EP2960520A1 - Method and device for venting a vacuum chamber - Google Patents

Abstract

A method for flooding a vacuum chamber connected to a vacuum pump, in particular a turbomolecular pump, in which flooding of the vacuum chamber simultaneously flooding the vacuum pump comprising a rotor and a stator is characterized in that the flooding occurs immediately after a respective shutdown of the pump rotor takes place and the flood rate is increased during a respective flood process, as soon as the pressure in the vacuum pump has reached a predefinable limit. There is also provided a suitable apparatus for carrying out the method.

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 flooding of the vacuum chamber simultaneously flooding the vacuum pump comprising a rotor and a stator. It further relates to a device suitable in particular 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 generate a vacuum in a vacuum chamber, also referred to as a recipient. After switching off the vacuum pumps are often vented via associated flood valves. For example, turbomolecular pumps should be vented after shutdown to prevent back diffusion of hydrocarbons from the fore-vacuum side through the pump.

So far, the flood valves assigned to the vacuum pumps have a very small cross-section, since it was assumed that the vacuum pump is flanged blindly at the point of use, that is to say is completed and accordingly has no additional volume. Thus, the pressure in the switched-off vacuum pump must not rise too much while the pump rotor is still rotating, otherwise too great a force, i. Gas loads acting on the rotor.

Increasingly, however, the vacuum chambers at the site remain connected to the respective vacuum pumps. For flooding a respective vacuum chamber is therefore often the respective vacuum pump associated flood valve used, which is usually controlled by the drive electronics of the vacuum pump, in particular turbomolecular pump. Although the vacuum pump is switched off during the flooding process, ie the pump rotor is de-energized, the pump rotor often rotates at least intermittently and is then braked faster due to the higher pressure as a result of the flooding. The flow rate of the respective vacuum pump associated flood valve, that is, the flow rate at which the serving for aeration gas can be supplied, has hitherto adapted to the size of the respective vacuum pump or turbomolecular pump. This takes into account the fact that the rate of flow and, correspondingly, the rate of pressure rise in the vacuum pump must initially not exceed a certain value, since otherwise excessive forces act on the still rotating pump rotor. After the vacuum chambers, however, become increasingly larger, in particular 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 about 1000 mbar, takes a very long time.

In the EP 1 739 308 B1 a rotary vacuum pump with associated flood valve is known, in which the flood valve is driven to flood the pump in response to detected deviations or fluctuations in the rotational frequency of the pump rotor. The relevant effort to control the flood valve is correspondingly high.

The invention has for its object to provide a method and an apparatus of the type mentioned above, which also in relatively large volume of the vacuum chamber in the simplest possible way rapid flooding of the vacuum chamber without affecting the already switched off, but still rotating rotor connected to the vacuum chamber Allow vacuum pump.

This object is achieved by a method having the features of claim 1 and by a device having the features of claim 11. Preferred embodiments of the method according to the invention and preferred embodiments of the device according to the invention are specified in the dependent claims.

The inventive method is characterized in that the flooding occurs immediately after a respective shutdown of the pump rotor and the flood rate is increased during a respective flood process, as soon as the pressure in the vacuum pump has reached a predetermined limit.

Due to such an embodiment of the method, a relatively larger vacuum chamber can be flooded very quickly without the risk of damage or damage to the already switched off, but at least temporarily rotating rotor of the vacuum chamber connected to the vacuum chamber. In this case, the invention makes use of the fact that, starting from a certain pressure in the vacuum pump, at least substantially no disadvantageous forces caused by a gas load are transferred to the outgoing, i.e. still rotating shut-off pump rotor act, so that after reaching this pressure limit, the flood rate for the rest of the flooding process compared to the previous flood rate can be increased, whereby the flooding process is accelerated as a whole.

Flooding immediately after switching off the pump rotor means that the pump rotor is still rotating when the flooding process is started. In particular, it can not be ruled out that a certain period of time, which depends in particular on the particular concrete conditions, can pass between the switch-off process and the beginning of the flooding process.

