EP3489516B1 - Vacuum pump - Google Patents

Description

The present invention relates to a vacuum pump having a first working pump section and at least one second working pump section.

The prior art is described below using the example of rotary vane vacuum pumps with two working pump sections.

A known vacuum pump of the type mentioned is designed in such a way that the working pump sections are connected in parallel. In this way, a relatively high pumping speed is achieved at the beginning of a pumping process. However, the parallel connection of the working pump sections is disadvantageous with regard to the final pressure that can be achieved, that is to say the minimum pressure that can be achieved at the inlet of the vacuum pump.

For applications in which a particularly low final pressure is required, it is known in the prior art to connect two working pump sections in series. In this way - with working pump sections that are otherwise identical in construction - a significantly lower final pressure can be achieved. However, the pumping speed at high inlet pressures, especially at the beginning of a pumping process, is greatly reduced compared to parallel operation.

Vacuum pumps of the type mentioned above that operate in parallel are therefore suitable for applications in which rapid pumping out has priority over a low achievable final pressure. Conversely, vacuum pumps working in series are particularly suitable for applications in which rapid pumping is less important, but a particularly low final pressure should be achievable.

The achievable final pressure and pumping speed at high inlet pressures are therefore in conflict of objectives.

the U.S. 3,837,764 A discloses a special type of vacuum pump with orbiting conveying elements, two working pump sections being provided and it being possible to switch between a parallel and a series connection of the working pump sections. the EP 0 730 093 A1 discloses a further special type of vacuum pump with orbiting conveying elements, namely a dry-running scroll pump, with two working pump sections being provided and it being possible to switch between a parallel and a series connection of the working pump sections. the DE 20 2015 004 596 U1 discloses switching between parallel and series connection of separate vacuum pumps. the DE 42 43 793 A1 , the JP S57 157785 U and the DE 40 01 668 A1 disclose multi-stage rotary vane pumps with means for switching between parallel and series connection of two working pump sections.

It is an object of the invention to improve the performance of a vacuum pump of the type mentioned at the outset, in particular to achieve both a high pumping speed at high pressures, in particular at the beginning of a pumping process, and a low achievable final pressure. In particular, the goal conflict described should be resolved.

This object is achieved by a vacuum pump with the features of claim 1, and in particular in that a control device is provided with which the working pump sections can be switched between a series connection and a parallel connection.

In this way, depending on the operating state of the vacuum pump, that operating mode, i.e. series or parallel connection, can be selected which provides better performance in this operating state. The vacuum pump can therefore be used to For example, at the beginning of a pumping process, the working pumping sections can be operated in parallel in order to achieve a high pumping speed, and later, in particular as soon as the pumping speed in series operation exceeds that of parallel operation, switch to series operation in order to achieve further effective evacuation down to a particularly low one To ensure final pressure.

The vacuum pump according to the invention can be used flexibly for various applications. In addition, the manufacturer can dispense with offering mechanically different vacuum pumps on the one hand with parallel connection and on the other hand with series connection. This can drastically reduce the number of parts and thus save costs. The additional design effort for the control device, on the other hand, can be kept low. Furthermore, there is a cost advantage from the fact that smaller pumps can now be used by parallel connection in applications in which larger pumps were previously used.

As far as high or low pressures are referred to herein, these relate to the specific vacuum application and are not to be understood as absolute. For the simple case that in the initial state of the pump there is atmospheric pressure both at the inlet and at the outlet, high pressure refers in particular to values close to atmospheric pressure.

The following description refers primarily to vacuum pumps with exactly two working pump sections that work according to the same pumping principle. The examples mentioned can, however, also be transferred to pumps with three or more working pump sections and, in particular, also to pumps with different types of working pump sections.

According to one embodiment, the vacuum pump is a rotary displacement vacuum pump, in particular a rotary vane pump. In particular, both or all of the work pump sections operate according to the rotary displacement or rotary slide principle. For example, the work pumping sections are driven by a common shaft. This is a structurally simple and therefore inexpensive solution.

According to a further embodiment, the control device is designed to carry out the switchover when a predefined and / or predefinable switchover gas pressure is reached. This is advantageous because the pumping speed is dependent on the operating pressure prevailing at the time and the pumping speed can therefore be selected precisely.

