EP2960520B1 - Method and device for venting a vacuum chamber - Google Patents

Description

The present invention relates to a method for flooding a vacuum chamber connected to a vacuum pump, in particular a turbomolecular pump, in which the vacuum pump comprising a rotor and a stator is simultaneously flooded with the flooding of the vacuum chamber. It also relates to a device, particularly suitable for carrying out the method, for flooding a vacuum chamber connected to a vacuum pump, in particular a turbomolecular pump.

Vacuum pumps, such as turbomolecular pumps, can be used to create a vacuum in a vacuum chamber, also known as a recipient. After switching off, the vacuum pumps are often ventilated via assigned flood valves. For example, turbomolecular pumps should be vented after they have been switched off in order to prevent backdiffusion of hydrocarbons from the forevacuum side through the pump.

The flood valves assigned to the vacuum pumps have so far had a very small cross section, since it was assumed that the vacuum pump was flanged blind at the place of use for flooding, that is to say is closed and accordingly has no additional volume. Thus, the pressure in the switched-off vacuum pump must not increase too much when the pump rotor is still rotating, since otherwise excessive forces, i.e. Gas loads on the rotor.

However, the vacuum chambers increasingly remain connected to the relevant vacuum pumps on site. The flood valve assigned to the vacuum pump in question is therefore often used to flood a respective vacuum chamber used, which is usually controlled by the drive electronics of the vacuum pump, in particular turbomolecular pump. The vacuum pump is switched off during the flooding process, that is to say the pump rotor is de-energized, but the pump rotor frequently rotates at least temporarily and is then braked more quickly by the higher pressure resulting from the flooding. The flood rate of the flood valve assigned to the respective vacuum pump, that is to say the flow rate at which the gas serving for ventilation can be supplied, has hitherto been adapted to the size of the respective vacuum pump or turbomolecular pump. This takes into account the fact that the flood rate and, accordingly, the rate of pressure rise in the vacuum pump must not initially exceed a certain value, since otherwise excessive forces act on the pump rotor, which is still rotating. Since the vacuum chambers are now becoming increasingly larger, particularly in the case of mass spectrometers, a respective flooding process, for example a flooding process starting from a negative pressure in the range from 300 mbar to approximately 1,000 mbar, takes a very long time.

In the EP 1 739 308 B1 a rotary vacuum pump with an associated flood valve is known, in which the flood valve for flooding the pump is controlled as a function of detected deviations or fluctuations in the rotational frequency of the pump rotor. The effort involved in controlling the flood valve is correspondingly high. JP H01 8714 Y2 , EP 2 053 249 A2 and EP 2 466 145 A2 also belong to the relevant state of the art.

The invention is based on the object of specifying a method and a device of the type mentioned at the outset which, even with a relatively large volume of the vacuum chamber, allow the vacuum chamber to be flooded in a simple manner without impairing the rotor which has already been switched off but is still rotating and which is connected to the vacuum chamber Allow vacuum pump.

According to the invention, this object is achieved by a method having the features of claim 1 and by a device having the features of claim 5. Preferred embodiments of the method according to the invention and preferred embodiments of the device according to the invention are specified in the subclaims.

The method according to the invention is characterized in that the flooding takes place immediately after the pump rotor has been switched off and the flooding rate is increased during a respective flooding process as soon as the pressure in the vacuum pump has reached a predefinable limit value.

Due to such an embodiment of the method, a relatively larger vacuum chamber can also be flooded very quickly in a relatively simple manner without the risk of impairing or damaging the rotor, which has already been switched off but is at least temporarily still rotating, of the vacuum pump connected to the vacuum chamber. The invention takes advantage of the fact that above a certain pressure in the vacuum pump, at least essentially no more adverse forces caused by a gas load on the escaping, i.e. Pump rotor still switched off act, so that after reaching this pressure limit, the flood rate for the remaining flood process can be increased compared to the previous flood rate, thus accelerating the flood process as a whole.

Flooding immediately after the pump rotor is switched off means that the pump rotor is still rotating when the flooding process is started. In particular, it cannot be ruled out that a certain period of time may elapse between the switch-off process and the start of the flood process, in particular depending on the respective specific conditions.