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 chosen such that at least essentially no forces act on the still rotating pump rotor switched off, ie. Impairment or damage to the pump rotor can be avoided by excessive gas loads.

It has been shown that with the hitherto customary vacuum pumps, in particular turbomolecular pumps, from a pressure of approximately 300 mbar, essentially no disadvantageous forces act on the rotating pump rotor which has been switched off. As a predefinable limit value of the pressure in the vacuum pump, a pressure value in the range from 100 to 400 mbar, in particular from 250 to 300 mbar, is therefore preferably selected.

In order to reduce the risk of damage or damage to the still rotating pump rotor to a minimum, the rate of flow is preferably selected during a respective flooding operation until reaching the predeterminable limit value of the pressure in the vacuum pump so that a predeterminable pressure rise rate in the vacuum pump is not exceeded ,

It has been found that the risk of deterioration or damage of the still rotating pump rotor at a pressure rise rate up to about 15 mbar can be virtually eliminated. As a predefinable pressure rise rate in the vacuum pump, therefore, a pressure increase rate in the range of 1 to 50 mbar / s, in particular 10 to 20 mbar / s, is preferably selected.

According to an advantageous expedient embodiment of the method according to the invention, the flooding takes place until reaching the predefinable limit value of the pressure in the vacuum pump via an activated first fluid cross section and the flooding after reaching this limit value of the pressure in the vacuum pump via an enabled second fluid cross section that is larger than the first fluid cross section.

In this case, the switching over from the first fluid cross section to the relatively larger second fluid cross section can take place, for example, by virtue of the fact that, in addition to an activated first flow valve, a second flow control valve is released. It is particularly advantageous if the first flood valve is assigned to the vacuum pump, while the second flood valve of the vacuum pump or the vacuum chamber can be assigned. Thus, the fact is taken into account that the vacuum pump is usually associated anyway at least one flood valve, which can be used in accordance with the flood of the vacuum chamber.

According to a further advantageous embodiment of the method according to the invention, the flooding via a vacuum pump or the vacuum chamber associated flood valve, which is clocked until reaching the predetermined limit value of the pressure in the vacuum pump for a pulsed unlocking of the flood valve with a first duty cycle and after reaching this limit the pressure in the vacuum pump is clocked with a larger compared to the first duty cycle second duty cycle or completely unlocked. Thus, it suffices, for example, a flood valve, which is clocked in the manner of a pulse width modulation. In this context, a larger duty cycle is to be understood as meaning that with a larger duty cycle the proportion of the open or disconnection times of the flood valve is greater than with a smaller duty cycle.

Furthermore, in particular such an embodiment of the method according to the invention is also conceivable in which the flooding is effected via a flood valve associated with the vacuum pump or the vacuum chamber, which allows two different sizes of flooding gas streams and after a predeterminable time of the smaller one is switched to the larger flow of flooding gas, after which the predeterminable limit value of the pressure in the vacuum pump has been reached. In this case, the control of such a flood valve does not necessarily take place by the control device associated with the vacuum pump, for example integrated into the vacuum pump or permanently connected to the vacuum pump. It is, for example, a control by adjusting means directly on the flood valve conceivable comprising 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 a respective switching off of the pump rotor. It is correspondingly characterized in that the control device is designed so and the valve assembly via the control device is controlled so that the rate of flow is increased during a respective flood process, as soon as the pressure in the vacuum pump has reached a predetermined limit.

In this case, the predefinable limit value of the pressure in the vacuum chamber is preferably selected such that at least substantially no forces act on the still rotating pump rotor that is still turned off.

According to a preferred practical embodiment of the device according to the invention, the valve arrangement comprises at least one flood valve associated with the vacuum pump and / or at least one flood valve associated with the vacuum chamber, which can be controlled accordingly by the control device.

