EP2520807B1 - Vacuum pump with rotor - Google Patents

Description

The invention relates to a vacuum pump according to the preamble of claim 1 and a method for balancing a rotor of such a vacuum pump.

A vacuum pump according to the preamble of claim 1 is known from EP 1 619 395 A1 known. Moreover, a vacuum pump having a balancing means for changing a balancing state of a rotor of the vacuum pump and a sensor for detecting the balancing state in the EP 1 273 803 A2 disclosed. Furthermore, devices for determining a state of balance of a rotating body in the US 5 544 073 A or US 4 046 704 A disclosed.

The running quality of a vacuum pump, in particular one with a fast-rotating rotor, depends crucially on the balancing quality of the rotor or the rotors. In the manufacturing process of a vacuum pump, a very high balancing quality can be achieved, since the balancing process is carried out under the best conditions and partly in special devices.

Previously, vacuum pumps, in particular molecular and turbomolecular vacuum pumps, were only used in clean applications where the lowest possible end pressure was of prime importance. Today they are exposed to very different conditions. Vacuum pumps are increasingly being used to extract process gases, which in some cases lead to extreme process deposits on the rotor and in the pumping system. The balancing quality of a vacuum pump can deteriorate to a high degree of contamination within just a few months so far that a further operation is permitted only after re-balancing.

In the prior art measures against this problem are known.

One of these measures is targeted temperature management. In this individual areas of the vacuum pump are subjected to a heat treatment in order to avoid deposits.

Another solution for limiting deposits is to add inert gas. The goal is either a substantial delimitation of the process components from the surfaces of the vacuum pump or an acceleration of the pumping speed.

Functional coatings of surfaces as well as optimization of the gas guidance geometry are also used.

Ultimately, these measures delay the inevitable only by slowing down the deposition process. The balancing quality continues to decline and sooner or later a state is reached where the balancing quality must be improved. This usually means an exchange of the vacuum pump, so high material costs and time loss, as intervened to replace in the process.

It is therefore an object of the invention to provide a vacuum pump in which the imbalance change can be handled more cheaply.

The object is achieved by a vacuum pump having the features of the first claim and a method having the features of claim 10. The dependent claims 2 to 9 indicate advantageous developments.

The claimed features create a vacuum pump whose balancing quality can be improved in the simplest way. This can be done at the customer's site. The invention can be carried out so that the vacuum pump does not have to be removed from the customer's device. Instead of a costly exchange with possibly subsequent disassembly of the vacuum pump, a fast rebalancing occurs in a process break. This achieves an enormous cost and time advantage.

Reference to exemplary embodiments and their developments, the invention will be explained in more detail and the representation of its benefits to be deepened.

Fig. 1:

Schematische Anordnung mit Vakuumpumpe;

Fig. 2:

Schematische Darstellung der Komponenten einer Vakuumpumpe mit einem in Wälzlager und Magnetlager gelagerten Rotor;

Fig. 3:

Schematische Darstellung der Komponenten einer Vakuumpumpe mit einem in fünf Achsen aktiv magnetisch gelagerten Rotor;

Fig. 4:

Prinzipdarstellung zur Verdeutlichung des Wuchtzustands;

Fig. 5:

Prinzipdarstellung zur Veranschaulichung der Änderung des Wuchtzustands;

Fig. 6:

Schnitt durch einen glockenförmigen Rotor mit Wuchtbohrungen;

Fig. 7:

Draufblick auf einen glockenförmigen Rotor mit Wuchtmitteln;

Fig. 8:

Schnitt, der nicht zur Erfindung gehört, durch einen glockenförmigen Rotor in Höhe der Wuchtmittel.

