Vacuum pump and method for controlling heating

Abstract

The invention relates to a vacuum pump (1) comprising: - a heating module (5) comprising at least one electrical heating element (6) which is configured to heat the stator (4) of the vacuum pump (1) when it is electrically powered, characterised in that the heating module (5) further includes a heating control unit (8) which is configured to: - measure the value of a parameter representative of the voltage of the electrical network to which the vacuum pump (1) is electrically connected, - supply a supply voltage (U) to the at least one heating element (6) by adapting the electrical power of the electrical network by taking into account the measured value of the parameter representative of the voltage of the electrical network (Ures) in order to reach a predetermined setpoint temperature.

Description

Description Title: Vacuum pump and heating control method Technical field of the invention

[0001] The invention relates to a vacuum pump, such as a dry vacuum pump or a turbomolecular vacuum pump. The invention also relates to a method for controlling the heating of a vacuum pump. Technical background

[0002] Thermal management of vacuum pumps is critical. Gases and evaporated substances of different chemistries can circulate within vacuum pumps and, due to changes in temperature or pressure conditions, can deposit on the internal surfaces of the vacuum pump and cause clearance restrictions that can lead to seizure or crash of the vacuum pump.

[0003] It is known to heat the vacuum pump to prevent condensation or solidification of reaction products and thus limit the formation of deposits.

[0004] To do this, a central unit of the vacuum pump controls the electrical power supplying the heating elements, by modulating the electrical power of the mains to which the vacuum pump is electrically connected.

[0005] However, vacuum pumps are installed all over the world and the voltage ranges and quality of the electrical networks to which they are connected vary greatly.

[0006] Vacuum pump manufacturers are therefore forced to manage several heating element references, each adapted to the voltage of the electricity network of the country in which the vacuum pump is intended to be used. This can be costly, particularly due to the large number of certifications that may be required.

[0007] Another disadvantage is that heating depends on the quality of the electrical network. Micro-cuts, voltage dips, or surges can occur more or less frequently on certain electrical networks. Voltage losses can lead to a loss of heating quality, as the temperature setting may be more difficult or take longer to reach, especially in low-voltage countries. Power surges can be dangerous for people or can damage heating elements. Summary of the invention

[0008] An aim of the present invention is to provide a vacuum pump which at least partially overcomes the drawbacks of the state of the art.

[0009] To this end, the invention relates to a vacuum pump comprising: - a motor and at least one rotor configured to be driven in rotation by the motor in a stator of said vacuum pump, - a heating module comprising at least one electric heating element configured to heat the stator of the vacuum pump when it is electrically powered, - at least one temperature sensor configured to measure the temperature of the at least one rotor or the stator, characterized in that the heating module further comprises a heating control unit comprising: - a measuring device configured to measure the value of a parameter representative of the voltage of the electrical network to which the vacuum pump is electrically connected, and - a control unit configured to provide a supply voltage to the at least one heating element by adapting the electrical power of said electrical network by taking into account the measurement from the temperature sensor and the value of the parameter representative of the voltage of said electrical network measured by the measuring device, to reach a predetermined set temperature.

[0010] Thus, instead of adapting the supply voltage of the heating elements to regulate the stator temperature from an assumed voltage of the electrical network, the heating control unit measures a parameter representative of the voltage of the electrical network and deduces from it an adapted supply voltage of the heating elements, taking into account the actual value of the electrical network and therefore any voltage drops or overvoltages. In the event of a drop in the network voltage, the temperature regulation taking into account the measured network voltage makes it possible to increase the power more quickly than by waiting for a return of the control by temperature measurement, which would be slower and whose power increments until reaching the setpoint would be unsuitable and therefore also slower.In case of network voltage overloads, temperature control taking into account the measured network voltage helps prevent possible damage. heating elements in the more or less long term. Temperature control can therefore automatically adapt to fluctuations in the voltage of the electrical network and therefore be more efficient and robust. This ensures that the heating elements are correctly supplied and therefore that the stator temperature can be controlled.

[0011] The vacuum pump may further include one or more of the features described below, taken alone or in combination.

[0012] The heating control unit can also be configured to receive operating information from the vacuum pump and to take it into account when determining the supply voltage of the at least one heating element.

[0013] The operating information can be the setpoint at which the user wishes to control the stator temperature and / or the type of heating element, i.e. for example resistive or inductive or radiative and / or the nominal supply voltage.

