Method for detecting deposited layer and associated turbo-molecular vacuum pump

Abstract

The method comprises the following steps: a 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 a drift amount of the temperature over time and compares it with a predetermined threshold value, and when the calculated drift amount is greater than or equal to the predetermined threshold value, the temperature sensor (17) detects the temperature of the rotor (5). A monitoring unit (19) detects an abnormal overheating representative of the deposited layer and issues at least one alarm signal and / or command to stop the pump (1). The invention relates to a corresponding turbo molecular vacuum pump.

Description

Technical Field

[0001] The present invention relates to a turbomolecular vacuum pump. In particular, the present invention relates to a method for detecting a deposition layer in such a turbomolecular vacuum pump. Background Art

[0002] To produce a high vacuum in a chamber, a turbomolecular vacuum pump must be used, which includes a stator in which a rotor is driven to rotate rapidly, for example, at a speed of more than 30,000 revolutions per minute.

[0003] In some methods of using a vacuum pump, such as in semiconductor or LED manufacturing methods, a deposition layer will form inside the vacuum pump. The deposition layer will cause the rotor to heat up through friction, resulting in rotor creep and then possibly cracking.

[0004] To avoid the condensation of reaction products inside the pump, it is common practice to heat the stator and the pipes. Limiting the temperature below the allowable temperature of the rotor can reduce the formation of deposits inside the pump, but cannot completely eliminate it.

[0005] Therefore, maintenance operations must be scheduled regularly to clean the vacuum pump frequently. However, these maintenance operations are contrary to the requirements of productivity. Therefore, methods for monitoring the formation of deposits inside the vacuum pump are sought to extend the interval between maintenance operations as much as possible. However, one of the difficulties is that the internal situation of the vacuum pump cannot be observed without shutting down and disassembling all or part of the vacuum pump. Additionally, in some applications, exposing the inside of the vacuum pump to air may be dangerous.

[0006] Several known sensor technologies make it possible to monitor these deposits and their growth in the vacuum pump.

[0007] For a turbomolecular vacuum pump, a known method is to measure the motor current or the position of the magnetically levitated rotor to determine the possible by-products. Changes in the motor current or the position of the magnetically levitated rotor can provide information about the presence of deposits. However, this strategy is not precise enough, especially because the increase in current is usually detected too late, only a few seconds or fractions of a second before the collision, and intervention may not be possible in time. Summary of the Invention

[0008] One object of the present invention is to provide an alternative that enables rapid detection of the formation of a deposition layer in a turbomolecular pump to give a warning when the turbomolecular pump needs to be cleaned.

[0009] To this end, the subject of the present invention is a method for detecting a deposited layer in a turbomolecular vacuum pump, which turbomolecular vacuum pump comprises a stator, a rotor configured to rotate within the stator, and at least one temperature sensor arranged in the stator for measuring temperature. The temperature may be a temperature representative of the rotor temperature, in particular the temperature of the rotor itself. The at least one temperature sensor is configured to transmit at least one measured value of the temperature to a monitoring unit of the pump.

[0010] According to the invention, the method comprises the following steps:

[0011] - The at least one temperature sensor measures the temperature and transmits the measured value of the temperature to the monitoring unit,

[0012] - The monitoring unit calculates the amount of drift of the temperature over time based on the measured value of the temperature transmitted by the at least one temperature sensor,

[0013] - The monitoring unit compares the calculated value of the drift amount with a predetermined threshold,

[0014] - When the calculated value of the drift amount is greater than or equal to the predetermined threshold, the monitoring unit detects abnormal overheating representative of the deposited layer and issues at least one alarm signal and / or at least one command signal to stop the pump.

[0015] The deposited layer may be formed, for example, on the stator, in particular on a part of the cylindrical skirt (such as a Holweck skirt) of the stator facing the rotor. It may be a lower part of the stator in the direction of the rotor rotation axis, and a higher part is located on the suction side of the pump.

[0016] The method may further comprise one or more features described individually or in combination below.

[0017] The pump may comprise a magnetic bearing configured to guide the rotor to rotate about the rotation axis. The monitoring unit may control the magnetic bearing so that the rotation axis is offset by a predetermined time in at least one direction perpendicular to the rotation axis or along a circular trajectory.

[0018] The term "offset" should be understood as a parallel movement / displacement of the rotation axis relative to its initial position. The initial position is located at or substantially at the center of the magnetic bearing.