The switching gas pressure can be, for example, a gas pressure prevailing at an inlet of the vacuum pump. This makes it possible to take advantage of the fact that the inlet pressure of a vacuum pump is usually monitored anyway, so that no additional pressure-determining devices are necessary.

Advantageous values for the switching gas pressure are below 1 hPa and / or above 0.01 hPa, preferably above 0.10 hPa.

In a further development, the control device is designed to switch over as a function of known pumping speed curves of the vacuum pump with series connection and with parallel connection in each case as a function of a gas pressure prevailing at an inlet of the vacuum pump. In particular, switching between series and parallel connection can take place at or at an intersection of the pumping speed curves.

In a further development, the control device is designed to start a pumping process with a parallel connection of the working pumping sections and to switch to a series connection of the working pump sections as soon as the pumping speed of the vacuum pump connected in parallel is less than or at least substantially equal to a pumping speed of the vacuum pump connected in series. In this way, an advantageous pumping speed can be set in each case.

According to the invention, the control device comprises at least one switchover valve, in particular a solenoid valve. Such switching valves allow simple, reliable control or switching. For example, a three-way valve, in particular with an operating voltage of 24V, can be provided.

According to the invention, the switching valve has two switching positions, one of which is assigned to the series connection and the other to the parallel connection.

In addition, according to the invention, the switching valve has at least one third switching position in which the working pump sections are separated from an inlet of the vacuum pump. As a result, the working pump sections and an outlet of the vacuum pump can be securely separated from the inlet. Thus, in particular, the function of an inlet or safety valve can also be taken over by the switchover valve. The vacuum pump therefore in particular has no additional inlet or safety valve. This not only saves costs, but also avoids a disadvantage that is frequently encountered with inlet valves, namely that low differential pressures often lead to insufficient closure of the inlet in differential pressure inlet valves. The switching valve, however, can effectively close the inlet at any differential pressures.

A high level of operational reliability can be achieved, for example, if the switchover valve is de-energized in the third switching position or if the switchover valve is designed in such a way that it automatically switches to the third in the de-energized state Switch position assumes and holds. In the event of a power failure, this prevents the process gas from flowing back into the recipient and, in particular, prevents the pump shaft from rotating in the opposite direction.

The switching valve can be designed as a 5/3-way valve, for example. This allows a structurally simple design.

In a further embodiment, a drive for at least one of the, in particular both or all, of the working pump sections comprises a direct current motor which is electrically connected in series with the switching valve. In this way, the motor can be controlled synchronously with the switchover valve in a simple manner. In particular, the currentless state can lead to the switching of the switchover valve in a safety position or the third switching position.

In a further exemplary embodiment, the control device comprises at least one further valve which, in order to implement the series connection, separates the first working pump section from an outlet of the vacuum pump.

Further embodiments of the invention can be found in the dependent claims, the description and the figures.

Fig. 1

zeigt eine Rotationsverdrängervakuumpumpe des Standes der Technik in einer Seitenansicht.

Fig. 2

zeigt die Vakuumpumpe der Fig. 1 in einer Schnittansicht entlang der Linie A-A von Fig. 1.

Fig. 3

zeigt für eine erfindungsgemäße Vakuumpumpe eine Auftragung des Saugvermögens in Abhängigkeit von einem Einlassdruck jeweils für eine Reihen- und eine Parallelschaltung der Arbeitspumpabschnitte.

Fig. 4

zeigt ein Schaltbild eines 5/3-Wegeventils zur Umschaltung zwischen Reihen- und Parallelbetrieb zweier Arbeitspumpabschnitte.

The invention is explained below by way of example only with reference to the schematic drawing.

Fig. 1

Figure 12 shows a rotary positive displacement vacuum pump of the prior art in a side view.

Fig. 2

shows the vacuum pump of the Fig. 1 in a sectional view along the line AA of Fig. 1 .

Fig. 3

shows a plot of the pumping speed as a function of an inlet pressure for a vacuum pump according to the invention, in each case for a series and a parallel connection of the working pump sections.

Fig. 4

shows a circuit diagram of a 5/3-way valve for switching between series and parallel operation of two working pump sections.

