EP2151542A2 - Rotating piston pump with pockets for lubricant - Google Patents

Abstract

The pump has a rotor rotatable around a rotation axis (R) in a chamber (4) of a housing (1). The rotor exhibits a sliding surface (15) at a side, where the surface forms a sliding pairing with another sliding surface (16) of the chamber. A pocket is formed in one of the surfaces for lubricants. The pocket is limited with respect to the rotation axis in a circumferential direction and radially outside by the former surface. The pocket is formed such that a hydrodynamic lubricating film is developed between the surfaces by the rotating rotor. The rotor is made of sintered steel or plastic.

Description

The invention relates to rotary piston pumps and is directed in particular to vacuum pumps.

Passenger cars and light commercial vehicles have long been equipped with pneumatic brake booster. Were the necessary for the brake booster negative pressure in passenger car gasoline engines formerly applied by acting behind the throttle of the intake manifold vacuum, so these Saugrohrunterdrücke sufficient for diesel engines and modern gasoline engines with gasoline direct injection because of different load control concepts no longer. These engine concepts therefore use separate vacuum pumps driven by the combustion engine. The pumps, which are usually designed in rotary vane type, are mechanically driven by the camshaft of the engine in the majority of applications and are usually flange-mounted on the front side of the cylinder head. In recent years, in terms of efficiencies, pumps with only one rotary vane have prevailed over multi-vane vane pumps. Despite the comparatively good efficiencies of the single-leaf vacuum pumps, the drive of the pump, which is permanent during operation of the internal combustion engine, must continue to pay attention to a reduction in the drive power required for the pump against the background of the CO ₂ problem and the constant compulsion to reduce fuel consumption. A starting point for improving the efficiency is the reduction of the friction power at the end face of the pump rotor.

After DE 33 01 098 A1 Lubricant is supplied to the two bearing gaps on the end faces of a rotor of a vacuum pump. The rotor is rotatable about an axis of rotation between two side plates facing its end faces. The side plates are axially movable and are acted upon in the direction of the respective facing end face of the rotor with a pneumatic pressure to seal the delivery chamber of the pump. The rotor has at both end faces in each case a peripheral Gleitdichtfläche surrounding the rotation axis. Radially within this annular sliding surface, the end face of the rotor is axially withdrawn a bit. The two peripheral sliding surfaces provide in cooperation with the axially movable side plates for the tightness of the delivery chamber, while the recessed, central region through the respective side plate through lubricant is supplied. The side plates are for this purpose of open porosity and saturated with the lubricant. The friction between the side plates and the peripheral sliding surfaces of the rotor should still be considerable due to mixed friction. The execution of the side plates with the porosity required for the lubrication with sufficient stability and wear resistance will also not be unproblematic.

In one of the DE 33 25 261 A1 known vacuum pump is used as a sealing and lubricating oil centrally supplied to one end face of the rotor and guided via two radially branching off from the central feed throttle channels in a reclaimed at the end face of the rotor annulus. The two narrow throttle passages each extend radially beyond an inner sliding sealing surface of the rotor to open into the recessed annular space which extends in the face of the rotor about an inner sliding surface and is circumferentially enclosed by a peripheral sliding surface sealing the housing cover. Also in this embodiment, the friction in the sliding bearing clearance between the sliding surface of the housing cover and the two sliding surfaces of the rotor, the inner sliding surface and the peripheral sliding surface, should be considerable.

The JP 2000-337267 A discloses a lubrication of the frontal bearing gaps for a hydraulic pump. The working fluid also serves as a lubricant. An improvement in the lubricating effect is achieved in that formed in the front side of the conveying chamber bounding chamber walls, between the formed in these chamber walls inlet and outlet openings for the working and lubricating medium each have many small, circular depressions and about the axis of rotation of the rotor on a Circle are evenly distributed. The depressions act as lubrication pockets, but you will not learn more about the mode of action and the shape of the wells.

The JP 10-068393 A teaches to improve the lubrication of a vacuum pump, to form in a forming with the chamber wall, the sliding bearing gap sliding surface of the rotor a plurality of pockets which are seen in the plan view of the end face of the rotor are each completely within the sliding surface, thus beerbstandet in the circumferential direction of each other and both radially be limited inwardly and outwardly from the sliding surface. The pockets each have the shape of a slender, curved around the axis of rotation part ring. In order to reduce the wear in the sliding bearing gap to a practically relevant extent, this solution also requires a thick lubricant film, associated with corresponding leakage losses and with regard to the efficiency of the pump.

It is an object of the invention to reduce the friction of the front tribological pairing between chamber wall and rotor of a rotary piston pump with little technical effort at the lowest possible leakage.

The subject of the invention is a rotary piston pump comprising a housing with a delivery chamber and at least one rotor rotatable about a rotation axis in the delivery chamber. The rotor has on its two end faces sliding surfaces which each form a sliding pair with axially facing sliding surfaces of the chamber. The end-side chamber walls which form said sliding surfaces of the chamber are preferably not movable, but stationary in the housing. In at least one of the sliding surfaces, i. in at least one of the front-side sliding surfaces of the rotor or in at least one of the front-side sliding surfaces of the chamber, at least one pocket for lubricant is formed. The pocket is bounded circumferentially with respect to the axis of rotation and radially outward by the sliding surface containing the pocket.

According to the invention, the pocket is shaped so that, when the rotor is rotating, a hydrodynamic lubricating film builds up in the gap of the bearing bearing the pocket. Once the rotor reaches the transition speed of the mating pair, the hydrodynamic lubricant film is viable and the rotor begins to slide on the lubricant. When crossing the Transitional speed, the rotor slides in the fully supporting area, and there is only liquid friction. In this way, the sliding surfaces of the sliding pair are separated and solid friction avoided, while the axial thickness of the axially limited by the sliding surfaces gap can still be kept low. The pocket is shaped so that the hydrodynamic lubricant film builds up at the speeds typical for the operation of the rotary piston pump, in which the rotary piston pump is predominantly operated. The bag has for this purpose a sufficient volume and a suitable shape, in particular, it has a care for the lubricating film construction depth profile. The pocket is preferably shaped such that the hydrodynamic lubricating film sets in the sliding gap immediately after the trailing end of the pocket in the direction of rotation of the rotor. The same or the axially opposite sliding surface can or may contain one or more further pocket (s) that do not meet this condition, as long as in the gap of the sliding surfaces as a whole from the transition speed prevails the hydrodynamic lubrication state. If, as preferred, several pockets according to the invention are provided, it is sufficient if these pockets bring about the construction of the hydrodynamic shear film only in combination.

