KR102141077B1 - Vacuum pump system for evacuating a chamber, and method for controlling a vacuum pump system - Google Patents

Abstract

The vacuum pump system for evacuating the chamber 10 includes main pump systems 12 and 14 connected to the chamber 10. The auxiliary pump system 20 is connected to the main pump systems 12 and 14, and the auxiliary pump system 10 includes an ejector pump. By providing such an auxiliary pump, it is possible to achieve an increase in efficiency, especially when the vacuum pump system is operated within the limit pressure range. Using the method of the present invention, the rotational speed of at least one pump of the main pump system 12, 14 depends on the pressure measured at the outlet 16 or inlet 50 of the main pump system 12, 14 Controlled.

Description

A vacuum pump system for evacuating the chamber and a method for controlling the vacuum pump system {VACUUM PUMP SYSTEM FOR EVACUATING A CHAMBER, AND METHOD FOR CONTROLLING A VACUUM PUMP SYSTEM}

The present invention relates to a method for controlling a vacuum pump system, as well as evacuating the chamber or maintaining the chamber in a predetermined vacuum, particularly below 10 mbar.

Vacuum pump systems include a plurality of vacuum pumps. In this context, it is known to provide a main pump system with one or more vacuum pumps supported by an auxiliary pump system. Typically, the auxiliary pump system is arranged downstream of the main pump system as viewed in the delivery direction, or is connected to the outlet of the main pump system. The auxiliary pump system pumps the gas against atmospheric pressure and reduces the pressure in the outlet region of the main pump system so that the main pump system does not need to pump against atmospheric pressure. It is thereby possible to realize very small limit pressures in the chamber or recipient to be vacuumed. Such vacuum pump systems are described, for example, in WO 03/023229, US 5,709,537 or WO 03/093678.

It is an object of the invention to increase the energy efficiency of a vacuum pump system for evacuating a chamber.

The object is achieved with a method for controlling a vacuum pump system as defined in claim 1 and a vacuum pump system as defined in claim 8.

The present vacuum pump system for evacuating the chamber or receiver comprises, in particular, a main pump system directly connected to the chamber. The main pump system can include one, in particular a plurality of vacuum pumps. Preferably, the vacuum pumps provided in the main pump system are screw-type vacuum pumps or Roots pumps. In particular, pumps with high internal compression are used in the main pump system. Internal compression describes the ratio of the volume at the pump inlet before compression to the vacuum to the volume at the pump outlet after compression. Higher internal compression ratios of 1:10 for example make it possible to pump large gas volumes. At the start of the vacuum, those pumps that pump large volumes in a short time are very useful. When the limit pressure in the chamber is reached, the operation of such large-volume pumps must continue with large energy consumption to maintain a low pressure in the chamber to maintain a vacuum or to maintain a low limit pressure. Since the main pump system must pump only small gas volumes, especially within the limit pressure range, an auxiliary pump system is provided downstream of the main pump system connected to the outlet of the main pump system.

According to the invention, the auxiliary pump system comprises an ejector pump. Especially when the vacuum system is operated within the limit pressure range, ejector pumps have the advantage of enabling them to pump low gas consumption and remain pumped rather than pumping small gas volumes. According to the invention, this provides the inevitable advantage that by providing an eject pump to the auxiliary pump system, it is possible to reduce the rotational speed of at least one of the main pump systems within the limit pressure range. Therefore, the energy consumption of the pump of this main pump system is greatly reduced. By providing an ejector pump in the auxiliary pump system, energy efficiency can thus be greatly increased.

The ejector pump can be a liquid or gas ejector pump. Depending on the application, it may be desirable to provide a gas ejector pump when the gases are pumped, but the liquid ejector pump has the advantage that the liquid can be separated from the pumped gas in a simple manner.

Using the vacuum pump system of the present invention, it is possible to achieve and maintain low inlet pressures at a high efficiency pumping rate. It is particularly preferred to use a vacuum pump system to maintain a low pressure for an extended process time after vacuuming the chamber, ie after the chamber has been evacuated, for example, from atmospheric pressure to a low pressure, particularly below 10 mbar.

