Pump including a spring fastened to positioning elements

Abstract

A pump including a rotor; a first housing part and a second housing part, between which the rotor is arranged such that it can be rotated about a rotational axis relative to the first and second housing part; at least one positioning element which positions the second housing part with respect to its angular position about the rotational axis relative to the first housing part; and a spring, wherein the second housing part is arranged between the spring and the rotor, wherein the spring is fastened to the at least one positioning element or the second housing part.

Claims

1. A pump, comprising: a rotor; a first housing part and a second housing part, between which the rotor is arranged, the rotor being configured to be rotated about a rotational axis relative to the first and second housing part; two or more positioning elements which position the second housing part with respect to its angular position about the rotational axis relative to the first housing part; and a spring which includes, or forms, two or more fastening elements, a main portion and at least one supporting portion, wherein a spring gap exists between the second housing part and the main portion such that said main portion is configured to flex towards and away from the second housing part along the rotational axis, and the at least one supporting portion is supported on the second housing part, wherein the second housing part is arranged between the spring and the rotor, wherein the spring is fastened to said two or more positioning elements by the two or more fastening elements.

2. The pump according to claim 1, wherein the spring is fastened, secured against rotating about the rotational axis, in a positive fit.

3. The pump according to claim 2, wherein said two or more positioning elements are formed by the first housing part or are anchored in the first housing part as a part which is separate from the first housing part.

4. The pump according to claim 1, wherein said two or more positioning elements are formed by the first housing part or are anchored in the first housing part as a part which is separate from the first housing part.

5. The pump according to claim 4, wherein a third housing part which surrounds the rotor over its circumference is arranged between the first housing part and the second housing part, wherein the third housing part is: a part which is separate from the first and second housing part, a portion of the first housing part which is formed by the first housing part, or a portion of the second housing part which is formed by the second housing part.

6. The pump according to claim 1, wherein a third housing part which surrounds the rotor over its circumference is arranged between the first housing part and the second housing part, wherein the third housing part is: a part which is separate from the first and second housing part; a portion of the first housing part which is formed by the first housing part; or a portion of the second housing part which is formed by the second housing part.

7. The pump according to claim 1, wherein at least some of the main portion is arranged between the rotational axis and the at least one supporting portion.

8. The pump according to claim 1, wherein the two or more positioning elements each include a cavity with which the two or more fastening elements of the spring engage.

9. The pump according to claim 8, wherein each cavity is an annular groove which extends over the circumference of each respective positioning element, each positioning element is cylindrical or pin-shaped, and exhibits a width, extending along a longitudinal axis of each positioning element, which is dimensioned such that each respective fastening element of the spring is accommodated in the annular groove with a clearance along the longitudinal axis.

10. The pump according to claim 1, wherein the pump includes a pump shaft which is non-rotationally connected to the rotor and configured to be rotated about the rotational axis, wherein the pump shaft is mounted and configured to be rotated in the first housing part and in the second housing part.

11. The pump according to claim 10, wherein the spring includes a cavity through which the pump shaft or the structure of the second housing part which forms the pump shaft mounting extends.

12. The pump according to claim 1, wherein an accommodating housing which comprises a circumferential wall which extends around the rotational axis, and an end-facing wall which is arranged on the end-facing side of the circumferential wall, wherein the second housing part is surrounded over its circumference by the circumferential wall, and the main portion of the spring is supported on the end-facing wall.

13. The pump according to claim 12, an axial securing element which is fastened to the accommodating housing, wherein a pump assembly includes at least the first housing part, the second housing part, the rotor and a pump shaft and when tensed the spring presses the first housing part of the pump assembly against the axial securing element, wherein the axial securing element prevents the spring from being relaxed.

14. The pump according to claim 12, wherein a seal which is arranged between the second housing part and the accommodating housing seals off a first space, which is formed between the end-facing wall and the second housing part, in relation to a second space which is formed between the circumferential wall and the third housing part, wherein at least one of the first space is connected to a pump chamber, in which the rotor is arranged, by a first channel, and the second space is connected to the pump chamber by a second channel, and the first space is arranged on a suction side and the second space is arranged on a pressure side, or the second space is arranged on a suction side and the first space is arranged on a pressure side.

