GEROTOR PUMP

Abstract

A gerotor pump includes a rotor wherein only on the face wall of the rotor that lies adjacent to a pressure kidney and a suction kidney, a lubrication surface inclined in the direction of rotation of the rotor, relative to the surface plane of the face wall of the rotor, is disposed on each tooth, in each instance, over its tooth height, either starting directly in the center tooth plane or starting “offset” ahead of the center tooth plane in the direction of rotation of the rotor, which surface is formed from a level surface or multiple, always level partial surfaces that follow one another, which enclose an angle of inclination relative to the surface plane of the face wall of the rotor, in each instance, which angle lies in the range from 0.2° to 7°, in each instance.

Claims

1. Gerotor pump having an inner gear having outer teeth, the rotor (1), and an outer gear having inner teeth, the gear ring (2), which is guided in a circular working chamber of a pump housing (3), in such a manner that the two gear wheels stand in meshing engagement and rotate about their own axes, which are, however, offset relative to one another, wherein the rotor (1) is mounted on a bearing sleeve (4) on one side, and side walls (6) are disposed on both sides of the face walls (5) of the gear wheels that mesh with one another,, in each instance, which walls are either integrated into the pump housing (3) or can be disposed on the pump housing (3) as covers (7), wherein an arc-shaped pressure kidney (8) is disposed in at least one of these side walls (6), on both sides of the eccentricity plane that contains the axes of rotor (1) and gear ring (2), which axes are offset relative to one another and an arc-shaped suction kidney (9) is disposed on the opposite side, in each instance, wherein only on the face wall (5) of the rotor (1) that lies adjacent to the pressure kidney (8) and the suction kidney (9), a lubrication surface (11) inclined in the direction of rotation (R) of the rotor (1)f relative to the surface plane of the face wall (5) of the rotor (1), is disposed on each tooth (10), in each instance, over its tooth height (H), either starting directly, in the center tooth plane (H) or starting “offset” ahead of the center tooth plane (M) in the direction of rotation (R) of the rotor (1), which surface is formed from a level, surface or multiple, always level partial surfaces that follow one another, which enclose an angle of inclination (α, β, γ, . . . ) relative to the surface plane of the face wall (5) of the rotor (1), in each instance, which angle lies in the range from 0.2° to 7°, in each instance.

2. Gerotor pump according to claim 1, wherein the lubrication surface (11) of the face wall (5), inclined in the direction of rotation (R) of the rotor (1), is formed by two level partial surfaces that follow one another, in each instance, which surfaces enclose an angle of inclination (α) or (β) relative to the surface plane of the face wall (5) of the rotor (1), in each instance, wherein (α) is smaller than, (β), and the partial surface of the lubrication surface (11) that is inclined at the greater angle of inclination (β), makes a transition into the surface plans of the face wall (5) of the rotor (1) at the surface run-out (14).

3. Gerotor pump according to claim 1, wherein the lubrication surfaces (11) disposed in the face wall of the rotor (1), on each tooth (10), over the entire tooth height (H), are disposed “offset” ahead of the tooth center plane (M) in the direction of rotation (R) of the rotor (1), in such a manner that they start parallel to the tooth center plans (M) and offset by the offset (V) of maximally 20% of the tooth root width (B).

4. Gerotor pump according to claim 1, wherein the bearing sleeve (4) comprises a ceramic material that has a low roughness depth on its bearing surface.

5. Gerotor pump according to claim 1, wherein the guide length (F) of the bearing sleeve (4) amounts to 2 times to 2.3 times the bearing diameter (D).

6. Gerotor pump, according to claim 1, wherein the guide length (F) of the bearing sleeve (4) amounts to about 53% to 60% of the total length (L) of the bearing sleeve (4).

