JPH068316Y2 - Vertical turbo molecular pump - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a vertical turbo molecular pump.

[Conventional technology]

Fig. 6 shows a conventional vertical turbo molecular pump using a magnetic bearing and a slide bearing.

An intake port 2 is provided in the upper part of the casing 1 and an exhaust port 3 is provided in the lower part of the casing 1, and a plurality of moving blades 5 mounted on a rotor 6 are provided in a groove-shaped space between a plurality of stationary blades 4 provided in the casing 1. By rotating at high speed, the exhaust action is obtained and the suction port 2 side is made a high vacuum.

In order to rotate the rotor 6 at a high speed as described above, the upper bearing of the rotor is installed from the lower part of the casing 1 at a distance from the permanent magnet 8a mounted on the rotor center shaft 7 and the center shaft 7 around the rotor center shaft 7. A magnetic bearing 8 is opposed to a permanent magnet 8b mounted on a supporting base 10 extending upward by a gap that is magnetically repulsive. On the other hand, the lower bearing is the axial direction of the rotor central shaft 7 and is perpendicular to the axis. It is composed of a sliding bearing 9 having a load capacity in the direction, such as a spiral groove bearing.

Furthermore, the rotor 6 shakes greatly (vibrates) due to disturbance.
In this case, the rotating parts such as the upper bearing 8, the motor 11, the moving vanes 5 and 4 and the stationary part do not come into contact with each other and are damaged.
As a protection device, ball bearings 12 and 13 which are rotatable even in a vacuum are provided above and below the rotor center shaft 7.

That is, each of the ball bearings 12 and 13 has its race outer side attached to the support base 10 and its race inner side wall with a slight gap from the outer periphery of the rotor center shaft 6. When the rotor 6 vibrates greatly in the direction perpendicular to the axis, the upper and lower ball bearings 12 and 13 come into contact with the rotary shaft 7 to limit the vibration and prevent damage. Further, in the case of swinging up and down so as to jump up in the axial direction, the jumping-up prevention metal fitting 14 attached to the rotor center shaft 7 comes into contact with the ball bearing 13 at the lower part to prevent damage. ing.

[Problems to be solved by the invention]

Since the conventional vertical turbo molecular pump has the above-described configuration, the rotor 6, that is, the central axis 7 of the rotor is rotating at a high speed and the ball bearing is used in vacuum.
Due to insufficient lubrication of 12, 13 and the like, the ball bearings 12, 13 deteriorate in function as a protective device due to several contact operations, and must be replaced.

In addition to this, since the ball bearings 12 and 13 have almost no vibration damping (damping) function, the impact force exerted on the support base 10 is large, and the reaction force is naturally large, so that the ball bearings 12 and 13 are in contact with each other. During repeated use, seizure suddenly occurs and loses its function as a protective device.
May be damaged.

The present invention is intended to solve such a problem.

[Means for solving problems]

According to the present invention, in the vertical turbo molecular pump in which the upper bearing has a magnetic bearing by a permanent magnet, the lower bearing has a sliding bearing, and the rotor central axis is supported by the upper and lower bearings, a concave shape concentric with the rotor central axis is provided on the rotor side. A groove is provided, and a protrusion that is loosely fitted in the recessed groove is provided on the casing side, and the protrusion has an axially provided slit to constitute a rotor vibration damping device.

[Action]

Since the present invention is configured as described above, when the rotor shakes largely due to external disturbance, the concave groove of the rotor comes into contact with the protrusion provided on the casing side that constitutes the vibration damping device of the rotor. A frictional force is generated between the protrusion and the protrusion.
Further, since the protrusion has a slit in the axial direction, it acts as a leaf spring and causes a spring force to act on the rotor via the concave groove.

The value of the spring force is determined by the spring rigidity of the protrusion having the slit, and the spring rigidity of the protrusion is determined by the length of the slit. Therefore, by appropriately setting the length of the slit, the spring rigidity of the protrusion with respect to the frictional force between the concave groove and the protrusion, that is, the spring force acting from the protrusion on the rotor is deflected. Can be set to an appropriate value for damping and converging, and the frictional force and the spring force effectively dampen the vibration of the rotor. As a result, even if the rotor vibrates significantly, the rotor center axis does not normally contact the bearing, so that the function of the bearing does not deteriorate, and the impact force that acts on the rotor, casing, and bearing due to the vibration of the rotor is generated. Can be reduced.