According to a preferred practical embodiment of the method according to the invention, the predeterminable limit value of the pressure in the vacuum chamber is selected such that at least essentially no more forces act on the pump rotor that is still rotating, i.e. Impairment or damage to the pump rotor due to excessive gas loads can be avoided.

It has been shown that in the previously common vacuum pumps, in particular turbomolecular pumps, from a pressure of approximately 300 mbar, essentially no more disadvantageous forces act on the rotating switched off pump rotor. Accordingly, a pressure value in the range from 100 to 400 mbar, in particular from 250 to 300 mbar, is preferably selected as the predefinable limit value of the pressure in the vacuum pump.

In order to reduce the risk of impairment or damage to the still rotating pump rotor to a minimum, the flood rate during a respective flood process until the predeterminable limit value of the pressure in the vacuum pump is reached is preferably chosen such that a predeterminable pressure rise rate in the vacuum pump is not exceeded .

It has been found that the risk of impairment or damage to the pump rotor, which is still rotating, can practically be ruled out at a pressure rise rate of up to approximately 15 mbar. A preselectable rate of pressure rise in the vacuum pump is therefore preferably a rate of pressure rise in the range from 1 to 50 mbar / sec, in particular from 10 to 20 mbar / sec.

According to the method according to the invention, the flooding takes place via an activated first fluid cross-section until the predeterminable limit value of the pressure in the vacuum pump is reached and the flooding takes place after this limit value of the pressure in the vacuum pump has been reached via an activated second fluid cross-section that is larger than the first fluid cross-section.

The switching from the first fluid cross-section to the relatively larger second fluid cross-section takes place in that, in addition to an activated first flood valve, a second flood valve is activated.

The first flood valve is assigned to the vacuum pump, while the second flood valve is assigned to the vacuum chamber. This takes into account the fact that the vacuum pump is generally assigned at least one flood valve anyway, which can also be used accordingly for flooding the vacuum chamber.

According to a method which is not part of the invention, the flooding takes place via a flood valve assigned to the vacuum pump or the vacuum chamber, which is clocked with a first duty cycle until a predefined limit value of the pressure in the vacuum pump is reached for pulsed activation of the flood valve and after this has been reached Limit value of the pressure in the vacuum pump is clocked with a larger duty cycle than the first duty cycle or is fully activated. A flood valve, for example, which is clocked in the manner of a pulse width modulation, is therefore sufficient. In this context, a larger duty cycle is to be understood to mean that, with a larger duty cycle, the proportion of the open or release times of the flood valve is greater than with a smaller duty cycle.

According to a method which is not part of the invention, the flooding is carried out via a flood valve assigned to the vacuum pump or the vacuum chamber, the two differently large flood gas flows possible and after a predeterminable time from the smaller is switched to the larger flood gas flow, after which the predetermined limit value of the pressure in the vacuum pump has been reached. The control of such a flood valve does not necessarily have to be carried out by the control device assigned to the vacuum pump, for example integrated into the vacuum pump or permanently connected to the vacuum pump. For example, control by actuating means directly on the flood valve is also conceivable, which comprise two channels.

The device according to the invention for flooding a vacuum chamber connected to a vacuum pump, in particular a turbomolecular pump, comprises a control device and a valve arrangement for simultaneously flooding the vacuum chamber and the vacuum pump comprising a rotor and a stator immediately after the pump rotor has been switched off. It is accordingly characterized in that the control device is designed and the valve arrangement can be controlled via the control device in such a way that the flood rate is increased during a respective flood process as soon as the pressure in the vacuum pump has reached a predefinable limit value.

The predeterminable limit value of the pressure in the vacuum chamber is preferably selected such that at least essentially no more forces act on the pump rotor which is still rotating and is switched off.

According to the device according to the invention, the valve arrangement comprises at least a first flood valve assigned to the vacuum pump and at least a second flood valve assigned to the vacuum chamber, which can be controlled accordingly by the control device.

The first and the second flood valve can be controlled in such a way that the predefinable limit value is reached of the pressure in the vacuum pump, the first flood valve is activated and, when this limit value of the pressure in the vacuum pump is reached, the second flood valve is activated in addition to the first flood valve.

