WO2014117991A2

WO2014117991A2 - Vacuum pump, in particular rotary-lobe pump

Info

Publication number: WO2014117991A2
Application number: PCT/EP2014/050459
Authority: WO
Inventors: Dirk STRATMANN; Armin Bertsch; Wolfgang Giebmanns
Original assignee: Oerlikon Leybold Vacuum Gmbh
Priority date: 2013-01-30
Filing date: 2014-01-13
Publication date: 2014-08-07
Also published as: WO2014117991A3; DE202013000913U1

Abstract

A vacuum pump such as a rotary-lobe pump has a pump chamber (10) in which pump elements (12) are arranged. A pressure side (30) is connected to a suction side (20) of the pump chamber (10) via a connecting duct (22). Furthermore, a valve device (24) is arranged in a passage opening (32) of the connecting duct (22). To vary the effective cross-sectional area of the passage opening (32), the valve device (24) is, in one of the preferred embodiments, assigned an adjustable aperture device (42).

Description

Vacuum pump, in particular Roots pump

The invention relates to a vacuum pump, in particular a Roots or Roots pump.

Vacuum pumps have pumping elements arranged in a pumping chamber, in which Roots pumps are two Roots. By the rotation of the Wälzkolben carried a pumping of the medium from a suction side of a pumping chamber to a pressure side. The capacity of Roots pumps is limited in particular by a maximum pressure difference between the suction side and pressure side. This is approx. 30 mbar for Roots pumps with a large-volume pump chamber and up to 100 mbar for smaller Roots pumps. When the maximum pressure difference is exceeded, a thermal overload of the Roots pump, in particular of the drive motor can take place. In order to avoid such overloads, some Roots pumps have a connection channel connecting the pressure side to the suction side, through which the conveyed medium can flow back from the pressure side to the suction side. In the connecting channel, a valve, the so-called bypass valve, arranged. Upon reaching a predetermined pressure difference opens the usually weight and / or spring-loaded valve.

Such, in the connecting channel of a Roots pump arranged valve is known for example from DE 28 44 019. It deals this is a poppet valve which has a plate-shaped valve body for closing a passage opening in the connecting channel.

In modern manufacturing processes, such as vacuum coating process very short process times must be realized. For example, cycle times of less than a minute must be realized. As a result, the vacuum pumps used, in particular Roots pumps, have to pass through the entire operating range of the pump within a few seconds. This results in that the bypass valve of the Roots pump is opened very quickly or suddenly. Due to the impact of the valve disk or connected to the valve components occur increased operating noise. Furthermore, this can cause damage to the pump housing. To avoid damage and to reduce operating noise, special valves have been developed in which the valve disk is not only spring-loaded, but also has a hydraulic damper. As a result, the rapid, or sudden movement of the valve disk is damped.

Poppet valves with or without hydraulic or mechanical damping have the disadvantage that large masses must be moved. As a result, such poppet valves are sluggish. In particular large-volume Roots pumps correspondingly large poppet valves must be provided so that in a short time a sufficient amount of medium can flow back through the connecting channel. This has the further disadvantage that a large space is required for the poppet valve. This leads to large pump housing dimensions and thus to increased costs. Another disadvantage of spring and weight-loaded poppet valves is that due to the acceleration of gravity, the mounting position must be considered. A special arrangement of the poppet valve in a 45 ° angle to the conveying direction of the Roots pump is known from DE 2844019. This makes it possible, the Roots pump at least in two different Install mounting positions in which the poppet valve is always arranged at a 45 ° angle to the acceleration of gravity.

To realize large flow areas, it is also known to provide a flapper valve as a bypass valve. Such a flap valve is described, for example, in DE 102008034073. The provision of flap valves also has the advantage that they have a small space. The flapper valve is spring loaded. In particular, by designing the spring force applied by the spring, the pressure difference between the pressure side and the suction side is defined at which the flapper valve opens. To operate the same pump at different operating points, which occur in particular in different applications, for example, by means of a clamping device, the spring force can be adjusted. This is expensive and possible only in a relatively small power range. In order to realize a greater variation of the spring force, it is therefore necessary to replace the spring. This is extremely expensive and can only be done with the help of special tools. The springs can only be replaced by service personnel of the manufacturer and not by the customer himself.

The object of the invention is to provide a vacuum pump, in particular a Roots pump, whose bypass valve can be adjusted in a simple manner for operation at different operating points.

The object is achieved by the features of claim 1 or 10.

