Vacuum pump for pumping a gaseous medium

Abstract

A vacuum pump for conveying a gaseous medium comprises a pumping system having at least one gas inlet and at least one outlet, a sensing unit configured and designed to detect at least one characteristic parameter of the medium, a determination unit configured and designed to determine a moisture characteristic, which is a measure of the moisture content of the medium, based on the at least one characteristic parameter and / or a time course of the at least one characteristic parameter, and a control unit configured and designed to operate the vacuum pump in a condensation avoidance mode in which at least one operating parameter of the vacuum pump is influenced to increase the vapor capacity of the vacuum pump.

Description

[0001] The invention relates to a vacuum pump for conveying a gaseous medium, a method for operating the vacuum pump and a measuring device for determining the moisture content of a gaseous medium.

[0002] Various types of vacuum pumps are known from the prior art. Examples of vacuum pumps include scroll vacuum pumps and rotary lobe vacuum pumps. Such vacuum pumps are referred to as dry-running vacuum pumps because they do not rely on greases or oils for sealing and / or lubrication.

[0003] A scroll pump is a positive displacement pump that can be used, among other things, as a compressor or a vacuum pump. Scroll pumps are also known as spiral pumps or spiral fluid pumps. Scroll vacuum pumps can be used to create a vacuum in a container connected to the pump's gas inlet.

[0004] The pumping principle underlying a scroll vacuum pump is known from the prior art and is explained below. A pumping stage of a scroll vacuum pump has two nested, for example Archimedean, spiral cylinders, which are also referred to below as spiral elements. Each spiral element consists of a wall that extends axially from a support and has a free end face facing away from the support.

[0005] The spiral elements are interlocked in such a way that they enclose crescent-shaped volumes in sections. One spiral remains stationary, while the other can be moved along a circular path via an eccentric drive.

[0006] The movable spiral thus performs a so-called centrally symmetrical oscillation, which is also referred to as "wobbling." A crescent-shaped volume enclosed between the spiral cylinders moves within the spiral elements during the wobbling of the movable spiral, thereby conveying gas from a radially outer gas inlet to a radially inner gas outlet located in the center of the spiral. To seal the conveying chambers of conventional scroll vacuum pumps, seals (so-called tip seals) are provided on the end faces of the spiral walls.

[0007] In some applications, vacuum pumps are used to convey gaseous media containing a certain amount of moisture, i.e., a certain percentage of water vapor. Key characteristics of vacuum pumps in this context are water vapor tolerance and water vapor capacity, which are defined according to ISO 21360. Water vapor tolerance is defined as the suction pressure up to which pure water vapor can be pumped without the medium condensing inside the pump. Water vapor capacity is the maximum amount of water vapor that can be pumped without the medium condensing inside the pump. Analogous principles apply to other gaseous substances that could condense inside a pump.

[0008] It is an object of the present invention to provide a vacuum pump for a gaseous medium with an increased vapor capacity. The gaseous medium is, for example, pure water vapor or a gas mixture containing water vapor. Besides water, other components are also conceivable that could condense during operation of the pump, so that there is a risk of deposits forming inside the pump and / or parts of the pump being corroded.

[0009] The aforementioned problem is solved according to the invention by a vacuum pump having the features of claim 1 and by a vacuum pump having the features of claim 2.

[0010] A vacuum pump comprises a pumping system that has at least one gas inlet and at least one outlet. The pumping system is understood to be that part of the pump which includes the pumping-active components of the pump.

[0011] The vacuum pump can be a dry-running vacuum pump. For example, the vacuum pump could be a scroll vacuum pump or, preferably, a multi-stage rotary vane vacuum pump. However, other types of dry-running vacuum pumps are also conceivable. Scroll vacuum pumps, for instance, offer the advantage over rotary vane pumps of being particularly energy-efficient. This is primarily because they have a dry pumping system, and the compression of the medium is achieved by a multitude of spiral turns, whereas rotary vane pumps require the circulation and pumping of oil. An IPM (Interior Permanent Magnet) motor is preferably used as the drive element in scroll vacuum pumps. Furthermore, scroll vacuum pumps operate with comparatively low wear. In the case of a scroll vacuum pump, the pumping system includes, for example, a stationary spiral component and a spiral component that is movably arranged relative to the stationary component.

[0012] The vacuum pump further comprises a sensor unit configured and designed to detect at least one characteristic parameter of the medium. In particular, the sensor unit is configured and designed to detect exactly one characteristic parameter of the medium, thereby saving computing resources and reducing the complexity of the pump. However, the sensor unit can also be configured and designed to detect two or more characteristic parameters of the medium, thus providing more data for further analysis.

[0013] The vacuum pump further comprises a determination unit configured and designed to determine a humidity parameter based on at least one characteristic parameter and / or a time-dependent profile of that parameter. The humidity parameter is a measure of the moisture content of the medium, in particular the water vapor content. The time-dependent profile can be constant or variable. The determination unit may include a memory for (temporarily) storing the time-dependent profile.

[0014] In the context of the present invention, the term "moisture" is not limited to the water (vapor) content of the medium. It also includes the content of other (gaseous) substances or components that could condense inside the pump during operation. Examples of such components are acids, bases, alcohols, cleaning agents, or combinations thereof.

[0015] Furthermore, the vacuum pump includes a control unit that is set up and configured to operate the vacuum pump in a condensation avoidance mode in which at least one operating parameter of the vacuum pump is influenced in order to increase a vapor capacity, in particular water vapor capacity, of the vacuum pump.

[0016] The operating parameter is, for example, the operating temperature of the vacuum pump. The control unit can be configured and designed to influence exactly one, two, or more operating parameters of the vacuum pump. For example, the control unit is configured and designed to influence only the operating temperature of the vacuum pump, in particular to increase it.