According to a further possible embodiment of the device according to the invention, the flood valve assigned to the vacuum pump can be controlled by the control device in such a way that it is clocked with a first duty cycle until the predeterminable limit value of the pressure in the vacuum pump is reached for a pulsed activation of the flood valve and after this limit value has been reached of the pressure in the vacuum pump is clocked with a larger second duty cycle in comparison to the first duty cycle or is fully activated.

The control device is preferably assigned to the vacuum pump, so that the control device which is already provided for the vacuum pump as a rule can also be used at the same time to control the flooding process or the at least one flooding valve.

According to an alternative expedient embodiment of the device according to the invention, the flood valve assigned to the vacuum pump enables two flood gas streams of different sizes and it can be controlled by the control device in such a way that it is switched from the smaller to the larger flood gas stream after a predeterminable time, after which the predefinable limit value of the pressure in the Vacuum pump was reached. As already mentioned, the control device does not necessarily have to be assigned to the vacuum pump. For example it is it is also conceivable to actuate the flood valve directly on the flood valve by actuating means.

Fig. 1

eine schematische Darstellung einer beispielhaften Ausführungsform einer erfindungsgemäßen Vorrichtung zum Fluten einer mit einer Vakuumpumpe, insbesondere Turbomolekularpumpe, verbundenen Vakuumkammer,

Fig. 2

ein rein schematisches Diagramm, in dem mit einer gestrichelten Linie der sich mit einer herkömmlichen Flutungsvorrichtung und mit einer durchgehenden Linie der sich mit der erfindungsgemäßen Flutungsvorrichtung während eines jeweiligen Flutungsvorgangs ergebende zeitliche Verlauf des Drucks in der Vakuumpumpe dargestellt ist, und

Fig. 3

ein rein schematisches Diagramm, in dem mit einer gestrichelten Linie der sich mit einer herkömmlichen Flutungsvorrichtung und mit einer durchgehenden Linie der sich mit der erfindungsgemäßen Flutungsvorrichtung während eines jeweiligen Flutungsvorgangs ergebende zeitliche Verlauf der Flutrate dargestellt ist.

The invention is described below using an exemplary embodiment with reference to the drawing; in this show:

Fig. 1

1 shows a schematic representation of an exemplary embodiment of a device according to the invention for flooding a vacuum chamber connected to a vacuum pump, in particular a turbomolecular pump,

Fig. 2

a purely schematic diagram, in which a dashed line is shown with a conventional flooding device and with a continuous line of the time course of the pressure in the vacuum pump resulting with the inventive flooding device during a respective flooding process, and

Fig. 3

a purely schematic diagram in which a dashed line is shown with a conventional flooding device and with a solid line of the time course of the flooding rate resulting with the inventive flooding device during a respective flooding process.

Fig. 1 shows a schematic representation of an exemplary embodiment of a device 10 according to the invention for flooding a vacuum chamber 14 connected to a vacuum pump 12. The vacuum pump 12 can in particular be a turbomolecular pump. The vacuum pump 12 can be provided with a backing flange 20 to which a backing pump can be connected.

The device 10 comprises a control device 16 and a valve arrangement 18 for simultaneously flooding the vacuum chamber 14 and the vacuum pump 12 comprising a rotor and a stator immediately after the pump rotor has been switched off, so that the pump rotor is indeed switched off during a respective flooding process, that is to say is de-energized , but at least still rotating at times.

The control device 16 is designed in such a way and the valve arrangement 18 can be controlled via the control device 16 in such a way that the flood rate, that is to say the flow rate of the supplied flood gas, is increased during a respective flood process as soon as the pressure in the vacuum pump 12 reaches a predefinable limit value p _G ( see also Fig. 2 ) has reached.

The predeterminable limit value p _{G of} the pressure in the vacuum pump 12 is preferably selected such that at least essentially no more forces act on the pump rotor which is still rotating and is therefore not impaired by an excessively high gas load. A pressure value in the range of 300 mbar can, for example, be selected as the predefinable limit value p _{G of} the pressure in the vacuum pump 12.

