External rotor pump with a surface structure having a load-bearing region and a non-load bearing region

Abstract

An external rotor pump has an outer rotor with a sliding surface which is arranged on the outer side thereof, and an opposing body in which the outer rotor is mounted rotatably by way of the sliding surface thereof on an inner guide surface of the opposing body and is in mechanical contact with the inner guide surface. An inner rotor which is mounted such that it can be rotated eccentrically with respect to the outer rotor is provided. The sliding surface or the inner guide surface has a surface structure which has a load-bearing region and a non-load-bearing region which is depressed in contrast with the former.

Claims

1. An external rotor pump, comprising: a first component which is constructed as an external rotor and which has a sliding face which is arranged on an outer side thereof; a second component which is constructed as a counter-rotation member and in which the external rotor is rotatably supported by way of the sliding face thereof on an inner guiding face of the counter-rotation member and is in mechanical contact therewith; an internal rotor which is rotatably supported eccentrically relative to the external rotor; wherein one of the rotors is drivable in order to be caused to carry out a rotational movement and the rotors are coupled to each other such that, when the drivable rotor is driven, the other rotor is thereby also caused to carry out a rotational movement in order to convey fluid from an intake region to a pressure region of the external rotor pump, the sliding face or the inner guiding face has a surface structure which has a load-bearing region and a non-load-bearing region which is recessed relative thereto so that the non-load-bearing region remains unaffected by contact between the guiding face and the sliding face which is supported thereon, the external rotor pump further comprises at least one lubricant supply channel for selectively supplying lubricant to lubricate a boundary layer between the sliding face and the inner guiding face, and at least one lubricant discharge channel for discharging the lubricant, the lubricant supply channel is arranged such that it opens at a location in the boundary layer, at which, during operation of the pump, the load-bearing region is at least temporarily located so that it is provided at that location with the lubricant provided from the lubricant supply channel, and the lubricant discharge channel is arranged such that the input thereof is arranged adjacent to a location of the boundary layer at which the non-load-bearing region is at least temporarily located during operation of the pump so that, from this location via the corresponding lubricant discharge channel, lubricant is discharged from the non-load-bearing region.

2. The external rotor pump as claimed in claim 1, wherein: the first or second component which has the load-bearing region has a component body produced from at least one base material, and the load-bearing region has on a surface thereof a carrier material which, with respect to at least one of the base materials, has a reduced friction coefficient or a higher wear resistance, or both.

3. The external rotor pump as claimed in claim 2, wherein a layer of carrier material is formed on the component body on the load-bearing portion.

4. The external rotor pump as claimed in claim 2, wherein the carrier material comprises one or more of: carbon, lubricant varnish, and hard metal.

5. The external rotor pump as claimed in claim 4, wherein at least one of the base materials comprises one or more of: a plastics material, a light metal or a light metal alloy, a composite material, a sintered material, and a steel material.

6. The external rotor pump as claimed in claim 2, wherein at least one of the base materials comprises one or more of: a plastics material, a light metal or a light metal alloy, a composite material, a sintered material, and a steel material.

7. The external rotor pump as claimed in claim 1, wherein the first or second component which has the load-bearing region has a component body, produced from at least one base material, and a sliding member, the sliding member is arranged and fitted on the component body such that the sliding member forms at least a portion of the load-bearing region and has a carrier material which, with respect to at least one of the base materials, has a reduced friction coefficient or a higher wear resistance, or both.

8. The external rotor pump as claimed in claim 7, wherein the sliding member has a ring which surrounds the component body.

9. The external rotor pump as claimed in claim 1, wherein the non-load-bearing region of the external rotor or the counter-rotation member is constructed at least partially in thea form of at least one linear recess in the sliding face or the inner guiding face.

10. The external rotor pump as claimed in claim 9, wherein the non-load-bearing region of the external rotor or the counter-rotation member is constructed at least partially in a form of a plurality of linear recesses which extend parallel with each other in the sliding face or the inner guiding face.

