SCREW SPINDLE PUMP

Description

[0001] The invention relates to a screw spindle pump comprising a spindle housing in which a drive spindle and at least one running spindle meshing with the drive spindle are accommodated in spindle bores.

[0002] Such a screw pump is used to pump a fluid, for example, fuel or a supply or cooling fluid or the like. Pumping occurs via at least two intermeshing spindles, namely a drive spindle coupled to a drive motor and a running spindle, which are housed in a spindle housing. For this purpose, the spindle housing has intersecting spindle bores corresponding to the number of spindles. The spindle housing is usually housed in a pump or outer housing, through which the fluid to be pumped is supplied and discharged.

[0003] The operating principle is based on the drive spindle and the idler spindle meshing with each other, and a conveying volume is displaced axially due to the spindle rotation. The drive spindle has a cylindrical spindle core and usually two spindle profiles encircling the spindle core. These spindle profiles form two circumferential profile valleys, into which corresponding spindle profiles of the idler spindle engage. In addition to such a two-spindle design, it is also conceivable to design the screw spindle with three spindles, i.e., two idler spindles are provided, which are arranged 180° offset next to the central drive spindle and mesh with it.

[0004] As described, the drive spindle must be coupled to a drive motor, as the drive spindle is actively rotated while one or both of the idler spindles are merely driven. To couple the drive spindle to the drive motor or its drive shaft, a coupling element is arranged on the front side of the drive spindle. This coupling element is connected to the drive spindle in a rotationally fixed manner using a corresponding form-locking geometry. This form-locking connection provides at least a rotationally fixed connection in one direction of rotation. Depending on the design, a rotationally fixed connection in the other direction of rotation can also be provided, allowing the drive direction and thus also the spindle rotation direction to be switched.

[0005] Such a screw spindle pump is known, for example, from DE 43 08 755 A1. This document describes a claw coupling that couples the motor drive shaft to the drive spindle. Two intersecting grooves are ground into one axial end of the drive spindle, forming two opposing claws with a triangular cross-section. The disc-shaped coupling element has a circular cross-section and is provided with two triangular recesses into which the triangular claws of the drive spindle engage. A slot is provided centrally on the coupling element, into which the end section of the motor-side drive shaft engages.

[0006] DE 10 2015 101 443 A1 discloses a screw pump in which the spindle end, at which the coupling element is to be arranged, has a flat, surface-like design. The spindle profiles also end at this end face. At two opposite positions, contact surfaces that are perpendicular to one another (as viewed radially) are formed by material removal. The coupling element has a corresponding, three-dimensional receiving and engagement geometry, which is designed such that axial engagement sections are provided that engage, as it were, in the two opening profile valleys and bear against the contact surfaces formed in their area, so that, viewed in the circumferential direction, a flat, rotationally fixed connection of the coupling element to the drive spindle is achieved, while at the same time the coupling element sits axially on the flat end face.

[0007] The document DE 10 2020 108 038 discloses a coupling element for a screw spindle, which has recesses on its circumference which are in operative connection with axially projecting elements of the screw spindle.

[0008] Although such couplings, which are often also referred to as claw couplings, have generally proven themselves, there is a need for a screw pump with improved coupling.

[0009] The invention is therefore based on the problem of providing a screw pump with an improved coupling device.

[0010] To solve this problem, the invention provides a screw spindle pump comprising a spindle housing in which a drive spindle and at least one idler spindle meshing with the drive spindle are received in spindle bores, wherein the drive spindle has a cylindrical core and at least two spindle profiles encircling the spindle core, and on one end face of the drive spindle, in a recess axially delimited by a flat bottom surface, into which the two profile valleys between the two spindle profiles open offset by 180°, a disc-shaped coupling element is arranged, which has a plug-in receptacle for a drive shaft of a drive motor and which is coupled in a rotationally fixed manner to the drive spindle in at least one direction of rotation of the drive spindle via a positive engagement with axially projecting projections that laterally delimit the recess and engage in lateral receptacles of the coupling element,wherein the base surface in the region of the mouths of the two profile valleys is delimited by the spindle core and the coupling element is rounded in the element areas adjacent to the mouth areas, corresponding to the shape of the spindle core, wherein the diameter of the coupling element in the region of the rounded element sections corresponds at most to the diameter of the spindle core or is smaller than the diameter of the spindle core.