Show it:

Fig. 1:

Schematic arrangement with vacuum pump;

Fig. 2:

Schematic representation of the components of a vacuum pump with a stored in bearings and magnetic bearing rotor;

3:

Schematic representation of the components of a vacuum pump with an active magnetically mounted in five axes rotor;

4:

Schematic representation to illustrate the balancing state;

Fig. 5:

Schematic representation to illustrate the change in the balancing state;

Fig. 6:

Section through a bell-shaped rotor with balancing holes;

Fig. 7:

An overview of a bell-shaped rotor with balancing tools;

Fig. 8:

Section, which does not belong to the invention, by a bell-shaped rotor in the amount of balancing means.

In a slender illustration shows Fig. 1 an arrangement with a vacuum pump. A chamber 2, in which, for example, a coating process takes place, has a chamber flange 4, to which a vacuum-tight vacuum pump 10 is attached in a gas-tight manner. In its interior, the vacuum pump houses a rotor 20. Gas, which is conveyed and compressed in the vacuum pump, is transferred to the gas outlet line 6, which leads, for example, to a backing pump, not shown, which then compresses the gas to atmospheric pressure. The vacuum pump has a pump electronics 12, which can be flanged directly to the vacuum pump. Within the pump electronics electronic assemblies are provided for various tasks, such as drive modules, interface controls and the like. With the pump electronics, a display element 16 is connected, which can be designed as a screen in the housing of the pump electronics, as a detachably connected handset with optical signal instrument or connected via an interface computer.

A first embodiment of the interior of the vacuum pump is shown in FIG Fig. 2 shown schematically. The rotor 20 has a shaft 22 which carries at least one disc hub 24 to which a ring of blades 26 is attached. A first end of the shaft is supported by a radial permanent magnet bearing 44 comprising a bearing stator 46 and a bearing rotor 48. A fishing camp 36 prevents the contact of Lagerstator and bearing rotor in the case of high and excessive deflection of leading forces on the rotor.

A second end of the shaft is opposite the first. In its vicinity, the shaft is rotatably supported by a rolling bearing 50 in the axial and radial directions.

Between permanent magnet bearing and roller bearings, a motor magnet 40 is mounted on the shaft, which cooperates with a powered motor stator 38 and the shaft in rapid rotation about a rotation axis 200.

Between disc hub and motor magnet, the rotor has a Holwecknabe 30 rotatably connected to the shaft, which carries a Holweckzylinder 32.

To balance the rotor has this balancing. These include in the example of Fig. 2 Balancing holes and introduced therein, for example, screwed, balancing weights. A first plurality of balancing bores 102 with balancing weights 104 are provided near the permanent magnet bearing. A second plurality of balancing bores 106 with balancing weights 108 are mounted in the axle hub.

The energization of the motor stator is effected by a drive control 130 connected to the motor stator by means of current supply lines. A rotor position detection unit 132 is connected to the energizing lines by means of position detection taps 142 and evaluates the rotor position from the signals of the energizing lines, for example the counter-electromotive force induced by the motor magnet. Conceivable is the use of Hall probes or the like, but the example shown has a cost advantage by eliminating components and avoids a source of error. The rotor position detection unit may be part of the drive control and, for example, an in the motor control running in the case of a sinusoidally commutated synchronous motor to determine the rotor position.

With the rolling bearing, a vibration sensor 52 is connected, which receives the vibrations of the rolling bearing. In this vibration signal, the information about the imbalance of the rotor 20 is included. The vibration sensor is operatively connected via a sensor connection 144 to an evaluation unit 134. This is also operatively connected by means of a position detection connection 148 with the rotor position detection unit.

The evaluation unit is designed so that it generates the information about the imbalance from the vibration signal and assigns the information about the rotor position. By an assignment means, for example, provided on the Holwecknabe recess 100 on the rotor, it is possible to unambiguously allocate the information about the unbalance the balancing bores and balancing weights.

Before the interaction of the parts and the method are described in more detail, provides Fig. 3 a likewise suitable embodiment of the inner life of the vacuum pump 10 before.

The rotor 20 comprises in this example, in addition to the shaft 22 a bell-shaped body 28, often called also short bell, which carries the blades 26. Through the bell, a cavity is created, in which the shaft is arranged. Surrounding it, it at least partially incorporates the components of a magnetic bearing to support the rotor in five axes.