11. The external rotor pump as claimed in claim 10, wherein a movement direction of the external rotor with respect to the counter-rotation member defines, when the drivable rotor is driven, a reference direction on the sliding face or the inner guiding face and the linear recesses have one of the following paths: linear and parallel or anti-parallel with respect to the reference direction, linear, jagged or undulating and extending at least partially obliquely with respect to the reference direction, or linear, jagged or undulating and angled so that an angle forms an arrow-shape with an arrow direction which extends in or counter to the reference direction.

12. The external rotor pump as claimed in claim 1, wherein the load-bearing region is structured such that a maximum surface pressure which is applied thereto during operation of the external rotor pump, at least in one operating mode of the external rotor pump, does not vary by more than 10%.

13. The external rotor pump as claimed in claim 1, wherein the load-bearing region is structured such that a maximum surface pressure which is applied thereto during operation of the external rotor pump, at least in one operating mode of the external rotor pump, does not vary by more than 5%.

14. The external rotor pump as claimed in claim 1, wherein the load-bearing region is structured such that a maximum surface pressure which is applied thereto during operation of the external rotor pump, at least in one operating mode of the external rotor pump, does not vary by more than 2%.

15. The external rotor pump as claimed in claim 1, wherein the pump is a hydraulic external rotor pump.

16. An external rotor pump, comprising: a first component which is constructed as an external rotor and which has a sliding face which is arranged on an outer side thereof; a second component which is constructed as a counter-rotation member and in which the external rotor is rotatably supported by way of the sliding face thereof on an inner guiding face of the counter-rotation member and is in mechanical contact therewith; and an internal rotor which is rotatably supported eccentrically relative to the external rotor; wherein one of the rotors is drivable in order to be caused to carry out a rotational movement and the rotors are coupled to each other such that, when the drivable rotor is driven, the other rotor is thereby also caused to carry out a rotational movement in order to convey fluid from an intake region to a pressure region of the external rotor pump, the sliding face or the inner guiding face has a surface structure which has a load-bearing region and a non-load-bearing region which is recessed relative thereto so that the non-load-bearing region remains unaffected by contact between the guiding face and the sliding face which is supported thereon, the first or second component which has the load-bearing region has a component body produced from at least one base material, the load-bearing region has on a surface thereof a carrier material which, with respect to at least one of the base materials, has a reduced friction coefficient or a higher wear resistance, or both, the carrier material comprises one or more of: carbon, lubricant varnish, and hard metal, and wherein the carbon is DLC carbon and the hard metal is chromium.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic view of a pendulum/slider pump according to a preferred embodiment of the invention.

(2) FIG. 2 is a schematic view of an internally toothed wheel pump (without any sickle-like member) according to another preferred embodiment of the invention.

(3) FIG. 3 is a schematic perspective view of a counter-rotation member according to a preferred embodiment of the pump with a visible guiding face, which has a surface structure with a groove as a non-load-bearing region.

(4) FIGS. 4A-4F schematically show a plurality of cross-sections through pumps according to different preferred embodiments of the invention in order to illustrate the surface structure of the external rotor or the counter-rotation member in comparison with a conventional external rotor pump.

(5) FIGS. 5A-5E show other surface structures from a large number of mutually parallel linear load-bearing and non-load-bearing regions according to other preferred embodiments of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

(6) Reference is first made to FIG. 1, wherein the same reference numerals have the same meaning in all the Figures. In FIG. 1, an external rotor pump 1 is shown in the form of a pendulum/slider pump. It has an external rotor 3 which is supported on a circumferential interface 8 with the sliding face 8b thereof which extends on the outer periphery thereof in a counter-rotation member 2. The counter-rotation member 2 is constructed as a pump housing on the inner face thereof which acts as a guiding face 8a for the external rotor 3 and which is directed toward the (virtual) rotation axis thereof. Furthermore, there is provided an inner rotor 4 which in turn is arranged inside the external rotor 3 and which is rigidly connected to a rotatably supported shaft 5 so that the inner rotor 4 can be driven via the shaft 5. The outer diameter of the internal rotor 4 is smaller than the inner diameter of the external rotor 3 so that there is a hollow space between the two rotors 3 and 4 whose position changes during conveying operation of the pump 1. Between the external rotor 3 and the driven internal rotor 4 there is a mechanical coupling. In addition, the internal rotor has a plurality of radially extending, shaft-like recesses in which there are located pendulum pieces 7 which are supported in the corresponding recesses so as to be able to be freely moved and tilted in a limited manner.