The pocket flattens in the circumferential direction, in the direction of its trailing end, thus tapering, preferably over its entire radially measured width. If the taper extends only over part of the radial pocket width, this tapered width region is preferably arranged radially in the middle region of the sliding surface. The pocket forms a wedge in the gap of the sliding surfaces at the trailing end. In the tapered region, the pocket may have a variable inclination in the course of the rise to the sliding surface containing it, in particular an inclination which decreases towards the trailing end, so that the bottom of the pocket in the region of the wedge towards the opposite Sliding surface of the sliding couple bulges around. In likewise preferred embodiments, the inclination is constant over at least one larger, preferably the predominant part of the wedge. The pocket bottom may include in the rise one or more curved section (s) in combination with one or more straight section (s). It may also have one or more stages in the wedge-shaped gap, but a continuous course is preferred. It can with respect to the axially opposite sliding surface from the outlet in the sliding surface in the circumferential direction may even have one or more concave sections, as long as the hydrodynamic lubricant film is still built up.

The wedge preferably extends over at least a quarter, more preferably over at least half of the pocket depth, the reference depth being the maximum depth of the pocket. For example, the bag may be perpendicular to the bottom of the bag, i. in the axial direction, or increase with increasing inclination and only from half the pocket depth or already before tapering gradually. In particular, the taper can already be used immediately in the pocket bottom, i. From the pocket bottom flatten out directly with an inclination to the sliding surface containing them. The inclination to the sliding surface should be at most in the trailing end region of the wedge at most 45 °, more preferably at most 30 °, both in the case of a constant and in the case of a variable inclination. At least at the trailing end of the wedge, when leaving the sliding surface, the mentioned angle values should not be exceeded. Lower angles of inclination are advantageous in view of the shear forces acting on the structure of the hydrodynamic lubricant film in the lubricant, in particular in the outlet of the wedge. Thus, an inclination directly at the end of the wedge of at most 15 ° is particularly preferred, it also corresponds to preferred embodiments, when the inclination decreases continuously, at least at the end of the wedge, the wedge can expire in particular tangentially into the sliding surface. With regard to the wedge length measured in the circumferential direction, it is advantageous if the wedge extends over at least half the pocket length, wherein the advantage of this geometry feature increases with decreasing pocket length.

It is advantageous if the bag expires at its trailing end in the sliding surface flat, with less inclination than at its leading end. At the leading end of the bag can steeply, in particular vertically, rise to the sliding surface, with a chamfer at the transition to the sliding surface as belonging to the steep wall, since chamfers serve only the deburring, but do not cause hydrodynamic film structure. However, the invention also relates to embodiments in which the bag also terminates wedge-shaped at the leading end. The geometric asymmetry with a pronounced wedge at the trailing end to produce the hydrodynamic lubricating film and at the leading end steep or at least significantly steeper to the Sliding surface rising pocket is preferred, however, as this minimizes the area ratio of the pocket relative to the sliding surface.

Preferably, there is a fluidic connection between the pocket and a radially outer edge of the sliding surface containing them only over the axial gap between the sliding surfaces facing each other, so that lubricant can penetrate only radially outward from the pocket via the sliding surfaces forming sliding surfaces. Alternatively, however, a connection can additionally be provided between the pocket and the radially outer edge of the sliding surface or pocket and a circumferential surface radially adjoining the sliding surface, either in the form of a connecting channel lying below the sliding surface or open on the sliding surface. However, such an optional connection channel is designed so that it provides the flow of lubricant from the bag considerable resistance to flow, which is several times greater than in the case of a pocket which passes through the sliding surface radially with its full pocket cross-section. A radial boundary of the pocket by the sliding surface is thus also seen when a narrow in the circumferential direction or in the depth direction of the pocket flat connecting channel has a flow cross-section which is smaller by a multiple than a largest pocket cross-section. An optional connection channel can be used to selectively use lubricant on the bag radially outward into the chamber and there for lubrication, for example, the tip of a wing of a vane pump. In any case, the optional connecting channel is dimensioned such that, in spite of the drainage of lubricant facilitated by it, the hydrodynamic lubricating film forms.

The trailing end of the pocket can, seen in plan view of the sliding surface, run straight over its entire radial width and run at least essentially radially, ie pass over the pocket into the sliding surface via a radial edge line. Instead, the pocket may also be undercut in plan view of the sliding surface, so that it has a circumferentially extending extension at the trailing end which is bounded radially inwards, in the direction of the axis of rotation of the rotor, by the sliding surface. The undercut counteracts a flow of the lubricant radially inwardly, in particular in preferred embodiments, in which the pocket radially inward, ie in the direction of the axis of rotation, on an inner peripheral surface opens, so that the sliding surface passes radially in the direction of the axis of rotation. The sliding surface is in such embodiments extends annularly around the axis of rotation. A radially inwardly passing through the sliding surface has the advantage that such a pocket can be supplied with lubricant from the central region within the annular sliding surface.

In preferred embodiments, further pockets in the manner according to the invention are formed in the sliding surface containing the pocket. The pockets are circumferentially spaced from each other about the axis of rotation, preferably a portion of the sliding surface remains between them, and are bounded radially outward by the sliding surface containing them. The pockets are advantageously arranged distributed around the axis of rotation at least substantially uniformly. The angular distances of respectively adjacent pockets are substantially the same in such embodiments. In the case of a rotary vane pump with a single vane, which passes radially through the rotor, is regarded as a uniform angle division, an arrangement in which the pockets are distributed symmetrically with respect to the wing. The pockets are seen in plan view of the sliding surface and in cross section preferably equal to each other, but may in principle also differ from each other. You can also deviate from each other in the depth profile, but more preferably they are equal to each other in the depth profile. The depth profile is the course of the axial depth in the circumferential direction on a cylindrical surface which cuts the pocket about the axis of rotation.

