EP0834017A1

EP0834017A1 - Vacuum pump

Info

Publication number: EP0834017A1
Application number: EP96922830A
Authority: EP
Inventors: Christian Dahmlos; Dietmar Rook; Ralf Steffens
Original assignee: SIHI INDUSTRY CONSULT GmbH; SIHI Ind Consult GmbH
Current assignee: Sterling Industry Consult GmbH
Priority date: 1995-06-21
Filing date: 1996-06-18
Publication date: 1998-04-08
Anticipated expiration: 2016-06-18
Also published as: JPH11508343A; WO1997001037A1; ATE186102T1; DE59603493D1; DK0834017T3; JP3957083B2; PT834017E; EP0834017B1; GR3032483T3; KR19990083660A; US5904473A; KR100390254B1; ES2140108T3; TW454066B

Abstract

PCT No. PCT/EP96/02630 Sec. 371 Date Dec. 17, 1997 Sec. 102(e) Date Dec. 17, 1997 PCT Filed Jun. 18, 1996 PCT Pub. No. WO97/01037 PCT Pub. Date Jan. 9, 1997A vacuum pump contains two rotary displacement rotor (8) that engage each other, in particular in a convoluted manner, inside in expansion chamber through which flows a stream in the axial direction. The rotors are mounted in cantilever at the delivery side and are linked each to a driving motor (35, 36). Each rotor (8) forms together with its shaft (20), a stationary bearing body (7) and a bearing (21, 22) delimited by the shaft (20) and the bearing body (7) a module that may be removed as a single unit from the housing (3). The rotor (35) of the driving motor is preferably also part of said module.

Description

VACUUM PUMP

The invention relates to a vacuum pump with a pair of circumferential, in particular screw-shaped, intermeshing rotors rotating within an axially through-flow chamber, which are overhung by a shaft mounted on the pressure side, each of which is arranged with the rotor of a motor located outside the housing forming the chamber connected is.

This design has the advantage that all the organs relating to the storage and the drive of the rotors are arranged on the pressure side, and outgassings originating from them can therefore reach the suction side of the pump less easily. This eliminates the need for complex seals. However, known pumps of this type (EP-A 472933 = US-A 5,197,861 and US-A 5,354 179; EP-A 558921 = US-A 5,393,201; US-A 5,295,798; US-A 5,314,312; US-A 5,329,216; JP- Abstract 2283890) the disadvantage that the rotating parts are difficult to access and must be separated from one another, for example, to be removed from the housing for maintenance purposes. This requires particularly qualified personnel, who are usually only available to the pump manufacturer.

The invention avoids these disadvantages in that each rotor, together with the associated shaft and a stationary bearing body that can be fixed to the housing, forms a unit that can be pulled off the entire housing. In this unit the drive-sensitive storage functions contracted. It can be preassembled, adjusted and balanced for exchange purposes by the manufacturer and sent to the manufacturer as a whole for maintenance purposes, while the remaining maintenance, including assembly and disassembly, can be left to the less specialized personnel available to the user.

So that each rotor assembly can be preassembled independently of the other, a separate bearing body is expediently assigned to each rotor. However, there may be applications in which a common bearing body can be provided for both rotors.

The housing forming the scooping space is expediently delimited on the pressure side by a base plate in or on which the bearing body can be centered and / or fixed. This base plate can be connected in one piece to the chamber housing. Appropriately, however, it is a separate part. It can also be part of the motor housing, which is usually arranged on the base plate on the side remote from the pump chamber housing.

As is known from the prior art mentioned at the outset, it is expedient if at least one rotor bearing is arranged within the rotor in a space which is only open to the pressure side on a tubular part of the bearing body which projects into the rotor. In this way it is achieved that the rotor shaft is only subjected to slight bending stresses and that consequently the deformation-related changes in the play of one rotor relative to the other and between the rotors and the housing can be kept low. This also allows a favorable dimensioning of the rotor shaft, as a result of which the radial space requirement associated with the rotor inner bearing is partially compensated for.

