Method for controlling the operating parameters of a turbomolecular vacuum pump

Abstract

A method for controlling the operating parameters of a turbomolecular vacuum pump (1) comprising: - a stator (2), - a rotor (3), - a motor (16) configured to drive the rotor (3) to rotate in the stator (2), - an internal heating device (21) arranged in the gas flow path of the vacuum pump (1) and configured to heat the rotor (3), - a temperature sensor configured to measure the temperature of the rotor (3), - an external heating device (27) configured to heat the stator (2), characterized in that the control method comprises: - a nominal operating mode in which the rotor (3) is heated via the internal heating device (21) as long as the measured temperature of the rotor (3) is less than a given temperature threshold for a parameter representative of the power consumed by the motor (16), and - an overspeed operating mode in which the internal heating of the rotor (3) is cut when the measured temperature of the rotor (3) is greater than or equal to the temperature threshold.

Description

Description Title of the invention: Method for controlling the operating parameters of a turbomolecular vacuum pump Technical field of the invention

[0001] The present invention relates to a method for controlling the operating parameters of a turbomolecular vacuum pump. The present invention also relates to a turbomolecular vacuum pump. Technical background

[0002] Generating a high vacuum in an enclosure requires the use of turbomolecular vacuum pumps consisting of a stator in which a rotor is driven into rapid rotation, for example rotation at more than thirty thousand revolutions per minute.

[0003] In some processes in which turbomolecular vacuum pumps are used, such as semiconductor, photovoltaic panel or LED manufacturing processes, a layer of deposit can form in the vacuum pump. These deposits can lead to a clearance restriction between the stator and the rotor, which can cause the rotor to seize. It is known to heat the stator to prevent condensation of reaction products and thus limit the formation of deposits in the vacuum pump and increase its service life.

[0004] In addition to limiting deposit formation, it may be necessary to increase the rotor operating temperature for other reasons. For example, increasing the temperature may be necessary to increase the gas flow to be pumped or to facilitate the pumping of heavier gas species.

[0005] However, care is taken to ensure that the rotor temperature does not exceed a certain high threshold in order to preserve its mechanical strength. Indeed, the rotor's mechanical resistance to centrifugal forces decreases as the temperature increases. Irreversible deformations of the rotor (or creep) can occur at high temperatures and risk causing the stator to touch the most expanded part of the rotor. We also seek to avoid overheating the pumped gases to limit the risks of thermal cracking, i.e. a chemical degradation of the pumped gas molecules when they are heated too much, with the production of non-volatile by-products such as carbon black.

[0006] Furthermore, when a heated vacuum pump is faced with the entry of a large gas flow to be pumped, causing an overload of the motor that cannot be absorbed by the vacuum pump, the vacuum pump limits the rotation speed of the rotor until the pumping load falls below a tolerable threshold. The pumping capacity of the turbomolecular vacuum pump is therefore reduced in these particular situations, the time to absorb these large gas flows. Summary of the invention

[0007] One of the aims of the present invention is to propose a method for controlling the operating parameters of an optimized heated turbomolecular vacuum pump, in particular for pumping cycles alternating periods of significant gas flows to be pumped with periods of moderate gas flows to be pumped.

[0008] To this end, the invention relates to a method for controlling the operating parameters of a turbomolecular vacuum pump comprising: - a stator, - a rotor, - a motor configured to drive the rotor in rotation in the stator, - an internal heating device arranged in the gas flow path of the vacuum pump and configured to heat the rotor, - a temperature sensor configured to measure the rotor temperature, - an external heating device configured to heat the stator, characterized in that the control method comprises: - a nominal operating mode in which the rotor is heated via the internal heating device, as long as the measured temperature of the rotor is below a temperature threshold for a parameter representative of the power consumed by the given motor and - an overspeed operating mode in which the internal heating of the rotor is cut off when the measured rotor temperature is greater than or equal to the temperature threshold.

[0009] The temperature threshold depends on the parameter representing the (electrical) power consumed by the motor, which can be the current or the power consumed by the motor. The electrical power consumed by the motor is itself representative of the gas flow to be pumped. The greater the flow to be pumped, the greater the power consumed by the motor, and vice versa.

