Method for detecting deposition layers and associated turbomolecular vacuum pump

Abstract

The present invention relates to a method for detecting a buildup layer in a turbomolecular vacuum pump (1) comprising a stator (3), a rotor (5), and at least one temperature sensor (17). The method comprises the following steps: the temperature sensor (17) measures a temperature representative of the temperature of the rotor (5) and transmits it to a monitoring unit (19). The monitoring unit (19) calculates the temperature drift over time and compares it with a predetermined threshold. If the calculated drift value is equal to or greater than the predetermined threshold, the monitoring unit (19) detects abnormal overheating representative of a buildup layer and issues at least one warning signal and / or a stop command to shut down the pump (1). The present invention also relates to a corresponding turbomolecular vacuum pump.

Description

[Technical Field]

[0001] The present invention relates to a turbomolecular vacuum pump, and in particular to a method for detecting a deposit layer in the turbomolecular vacuum pump. [Background technology]

[0002] To create a high vacuum in a vacuum chamber, it is necessary to use a turbomolecular vacuum pump, which has a stator and a rotor driven within it, the rotor rotating at high speeds, for example, more than 30,000 revolutions per minute. Depending on the process in which vacuum pumps are used, such as in the manufacturing of semiconductors and LEDs, a deposit layer of reaction products may form inside the vacuum pump. This deposit layer heats the rotor due to friction, causing creep and potentially causing cracks in the rotor. Summary of the Invention [Problem to be solved by the invention]

[0003] It is known to heat the stator and piping to prevent condensation of reaction products in the pump. By limiting the heating temperature below the rotor's allowable temperature, it is possible to reduce the formation of deposits in the pump, but it is not possible to completely prevent this formation.

[0004] Therefore, it is necessary to schedule regular maintenance work to frequently clean the vacuum pump. However, these maintenance work conflicts with production speed requirements. Therefore, a method for monitoring the formation of deposits inside the vacuum pump is needed to maximize the interval between maintenance work. However, one of the difficulties with this monitoring method is that the inside of the vacuum pump cannot be observed without shutting down the vacuum pump and disassembling it in whole or in part. Furthermore, depending on the application, it may be dangerous to expose the inside of the vacuum pump to the outside air.

[0005] Several known sensor technologies make it possible to monitor these deposits and their growth within the vacuum pump. In the case of turbomolecular vacuum pumps, it is known to measure the motor current or the position of the magnetically levitated rotor to determine the presence of reaction by-products in the manufacturing process. Changes in the motor current or the position of the magnetically levitated rotor provide information about the presence of deposits. However, this method may not be sufficiently accurate. In particular, the increase in current is usually detected very late—only a few seconds or even a fraction of a second before rotor failure—which may make timely intervention impossible.

[0006] One of the aims of the present invention is to propose an option to quickly detect the formation of a deposit layer on a turbomolecular pump and to warn that the turbomolecular pump needs to be cleaned. [Means for solving the problem]

[0007] To this end, the subject of the present invention is a method for detecting a deposition layer in a turbomolecular vacuum pump comprising a stator, a rotor arranged to rotate within the stator, and at least one temperature sensor arranged within the stator to measure the temperature. The measured temperature may be a temperature representative of the temperature of the rotor, in particular the temperature of the rotor, and the at least one temperature sensor is configured to transmit at least one measurement value of said temperature to a monitoring unit of said pump.

[0008] According to the present invention, the method comprises: the at least one temperature sensor measuring the temperature and transmitting the temperature measurement to the monitoring unit; said monitoring unit calculating a drift of said temperature over time from said temperature measurements transmitted by said at least one temperature sensor; the monitoring unit comparing the calculated drift value with a predetermined threshold; The monitoring unit detects abnormal overheating, indicating the presence of a deposit layer, when the calculated drift value is equal to or greater than the predetermined threshold value, and issues at least one warning signal and / or at least one stop command signal to stop the pump.

