Scroll vacuum pump and its method of operating

Abstract

Scroll vacuum pump with a pumping system (11, 13) comprising a stationary spiral component (11) and a movable spiral component (13) that interacts with it effectively for pumping, a drive shaft (17) rotating about a rotary axis (15) during operation with an eccentric section (19) for driving the movable spiral component (13), and an electric drive motor (21, 23) for the drive shaft (17), wherein an axial gap dimension is present between the two spiral components (11, 13), and wherein an adjusting means (113) is provided which is designed to adjust the axial gap dimension.

Description

[0001] The invention relates to a scroll vacuum pump with the features of claim 1 and a method for operating a scroll vacuum pump with the features of claim 14.

[0002] The scroll vacuum pump comprises a pumping system that includes a stationary spiral component and a movable spiral component that interacts with it effectively for pumping, a drive shaft that rotates around a rotary axis during operation with an eccentric section for driving the movable spiral component, and an electric drive motor for the drive shaft.

[0003] Scroll vacuum pumps are generally known, e.g. from EP 3 153 708 A2, EP 3 617 511 A2, EP 3 647 599 A2, EP 4 174 285 A1 and EP 4 253 720 A2. Document WO 2021 / 176222 A1, for example, discloses a scroll vacuum pump according to the preamble of claim 1 and a method for operating such a pump according to the preamble of claim 14.

[0004] A scroll pump is a positive displacement pump that compresses against atmospheric pressure and can be used, among other things, as a compressor. A scroll vacuum pump can be used to create a vacuum in a receiver connected to a gas inlet of the scroll vacuum pump.

[0005] Scroll vacuum pumps are also known as spiral vacuum pumps or spiral conveying devices. The pumping principle underlying a scroll vacuum pump is fundamentally known from the prior art and is therefore only briefly explained below.

[0006] Typically, the pumping system of a scroll vacuum pump comprises two nested or interlocked spiral cylinders, for example, Archimedean spirals, which are also simply referred to as spirals. Each spiral cylinder includes at least one spiral wall with a support, in particular a plate-shaped one, provided at one end face of the spiral wall. The outer turns of the spiral cylinder, for example, the two or three outermost turns of the spiral cylinder, can be formed by wall sections that are each at a constant circumferential distance from the center of the spirals. Even though these wall sections are strictly speaking not spiral sections but circular segments, in the context of this disclosure they are considered part of the spiral and referred to as turns of the spiral.

[0007] The spiral cylinders are nested inside each other in such a way that the two spiral cylinders partially enclose crescent- or sickle-shaped volumes (pumping chambers). One of the two spirals is fixed within the pump housing, while the other spiral, along with its support, can be moved along a circular path via the eccentric section of the drive shaft. This is why this spiral, together with its support, is also referred to as the orbiter. This movable spiral component thus performs a so-called centrally symmetrical oscillation, which is also known as "orbiting" or "wobbling."A crescent-shaped volume (pumping chamber) enclosed between the spiral cylinders moves increasingly inwards during the orbiting of the movable spiral component within the spirals, whereby the process gas to be pumped is conveyed by means of the moving volume from a radially outer gas inlet of the pumping system to a radially inner gas outlet of the pumping system, which is located in particular in the center of the spiral.

[0008] The eccentric drive, i.e., the drive shaft with the eccentric section, is located inside the scroll vacuum pump housing on the side of the support facing away from the orbiter's spiral. In practice, it is usually surrounded by a deformable sleeve, such as a bellows. This sleeve serves both to seal the drive against the intake area and to prevent the orbiter from rotating, as it could otherwise spin freely without this anti-rotation device. To ensure this anti-rotation, the deformable sleeve can be connected to the support at one end, while the other end, opposite the first, can be screwed to a base inside the housing using several fasteners. The deformable sleeve (e.g., bellows) is permanently sealed, thus preventing leakage from the pump housing and the moving spiral component.

[0009] The assembly comprising the orbiter and the deformable sleeve (e.g., bellows) can be pre-assembled during pump assembly, allowing it to be inserted into the pump housing as a single unit. The second end of the deformable sleeve can then be screwed to the housing base using the provided fasteners. Typically, the spiral walls of the moving spiral component and the spiral walls of the stationary spiral component are each equipped with a separate sealing element on their end face facing away from the support. In the field of scroll vacuum pumps, this is also known as a TipSeal. These TipSeals, usually made of plastic, ensure the sealing of the volumes enclosed by the spiral walls and are therefore crucial for the vacuum performance of a scroll vacuum pump.

[0010] TipSeals also have disadvantages. They have a limited lifespan and therefore need to be replaced regularly, which increases the maintenance required for scroll vacuum pumps. TipSeals also generate abrasion. Furthermore, they are sensitive to certain external influences, such as radioactive radiation, to which scroll vacuum pumps may be exposed in certain applications.

[0011] Scroll vacuum pumps without TipSeals on the scroll walls are known, but require extremely precise relative positioning between the stationary and moving scroll components to achieve a precisely defined axial gap – relative to the axis of rotation – between the end faces of the scroll walls of one component and the so-called groove base or scroll base (hereinafter referred to simply as the scroll base), i.e., the side facing the support of the other scroll component. To understand the dimensions involved, it's important to realize that an axial gap in the range of 10 to 30 µm is necessary for acceptable vacuum performance, and even slightly larger axial gaps, by just a few micrometers, can result in a significant deterioration in vacuum performance. Furthermore, it should be noted that the two axial gaps can be the same or different.The axial gap between the spiral wall end faces of the orbiter and the groove base of the spiral casing on the one hand, and the axial gap between the spiral wall end faces of the spiral casing and the groove base of the orbiter on the other hand, can either be the same or different from each other.

[0012] An exact axial gap dimension plays a rather subordinate role in scroll vacuum pumps with TipSeals, since tolerances regarding the relative position between the two spiral components can be compensated for to a certain extent by the TipSeals.

[0013] For the sake of a uniform definition, within the scope of the present disclosure, the axial gap dimension is understood to be the gap dimension between the end face of a respective spiral wall of one spiral component and the groove base of the other spiral component, even if the spiral wall is provided with a sealing element (TipSeal), i.e. in this case, the axial gap dimension is understood not as the gap dimension with respect to the end face of the sealing element, but also with respect to the end face of the spiral wall provided with the sealing element.

[0014] Scroll vacuum pumps without TipSeals and with sufficiently high vacuum performance would be advantageous not only because of the reduced maintenance effort, the absence of abrasion, and their insensitivity to certain external influences, but would also lead to a constant vacuum performance of the scroll vacuum pump over time, since without TipSeals there would be no components that significantly influence the vacuum performance but are also subject to wear.

[0015] Scroll vacuum pumps without TipSeals could therefore also be used in applications of practical interest where the focus is not so much on a particularly high vacuum performance, but rather on a vacuum performance that is as constant as possible over time.

[0016] Against this background, it becomes clear that scroll vacuum pumps without TipSeals and with a precisely defined axial gap dimension could open up new markets.

[0017] The object of the invention is to improve scroll vacuum pumps of the type mentioned above in such a way that an exact axial gap dimension is given.

[0018] This problem is solved according to a seventh aspect of the present disclosure by the features of the characterizing part of claim 1 and according to an eighth aspect of the present disclosure by the features of the characterizing part of claim 14.

[0019] The aspects of this disclosure revealed below may be combined with one another in any way, provided they do not contradict each other. These aspects are those defined in the claims and those not claimed independently, as well as their further developments specified in the following description (including the description of the figures), which are also referred to as embodiments, exemplary embodiments, or examples. Further developments of one aspect may be combined with other aspects and their further developments in any way, provided this does not lead to contradictions.

[0020] According to the seventh aspect of the present disclosure, in a scroll vacuum pump of the type mentioned at the outset, an adjusting means is provided which is configured to adjust an axial gap dimension present between the two spiral components, by the adjusting means being configured to actively or passively influence a thermal expansion occurring during pump operation of at least one component, and / or by the adjusting means being configured to influence the heat transfer within the pump.

[0021] In the context of this disclosure, heat transport also includes thermal radiation, i.e., the absorption or removal of heat by thermal radiation.

[0022] If the thermal expansion of a component is influenced, then that component forms part of the actuating device. If heat transfer is influenced, then the device(s) by which this influence is effected form part of the actuating device.

[0023] The component whose thermal expansion can be influenced is, for example, a component that directly or indirectly affects the axial position of the movable spiral component. This component can be, for example, the pump housing, the drive shaft, a rolling bearing, an inner ring of a rolling bearing, an outer ring of a rolling bearing, a bearing sleeve, or an adapter sleeve. Within the scope of this disclosure, an adapter sleeve is a sleeve-shaped section in the pump housing or on or in the drive shaft, e.g., a section containing one or more bearings, or a section on the drive shaft.

[0024] According to some embodiments, the adjusting means may include the provision that at least one section of the component is made of a material with a thermal conductivity greater than 100 W / mK. In particular, a material other than steel may be used. Alternatively or additionally, the component may include at least a first section and at least a second section, wherein the adjusting means includes the provision that the two sections are made of materials with different thermal conductivities. The aforementioned material, or the material with the higher thermal conductivity, may, for example, be aluminum bronze.