[0011] The screw pump according to the invention has a flow-optimized coupling or connection between the drive spindle and the coupling element. In particular, the geometry of the coupling element is selected such that the coupling element only slightly reduces the delivery cross-section of the respective profile valley at its mouth on the spindle face, if at all. Thus, the free delivery cross-section is almost unaffected by the coupling element and, consequently, the flow, viewed in the axial direction, is not significantly impaired, which leads to an improvement in delivery performance.

[0012] To achieve this, a specifically designed coupling element is provided which is disc-shaped and has two laterally open receptacles, each of which is engaged by a projection projecting axially from the end face of the drive spindle. This positive engagement enables a rotationally fixed connection in one, preferably of course, both directions of rotation. These axially projecting projections define a recess on the end face of the spindle which has a flat bottom surface, and the coupling element is inserted into this recess. The bottom surface of the recess is formed, among other things, by the spindle core of the drive spindle, since, as described, the two profile valleys open at this end face. Rounded edges, formed by the spindle core, are therefore provided opposite one another.The coupling element is designed in such a way that it is also rounded in the element areas adjacent to the mouth of the profile valleys, i.e., corresponding to the shape of the spindle core. The diameter of the coupling element in the area of ​​these rounded element sections, which are also opposite one another, corresponds at most to the diameter of the spindle core or is smaller than the diameter of the spindle core. This means that, due to its diameter-related design in relation to the spindle core diameter, the coupling element does not protrude into the free flow cross-section of the respective opening profile valley in the area of ​​these element sections, so that the flow cross-section is not necessarily reduced and thus the flow is not impeded.Unlike the screw pumps known from the prior art, in which the coupling elements project radially far into the free flow cross-section due to their dimensioning or geometry and consequently greatly reduce it, the coupling element of the screw pump according to the invention no longer represents a significant flow obstacle. The pumped fluid can therefore flow axially past the coupling element almost unhindered, which has an extremely advantageous effect on the pump operation.

[0013] In a further development of the invention, the coupling element can have a cylindrical base section from which four element projections protrude laterally, with two adjacent element projections defining a lateral receptacle. These element projections serve only to define or limit the positive-lock geometry, i.e., the receptacles into which the axial spindle-side projections engage. Consequently, they merely have a driver function, as they achieve the rotationally fixed coupling in the circumferential direction. It is therefore possible to design these element projections narrowly for optimized flow, so that they do not significantly reduce the flow cross-section.The end face of the drive spindle can be machined using two cross-ground surfaces in such a way that the protruding projections that laterally border the recess, which, as described, axially continue the two spindle profiles, provide corresponding, defined engagement geometries in the correspondingly shaped receptacles. This slightly expands the flat bottom surface of the recess, in addition to the surface section formed by the spindle core, in this area, with the element projections covering these expanded areas from an axial perspective.

[0014] It is expedient if the receptacles on the coupling element extend into the base section. The base section houses the plug-in receptacle for the motor-side drive spindle, which is designed, for example, as an elongated, rectangular plug-in receptacle with an elongated cross-section. Since the coupling element ultimately only has the task of establishing, on the one hand, the rotationally fixed connection to the motor-side drive shaft through its engagement in the plug-in receptacle, and, on the other hand, the rotationally fixed connection of the coupling element to the drive spindle, each receptacle can extend relatively far into the cylindrical base areas, which in turn means that the driver-like element projections protruding from the base area can be dimensioned correspondingly shorter.

[0015] The element projections themselves are conveniently triangular in shape and taper towards their free end, so they are overall very narrow and also relatively short.

[0016] The thickness of each element projection can decrease toward its free end. The coupling element is thus reduced in material as much as possible.