[0017] The vacuum pump according to the invention therefore has a specially configured operating mode in which the vacuum pump can be operated as needed. In this mode, condensation of the pumped medium within the vacuum pump is avoided and the vapor capacity of the vacuum pump is simultaneously increased.

[0018] Condensation can cause pump components to wear out or corrode more quickly, particularly the tip seals of scroll vacuum pumps, and / or lead to deposits forming on pump components that come into contact with the medium. This negatively impacts the service life of the vacuum pump and increases maintenance costs. Furthermore, condensation can increase the ultimate pressure achievable by the pump. Therefore, preventing condensation can extend the service life of the vacuum pump. Simultaneously, by influencing at least one operating parameter of the vacuum pump, its vapor capacity can be increased. The vacuum pump according to the invention is thus characterized not only by improved pumping characteristics but also by an extended service life.

[0019] The sensing unit, the determination unit, and the control unit can be structurally separate units. However, they can also form a single structural unit, meaning they can be arranged in the same housing. In particular, the sensing unit, the determination unit, and / or the control unit are part of an electronic system or pump controller for controlling the operation of the vacuum pump, which can be an integral part of the vacuum pump itself or structurally separate from it. The sensing unit, the determination unit, and / or the control unit can be implemented as software modules of the pump controller, with the sensing unit potentially including hardware in the form of sensors installed in the pump.

[0020] Another vacuum pump, in particular a dry-running vacuum pump, for pumping a gaseous medium comprises a pumping system having at least one gas inlet and at least one outlet, and a control unit configured and designed to operate the vacuum pump in a condensation avoidance mode in which at least one operating parameter of the vacuum pump, in particular an operating temperature of the vacuum pump and / or a state of a gas ballast valve of the vacuum pump, is influenced in order to increase a vapor capacity of the vacuum pump, wherein the control unit comprises an actuating means by which the vacuum pump can be manually moved into the condensation avoidance mode.

[0021] The vacuum pump can be switched to condensation prevention mode, for example, when operating in normal mode and / or when starting up. This means the vacuum pump can be manually switched to condensation prevention mode and / or started in this mode using the actuator (e.g., if the user knows their application requires it, such as after system maintenance and expecting to pump moist gas). This ensures that no condensate forms in the pump and / or that any condensate that has already formed, for example, during periods of inactivity, is drained away.

[0022] Manually switching the vacuum pump to condensation avoidance mode can be done in response to a warning signal, preferably provided by the control unit, e.g. visual and / or audible, to ensure that the user recognizes the need to initiate the condensation avoidance mode.

[0023] For easy operation, the actuator can include a human-machine interface such as a switch, a button, a touch element, and / or automatic speech recognition. It is also possible to integrate the actuator into the control unit's software, allowing it to be operated manually, for example, via the control unit's graphical user interface (GUI).

[0024] The features of the aforementioned vacuum pumps can be combined as needed. In particular, the first described variant can include, in addition to the detection unit and the determination unit, a manually operated actuator to allow this pump to also be manually switched to condensation prevention mode.

[0025] Further embodiments are specified in the claims, the description and the accompanying drawings.

[0026] According to one embodiment, the operating parameter value of the vacuum pump in condensation avoidance mode differs from the value of the operating parameter in normal operation of the vacuum pump, particularly under otherwise comparable operating conditions. The magnitude of the difference between the values ​​can be kept constant over time and / or varied over time. For example, the value of the operating parameter of the vacuum pump in condensation avoidance mode can be continuously and / or gradually increased and / or decreased, particularly starting from a value of the operating parameter in normal operation of the vacuum pump.

[0027] According to one embodiment, the control unit is configured and designed to put the vacuum pump into condensation prevention mode when the humidity level falls below or exceeds a predetermined threshold. In other words, the control unit can automatically put the vacuum pump into condensation prevention mode, in particular switch it on and / or start it in this mode, which significantly simplifies the operation of the vacuum pump.

[0028] The predetermined threshold can be stored in the vacuum pump's memory, particularly in the control unit. Alternatively, the predetermined threshold can also be stored in a cloud.

[0029] According to one embodiment, the control unit is configured and designed to cyclically switch the vacuum pump into condensation prevention mode in order to remove any accumulated condensate. This can be done automatically or as a precaution, independent of any detected operating parameter of the vacuum pump. This embodiment is particularly advantageous for a vacuum pump that does not have a detection unit or a determination unit.

[0030] The duration of pump operation in condensation prevention mode and / or the cycle frequency can be manually adjusted. It is also possible to factor in the pump's usage type and / or intensity when determining the cycle frequency (e.g., considering load / pump speed). The cycles do not necessarily have to be regular.

[0031] According to one embodiment, the control unit is configured and designed to switch the scroll vacuum pump from condensation prevention mode to normal operating mode when the humidity value determined by the measuring unit no longer falls below or exceeds the predetermined threshold. In particular, the control unit is configured and designed to reduce the operating temperature of the vacuum pump again when the humidity value determined by the measuring unit no longer falls below or exceeds the predetermined threshold.

[0032] According to one embodiment, the control unit is configured and designed to adjust at least one operating parameter of the vacuum pump based on the humidity value. This means the control unit can actively vary the operating parameter.

[0033] According to one embodiment, the control unit is designed and configured to keep at least one operating parameter of the vacuum pump constant over time in condensation avoidance mode or to vary it according to a fixed scheme. It can also be provided that the operating parameter is changed stepwise and / or continuously as required. This allows the (water) vapor capacity of the vacuum pump to be increased even further.