[0009] The deposition layer is formed, for example, on the stator, in particular on the part of the stator facing the cylindrical skirt of the rotor, such as a Holweck skirt. The deposition layer is particularly formed on the lower part of the stator along the rotation axis of the rotor, the upper part of the stator being located on the side of the intake of the pump.

[0010] The method may further include one or more of the features described below, either separately or in combination. The pump comprises a plurality of magnetic bearings supporting the rotor for rotation about the axis of rotation, and the monitoring unit is capable of controlling the magnetic bearings to offset the axis of rotation in at least one direction perpendicular to the axis of rotation or in a circular orbit for a predetermined period of time. The term "offset" means to shift / displace the rotation axis in a parallel direction from its initial position, which is centered or substantially centered between the magnetic bearings.

[0011] The temperature measuring step is performed at least when the rotation axis is offset. The monitoring unit controls the magnetic bearings so that, at the end of the offset control, the rotation axis returns to its initial position, i.e., centered or substantially centered between the magnetic bearings.

[0012] The warning signal and / or the stop command signal is generated in the pump. The monitoring unit transmits the warning signal and / or the stop command signal to at least one device coupled to the pump. The signals may be digital and / or analog signals. The signal generated by the pump may be a visual and / or an acoustic signal.The predetermined threshold may be less than or equal to 2°C / min.

[0013] The predetermined threshold may in particular be in the range of 0.3°C / min to 2°C / min. According to one embodiment of the present invention, the predetermined threshold can be set, for example, the predetermined threshold is set to 2°C / min.

[0014] According to one embodiment of the present invention, the predetermined threshold is variable and is a function of the motor current consumed by the pump motor driving it in rotation.

[0015] Furthermore, according to another embodiment of the present invention, the predetermined threshold may be set at least in the first iteration of the method of the present invention, and in at least one subsequent iteration, this predetermined defined threshold may be changed.

[0016] The set defined threshold may be greater than the variable predetermined threshold. The variable predefined threshold can be calculated according to the following equation (1): where a is the first coefficient, b is the second coefficient, Imotor is the motor current, and Imax is the maximum value of the motor current.

[0017]

number

[0018] The variable threshold may be selected from at least one predetermined threshold range, the first factor may be equal to the minimum value of the threshold range, and the second factor may be equal to the upper limit of the threshold range minus the first factor.

[0019] The variable threshold may also depend on at least one criterion: the nature of the gas being pumped and / or a temperature representative of the temperature of the rotor at the moment the drift is calculated. The first coefficient is decreased when the temperature measured at the moment the drift is calculated is equal to or greater than a predetermined temperature.

[0020] The invention also relates to a turbomolecular vacuum pump configured to at least partially implement the aforementioned detection method, the pump comprising a stator, a rotor configured to rotate within the stator, at least one temperature sensor arranged within the stator, and a monitoring unit, the at least one temperature sensor configured to measure a temperature representative of the temperature of the rotor, in particular the temperature of the rotor.

[0021] The pump may be a magnetic bearing pump. The at least one temperature sensor is configured to transmit measurements of said temperature to a monitoring unit.

[0022] The pump monitoring unit comprises at least one processing element configured to perform the following operations: A drift in temperature over time is calculated from the temperature measurements transmitted by the at least one temperature sensor. The calculated value of the drift is compared to a predetermined threshold. If the calculated value of the drift is equal to or greater than the predetermined threshold, abnormal overheating indicative of a buildup layer is detected and at least one warning signal and / or at least one stop command signal is issued to stop the pump.

