JP2013104430A - Friction vacuum pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a Holweck pump stage having improved vacuum data.SOLUTION: A rotor 2 is rotatably supported by a rolling bearing 4, and includes a hub 8 and a sleeve 10 fixed on the hub. The vacuum pump includes the rotor 2 where the sleeve 10 has a first end 12 and a free second end 14 on the opposite side to the hub, and a stator 20 that has a clearance 30 having a clearance width 100 concentrically with the sleeve and is arranged to cover the sleeve. In order to improve the vacuum data, it is proposed to decrease the clearance width toward the rolling bearing.

Description

  The present invention relates to a vacuum pump according to the superordinate concept of claim 1.

  For decades, turbomolecular pumps that have been successful in the market in many different industrial applications, such as in gas analysis and semiconductor manufacturing, have been formed in part as so-called composite pumps. Compound pump means that the pump rotor is provided with a molecular pump stage in addition to the turbomolecular pump section.

  Such a successful structural type of molecular pump stage is called the Holweck pump stage in the name of the inventor. In most cases, a smooth sleeve rotates within a stator located inside or outside the sleeve, and the stator generally has a plurality of helical grooves on the side facing the sleeve. There is a gap between the stator and the sleeve, and the gap is generally less than 1 mm wide, often only a fraction of a mm, for example a multiple of 0.1 mm.

  For determining the size of the gap, geometrical data such as manufacturing tolerances, the influence of the centrifugal force during operation on the sleeve diameter and thermal expansion are decisive factors. These effects create a wide gap size, which limits the quality of the vacuum data, eg compression.

  Accordingly, it is an object of the present invention to provide a Holbeck pump stage having improved vacuum data.

This problem is solved by a vacuum pump having the features of claim 1. The dependent claims 2 to 13 provide advantageous variants of the invention.
The gap width of the gap between the sleeve and the stator changes. In this case, the gap width of the gap preferably changes in the axial direction of the vacuum pump and takes different values at various heights in the axial direction. The non-constant gap width can easily be adapted to the maximum rotor radial displacement expected within the respective axial height range, thereby increasing pump efficiency.

The sleeve may have a first end and a free second end opposite the hub.
According to a preferred embodiment, the rotor of the vacuum pump is rotatably supported by a rolling bearing and the clearance width is reduced towards the rolling bearing. A narrow gap is achieved based on the small play of the rolling bearing, which significantly improves the vacuum data. For example, in the case of a light gas such as helium, the compression can be sufficiently improved, for example, 10 times.

  In addition to rolling bearings, permanent magnetic bearings can be used to support the rotor. In this case, it is particularly advantageous that the required gap shape is applied, since permanent magnetic bearings have a large play and therefore require a large gap. At this time, the gap is preferably wide in the direction of the permanent magnetic bearing and narrow in the direction of the rolling bearing, or has a gap width increasing in the direction of the permanent magnetic bearing. However, in the prior art, the clearance has been determined according to the play of the permanent magnetic bearing. By utilizing the features of claims 1 to 13, a gap is achieved which, at least in part, does not take into account play in the permanent magnetic bearing, unlike the methods which have been used for decades. Therefore, a particularly advantageous increase in efficiency is obtained when the rotor is supported by permanent magnetic bearings and rolling bearings.

  It is preferred that the sleeve and the stator are part of the Holbeck pump stage or form the Holbeck pump stage. The sleeve may be supported by a hub. The sleeve is preferably formed concentrically and in particular rotationally symmetric with respect to the axis of rotation of the vacuum pump, and preferably has the shape of a cylindrical sleeve coaxial with the axis of rotation.