(7) The pendulum pieces 7 each have spherical pendulum heads which protrude from the recesses of the internal rotor 4 and which engage in corresponding recesses at the inner side of the external rotor 3 and are supported in an articulated manner at that location. When the internal rotor 4 is driven by way of the shaft 5, a torque is consequently applied by the pendulum pieces 7 to the external rotor 3 which converts it into a rotation in the same direction as the rotation of the internal rotor 4.

(8) The pump housing, that is to say, the counter-rotation member 2, has at the outer periphery thereof two projections, wherein there is provided in one of them a rotation axis 6 about which the counter-rotation member is rotatably supported through a limited angle. If, as indicated by an arrow, a force 10 is applied to the opposing projection, the rotation axis of the counter-rotation member 2 indicated by way of a cross and consequently also the external rotor 3 which is supported therein rotates with respect to the shaft 5 of the internal rotor 4, as indicated by the line 9a (starting position) and 9b (position after rotation). In this manner, it is possible to adjust the conveying quantity of the pump in a variable manner within specific limits. In this instance, in the starting position, the rotation axes of the external rotor 3 and the internal rotor 4 coincide so that both rotors run concentrically and the conveying chambers between the pendulum sliders 7 do not change. The pump therefore does not convey in this position (zero delivery). However, if the counter-rotation member 2 and consequently also the external rotor 3 which is supported therein is rotated by the force 10 to the position 9b, the rotation axis of the driven internal rotor 4 is located eccentrically with respect to the external rotor 3 so that the conveying chambers in the hollow space between the rotors in the region of the individual pendulum pieces periodically increase (intake region 11a) and decrease again (pressure region 11b) and consequently the medium which is intended to be conveyed can generally be pumped.

(9) At the interface 8, either the guiding face 8a of the counter-rotation member 2 or the sliding face 8b of the external rotor 3 has a surface structure. Solutions in which both the guiding face 8a and the sliding face 8b each have a surface structure are possible, preferably in such a manner that, during the contact of both faces, the surface structures of both faces do not overlap but instead each only covers a part-region of the contact face between both faces so that a possible increase of friction can be prevented by means of direct interaction between the surface structures of the guiding face 8a and the sliding face 8b from the beginning and in a structurally independent manner.

(10) FIG. 2 shows another embodiment of the pump 1 according to the invention in the form of an internally toothed wheel pump (without a sickle-like member). There is again provided a pump housing which acts as a counter-rotation member 2 for an external rotor 3 which is rotatably supported therein. As with the pump from FIG. 1, a guiding face 8a which is located on the inner face of the counter-rotation member 2 and a sliding face 8b which is located on the outer periphery of the external rotor 3 meet at an interface 8. Furthermore, there is again provided an internal rotor 4 which is rotatably supported about a shaft 5 at the inner side of the external rotor 3. In order to couple the two rotors, the internal rotor 4 is constructed as a toothed wheel which engages in a toothed ring which is constructed at the inner side of the external rotor 3. The rotation axes of the external rotor 3 and internal rotor 4 which extend parallel with each other are located eccentrically with respect to each other. The outer diameter of the internal rotor 4 is again smaller than the internal diameter of the external rotor 3 so that a hollow space exists between the two rotors 3 and 4 and the position thereof changes during conveying operation of the pump 1. There are thus continuously produced intake regions 11a at which the hollow space increases, and pressure regions which the hollow space adjoins when the internal rotor 4 runs in the toothed ring of the external rotor 3. The counter-rotation member 2 has a conveying medium supply channel 12 and a conveying medium discharge channel 13. Furthermore, in order to lubricate the pump 1, a lubricant supply channel 11c and a lubricant discharge channel 11d are provided (in FIG. 1, the corresponding conveying medium and lubricant channels are not explicitly shown, but are also present).