In embodiments with only a single pocket, this pocket may in particular be arranged so that it counteracts a light tilting position of the rotor axis which is present in some applications in pump operation. In such an additional function, the pocket is arranged in one of the end-side sliding surfaces of the chamber, ie stationary with respect to the chamber. The tilting position of the rotor, if present during operation, is known in advance, so that the bag can be arranged accordingly. If a plurality of pockets of the type according to the invention are formed in the respective sliding surface of the chamber in the circumferential direction, these pockets are arranged so as to at least partially compensate the tilting position, for example by providing the pockets in the circumferential direction only in half of the sliding surface, in the the gap between the sliding surfaces is smaller due to the tilted position than in the other hemisphere. On the other hand, however, pockets can also be distributed over the entire circumference, with the ratio of pocket area to remaining sliding area being greater than in the other hemisphere of the relevant sliding area in order to compensate for a tilted position in the corresponding hemisphere.

As mentioned, the pocket or preferably a plurality of pockets may or may not be formed in one of the sliding surfaces of the rotor or one of the chamber sides of the rotor facing side. The word "or" is always understood in the usual logical sense as an "inclusive or", ie includes both the meaning of "either ... or" as well as the meaning of "and", as far as the specific context is not exclusively only one limited meaning. A single or multiple pockets may or may therefore be provided, for example, only in one or only in both frontal sliding surfaces of the rotor, these two embodiments are particularly preferred, or only in one of the two sliding pairings co-forming sliding surfaces of the chamber or only in both frontal sliding surfaces the chamber. In further embodiments, a single pocket or pockets may also be formed in one or both of the sliding surface (s) of the rotor and additionally in one or both facing sliding surfaces of the chamber, including, for example, the case where a single pocket or a plurality of pockets only on one of the two end faces of the rotor and a single or more pockets is formed only in that sliding surface of the chamber or are, which forms a sliding pair on the opposite end face of the rotor with the local Rotorgleitfläche. The invention also includes the case that the rotor on one or both ends has a single or more pockets and the chamber is also provided on the same face also with a single or more pockets of the type according to the invention, which associated with the same sliding pair Bags of the rotor and the chamber are radially offset from each other so that they do not overlap during rotation of the rotor.

One preferred type is vane pumps having a single or multiple vanes (s) slidably guided by the rotor, and also swing vane pumps. Among the rotary vane machines in turn single-wing designs are preferred, ie Versions in which the rotor with the wing divides the delivery chamber into only two cells. The rotary piston pump can be designed with a variable or constant delivery volume. It can be multi-stroke, but is preferably one-stroke. A plurality of rotors, for example two rotors, may be arranged in the delivery chamber, with a pair of bearings preferably being formed in accordance with the invention in each case on both rotors at at least one axial end side. In the embodiments as a rotary valve, swing or possibly also pendulum slide pump, the bag is advantageously formed in shaping on the rotor in a peripheral region of the sliding surface, which is not penetrated by a wing, a sliding or swing wing. In embodiments in which the sliding surface with the at least one pocket according to the invention is not interrupted in the circumferential direction, but extends completely circumferentially around the axis of rotation, this consideration plays no role. If several pockets are shaped and arranged according to the invention in the relevant sliding surface, the plurality of pockets are advantageously arranged in the rotor around the axis of rotation in such a number that at least one of the pockets is arranged in the angular region of each cell of the cell pump. In single-leaf embodiments, per cell, which forms the rotor with its one-piece or divided wing, preferably at least two of the pockets according to the invention are arranged.

The rotary piston pump preferably requires a gaseous working fluid while the lubricant is preferably liquid. In particular, the invention is directed to a vacuum pump which is installed in a motor vehicle or intended for installation in a motor vehicle. The pump can generate the vacuum required for a brake booster. It is preferably powered by the engine, which is preferably an internal combustion engine. For such vacuum pumps, it is usual that the rotor on the circumference of a rotor bearing portion provided with a floating sliding bearing and thus axially fixed, but is movable either within the axial tolerance or a deliberately provided axial play between the end faces of the delivery chamber. On the drive side acts on the corresponding diameter of the bearing portion projection surface of the rotor, the pressure of the crankcase of the engine, which generally corresponds approximately to the atmospheric pressure, while at the opposite, opposite projection surface of the rotor in the a relatively high negative pressure acts on a large number of operating states of the pump, so that the rotor is pressed against the relevant sliding surface of the chamber. It arises according to the pressure gradient, a considerable axial thrust, which leads to a large friction in the case of planning in the prior art frontal geometry of the rotor, countermeasures are not taken according to the invention. The mixed friction states in the axial thrust bearing of the rotor due to unfavorable tribological conditions entail the risk of wear, which in many cases must be prevented by a coating of the chamber wall which causes costs. In the inventive design can be dispensed with a coating only for the purpose of Reibverschleißminderung, even if a coating as an additional measure should not be excluded categorically.

Basically, the invention is not limited to the field of vacuum pumps. The medium to be conveyed may also be a liquid and in such embodiments also simultaneously form the lubricant. Preferred examples of liquid pumps are lubricating oil pumps for supplying an internal combustion engine of a vehicle or another unit of a vehicle with lubricant or hydraulic fluid. Such a pump is preferably driven by the engine of the vehicle.

If the rotary piston pump is rotationally driven as a function of the rotational speed of a drive motor, preferably an internal combustion engine, for example as preferably via a mechanical coupling, the sliding pairing with the at least one pocket according to the invention is preferably designed such that the transition rotational speed for the construction of the hydrodynamic lubricating film is already in idling operation of the drive motor is exceeded. As already mentioned, the pump may be mounted in a vehicle or provided for use in a vehicle, and the drive motor may in particular be the drive motor of the vehicle.