Description

[0024] These representations show, in

[0025] FIG. 1: a gerotor pump, in section, in a side view;

[0026] FIG. 2: the spatial view of the side wall 6 of the cover 7, of a gerotor pump according to the state of the art, structured analogous to FIG. 1, and used here in accordance with the task, having the wear tracks 13 usual in the state of the art;

[0027] FIG. 3: the top view of a rotor 1 structured according to the invention, having a level lubrication surface 11 inclined at an angle of inclination α;

[0028] FIG. 4: the top view of the tooth wall of a tooth 10, shown as a detail of a further possible embodiment according to the invention, having a level lubrication surface 11 that begins “offset” in the direction of rotation R of the rotor 1, ahead of the tooth center plane M, and is inclined at an angle of inclination α, of a rotor equipped with these tooth walls, structured analogous to FIG. 3;

[0029] FIG. 5: the top view of a rotor 1 structured according to the invention, having an inclined lubrication surface 11 stepped at two angles of inclination α and β;

[0030] FIG. 6: the top view of the tooth wall, shown as a detail, of a tooth 10 of a further possible embodiment according to the invention, having a level lubrication surface 11 that begins “offset” in the direction of rotation R of the rotor 1, ahead of the tooth center plane M, and is inclined at two angles of inclination α and β, of a rotor equipped with these tooth walls, structured analogous to FIG. 5.

[0031] The gerotor pump according to the invention, shown in FIG. 1, having an inner gear with outer teeth, as shown in FIGS. 3 to 6, the rotor 1, and an outer gear having inner teeth, the gear ring 2, which is guided in a circular working chamber of a pump housing 3, in such a manner that the two gears stand in meshing engagement and rotate about their own axes, which are, however, offset relative to one another, wherein the rotor 1 is mounted on a bearing sleeve 4 on one side, and side walls 6 are disposed on both sides of the face walls 5 of the gear wheels that mesh with one another, in each instance, which walls are either integrated into the pump housing 3 or can be disposed on the pump housing 3 as covers 7, wherein an arc-shaped pressure kidney 8 is disposed in at least one of these side walls 6, on both sides of the eccentricity plane that contains the axes of rotor 1 and gear ring 2, which axes are offset relative to one another, and an arc-shaped suction kidney 9 is disposed on the opposite side, in each instance, is characterized in that on the face wall 5 of the rotor 1 that lies adjacent to the pressure kidney 8 and the suction kidney 9, a lubrication surface 11 inclined in the direction of rotation R of the rotor 1, relative to the surface plane of the face wall 5 of the rotor 1, is disposed on each tooth 10, in each instance, over its tooth height H, either starting in the center tooth plane M or starting “offset” ahead of the center tooth plane M in the direction of rotation R of the rotor 1, which surface is formed from a level surface or multiple level partial surfaces that follow one another, which enclose an angle of inclination α, β, γ, . . . relative to the surface plane of the face wall 5 of the rotor 1, in each instance, which angle lies in the range from 0.2° to 7°, in each instance.

[0032] By means of these lubrication surfaces 11, disposed on/in the face wall/face walls 5 of the rotor 1, which lie adjacent to the pressure kidney 8 and the suction kidney 9, on each tooth 10 of the rotor 1, according to the invention, inclined in the direction of rotation R of the rotor 1, the wear behavior of the gerotor pumps used in the state of the art, according to the task, as shown in FIG. 2, in a spatial representation of the side wall 6 of the cover 7, can be clearly reduced.

[0033] The wear tracks 13 shown in FIG. 2, which are usual in the current state of the art, are attributable to the fact in the case of poorly lubricating conveyed media, such as low-viscosity conveyed media/oils, a supporting lubricant film can no longer build up between the face wall 5 of the rotor 1 and the adjacent side wall 6 of the pump housing 3 or of the cover 7, provided with the pressure kidney 8 and the suction kidney 9, because the slide speeds are too low, so that the system makes a transition into the state of mixed friction, wherein because of the bearing play, the rotor 1 runs up against the adjacent side wall 6 of the gerotor pump and increasingly “tilts” due to stress on one side brought about by the pressure difference between the pressure in the pressure kidney 8 and the pressure in the suction kidney 9, and, in this regard, continues to “mill itself” deeper and deeper into the adjacent side wall/side walls 6 up to a maximally possible tilt angle of the rotor 1, which results from the possible guide play “on” (i.e. together with) the guide sleeve.

