EP3230592B1 - Gerotor pump - Google Patents

Description

The invention relates to a gerotor pump for rotors with tooth tip diameters of approx. 20 to approx. 40 mm, which work with delivery pressures in the range between 3 to 20 bar and for pumping hardly lubricating media, such as an oil pump in the motor vehicle sector for pumping engine oils with low viscosity.

In the prior art, there are a number of applications on the principle and mode of operation of gerotor pumps with an externally toothed inner wheel and an internally toothed ring gear, the outer wheel, which is guided in a circular recess of a housing ring in such a way that both gears are in meshing engagement and around their own, but mutually offset axes rotate, with the engaging rotors forming pressure spaces (pressure chambers) with one another, which change cyclically in size and position.

On both sides of these intermeshing gear wheels, end walls are arranged as a cover and / or housing, with the one containing the axes in at least one of the end walls / cover on both sides, in section as Center line appearing eccentricity plane, on the one hand an arcuate pressure groove and on the other hand an arcuate suction groove is arranged.

These gear pumps, which work according to the gerotor principle, require precise compliance with the eccentricity and, when used in the automotive sector, production that is as cost-effective as possible, with high reliability and a long service life.

In the DE 10 2012 205 406 A1 A gerotor pump is described above, in which the pressure pulsation is to be reduced by means of curved lines of action deviating from the straight line and an edge area of the end wall of the gear wheel which is beveled along the entire tooth profile, which reduces the noise generated during operation of the above. Gerotor pump.

With this solution, due to the gap connection resulting from this solution, a deterioration in the sealing behavior between the edge regions of the tooth flanks when this displacement machine is in operation is accepted between the tooth chambers.

Also one in the DE 10 2006 047 312 A1 The solution presented in connection with a gerotor pump serves to reduce the pressure peaks when operating this hydraulic machine.

When solving the DE 10 2006 047 312 A1 Rectangular recesses are arranged on both sides of the gear, on both sides of the apex on the tooth head, which cause a short circuit with the adjacent pressure chamber at the times at which the pressure chamber has a minimum or maximum volume, whereby a backflow of the fluid to the adjacent chamber, and thus a pressure equalization is made possible. As a result of the resulting reduction in the positive and negative pressure peaks, the operating behavior of the hydraulic machine should be designed to be wear-resistant.

In the DE 26 06 172 C2 Another design of a gerotor pump with small radial dimensions is described above, in which the leakage losses are to be kept small by the one-sided attachment of a sealing ring positioned against a continuous end wall of the gerotor pump in an annular groove on the adjacent gear end face. However, this one-sided attachment of a sealing element on the inner rotor has the effect that the gear wheel is pressed with considerable force against the opposite end wall provided with the opening. In order to reduce the very high frictional forces resulting from the high normal force, there are two pressure compensation surfaces connected to the adjacent displacement chambers in the form of two on the end face of the gear wheel opposite the sealing element, at the top of each tooth head, over part of the tooth head height, symmetrically to the tooth center axis Arranged wells which are separated from one another by a radial web. By means of these pressure compensation surfaces, the high normal force causing a frictional force, the axial sealing force, which is caused by the one-sided seal, is to be reduced or compensated so that there is still a pressure force of the gear wheel that reduces the leakage gap on the end wall provided with the opening, this pressure force however, it is reduced to such an extent that "excessive" friction no longer occurs. The radial web arranged between the two displacement chambers on the end face of the tooth head ensures that the displacement chambers arranged adjacent to one another on the tooth head are not short-circuited.

However, with this solution of a gerotor pump with a small radial diameter, the applied pump pressure on the gear / inner rotor causes a tilting force that causes partial contact of the inner rotor over approx. 180 ° of the angle of rotation with the opposite end wall of the gerotor pump, and a not insignificant wear has the consequence.

This problem of wear and tear, as well as the frictional forces that inevitably occur with such designs, occur to a greater extent when pumping media with low viscosity and also result in high drive torques.

To reduce fuel consumption, low-viscosity engine oils have been increasingly used in the automotive sector in recent years.

When passing through (conveying) media that are barely lubricating, there is therefore the need to use very hard and at the same time corrosion-resistant materials, even with oil pumps. Ceramic or hard metal.

The use of these materials makes sense for all tribologically stressed functional components of the gerotor pump, in order to avoid the constant wear and tear when using soft materials.

From a manufacturing point of view, in particular for cost reasons, however, the manufacture of the pump housing from ceramic or hard metal is very cost-intensive.