[0010] It is therefore possible to vary the temperature threshold with the power consumed and therefore with the gas flow to be pumped to activate or cut off the internal heating so that the temperature remains within a given temperature range, in relation to the quantity of gas flow to be pumped.

[0011] Thus, when the vacuum pump is used on pumping cycles alternating periods of significant gas flows to be pumped, i.e., greater than the nominal gas flows, for example at least 1.5 times greater, with periods of moderate, and therefore nominal, gas flows to be pumped, the switching on and off of the internal heating can be synchronized with the variations in the gas flow to be pumped. Instead of switching off and on the internal heating blindly, i.e., instead of regulating the temperature by taking the temperature into account only, the internal heating can be switched off during periods of high power (and therefore significant gas flows to be pumped). Taking into account the power consumed by the motor thus makes it possible to match the periods of high gas flows with the periods when the internal heating is switched off.Cutting off the internal heating prevents excessive heating of strong gas flows to limit the risks of thermal cracking, i.e. chemical degradation of the molecules of the pumped gases when they are heated too much, with the production of non-volatile by-products such as carbon black.

[0012] The control method may further comprise one or more of the features described below, taken alone or in combination.

[0013] The temperature threshold is variable.

[0014] It is below a maximum temperature threshold. The maximum temperature threshold is, for example, between 130°C and 140°C.

[0015] For example, the temperature threshold decreases, for example linearly, within a given temperature range, with the increase in the parameter representing the power consumed by the engine. The given temperature range is for example between 100°C and 140°C, such as between 118°C and 120°C. The internal heating is cut off a little lower in temperature at high power than at low power to anticipate the upcoming increase in rotor temperature due to the increase in the gas flow to be pumped, this increase in the gas flow to be pumped causing an increase in rotor temperature due to the compression of the gases but which is relatively slow.

[0016] The power consumed by the motor can be capped at a maximum motor consumption threshold, for example 1000W or the current consumed by the motor can be capped at a maximum motor consumption threshold, for example 10A.

[0017] The power consumed in overspeed operating mode is, for example, at least twice the power consumed in nominal operation.

[0018] According to an application example, the vacuum pump is used for cyclic pumping of process chambers of equipment, in which manufacturing processes take place, comprising manufacturing steps where the gas flows to be pumped are moderate and cleaning steps where the gas flows to be pumped are large.

[0019] The invention also relates to a turbomolecular vacuum pump comprising: - a stator, - a rotor, - a motor configured to drive the rotor in rotation in the stator, - an internal heating device arranged in the gas flow path of the vacuum pump and configured to heat the rotor, - a temperature sensor configured to measure the rotor temperature, - an external heating device configured to heat the stator, characterized in that the motor is configured on the one hand, to be able to drive the rotor with a nominal power and on the other hand, to be able to drive the rotor with an overspeed power, greater than the nominal power, and in that the vacuum pump comprises a control unit configured to implement a control method as described previously.

[0020] The nominal rotation speed of the rotor can therefore be maintained without any particular risk to the life of the vacuum pump. The overspeed operating mode is automatic; the user does not have to change the vacuum pump temperature setpoint and does not need to know any information external to the vacuum pump, such as the duration, flow rate and nature of the pumped gases.

[0021] The turbomolecular vacuum pump may further comprise one or more of the features described below, taken alone or in combination.

[0022] The motor can be configured to provide a suitable rated power to be able to pump a maximum continuous flow rate, nitrogen equivalent, of less than 5 Pa.m 3 / s. The nominal power is for example between 80W and 200W.

[0023] The engine can be configured to provide an overspeed power suitable for pumping a nitrogen equivalent flow rate greater than or equal to 5 Pa.m 3 / s, such as greater than 6.755 Pa.m 3 / s. The overspeed power is, for example, at least twice the nominal power. For example, it is greater than 600W.

[0024] The temperature sensor is for example an infrared temperature sensor.

[0025] The internal heater comprises, for example, radiating elements arranged in the helical grooves of a sleeve of the vacuum pump stator. The radiating internal heater has the advantage of having a short response time, so that the heater can be switched off in less than one minute after the stop command.