[0019] At least when the rotation axis is offset, the temperature measurement step is performed.

[0020] At the end of the offset control, the monitoring unit may control the magnetic bearing so that the rotation axis returns to the initial position, i.e., the center or substantially the center between the magnetic bearings.

[0021] The alarm signal and / or the stop command signal may be generated at the pump.

[0022] The monitoring unit can transmit an alarm signal and / or a stop command signal to at least one device associated with the pump.

[0023] The signal can be digital and / or analog.

[0024] The signal generated at the pump can be a visual signal and / or an audible signal.

[0025] The predetermined threshold can be less than or equal to 2 °C / minute.

[0026] The predetermined threshold can especially be between 0.3 °C / minute and 2 °C / minute.

[0027] According to one embodiment, the predetermined threshold can be set. For example, the set predetermined threshold can be 2 °C / minute.

[0028] According to one embodiment, the predetermined threshold can be variable and is a function of the motor current consumed by the motor configured to drive the rotor rotation of the pump.

[0029] According to another embodiment, the predetermined threshold can be set at least in the first iteration of the method, and the predetermined threshold can be variable in at least one subsequent iteration of the method.

[0030] The set predetermined threshold can be greater than the variable predetermined threshold.

[0031] The variable predetermined threshold can be calculated according to the following formula: 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.

[0032] The variable threshold can be selected from at least one predetermined threshold range.

[0033] The first coefficient can be equal to the minimum boundary value of the threshold range.

[0034] The second coefficient can be equal to the maximum boundary value of the threshold range minus the first coefficient.

[0035] The variable threshold can also depend on at least one of the following criteria: the nature of the gas being pumped, and / or the temperature representing the rotor temperature at the moment of calculating the drift amount.

[0036] When the temperature measured when calculating the drift amount is greater than or equal to the predetermined temperature, the first coefficient can be reduced.

[0037] The present invention also relates to a turbomolecular vacuum pump configured to at least partially perform the aforementioned detection method. The pump includes a stator, a rotor configured to rotate within the stator, at least one temperature sensor disposed within the stator and includes a monitoring unit. The at least one temperature sensor is configured to measure a temperature. This temperature may be a temperature representative of the rotor temperature, in particular the temperature of the rotor itself.

[0038] The pump may be a magnetic bearing pump.

[0039] The at least one temperature sensor is configured to transmit a measured value of the temperature to the monitoring unit.

[0040] The monitoring unit includes at least one processing element configured to:

[0041] - Calculate a drift amount of the temperature over time based on the measured value of the temperature transmitted by the at least one temperature sensor,

[0042] - Compare the calculated value of the drift amount with a predetermined threshold, and

[0043] - When the calculated value of the drift amount is greater than or equal to the predetermined threshold, detect an abnormal overheating representative of a deposition layer and issue at least one alarm signal and / or at least one command signal to stop the pump.

[0044] The temperature sensor may be selected from an infrared sensor, a magnetothermal sensor, and a positive temperature coefficient probe.

[0045] The monitoring unit may be disposed in whole or in part inside or outside the housing of the pump. Description of the Drawings

[0046] Other advantages and features of the present invention will become more apparent upon reading the following description and the drawings, which are given by way of illustrative and non-limiting examples, in which:

[0047] Figure 1 An axial cross-sectional view of a turbomolecular vacuum pump according to an exemplary embodiment is shown.

[0048] Figure 2 Is a graph showing the trend of the rotor temperature over time and the drift amount of the temperature over time.

[0049] In these figures, the same elements have the same reference numerals.

[0050] The following embodiments are examples. Although one or more embodiments are described in the specification, this does not necessarily mean that each description relates to the same embodiment, nor that these features are only applicable to a single embodiment. Individual features of different embodiments may also be combined or interchanged to provide other embodiments.

[0051] In the description, certain elements may be indexed, such as a first element or a second element. In this case, this is simply an index used to distinguish and name similar but not identical elements. This indexing does not imply that one element is superior to another, and such naming can be easily interchanged without departing from the scope of the present invention. This indexing also does not imply any chronological order. Detailed Description

[0052] Turbo molecular vacuum pump

[0053] Figure 1 An exemplary embodiment of a turbomolecular vacuum pump 1 is shown. The turbomolecular vacuum pump 1 is the pump 1 hereinafter referred to.