As an alternative to the invention defined in the claims, it is possible in a low-cost simple embodiment to change the passage opening of the connecting channel in which the valve device is arranged in cross-section by inserting a diaphragm into the passage opening. Although this also requires a certain assembly effort, but this is much lower than the setting and especially as the replacement of the valve spring. The replacement of the diaphragm and thus the changing of the effective cross-sectional area may optionally be carried out by the customer himself, provided that the required special tool is present or not required. Depending on the installation position of the valve device, it is also possible to provide or remove additional weights on the valve device in addition to or instead of the provision of diaphragms. Such a change in the dead weight of the valve flap, the required pressure difference between the suction side and the pressure side is changed, which is required to open the valve. By providing diaphragms and / or additional weights, it is possible, for example, to realize a Roots pump with a volumetric flow rate between 1000qm / h and 6000qm / h differential pressures between 50 mbar and 300 mbar. Although the provision of diaphragms and / or additional weights represents a certain installation effort, this is an independent invention, which represents in particular a cost-effective solution of the problem. This also has the advantage that it can be easily retrofitted with existing vacuum pumps.

However, the solution of the above object is particularly preferred by the features of claim 1 or 10, wherein these features may optionally be combined with the provision of additional panels or additional weights.

The vacuum pump according to the invention is in particular a Roots pump. The vacuum pump has arranged in a pumping chamber pumping elements and in particular Wälzkolben. Furthermore, the pressure side of the suction chamber is connected to the suction side of the suction chamber via a connecting channel. In the connecting channel, a valve device is arranged in a passage opening.

In a first particularly preferred embodiment of the invention, the valve device arranged in the connecting channel is adjustable Aperture device assigned, in particular upstream in the flow direction. By adjusting the diaphragm device, it is possible to bring about a change in the effective cross-sectional area of the passage opening and / or a change in the flow-through characteristic. By providing an adjustable diaphragm device and thus effected changing the effective cross-sectional area is easy to adjust the vacuum pump to different operating points possible. This makes it possible, for example, always to exploit the engine power or to avoid overloading the engine by exceeding the permissible engine temperature. This is due to the fact that the required motor power of the pump motor is not only proportional to the differential pressure but in particular also to the delivered mass flow. Thus, at low mass flows, the potential engine power can not be exploited, while at high mass flows, the required engine power leads to an undesirable increase in engine temperature, especially in continuous operation. This problem can be avoided by providing an adjustable aperture device. By adjusting the diaphragm device and thus by the definition of the effective cross-sectional area effected thereby, the desired opening pressure can be adjusted depending on the operating conditions. As a result, the engine power can be fully utilized for the respective application and, as a rule, a shutdown of the engine, in particular due to overheating, can be avoided.

If, for example, a diaphragm is provided in the case of a flap valve in the flow direction immediately before the valve flap, a larger opening pressure can be set, for example, with the same spring force, in which the effective cross-sectional area is reduced by partially closing the diaphragm. Accordingly, a smaller opening pressure can be adjusted by opening the aperture. For this purpose, it is particularly preferred that the diaphragm device has an adjustable diaphragm element. Preferably, a plurality of diaphragm elements are provided, wherein the diaphragm elements in Particularly preferred embodiment independently, ie, for example, individually or in groups are adjustable. In this case, the adjustment of the at least one diaphragm element for changing the effective cross-sectional area can be effected by displacement and / or rotation of the diaphragm element. By moving the diaphragm element can be changed in a simple manner, the aperture and thus the effective cross-sectional area. In a non-circular but eg. In cross-section semicircular or rectangular aperture element can also be done by rotating the diaphragm element, a change in the effective cross-sectional area.

In particular, the position of the diaphragm device is pressure-independent, so that the effective cross-sectional area is determined only by the position of the diaphragm device and does not depend on the differential pressure.

In a particularly preferred embodiment, at least one sealing element is provided between the diaphragm device and the valve device. If the diaphragm device has a plurality of diaphragm elements, in particular a plurality of sealing elements or a common sealing element are provided. By providing the sealing elements it is ensured that only the static pressure acts on the valve device, in particular the valve flap. The static pressure primarily determines the required opening force.

In a preferred embodiment of the invention, the diaphragm device and in particular the at least one diaphragm element of the diaphragm device are connected to an actuating device. The adjusting device may be a manually operable actuator. For example. can be provided with slidable aperture elements adjusting screws. Furthermore, it is possible to use an electromagnetic, pneumatic and / or hydraulic adjusting device for adjusting the diaphragm device and in particular the at least one diaphragm element provided. Particularly preferred is the provision of a stepping motor, for example, the actuation of an adjusting spindle or a sliding crank mechanism. In particular, by means of a stepping motor and a rotation of individual aperture elements is possible in a simple manner.

