JP4218765B2 - Turbo molecular pump - Google Patents

Description

  The present invention relates to a turbo molecular pump in which gas is exhausted by a rotor that rotates at high speed.

An example of a conventional turbomolecular pump is shown in FIG. In this turbo molecular pump, a blade exhaust part L ₁ and a groove exhaust part L ₂ are constituted by a rotor (rotating part) R and a stator (fixed part) S inside a cylindrical pump casing 14. The lower part of the pump casing 14 is covered with a base 15, which is provided with an exhaust port 15 a. A flange 14 a for connecting to a device to be evacuated and piping is provided on the upper portion of the pump casing 14. The stator S includes a fixed tubular portion 16 erected at the center of the base 15, and is mainly composed of a fixed portion of the blade pumping section L ₁ and groove pumping section L _2.

  The rotor R is composed of a main shaft 10 inserted into the fixed cylindrical portion 16 and a rotating cylindrical portion 12 attached thereto. A drive motor 18 is provided between the main shaft 10 and the fixed cylindrical portion 16, and an upper radial bearing 20 and a lower radial bearing 22 are provided above and below the drive motor 18. An axial bearing 24 having a target disk 24a at the lower end of the main shaft 10 and upper and lower electromagnets 24b on the stator S side is disposed below the main shaft 10. With such a configuration, the rotor R rotates at high speed while receiving active control of five axes.

A rotating blade 30 is integrally provided on the outer periphery of the upper portion of the rotating cylindrical portion 12 to form an impeller, and a fixed blade 32 arranged alternately with the rotating blade 30 is provided on the inner surface of the casing 14. but constitute a blade pumping section L ₁ which performs exhaust by the interaction between the stationary blades 32 is stationary and the rotary blades 30 rotating at a high speed.

Further, the lower blade pumping section L ₁ is is provided a thread groove pumping section L _2. That is, the rotating cylindrical portion 12 is provided with a screw groove portion 34 having a screw groove 34 a formed on the outer peripheral surface thereof so as to surround the fixed cylindrical portion 16, while the stator S has an outer periphery of the screw groove portion 34. An encircling thread groove spacer 36 is disposed. Thread groove exhaust portion L ₂ performs exhaust by the drag effect of the threaded groove 34a of the screw groove 34 rotating at a high speed.

Thus, by having the thread groove exhaust part L ₂ on the downstream side of the blade exhaust part L ₁ , a wide-area turbo molecular pump that can cope with a wide flow rate range is configured. In this example, the thread groove of the thread groove exhaust portion L ₂ shows an example of forming the rotor R side, it has also been made to form a thread groove on the stator S side.

  The turbo molecular pump as described above is assembled as follows. First, the stepped surface 36a on the lower surface of the thread groove spacer 36 is fitted and attached to the annular convex portion 15b formed on the base portion 15. Next, the rotor R is set at a predetermined position, and a normal half-split stationary blade 32 is assembled between the rotor blades 30 from both sides, and a ring-shaped stationary blade spacer 38 having step surfaces on the top and bottom is placed thereon. Thereafter, this process is sequentially repeated to form a laminated structure of the fixed blades 32 surrounding the rotor R.

  Finally, the casing 14 is mounted around the above laminated structure from above, and the lower flange 14b is fixed to the base 15 of the stator S with a bolt or the like, and the uppermost step surface 14c on the inner peripheral surface of the casing 14 is the uppermost step. The fixed blade spacer 38 is pressed to fix the laminated structure and the thread groove spacer 36. As can be seen from such a configuration, the edge of each fixed wing 32 is pressed from above and below by the upper and lower fixed wing spacers 38. It is restrained by being pressed by the 15 convex portions 15b so as not to rotate in the circumferential direction.

  Although not shown, the screw groove spacer 36 may be firmly bolted to the fixed cylindrical portion 16 of the stator S in order to ensure the fixing of the screw groove spacer 36 to the fixed cylindrical portion 16 of the stator S. ing.

  In such a turbo molecular pump, rotation abnormality due to the eccentricity of the rotor R, destruction of the rotor blade 30 and the like may occur. In this case, the rotor R or a fragment thereof may collide with the fixed blade spacer 38 or the thread groove spacer 36 and a great force may be applied to the stator S side in the radial direction or the circumferential direction.