[0054] According to one embodiment, the pump 1 may be a magnetic levitation pump (Maglev pump).

[0055] The pump 1 includes a stator 3, and a rotor 5 is configured to rotate about a rotation axis I-I within the stator 3. This rotation is a high-speed rotation, for example, more than thirty thousand revolutions per minute.

[0056] During operation, the gas to be pumped enters through the suction port 7, passes through the stages of the pump 1, and is then discharged to the discharge port 9 of the pump 1. The discharge port 9 may be intended to be connected to a main pumping system.

[0057] The rotor 5 may include an inner bowl 11 centered on the rotation axis I-I, and at least one surface of the inner bowl 11 is arranged to face the bell-shaped member 13 of the stator 3. According to the shown example, in the orientation of the pump 1 as shown, the shown bell-shaped member 13 is located below the inner bowl 11 and on the rotation axis I-I. During operation, the rotor 5 rotates within the stator 3, and there is no contact between the inner bowl 11 and the bell-shaped member 13. Figure 1 The rotor 5 may also include a skirt, such as a cylindrical skirt, especially a Holweck skirt 14. The Holweck skirt 14 may be formed by a smooth cylindrical body. During operation, the cylindrical skirt or the Holweck skirt 14 may rotate facing a groove (such as a spiral groove) of the stator 3. The spiral groove of the stator 3 enables the compression of the gas to be pumped and guides it to the discharge port 9. At the lower part of the rotor 5, the inner bowl 11 arranged facing the bell-shaped member 13 of the stator 2 is also formed by the inside of the cylindrical skirt or the Holweck skirt 14.

[0058] The rotor 5 may be fixed to a drive shaft 15, and the drive shaft 15 is driven by an internal motor of the pump 1 to rotate within the stator 3. The drive shaft 15, for example, passes through the bell-shaped member 13 of the stator 3. The rotor 5 may be laterally and axially guided by a magnetic force or a mechanical bearing 16 that supports the drive shaft 15 of the rotor 5 and is located within the stator 3.

[0059] The rotor 5 may be fixed to a drive shaft 15, and the drive shaft 15 is driven by an internal motor of the pump 1 to rotate within the stator 3. The drive shaft 15, for example, passes through the bell-shaped member 13 of the stator 3. The rotor 5 may be laterally and axially guided by a magnetic force or a mechanical bearing 16 that supports the drive shaft 15 of the rotor 5 and is located within the stator 3.

[0060] For a magnetic levitation pump (Maglev pump), the magnetic bearings 16 can guide the rotation of the rotor 5. These magnetic bearings 16 make it possible to control the position of the rotation axis I-I of the rotor 5. For example, the rotation axis I-I can be kept at the center or approximately at the center of the magnetic bearings 16. It is also possible to offset the rotation axis I-I in a given direction, for example by modifying the position setpoint of the servo control of the rotation axis I-I.

[0061] Also referring Figure 2 , the pump 1 can include at least one temperature sensor 17. The temperature sensor 17 is arranged to measure at least one temperature T°. This temperature T° can be the temperature of the rotor 5 or a temperature representative of the temperature of the rotor 5.

[0062] If necessary, the temperature sensor 17 can measure the temperature of the stator 3 and / or the temperature of at least one other element of the pump 1.

[0063] For example, it can be an infrared sensor, a magnetothermal sensor, or even a positive temperature coefficient probe.

[0064] The temperature sensor 17 can be arranged inside the stator 3. In particular, it can be arranged in the lower part of the pump 1 in the orientation Figure 1 shown, more specifically, near the gas outlet, where the pressure is the highest and thus the deposition risk is also the greatest. According to a specific exemplary embodiment, the temperature sensor 17 can be arranged at the bell-shaped part 13 of the stator 3, facing the inner bowl 11 of the rotor 5. In particular, the temperature sensor 17 can be arranged, for example, in the lower part of the stator 3 in order to measure the temperature representative of the lower part of the Holweck skirt 14.

[0065] In Figure 1 the example only a single temperature sensor 17 is shown, which will be described below. Obviously, multiple temperature sensors can be provided to measure the temperature T° of the rotor 5.

[0066] The temperature sensor 17 can transmit one or more temperature measurement values T° to the monitoring unit 19.