It is known to provide the rotor shafts with interacting gearwheels which bring about the synchronization of the shafts or, in addition to electronic synchronization, enable emergency synchronization. So that these gears are not contaminated by direct contact with the pumped medium and so that they can possibly be lubricated without the lubricant getting into the scooping chamber, according to the invention they are arranged on the motor side of a flange plate which delimits a space sealed from the scooping chamber for this purpose and belongs to the unit which can be pulled off with the rotor. Instead of the gears, it can also be a pulse encoder disk or the gears also serve as encoder disks.

The flange plate is expediently sealed off from the pumping chamber in that the flange plate is sealed off from the base plate or the motor housing, while the base plate or the motor housing is sealed off from the pumping chamber housing. This enables the flange plate to be mounted and centered on the motor housing. The scoop chamber (or its jacket and cover) can be removed for maintenance of the scoop chamber and the rotor surfaces, without this affecting the tight closure of the spaces accommodating the synchronization disks.

The motor housing is expediently sealed in a dust-tight manner from the atmosphere. It is therefore not necessary to seal the spaces receiving the synchronization disks from the drive.

The motor rotor expediently also belongs to the rotor unit which can be removed overall from the housing. The same applies to the synchronization gear wheel or the pulse generator disk which is rotatably connected to the rotor assembly and which is part of a device for measuring the angle of rotation of the rotor.

The invention makes it possible to considerably reduce the cost of warehousing by the fact that pumps of different delivery dates belonging to the same series differ essentially only in the length of the rotors, the scoop chamber housing and possibly the tubular parts of the bearing body. Instead of this or in addition, they can also differ from the design of the displacement projections on the circumference of the rotors.

The invention is explained in more detail below with reference to the drawing which illustrates an advantageous embodiment of the invention. In it show:

1 shows a longitudinal section in the plane of both rotor axes,

2 shows a longitudinal section transversely thereto,

3 shows a horizontal section along line III-III of FIG. 1 and

4 shows a plan view partly in section along line IV of FIG.

The motor housing 2 rests on the foot part 1, which is possibly integrally connected at the top to the flange-like base plate 3 on which the pump chamber housing 4 is built. This is closed at the top by a cover 5 which contains a suction opening 6

On the base plate 3, the flange plates 50 of the bearing bodies 7 are fastened in a manner to be explained later, each of which is used for mounting a rotor 8, the circumference of which preferably has two-helical displacement projections 9, which engage in a manner of a tooth engagement in the conveying cavities 10 engage between the displacer projections 9 of the adjacent rotor. In addition, the displacer projections 9 cooperate on the circumference with the inner surface of the pump chamber housing part 4. The rotors 8 are connected to the suction chamber 11 at the top and to the pressure chamber 12 at the bottom.

The pressure chamber 12 communicates with the pressure outlet 17 through the channel 16. These parts are provided at the lower end of the vertically positioned scoop chamber housing.

Each rotor 8 is connected in a rotationally fixed manner to a shaft 20 which is supported at the bottom in the bearing body 7 by a permanently lubricated roller bearing 21. A second, also permanently lubricated roller bearing 22 is located at the upper end of a tubular part 23 of the bearing body 7, which projects into a concentric bore 24 of the rotor 8 which is open at the bottom, that is to say on the pressure side. This bearing 22 is preferably located above the center of the rotor 8. The tubular part 23 of the bearing body preferably extends through the greater part of the length of the rotor 8. The end of the tubular part 23 is substantially higher than the pressure outlet 17 when the pump is arranged vertically This is helpful for protecting the bearing and drive region from the ingress of liquid or other heavy contaminants from the scooping area.

