WO2022078738A1 - Method for controlling an operating power of a vacuum pump, and vacuum pump - Google Patents

Method for controlling an operating power of a vacuum pump, and vacuum pump Download PDF

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Publication number
WO2022078738A1
WO2022078738A1 PCT/EP2021/076405 EP2021076405W WO2022078738A1 WO 2022078738 A1 WO2022078738 A1 WO 2022078738A1 EP 2021076405 W EP2021076405 W EP 2021076405W WO 2022078738 A1 WO2022078738 A1 WO 2022078738A1
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WO
WIPO (PCT)
Prior art keywords
vacuum pump
volume
pumped
operating power
predetermined period
Prior art date
Application number
PCT/EP2021/076405
Other languages
French (fr)
Inventor
Paul DECORDE
Yacine SAIDI
Original Assignee
Pfeiffer Vacuum
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Pfeiffer Vacuum filed Critical Pfeiffer Vacuum
Priority to KR1020237008505A priority Critical patent/KR20230085133A/en
Publication of WO2022078738A1 publication Critical patent/WO2022078738A1/en

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C25/00—Adaptations of pumps for special use of pumps for elastic fluids
    • F04C25/02—Adaptations of pumps for special use of pumps for elastic fluids for producing high vacuum
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C23/00—Combinations of two or more pumps, each being of rotary-piston or oscillating-piston type, specially adapted for elastic fluids; Pumping installations specially adapted for elastic fluids; Multi-stage pumps specially adapted for elastic fluids
    • F04C23/001—Combinations of two or more pumps, each being of rotary-piston or oscillating-piston type, specially adapted for elastic fluids; Pumping installations specially adapted for elastic fluids; Multi-stage pumps specially adapted for elastic fluids of similar working principle
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C28/00—Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids
    • F04C28/28—Safety arrangements; Monitoring
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C2220/00—Application
    • F04C2220/10—Vacuum
    • F04C2220/12—Dry running
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C2240/00—Components
    • F04C2240/80—Other components
    • F04C2240/81—Sensor, e.g. electronic sensor for control or monitoring
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C2270/00—Control; Monitoring or safety arrangements
    • F04C2270/02—Power
    • F04C2270/025—Controlled or regulated
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C2270/00—Control; Monitoring or safety arrangements
    • F04C2270/18—Pressure
    • F04C2270/185—Controlled or regulated