According to the invention, the valve means is provided in parallel with the ejector pump. Here, the valve means may comprise, for example, a spring-loaded switchable valve or a return valve. Providing such a balance means is advantageous in that the large pump volumes are pumped, especially at the start of the vacuum, so that the main pump system pumps the medium immediately for atmospheric pressure. This is especially possible at the start of the vacuum, since the pressure difference is still relatively low. Pumping through the valve means is advantageous in that the volumes of gas that cannot be pumped by the ejector pump can be pumped because of the limited transfer rate.

By providing an ejector pump, it is an essential advantage of the present vacuum pump system that the pressure is reduced in the outlet region of the main pump system. This results in a reduction of the differential pressure between the inlet and outlet of the pump of at least one of the main pump systems, thereby improving the sealability of the pump. In particular, the sealability of the sealing gap of the corresponding pump is thereby improved.

According to the invention a differential pressure gauge is provided for measuring the differential pressure between the auxiliary pump system and the valve means. Thus, it is possible to switch off the auxiliary pump system completely or partially when the differential pressure falls below a predetermined value. This is particularly advantageous at the start of the vacuum, since the auxiliary pump system is not yet required at this time and the energy consumption of the entire system can be reduced by switching off the auxiliary pump system. According to the invention it is therefore desirable to switch on the auxiliary pump system only when a certain differential pressure is exceeded, so that the energy efficiency can be further improved.

It is further preferred to arrange the pressure sensor in particular in the outlet region of the main pump system. Thus, it is possible, for example, to reduce the rotational speed of at least one of the pumps in the main pump system, particularly when reaching a pressure limit close to the intended limit pressure. The volume of gas to be pumped is relatively small, especially when the rather low pressure already prevails within the outlet region of the main pump system. Consequently, the volume of gas can be pumped by at least one of the main pump systems even at low rotational speeds, especially since this volume of gas can be pumped by the ejector pump in a simple manner. The now possible reduction in the rotational speed of at least one of the main pump systems leads to significant savings in energy. In this context it is advantageous that the return flow of any pumped medium does not occur at low rotational speeds.

Instead of providing a pressure sensor in the outlet region of the main pump system, it is also possible to provide a pressure sensor in the inlet portion of the main pump system. This is particularly advantageous when combined with a switchable valve provided in parallel with the ejector pump. In the open state of the valve, the pressure in the outlet region of the main pump system is reduced so that the pressure measurement in this region has only a small beneficial value. As such, if a switchable valve is provided, it is desirable to control the switching of the valve depending on the pressure of the inlet area of one of the pumps of the main pump system or the inlet area of the main pump system.

In a further preferred embodiment, a control means is provided and preferably it is a common central control means that allows all the pumps of the main pump system and the auxiliary pump system to be controlled. In addition, this control means is used to control the switchable valve, if one is provided. In particular, the control means depends on the pressure measured by the at least one pressure sensor to control the rotational speed of at least one of the main pump systems.

The invention further relates to a method for controlling a pump system for evacuating a chamber. Such a pump system includes a main pump system connected to the chamber. The outlet of the main pump system is connected to the auxiliary pump system.

As described above, the vacuum pump system is preferably implemented in an advantageous manner; The implementation of the method according to the invention does not require an ejector pump in the auxiliary pump system.

According to the method of the invention, the pressure is determined in the outlet and/or inlet regions of the main pump system. Instead of the measured pressure, the rotational speed of at least one pump of the main pump system is controlled. To enable the performance of these method steps, it is preferred that the pump system has a pressure sensor in the outlet region and/or the inlet region. In particular, the method enables increased energy efficiency when the vacuum pump system is operated within a limit pressure range. Only very small gas volumes should be pumped so that the rotational speed of at least one of the main pump systems within the limit pressure range can be reduced. The gas to be pumped is in particular also pumped by the auxiliary pump, the energy consumption of the auxiliary pump being considerably lower than that of the main pump system.

Preferably, the rotational speed of at least one pump of the main pump system is reduced when the pressure falls below a predetermined limit value. In addition, it is further possible to define a lower pressure limit value, in which the rotational speed is reduced again when the pressure is further lowered. In particular, a change in the rotational speed of at least one of the main pump systems can also be performed in a stepless manner.

For example, in order to compensate for fluctuations in pressure and/or inaccuracies in the pressure sensor, it is desirable that the rotational speed is lowered only after a predetermined period of time.

