 13 Outer Preload Spring 14a Preload 14b Preload 14c Preload 14d Preload

Claims (4)

[Claims] 1. A rotary cylinder for fixing and supporting an anode target, and a rotary shaft coaxially coupled to the inside of the rotary cylinder.
A rotating anode X-ray tube comprising: an anode fixing portion arranged between the rotating shaft and the rotating cylinder; and a pair of bearings interposed between the anode fixing portion and the rotating shaft. A pair of springs for pressing the side surface of the outer ring to the outer ring of one of the pair of bearings, wherein the spring force pushing from the inside of the bearing is larger than the spring force pushing from the outside of the bearing Anode X-ray tube. 2. A rotary anode X-ray tube according to claim 1, wherein the spring pushed from the inside of said bearing is a coil-shaped spring, and a guide ring is interposed between said coil-shaped spring and said outer ring. 3. The rotary anode X-ray tube according to claim 1, wherein both the spring pushing from the inside of the bearing and the spring pushing from the outside of the bearing press the outer ring via a guide ring. 4. A stepped sleeve accommodating and arranging a spring for pushing from the inside of the bearing, wherein the length of the stepped sleeve is a guide ring of the spring pushing from the inside of the bearing, and 0.1 to 0.1
The rotary anode X-ray tube according to claim 1, wherein the rotary anode X-ray tube is set to have a space of 0.4 mm.