Definitions

  • the present invention relates to a vacuum pump and a method for controlling an operating power of a vacuum pump, notably a vacuum pump that can comprise multiple pumping stages in series in which a gas to be pumped circulates between a suction and a discharge.
  • the loading/unloading airlock comprises a first door connecting the interior of the chamber with a zone under atmospheric pressure such as a clean room for the loading of at least one substrate, and a second door for the unloading of the substrate into a process chamber after evacuation.
  • a zone under atmospheric pressure such as a clean room for the loading of at least one substrate
  • a second door for the unloading of the substrate into a process chamber after evacuation.
  • the motor power consumed by the vacuum pump increases when the pumping load increases, which is notably the case each time the airlock at atmospheric pressure is evacuated.
  • the motor current of the vacuum pump can be kept at a maximum power value. A capping of the power of the vacuum pump makes it possible to prevent it from tripping out or overheating.
  • the configuration of the vacuum pump can be adapted in the factory, during its production, so as to cap the operating power as a function of the volume of the chamber to which the vacuum pump is intended to be connected.
  • the subject of the invention is a method for controlling an operating power of a vacuum pump configured to be connected to a volume in which gases are wanted to be pumped, the method comprising:
  • a pressure measured at a discharge of the vacuum pump is compared with a first predetermined threshold, and, when an initiation of an evacuation is detected,
  • the vacuum pump can be connected directly to the volume to be pumped or connected via a supplementary vacuum pump or via a pipe set linking the suction of the vacuum pump to the volume to be pumped.
  • the supplementary vacuum pump corresponds to a vacuum pump that has its own motor.
  • the supplementary vacuum pump is, for example, a volumetric vacuum pump of Roots type.
  • the trend of the parameter corresponds to the mean slope (or mean differential), over the first or second predetermined period, of the trend over time of the parameter.
  • the estimation of a volume to be pumped comprises a first estimation of the volume to be pumped made on the basis of the trend of the operating power parameter of the vacuum pump and a second estimation of the volume to be pumped made on the basis of the trend of the pressure parameter measured at the discharge of the vacuum pump, the volume to be pumped being estimated as a priority on the basis of the parameter for which the trend is the most regular over the second predetermined period (slope always positive or negative or the lowest number of changes of sign of the differential).
  • an alarm is issued when the deviation between the volume estimated on the basis of the pressure parameter at the discharge and the volume estimated on the basis of the operating power parameter of the vacuum pump exceeds a predetermined value.
  • the estimation of the volume to be pumped on the basis of the operating power of the vacuum pump comprises the estimation of a mean slope of decreasing of the operating power of the vacuum pump during the second predetermined period and the comparison of this estimated slope with saved power slope values associated with different volumes to be pumped.
  • the estimation of the volume to be pumped on the basis of the operating power of the vacuum pump can comprise the estimation of a mean slope of increasing of the operating power of the vacuum pump during the second predetermined period and the comparison of this estimated slope with saved power slope values associated with different volumes to be pumped.
  • the estimation of the volume to be pumped on the basis of the pressure measured at the discharge of the vacuum pump comprises the estimation of a mean slope of decreasing of the pressure measured at the discharge of the vacuum pump during the second predetermined period and the comparison of this estimated slope with saved pressure slope values associated with different volumes to be pumped.
  • the second predetermined period is between 3 and 15 seconds, notably 10 seconds for a vacuum pump alone.
  • the second predetermined period is between 10 and 100 seconds, notably 30 seconds, for a primary vacuum pump connected in series with a supplementary vacuum pump.
  • the first predetermined period is between 50 ms and two seconds, notably one second.
  • the volume to be pumped corresponds to the volume of a chamber connected to a suction of the vacuum pump.
  • the connection can be made directly or via another vacuum pump.
  • the present invention relates also to a vacuum pump configured to be connected to a chamber in which gases are wanted to be pumped and that comprises a pressure sensor positioned at a discharge of the vacuum pump, said vacuum pump comprising a processing unit configured to:
  • a pressure measured at the discharge of the vacuum pump is compared with a first predetermined threshold, and, when an initiation of evacuation is detected,
  • the vacuum pump is a multistage primary vacuum pump.
  • the vacuum pump is configured to be connected in series with a supplementary vacuum pump, said supplementary vacuum pump being positioned upstream of the vacuum pump.
  • FIG. 1 represents a diagram of a vacuum pump connected to a chamber
  • FIG. 1 represents a perspective schematic view of the vacuum pump of figure 1;
  • FIG. 1 represents a flow diagram of the different steps of the method for controlling the operating power of the vacuum pump according to a first embodiment
  • FIG. 4 represents two curves cl and c2 showing the trend over time of the pressure at the discharge of the vacuum pump during an evacuation for two different volumes to be pumped;
  • FIG. 5 represents an estimative curve of a volume to be pumped as a function of a mean pressure slope over a predetermined period, here 10 seconds, determined notably from the curves cl or c2 of figure 4;
  • FIG. 29 represents a flow diagram of the different steps of the method for controlling the operating power of the vacuum pump according to a second embodiment
  • FIG. 7 represents three curves pl, p2, p3 showing the trend over time of the operating power of the vacuum pump during an evacuation for three different volumes to be pumped;
  • FIG 8 represents an estimative curve of a volume to be pumped as a function of a mean power slope over a predetermined period, here 10 seconds, determined notably from the curves pl, p2 or p3 of figure 7;
  • FIG. 32 [Fig 9] represents a diagram of two pumps connected in series and connected to a chamber
  • FIG 10 represents three curves ql, q2, q3 respectively representing the operating power of the vacuum pump and of the supplementary vacuum pump, as well as the pressure at the discharge of the vacuum pump.
  • the present invention relates to a vacuum pump and a method for controlling an operating power of a vacuum pump.
  • the vacuum pump is, for example, a multi-stage primary vacuum pump.
  • Figure 1 represents a simplified diagram of an installation 1 comprising such a vacuum pump 2 of dry type and a chamber 3 to which the vacuum pump 2 is connected, for example via a valve 4, for pumping the chamber 3.
  • Significant gas flows of the order of several slm or several tens of slm, can be introduced into the chamber 3, for example cyclically, during so-called “process” steps if the chamber 3 is a process chamber.
  • the chamber 3 corresponds, for example, to a process chamber for the fabrication of electronic substrates which goes alternately from an atmospheric pressure when the substrate is introduced into or removed from the process chamber to a very low pressure, for example less than 10 Pa during the substrate deposition or etching phases.
  • a process chamber for the fabrication of electronic substrates which goes alternately from an atmospheric pressure when the substrate is introduced into or removed from the process chamber to a very low pressure, for example less than 10 Pa during the substrate deposition or etching phases.
  • Figure 2 presents a perspective, partly cross-sectional and transparent schematic view of the vacuum pump 2 of figure 1.
  • the vacuum pump 2 comprises a stator 5, a first shaft 6 and a second shaft 7 on which are arranged, respectively, a first rotor 8a and a second rotor 8b.
  • the rotors 8a and 8b are configured to rotate synchronously in reverse directions in the stator 5 to drive a gas to be pumped G from a suction 9 of the vacuum pump 2 to a discharge 10 of the vacuum pump 2.
  • the rotors 8a and 8b have, for example, lobes of identical profiles, such as of “Roots” or “Claw” type.
  • the pumping rotors can be of “screw” type.
  • the vacuum pump 2 comprises at least one pumping stage, five stages in the case of the example of figure 1, respectively denoted Tl, T2, T3, T4 and T5.
  • Each pumping stage comprises a respective inlet and outlet.
  • the successive pumping stages are connected in series one after the other by respective inter-stage channels 14 (visible in figure 2) connecting the outlet of the pumping stage which precedes to the inlet of the stage which follows.
  • the gas sucked from the inlet is captive in the volume generated by the rotors 8a, 8b, then is driven by the rotors 8a, 8b to the discharge 10 (the direction of circulation of the gases is illustrated by the arrows G in figures 1 and 2).
  • the vacuum pump 2 is notably said to be “dry” because, in operation, the rotors 8a, 8b revolve inside the stator 5 with no mechanical contact between them or with the stator 5, which makes it possible not to use oil in the pumping stages TITS.