[0025] According to some embodiments, the component may comprise at least a first section and at least a second section, wherein the actuating means comprises the two sections having different coefficients of thermal expansion. In particular, it may be provided that one of the sections has a negative coefficient of thermal expansion.

[0026] Because sections of the component differ in their coefficient of thermal expansion, thermal expansion of the component during pump operation can be at least partially compensated. Since all properties of a scroll vacuum pump component are generally known, the thermal behavior of the component during pump operation is also generally known, i.e., predictable, so that thermal expansion of the component can be predicted and consequently at least partially compensated by a targeted material pairing.

[0027] According to some embodiments, the actuating means may include a heating device and / or a cooling device designed to directly or indirectly subject at least one area of ​​the component to thermal stress.

[0028] For example, one or more so-called "heat pipes" (also known as heat tubes) can be used as heating or cooling devices to selectively supply or remove heat to a specific location. Such "heat pipes" are fundamentally familiar to those skilled in the art from many technical fields.

[0029] According to some embodiments, the actuating device can include a motor control unit for the drive motor, wherein the motor control unit is configured to influence the efficiency of the drive motor by changing the current flow in order to thermally stress the drive shaft. In particular, it can be provided that the change in the current flow to the drive motor is achieved by deviating from a sinusoidal waveform, thereby increasing losses and thus heat generation.

[0030] According to some embodiments, the actuator may include one or more temperature sensors. The temperature sensor(s) can be used in a control system to regulate the heating and / or cooling system.

[0031] According to some embodiments, the actuating device can be designed to control the drive motor and a motor fan in such a way that the drive motor is operated in a loss mode leading to excessive heat generation and the influence of the heat generation on the component is specifically controlled by the motor fan.

[0032] In this concept, the drive motor is operated in a deliberately "energy-inefficient" manner, so that waste heat is generated which would not be generated in a normal, i.e., energy-efficient, operation, whereby the transport of this heat within the pump can be specifically influenced by appropriate control of the motor fan, in particular the component can be subjected to more or less heat.

[0033] According to some embodiments, the component may comprise at least a first section and at least a second section, wherein the adjusting means comprises that one of the two sections or the entire component has a surface having a thermal emissivity ε of at least 0.25, preferably at least 0.3, at 50°C. Alternatively or additionally, the adjusting means comprises that the surface of the component is at least partially provided with a coating having a higher thermal emissivity ε than the uncoated component.Alternatively or additionally, the adjusting means comprises that the surface of the component is at least partially treated by oxidation, the component comprises a metallic material containing at least one metallic element, and the treated portion of the surface includes an outer layer comprising a compound of the metallic element formed by the oxidation treatment. In particular, it may be provided that the treated portion of the surface has a coloration, wherein the compound of the metallic element is colored and / or the outer layer contains a dye, preferably the coloration being a blackening.

[0034] These embodiments each achieve an improvement in the heat dissipation from the component in question, which occurs through thermal radiation.

[0035] According to some embodiments, the actuating means may include a volume bounded by the component that is at least partially filled with a medium.

[0036] The choice of medium allows for targeted control of heat transfer between the component and its environment. The component could, for example, be a bellows positioned between the moving spiral element and a pump housing. As mentioned elsewhere, a bellows is a well-known component of a scroll vacuum pump. Alternatively, the component could be rigid and contain one or more cavities filled with the medium. These cavities could be filled with different media. The component could, for example, be the drive shaft.

[0037] The medium can be, for example, a gas or a liquid that exhibits a comparatively high thermal conductivity. The gas is particularly suitable if it has long-chain molecules and / or a relatively high number of thermodynamic degrees of freedom. Tetrafluoromethane, for example, can serve as the gas. The liquid is, for example, water or an oil, especially a relatively low-viscosity oil.

[0038] According to some embodiments, the actuating means can include a fan device that is attached to or formed on a component that rotates during pump operation. In particular, the rotating component is the drive shaft.

[0039] In this way, the rotating component acts as a fan, which can be used to specifically influence the heat transfer within the pump.

[0040] According to some embodiments, the actuating means can comprise an actuating device and one or more air guide elements (e.g., flaps) that can be adjusted by means of the actuating device. Such air guide elements can, for example, be arranged in a hood attached to a pump housing, which surrounds the stationary spiral component also attached to the pump housing and in which a fan is housed. By means of such elements, the intensity and direction of the airflow, e.g., a cooling airflow generated by the aforementioned fan, can be influenced. This allows the temperature balance of the scroll vacuum pump to be specifically controlled. The heat transfer within the pump can be influenced by such elements, and / or the thermal expansion of at least one component occurring during pump operation can be actively or passively controlled by such elements.

[0041] The eighth aspect of the present disclosure relates to a method according to the invention for operating a scroll vacuum pump with a pumping system comprising a stationary spiral component and a movable spiral component that interacts with it effectively in a pumping manner, a drive shaft rotating about a rotary axis during operation with an eccentric section for driving the movable spiral component, and an electric drive motor for the drive shaft, wherein the method comprises adjusting an axial gap dimension existing between the two spiral components by directly or indirectly subjecting one component to thermal stress at least in certain areas, and / or by influencing the heat transfer within the pump.

[0042] In connection with this aspect of the present disclosure, heat transport also includes thermal radiation, i.e., the absorption or removal of heat by thermal radiation.

[0043] As also explained above in connection with the seventh aspect of the present disclosure, the component whose thermal expansion is affected can be a component that directly or indirectly influences the axial position of the movable spiral component. The component can therefore be, for example, a pump housing, the drive shaft, a rolling bearing, an inner or outer ring of a rolling bearing, a bearing sleeve, or an adapter sleeve.

[0044] By applying thermal stress or influencing heat transfer, the thermal expansion of the component that occurs during pump operation can be actively controlled. This allows the force with which the component directly or indirectly acts on the movable spiral component to be changed, thereby adjusting the axial gap dimension accordingly.

[0045] According to some embodiments, the drive shaft can be thermally stressed by influencing the efficiency of the drive motor through changes in its current supply. As also explained in connection with the seventh aspect of this disclosure, the current supply to the drive motor can be changed by deviating from a sinusoidal waveform, thereby increasing losses and thus heat generation. With this concept, a motor controller can therefore be used to adjust the axial gap dimension.

[0046] Alternatively or additionally, further eddy current losses can be induced, especially by additional harmonic components.

[0047] For all aspects of the present disclosure explained above, i.e., both for a scroll vacuum pump according to the invention and for a method according to the invention, it can be provided according to some exemplary embodiments that the actuating means comprises at least one pressure sensor, wherein the actuating means is configured to adjust the axial gap dimension as a function of at least one pressure measured by means of the pressure sensor. This can be done in particular within the framework of a control system. The measured pressure can, for example, be the pressure in a suction area of ​​the scroll vacuum pump.

[0048] Unless expressly mentioned otherwise, in each of the disclosed aspects the scroll vacuum pump may include a control device configured to perform the functions required for the respective axial gap adjustment concept, and which may be integrated into a control device controlling the actual pumping operation of the scroll vacuum pump or provided separately, but then configured to communicate with the control device controlling the pumping operation.

[0049] According to a first aspect of the present disclosure which is not independently claimed, an axial gap dimension is present between the two spiral components, wherein an adjusting means is provided which is designed to adjust the axial gap dimension.

[0050] The adjusting device makes it possible to precisely define the axial gap dimension, i.e., the axial distance between the end faces of the spiral walls and the respective spiral base, relative to the axis of rotation of the drive shaft rotating during operation.

[0051] As mentioned in the introduction, the stationary spiral component is also called the spiral casing and the movable spiral component is also called the orbiter.

[0052] Setting the axial gap also includes maintaining the axial gap at a setpoint, which may be specified by the scroll pump manufacturer for a particular application or can be set by the user. Such maintenance of the axial gap may involve changes to the axial gap if, during pump operation, deviations from the setpoint occur due to thermal influences or other reasons, necessitating a change.

[0053] "Adjusting" the axial gap dimension also includes "changing" the axial gap dimension in the sense of altering a target value. Such a change may be necessary, for example, if different axial gap sizes are required for different operating conditions or applications.

[0054] The "adjustment" of the axial gap dimension also includes measures that allow one or both of the spiral components to adjust themselves—and thus the relative position between the two spiral components—for example, in the sense of "alignment," particularly after a break-in period for the scroll vacuum pump. When the present disclosure refers to a break-in period, e.g., in the sense of a grinding-in, this refers to the grinding-in of sealing elements (tip seals) located on the end faces of the spiral walls, even if the presence of sealing elements is not explicitly mentioned in the respective context.

[0055] The term "control device" is to be understood broadly and can also include a "passive" measure, for example a specific material pairing, a special coefficient of thermal expansion or a special thermal emissivity on a component or on a section of a component of the scroll vacuum pump or a combination of different coefficients of thermal expansion or special thermal emissivities.

[0056] An "active" actuator can, for example, comprise an arrangement with at least one component or assembly and an associated control system. By appropriately controlling the component or assembly, a desired actuation effect can be achieved.