In a further preferred embodiment, it is possible that the diaphragm device is designed as a throttle valve. In this embodiment, it is thus preferable to arrange a throttle valve upstream of the valve device in the flow direction. By corresponding rotation or pivoting of the throttle valve, it is also possible to change the effective cross-sectional area. The throttle valve is preferably connected to an actuator as described above.

Furthermore, it is possible that the diaphragm device has both one or more adjustable diaphragm elements and a throttle valve. As a result, a very fine adjustment of the pressure difference, in which the valve device in particular opens the valve flap, possible. A throttle valve (without sealing element), e.g. upstream of a flapper valve produces, as aerodynamic drag, flow losses which reduce the pressure prevailing at the flapper valve and thus allow the opening pressures of the flapper valve to operate at other operating points.

In a further independent embodiment of the invention, the valve device itself is designed as a throttle valve. There is thus a function of a differential pressure, a partial and / or complete opening of the throttle. The actuation of the throttle valve is in turn carried out by appropriate adjusting devices as described above.

Below, the different embodiments of the invention will be explained in more detail with reference to the drawings. Show it:

Fig. 1 is a schematic sectional view of a Roots pump

2 is an enlarged view of the arranged in the connecting channel of the Roots pump flap valve,

Fig. 3 is a schematic enlarged cross-sectional view of a

Flapper valves with aperture device,

A schematic sectional view taken along the line IV-IV in

3,

Fig. 5 is a schematic sectional view of an embodiment of the invention, in which the flapper valve is combined with a throttle valve and

Fig. 6 is a schematic sectional view of a throttle valve designed as a valve device.

A Roots pump according to the invention has two Wälzkolben 12 arranged in a pump chamber 10. The Wälzkolben 12 rotate synchronized in opposite directions in the direction of arrow 13 about perpendicular to the plane extending axes of rotation 14. The Wälzkolben 12 are arranged in a housing 16. By the Wälzkolben 12 conveying the medium takes place in the direction of a reed 18 from a suction side 20 in the direction of a pressure side 30th

In particular, in order to avoid overheating, a connection channel 22 arranged laterally next to the pump chamber 10 is provided in the housing 16. The connecting channel 22 preferably extends over the entire width of the pump housing running perpendicular to the plane of the drawing 16. The connecting channel thus preferably has a rectangular cross-section.

In the connecting channel 22, a valve device 24 is arranged. When a maximum pressure difference between pressure side 30 and suction side 20 is exceeded, the spring-loaded valve device 24 opens automatically, so that part of the fluid delivered flows back from the pressure side in the direction of a section 26 to the suction side 20.

The valve device 24 has a valve flap 28 (FIG. 2) which closes off a rectangular passage opening 32 of the connection channel 22. The passage opening 32 preferably extends substantially over the entire width of the connection channel 22 and thus approximately the entire housing 16. The valve flap 28 is pivotable about a pivot axis 34 in the direction of an arrow 36. By means of a pivot spring 34 surrounding the torsion spring 40, a holding or closing force is applied to the valve flap 28. Because of this closing force, the valve 24 opens only from a defined pressure difference between the pressure side 30 and the suction side 20 (FIG. 1) of the suction chamber 10.

In the illustrated embodiment, the pivot axis 34 is disposed on the side facing away from the pumping chamber 10 side, so that for opening the valve flap 28, a pivoting of the valve flap takes place in a housing corner. Due to the thus required for the flap valve small space relatively small outer dimensions of the pump housing 16 can be realized.

In a simple, cost-effective embodiment, which can also be retrofitted in particular, it is possible to provide apertures in the passage opening 32. These can be mounted by opening a housing cover 38. By providing different apertures, the effective cross-sectional area of the passage opening 32 can be changed. hereby there is a change in the pressure difference at which the valve flap 28 opens. About the mounting cover 38, it is also possible to provide additional weights on the valve flap or to remove it. This also makes it possible to vary the differential pressure.

A preferred embodiment of the invention with adjustable diaphragm means 42 is shown in Figures 3 and 4. The diaphragm device 42 is arranged in FIG. 3 below the valve flap 28 or upstream in the flow direction of the valve flap 28. The valve device 24 corresponds to the valve device 24 described with reference to FIGS. 1 and 2. On the underside of the valve flap 28, a sealing element 43 is provided, which extends in particular over the entire underside of the valve flap 28. This ensures that the individual diaphragm elements, which are in particular the diaphragm blades 44 in the exemplary embodiment shown, are always sealed with respect to the valve flap 28.

