Vacuum pump and heating control method

Abstract

A 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 electrically powered, characterized in that the heating module (5) further comprises a heating control unit (8) 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 at least one heating element (6) by adapting the electrical power of said electrical network, taking into account the value of the parameter representative of the voltage of said electrical network (Ures) measured to reach a predetermined setpoint temperature. Figure 1

Description

Title of the invention: 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 in vacuum pumps and can, due to changes in temperature or pressure conditions, be deposited on the internal surfaces of the vacuum pump and cause clearance restrictions which 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] For this purpose, a central unit of the vacuum pump controls the electrical power supplying heating elements, by modulating the electrical power of the sector to which the vacuum pump is electrically connected.

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

[0006] Vacuum pump manufacturers are therefore forced to manage several different heating element references, each adapted to the voltage of the electrical grid in the country where 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 drawback is that heating performance depends on the quality of the electrical grid. Micro-interruptions, voltage dips, or surges can occur more or less frequently on certain electrical grids. Voltage drops can lead to a loss of heating quality, as the temperature setpoint may be more difficult or take longer to reach, particularly in countries with low voltage. Surges can be dangerous for people or can damage the heating elements. Summary of the invention

[0008] One object of the present invention is to provide a vacuum pump that at least partially resolves the drawbacks of the prior 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 vacuum pump stator when electrically powered, characterized in that the heating module further comprises a heating control unit configured to: - measure the value of a parameter representative of the voltage of the electrical network to which the vacuum pump is electrically connected, - provide a supply voltage to at least one heating element by adapting the electrical power of said electrical network by taking into account the value of the parameter representing the voltage of said electrical network measured to reach a predetermined setpoint temperature.

[0010] Thus, instead of adapting the supply voltage to the heating elements to regulate the stator temperature based on an assumed mains voltage, the heating control unit measures a parameter representative of the mains voltage and deduces an appropriate supply voltage for the heating elements, taking into account the actual mains voltage and therefore any potential voltage dips or surges. The temperature regulation can thus automatically adapt to mains voltage fluctuations. 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 for determining the supply voltage of at least one heating element.

[0013] The operating information can be the stator temperature measurement and / or the setpoint to 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 operating information of the vacuum pump can be an operating state: in normal operation (nominal rotation speed) / in stop / in standby (reduced rotation speed).

[0015] The heating control unit can also be configured to identify the regulation algorithm of at least one heating element to be applied according to the type of heating element of the vacuum pump heating module.

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

[0017] According to one embodiment, the heating module comprises: - at least one pair of heating elements comprising a first and a second electrical resistance, the electrical resistances 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 provide the supply voltage to the terminals of either the first or second circuit depending on the voltage of the electrical network.

[0019] Using the same components, the electrical circuit of the heating module can be adapted so that the heating elements are compatible with the mains voltage. The same heating module, including 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. Furthermore, since this operation is automatic, potential 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, - provide a supply voltage to at least one heating element by adapting the electrical power of said electrical network by taking into account the value of the parameter representing the voltage of said electrical network measured to reach a predetermined setpoint temperature. Brief description of the figures

[0021] Other advantages and features will become apparent upon reading the description of the invention, as well as the accompanying drawings in which:

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

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

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

[0025] [Fig. 4] Fig. 4 shows a flowchart of a heating control method of the vacuum pump in [Fig. 1].

[0026] In these figures, identical elements bear 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. Simple features of different embodiments can also be combined or interchanged to provide other embodiments, without departing from the scope of the invention as defined by the claims.

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

[0029] The vacuum pump 1 includes 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 power supply of its motor 2, to an electrical network.