[0017] The plug-in receptacle itself preferably has a square shape. The plug-in receptacle can have a rectangular, i.e. somewhat elongated shape, with its longer axis extending between the two rounded element sections and its shorter axis between the two receptacles. This configuration enables an extremely compact, small-format design of the coupling element. This is because this orientation of the rectangular plug-in receptacle makes it possible to extend the two quasi-V-shaped receptacles of the coupling element relatively far into the cylindrical base section. They end shortly before the plug-in receptacle, which, as already described, ultimately means that the element projections on the coupling element side can be designed short.

[0018] The coupling element itself can be made of plastic, i.e., a plastic component manufactured using an injection molding process that exhibits the desired mechanical and physical properties, e.g., with regard to its hardness, temperature resistance, etc. Alternatively, the coupling element can also be made of metal, for example, aluminum or steel.

[0019] As described, the screw spindle pump usually also has a drive motor or one is attached to it, which is mounted axially on the outer housing and whose drive shaft is necessarily axially aligned with the longitudinal axis of the drive spindle. This is because the drive shaft engages, as described, in the plug-in receptacle of the coupling element, which is also located centrally in the longitudinal axis of the drive spindle. The operating principle of the screw spindle pump is based on the fluid being pumped axially, i.e. it leaves the spindle assembly axially and flows past the coupling element, which, as explained, does not reduce the flow cross-section or reduces it negligibly due to its inventive geometry. The motor-side drive shaft usually also has a cylindrical cross-section, and the corresponding plug-in geometry, for example a square or rectangular engagement pin, is formed at the end of the shaft.Since the pumped fluid leaves the spindle assembly axially, it flows past the coupling element as described, but inevitably also past the drive shaft, at least in the coupling area to the coupling element. In order to avoid any flow obstructions in the transition from the coupling element to the drive shaft, a useful development of the invention provides a drive motor, wherein the diameter of the cylindrical drive shaft of the drive motor corresponds at most to the diameter of the cylindrical spindle core. This means that here, too, a diameter adjustment is provided, ensuring that the drive spindle cross-section, viewed radially, does not interfere with the flow cross-section of the drive spindle and, in a sense, subsequently reduce it at the spindle-side outlet.This means that even in the transition area between the coupling element and the drive spindle, there is no step or flow obstruction relative to the spindle core diameter, allowing for virtually unhindered axial outflow. This axial outflow always occurs, regardless of whether the screw spindle pump is a dry-running pump, in which the volume pumped by the spindle assembly flows directly to a pump outlet after exiting the spindle assembly without circulating through the drive motor to cool it, or whether the screw spindle pump is a wet-running pump, in which a portion of the pumped fluid enters the motor housing to cool components there and is then recirculated back into the pump or outer housing. The diameter of the drive shaft can also be smaller than the spindle core diameter of the drive spindle; it can also correspond to the diameter of the cylindrical base section of the coupling element.

[0020] As described, the screw pump can be a 2-spindle pump, with a drive spindle and only one idler spindle positioned to the side. Alternatively, it can also be a 3-spindle pump, with a central drive spindle and two idler spindles positioned to the left and right of it, meshing with it.

[0021] In addition to the screw spindle itself, the invention further relates to the use of such a screw spindle pump in a motor vehicle for pumping an operating fluid. This operating fluid can be fuel or another fluid, such as a cooling fluid, for example, for cooling a traction or drive battery, or another useful fluid, such as a windshield washer fluid or the like. Such screw spindle pumps can also be used in other land or air vehicles, such as airplanes or drones, although the possible applications are not limited thereto.

[0022] In particular, the screw pump is used as a coolant pump, especially for pumping a coolant used to cool an energy storage device. This can be any coolant.

[0023] Further advantages and details of the present invention will become apparent from the exemplary embodiments described below and from the drawings. Fig. 1 a sectional schematic diagram of a screw spindle pump according to the invention with one drive spindle and two idler spindles, Fig. 2 an exploded view of the drive spindle and the coupling element not inserted into the recess, Fig. 3 the arrangement of Fig. 2 showing the relevant diameters on the spindle core and the base section, Fig. 4 a top view of the front side of the drive spindle with a view into the recess receiving the coupling element, Fig. 5 the arrangement of Fig. 4 with inserted coupling element as top view, Fig. 6 the arrangement of Fig. 5 as a perspective view, Fig. 7 a sectioned exploded view of a part of the screw pump with a schematic representation of the drive shaft of the drive motor, and Fig. 8 the arrangement of Fig. 7 in the assembled, cut state shown.