In the tubular part 23 of the bearing body, cooling channels 25 are provided which are connected to a cooling water source via channels 26 and to a cooling water drain via corresponding channels which do not appear in the drawing. The cooling channels 25 are preferably formed by helical screw-ins which are tightly covered by a sleeve. The cooling of the rotor bearings extends the service life and maintenance intervals of these bearings. Furthermore, the cooling also keeps the peripheral surface of the tubular part 23 of the bearing body at a low temperature. This circumferential surface is opposite the inner circumferential surface of the cavity 24 of the rotor with a small distance. These surfaces are designed in such a way that they are capable of good heat exchange and thus heat from the rotor indirectly via the tubular one Part 23 of the bearing body and its cooling devices 25 can be removed. To improve the heat exchange between the opposing surfaces of the tubular part 23 of the bearing body and the rotor cavity 24, these can be designed in a suitable manner. For example, they can be treated or burnished in such a way that the radiation exchange is favored by high absorption coefficients. The convective heat exchange by means of the gas layer located between them can be improved by a small surface distance and a suitable surface structure, which leads to an increase in the heat transfer coefficient. For this purpose, one surface or both can be made rough or with heat exchange ribs or threads or the like. It is also possible to supply a sealing gas to the rotor cavity 24 through the bearing body or the shaft 20, which is discharged from the pressure chamber 12 with the pumped medium. In addition to shutting off the bearing region, it can also be used for additional cooling of the bearing, the bearing body and the rotor, but it is expedient not to pass it through the bearing or bearings so as not to contaminate them, but via a channel 28 forming a bypass.

Suitable sealing and / or locking devices are provided to protect the bearing and drive area from influences penetrating from the suction chamber. It is particularly advantageous to equip the opposing surfaces of the bearing body 23 and the inner surfaces of the rotor cavity 24 on one side or on both sides with a conveying thread, not shown, which exerts a conveying effect from the rotor cavity 24 to the pressure chamber 12. Because of their higher density, this conveying effect primarily affects solid or liquid particles and thereby prevents them from penetrating into the bearing and drive area. The conveying thread is expediently designed such that this effect is still effective even at a considerably reduced speed.

The conveying effect can also be brought about in that the gap between the rotor and the bearing body widens conically towards the pressure chamber. The gap width (distance of the surface of the bearing body from the surface of the rotor) remains essentially constant. In addition, in this case too, the opposing surfaces can be provided with a conveying thread on one side or on both sides; However, this is not necessary.

Since the gap between the rotor and the bearing body is equipped with a conveying thread or a conical effect that acts very effectively against the penetration of liquid sealing or solid particles can often be dispensed with additional sealing devices; however, they can be provided, preferably in a non-contact or low-contact design, for example labyrinth seals or piston ring-like seals.

Due to the sealing effect of the delivery thread or the taper of the gap, the pump according to the invention is insensitive to the presence of liquid in the pumping chamber as long as the rotors are rotating. This insensitivity also exists in the stationary state thanks to the high bearing arrangement in the rotor, as long as the liquid in the scooping chamber does not reach the storage level. It is not only important if the pumped medium carries a liquid surge, but can also be used for cleaning and / or cooling the pump by liquid injection. For example, cleaning or cooling liquid can be sprayed through nozzles, one of which is indicated at 27. The same or separate nozzles 27 can be used for spraying in the cleaning liquid and the cooling liquid.

If very heavy contamination is to be expected, there is the option of spraying cleaning fluid continuously during operation. When operating a vacuum pump, the cleaning liquid should, as far as it can get into the suction chamber, have a vapor pressure below the suction pressure. If the pump is multi-stage and the contamination (for example, depending on the pressure) is mainly reflected in the second and / or subsequent stages, there is the possibility of limiting the injection of the cleaning liquid to the second or subsequent stage and thereby to separate the suction side.

In most cases, however, the cleaning operation does not take place continuously, but periodically when cleaning needs are determined (for example as a result of an increase in the drive torque). Thanks to the pump's insensitivity to liquids, relatively large amounts of liquid can be used. If the operating speed cannot be maintained due to the amount or type of cleaning fluid used, the speed can be reduced accordingly. Suitable control devices are provided for this. For example, the speed can be controlled as a function of the drive torque, which automatically leads to a corresponding reduction in the speed compared to the operating speed when the power requirement is increased. The continuous rotation of the rotors during the cleaning phase not only serves to seal the rotor bearing, but also promotes cleaning liquid on the dirty surfaces.

The pumping effect in the gap between the rotor and bearing body can also be used to pump sealing gas independently of an external compressed gas source. In general, however, the effect of such a compressed gas source will be preferred to convey the sealing gas in order to be independent of the rotor speed in the sealing gas supply.

