This is a U.S. national stage of application No. PCT/EP2007/062316, filed on 14 Nov. 2007. Priority is lcaime in the following application: Country: Germany, Application No.: 10 2006 053 933.8, Filed: 15 Nov. 2006; the content of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a side-channel pump for pumping a medium from an inlet channel to an outlet channel having a driven impeller that is rotatable in a pump housing, at least one ring of rotor chambers arranged in one of the end faces of the impeller, at least one partially annular channel arranged in the pump housing opposite the ring of rotor chambers and extending from the inlet channel to the outlet channel, with an edge arranged on the end face of the impeller radially outside the ring of rotor chambers, a section of the pump housing located opposite the edge, and an annular gap arranged between the edge of the impeller and the section of the pump housing.
2. Prior Art
Side-channel pumps of this type are frequently used, for example, in present-day motor vehicles for pumping fuel or windshield-washer fluid. The pump housing is composed of two housing parts which are held at a distance from one another by an intermediate ring having dimensions corresponding to a height of an impeller. In order to keep losses through leakage as small as possible, the distance between the impeller and the pump housing is usually only a few hundredths of a millimeter. This, however, gives rise to the danger of the impeller rubbing against the pump housing, leading to increased friction and a reduction in the efficiency of the side-channel pump. The danger of the impeller rubbing is increased by manufacturing tolerances and by axial forces acting on the impeller. Such forces acting on the impeller are produced, for example, if the inlet channel is arranged on one end face of the impeller and the outlet channel on the other end face of the impeller.
SUMMARY OF THE INVENTION
The invention is based on developing a side-channel pump such that it largely avoids the impeller rubbing against the pump housing.
This problem is solved according to one embodiment of the invention in that an annular gap has at least one pocket for receiving the pumped medium, the at least one pocket formed by an increase in the distance of the edge of the impeller from the section of the pump housing located opposite thereto.
As a result of this configuration, during operation an edge of the impeller is subjected by the pocket, to an axial pressure loading, whereby the impeller is maintained at a distance from the housing part. It is ensured by means of the position of the pocket that axial forces act on a radially outer edge of the impeller. The forces for maintaining the impeller in a specified position in the pump housing are kept low as a result of a lever effect.
According to another advantageous of the invention, a plurality of pockets, distributed around the circumference of the annular gap and spaced from one another, contribute to providing especially reliable support of the impeller forces.
Pumping of the medium from one of the pockets to an adjacent pocket during rotation of the impeller would lead to unnecessary churning of the medium and therefore to heating thereof and to unnecessary energy consumption. According to another advantageous embodiment of the invention, such pumping is avoided if the distance between adjacent pockets is at least equal to a length of a pocket.
According to another embodiment of the invention, tilting of the impeller is reduced if the pockets are arranged on both end faces of the impeller. Preferably, three pockets are arranged on each side of the impeller.
According to another advantageous development of the invention, feeding of the pockets with the pumped medium from the radially outer circumferential gap between impeller and pump housing is implemented if the pockets extend from the edge of the impeller until beyond the radial boundary of the impeller. This radially outer peripheral gap between pump housing and impeller is constantly filled with the pumped medium through leakage. An intermediate pressure, which is lower than a pressure, inside the pump and greater than the intake pressure prevails constantly in the radially outer circumferential gap. The intermediate pressure differs at almost all angular positions along the partially annular channel from the pressure in the annular gap between impeller and pump housing. The intermediate pressure is therefore especially suited to compensating tilting moments on the impeller.
According to another embodiment of the invention, the impeller has a hydraulic bearing by which it automatically adjusts the distance from the pump housing when the pockets are arranged as recesses in the impeller.
An unbalanced mass in the impeller is avoided according to another embodiment of the invention if the pockets are arranged as recesses in the pump housing. In addition, tilting moments induced in the impeller by the arrangement of the inlet channel and the outlet channel is compensated by an irregular arrangement of the pockets around the circumference of the impeller. Self-evidently, pockets may be arranged both in the impeller and in the pump housing.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention makes possible numerous embodiments. For further clarification of its basic principle, two of the embodiments are represented in the drawing and are described below. In the drawing:
FIG. 1 is a longitudinal section through a side-channel pump according to the invention with adjacent regions of an electric motor;
FIG. 2 is a sectional representation through the inventive side-channel pump from FIG. 1 along the line II-II; and
FIG. 3 is a longitudinal section through a further embodiment of an inventive side-channel pump.
DETAILED DESCRIPTION OF THE DRAWINGS
FIG. 1 is a longitudinal section through a side-channel pump 1 with adjacent regions of an electric motor 2. The side-channel pump 1 has an impeller 4 which is rotatable in a pump housing 3. The impeller 4 is arranged on a shaft 5 of the electric motor 2. The pump housing 3 has two housing parts 7, 7′ which are spaced apart by an annular element 6, and a casing 8. The dimensions of the annular element 6 are such that the housing parts 7, 7′ are located opposite the end faces of the impeller 4 with a small clearance. The casing 8 holds the side-channel pump 1 in a specified position with respect to the electric motor 2 and tensions the housing parts 7, 7′, of the pump housing 3 against the annular element 6. An inlet channel 9 is arranged in one of the housing parts 7, while the other housing part 7′ has an outlet channel 10. The inlet channel 9 and the outlet channel 10 are each connected to respective partially annular channels in 11, 12 arranged in the housing parts 7, 7′. In the region of the partially annular channels 11, 12, the impeller 4 has rings of rotor chambers 13, 14 delimited by guide vanes. The partially annular channels 11, 12 form, with the rotor chambers 13, 14, a pumping chamber leading from the inlet channel 9 to the outlet channel 10 for pumping a medium when the impeller 4 is driven. The impeller 4 has an edge 15 on its end face in its radially outer region, as viewed from the rotor chambers 13, 14. Between the periphery of the impeller 4 and the annular element 6, the side-channel pump 1 has a circumferential gap 16 filled by leakage with the medium to be pumped. Between the edge 15 and the opposite section 17 of the pump housing 3, the side-channel pump 1 has an annular gap 18 with widened portions 19. The widened portions 19 are produced by pockets 20 arranged in the pump housing 3. The widened portions 19 extend from the end-face edge 15 of the impeller 4 up to the circumferential gap 16. It is thereby ensured that the pockets 20 are filled constantly with the medium to be pumped.
FIG. 2 shows, in a sectional representation through the side-channel pump 1 from FIG. 1 along the line II-II. In a preferred embodiment there are a total of three pockets 20 are arranged around the circumference of the impeller 4, using the example of one of the housing parts 7′. For clarity, the radially outer boundary of the impeller 4 is shown by a broken line in the drawing.
FIG. 3 is another embodiment of the inventive side-channel pump 1, which differs from that in FIGS. 1 and 2 in that pockets 21 of the annular gap are arranged in an impeller 22. By contrast, housing parts 23, 23′ of the side-channel pump 1 have no recesses. The side-channel pump 1 is otherwise constructed as described with reference to FIGS. 1 and 2.
Thus, while there have shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.