[0067] The temperature sensor 17 can be a sensor already existing in the pump 1, the temperature measurement value of which is transmitted to the monitoring unit 19, mainly for controlling the temperature of the pump 1 via heating elements (such as resistive or radiative heating elements, such as heating tapes or heating cartridges). It can also be a temperature sensor the temperature measurement value of which is used for calculating the rotor creep.

[0068] The monitoring unit 19 can be arranged entirely or partially inside or outside the housing of the pump 1. In the example shown, the monitoring unit 19 is received inside the stator 3 of the pump 1. This arrangement is not restrictive.

[0069] The monitoring unit 19 can receive one or more temperature measurement values T° transmitted by the temperature sensor 17.

[0070] The monitoring unit 19 can calculate the drift of temperature over time based on the temperature measurement value T° transmitted by the temperature sensor 17.

[0071] The drift of temperature over time Enables the thermal power of the rotor 5 to be inferred. Specifically, the drift of temperature over time Multiplied by the thermal inertia of the rotor 5 corresponds to the thermal power of the rotor 5. When a deposition layer is formed in the vacuum pump 1, the deposition layer causes the rotor 5 to heat up through friction. Therefore, in the presence of friction, the thermal power exceeds the normal operating range. More specifically, the thermal power exceeds a predetermined limit. This is reflected by the drift of temperature over time Exceeding the predetermined thresholds s, s(Imotor).

[0072] The monitoring unit 19 can compare the calculated value of the drift With the predetermined thresholds s, s(Imotor).

[0073] When the calculated value of the drift Is greater than or equal to the preset thresholds s, s(Imotor), the monitoring unit 19 can detect abnormal overheating representing the deposition layer. Since the drift enables the degree of temperature change over time to be determined, the drift calculation enables such overheating to be detected quickly and clearly. Through the drift calculation, the temperature change is amplified and can be detected more clearly.

[0074] The monitoring unit 19 can issue at least one alarm signal and / or at least one command signal to stop the pump 1.

[0075] The monitoring unit 19 can include one or more processing elements so that the above one or more receiving, calculating, comparing, detecting, and issuing operations can be performed. It can be a computer, a processor, a microcontroller, or any other unit capable of performing these operations.

[0076] The monitoring unit 19 can control the magnetic bearing 16 to keep the rotational axis I-I at or approximately at the center of the magnetic bearing 16. The monitoring unit 19 can also control the magnetic bearing 16 by modifying the position setpoint of the servo control of the rotational axis I-I to offset the rotational axis I-I in a given direction. This control is particularly advantageous in the case of a magnetic levitation pump (Maglev pump).

[0077] The pump 1 is configured to at least partially perform a method for detecting a deposition layer in the pump 1.

[0078] Method for detecting a deposited layer

[0079] A method for detecting a deposition layer includes the following steps.

[0080] The temperature sensor 17 can measure the temperature T° of the rotor 5 and transmit one or more temperature measurement values T° to the monitoring unit 19. Figure 2 The curve C1 shown by the solid line in shows an example of the trend of the temperature T° of the rotor 5 changing with time t.

[0081] The temperature measurement value T° can be transmitted from the temperature sensor 17 to the monitoring unit 19.

[0082] When the pump 1 is running, the temperature T° of the rotor 5 can be continuously measured.

[0083] Alternatively, within a so-called inspection period, the temperature T° of the rotor 5 can be measured regularly. These inspection periods can be predefined or arranged. As a variant, the inspection period can be initiated according to user requirements. In the absence of air flow, the inspection period is preferably arranged or selected by the user. For the pump 1 with magnetic bearings 16, this inspection period is particularly advantageous.

[0084] During these inspection periods, the monitoring unit 19 can issue at least one command to the magnetic bearing 16 to offset the rotational axis I-I of the rotor 5.

[0085] According to one embodiment, the method can include at least one preparatory step for checking whether at least one condition is met before issuing the offset instruction. This condition can particularly be a temperature condition. Specifically, in a non-limiting manner, it can be checked whether the temperature T° of the rotor 5 is stable or decreasing. If the temperature T° of the rotor 5 does not fluctuate, especially if it does not rise by a predetermined degree within a predetermined time period, the temperature T° of the rotor 5 can be considered stable. For example, if the temperature T° of the rotor 5 does not rise by more than 0.1° in the past 10 minutes, the temperature T° of the rotor 5 can be considered stable.

[0086] As a variant or alternative to the stable or decreasing temperature T° of the rotor 5, other conditions can be checked to allow the offset command.