The rotor has balancing means comprising balancing bores and balancing weights. The balancing bores 102 of the first balancing plane and the balancing weights 104 located therein are located on the front side of the bell on which the shaft opposite outside. The balancing bores 106 and the balancing weights 108 of the second balancing plane contained therein are provided on the casing of the bell between two blade rows. In order to ensure the accessibility of the balancing weights even after prolonged operation of the rotor and resulting deposits, the balancing bores and balancing weights can be protected. For this purpose, a cover 80 may be provided which protects the balancing bores of the first level and is releasably connected to the bell. Between the rows of blades, a closure 82 may be provided, which is designed, for example, as a circulating around the bell metal band.

An assignment means, which is designed for example as a small recess 100 in the form of a reduction, allows an assignment of the balancing bores to the position of the motor magnet and thus the assignment of the balancing state of the rotor to the balancing bores.

For protection against deposits, the assignment means, in the example shown, the recess, be similar to the balancing holes covered. In Fig. 3 an alternative is shown, which is also applicable to the balancing bores and balancing weights. By means of a blocking gas inlet 84, sealing gas is admitted under the bell, whereby both the bell and the magnetic bearing are protected from process gases. The marking is now arranged on the bell so that they are flown by the sealing gas and thus process deposits on the marking are suppressed.

The magnetic bearing comprises a bell-side end of the shaft associated upper radial bearing stator 60, an upper radial sensor 62, a lower radial bearing stator 64, and a lower radial sensor 66. With these radial bearings, the storage is effected in two perpendicular spatial directions. The radial sensors provide information about the position of the shaft within the radial bearing stators.

The remaining fifth axis is oriented along the axis of rotation 200 and is supported by a thrust bearing. Serve for this purpose an axial bearing stator 68 and the rotor side a thrust washer 70th

The energization of the coils of the radial and axial bearing stators is adjusted in accordance with the signals of the radial and axial sensors by a magnetic bearing controller 136 connected to the sensors and the coils. The signals from the sensors contain the information about the balancing state of the rotor.

A sufficient number of backup bearings 36 ensures the storage in de-energized storage.

A drive causes the shaft and thus the rotor to rotate rapidly and comprises a motor stator 38 and a motor rotor 40. The energization of the motor stator is effected by the drive controller 130 via supply lines 140.

A rotor position detection unit 132 is provided, which detects the rotational position of the rotor in a suitable form. In the example shown, position detection taps 142 are provided with which the position information is determined from the counter-motor force induced by the motor magnet of the motor rotor.

An evaluation unit 134 is operatively connected to the rotor bearing detection unit 132 and to the magnetic bearing control 136. It is designed so that a rotor position is assigned to the determined from the magnetic bearing sensor signals balance state of the rotor. Due to the marking of the balancing state is then clearly associated with the balancing bores and balancing weights.

The interaction of the aforementioned on hand of the Fig. 2 and 3 parts described should be based on the Fig. 4 be explained in more detail. Schematically illustrated are the first balancing plane 204 and the second balancing plane 206, in which balancing weights 104 and 108 are provided. With these balancing weights, the rotor is balanced as well as possible during production, so that a smooth running around the axis of rotation 200 results.

The motor rotor has a pronounced direction 202, which follows, for example, from the magnetization direction of a motor magnet. This direction is fixedly assigned to the positions of the balancing bores, since the motor rotor and balancing bores are stationary on the rotor. Again, stationary on the rotor is the marker 100.

During operation, deposits on the rotor occur, for example. Since such deposits never take place completely rotationally symmetric, they lead to a change in the balancing state, which in the Fig. 4 is represented by an imbalance 208 in an unbalance plane 210. The unbalance leads to a troubled run around the axis of rotation and it is now the goal to compensate for this imbalance by changing the balancing weights of the various balancing planes.