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

[0031] A dry vacuum pump 1 is a positive displacement vacuum pump configured to draw in, transfer, and then discharge the gas to be pumped at atmospheric pressure or above, using two rotors 3. For example, it is a multistage primary vacuum pump comprising between two and ten pumping stages (five in the illustrative example) or a Roots compressor comprising one to three pumping stages. Each pumping stage of the stator 4 is formed by a pumping chamber receiving two coupled 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 interstage channels connecting the outlet of the preceding pumping stage to the inlet of the following stage. During rotation, the gas drawn 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 to the next stage.The vacuum pump 1 is specifically described as "dry" because, during operation, the rotors 3 rotate inside the stator 4 without any mechanical contact between themselves or with the stator 4, thus eliminating the need for 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 rotating 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 A turbomolecular vacuum pump 1 is connected to a primary vacuum pump. The turbomolecular vacuum pump 1 may consist of only one turbomolecular stage or one turbomolecular stage and a molecular stage downstream of the turbomolecular stage in the gas flow direction. In the turbomolecular stage, the rotor 3 has at least two blade stages and the stator 4 has at least one vane stage. The blade and vane stages are arranged axially along the axis of rotation of the rotor 3. In one embodiment, the rotor 3 has a Holweck skirt in the molecular stage formed by a smooth cylinder, which rotates opposite helical grooves in the stator 4.

[0033] The vacuum pump 1 may further include a central control unit 7 such as an electronic board, comprising one or more controllers or microcontrollers or processors and memory. The central control unit 7 is configured to execute sequences of program instructions enabling, in particular, the control of the rotational speed of at least one rotor 3 and the receiving and supplying of operating information from the vacuum pump 1, such as supplying a setpoint temperature, for example, received via a user interface, or supplying temperature measurement signals from the stator 4, for example, from temperature sensors of the vacuum pump 1.

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

[0035] The heating module 5 further includes a heating control unit 8 such as an electronic board, which includes one or more controllers or microcontrollers or processors and a memory, for executing sequences of program instructions enabling the implementation of a heating process for the vacuum pump 1.

[0036] The heating control unit 8 and the central control unit 7 may be part of the same electronic board or may be independent electronic boards. Physically independent units 7 and 8 allow for the standardization of the central control units 7 of the vacuum pumps 1, with the option of adding or not adding a heating module 5.

[0037] The heating control unit 8 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, such as the electrical network voltage, - provide a supply voltage U to the at least heating element 6 by adapting the electrical power of the electrical network by taking into account the value of the parameter representing the voltage of said electrical network Ures measured to reach a predetermined setpoint temperature.

[0038] The electrical network is the distribution network designed to supply the electrical power needed to supply a set of electrical machines, including the vacuum pump 1. By way of illustration, the voltage of the electrical network can be: Country Single-phase Three-phase Japan 100V or 200V 200V or 415V Taiwan 110V 220V or 380V United States of America - Canada 120V or 240V 240V or 480V Mexico 127V 220V Europe - China - South Korea 220V - 240V 380V and 400V

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

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

[0041] In a manner known per se, in the on / off control algorithm, the heating elements 6 are powered when the measured temperature is below the setpoint and the power supply is cut off when the measured temperature is above the setpoint. In the proportional or PID control algorithm, the power supply to the heating elements 6 is increased or decreased according to the difference observed between the 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 Ures (function schematized by block 15 on [Fig.4]), for example by transforming the measured supply voltage into a succession of squares whose duration and / or frequency varies so as to reach the supply voltage U determined by the regulation algorithm.

[0043] The measurement of the representative parameter 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 500msec, so that the supply voltage to be provided to the heating elements 6 can be regularly recalculated and controlled to the temperature measurement of the stator 4.

[0044] Thus, instead of adapting the supply voltage U of the heating elements 6 to regulate the temperature of the stator 4 based on an assumed voltage from the electrical grid, the heating control unit 8 measures a parameter representative of the electrical grid voltage Ures and deduces an appropriate supply voltage U for the heating elements, taking into account the actual value of the electrical grid and therefore any potential voltage drops or surges. The temperature regulation can therefore adapt automatically to fluctuations in the electrical grid voltage. This ensures that the heating elements 6 are correctly supplied and thus that the temperature of the stator 4 can be controlled.

[0045] According to one 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 the determination of the supply voltage U of the heating elements 6 ([Fig.1]).

[0046] The operating information Ifon of the vacuum pump 1 can be the temperature measurement of the stator 4 and / or 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.

[0047] The operating information Ifon of the vacuum pump 1 can be an operating state: normal operation (nominal rotation speed) / stopped / standby (reduced rotation speed). The process can thus modify the setpoint temperature, for example, to switch off the heating if the vacuum pump 1 is stopped or standby, thereby saving energy.