[0026] Brief description of the figures

[0027] Other advantages and characteristics will appear on reading the following description of a particular embodiment of the invention, but in no way limiting, as well as the appended drawings in which:

[0028] [Fig. 1] Figure 1 shows an axial sectional view of a turbomolecular vacuum pump.

[0029] [Fig. 2] Figure 2 shows a flowchart of elements of the vacuum pump of Figure 1.

[0030] [Fig. 3] Figure 3 is a schematic view of equipment connected to a turbomolecular vacuum pump, itself connected to a primary pumping system.

[0031] [Fig.4] Figure 4 is a graph showing an example of a temperature threshold (on the ordinate, in degrees Celsius) varying with the power consumed by the motor (on the abscissa, in Watts).

[0032] [Fig.5] Figure 5 is a graph showing, as a function of time (in minutes), for a turbomolecular vacuum pump used for pumping a process chamber in which a manufacturing process takes place alternating manufacturing steps with cleaning steps: - a curve A of the evolution of the measured rotor temperature (left ordinate in degrees Celsius), - a curve B showing the evolution of the power (right ordinate in Watts) consumed by the motor, - a curve C of the power supply to the radiative elements of the internal heating device of the vacuum pump (right ordinate in Watts), and - a curve D showing the evolution of the temperature threshold (left ordinate in degrees Celsius).

[0033] In these figures, identical elements have the same reference numbers. Detailed description

[0034] The following embodiments are examples. Although the description refers to one or more embodiments, this does not necessarily mean that each reference relates to the same embodiment, or that the features apply only to a single embodiment. Single features of different embodiments may also be combined or interchanged to provide other embodiments, without departing from the scope of the invention, as defined by the claims.

[0035] "Upstream" means an element that is placed before another in relation to the direction of gas flow. Conversely, "downstream" means an element placed after another in relation to the direction of gas flow to be pumped.

[0036] Figure 1 illustrates an exemplary embodiment of a turbomolecular vacuum pump.

[0037] The turbomolecular vacuum pump 1 comprises a stator 2 in which a rotor 3 is configured to rotate at high speed in axial rotation, for example rotation at more than thirty thousand revolutions per minute.

[0038] In the embodiment of Figure 1, the turbomolecular vacuum pump 1 is said to be hybrid: it comprises a turbomolecular stage 4 and a molecular stage 5 located downstream of the turbomolecular stage 4 in the direction of circulation of the pumped gases (represented by the arrows F1 in Figure 1). The pumped gases enter through the suction port 6, first pass through the turbomolecular stage 4, then the molecular stage 5, to then be evacuated to a discharge port 7 of the turbomolecular vacuum pump 1. In operation, the discharge port 7 is connected to a primary pump.

[0039] An annular inlet flange 8 surrounds, for example, the suction port 6 to connect the vacuum pump 1 to an enclosure whose pressure is to be lowered.

[0040] In the turbomolecular stage 4, the rotor 3 comprises at least two stages of blades 9 and the stator 2 comprises at least one stage of fins 10. The stages of blades 9 and fins 10 follow one another axially along the axis of rotation ll of the rotor 3 in the turbomolecular stage 4. The rotor 3 comprises, for example, more than four stages of blades 9, such as, for example, between four and twelve stages of blades 9 (seven in the example illustrated in FIG. 1).

[0041] Each stage of blades 9 of the rotor 3 comprises inclined blades which extend in a substantially radial direction from a hub 11 of the rotor 3 fixed to a drive shaft 12 of the vacuum pump 1, for example by screwing. The blades are distributed regularly around the periphery of the hub 11.

[0042] Each stage of fins 10 of the stator 2 comprises a crown from which extend, in a substantially radial direction, inclined fins, distributed regularly around the inner periphery of the crown. The fins of a stage of fins 10 of the stator 2 engage between the blades of two successive stages of blades 9 of the rotor 3. The blades 9 of the rotor 3 and the fins 10 of the stator 2 are inclined to guide the pumped gas molecules towards the molecular stage 5.

[0043] Here, in the molecular stage 5, the rotor 3 further comprises a skirt 13, called a Holweck skirt, downstream of the at least two blade stages 9, formed by a smooth cylinder, which rotates opposite helical grooves 14 of the stator 2. The helical grooves 14 are arranged one above the other. There are for example between three and ten helical grooves 14, such as six. The helical grooves 14 of the stator 2 make it possible to compress and guide the pumped gases towards the discharge orifice 7.

