Flushing arrangement for tribocontact surfaces and vane pump with such an arrangement

Abstract

Flushing arrangement for sliding partners for use in a vane pump, which bear against each other at two tribocontact surfaces (8, 9) sliding against each other in a provided direction of movement, wherein one sliding partner is a hub ring (6) and the other sliding partner is a housing (10), characterized in that - the tribocontact surface of the hub ring (10) is surface-structured in two diametrically opposed flattens (8, 9) by an elongated groove profile (2) in which lubricant is located; - the grooves (2) extend essentially in the direction of movement; and - a gap height of the grooves (2) forming a depth of the groove profile is in the range of 0.05 to 0.20 mm.

Description

[0001] The present invention relates to a flushing arrangement for tribocontact surfaces for their cooling and lubrication and in particular to a vane pump with an adjustable stroke ring, which is provided with a flushing arrangement according to the invention.

[0002] Tribology is the fundamental study of friction, lubrication, and wear in bearings, guides, gears, motors, and other machine elements. Besides the development of suitable lubricants, current developments focus on material selection, surface coatings, and surface topography. Beyond mechanical engineering, there are numerous other fields where friction and wear are of great importance, such as endoprosthetics.

[0003] In hydraulic machines, such as vane pumps, but also in other machines with components in frictional contact, the fundamental problem is adhesive wear and the resulting abrasive wear at so-called tribological contact points, especially when these contact points / surfaces are subjected to normal forces and only move microscopically, i.e., very little, relative to each other, at least for a certain period of time. A kind of dry running occurs at the contact point, in which the tribological partner, the fluid, is barely or not at all present. The result is overheating of the surfaces, coking of any residual fluid, fretting corrosion, and ultimately, premature adhesive wear. Adhesive wear can also occur with macro-movements, generating a great deal of frictional heat.

[0004] As an application-related example, a pump unit with a main pump and a charging pump whose delivery volume is adjustable and which is designed as a vane pump may be mentioned here, as is known, among other things, from the prior art, for example according to DE 10 2007 032 103 A1.

[0005] This pump unit comprises an axial piston pump as the main pump, whose drive shaft also drives the vane pump. The rotor of the vane pump is fixed directly to the extended drive shaft of the main pump. Both pumps are housed in a common casing. Alternatively, the vane pump can have its own drive shaft, which is coupled to the drive shaft of the main pump, for example, via a bushing.

[0006] The rotor of the vane pump incorporates a number of slots, essentially located in axial planes parallel to the rotor axis. Each slot accommodates a radially movable pump vane, which, due to the centrifugal force generated during rotor rotation and any additional positive guidance, seals against the inner wall of a piston ring and slides along it. The piston ring is mounted in the housing so that it can be displaced radially relative to the rotor's axis of rotation, thus changing the eccentricity of the piston ring's inner wall to the axis of rotation and consequently the displacement volume of the vane pump. According to DE 10 2007 032 103 A1, the piston ring is mounted externally on diametrically opposed parallel bearing surfaces against corresponding mating surfaces of the housing.The adjustment is made depending on the output pressure of the vane pump, whereby the pressure acts on an effective surface on the hub ring, determined by the distance between the two bearing surfaces and the axial extent of the hub ring, and acts against a spring.

[0007] In the well-known vane pump, the ratio between the guide length and guide width of the piston ring in the pump housing is not very favorable. The smaller this ratio, the greater the risk of jamming. This is related to the lever arm available to the frictional forces.

[0008] From DE 10 2006 050 246 A1 a hydrodynamic sliding bearing for rotary motion is known, the sliding surface of which is provided with grooves circumferential around the axis of rotation.

[0009] From DE 602 16 340 T2, a low-friction sliding element for a reciprocating machine is known. The corresponding sliding contact surface has tiny recesses that extend perpendicular to the reciprocating motion.

[0010] From DE 601 24 055 T2, a sliding surface structure for an internal combustion engine and an internal combustion engine with this sliding surface structure are known. The corresponding sliding surfaces contain a basic structure with microscopic irregularities.