  Due to such an abnormal force, not only the deformation of the fixed wing 32 and the spacers 36 and 38, but also the damage of the casing 14 and the fixed cylindrical portion 16 or the breakage of these joint portions, or the connection piping portion between these and the outside. There is a possibility of breaking. Such breakage or breakage on the stator S side breaks the vacuum of the entire processing apparatus in which the turbo molecular pump is used, causing damage to the processing apparatus itself or products in the middle of processing. Can lead to accidents that lead to accidents.

  In view of the above, an object of the present invention is to provide a highly safe turbo molecular pump that does not lead to damage to a stator or casing and a vacuum system associated therewith even if an abnormality occurs on the rotor side. And

  The invention according to claim 1 is a turbo-molecular pump having a blade exhaust part and a groove exhaust part constituted by a rotor and a stator inside a pump casing, wherein the stator fixes at least a part of the stator to the pump casing. At least a part of the rotor is provided with a fragile part that is broken when an abnormal torque is applied from the rotor due to abnormal rotation or destruction of the rotor itself, and at least a part between the stator and the pump casing Friction reduction in which the stator of the blade exhaust part and the groove exhaust part is rotated after the fragile part is broken when an abnormal torque acts on at least a part of the stator due to abnormal rotation or destruction of the rotor itself. A turbo molecular pump characterized by having a structure.

The invention according to claim 2 is the turbo molecular pump according to claim 1, wherein the friction reducing structure rotates both the blade exhaust part and the stator of the groove exhaust part.
The invention according to claim 3 is the turbo molecular pump according to claim 1 or 2, wherein the friction reducing structure is a low friction member or a bearing.

According to a fourth aspect of the present invention, in the turbomolecular pump having a blade exhaust part and a groove exhaust part constituted by a rotor and a stator inside the pump casing, the stator of the groove exhaust part is a step provided in the pump casing. A flange portion is engaged with the surface and fixed , and at least a part of the engaging portion between the flange portion of the stator of the groove exhaust portion and the stepped surface of the pump casing, at least a portion of the stator itself A brittle portion that breaks when an abnormal torque is applied from the rotor due to abnormal rotation or destruction, and when the abnormal torque acts from at least a part of the stator due to abnormal rotation or destruction of the rotor itself, the groove A turbo molecular pump characterized in that a stator of an exhaust part is configured to rotate along the engaging part.

The invention according to claim 5 is the turbo molecular pump according to claim 4 , wherein the stator of the blade exhaust part is fixed to the flange part of the stator of the groove exhaust part.

According to a sixth aspect of the present invention, in the turbomolecular pump having a blade exhaust part composed of a rotor and a stator inside a pump casing, the blade exhaust part includes a fixed blade and a fixed blade spacer for fixing the fixed blade. A cylindrical low-friction structure is provided so as to surround the fixed blade spacer, and the cylindrical low-friction structure has an abnormal torque from the rotor due to abnormal rotation or destruction of the rotor itself in the fixed blade spacer. The turbomolecular pump is configured to break the fastening member that fastens the fixed blade spacer when allowed to act to allow the fixed blade spacer to rotate.

  According to the present invention, when abnormal torque is transmitted to the stator due to abnormality of the rotor or the like, the restraint of the structure of the stator is quickly released, or a friction reducing structure or an impact absorbing structure is configured between the stator and the casing. Thus, the rotational energy of the rotor is absorbed and the torque transmission to the pump casing is hindered to prevent the pump casing and the external connection with the pump casing from being broken. Therefore, even if an abnormality occurs on the rotor side, it is possible to provide a highly safe turbo molecular pump that does not lead to damage on the stator side or vacuum system.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 and 2, it shows a turbo molecular pump, a blade pumping section L ₁ which is formed by placing the rotating blades 30 and stationary vanes 32 alternately, the screw groove 34 and screw groove spacer 36 configuration of the whole and a thread groove pumping section L ₂ having, and stationary vanes 32 and stator blade spacers 38 and the screw groove spacer 36 structure is pressed by the casing 14 is abbreviated illustration is the same as FIG. 13.