[0034] This wear cannot be completely prevented even with very cost-intensive slide pairings, because all traditional slide bearing pairings fail in this mixed friction range, thereby causing constantly advancing wear to occur in long-term operation, even in the case of very expensive slide pairings, even in combination with cost-intensive coatings or the like, which wear cannot be mastered and results in a continuous loss of the degree of effectiveness of the pump, as the result of constantly increasing wear-related leakage losses.

[0035] The lubrication surface 11 according to the invention, disposed on each tooth 10 of the rotor 1 on/in the face wall 5 of the rotor 1 adjacent to the pressure kidney 8 and the suction kidney 9, inclined in the direction of rotation R of the rotor 1, brings about the result that even under disadvantageous general conditions, such a great working pressures, when conveying poorly lubricating conveyed media, with simultaneously low slide

[0036] speeds of the slide partners, and cost-advantageous slide

[0037] pairings, a hydrodynamically supporting lubricant film builds up between the face wall 5 of the rotor 1 and the side wall 6 of the gerotor pump that lies adjacent to it.

[0038] It is characteristic, in this connection, that the lubrication surface 11, which is inclined in the direction of rotation R of the rotor 1 relative to the surface plane of the face wall 5, is configured to be level, as shown in FIGS. 3 and 4, and consists of a level surface that encloses an angle of inclination α relative to the surface plane of the face wall 5 of the rotor 1, which angle lies in the range from 0.2° to 7°.

[0039] Very good results were achieved, for example, with a level lubrication surface as shown in FIG. 3, which is inclined at an angle of inclination α of 0.5° relative to the surface plane of the face wall 5 of the rotor 1.

[0040] In a further exemplary embodiment, as shown in FIG. 5, the lubrication surface 11 disposed on the face wall 5 of the rotor 1 on each tooth 10 is formed by two level partial surfaces that follow one another, in each instance, which surfaces enclose an angle of inclination α or β relative to the surface plane of the face wall 5 of the rotor 1, in each instance, wherein α is smaller than β, and the partial surface of the lubrication surface 11 that is inclined at the greater angle of inclination β makes a transition into the surface plane of the face wall 5 of the rotor 1 at the surface run-out 14.

[0041] In this exemplary embodiment, shown in FIG. 5, the angle of inclination α amounts to 0.2°, and the angle of inclination β amounts to 5°. The two partial surfaces of the lubrication surface 11 together form a surface separator 15 and, in this regard, lie against one another at an obtuse angle, wherein the partial surface of the lubrication surface 11 that is inclined at the “second” angle of inclination β makes a transition into the surface plane of the face wall 5 of the rotor 1 at the surface run-out 14. The two partial surfaces of the lubrication surface 11 make a transition into the surface plane of the face wall 5 of the rotor 1 in the direction of the rotor center, along a steep surface edge 16. In the present exemplary embodiment, the rotor 1 consists of a material SintD39, the gear ring 2 also consists of SintD39, the bearing ring 12 consists of St38, and the pump housing 3 consists of the material AlSi9Cu3.

[0042] The level partial surfaces of the lubrication surface 11 shown in the exemplary embodiment according to FIG. 5, disposed on each tooth 10, running in the inclination plane E, tangential to the direction of rotation and parallel to the center axis of the rotor 1, at the aforementioned angles of inclination α and β, can be produced in simple and cost-advantageous manner, in terms of production technology, and guarantee an optimal solution for the task according to the invention under the aforementioned conditions of use.

[0043] It is also in accordance with the invention if, as shown in FIGS. 4 and 6, the lubrication surfaces 11 disposed in the face wall 5 of the rotor 1, on each tooth 10, over the entire tooth height H, are disposed “offset” ahead of the tooth center plane M in the direction of rotation R of the rotor 1, in such a manner that they start parallel to the tooth center plane M and offset by the offset V of maximally 20% of the tooth root width B.

[0044] In this way, as in the case of an axial slide bearing, a local pressure buildup is brought about, which once again measurably reduces the friction force between the rotor 1 and the cover 7.