  • the vacuum pump 2 of dry type is a multi-stage primary vacuum pump.
  • a primary vacuum pump is a volumetric vacuum pump, which, using two rotors 8a and 8b, sucks, transfers then discharges the gas to be pumped at atmospheric pressure.
  • the chamber 3 therefore defines a volume in which gases are wanted to be pumped.
  • the connection between this chamber 3 and the vacuum pump 2 is made at the suction 9 of the vacuum pump 2.
  • the vacuum pump 2 can also comprise a pressure sensor 12 positioned, for example, at its discharge 10. The variations of this pressure measured at the discharge 10 can be representative of the pressure variations inside the chamber 3 comprising the volume to be pumped when these variations are significant.
  • the vacuum pump 2 also comprises a processing unit 13 which can be connected to the pressure sensor 12 situated at the discharge 10.
  • the processing unit 13 can comprise one or more controllers or microcontrollers or processors and a memory for executing series of programme instructions implementing different functions linked to the vacuum pump 2 and notably the various steps of the method for controlling the maximum operating power of the vacuum pump 2 which will be described hereinafter in the description.
  • Figure 3 represents a flow diagram of the different steps of the method for controlling the operating power of the vacuum pump 2 according to a first embodiment in which the vacuum pump 2 comprises a pressure sensor 12 at its discharge 10.
  • the first step 101 relates to the measurement of a pressure measured by the pressure sensor 12 positioned at the discharge 10 of the vacuum pump 2.
  • the pressure measurements are performed at regular time intervals, for example every 50 ms.
  • the second step 102 relates to the detection of an initiation of an evacuation, that is to say a phase in which the pressure inside the chamber 3 is high, for example a pressure close to atmospheric pressure and in which a pumping cycle is begun to evacuate and reduce the pressure in the chamber 3 to a predetermined pressure.
  • This detection is performed on the basis of the pressure measurements performed during the step 101.
  • This detection is performed by comparing the trend, over a first predetermined period, of the pressure value measured at the discharge 10 with a first predetermined threshold.
  • the first predetermined period is, for example, less than 2 s, notably of the order of 1 s.
  • the parameter used to characterize the trend corresponds, for example, to the mean slope or mean differential (time differential) of the trend of the pressure at the discharge 10 (as a function of time) during the first predetermined period.
  • Figure 4 represents an example of trend of the pressure measured by the pressure sensor 12 at the discharge 10 of the vacuum pump 2 for two different chamber volumes 3 upon an initiation of an evacuation.
  • the initiation of an evacuation is detected when the pressure increases.
  • the pressure is, for example, approximately 1000 mbar at the discharge of the vacuum pump 2, then it increases abruptly (in 1 s to 2 s) to 1800 mbar as represented in figure 4 at the time tO (the two curves cl and c2 are overlaid during this pressure increase).
  • the trend of the pressure is, for example, determined by a calculation of time differential of the pressure measured at the discharge of the vacuum pump 2 over a time of between 50 ms and 2 seconds, for example one second, which will serve as indicator. When this differential is positive and greater than a first predetermined threshold, for example 100 mbar/sec, then an initiation of evacuation is detected.
  • a first predetermined threshold for example 100 mbar/sec
  • the initiation of an evacuation can be confirmed by a pressure measurement above a predetermined threshold, for example 1500 mbar.
  • a predetermined threshold for example 1500 mbar.
  • the first curve cl is associated with a first volume of 2 m 3 (or 2000 L) and the second curve c2 is associated with a second volume of 1 m 3 (or 1000 L).
  • the pressure at the instant tO therefore goes from approximately 1000 mbar (100 000 Pa) to approximately
  • the value of the mean slope is greater (in absolute value) than the first predetermined threshold, then an initiation of an evacuation is detected.
  • the pressure in the chamber is high, for example substantially equal to atmospheric pressure and decreases strongly when the evacuation is initiated. This strong reduction can be detected in the pressure measured at the discharge 10 of the vacuum pump 2 since the pressure at the discharge 10 of the vacuum pump 2 then increases strongly because of the great quantity of gas which is pumped.
  • the first predetermined threshold can be adjusted according to the type of vacuum pump 2 to which the method for controlling the operating power is applied.
  • the third step 103 relates to an estimation of a volume to be pumped on the basis of the trend, over a second predetermined period, of the pressure measured in the step 101.
  • This third step 103 is performed when an initiation of an evacuation is detected in the step 102 and when the maximum pressure value measured no longer increases (zero differential).
  • the second predetermined period is greater than the first predetermined period and is, for example, between 5 s and 15 s, notably 10 s as in the present example.
  • the trend of the pressure is, for example, determined by the value of the mean slope (or mean time differential) over the second predetermined period of the curve representing the pressure at the discharge 10 as a function of time.
  • the curve cl has a mean slope fl of -15 mbar/s (-1500 Pa/s) over the first 10 seconds from tl, whereas the curve c2 has a mean slope f2 of -
  • the mean slope values of pressure over 10 seconds and the volumes associated with these mean slope values can be stored in the form of a table or in the form of a curve whose x-axis and y-axis respectively correspond to the mean slope values and to the volume values, or vice versa.
  • This curve is, for example, obtained by extrapolation from a few determined values.
  • Figure 5 represents an example of such a curve.
  • the fourth step 104 relates to the application of a maximum operating power as a function of the volume estimated in the step 103.
  • a maximum operating power as a function of the volume estimated in the step 103.
  • the maximum power can be set at 4000 W and, when the estimated volume to be pumped is 2 m 3 , the maximum power can be set at 3500 W.
  • the values of the maximum powers as a function of the volume to be pumped can be saved in a database in the form of a table or of a curve for example.
  • the maximum operating power is thus limited as a function of the volume to be pumped such that, the greater the volume, the more the operating power is reduced.
  • the monitoring of the trend of the pressure at the discharge 10 of the vacuum pump 2 makes it possible to be able to detect the initiation of an evacuation and to estimate the volume to be pumped upon the evacuation and makes it possible to determine a maximum power of the vacuum pump 2 to be applied to limit the risk of malfunctioning of the vacuum pump 2 during the evacuation.
  • Figure 6 represents a flow diagram of the different steps of the method for controlling the operating power of the vacuum pump 2 according to a second embodiment.
  • the pressure sensor 12 at the discharge 10 is not necessary.
  • the first step 201 relates to the determination of an operating power or operating load of the vacuum pump 2. This determination is for example made by a processing unit 13 of the vacuum pump 2 such as the processing unit 13 described previously and can be done by measuring a parameter representative of the operating power of the vacuum pump 2 such as the motor current.
  • the operating power depends on the quantity of gas to be pumped and therefore on the pressure in the chamber 3.
  • the second step 202 relates to the detection of an initiation of an evacuation, that is to say a phase in which the pressure in the chamber 3 is high, for example a pressure close to atmospheric pressure, and in which a pumping cycle is begun to evacuate and reduce the pressure in the chamber 3 to a predetermined pressure.
  • Figure 7 represents an example of representative curves denoted pl, p2 and p3 of the trend of the operating power of the vacuum pump 2 for three different chamber 3 volumes upon an initiation of an evacuation.
  • the first curve pl is associated with a first volume of 1000 L (1 m 3 )
  • the second curve p2 is associated with a second volume of 200 L (0.2 m 3 )
  • the third curve p3 is associated with a third volume of 20 L (0.02 m 3 ).
  • the variation of the operating power is a function of the pressure in the chamber 3 comprising the volume to be pumped. It is thus possible, as for the pressure at the discharge 10, to detect the initiation of an evacuation when the operating power varies beyond a first predetermined threshold.
  • An initiation of an evacuation is detected when the increase in power exceeds a predetermined threshold for a first predetermined period of between 50 ms and 2 s, for example 1 s. For that, the time differential is for example determined over this first predetermined period and it is compared to a predetermined threshold, for example 300 W/s.
  • the power before the initiation of the evacuation is approximately 800 W and goes rapidly (less than 2 s) to a value greater than 4000 W (approximately 5800 W for the curve pl and approximately 4500 W for the curves p2 and p3) for the different curves, such that the time differential over 1 s exceeds the first predetermined threshold and an initiation of an evacuation is therefore detected.