[0014] The vacuum pump operating information can be an operating state: in normal operation (nominal rotation speed) / stopped / on standby (reduced rotation speed).

[0015] The heating control unit may further be configured to identify the control algorithm of the at least one heating element to be applied based on the type of heating element of the vacuum pump heating module.

[0016] The at least one heating element of the heating module comprises, for example, an electrical resistance and / or a radiative and / or inductive element.

[0017] According to an exemplary embodiment, the heating module comprises: - at least one pair of heating elements comprising a first and a second electrical resistor, the electrical resistors having the same ohmic values, and - an electrical circuit comprising a first circuit connecting the heating elements in parallel, a second circuit connecting said heating elements in series, and a controllable switching device.

[0018] The heating control unit is configured to control the switching device to supply the supply voltage to the terminals of either the first circuit or the second circuit depending on the voltage of the electrical network.

[0019] It is thus possible, using the same components, to adapt the electrical circuit of the heating module so that the heating elements are adapted to the voltage of the electrical network. The same heating module, which includes heating elements with a low supply voltage, can therefore be used on vacuum pumps that can be connected to a wide range of electrical networks. In addition, since this operation is automatic, possible connection errors that could damage the heating elements are avoided.

[0020] The invention also relates to a method for controlling the heating of a vacuum pump as described above, characterized in that it comprises the following steps: - measure the value of a parameter representative of the voltage of the electrical network to which the vacuum pump is electrically connected, - providing a supply voltage to the at least one heating element by adapting the electrical power of said electrical network by taking into account the value of the parameter representative of the voltage of said electrical network measured to reach a predetermined set temperature. Brief description of the figures

[0021] Other advantages and characteristics will appear on reading the description of the invention, as well as the attached drawings in which:

[0022] [Fig.1] Figure 1 shows a very schematic view of a vacuum pump.

[0023] [Fig.2] Figure 2 shows a wiring diagram of a heating module of the vacuum pump of Figure 1 having a switching device in a first switching state.

[0024] [Fig.3] Figure 3 shows a diagram similar to Figure 2 for a second switching state of the switching device.

[0025] [Fig.4] Figure 4 shows a flowchart of a method for controlling the heating of the vacuum pump of Figure 1.

[0026] In these figures, identical elements have the same reference numbers. Detailed description

[0027] 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.

[0028] Figure 1 shows an example of a vacuum pump 1.

[0029] The vacuum pump 1 comprises a motor 2 and at least one rotor 3 configured to be driven in rotation by the motor 2 in a stator 4 (or pump body) of said vacuum pump 1. The vacuum pump 1 is configured to be electrically connected, in particular for the electrical power supply of its motor 2, to an electrical network.

[0030] The vacuum pump 1 can be a so-called dry vacuum pump (figure 1) or a turbomolecular vacuum pump.

[0031] A dry vacuum pump 1 is a positive displacement vacuum pump, which is configured to, using the two rotors 3, suck, transfer and then discharge the gas to be pumped at atmospheric pressure or above. It is for example a multi-stage primary vacuum pump which comprises between two and ten pumping stages (five in the illustrative example) or a Roots compressor which comprises one to three pumping stages. Each pumping stage of the stator 4 is formed by a pumping chamber receiving two mating rotors 3, the pumping chambers comprising a respective inlet and outlet. The successive pumping stages are connected in series one after the other by respective inter-stage channels connecting the outlet of the preceding pumping stage to the inlet of the following stage. During rotation, the gas sucked in from the inlet is trapped in the volume generated by the rotors 3 and the stator 4, then is driven by the rotors 3 towards the next stage.The vacuum pump 1 is notably called "dry" because in operation, the rotors 3 turn inside the stator 4 without any mechanical contact between them or with the stator 4, which makes it possible not to use oil in the pumping chamber(s).

[0032] According to another example, the vacuum pump 1 is a turbomolecular vacuum pump and comprises a single rotor 3 (not shown). The rotor 3 is configured to be driven by the motor 2 in rotation at high speed in the stator 4, for example at more than twenty thousand revolutions per minute. The rotor 3 is guided laterally and axially by magnetic or mechanical bearings. In operation, the discharge port of the turbomolecular vacuum pump 1 is connected to a primary vacuum pump. The turbomolecular vacuum pump 1 may comprise only one turbomolecular stage or one turbomolecular stage and one molecular stage downstream of the turbomolecular stage in the direction of gas flow. In the turbomolecular stage, the rotor 3 comprises at least two stages of blades and the stator 4 comprises at least one stage of fins. The stages of blades and fins follow one another axially along the axis of rotation of the rotor 3. According to an exemplary embodiment, the rotor 3 comprises a Holweck skirt in the molecular stage formed by a smooth cylinder, which rotates opposite helical grooves of the stator 4.