The effects of imbalance are contained in the sensor signals. The detection can be measured by sensors in two directions perpendicular to the axis of rotation. Alternatively, a sensor may be provided which measures only in one direction and whose signal is then analyzed phase-related, because during the revolution about the axis of rotation, the imbalance is once in the direction and once perpendicular to the sensor direction.

The evaluation unit is now designed so that it is out of the imbalance changed balancing state derives a necessary change of individual balancing weights in the balancing planes and assigns them to the rotor position. The absolute value of the unbalance can be output. A simpler embodiment, however, provides to design the evaluation unit so that it determines only the relative change of the balancing state based on the balancing state after the pump has been manufactured. From this follows the necessary change in the balancing means, in the example shown, the individual balancing weights. These changes are first assigned to the rotor position, that is, the direction 202. Since this is in a fixed relationship to the assignment means, the changes are also assigned to this. After issuing the necessary changes in the balancing weights via the display element 16, which is accordingly adapted to output the information about the change of the balancing means, a service technician is able to make the necessary changes by looking up the allocation means of the rotor, for example the recess and starting from this, looking for the individual balancing bores and adapts the balancing weights contained therein. The adjustment can be a simple replacement of the balance weight.

The course of the balancing state and the method for balancing should be followed by the schematic representation for a two-dimensional case Fig. 5 be explained in more detail.

In the balancing plane 102, the balancing weights 104a to 104d are provided, which are distributed on the rotor over the circumference and arranged at a distance from the rotation axis 200. A first spatial direction 212 and a second orthogonal spatial direction 214 span the balancing plane.

The rotor can never be made so accurately that the center of mass coincides with the axis of rotation. He is therefore in a production balance state 230, the smooth running of the rotor at the required high speeds not possible. Therefore, the balance weights are added to achieve an initial balance state 232 where the center of gravity is sufficiently close to the axis of rotation. The masses are used in the initial state 240a to 240d, the rotor is in the Ausgangsuchtuchtzustand after this process step.

During use of the pump, deposits progressively change the balancing state according to the balancing curve 250 until the balancing state is achieved by deposits 234. This balancing condition requires rebalancing of the rotor for further operation of the pump.

As described above, the balancing state is included in the sensor signals. The evaluation unit is designed and configured to calculate the changes of the balancing means and to assign them to the rotor position and the allocation means to the balancing means. Alternatively, the absolute value of the imbalance can also be calculated and output. In both cases, as part of the process, the balancing state of the rotor is monitored and assigned to a rotor position.

The method now provides that upon a change in the balancing state, for example by the abovementioned deposits, balancing means provided on the rotor are changed to improve the balancing state. In the example, with the aid of the mass changes 244a to 244d, the balancing weights are brought to the mass according to balances 242a to 242d. As a result, the new balancing state 236 is reached which allows further operation of the rotor.

A development of the balancing shows Fig. 6 as a section through a rotor Fig. 3 , whereby the measure also after a rotor after Fig. 2 is applicable. In outline, the circumferential row of blades 26 can be seen. These are attached to the bell 28. About the scope the bell balancing bores 106 are distributed. All or part of the balancing bores may be designed as continuous as the balancing bore 112.

The assignment means may be used instead of or in addition to that in the Fig. 2 and 3 shown recess comprise a balancing bore with a larger diameter 110.

The allocation means provides a non-rotationally symmetric distribution of the balancing means in the circumferential direction. In Fig. 6 this is shown. The balancing bores 106 are located at a normal distance 220, wherein asymmetrically placed bores 114 are provided, which have a shortened distance 222 to at least one of the closest balancing bores.