[0023] The temperature sensor can be selected from an infrared sensor, a magneto-thermal sensor, and a positive temperature coefficient probe. The monitoring unit may be located entirely or partially within, or external to, the casing of the pump. Other advantages and features of the invention will appear more clearly on reading the following description and the accompanying drawings, given as illustrative and non-limiting examples. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is an axial cross-sectional view of a turbomolecular vacuum pump according to an embodiment of the present invention. [Figure 2] 1 is a graph showing the trend of rotor temperature as a function of time and the drift in temperature over time. DETAILED DESCRIPTION OF THE INVENTION

[0025] Hereinafter, an embodiment of the present invention will be described with reference to the drawings, in which the same elements are designated by the same reference numerals. The following embodiments are exemplary. Although the description refers to one or more embodiments, this does not necessarily mean that each reference relates to the same embodiment or that each feature applies only to a single embodiment. Individual features of different embodiments may be combined or interchanged to form other embodiments.

[0026] In this specification, some elements may be indexed, e.g., first element, second element, etc. In this case, this is simply an index to distinguish and name similar but not identical elements. This index does not imply a priority of one element over another, and such naming can be easily interchanged without departing from the scope of the present invention. Also, this index does not imply a chronological order.

[0027] "Turbomolecular vacuum pump" 1 shows an exemplary embodiment of a turbomolecular vacuum pump 1 of the present invention, which will be referred to hereinafter simply as pump 1. According to one embodiment of the present invention, the pump 1 is a magnetic levitation pump (Maglev pump). The pump 1 includes a stator 3, and a rotor 5 rotates around a rotation axis II within the stator 3. The rotation speed is high, for example, 30,000 revolutions per minute or more.

[0028] In operation, the gas to be pumped enters at the inlet 7, passes through each stage of the pump 1, and exits at the outlet 9 of the pump 1. This outlet 9 can be coupled to a primary pumping system. The rotor 5 is centered on the axis of rotation II and includes an internal bowl 11 having at least one surface disposed facing a bell-shaped portion 13 of the stator 3. In the illustrated example, the bell-shaped portion 13 is located below the internal bowl 11 in the orientation of the axis of rotation II and the pump 1, as shown in Figure 1. During operation, the rotor 5 rotates within the stator 3 without contact between the internal bowl 11 and the stator bell-shaped portion 13.

[0029] The rotor 5 is provided with, for example, a cylindrical skirt, in particular a Holweck skirt 14, which may be formed in a smooth cylindrical shape. In operation, the cylindrical skirt or Holweck skirt 14 rotates against, for example, a helical groove in the stator 3, which enables the pumped gas to be compressed and directed towards the discharge port 9. The inner side of the cylindrical skirt or Holweck skirt 14 also forms an inner bowl 11, which is arranged below the rotor 5 and opposite the bell-shaped portion 13 of the stator 2.

[0030] The rotor 5 is fixed to a drive shaft 15 that is driven to rotate within the stator 3 by an internal motor of the pump 1. The drive shaft 15 passes through, for example, the bell-shaped portion 13 of the stator 3. The rotor 5 is supported on the drive shaft 15 of the rotor 5 and is guided laterally and axially by a number of magnetic or mechanical bearings 16 located within the stator 3. In the case of a magnetic levitation pump (Maglev pump), a plurality of magnetic bearings 16 support the rotation of the rotor 5. The position of the rotation axis II of the rotor 5 can be controlled by these magnetic bearings 16. For example, the rotation axis II can be kept at or approximately at the center of the magnetic bearings 16. Also, the rotation axis II can be offset in a predetermined direction by, for example, changing the position setting value of the servo control of the rotation axis II.

[0031] 2, the pump 1 comprises at least one temperature sensor 17. This temperature sensor 17 is arranged to measure at least one temperature T°, which may be the temperature of the rotor 5 or a temperature that may be representative of the temperature of the rotor 5. A temperature sensor 17 measures the temperature of the stator 3 and / or the temperature of at least one other element of the pump 1, as appropriate. Examples of the temperature sensor 17 include an infrared sensor, a magneto-thermal sensor, and even a positive temperature coefficient probe.