(11) Preferred embodiments for the surface structure of the guiding face 8a or the sliding face 8b are illustrated by way of example in FIGS. 3 to 5. In this instance, FIG. 3 shows a counter-rotation member 2 of an external rotor pump 1 with the guiding face 8a thereof. Such a counter-rotation member 2 may in particular be used for the pump constructions according to FIG. 1 or FIG. 2. Along the guiding face 8a, a circumferential recess in the form of a circular groove 14 is preferably formed centrally in the guiding face 8a. However, the path of the groove does not have to be circumferential. It is preferably adapted to surface pressures which may be present in the guiding face 8a. The groove width may also be adapted thereto. In particular the groove width may also vary over the path of the groove. The circular face defined by the circular groove 14 is substantially perpendicular to the rotation axis of an external rotor 3 when it is inserted in the counter-rotation member 2, as shown in FIGS. 1 and 2. The surface region of the guiding face 8a defined by the groove 14 constitutes a non-load-bearing region of the guiding face 8a, whilst the remaining peripheral surface regions which adjoin the groove 14 at both sides form the load-bearing region which comes into contact with the sliding face 8b of the external rotor 3.

(12) Different embodiments of preferred surface structures for the guiding face 8a or for the sliding face 8b are illustrated in FIGS. 4B to 4F in the form of cross-sections through the counter-rotation member 2 and the adjacent external rotor 3. The cross-sections shown accordingly always extend in this instance with respect to the counter-rotation member 2 in the manner as illustrated in the specific case of FIG. 3 with reference to the line of section A-A.

(13) FIG. 4A first shows in the same manner the starting point according to the prior art, in which both the guiding face 8a and the sliding face 8b are each constructed as smooth surfaces on the counter-rotation member 2 or the external rotor 3 and form the interface 8 at the contact location thereof. Accordingly, the contact face extends between the counter-rotation member 2 and the external rotor 3 over the entire overlapping bearing width B thereof.

(14) FIG. 4B relates to a preferred embodiment of the invention in which two sliding members 15 which are constructed as sliding rings are fitted to the sliding face 8b of the external rotor 3 and are constructed from a particularly low-friction and low-wear material. The material may in particular have one or more CrMo steels or one or more heat-treated steels and preferably at least substantially comprise one or more of these materials. In this manner, it is possible to construct the component member of the external rotor 3 from a less low-wear material, such as, for instance, a light metal or plastics material, without increasing the friction and the wear at the interface 8. The guiding face 8a of the counter-rotation member 2 remains in this embodiment preferably without a surface structure so that the sliding rings 15 can slide thereon in a low-friction manner to the greatest possible extent.

(15) FIGS. 4C and 4D relate to two mutually related additional preferred embodiments of the invention in which in each case one of the two faces which are in contact at the interface 8 has a surface structure which is formed by way of a continuous groove 14. The groove 14 constitutes in each case a non-load-bearing region of the corresponding face, whilst the remaining surface region acts as a load-bearing region. In FIG. 4C, the groove is formed in the sliding face 8b, whilst the guiding face 8a of the counter-rotation member 2 does not have any surface structure. FIG. 4D shows in contrast the reverse case which is also illustrated in FIG. 3, in which the groove 14 is located in the guiding face of the counter-rotation member 2. In both cases, the effective support face, that is to say, the contact face between the guiding face 8a and the sliding face 8b, consequently has an effective bearing width B*<B which, as shown, can be divided in particular into two portions of equal width which form the load-bearing region and which have the width B*/2 on the left and right of the groove 14 which constitutes the non-load-bearing region.

(16) FIGS. 4E and 4F relate to preferred developments of the solutions according to FIGS. 4C and 4D in which the load-bearing regions are in each case provided with a layer 16 of a particularly low-wear and low-friction carrier material which in particular may have chromium, DLC carbon or a lubricant varnish. The layer may in particular be constructed in the form of a coating. Using the layer, the friction which occurs at the interface 8 and the related wear can be further reduced. In a variant of these embodiments, however, the layer 16 is at least partially constructed by means of a selective material change, in particular by means of implantation of foreign materials in the load-bearing regions of the face or faces which has/have the surface structure so that these regions have an increased friction and wear resistance with respect to the previously unprocessed surface structure or the component body. Suitable foreign materials include in particular nitrogen, argon and ion gases generally and multi-ions, in particular metal or complex ions.