[0044] The rotor 3 further comprises an internal bowl 15, coaxial with the axis of rotation 11, formed under the skirt 13 and arranged opposite a bell 17 of the stator 2, projecting under the rotor 3. In operation, the rotor 3 rotates in the stator 2 without contact between the internal bowl 15 and the bell 17.

[0045] The rotor 3 can be made from a single piece (monobloc) or it can be an assembly of several parts. It is for example made from aluminum (or aluminum alloy) and / or nickel. It can have a coating, such as nickel, in particular to better resist corrosion. It is for example made from nickel-plated aluminum.

[0046] The rotor 3 is driven in rotation in the stator 2 by a motor 16 of the vacuum pump 1. The motor 16 is for example arranged in the bell 17 of the stator 2, itself arranged under the internal bowl 15 of the rotor 3, the drive shaft 12 passing through the bell 17 of the stator 2.

[0047] The rotor 3 is guided laterally and axially by magnetic or mechanical bearings 18 supporting the drive shaft 12 of the rotor 3, located in the stator 2. There are for example first bearings 18 supporting and guiding a first end of the drive shaft 12 in a base of the bell 17 of the stator 2 and second bearings 18 supporting and guiding a second end of the drive shaft 12 arranged at the top of the bell 17.

[0048] Other electrical or electronic components may be received in the bell 17 of the stator 2, such as position sensors.

[0049] The vacuum pump 1 may comprise a cooling device configured to cool the bell 17, arranged for example in the bell 17 or in thermal contact with the bell 17, such as a hydraulic circuit, in order to be able to continuously cool the elements that it contains such as in particular the bearings 18, the motor 16 and other electrical or electronic components to enable their operation.

[0050] The vacuum pump 1 may comprise a purge device 20 configured to inject a purge gas into the gap located between the bell 17 of the stator 2 and the internal bowl 15 of the rotor 3. The purge gas is preferably air or nitrogen, but may also be another neutral gas such as helium or argon. The purge device is for example configured to inject a purge gas at at least one bearing 18 located in the stator 2, supporting and guiding the drive shaft 12 of the rotor 3 so that the flow of purge gas passes through the at least one bearing 18 before exiting the bell 17 of the stator 2 and circulating in the gap. The circulation of the purge gas is shown diagrammatically by arrows f2 in FIG. 1.

[0051] The vacuum pump 1 comprises an internal heating device 21 arranged in the gas flow path of the vacuum pump 1 and configured to heat the rotor 3.

[0052] The internal heating device 21 may comprise radiative elements, for example arranged in the helical grooves 14 of a sleeve 22 of the stator 2 of the vacuum pump 1. The internal radiative heating device 21 has the advantage of having a short response time, so that the heating can be switched off in less than one minute after the stop command.

[0053] The internal heating device 21 comprises, for example, on the one hand, an electrical circuit 29 comprising at least one resistive element without thermal contact with the stator 2 but capable of evacuating heat by infrared radiation, called radiative element 30, the radiative element 30 being inserted in the pumped gas path opposite the rotor 3 and, on the other hand, a switch 28 electrically connected to the electrical circuit 29 and controllable by a control unit 31 of the vacuum pump 1 to authorize or cut off the electrical supply to the radiative elements 30 (figure 2).

[0054] The turbomolecular vacuum pump 1 further comprises a temperature sensor 23 configured to measure the temperature of the rotor 3. The temperature sensor 23 is for example an infrared temperature sensor. The infrared sensor is contactless, which makes it possible to measure the temperature of the rotating rotor 3 with high precision in the temperature ranges between 50°C and 250°C.

[0055] The temperature sensor 23 can be configured to measure the temperature of the skirt 13 of the rotor 3 (the cylindrical part), in particular in a lower part, that is to say located on the side of the discharge orifice 7 of the vacuum pump 1, so as to target the place of the rotor 3 which is subjected to the most mechanical stress.