[0034] According to one embodiment, the vacuum pump additionally comprises a measuring unit configured and designed to detect at least one operating parameter of the vacuum pump, wherein the control unit is configured and designed to operate the vacuum pump in condensation avoidance mode based on the humidity characteristic and the operating parameter of the vacuum pump. The operating parameter can be a temperature of the vacuum pump, in particular the temperature of a component of the pump system.

[0035] According to one embodiment, the detection unit comprises at least one pressure measuring device for measuring the pressure of the medium. That is, the characteristic parameter detected by the detection unit is the pressure of the medium. The pressure can be determined directly or indirectly. A measuring device based on an indirect measuring principle is described below.

[0036] According to one embodiment, the detection unit comprises at least one pressure sensor, preferably arranged at the gas inlet, for measuring the intake pressure of the vacuum pump. The determination unit is configured and designed to determine the humidity characteristic based on a temporal profile and / or a magnitude of the intake pressure. That is, the characteristic parameter detected by the detection unit is the intake pressure. An intake pressure that is too high over a certain period (compared, for example, to conditions that would be expected with a "dry" gas / gas mixture of the same composition) can indicate the presence of (water) vapor in the medium. If, for example, the operating temperature of the pump is also particularly low, it can be advantageous to put the vacuum pump into condensation prevention mode.

[0037] According to one embodiment, the detection unit and / or the measuring unit comprises at least one moisture sensor for measuring the moisture content of the medium or of a surface of the vacuum pump, wherein the determination unit is configured and designed to determine the moisture characteristic value based on the measured moisture (the measured moisture may correspond to the moisture characteristic value).

[0038] The methods mentioned for determining the moisture value can be combined as needed.

[0039] According to one embodiment, the vacuum pump further comprises a temperature control device for influencing the operating temperature of the vacuum pump, wherein the control unit is configured and designed to influence the operating temperature of the vacuum pump by controlling the temperature control device, in particular to increase it. This allows the steam capacity of the vacuum pump to be improved in a simple and effective manner, while simultaneously increasing its service life.

[0040] The temperature control device is preferably located at or just before the outlet, as condensation is most likely to occur there. This arrangement therefore makes the temperature control particularly efficient.

[0041] For a particularly compact and robust design, the temperature control device can be integrated into a housing, especially a hood, of the vacuum pump.

[0042] The temperature control device can include or be designed as a fan, preferably with a rotatably mounted propeller to generate an airflow for dissipating heat from the vacuum pump. In the case of a scroll vacuum pump, the propeller's axis of rotation can be arranged coaxially with the stationary spiral component. The fan is preferably selectively controllable to adjust heat dissipation as needed.

[0043] Controlling the temperature control device via the control unit can include reducing the speed of the temperature control device, particularly to 10% to 60%, more specifically 20% to 50%, and more specifically 30% to 40% of its maximum speed. This can, in particular, increase the operating temperature of the vacuum pump by approximately 5°C to 15°C. Surprisingly, this comparatively small temperature change is sufficient to significantly increase the steam capacity of the vacuum pump. Another embodiment provides for the fan to be switched off cyclically, which is particularly easy to implement, especially with relatively inexpensive fans where speed control is not possible.

[0044] Controlling the temperature control device by the control unit can also include switching off the temperature control device to increase the operating temperature of the vacuum pump even faster.

[0045] The temperature control device may be switched off and / or its speed reduced for a limited time to prevent the vacuum pump from overheating and damaging its components. In particular, the control unit may be configured and designed to increase the speed of the temperature control device again and / or to control the temperature control device accordingly when the operating temperature of the vacuum pump exceeds a predetermined threshold.

[0046] Additionally or alternatively, the temperature control device can include or be designed to include at least one heating element and / or at least one heating cartridge to locally increase the operating temperature of the vacuum pump. The fan and the heating element and / or heating cartridge can be combined as needed to achieve optimal control of the pump temperature.

[0047] According to one embodiment, the vacuum pump comprises at least one controllable gas ballast valve, which can be controlled by the control unit. In particular, the control unit is designed and configured to at least partially open and / or close the gas ballast valve as needed in condensation prevention mode to counteract the formation of condensate within the pump. That is, the operating parameter to be controlled is the (open) state of the gas ballast valve. Actuating the gas ballast valve introduces additional dry gas into the pump, which increases its vapor tolerance. Vapor tolerance can also be improved by using a larger amount of gas ballast.

[0048] This concept can be implemented in addition to or as an alternative to influencing another operating parameter (e.g., temperature). This means that the aforementioned concepts for influencing at least one operating parameter of the vacuum pump can be combined as needed.

[0049] The invention further relates to a measuring device for determining the moisture content of a medium, in particular the water vapor content in a gaseous medium, especially for a vacuum pump for conveying a gaseous medium, preferably according to at least one of the previous embodiments.

[0050] The measuring device comprises at least one piezo pressure sensor, in particular at least one piezoelectric pressure sensor and / or at least one piezoresistive pressure sensor, at least one Pirani pressure sensor, and an evaluation unit configured and designed to determine a moisture characteristic value, which is a measure of the moisture content of the medium, in particular a measure of the water vapor content in the medium, based on a difference between a first pressure value measured by the piezo pressure sensor and a second pressure value measured by the Pirani pressure sensor.

[0051] The first pressure value is independent of the humidity or water vapor content of the medium, as it is measured based on the piezoelectric effect. Specifically, the humidity of the medium has no influence on the voltage measured at the piezoelectric crystal of the piezoelectric pressure sensor, which is a measure of the pressure acting on the crystal. The first pressure value therefore serves as a reference value. The second pressure value, however, is dependent on the humidity of the medium, since the heat transfer from the measuring wire of the Pirani pressure sensor to the medium depends not only on the pressure of the medium but also on its composition. The difference between the first and second pressure values ​​is therefore—given a known gas composition—a measure of the humidity of the medium. This method of determining the humidity characteristic is particularly simple and cost-effective.The measuring device can be calibrated for any gas composition to be pumped in a "dry" state. In this case, the first and second pressure readings should not differ significantly from each other.