[0045] It is also essential to the invention that the bearing sleeve 4 consists of a ceramic material that has a low roughness depth on its bearing surface.

[0046] In the present exemplary embodiments, the roughness values of the bearing surface of the bearing sleeve 4 lie around Rz=1, wherein the bearing sleeve 4 itself consists of the material Al.sub.2O.sub.3.

[0047] The roughness of the related bearing bore of the rotor 1 lies at Rk<=3 in the present exemplary embodiment.

[0048] In all the embodiments, even after 2,100 h long-term testing under maximal stress, no wear could be detected using measurement technology, neither on the bearing sleeve 4 nor on the rotor 1.

[0049] Furthermore, surprisingly, a microdynamic effect that could not be explained even now occurred on the “bearing surface” of the rotor 1, on the cover 7, in the form of “self-polishing,” which effect cannot be explained at the present time using slide bearing theory, because the definitively present mixed friction would have to produce progressive wear tracks because of the direct body contact, according to current theory. However, this wear could not be detected even according to long-term tests under maximal stress.

[0050] It is furthermore characteristic that the guide length F of the bearing sleeve 4 amounts to 2 times to 2.3 times the bearing diameter D.

[0051] In this way, deformation of the sleeve bore and resulting “tilting” of the rotor 1 is effectively reduced, even in the case of pump housings 3 composed of light metal (for example Al alloys).

[0052] It is advantageous, independent of sleeve fixation, particularly in the case of cast housings, that the region surrounding the sleeve guide is configured with great rigidity, in terms of design, in order to effectively prevent possible deformation of the sleeve bore caused by the “work load” of the rotor 1 that acts on the bearing sleeve 4.

[0053] It is also characteristic that the guide length F of the bearing sleeve 4 amounts to about 53% to 60% of the total length L of the bearing sleeve 4.

[0054] In connection with the aforementioned configuration of the area surrounding the sleeve bore, the guide length F of the bearing sleeve 4, according to the invention, guarantees not only positioning in a secure position, whether by means of adhesion or by means of press fit, of the bearing sleeve 4 in the pump housing 3, in connection with the use of a bearing sleeve 4 composed of a material having a high modulus of elasticity (for example ceramic/modulus of elasticity approximately 380 to 400 GPa), with simultaneously bending-resistant configuration of the bearing sleeve (in other words counteracting bending of the bearing sleeve 4 at great radial stress), but also reliable positioning of the rotor 1 in the pump housing 3.

[0055] It is also advantageous if the pump housing 3 is produced from an aluminum casting. This allows not only cost-advantageous production that is simple in terms of production technology, but at the same time allows great reliability and a long useful lifetime.

[0056] Thereby it has been made possible, by means of the solution according to the invention, to develop a gerotor pump having sleeve-guided rotors, which clearly reduce an over-proportional increase in the drive moment, with a simultaneous loss of the degree of effectiveness, even when using low-viscosity conveyed media, such as “thin, light oil,” in connection with use in smaller pump systems, the rotors of which have tooth tip diameters from approximately 20 to approximately 40 mm, and the conveying pressures of which lie in the range from 3 to 20 bar, and even at low speeds of rotation in the range from 500 to 1,000 rpm and a high conveying pressure, so that the gerotor pump according to the invention always guarantees a high degree of pump effectiveness, with great reliability and a long useful lifetime.

REFERENCE SYMBOL LIST

[0057] 1 rotor [0058] 2 gear ring [0059] 3 pump housing [0060] 4 bearing sleeve [0061] 5 face wall [0062] 6 side wall [0063] 7 cover [0064] 8 pressure kidney [0065] 9 suction kidney [0066] 10 tooth [0067] 11 lubrication surface [0068] 12 bearing ring [0069] 13 wear tracks [0070] 14 surface run-out [0071] 15 surface separator [0072] 16 surface edge [0073] H tooth height [0074] B tooth root width [0075] M tooth center plane [0076] R direction of rotation [0077] F guide length [0078] L total length [0079] D bearing diameter [0080] E inclination plane [0081] V offset [0082] α, β, γ angles of inclination