[0032] The temperature sensor 17 is located in the stator 3, particularly in the lower part of the pump 1 in FIG. 1 , more specifically on the gas outlet side where the pressure is highest and therefore the risk of deposits is greatest. According to a particular exemplary embodiment, the temperature sensor 17 is located in the bell-shaped part 13 of the stator 3 facing the inner bowl 11 of the rotor 5. In particular, the temperature sensor 17 is located, for example, in the lower part of the stator 3 and measures a temperature representative of the temperature at the bottom of the Holweck skirt 14.

[0033] 1, only one temperature sensor 17 is shown, and the following description will be based on this. Of course, it is also possible to provide multiple temperature sensors for measuring the temperature T° of the rotor 5. The temperature sensor 17 transmits one or more temperature measurements T° to the monitoring unit 19 .

[0034] The temperature sensor 17 may be a sensor already present in the pump 1, whose temperature measurements are transmitted to the monitoring unit 19. It is used in particular to control the temperature of the pump 1 via a heating element, such as a resistive or radiant heating element, such as a heating belt or a heating cartridge. The temperature measurements of the temperature sensor 17 may also be used to calculate the creep of the rotor.

[0035] The monitoring unit 19 can be located in all or part of, inside or outside the casing of the pump 1. In the example shown, the monitoring unit 19 is housed inside the stator 3 of the pump 1. This location is not limiting. The monitoring unit 19 receives the temperature measurements T° transmitted by the temperature sensor 17 . From the temperature measurement T° transmitted by this temperature sensor 17, the monitoring unit 19 is able to calculate the drift of the temperature over time dT° / dt.

[0036] The thermal output of the rotor 5 can be estimated from this temperature drift over time dT° / dt. In particular, the thermal output of the rotor 5 is calculated by multiplying the temperature drift over time dT° / dt by the thermal inertia of the rotor 5. When a deposit builds up inside the vacuum pump 1, this deposit heats up the rotor 5 due to friction. Therefore, when friction occurs, its heat output is outside the normal operating range. More specifically, its heat output exceeds a predetermined limit. This is reflected by the drift of temperature with respect to time, dT° / dt, exceeding a predetermined threshold s,s(Imotor).

[0037] The monitoring unit 19 compares the calculated value of the drift dT° / dt with a predetermined threshold value s,s(Imotor). If the calculated value of the drift dT° / dt is equal to or greater than a predefined threshold value s,s(Imotor), the monitoring unit 19 can detect abnormal overheating due to the deposition layer. Calculating the drift allows for a fast and clear detection of such overheating, since it allows the scale of the temperature change to be determined as a function of time. Calculating the drift amplifies the temperature change, allowing for a clearer detection of abnormal overheating.

[0038] The monitoring unit 19 issues at least one warning signal and / or at least one stop command signal to stop the pump 1 . The monitoring unit 19 may include one or more processing elements that enable it to perform one or more of the above-mentioned receiving, calculating, comparing, detecting, and outputting operations, and may be a computer, processor, microcontroller, or any other unit capable of performing these operations.

[0039] The monitoring unit 19 can control the magnetic bearings 16 to keep the rotation axis II at or near the center of the magnetic bearings 16. The monitoring unit 19 can also control the magnetic bearings 16 to offset the rotation axis II in a predetermined direction by changing the position setting of the servo control of the rotation axis II. Such control is particularly advantageous in the case of a magnetic levitation pump (Maglev pump). The pump 1 is configured to at least partially implement a method for detecting a deposition layer within the pump 1 .

[0040] "Method for detecting sedimentary layers" The method for detecting the deposition layer includes the steps described below. First, the temperature sensor 17 measures the temperature T° of the rotor 5 and transmits the temperature measurement or measurements T° to the monitoring unit 19. The solid curve C1 in Figure 2 shows an example of the trend of the temperature T° of the rotor 5 as a function of time t.