[0087] The offset of the rotational axis I-I of the rotor 5 will fill the gap between, for example, the cylindrical skirt of the rotor 5 (such as the Holzwarth skirt 14) and the possible deposits on the stator 3 (especially the part of the stator 3 facing the cylindrical skirt (Holzwarth skirt) 14). Then, friction will occur on the skirt 14 of the rotor 5 and local overheating may occur.

[0088] The offset command can be executed in a given direction perpendicular to the rotational axis I-I. As a variant, the offset command can be executed in multiple directions or on a circular trajectory.

[0089] When the rotation axis I-I is offset, the temperature sensor 17 can measure the temperature T° of the rotor 5 and transmit one or more temperature measurement values T° to the monitoring unit 19.

[0090] The duration of the offset command is predefined and should be sufficient to allow measurement of the change in the temperature T° of the rotor 5, for example, between three seconds and one minute, or even 10 minutes, in each direction.

[0091] Once the offset command is completed, the monitoring unit 19 can control the magnetic bearing 16 so that the rotation axis I-I returns to its central or substantially central position. The mechanical clearance is re-established and the friction disappears.

[0092] Therefore, excessive deposits in the pump 1 can be detected without having to wait until continuous friction causes an emergency stop of the pump 1. Simple cleaning and maintenance of the pump 1 should be arranged quickly and easily.

[0093] Whether the temperature T° of the rotor 5 is measured continuously or during an inspection period, the method includes the following steps.

[0094] The monitoring unit 19 can calculate the drift of the temperature over time based on the temperature measurement value T° received from the temperature sensor 17 Figure 2 The curve C2 shown in dashed lines in the figure shows the drift of the temperature over time The trend of change over time t.

[0095] According to an exemplary embodiment, the drift of the temperature over time can be calculated at different frequencies based on multiple time bases. For example, the drift can be calculated every millisecond, every second, every ten seconds, or at other frequencies Multiple drifts calculated at different frequencies / time bases can be calculated The average value. In the following description, the calculated drift The value refers to the drift of the temperature over time calculated at time t Or the average value of multiple drifts.

[0096] Then, the monitoring unit 19 can compare the calculated drift The value with predefined thresholds s, s(Imotor).

[0097] The thresholds s, s(Imotor) can be set or can be variable. It is also conceivable that a predetermined threshold s is set at least during the first iteration of the method, and then, during at least one subsequent iteration of the method, the predetermined threshold s(Imotor) can be variable. In this case, the set predetermined threshold s is preferably greater than the variable predetermined threshold s(Imotor).

[0098] For example, the thresholds s, s(Imotor) can be less than or equal to 2 °C / minute.

[0099] Specifically, when the threshold s is set, it can be 2 °C / minute.

[0100] When the threshold s(Imotor) is variable, the conceivable range is also variable. For example, the variable threshold s(Imotor) can be between 0.3 °C / minute and 2 °C / minute.

[0101] When the threshold s(Imotor) is variable, it can at least be a function of the motor current. The motor current refers to the current consumed by the motor of the pump 1 to drive the rotor 5 to rotate.

[0102] The variable predetermined threshold s(Imotor) can be calculated according to the following formula (1):

[0103]

[0104] In this formula, 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. For example, the motor current is between 0 A and 10 A.

[0105] The first coefficient a can correspond to the conceivable minimum threshold, that is, the minimum boundary value of the threshold range. According to the aforementioned range example [0.3 °C - 2 °C], the minimum boundary value is 0.3 °C, then the first coefficient a can be equal to 0.3.

[0106] The second coefficient b can be selected according to the selected first coefficient a, and is selected such that when the motor current Imotor is the maximum value Imax, the value of the threshold s(Imax) is the largest, that is, equal to the maximum boundary value of the threshold range. Therefore, when the motor current Imotor is the maximum value Imax, formula (1) becomes:

[0107]

[0108] Then the second coefficient b can be calculated according to the following formula (2):

[0109] (2) b = s(Imax) - a

[0110] Therefore, the second coefficient b corresponds to the maximum boundary value of the threshold range minus the first coefficient a. According to the previous range example [0.3 °C - 2 °C], the maximum boundary value is 2 °C / minute, and when the value of the first coefficient a is 0.3, the second coefficient b is equal to 1.7.