[0056] The temperature sensor 23 is for example arranged behind (under) the skirt 13 of the rotor 3, between the stator 2 and the internal bowl 15 of the rotor 3 (figure 1). In this way, the temperature sensor 23 is not arranged in the gas pumping path and therefore is little subject to corrosive attacks from the pumped gases and can benefit from protection by the purge gas.

[0057] The vacuum pump 1 also comprises an external heating device 27 configured to heat the stator 2 of the vacuum pump 1.

[0058] The external heating device 27 is for example configured to heat the external casing 19 (or housing) of the stator 2 of the vacuum pump 1. Alternatively or in addition, the external heating device 27 can be configured to heat the stator 2 at the discharge of the vacuum pump 1, in particular around the discharge orifice 7.

[0059] The external heating device 27 comprises for example one or more heating resistive belts or one or more heating cartridges, the electrical supply of which can be controlled by the control unit 31, independently of the internal heating device 21. The heating can in particular be controlled around a set temperature by means of an additional temperature sensor configured to measure the temperature of the stator 2. The regulation time constant of the external heating device 27 is much greater than the regulation time constant of the internal heating device 21 due to the differences in response times of the temperature sensors and the heating devices.

[0060] The motor 16 is, on the one hand, configured to be able to drive the rotor 3 with a nominal power. The nominal power is adapted to the mechanical characteristics of the rotor 3 and to the pumping of a maximum continuous gas flow at the speed of nominal rotation. The nominal power is considered to be an average value. For example, it is between 80W and 200W. The nominal power is generally defined by a maximum continuous gas flow to be pumped in nitrogen or argon equivalent. These values ​​are generally indicated by the manufacturer and available in the user manual or in the technical data sheet of the vacuum pump 1. They allow the user to choose the vacuum pump adapted to the gas flows to be pumped.

[0061] For example, the motor 16 is configured to provide a rated power suitable for being able to pump a maximum continuous flow rate, nitrogen equivalent, of less than 3000sccm (or 5 Pa.m 3 / s).

[0062] On the other hand, the motor 16 is configured to be able to drive the rotor 3 with an overspeed power, greater than the nominal power. This overspeed power is requested for limited durations in time, for example less than fifteen minutes, and under certain heating conditions of the rotor 3.

[0063] The overspeed power is, for example, at least twice the nominal power. For example, it is greater than 600W.

[0064] For example, the engine 16 is configured to provide an overspeed power adapted to be able to pump a nitrogen equivalent flow greater than or equal to 3000sccm (or 5 Pa.m 3 / s), such as greater than 4000sccm (or 6.755) (while the mechanical characteristics of rotor 3 are suitable for pumping a maximum continuous flow rate less than 3000sccm (or 5 Pa.m 3 / s)).

[0065] The motor 16 is oversized compared to the mechanical characteristics of the rotor 3 which are suitable for nominal operation.

[0066] The control unit 31, such as an electronic card, comprises one or more controllers or microcontrollers or processors and a memory, for executing sequences of program instructions making it possible to implement a method for controlling the operating parameters of the turbomolecular vacuum pump 1, in particular by controlling the internal heating device 21. The control unit 31 is for example arranged in the base of the stator 2 and cooled by the cooling device.

[0067] The control method comprises a nominal operating mode in which the rotor 3 of the vacuum pump 1 is heated via the internal heating device 21, as long as the measured temperature of the rotor 3 is lower than a temperature threshold for a parameter representative of the power consumed by the given motor 16.

[0068] The control method includes an overspeed operating mode (called "boost" in English) in which the internal heating of the rotor 3 is cut off when the measured temperature of the rotor 3 is greater than or equal to the temperature threshold.

[0069] The temperature threshold depends on the parameter representing the (electrical) power consumed by the motor 16, which may be the current or the power consumed by the motor 16. The electrical power consumed by the motor 16 is itself representative of the gas flow to be pumped. The greater the flow to be pumped, the greater the power consumed by the motor 16, and vice versa.

[0070] For example, it is expected that the power consumed in overspeed operating mode is at least twice the power consumed in nominal operation.

[0071] The temperature threshold is lower than a maximum temperature threshold. The maximum temperature threshold is, for example, between 130°C and 140°C. This is the upper threshold that must not be exceeded in order to preserve the mechanical strength of rotor 3.