The valve assembly 18 includes at least one of the vacuum pump 12 associated venting valve 18 ₁ and at least one of the vacuum chamber 14 associated venting valve 18 _2, which are controllable by the control device sixteenth

The flood valves 18 ₁ , 18 _{2 are} through the The control device 16 can be controlled such that the first flood valve 18 _{1 is} activated until the predefinable limit value p _{G of} the pressure in the vacuum pump 12 is reached and, when this limit value p _{G of} the pressure in the vacuum pump 12 is reached, the second flood valve 18 _{1 in} addition to the first flood valve 18 _{1 2 is} unlocked.

The valve arrangement 18 can also include a flood valve 18 ₁ assigned to the vacuum pump 12, which can be controlled by the control device 16 in such a way that until a predeterminable limit value p _{G of} the pressure in the vacuum pump 12 is reached with a pulsed activation of the flood valve 18 ₁ clocked first duty cycle and after reaching this limit value p _{G of} the pressure in the vacuum pump 12 is clocked with a larger than the first duty cycle second duty cycle or completely unlocked. The relevant flood valve 18 ₁ can thus be controlled in the manner of a pulse width modulation.

In such a case, the control device 16 can in particular be assigned to the vacuum pump 12.

Alternatively, the valve arrangement 18 can also include a flood valve 18 ₁ assigned to the vacuum pump 12, which enables two flood gas streams of different sizes and can be controlled by the control device 16 in such a way that after a predeterminable time it is switched from the smaller to the larger flood gas stream, after which the one that can be predetermined Limit value p _{G of} the pressure in the vacuum pump 12 was reached. In this case, the control 16 does not necessarily have to be assigned to the vacuum pump 12. The control of the flood valve can, for example, also take place directly on the flood valve via adjusting means which comprise two channels.

wobei mit "p" der Druck in der Vakuumpumpe 12, mit "Q" die Flutgaslast, mit "t" die aktuelle Zeit und mit "V" das Gesamtvolumen der Vakuumkammer 14 und der Vakuumpumpe 12 angegeben sind. Fig. 2 shows a purely schematic diagram, in which a dashed line shows the temporal course of the pressure p in the vacuum pump 12 which results with a conventional flooding device according to the prior art and with a continuous line with the flooding device 10 according to the invention during a respective flooding process is. The pressure results from the relationship $\mathrm{p}=\frac{\mathrm{Q}\cdot \mathrm{t}}{\mathrm{V}},$

with "p" the pressure in the vacuum pump 12, with "Q" the flood gas load, with "t" the current time and with "V" the total volume of the vacuum chamber 14 and the vacuum pump 12.

As shown in the diagram Fig. 2 It can be seen that the conventional flooding device has an at least substantially constant pressure rise rate in the vacuum pump 12 during the entire flooding process (see the dashed line). In contrast, with the device 10 according to the invention, this rate of pressure increase in the vacuum pump 12 rises sharply when the limit value p _{G of} the pressure in the vacuum pump 12 is reached (see the continuous line), so that the entire flooding process is greatly accelerated.

Fig. 3 shows a purely schematic diagram, in which a dashed line is used to show the temporal course of the flood rate that occurs with the conventional flooding device and with a continuous line that results with the inventive flooding device 10 during a respective flooding process. As can be seen from this diagram, the conventional flooding device results in an at least essentially constant temporal course of the flooding rate during the entire flooding process (see the dashed line), while the flooding device 10 according to the invention achieves the flooding rate when reached the limit value p _{G of} the pressure in the vacuum chamber (cf. again Fig. 2 ) rises abruptly, which, as already mentioned, significantly accelerates the entire flooding process.