To move the lamellar diaphragm elements 44, an adjusting spindle 46 is provided in the illustrated embodiment. This adjusting spindle 46 protrudes through a projection 48 of the diaphragm element 44, in which a thread is provided. By rotating the spindle 46, the diaphragm element 44 can thus be displaced in the direction of an arrow 50.

In the illustrated embodiment, a plurality of diaphragm elements 44 (FIG. 4) are provided, which are connected to one another, so that the diaphragm elements 44 can be displaced via a common adjusting spindle 46. However, it is possible, for example, to provide a plurality of adjusting spindles, so that individual diaphragm elements can be moved separately or in groups.

Changing the effective cross-sectional area thus takes place, in the exemplary embodiment illustrated in FIGS. 3 and 4, by displacing the diaphragm elements 44 in the direction of the coil 50 Cross-sectional area of the diaphragm device could alternatively be done by pivoting diaphragm elements. In this case, the diaphragm elements preferably have a non-circular, for example semicircular or rectangular cross-section.

In a further embodiment according to the invention (FIG. 5), the same valve device 24 is again provided. In this embodiment, however, is not provided in the flow direction in front of the valve flap 28, a diaphragm device according to the embodiment shown in Figures 3 and 4. Instead, a throttle flap 52 of the valve device 24 is connected upstream as a diaphragm device. To vary the pressure difference across the valve device 24, the throttle flap 52 can be pivoted about a pivot axis 54 in the direction of an arrow 56. In this way, in a simple manner, the gas flow in the direction of arrow 57 by turning the flap 52 in the direction of arrow 56, a more or less large aerodynamic resistance are applied, which in turn causes a pressure drop through which the operating point at which opens the valve means can vary. The "active" pressure difference of the spring-loaded flap valve always remains the same.

In a further preferred embodiment, the entire valve device is replaced by a throttle valve (FIG. 6). The throttle valve substantially corresponds to the throttle flap 52 and is also pivotable about an axis 54. Since the sealed in the closed state valve flap 28 is omitted in this embodiment, additional sealing elements 58 are provided, which can be arranged either on a housing extension 60 or at corresponding outer regions of the throttle valve 52.

In all the above embodiments, it is preferable that for adjusting the individual diaphragm elements and for adjusting the throttle valves, an adjusting device, such as an electric motor or the like is provided. Furthermore, it is possible that the adjusting device is connected to a control device, such as the control device of the vacuum pump. In particular, the control device is a frequency converter. Furthermore, the control device can have sensors for measuring pressure, for example in the connecting channel, so that an adjustment of the diaphragm device or the throttle valve can take place as a function of operating data and / or measured pressures.

Claims

claims

1. Vacuum pump, in particular Roots pump, with in a pump chamber (10) arranged pumping elements (12), a pressure side (30) with a suction side (20) of the pump chamber (10) connecting the connecting channel (22) and one in a passage opening (32) of the connecting channel (22) arranged valve means (24), characterized in that the valve means (24) is associated with an adjustable diaphragm means (42) for changing an effective cross-sectional area of the passage opening (32).

2. Vacuum pump according to claim 1, characterized in that the diaphragm device (42) has an adjustable diaphragm element (44).

3. Vacuum pump according to claim 2, characterized in that the diaphragm device (44) has a plurality of, in particular independently adjustable diaphragm elements (44).

4. Vacuum pump according to claim 2 or 3, characterized in that the at least one diaphragm element (44) for changing the effective cross-sectional area is displaceable and / or rotatable.

5. Vacuum pump according to one of claims 1 to 4, characterized in that between the diaphragm device (42), in particular the at least one diaphragm element (44) and the valve device (24) one or more sealing elements (43) are provided.

Vacuum pump according to one of claims 1 to 5, characterized in that the valve device (24) is designed as a weight and / or spring-loaded flapper valve.

Vacuum pump according to one of claims 1 to 6, characterized in that the diaphragm device (42), in particular the at least one diaphragm element (44) is connected to an actuating device.

Vacuum pump according to claim 7, characterized in that the adjusting device is connected to a control device of the pump.

Vacuum pump according to claim 1, characterized in that the diaphragm device (42) as a throttle valve (52) is formed, which is preferably upstream of the valve means (24) in the flow direction.

Vacuum pump, in particular Roots pump, with in a pump chamber (10) arranged pumping elements (12) a pressure side (30) with a suction side (20) of the pump chamber (10) connecting the connecting channel (22) and one in a passage opening (32) of the connecting channel (22) arranged valve device (24), characterized in that the valve device (24) is designed as a throttle valve (52), which is connected to change an open position with an actuating device.