[0072] The temperature threshold is variable. It depends on the parameter representative of the power consumed by the motor 16, such as the power or current consumed by the motor 16 over a given temperature range.

[0073] For example, the temperature threshold decreases, for example linearly, with the increase in the parameter representing the power consumed by the motor 16 within the temperature range. The higher the power or current consumed by the motor 16, the more quickly the internal heating is switched off.

[0074] The given temperature range is for example between 100°C and 140°C or between 100°C and at least 10°C lower than the maximum temperature threshold, such as between 100°C and 120°C as between 118°C and 120°C. Below the lower limit of the temperature range, deposits may form in the vacuum pump 1. Above the upper limit of the temperature range, the rotor 3 may creep.

[0075] The power (or current) consumed by motor 16 can be capped at a maximum motor consumption threshold. The maximum motor consumption threshold is, for example, 1000W (or 10A).

[0076] For example, and as shown in Figure 4, over the given power range 0-1000W, if the power consumed by the motor 16 is very high, such as the maximum motor consumption threshold, here 1000W, the temperature threshold beyond which the internal heating is cut off may be a lower limit of the given temperature range, for example 118°C. If the power consumed by the motor 16 is very low, such as zero, the temperature threshold beyond which the internal heating is cut off may be a high limit, higher than the lower limit, for example 10°C less than the maximum temperature threshold, such as 120°C. Between the two extreme powers of the given range, the temperature threshold beyond which the internal heating is cut off may evolve linearly with the power, such as according to the following formula:

[0077] Temperature threshold = 120 (°C) - 0.002 (°C / W) P motor (W)

[0078] If the parameter representing the power consumed by the motor 16 is the current, the temperature threshold can change according to the formula:

[0079] Temperature threshold = 120 (°C) - 0.2 (°C / A) * I motor (A)

[0080] In operation, the control unit 31 actively controls, on the one hand, the external heating device 27 to heat the external casing 19 of the stator 2 and, on the other hand, the internal heating device 21 by controlling the electrical supply of the radiative elements 30. The temperature of the rotor 3 of the vacuum pump is measured by the temperature sensor 23 and a parameter representative of the power consumed by the motor 16, such as the electrical power or the current, is determined. Determining the temperature of the rotor 3 is more suitable than determining the stator 2 to be sufficiently responsive. These signals (measured temperature and current or power consumed) are transmitted to the control unit 31.

[0081] Thus, when the vacuum pump 1 is used on pumping cycles alternating periods of significant gas flows to be pumped, i.e., greater than the nominal gas flows, for example at least 1.5 times greater, with periods of moderate, and therefore nominal, gas flows to be pumped, the switching on and off of the internal heating can be synchronized with the variations in the gas flow to be pumped. Instead of switching off and on the internal heating blindly, i.e., instead of regulating the temperature by taking into account only the temperature, the internal heating can be switched off during periods of high power (and therefore significant gas flows to be pumped). Taking into account the power consumed by the motor 16 thus makes it possible to match the periods of high gas flows with the periods of switching off the internal heating.Cutting off the internal heating prevents excessive heating of strong gas flows to limit the risk of thermal cracking, i.e. degradation. chemical breakdown of the molecules of the pumped gases when they are heated too much, with the production of non-volatile by-products such as carbon black.

[0082] With the temperature threshold decreasing with the increase in the parameter representing the power consumed by the engine 16 over a given temperature range, the internal heating is cut off a little lower in temperature at high power than at low power to anticipate the increase in temperature of the rotor 3 to come due to the increase in the gas flow to be pumped, this increase in the gas flow to be pumped causing an increase in temperature of the rotor 3 due to the compression of the gases but which is relatively slow. Indeed, since the rotor 3 is very slow to heat up, the increase in the pumped gas flow only has an impact on the temperature of the rotor 3 (and therefore on the cut-off of the internal heating) well after the start of the pumping of this high gas flow, and continues well after the end of this pumping.The evolving temperature threshold makes it possible to stabilize the heating while getting as close as possible to the upper temperature limit to avoid the formation of deposits in the vacuum pump 1 while limiting the risks of thermal cracking and the risks of creep.

[0083] The oversized 16 engine can absorb this large gas flow.