[0011] From DE 101 63 292 A1, a bearing half with grooves to prevent the escape of lubricating oil is known. The bearing half is designed for rotary motion and has circumferentially extending grooves.

[0012] From DE 15 74 508 A, an air bearing for planar recording media made of an elastic material is known. The air bearing has grooves running transversely to the direction of movement of the recording media.

[0013] A bearing with micropores is known from DE 697 30 035 T2.

[0014] From DE 10 2008 036 273 A1, a rotary piston pump with pockets for lubricant is known. The pockets are part of the sliding pair between the rotor and the chamber in which the rotor rotates.

[0015] A hydrodynamic radial sliding bearing is known from DE 10 2008 060 369 A1. The corresponding tribological contact comprises a grooved structure, the grooves of which extend at least approximately parallel to the corresponding axis of rotation.

[0016] A semi-cylindrical bearing shell is known from DE 27 11 983 A1. This shell is provided with several oil grooves that intersect to form a diamond-shaped pattern.

[0017] In light of these circumstances, the object of the present invention is to design tribo-contact points in general such a way that frictional forces are kept low. In particular, the invention aims to minimize increases in frictional forces during operation due to adhesive and abrasive wear, as well as those resulting from excessive heat input. A specific objective of the invention is to improve the tribo-contact points of a piston ring and its sliding partner in a vane pump in such a way that the frictional forces, and thus the risk of piston ring jamming, are kept low.

[0018] This problem is solved by a flushing arrangement for tribocontact surfaces, particularly on the hub ring of a vane pump and its sliding partners, according to the features of claim 1. Advantageous embodiments of the invention are the subject of the dependent claims.

[0019] The invention therefore provides a flushing arrangement of tribocontact surfaces, consisting of two tribocontact surfaces sliding against each other, wherein at least one of the tribocontact surfaces has a number of grooves or groove sections extending substantially in the direction of movement. According to the invention, the surface contour forms a number of elongated grooves or groove sections, the gap heights of which preferably differ with respect to any two adjacent grooves. Alternatively or additionally, the grooves can extend in a labyrinth shape, whereby the general orientation of the grooves should, however, fundamentally run in the direction of movement of the surface-structured contact surface.

[0020] A particularly advantageous design features grooves between the different pressure potentials arranged in a zigzag or wave pattern. Groove sections running at an angle to the direction of movement are especially beneficial, as fluid is drawn from the grooves into the contact areas of the tribological contact surfaces during adjustment. Preferably, the groove depth alternates from groove to groove.

[0021] The grooves, acting as gaps, connect at least two different lubricant pressure potentials that are spaced apart in the direction of movement of the tribocontact surfaces. This creates a pressure difference or pressure gradient along the tribocontact surfaces. This effect can be utilized by designing and / or orienting the grooves in such a way that the pressure gradient causes the lubricant to essentially jump across the separating ridges that form between the grooves. This flushes away abrasive particles and dirt particles adhering to the ridge surfaces (contact surface sections facing the opposite contact surface) from the fluid, while also cooling and lubricating the ridges. Several options are proposed regarding the design and / or orientation of the grooves, which can be used individually or in combination: 1. Different gap heights of adjacent (bordering) grooves

[0022] The flow rate through the gap is proportional to the cube of the respective gap height. In contrast, the groove cross-section is only proportional to the cube of the gap height. For this reason, the ratio of flow rate to groove cross-section (i.e., the lubricant velocity) differs significantly from one groove to the next. The static pressure of the stationary lubricant (liquid) at the higher pressure potential is reduced in the grooves by the dynamic pressure component, which is proportional to the cube of the previously defined lubricant velocity. This results in considerable static pressure differences from one groove to the next.

[0023] The separating and sealing surfaces between adjacent grooves are thus lubricated, cooled, and cleaned by the flow rates triggered by the pressure differences between them. This prevents or at least reduces both primary adhesive and secondary abrasive wear (including that caused by the washing away of dirt particles or lubricant degradation products such as coking).