In principle, it is also conceivable that, within the scope of the invention, the gap width does not decrease in the direction of the rolling bearing, but increases, for example, constantly or stepwise in the direction of the rolling bearing.
According to one embodiment, the vacuum pump comprises two sleeves arranged in series in the axial direction, which sleeves may in particular form a common Holbeck stage together or be part of a common Holbeck stage. Good. In this case, the two sleeves may together form at least part of a particularly cylindrical sleeve-shaped surface and / or a smooth surface of the rotor that form a gap with the stator. A hub to which at least one of the sleeves is secured may in this case be present between the sleeves in the axial direction and the sleeve may extend in the opposite axial direction with respect to the hub. Both sleeves can in principle be arranged on the same hub or be supported by the same hub. The sleeve may be supported by different hubs, in which case the two hubs are axially spaced from each other and / or one of the two hubs is permanently magnetized with the other hub of the vacuum pump It is arranged between the bearings.

  The sleeve of the vacuum pump is connected to or supported by the hub within a range spaced from its axial end or within a range disposed between its axial ends. In this case, the sleeve extends from the hub in the opposite axial direction.

  The vacuum pump may include a stator arranged concentrically inside the sleeve and a stator arranged concentrically outside the sleeve, in which case each stator forms a gap having a gap width with the sleeve. , And in this case, both gaps are preferably pumped in parallel to each other, i.e., merged at, for example, their downstream ends. Thus, the gap formed by the inner stator is capable of receiving the gas to be supplied through one or more openings in the hub, and each of the one or more openings is one for the gap. Form a gas inlet. Both gaps may each be part of one Holbeck stage. The gap width of the gap formed by the outer stator and / or the gap width of the gap formed by the inner stator may vary in particular in the axial direction and may decrease especially towards the rolling bearing. According to one advantageous embodiment, the gap width of the gap formed by the inner stator varies more than the gap width formed by the outer stator and may increase or decrease more particularly towards the rolling bearing. You may let them. As an alternative or additional aspect, the minimum gap width of the gap formed by the inner stator may be smaller than the minimum gap width of the gap formed by the outer stator. This compensates for the different pumping characteristics of both pump stages based on the different radial spacing of both gaps from the axis of rotation and the different relative speeds formed thereby, resulting in an improvement especially in parallel operation of the pump stages. Pump characteristics are achieved. The gap width of one gap, in particular the gap width formed by the outer stator, may in principle be constant.

  In parallel pumping arrangements of the outer surface and the inner surface of the sleeve or sleeves, it is also advantageous that a gap width is formed that decreases towards the rolling bearing. In this case, the gap width reduction allows a very precise tuning of the compression of the different pumping gaps in parallel with each other, for example between a stationary component and a moving component (or a stationary component and a non-moving component). The effect of different relative speeds on the compression can be compensated.

  According to an advantageous embodiment, the gap width is reduced or increased linearly or stepwise. The gap width may in principle vary over part of the gap length or over the entire length of the gap length. The gap width may vary, for example, in the first section and may be constant in the second section. Similarly, the gap width may vary differently in the various sections and may increase or decrease, for example in the first section constantly and in particular linearly and in the second section in steps. May be. The gap width may increase or decrease in the same axial direction over its entire length, but the gap width may increase in the axial direction in the first section and decrease in the same axial direction in the other sections. The various sections are preferably formed by axial length sections with different gaps. The change in axial gap width that exists over a portion of the sleeve's axial length or over the entire length of the sleeve's axial length may be provided over the entire circumference of the sleeve, but this is not necessarily the case. It does not have to be.

The gap may be formed in a substantially conical or frustoconical shape over at least a part of its axial length and in particular over substantially the entire length of its axial length.
The invention will be described in detail and their advantages will be elucidated by way of an example and modifications thereof.

FIG. 1 shows a schematic cross-sectional view of a Holbeck stage rotor and stator having two rolling bearings. FIG. 2 shows a schematic cross-sectional view of a Holbeck stage rotor and stator supported by rolling and permanent magnetic bearings. FIG. 3 shows a schematic cross-sectional view of the Holbeck stage sleeve and stator. FIG. 4 shows a schematic cross-sectional view of a turbomolecular pump element and a rotor having a plurality of sleeves and a stator. FIG. 5 shows a schematic cross-sectional view of a rotor having sleeves acting in parallel.