The use of sleeve-guided rotors with low-wear bearing sleeves made of ceramic or hard metal has been common for decades. The fixing of these sleeves in pump housings made of cast / light metal by means of glue or the like is also possible. known for years.

In connection with the use of sleeve-guided rotors, especially in smaller pump systems, the rotors of which have a tooth tip diameter of approx. 20 to approx. 40 mm and which work with delivery pressures in the range of 3 to 20 bar, this is particularly beneficial at low speeds in the range of 500 Up to 1,000 rpm and high working pressure, a disproportionate increase in drive torque with a simultaneous loss of efficiency is noticeable.

The reason for this is that if the sliding speed is too low in connection with the use of low-viscosity pumping media, a dynamic load bearing occurs The lubricating film can no longer build up, so that the system changes to the state of mixed friction.

Even when using low-wear bearing sleeves made of ceramic or hard metal, with sleeve-guided rotors, especially in connection with the use of pump housings made of cast / light metal, measurable signs of wear occur in the area of the suction groove on both sides of the housing and / or on the cover, with rising and falling working pressures Viscosity of the medium to be conveyed is due to the rotor starting up on the housing and / or on the cover, and with the duration of use it results in increasing leakage losses between the pressure and suction side of the gerotor pump.

This leads to a disproportionate increase in the drive torque with a simultaneous loss of efficiency of the pump, which, in addition to the reliability, also severely affects the service life of the gerotor pump described above.

The invention is therefore based on the object of developing a gerotor pump with a sleeve-guided rotor which eliminates the aforementioned disadvantages of the prior art and which, when using low-viscosity pumping media such as "low viscosity oil", in conjunction with use in smaller pump systems , whose rotors have tooth tip diameters of approx. 20 to approx. 40 mm and whose delivery pressures are in the range of 3 to 20 bar, and which at low speeds in the range of 500 to 1,000 rpm and high delivery pressures cause the disproportionate increase in the drive torque at the same time Significantly reduce the loss of efficiency, so that the gerotor pump according to the invention always ensures a high pump efficiency with high reliability and a long service life.

According to the invention, this object is achieved by a gear pump according to the features of the independent claim of the invention.

Advantageous embodiments, details and features of the invention emerge from the subclaims and the graphic representations of the solution according to the invention.

Figur 1 :

eine Gerotorpumpe, im Schnitt, in der Seitenansicht;

Figur 2 :

den räumlichen Blick auf die Seitenwand 6 des Deckels 7, einer gemäß dem Stand der Technik analog zur Figur 1 aufgebauten und gegenwärtig aufgabengemäß eingesetzten Gerotorpumpe, mit den im Stand der Technik üblichen Verschleißspuren 13;

Figur 3 :

die Draufsicht auf einen erfindungsgemäß aufgebauten Rotor 1 mit einer ebenen unter einem Neigungswinkel α geneigten Schmierfläche 11;

Figur 4 :

die Draufsicht auf die als Einzelheit dargestellte Zahnwandung eines Zahnes 10 einer weiteren möglichen erfindungsgemäßen Ausführungsform mit in Rotationsrichtung R des Rotors 1 vor der Zahnmittenebene M "versetzt" beginnender, ebener, unter einem Neigungswinkel α geneigter Schmierfläche 11 eines mit diesen Zahnwandungen ausgestatteten, analog zur Figur 3 aufgebauten Rotors;

Figur 5 :

die Draufsicht auf einen erfindungsgemäß aufgebauten Rotor 1 mit unter zwei Neigungswinkeln α und β abgestuft geneigter Schmierfläche 11;

Figur 6 :

die Draufsicht auf die als Einzelheit dargestellte Zahnwandung eines Zahnes 10 einer weiteren möglichen erfindungsgemäßen Ausführungsform mit in Rotationsrichtung R des Rotors 1 vor der Zahnmittenebene M "versetzt" beginnender, unter zwei Neigungswinkeln α und β abgestuft geneigter Schmierfläche 11 eines mit diesen Zahnwandungen ausgestatteten, analog zur Figur 5 aufgebauten Rotors.