The scoop housing 4 may include a chamber 30 (FIGS. 2 and 4) which rotates all or a large part of the circumference and circulates through the cooling water in order to keep the housing at a predetermined temperature. Cooling of the housing jacket is not necessary in all cases. However, it is advantageously possible in the context according to the invention because the rotors 8 are also cooled and their thermal expansion is therefore limited. There is no need to fear that the rotors only start against the housing because they expand while the housing is kept at a lower temperature.

The pump according to the invention can be equipped with pre-inlet. This means that in the areas of high, possibly even medium compression, channels 31 are provided in the housing, through which gas of higher pressure than the compression stage in this area of the scooping area is admitted into the scoop chamber, according to known Principles to effect cooling and / or noise reduction. According to an advantageous feature of the invention, the pre-inlet gas can be removed directly from the pressure side of the pump by being cooled in the cooling pockets 30 of the pump chamber shell 4. For this purpose, it can be passed through heat exchanger tubes 32.

The roller bearings 21, 22 in the example shown are angular contact ball bearings which are set against one another by a spring 29. Each shaft 20 preferably carries directly below the bearing 21, i.e. without an intermediate clutch, the rotor 35 of the drive motor, the stator 36 of which is arranged in the motor housing 2. The motor housing can be equipped with cooling channels 38.

The flange plates 50, which consist of one piece with the bearing bodies 7 in the example shown, are placed on the top of the base plate 3 with their outer edges 51, which essentially follow the circumference of the suction chamber housing 4, and their abutting inner edges 52. The flange plates 50 are opposite Base plate 3 sealed. The end faces 53 following in radial section of a secant, on which they abut one another, are also equipped with a sealing insert.

Underneath the flange plates 50, between the edges 51, 52, there is a recess which, with the top of the base plate 3, encloses a space 39 which serves to accommodate synchronization gearwheels 40 which are rotatably fixed on the shafts by known means 20 are arranged between the bearings 21 and the motor rotors. So that they can mesh with one another in the area of the inner edges 52 of the flange plates 50, the inner edges have a cutout at a corresponding point through which the gearwheels extend. Below this section, a web remains on each side, to which the reference line in FIG. 1 refers to the reference number 52 which generally designates the inner edge. This web is advantageous not only for reasons of stability, but also because it enables a circumferential seal on the one hand against the base plate 3 and on the other hand between the flattened secant surfaces of the flange plates 50.

The recesses 39 in the flange plates 50 have a diameter that is larger than the diameter of the synchronization gears 40. They are arranged a little eccentrically in relation to the inner edges 52, so that the synchronization gears 40 despite the assembly of the rotor units the presence of the sealing web at 52 can be used.

Since the space 39 containing the synchronization gears 40 is completely separated from the scooping space, there is no risk of contamination for the synchronization gears. They are only used for emergency synchronization of the rotors. Your teeth do not normally come into contact with each other. Lubrication is therefore generally not necessary. Although it can be used if desired, the dry running of the synchronization gearwheels simplifies the construction because a seal between the space 39 and the drive motors is not required.

The synchronization gearwheels 40 can also serve as pulse encoder disks or can be supplemented by additional pulse encoder disks which are sensed by sensors 42, one of which is shown in FIG. These sensors 42 are connected to a control device which monitors the respective rotational position of the rotors with respect to a target value and corrects them via the drive. It is a matter of electronic synchronization of the rotors, which is known as such and therefore does not require any further explanation here. The game between the teeth of the Synchronisa- tion gears 40 is slightly less than the backlash between the displacement projections 9 of the rotors 8. However, it is greater than the synchronization tolerance of the electronic synchronization device. If the latter function properly, neither the flanks of the displacement projections 9 nor the teeth of the synchronization gears 40 come into contact with one another. In the event that the latter should come into contact with one another, they are provided with a wear-resistant and possibly low-friction coating.

In addition to the drive power and speed, the performance data of the pump are determined by the displacement or delivery volume formed on the rotors and thus by the length of the rotors. The delivery data can therefore be changed by changing the length of the pump part containing the rotors. A series of pumps with different performance data is therefore preferably characterized in that the individual pumps in this series differ in the gradation of the length of these parts, to which the pump chamber housing, the rotors and, if applicable, the tubular parts of the projecting into the rotors Bearing body belong.