[0033] The vacuum pump 1 may further comprise a central control unit 7 such as an electronic card, comprising one or more controllers or microcontrollers or processors and a memory. The central control unit 7 is configured to execute sequences of program instructions making it possible in particular to control the rotation speed of the at least one rotor 3 and to receive and provide operating information from the vacuum pump 1, such as providing a set temperature for example received by a user interface, or providing signals for measuring the temperature of the stator 4 or of the at least one rotor 3, from at least one temperature sensor 20 of the vacuum pump 1, such as an infrared sensor, a magnetothermal sensor, a positive temperature coefficient probe, a thermocouple or a thermistor.

[0034] The vacuum pump 1 further comprises a heating module 5 comprising at least one electrical heating element 6 such as an electrical resistor and / or a radiative or inductive element, configured to heat the stator 4 of the vacuum pump 1 when it is electrically powered. The heating elements 6 may be configured to receive a low supply voltage such as a single-phase voltage, for example between 100V and 240V, or they may be configured to be powered with a high supply voltage such as a three-phase voltage, for example between 180V and 530V, this value range taking into account a safety margin of 20% on the lower terminal and 10% on the upper terminal to take into account fluctuations in the electrical network.

[0035] The heating module 5 further comprises a heating control unit 8 such as an electronic card, which 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 heating the vacuum pump 1.

[0036] The heating control unit 8 and the central control unit 7 may be part of the same electronic card or may be independent electronic cards. Units 7, 8 that are physically independent of each other make it possible to standardize the central control units 7 of the vacuum pumps 1, with the possibility of adding a heating module 5 to them or not.

[0037] The heating control unit 8 comprises: - a measuring device configured to measure the value of a parameter representative of the voltage of the electrical network to which the vacuum pump 1 is electrically connected, such as the voltage of the electrical network, and - a control unit configured to supply a supply voltage U to the at least one heating element 6 by adapting the electrical power of the electrical network by taking into account the temperature measurement of the stator 4 or of the at least one rotor 3 from the temperature sensor 20 and the value of the parameter representative of the voltage of said electrical network Lires measured by the measuring device to reach a predetermined set temperature.

[0038] The electrical network is the distribution network intended to provide the electrical power to power a set of electrical machines including the vacuum pump 1. As an illustration, the voltage of the electrical network can be:

[0039] The supply voltage to be supplied to the heating elements 6 is determined from a temperature setpoint, a temperature measurement of the stator 4 and a regulation algorithm, in particular a closed-loop control. The heating control unit 8 receives, for example, the temperature setpoint from the central control unit 7 and temperature measurement signals either from the unit control unit 7, or directly from the temperature sensors of the vacuum pump 1.

[0040] Possible control algorithms are, for example, closed-loop, on-off, proportional or PID (proportional, integral, derivative) controls.

[0041] In a manner known per se, in the on / off control algorithm, the heating elements 6 are powered when the measured temperature is lower than the temperature setpoint and the power supply is cut off when the measured temperature is higher than the setpoint. In the proportional or PID control algorithm, the power supply to the heating elements 6 is increased or decreased depending on the difference observed between the temperature setpoint and the measured temperature with a proportional, integral and derivative component.

[0042] The supply voltage U of the heating elements 6 thus determined is then obtained by adapting the voltage of the electrical network Lires (function shown diagrammatically by block 15 in figure 4), for example by transforming the measured supply voltage into a succession of slots whose duration and / or frequency varies so as to reach the supply voltage U determined by the regulation algorithm.

[0043] The measuring device is for example configured to measure the voltage of the electrical network Lires at the level of a supply phase of the vacuum pump 1.

[0044] The measurement of the parameter representative of the voltage of the electrical network can be carried out periodically, for example with a period of less than 1 second, such as every 500 msec, so that the supply voltage to be supplied to the heating elements 6 can be regularly recalculated and controlled by the temperature measurement of the stator 4.

[0045] Thus, instead of adapting the supply voltage U of the heating elements 6 to regulate the temperature of the stator 4 from an assumed voltage of the electrical network, the heating control unit 8 measures a parameter representative of the voltage of the electrical network Lires and deduces therefrom a suitable supply voltage U of the heating elements, taking into account the actual value of the electrical network and therefore any voltage drops or overvoltages. The temperature regulation can therefore automatically adapt to fluctuations in the voltage of the electrical network. This ensures that the heating elements 6 are correctly supplied and therefore that the temperature of the stator 4 can be controlled.