In preferred embodiments, an axially flying bearing of the rotor is realized. By the invention, an axial sliding bearing gap is formed between the sliding pair of axially facing sliding surfaces by the rotor when the transition speed of the opposite sliding surface of the chamber of the hydrodynamic lubricating film worn lifts off. Advantageously, the pairing on the opposite end face of the rotor is also formed so that there forms a hydrodynamic lubricating film, wherein the lubricant film thicknesses of the two lubricating films adjust the axial balance of forces accordingly. Axial flying or floating bearing allows for this adjustment. If, during operation of the pump, an axial thrust occurs in a certain direction as exemplarily described above, a single or more preferred pocket (s) according to the invention is expediently provided in the case of the sliding pair which has to absorb the axial thrust whose axial sliding surfaces therefore press against each other axially examined.

Since the bag (s) formed in accordance with the invention are preferably formed without undercut in the depth direction, the rotor can be reduced by means of a forming tool to the bag (s) by forming the rotor tool, i. be produced without additional processing and thus virtually cost-neutral. By means of a subsequent machining process, for example a grinding process, the end face of the rotor is thus produced without additional manufacturing effort a suitable wedge gap geometry which is effective in tribological interaction with the preferably plane chamber wall. At the same time there are cost reduction potentials, because of the inventive lubricating pocket (s) can be dispensed with an additional anti-wear coating one of the sliding bearing gap forming sliding surfaces. The rotor can be molded in particular by pressing and sintering as a sintered part made of metal or plastic or by injection molding of plastic as an injection molded part.

Advantageous features are also described in the subclaims and their combinations.

Figur 1

eine erfindungsgemäße Rotationskolbenpumpe in einem Längsschnitt,

Figur 2

die Rotationskolbenpumpe in einer zum Längsschnitt der Figur 1 orthogonalen Draufsicht und mit einem Rotor, der Schmiertaschen eines ersten Ausführungsbeispiels aufweist,

Figur 3

eine Draufsicht auf eine Stirnfläche eines Rotors mit Schmiertaschen eines zweiten Ausführungsbeispiels,

Figur 4

den in Umfangsrichtung um eine Rotationsachse des Rotors erstreckten Schnitt A-A der Figur 3,

Figur 5

ein Detail der Figur 4,

Figur 6

eine Draufsicht auf eine Stirnfläche eines Rotors mit Schmiertaschen eines dritten Ausführungsbeispiels,

Figur 7

den in Umfangsrichtung um eine Rotationsachse des Rotors erstreckten Schnitt B-B der Figur 6,

Figur 8

Schmiertaschen eines vierten Ausführungsbeispiels,

Figur 9

Schmiertaschen eines fünften Ausführungsbeispiels,

Figur 10

Schmiertaschen eines sechsten Ausführungsbeispiels und

Figur 11

Schmiertaschen eines siebten Ausführungsbeispiels.

Embodiments of the invention are explained below with reference to figures. The features disclosed in the exemplary embodiments form each individually and in each combination of features the subject-matter of the claims and also the embodiments discussed above in an advantageous manner. Show it:

FIG. 1

a rotary piston pump according to the invention in a longitudinal section,

FIG. 2

the rotary piston pump in a longitudinal section of the FIG. 1 orthogonal plan view and with a rotor having lubrication pockets of a first embodiment,

FIG. 3

a plan view of an end face of a rotor with lubrication pockets of a second embodiment,

FIG. 4

the circumferentially about an axis of rotation of the rotor extending section AA of the FIG. 3 .

FIG. 5

a detail of FIG. 4 .

FIG. 6

a plan view of an end face of a rotor with lubricating pockets of a third embodiment,

FIG. 7

the circumferentially about an axis of rotation of the rotor extending section BB of FIG. 6 .

FIG. 8

Lubrication pockets of a fourth embodiment,

FIG. 9

Lubrication pockets of a fifth embodiment,

FIG. 10

Lubrication pockets of a sixth embodiment and

FIG. 11

Lubrication pockets of a seventh embodiment.

FIG. 1 shows a rotary piston pump in a longitudinal section. It is a vacuum pump, for example for generating a negative pressure for a brake booster of a motor vehicle. The pump is driven by the combustion engine of the vehicle. It comprises a housing 1 with a housing structure 2 and a cover 3, which is detachably connected to the housing structure 2.

FIG. 2 shows the pump in a plan view from the side of the lid 3 ago, with the lid 3 is removed. The housing 1 forms a delivery chamber 4 with an inlet 5 and an outlet 6 for the fluid to be delivered, in the exemplary embodiment air. The inlet 5 and the outlet 6 open at an inner circumferential surface 14 of the housing 1, in the embodiment of the housing structure 2, in the chamber 4. The inlet 5 is provided with a valve which allows a flow only in the chamber 4. The inlet 5 merges with an additional outlet 7. The outlet 6 is closed by a lamella valve 8 and the outlet 7 by a lamella valve 9, so that fluid through the outlet 6 and also through the outlet 7 only out of the chamber, but not in the chamber can flow in. The additional outlet 7 acquires significance only in the case of a temporary reversal of the direction of rotation V.

A rotor 10 is rotatably disposed about a rotation axis R in the chamber 4. The rotor 10 is slidably mounted for rotation axially axially rotatable outside the chamber 4 along a rotor bearing section 11, for which purpose the bearing section 11 and by way of example the housing structure 2 form an axially relative to each other Oleitlagerpaarung. The rotor 10 has at the end facing away from the delivery chamber 4 a connection for a rotation secured connection directly with a camshaft or a drive wheel, via which it is in the mounted state of the internal combustion engine, for example, driven by the camshaft.