[0052] The piezo pressure sensor can include at least one piezoelectric pressure sensor and / or at least one piezoresistive pressure sensor.

[0053] When the measuring device is used in a vacuum pump according to the invention, the evaluation unit can be integrated into the determination unit.

[0054] The invention also relates to a method for operating a vacuum pump for conveying a gaseous medium, in particular according to at least one of the previous embodiments.

[0055] The method comprises detecting at least one characteristic parameter of the medium, determining a moisture characteristic value, which is a measure of the moisture content of the medium, in particular a measure of the water vapor content in the medium, based on the at least one characteristic parameter and / or a time course of the at least one characteristic parameter, and operating the vacuum pump in a condensation avoidance mode in which at least one operating parameter of the vacuum pump, in particular the operating temperature of the vacuum pump and / or a state of a gas ballast valve of the vacuum pump, is influenced in order to increase a vapor capacity of the vacuum pump.

[0056] The features of the invention described in relation to the vacuum pumps are transferable to the measuring device and the method.

[0057] The vacuum pumps according to the invention are characterized by an improved service life and an increased steam capacity.

[0058] The invention is described below by way of example with reference to the drawing. The drawing shows: Fig. 1a a cross-sectional view of a scroll vacuum pump, Fig. 1b, 1c enlarged view and detail views of the scroll vacuum pump respectively Fig. 1a , Fig. 2 a side view of the scroll vacuum pump from Fig. 1a , Fig. 3 a representation of part of the pumping system of the scroll vacuum pump of Fig. 1a , Fig. 4 a cross-sectional view of part of the scroll vacuum pump of Fig. 1a , Fig. 5 a block diagram of the electronic equipment of the scroll vacuum pump from Fig. 1a , and Fig. 6 a block diagram of a measuring device for determining the humidity of a gaseous medium. The invention is described below using the example of a scroll vacuum pump. However, the invention is also applicable to other types of preferably dry-running vacuum pumps, for example, rotary lobe vacuum pumps, preferably multi-stage rotary lobe vacuum pumps.

[0059] The in Fig. 1a The scroll vacuum pump shown comprises a pumping system with a stationary scroll element 11 and a movable scroll element 13, which interact effectively during operation. Furthermore, the scroll vacuum pump includes a drive shaft 17 rotating about a rotary axis 15 during operation, with an eccentric section 19 for driving the movable scroll element 13.

[0060] The scroll vacuum pump is equipped with an electric drive motor 21, 23, which serves to rotate the drive shaft 17 about the axis of rotation 15. The electric drive motor comprises a radially inner motor rotor 21 and a radially outer motor stator 23.

[0061] The drive shaft 17 is rotatably mounted on the pump housing 41 at two axially spaced bearing points 25, 27. The front rolling bearing 25 is designed as a fixed bearing, while the rear rolling bearing 27 is designed as a floating bearing.

[0062] One embodiment provides that the two bearing points 25, 27 are located on the side of the drive motor 21, 23 facing the eccentric section 19 of the drive shaft 17. All bearing points 25, 27 are thus located within the pump housing 41 in front of the drive motor 21, 23. The eccentric section 19 is integrally connected to the front end of the drive shaft 17, and the drive motor 21, 23 is located on the rear end of the drive shaft 17.

[0063] The drive motor 21, 23 can be pushed onto the rear end of the drive shaft 17 using this basic structure, which simplifies the assembly and replacement of the drive motor or parts of the drive motor.

[0064] The balancing concept for balancing the rotating system, which includes the drive shaft 17 and the movable spiral component 13, comprises a front balancing weight 29 and a rear balancing weight 31, both attached to the drive shaft 17 by means of a screw 38. The front balancing weight 29 is located in the area of ​​the front end of the drive shaft 17 and the eccentric section 19. The rear balancing weight 31 is located in front of the rear bearing 27 and thus in front of the drive motor 21, 23.

[0065] Optionally, a pressure element 87 is also mounted on the front face of the rear end of the drive shaft 17 ( Fig. 1b ) provided, which is rotationally symmetrical and therefore does not serve as a balancing weight.

[0066] The pressure element 87 and the balancing weight 31 are each connected to the drive shaft 17 by a screw 83. This clamps the motor rotor 21 between the rotationally symmetrical pressure element 87 or the pressure element 31, which also serves as a balancing weight, on the one hand, and a support, this support being formed by a shoulder 17a on the drive shaft 17.

[0067] Furthermore, a sleeve element 33 is provided, which is arranged between the drive shaft 17 and the motor rotor 21. The sleeve element 33 is rotationally fixed to the motor rotor 21, this connection being made by press-fitting. Thus, the pressed-together unit consisting of the motor rotor 21 and the sleeve element 33 can be slid onto the rear end of the drive shaft 17 during assembly. A clearance fit exists between the sleeve element 33 and the drive shaft 17.

[0068] In the area of ​​the aforementioned shoulder 17a, a wave spring 99 is arranged between the sleeve element 33 and the loose bearing 27.