These representations show in

Figure 1:

a gerotor pump, in section, in side view;

Figure 2:

the spatial view of the side wall 6 of the cover 7, one according to the prior art analogous to Figure 1 constructed gerotor pump that is currently used in accordance with the task, with the usual wear marks 13 in the prior art;

Figure 3:

the top view of a rotor 1 constructed according to the invention with a flat lubricating surface 11 inclined at an angle of inclination α;

Figure 4:

the plan view of the tooth wall shown as a detail of a tooth 10 of a further possible embodiment according to the invention with in the direction of rotation R of the rotor 1 in front of the tooth center plane M "offset" beginning, planar, at an inclination angle α inclined lubrication surface 11 equipped with these tooth walls, analogous to Figure 3 assembled rotor;

Figure 5:

the top view of a rotor 1 constructed according to the invention with the lubricating surface 11 inclined at two angles of inclination α and β;

Figure 6:

the plan view of the tooth wall shown as a detail of a tooth 10 of a further possible embodiment according to the invention with in the direction of rotation R of the rotor 1 in front of the tooth center plane M "offset" beginning, at two angles of inclination α and β graded lubrication surface 11 equipped with these tooth walls, analogous to Figure 5 assembled rotor.

The invention, in the Figure 1 shown, gerotor pump with an externally toothed, as in the Figures 3 to 6 shown inner wheel, the rotor 1, and an internally toothed outer wheel, the ring gear 2, which is guided in a circular working chamber of a pump housing 3 in such a way that both gears are in meshing engagement and rotate about their own, but mutually offset axes, the rotor 1 is mounted on one side on a bearing sleeve 4, and on both sides of the end walls 5 of the intermeshing gears each side walls 6 are arranged, which can either be integrated in the pump housing 3 or arranged as a cover 7 on the pump housing 3, in at least one of these side walls 6, on both sides of the eccentricity plane containing the mutually offset axes of rotor 1 and toothed ring 2, a circular arc-shaped pressure kidney 8 and opposite a circular arc-shaped suction kidney 9 are arranged, characterized in that on the end wall 5 of the adjacent to the pressure kidney 8 and the suction kidney 9 Rotor 1 on each tooth 10 via its Z ahnhöhe H each one, either in the Tooth center plane M beginning or in the direction of rotation R of the rotor 1 in front of the tooth center plane M "offset" beginning, to the surface plane of the end wall 5 of the rotor 1 in the direction of rotation R of the rotor 1 inclined lubrication surface 11 is arranged, which consists of a flat surface or several adjoining, flat partial surfaces are formed which each enclose an angle of inclination α, β, γ ... which is in the range of 0.2 ° to 7 ° with respect to the surface plane of the end wall 5 of the rotor 1.

By means of this inclined lubrication surfaces 11 arranged according to the invention in the direction of rotation R of the rotor 1 in the direction of rotation R of the rotor 1, the inclined lubrication surfaces 11, which are arranged on the end wall / end walls 5 of the rotor 1 adjacent to the suction kidney 9, can Figure 2 , in a three-dimensional representation of the side wall 6 of the cover 7, shown wear behavior of the gerotor pumps used according to the task in the prior art are significantly reduced.

The ones in the Figure 2 The traces of wear 13 shown in the current state of the art can be traced back to the fact that with poorly lubricating pumping media, such as low-viscosity pumping media / oils, between the end wall 5 of the rotor 1 and the adjacent side wall 6 provided with the pressure kidney 8 and the suction kidney 9 of the pump housing 3 or the cover 7, a load-bearing lubricating film can no longer build up, since the sliding speeds are too low, so that the system changes to the state of mixed friction, whereby due to the bearing play, the rotor 1, due to a pressure difference between the pressure in the pressure kidney 8 and the pressure in the suction kidney 9, caused one-sided load on the adjacent side wall 6 of the gerotor pump starts, increasingly "tilts", and thereby up to a maximum possible tilt angle of the rotor 1, which is derived from the possible guide play " on "(ie together with) the guide sleeve, progressively deeper and deeper into the adjacent side wall / Se ite walls 6 "milled in".

This wear cannot be completely prevented even with very cost-intensive sliding pairings, since all classic sliding bearing pairings fail in this mixed friction range, which means that in continuous operation, even with very expensive sliding pairings, even in connection with cost-intensive coatings or the like, constantly increasing wear occurs cannot be controlled and results in a continuous loss of efficiency of the pump as a result of constantly increasing leakage losses caused by wear.

The inclined lubrication surface 11 arranged according to the invention on each tooth 10 of the rotor 1 in the direction of rotation R of the rotor 1, on / in the pressure kidney 8 and the end wall 5 of the rotor 1 adjacent to the suction kidney 9 causes, even under unfavorable conditions, such as high working pressures, When pumping poorly lubricating media, with low sliding speeds of the sliding partners, and inexpensive sliding pairings, the build-up of a hydrodynamically load-bearing lubricating film between the end wall 5 of the rotor 1 and the side wall 6 of the gerotor pump adjacent to it.