[0057] In some examples, the adjusting device may be designed to set the axial gap dimension outside of pump operation. The axial gap dimension can, for example, be set once during the installation of the scroll vacuum pump. This is also referred to as the initial axial gap setting. Alternatively or additionally, the adjusting device may be designed so that the axial gap dimension can be set in certain situations, such as during maintenance of the scroll vacuum pump or when preparing for a new application. The axial gap dimension can be set manually, for example.

[0058] In some examples, the actuating device may be designed to adjust the axial gap dimension during pump operation.

[0059] The settings can be adjusted manually, for example.

[0060] In other examples, adjustment can be achieved within a control system. In such a system, the axial gap is the controlled variable, its value continuously measured as the actual value and compared to a target value – which may depend on one or more parameters. The manipulated variable for influencing the axial gap can vary. For example, the speed of a fan can serve as the manipulated variable, influencing the heat transfer within the pump so that more or less heat reaches a specific component or section of a component. The thermal expansion of this component is to be influenced by the fan in order to mechanically actuate the moving spiral component accordingly and thus adjust the axial gap.

[0061] The control example explained above is intended only to illustrate how the axial gap dimension can be adjusted within a control system during pump operation.

[0062] If the actuating device is appropriately designed, manual adjustment is also possible during pump operation. "Manual" in this context includes operating or adjusting any type of actuator, whether by hand or with a tool.

[0063] According to some examples, the actuating device may be designed to actuate one of the two spiral components, in particular the movable spiral component, or both spiral components. This actuation is effected primarily mechanically. The mechanical actuation can be direct or indirect, whereby indirect mechanical actuation means that the spiral component in question is actuated via another component.

[0064] In other words, applying pressure is an active measure for adjusting the axial gap dimension. This is in contrast to a passive measure, such as selecting materials with different coefficients of thermal expansion.

[0065] Applying force to one of the two spiral components, particularly mechanical force and especially mechanical force to the movable spiral component, can exploit the fact that the mounting of the movable spiral component on the eccentric section of the drive shaft allows a certain slight axial movement. The movable spiral component can be mounted, for example, by a rolling bearing. In particular, a so-called flange bearing is used to mount the movable spiral component on the eccentric section of the drive shaft. Alternatively, separate ball bearings can be used for mounting.

[0066] According to some examples, the actuating means may be designed to act on the spiral component or both spiral components at one point, in particular on the axis of rotation, and / or at several points, in particular distributed around the axis of rotation.

[0067] According to further examples, the adjusting device can be designed to influence the axial relative position between the two spiral components with respect to the axis of rotation.

[0068] Furthermore, according to some examples, the adjusting means can be designed to move one of the two spiral components, in particular the movable spiral component, or both spiral components in the axial direction or to tilt them with respect to the axis of rotation.

[0069] According to some examples, a measuring device may be provided that is designed to measure the axial gap dimension at one or more points. The measurement of the axial gap dimension can, in particular, be carried out continuously during pump operation.

[0070] For example, the axial gap dimension can be measured directly by determining the size of the respective axial gap between an end face of a spiral wall of one spiral component and the base, i.e., the spiral root, of the other spiral component. Alternatively, the axial gap dimension can be measured indirectly by determining a value of another quantity that can serve as the axial gap dimension, e.g., a value for the axial distance between a pump housing and a section, e.g., the base, i.e., the spiral root, of the moving spiral component or the rear of the support of the moving spiral component.

[0071] Measuring the axial gap involves more than just determining a single value. Multiple values ​​can be measured at different locations, allowing for the detection and quantitative determination of any misalignment of one or both of the spiral components. In other words, measuring the axial gap also includes measuring the misalignment of one or both spiral components. Misalignment refers to a position of the respective spiral component in which its central axis, and thus its spiral walls, are not exactly parallel to the axis of rotation of the drive shaft.

[0072] The measuring device can include at least one non-contact distance sensor, for example, an eddy current sensor. Such a distance sensor can be a component of an actuating device, e.g., an active magnetic bearing.

[0073] As mentioned at the outset, the invention is particularly advantageous for scroll vacuum pumps without TipSeals. Accordingly, according to some examples, the spiral walls of the movable spiral component and the spiral walls of the stationary spiral component each have no separate sealing element, i.e., no TipSeals, on their end face facing away from the spiral base.

[0074] The ability to adjust the axial gap between the two scroll components can also be advantageous even when TipSeals are present. Accordingly, in some designs, the scroll walls of the moving scroll component and the scroll walls of the stationary scroll component may each be provided with a separate sealing element on their end face facing away from the scroll base. Adjusting the axial gap in a scroll vacuum pump with TipSeals can be beneficial, for example, to ensure reduced or more uniform wear of the TipSeals. Adjusting the axial gap can also involve aligning the scroll components to correct, for example, misalignment or runout. This, too, is advantageous in terms of reducing or ensuring more uniform wear of the TipSeals.

[0075] In some examples of the present disclosure, hybrid configurations are also possible, i.e., it may be provided that the spiral walls of one spiral component do not have a separate sealing element on their end face facing away from the spiral base, and that the spiral walls of the other spiral component are provided with a separate sealing element on their end face facing away from the spiral base. Both configurations are conceivable, i.e., the stationary spiral component may be provided with TipSeals while the movable spiral component does not, or vice versa.

[0076] A second aspect of the present disclosure, not claimed independently, relates to a method for operating a scroll vacuum pump with a pumping system comprising a stationary scroll component and a movable scroll component that interacts with it in a pumping capacity, a drive shaft rotating about a rotary axis during operation with an eccentric section for driving the movable scroll component, and an electric drive motor for the drive shaft, wherein the method comprises adjusting an axial gap dimension existing between the two scroll components.

[0077] Adjusting the axial gap dimension, including "holding" and "changing" as explained above, can be done during pump operation, particularly within the framework of a control system, for example as explained above.

[0078] Operating the scroll vacuum pump also includes its commissioning or the commissioning of a vacuum system comprising the scroll vacuum pump, such as a pump stand; i.e., operating the pump also includes adjusting the axial gap dimension outside of pump operation, for example once during pump installation and / or in certain situations such as during maintenance or when preparing for a new application.

[0079] According to some examples of the first and second aspects, it can be provided that an axial offset exists between the motor rotor and the motor stator of the drive motor such that an axially acting force is generated on the motor rotor during operation of the drive motor, wherein the drive shaft is coupled to the motor rotor in such a way that the axial force is transmitted to the drive shaft, and wherein a control for the drive motor is provided with which the drive motor can be controlled in such a way that the magnitude of the axial force changes.

[0080] This arrangement with the axial offset between the motor rotor and motor stator of the drive motor and with the control designed to change the axial force represents a further development of the first aspect (scroll vacuum pump), while this way of controlling the drive motor to change the axial force represents a further development of the second aspect (method).

[0081] By appropriately controlling the drive motor, which in particular includes appropriate current supply, the force acting in the axial direction on the drive shaft and thus a force which the drive shaft exerts on the movable spiral component can be specifically adjusted in order to adjust the axial gap dimension in the desired way.

[0082] This concept of generating an axial force is known in itself in connection with a drive motor of a scroll vacuum pump (EP 3 153 708 A1), but not the use of this concept for setting an axial gap dimension.

[0083] According to a third aspect of the present disclosure which is not independently claimed, a scroll vacuum pump of the type mentioned at the outset is provided to include an adjusting means which is configured to adjust an axial gap dimension existing between the two spiral components, by comprising at least one active magnetic bearing for the movable spiral component.

[0084] An active magnetic bearing is a magnetic bearing in which a variable bearing force can be generated by means of controlled electromagnets.

[0085] The magnetic bearing can, for example, be located on the back side of the movable spiral component. The back side is understood to be the side facing away from the stationary spiral component.

[0086] The magnetic bearing can include a sensor, in particular an eddy current sensor, with which the axial gap dimension can be measured. The sensor can be designed or arranged such that the axial gap dimension can be measured either directly or indirectly by determining a value of another quantity that can serve as the axial gap dimension, for example, a value for the axial distance between a pump housing and a section of the moving spiral component.

[0087] According to a fourth aspect of the present disclosure which is not independently claimed, a scroll vacuum pump of the type mentioned at the outset includes an adjusting means which is configured to adjust an axial gap dimension existing between the two spiral components by providing a bellows arranged between the movable spiral component and a pump housing, and by the adjusting means being configured to vary the pressure within the bellows.

[0088] As explained above, a bellows is a known component of a scroll vacuum pump. In this aspect of the present disclosure, the bellows forms part of the actuating means.

[0089] By varying the pressure within the bellows, the movable spiral component is subjected to a greater or lesser degree of mechanical stress. As mentioned elsewhere, this allows for the exploitation of the fact that the mounting of the movable spiral component, for example by means of a flange bearing designed as a rolling bearing, permits a slight movement of the movable spiral component in the axial direction.

[0090] The actuating device can comprise at least one pressure sensor and a valve assembly on the bellows. The pressure sensor can serve to measure the pressure within the bellows and / or within the pump housing. In particular, the pressure measurement is performed by means of the pressure sensor in a suction area of ​​the scroll vacuum pump. The valve assembly can, for example, comprise a solenoid valve. Varying the pressure within the bellows can be achieved, for example, by placing the valve assembly in a connection between a suction area of ​​the scroll vacuum pump and the bellows, or in a connection between a point of the pump's active structure, in particular between the spiral walls of the spiral components, and the bellows.