[0024] Fig. 1 shows a screw pump 1 according to the invention, comprising an outer housing 2 with an axially arranged inlet connection 3 and a radially arranged outlet connection 4. Arranged in the outer housing 2, which can also be referred to as the pump housing, is a spindle housing 5, in which, in the illustrated embodiment, three spindles—namely, a central drive spindle 6 and two idler spindles 7 arranged on either side of the drive spindle 6—are received in corresponding, intersecting spindle bores. The spindles 6, 7 each have spindle profiles that mesh with one another.

[0025] Furthermore, a drive motor 8 is provided, which is only shown in principle here and can be a dry or wet running drive motor. This has a drive shaft 9, shown only stylized here, which is connected in a rotationally fixed manner to the drive spindle 6 via a coupling element 10. This means that the drive spindle 6 is actively driven by the drive motor 8. A rotation of the drive spindle 6 inevitably leads to a rotation of the two running spindles 7 due to the spindle profile engagement. Via the intermeshing spindle profiles and the spindle rotation, corresponding delivery volumes are moved or displaced axially, via which the fluid is conveyed in a conventional manner. The fluid is sucked in axially via the inlet nozzle 3, conveyed along the spindle assembly and exits at the motor-side end of the spindle assembly, from where it flows via a corresponding flow geometry to the outlet nozzle 4.

[0026] Fig. 2 shows in the form of an exploded view the drive spindle 6 and the coupling element 10 in an enlarged, perspective view. The drive spindle 6, made of metal or plastic, has a spindle core 11 with a cylindrical cross-section, around which two spindle profiles 12 run, so that corresponding profile valleys 13 are formed. At one axial end, the drive spindle 6 has a recess 14, which is axially delimited by a flat bottom surface 15 and which is laterally delimited by two projections 16, wherein these two projections 16 are formed as an extension of the spindle profiles 12 running into the bottom surface 15. The projections 16 are machined to remove material, which will be discussed below in connection with Fig. 4will be discussed in more detail below, so that overall a base surface 15 results which, on the one hand, is formed in sections by the spindle core 11, and, on the other hand, due to the mechanical machining of the projections 16 of adjoining base sections, which will be discussed in more detail below.

[0027] The coupling element 10, also made of metal or plastic, is disc-shaped, thus having a defined maximum thickness. It comprises a cylindrical base section 17, which has two opposing, rounded element regions 18. Furthermore, in the example shown, four laterally projecting element projections 19 are provided on the base section 17, each defining a V-shaped receptacle 20 between them, into which the projections 16 engage in the assembled position, when the coupling element 10 is inserted into the recess 14.

[0028] How Fig. 2 , but also Fig. 3shows, the bottom surface 15 is formed and bordered at least in sections by the cylindrical spindle core 11. This rounded border, resulting from the cylindrical shape of the spindle core 11, is present at the mouth of the respective profile valley 13, since the profile valley is defined by the spindle core 11. The spindle core 11 has a core diameter DK , which in Fig. 3 is shown.

[0029] As described, the coupling element 10 also has a disc-shaped, cylindrical base section 17, which has a base section diameter DB, which in Fig. 3is also shown. The design of the size or geometry of the coupling element 10 is now selected such that the diameter of the base section 17 is less than or equal to the diameter of the spindle core; consequently, DB ≤ DK applies. This means that in the assembled position, the rounded element regions 18, at which the base section diameter DB is given, inevitably do not protrude into the flow cross-section or mouth cross-section of the respective profile valley 13. Consequently, the coupling element 10 does not pose any flow obstruction, at least in the region of the rounded element sections 18.

[0030] Fig. 4 shows a plan view of the end face of the drive spindle 6 with a view of the recess 14. Shown are the two profile valleys 13 opening there, as well as the spindle core, which defines the rounded edge of the base surface 15 in the opposite edge sections 21.

