WO2002090775A1

WO2002090775A1 - Rotary piston pump

Info

Publication number: WO2002090775A1
Application number: PCT/EP2002/003771
Authority: WO
Inventors: Peter Schnabl
Original assignee: Peter Schnabl
Priority date: 2001-05-09
Filing date: 2002-04-05
Publication date: 2002-11-14
Also published as: DE10122355A1

Abstract

The invention relates to a rotary piston pump comprising a casing (10) with a cylindrical annular space (14) and an annular piston (12a, 12b), which is arranged inside the annular space (14) in a manner that permits it to rotate and to be axially displaced. The facing end surfaces (20, 26) of the annular space (14) and of the annular piston (12a, 12b) are provided as continuous undulated surfaces with axially parallel amplitudes, and at least one respective inlet channel and one outlet channel (56, 58) for supplying or discharging a working fluid into or from the annular space (14) are provided inside the housing (10). The rotary piston pump is realized in the form of an electric machine in which the annular space (14) is surrounded by a stator winding (54), which generates a rotating field, and the annular piston (12a, 12b) forms the rotor.

Description

Rotary pump

The invention relates to a rotary lobe pump, comprising a housing with a cylindrical annular space and an annular piston which is rotatably and axially displaceably arranged in the annular space, the facing end faces of the annular space and the annular piston being designed as continuous shaft surfaces with axially parallel amplitudes, and in which the housing each have at least one inlet and one outlet channel for supplying or discharging a working fluid to and from the annular space.

A rotary lobe pump of the type mentioned above is described, for example, in the unpublished German patent application 199 53 168. The invention has for its object to design a pump of the type mentioned above so that the medium to be pumped can be pumped completely leak-free.

This object is achieved in that the rotary lobe pump is designed in the manner of an electrical machine in which the annular space is surrounded by a stator winding generating a rotating field and the annular piston forms the rotor. The ring piston can be designed as a short-circuit or squirrel-cage rotor of a three-phase asynchronous motor. The three-phase current acting in the stator winding generates a magnetic rotating field which exerts an "induced" torque on the ring piston, which acts as a rotor. The ring piston itself can consist of an iron core, in which, to increase the magnetic flux, a cage can be embedded, which consists of a material with very good electrical conductivity, for example silver or copper. A high magnetic flux is generated by this arrangement, which in turn is synonymous with a high induced torque in the ring piston. The housing containing the annular space itself preferably consists of an electrically non-conductive material in order to prevent induced eddy currents in the housing.

In an alternative embodiment, the ring piston is designed as a synchronous rotor, in which a plurality of permanent magnets are permanently installed. The stator winding for generating the rotating field is designed analogously to the embodiment described above. In this case, the ring piston forming the rotor rotates to the rotating field without slipping. This has the advantage that no heat is developed in the annular piston, which could possibly have an adverse effect on the medium to be conveyed.

According to one aspect of the invention, in order to achieve the object on which the invention is based, it is proposed that the rotary lobe pump be designed in the manner of an eddy current clutch with a drivable excitation part mounted outside the annular space and coaxially to the latter and a secondary part formed by the annular piston. The exciter part, which is designed as a magnet wheel, induces voltages in the secondary part which produce currents when the two coupling halves lead out a relative movement against one another. These eddy currents in the ring piston create a secondary magnetic field that counteracts the relative movement with respect to the magnet wheel. This creates a torque that depends on the slip speed. The magnet wheel can be driven from the outside in any way.

The solution according to the invention offers the possibility of producing the pump in a completely encapsulated design, in which the only connections of the annular space to the outside are the inlet and outlet channels. As a result, media can be conveyed with the pump according to the invention that have no contact with the Should have outside air, be it that the medium is dangerous to the outside world, or that the medium could be contaminated by contact with the outside world.

The annular piston is preferably designed in the form of a cylindrical tube section. The free space within the ring piston can be used to connect the two halves of the housing, which is preferably in two parts, also within the ring or rotary piston. The housing wall between the stator winding and the annular space is preferably extremely thin-walled in order to keep the air gap between the stator and rotor as small as possible. This can improve the efficiency when driving the annular piston.

By eliminating a drive shaft for the annular piston, the inlet and outlet channels can be provided both inside and outside the annular space.

In the solution according to the invention, as in the rotary piston machine described in the above-mentioned earlier application, the respective inlet and outlet openings of the at least one inlet and outlet channel are provided in the annulus within an axial region of the annulus outer surface, which is defined by the maximum axial distance the troughs of the mutually facing end faces is determined. It is advantageous if the inlet and outlet channels are formed outside the axial height of the stator. This separates the functions of the electric drive and the pump from each other. There is no geometric overlap. This offers the possibility of constructively designing the function of the pump on the one hand and the drive on the other hand in terms of their respective efficiency.

