Side-channel pump

Abstract

A side-channel pump having a pump housing in which an operating chamber which is provided with a side channel and a motor are arranged, and having an impeller in the operating chamber which rotates with a shaft which is driven by the motor. A cooling circuit extends from the operating chamber to the motor and from the motor to a suction portion of the pump, wherein the cooling circuit is supplied from an operating chamber whose outlet side is connected to an outlet opening of the side-channel pump. Using the pump, gas can be drawn in without the pump becoming overheated.

Claims

1. A side-channel pump comprising: a shaft rotatably supported in a pump housing and driven by a motor; a plurality of operating chambers arranged within the pump housing, each operating chamber provided with a side channel; an impeller provided within each of the plurality of operating chambers and rotatable therein, each impeller operatively connected to the shaft; and a cooling circuit extending from one of the plurality of operating chambers to the motor, and from the motor to a suction portion of the side-channel pump, wherein the one of the plurality of operating chambers is connected to an outlet opening of the side-channel pump, wherein the suction portion is arranged in the one of the plurality of operating chambers, and wherein the cooling circuit opens into the one of the plurality of operating chambers via a gap formed between the shaft and a portion of the pump housing surrounding the shaft, wherein the gap is defined by the shaft and the portion of the pump housing.

2. The side-channel pump as claimed in claim 1, wherein the cooling circuit extends between a rotor and a stator of the motor.

3. The side-channel pump as claimed in claim 1, wherein an electronic control system is received in the pump housing and the cooling circuit extends between the motor and the electronic control system.

4. The side-channel pump as claimed in claim 1, wherein an annular gap is formed between the pump housing and the motor.

5. The side-channel pump as claimed in claim 4, wherein the cooling circuit extends through the annular gap.

6. The side-channel pump as claimed in claim 4, wherein the motor is surrounded by an outer pipe and the outer pipe adjoins the annular gap.

7. The side-channel pump as claimed in claim 6, wherein the motor comprises an inner pipe which is arranged between a rotor and a stator of the motor.

8. The side-channel pump as claimed in claim 7, wherein the stator completely fills the space between the inner pipe and the outer pipe over a longitudinal portion of the motor.

9. The side-channel pump as claimed in claim 8, wherein a space which surrounds end windings of the stator is filled with a casting compound.

10. The side-channel pump as claimed in claim 1, wherein the pump housing is provided with a ventilation valve.

11. The side-channel pump as claimed in claim 3, wherein the electronic control system is configured to operate the side-channel pump with an overspeed when the operating chamber of the side-channel pump is filled with gas and to reduce the speed to an operating speed when liquid enters the side-channel pump.

Description

(1) The invention is described by way of example below with reference to the appended drawings and advantageous embodiments. In the drawings:

(2) FIG. 1: is a schematic illustration of a side-channel pump according to the invention;

(3) FIG. 2: shows an arrangement of a side-channel pump according to the invention and a liquid gas tank; and

(4) FIG. 3: shows another embodiment of a side-channel pump according to the invention.

(5) In a side-channel pump according to the invention in FIG. 1, a shaft 14 is rotatably supported in a pump housing 15. The pump housing 15 is provided with an inlet opening 16 and an outlet opening 17, wherein the inlet opening 16 is arranged concentrically relative to the shaft 14. The end of the pump housing 15 opposite the inlet opening 16 is closed so that the end of the shaft 14 is received inside the housing 15. By one end of the shaft 14 opening in the inlet opening 16 and the other end of the shaft 14 being received in the pump housing 15, the pump has no seals in the sense that there is no location at which the inner space and the outer space of the pump are separated only by a shaft seal. This has the advantage that discharge of the conveyed medium can be reliably prevented.

(6) In the pump housing 15 there is further received a drive motor which comprises a rotor 19 which is connected to the shaft 14 and a stator 20. The motor is controlled and in particular the speed of the motor is adjusted via an electronic control system 35.