In Fig. 1 a rotary displacement vacuum pump of the prior art designed as a rotary vane vacuum pump and hereinafter referred to as vacuum pump 10 is shown. The vacuum pump 10 sucks in a working medium at an inlet 28 and conveys it to an outlet 30, which is open to the atmosphere, for example.

Fig. 2 FIG. 11 shows a sectional view of the vacuum pump 10 along the section line AA according to FIG Fig. 1 . The section runs parallel along an axis of rotation of a rotor 12 of the vacuum pump 10. The vacuum pump 10 comprises a safety valve 20, which prevents the working medium from flowing back if the pump fails. The safety valve 20 is pilot controlled by a pressure pilot control.

The vacuum pump 10 also includes a motor 26 for driving the rotor 12 of the vacuum pump 10. A coupling 27 is provided between the motor 26 and the rotor 12, which coupling can in particular be designed as a magnetic coupling.

Two work pump sections and a control pump section are formed on the rotor 12. A first work pumping section is defined by a slide 14 and a delivery chamber 15. A second work pumping section is defined by a slide 16 and a delivery chamber 17. In the control pumping section, the rotor has a slide 18 which rotates in a delivery chamber 19 to a To promote control fluid for the pressure pilot control. The vacuum pump 10 shown thus works in the first working pump section, in the second working pump section and in the control pump section, in each case according to the rotary vane pump principle. A plurality of slides 14 and 18 can also be provided in a respective pumping section.

The rotor 12 is received with its control section 18, 19 in a receiving part 24 and is supported and rotatably mounted therein. The receiving part 24 forms with an outer surface 32 a cylindrical basic shape which is aligned concentrically to the axis of rotation of the rotor 12.

In the in Fig. 3 The diagram shown represents the abscissa an inlet pressure of a vacuum pump according to the invention in logarithmic scale graduation. The ordinate shows the pumping speed of the pump on a simple scale. The diagram shows two pumping speed curves depending on the inlet pressure, namely a first pumping speed curve SP, which shows the pumping speed curve when the work pump sections are connected in parallel, and a second pumping speed curve SR, which shows the pumping speed curve when the work pump sections are connected in series.

Fig. 3 impressively illustrates that the pumping speed at a high inlet pressure, i.e. especially at the beginning of a pumping process starting from atmospheric pressure, is significantly greater in parallel operation than in series operation. However, only a significantly higher final pressure is achieved in parallel operation.

The pumping speed curves intersect - in the example shown here - at an inlet pressure of 0.15 hPA. The point of intersection and the courses themselves are, however, dependent on the structural design of the respective working pump sections and on their relative size to one another. The following applies that the smaller the size differences of the working pumping sections, the greater the gains in pumping speed.

The point of intersection can advantageously be used as a switching point for the control device of the vacuum pump to switch between parallel and series operation. In particular, a switching gas pressure corresponding to the point of intersection is determined and used as a basis for the control.

The diagram is used to describe a pumping process Fig. 3 read from right to left. An advantageous pumping process, in particular starting from atmospheric pressure, proceeds in such a way that parallel operation is started and there the high pumping speed according to SP is used for rapid evacuation. However, as soon as the pumping speed in parallel operation falls below that which is possible in series operation, the system switches to series operation so that the higher pumping speed according to SR can be used in the lower pressure range and a lower final pressure can be achieved.

In Fig. 4 a switching valve 40 is shown, which is designed as a 5/3-way valve and controls a vacuum pump according to the invention. The switching valve 40 has three switching positions (a), (b) and (c), in which two working pump sections 42 and 44 are connected in different ways. The switching valve 40 is designed as a solenoid valve for the purpose of selecting the desired switching position, although a corresponding solenoid arrangement is not shown in more detail.

Also shown are a number of fluid channels which connect an inlet 28 of the vacuum pump via the switchover valve 40 and the working pump sections 42, 44 to an outlet 30 of the vacuum pump. Furthermore, a switching valve 46 is provided, which can optionally be shut off.

In switching position (a), all connections of the switching valve 40 are separated from one another. In this position, no fluid can consequently flow from inlet 28 to outlet 30 and vice versa. This switch position corresponds in particular to the third switch position described above. In particular, it can be assumed when the switching valve 40 is de-energized.