Further advantageous embodiments of the rotary lobe pump according to the invention result from the further subclaims.

The following description in conjunction with the accompanying drawings explains the invention using exemplary embodiments. Show it: Figure 1 is a schematic, perspective, partially broken

Representation of a rotary piston machine with a piston / annulus arrangement, as described in DE 199 53 168,

FIG. 2 shows a section through the housing of the arrangement shown in FIG. 1 containing the axis,

Figure 3 is a schematic, perspective, partially broken

Representation of a rotary piston machine with a double piston,

FIG. 4 shows a schematic section through the double piston arrangement according to FIG. 3 containing the axis,

4a shows the detail A from FIG. 4 on an enlarged scale for a modified embodiment,

FIGS. 5 to 10 each show a development view of the sliding end faces of the housing ring space and the double piston of a double-piston machine according to FIGS. 3 and 4 working as a pump,

FIG. 11 shows a schematic section containing the axis through a first embodiment of the rotary lobe pump according to the invention,

FIG. 12 shows a perspective, partially sectioned illustration of the ring piston forming the rotor,

Figure 13 is a partial section containing the axis through another

Embodiment of the rotary lobe pump according to the invention.

In order to better understand the mode of operation of the rotary lobe machine from which the rotary lobe pump according to the invention is derived, reference is first made to the Figures 1 to 10 referenced, which show a solution described in the unpublished DE 199 53 168.

The rotary piston machine shown in FIGS. 1 and 2 comprises a cylindrical housing 10 and an annular piston 12 designed in the form of a tubular section, which is rotatably and axially displaceably guided in an annular cavity 14 of the cylindrical housing 10. The piston is connected in a rotationally fixed but axially displaceable manner on the shaft 18, which passes through the housing 10, via a radial base, which is indicated by dashed lines in FIG. 1 and is designated by 16, or via radial spokes. Such a rotationally fixed connection, which enables an axial displacement, can take place, for example, via a spline, as shown in FIG.

The annular space 14 has an annular end surface 20, which can have a rectilinear or curved cross section and which runs in a wave-like manner in the circumferential direction with an axially parallel wave amplitude. As can be seen in FIGS. 5 to 10, the wavy line is approximately sinusoidal and has two wave crests or maxima 22 and two wave troughs or minima 24 in the example shown.

The end face or end face 26 of the annular piston 12 facing the end face 20 of the annular space 14 is also formed in a wavy line, as can be seen in FIG. 1. This end surface also has two maxima or wave crests 28 and two wave troughs 30 (FIGS. 5 to 10). However, this wavy line is designed such that the half-width of a wave crest measured in the circumferential direction, i.e. the width of the wave crest in the axial center between a wave minimum and a wave maximum is less than the half-value width of a wave trough. The arrangement could also be reversed insofar as the end face 26 of the annular piston is selected to be sinusoidal and the end face 20 of the annular space 14 has narrower wave crests and wider wave troughs.

It is important to note that both mutually facing wave surfaces must not be identical, that is to say sinusoidal or cosine-shaped, in which case the surfaces would block. The aim is an axial movement of the rotary piston in the manner of a harmonic vibration without extreme accelerations near the turning points. For example, assuming that one of the wave surfaces is at least approximately sinusoidal or cosine-shaped, the requirement that the other wave surface only slide with one point on this sinusoidal or cosine-shaped wave surface results in this wave surface being narrower wave crests and wider wave troughs than the sinusoidal Has wave surface.

In FIG. 2, one of the inlet and outlet channels 32 can also be seen in the housing 10, which ends at the inner boundary wall 15 of the annular space 14 and serves to supply or discharge a working fluid to the annular space 14, as is shown in FIGS. 5 to 10 is explained in more detail.

The piston 12 is tensioned against the end face 20 of the annular space 14 by a helical spring 34 arranged coaxially to the shaft 18. Instead of the helical spring, a plate spring can also be used, which can simultaneously serve to connect the piston to the shaft in a rotationally fixed manner. The axial length is shortened with the disc spring.

In the embodiment of the rotary piston machine according to the invention shown in FIGS. 3 and 4, two piston / housing arrangements of the type shown in FIG. 1 are arranged coaxially with one another, the spring 34 being omitted. The two pistons are combined to form a single double piston, the same parts being identified in the figures with the same reference numerals as in FIGS. 1 and 2.

The arrangement of the end faces 20 of the annular spaces 14 is selected such that the maxima and minima of the two end faces 20 each lie on a common generatrix of the cylindrical annular spaces 14, as is also shown in FIGS. 5 to 16.

The end faces 26 of the double piston 12, on the other hand, are shaped such that the maximum or the wave crest 28 of one end face with a minimum or the wave trough 30 of the opposite end face lies jointly on a generatrix of the cylindrical annular piston 12.