[0041] The temperature measurement T° is transmitted by the temperature sensor 17 to the monitoring unit 19 . When the pump 1 is running, the temperature T° of the rotor 5 is measured continuously. Alternatively, the temperature T° of the rotor 5 can be measured periodically during so-called check periods. These check periods can be preset, scheduled check periods. Alternatively, the check periods can be initiated upon user request. The check periods are preferably scheduled or selected by the user when there is no gas flow. Such check periods are particularly advantageous for pumps 1 having multiple magnetic bearings 16. During these check periods, the monitoring unit 19 sends at least one command to the magnetic bearings 16 to offset the axis of rotation II of the rotor 5 .

[0042] According to one embodiment of the present invention, the method of the present invention can include at least one preliminary step for verifying whether at least one condition is met before commanding an offset. This is in particular a temperature condition. In particular, and without limitation, it can be verified whether the temperature T° of the rotor 5 is stable or decreasing. The temperature T° of the rotor 5 can be considered stable if it is not fluctuating, in particular if it has not increased by a predetermined temperature amount over a predetermined period of time. As a representative example, the temperature T° of the rotor 5 can be considered stable if it has not increased by more than 0.1° over the past 10 minutes. In addition to a stable or decreasing temperature T° of the rotor 5, other conditions can alternatively be checked to enable an offset command.

[0043] The offset of the rotation axis II of the rotor 5 may, for example, close the gap between the cylindrical skirt (such as the Holweck skirt 14) of the rotor 5 and deposits on the stator 3, particularly the part of the stator 3 facing the cylindrical skirt (Holweck skirt) 14. As a result, friction may occur on the skirt 14 of the rotor 5, which may result in localized overheating.

[0044] The offset command can be performed in only one direction perpendicular to the axis of rotation II. Alternatively, the offset command can be performed in multiple directions or on a circular trajectory. When the axis of rotation II is offset, the temperature sensor 17 measures the temperature T° of the rotor 5 and transmits the temperature measurement T° to the monitoring unit 19 . The duration of the offset command is predefined and must be long enough to allow the change in temperature T° of the rotor 5 to be measured, for example up to 10 minutes per direction.

[0045] When the offset command ends, the monitoring unit 19 controls the magnetic bearings 16 so that the rotation axis II returns to a center position or a near-center position, the mechanical play is regenerated, and the friction disappears. In this way, excessive buildup in the pump 1 can be detected without waiting until continuous friction causes the pump 1 to shut down. A quick cleaning maintenance of the pump 1 can then simply be scheduled.

[0046] Whether the temperature T° of the rotor 5 is measured continuously or during a check period, the method comprises the following steps: "The monitoring unit 19 calculates the temperature drift dT° / dt with respect to time from the temperature measurement value T° received from the temperature sensor 17." The dashed curve C2 in FIG. 2 shows the trend of the temperature drift dT° / dt with respect to time as a function of time t.

[0047] According to an exemplary embodiment, the temperature time drift dT° / dt is calculated at different frequencies based on multiple time bases. For example, the drift dT° / dt can be calculated every millisecond, every second, every 10 seconds, or at other frequencies. An average of multiple drifts dT° / dt calculated at different frequencies / time bases can also be calculated. In the following description, a calculated value of drift dT° / dt refers to the temperature time drift dT° / dt calculated at a certain time t, or an average of multiple drifts.

[0048] The monitoring unit 19 compares the calculated drift value dT° / dt with a predefined threshold value s,s(Imotor). The thresholds s, s(Imotor) can be set, or alternatively can be variable. It is also possible to set a predetermined threshold s during at least the first iteration of the method of the invention, and then make the predetermined threshold s(Imotor) variable during at least the next iteration of the method of the invention. In this case, the set predetermined threshold value s is preferably greater than the variable predefined threshold value s(Imotor). As an example, the threshold s,s(Imotor) can be set to 2°C / min or less. In particular, when the threshold s is set, it can be set to 2°C / min.