15. The pump according to claim 12, wherein the main portion of the spring is supported on an annular projection formed by the end-facing wall.

16. The pump according to claim 1, wherein the spring includes an elastomer material or polymer material.

17. The pump according to claim 16, wherein the spring is formed from an elastomer material or polymer material or from a metal spring which is partially or completely coated in the elastomer material or polymer material, or by injection moulding the elastomer material or polymer material around the metal spring.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention has been described on the basis of a number of examples and embodiments. Particularly preferred embodiments of the invention are described on the basis of figures. The features thus disclosed, individually and in any combination of features, advantageously develop the subject-matter of the invention. There is shown:

(2) FIG. 1 a pump assembly;

(3) FIG. 2 the pump assembly from FIG. 1, inserted into an accommodating housing;

(4) FIG. 3 a perspective view of the pump assembly from FIG. 1;

(5) FIG. 4 the spring of the pump assembly from FIG. 3;

(6) FIG. 5 a first alternative embodiment of a spring;

(7) FIG. 6 a second alternative embodiment of a spring;

(8) FIG. 7 a third alternative embodiment of a spring;

(9) FIG. 8 a fourth alternative embodiment of a spring;

(10) FIG. 9 a fifth alternative embodiment of a spring;

(11) FIG. 10 a sixth alternative embodiment of a spring;

(12) FIG. 11 a representation of an individual tooth of a toothed gearing, in a sectional plane which extends parallel to the rotational axis;

(13) FIG. 12a a first variant of a tooth from FIG. 11, from the direction of view indicated in FIG. 11;

(14) FIG. 12b a second variant of a tooth from FIG. 11, from the direction of view indicated in FIG. 11;

(15) FIG. 12c a third variant of a tooth from FIG. 11, from the direction of view indicated in FIG. 11;

(16) FIG. 13 another embodiment of a tooth, in a sectional plane parallel to the rotational axis;

(17) FIG. 14a a first variant of a tooth from FIG. 13, from the direction of view indicated in FIG. 13;

(18) FIG. 14b a second variant of a tooth from FIG. 13, from the direction of view indicated in FIG. 13;

(19) FIG. 14c a third variant of a tooth from FIG. 13, from the direction of view indicated in FIG. 13; and

(20) FIG. 15 a cross-section view through the pump assembly from FIGS. 1 to 3.

DETAILED DESCRIPTION OF THE INVENTION

(21) FIG. 1 shows a pump assembly which can be inserted into an accommodating housing 20, as shown in FIG. 2. The pump assembly comprises a spring 5 which is for example embodied as a disc spring and which is shown in various embodiments in FIGS. 4 to 10.

(22) The pump or pump assembly from FIG. 1 comprises a rotor 4 which is non-rotationally connected to a pump shaft 10 of the pump 1 via a shaft-hub connection 30. The rotor 4 comprises cavities which serve as a guide and are in particular slot-shaped. A delivery element 13, in particular a vane, is assigned to each cavity. The vane 13 can be shifted radially back and forth in its cavity, away from and towards the rotational axis of the rotor 4, in particular guided with one translational degree of freedom, as can best be seen from FIG. 15. The vanes 13 are rotated along with the rotor 4. The pump 1 comprises an annular housing part 12, which for better identification may be referred to as the third housing part 12. The third housing part 12 can be embodied as a stroke ring. The third housing part 12 is trapped between a first housing part 2 and a second housing part 3 and is non-rotational in relation to the first and second housing parts 2, 3. The space which extends annularly around the pump shaft 10, and which is surrounded by the inner circumference of the third housing part 12 and axially delineated by the first and second housing parts 2, 3, can also be referred to as the pump chamber 26. The rotor 4 and the vanes 13 are arranged in the pump chamber 26.