[0091] If the pressure measurement is carried out using the pressure sensor in the suction area of ​​the scroll vacuum pump, then this is done in particular in the area of ​​the pump housing outside the bellows or in a suction area of ​​the pump housing or in a suction area of ​​the stationary spiral component.

[0092] According to a fifth aspect of the present disclosure, which is not independently claimed, a scroll vacuum pump of the type mentioned at the outset comprises an adjusting means configured to adjust an axial gap dimension existing between the two spiral components by configuring the adjusting means to vary a preload of the drive shaft, a rotary bearing of the drive shaft or a bearing sleeve of the drive shaft.

[0093] The respective means that creates the preload forms a component of the adjusting device.

[0094] According to some examples, the actuating device may include a length-variable assembly supported on an abutment, in particular a rotor of the drive motor, and designed to mechanically actuate the drive shaft directly or indirectly in the axial direction with respect to the axis of rotation. This actuation may, for example, be effected via a rotary bearing of the drive shaft.

[0095] In these examples, it is therefore possible to change the axial extension of the length-changing device relative to the axis of rotation. The length-changing device could be, for example, a spring assembly, such as a wave spring, an elastic element that can be acted upon by a fluid, or an element made at least partially of a bimetal.

[0096] According to a sixth aspect of the present disclosure, which is not independently claimed, a scroll vacuum pump of the type mentioned at the outset is provided with an adjusting means which is configured to adjust an axial gap dimension existing between the two spiral components, by the adjusting means comprising at least one actuator, preferably a piezo actuator, which is configured to act mechanically on the stationary spiral component or the movable spiral component directly or indirectly in the axial direction with respect to the axis of rotation.

[0097] In particular, it may be provided that the actuator is arranged between the two spiral components, between the stationary spiral component and a pump housing, between the movable spiral component and a pump housing, or between a support and the drive shaft or a component connected to the drive shaft.

[0098] With such an actuator, it is possible to mechanically actuate the stationary spiral component or the movable spiral component in order to set a desired axial gap dimension by utilizing a certain slight axial mobility of the movable spiral component.

[0099] According to some examples, the positioning device may comprise several actuators distributed around the axis of rotation. These actuators may be evenly distributed around the axis of rotation. For example, three actuators may be provided, each spaced angularly apart by 120°.

[0100] By controlling the actuators differently, the movable spiral component can be tilted relative to its axis of rotation, provided that the bearing of the movable spiral component and the points where the actuators act directly or indirectly on the movable spiral component fundamentally permit such tilting. This can, for example, compensate for misalignment or runout of the spiral components due to tolerances.

[0101] Using a control unit of the scroll vacuum pump, these actuators can be controlled either together or independently of each other in such a way that the axial distance between the pump housing and the scroll housing can be changed, and thus the axial gap between the scroll housing and the orbiter can be adjusted. Misalignment of the scroll housing relative to a pump housing can also be corrected by controlling the circumferentially distributed actuators accordingly.

[0102] According to a ninth aspect of the present disclosure which is not independently claimed, a scroll vacuum pump of the type mentioned at the outset is provided by an adjusting means which is configured to adjust an axial gap dimension existing between the two spiral components by having the adjusting means configured to manually adjust the axial gap dimension.

[0103] Manual adjustment of the axial gap dimension can be performed outside of pump operation as part of an initial axial gap adjustment. Alternatively or additionally, the adjusting device can be designed to allow manual adjustment of the axial gap dimension during pump operation.

[0104] According to some examples, the actuating means can include at least one actuating element that can be operated by means of a tool and is arranged between the two spiral components and / or between the stationary spiral component and a pump housing and / or between the movable spiral component and a pump housing.

[0105] The actuating element can, for example, be a threaded pin located between the spiral casing and the pump housing. Several threaded pins can be arranged distributed around the circumference.

[0106] Such threaded pins can also be operated during pump operation.

[0107] The adjusting device can comprise a clamping system that is manually adjustable between a released state and a clamped state, wherein in the released state of the clamping system the stationary spiral component can be brought into a predetermined or predeterminable target position relative to the movable spiral component by adjusting it relative to the clamping system, and wherein the target position of the stationary spiral component can be fixed by adjusting the clamping system into the clamped state.

[0108] A support for the stationary spiral component can be provided either additionally or as a component of the clamping system, wherein, in the released state of the clamping system, the stationary spiral component can be brought into the desired position by adjusting it relative to the support.

[0109] The clamping system's functionality can be based, for example, on the principle of a collet chuck in a tool holder. Accordingly, several flexible or elastically deflectable ring segments can be provided, arranged circumferentially. By means of an annular clamping element, which has a clamping surface (e.g., conical), the ring segments can be moved in such a way that the stationary spiral component is clamped by the ring segments together and thus fixed in the desired position.

[0110] The ring segments can together form a support, as mentioned above, for the stationary spiral component.

[0111] With such a clamping system it is also possible to compensate for misalignments, i.e. to correct misalignments of the stationary spiral component relative to a pump housing.

[0112] According to some examples, the adjusting device can comprise an adjusting screw extending through a channel formed in the drive shaft, wherein the adjusting screw can be actuated at its rear end section by means of a tool and, with its front end section, directly or indirectly acts upon the movable spiral component. This actuation can, for example, be effected via an elastically deformable component. This component could, for example, be a spring-loaded pressure plate.

[0113] This concept also takes advantage of the fact that the bearing of the movable spiral component, which is provided, for example, by a flange bearing designed as a rolling bearing, allows a certain slight axial movement.

[0114] In this case, and in other concepts that utilize a certain slight axial movement in the bearing of the movable spiral component, it is advantageous if this bearing has sufficient clearance. To ensure this clearance, the bearing can be elastically supported – for example, by means of spring elements – against another component. This other component could be, for example, the drive shaft or a pump housing.

[0115] According to some examples, a gas bearing, particularly an axial one, can be provided, which may in particular be an air bearing. The gas bearing can, for example, be arranged on the back side of the movable spiral component. The gas bearing can be implemented by narrow gaps between the components involved, in conjunction with a pressurized gaseous medium, e.g., air. By varying the gas pressure of the gas bearing, the positioning of at least one of the components involved, and thus at least indirectly the movable spiral component, can be achieved, thereby adjusting the axial gap dimension.

[0116] This gas bearing can be designed to be connected to a section within the scroll vacuum pump that operates at a specific pressure level required for the gas bearing. Different pressure levels exist within a scroll vacuum pump and are therefore available and can be used, for example, for the aforementioned gas bearing. It can be arranged that the gas bearing is specifically connected to a particular pressure zone and thus brought to the pressure level of that zone. Depending on the desired properties of the gas bearing, a suitable control device can switch between the different pressure zones and thus pressure levels for the gas bearing.

[0117] Such use of different existing pressure levels within the scroll vacuum pump can also occur in other aspects of the present disclosure and its further developments.

[0118] According to a tenth aspect of the present disclosure which is not independently claimed, a scroll vacuum pump of the type mentioned at the outset is provided by an adjusting means which is configured to adjust an axial gap dimension existing between the two scroll components, by the adjusting means being configured to enable one or both of the scroll components to self-adjust, in particular after a break-in period.

[0119] The respective spiral component, which can adjust itself, forms part of the adjusting device.

[0120] Such an adjusting device makes it possible to automatically establish a relative position between the two spiral components after a settling-in period that depends on the specific circumstances.

[0121] According to some examples, the spiral walls of the movable spiral component and / or the spiral walls of the stationary spiral component may each be provided with a plastically deformable material on their end face facing away from the spiral base. This material could be, for example, a paste or a grease.

[0122] In these examples, it is preferably intended that the spiral walls do not have TipSeals. However, it is also possible in principle to combine this concept of plastically deformable material with TipSeals.

[0123] This allows the end faces of the spiral walls to "wear in" during a break-in period. During this "wearing in" process, the relative movement between each end face and the opposing surface—that is, the spiral base of the other spiral component—causes wear on the end face, initially smoothing out irregularities and peaks. As the scroll vacuum pump continues to operate, the wear increases, at least locally. This results in a more uniform axial gap across the circumference.

[0124] In connection with this concept, it may be stipulated that the relative position between the movable spiral component and the stationary spiral component is readjusted after a certain period of time. However, such readjustment is not mandatory.

[0125] According to some examples, it can be provided that the spiral walls of the movable spiral component and / or the spiral walls of the stationary spiral component are each provided on their end face facing away from the spiral base with a separate sealing element (TipSeal) which is movably arranged in a recess, in particular a groove-shaped one, and is axially prestressed in the direction of the respective other spiral component by means of at least one prestressing means.

[0126] The sealing element and the recess can, according to some examples, have a cross-sectional shape other than a rectangle. At least on one side, the inner wall of the recess and the side wall of the sealing element facing this inner wall can be inclined relative to the respective spiral wall and thus to the axis of rotation of the drive shaft. The cross-sectional shape can, for example, be a trapezoid that tapers away from the base of the spiral of the component containing the respective spiral wall. However, a trapezoidal shape is not mandatory. Other cross-sectional shapes are also possible, which have an inclined inner wall or side wall on at least one side.