In switching position (b) of the switching valve 40, the working pump sections are connected in parallel. The switching valve 46 is open. In this position, a high pumping speed can be achieved for high inlet pressures.

In the switching position (c), however, the work pump sections 42 and 44 are connected in series. For this purpose, the switching valve 46 is closed, which is indicated by a cross line. This switching position is preferably selected at low inlet pressures in order to be able to achieve a particularly low final pressure.

The changeover valve 40 thus realizes the changeover between series and parallel operation to increase performance on the one hand and at the same time a function as a safety valve on the other hand. Despite the structurally simple structure, the diverse advantages described herein can be achieved. If the invention for the development of the vacuum pump 10 according to Fig. 1 and 2 should be used, the safety valve 20 and the control pump section 18, 19 for the pressure pilot control of the safety valve 20 can be saved in particular by the safety function of the switching valve.

List of reference symbols

10

Vacuum pump

12th

rotor

14th

Gate valve of the first working pumping section

15th

Delivery chamber of the first working pumping section

16

Second working pumping section slide

17th

Conveying space of the second working pumping section

18th

Control pumping section slide

19th

Conveying space of the control pumping section

20th

Safety valve

24

Receiving part

26th

engine

27

coupling

28

inlet

30th

Outlet

32

Exterior surface

40

Changeover valve

42

Working pumping section

44

Working pumping section

46

Switching valve

SP

Pumping speed curve in parallel operation

SR

Pumping speed curve in series operation

Claims (12)

1. A vacuum pump comprising

   a first working pump section (42);

   at least a second working pump section (44); and

   a control device (40, 46) by which a switch can be made between a series connection and a parallel connection of the working pump sections, wherein the control device comprises at least one switchover valve (40) which has two switching positions, of which the one is associated with the series circuit and the other is associated with the parallel circuit,

   characterized in that
   the switchover valve (40) has at least a third switching position in which the working pump sections (42, 44) are separated from an inlet (28) of the vacuum pump.
2. A vacuum pump in accordance with claim 1,
   characterized in that
   the vacuum pump is a rotary displacement vacuum pump, in particular a rotary vane pump.
3. A vacuum pump in accordance with claim 1 or claim 2,
   characterized in that
   the control device (40, 46) is configured to perform the switchover when a predefined and/or predefinable switchover gas pressure is reached.
4. A vacuum pump in accordance with claim 3,
   characterized in that
   the switchover gas pressure is a gas pressure present at an inlet (28) of the vacuum pump.
5. A vacuum pump in accordance with claim 3 or claim 4,
   characterized in that
   the switchover gas pressure is below 1 hPa and/or above 0.01 hPa, preferably above 0.10 hPa.
6. A vacuum pump in accordance with at least one of the preceding claims,
   characterized in that
   the control device (40, 46) is configured to perform the switchover in dependence on known pumping speed curves of the vacuum pump in a series connection and in a parallel connection, in each case in dependence on a gas pressure present at an inlet (28) of the vacuum pump.
7. A vacuum pump in accordance with at least one of the preceding claims,
   characterized in that
   the control device (40, 46) is configured to start a pumping process with a parallel connection of the working pump sections (42, 44) and to switch to a series connection of the working pump sections as soon as the pumping speed of the vacuum pump in parallel connection is smaller than or at least substantially equal to a pumping speed of the vacuum pump in series connection.
8. A vacuum pump in accordance with at least one of the preceding claims,
   characterized in that
   the switchover valve (40) is a solenoid valve.
9. A vacuum pump in accordance with at least one of the preceding claims,
   characterized in that
   the switchover valve (40) is currentless in the third switching position.
10. A vacuum pump in accordance with at least one of the preceding claims,
    characterized in that
    the switchover valve (40') is configured as a 5/3-way valve.
11. A vacuum pump in accordance with at least one of the preceding claims,
    characterized in that
    a drive for at least one of the working pump sections (42, 44) comprises a direct-current motor which is electrically connected in series to the switchover valve (40).
12. A vacuum pump in accordance with at least one of the preceding claims,
    characterized in that
    the control device comprises at least one further valve (46) which separates the first working pump section (42) from an outlet (30) of the vacuum pump in order to implement the series connection.

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