In FIG. 3, 33 denotes a guide groove formed in the radially outer wall of the annular space 14, into which a pin 35 attached to the piston 12 engages. The guide groove follows the waveform in the circumferential direction End surface 20 and thus controls the translational movement of the piston 12 without the end surfaces 20 and 26 touching. However, this solution is only optional.

Figure 4a shows yet another way to reduce the sliding friction between the end surfaces 20 and 26 and thus the wear of these surfaces. In a recess in the end surface 26 of the piston 12, a roller 37 is rotatably mounted so that it can roll on the end surface 20 of the annular space 14.

FIGS. 5 to 10 relate to a rotary piston machine operated as a pump of the type described in FIGS. 3 and 4. Two pairs of inlet openings 36 (suction line) and outlet openings 38 (pressure line) are provided per cylinder. There are two cycles per working stroke. Relative to the direction of rotation of the piston 12 pointing in the direction of arrow A, the outlet opening 38 lies in front of a wave crest 22 and the inlet or suction opening 36 behind the wave crest 22. The shape of the inlet opening 36 and the outlet opening 38 is usually not circular in practice, but is designed depending on the intended use of the rotary lobe machine and also on the type of medium flowing through in order to achieve optimal control of the medium flow.

Figure 5 shows the piston 12 at top dead center. Four separate cavities are formed between the upper end surface 20 'of the annular space 14 and the upper end surface 26 of the piston 12. The outlet openings 38 are approximately closed. When the piston 12 rotates in the direction of arrow A, the inlet openings 36 are gradually opened, so that the medium to be conveyed is sucked into the cavity lying between 90 and 180 ° and the cavity lying between 270 and 360 °. In the lower half of the rotary lobe pump, on the other hand, the cavity lying in the direction of rotation between 90 ° and 270 ° has reached its maximum expansion. The suction phase has ended here. The printing phase, i.e. the suction of the sucked medium through the outlet opening 38 begins.

The following FIGS. 6 to 10 show the further phases of the work of the pump when the piston 12 progresses in the direction of arrow A relative to the housing 10.

It can be seen that the control of the inlet and outlet openings takes place entirely without valves solely by the piston itself and that besides that rotating and axially oscillating pistons no further moving parts are required. In particular, no movable sealing elements are required. Since the piston is completely symmetrical, there is no imbalance.

Two exemplary embodiments of the rotary lobe pump according to the invention, which works according to the principle described above, will now be explained below with reference to FIGS. 11 to 13. The parts which are identical to the parts of the embodiment described in FIGS. 1 to 4A are also identified by the same reference numerals.

The most important difference between the embodiment shown in FIGS. 11 and 13 and the previously described solution is that the central shaft to which the ring piston is connected in the solution according to FIGS. 1 to 4A is omitted in the embodiments of FIGS. 11 to 13 , The housing 10 consists of two halves 10A and 10B which lie closely together along an axis-normal parting plane 40 and are firmly connected to one another by a clamping bolt 42. The annular piston 12 is designed as a cylindrical tube section and likewise consists of two halves 12A and 12B, which abut one another in a central plane normal to the axis. In the ring piston 12 made of iron, a cage 44 is embedded, which consists of a first ring 46, a second ring 48 and the connecting rods 50 arranged axially parallel and connecting the two rings (see also FIG. 12). The cage is preferably made of a material with high electrical conductivity, such as silver or copper.

In an axially central section 52, the housing 10 has a reduced outer diameter. This section 52 is surrounded by a stator winding 54, which can generate a rotating field. The rotating field generated by the three-phase current exerts an "induced" torque on the annular piston 12 functioning as a rotor. The annular piston 12 can thus be driven without contact, so that the annular space 14 can be completely encapsulated.

As can be seen in FIG. 11, the inlet and outlet channels 56, 58, through which the medium to be pumped enters and exits the annular space 14, are provided in the sections of the housing 10 outside the stator winding 54. Thus the position of the inlet ^'and outlet openings can in the wall of the annular space 14 can be optimized regardless of the electrical properties of the pump drive.

The embodiment according to FIG. 13 shows a drive of the annular piston 12 in the manner of an eddy current clutch. The same parts of the rotary lobe pump are again identified by the same reference numerals as in the previous embodiments.

Coaxial to the cylindrical housing 10, a pole wheel 62 is rotatably mounted thereon by means of ball bearings 60. This pole wheel 62 carries excitation windings 63 and has a ring gear 64 via which it can be driven. The rotation of the magnet wheel 62 induces secondary stresses in the iron or steel annular piston 12, which produce currents when the rotary piston and the magnet wheel rotate relative to one another. The eddy currents in the rotary lobe generate a secondary magnetic field which counteracts the relative movement with respect to the pole wheel 62. This creates a torque that depends on the slip speed. The rotary piston or annular piston 12 can thus also be driven without contact, so that the pump cavity can be completely closed.