The pump is designed as a single-vane vane pump. A wing 13 passes through the rotor 10 in the radial direction and is guided by the rotor 10 in a rotor slot 12 radially reciprocating back and forth. The rotor 10 and the wing 13 divide the delivery chamber 4 into two delivery cells, one of which is connected to the inlet 5 and the other to the outlet 6. The rotor 10 is arranged eccentrically in the chamber 4, so that it fluidly separates the two conveyor cells and in particular the inlet 5 and the outlet 6 with its outer circumferential surface. In FIG. 2 take the rotor 10 and the wing 13 just a symmetry position, in which the two conveyor cells are the same size. If the rotor 10 rotates in the direction of rotation V, the in FIG. 2 lower delivery cell and reduces the in FIG. 2 upper delivery cell, so that working fluid is sucked through the inlet 5 into the increasing delivery cell and discharged from the decreasing delivery cell through the outlet 6 under elevated pressure. During the rotational movement, the wing tips of the wing 13 travel along the circumferential surface 14 of the chamber 4, so that the delivery cells are fluidly separated from one another via the sealing gap between the wing tip and the peripheral surface 14. Radially opposite the conveying cells are as mentioned separated by the sealing gap between the outer peripheral surface of the rotor 10 and the peripheral surface 14 of the chamber 4 from each other. For the fluidic separation of the delivery cells also provide axially facing sliding sealing surfaces of the rotor 10 and the wing 13 on the one hand and the chamber 4 on the other.

For the axial sealing of the delivery cells, the rotor 10 has a sliding surface 15 on an end face remote from the drive side and a sliding surface 17 on the other end side facing the drive side. The sliding surfaces 15 and 17 form with axially opposite sliding surfaces 16 and 18 of the housing 1 each have a sliding pair. The frontal sliding surfaces of the wing 13 are not provided with their own reference numerals, but form with the axially facing chamber walls each have a further pair of bearings. The housing-side sliding surface 16 on the end face of the rotor 10 facing away from the drive side is formed by the cover 3, while the housing structure 2 forms the counter-sliding surface 18 for the rotor sliding surface 17. In order to reduce frictional wear of the sliding mating and to improve the sealing of the delivery cells, the lubricating pairings, a lubricating oil or other suitable lubricant is supplied.

In particular, as in the exemplary embodiment, the lubricant can be conducted into a central cavity passing axially through the rotor 10 and from there spreading over the sealing gaps 15 and 16 on the one hand and the sliding surfaces 17 and 18 on the other hand. Thus, a lubricant channel lead in particular through the bearing section 11. At the end face facing the bearing section 11, it is possible to provide in the rotor 10, for example, a circumferentially extending distributor groove into which the lubricant channel opens. The lubricant passes through the centrifugal force acting on the rotating rotor 10 through the axial sliding gap of the sliding pair of sliding surfaces 17 and 18 in the chamber 4 and thereby ensures adequate lubrication of the sliding pair 17 and 18. The lubricant passes through the central cavity of the Rotor 10 at the other end face and there also distributed supported by the centrifugal force radially outwards and provides for the lubrication of the sliding surfaces formed by the sliding surfaces 15 and 16 and also the sliding pairings formed with the wing 13.

The rotor 10 is provided in the side facing away from its drive side sliding surface 15 with pockets 20 in which the lubricant collects. The pockets 20 may also be referred to as lubrication pockets. In the sliding surface 15 a total of four pockets 20 are formed, in each case two pockets 20 on both sides of the wing 13. The wing 13 divides the sliding surface 15 in two Gleitflächenhemissphären, by way of example and preferably the same further as also preferably shaped as circular ring segments. The pockets 20 are uniformly distributed in the two hemispheres in the sense of a uniform distribution over the circumference of the lubricant. The sliding surface 15 separates the pockets 20 in the circumferential direction from each other and limits them radially outward, so forms radially outward of the two slots 12 a circumferential sliding pair with the axially opposite sliding surface 16. The pockets 20 are radially inwardly in the direction of the axis of rotation R. open, so open at an inner peripheral surface of the rotor 10. The lubricant passes from the central cavity of the rotor 10 into the cavity opening into the pockets 20, accumulates in it and is supported in the operation of the pump by the centrifugal force radially outward to to lubricate the sliding pair of the sliding surfaces 15 and 16 and at the same time to seal the axial sliding gap formed between the sliding surfaces 15 and 16 and thus contribute to the fluidic separation of the delivery cells. If the sliding pair of sliding surfaces 17 and 18 also pockets, preferably inventive pockets, these may open radially into the said distribution groove and be supplied via this with the lubricant.

The pockets 20 pass respectively at their leading in the direction of rotation V end 23 along a curved in plan view of the sliding surface 15 Taschenöffnungsrand in the sliding surface 15, while they pass at their trailing end 24 each along a straight radial opening edge in the sliding surface 15. The leading edge drops from a tangent to the edge with everywhere continuous curvature against the direction of rotation V in the direction of the trailing end 24 from. This smoothes the flow of the lubricant into the respective pocket 20, counteracts recirculation and the formation of dirt traps. As a result, the circumferentially measured length L in each of the pockets 20 continuously decreases in the radial direction from inside to outside.

In particular, the pockets 20 are each shaped so that a hydrodynamic lubricant film builds up between the sliding surfaces 15 and 16 during operation of the pump as soon as the transition speed required for this purpose is exceeded. The pockets 20 are shaped and arranged to exceed the transition speed in the wear-related operating conditions of the pump. Is the pump for a drive by a Internal combustion engine of a vehicle provided or mounted in the vehicle so, the design is preferably such that the transition speed is below the speed that reaches the rotor 10 when the engine is idling. The pockets 20 each flat in the direction of their trailing end 24 continuously, so that they form with the axially opposite sliding surface 16 to a trailing end 24 tapered wedge gap. The lubricant is due to the force acting in the lubricant upon rotation of the rotor 10 thrust forces at the trailing end 24 of each of the pockets 20 between the sliding surfaces 15 and 16 and forms there when the transition speed is exceeded, a bearing lubricating film, the sliding surfaces 15 and 16 separated from each other and in the axial sliding gap ensures pure fluid friction. Due to the inventive design of the sliding pair 15 and 16 with the pockets 20, a rotor 10 axially supporting axial plain bearing is created in combination with the axially flying or floating slide bearing of the rotor 10. The sliding mating 15 and 16 with the pockets 20 is preferably further designed so that this thrust bearing also carries full and works at the transition speed is exceeded only in the field of fluid friction when it takes a stemming from the drive side at 11 axial force, an axial thrust must, as is the case in particular in preferred installation situations in which the vacuum pump is arranged on the housing or in a modification in the housing of an internal combustion engine of a motor vehicle.