[0049] When the threshold s(Imotor) is variable, the assumed range can also be variable, for example, the variable threshold s(Imotor) is set to a range from 0.3°C / min to 2°C / min. If the threshold value s(Imotor) is variable, it can be a function of at least the motor current, which is the current consumed by the motor of the pump 1 when it drives the rotor 5 to rotate.

[0050] The above-defined variable threshold s(Imotor) is calculated according to the following equation (1):

[0051]

number

[0052] In this equation (1), a is the first coefficient, b is the second coefficient, Imotor is the motor current, and Imax is the maximum value of the motor current. The motor current is in the range of 0 A to 10 A, for example. The first coefficient a corresponds to the assumed minimum threshold value, i.e., the lower limit of the threshold range. In the above-mentioned range example [0.3°C to 2°C], the lower limit is 0.3°C, and the first coefficient a is 0.3.

[0053] The second coefficient b can be selected as a function of the selected first coefficient a, and can be selected so that the value of threshold s(Imax) is maximum, i.e., equal to the upper limit of the threshold range, when the motor current Imotor is at its maximum value Imax. Thus, when the motor current Imotor is at its maximum value Imax, equation (1) becomes:

[0054]

number

[0055] Next, the second coefficient b is calculated according to the following equation (2):

[0056]

number

[0057] Therefore, the second coefficient b corresponds to the upper limit of the threshold range excluding the first coefficient a. According to the above-mentioned range example [0.3°C to 2°C], the upper limit is 2°C / min, and if the value of the first coefficient a is 0.3, the second coefficient b is 1.7. The variable threshold s(Imotor) may further depend on one or more other criteria, such as the nature of the gas being pumped and / or the temperature T° of the rotor 5 (representing the temperature of the rotor 5 at the time t at which the drift dT° / dt is calculated). In particular, the first coefficient a can be increased or decreased. The increase or decrease in the first coefficient a can be on the order of a factor of ten.

[0058] For example, the higher the temperature of the rotor 5, the lower the threshold value s(Imotor) and / or the lower the first coefficient a. In particular, when the temperature T° of the rotor 5 (representing the temperature of the rotor 5 at the time t at which the drift dT° / dt is calculated) rises or reaches a predetermined temperature, the lower the first coefficient a. Conversely, the first coefficient a can be increased if the temperature T° of the rotor 5 (representing the temperature of the rotor 5), measured at the time t at which the drift dT° / dt of the rotor 5 is calculated, decreases or falls below a predetermined temperature. The second coefficient b can also be changed depending on the temperature of the rotor 5.

[0059] As an illustrative and non-limiting example, for a temperature T° of the rotor 5 at time t where the drift dT° / dt is calculated to be less than 130° C., for example 100° C., the first coefficient a may be 0.3 as described above. As another example, for a temperature T° of the rotor 5 at time t where the drift dT° / dt is calculated to be 130° C. or greater, the first coefficient a may be reduced to, for example, 0.2.

[0060] As an alternative, or in addition to taking into account the temperature T° of the rotor 5, it is also conceivable to vary the variable threshold s(Imotor), in particular at least the first coefficient a, depending on the nature of the gas being pumped. More specifically, so-called light gases have high electrical conductivity and can enhance the cooling effect of the rotor 5, so that the variable threshold s (Imotor) or the first coefficient a can be reduced by, for example, about one-tenth. So-called light gases are gases lighter than air, such as helium (symbol He) and hydrogen (symbol H). On the other hand, for so-called heavy gases, the variable threshold s (Imotor) or the first coefficient a can be increased, for example, by a factor of 10. So-called heavy gases are gases that are heavier than air, such as hydrogen bromide (symbol HBr).

[0061] "The monitoring unit 19 determines abnormal overheating indicative of a deposition layer based on a comparison between the calculated value of the drift dT° / dt and a predetermined threshold value s,s(Imotor)." In particular, if the calculated value of the drift dT° / dt is equal to or greater than a predetermined threshold value s,s(Imotor), the monitoring unit 19 detects this as an abnormal overheating, which is indicative of a deposit layer.