[0031] The end face is mechanically machined using corresponding cross-grinding, which, on the one hand, results in an enlargement of the base surface 15 over the spindle core surface. On the other hand, this results in a specific form-fitting or engagement geometry of the projections 16, which have two V-shaped contact surfaces 22, with which they lie flat against corresponding contact surfaces of the coupling element 10 or are positioned closely spaced from them by a narrow gap. The coupling element 10 is shown in dashed lines.

[0032] The formation of the cross-cuts results in four lateral enlargement sections of the base surface 15, so that an X-shape is created, as Fig. 4 clearly shows.

[0033] The coupling element 10 is now inserted into this recess 14, the Figures 5 and 6 show appropriate supervision ( Fig. 5 ) and a perspective view ( Fig. 6). Since the base section diameter DB corresponds at most to the core diameter DK, the rounded sections 18 of the coupling element 10 do not protrude into the flow cross-section defined by the spindle core 11, as the Figures 5 and 6 The element projections 19 each define two V-shaped, laterally open receptacles 20, which are defined by two contact surfaces 23. The receptacles 20 extend into the base section 17, ending shortly before a plug-in receptacle 24, which is square or rectangular in cross-section and serves to receive a correspondingly shaped engagement pin of the drive shaft 9. In the assembly position according to the Figures 5 and 6 The receptacles 20 accommodate the two projections 16 in a quasi-positive or form-fitting manner. Due to the contact of the surfaces 22, 23 and the respective V-shaped engagement, a rotationally fixed connection is ensured both during clockwise and counterclockwise rotation.

[0034] The element projections 19 extend as described from the base section 17, so that here too a quasi X-shape is created, corresponding to the X-like shape of the recess or the bottom surface 15. The element projections 19 also ultimately do not protrude into the mouth cross-section of the respective profile valley 13 on the front surface, so that consequently the coupling element 10 represents no or almost no flow obstacle for the fluid flow. Only the Fig. 5 The element projection 19 shown top right and bottom left protrudes slightly into the flow cross-section, but its obstacle function is negligible.

[0035] As the Figures 5 and 6 As shown, the element projections 19 taper toward their free end, and their thickness also decreases toward their free end. Appropriate bevels or chamfers are formed on both sides, so that even upside-down installation is possible without any problems.

[0036] How Fig. 5 As shown, the coupling element 10 lies, axially seen, almost completely on the base surface 15 or covers it axially. Only the Fig. 5 Element projection 19 shown top right and the one in Fig. 5 The element projection 19 shown at bottom left extends slightly radially beyond the base surface 15 into the flow cross-section. However, this interference or cross-sectional overlap is small, so that the flow-hindering effect is almost negligible.

[0037] Fig. 7 An exploded view of the inner housing 5 shows a screw pump with only two spindles, namely a drive spindle 6 and only one idler spindle 7, compared to the 3-spindle embodiment according to the previous figures. This serves to illustrate that a coupling according to the invention can be provided in both a 3-spindle and a 2-spindle screw pump 1.

[0038] In the exploded view according to Fig. 7 At the axial end of the drive spindle 6, an identical recess 14 is formed as described above, and an identical coupling element 10 is inserted into this recess 14. Also shown is the drive shaft 9 of the drive motor with the end-side plug-in pin 25, which engages positively in the plug-in receptacle 24. In the assembly position, as shown in Fig. 8As shown, the insertion pin 25 engages in the insertion receptacle 24, while at the same time the coupling element 10 is placed in the recess 14. A rotation of the drive shaft 9 therefore inevitably leads, coupled via the coupling element 10, to a rotation of the drive shaft 6 and, via this, also of the drive spindle 7, so that the pump can pump the fluid. Due to the geometry of the projections 16 and the receptacles 20 and the respective V-shaped design via the corresponding contact surfaces, a rotation of the drive shaft 9 and thus of the drive spindle 6 is possible both clockwise, i.e. in the pumping direction, and also counterclockwise if necessary, since a rotationally fixed coupling is provided in both directions of rotation.