(17) FIGS. 5A-5E show additional preferred embodiments for the surface structure, which are advantageous in particular in the field of hydrodynamic friction when a lubricant is used at the interface 8. In this instance, the surface structure has in each case a plurality of linear line-like recesses which extend at least substantially parallel with each other, in particular grooves, which are in this instance illustrated as a dark line, respectively. The structuring may in particular be produced by way of spray coating by suitable parameters for the selection of feed, direction and thickness of the injection coating produced. Alternatively, the component of the pump 1 which has the surface structure may be cast or pressed, wherein the surface structure is predetermined in this instance in each case by means of a casting mould or pressing mould. Furthermore, a structuring of the surface by means of laser beam technology is also possible. Adjacent recesses preferably have a spacing in the order of magnitude of the recess depth itself, in particular the spacing may be equal to the recess width or less than ten times the width. In this manner, the wetting of the surface structure with lubricant and consequently a consistent friction reduction can be promoted.

(18) In FIG. 5A, the linear recesses of the non-load-bearing regions of the surface structure extend substantially in a straight line and parallel or antiparallel with the movement direction of the external rotor with respect to the counter-rotation member when the drivable rotor is driven which in this instance a reference direction constitutes. In another variant, non-load-bearing regions, as also shown in FIG. 5B, may extend at least partially in an inclined manner with respect to the reference direction. In this instance, the lines themselves may preferably be constructed so as to extend in a linear manner (as shown) or jagged manner per se or in an undulating manner. In another variant which is shown in FIG. 5C, the non-load-bearing regions also extend in a linear, jagged or undulating manner and are additionally generally angled so that the angle forms an arrow shape with an arrow direction which extends at least substantially in or counter to the reference direction. In FIG. 5D, another variant is shown in the form of a modification of the arrow shape from FIG. 5C in which at least one of the line segments which form the arrow shape is not constructed in a linear manner, but instead in a curved manner. The surface structure which is defined in this manner may also be referred to as an undulating form. Finally, FIG. 5E shows another variant in which the non-load-bearing regions are arranged in a curved shape which extends transversely relative to the reference direction. The spacing of adjacent non-load-bearing regions is in this instance preferably selected to be so small that always at least two adjacent load-bearing regions which are separated by a non-load-bearing region come into contact at the same time with the corresponding counter-face 8a or 8b at the interface 8 so that smooth running or sliding of the external rotor 3 with respect to the counter-rotation member 2 is ensured. All of these shapes have in common that they at least substantially have no line portions which extend perpendicularly to the reference direction since they could have a negative influence on the smooth running and consequently also the friction and wear which occur. Furthermore, the lubricant may also in each case flow at least also in the reference direction or in the opposite direction thereto in the recesses so that, as a result of the mentioned line shapes, lubricant inclusions which disrupt the smooth running are also effectively counteracted.

(19) Whilst at least one exemplary embodiment has been described above, it should be noted that there are a large number of variations thereof. It should also be noted that the described exemplary embodiments constitute only non-limiting examples and it is not intended to thereby limit the scope, the applicability or the configuration of the devices and methods described here. Instead, the above description will provide the person skilled in the art with an indication for implementing at least one exemplary embodiment, wherein it will be understood that different modifications in the operating method and the arrangement of the elements described in an exemplary embodiment can be carried out, without deviating from the subject-matter which has been set out in the appended claims and the legal equivalents thereof.

LIST OF REFERENCE NUMERALS

(20) 1 External rotor pump 2 Counter-rotation member 3 External rotor 4 Internal rotor 5 Shaft 6 Rotation axis 7 Pendulum pieces 8 Interface 8a Guiding face 8b Sliding face 9a Starting position (zero delivery) 9b Position after rotation (delivery) 10 Force 11a Intake region 11b Pressure region 11c Lubricant supply channel 11d Lubricant discharge channel 12 Conveying medium supply channel 13 Conveying medium discharge channel 14 Recess in the surface structure, in particular groove 15 Sliding member, in particular sliding ring 16 Carrier material or a layer having such material B Bearing width in solution from the prior art B* Effective bearing width in solution according to the invention

(21) The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.