[0084] It is therefore possible to absorb large gas flows without slowing down the rotor 3. The nominal rotation speed of the rotor 3 can therefore be maintained without any particular risk to the service life of the vacuum pump 1.

[0085] Provision may be made to signal when the vacuum pump 1 switches to overspeed operating mode, i.e. when the internal heating of the rotor 3 is cut off because the temperature of the rotor 3 has exceeded the temperature threshold. For this, the control unit 31 may comprise a signaling device 32 configured to emit a signal such as an electrical, electronic or light signal, making it possible to signal the switch to the overspeed operating mode.

[0086] The overspeed operating mode is exited to return to nominal operating mode, i.e. the internal heating is restored, if the measured temperature of rotor 3 decreases and falls below the temperature threshold. This situation is caused by the end of pumping of the large flow of gas. The overspeed operating mode is therefore occasional, for example, more than one minute, and for example, less than fifteen minutes.

[0087] According to an example of application shown in Figure 3, the vacuum pump 1 is used for the cyclic pumping of a process chamber 101 of a piece of equipment 100 in which manufacturing processes take place, in particular of 102 semiconductor elements or photovoltaic panels or flat screens.

[0088] The inlet annular flange 8 of the turbomolecular vacuum pump 1 is fluidically connected to the process chamber 101 of such equipment 100 and the discharge orifice 7 is fluidically connected for example to a primary pump 103.

[0089] The manufacturing processes taking place in the process chamber 101 comprise different steps occurring one after the other over time, in particular manufacturing steps 104 and cleaning steps 105. The graph in FIG. 5 illustrates a manufacturing process alternating manufacturing steps 104 with cleaning steps 105.

[0090] The manufacturing steps 104 include, for example, etching steps, waiting steps, etc. They require the pumping of a moderate, and therefore nominal, gas flow, for example less than 2slm (or 3.37 Pa.m 3 / s).

[0091] Cleaning steps 105 are regularly interspersed between the manufacturing steps 104 for cleaning the walls of the process chamber 101. These steps 105 require the pumping of significant gas flows, for example of oxygen, for example of the order of 4slm (or 6.75 Pa.m 3 / s).

[0092] The 105 cleaning steps typically last a few minutes, once or twice an hour.

[0093] In the graph of Figure 5, curve A shows the evolution of the measured temperature of the rotor 3 of the vacuum pump 1 during the manufacturing process, curve B shows the evolution of the power consumed by the motor 16, curve C the power supply of the radiative elements 30 of the internal heating device 21 of the vacuum pump 1 and curve D shows the evolution of the temperature threshold.

[0094] We see that during manufacturing steps 104, the power consumed (curve B) by the motor 16 is of the order of 100W. It is less than 1000W, the maximum motor consumption threshold.

[0095] For this consumed power of 100W, the temperature threshold (curve D) is 119.8°C. It can be seen that during these manufacturing steps 104, the measured temperature of the rotor 3 (curve A) decreases slowly because the gas flow to be pumped has gone from significant to moderate. The measured temperature of the rotor is below this temperature threshold of 119.8°C.

[0096] The radiative elements are therefore supplied (curve C).

[0097] Vacuum pump 1 is in nominal operating mode.

[0098] When a cleaning step 105 begins, the power consumed increases sharply due to the strong gas flow to be pumped (curve B), the power consumed peaking at the maximum motor consumption threshold of 1000W.

[0099] The increase in power consumption causes a proportional decrease in the temperature threshold (curve D). The measured temperature of rotor 3 increases progressively due to the strong gas flow to be pumped.

[0100] When the measured temperature of the rotor 3 is greater than or equal to the temperature threshold (intersection of curves A and D), the vacuum pump 1 switches to overspeed operating mode, which cuts off the power supply to the radiative elements 30 of the internal heating device 21 (curve C). The internal heating is cut off without waiting for a significant rise in the temperature of the rotor 3.

[0101] Throughout the cleaning step 105, the power consumed in overspeed operating mode is at least twice the power consumed in nominal operation, here ten times higher. The measured temperature of the rotor 3 increases but does not have time to go beyond the maximum temperature threshold of 130°C.

[0102] At the end of the cleaning step 105, the power consumed decreases due to the reduction in the gas flow to be pumped. The temperature also begins to decrease but less quickly.