FIG. 3 shows a plan view of the end face of a rotor 10, in the sliding surface 15 pockets 21 are formed according to a second embodiment. Apart from the pockets 21, the rotor 10 corresponds to the rotor 10 of Figures 1 and 2 and can replace it in the pump. The pockets 21 are rectangular in the radial plane shown. They each pass both at the leading end 23 and at the trailing end 24 along a straight, approximately radially pointing opening edge into the sliding surface 15. The two opening edges extend parallel to each other. The circumferentially extending radially outer opening edge interconnecting the opening edges at the leading end 23 and trailing end 24 is an arc portion on a circle about the axis of rotation R, but could be simply straight, for example. The pockets 21 are open at their radially inner side as in the first embodiment, thus open with their full pocket cross section on the inner circumferential surface of the rotor 10 in the central Cavity. In FIG. 3 are the dimensions of the opening edge, along which the respective pocket 21 merges into the sliding surface 15, registered. The length measured in the circumferential direction is L and the width measured in the radial direction is designated B. The length L is constant over the entire width B.

In FIG. 4 is the sliding pair formed by the sliding surfaces 15 and 16 of the second embodiment in the in FIG. 3 registered section AA shown (without break edges). FIG. 4 is the settlement of the circular cylindrical section AA. In the sectional area AA, the shape of the cross section of the pockets 21 can be seen. FIG. 5 shows one of the pockets 21 in an enlarged view. D denotes the same pocket depth for all pockets 21, which is measured in the axial direction between the lowest point of the respective pocket 21, the pocket bottom, and the plane sliding surface 15 which extends radially to the axis of rotation R. The pockets 21 rise from the bottom of the bag with the same constant inclination α in each case in the direction of the trailing end 24 of the respective pocket 21. The inclination α is less than 30 °, in the embodiment, it is about 15 °. At the leading end, the pockets 21 rise from the bottom of the bag into the sliding surface 15 steeply, in the embodiment as preferred with an inclination angle β of about 90 ° to the sliding surface 15. The opening edge at the leading end 23 may be chamfered, with such a chamfer than for steeply rising pocket wall is expected. The pockets 21 and the axially opposed sliding surface 16 define a substantially triangular wedge-shaped gap which tapers towards the trailing end of each pocket 21.

A modification to the first embodiment is thus that the pockets 21 have a different course at the leading end by being straight there and not, as is preferred, continuously falling against the direction of rotation V. Further, in the sliding surface 15, a larger number of the pockets 21 are formed as in the first embodiment. As in the first embodiment, the pockets 21 on both sides of an extending through the slot 12, imaginary dividing plane symmetrical and arranged distributed uniformly in the two hemispheres of the sliding surface 15 in the circumferential direction.

FIG. 6 shows an end view of a rotor 10, which has in the illustrated sliding surface 15 pockets 22 of a third embodiment, but otherwise the first and second Embodiment corresponds. The pockets 22 have an undercut with respect to the radial direction, so that over a part of their circumferentially measured length L, which is correspondingly variable in the third embodiment, a web is obtained, which is part of the sliding surface 15, and one through the Undercut obtained projection 25 in each of the pockets 22 radially bounded in the direction of the axis of rotation R. Each of the pockets 22 is extended by its extension 25 in the circumferential direction, namely as preferred against the direction of rotation V, ie at the trailing end. The extensions 25 are each formed in the region of the radial center of the sliding surface 15. The pockets 22 thus extend radially outward from their mouth into the central cavity of the rotor 10, first over a width region of shorter length L, and progressing radially outward into an outer region elongated by the extension 25, but as in the other embodiments bounded radially on the outside by a remaining there peripheral strip of the sliding surface 15 without interruption.

FIG. 7 shows the sliding pair of the sliding surfaces 15 and 16 in the development of Kxeiszylinderschnitts BB of FIG. 6 (without break lines). The pockets 22 form with the opposite sliding surface 16 each at the trailing end of a wedge gap by the pockets 22 rise from the respective pocket bottom with a constant inclination α to the trailing end 24 to the axial height of the sliding surface 15. The wedge gap is the same as the first and second embodiments. By way of example, the pockets 22 at the leading end 23 are modified relative to the second exemplary embodiment in that they rise there from the pocket bottom with a pronounced curvature into the chamber wall which is then again orthogonal to the sliding surface 15. A chamfering advantageously present at the leading edge of the opening is again neglected, since it plays no role in terms of flow technology.

As a result of the undercut, as already mentioned, a web is obtained radially in the region of the extension 25 thus obtained, which preferably forms part of the sliding surface 15. In particular, by such a remaining Gleitflächensteg an escape of the lubricant is counteracted in the central cavity of the rotor 10. Although the sliding surface 15 preferably remains in the region of the said web, this advantageous effect is indeed achieved in a weakened form, but in principle also when the obtained by the undercut web does not extend axially all the way to the sliding surface 15, but still represents a narrowed flow cross-section radially inwardly, which throttles the outflow into the central cavity at the trailing end 24. The undercut may be preferred as in FIG. 6 as an example, be stepped, but alternatively it can also widen radially from the radially inner mouth region in the direction of the trailing end 24 radially outward, as long as only an outflow radially inward at the trailing end 24 is counteracted. The wedge-shaped gap can, as shown by way of example, extend at the trailing end over the entire width B of the pockets 22 or, in a modification, only over the radial width of the respective extension 25. However, an extent over the entire radial width B is preferred.

The pockets 22 are seen in the radial plane at the leading end 23 are each continuously curved and fall as in the first embodiment in the direction of the trailing end 24 from a set to the opening edge of the front end 23 tangent. As in the first embodiment, the formation of dirt traps and recirculations are thereby prevented at the leading end. For undercut is nachzutragen still be that in the region of the circumferentially elongated extension 25 is a larger pocket length L than in the radially inner and narrower pocket area is available to form the wedge-shaped gap. The pockets 22 can accordingly increase in the region of the respective extension 25 with a smaller inclination α in the direction of the trailing end 24, since the increase can be distributed over a greater length.

The FIGS. 8 to 11 each show a development of a circular cylindrical sectional area in the manner of the sectional views of FIGS. 4 and 7 (each without break line). Shown are pockets that are modified with respect to their cross-section, ie their axial depth profile, compared to the second and the third embodiment.