FIG. 1 schematically shows a rotor 2 and a stator 20 of a vacuum pump. The rotor 2 has a hub 8 that supports a sleeve 10.
The rotor 2 is rotatably supported by a rolling bearing 4, and the rolling bearing 4 is present at an interval 102 with respect to the hub 8. In order to further support the rotor 2, a second rolling bearing 6 may be provided.

  A stator 20 is provided concentrically with the sleeve 10, and the stator 20 forms a gap 30 and surrounds the sleeve 10. The stator 20 has a helical groove 24 on its radially inner surface or has a corresponding pump structure suitable for achieving the pumping effect. A web 22 is left between the grooves. The gap 30 has a width 100, which is determined between the surface of the web 22 facing the sleeve 10 and the surface of the sleeve 10. In addition to or instead of the stator-side pump structure, the sleeve 10 may have a suitable pump structure to achieve the pumping effect, where the gap width 100 of the gap 30 is in this case Is also related to the surface of the web of the pump structure.

  The rotor 2 is rotated by a driving device. In this case, the drive device may include a motor coil 42 on the stator side and a drive magnet 44 on the rotor side. The number of rotations is determined so that a molecular pump effect is formed in the gap 30 between the sleeve 10 and the stator 20. As a result, the gas is pumped in the direction 104 directed to the rolling bearing 4.

  The sleeve may have a first end 12 at which the sleeve may be fixed to the hub 8. In this case, an adhesive bond may be made, which advantageously facilitates selection of the hub 8 and sleeve 10 material pair. The second end 14 is opposite to the hub 8 and is a free end (that is, free). Depending on the length of the sleeve 10, the second end 14 may be disposed between the hub 8 and the rolling bearing 4. As an alternative, the rolling bearing 4 may be present between the hub 8 and the second end 14.

  The sleeve 10 is enlarged by the rotation. Therefore, it is advantageous to form the sleeve 10 and the disk 8 from different materials, the sleeve 10 being made of, for example, carbon fiber reinforced plastic (CFK) and the hub 8 being made of aluminum. In this case, it is observed that the hub 8 expands more than the sleeve 10 under the influence of centrifugal force and temperature. When the second rolling bearing 6 is used, the elongation of the hub 8 is a specific value. Here, it is proposed that the gap 30 is not determined based on this elongation, but formed so that the gap width 100 decreases toward the rolling bearing 4. This conical gap 30 results in better vacuum data in the pumping direction. In fact, for light gases, for example, compression is significantly improved by a factor of ten. Based on the small play of the rolling bearing 4, in this case the gap width 100 can be minimized.

  In an advantageous variant, the second end 14 is arranged at an axial height in the range between 0.8 and 1.2 times the distance 102 between the hub 8 and the rolling bearing 4. ing. The advantage of the improvement of the vacuum data is thereby noticeable because the displacement of the sleeve 10 is small and a very narrow gap 30 can be selected within this range of axial height.

  Accordingly, in a next advantageous variant, the second end 14 is present at the height of the rolling bearing 4 because at this time the maximum operating pressure is formed inside the gap 30 and the minimum gap width 100. Because it is done.

  FIG. 2 shows a modification in which a permanent magnetic bearing 40 is provided instead of the second rolling bearing 6 in order to support the rotor 2. The advantage of such a bearing 40 is that it is suitable for high vacuum and has no wear. However, the permanent magnetic bearing 40 has a rigidity smaller than that of the rolling bearings 4 and 6 in the radial direction even when the latest magnetic material is used in the case of the structural dimensions possible in the vacuum pump. This is because, for example, not only in the permanent magnetic bearing 40 but also in the range of the hub 8 existing in the interval 102 to the rolling bearing 4 depending on the operating conditions such as the assembly posture, the radius of the rotor 2 Means greater directional displacement. Therefore, depending on the prior art, the gap width 100 of the gap 30 between the stator 20 and the sleeve 10 has been determined based on the displacement of the hub 8 over its entire length. In this case, the elongation due to the centrifugal force of the sleeve 10 was also taken into account, depending on the material of the sleeve. Here, it is proposed that the gap width 100 decreases toward the rolling bearing 4. This improves the vacuum data based on the pumping effect raised by the decreasing dimension in the pumping direction 104. This is particularly the case when the permanent magnetic bearing 40 is attached to the first end 12 of the sleeve 10 according to a variant of the idea, i.e. in particular in the axial direction of the sleeve 10. This is achieved when spaced from the portion 12 but when the spaced distance is less than from the second end 14 of the sleeve 10.