(7) The pump according to the invention comprises two side-channel stages in which an impeller 22 rotates in each case in an operating chamber 23. The impellers 22 have vanes which are arranged in a star-like manner and which have open intermediate vane spaces which are surrounded closely by the housing 15. In a state axially beside the impeller 22, the housing 15 forms a side channel 24 which is open in the direction toward the impeller 22 and in which the conveying medium is conveyed by means of momentum exchange with the impeller 22. The inlet end of the side channel 24 is located opposite an inlet opening of the operating chamber 23, which opening is formed in the housing and cannot be seen in FIG. 1. The medium which enters through the inlet opening arrives through the intermediate spaces of the vanes at the side-channel 24. From the outlet opening of the previous operating chamber 23, a channel 25 which is indicated only schematically in FIG. 1 extends through the pump housing 15 as far as the inlet opening of the following operating chamber 23. The conveyed medium thus passes successively through the two side-channel stages of the pump.

(8) The inlet stage 26 of the pump is configured as a centrifugal stage. An impeller 27 which is connected to the shaft 14 is provided with channels 18 which extend from a central region to a peripheral region of the impeller 27. The medium which is introduced in the central region into the channels 18 is moved outward by means of the centrifugal force. From the outer end of the impeller 27, a channel extends through the pump housing 15 to the inlet opening of the first operating chamber 23.

(9) The pump housing 15 surrounds the operating chambers 23 of the pump and the motor 19, 20 with a spacing so that within the pump housing an annular gap 40 which surrounds the operating chambers 23 and the motor 19, 20 is formed. The outlet side of the second side-channel stage opens in the annular gap 40. The outlet opening 17 of the pump is also connected to the annular gap 40. The medium which is conveyed by the pump therefore moves from the outlet side of the second side-channel stage through the annular gap 40 to the outlet opening 17 of the pump.

(10) The stator 20 of the drive motor is surrounded by an outer pipe 41. The outer pipe 41 extends along the motor and at the same time forms the inner delimitation of the annular gap 40. Toward the inner side, the stator 20 of the drive motor is delimited by an inner pipe 42. The space between the inner pipe 42 and the outer pipe 41 is completely filled by the stator 20. The stator 20 is in direct extensive contact with the inner pipe 42 and the outer pipe 41 so that good heat transmission between the stator 20 and the inner pipe 41 and the outer pipe 42 is ensured. In the region of the end windings 43, the space between the stator 20 and the inner pipe 42 and the outer pipe 41 is filled with a thermally conductive casting compound 47.

(11) Between the drive motor 19, 20 and the electronic control system 35, a plurality of channels 44 extend radially inward from the annular gap 40. The channels 44 open in the motor gap 45 between the rotor 19 and the inner pipe 42 of the stator 20. The motor gap 45 extends over the entire length of the drive motor 19, 20 and merges into a gap 46 which is enclosed between the pump housing 15 and the shaft 14. The gap 46 opens in the operating chamber 23 of the second side-channel stage of the pump and is therefore referred to below as a chamber gap 46.

(12) The channels 44, the motor gap 45 and the chamber gap are components of a cooling circuit which extends from the operating chamber 23 of the second side-channel stage through the annular gap 40, the channels 44, the motor gap 45 and the chamber gap 46 back into the operating chamber 23 of the second side-channel stage of the pump. The cross-section of the cooling circuit is significantly smaller than the cross-section of the outlet opening 17 so that only a small portion of the conveyed medium moves as a cooling medium along the cooling circuit, whilst the larger portion of the conveyed medium leaves the pump through the outlet opening 17.

(13) The cooling medium is kept moving in the cooling circuit by the pressure difference between the outlet side of the second side-channel stage of the pump and the chamber gap 46. The pressure difference corresponds to approximately half of the pressure difference between the inlet side and the outlet side of the second side channel stage of the pump.

(14) The cooling circuit is configured in such a manner that it is in extensive contact with the inner pipe 42 and the outer pipe 41 of the stator 20 and can thereby effectively discharge heat from the stator 20. With the channels 44, the cooling circuit extends between the drive motor 19, 20 and the electronic control system 35 so that at the same time the electronic control system is also cooled. In the motor gap 45, the cooling medium is, except for with the stator 20, in extensive contact with the rotor 19 so that it is also cooled in an effective manner. After it has been returned into the operating chamber 23, the cooling medium is mixed with the conveyed medium which enters through the inlet opening into the operating chamber 23 so that the heat which is absorbed by the cooling medium is distributed in the volume flow.