  • This detection of an evacuation can be confirmed by a power value exceeding 4000 W.
  • the value of the mean slope (or mean time differential) of the trend of the power during the first predetermined period, here 1 s, is compared to the value of the first predetermined threshold, for example
  • This first predetermined threshold can be adjusted according to the type of vacuum pump 2 to which the method for controlling the operating power of the vacuum pump 2 is applied.
  • the third step 203 relates to an estimation of a volume to be pumped based on the trend, over a second predetermined period, of the operating power of the vacuum pump 2.
  • This third step 203 is performed when an initiation of an evacuation is detected in the step 202 and the power goes through a maximum value (zero differential).
  • the second predetermined period is greater than the first predetermined period and is, for example, between 5 s and 15 s, notably 10 s in the present case.
  • the first curve pl has a mean slope of -27 W/s over the first 10 seconds from tl
  • the second curve p2 has a mean slope of -53 W/s over the first 10 seconds from tl
  • the curve p3 has a mean slope of -350 W/s.
  • These mean slopes can then be compared to mean slope values stored in a database.
  • the mean slope values of operating power over 10 seconds and the volumes associated with these mean slope values can be stored in the form of a table or in the form of a curve whose x-axis and y-axis correspond respectively to the mean slope values and to the power values, or vice versa. This curve is, for example, obtained by extrapolation from a few determined values.
  • Figure 8 represents an example of such a curve denoted g with the power slope in watts/sec on the y-axis and the volume in litres on the x-axis.
  • This curve shows a substantially hyperbolic decrease and can be approximated by two linear regressions associated with two curve portions, a first straight line gl associated with the volumes less than 50 L and a second straight line g2 associated with the volumes greater than or equal to 50 L.
  • the mean slope of -27 W/s is associated with a volume of 1000 L
  • the mean slope of -53 W/s is associated with a volume of 200 L
  • the slope of -350 W/s is associated with a volume of 20 L.
  • the fourth step 204 relates to the application of a maximum operating power as a function of the volume estimated in the step 203.
  • a maximum operating power as a function of the volume estimated in the step 203.
  • the maximum power is set at 3500 W
  • the maximum power is set at 4000 W
  • the estimated volume to be pumped is 20 L (0.02 m 3 )
  • the maximum operating power values and the associated estimated volumes are, for example, saved in a database.
  • the databases and curves described in the steps 203 and 204 can be saved in the memory of the processing unit 13 or in a memory external to the processing unit 13 to which the processing unit 13 is connected.
  • the trends of the pressure and operating power over the first predetermined period can be used to detect the initiation of an evacuation.
  • the pressure measurement is, for example, used as a priority for the detection and the power can be used as confirmation.
  • an alarm can be issued, for example an audible and/or visual signal.
  • priority parameter that for which the trend is the most regular, that is to say the parameter for which the number of changes of sign of the differential associated with its trend is the lowest (curve always increasing for example) over the first predetermined period.
  • the trends of the pressure and the operating power over the second predetermined period can then each be used to independently estimate the volume of gas to be pumped.
  • the two estimated volumes can be compared.
  • the estimated volume can correspond to the average value of the two estimated volumes or the volume estimated by one of the methods can be retained as a priority, for example the volume obtained by the parameter for which the trend is the most regular, that is to say for which the differential exhibits the fewest changes of sign (always increasing or always decreasing over the second predetermined period for example).
  • the maximum power to be used during the pumping is then determined from a database or from a correspondence curve as described previously.
  • an alarm can be issued, for example an audible and/or visual signal and the volume retained can correspond to the greatest estimated volume so as to limit the risk of overheating in case of prolonged pumping.
  • the installation 1 comprises a primary vacuum pump 2, that is to say whose discharge emerges into air at atmospheric pressure, and a supplementary vacuum pump 2’ positioned in series and upstream of the vacuum pump 2.
  • the “upstream” and “downstream” positions are defined here with respect to the direction of suction of the gas by the vacuum pumps 2 and 2’.
  • the suction 9’ of the supplementary vacuum pump 2’ is connected to an orifice of the chamber 3 and the discharge 10’ of the supplementary vacuum pump 2’ is connected to the suction 9 of the vacuum pump 2.
  • a pressure sensor 12 can be positioned at the discharge 10 of the vacuum pump 2.
  • the supplementary vacuum pump 2’ is a vacuum pump comprising its own motor, for example a volumetric vacuum pump of roots type.
  • Figure 10 represents three curves denoted ql, q2 and q3 corresponding respectively to the trend over time of the operating power of the vacuum pump 2, of the trend over time of the operating power of the supplementary vacuum pump 2’ and of the trend over time of the pressure at the discharge 10 of the vacuum pump 2.
  • the pressure at the discharge 10 of the vacuum pump 2 is, for example, given by the sensor 12.
  • the instant tO corresponds to the initiation of an evacuation. It can be seen that, from the instant tO, the operating power of the vacuum pump 2 increases strongly (curve ql) to a time t2 from which the operating power of the vacuum pump 2 decreases. The operating power of the supplementary vacuum pump 2’ remains low up to the time t2 then increases strongly.
  • the vacuum pump 2 which contributes to the evacuation and, from the time t2, the contribution of the vacuum pump 2 decreases in favour of the supplementary vacuum pump.
  • the time t2 corresponds to the moment when a certain pressure is reached in the chamber 3. It can also be seen that the pressure at the discharge 10 of the vacuum pump 2 increases strongly over a short period after the instant tO then decreases regularly.
  • the mean slopes over predefined periods associated with the trends over time of the operating power of the vacuum pump 2 and of the pressure at the discharge of the vacuum pump 2 can make it possible, on the one hand, to detect an initiation of an evacuation and, on the other hand, to estimate the volume to be pumped.
  • the initiation of an evacuation is, for example, detected when the slope of the trend of the operating power of the vacuum pump 2 over a first predetermined period, for example a period of between 100 ms and 2 seconds, is greater than a predetermined threshold.
  • the initiation of an evacuation can be detected when the slope of the trend of the pressure at the discharge 10 of the vacuum pump 2 over the first predetermined period is greater (in absolute value) than another predetermined threshold.
  • the estimation of the volume to be pumped is, for example, performed by comparing the slope of the trend of the operating power of the vacuum pump 2 over a second predetermined period, for example a period of between 10 s and 100 s, notably 30 s, with slope values saved in a database.
  • the estimation of the volume to be pumped can be performed by comparing the slope of the trend of the pressure at the discharge 10 of the vacuum pump 2 over the second predetermined period with slope values saved in a database.
  • the database also comprises values of volume to be pumped associated with these slope values (of the pressure curve or of the operating power curve).
  • the database is, for example, saved in a memory of the processing unit 13.
  • the slope pl associated with the curve ql can be used to determine a volume to be pumped and the slope p3 of the curve q3 can also be used to determine the volume to be pumped.
  • the curve q3 associated with the pressure at the discharge 10 will be used as a priority because its variations are much smaller during the second predetermined period.
  • the method for controlling the power of a vacuum pump can also be used for a primary pump connected in series with another pump positioned upstream, between the chamber comprising the volume to be pumped and the primary vacuum pump 2.
  • the monitoring of operating parameters of a vacuum pump 2 such as the operating power of the vacuum pump or the pressure at the discharge 10 of the vacuum pump 2 thus make it possible to detect an initiation of an evacuation and to estimate the volume to be pumped, for example the volume of a chamber 3 intended for the fabrication of “wafers”, and thus be able to adapt the maximum operating power of the vacuum pump 2 during the evacuation without risking the vacuum pump 2 overheating or tripping out. That makes it possible to avoid a manual configuration in the factory based on the application to which the vacuum pump 2 is dedicated and having to know, during the production of the vacuum pump 2, the volume of the chamber 3 to which the vacuum pump 2 will be connected.
  • the present invention relates also to a vacuum pump 2 comprising a processing unit 13 configured to perform the steps of the method for controlling the operating power according to one of the embodiments presented previously.