[0069] A pin-shaped positioning element 85 serves as a positioning aid for the pressure element 87 or the balancing weight 31, as an anti-rotation device when tightening the screw 83, and as a circumferentially effective positive-locking connection between the motor rotor 21 or the sleeve element 33 on the one hand and the drive shaft 17 on the other. This positioning pin 85 extends parallel to the axis of rotation 15 of the drive shaft 17 and is arranged at a radial distance from the axis of rotation 15. During assembly, the positioning pin 85 can be inserted axially into a recess formed jointly by the drive shaft 17 on the one hand and the motor rotor 21 or the sleeve element 33, which is non-rotatably connected to the motor rotor 21, on the other. In the assembled state, the positioning pin 85 projects axially to the rear and is received at its rear end in a positioning receptacle located on the side of the pressure element 87 or the sleeve element 33 facing the rear end of the drive shaft 17.31 is designed as a blind hole.

[0070] The clamping of the motor rotor 21 by means of the pressure element 87 or 31 is effected by the pressure element 87 or 31 interacting with the axially rear end of the sleeve element 33 or with the motor rotor 21.

[0071] As an assembly aid when pressing the sleeve element 33 into the motor rotor 21, a radial groove 101 is provided at the front end of the motor rotor 21 in the assembled state, which serves as a marking for the assembler and thus indicates the installation orientation of the motor rotor 21.

[0072] The drive motor is not completely enclosed within the pump housing 41. The motor cover 103 has a receiving space with an axial depth dimensioned such that the rear end of the drive motor, projecting axially backwards from the pump housing 41, is received in this receiving space.

[0073] Furthermore, the motor rotor 21 is provided with axially projecting cooling projections 47 on its rear end face. A special feature is that these cooling projections 47 are arranged only on this rear end face of the motor rotor 21, and the front end face of the motor rotor 21 does not have any such cooling projections. This advantageously saves axial installation space. The cooling projections 47 are designed to act as balancing weights.

[0074] At the front end of the pump housing 41 is the pump system with the stationary spiral component 11 and the movable spiral component 13. The stationary spiral component 11, also referred to as the spiral housing, is screwed onto the front end of the pump housing 41 and is surrounded by a cover 105 also attached to the pump housing 41.

[0075] The housing 105 contains a temperature control device for regulating the operating temperature of the scroll vacuum pump. In one embodiment, the temperature control device is designed as a fan 95. The fan 95 can be operated with a supply voltage of 24V, 48V, or 230V. The operation of the fan 95 is controlled by a control unit 115 of an electronic assembly 45 of the scroll vacuum pump, which will be referred to later in relation to Fig. 5 will be discussed in more detail.

[0076] The movable spiral component 13 is connected to the eccentric section 19 via a flange bearing 91 designed as a rolling bearing. A thrust washer 93 is located axially between the movable spiral component 13 and the eccentric section 19. A shim 94 is located between a circumferential shoulder of the drive shaft 17 at the transition to the eccentric section 19 and the flange bearing 91. Correct circumferential alignment between the stationary spiral component 11 and the pump housing 41 is ensured by a positioning pin 97.

[0077] In Fig. 3 The interaction of the nested spiral walls 49, 69 of the spiral components 11, 13 is shown, which enclose sectionally crescent- or sickle-shaped volumes. During operation of the pump, gas enters via the gas inlet 67, which is in Fig. 3 only indicated with regard to its position, incoming gas flows to the center of the pumping system and via the inlet opening 55 into the outlet channel 59 (cf. Fig. 4 ), when the outlet valve 56 opens at a sufficiently high pressure. The pumped gas passes through the outlet channel 59 to the radial outlet 57 and thus to the outlet flange 78, when - as in Fig. 4 shown - the axial outlet opening 65 is closed by means of a plug 66.

[0078] In an alternative configuration, the radial outlet 57 can be closed and the plug 66 removed to create an axial outlet from the pump system.

[0079] If overpressure develops in the pump system during operation, it can be relieved by the pressure relief valves 61b and 63b to prevent excessive power consumption by the scroll vacuum pump. A special feature of this arrangement is that several – in this case two – bypass channels 61 and 63 are provided, each with exactly one pressure relief valve 61b or 63b respectively (see figure). Fig. 4 This ensures that the scroll vacuum pump has a relatively high pumping speed with comparatively low power consumption.

[0080] The representation in Fig. 2 The figure, which shows a view of the scroll vacuum pump on the hood 105, illustrates the arrangement of an inlet flange 77 and an outlet flange 78. The gas to be pumped enters the pumping system, which comprises the two spiral components 11 and 13, via the inlet flange 77 and is expelled via the outlet flange 78.

[0081] The scroll vacuum pump is equipped with a three-phase asynchronous motor 21, 23 for driving the drive shaft 17. In this embodiment, the diameter of the drive shaft 17 in the area of ​​the sleeve element 33 is 24 mm. The appropriately dimensioned sleeve element 33, pressed onto the motor rotor 21, serves to adapt the diameter of the drive shaft 17 in this area to the inner diameter of the motor rotor 21. However, a single-phase IPM motor (IPM = Internal Permanent Magnet) or a synchronous reluctance motor can also be used as the rotary drive for the drive shaft 17. The choice of drive motor is based on the desired performance, target energy consumption, customer requirements, and application conditions. Such motors, especially IPM motors, are characterized by high efficiency.

[0082] The balancing system comprises, for balancing the rotating system, which in particular includes the drive shaft 17 and the movable spiral component 13 of the pump system, a front balancing weight 29 and a rear balancing weight 31. In the illustrated embodiment, the rear balancing weight 31 is located in front of the rear bearing point 27. The pressure element 87 for clamping the motor rotor 21 is designed to be rotationally symmetrical.

[0083] The two balancing weights 29, 31 are made of the same material, for example, steel. However, the two balancing weights 29, 31 can be made of different materials. According to one aspect of the invention, it is therefore provided that the front balancing weight 29 is made of brass and the rear balancing weight 31 is made of steel.