It is characteristic in this context that the lubricating surface 11 inclined in the direction of rotation R of the rotor 1 relative to the surface plane of the end wall 5 is flat, as in FIG Figures 3 and 4th shown, is formed, and consists of a flat surface which, with respect to the surface plane of the end wall 5 of the rotor 1, includes an angle of inclination α which is in the range from 0.2 ° to 7 °.

Very good results are achieved, for example, with a flat lubricating surface, as in the Figure 3 shown, which is inclined with respect to the surface plane of the end wall 5 of the rotor 1 at an inclination angle α of 0.5 °.

In a further embodiment, as in the Figure 5 shown, the arranged on the end wall 5 of the rotor 1 on each tooth 10 lubricating surface 11 is formed from two adjoining, flat partial surfaces, which are opposite the surface plane of the end wall 5 of the rotor 1 Include an angle of inclination of α or β, where α is smaller than β, and the partial surface of the lubricating surface 11 inclined at the larger angle of inclination β merges into the surface plane of the end wall 5 of the rotor 1 at the surface outlet 14.

In this in the Figure 5 The embodiment shown is the angle of inclination α 0.2 ° and the angle of inclination β 5 °. Both partial surfaces of the lubricating surface 11 together form a surface separating end 15 and lie against one another at an obtuse angle, the partial surface of the lubricating surface 11 inclined at the "second" angle of inclination β at the surface outlet 14 merging into the surface plane of the end wall 5 of the rotor 1. Both partial surfaces of the lubricating surface 11 merge in the direction of the rotor center along a steep surface edge 16 into the surface plane of the end wall 5 of the rotor 1. In the present exemplary embodiment, the rotor 1 is made of the material SintD39, the toothed ring 2 is also made of SintD39, the bearing ring 12 is made of St38 and the pump housing 3 is made of the material AISi9Cu3.

The in the embodiment, according to Figure 5 , shown, arranged on each tooth 10, in the, tangential to the direction of rotation and parallel to the center axis of the rotor 1 extending inclination plane E under the vg. Inclination angles α and β inclined, flat partial surfaces of the lubricating surface 11 are simple and inexpensive to manufacture in terms of manufacturing technology and ensure under the above. Conditions of use an optimal solution to the problem according to the invention.

According to the invention, if, as in the Figures 4 and 6th shown, which are arranged in the end wall 5 of the rotor 1 on each tooth 10 over the entire tooth height H arranged lubrication surfaces 11, in the direction of rotation R of the rotor 1 in front of the tooth center plane M "offset" so that they are parallel to the tooth center plane M and around the offset V begin offset by a maximum of 20% of the tooth root width B.

As in the case of an axial sliding bearing, this causes a local pressure build-up, which measurably reduces the frictional force between the rotor 1 and the cover 7 again.

It is also essential to the invention that the bearing sleeve 4 consists of a ceramic material which has a small surface roughness on its bearing surface.

In the present exemplary embodiments, the roughness values of the bearing surface of the bearing sleeve 4 are around Rz = 1, the bearing sleeve 4 itself being made of the material Al ₂ O ₃ .

The roughness of the associated bearing bore of the rotor 1 is Rk <= 3 in the present exemplary embodiment.

In all of the exemplary embodiments, even after more than 2,100 hours of endurance testing under maximum load, no wear was detectable in terms of measurement, either on the bearing sleeve 4 or on the rotor 1.

On the "bearing surface" of the rotor 1, on the cover 7, a previously inexplicable microdynamic effect occurred surprisingly in the form of a "self-polishing" which is currently not explainable with the plain bearing theory, since the definitely existing mixed friction due to the direct body contact is more common Theory should produce progressive signs of wear. However, this wear was not detectable even after long-term tests under maximum load.

It is also characteristic that the guide length F of the bearing sleeve 4 is twice to 2.3 times the bearing diameter D.

This effectively reduces deformation of the sleeve bore and the resulting "tilting" of the rotor 1, even with pump housings 3 made of light metal (e.g. aluminum alloys).

Regardless of the sleeve fixation, it is advantageous, in particular in the case of cast housings, that the surrounding area of the sleeve guide is structurally included high rigidity is formed in order to effectively prevent a possible deformation of the sleeve bore by the "working load" of the rotor 1 acting on the bearing sleeve 4.

It is also characteristic that the guide length F of the bearing sleeve 4 is approximately 53% to 60% of the total length L of the bearing sleeve 4.

In connection with the aforementioned formation of the surrounding area of the sleeve bore, the inventive guide length F of the bearing sleeve 4 ensures, in addition to a secure positioning, whether by gluing or by a press fit, of the bearing sleeve 4 in the pump housing 3, in conjunction with the use of a bearing sleeve 4 made of a material with a high modulus of elasticity (e.g. ceramic / modulus of elasticity approx. 380 to 400 GPa) with a simultaneous flexurally rigid design of the bearing sleeve (that counteracts deflection of the bearing sleeve 4 in the case of high radial loads), reliable positioning of the rotor 1 in the pump housing 3.