(23) As can best be seen from FIG. 15, at least one delivery chamber 27, 28 is formed radially between the rotor 4 and the third housing part 12. The embodiment shown here comprises two delivery chambers, namely a first delivery chamber 27 and a second delivery chamber 28.

(24) A delivery cell 29 is respectively formed between adjacent vanes 13 and changes its volume as a function of the rotational position of the rotor 4 about its rotational axis. Since the pump comprises a number of vanes 13, it also exhibits a corresponding number of delivery cells 29. A number of delivery cells are situated in each of the delivery chambers 27, 28.

(25) The vanes 13 and the rotor 4 form a first sealing gap with the first housing part 2 and a second sealing gap with the second housing part 3.

(26) The third housing part 12, in particular the stroke ring, and/or the vanes 13 can be magnetised, such that the vanes 13 abut the inner circumferential surface of the third housing part 12 due to magnetic force, including in particular when the rotor 4 is not being rotated. This allows pressure to be built up in good time during a start or cold start, i.e. when the pump shaft 10 begins to be rotated. Alternatively or additionally, the vanes 13 can be pressed outwards, i.e. away from the rotational axis of the rotor 4 and towards the inner circumferential surface of the third housing part 12, due to the centrifugal force while the rotor 4 rotates. The vanes 13 and/or each of the vanes 13 forms a third sealing gap with the inner circumferential surface of the third housing part 12.

(27) The inner circumferential surface of the third housing part 12 exhibits a contour which causes the vanes 13 to extend (increasing the volume of the delivery cell 29) at least once and to retract (decreasing the volume of the delivery cell 29) at least once during one complete revolution of the rotor 4. The pump 1 shown in the example is a twin-stroke pump, i.e. comprises two delivery chambers 27, 28, wherein the vanes 13 for each delivery chamber 27, 28 extend once and retract once when they are moved through the delivery chamber 27, 28 by means of rotating the rotor 4. This means that the vanes 13 extend, retract, extend and retract again in other words, extend twice and retract twice during one complete revolution of the rotor 4. A delivery cell 29 is respectively formed between adjacent vanes 13 and is increased and/or decreased in volume by extending and retracting the vanes 13 which delineate it, namely as a function of the contour of the inner circumferential surface of the third housing part 12.

(28) As can best be seen from FIG. 3, the pump 1 comprises an opening or channel 3b which ports into the region of the delivery chamber 27, 28 in which the volume of the delivery cells 29 decreases while the rotor 4 rotates. This means that fluid, such as for example oil, situated in the delivery cells is displaced through the channel 3b, which in this case serves as an outlet.

(29) The pump 1 comprises an opening and/or channel 2b which ports into the region of the delivery chamber 27, 28 in which the volume of the delivery cells 29 increases while the rotor 4 rotates. This means that fluid is delivered or suctioned through the channel 2b into the expanding delivery cell 29. Since the pump 1 in this example is a two-stroke pump, it comprises two inlet channels 2b and two outlet channels 3b, wherein the first inlet channel 2b and the first outlet channel 3b port into the first delivery chamber 27, and the second inlet channel 2b and the second outlet channel 3b port into the second delivery chamber 28. A reverse configuration of the inlet and outlet channels 2b, 3b is equally conceivable, i.e. the channel 2b can be the outlet channel, and the channel 3b can be the inlet channel.

(30) When the rotor 4 rotates, fluidin particular, liquidis suctioned through the channel 2b into the expanding delivery cells 29 and transported into the region which the channel 3b ports into, wherein the fluid is outputted from the then-contracting delivery cells 29 via the channel 3b.

(31) The pump 1 comprises at least one positioning element 6 (two positioning elements 6 in the example shown). The positioning elements 6 are pins and/or are pin-shaped. The positioning element 6 is firmly anchored in the first housing part 2. The first housing part 2 comprises a blind bore 2a into which a first end of the pin-shaped positioning element 6 is pressed.