[0039] How Fig. 8 further shows the diameter of the drive shaft 9, in Fig. 8marked with DA, smaller than the core diameter DK of the spindle core 11. The diameter DA corresponds essentially to the diameter of the base section DB of the coupling element 10. This is clearly shown in Fig. 8 shown. As a result, there is also no step forming a flow obstruction at the transition from the coupling element 10 to the drive shaft 9, which would be the case if the diameter DA were larger than the base section diameter DB. This means that the fluid exiting axially from the spindle assembly is ultimately exposed to almost no flow obstruction at all, apart from the two short element projections 19, which only slightly extend into the flow cross-section, as described above. Otherwise, the fluid can flow completely free of flow, unlike with previously known coupling devices, as described in the introduction.

[0040] Such a screw pump 1, regardless of whether it is a pump with two spindles or three spindles, can be used to pump a wide variety of fluids. It is preferably used in the automotive sector, where it serves either as a fuel pump or as a feed pump for another operating fluid, in particular for a coolant used to cool an energy storage device in the motor vehicle. The energy storage device is a large-volume traction storage device in an electric vehicle. It is therefore a coolant pump. Other applications are of course equally conceivable, for example as a feed pump for a washing fluid used for wiping the vehicle's windshield or similar.

Claims

1. Screw spindle pump, comprising a spindle housing (5), in which a drive spindle (6) and at least one running spindle (7) meshing therewith are received in spindle bores, wherein the drive spindle (6) has a cylindrical spindle core (11) and at least two spindle profiles (12) around the circumference of the spindle core (11), and, on an end face of the drive spindle (6), in a depression (14) which is axially delimited by a planar bottom surface (15) and in which the two profile valleys (13) open out between the two spindle profiles (12) in a manner offset by 180°, there is arranged a disk-shaped coupling element (10), which has an insertion receptacle (24) for a drive shaft (9) of a drive motor (8) and which is coupled to the drive spindle (6) for conjoint rotation therewith in at least one direction of rotation of the drive spindle (6) via a form-fitting engagement with axially protruding projections (16) that laterally delimit the depression (14) and engage in lateral receptacles (20) of the coupling element (10), wherein the bottom surface (15) is delimited by the spindle core (11) in the region of the openings of the two profile valleys (13), characterized in that the coupling element (10) has a rounded configuration, corresponding to the shape of the spindle core (11), in the element regions (18) that adjoin the regions of the opening, wherein the diameter (DB) of the coupling element (10), in the region of the rounded element regions (18), corresponds at most to the diameter (DK) of the spindle core (11) or is smaller than the diameter (DK) of the spindle core (11).

2. Screw spindle pump according to Claim 1, characterized in that the coupling element (10) has a cylindrical base portion (17) from which four element projections (19) protrude, wherein two adjacent element projections (19) delimit a lateral receptacle (20).

3. Screw spindle pump according to Claim 2, characterized in that the receptacle (20) extends into the base portion (17).

4. Screw spindle pump according to Claim 2 or 3, characterized in that the element projections (19) are triangular and taper toward their free end.

5. Screw spindle pump according to one of Claims 2 to 4, characterized in that the thickness of each element projection (19) decreases toward its free end.

6. Screw spindle pump according to one of Claims 2 to 5, characterized in that the insertion receptacle (24) has a square shape.

7. Screw spindle pump according to Claim 6, characterized in that the insertion receptacle (24) has a rectangular shape, wherein said insertion receptacle extends between the two rounded element portions (18) by way of its longer axis and between the two receptacles (20) by way of its shorter axis.

8. Screw spindle pump according to one of the preceding claims, characterized in that the coupling element (10) is made of plastic or metal.

9. Screw spindle pump according to one of the preceding claims, characterized by a drive motor (8), wherein the diameter (DA) of the cylindrical drive shaft (9) of the drive motor (8) corresponds at most to the diameter (DK) of the cylindrical spindle core (11).

10. Screw spindle pump according to one of the preceding claims, characterized in that a central drive spindle (6) and two running spindles (7) arranged on either side of the drive spindle are provided.

11. Use of a screw spindle pump (1) according to one of the preceding claims in a motor vehicle for the purpose of delivering an operating liquid.

12. Use according to Claim 11, characterized in that the screw spindle pump (1) is used as a coolant pump, in particular for delivering a coolant serving to cool an energy store.