It is also advantageous if the pump housing 3 is made of cast aluminum. In addition to a cost-effective, technically simple production, this also enables high reliability and a long service life.

Thus, by means of the solution according to the invention, it has been possible to develop a gerotor pump with sleeve-guided rotors which, even when using low-viscosity pumping media such as "low-viscosity, low-viscosity oil", is used in conjunction with smaller pump systems whose rotors have tooth tip diameters of approx. 20 to approx. 40 mm and whose delivery pressures are in the range from 3 to 20 bar, and which, even at low speeds in the range from 500 to 1,000 rpm and high delivery pressure, significantly reduce the disproportionate increase in the drive torque with a simultaneous loss of efficiency, so that the gerotor pump according to the invention at high reliability and long service life always guarantees a high level of pump efficiency.

Composition of reference symbols

1

rotor

2

Toothed ring

3

Pump housing

4th

Bearing sleeve

5

Front wall

6th

Side wall

7th

cover

8th

Pressure kidney

9

Suction cup

10

tooth

11

Lubrication surface

12

Bearing ring

13

Wear marks

14th

Run-out

15th

Surface separators

16

Surface edge

H

Tooth height

B.

Tooth root width

M.

Tooth center plane

R.

Direction of rotation

F.

Guide length

L.

overall length

D.

Bearing diameter

E.

Slope plane

V

Offset

α, β, γ

Inclination angle

Claims (6)

1. Gerotor pump having an inner gear with outer teeth, the rotor (1), and an outer gear with inner teeth, the gear ring (2), which is guided in a circular working chamber of a pump housing (3) in such a manner that both gears stand in meshing engagement and rotate about their own but relatively offset axes, wherein the rotor (1) is mounted on a bearing sleeve (4) on one side, and side walls (6), which are either integrated into the pump housing (3) or can be disposed on the pump housing (3) as covers (7), are disposed on both sides of face walls (5) of the meshing gears, wherein, in at least one of these side walls (6), on both sides of an eccentricity plane that contains the relatively offset axes of the rotor (1) and the gear ring (2), an arc-shaped pressure kidney (8) and an opposing arc-shaped suction kidney (9) are disposed, respectively, characterized in that
   only on the face wall (5) of the rotor (1) adjacent to the arc-shaped pressure kidney (8) and the arc-shaped suction kidney (9), on each tooth (10) over its entire tooth height (H), a lubrication surface (11), which is inclined in a direction of rotation (R) of the rotor (1), relative to a surface plane of the face wall (5) of the rotor (1), is disposed either starting directly in a center tooth plane (M) or starting "offset" ahead of the center tooth plane (M) in the direction of rotation (R) of the rotor (1), wherein the lubrication surface is formed by a planar surface or a plurality of always planar partial surfaces that follow one another, which respectively enclose an angle of inclination (α, β, γ,...) relative to the surface plane of the face wall (5) of the rotor (1) that is in the range from 0.2° to 7°, respectively.
2. Gerotor pump according to claim 1, characterized in that the lubrication surface (11) of the face wall (5) that is inclined in the direction of rotation (R) of the rotor (1) is respectively formed by two planar partial surfaces that follow one another, which respectively enclose an angle of inclination (α) or (β) relative to the surface plane of the face wall (5) of the rotor (1), 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 a surface run-out (14).
3. Gerotor pump according to claim 1, or according to claims 1 and 2, characterized in that the lubrication surfaces (11) disposed in the face wall (5) of the rotor (1), on each tooth (10) over the entire tooth height (H), "offset" ahead of the center tooth plane (M) in the direction of rotation (R) of the rotor (1), are disposed in such a manner that they start parallel to the tooth center plane (M) and offset by the offset (V) of maximally 20% of a tooth root width (B).
4. Gerotor pump according to one or more of claims 1 to 3, characterized in that the bearing sleeve (4) comprises a ceramic material that has a low roughness depth on its bearing surface.
5. Gerotor pump according to one or more of claims 1 to 4, characterized in that a guide length (F) of the bearing sleeve (4) amounts to 2 times to 2.3 times a bearing diameter (D).
6. Gerotor pump according to one or more of claims 1 to 5, characterized in that the guide length (F) of the bearing sleeve (4) amounts to about 53% to 60% of a total length (L) of the bearing sleeve (4).

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