In this example , when an abnormal torque is applied to the stationary blade 32 due to an abnormality on the rotor R side, a part of the stationary blade spacer 38 escapes radially outward. That is, in this example , the uppermost and lowermost fixed blade spacers 38a and 38b are composed of two halved spacer pieces 40. Then, on the inner peripheral surface of the casing 14, in a circumferential direction having a width slightly larger than the thickness of the fixed blade spacers 38a and 38b at positions facing the back surfaces of the uppermost and lowermost fixed blade spacers 38a and 38b. Extending grooves 42 and 44 are provided over the entire circumference.

  In the turbo molecular pump configured as described above, during normal operation, a large torque does not act on the fixed blade 32 or the fixed blade spacer 38 in the circumferential direction or the radial direction. It is constrained by mutual friction and maintains its position. The uppermost and lowermost fixed blade spacers 38 a and 38 b maintain a ring shape, and hold each fixed blade 32 together with the other fixed blade spacers 38.

  If for some reason an abnormality occurs in the rotation of the rotor R, or the rotor R is damaged and a large force is applied to both or either of the fixed blade spacers 38a and 38b in the circumferential direction and the radial direction, the fixed blade spacers 38a and 38b When pushed outward, the half-spaced spacer pieces 40 are separated into the circumferential grooves 42 and 44, and the other fixed blade spacers 38 are also free from rotation in the axial direction with respect to the stator S. Become. As a result, the fixed blade 32 and the fixed blade spacer 38 rotate together with the rotor R, so that the rotational energy of the rotor R is gradually absorbed, and the rotor R eventually stops. Since the fixed blade 32 and the fixed blade spacer 38 are released from the restraint on the casing 14, the torque of the rotor R is not transmitted to the casing 14, and the casing 14 is not damaged or the connection with the outside is not broken. .

In the above-described example , the uppermost and lowermost fixed blade spacers 38a and 38b are divided. However, only one of them may be divided, and the fixed blade spacer 38 positioned in the middle may be divided. May be. Further, the number of divisions may be two or more.

3 and 4 show another turbomolecular pump. This example is also configured to release the restraint of the fixed wing 32 at an early stage when an abnormality occurs. In this example , as shown in FIG. 4, a support pin 46 is provided between the blades 32c of the uppermost fixed wing 32a in the axial direction, and similarly, a support pin 48 is provided between the blades of the lowermost fixed wing 32b. A plurality are provided at equal intervals in the circumferential direction.

That is, the support pin 46 is spanned like a “sticker rod” between the step surface 14c and the uppermost fixed blade spacer 38c, and its length is slightly larger than the thickness of the uppermost fixed blade 32a. It is set large. Similarly, the support pin 48 is stretched between the thread groove spacer 36 and the lowermost fixed blade spacer 38d, and the length thereof is set to be slightly larger than the thickness of the lowermost fixed blade 32b. Therefore, gaps T ₁ and T ₂ are formed between the uppermost fixed blade 32a and the stepped surface 14c of the casing 14, and the lowermost fixed blade spacer 38d and the lowermost fixed blade 32b.

These support pins 46 and 48 are sufficient to support the fixed blade spacer 38 during normal operation, and are strong enough to be easily broken when a twist or torque is generated between the stator S and the rotor R during abnormal operation. And set to number. The widths of the gaps T ₁ and T ₂ are set to, for example, 50 to 100 μm so that the fixed blade 32a does not “rattle” during normal operation.

In the turbo molecular pump configured as described above, the state shown in FIG. 3 is maintained during normal operation, but the rotor R is broken or abnormally rotated, and a twist or torque is generated between the stator S and the rotor R. In some cases, the support pins 46, 48 fall or break. As a result, the upper and lower gaps T ₁ and T ₂ are dispersed in the middle layered structure, and the restraint in the axial direction of each fixed blade 32 and fixed blade spacer 38 is released. As a result, each fixed blade spacer 38 becomes rotatable with respect to the casing 14, and the torque transmitted to the casing 14 side can be reduced and damage can be prevented. In this example, the support pins 46 and 48 are provided above and below, but either one may be provided.