[0048] The heating control can thus be finely achieved according to the operating conditions of the vacuum pump 1.

[0049] According to one embodiment, the heating control unit 8 is further configured to identify the regulation algorithm for said at least one heating element 6 to be applied according to the type of heating element 6 of the vacuum pump 1.

[0050] To identify the regulation algorithm for 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 pre-recorded algorithm base in the central control unit 7 or in the heating control unit 8.

[0051] The type of heating element 6, such as an electrical resistance and / or a radiative or inductive element and / or the nominal supply voltage, can be recorded in the heating control unit 8 and / or can be information provided by the heating elements 6 themselves.

[0052] 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 heating element 6 or in the heating control unit 8, the value of the resistance defining the type of heating element 6.

[0053] Thus, the heating control unit 8 can be an independent module from the central control unit 7, implemented with the heating module 5 in the vacuum pumps 1, regardless of the type of heating elements 6 in the heating module 5. The heating control unit 8 can itself detect the type of heating element 6 installed and select the control algorithm to apply from the algorithm library. The heating control unit 8 can therefore be standardized for any type of heating element 6.

[0054] According to an example of an embodiment illustrated in [Fig.2], the heating module 5 comprises at least one pair of heating elements 6 and an electrical circuit.

[0055] The pair of heating elements 6 comprises a first and a second electrical resistances, the electrical resistances having the same ohmic values.

[0056] 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.

[0057] The controllable switching device 11 includes, 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.

[0058] The heating control unit 8 is configured to control the switching device 11 according to a first switching state ([Fig.2]) or according to a second state switching ([Fig.3]) in order to provide the supply voltage U across the terminals of either the first circuit 9 or the second circuit 10 depending on the voltage of the electrical network Ures.

[0059] The heating control unit 9 is, for example, configured to compare the measured voltage of the electrical network Ures with a switching threshold and to control the switching device 11 according to the result of the comparison. This comparison can be carried out programmatically ("software") or by means of electronic components ("hardware").

[0060] According to an embodiment illustrated in [Fig. 4], the electrical circuit of the heating module 5 includes a comparator 14, one input of which is connected to the electrical network Ures via a step-down converter 16 configured to filter, rectify, and reduce the voltage of the electrical network Ures, and the other input is connected to a reference voltage Us. The output of the comparator 14 is used to control the relays 12a, 12b, and 13 of the switching device 11. The same comparison can be performed programmatically.

[0061] If, for example, the control algorithm associated with the heating element type 6 recommends a low supply voltage such as a single-phase voltage, for example 110V, and the measured mains 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.

[0062] If, on the other hand, the measured mains voltage Ures is equal to the mains voltage specified by the control 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 [Fig. 3], showing the relays 12a and 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.

[0063] Thus, using the same components, the electrical circuit of the heating module 5 can be adapted so that the heating elements 6 are compatible with the voltage of the 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 that can be connected to a wide range of electrical networks. Furthermore, since this operation is automatic, potential connection errors that could damage the heating elements 6 are avoided.

Claims

Demands

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, characterized in that the heating module (5) further comprises a heating control unit (8) 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, - provide a supply voltage (U) to at least one heating element (6) by adapting the electrical power of said electrical network taking into account the value of the parameter representative of the voltage of said electrical network (Ures) measured to reach a predetermined setpoint temperature.

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

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

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

5. Vacuum pump (1) according to any 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 resistance, the electrical resistances 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 switching device

6.

7. (11) controllable, the heating control unit (8) being configured to control the switching device (11) to provide the supply voltage (U) across either the first circuit (9) or the second circuit (10) depending on the voltage of the electrical network (Ures). Vacuum pump (1) according to the preceding claim, characterized in that the heating control unit (8) is configured to drive the switching device (11) to provide the supply voltage (U) across the terminals of either the first circuit (9) or the second circuit (10) depending on the voltage of the electrical network (Ures). Method for controlling the heating of a vacuum pump (1) according to any 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, - provide a supply voltage (U) to at least one heating element (6) by adapting the electrical power of said electrical network taking into account the value of the parameter representative of the voltage of said electrical network (Ures) measured to reach a predetermined setpoint temperature.

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