[0062] That is, if such overheating is detected during the check, the monitoring unit 19 issues at least one warning signal and / or at least one stop command signal to stop the pump 1 . Alternatively, if during the check period a detection is made with an offset of the rotation axis II, the monitoring unit 19 can issue a warning signal without an immediate stop, but only with a request for immediate maintenance. The warning signal (or prompt maintenance request) and / or shutdown command signal may be digital and / or analog. A warning signal (or emergency maintenance request) and / or a stop command signal can be generated at the pump 1 by the monitoring unit 19. This can be a visual and / or an audio signal.

[0063] The monitoring unit 19 of the pump 1 can also send warning signals (or emergency maintenance requests) and / or shutdown command signals to at least one piece of equipment linked to this monitoring unit 19, commonly referred to as a "tool", configured to manage a chamber to which the pump 1 is fluidly coupled for pumping gas. The device can then command the stop of pump 1, shut off the gas injected into the chamber, close the shut-off valve between the chamber and pump 1, and take all necessary measures to protect the device.

[0064] According to another example, the monitoring unit 19 may also send warning signals (or emergency maintenance requests) and / or shutdown command signals to a central monitoring unit linked to multiple pumps 1 or multiple pieces of equipment. Thus, by monitoring the trend of the temperature T° of the rotor 5, more particularly the drift dT° / dt of the temperature as a function of time, the appearance of a deposit layer can be easily detected when this drift dT° / dt reaches a set predefined threshold s or said variable predefined threshold s(Imotor). Furthermore, if temperature sensor 17 is already used to regulate the temperature of pump 1, there is no need to add another temperature sensor for this function, which can provide a warning to the user that pump 1 needs to be cleaned and / or to stop pump 1 and isolate the chamber to allow pump 1 to be cleaned. [Explanation of symbols]

[0065] 1 pump 3 Stator 5 rotors 7 Intake port 9 Discharge port 11 Inner Bowl 13 Bell-shaped part 14 Holweck Skirt 15 Drive shaft 16 Magnetic or mechanical bearings 17 Temperature Sensor 19 Monitoring Unit II Rotation axis

Claims

1. 1. A method for detecting a deposit layer in a turbomolecular vacuum pump (1), comprising a stator (3), a rotor (5) configured to rotate within said stator (3), and at least one temperature sensor (17) arranged within said stator (3) for measuring a temperature (T°) representative of the temperature of said rotor (5), said temperature sensor (17) being configured to transmit the at least one temperature measurement value to a monitoring unit (19) of the pump (1), comprising: measuring said temperature (T°) by said at least one temperature sensor (17) and transmitting said temperature (T°) measurement to said monitoring unit (19); Calculating in said monitoring unit (19) from the temperature (T°) measurements transmitted by said at least one temperature sensor (17) a drift in temperature over time (dT° / dt); comparing the calculated drift (dT° / dt) value with predetermined thresholds (s, s(Imotor)) in the monitoring unit (19); and if the calculated drift ((dT°) / dt) is equal to or greater than the predetermined threshold (s, s(Imotor)), the monitoring unit (19) detects an abnormal overheating indicative of a build-up layer and issues at least one warning signal or at least one stop command signal to shut down the pump (1).

2. The pump (1) comprises a plurality of magnetic bearings (16) that support the rotor (5) so that the rotor (5) rotates around a rotation axis (II); The monitoring unit (19) controls the plurality of magnetic bearings (16) to offset the rotation axis (II) in at least one direction perpendicular to the rotation axis (II) for a predetermined time; 2. A method for detecting a deposit layer in a turbomolecular vacuum pump according to claim 1, characterized in that the step of measuring the temperature is carried out at least when the axis of rotation (II) is offset.