Claims

Patent claims

1. Rotary lobe pump comprising a housing (10) with a cylindrical annular space (14) and an annular piston (12) which is rotatably and axially displaceable in the annular space (14), the mutually facing end faces (20, 26) of the annular space ( 14) and the annular piston (16) are designed as continuous shaft surfaces with an axially parallel amplitude, and in the housing (10) at least one inlet and one outlet channel (56, 58) for supplying or removing a working fluid from the annular space (14 ) are formed, characterized in that the rotary lobe pump is designed in the manner of an electrical machine, in which the annular space (14) is surrounded by a stator winding (54) producing a rotating field and the annular piston (12) forms the rotor.

2. Rotary lobe pump according to claim 1, characterized in that the annular piston (12) is designed as a short-circuit or squirrel-cage rotor of a three-phase asynchronous motor.

3. Rotary lobe pump according to claim 1 or 2, characterized in that the housing (10) consists of an electrically non-conductive material.

4. Rotary lobe pump according to one of claims 1 to 3, characterized in that the annular piston (12) consists essentially of an iron core.

5. Rotary lobe pump according to claim 4, characterized in that in the

Iron core is embedded in a cage (44) made of a material which has an increased electrical conductivity compared to iron.

6. Rotary lobe pump according to claim 1, characterized in that the annular piston (12) is designed as a synchronous rotor, in which a plurality of permanent magnets is permanently installed.

7. Rotary piston pump comprising a housing (10) with a cylindrical annular space (14) and an annular piston (12) which is rotatably and axially displaceable in the annular space (14), the mutually facing end faces (20, 26) of the annular space (14 ) and the annular piston (16) are designed as continuous shaft surfaces with an axially parallel amplitude, and in the housing (10) at least one inlet and one outlet channel (56, 58) for supplying or removing a working fluid from the annular space (14) are formed, characterized in that the rotary lobe pump is designed in the manner of an eddy current clutch with an excitable part (62) which is drivable outside the annular space (14) and coaxially to the latter and a secondary part formed by the annular piston (12).

8. Rotary lobe pump according to one of claims 1 to 7, characterized in that the annular piston (12) is designed in the form of a cylindrical tube section.

9. Rotary lobe pump according to one of claims 1 to 8, characterized in that the respective inlet and outlet opening (36, 38) of the at least one inlet and outlet channel (56, 58) in the annular space (14) within an axial region of the annular surface area lie, which is determined by the maximum axial distance of the troughs of the mutually facing end faces (20, 26).

10. Rotary lobe pump according to one of claims 1 to 9, characterized in that the inlet and outlet channels (56, 58) are formed outside the axial height of the stator winding (54).

11. Rotary lobe pump according to one of claims 1 to 10, characterized in that at least two wave crests (22, 28) and two wave troughs (24, 30) are provided at 360 ° of the circumference, the half-width of the wave crests (28) measured in the circumferential direction. at least one of the end faces is smaller than that of the troughs (30) of the same end face.

12. Rotary lobe pump according to one of claims 1 to 4, characterized in that a groove (33) is formed in an outer surface of the annular piston (12) or the annular space (14) into which one with the other part (annular space 14, annular piston) 12) engages the connected guide element (31), the course of the groove in the circumferential direction corresponding to that of the waveform of the end face (20) of the annular space (14).

13. Rotary lobe pump according to one of claims 1 to 4, characterized in that in one of the mutually facing end faces (20, 26) of the annular space (14) and the annular piston (12) a guide element (37) intended for rolling contact with the other end face. is rotatably mounted.

14. Rotary piston machine according to one of claims 1 to 13, characterized in that the inlet opening (36) and the outlet opening (38) are arranged in the circumferential direction in front of or behind a wave crest (22) of the end face (20) of the annular space (14).

15. Rotary lobe pump according to one of claims 1 to 14, characterized in that at least two inlet openings (36) and two outlet openings (38) are provided per end face of the annular piston (12).

16. Rotary lobe pump according to one of claims 1 to 15, characterized in that the inlet opening and / or the outlet opening is provided on the radially inner boundary wall (15) of the annular space (14).

17. Rotary lobe pump according to one of claims 1 to 16, characterized in that one of the end faces (20, 26) which come into contact with one another is sinusoidal.

18. Rotary lobe pump according to one of claims 1 to 17, characterized in that the annular space (14) and the annular piston (12) have mutually associated shaft surfaces (20, 26) at both axial ends.

19. Rotary lobe pump according to claim 18, characterized in that the maxima and minima of the two identically shaped end faces (20) of the annular space (14) each lie on the same generatrix of the cylindrical outer surface of the annular space (14) and that the maximum (28) of the one End surface (26) of the annular piston (12) with a minimum (30) of the other end surfaces (26) on the same generatrix of the piston surface.