[0127] According to some examples, the spiral walls of the movable spiral component and / or the spiral walls of the stationary spiral component can each be provided with a separate sealing element on their end face facing away from the spiral base. This sealing element comprises a different material on its side facing the other spiral component than on its side facing away from the other spiral component. The materials can differ, for example, in hardness. Preferably, the material on the side facing the other spiral component is softer than the other material. The term "hardness" refers to the same definition for both materials.

[0128] The invention is described below by way of example with reference to the drawing. The drawing shows: Fig. 1 shows an example of a conventional scroll vacuum pump to illustrate the basic structure of such a scroll vacuum pump, and Figs. 2 to 10 each show one or more examples of a scroll vacuum pump with the basic structure according to Fig. 1 , whereby the Fig. 5 , 6 and 7 each relate to an aspect of the invention.

[0129] Fig. 1 Figure 1 shows a conventional scroll vacuum pump with a basic design, which is described below. The design and operation of such a scroll vacuum pump are known to those skilled in the art. This conventional scroll vacuum pump can be further developed in various ways according to the invention. Different aspects are subsequently described with reference to the following: Fig. 2 bis 10 explained, whereby the Fig. 5 , 6 and 7 each relate to an aspect of the invention.

[0130] The scroll vacuum pump according to Fig. 1 The scroll vacuum pump comprises a pumping system with a stationary scroll element 11 and a movable scroll element 13, which interact to pump effectively during operation. Furthermore, the scroll vacuum pump includes a drive shaft 17 rotating about an axis of rotation 15 during operation, with an eccentric section 19 for driving the movable scroll element 13. The scroll vacuum pump is also 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, also referred to as the rotor, and a radially outer motor stator 23.

[0131] The drive shaft 17 is rotatably mounted on the pump housing 41 at two axially spaced bearing points 25, 27. The front bearing point 25 is formed by a front rolling bearing, which is designed as a fixed bearing, while the rear bearing point 27 is formed by a rear rolling bearing, which is designed as a floating bearing. For supporting the drive shaft 17, the pump housing 41 is provided with a sleeve-shaped section, which is hereinafter also referred to as the bearing sleeve 115. The two rolling bearings 25, 27 are thus located radially between the drive shaft 17 and the bearing sleeve 115.

[0132] Both 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. Thus, all bearing points 25, 27 are located within the pump housing 41 in front of the drive motor 21, 23. The bearing points 25, 27 are located in the atmospheric zone of the pump, i.e., not in the area where a vacuum exists during pump operation. The eccentric section 19 is integrally connected to the front end of the drive shaft 17, and the drive motor 21, 23 is mounted on the rear end of the drive shaft 17. This design allows the drive motor 21, 23 to be slid onto the rear end of the drive shaft 17. This simplifies the assembly and replacement of the drive motor 21, 23 or parts thereof.

[0133] 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, which are attached to the drive shaft 17. 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.

[0134] Variations of this basic design also allow for other balancing concepts. For example, the rear balancing weight or an additional balancing weight can be located at the rear end of the drive shaft in the area of ​​the drive motor.

[0135] Furthermore, a pressure element 87 is provided on the front side of the rear end of the drive shaft 17, which is rotationally symmetrical and does not serve as a balancing weight.

[0136] The pressure element 87 is connected to the drive shaft 17 by means of a central screw 83. To adapt the outer diameter of the rear section of the drive shaft 17 to the inner diameter of the motor rotor 21, the rear section of the drive shaft 17 is provided with a sleeve element 33. The sleeve element 33 is clamped to the motor rotor 21 by means of the pressure element 87 and the central screw 83. The sleeve element 33 is secured to the drive shaft 17 by means of a positioning pin 33a. Furthermore, an annular intermediate element 34 is arranged axially between a shoulder 17a formed on the drive shaft 17 and the motor rotor 21. The motor rotor 21 is clamped between the pressure element 87 and the shoulder 17a of the drive shaft 17, which serves as an abutment for the intermediate element 34, via the intermediate element 34.In the area of ​​the shoulder 17a, a wave spring 99 is arranged between the loose bearing 27 forming the rear bearing point 27 and the intermediate element 34.

[0137] The drive motor 21, 23 is arranged completely within the pump housing 41, i.e., the drive motor 21, 23 is surrounded by the pump housing 41 in the circumferential direction over its entire axial length and does not protrude to the rear. At its rear end, the pump housing 41 is closed by means of a separate motor cover 103.

[0138] 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 hood 105, which is also attached to the pump housing 41 and in which a fan 95 is also housed.

[0139] The movable spiral component 13 is mounted on 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. In variations of this basic design, several positioning pins 79 may also be provided.

[0140] The stationary spiral component 11 comprises a spiral arrangement with spiral walls 49 and a spiral base 51, as well as a support 53 for the spiral arrangement, the latter forming the spiral base 51 with its side facing the movable spiral component 13. For example, two radially outer spiral walls 49 can be provided, which lie on concentric circles and are interrupted in the circumferential direction. This creates a parallel pumping structure consisting of parallel pumping channels formed by the respective spiral grooves between the spiral walls 49, which transition into a spirally extending pump channel extending radially inwards. This pump channel is formed by a spirally extending spiral groove and is bounded by a spirally extending spiral wall 49.

[0141] The movable spiral component 13 also comprises a spiral arrangement with spiral walls 69 and a spiral base 71, as well as a plate-shaped support 73 for the spiral arrangement, the side of which facing the stationary spiral component 11 forms the spiral base 71. Corresponding to the spiral arrangement of the stationary spiral component 11, two radially outer spiral walls 69 can be provided, which lie on concentric circles and are interrupted circumferentially in the region of a gas inlet (not shown). A radially inner spiral wall 69 extends in a spiral shape.

[0142] Both the spiral walls 49 of the stationary spiral component 11 and the spiral walls 69 of the movable spiral component 13 are provided at their ends facing away from the respective spiral base 51 or 71 with an elongated sealing element 75 (TipSeal).

[0143] The spiral arrangements of the two spiral components 11, 13 described above can also be designed differently.

[0144] The gas to be pumped enters the pumping system comprising the two spiral components 11, 13 via an inlet flange 77 and is expelled via an outlet flange (not shown).

[0145] The pump housing 41 is supported on a base formed by an electronics housing 43. The pump housing 41 is screwed to the electronics housing 43. The electronics housing 43, which is not fully shown, has feet (not shown) on its underside. The electronics housing 43 contains electronic components, including electronic, electrical, and electromechanical components, which serve, among other things, to supply power and control the scroll vacuum pump.

[0146] Furthermore, the scroll vacuum pump includes a gas ballast valve (not shown). In variations of this basic design, a multi-stage gas ballast system can be used instead of a single gas ballast valve.

[0147] 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 corrugated bellows 89. The corrugated 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 corrugated bellows 89 is attached to the side of the movable spiral component 13 facing the drive. The rear end of the corrugated bellows 89 is attached to a housing base inside the pump housing 41 by means of screws.

[0148] As explained in the introduction, an axial gap exists between the end faces of the spiral walls 49 and 69 of one spiral component 11 and 13, respectively, and the spiral base 71 and 51 of the other spiral component 13 and 11, respectively. This gap is generally referred to as the axial gap dimension within the scope of this disclosure. The axial gap dimension influences the vacuum performance of the scroll vacuum pump and thus, in particular, its pumping speed and the minimum ultimate pressure that can be achieved with the scroll vacuum pump.

[0149] The present disclosure provides the possibility of adjusting the axial gap dimension, either during or outside of pumping operation, depending on the example. Some examples allow the axial gap dimension to be adjusted selectively during or outside of pumping operation. Different possibilities for adjusting the axial gap dimension are explained below in conjunction with the figures, with these individual aspects of the present disclosure being illustrated using the example of a conventional scroll vacuum pump having a basic structure as described above. Fig. 1 This has been explained. The aspects described below are mostly presented schematically in order to illustrate the respective concept.

[0150] In the example of the Fig. 2 The adjusting means for setting the axial gap dimension includes an active magnetic bearing 113, which is arranged on the back, i.e. on the side facing away from the stationary spiral component 11 (spiral housing), of the movable spiral component 13 (orbiter).

[0151] The schematic representation in Fig. 2 Figure 1 shows a first coil 113a and a second coil 113b of the magnetic bearing, which are arranged axially offset from each other. The axial gap dimension present in each case can be measured using a sensor 113c of the magnetic bearing 113. The sensor 113c can be designed as an eddy current sensor. Alternatively, one or more Hall sensors can be used as sensor 113c.

[0152] A control device of the scroll vacuum pump (not shown) is designed to regulate the active magnetic bearing 113, i.e. to set a desired axial gap by changing the bearing force as a function of the axial gap dimension measured by the sensor 113c.

[0153] The scroll vacuum pump can also be equipped with one or more pressure sensors. A pressure sensor can, for example, be used to measure the pressure in the suction area of ​​the scroll vacuum pump. The desired axial gap dimension can depend on the measured suction pressure. The concept for adjusting the axial gap dimension according to... Fig. 2 It can therefore be provided that the axial gap dimension is varied depending on the measured intake pressure.