[0111] The variable threshold s(Imotor) can also depend on one or more other criteria. These criteria can be, for example, the nature of the gas being pumped, and / or the temperature T° of the rotor 5 / at the moment t when calculating the drift a representative value of the temperature of the rotor 5 at the moment t. Specifically, the first coefficient a can be increased or decreased. The increment or decrement of the first coefficient a can be on the order of one-tenth.

[0112] For example, the higher the temperature of the rotor 5, the lower the threshold s(Imotor) will be, and / or at least the first coefficient a can be decreased. In particular, when the temperature T° of the rotor 5 / at the moment t when calculating the drift the representative value of the temperature of the rotor 5 measured at the moment t rises or reaches a predetermined temperature, at least the first coefficient a can be decreased. On the contrary, when the temperature T° of the rotor 5 / at the moment t when calculating the drift the representative value of the temperature of the rotor 5 measured at the moment t decreases or is lower than a predetermined temperature, the first coefficient a can be increased. The second coefficient b can also be modified according to the temperature of the rotor 5.

[0113] As an exemplary and non-limiting example, if at the moment t when calculating the drift the temperature T° of the rotor 5 is less than 130 °C, for example 100 °C, then the first coefficient a can be 0.3 as described above. According to another example, if at the moment t when calculating the drift the temperature T° of the rotor 5 is equal to or greater than 130 °C, for example 100 °C, then the first coefficient a can be decreased to, for example, 0.2.

[0114] As a variant or alternative including the temperature T° of the rotor 5, it is also conceivable to adjust the variable threshold s(Imotor), especially at least the first coefficient a, according to the nature of the gas being pumped.

[0115] More specifically, so-called light gases have high conductivity and enable enhanced cooling of the rotor 5. In this case, the variable threshold s(Imotor) or the first coefficient a can be decreased, for example, by one-tenth. So-called light gases refer to gases lighter than air, such as helium (symbol He), hydrogen (symbol H).

[0116] On the contrary, for so-called heavy gases, the variable threshold s(Imotor) or the first coefficient a can be increased, for example, by one-tenth. So-called heavy gases refer to gases heavier than air, such as hydrogen bromide (symbol HBr).

[0117] Furthermore, based on the calculated drift amount and the comparison result of the value with the predetermined thresholds s and s(Imotor), the monitoring unit 19 can detect or fail to detect overheating of the rotor 5. In particular, when the calculated drift amount is greater than or equal to the predetermined thresholds s and s(Imotor), the monitoring unit 19 can detect abnormal overheating representing the deposition layer.

[0118] When such overheating is detected during continuous inspection, the monitoring unit 19 can issue at least one alarm signal and / or at least one command signal to stop the pump 1.

[0119] Alternatively, if detected during the inspection cycle and the axis of rotation I-I is offset, the monitoring unit 19 can issue an alarm signal, but does not require immediate stop, only requires prompt maintenance.

[0120] The alarm signal (or prompt maintenance request) and / or the stop command signal can be digital and / or analog.

[0121] The alarm signal (or prompt maintenance request) and / or the stop command signal can be generated by the monitoring unit 19 at the pump 1. It can be a visual and / or audible signal.

[0122] The monitoring unit 19 can also send the alarm signal (or prompt maintenance request) and / or the stop command signal to at least one device associated with the monitoring unit 19 of the pump 1. This device is usually referred to as a "tool" and is configured to manage a chamber fluidly connected to the pump 1 for pumping gas. Then, this device can decide to command the pump 1 to stop operating and may take all necessary measures to protect the device, such as cutting off the gas injected into the chamber and closing the shut-off valve between the chamber and the pump 1.

[0123] According to another example, the monitoring unit 19 can also transmit the alarm signal (or prompt maintenance request) and / or the stop command signal to a central monitoring unit associated with multiple pumps 1 or multiple devices.

[0124] Therefore, by monitoring the trend of the temperature T° of the rotor 5, more specifically the drift amount of the temperature over time When the drift amount reaches the set predetermined threshold s or the variable predetermined threshold s(Imotor), the appearance of the deposition layer can be simply detected. Additionally, when the temperature sensor 17 has been used for temperature regulation of the pump 1, there is no need to add another temperature sensor to achieve this function. In this way, the user can be alerted that the pump 1 needs to be cleaned, and / or the pump 1 can be stopped and the chamber isolated to allow cleaning of the pump 1.