[0046] According to an exemplary embodiment, the heating control unit 8 is further configured to receive operating information Ifon from the vacuum pump 1, provided by the central control unit 7, and to take it into account for determining the supply voltage U of the heating elements 6 (figure 1).

[0047] The operating information Ifon of the vacuum pump 1 can be the setpoint at which the user wishes to control the temperature of the stator 4 and / or the type of heating element 6, i.e. for example resistive or inductive or radiative and / or low or high supply voltage.

[0048] The operating information Ifon of vacuum pump 1 can be an operating state: in normal operation (nominal rotation speed) / stopped / on standby (reduced rotation speed). The process can thus change the set temperature, for example, to switch off the heating if vacuum pump 1 is stopped or on standby, which allows energy savings.

[0049] Heating control can thus be finely achieved depending on the operating conditions of the vacuum pump 1.

[0050] According to an exemplary embodiment, the heating control unit 8 is further configured to identify the regulation algorithm of said at least one heating element 6 to be applied as a function of the type of heating element 6 of the vacuum pump 1.

[0051] To identify the regulation algorithm of the at least one heating element 6 to be applied, the heating control unit 8 can first identify the type of heating element 6 of the heating module 5 and then select the appropriate algorithm from a base of algorithms pre-recorded in the central control unit 7 or in the heating control unit 8.

[0052] The type of heating element 6, such as an electrical resistance and / or a radiative or inductive element and / or the nominal supply voltage, may be recorded in the heating control unit 8 and / or may be information provided by the heating elements 6 themselves.

[0053] To identify the type of heating element 6 of the heating module 5, the heating control unit 8 can be configured to measure a resistance between two terminals of an electrical circuit, for example arranged at the level of the heating element 6 or in the heating control unit 8, the value of the resistance defining the type of heating element 6.

[0054] Thus, the heating control unit 8 can be an independent module of the central control unit 7, implemented with the heating module 5 in the vacuum pumps 1, regardless of the type of heating elements 6 of the heating module 5. The heating control unit 8 can itself detect the type of heating element 6 implemented and select the regulation algorithm to be applied from the algorithm library. The heating control unit 8 can therefore be standardized for any type of heating element 6.

[0055] According to an exemplary embodiment illustrated in FIG. 2, the heating module 5 comprises at least one pair of heating elements 6 and an electrical circuit.

[0056] The pair of heating elements 6 comprises a first and a second electrical resistor, the electrical resistors having the same ohmic values.

[0057] The electrical circuit comprises a first circuit 9 connecting the heating elements 6 of a pair in parallel, a second circuit 10 connecting said heating elements 6 in series and a switching device 11 controllable by the heating control unit 9. If there is more than one pair of heating elements 6, the heating elements 6 of each pair are connected like the first pair, the electrical circuits of each pair being connected in parallel.

[0058] The controllable switching device 11 comprises, for example, first relays 12a, 12b respectively arranged on each branch of the first circuit 9 connecting the heating elements 6 of the pair in parallel and a second relay 13 arranged on the branch of the second circuit 10 connecting the heating elements 6 of the pair in series.

[0059] The heating control unit 8 is configured to control the switching device 11 according to a first switching state (figure 2) or according to a second switching state (figure 3) in order to supply the supply voltage U to the terminals of one or other of the first circuit 9 or the second circuit 10 depending on the voltage of the electrical network Lires.

[0060] The heating control unit 9 is for example configured to compare the measured electrical network voltage Lires with a switching threshold and to control the switching device 11 according to the result of the comparison. This comparison can be carried out by programming (“software” in English) or by means of electronic components (“hardware” in English).

[0061] According to an exemplary embodiment illustrated in Figure 4, the electrical circuit of the heating module 5 comprises a comparator 14, one input of which is connected to the measuring device providing a measurement of the electrical network lires. The measuring device may further comprise a voltage step-down converter 16 configured to filter, rectify and step-down the voltage of the electrical network lires. The other input of the comparator 14 is connected to a reference voltage Us. The output of the comparator 14 makes it possible to control the relays 12a, 12b, 13 of the switching device 11. The same comparison may be carried out by software programming.