In a preferred embodiment of the method, the pressure difference between the auxiliary pump system and the valve means arranged in parallel with the auxiliary pump system is determined. Depending on the pressure difference, at least one pump in the auxiliary pump system is switched on and off. The auxiliary pump system is switched off, especially when the pressure difference falls below the limit value. This is a range in which the auxiliary pump system does not support the main pump system, or only supports a small degree, so power consumption by the auxiliary pump system can be saved by switching off the auxiliary pump system.

In particular, due to the provision of an auxiliary pump system controlled according to the invention, it is possible to control the cooling water flow in other preferred embodiments of the method. This is due to the fact that a reduction in the pressure in the outlet region of the main pump system resulting from the provision of an auxiliary pump system enables a reduction in the compression performance of the main pump system. This leads to a reduction in mechanical friction and thus a reduction in the amount of heat generated. It is thereby possible to achieve significantly less heating of the coolant, such as coolant. Consequently, the cooling liquid heated by the vacuum pump system should preferably be cooled less before returning to the cooling system. This already leads to energy savings. In addition, the cooling fluid can be pumped through the cooling system at a lower rate, for example, because of the low heat generation, sufficient heat is still released by the cooling liquid. This also leads to significant savings in energy.

The present invention will be described in more detail with reference to preferred embodiments and accompanying drawings below.

1 is a schematic diagram of a first embodiment of a vacuum pump system.
2 shows a flow chart of a possible control of the vacuum pump system.
3 is a schematic diagram of a second embodiment of a vacuum pump system.
4 is a schematic diagram of a third embodiment of a vacuum pump system.

In the embodiment illustrated in FIG. 1, the chamber or receiver 10 is connected in series with the Roots pump 12 first and then with the screw-type pump 14. In this case, the two pumps form the main pump system. The auxiliary pump 20 illustrated in the embodiment is a gas ejector pump and is connected to the main pump system via an outlet 16 or conduit 18 of the screw-type pump 14. In the illustrated embodiment, a valve means in the form of a check valve 22 is provided in parallel with the auxiliary pump 20. In addition to being connected to the outlet of the ejector pump 20, the conduits 24 and 26 of the check valve 22 are coupled to, for example, one conduit 28 connected to the atmosphere. Of course, means for recovering ejector gas or the like can also be provided.

The pressure sensor 30 is provided in the area of the outlet 16 of the main pump system. The pressure sensor 30 is connected to the control means 32. In particular, two control means 32 which are frequency converters serve to control the two pumps 12, 14, in particular to control the rotational speed of these two pumps.

In the embodiment illustrated in Figure 1, the rotational speed of at least one of the two pumps 12, 14 of the main pump system is controlled for the implementation of the method according to the invention. This is done depending on the pressure measured in the region of the outlet 16 by the pressure sensor 30. It is thereby possible to reduce the rotational speed of at least one of the two pumps 12, 14, especially when a limit pressure in the chamber 10 or a pressure near the limit pressure is reached. This is possible in this operating state, since only small volumes of gas are pumped from the chamber 10. Such a small gas volume can be pumped by the ejector pump 20. If the pressure measured by the pressure sensor 30 exceeds the limit value again, this is due to the fact that the volume of gas to be pumped has increased and cannot be completely delivered by the ejector pump 20. In the control of the present invention, this in particular causes the rotational speed of at least one of both pumps 12, 14 of the main pump system to increase again.

Such control is schematically illustrated in FIG. 2. Here, “pex” refers to the pressure measured by the pressure sensor 30 at the outlet 16 of the main pump system. In step 34, it is determined whether this pressure is less than 800 mbar. Unless this is the case, pressure is determined, for example, again at regular intervals. As soon as the pressure (“pex”) at the outlet 16 falls below 800 mbar, the timer 36 is first set to 60 s, for example. In step 38, it is checked if a 60 s time period has elapsed. Only after that, the pressure in the outlet 16 is checked again in step 40. By providing a timer, it can be ensured that the change in the rotational speed of the pump has not already been made at some pressure fluctuations. If the pressure at the outlet 16 is still less than 800 mbar, the rotational speed of both pumps 12 and 14 is reduced by the frequency converters 32 in step 42, in particular. When the pressure at the outlet increases again above 800 mbar, control flow resumes from step 34. In step 44, the pressure at outlet 16 is again determined. If, for example, the upper limit of 900 mbar is exceeded, the rotational speed of the pumps 12, 14 is increased again in step 46. As long as the pressure is below 900 mbar, the rotational speeds of the pumps 12, 14 remain reduced. After the rotation speed is increased in step 46, the pressure is checked again as provided in step 34.