It can be seen that each rotor with the associated bearing and drive devices forms an independently mountable structural unit which, in addition to the rotor, comprises the bearings 21, 22, the bearing body 7, the cooling devices provided therein, the shaft 20, the synchronization gear 40, the associated sensor 42 and the motor rotor 35. These units are completely pre-assembled in the pump. They can be easily removed or inserted from the base plate 3 after the removal of the pumping chamber housing. Their replacement can therefore be left to the user, while the manufacturer takes care of the maintenance of the sensitive units as such.

FIGS. 2 and 4 illustrate that the suction space 11 is separated from the scooping space by a cover plate 14, which prevents a direct passage of the sucked medium from the suction opening 6 into the scooping space. Instead, it first passes through one or the other of two openings 61 into the head space 62 of one of two settling spaces 63, which are attached as special containers 68 to the broad sides of the scooping space housing 4. The head space 62 is open at the bottom towards the settling space 63 and laterally delimited by partitions 64 from two side spaces 65, which are also open towards the settling space 63 and through an opening 66, which are arranged on both sides of the opening 61, with the scooping space connected to the pump. The medium drawn in passes from the suction opening 6 through the suction chamber 11 into a middle head space 62, is redirected downward into the settling space 63, is redirected therein upward to one of the side head spaces 65 and from here passes through the opening 66 into the scooping space. The openings 61, 62 through which the medium flows into the settling space 63 are thus spatially offset from the openings 65, 66 through which it flows back into the scooping space. The deflection thereby forced onto the gas flow has the result that liquid or solid particles carried along by it are thrown downward into the settling space 63 due to the inertia effect. In particular, this also applies to any liquid surge. If liquid gushes are often to be expected, the settling areas can be provided with discharge devices for the liquid contained therein. Irrespective of this or possibly also functionally connected thereto, a fill level meter 67 can be provided.

The pump is preferably of an isochoric design in order to be able to convey larger quantities of liquid without damage.

Claims

claims

1. Vacuum pump with a pair of circumferential, in particular helically interlocking, displacement rotors (8) that circulate within an axially flow-through chamber, which are carried by a shaft (20) mounted on the pressure side, each of which with the rotor (35) one outside the one Scooping chamber forming the housing (4) is connected to the motor, characterized in that each rotor (8) with the associated shaft (20) and a special stationary bearing body (7) which can be fixed to the housing, one of the rest of the Ge ¬ housing removable unit forms.

2. Vacuum pump according to claim 1, characterized in that each rotor (8) is assigned a separate bearing body (7).

3. Vacuum pump according to claim 1 or 2, characterized in that the housing (4) forming the delivery chamber adjoins the pressure side on a base plate (3) on which the bearing body (7) can be fixed.

4. Vacuum pump according to one of claims 1 to 3, characterized in that a flange plate (50), which is removable with the rotor assembly, delimits a space sealed from the suction chamber, in which a synchronization gear (40) and / or one Pulse generator is provided.

5. Vacuum pump according to claim 3 or 4, characterized in that a motor housing accommodating the motors (37) is arranged on the base plate (3) on the side remote from the pump chamber (4).

6. Vacuum pump according to one of claims 1 to 5, characterized in that at least one rotor bearing (22) within the rotor (8) in an only towards the pressure side (12) open space (24) of the rotor at one in the rotor (8 ) protruding tubular part (23) of the bearing body (7) is arranged.

7. Vacuum pump according to one of claims 1 to 6, characterized in that the motor rotor (35) is one of the removable rotor assemblies.

8. Vacuum pump according to one of claims 1 to 7, characterized in that the synchronization gear or the pulse generator disk belongs to the overall removable rotor assembly.

9. Series of vacuum pumps according to one of claims 1 to 8, characterized gekenn¬ characterized in that pumps different delivery data apart from the drive essentially only by the length of the rotors, the baffle housing and possibly the tubular parts of the bearing body and possibly the execution distinguish the displacement projections on the circumference of the rotors (8).