Abstract

The present invention relates to a method for controlling an operating power of a vacuum pump, notably a vacuum pump that can comprise multiple pumping stages in series in which a gas to be pumped circulates between a suction and a discharge and also to a vacuum pump configured to be connected to a chamber in which gases are wanted to be pumped and that comprises a pressure sensor positioned at a discharge of the vacuum pump.

Description

Description
Title of the invention: Method for controlling an operating power of a vacuum pump, and vacuum pump
[1] The present invention relates to a vacuum pump and a method for controlling an operating power of a vacuum pump, notably a vacuum pump that can comprise multiple pumping stages in series in which a gas to be pumped circulates between a suction and a discharge.
[2] In some applications, for example the fabrication of semiconductor substrates or of flat screens, it is necessary to pump a gas into a chamber that can have a significant volume. That is for example the case of certain airlock chambers for loading and unloading (also called “loadlock”).
[3] The loading/unloading airlock comprises a first door connecting the interior of the chamber with a zone under atmospheric pressure such as a clean room for the loading of at least one substrate, and a second door for the unloading of the substrate into a process chamber after evacuation. Each loading or unloading of substrates requires the pressure in the chamber to be lowered and then raised alternately. Such pressure variations can also occur in the absence of loading/unloading airlocks upon the evacuation of the process chamber for processing substrates from atmospheric pressure.
[4] The motor power consumed by the vacuum pump increases when the pumping load increases, which is notably the case each time the airlock at atmospheric pressure is evacuated. To prevent the motor power consumed from being too high over excessively long periods, for example because of a significant volume to be evacuated, the motor current of the vacuum pump can be kept at a maximum power value. A capping of the power of the vacuum pump makes it possible to prevent it from tripping out or overheating.
[5] However, capping the vacuum pump can result in a loss of performance that is unnecessary in other cases, notably for the evacuation of chambers of small volume because the increase in power is occasional and can be absorbed without risks for the vacuum pump. [6] In order to overcome this problem, the configuration of the vacuum pump can be adapted in the factory, during its production, so as to cap the operating power as a function of the volume of the chamber to which the vacuum pump is intended to be connected.
[7] However, such a factory configuration leads to supplementary steps to be implemented such as the tracing of the vacuum pumps during their production and means having to use the duly configured vacuum pump for just one, unique category of applications.
[8] It is therefore sought to provide a solution that makes it possible to at least partially overcome the abovementioned drawbacks.
[9] To this end, the subject of the invention is a method for controlling an operating power of a vacuum pump configured to be connected to a volume in which gases are wanted to be pumped, the method comprising:
- a step of detection of an initiation of an evacuation in which, over a first predetermined period, the trend of at least one parameter out of the following parameters:
- an operating power of the vacuum pump,
- a pressure measured at a discharge of the vacuum pump, is compared with a first predetermined threshold, and, when an initiation of an evacuation is detected,
- a step of estimation of a volume to be pumped based on the trend, over a second predetermined period, of at least one parameter out of the following parameters:
- an operating power of the vacuum pump,
- a pressure measured at the discharge of the vacuum pump, and
- a step of limiting of the operating power of the vacuum pump in which the operating power of the vacuum pump is limited as a function of the estimated volume.
[10] The vacuum pump can be connected directly to the volume to be pumped or connected via a supplementary vacuum pump or via a pipe set linking the suction of the vacuum pump to the volume to be pumped. The supplementary vacuum pump corresponds to a vacuum pump that has its own motor. The supplementary vacuum pump is, for example, a volumetric vacuum pump of Roots type.
[11] According to another aspect of the present invention, the trend of the parameter corresponds to the mean slope (or mean differential), over the first or second predetermined period, of the trend over time of the parameter. [12] According to another aspect of the present invention, the estimation of a volume to be pumped comprises a first estimation of the volume to be pumped made on the basis of the trend of the operating power parameter of the vacuum pump and a second estimation of the volume to be pumped made on the basis of the trend of the pressure parameter measured at the discharge of the vacuum pump, the volume to be pumped being estimated as a priority on the basis of the parameter for which the trend is the most regular over the second predetermined period (slope always positive or negative or the lowest number of changes of sign of the differential).
[13] According to another aspect of the present invention, an alarm is issued when the deviation between the volume estimated on the basis of the pressure parameter at the discharge and the volume estimated on the basis of the operating power parameter of the vacuum pump exceeds a predetermined value.
[14] According to another aspect of the present invention, the estimation of the volume to be pumped on the basis of the operating power of the vacuum pump comprises the estimation of a mean slope of decreasing of the operating power of the vacuum pump during the second predetermined period and the comparison of this estimated slope with saved power slope values associated with different volumes to be pumped. When the vacuum pump is positioned in series with a supplementary vacuum pump positioned upstream of the vacuum pump, the estimation of the volume to be pumped on the basis of the operating power of the vacuum pump can comprise the estimation of a mean slope of increasing of the operating power of the vacuum pump during the second predetermined period and the comparison of this estimated slope with saved power slope values associated with different volumes to be pumped.
[15] According to another aspect of the present invention, the estimation of the volume to be pumped on the basis of the pressure measured at the discharge of the vacuum pump comprises the estimation of a mean slope of decreasing of the pressure measured at the discharge of the vacuum pump during the second predetermined period and the comparison of this estimated slope with saved pressure slope values associated with different volumes to be pumped.
[16] According to another aspect of the present invention, the second predetermined period is between 3 and 15 seconds, notably 10 seconds for a vacuum pump alone.
[17] According to another aspect of the present invention, the second predetermined period is between 10 and 100 seconds, notably 30 seconds, for a primary vacuum pump connected in series with a supplementary vacuum pump. [18] According to another aspect of the present invention, the first predetermined period is between 50 ms and two seconds, notably one second.
[19] According to another aspect of the present invention, the volume to be pumped corresponds to the volume of a chamber connected to a suction of the vacuum pump. The connection can be made directly or via another vacuum pump.
[20] The present invention relates also to a vacuum pump configured to be connected to a chamber in which gases are wanted to be pumped and that comprises a pressure sensor positioned at a discharge of the vacuum pump, said vacuum pump comprising a processing unit configured to:
- detect an initiation of an evacuation in which, over a first predetermined period, the trend of at least one parameter out of the following parameters:
- an operating power of the vacuum pump,
- a pressure measured at the discharge of the vacuum pump, is compared with a first predetermined threshold, and, when an initiation of evacuation is detected,
- estimate a volume to be pumped on the basis of the trend, over a second predetermined period, of at least one parameter out of the following parameters:
- an operating power of the vacuum pump,
- a pressure measured at the discharge of the vacuum pump,
- limit the operating power of the vacuum pump as a function of the estimated volume. The greater the estimated volume to be pumped, the more the operating power is limited so as to prevent the pump from overheating or tripping out.
[21] According to another aspect of the present invention, the vacuum pump is a multistage primary vacuum pump.
[22] According to another aspect of the present invention, the vacuum pump is configured to be connected in series with a supplementary vacuum pump, said supplementary vacuum pump being positioned upstream of the vacuum pump.
[23] Other features and advantages of the invention will emerge more clearly on reading the following description, given as an illustrative and nonlimiting example, and the attached drawings in which:
[24] [Fig 1] represents a diagram of a vacuum pump connected to a chamber;
[25] [Fig 2] represents a perspective schematic view of the vacuum pump of figure 1;
[26] [Fig 3] represents a flow diagram of the different steps of the method for controlling the operating power of the vacuum pump according to a first embodiment; [27] [Fig 4] represents two curves cl and c2 showing the trend over time of the pressure at the discharge of the vacuum pump during an evacuation for two different volumes to be pumped;
[28] [Fig 5] represents an estimative curve of a volume to be pumped as a function of a mean pressure slope over a predetermined period, here 10 seconds, determined notably from the curves cl or c2 of figure 4;
[29] [Fig 6] represents a flow diagram of the different steps of the method for controlling the operating power of the vacuum pump according to a second embodiment;
[30] [Fig 7] represents three curves pl, p2, p3 showing the trend over time of the operating power of the vacuum pump during an evacuation for three different volumes to be pumped;
[31] [Fig 8] represents an estimative curve of a volume to be pumped as a function of a mean power slope over a predetermined period, here 10 seconds, determined notably from the curves pl, p2 or p3 of figure 7;
[32] [Fig 9] represents a diagram of two pumps connected in series and connected to a chamber;
[33] [Fig 10] represents three curves ql, q2, q3 respectively representing the operating power of the vacuum pump and of the supplementary vacuum pump, as well as the pressure at the discharge of the vacuum pump.
[34] In these figures, identical elements bear the same references.
[35] The following embodiments are examples. Although the description refers to one or more embodiments, that does not necessarily mean that each reference relates to the same embodiment, or that the features apply only to a single embodiment. Simple features of different embodiments can also be combined or interchanged to provide other embodiments.
[36] The present invention relates to a vacuum pump and a method for controlling an operating power of a vacuum pump. The vacuum pump is, for example, a multi-stage primary vacuum pump. Figure 1 represents a simplified diagram of an installation 1 comprising such a vacuum pump 2 of dry type and a chamber 3 to which the vacuum pump 2 is connected, for example via a valve 4, for pumping the chamber 3. Significant gas flows, of the order of several slm or several tens of slm, can be introduced into the chamber 3, for example cyclically, during so-called “process” steps if the chamber 3 is a process chamber. In fact, the chamber 3 corresponds, for example, to a process chamber for the fabrication of electronic substrates which goes alternately from an atmospheric pressure when the substrate is introduced into or removed from the process chamber to a very low pressure, for example less than 10 Pa during the substrate deposition or etching phases. These process steps can precede and follow so-called “idle” steps during which the gas flows introduced are low or nil.
[37] Significant flows can also be introduced repetitively over time if the chamber 3 is a loading/unloading airlock, or “loadlock”.
[38] Figure 2 presents a perspective, partly cross-sectional and transparent schematic view of the vacuum pump 2 of figure 1.