[0024] The depth of the grooves and the depth difference depend on the requirements for volumetric losses and cooling / lubrication, depending on the energy input and the tendency to run dry. 2. Reduction of the groove spacing to a minimum depending on the maximum permissible surface pressure

[0025] It is advantageous to increase the number of grooves up to a limit (resulting from a maximum surface pressure) to ensure even and finely distributed lubrication / cooling. Furthermore, more lubricant will flow (leak) through the resulting thin sealing ribs / ridges between the grooves for cooling / lubrication. 3. Groove profile at least partially transverse to the direction of movement

[0026] Furthermore, it is advantageous if the grooves are not aligned with the direction of movement of the tribological contact surfaces, or at least not everywhere (although this is also possible in principle). The grooves can thus have a wave-like shape, zigzag shape, diagonal orientation, etc. This allows lubricant to be conveyed across the support ribs simply through the relative movement, and also prevents the opposing contact surface (i.e., the opposite contact surface) from being constantly covered at the same point. Additionally, a slight flow of lubricant occurs across the rib from one groove section to the next within the same groove, since a pressure gradient exists between successive groove sections along the entire length of the groove. 4. Groove pattern in labyrinthine form

[0027] In this groove configuration, the pressure drop during flow through each groove results in a pressure difference or pressure gradient along each groove section due to the hydraulic resistance caused by the groove. Since groove sections with different pressure levels are adjacent to each other, the aforementioned overflow of water across the support webs occurs between the adjacent groove sections.

[0028] The invention is explained in more detail below with reference to preferred embodiments and the accompanying figures.

[0029] They show Fig. 1 An axial view of the hub ring of a vane pump located in a housing, the bearing surfaces (tribocontact surfaces) of which are provided with grooves for flushing according to the invention, Fig. 2 a top view of a tribocontact surface with a surface profile according to a first embodiment, Fig. 3 a top view of a tribocontact surface with a surface profile according to a second embodiment, Fig. 4 a top view of a tribocontact surface with a surface profile according to a third embodiment, Fig. Figure 5 shows a preferred cross-sectional shape for grooves which are located on the tribocontact surface according to the Fig. 2, Fig. 3 to Fig. 4 are formed, and Fig. 6 the hub ring Fig. 1 with visibility of one of the two storage areas.

[0030] According to Fig. 1 Two corresponding guide areas 8 and 9 are located on opposite sides of a piston ring 6 of a vane pump and an elongated recess 12 of a housing 10 in which the piston ring is located. These guide areas 14 and 15 are located on the housing. The housing 10 has a suction channel 21 that opens into a suction nozzle 22 and a pressure channel 23 that extends from a pressure nozzle 24. The guide areas 8 and 9 on the piston ring are formed by bearing surfaces (tribocontact surfaces) located on the outer circumference. These surfaces run parallel to each other and parallel to a displacement axis 16 of the piston ring 6 and are diametrically opposed to each other in the same direction as the two nozzles 22 and 24.Accordingly, the guide areas 14 and 15 on the housing are bearing surfaces (tribocontact surfaces), whereby these bearing surfaces have a greater extent in the direction of the displacement axis than the bearing surfaces on the stroke ring, so that the bearing surfaces of the stroke ring are in full contact. To adjust the delivery volume of the vane pump, a radially applied force is applied to the stroke ring 6 from the outside in the direction of the displacement axis 16, thereby changing the distance of the axis of the stroke ring 6 to the axis 18 of the [unclear - possibly "in the housing"]. Fig. The position of the rotor of the vane pump, which is not visible, is altered. During adjustment, the bearing surfaces 8 and 9 of the stroke ring 6 slide along the opposing guide areas 14 and 15 on the housing 10. The bearing surfaces 9 and 15 are subjected to a higher load because they are located outside the pressure plate 24, and the stroke ring 6 is subjected to the pump pressure from the inside in the area of ​​the pressure plate 24.