(32) The pin-shaped positioning element 6 positions the second housing part 3 and the third housing part 12 with respect to their angular positions about the rotational axis relative to the first housing part 2. The second housing part 3 and the third housing part 12 comprise cavities, apertures, bores or elongated holes, preferably exhibiting a radial extent, through which the positioning element 6 extends. In the example shown, the third housing part 12 comprises a cavity 12a for this purpose. The second housing part 3 comprises a transit bore through which the positioning element 6 extends. The pin-shaped second end of the positioning element 6 protrudes past the end-facing side which points away from the pump chamber 26. This protruding portion of the positioning element 6 comprises a cavity, such as for example an annular groove 6a, or at least a part thereof, which extends over the circumference of the positioning element 6. A securing element or fastening element 5a is arranged in the cavity 6a and fastened to the positioning element 6 and/or in the annular groove 6a, in particular in a force fit and/or positive fit. The fastening element 5a prevents the first housing part 2, the second housing part 3 and the third housing part 12 from axially falling apart; in other words, it prevents the second and third housing part 3, 12 from being removed from the positioning element 6.

(33) The spring 5 can for example be embodied as: a disc spring; a star disc or other element exhibiting geometries of a star disc; or a corrugated spring or other element comprising structures of a corrugated spring. In the example featuring a disc spring, the latter can comprise a main portion 5c which is connected to the fastening element 5a via an arm 5b. In the example shown, the (disc) spring 5 comprises two fastening elements 5a which are respectively connected to the main portion 5c via an arm 5b. On the one hand, the fastening element 5a prevents the housing parts 2, 3, 12 from detaching from each other; on the other hand, it enables the spring 5 to be fastened to the pump unit and/or the positioning element 6. The main portion 5c of the spring 5 is arranged such that it is offset with respect to the fastening element 5a and/or supporting portion 5d along the rotational axis of the rotor 4 or pump shaft 10. The fastening element 5a, and/or the supporting portion 5d which points towards the second housing part 3, abut the second housing part 3 or are supported on it. The fastening element 5a and/or the supporting portion 5d abut, over as broad an area as possible, at least one correspondingly formed and preferably level surface of the second housing part 3. The main portion 5c, by contrast, is spaced from the second housing part 3 by a gap or spring gap. The main portion 5c can therefore flex towards the second housing part 3, thus tensing the spring 5, and flex away from the second housing part 3, thus relaxing the spring 5. The main portion 5c can abut, preferably over as broad an area as possible, at least one surface which is for example level and which is formed by a substantially annular collar of the end-facing wall 20c. When considering the rigidity/tensions and/or the spring diagram (force/displacement curve) of the spring 5, the spring 5 in particular preferably abuts the second housing part 3 and the accommodating housing 20, in particular the end-facing wall 20c or the at least one surface of the substantially annular collar, over as broad an area as possible.

(34) The main portion 5c of the spring 5 comprises an aperture 5e which is in particular circular and through which a portion of the second housing part 3 extends. This enables a compact design to be achieved.

(35) The spring 5 can comprise or be a spring made of metal, which can optionally be at least partially or completely coated in a plastic material, including by injection-moulding the plastic around the spring, or provided with integrally moulded geometries, wherein the plastic material is in particular an elastomer or a material in which the main constituent is an elastomer. The coating, surrounding injection-mould or integrally moulded geometries mean that the spring 5 take perform an additional function as a seal.

(36) The pump shaft 10 is rotatably mounted on the first and second housing part 2, 3, in particular by means of a slide bearing in each case.

(37) An outer structure, such as for example an outer toothed gearing, is formed on the pump shaft 10 between the portion of the pump shaft 10 which is rotatably mounted in the second housing part 3 and the portion of the pump shaft 10 which is rotatably mounted in the first housing part 2, and is in a positive-fit engagement with a corresponding inner structure, in particular an inner toothed gearing of the rotor 4, in order to establish a shaft-hub connection 30. The outer diameter of the outer structure of the pump shaft 10 is larger than the diameter of the portion of the pump shaft 10 which is mounted in the first housing part 2 and/or in the second housing part 3. The pump shaft 10 is arranged, axially fixed, between the first and second housing parts 2, 3, i.e. such that shifting the pump shaft 10 along the rotational axis is substantially impossible in both directions. For this purpose, the inner diameter of the portions of the first housing part 2 and second housing part 3 which mount the pump shaft 10 is smaller than the outer diameter of the outer structure of the pump shaft 10.