〔Example〕

A first embodiment of the present invention is shown in FIG. In this embodiment, the same parts as those of the conventional turbo molecular pump shown in FIG. 6 are designated by the same reference numerals, and the description thereof will be omitted.

A concave groove 6a is provided on the low vacuum side (lower side) of the upper portion of the rotor 6 concentrically with the central axis of the rotor 6. On the other hand, the shake damping device 15 is attached to the upper part of the support base 10. This shake damping device 15 is formed by a projection in the axial direction, and the tip portion 15a thereof is formed into a concave groove 6
Play in a.

As the shake damping device 15, for example, a polymer material such as a fluororesin, a composite material based on GFRP, or the like, which is formed of a material having a large damping action and a small friction coefficient, is used. The shape is typically a cylinder, but other shapes may be used. The protrusion of the vibration damping device 15 has a slit in the cylinder in the axial direction, or only a part of the fan-shaped portion with the slit is made to function, and the rigidity of the spring (spring force) is adjusted so that the vibration of the rotor is attenuated most appropriately. ) And the coefficient of friction.

On the other hand, the surface of the concave groove 6a is usually formed by a turning surface, a grinding surface, etc., but an oxide film treatment, an ion plating treatment, etc. are performed to further reduce the friction coefficient and reduce the performance of the shake damping device 15. Also, the reliability can be improved.

The tip portion 15a of the shake damping device 15 and the concave groove 6 of the rotor 6
As for the gap with a, the rotor central shaft 7 has a ball bearing 1
It is set so that the tip portion 15a of the shake attenuator and the concave groove 6a come into contact with each other before coming into contact with the members 2 and 13.

Since the present embodiment is configured as described above, when the rotor swings in the direction perpendicular to the central shaft 7 due to disturbance or the like, the runout damping is performed before the ball bearings 12 and 13 come into contact with the central shaft 7. The tip portion 15a of the device 15 and the concave groove 6a contact each other. By the contact between the tip end portion 15a of the shake damping device 15 and the concave groove 6a, a frictional force acts between them. Further, since the projection of the shake damping device 15 is provided with a slit in the axial direction, the shake damping device 15 acts as a leaf spring, and the tip portion 15a of the shake damping device 15 and the concave groove 6a come into contact with each other. Sometimes
A spring force in a direction to push back the rotor 6 acts on the rotor 6 via the concave groove 6a.

When the rotor 6 shakes due to disturbance or the like, the rotor 6
In order to damp the vibration of the vibration damping device 15, it is necessary to match the friction coefficient of the vibration damping device 15 with the spring rigidity. That is, as shown in FIG. 2, due to the relationship between the coefficient of friction and the spring rigidity, the stable range A in which the vibration (vibration) of the rotor 6 is attenuated and converged and this is diverged and large in the rotor 6 and the vibration damping device 15. There is an unstable range B that can be impacted and lead to damage.

As shown in FIG. 2, whether the vibration of the rotor 6 diverges or converges is determined by the spring rigidity and the coefficient of friction of the vibration damping device 15, and in addition to this, the weight, rotation speed and size of the rotor 6 etc. Determined by

The rotor 6 has various weights, rotational speeds and dimensions depending on the pumping speed of the pump, but the friction coefficient of the vibration damping device 15 is usually constant in the range of μ = 0.1 to 0.4. Therefore, in the present embodiment, the spring rigidity of the vibration damping device 15 is adjusted so that the rotor 6 does not contact the ball bearings 12 and 13 as much as possible within the stable range, and the vibration damping device 15 is adjusted.
Set the spring stiffness of.

As shown in FIG. 3, the length of the portion between the axial slits in the tip portion 15a of the shake damping device 15 is b, the length (depth) of the slit is t, and the thickness of the tip portion 15a is t. In this case (FIG. 3 shows the case where the tip portion 15a is a cylinder for convenience), the spring rigidity K of the shake damping device 15 is here E is the elastic coefficient, and the spring rigidity K can be arbitrarily set by selecting the length of the slit.