5 to 7, the first embodiment of the present invention showing a turbo molecular pump, the stationary vane spacers 50 except the uppermost blade pumping section L ₁ of the present invention, as shown in FIGS. 6 and 7 In addition, female threads 50a and screw insertion holes 50b are alternately provided along the circumferential direction at the peripheral portion, and bolts 52 as fastening members are inserted into the screw insertion holes 50b of the upper fixed blade spacer 50. Each fixed blade spacer 50 is sequentially fastened by being screwed into the female screw 50 a of the lower fixed blade spacer 50. The lowermost fixed blade spacer 50 is screwed onto the upper portion of the thread groove spacer 54.

  These bolts 52 are set to have such a strength as to break when the rotor R breaks or rotates abnormally and abnormal torque is transmitted to the spacer 50. Such setting of the strength of the bolt 52 is performed by selecting the thickness or material of the bolt 52 or by forming a breakage inducing portion such as a notch at a predetermined location.

Thread groove spacer 54 of the thread groove pumping section L ₂ is also fixed by screwing this by a bolt 56 mounted on the lower side of the slit-shaped threaded mounting holes 55 that the base 15 of the stator S. The strength of the bolt 56 is set so as to be broken when a predetermined torque is transmitted to the spacer 54.

  Further, in this example, the inside of the convex portion 17a that supports the lower end portion of the thread groove spacer 54 is notched, and the height H of the contact surface 17b that contacts the lower end portion of the thread groove spacer 54 is as shown in FIG. It is smaller than the case. Further, in this embodiment, a cylindrical low friction member 58 that is formed of a material having a small friction coefficient and constitutes a friction reducing structure is interposed between the spacers 50 and 54 and the casing 14 of the stator S. ing.

  In the turbo molecular pump configured as described above, when an abnormal torque acts on each fixed blade spacer 50 and the thread groove spacer 54, the bolts 52 and 56 that fasten the fixed blade spacer 50 and the thread groove spacer 54 to the stator S break. These constraints are released and the stator S is rotatable. As a result, the rotational energy of the rotor R is absorbed and the torque transmitted from the rotor R to the stator S is reduced, thereby preventing the stator S from being damaged.

Further, since the low friction member 58 is provided between the fixed blade spacer 50 and the thread groove spacer 54 and the casing 14, after the bolts 52 and 56 are broken, the fixed blade spacer 50 and the screw groove spacer 54 and the casing 14 The frictional force acting between them is also reduced, and the contact surface between the thread groove spacer 54 and the base 15 is set to be small, so that the force transmitted to the stator S side can also be reduced. A circumferential groove 42 is formed on the back of the uppermost fixed blade spacer 38. The circumferential groove 42 is formed on the back of the uppermost fixed blade spacer 38 in the same meaning as in the above example .

FIG. 8 shows a second embodiment of the present invention. In this embodiment, the casing 14 is divided into an intake side casing 14A and an exhaust side casing 14B, which are connected to each other. . Structure of the stationary vane spacers 50 of the blade exhaust portion L ₁ are fixed sequentially fastening bolt 52 is similar to the previous embodiment.

  On the other hand, a stepped surface 60 is provided at the upper end of the exhaust side casing 14B, and a flange portion 54a that engages with the stepped surface is formed on the thread groove spacer 54. Is fixed to the exhaust casing 14B. The strength of these bolts 56 is also set to such an extent that the bolt 56 is broken at a predetermined torque. Also in this embodiment, cylindrical low friction members (friction reduction structures) 58a and 58b are provided between the fixed blade spacer 50 and the intake side casing 14A and between the thread groove spacer 54 and the exhaust side casing 14B, respectively. Is intervening. The turbo molecular pump of this embodiment can also exhibit the same operational effects as the previous embodiment.

FIG. 9 shows a modification of the second embodiment of FIG. The thread groove spacer 54, which is the stator of the thread groove exhaust portion of this example, is fixed by fixing the bolt 56 to the stepped surface 60 at the upper end of the flange portion 54a at the upper end of the exhaust side casing 14B as in the previous embodiment. Is attached. A low friction member (friction reduction structure) 58b is interposed between the thread groove spacer 54 and the exhaust casing 14B. In the previous embodiment, the lower end of the thread groove spacer 54 is in contact with the inner surface of the stator base 15 and is restrained here, but in this embodiment, the lower end of the spacer 54 is the stator base 15. a gap T ₃ is formed between the, not constrained by the casing. This is due to the following reasons.