It is particularly advantageous if the valve assembly comprises at least a first and a second flood valve and these flood valves are controlled by the controller so that until reaching the predetermined limit the pressure in the vacuum pump, the first flood valve is released and upon reaching this limit value of the pressure in the vacuum pump in addition to the first flood valve, the second flood valve is released. In this case, the first flood valve is preferably associated with the vacuum pump, while the second flood valve may be associated with the vacuum pump or the vacuum chamber.

According to a further possible embodiment of the device according to the invention, the valve arrangement comprises a flood valve associated with the vacuum pump or the vacuum chamber, which can be controlled by the control device such that it reaches a predetermined limit value of the pressure in the vacuum pump for a pulsed release of the flood valve with a first Duty cycle is clocked and clocked after reaching this limit value of the pressure in the vacuum pump with a larger compared to the first duty cycle second duty cycle or completely unlocked. In this case, a flood valve is sufficient to flood the vacuum chamber and the connected vacuum pump.

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

According to a further alternative expedient embodiment of the device according to the invention, the valve arrangement may also comprise a flood valve associated with the vacuum pump or the vacuum chamber, which allows two differently sized flood gas flows and is controllable by the control device such that it is switched from the smaller to the larger flow of flooding gas after a predeterminable time , after which the predefinable limit value of the pressure in the vacuum pump has been reached. As already mentioned, the control device does not necessarily have to be assigned to the vacuum pump. It is for example also conceivable to control the flood valve by adjusting means directly to the flood valve.

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 will be described in more detail below with reference to an embodiment with reference to the drawing; in this show:

Fig. 1

1 is 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 is shown with a dashed line with a conventional flooding device and a solid line of the resulting with the flooding device according to the invention during a respective flooding process time course of the pressure in the vacuum pump, and

Fig. 3

a purely schematic diagram in which is shown with a dashed line with a conventional flooding device and with a continuous line of the resulting with the flooding device according to the invention during a respective flooding process time course of the flood rate.

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

The device 10 comprises a control device 16 and a valve arrangement 18 for simultaneous flooding of the vacuum chamber 14 and the vacuum pump 12 comprising a rotor and a stator immediately after a respective switching off of the pump rotor, so that the pump rotor is switched off during a respective flooding operation, that is to say de-energized , but at least temporarily still rotates.

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

In this case, the predeterminable limit value p _{G of} the pressure in the vacuum pump 12 is preferably selected such that at least essentially no forces act on the still rotating pump rotor which is still turned off, ie this is not impaired by an excessive gas load. As a predeterminable limit value p _{G of} the pressure in the vacuum pump 12, for example, a pressure value in the range of 300 mbar can be selected.

The valve assembly 18 may in particular comprise at least one of the vacuum pump 12 associated flood valve 18 ₁ and / or at least one of the vacuum chamber 14 associated flood valve 18 ₂ , which are controlled by the control device 16 accordingly.

In this case, the valve assembly 18, for example, at least a first and a second flood valve 18 ₁ , 18 ₂ include, and the flood valves 18 ₁ , 18 ₂ can through the Control device 16 be controlled so that until reaching the predetermined limit p _{G of} the pressure in the vacuum pump 12, the first flood valve 18 ₁ or 18 _{2 is} released and upon reaching this limit p _{G of} the pressure in the vacuum pump 12 in addition to the first flood valve 18 _first or 18 ₂ the second flood valve 18 ₂ or 18 _{1 is} released. In this case, the first flood valve 18 _1, in particular the vacuum pump 12 and the second flood valve 18 _{2 of} the vacuum pump 12 or the vacuum chamber 14 may be assigned.

Alternatively, the valve arrangement 18 may include, for example, a flood valve 18 ₁ or 18 _{2 associated with} the vacuum pump 12 or the vacuum chamber 14, which can be controlled by the control device 16 until it reaches the predeterminable limit value p _{G of} the pressure in the vacuum pump 12 for a pulsed disconnection of the flood valve 18 ₁ or 18 _{2 is} clocked with a first duty cycle and clocked after reaching this limit p _{G of} the pressure in the vacuum pump 12 with a larger compared to the first duty cycle second duty cycle or completely unlocked. The respective flood valve 18 ₁ or 18 ₂ can thus be controlled in the manner of a pulse width modulation.