Therefore, in this embodiment, the spring rigidity can be set to an appropriate value by selecting the length of the slit for the frictional force of the vibration damping device 15, and the vibration damping device 15 can be set within the stable range A. In, the shake of the rotor 6 can be effectively attenuated and converged. As a result, the ball bearings 12 and 13 do not come into contact with the central shaft 7, and it is possible to prevent the deterioration of their functions. Further, the damping action of the vibration damping device 15 reduces the impact force applied to the rotor, the casing, the bearing, and the like.

Second and third embodiments of the present invention are shown in FIGS. 4 and 5, respectively. Also in these examples, the same parts as those of the conventional turbo molecular pump shown in FIG. 6 are denoted by the same reference numerals, and the description thereof will be omitted.

In the second embodiment shown in FIG. 4, the tip portion 215a extending in the axial direction of the shake damping device 215 constituted by a protrusion provided on the outer periphery of the support base 10 of the casing is attached to the lower vacuum of the rotor 6. It is loosely fitted in the concave groove 26a on the side.

In the third embodiment shown in FIG. 5, the tip end portion of the protrusion 315a extending below the shake damping device 315 disposed in the intake port 2 and attached to the casing 1 is provided on the high vacuum side of the rotor 6. It is loosely fitted in the concave groove 36a.

The shake dampener is made of a material similar to that of the first embodiment.

Also in these second and third embodiments, similarly to the first embodiment, when the rotor swings in the direction perpendicular to the central axis 7, before the ball bearings 12 and 13 contact the central axis 7. The tip portion 215a of the vibration damping device 215 or the vibration damping device 3
The tip end of the protrusion 315a of 15 comes into contact with the concave groove 26a or 36a, and the vibration of the rotor is effectively damped.

Further, in the third embodiment, the vertical gap between the tip of the protrusion 315a and the concave groove 36a is configured to be smaller than the distance between the jump-up prevention fitting 14 and the lower ball bearing 13. In addition, it also has a function of dampening the jumping up of the rotor in the direction of the central axis 7 and dampening the impact force to the ball bearing 13 below.

In the first and second embodiments as well, as in the third embodiment, the gap between the tip portion of the shake damping device and the concave groove in the upward direction is made smaller than the distance between the jump-up prevention fitting and the lower ball bearing. Thus, it is possible to provide a function of damping the jumping up of the rotor in the central axis direction.

[Effect of device]

 The present invention can bring the following effects.

(1) The spring rigidity of the vibration damping device configured by the protrusion having the slit in the axial direction can be set to an appropriate value for the friction coefficient by selecting the length of the slit, which allows The runout of the rotor can be effectively damped. Therefore, a bearing such as a ball bearing normally does not operate, and there is almost no need to replace the bearing, which significantly reduces maintenance time and cost.

(2) Even if there is a large disturbance that cannot be damped by the vibration damping device, the energy is significantly reduced by the vibration damping device before the bearing is activated. It can prevent the rotor from losing its function and damaging the rotor.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of a first embodiment of the present invention, FIG. 2 is an explanatory view of a stable / unstable range in the same embodiment, and FIG. 3 shows a tip portion of a shake damping device in the same embodiment. Fig. 3 (a)
Is a vertical sectional view thereof, FIG. 3 (b) is a plan view thereof, FIG. 4 is a vertical sectional view of a second embodiment of the present invention, and FIG. 5 is a vertical sectional view of a third embodiment of the present invention. , FIG. 6 is a sectional view of a conventional turbo molecular pump. DESCRIPTION OF SYMBOLS 1 ... Casing, 6 ... Rotor, 6a, 26a, 36a ... Recessed groove, 7 ... Central axis of rotor, 8 ... Magnetic bearing, 9 ... Sliding bearing, 15,215,315 ... Runout damping device, 15a, 215a ... Tip part of runout damping device , 315a… Projection of runout damping device.

Claims (1)

[Scope of utility model registration request] 1. A vertical turbomolecular pump in which the upper bearing comprises a magnetic bearing of a permanent magnet, the lower bearing comprises a sliding bearing, and the rotor central axis is supported by the upper and lower bearings, the rotor side being concentric with the rotor central axis. The vertical shape is characterized in that a concave groove is provided, and a protrusion that is loosely fitted in the concave groove is provided on the casing side, and that the protrusion has a slit in the axial direction to form a shake damping device of the rotor. Turbo molecular pump.