[0062] If, for example, the regulation algorithm associated with the type of heating element 6 recommends a low supply voltage such as a single-phase voltage, for example 110V, and the measured electrical network voltage Ures is a three-phase voltage, i.e., twice the recommended voltage, for example 220V, then the heating control unit 8 can control the switching device 11 so that the supply voltage U is delivered to the terminals of the second circuit 10 connecting the heating elements 6 in series. Thus, half of the supply voltage U can be delivered to the terminals of each heating element 6. This first switching state is illustrated by FIG. 2 showing the first relays 12a, 12b of the switching device 11 open on the parallel branches of the first circuit 9 and the relay 10 closed on the branch of the second circuit 10.

[0063] If, on the other hand, the measured electrical network voltage Ures is equal to that of the electrical network voltage recommended by the regulation algorithm, then the heating control unit 8 can control the switching device 11 so that the supply voltage U is delivered to the terminals of the first circuit 9 connecting the heating elements 6 in parallel. Thus, the supply voltage U can be delivered to the terminals of each heating element 6. This second switching state is illustrated in Figure 3 showing the relays 12a, 12b closed on the parallel branches of the first circuit 9 and the relay 13 open on the branch of the second circuit 10 connecting the heating elements 6 in series.

[0064] It is thus possible, using the same components, to adapt the electrical circuit of the heating module 5 so that the heating elements 6 are adapted to the voltage of the Ures electrical network. The same heating module 5 comprising the heating elements 6 having a low supply voltage can therefore be used on vacuum pumps 1 which can be connected to a wide range of electrical networks. Furthermore, since this operation is automatic, possible connection errors which could damage the heating elements 6 are avoided.

Claims

CLAIMS

1. Vacuum pump (1) comprising: - a motor (2) and at least one rotor (3) configured to be driven in rotation by the motor (2) in a stator (4) of said vacuum pump (1), - a heating module (5) comprising at least one electric heating element (6) configured to heat the stator (4) of the vacuum pump (1) when it is electrically powered, - at least one temperature sensor (20) configured to measure the temperature of the stator (4) or of the at least one rotor (3), characterized in that the heating module (5) further comprises a heating control unit (8) comprising: - a measuring device configured to measure the value of a parameter representative of the voltage of the electrical network to which the vacuum pump (1) is electrically connected, and - a control unit configured to supply a supply voltage (U) to the at least one heating element (6) by adapting the electrical power of said electrical network by taking into account the measurement from the temperature sensor (20) and the value of the parameter representative of the voltage of said electrical network (lires) measured by the measuring device, to reach a predetermined set temperature.

2. Vacuum pump (1) according to the preceding claim, characterized in that the heating control unit (8) is also configured to receive operating information (Ifon) from the vacuum pump (1) and to take it into account for determining the supply voltage (U) of the at least one heating element (6).

3. Vacuum pump (1) according to one of the preceding claims, characterized in that the heating control unit (8) is further configured to identify the regulation algorithm of the at least one heating element (6) to be applied depending on the type of heating element (6) of the heating module (5) of the vacuum pump (1).

4. Vacuum pump (1) according to one of the preceding claims, characterized in that the at least one heating element (6) comprises an electrical resistance and / or a radiative and / or inductive element.

5. Vacuum pump (1) according to one of the preceding claims, characterized in that the heating module (5) comprises: - at least one pair of heating elements (6) comprising a first and a second electrical resistor, the electrical resistors having the same ohmic values, and - an electrical circuit comprising a first circuit (9) connecting the heating elements (6) in parallel, a second circuit (10) connecting said heating elements (6) in series, and a controllable switching device (11), the heating control unit (8) being configured to control the switching device (11) to supply the supply voltage (U) to the terminals of either the first circuit (9) or the second circuit (10) as a function of the voltage of the electrical network (lires).

6. Vacuum pump (1) according to the preceding claim, characterized in that the heating control unit (8) is configured to control the switching device (11) to supply the supply voltage (U) to the terminals of one or other of the first circuit (9) or the second circuit (10) depending on the voltage of the electrical network (Lires).

7. Method for controlling the heating of a vacuum pump (1) according to one of the preceding claims, characterized in that it comprises the following steps: - measure the value of a parameter representative of the voltage of the electrical network to which the vacuum pump (1) is electrically connected, - providing a supply voltage (U) to the at least one heating element (6) by adapting the electrical power of said electrical network by taking into account the value of the parameter representative of the voltage of said electrical network (lires) measured to reach a predetermined set temperature.

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