In the turbo molecular pump of the type blade pumping section L ₁ and the thread groove exhaust portion L ₂ are integrated, the destruction of the rotor R is prone from the lower end of the threaded portion. First, the upper end of the thread groove 34 is constrained by the blade exhaust, whereas the lower end is not constrained. This is because the amount of elastic deformation increases as it goes. Second, because the absolute pressure of the process gas used in semiconductor manufacturing and the like is high, the lower end side of the thread groove is susceptible to corrosion, and as a result, cracks due to stress during elastic deformation are likely to occur. is there.

As shown in FIG. 8, when the lower end of the thread groove spacer 54 is fixed or in contact with the casing 14B, when the thread groove spacer 54 is deformed to the outer peripheral side, the deformation or the contact portion restrains the deformation. Force applied in the direction is directly transmitted to the casing. On the other hand, in this modification, since between the lower end and the casing 14B of the screw groove spacer 54 there is a gap T _3, without being bound by some casing be modified outwardly while sliding inside the low-friction member 58b rotates Thus, the rotational energy can be lost.

FIG. 10 shows another modified example in which the second embodiment shown in FIG. 8 is further improved. This modified example is applied to the boundary portion between the main body of the thread groove spacer 54 and the flange portion 54a. The notch-shaped breaking groove portion 70 is provided so as to extend over the entire length in the circumferential direction, thereby forming the fragile portion 72. According to this modification, when an abnormal torque of a certain threshold value or more acts on the thread groove spacer 54, the fragile portion 72 shears and breaks along the breaking groove 70, and the main body of the thread groove spacer 54 moves from the flange portion 54a. To separate. Accordingly, the thread groove spacer 54 rotates together with the rotor R via the low friction member 58b and gradually consumes the rotational energy.

FIG. 11 shows a third embodiment. In this embodiment, the casing 14 is divided into an intake side casing 14A and an exhaust side casing 14B, and between the fixed blade spacer 50 and the intake side casing 14A. In addition, ball bearing devices (friction reduction structures) 80a and 80b are provided between the thread groove spacer 54 and the exhaust casing 14B. These ball bearing devices 80a and 80b are configured such that balls are arranged between the inner rings 82a and 82b and the outer rings 84a and 84b, respectively. In this embodiment, the inner rings 82a and 82b are thicker than the outer rings 84a and 82b. It is thicker than the wall thickness of 84b, and therefore the rigidity is set high.

  In this embodiment, since the mechanical strength of the inner rings 82a and 82b of the ball bearing devices 80a and 80b is large, an abnormality occurs on the rotor R side, and the rotor R and its fragments collide with the stator S. Even if a large amount of force is applied locally, the deformation of the raceways of the inner rings 82a and 82b is prevented, and the ball bearing devices 80a and 80b always rotate stably. The outer rings 84a and 84b are supported by the casings 14A and 14B, and even if they are made thin, there is little influence on the raceway surface.

  Further, as a friction reducing structure, a roller bearing can be used instead of the ball bearing. In this case, the same effect as described above can be obtained by making the inner ring thicker than the outer ring.

FIG. 12 (a) but showing still another turbo-molecular, in this example, the thread groove pumping section L _2, the shock absorbing member between the screw groove spacer 54 and the ball bearing unit 80b (shock absorbing structure) 86 Is provided. As the shock absorbing member 86, a relatively flexible metal material, a polymer material, or a composite material thereof is used. Thus, by providing an impact absorbing structure between the stator S and the pump casing 14, it is possible to prevent the impact torque transmitted from the rotor R to the stator S from being transmitted to the casing 14, and to destroy the casing 14 and the vacuum. Can be prevented. In addition, the above effect can be further enhanced by using a friction reducing structure such as the ball bearing device 80b and an impact absorbing structure in combination.

  In FIG. 12B, the shock absorbing member 86 is configured as a composite material in which a relatively rigid stainless plate 88 and a relatively soft lead plate 90 having a high shock absorbing function are stacked. It has both an impact absorption function and a shape maintenance function.

In the above, the various configurations of the present invention has been applied to a wide area turbo-molecular pump having a blade pumping section L ₁ and the thread groove pumping section L _2, in accordance with the respective purpose, the configuration of the present invention only blade pumping section L ₁ or it may be employed to pump having only the thread groove pumping section L _2, the configuration of the present invention only one of the exhaust part in a wide area turbo-molecular pump having both blade pumping section L ₁ and the thread groove exhaust portion L ₂ Of course, may be adopted. Needless to say, the configurations of the above-described embodiments may be combined as appropriate.