(38) The end-facing side of the first housing part 2 which points away from the pump space comprises an annular pocket in which a shaft seal 11 is arranged. The shaft seal 11 is fastened, rotationally fixed, to the first housing part 2 and forms a sealing gap with the pump shaft 10. The shaft seal 11 seals off the pump space with respect to the outside.

(39) The end of the pump shaft 10 which lies opposite the end arranged in the region of the spring 5 comprises an outer structure for a shaft-hub connection 30 comprising a toothed wheel 21, in particular a sprocket. The toothed wheel 21 is seated non-rotationally on the pump shaft 10. The toothed wheel 21 can be driven by a chain which is in turn driven by for example a crankshaft or other shaft which can be connected to for example an engine of the vehicle. For fastening it to the pump shaft 10, the toothed wheel 21 comprises an inner thread via which it is screwed to an outer thread of the pump shaft 10, up against a collar of the pump shaft 10. A rotational securing device 22 which is seated, secured against rotating, on the shaft 10 secures the toothed wheel 21 against becoming unintentionally detached. The rotational securing device 22 comprises an angled portion 22a which engages with the toothed wheel 21 in a positive fit, thus preventing the toothed wheel 21 from becoming detached.

(40) The pump unit from FIG. 1 is inserted into an accommodating housing, for example a cup-shaped accommodating housing 20, such as for example a housing cup (FIG. 2). The accommodating housing 20 comprises a circumferential wall 20d which circumferentially surrounds the pump unit 1 from FIG. 1. The accommodating housing 20 also comprises an end-facing wall 20c which is connected to the circumferential wall 20d, wherein the main portion 5c of the spring 5 is supported on the end-facing wall 20c, in particular on a projection 20a of the end-facing wall 20c which is for example an annular projection.

(41) The pump unit from FIG. 1 is held between the end-facing wall 20c and an axial securing element 9, in particular an axial securing ring arranged in an annular groove 20b of the circumferential housing 20, such that the spring 5 is tensed.

(42) A first space 23 (pressure space), into which the fluid (liquid) delivered by the pump 1 is delivered, is formed between the end-facing wall 20c and a second seal 8 which is arranged in an annular groove arranged on the outer circumference of the second housing part 3 and which forms a sealing gap with the circumferential wall 20d. The space 23 is in turn connected to a fluid consumer, such as for example a lubricant consumer, in particular a transmission, by means of a channel (not shown). A second space 24 (suction space), from which fluid is delivered into the space 23 via the pump 1, is formed between the second seal 8 and a first seal 7 which is arranged in an annular groove arranged on the outer circumference of the first housing part 2 and which forms a sealing gap with the circumferential wall 20d. The space 24 can for example be connected to a storage container for the fluid by means of a channel. When the fluid is being delivered, the pressure in the space 23 is increased as the rotational speed increases, whereby the second housing part 3 jams the third housing part 12 firmly between the first and second housing part 2, 3, in addition to the biasing force of the spring 5. The first, second and third housing parts 2, 3, 12 are thus sealed off with respect to each other. The connection between the axial securing element 9 and the first housing part 2 is embodied to be strong enough that it can withstand, i.e. is not detached by, the axial force on the axial securing element 9 which is generated by the pressure in the space 23. As an alternative to forming the axial securing element 9 as a spring washer, a housing cover can be fastened to the accommodating housing 20 on which the first housing part 2 is axially supported. The spring 5 used in FIG. 3 is shown in FIG. 4. The spring 5 from FIG. 8 is similar to the spring 5 from FIG. 4.