The control device 16 may be assigned in such a case, in particular the vacuum pump 12.

According to a further alternative exemplary embodiment, the valve arrangement 18 may also comprise a flood valve 18 ₁ or 18 _{2 associated with} the vacuum pump 12 or the vacuum chamber 14, which allows two different sizes of flood gas flows and can be controlled by the control device 16 so that it is after a predeterminable time is switched from the smaller to larger flood gas stream, after which the predetermined limit value p _{G of} the pressure in the vacuum pump 12 has been reached. The controller 16 does not necessarily have to be assigned to the vacuum pump 12 in this case. The activation of the flood valve For example, can also be done via adjusting means, which include two channels, directly to the flood valve.

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 1 shows a purely schematic diagram in which a dashed line shows the time profile of the pressure p in the vacuum pump 12 resulting with a conventional flooding device according to the prior art and with a continuous line of the flood device 10 according to the invention during a respective flooding process is. This results in the pressure from the relationship $\mathrm{p}=\frac{\mathrm{Q}\cdot \mathrm{t}}{\mathrm{V}}.$

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

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

Fig. 3 shows a purely schematic diagram in which is shown with a dashed line with the conventional flooding device and with a continuous line of the resulting with the flooding device 10 according to the invention during a respective flood process time profile of the flood rate. As can be seen from this diagram, with the conventional flooding device an at least substantially constant time profile of the flood rate results during the entire flooding process (see the dashed line), while with the flooding device 10 according to the invention the flood rate is reached the limit value p _{G of} the pressure in the vacuum chamber (see also again Fig. 2 ) increases abruptly, which, as already mentioned, the entire flooding process is significantly accelerated.

LIST OF REFERENCE NUMBERS

10

contraption

12

vacuum pump

14

vacuum chamber

16

control device

18

valve assembly

18 ₁

flood valve

18 ₂

flood valve

20

fore-vacuum flange

p _G

Limit value of the pressure in the vacuum pump

Claims (15)