  A modification in which the sleeve 10 is manufactured from carbon fiber reinforced plastic (CFK) is advantageous, whereby a very small gap 30 is achieved towards the rolling bearing 4, in particular at the height of the rolling bearing 4. .

  Other form features that can be combined with the above features will be described with reference to FIG. The rotor 2 and stator 20 and the course of the gap width 100 over the gap length are shown on the right side of the figure.

  The first end 12 of the sleeve 10 may be connected to the hub 8 by, for example, an adhesive bond, an inset connection or a shrink fit connection. As an alternative, the sleeve 10 may protrude axially beyond the hub 8, as indicated by the dotted line in FIG. In this case, the hub 8 is arranged between a first end 12 ′ indicated by a dotted line of the sleeve 10 protruding beyond the hub 8 and a second end 14 of the sleeve 10. At this time, the stator 20 may be correspondingly extended as indicated by the dotted line. To simplify manufacturing, it is also conceivable to divide the stator 20 along the stator parting line 110 and form it as a plurality of parts.

  Instead of a continuous linear change in gap width across the gap length 108, a change in gap width may be made for each section. As an example, a division into first and second sections 90 and 92 is shown. With the first course 94 shown as an example, the gap width first decreases linearly and then always shifts to a constant part. According to the second process 96 shown as an example, the gap width is reduced stepwise, and the gap width jumps (steps) from the second end portion 14 toward the first end portion 12. To increase. In other words, the gap width decreases in a jump shape (step shape) from the first end portion 12 toward the second end portion 14.

  The modification shown in FIG. 4 shows the rotor 2 supported by the rolling bearing 4 and the permanent magnetic bearing 40. A turbo molecular pump structure 50 may be provided between the hub 8 and the permanent magnetic bearing 40, and the turbo molecular pump structure 50 may surround components of the permanent magnetic bearing 40.

  The hub 8 supports the first sleeve 10 and in addition to the second sleeve 16, which is fixed to the hub 8 or formed integrally with the hub 8 and of the hub. The first sleeve 10 is disposed on the opposite side. The stator 20 forms a gap and surrounds the first sleeve and the second sleeve 16 concentrically. This gap extending over the length of both sleeves 10, 16 is formed on the basis of the viewpoints already shown. In particular, the gap width decreases in the direction of the rolling bearing 4 over the gap length 108. This arrangement allows the use of metal as the material for the second sleeve 16 because the gap now has the largest gap width within the range of maximum expansion due to centrifugal force. is there.

  The hub 8 may be divided along the hub dividing line 112 in the direction of the longitudinal axis of the rotor, so that a second hub 8b is formed, and the second hub 8b is spaced from the first hub. It may be provided.

There may be other sleeves for forming the molecular pump section, for example a third sleeve 18 arranged concentrically inside the first sleeve 10.
According to the variant shown schematically in FIG. 5, at least one opening 60 is provided on the hub 8 fixed to the rotor 2, and concentric with the first sleeve 10 and of the first sleeve 10. It is proposed to arrange the intermediate stator 62 radially inward. The intermediate stator 62 forms a pumping internal gap 64 together with the first sleeve 10. The first sleeve 10 further forms a gap 30 to form a pumping action in cooperation with the stator 20 that concentrically surrounds the first sleeve 10. This arrangement forms one pump stage operating in parallel or two pump stages operating in parallel, with gas being supplied along the outside and the inside of the first sleeve in one or two pump stages. Is done. In a molecular pump, the pumping action is a function of the relative velocity of the moving structural part with respect to the stationary structural part. Therefore, it is not easy to provide an effective parallel pumping arrangement. Here, it is proposed that the gap width 100 of the gap 30 and / or the gap width 106 of the gap 64 decreases toward the rolling bearing 4. This reduction allows fine adjustment of the compression achieved by the respective gaps 30, 64, ie, the pressure ratio between the gap start and gap ends, by selecting the gap width change. This fine tuning provides a highly effective parallel pumping holbeck stage with better efficiency data than in the prior art.