3. 2. The method for detecting a deposit layer in a turbomolecular vacuum pump according to claim 1, characterized in that the warning signal and the stop command signal are generated in the pump (1) and the monitoring unit (19) transmits the warning signal or the stop command signal to at least one device connected to the pump (1).

4. 2. The method for detecting a deposit layer in a turbomolecular vacuum pump according to claim 1, characterized in that the predetermined threshold value (s, s(Imotor)) is less than or equal to 2°C / min, in particular in the range of 0.3°C / min to 2°C / min.

5. 2. A method for detecting a deposit layer in a turbomolecular vacuum pump according to claim 1, characterized in that a predefined threshold value (s) is set.

6. 2. The method for detecting a deposition layer in a turbomolecular vacuum pump according to claim 1, characterized in that the predetermined threshold value (s(Imotor)) is variable and is a function of the motor current consumed by the motor of the pump (1) configured to drive the rotor (5) in rotation.

7. the predetermined threshold(s) is set in at least a first iteration of the detection method; 2. The method for detecting a deposit layer in a turbomolecular vacuum pump according to claim 1, characterized in that the predetermined threshold (s(Imotor)) is variable in at least one subsequent iteration of the method, and the set predetermined threshold (s) is greater than the variable defined threshold (s(Imotor)).

8. 7. The method for detecting a deposit layer in a turbomolecular vacuum pump according to claim 6, wherein said variable predefined threshold (s(Imotor)) is calculated according to the following formula: [Equation 1] where a corresponds to the first coefficient, b corresponds to the second coefficient, Imotor corresponds to the motor current, and Imax corresponds to the maximum value of the motor current.

9. the variable threshold (s(Imotor)) is selected from at least one predetermined threshold range; 9. The method for detecting a deposit layer in a turbomolecular vacuum pump according to claim 8, wherein the first coefficient (a) is equal to the minimum value of the threshold range, and the second coefficient (b) is equal to the maximum value of the threshold range minus the first coefficient (a).

10. 7. The method for detecting deposit layers in turbomolecular vacuum pumps according to claim 6, characterized in that the variable threshold value s(Imotor) also depends on at least one criterion chosen from the nature of the gas being pumped or the temperature (T°) representing the temperature of the rotor (5) at the instant (t) at which the drift (dT° / dt) is calculated.

11. 10. The method for detecting a deposit layer in a turbomolecular vacuum pump according to claim 9, characterized in that the first coefficient (a) is decreased when the temperature (T°) measured at the moment (t) at which the drift (dT° / dt) is calculated is equal to or greater than a predetermined temperature.

12. A turbomolecular vacuum pump (1) configured to at least partially implement the detection method according to any one of claims 1 to 11, comprising: The pump (1) a stator (3); a rotor (5) configured to rotate within the stator (3); at least one temperature sensor (17) arranged in the stator (3) and configured to measure a temperature (T°) representative of the temperature of the rotor (5); A monitoring unit (19), the at least one temperature sensor (17) is configured to transmit a measurement of the temperature (T°) to the monitoring unit; The monitoring unit (19) comprises at least one processing element, The processing element calculating a drift in temperature over time (dT° / dt) from the temperature (T°) measurements transmitted by the at least one temperature sensor (17); comparing the calculated drift (dT° / dt) value with a predetermined threshold (s, s(Imotor)); 1. A turbomolecular vacuum pump according to claim 1, further comprising: a first detecting means for detecting an abnormal overheating indicative of a build-up layer, the first detecting means for detecting an abnormal overheating indicative of a build-up layer, the first issuing at least one warning signal and / or at least one stop command signal, and stopping the pump (1) if the calculated value of the drift (dT° / dt) is equal to or greater than the predetermined threshold value (s, s(Imotor)).

13. 13. Turbomolecular vacuum pump according to claim 12, characterized in that the temperature sensor (17) is selected from the group consisting of an infrared sensor, a magneto-thermal sensor and a positive temperature coefficient probe.

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