Claims

1. A method for detecting a deposition layer in a turbomolecular vacuum pump (1), said 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), said temperature sensor (17) being configured to measure a temperature (T°) representative of the temperature of said rotor (5) and to transmit at least one temperature measurement value to a monitoring unit (19) of said pump (1), characterized in that, The method comprises the following steps: - The at least one temperature sensor (17) measures the temperature (T°) and transmits the measured value of the temperature (T°) to the monitoring unit (19), - The monitoring unit (19) calculates the drift of the temperature over time based on the measured value of the temperature (T°) transmitted by the at least one temperature sensor (17). - The monitoring unit (19) compares the calculated drift amount with a predetermined threshold value (s, s(Imotor)). - When the calculated drift amount has a value greater than or equal to the predetermined threshold value (s, s(Imotor)), the monitoring unit (19) detects an abnormal overheating of the deposition layer and issues at least one alarm signal and / or at least one command signal to stop the pump (1).

2. The detection method according to the previous claim, wherein, The pump (1) comprises a magnetic bearing (16), the magnetic bearing (16) being configured to guide the rotor (5) to rotate about a rotation axis (I-I), and the monitoring unit (19) controls the magnetic bearing (16) to offset the rotation axis (I-I) in at least one direction perpendicular to the rotation axis (I-I) for a predetermined time, and performs a temperature measurement step at least when the rotation axis (I-I) is offset.

3. The detection method according to any one of the preceding claims, wherein, The alarm signal and / or the stop command signal are generated at the pump (1), and / or the monitoring unit (19) transmits the alarm signal and / or the stop command signal to at least one device associated with the pump (1).

4. The detection method according to any one of the preceding claims, wherein, The predetermined threshold value (s, s(Imotor)) is less than or equal to 2 °C / minute, in particular between 0.3 °C / minute and 2 °C / minute.

5. The detection method according to any one of claims 1 to 4, wherein, The predetermined threshold value (s) is set.

6. The detection method according to any one of claims 1 to 4, wherein, 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) to rotate.

7. The detection method according to any one of claims 1 to 4, wherein, The predetermined threshold value (s) is set at least in a first iteration of the method, and the predetermined threshold value (s(Imotor)) is variable in at least one subsequent iteration of the method, and the set predetermined threshold value (s) is greater than the variable predetermined threshold value (s(Imotor)).

8. The detection method according to any one of claims 6 and 7, wherein, The variable predetermined threshold value (s(Imotor)) is calculated according to the following formula: - - a corresponds to a first coefficient, - b corresponds to a second coefficient, - Imotor corresponds to the motor current, - Imax corresponds to the maximum value of the motor current.

9. The detection method according to the preceding claim, wherein: - The variable threshold value (s(Imotor)) is selected from at least one predetermined threshold range, and - The first coefficient (a) is equal to the minimum boundary value of the threshold range, and the second coefficient (b) is equal to the maximum boundary value of the threshold range minus the first coefficient (a).

10. The detection method according to any one of claims 6 to 9, wherein, The variable threshold s(Imotor) also depends on at least one of the following criteria: the nature of the gas being pumped, and / or a temperature (T°) representative of the temperature of the rotor (5) at the moment (t) of calculating the amount of drift .

11. The detection method according to claims 9 and 10, wherein, When the measured temperature (T°) at the moment (t) of calculating the drift amount is greater than or equal to a predetermined temperature, the first coefficient (a) is decreased.

12. A turbomolecular pump (1) configured to at least partially perform the detection method according to any one of the preceding claims, the pump (1) comprising: - A stator (3), - A rotor (5) configured to rotate within the stator (3), - At least one temperature sensor (17) arranged within 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) being configured to transmit the measured value of the temperature (T°) to the monitoring unit (19), and the monitoring unit (19) comprising at least one processing element configured to: - Calculate the drift of temperature over time based on the measured value of the temperature (T°) transmitted by the at least one temperature sensor (17) - Compare the calculated drift amount with a predetermined threshold value (s, s(Imotor)), and - When the calculated drift amount is greater than or equal to the predetermined threshold value (s, s(Imotor)), an abnormal overheating representative of the deposition layer is detected, and at least one alarm signal and / or at least one command signal is issued to stop the pump (1).

13. The turbomolecular vacuum pump (1) according to the previous claim, wherein, The temperature sensor (17) is selected from an infrared sensor, a magnetothermal sensor, and a positive temperature coefficient probe.

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