[0154] Fig. 3 This illustrates another possibility for adjusting the axial gap between the spiral casing 11 and the orbiter 13. As in conjunction with Fig. 1 As previously explained, a bellows 89 is arranged between the orbiter 13 and the pump housing 41. The bellows 89 is attached to the front of the rear of the orbiter 13 and supported at the rear by the pump housing 41. Consequently, the orbiter 13 is subjected to an axially acting force by the bellows 89, which depends, among other things, on the pressure prevailing within the bellows 89.

[0155] The concept of this example is to use the bellows 89 to mechanically actuate the orbiter 13 in the axial direction and thus to set a desired axial gap dimension. As explained elsewhere, this takes advantage of the fact that the flange bearing 91, which supports the orbiter 13 on the eccentric section 19 of the drive shaft 17, allows a slight axial movement of the orbiter 13.

[0156] The pressure p2 within the bellows 89 can be varied by means of a schematically depicted valve arrangement 121 with a control device 123 for the valve arrangement 121. The interior of the bellows 89 is connected to the intake area of ​​the scroll vacuum pump via a line 127, the valve arrangement 121, and another line 125. The line 127 can include, among other things, a filter assembly with one or more filter elements and a check valve assembly with one or more check valve elements. The pressure p1 in the intake area of ​​the scroll vacuum pump varies during operation and can be measured by means of a pressure sensor 119, which is only schematically indicated. However, such a pressure sensor located in the intake area is not strictly necessary. Determining a pressure value required for this concept can also be done using another pressure sensor, such as...The pressure sensor can be located in the so-called customer chamber, i.e., a receiver in which a vacuum is created during operation by means of the scroll vacuum pump, or at another point in the pumping system. Alternatively, a measure of the pressure can be estimated from other pump parameters, such as the power consumption of the scroll vacuum pump.

[0157] With the control device 123, which can be provided separately or integrated into a control device of the scroll vacuum pump (not shown), the pressure inside the bellows 89, which is typically on the order of 1 bar, can be varied by appropriately controlling the valve arrangement 121 in order to vary the axial force exerted by the bellows 89 on the rear of the orbiter 13 and thus to adjust the axial gap dimension.

[0158] The valve arrangement 21 can, for example, be designed as a solenoid valve, which can be arranged, for example, in a bore formed in the bellows 89.

[0159] Fig. 4 Figure 1 illustrates two different ways of adjusting the axial gap dimension. Both methods can be implemented together on a single scroll vacuum pump, although this is not mandatory. Each of these two methods can also be implemented on a single scroll vacuum pump, either alone or in combination with one of the other disclosed aspects of this disclosure.

[0160] As in connection with Fig. 1 As explained above, a wave spring 99 is arranged between the floating bearing 27, which forms the rear bearing point for the drive shaft 17, and the intermediate element 34. In the conventional scroll vacuum pump according to Fig. 1 The wave spring 99 causes a fixed, unchangeable preload, the magnitude of which depends on the properties of the wave spring 99.

[0161] One aspect is to actively influence the preload at the axial location where the wave spring 99 is situated. For this purpose, this aspect provides that, instead of the conventional wave spring 99, either a modified wave spring 99 or another length-variable device is arranged, which can be actuated by means of a device not shown, whereby the actuation can be controlled, for example, by the control unit of the scroll vacuum pump.

[0162] For example, a modified wave spring 99, made of a bimetal, can be provided, in which the temperature within this wave spring 99 can be selectively changed to precisely alter its stiffness. The wave spring 99, or the section of the wave spring 99, can be selectively heated or cooled for this purpose. A so-called "heat pipe" (explained in more detail below) can be used for this.

[0163] Instead of a wave spring 99, a variable-length device 129 can be provided between the floating bearing 27 and the intermediate element 34. For example, the variable-length device 129 can be an elastic element whose interior can be selectively pressurized by a fluid. This takes advantage of the fact that there are different areas inside a scroll vacuum pump that are located at different pressure levels, i.e., where different pressures prevail. It has already been mentioned that, for example, the pressure inside the bellows 89 is typically on the order of 1 bar. In the suction area of ​​the scroll vacuum pump, a significantly lower pressure (vacuum) prevails during operation.These examples illustrate that different pressure ranges of the scroll vacuum pump are available for applying pressure to an elastic element 129, which serves as a variable-length element and can, for example, be pressurized by a gas. This means that different pressure ranges exist within the scroll vacuum pump. This can be utilized by selectively connecting the elastic element 129 to a specific pressure range and thus bringing it to the pressure level of that range. Depending on the desired preload to be generated by the elastic element 129, a suitable control device can switch between the different pressure ranges and thus pressure levels.

[0164] The other aspect, which is in Fig. 4 As illustrated, this is a concept whereby the adjusting means for setting the axial gap includes at least one actuator, for example a piezo actuator, which serves to mechanically actuate the spiral housing 11 or the orbiter 13 directly or indirectly in the axial direction.

[0165] Fig. 4 Figure 1 illustrates an example where actuators 117 are arranged between the spiral casing 11 and the pump housing 41. Only one piezo actuator 117 is in Fig. 4 schematically represented. In one possible example, several actuators 117 are preferably arranged symmetrically around the axis of rotation 15. For example, three piezo actuators 117 can be provided with an angular separation of 120°.

[0166] By means of a control unit (not shown) of the scroll vacuum pump, these piezo actuators can be controlled either together or independently of one another in such a way that the axial distance between pump housing 41 and spiral housing 11 can be changed and thus the axial gap dimension between spiral housing 11 and orbiter 13 can be adjusted. Correction of misalignments of the spiral housing 11 relative to the housing 41 is also possible, for example, by controlling the circumferentially distributed actuators 117 accordingly.

[0167] The position of such actuators between the spiral housing 11 and the pump housing 41 is shown in Fig. 4 Figure 117 is shown as a possible example of the positioning of such actuators 117. The actuators 117 can also be arranged at other locations between two components of the scroll vacuum pump, specifically at locations where it is possible to apply a direct or indirect mechanical force to one of the two scroll sections 11, 13 in the axial direction. For example, one or more actuators 117 can be arranged between the two scroll sections 11, 13 or between the movable scroll section 13 and the pump housing 41. Since the drive shaft 17 is connected to the orbiter 13 at its front end, it is also possible to apply a mechanical force to the drive shaft 17 in order to change the axial position of the orbiter 13 relative to the scroll housing 11 by means of the drive shaft 17.For example, one or more actuators 117 can be arranged between a support provided, for example, by the pump housing 41 and the drive shaft 17 or a component connected to the drive shaft 17.

[0168] If - as in Fig. 4 As shown, if one or more actuators 117 are arranged between the spiral casing 11 and the pump housing 41, an initial axial gap adjustment can be achieved by first setting the desired axial gap dimension using the actuator(s) 117 and then fixing the set state by screwing the spiral casing 11 to the pump housing 41. An axial gap adjustment during pump operation is also possible with one or more such actuators 117 if the spiral casing 11 and the pump housing 41 are not rigidly screwed together, but are connected in another way such that a set axial gap dimension is sufficiently fixed, yet can still be changed using the actuators 117. This can be achieved, for example, by...The adjustment of the spiral casing 11 to the pump housing 41 is achieved by a movable mounting that is sufficiently rigid to prevent any set axial gap dimension from changing spontaneously during operation, but whose rigidity can be overcome by means of the actuator(s) 117 to change the axial gap dimension. For this purpose, the spiral casing 11 can, for example, be mounted on pins so as to be axially displaceable and axially preloaded towards the pump housing 41 by means of springs, with a suitable sealing device providing the necessary seal between the spiral casing 11 and the pump housing 41.

[0169] The Fig. 5 , 6 and 7Illustrate different possibilities for realizing an aspect of the invention, according to which the axial gap dimension between the two spiral components 11, 13 is adjusted by actively or passively influencing a thermal expansion occurring during pump operation of at least one component by directly or indirectly subjecting this component or another component to thermal stress at least partially, or by influencing the heat transport within the pump.

[0170] These measures, hereinafter also referred to as thermal measures or thermal concepts, can be combined with one another. In some cases, combinations are inevitable. For example, influencing the heat transfer within the pump can thermally stress a component, which in turn actively influences the thermal expansion of that component.

[0171] A combination of the aforementioned measures is not necessarily required. For example, the thermal expansion of a component can be passively influenced without affecting heat transfer within the pump or actively applying targeted thermal stress to a component. A component might, for instance, be made of materials with different coefficients of thermal expansion. During pump operation, the temperature inside the pump rises, causing the different sections of the component to expand to varying degrees. Since the overall thermal behavior of the materials, and thus of the component in question, is known and therefore predictable, if the temperature rise occurring during pump operation is also known and therefore predictable, the effect of this thermal behavior on, for example, the moving spiral component can be predicted.

[0172] The selection of materials with different coefficients of thermal expansion is therefore a passive measure for adjusting the axial gap. As mentioned elsewhere, the term "adjusting" also includes "maintaining" the axial gap at a predetermined setpoint. By selecting the appropriate material and predicting the thermal expansion behavior of the component in question, it can be ensured that the axial gap remains at a generally desired setpoint during pump operation, despite the heating of the scroll vacuum pump's interior. Materials with a negative coefficient of thermal expansion can also be used. This opens up additional possibilities for actively or passively influencing the thermal expansion of the component.