Method for flooding a vacuum chamber (14) connected to a vacuum pump (12), in particular turbomolecular pump, in which flooding of the vacuum chamber (14) simultaneously flooding the vacuum pump (12) comprising a rotor and a stator,
characterized in that the flooding occurs immediately after a respective shutdown of the pump rotor and the flood rate is increased during a respective flood process, as soon as the pressure in the vacuum pump has reached a predeterminable limit value (p _G ). Method according to claim 1,
characterized in that the predeterminable limit value (p _G ) of the pressure in the vacuum pump (12) is selected such that at least substantially no forces act on the still rotating pump rotor switched off. Method according to claim 1 or 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 predeterminable limit value (p _G ) of the pressure in the vacuum pump (12). Method according to at least one of the preceding claims,
characterized in that the flow rate during a respective flood process until reaching the predetermined limit value (p _G ) of the pressure in the vacuum pump (12) is selected so that a predeterminable pressure rise speed in the vacuum pump (12) not is exceeded, in particular as a predefinable pressure rise speed in the vacuum pump (12), a pressure rise rate in the range of 1 to 50 mbar / sec, in particular from 10 to 20 mbar / sec, is selected. Method according to at least one of the preceding claims,
characterized in that the flooding until reaching the predeterminable limit value (p _G ) of the pressure in the vacuum pump (12) via an activated first fluid cross section and the flooding after reaching this limit value (p _G ) of the pressure in the vacuum pump (12) via a unlocked second fluid cross-section is greater than the first fluid cross-section. Method according to claim 5,
characterized in that the switching from the first fluid cross section to the relatively larger second fluid cross section is effected in that in addition to an unlocked first flood valve (18 ₁ ) a second flood valve (18 ₂ ) is released, wherein in particular the first flood valve (18 ₁ ) of the vacuum pump (18 12) and the second flood valve (18 ₂ ) of the vacuum pump (12) or the vacuum chamber (14) is assigned. Method according to one of claims 1 to 4,
characterized in that the flooding via one of the vacuum pump (12) or the vacuum chamber (14) associated with flood valve (18 ₁ or 18 ₂ ) takes place until reaching the predetermined limit value (p _G ) of the pressure in the vacuum pump (12) for a pulsed disconnection of the flood valve (18 ₁ or 18 ₂ ) is clocked with a first duty cycle and clocked after reaching this limit (p _G ) of the pressure in the vacuum pump (12) with a larger compared to the first duty cycle second duty cycle or whole is unlocked. Method according to one of claims 1 to 4,
characterized in that the flooding over one of the vacuum pump (12) or the vacuum chamber (14) associated flood valve (18 ₁ or 18 ₂ ) takes place, which allows two different large flood gas flows and after a predetermined time after which the predetermined limit (p _G ) of the pressure in the vacuum pump (12) has been reached, is switched from the smaller to the larger flow of fl uid gas. Device (10) for flooding a vacuum chamber (14) connected to a vacuum pump (12), in particular turbomolecular pump, in particular for carrying out the method according to at least one of the preceding claims, with a control device (16) and a valve arrangement (18) for simultaneous flooding the vacuum chamber (14) and the vacuum pump (12) comprising a rotor and a stator immediately after each switching off of the pump rotor, the control device (16) being designed and the valve arrangement (18) being controllable via the control device (16) such that the flood 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 ). Device according to claim 9,
characterized in that the predeterminable limit value (p _G ) of the pressure in the vacuum pump (12) is selected such that at least substantially no forces act on the still rotating pump rotor switched off. Device according to claim 9 or 10,
characterized gekennzeichet that the valve assembly (18) at least one of the vacuum pump (12) associated with the venting valve (18 ₁₎ and / or at least one of the vacuum chamber (14) associated with the venting valve (18 _2), the or by the control device (16) can be controlled accordingly. Device according to one of claims 9 to 11,
characterized in that the valve arrangement (18) comprises at least a first and a second flood valve (18 ₁ , 18 ₂ ) and these flood valves (18 ₁ , 18 ₂ ) by the control device (16) are controlled so that until reaching the predetermined Limit value (p _G ) of the pressure in the vacuum pump (12), the first flood valve (18 ₁ or 18 ₂ ) is released and upon reaching this limit (p _G ) of the pressure in the vacuum pump (12) in addition to the first flood valve (18 ₁ or 18 ₂ ) the second flood valve (18 ₁ or 18 ₂ ) is released, wherein in particular the first flood valve (18 ₁ ) of the vacuum pump (12) and the second flood valve (18 ₂ ) of the vacuum pump (12) or the vacuum chamber (14) assigned. Device according to one of claims 9 to 11,
characterized in that the valve arrangement (18) comprises one of the vacuum pump (12) or the vacuum chamber (14) associated with the flood valve (18 ₁ or 18 ₂ ) which is controlled by the control device (16) so that it is until reaching the predetermined limit value (p _G ) of the pressure in the vacuum pump (12) for a pulsed release of the flood valve (18 ₁ or 18 ₂ ) is clocked with a first duty cycle and after reaching this limit value (p _G ) of the pressure in the vacuum pump (12 ) is clocked with a larger compared to the first duty cycle second duty cycle or completely unlocked. Device according to one of claims 9 to 11,
characterized in that the valve arrangement (18) comprises one of the vacuum pump (12) or the vacuum chamber (14) associated with the flood valve (18 ₁ or 18 ₂ ), which allows two different sized flood gas flows and by the control device (16) is controlled so in that after a predeterminable time, when the predeterminable limit value (p _G ) of the pressure in the vacuum pump (12) is reached, it is switched over from the smaller to the larger flow of flooding gas. Device according to one of claims 9 to 14,
characterized in that the control device (16) of the vacuum pump (12) is associated.

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