[0103] The decrease in power consumption causes a proportional increase in the temperature threshold (curve D).

[0104] When the measured temperature of the rotor 3 becomes lower than the temperature threshold (intersection of curves A and D), the vacuum pump 1 switches to nominal operating mode, which restores the power supply to the radiative elements 30 of the internal heating device 21 (curve C).

[0105] The switching on and off of the internal heating can be synchronized with the variations in the gas flow to be pumped to regulate the temperature by switching off the internal heating during periods of high power (and therefore large gas flows to be pumped). The overspeed operating mode is automatic, the user does not have to change the temperature setpoint of vacuum pump 1 and does not need to know information external to vacuum pump 1 such as the duration, flow rate and nature of the pumped gases.

Claims

CLAIMS

1. Method for controlling the operating parameters of a turbomolecular vacuum pump (1) comprising: - a stator (2), - a rotor (3), - a motor (16) configured to drive the rotor (3) in rotation in the stator (2), - an internal heating device (21) arranged in the gas flow path of the vacuum pump (1) and configured to heat the rotor (3), - a temperature sensor configured to measure the temperature of the rotor (3), - an external heating device (27) configured to heat the stator (2), characterized in that the control method comprises: - a nominal operating mode in which the rotor (3) is heated via the internal heating device (21), as long as the measured temperature of the rotor (3) is lower than a temperature threshold for a parameter representative of the power consumed by the given motor (16), and - an overspeed operating mode in which the internal heating of the rotor (3) is cut off when the measured temperature of the rotor (3) is greater than or equal to the temperature threshold.

2. Control method according to claim 1, characterized in that the temperature threshold is variable and decreases within a given temperature range, in particular between 100°C and 140°C, such as between 118°C and 120°C, with the increase in the parameter representative of the power consumed by the engine (16).

3. Control method according to the preceding claim, characterized in that the decrease is linear.

4. Control method according to one of the preceding claims, characterized in that the power consumed by the engine (16) is capped at a maximum engine consumption threshold.

5. Control method according to one of the preceding claims, characterized in that the power consumed in overspeed operating mode is at least twice the power consumed in nominal operation.

6. Control method according to one of the preceding claims, characterized in that the parameter representative of the power consumed by the motor (16) is the current or the power consumed.

7. Control method according to one of the preceding claims, characterized in that the vacuum pump (1) is used for cyclic pumping of process chambers (101) of equipment (100), in which manufacturing processes take place comprising manufacturing steps (104) where the gas flows to be pumped are moderate and cleaning steps (105) where the gas flows to be pumped are significant.

8. Turbomolecular vacuum pump (1) comprising: - a stator (2), - a rotor (3), - a motor (16) configured to drive the rotor (3) in rotation in the stator (2), - an internal heating device (21) arranged in the gas flow path of the vacuum pump (1) and configured to heat the rotor (3), - a temperature sensor configured to measure the temperature of the rotor (3), - an external heating device (27) configured to heat the stator (2), characterized in that the motor (16) is configured on the one hand, to be able to drive the rotor (3) with a nominal power and on the other hand, to be able to drive the rotor (3) with an overspeed power, greater than the nominal power, and in that the vacuum pump (1) comprises a control unit (30) configured to implement a control method according to one of the preceding claims.

9. Vacuum pump (1) according to the preceding claim, characterized in that the motor (16) is configured to provide a nominal power suitable for being able to pump a maximum continuous flow rate, nitrogen equivalent, less than 5 Pa.m 3 / s.

10. Vacuum pump (1) according to one of claims 8 or 9, characterized in that the motor (16) is configured to provide an overspeed power suitable for being able to pump an equivalent nitrogen flow rate greater than or equal to 5 Pa.m 3 / s, such as greater than 6.755 Pa.m 3 / s.

11. Turbomolecular vacuum pump (1) according to one of claims 8 to 10, characterized in that the temperature sensor (23) is an infrared temperature sensor.

12. Turbomolecular vacuum pump (1) according to one of claims 8 to 11, characterized in that the internal heating device (21) comprises radiative elements arranged in the helical grooves (14) of a sleeve (22) of the stator (2) of the vacuum pump (1).

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