In the in FIG. 8 shown fourth embodiment, the pockets are designated 26. They each rise from the pocket bottom in the direction of the trailing end 24 with a variable inclination α up to the sliding surface 15. The leading ends 23 each correspond to the second embodiment, the local inclination β is again about 90 °, with a chamfer is neglected. The wedge-gap-inducing rejuvenation sets like in the second embodiment, directly at the steep pocket wall of the leading end 23, thus extending over at least substantially the entire length L of the respective pocket 26. The inclination α decreases continuously in the direction of the trailing end 24, so that the bottom of the Pockets 26 in each case continuously bulges around in the direction of the opposite sliding surface 16, in relation to the sliding surface 16 is thus formed round convex. The inclination α is in the bag base between 40 and 60 °, but could well be up to 90 ° or less than 30 °. At the bottom of the bag could also be as in the third embodiment, a pronounced Kehlung be present. The inclination α is at the trailing end 24 at the transition into the sliding surface 15 less than 15 °, in particular, the bottom of the pocket 26 can pass tangentially into the sliding surface 15, so the inclination α continuously decrease to the value "zero".

FIG. 9 shows pockets 27 of a fifth embodiment which differ substantially from the pockets of the other embodiments in that a wedge-shaped gap is also formed at the leading end 23 of each pocket 27. In Ausführungsbcispicl the pockets 27 are symmetrical in the cross section shown with respect to the direction of rotation V and the opposite direction, ie the pockets 27 each rise from the pocket bottom in and against the direction of rotation V with the same inclination to the sliding surface 15. The course of the inclination α thus corresponds to the course of the inclination β. By way of example, consistency is assumed for the inclinations α and β. An advantage of forming a wedge gap with both the leading end 23 and the trailing end 24 is that the rotor 10 is rotationally invariant with respect to the formation of the hydrodynamic lubricating film, which may be advantageous for certain applications. On the other hand, the double formation of a wedge gap at the expense of the sliding surface 15, which is thereby reduced, which may be compensated by a widening in the radial direction.

FIG. 10 shows pockets 28 of a sixth embodiment. In the pockets 28, the wedge-shaped gap at the trailing end 24 only extends over approximately half the total length of each pocket 28 and only over one to two quarters of the pocket depth D. Seen in cross-section in this way in the region of the leading end 23 a pronounced Collection space for the lubricant and in the region of the trailing end 24 a smaller wedge gap than in the previous examples obtained.

FIG. 11 shows pockets 29 of a seventh embodiment. The wedge gap is even flatter than in the pockets 28 of the sixth embodiment and also slightly longer. The inclination α is correspondingly lower and in the wedge gap is less than 10 ° everywhere. The wedge-shaped gap therefore extends over slightly more than half the length L and between one-sixth and one-fourth of the pocket depth D of the respective pocket 29. The pockets 29 are also modified relative to the pockets 28 in the region of the leading end 23, where they have a pronounced Have Kehlung, which has approximately the shape of a semicircle, for example. Overall, the bottom of the bag is formed by the trough-shaped groove and the subsequent wedge gap in the direction of the trailing end 24. The chamber wall immediately at the leading end 23 corresponds to the third embodiment ( FIG. 7 ).

The pockets 20, 21 and 22 of the first, second and third embodiments may optionally have any of the different depth profiles, that is, each of the depth profiles may be combined with each of the pocket contour related to the radial direction and the circumferential direction. Further, wedge gaps at the leading end 23 and at the trailing end 24, as exemplified in FIG. 9 are also obtained with a variable inclination α and β, for example in the manner of the wedge gap of FIG. 8 , Likewise, the wedge column of the FIGS. 10 and 11 in the direction of the trailing end 24 a variable inclination α, for example, congruent to the embodiment of FIG. 8 exhibit. The pockets 28 and 29 may also run out to the leading end 23 in a wedge-shaped gap, but a particularly large proportion of the sliding surface 15 would be claimed by the thus shaped pocket 28 or 29 by such a geometry in relation to the length of the respective wedge gap.

Reference numerals:

1

casing

2

housing structure

3

cover

4

chamber

5

inlet

6

outlet

7

outlet

8th

Valve

9

Valve

10

rotor

11

bearing section

12

slot

13

wing

14

peripheral surface

15

Sliding surface rotor

16

Sliding surface cover

17

Sliding surface rotor

18

Sliding surface housing structure

19

-

20

bag

21

bag

22

bag

23

leading end

24

trailing end

25

extension

26

bag

27

bag

28

bag

29

bag

α

Tilt

β

Tilt

B

width

D

depth

L

length

R

axis of rotation

V

direction of rotation

Claims (19)