  In addition to the first sleeve 10, the third sleeve 18 may be disposed concentrically with the first sleeve 10 and radially inward of the intermediate stator 62. That is, another pump passage is formed. Other sleeves may be combined as shown in FIG.

2 Rotor 4 Rolling bearing 6 Second rolling bearing 8 Hub (disc)
8b 2nd hub 10 1st sleeve 12, 12 '1st end part 14 2nd end part 16 2nd sleeve 18 3rd sleeve 20 stator 22 web 24 groove | channel 30, 64 clearance 40 permanent magnetic bearing 42 Motor coil 44 Drive magnet 50 Turbo molecular pump structure 60 Aperture 62 Intermediate stator 90 First section 92 Second section 94 Progress of gap width (linear)
96 Progress of gap width (in stages)
100, 106 Gap width 102 Gap 104 Pumping direction 108 Gap length 110 Stator dividing line 112 Hub dividing line

Claims (13)

A rotor (2) having at least one hub (8) and at least one sleeve (10) fixed to the hub and a gap (30, 64) having a gap width (100, 106) are formed to form a sleeve ( 10) a vacuum pump comprising at least one stator (20) arranged concentrically with respect to 10)
A vacuum pump characterized in that the gap width (100, 106) varies. The vacuum pump according to claim 1, wherein
The rotor (2) is rotatably supported by a rolling bearing (4);
A vacuum pump characterized in that the gap width (100, 106) decreases towards the rolling bearing (4). The vacuum pump according to claim 1 or 2,
A vacuum pump, characterized in that a permanent magnetic bearing (40) is provided to support the rotor (2). The vacuum pump according to claim 3,
A vacuum pump characterized in that a permanent magnetic bearing (40) is attached to the first end (12, 12 ') of the sleeve (10). The vacuum pump according to any one of claims 2 to 4,
A vacuum pump, characterized in that a free second end (14) on the opposite side of the hub (8) of the sleeve (10) is arranged at the height of the rolling bearing (4). The vacuum pump according to any one of claims 2 to 5,
Of the sleeve (10), the free second end (14) opposite the hub (8) is 0. 0 of the distance (102) between the hub (8) and the rolling bearing (4). A vacuum pump, characterized in that it is arranged at an axial height in the range between 8 and 1.2 times. The vacuum pump according to any one of claims 3 to 6,
A vacuum pump characterized in that a turbo molecular pump structure (50) is provided between the hub (8) and the permanent magnetic bearing (40). The vacuum pump according to any one of claims 1 to 7,
A vacuum pump characterized in that the first end (12, 12 ') of the sleeve (10) is fixed to the hub (8). The vacuum pump according to any one of claims 1 to 8,
2. A vacuum pump characterized in that the second sleeve (16) is fixed to the hub (8) and arranged on the opposite side of the hub (8) from the first sleeve (10). The vacuum pump according to claim 9,
A vacuum pump characterized in that the second sleeve (16) is fixed to a second hub (8b) disposed between the hub (8) of the vacuum pump and the permanent magnetic bearing (40). . The vacuum pump according to any one of claims 1 to 10,
A vacuum pump characterized in that the sleeve (10) is joined to the hub (8) by adhesive bonding. The vacuum pump according to any one of claims 1 to 11,
The hub (8) has at least one opening (60);
The opening (60) allows gas to flow between the sleeve (10) and the intermediate stator (62) arranged concentrically inside the sleeve (10),
A pump action inner clearance (64) is formed between the intermediate stator (62) and the sleeve (10),
A vacuum pump characterized in that the gap width (106) of the pumping inner gap (64) varies and decreases in particular towards the rolling bearing (4) of the vacuum pump. The vacuum pump according to any one of claims 1 to 12,
A vacuum pump characterized in that the gap width (100, 106) increases or decreases linearly or stepwise.

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