[0173] For the thermal concepts disclosed herein for adjusting the axial gap, different coefficients of thermal expansion of the respective components are not essential. Thermal measures can include the targeted heating or cooling of one or more components in order to influence their thermal expansion and thus the axial gap. As already explained elsewhere, thermal measures can, for example, utilize an existing fan of the scroll vacuum pump. Alternatively or additionally, it is possible to equip the vacuum pump with one or more so-called "heat pipes" (also known as heat tubes). With such heat pipes, which are generally known to those skilled in the art, heat can be selectively supplied to or removed from a specific location.

[0174] Fig. 5 This illustrates two different measures for passively influencing the thermal expansion of components of the scroll vacuum pump, namely the drive shaft 17 on the one hand and the bearing sleeve 115 on the other, which are based on Fig. 1 The basic structure described above represents an integral part of the pump housing 41.

[0175] According to one measure, a section 17b of the drive shaft 17 can be made of a material with a negative coefficient of thermal expansion. When the temperature inside the scroll vacuum pump increases, the axial length of this section 17b decreases, while the other sections of the drive shaft 17 expand axially. Overall, due to the predictability of the thermal effects, the axial length of the drive shaft 17 can be kept at least substantially constant, regardless of the temperatures encountered in practice within the scroll vacuum pump. The axial position of the orbiter 13, which is connected to the front end of the drive shaft 17, thus remains unchanged during pump operation.Alternatively, by selecting the material of section 17b and its axial length, the thermal expansion behavior of the drive shaft 17 can be predetermined such that, for a specific temperature, for example, a normal operating temperature inside the scroll vacuum pump, a specific axial position of the orbiter 13 is established, which differs from the axial position of the orbiter 13 at an internal temperature of the scroll vacuum pump below the normal operating temperature. By additional measures, namely the thermal stress on one or more sections of the drive shaft 17, for example, by selectively heating section 17b or selectively cooling one or more other sections of the drive shaft 17, the axial gap dimension can be specifically adjusted during pump operation.

[0176] Alternatively or additionally to the provision of section 17b of the drive shaft 17 described above, the bearing sleeve 115 can be made of a material whose coefficient of thermal expansion differs from that of the material of the remaining pump housing 41. The bearing sleeve 115 is then no longer an integral part of the pump housing 41, but is connected to it in such a way that good heat transfer by thermal conduction between the bearing sleeve 115 and the pump housing is ensured. A thermally induced change in the axial length of the bearing sleeve 115 changes the axial position of the drive shaft 17 relative to the pump housing 41 and thus the position of the orbiter 13 relative to the pump housing 41 and consequently also relative to the stationary spiral component 11. In this way, the axial gap dimension can also be adjusted.

[0177] Fig. 6 This illustrates two thermal measures that can be used individually or in combination.

[0178] One measure involves utilizing the rotation of the drive shaft 17. In this case, a rotor blade 131 is mounted on the outside of the drive shaft 17 in the axial area between the flange bearing 91 and the front bearing point formed by the fixed bearing 25. Several rotor blades 131 spaced apart circumferentially can be provided. This creates a fan mechanism in this axial area through the rotating drive shaft 17 and the one or more rotor blades 131, which can influence heat transfer within the scroll vacuum pump. This fan effect can, in particular, cool the orbiter 13.

[0179] At the aforementioned axial location, the entire circumference of the drive shaft is not available, as the front balancing weight 29 requires space. Nevertheless, a cooling effect of the drive shaft 17 can be achieved by the one or more rotor blades 31. The additional mass of the one or more rotor blades 131 can be taken into account in the design of the front balancing weight 29 and its attachment to the drive shaft 17, so that a balanced state is maintained despite the presence of the one or more rotor blades 131.

[0180] Heat dissipation can be further improved by providing the rear of the support 73 of the orbiter 13 with a heat dissipation structure, for example with ribs or fins, to dissipate heat into the gas medium within the bellows 89.

[0181] The other thermal measure, which is in Fig. 6 The mechanism shown consists of generating an airflow through the interior of the scroll vacuum pump. For this purpose, an air supply line leads from outside the pump housing 41 through it into the interior of the scroll vacuum pump located within the bellows 89, and from there to the outside via an exhaust air line 135, which also leads through the pump housing 41. As schematically illustrated by the example of the exhaust air line 135, a recess 133 can be provided in the bearing sleeve 115 of the pump housing 41, from which the exhaust air line 135 originates.

[0182] The airflow through the scroll vacuum pump can be regulated by means of a valve arrangement 139 with an associated control unit 141. The control unit 141 can be provided separately for the valve arrangement 139 or integrated into a control unit of the scroll vacuum pump (not shown).

[0183] By means of such a controllable airflow through the interior of the scroll vacuum pump, the interior of the scroll vacuum pump can be cooled in a targeted manner, and thus the heat transfer within the scroll vacuum pump can be influenced. Additionally, this cooling airflow can be used to generate a cooling effect in the area of ​​the drive motor 21, 23.

[0184] In practice, it is observed that during pump operation, the temperature of the orbiter 13 is typically about 20K to 30K higher than the temperature of the stationary spiral casing 11. Therefore, removing heat from the orbiter 13 is a particularly effective measure to influence thermal expansion of the orbiter 13 and thus to adjust the axial gap between the orbiter 13 and the stationary spiral casing 11.

[0185] According to a Fig. 7 In the illustrated embodiment, heat dissipation from the orbiter 13 can be achieved by actively controlling the fan 95 of the scroll vacuum pump. The speed of the fan 95, and thus its cooling effect, can be changed, for example, by means of a control unit of the scroll vacuum pump (not shown). The fan 95 can also have its own control unit that can communicate with that of the scroll vacuum pump. The arrows W in Fig. 7 Figure 1 illustrates how heat is transferred from the orbiter 13 to the pump housing 41 via the flange bearing 91, the front fixed bearing 25, the rear floating bearing 27, and the drive shaft 17 itself. The heat can then be dissipated to the environment via the pump housing 41.

[0186] The above in conjunction with the Fig. 2 bis 7 The examples described serve to adjust the axial gap dimension during pump operation. As explained in the introduction, this disclosure also includes adjusting means designed to adjust the axial gap dimension outside of pump operation. For example, an initial axial gap adjustment can be performed during the assembly of the scroll vacuum pump. Alternatively or additionally, the axial gap dimension can be adjusted during maintenance or when preparing the scroll vacuum pump for a new application. The adjustment can be performed manually, either by hand or using a tool.

[0187] An example of manual adjustment of the axial gap dimension shows Fig. 8 . Instead of the conventional basic structure (cf. Fig. 1 In addition to the central screw 83 provided at the rear end of the drive shaft 17, an adjusting screw 143 is provided here, which passes through a passage formed in the drive shaft 17. An external thread is formed at the front free end of the shaft 143a of the adjusting screw 143, which interacts with an internal thread in a bore formed in the pressure plate 93 in the manner of a spindle drive, in which the front free end of the shaft 143a forms a threaded spindle and the pressure plate the spindle nut. Since the pressure plate 93 is arranged in a rotationally secure manner between the front end of the drive shaft 17 and the rear of the orbiter 13, the axial position of the pressure plate 93, and thus of the orbiter 13, can be changed and adjusted by turning the adjusting screw 143.With the engine cover 103 removed, the head of the adjusting screw 143 is accessible from the outside and can be operated using a conventional tool, for example a screwdriver or an Allen key.

[0188] The required clearance of the flange bearing 91 for this adjustment option is ensured by a spring assembly 145, which is arranged between the drive shaft 17 and the inner ring of the flange bearing 91. The spring assembly 145 can, for example, be a wave spring.

[0189] Fig. 9 This shows another example of the concept, where the adjusting device for the axial gap dimension is designed to allow manual adjustment of the axial gap dimension. The scroll vacuum pump is shown here in a highly schematic form and can, in turn, have a basic structure as illustrated by... Fig. 1 explained.

[0190] In the Fig. 9 In the illustrated example, the adjusting device comprises a clamping system 151 for the spiral casing 11, which is shown only schematically. This clamping system 151 functions according to the principle of a collet chuck, which is generally known to those skilled in the art. A support for the spiral casing 11, which here forms part of the clamping system 151, comprises several circumferentially distributed ring segments 153 arranged on the pump casing 41, which are also shown schematically and act as clamping jaws. The ring segments 153 can be separate elements that are suitably connected to the pump casing 41. However, the ring segments 153 can also be formed integrally with the pump casing 41.

[0191] The ring segments 153 are elastically deflectable by means of an annular clamping element 155 belonging to the clamping system 151. In the example shown here, this clamping ring 155 comprises a conical surface on its inner side, via which the clamping ring 155 interacts with corresponding mating surfaces of the ring segments 153. The clamping ring 155 can be screwed axially to the pump housing 41.