[0031] According to the Fig. 2 generally has a tribocontact surface, which in the exemplary embodiment according to Fig. 1. Let the bearing surface 9 be a number of parallel, spaced-apart grooves 2, which generally extend along a predetermined direction of movement of the tribocontact surface 9. Between the grooves 2, support or sealing ribs 4 are formed, which define a bearing surface (-line) at their free upper edge, which is connected to a Fig. The two opposing contact surfaces (opposite tribocontact surfaces), not shown in further detail, are in sliding contact. To reduce friction between the contact surfaces, a lubricant, preferably liquid, such as oil, is provided, which is applied to or injected into the contact surfaces.

[0032] It was assumed that, viewed in the direction of movement of the tribocontact surface 9, the lubricant is under higher pressure on one side of the tribocontact surface 9 than on the other side of the tribocontact surface 9. Therefore, a pressure gradient exists across the tribocontact surface in the direction of movement.

[0033] According to the Fig. 2. The grooves 2 are designed in such a longitudinal orientation that groove sections are formed which extend transversely or at an angle to the direction of movement. Specifically, the grooves have, according to the Fig. 1. A zigzag shape along the direction of movement.

[0034] This shape allows the groove sections of two immediately adjacent grooves 2 to abut each other. These grooves are positioned one behind the other in the direction of movement and therefore exhibit different partial pressure levels. These pressure differences cause water to flow over the sealing ribs 4 separating the grooves 2, thereby flushing away any adhering particles and lubricating and cooling the contact surfaces. This flow occurs not only between adjacent grooves, but also between groove sections of the same groove that are positioned one behind the other in the direction of higher to lower pressure potential and run at an angle to each other, due to the pressure gradient between these groove sections.

[0035] Preferably, immediately adjacent grooves 2 are formed with different groove depths. In the simplest version, two different depth values ​​are provided, which are distributed alternately between the adjacent grooves and are preferably essentially constant over the entire groove length. However, it should also be noted that the respective groove depths can change along the length of the groove (for example, increase or decrease).

[0036] In the embodiment according to Fig. 3. The grooves 2 are straight and parallel to each other along the intended direction of movement of the respective tribocontact surface 9. Since, in this case, the pressure gradient along the contact surface 9 is uniform in all grooves 2, there is initially no pressure difference between two grooves 2 (90°) perpendicular to the direction of movement. However, in this case, the adjacent grooves 2 necessarily have different groove depths according to the optional configuration as shown. Fig. 1. This creates a local pressure difference in the (90°) transverse direction to the direction of movement. The effect is the same as in the first embodiment.

[0037] In the embodiment according to Fig. Figure 4 shows the contour of the tribocontact surface 9, a labyrinth profile consisting of a groove 2 which, in this case, extends across the tribocontact surface 9 with right-angled bends and parallel sections. Thus, comparable to the first preferred embodiment of the invention, groove sections lie directly one behind the other in the direction of movement, each with a different length, up to the area with higher pressure potential at the front of the tribocontact surface 9. However, a pressure difference exists between different groove sections because the groove sections are located at different distances from the sides with higher and lower pressure potential. A pressure gradient between adjacent groove sections also results from the different lengths of adjacent groove sections and thus different gap lengths.An overflow of flushing fluid (lubricating fluid) therefore takes place both between the groove sections running perpendicular to and between those running parallel to the direction of movement.

[0038] As a result, adjacent groove sections located directly behind one another in the direction of movement are subjected to different pressure levels, thus achieving the same effect as described above using the first and second embodiments. Furthermore, in the case of multiple grooves, these can be formed with different groove depths.

[0039] In this regard, we should refer at this point to the Fig. Figure 5 shows a cross-sectional view of two immediately adjacent grooves as described above. As can be seen, both grooves have a pitched-circle profile, with both pitched circles having the same radius. However, the pitched-circle segment of one groove is larger than the pitched-circle segment of the immediately adjacent groove. This results in different groove depths and, in this case, also groove widths. The deeper groove has a depth of 0.15 mm, and the shallower groove has a depth of 0.10 mm. Therefore, the depth of one groove is only 2 / 3 that of the other. The cross-sectional area of ​​the grooves differs by a factor of 3 to 5.