(43) The fastening element 5a of the spring 5 from FIGS. 4 and 8 comprises two limbs which are arranged in the cavity 6a. In these embodiments, the spring 5 can be fastened to the positioning elements 6 by means of its fastening elements 5a by rotating it about the rotational axis of the rotor 4. The limbs each comprise two sliding surfaces 5g which point towards each other and are arranged with respect to each other such that the clear width formed between them expands towards the free end of the limbs. The thickness of the limbs is less than the clear width between the groove flanks of the cavity 6a in the positioning element 6. The portion of the reduced core diameter in the cavity 6a, i.e. the diameter of the positioning element 6 as measured at the base of the groove, is trapped between the two limbs of the fastening element 5a in a positive fit. While the spring 5 is fastened to the positioning elements 6, the limbs are elastically widened slightly, in that the sliding surfaces 5g which point towards each other slide off on the reduced-diameter portion of the cavity 6a. The limbs then in particular latch onto the reduced-diameter portion. To assist this, the limbs can each exhibit a concavely curved recess surface 5h. The recess surfaces 5h can abut the reduced-diameter portion, preferably over an area, when the fastening element 5a is completely arranged in the cavity 6a. This secures the spring 5 in a positive fit against rotating counter to the rotational direction in which the spring 5 has been rotated in order to fasten it to the positioning elements 6. The fastening element 5a comprises a projection between the limbs, which comprises an abutting surface which can abut the reduced-diameter portion of the positioning element 6 when the fastening element 5a is completely arranged in the cavity 6a.

(44) The fastening elements 5a shown in FIGS. 5 and 6 are similar to each other. The fastening element 5a is shaped as a closed ring and its inner circumference comprises three projections which enclose a diameter which is larger than the reduced-diameter portion in the cavity 6a and smaller than the outer diameter of the pin-shaped positioning element 6. The fastening element 5a from FIG. 5 exhibits facets or chamfers on its three projections, which the embodiment from FIG. 6 does not exhibit. In order to fasten the spring 5, the fastening elements 5a are respectively slid axially over a positioning element 6, until the three projections of the fastening element 5a latch into the cavity 6a. It also holds here that the thickness of the fastening element 5a is less than the clear width between the groove flanks of the cavity 6a.

(45) FIG. 7 shows a fastening element 5a which exhibits a recess 5f towards the outside, i.e. pointing away from the rotational axis. The spring 5 from FIG. 7 can be fastened to the positioning elements 6 by means of rotating it about the rotational axis. The two fastening elements 5a each comprise one free end which is arranged more distantly in relation to the arm 5b than the recess 5f. The free end, in particular a sliding surface 5g of the free end which points away from the rotational axis and slides off on the positioning element 6 while the spring 5 is fastened, is arranged more distantly in relation to the rotational axis than the recess 5f, in particular a recess surface 5h of the recess 5f which points away from the rotational axis. This embodiment causes the free end to be deflected by the positioning element 6 during fastening, in that the sliding surface 5g slides off on the positioning element 6 and the recess 5f flexes into the cavity 6a. This results in a positive-fit connection. The thickness of the fastening element 5a is also, as in the other embodiments from FIGS. 4 to 10, less than the clear width between the groove flanks of the cavity 6a.

(46) FIG. 9 shows an embodiment comprising a fastening element 5a which is shaped as a closed ring. The inner side of the ring of the annular fastening element 5a forms a contour featuring a first diameter portion 5a.sub.1 and a second diameter portion 5a.sub.2, which are connected via a constriction portion 5a.sub.3. The first diameter portion 5a.sub.1 exhibits an inner diameter which is larger than the outer diameter of the positioning element 6. The second diameter portion 5a.sub.2 exhibits an inner diameter which is smaller than the outer diameter of the positioning element 6 and larger than the diameter of the positioning element 6 in the cavity 6a. The clear distance between the flanks of the constriction portion 5a.sub.3 is smaller, in particular only slightly smaller, than the diameter of the positioning element 6 in the cavity 6a. In order to fasten the spring 5 to the at least one positioning element 6, the first diameter portion 5a.sub.1 of the fastening element 5a is fitted onto the positioning element 6. By rotating the spring 5, the second diameter portion 5a.sub.2 of the fastening element 5a is pivoted into the cavity 6a, whereby the constriction portion 5a.sub.3 is elastically widened at the reduced-diameter portion in the cavity 6a, and constricts again once it has moved past the reduced-diameter portion.