Another embodiment of the allocation means shows the Fig. 7 ,

In Fig. 7 is a plan view of a rotor 20 shown with bell 28, on the outer periphery of blades 26 are arranged. In the inner region near the axis of rotation 200 and at a distance 260 to this Verbindungsschrauben 150 are provided with which the bell at the in Fig. 3 attached shaft is attached. The assignment means in this example comprises an asymmetric connection screw 152. The asymmetry is achieved by a shorter distance 262 from the axis of rotation. Alternatively or additionally, this connection screw may have a different diameter. Other ways of making this connecting screw asymmetrical to the others are conceivable, for example with the aid of washers, markings, color design, to name a few. The balancing means comprises in this example balancing points 154 which are distributed over the circumference. At these locations material is removed, for example, in a cutting or grinding manner, whereby the Balance of the rotor is selectively changed. The asymmetrical connecting screw is assigned to one of the equalization points, so that the balance means uniquely assigns the balance to the rotor position.

In Fig. 8 is a section, not belonging to the invention, shown by a rotor with bell 28 at the level of balancing bores 112. On the outer periphery of the rotor blades 26 are attached. The number of blades and the number of balancing holes are in a proportionable ratio, in the example shown there are eight blades and five balancing holes. By this ratio of the number, it is possible to provide an associated balancing bore 156, which is uniquely associated, for example, with a blade edge 158 of a blade. The allocation means in this example comprises elements of the rotor, namely the blades, which are distributed in such a way as the balancing means, namely the balancing bores, about the axis of rotation 200, that an unambiguous assignment of the balancing means and to one of the elements arises.

In addition to balancing bores and compensation points, means such as eccentrically designed balancing rings are known in the prior art, by the rotation about the axis of rotation of the balancing state is selectively changed. Also on these solutions, the invention is applicable.

Claims (10)

1. A vacuum pump (10) having a rotor (20) which comprises balancing means; having a drive (38, 40) which is suitable for setting the rotor into rotation; having bearings (44, 50; 60, 62, 64, 66, 68, 70) which are suitable for supporting the rotor; having a sensor means which is suitable for detecting a balancing state of the rotor and which is furthermore suitable for cooperating with an evaluation unit (134) which is suitable for recognizing a change in the balancing state,
   wherein
   the vacuum pump is adapted to cooperate with a rotor position recognition unit (132) for determining a rotor position;
   an association means is provided for associating the balancing state with the rotor position such that an adaptation of the balancing means is made possible in order to combat the change in the balancing state; and characterized in that
   the association means is designed as a non-rotationally symmetrical design of the balancing means, in particular as a non-rotationally symmetrical distribution of balancing bores (114).
2. A vacuum pump in accordance with claim 1,
   characterized in that
   one of the bearings comprises a ball bearing (50) which supports the rotor (20) in a radial direction.
3. A vacuum pump in accordance with claim 1,
   characterized in that
   the bearings comprise an active magnetic radial bearing (60, 62, 64, 66).
4. A vacuum pump in accordance with any one of the preceding claims,
   characterized in that
   the sensor means comprises a vibration sensor (52), with the sensor means being configured to detect vibrations in at least one spatial direction.
5. A vacuum pump in accordance with claim 3,
   characterized in that
   the sensor means comprises a radial bearing distance sensor (62, 66).
6. A vacuum pump in accordance with any one of the claims 1 to 5,
   characterized in that
   the balancing state includes an absolute value and the position of an imbalance (208).
7. A vacuum pump in accordance with any one of the claims 1 to 5,
   characterized in that
   the balancing state includes a relative change in the imbalance (208).
8. A vacuum pump in accordance with any one of the preceding claims,
   characterized in that
   the balancing means comprises a plurality of balancing bores (102, 106; 110, 112, 114, 156) distributed over the rotor for receiving a respective balancing weight (104, 108; 104a, 104b, 104c, 104d).
9. A vacuum pump in accordance with any one of the preceding claims, characterized in that
   the balancing means, in particular the balancing bores (102, 106; 110, 112, 114, 156), is protected from process deposits.
10. A method for balancing a rotor (20) of a vacuum pump (10) in accordance with claim 1, wherein the rotor (20) has been brought into an initial balancing state (232),
    characterized in that
    the balancing state of the rotor (20) is monitored; in that the balancing state is associated with a rotor position; and in that, on a change in the balancing state, balancing means provided at the rotor (20) are changed to improve the balancing state.

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