[0084] The eccentric drive formed by the drive shaft 17 and the eccentric section 19 is located inside the pump housing 41 and is surrounded by a deformable sleeve in the form of a bellows 89. The bellows 89 serves, on the one hand, to seal the eccentric drive against the intake area of ​​the scroll vacuum pump and, on the other hand, to prevent rotation of the movable spiral component 13. For this purpose, the bellows 89 is attached to the side of the movable spiral component 13 facing the drive. The rear end of the bellows 89 is attached to a housing base inside the pump housing 41 by means of screws.

[0085] The pump housing 41 is supported on a base formed by an electronics housing 43 (see figure). Fig. 1a and 1bThe electronic housing 43 comprises a housing part 43a, which is provided on its underside with feet 107 made of rubber, which are received in recesses formed on the underside and are thus recessed.

[0086] The electronics housing 43 contains electronic equipment 45, comprising electronic, electrical, and electromechanical components that serve, among other things, to supply power and control the scroll vacuum pump. The pump housing 41 is screwed to the electronics housing 43.

[0087] The efficient operation of the scroll vacuum pump described above, using an IPM motor and due to the dry pumping system, has the advantage, among others, that the components of the scroll vacuum pump heat up comparatively little during operation. In particular, the pumping system of the scroll vacuum pump remains relatively cool. This, in turn, has the advantage that the wear of the components of the scroll vacuum pump is lower than with other pump types, which has a positive effect on service life and maintenance costs. The same applies to rotary lobe vacuum pumps.

[0088] However, it was recognized that the comparatively low component temperatures become noticeable when moist gaseous media, especially those containing a certain amount of water vapor, are pumped. Moist gases tend to condense on the cool surfaces of the pump. In particular, it was determined that moist media, especially those containing water vapor, preferentially condense on the stationary and / or movable spiral component 11, 13 near the opening 55, particularly in the region of the last two to three spiral turns (see Fig. 3 Condensation can cause parts of the pump to corrode and / or deposits to form, reducing the service life of scroll vacuum pumps.

[0089] Obvious countermeasures to avoid or prevent condensation, such as reducing pump power, negatively impact the steam capacity of scroll vacuum pumps. However, it is desirable for scroll vacuum pumps to have both the longest possible service life and the highest possible (water) steam capacity.

[0090] Surprisingly, it was discovered that the problem described above can be elegantly solved by changing an operating parameter of the pump. Specifically, the parameter is deliberately chosen differently than it would be under conventional, comparable operating conditions. That is, compared to normal operation, a special operating mode (condensation avoidance mode) is selected, in which, for example, the operating temperature and / or the state of a gas ballast valve of the vacuum pump are altered.

[0091] In particular, the operating parameter is modified to increase the temperature of a part of the pumping system in order to reduce the tendency for condensation. Even a relatively small temperature increase can lead to a noticeably increased (water) vapor tolerance and / or (water) vapor capacity.

[0092] Additionally or alternatively, dry gas is introduced into the vacuum pump by actuating a gas ballast valve (see reference numeral 79), which increases vapor tolerance. Vapor tolerance can also be improved by increasing the amount of gas ballast.

[0093] As mentioned at the beginning, (water) vapor compatibility is defined according to ISO 21360. The exhaust gas or outlet temperature of the pump is crucial here. Since the fan in scroll pumps is often located close to the outlet, vapor compatibility can be directly influenced by controlling the fan speed.

[0094] According to one embodiment of the invention, the aforementioned increase in the temperature of the scroll vacuum pump is based on a measured variable or parameter that characterizes the gaseous medium being pumped. This measured variable is, for example, the pressure and / or temperature of the medium, the suction pressure of the scroll vacuum pump, the composition of the medium, the moisture content of the medium, etc. Depending on the application, other parameters can also be included.

[0095] For this purpose, the electronic equipment 45 of the scroll vacuum pump described as an example includes a detection unit 111, a determination unit 113 and a control unit 115 (see Fig. 5 ), whereby the in Fig. 5 The sensor components of the detection unit 111, not shown, are preferably installed inside the scroll vacuum pump, particularly in the area of ​​the outlet 57 or upstream of it, possibly even in such a way that the pressure inside the pump system can be measured. Preferably, the characteristic parameter of the medium inside the pump system is determined (e.g., adjacent to the opening 55), since the condensation problem is usually greatest here.

[0096] The detection unit 111 is configured to determine the aforementioned characteristic parameter of the medium. For measuring the suction pressure of the scroll vacuum pump, the detection unit 111 can, for example, measure at least one pressure, preferably at the gas inlet 67 (see Figure 1). Fig. 3 ) include a pressure sensor (not shown).

[0097] To measure the pressure of the medium, the sensing unit 111 can additionally or alternatively use a piezo pressure sensor to measure a first pressure value that is independent of the medium's moisture content, and at least one Pirani pressure sensor to measure a second pressure value that depends on the medium's moisture content. The piezo pressure sensor is a piezoresistive and / or a piezoelectric pressure sensor.

[0098] The unit of measurement 113 is designed to determine a moisture index based on the difference between the pressure measured by the piezo pressure sensor and the pressure measured by the Pirani pressure sensor. The moisture index is a measure of the moisture content of the medium, specifically the water vapor content.

[0099] Optionally, the determination unit 113 is configured to determine the moisture characteristic based on the assumption that the intake pressure measured by the pressure sensor of the detection unit 111 is consistently high, as this indicates moisture in the aspirated gas / gas mixture. This method of determining the moisture characteristic also takes into account, for example, the operating temperature of the pump and / or the temperature and / or the (molecular) composition of the gas.

[0100] The aforementioned techniques for determining the moisture value can be combined to obtain the most accurate result possible.