[39] In the example of figures 1 and 2, the vacuum pump 2 comprises a stator 5, a first shaft 6 and a second shaft 7 on which are arranged, respectively, a first rotor 8a and a second rotor 8b. The rotors 8a and 8b are configured to rotate synchronously in reverse directions in the stator 5 to drive a gas to be pumped G from a suction 9 of the vacuum pump 2 to a discharge 10 of the vacuum pump 2. The rotors 8a and 8b have, for example, lobes of identical profiles, such as of “Roots” or “Claw” type. According to another example, the pumping rotors can be of “screw” type.
[40] The vacuum pump 2 comprises at least one pumping stage, five stages in the case of the example of figure 1, respectively denoted Tl, T2, T3, T4 and T5. Each pumping stage comprises a respective inlet and outlet. The successive pumping stages are connected in series one after the other by respective inter-stage channels 14 (visible in figure 2) connecting the outlet of the pumping stage which precedes to the inlet of the stage which follows. During rotation, the gas sucked from the inlet is captive in the volume generated by the rotors 8a, 8b, then is driven by the rotors 8a, 8b to the discharge 10 (the direction of circulation of the gases is illustrated by the arrows G in figures 1 and 2). The vacuum pump 2 is notably said to be “dry” because, in operation, the rotors 8a, 8b revolve inside the stator 5 with no mechanical contact between them or with the stator 5, which makes it possible not to use oil in the pumping stages TITS. In this exemplary embodiment, the vacuum pump 2 of dry type is a multi-stage primary vacuum pump. A primary vacuum pump is a volumetric vacuum pump, which, using two rotors 8a and 8b, sucks, transfers then discharges the gas to be pumped at atmospheric pressure.
[41] The chamber 3 therefore defines a volume in which gases are wanted to be pumped. The connection between this chamber 3 and the vacuum pump 2 is made at the suction 9 of the vacuum pump 2. The vacuum pump 2 can also comprise a pressure sensor 12 positioned, for example, at its discharge 10. The variations of this pressure measured at the discharge 10 can be representative of the pressure variations inside the chamber 3 comprising the volume to be pumped when these variations are significant.
[42] The vacuum pump 2 also comprises a processing unit 13 which can be connected to the pressure sensor 12 situated at the discharge 10. The processing unit 13 can comprise one or more controllers or microcontrollers or processors and a memory for executing series of programme instructions implementing different functions linked to the vacuum pump 2 and notably the various steps of the method for controlling the maximum operating power of the vacuum pump 2 which will be described hereinafter in the description.
[43] Figure 3 represents a flow diagram of the different steps of the method for controlling the operating power of the vacuum pump 2 according to a first embodiment in which the vacuum pump 2 comprises a pressure sensor 12 at its discharge 10.
[44] The first step 101 relates to the measurement of a pressure measured by the pressure sensor 12 positioned at the discharge 10 of the vacuum pump 2. The pressure measurements are performed at regular time intervals, for example every 50 ms.
[45] The second step 102 relates to the detection of an initiation of an evacuation, that is to say a phase in which the pressure inside the chamber 3 is high, for example a pressure close to atmospheric pressure and in which a pumping cycle is begun to evacuate and reduce the pressure in the chamber 3 to a predetermined pressure.
[46] This detection is performed on the basis of the pressure measurements performed during the step 101.
[47] This detection is performed by comparing the trend, over a first predetermined period, of the pressure value measured at the discharge 10 with a first predetermined threshold.
[48] The first predetermined period is, for example, less than 2 s, notably of the order of 1 s. The parameter used to characterize the trend corresponds, for example, to the mean slope or mean differential (time differential) of the trend of the pressure at the discharge 10 (as a function of time) during the first predetermined period.
[49] Figure 4 represents an example of trend of the pressure measured by the pressure sensor 12 at the discharge 10 of the vacuum pump 2 for two different chamber volumes 3 upon an initiation of an evacuation.
[50] The initiation of an evacuation is detected when the pressure increases. Before beginning an evacuation, the pressure is, for example, approximately 1000 mbar at the discharge of the vacuum pump 2, then it increases abruptly (in 1 s to 2 s) to 1800 mbar as represented in figure 4 at the time tO (the two curves cl and c2 are overlaid during this pressure increase). The trend of the pressure is, for example, determined by a calculation of time differential of the pressure measured at the discharge of the vacuum pump 2 over a time of between 50 ms and 2 seconds, for example one second, which will serve as indicator. When this differential is positive and greater than a first predetermined threshold, for example 100 mbar/sec, then an initiation of evacuation is detected.
[51] The initiation of an evacuation can be confirmed by a pressure measurement above a predetermined threshold, for example 1500 mbar. In figure 4, the first curve cl is associated with a first volume of 2 m3 (or 2000 L) and the second curve c2 is associated with a second volume of 1 m3 (or 1000 L). The pressure at the instant tO therefore goes from approximately 1000 mbar (100 000 Pa) to approximately
1800 mbar (180 000 Pa) for the two curves cl and c2. This pressure then decreases strongly in the first seconds then increasingly slowly.
[52] If, as in the present example, the value of the mean slope is greater (in absolute value) than the first predetermined threshold, then an initiation of an evacuation is detected. In fact, when an evacuation is initiated, the pressure in the chamber is high, for example substantially equal to atmospheric pressure and decreases strongly when the evacuation is initiated. This strong reduction can be detected in the pressure measured at the discharge 10 of the vacuum pump 2 since the pressure at the discharge 10 of the vacuum pump 2 then increases strongly because of the great quantity of gas which is pumped.
[53] Moreover, the first predetermined threshold can be adjusted according to the type of vacuum pump 2 to which the method for controlling the operating power is applied.
[54] The third step 103 relates to an estimation of a volume to be pumped on the basis of the trend, over a second predetermined period, of the pressure measured in the step 101.
[55] This third step 103 is performed when an initiation of an evacuation is detected in the step 102 and when the maximum pressure value measured no longer increases (zero differential).
[56] The second predetermined period is greater than the first predetermined period and is, for example, between 5 s and 15 s, notably 10 s as in the present example. The trend of the pressure is, for example, determined by the value of the mean slope (or mean time differential) over the second predetermined period of the curve representing the pressure at the discharge 10 as a function of time.
[57] The value of the mean slope of the trend of the pressure cl, c2 during this second predetermined period from the instant tl corresponding to the maximum pressure value or from the detection of the initiation of an evacuation (t0+l s for example) is then compared to values saved and associated with different volumes.
[58] In the case of figure 4, the curve cl has a mean slope fl of -15 mbar/s (-1500 Pa/s) over the first 10 seconds from tl, whereas the curve c2 has a mean slope f2 of -
30 mbar/s (-3000 Pa/s) over the first 10 seconds from tl. These mean slopes can then be compared to mean slope values stored in a database. The database is, for example, saved in a memory of the processing unit 13.
[59] The mean slope values of pressure over 10 seconds and the volumes associated with these mean slope values can be stored in the form of a table or in the form of a curve whose x-axis and y-axis respectively correspond to the mean slope values and to the volume values, or vice versa. This curve is, for example, obtained by extrapolation from a few determined values. Figure 5 represents an example of such a curve. This curve can be modelled by a linear regression to provide a linear equation (here y=66.667x+3000) giving the volume associated with a mean pressure slope.
[60] Thus, by comparing the determined slope value with the values saved in the database or from a pre-established curve equation, it is possible to estimate a volume associated with the determined slope. In the example of figure 4, the mean slope of -15 mbar/s (- 1500 Pa/s) is associated with a volume of 2 m3 and the mean slope of -30 mbar/s (- 3000 Pa/s) is associated with a volume of 1 m3.
[61] The fourth step 104 relates to the application of a maximum operating power as a function of the volume estimated in the step 103. In fact, to prevent overheating or prevent the vacuum pump 2 from tripping out, it may be necessary to limit the operating power of the vacuum pump 2. The greater the volume in the chamber 3 (and therefore the more significant the pumping time), the more the power of the vacuum pump 2 must be reduced. Thus, in the case of figure 4, when the estimated volume to be pumped is 1 m3, the maximum power can be set at 4000 W and, when the estimated volume to be pumped is 2 m3, the maximum power can be set at 3500 W. The values of the maximum powers as a function of the volume to be pumped can be saved in a database in the form of a table or of a curve for example. The maximum operating power is thus limited as a function of the volume to be pumped such that, the greater the volume, the more the operating power is reduced.
[62] The databases and curves described in the steps 103 and 104 can be saved in the memory of the processing unit 13 or in a memory external to the processing unit 13 to which the processing unit 13 is connected.
[63] Thus, the monitoring of the trend of the pressure at the discharge 10 of the vacuum pump 2 makes it possible to be able to detect the initiation of an evacuation and to estimate the volume to be pumped upon the evacuation and makes it possible to determine a maximum power of the vacuum pump 2 to be applied to limit the risk of malfunctioning of the vacuum pump 2 during the evacuation.
[64] Figure 6 represents a flow diagram of the different steps of the method for controlling the operating power of the vacuum pump 2 according to a second embodiment. In this second embodiment, the pressure sensor 12 at the discharge 10 is not necessary.
[65] The first step 201 relates to the determination of an operating power or operating load of the vacuum pump 2. This determination is for example made by a processing unit 13 of the vacuum pump 2 such as the processing unit 13 described previously and can be done by measuring a parameter representative of the operating power of the vacuum pump 2 such as the motor current. The operating power depends on the quantity of gas to be pumped and therefore on the pressure in the chamber 3.
[66] The second step 202 relates to the detection of an initiation of an evacuation, that is to say a phase in which the pressure in the chamber 3 is high, for example a pressure close to atmospheric pressure, and in which a pumping cycle is begun to evacuate and reduce the pressure in the chamber 3 to a predetermined pressure.
[67] Figure 7 represents an example of representative curves denoted pl, p2 and p3 of the trend of the operating power of the vacuum pump 2 for three different chamber 3 volumes upon an initiation of an evacuation.
[68] The first curve pl is associated with a first volume of 1000 L (1 m3), the second curve p2 is associated with a second volume of 200 L (0.2 m3) and the third curve p3 is associated with a third volume of 20 L (0.02 m3).
[69] The variation of the operating power is a function of the pressure in the chamber 3 comprising the volume to be pumped. It is thus possible, as for the pressure at the discharge 10, to detect the initiation of an evacuation when the operating power varies beyond a first predetermined threshold. [70] An initiation of an evacuation is detected when the increase in power exceeds a predetermined threshold for a first predetermined period of between 50 ms and 2 s, for example 1 s. For that, the time differential is for example determined over this first predetermined period and it is compared to a predetermined threshold, for example 300 W/s. In the case of figure 7, the power before the initiation of the evacuation is approximately 800 W and goes rapidly (less than 2 s) to a value greater than 4000 W (approximately 5800 W for the curve pl and approximately 4500 W for the curves p2 and p3) for the different curves, such that the time differential over 1 s exceeds the first predetermined threshold and an initiation of an evacuation is therefore detected. This detection of an evacuation can be confirmed by a power value exceeding 4000 W.