It is a cross-sectional view showing the main portion of the turbo molecular pump. FIG. 2 is a plan view of the uppermost and lowermost rotor blade spacers of FIG. 1. It is sectional drawing which shows the principal part of another turbo-molecular pump. FIG. 4 is a sectional view taken along line AA in FIG. 3. It is sectional drawing of the turbo-molecular pump of the 1st Embodiment of this invention. It is a top view which shows the rotary blade spacer of FIG. It is the BB sectional view taken on the line of FIG. It is sectional drawing of the turbo-molecular pump of the 2nd Embodiment of this invention. It is sectional drawing of the turbo-molecular pump of the modification of 2nd Embodiment shown in FIG. It is sectional drawing of the turbo-molecular pump of the other modification of 2nd Embodiment shown in FIG. It is sectional drawing of the turbo-molecular pump of the 3rd Embodiment of this invention. (A) It is sectional drawing of another turbo-molecular pump, (b) It is sectional drawing which shows other embodiment of an impact-absorbing structure. It is sectional drawing which shows the conventional turbo molecular pump.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Main axis | shaft 12 Rotating cylindrical part 14 Casing 15 Base 16 Fixed cylindrical part 18 Driving motor 30 Rotating blade 32 Fixed wing 34 Thread groove part 36, 54 Thread groove spacer 38, 38a, 38b, 38c, 50 Fixed wing spacer 42, 44 Circumferential grooves 46, 48 Support pins 52, 56 Bolt (fastening member)
58, 58a, 58b Low friction member (friction reduction structure)
72 Vulnerable parts 80a, 80b Ball bearing device (friction reduction structure)
86 Shock absorbing member R Rotor S Stator L ₁ Blade exhaust part L ₂ Thread groove exhaust part

Claims (6)

In the turbo molecular pump having a blade exhaust part and a groove exhaust part constituted by a rotor and a stator inside the pump casing,
At least a part of the stator that fixes at least a part of the stator to the pump casing is provided with a fragile part that is broken when an abnormal torque acts from the rotor due to abnormal rotation or destruction of the rotor itself,
When an abnormal torque acts on at least a part between the stator and the pump casing due to a rotation abnormality or destruction of the rotor itself on at least a part of the stator, the blade exhaust is broken after the fragile part is broken. A turbo-molecular pump, characterized in that a friction reducing structure is provided in which the stator of the part and the groove exhaust part are rotated.   2. The turbo molecular pump according to claim 1, wherein the friction reducing structure rotates a stator of the blade exhaust part and the groove exhaust part together.   The turbo molecular pump according to claim 1, wherein the friction reducing structure is a low friction member or a bearing. In the turbo molecular pump having a blade exhaust part and a groove exhaust part constituted by a rotor and a stator inside the pump casing,
The stator of the groove exhaust portion is fixed by engaging a flange portion with a step surface provided in the pump casing,
Abnormal torque acts on at least a part of the engaging portion between the flange portion of the stator of the groove exhaust portion and the stepped surface of the pump casing due to abnormal rotation or destruction of the rotor itself on at least a portion of the stator. A fragile part that breaks when
The stator of the groove exhaust portion rotates along the engaging portion when an abnormal torque acts on at least a part of the stator due to abnormal rotation or destruction of the rotor itself. Turbo molecular pump. The turbo molecular pump according to claim 4 , wherein a stator of the blade exhaust part is fixed to a flange part of the stator of the groove exhaust part. In the turbo molecular pump having a blade exhaust part composed of a rotor and a stator inside the pump casing,
The wing exhaust part has a fixed wing and a fixed wing spacer for fixing the fixed wing,
A cylindrical low friction structure is provided so as to surround the fixed blade spacer,
The cylindrical low friction structure breaks the fastening member that fastens the fixed blade spacer when the abnormal torque acts on the fixed blade spacer due to abnormal rotation or destruction of the rotor itself, thereby fixing the fixed blade spacer. A turbo-molecular pump configured to allow rotation of a blade spacer.

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