[0101] The Piezo pressure sensor 119 and the Pirani pressure sensor 121 can also be part of a system integrated into Fig. 6 schematically depicted measuring device 117 for determining the moisture content of the medium, in particular the water vapor content in the gaseous medium.

[0102] The measuring device 117 also includes an evaluation unit 123, which is set up to determine the humidity characteristic value based on the difference between the pressure value measured by the piezo pressure sensor 119 and the pressure value measured by the Pirani pressure sensor 121.

[0103] In addition, the measuring device 117 includes a communication interface (not shown) for exchanging data with an external device, such as the electronic equipment 45. In particular, the evaluation unit 123 is configured to transmit the moisture value to the control unit 115. This means that the measuring device 117 can perform the functions of the detection and determination units 111 and 113.

[0104] Optionally, the pressure sensor 119 of the measuring device 117 can be used to detect the suction pressure of the pump, so that only one pressure measuring device is required.

[0105] Pressure measurements in the intake area, in the outlet area and / or inside the pump system can also be carried out using separate pressure sensors.

[0106] The control unit 115 can automatically switch the scroll vacuum pump into a condensation prevention mode when the humidity level falls below or exceeds a predetermined threshold. In this mode, the pump's operating temperature is increased by reducing the speed of the fan 95, for example, by 5°C to 15°C. This prevents condensation from forming inside the pump and also increases its steam capacity. It has been found that this relatively small temperature increase is sufficient to increase the steam capacity of the scroll vacuum pump by up to 100%. Simultaneously, the scroll vacuum pump remains cool enough in condensation prevention mode to minimize wear and tear.

[0107] To reliably prevent the scroll vacuum pump from overheating, the control unit 115 is also designed to increase the speed of the fan 95 again if the pump's operating temperature exceeds a predetermined threshold. This counter-control can be implemented as part of the condensation prevention mode, meaning it achieves a compromise between preventing condensation and protecting the pump.

[0108] Furthermore, the control unit 115 is configured to automatically start the scroll vacuum pump in condensation prevention mode, for example, if condensate has formed while the pump was idle. If the vacuum pump does not have the necessary sensors, the condensation mode can also be activated manually by the user.

[0109] Furthermore, the control unit 115 is designed to automatically switch the scroll vacuum pump from condensation prevention mode back to normal operating mode when the humidity value no longer falls below or exceeds the predetermined threshold, or after a certain period of time which experience has shown to be sufficient to remove moist gas from the recipient to be evacuated.

[0110] Additionally, the scroll vacuum pump can be manually switched to condensation prevention mode during normal operation or when switched off. This can be done by activating a human-machine interface on the pump.

[0111] The pump temperature can also be regulated by taking into account an operating parameter of the pump itself.

[0112] For this purpose, the scroll vacuum pump can include a measuring unit (not shown) configured to record at least one operating parameter of the vacuum pump. The control unit 115 is accordingly configured to operate the scroll vacuum pump in condensation avoidance mode not only based on the humidity parameter but also based on the operating parameter of the scroll vacuum pump. This parameter can be a temperature, in particular a temperature of a part of the pump system (e.g., a temperature of component 11 and / or 13).

[0113] The detection unit 111 and / or the measuring unit comprise a moisture sensor (not shown) for measuring the moisture content of the medium or a surface of a part of the scroll vacuum pump's pumping system. The determination unit 113 is configured to determine the moisture characteristic value based on the measured moisture content.

[0114] In the Fig. 1c Sections BB of the scroll vacuum pump area are shown, where a gas ballast valve 79 is located. The gas ballast valve 79 shown on the left is fitted with a sealing cap 81. The gas ballast valve 79 shown on the right, however, has a rotary knob 82 for making adjustments.

[0115] The control unit 115 can be configured to automatically actuate the gas ballast valve 79 in condensation avoidance mode to increase the steam capacity of the scroll vacuum pump. However, it can also be configured to actuate the gas ballast valve 79 manually in condensation avoidance mode.

[0116] Controlling the speed of the fan 95 and operating the gas ballast valve 79 can be done individually or in combination, as required.

[0117] The measures described above, according to the invention, can be implemented – depending on the embodiment – ​​without or with only a few additional components and / or simple design modifications, possibly even just by means of a software update. In some cases, existing systems can even be easily retrofitted. Bezugszeichenliste

[0118] 11 Fixed spiral component, spiral housing 13 Moving spiral component, orbiter 15 Axis of rotation 17 Drive shaft 17a Shoulder 19 Eccentric section 21 Motor rotor 23 Motor stator 25 Front bearing (fixed bearing) 27 Rear bearing (floating bearing) 29 Front balancing weight 31 Rear balancing weight 33 Sleeve element 38 Screw 39 Balancing section of the rear balancing weight 41 Pump housing 43 Electronics housing 45 Electronics assembly 47 Cooling projection 49 Spiral wall of the fixed spiral component 55 Inlet opening 56 Outlet valve 57 Outlet 59 Outlet channel 61 Bypass channel 61a Bypass opening 61b Pressure relief valve 63 Bypass channel 63a Bypass opening 63b Pressure relief valve 63c Opening 65 Axial outlet opening 66 Plug 67 Gas inlet of the pump system 69 Spiral wall of the movable spiral component 77 Inlet flange 78 Outlet flange 79 Gas ballast valve 81 Cover of the gas ballast valve 82 Rotary knob 83 Central screw 85 Positioning elementPositioning pin 87 Pressure element 89 Bellows 91 Flange bearing 93 Pressure washer 94 Shim 95 Fan 97 Positioning pin 99 Wave spring 101 Radial indentation as marker 103 Motor cover 105 Hood 107 Foot 111 Detection unit 113 Determination unit 115 Control unit 117 Measuring device 119 Piezo pressure sensor 121 Pirani pressure sensor 123 Evaluation unit