(47) The spring 5 from FIG. 10 shows at least one fastening element 5a which is embodied to be hook-shaped, wherein a hook-shaped portion extends by more than 180 around a receiving portion 5a.sub.4. The receiving portion 5a.sub.4 is adjoined by a constriction portion 5a.sub.3 in which the clear distance is smaller than the diameter of the receiving portion 5a.sub.4. The diameter of the receiving portion 5a.sub.4 is larger than the diameter of the positioning element 6 in the cavity 6a and smaller than the outer diameter of the positioning element 6. The clear distance between the flanks of the constriction portion 5a.sub.3 is smaller, in particular slightly smaller, than the diameter of the positioning element 6 in the cavity 6a. By rotating the spring 5, the constriction portion 5a.sub.3 is initially pivoted or moved past the reduced-diameter portion in the cavity 6a, whereby the constriction portion 5a.sub.3 is elastically widened slightly and then constricts again.

(48) FIG. 11 shows a tooth 31 of an inner toothed gearing formed on the rotor 4. The features shown for the tooth 31 of the inner toothed gearing can alternatively or additionally apply to the tooth or teeth of the outer toothed gearing (not shown in detail).

(49) One tooth is described in the following, wherein the teaching applies analogously to a number of teeth, in particular to each tooth, of the outer toothed gearing and/or inner toothed gearing.

(50) The embodiments from FIGS. 11 and 13 are similar to each other, wherein one difference is that a tip surface 35, which in FIG. 13 is one roundly curved surface, is formed by a number of surface portions 35a to 35c in FIG. 11. Another difference is that the flank surface 34, which in FIG. 13 is roundly curved, is formed by a number of surface portions 34a to 34c in FIG. 11.

(51) As can be seen from FIGS. 11 and 13, the tooth 31 is formed on the rotor 4 via a root of the tooth and is therefore part of the inner toothed gearing. As mentioned, the tooth 31 can alternatively be part of an outer toothed gearing, wherein the tooth 31 can be formed on the pump shaft 10 via its root.

(52) The tooth 31 comprises a first end 32 and a second end 33. A convexly curved tip surface 35 which is curved convexly outwards, i.e. convexly away from the root of the tooth, is formed at the freely projecting end of the tooth 31 between the first end 32 and second end 33 and between the first and second flank surfaces 34, 36 of the tooth 31. In FIG. 11, the tip surface 35 is formed from a number of surface portions 35a to 35c. A linear first surface portion 35a. Which is arranged parallel to the rotational axis of the part on which the tooth 31 is formed, is formed approximately in the middle between the first end 32 and the second end 33. In the example from FIGS. 11 and 13, this is the rotational axis of the rotor 4; alternatively, it can be the rotational axis of the pump shaft 10. A linearly extending second surface portion 35b which is slightly inclined in relation to the rotational axis is formed between the first surface portion 35a, which extends linearly between the ends 32, 33, and the first end 32. A linear third surface portion 35c which is slightly inclined in relation to the rotational axis is arranged between the second end 33 and the first surface portion 35a. The first, second and third surface portions are arranged with respect to each other such that they form a tip surface 35 which is convexly curved or crowned away from the root of the tooth.

(53) In the embodiment from FIG. 13, the tip surface 35 is one surface, which is convexly curved away from the root of the tooth in one or alternatively two dimensions, between the first end 32 and the second end 33.