[0192] In a dissolved state, as it occurs in Fig. 9 As illustrated, the spiral housing 11 can be adjusted relative to the ring segments 153 to achieve a desired target position relative to the in Fig. 9 to be brought to the orbiter (not shown), i.e., to the movable spiral component of the scroll vacuum pump system. The spiral housing 11 is provided with a convex outer contour 157 on its outer circumference, e.g., a spherical ring section or individual dome-shaped projections, by which the spiral housing 11, in its released state, is held securely by the ring segments 153 under only slight tension, but can be adjusted relative to the ring segments 153. As soon as the spiral housing 11 is in the desired position, the clamping ring 155 is screwed onto the pump housing 41 and pushed onto the ring segments 153, causing the ring segments to deform radially inwards and thus clamping the spiral housing 11. In this clamped state of the clamping system 151, the relative position between the spiral housing 11 and the pump housing 41, and thus the relative position between the two spiral components, is fixed.

[0193] Fig. 10 This schematically illustrates an example of the concept whereby an adjusting device for setting the axial gap dimension is designed to enable at least one of the spiral components to self-adjust. The scroll vacuum pump in question can, in turn, have a basic structure as shown in the diagram below. Fig. 1 explained.

[0194] Fig. 10 Figure 1 shows a sealing element 75 (TipSeal) arranged on the end face 165 of the spiral wall 69 of the orbiter. The upper surface 160 of the seal 75 faces the spiral base 51 of the support 53 of the spiral casing. An axial gap is present between this upper surface 160 and the spiral base 51.

[0195] The geometry of the seal 75 and a recess 171 receiving the seal 75 on the end face 165 of the spiral wall 69 is known in itself from EP 4 174 285 A1. With regard to this geometry, which is described in Fig. 10 in a cross-section perpendicular to the longitudinal extent of the spiral wall 69 and the seal 75 and thus perpendicular to the axis of rotation of the drive shaft (cf. Fig. 1 Regarding possible deviations from the depicted geometry and the advantages of this concept, reference is made to the aforementioned EP 4 174 285 A1. As explained therein, one advantage of this concept is that during operation of the scroll vacuum pump, the pressure difference between adjacent pumping chambers (see the introductory explanation of the operation of the pumping system of a scroll vacuum pump) generates a force that causes the generally movable seal 75 to move within the recess 171 in Fig. 10 is pressed upwards against the spiral base 51 of the support 53. Depending on the pressure difference, forces act either on the right side or on the left side. Fig. 10 The respective inclined inner wall 173 of the recess 171 and the respective inclined side wall 161 of the seal 75 come together. On the one hand, this geometry allows the seal 75 to protrude further from the recess 171 as it wears down due to abrasion on its upper surface 160. This effectively provides automatic abrasion compensation. On the other hand, this geometry secures the seal 75 in the recess 171.

[0196] At the in Fig. 10 In the illustrated example, an elastic preloading device 167, comprising several springs 168, is also provided between the bottom 175 of the recess 171 and the underside 162 of the seal 75. This preloading device 167 enables an acceleration of the grinding process of the seal 75.

[0197] In the example shown, both the seal 75 and the recess 171 are trapezoidal in cross-section, with the trapezoidal shape of the seal 75 being smaller than that of the recess 171, i.e. the width of the opening 163 of the recess 171 being larger than the width of the seal 75 in the upper area encompassing the top 160.

[0198] The grinding in of the seal 75 is equivalent to a self-adjustment of the relevant spiral component, here the orbiter 13 comprising the spiral wall 69 shown, thereby adjusting the axial gap dimension.

[0199] This measure, either alone or in combination with other measures disclosed herein, can eliminate a relative misalignment between the two spiral components.

[0200] The in Fig. 10 The configuration shown may in particular be intended as a supplement to the other examples or combinations thereof disclosed herein. Bezugszeichenliste

[0201] 11 Fixed spiral component, spiral housing 13 Moving spiral component, orbiter 15 Rotation axis 17 Drive shaft 17a Shoulder 17b Section 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 33a Positioning pin 34 Intermediate element 41 Pump housing 43 Electronics housing 49 Spiral wall of the fixed spiral component 51 Spiral base 53 Support 69 Spiral wall of the moving spiral component 71 Spiral base 73 Support 75 Sealing element 77 Inlet flange 83 Central screw 87 Pressure element 89 Bellows 91 Flange bearing 93 Pressure washer 94 Washer 95 Fan 97 Positioning pin 99 Wave spring 103 Motor cover 105 Hood 113 Active magnetic bearing 113 First coil 113 Second coil 113 Eddy current sensor 115 Bearing sleeve 117 Actuator 119 Pressure sensor 121 Valve assembly 123 Control unit 125 Cable 127 Cable 129 Length-adjustable device 131 Rotor bladeFan assembly 133 Recess 135 Exhaust duct 137 Supply duct 139 Valve assembly 141 Control device 143 Adjusting screw 143a Shaft 145 Spring assembly 151 Clamping system 153 Ring segment 155 Ring-shaped clamping element 157 Outer contour 160 Top 161 Side wall 162 Bottom 163 Opening 165 Front 167 Preloading device 168 Spring 171 Recess 173 Inner wall 175 Bottom Hot water

Claims

1. A scroll vacuum pump comprising - a pump system (11, 13) which comprises a stationary spiral component (11) and a movable spiral component (13) cooperating with said stationary spiral component (11) in a pump-active manner; - a drive shaft (17) which rotates about an axis of rotation (15) during operation and which has an eccentric section (19) for driving the movable spiral component (13); - an electric drive motor (21, 23) for the drive shaft (17); - an adjustment means which is configured to set an axial gap dimension present between the two spiral components (11, 13), characterized in that the adjustment means is configured to set the axial gap dimension present between the two spiral components (11, 13) in that the adjustment means is configured to actively or passively influence a thermal expansion of at least one component that occurs during the pump operation, and / or in that the adjustment means is configured to influence the heat transport within the pump.

2. A scroll vacuum pump according to claim 1, wherein the component whose thermal expansion can be influenced is a component which directly or indirectly influences the axial position of the movable spiral component (13).

3. A scroll vacuum pump according to claim 1 or 2, wherein the adjustment means comprises that at least one section of the component is made of a material which has a thermal conductivity of more than 100 W / mK, and / or wherein the component comprises at least a first section and at least a second section, wherein the adjustment means comprises that the two sections consist of materials having different thermal conductivities.

4. A scroll vacuum pump according to at least one of the preceding claims, wherein the component comprises at least a first section and at least a second section, wherein the adjustment means comprises that the two sections have different coefficients of thermal expansion.

5. A scroll vacuum pump according to at least one of the preceding claims, wherein the adjustment means comprises a heating device and / or a cooling device which is configured to thermally act on at least one region of the component directly or indirectly.

6. A scroll vacuum pump according to at least one of the preceding claims, wherein the adjustment means comprises a motor control of the drive motor (21, 23), wherein the motor control is configured to influence the efficiency of the drive motor (21, 23) by changing the energization to thermally act on the drive shaft (17).

7. A scroll vacuum pump according to at least one of the preceding claims, wherein the adjustment means comprises one or more temperature sensors.

8. A scroll vacuum pump according to at least one of the preceding claims, wherein the adjustment means can be configured to control the drive motor (21, 23) and a motor fan such that the drive motor (21, 23) is operated in a loss mode leading to excessive waste heat and the influence of the waste heat on the component is intentionally influenced by the motor fan.

9. A scroll vacuum pump according to at least one of the preceding claims, wherein the component comprises at least a first section and at least a second section, wherein the adjustment means comprises that one of the two sections or the entire component has a surface which has a thermal emissivity ε of at least 0.25 at 50°C, and / or wherein the adjustment means comprises that the surface of the component is at least partly provided with a coating which has a higher thermal emissivity ε than the uncoated component, and / or wherein the adjustment means comprises that the surface of the component is at least partly treated by oxidation, the component comprises a metallic material which includes at least one metallic element, and the treated portion of the surface comprises an outer layer which comprises a compound of the metallic element formed by the oxidation treatment.

10. A scroll vacuum pump according to at least one of the preceding claims, wherein the adjustment means comprises that a volume limited by the component is at least partly filled with a medium.

11. A scroll vacuum pump according to at least one of the preceding claims, wherein the adjustment means comprises a fan device (17, 131) which is attached to or formed at a component rotating during the pump operation.

12. A scroll vacuum pump according to at least one of the preceding claims, wherein the adjustment means comprises an adjustment device and one or more air guiding members which can be adjusted by means of the adjustment device.

13. A scroll vacuum pump according to at least one of the preceding claims, wherein the adjustment means comprises at least one pressure sensor (119) and wherein the adjustment means is configured to set the axial gap dimension in dependence on at least one pressure measured by means of the pressure sensor (119).

14. A method of operating a scroll vacuum pump comprising - a pump system (11, 13) which comprises a stationary spiral component (11) and a movable spiral component (13) cooperating with said stationary spiral component (11) in a pump-active manner; - a drive shaft (17) which rotates about an axis of rotation (15) during operation and which has an eccentric section (19) for driving the movable spiral component (13); and - an electric drive motor (21, 23) for the drive shaft (17), characterized in that the method comprises setting an axial gap dimension present between the two spiral components (11, 13) in that a component is thermally acted on at least regionally in a direct or indirect manner and / or in that the heat transport within the pump is influenced.

15. A method according to claim 14, wherein the component is a pump housing (41), the drive shaft (17), a rolling element bearing (25, 27), an inner race or an outer race of a rolling element bearing (25, 27), a bearing sleeve (115) or an adapter sleeve.

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