[0040] Alternatively, it is of course also possible to design the grooves with different radii or even with different cross-sectional shapes, the latter possibly leading to different hydraulic resistances of the groove shapes.

[0041] Finally, in Fig. 6 a mere lifting ring 6 as a practical application possibility of the flushing arrangement according to the invention, as is used in particular in vane pumps for example according to the Fig. 1 is inserted. The hub ring is positioned between the bearing surfaces 14 and 15 of the housing 10 at the two diametrically opposed flats 8 and 9 (see Fig. 1) guided. The two flattened areas represent two tribocontact surfaces. The flattened area 9, i.e., the flattened area in the pressure region, is, according to the exemplary embodiment, according to Fig. 2 trained. Of course, training according to Fig. 3 or Fig. 4 possible. Likewise, the flattened area 8 can also be equipped with a flushing arrangement to improve cooling and lubrication.

[0042] According to Fig. 6 The bearing surfaces on the hub ring are equipped with the flushing arrangement according to one of the preceding embodiments. However, the counter-rotating component on the side of the pump housing can also, in principle, have a flushing arrangement according to the invention, either exclusively or in combination with the hub ring 6.

[0043] Profiling in a tribocontact surface can be achieved by embossing, pressing, machining, or laser cutting. According to the invention, the profiling depth is in the range of 0.05 to 0.20 mm.

Claims

[1] Flushing arrangement for sliding partners for use in a vane pump, which bear against each other at two tribocontact surfaces (8, 9) sliding against each other in a provided direction of movement, wherein one sliding partner is a hub ring (6) and the other sliding partner is a housing (10), characterized by , that - the tribocontact surface of the hub ring (10) is surface-structured in two diametrically opposed flattens (8, 9) by an elongated groove profile (2) in which lubricant is located; - the grooves (2) extend essentially in the direction of movement; and - a gap height of the grooves (2) forming a depth of the groove profile is in the range of 0.05 to 0.20 mm. [2] Flushing arrangement according to claim 1, characterized by, that the groove profile has adjacent grooves or groove sections and that the gap height is different at least between any two adjacent grooves (2) or groove sections, wherein in the case of several grooves (2) the gap heights are preferably alternating. [3] Flushing arrangement according to claim 1 or 2, characterized by , that at least two adjacent grooves (2) are aligned parallel to each other at least sectionally or over their entire length. [4] Flushing arrangement according to any one of claims 1 to 3, characterized by that the grooves (2) are wavy, zigzag or diagonal. [5] Flushing arrangement according to claim 1 or 2, characterized by , that the grooves (2) run in a labyrinthine pattern. [6] Flushing arrangement according to one of the preceding claims, characterized by , that the grooves (2) have at least longitudinal sections which are at an angle to the direction of movement of the surface-structured tribocontact surface (9). [7] Flushing arrangement according to one of the preceding claims, characterized by , that the grooves (2) connect at least two different detergent pressure potentials in the direction of movement in front of and behind the surface-structured tribocontact surface (9), thereby creating a pressure gradient along the surface-structured tribocontact surface (9). [8] Flushing arrangement according to one of the preceding claims, characterized by , that the grooves (2) have a rectangular, wedge-shaped or circular segment-shaped cross-section. [9] Vane pump which is adjustable in its stroke volume and has a vane-equipped rotor and a stroke ring (6) adjustable in a plane perpendicular to the axis of rotation of the rotor in a pump housing, the eccentricity of which can be adjusted by moving the stroke ring (6) along tribocontact surfaces (9) which are in sliding contact with the pump housing, characterized by a flushing arrangement according to one of the preceding claims. [10] Vane pump according to claim 9, characterized by , that on the hub ring (6) outside an area in which it is subjected to high pressure on the inside, a tribocontact surface is formed on the outside and this tribocontact surface and / or the tribocontact surface on the housing is equipped with a flushing arrangement according to one of claims 1 to 8. [11] Vane pump according to claim 10, characterized by that the hub ring and the housing each have two tribocontact surfaces and that at least one tribocontact surface on each pair of tribocontact surfaces is equipped with a flushing arrangement according to one of claims 1 to 8.

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