Claims

1. Vacuum pump, in particular a dry-running vacuum pump, for pumping a gaseous medium, comprising a pumping system having at least one gas inlet (67) and at least one outlet (57), a detection unit (111) configured and designed to detect at least one characteristic parameter of the medium, a determination unit (113) configured and designed to determine a moisture characteristic value, which is a measure of the moisture content of the medium, in particular of the water vapor content in the medium, based on the at least one characteristic parameter and / or a time course of the at least one characteristic parameter, and a control unit (115) configured and designed to operate the vacuum pump in a condensation avoidance mode in which at least one operating parameter of the vacuum pump,in particular an operating temperature of the vacuum pump and / or a state of a gas ballast valve (79) of the vacuum pump, is influenced in order to increase a vapor capacity of the vacuum pump.

2. Vacuum pump, preferably according to claim 1, in particular a dry-running vacuum pump, for pumping a gaseous medium with a pumping system having at least one gas inlet (67) and at least one outlet (57), and a control unit (115) configured and designed to operate the vacuum pump in a condensation avoidance mode in which at least one operating parameter of the vacuum pump, in particular an operating temperature of the vacuum pump and / or a state of a gas ballast valve (79) of the vacuum pump, is influenced in order to increase a vapor capacity of the vacuum pump, wherein the control unit (115) comprises an actuating means with which the vacuum pump can be manually moved into the condensation avoidance mode.

3. Vacuum pump according to claim 1 or 2, wherein a value of the operating parameter of the vacuum pump in condensation avoidance mode differs from a value of the operating parameter in normal operation of the vacuum pump.

4. Vacuum pump according to claim 1 or 3, wherein the control unit (115) is configured and designed to put the vacuum pump into condensation avoidance mode when the humidity parameter falls below or exceeds a predetermined threshold.

5. Vacuum pump according to at least one of claims 1, 3 and 4, wherein the control unit (115) is configured and designed to adjust the at least one operating parameter of the vacuum pump based on the humidity characteristic value.

6. Vacuum pump according to at least one of claims 1 and 3 to 5, wherein the control unit (115) is configured and designed to keep the at least one operating parameter of the vacuum pump constant over time in condensation avoidance mode or to vary it according to a fixed scheme.

7. Vacuum pump according to at least one of the preceding claims, further comprising a measuring unit which is configured and designed to detect at least one operating parameter of the vacuum pump, wherein the control unit (115) is configured and designed to operate the vacuum pump in the condensation avoidance mode based on the humidity characteristic value and the operating parameter of the vacuum pump.

8. Vacuum pump according to at least one of claims 1 and 3 to 7, wherein the sensing unit (111) comprises at least one pressure measuring device for measuring the pressure of the medium.

9. Vacuum pump according to at least one of claims 1 and 3 to 8, wherein the detection unit (111) comprises at least one pressure sensor preferably arranged at the gas inlet (67) for measuring an intake pressure of the vacuum pump, wherein the determination unit (113) is configured and designed to determine the moisture characteristic value based on a time course and / or an amount of the intake pressure.

10. Vacuum pump according to at least one of claims 1 and 3 to 9, wherein the detection unit (111) and / or the measuring unit comprises at least one moisture sensor for measuring the moisture of the medium or of a surface of the vacuum pump, wherein the determination unit (113) is configured and designed to determine the moisture characteristic value based on the measured moisture.

11. Vacuum pump according to at least one of the preceding claims, wherein the vacuum pump further comprises a temperature control device preferably arranged at the outlet (57) for influencing the operating temperature of the vacuum pump, in particular a fan and / or a heating element, wherein the control unit (115) is configured and designed to influence the operating temperature of the vacuum pump by controlling the temperature control device, in particular to increase it.

12. Vacuum pump according to claim 11, wherein controlling the temperature control device comprises reducing the rotational speed of the temperature control device, in particular to 10% to 60%, in particular 20% to 50%, in particular 30% to 40% of the maximum rotational speed of the temperature control device, or preferably switching off the temperature control device for a limited time.

13. Vacuum pump according to at least one of the preceding claims, wherein the vacuum pump comprises at least one controllable gas ballast valve (79) which can be controlled by the control unit (115).

14. Measuring device (117) for determining the humidity, in particular the water vapor content, of a gaseous medium, particularly for a vacuum pump for conveying a gaseous medium, preferably according to at least one of the preceding claims, comprising: at least one piezo pressure sensor (119), in particular at least one piezoelectric pressure sensor and / or at least one piezoresistive pressure sensor, at least one Pirani pressure sensor (121), and an evaluation unit (123) configured and designed to determine a humidity characteristic value, which is a measure of the humidity of the medium, in particular of the water vapor content in the medium, based on a difference between a first pressure value measured by the piezo pressure sensor (119) and a second pressure value measured by the Pirani pressure sensor (121).

15. Method for operating a vacuum pump for conveying a gaseous medium, in particular a vacuum pump for conveying a gaseous medium according to at least one of the preceding claims, the method comprising: detecting at least one characteristic parameter of the medium, determining a moisture characteristic value which is a measure of the moisture content of the medium, in particular of the water vapor content in the medium, based on the at least one characteristic parameter and / or a time course of the at least one characteristic parameter, and operating the vacuum pump in a condensation avoidance mode in which at least one operating parameter of the vacuum pump, in particular an operating temperature of the vacuum pump and / or a state of a gas ballast valve (79) of the vacuum pump, is influenced in order to increase a vapor capacity of the vacuum pump.

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