In FIGS. 3 and 4 illustrating alternative preferred devices of the invention as well as corresponding methods of the invention, similar and/or identical components are identified by the same reference numbers.

In the embodiment illustrated in FIG. 3, a differential pressure gauge 48 is provided in addition to the components provided in the embodiment illustrated in FIG. 1. Using a differential pressure gauge, the differential pressure between auxiliary pump 20 and check valve 22 is measured. When the differential pressure exceeds a predetermined limit value, the ejector pump 20 is switched off. Differential pressures are very prevalent, especially at the start of the process, when large gas volumes are pumped from the chamber 10. Such large gas volumes cannot be pumped by the ejector pump 20 but can be delivered directly through the check valve 22. This is possible because the pressure difference to the main pump system is still relatively small. At the start of operation, the pump 14 of the main pump system can still pump to the atmosphere. Only when the differential pressure between the check valve 22 and the ejector pump 20 is approximately low, the ejector pump 20 is activated, because at that moment at least the majority of the gas delivered is ejected by the ejector pump 20. Because it is pumped.

In the further embodiment illustrated in FIG. 4, a pressure sensor 52 connected to the inlet 50 of the main pump system is provided instead of a pressure sensor 20 connected to the outlet 16. Additionally, instead of the check valve 22, a switchable valve 54 is provided. Due to the provision of the switchable valve 54, it is no longer possible to perform control via pressure in the region of the outlet 16, since a switchable valve different from the check valve does not generate counter pressure. In the embodiment illustrated in FIG. 4, control is performed through a control device 56 connected to both the pressure sensor 52 and the switchable valve 54. In addition, the control device 56 is connected to the ejector pump 20 to switch on or off the ejector pump 20 depending on the operating conditions. In addition, the control device 56 is used to control the rotational pump speed of the two pumps 12 and 14 via the frequency converters 32.

Claims (12)

A vacuum pump system for evacuating the chamber (10),
The main pump system (12, 14) connected to the chamber 10,
An auxiliary pump system 20 connected to the outlet 16 of the main pump systems 12, 14, and
Valve means (22) connected in parallel with said auxiliary pump system (20)
Including,
The auxiliary pump system 20 includes an ejector pump,
The vacuum pump system further comprises a differential pressure gauge 48 for measuring the differential pressure between the auxiliary pump system 20 and the valve means 22,
Vacuum pump system. According to claim 1,
The valve means (22) comprises a check valve (check valve),
Vacuum pump system. According to claim 1,
Further comprising a pressure sensor 30 for determining the pressure of the outlet 16 of the main pump system (12, 14),
Vacuum pump system. According to claim 1,
Further comprising a pressure sensor 52 for determining the pressure of the inlet 50,
Vacuum pump system. The method according to any one of claims 1 to 4,
The main pump system (12, 14) comprises at least one of a screw-type pump (14) or Roots pump (Roots pump) (12),
Vacuum pump system. The method of claim 3 or 4,
Further comprising a control device (56) for controlling the rotational speed of at least one pump of said main pump system (12, 14) depending on the pressure measured by at least one pressure sensor (30, 52),
Vacuum pump system. A method for controlling a vacuum pump system for evacuating the chamber (10),
The vacuum pump system includes a main pump system (12, 14) connected to the chamber 10, and an auxiliary pump system (20) connected to an outlet (16) of the main pump system (12, 14),
The above method,
Determining the pressure of at least one of the outlet (16) or inlet (50) of the main pump system (12, 14), and
Controlling the rotational speed of at least one pump (12, 14) of the main pump system depending on the measured pressure
Including,
When the pressure falls below the limit value for the pressure difference between the auxiliary pump system 20 and the valve means 22 arranged in parallel to the auxiliary pump system 20, the auxiliary pump system 20 is Disabled,
Way. The method of claim 7,
When the pressure falls below the limit value, the rotational speed of at least one of the main pump systems 12, 14 is reduced,
Way. The method of claim 8,
When the pressure falls below the limit value, a decrease in the rotational speed is performed for at least a predetermined period of time,
Way. The method according to any one of claims 7 to 9,
Coolant flow is controlled depending on the temperature of the main pump system (12, 14),
Way. delete delete

Images