[71] As for the first embodiment with the pressure, the value of the mean slope (or mean time differential) of the trend of the power during the first predetermined period, here 1 s, is compared to the value of the first predetermined threshold, for example
300 W/s. If the mean slope of the trend of the operating power during the first predetermined period, here 1 s, is greater than this predetermined threshold, then an initiation of an evacuation is detected. This first predetermined threshold can be adjusted according to the type of vacuum pump 2 to which the method for controlling the operating power of the vacuum pump 2 is applied.
[72] The third step 203 relates to an estimation of a volume to be pumped based on the trend, over a second predetermined period, of the operating power of the vacuum pump 2.
[73] This third step 203 is performed when an initiation of an evacuation is detected in the step 202 and the power goes through a maximum value (zero differential).
[74] The second predetermined period is greater than the first predetermined period and is, for example, between 5 s and 15 s, notably 10 s in the present case.
[75] The value of the mean slope of the time trend of the operating power of the vacuum pump 2 during this second predetermined period from the time tl corresponding to the power maximum (zero differential) (in the case of figure 7, this instant tl is substantially the same for the three curves pl, p2 and p3) is then compared to values saved and associated with different volumes.
[76] In the case of figure 7, the first curve pl has a mean slope of -27 W/s over the first 10 seconds from tl, the second curve p2 has a mean slope of -53 W/s over the first 10 seconds from tl and the curve p3 has a mean slope of -350 W/s. These mean slopes can then be compared to mean slope values stored in a database. [77] The mean slope values of operating power over 10 seconds and the volumes associated with these mean slope values can be stored in the form of a table or in the form of a curve whose x-axis and y-axis correspond respectively to the mean slope values and to the power values, or vice versa. This curve is, for example, obtained by extrapolation from a few determined values. Figure 8 represents an example of such a curve denoted g with the power slope in watts/sec on the y-axis and the volume in litres on the x-axis. This curve shows a substantially hyperbolic decrease and can be approximated by two linear regressions associated with two curve portions, a first straight line gl associated with the volumes less than 50 L and a second straight line g2 associated with the volumes greater than or equal to 50 L.
[78] Thus, by comparing the mean slope value of power determined with the values saved in the database or based on one or more predefined correspondence curves, it is possible to estimate a volume associated with the mean power slope determined during the second predetermined period. In the example of figure 7, the mean slope of -27 W/s is associated with a volume of 1000 L, the mean slope of -53 W/s is associated with a volume of 200 L and the slope of -350 W/s is associated with a volume of 20 L.
[79] The fourth step 204 relates to the application of a maximum operating power as a function of the volume estimated in the step 203. In fact, to prevent overheating or prevent the vacuum pump 2 from tripping out, it may be necessary to limit the power of the vacuum pump 2. The greater the volume in the chamber 3 (and therefore the more significant the pumping time in the evacuation), the more the power of the vacuum pump 2 must be reduced. Thus, in the case of figure 7, when the estimated volume to be pumped is 1000 L (1 m3), the maximum power is set at 3500 W, when the estimated volume to be pumped is 200 L (0.2 m3), the maximum power is set at 4000 W and, when the estimated volume to be pumped is 20 L (0.02 m3), there is no power limit. The maximum operating power values and the associated estimated volumes are, for example, saved in a database. The databases and curves described in the steps 203 and 204 can be saved in the memory of the processing unit 13 or in a memory external to the processing unit 13 to which the processing unit 13 is connected.
[80] The different steps of the method described on the basis of figure 6 can be implemented by a processing unit 13 of the vacuum pump 2, such as the processing unit 13 described previously. [81] Moreover, according to a third embodiment, it is also possible to produce both an estimation of volume based on the pressure described previously on the basis of figure 3 and an estimation of volume based on the power described previously on the basis of figure 6 and thus determine a maximum operating power on the basis of these two parameters.
[82] The trends of the pressure and operating power over the first predetermined period, for example one second, can be used to detect the initiation of an evacuation. The pressure measurement is, for example, used as a priority for the detection and the power can be used as confirmation. In the case of different results between the pressure and the power, an alarm can be issued, for example an audible and/or visual signal. It is also possible to define as priority parameter that for which the trend is the most regular, that is to say the parameter for which the number of changes of sign of the differential associated with its trend is the lowest (curve always increasing for example) over the first predetermined period.
[83] The trends of the pressure and the operating power over the second predetermined period, for example ten seconds, can then each be used to independently estimate the volume of gas to be pumped.
[84] The two estimated volumes can be compared.
[85] If the difference between the two estimated volumes is less than a predetermined threshold (the predetermined threshold can correspond to a percentage of the estimated volume), the estimated volume can correspond to the average value of the two estimated volumes or the volume estimated by one of the methods can be retained as a priority, for example the volume obtained by the parameter for which the trend is the most regular, that is to say for which the differential exhibits the fewest changes of sign (always increasing or always decreasing over the second predetermined period for example). The maximum power to be used during the pumping is then determined from a database or from a correspondence curve as described previously.
[86] If their difference is greater than the predetermined threshold, an alarm can be issued, for example an audible and/or visual signal and the volume retained can correspond to the greatest estimated volume so as to limit the risk of overheating in case of prolonged pumping.
[87] Thus, the use of two distinct parameters, the pressure and the power, for the detection of an initiation of an evacuation and the estimation of a volume to be pumped makes it possible to obtain a confirmation and therefore improve the reliability of the detection and of the estimation of the volume to be pumped to even more reliably choose the maximum operating power.
[88] According to another embodiment represented in figure 9, the installation 1 comprises a primary vacuum pump 2, that is to say whose discharge emerges into air at atmospheric pressure, and a supplementary vacuum pump 2’ positioned in series and upstream of the vacuum pump 2. The “upstream” and “downstream” positions are defined here with respect to the direction of suction of the gas by the vacuum pumps 2 and 2’. Thus, the suction 9’ of the supplementary vacuum pump 2’ is connected to an orifice of the chamber 3 and the discharge 10’ of the supplementary vacuum pump 2’ is connected to the suction 9 of the vacuum pump 2. As in the preceding embodiment, a pressure sensor 12 can be positioned at the discharge 10 of the vacuum pump 2. The supplementary vacuum pump 2’ is a vacuum pump comprising its own motor, for example a volumetric vacuum pump of roots type.
[89] Figure 10 represents three curves denoted ql, q2 and q3 corresponding respectively to the trend over time of the operating power of the vacuum pump 2, of the trend over time of the operating power of the supplementary vacuum pump 2’ and of the trend over time of the pressure at the discharge 10 of the vacuum pump 2. The pressure at the discharge 10 of the vacuum pump 2 is, for example, given by the sensor 12. In figure 10, the instant tO corresponds to the initiation of an evacuation. It can be seen that, from the instant tO, the operating power of the vacuum pump 2 increases strongly (curve ql) to a time t2 from which the operating power of the vacuum pump 2 decreases. The operating power of the supplementary vacuum pump 2’ remains low up to the time t2 then increases strongly. Thus, between the times tO and t2, it is mainly the vacuum pump 2 which contributes to the evacuation and, from the time t2, the contribution of the vacuum pump 2 decreases in favour of the supplementary vacuum pump. The time t2 corresponds to the moment when a certain pressure is reached in the chamber 3. It can also be seen that the pressure at the discharge 10 of the vacuum pump 2 increases strongly over a short period after the instant tO then decreases regularly.
[90] As in the preceding embodiment, the mean slopes over predefined periods associated with the trends over time of the operating power of the vacuum pump 2 and of the pressure at the discharge of the vacuum pump 2 can make it possible, on the one hand, to detect an initiation of an evacuation and, on the other hand, to estimate the volume to be pumped. The initiation of an evacuation is, for example, detected when the slope of the trend of the operating power of the vacuum pump 2 over a first predetermined period, for example a period of between 100 ms and 2 seconds, is greater than a predetermined threshold. Alternatively or in addition, the initiation of an evacuation can be detected when the slope of the trend of the pressure at the discharge 10 of the vacuum pump 2 over the first predetermined period is greater (in absolute value) than another predetermined threshold.
[91] The estimation of the volume to be pumped is, for example, performed by comparing the slope of the trend of the operating power of the vacuum pump 2 over a second predetermined period, for example a period of between 10 s and 100 s, notably 30 s, with slope values saved in a database.
[92] Alternatively or in addition, the estimation of the volume to be pumped can be performed by comparing the slope of the trend of the pressure at the discharge 10 of the vacuum pump 2 over the second predetermined period with slope values saved in a database. The database also comprises values of volume to be pumped associated with these slope values (of the pressure curve or of the operating power curve). The database is, for example, saved in a memory of the processing unit 13. In the example of figure 10, the slope pl associated with the curve ql can be used to determine a volume to be pumped and the slope p3 of the curve q3 can also be used to determine the volume to be pumped. In the example of figure 10, the curve q3 associated with the pressure at the discharge 10 will be used as a priority because its variations are much smaller during the second predetermined period. Thus, the method for controlling the power of a vacuum pump can also be used for a primary pump connected in series with another pump positioned upstream, between the chamber comprising the volume to be pumped and the primary vacuum pump 2.
[93] The monitoring of operating parameters of a vacuum pump 2 such as the operating power of the vacuum pump or the pressure at the discharge 10 of the vacuum pump 2 thus make it possible to detect an initiation of an evacuation and to estimate the volume to be pumped, for example the volume of a chamber 3 intended for the fabrication of “wafers”, and thus be able to adapt the maximum operating power of the vacuum pump 2 during the evacuation without risking the vacuum pump 2 overheating or tripping out. That makes it possible to avoid a manual configuration in the factory based on the application to which the vacuum pump 2 is dedicated and having to know, during the production of the vacuum pump 2, the volume of the chamber 3 to which the vacuum pump 2 will be connected. [94] The present invention relates also to a vacuum pump 2 comprising a processing unit 13 configured to perform the steps of the method for controlling the operating power according to one of the embodiments presented previously.