(15) The cooling circuit is configured in such a manner that the pump according to the invention can be kept at a constant operating temperature during permanent operation when the pump conveys a liquid medium. If the pump instead conveys a gaseous medium, only a smaller quantity of heat is discharged and the pump becomes heated.

(16) In order to nonetheless prevent rapid overheating of the pump, the motor is configured in such a manner that it has a high thermal capacity. Both the rotor 19 and the stator 20 are to this end constructed in a very solid manner. In particular in the stator 20, a high thermal capacity is achieved by the space between the inner pipe 42 and the outer pipe 41 being completely filled. With this configuration of the stator 20, overheating is therefore counteracted in two respects. Firstly, as a result of the solid construction, a large quantity of heat can be absorbed. Secondly, as a result of the extensive contact of the inner pipe 42 and the outer pipe 41 with the cooling circuit, a large quantity of heat can be discharged. It is thereby possible, over a time period, for example, of more than minute, to convey gas without the pump becoming overheated.

(17) An application example of the pump according to the invention is shown in FIG. 2. The pump 28 according to the invention is connected to a liquid gas tank 29. A rising line 31 extends from the lower portion of the tank 29 toward the inlet opening 16 of the pump 28. There is connected to the outlet opening 17 of the pump 28 a line 34 which leads to a vehicle 32 which is intended to be filled with liquid gas 30. The volume flow of the pump is so large that it cannot be completely absorbed by the vehicle 32. In a separator 33, gas bubbles are separated from the volume flow and directed back into the tank 29.

(18) The tank 29 is filled to a level of approximately one third with liquid gas 30. The remaining space in the tank 29 and in the rising line 31 is filled with evaporated liquid gas, the pressure consequently corresponds to the vapor pressure of the liquid gas. If the pump 28 is moved from this state into operation, the liquid gas first enters the pump 28 in the gaseous state. Since, with the application of reduced pressure in the tank 29, liquid gas continues to evaporate, the suction power of the pump in this phase has to be large in order to nonetheless draw liquid gas in the liquid state through the rising line 31. According to the invention, this is achieved by the pump being operated in this phase with an overspeed which is substantially above the operating speed. The overspeed at which the pump is almost operated as a fan may be, for example, 6000 rpm. This speed is substantially above the speed at which the pump can be operated at the maximum level when liquid is conveyed. When conveying liquid, the pump is, for example, operated at a speed of 3000 rpm. The liquid is conveyed with a volume flow of, for example, 35 m.sup.3/h.

(19) In spite of the higher speed, the power of the pump when it is operated as a fan is lower than during normal operation in which liquid is conveyed. If a low power is sufficient to accelerate the pump to the overspeed, therefore, the operating chambers 23 of the pump are consequently filled with gas. The control system 35 is consequently configured to operate the electric motor 21 at the overspeed at a low power.

(20) As soon as liquid enters the pump, the resistance suddenly increases and the pump is braked. The control system 35 is configured in such a manner that the power of the electric motor 21 increases as soon as the pump 28 is braked to operating speed in order to keep the pump at this speed. This operating state is maintained until the tank of the vehicle 32 is filled. As soon as this is the case, the pump 28 is switched off.

(21) In the stopped state of the pump, liquid gas which is still contained in the pump continuously evaporates so that the operating chambers 23 after a sufficiently long waiting time return to the initial state again in which they are filled with gas. If another vehicle is intended to be filled, the pump can again at low power be accelerated to the overspeed. However, if the next filling operation takes place before the liquid has evaporated from the pump, the resistance is significantly higher and the pump is operated from the beginning at high power at operating speed so that liquid can be conveyed.

(22) In the alternative embodiment of FIG. 3, the pump housing 15 is provided with two ventilation valves 48 which open in the annular gap 46. The ventilation valves 48 are open as long as gas is conveyed. The ventilation valves 48 close when liquid medium is conveyed. With respect to the embodiment of FIG. 2, the gas discharged through the ventilation valves 48 is directed back into the tank 29 in the same manner as the gas separated with the separator 33.