Rotary piston pump, comprising a) a housing (1) with a chamber (4), b) a rotor (10) which is rotatable in the chamber (4) about a rotation axis (R) and which has a sliding surface (15) on one end face which forms a sliding pair with a sliding surface (16) of the chamber (4), c) and at least one pocket (20; 21; 22; 26; 27; 28; 29) for lubricants formed in one of the sliding surfaces (15, 16), d) is limited in the circumferential direction and radially outward of the sliding surface (15) containing it with respect to the axis of rotation (R), e) wherein the pocket (20; 21; 22; 26; 27; 28; 29) is shaped so that a hydrodynamic lubricant film builds up between the sliding surfaces (15, 16) when the rotor (10) rotates. Rotary piston pump according to the preceding claim, characterized in that the pocket (20; 21; 22; 26; 27; 28; 29) forms with the axially opposite sliding surface (16) a wedge-shaped gap which slopes in the direction of a rotational direction (V ) of the rotor (10) trailing end (24) of the pocket (20; 21; 22; 26; 27; 28; 29) tapers. Rotary piston pump according to the preceding claim, characterized in that the wedge gap extends over at least a quarter, preferably over half or most of the circumferentially measured length (L) of the pocket (20; 21; 22; 26; 27; 28; 29 ). Rotary piston pump according to one of the two preceding claims, characterized in that the wedge gap extends over at least a quarter, preferably over at least half the depth (D) of the pocket (20; 21; 22; 26; 27; 28; 29). Rotary piston pump according to one of the three preceding claims and at least one of the following features: the pocket (20; 21; 22; 26; 27; 28; 29) extends into the sliding surface (15) containing the pocket with an inclination (α) ≤ 45 °, preferably ≤ 30 °, measured on the sliding surface (15) ; - The pocket (20; 21; 22; 26; 27; 28; 29) tapers over at least one sixth of the circumferentially measured pocket length (L) with an inclination (α) ≤ 45 ° measured on the slide surface (15), preferably ≤30 °; the pocket (20; 21; 22; 26; 27; 28; 29) tapers over at least half of the pocket depth (D) with an inclination (α) ≤ 45 °, preferably ≤ 30 ° measured on the sliding surface (15) , The rotary wedge machine according to one of the four preceding claims, characterized in that the wedge gap extends over at least one sixth, preferably over at least half of the circumferentially measured length (L) of the pocket (20; 21; 22; 26; 27; 28; 29) relative to the sliding surface (15) containing the pocket (20; 21; 22; 26; 27; 28; 29) is tapered either with a constant inclination (α) or a continuously decreasing inclination (α). Rotary piston pump according to one of the preceding claims, characterized in that the pocket (20; 21; 22; 26; 27; 29) rises steeply at its side leading with respect to a direction of rotation of the rotor (10) to which the pocket (20; 21, 22 26, 27, 29) containing sliding surface (15) increases. A rotary piston pump according to any one of the preceding claims, characterized in that the pocket (20; 21; 22; 26; 27; 29) increases in the one circumferential direction to the sliding surface (15) containing it with a slope (α) smaller than an inclination (β) at which the pocket (20; 21; 22; 26; 27; 29) rises in the other circumferential direction to the sliding surface (15) containing it. Rotary piston pump according to one of the preceding claims, characterized in that a circumferentially measured length (L) of the pocket (20; 22) changes over the radial width (B) of the pocket (20; 22). Rotary piston pump according to one of the preceding claims, characterized in that the pocket (22) in the radial direction from the rotation axis (R) seen from an undercut (at 25) through which at the trailing end (24) a pocket (22) radially inside limiting web is obtained, which preferably forms a part of the sliding surface (15). Rotary piston pump according to one of claims 1 to 8, characterized in that a circumferentially measured length (L) of the pocket (21) over the entire radial width (B) of the pocket (21) is constant. Rotary piston pump according to one of the preceding claims, characterized in that the pocket (20; 22) has an end (23) leading in relation to a direction of rotation (V) of the rotor (10), which in a plan view points at the pocket (20; containing sliding surface (15) radially outward from an imaginary radial tangent to the leading end (23) against the direction of rotation (V) drops. Rotary piston pump according to one of the preceding claims, characterized in that the pocket (20; 21; 22; 26; 27; 28; 29) extends in the direction of the axis of rotation (R) into an inner peripheral surface of the rotor (10). Rotary piston pump according to one of the preceding claims, characterized in that in the sliding surface (16) of the chamber (4) only one pocket or a plurality of pockets (20; 21; 22; 26; 27; 28; 29), preferably of the same type, formed and in the case of only a single pocket this single pocket and in the case of multiple pockets all pockets of this sliding surface (16) in the circumferential direction is or are such that during operation of the pump resulting, known in advance tilted position of the axis of rotation (R) of the Rotor (10) is counteracted. Rotary piston pump according to one of the preceding claims and at least one of the following features: the pocket (20; 21; 22; 26; 27; 28; 29) is formed in the sliding surface (15) of the rotor (10); - The pocket is formed in the sliding surface (16) of the chamber (4); the pocket (20; 21; 22; 26; 27; 28; 29) is formed in the sliding surface (15) of the rotor (10) or in the sliding surface (16) of the chamber (4) and in the other sliding surface also formed at least one pocket, which preferably also corresponds to at least one of the preceding claims, wherein the pocket of the rotor and the pocket of the chamber are radially offset from each other, so that they can not cover at least substantially when the rotor is rotating; - The rotor (10) has on its other end face on a further sliding surface (17) which forms a further sliding pair with a further sliding surface (18) of the chamber (4), and in at least one of the further sliding surfaces (17, 18) at least one further pocket (20; 21; 22; 26; 27; 28; 29) for lubricant is formed in such a way that a hydrodynamic lubricating film also builds up between the other sliding surfaces (17, 18) when the rotor (10) rotates at least one further pocket (20; 21; 22; 26; 27; 28; 29) corresponds to one of the preceding claims. Rotary piston pump according to one of the preceding claims, characterized in that in at least one of the sliding surfaces (15, 16, 17, 18) a plurality of pockets (20; 21; 22; 26; 27; 28; 29) are formed and circumferentially spaced apart from each other and radially outwardly of the sliding surface (15) containing them, that the pockets (20; 21; 22; 26; 27; 28; 29) are shaped such that between the pockets (20; 21; 22; 26; 27; 28; 29) and the axially opposite sliding surface (16) of the hydrodynamic lubricating film and that at least two of the pockets (20; 21; 22; 26; 27; 28; 29) at least one of claims 2 to 15 correspond. Rotary piston pump according to one of the preceding claims, characterized in that the rotor (10) relative to the housing (1) axially reciprocally movable, preferably in a radial sliding bearing (at 11) is mounted axially overhung. Rotary piston pump according to one of the preceding claims and at least one of the following features: - The rotary piston pump is a vacuum pump; - The rotary piston pump is a vane pump, preferably a single-vane vane pump; - The rotary piston pump is installed in a motor vehicle or provided for installation and preferably has a drive wheel for a rotary drive of the rotor (10) by an internal combustion engine of the motor vehicle. Rotary piston pump according to one of the preceding claims and one of the following features: - The rotor (10) is a sintered part, preferably made of sintered steel; - The rotor (10) is molded from plastic, preferably by injection molding or as a sintered part; - The rotor (10) is formed in a process of primary forming, preferably in a sintering process or injection molding process, with the at least one pocket (20; 21; 22; 26; 27; 28; 29) tool falling.

Images