Reference list

10th

contraption

12th

Vacuum pump

14

Vacuum chamber

16

Control device

18th

Valve arrangement

18 ₁

Flood valve

18 ₂

Flood valve

20

Backing flange

p _G

Limit value of the pressure in the vacuum pump

Claims (9)

1. A method of flooding a vacuum chamber (14) connected to a vacuum pump (12), in particular to a turbomolecular pump, in which the vacuum pump (12) comprising a rotor and a stator is also flooded simultaneously with the flooding of the vacuum chamber (14),

   wherein the flooding takes place directly after a respective switching off of the pump rotor and the flooding rate is increased during a respective flooding process as soon as the pressure in the vacuum pump has reached a predefinable limit value (p_G);

   wherein the flooding takes place via a released first fluid cross-section up to the reaching of the predefinable limit value (p_G) of the pressure in the vacuum pump (12) and the flooding takes place via a released second fluid cross-section, which is larger than the first fluid cross-section, after the reaching of this limit value (p_G) of the pressure in the vacuum pump (12); and

   wherein the switching from the first fluid cross-section to the relatively larger second fluid cross-section takes place in that a second flood valve (18₂) is released in addition to a released first flood valve (18₁), with the first flood valve (18₁) being associated with the vacuum pump (12) and the second flood valve (18₂) being associated with the vacuum chamber (14).
2. A method in accordance with claim 1,
   characterized in that the predefinable limit value (p_G) of the pressure in the vacuum pump (12) is selected such that at least substantially no more forces act on the still rotating switched-off pump rotor.
3. A method in accordance with claim 1 or claim 2,
   characterized in that a pressure value in the range from 100 to 400 mbar, in particular from 250 to 300 mbar, is selected as the predefinable limit value (p_G) of the pressure in the vacuum pump (12).
4. A method in accordance with at least one of the preceding claims,
   characterized in that the flooding rate during a respective flooding process up to the reaching of the predefinable limit value (p_G) of the pressure in the vacuum pump (12) is selected such that a predefinable pressure increase speed in the vacuum pump (12) is not exceeded, with in particular a pressure increase speed in the range from 1 to 50 mbar/sec, in particular from 10 to 20 mbar/sec, being selected as the predefinable pressure increase speed in the vacuum pump (12).
5. An apparatus (10) for flooding a vacuum chamber (14) connected to a vacuum pump (12), in particular to a turbomolecular pump, in particular for carrying out the method in accordance with at least one of the preceding claims, said apparatus (10) comprising a control device (16) and a valve arrangement (18) for the simultaneous flooding of the vacuum chamber (14) and the vacuum pump (12) comprising a rotor and a stator directly after a respective switching off of the pump rotor, wherein the control device (16) is designed and the valve arrangement (18) is controllable via the control device (16) such that the flooding rate is increased during a respective flooding process as soon as the pressure in the vacuum pump (12) has reached a predefinable limit value (p_G); and
   wherein the valve arrangement (18) comprises at least one first flood valve (18₁) associated with the vacuum pump (12) and at least one second flood valve (18₂) associated with the vacuum chamber (14), with these flood valves being controllable by the control device (16) such that the first flood valve (18₁) is released up to the reaching of the predefinable limit value (p_G) of the pressure in the vacuum pump (12) and the second flood valve (18₂) is released in addition to the first flood valve on the reaching of this limit value (p_G) of the pressure in the vacuum pump (12).
6. An apparatus in accordance with claim 5,
   characterized in that the predefinable limit value (p_G) of the pressure in the vacuum pump (12) is selected such that at least substantially no more forces act on the still rotating switched-off pump rotor.
7. An apparatus in accordance with one of the claims 5 to 6,
   characterized in that the flooding valve (18₁) associated with the vacuum pump (12) is controllable by the control device (16) such that it is clocked with a first mark space ratio for a pulsed release of the flooding valve (18₁) up to the reaching of the predefinable limit value (p_G) of the pressure in the vacuum pump (12) and is clocked with a second mark space ratio, which is larger in comparison with the first mark space ratio, or is completely released after the reaching of this limit value (p_G) of the pressure in the vacuum pump (12).
8. An apparatus in accordance with one of the claims 5 to 6,
   characterized in that the flood valve (18₁) associated with the vacuum pump (12) enables two flooding gas flows of different sizes and is controllable by the control device (16) such that it is switched from the smaller flooding gas flow to the larger flooding gas flow after a predefinable time at which the predefinable limit value (p_G) of the pressure in the vacuum pump (12) is reached.
9. An apparatus in accordance with any one of the claims 5 to 8,
   characterized in that the control device (16) is associated with the vacuum pump (12).

Images