Claims

Claims
[Claim 1] Method for controlling an operating power of a vacuum pump (2) configured to be connected to a volume in which gases are wanted to be pumped, characterized in that the method comprises:
- a step (102, 202) of detection of an initiation of an evacuation in which, over a first predetermined period, the trend of at least one parameter out of the following parameters:
- an operating power of the vacuum pump (2),
- a pressure measured at a discharge (10) of the vacuum pump (2), is compared with a first predetermined threshold, and, when an initiation of an evacuation is detected,
- a step (103, 203) of estimation of a volume to be pumped based on the trend, over a second predetermined period, of at least one parameter out of the following parameters:
- an operating power of the vacuum pump (2),
- a pressure measured at the discharge (10) of the vacuum pump (2), and
- a step (104, 204) of limiting of the operating power of the vacuum pump (2) in which the operating power of the vacuum pump (2) is limited as a function of the estimated volume.
[Claim 2] Method according to Claim 1, in which the trend of the parameter corresponds to the mean slope, over the first or second predetermined period, of the trend over time of the parameter.
[Claim 3] Method according to Claim 1 or 2, wherein the estimation of a volume to be pumped comprises a first estimation (203) of the volume to be pumped made on the basis of the trend of the operating power parameter of the vacuum pump (2) and a second estimation (103) of the volume to be pumped made on the basis of the trend of the pressure parameter measured at the discharge (10) of the vacuum pump (2), the volume to be pumped being estimated as a priority on the basis of the parameter whose trend is the most regular over the second predetermined period.
[Claim 4] Method according to the preceding claim, wherein an alarm is issued when the deviation between the volume estimated on the basis of the pressure parameter at the discharge (10) and the volume estimated on the basis of the operating power parameter of the vacuum pump (2) exceeds a predetermined value.
[Claim 5] Method according to one of the preceding claims, wherein the estimation of the volume to be pumped on the basis of the operating power of the vacuum pump (2) comprises the estimation of a mean slope of decreasing of the operating power of the vacuum pump (2) during the second predetermined period and the comparison of this estimated slope with saved power slope values associated with different volumes to be pumped.
[Claim 6] Method according to one of the preceding claims, wherein the estimation of the volume to be pumped on the basis of the pressure measured at the discharge (10) of the vacuum pump (2) comprises the estimation of a mean slope of decreasing of the pressure measured at the discharge (10) of the vacuum pump (2) during the second predetermined period and the comparison of this estimated slope with saved pressure slope values associated with different volumes to be pumped.
[Claim 7] Method according to one of the preceding claims, wherein the second predetermined period is between 3 and 15 seconds, notably 10 seconds for a vacuum pump (2) alone.
[Claim 8] Method according to one of Claims 1 to 6, wherein the second predetermined period is between 10 and 100 seconds, notably 30 seconds, for a primary vacuum pump (2) connected in series with a supplementary vacuum pump (2’).
[Claim 9] Method according to one of the preceding claims, wherein the first predetermined period is between 50 ms and two seconds, notably one second.
[Claim 10] Method according to one of the preceding claims, wherein the volume to be pumped corresponds to the volume of a chamber (3) connected to a suction (9) of the vacuum pump (2).
[Claim 11] Vacuum pump (2) configured to be connected to a chamber (3) in which gases are wanted to be pumped and that comprises a pressure sensor (12) positioned at a discharge (10) of the vacuum pump (2), said vacuum pump (2) comprising a processing unit (13) configured to:
- detect (102, 202) an initiation of an evacuation in which, over a first predetermined period, the trend of at least one parameter out of the following parameters:
- an operating power of the vacuum pump (2),
- a pressure measured at the discharge (10) of the vacuum pump (2), is compared with a first predetermined threshold, and, when an initiation of evacuation is detected,
- estimate (103, 203) a volume to be pumped on the basis of the trend, over a second predetermined period, of at least one parameter out of the following parameters:
- an operating power of the vacuum pump (2),
- a pressure measured at the discharge (10) of the vacuum pump (2),
- limit (104, 204) the operating power of the vacuum pump (2) as a function of the estimated volume.
[Claim 12] Vacuum pump (2) according to the preceding claim, wherein the vacuum pump (2) is a multi-stage primary vacuum pump (2).
[Claim 13] Vacuum pump (2) according to Claim 11 or 12, configured to be connected in series with a supplementary vacuum pump, said supplementary vacuum pump being positioned upstream of the vacuum pump.
PCT/EP2021/076405 2020-10-16 2021-09-24 Method for controlling an operating power of a vacuum pump, and vacuum pump WO2022078738A1 (en)

Priority Applications (1)

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KR1020237008505A KR20230085133A (en) 2020-10-16 2021-09-24 Method for controlling operating power of vacuum pump and vacuum pump

Applications Claiming Priority (2)

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FRFR2010668 2020-10-16
FR2010668A FR3112171B1 (en) 2020-10-16 2020-10-16 Method for controlling an operating power of a vacuum pump and vacuum pump

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FR (1) FR3112171B1 (en)
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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH10253005A (en) * 1997-03-14 1998-09-25 Miura Co Ltd Deaerator system and operating method therefor
JP2001012379A (en) * 1999-06-29 2001-01-16 Aisin Seiki Co Ltd Vacuum pump with maintenance judging function
US8715400B2 (en) * 2009-12-24 2014-05-06 Sumitomo Seiko Chemicals Co., Ltd. Double vacuum pump apparatus, gas purification system provided with double vacuum pump apparatus, and exhaust gas vibration suppressing device in double vacuum pump apparatus
US20160265532A1 (en) * 2015-03-09 2016-09-15 Ebara Corporation Vacuum pump
WO2018010970A1 (en) * 2016-07-13 2018-01-18 Pfeiffer Vacuum Method for lowering the pressure in a loading and unloading lock and associated pumping unit
WO2019137700A1 (en) * 2018-01-09 2019-07-18 Pfeiffer Vacuum Vacuum pump of dry type and method for controlling a vacuum pump synchronous motor

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH10253005A (en) * 1997-03-14 1998-09-25 Miura Co Ltd Deaerator system and operating method therefor
JP2001012379A (en) * 1999-06-29 2001-01-16 Aisin Seiki Co Ltd Vacuum pump with maintenance judging function
US8715400B2 (en) * 2009-12-24 2014-05-06 Sumitomo Seiko Chemicals Co., Ltd. Double vacuum pump apparatus, gas purification system provided with double vacuum pump apparatus, and exhaust gas vibration suppressing device in double vacuum pump apparatus
US20160265532A1 (en) * 2015-03-09 2016-09-15 Ebara Corporation Vacuum pump
WO2018010970A1 (en) * 2016-07-13 2018-01-18 Pfeiffer Vacuum Method for lowering the pressure in a loading and unloading lock and associated pumping unit
WO2019137700A1 (en) * 2018-01-09 2019-07-18 Pfeiffer Vacuum Vacuum pump of dry type and method for controlling a vacuum pump synchronous motor

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TW202223239A (en) 2022-06-16
KR20230085133A (en) 2023-06-13
FR3112171B1 (en) 2022-07-08

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