(54) The tooth 31 from FIG. 11 comprises a first flank surface 34 and a second flank surface (on the hidden reverse side). These flank surfaces can be formed identically. The flank surface 34 comprises a first surface portion 34a which extends linearly, in particular as a plane, approximately in the middle between the first end 32 and the second end 33. A second surface portion 34b is formed between the first end 32 and the first surface portion 34a, and a third surface portion 34c is formed between the first surface portion 34a and the second end 33. The surface portions 34b, 34c are planes which are slightly angled in relation to the surface portion 34a, such as for example by 3 at most or by 1 at most.

(55) The tooth from FIG. 13 likewise comprises a first flank surface 34 and a second flank surface 36 (FIG. 14; hidden in FIG. 13) which can be embodied identically. The flank surface 34 extends from the first end 32 to the second end 33 and is convexly curved outwards.

(56) FIGS. 12a and 14a each show a tooth 31 in which the flank surfaces 34, 36 are convexly curved. FIGS. 12b and 14b each show a tooth 31 in which the tip surface 35 is convexly curved. FIGS. 12c and 14c each show a tooth 31 in which the tip surface 35 and the flank surfaces 34, 36 are convexly curved.

(57) Due to the convexly curved tip surface 35 and/or the convexly curved flank surfaces 34, 36, the pump shaft 10 can be tilted about its rotational axis in relation to the rotational axis of the rotor 4 by a small angle, such as for example 3 at most or 1 at most. The tooth 31 exhibits a tooth height h.sub.1 in the region of the first surface portion 34a, 35a or in the middle between the first end 32 and the second end 33, which decreases to a height h.sub.2 towards the first end 32 and the second end 33.

(58) The tooth 31 can exhibit a tooth width b.sub.1 in the region of the first surface portion 34a, 35a or in the middle between the first end 32 and the second end 33, which decreases to a tooth width b.sub.2 towards the first end 32, such as for example in the second surface portion 34b, 35b. The tooth 31 can exhibit the tooth width b.sub.1 in the region of the first surface portion 34a, 35a or in the middle between the first end 32 and the second end 33, which decreases to the tooth width b.sub.2 towards the second end 33, such as for example in the third surface portion 34c, 35c. The decrease in the tooth widths and/or tooth heights is shown in FIGS. 12a to 12c and in FIGS. 14a to 14c.

LIST OF REFERENCE SIGNS

(59) 1 pump 2 first housing part 2a cavity, such as for example a blind bore 2b opening, such as for example an outlet or inlet 3 second housing part 3a cavity, such as for example a transit bore 3b opening, such as for example an inlet or outlet 4 rotor 5 spring 5a securing element/fastening element 5a.sub.1 first diameter portion 5a.sub.2 second diameter portion 5a.sub.3 constriction portion 5a.sub.4 receiving portion 5b arm 5c main portion 5d supporting portion 5e cavity/aperture 5f recess 5g sliding surface 5h recess surface 6 positioning element/pin 6a cavity, such as for example an annular groove 7 first seal/sealing ring 8 second seal/sealing ring 9 axial securing element 10 pump shaft 11 shaft seal 12 third housing part/stroke ring 12a cavity 13 delivery element/vane 20 accommodating housing, such as for example a housing cup 20a projection 20b cavity, such as for example an annular groove 20c end-facing wall 20d circumferential wall 20e opening 21 toothed wheel, such as for example a sprocket 22 rotational securing device 22a angled portion 23 first space/pressure space 24 second space/suction space 25 spring gap 26 pump chamber 27 first delivery chamber 28 second delivery chamber 29 delivery cell 30 shaft-hub connection 31 tooth 32 first end 33 second end 34 first tooth flank surface/flank surface 34a first surface portion of the tooth flank surface 34b second surface portion of the tooth flank surface 34c third surface portion of the tooth flank surface 35 tip surface 35a first surface portion of the tip surface 35b second surface portion of the tip surface 35c third surface portion of the tip surface 36 second tooth flank surface/flank surface b.sub.1 tooth width b.sub.2 tooth width h.sub.1 tooth height h.sub.2 tooth height