Gear, gearwheel pair, and method for producing a gear

Abstract

A gearwheel pair for a gear unit, comprising a first gear and a second gear, which can be meshed with one another, wherein the first gear consists entirely or partially of metal or plastic and the second spur gear comprises an outer part having a gear rim made of a first plastic and having a number of injection-molded portions, an inlay part made of metal, and a connecting part, which is arranged between the inlay part and the outer part and is made of a second plastic for the interlocked and/or materially-bonded connection of the inlay part and the outer part and further relates to the second spur gear per se, a gear unit having such a gearwheel pair, and a method for producing a second gear, which is used for such a gear unit.

Claims

1. A gear, comprising: an outer part having a gear rim made of a first plastic and having a number of injection-molded portions, an inlay part made of metal, and a connecting part made of a second plastic, the connecting part arranged between the inlay part and the outer part for an interlocked and/or materially-bonded connection between the inlay part and the outer part, wherein the outer part has a plurality of depressions that mate to a plurality of corresponding projections of the connecting part, and wherein the plurality of depressions and corresponding projections are interlocked when mated, wherein the connecting part overlaps the injection-molded portions, and the connecting part has undercuts acting at least along and perpendicular to an axis of rotation of the gear, wherein acting at least along and perpendicular to the axis of rotation of the gear prevents movement of the outer part relative to the connecting part along and perpendicular to the axis of rotation, and wherein the plurality of corresponding projections comprise adjacent projections, and a projection has a length along the axis of rotation that is different than a length along the axis of rotation of an adjacent projection, and wherein the plurality of depressions of the outer part comprise adjacent depressions, and a depression has a depth along the axis of rotation that is different than a depth along the axis of rotation of an adjacent depression.

2. The gear as claimed in claim 1, wherein the plurality of corresponding projections are in stepped configuration with each adjacent projection having an increased length along the axis of rotation in a direction starting from an outermost projection to an inner most projection.

3. The gear as claimed in claim 2, wherein the plurality of depressions are in stepped configuration with each adjacent depression having an increased depth along the axis of rotation in a direction starting from an outermost depression to an inner most depression.

4. A gearwheel pair for a gear unit, comprising: a first gear, and a second gear, which can be arranged to mesh with the first gear, wherein the first gear consists entirely or partially of metal or plastic, and the second gear comprises: an outer part having a gear rim made of a first plastic and having a number of injection-molded portions, wherein the outer part has a plurality of depressions that mate to a plurality of corresponding projections of the connecting part, and wherein the plurality of depressions and corresponding projections are interlocked when mated, an inlay part made of metal, and a connecting part made of a second plastic, the connecting part arranged between the inlay part and the outer part for an interlocked and/or materially-bonded connection between the inlay part and the outer part, and the connecting part has undercuts acting at least along and perpendicular to an axis of rotation of the second gear, wherein acting at least along and perpendicular to the axis of rotation of the gear prevents movement of the outer part relative to the connecting part along and perpendicular to the axis of rotation, and wherein the plurality of corresponding projections comprise adjacent projections, and a projection has a length along the axis of rotation that is different than a length along the axis of rotation of an adjacent projection, and wherein the plurality of depressions of the outer part comprise adjacent depressions, and a depression has a depth along the axis of rotation that is different than a depth along the axis of rotation of an adjacent depression.

5. The gearwheel pair as claimed in claim 4, wherein the second gear has a second gear diameter and the inlay part has an inlay part diameter, and wherein a ratio between the inlay part diameter and the second gear diameter is between 0.1 and 0.8.

6. The gearwheel pair as claimed in claim 4, wherein the first gear has a first face width and the second gear has a second face width, and wherein the first face width is greater than the second face width.

7. The gearwheel pair as claimed in claim 4, wherein the first gear and the second gear each have a helix angle of between 10° and 30°.

8. The gearwheel pair as claimed in claim 4, wherein the connecting part has reinforcements to enhance the axial rigidity.

9. The gearwheel pair as claimed in claim 4, wherein the first plastic is a partially crystalline high-performance thermoplastic of the family of polyarylether ketones (PAEK), PPS (Polyphenylensulfid), or PPA (Polyphthalamid), and the second plastic differs from the first plastic in the mechanical properties and/or chemically.

10. The gearwheel pair as claimed in claim 4, wherein the first gear is connected to a driveshaft and the second gear is connected to an output shaft or wherein the second gear is connected to the driveshaft and the first gear is connected to the output shaft and the first gear meshes with the second gear.

11. The gearwheel pair as claimed in claim 10, further comprising a profile overlap between 1 and 2.

12. A method, comprising: producing a gear, wherein the gear comprises: an outer part having a gear rim made of a first plastic, an inlay part made of metal, and a connecting part made of a second plastic, which is arranged between the inlay part and the outer part for an interlocked and/or materially-bonded connection between the inlay part and the outer part, the first plastic is a high-performance thermoplastic or an industrial thermoplastic and/or the second plastic is a high-performance thermoplastic, an industrial thermoplastic, or a thermoset plastic, and injection molding the outer part while forming a number of injection-molded portions, and wherein the outer part has a plurality of depressions that mate to a plurality of corresponding projections of the connecting part, and wherein the plurality of depressions and corresponding projections are interlocked when mated, injection molding the connecting part between the outer part and the inlay part such that the connecting part overlaps the injection-molded portions and such that the connecting part has undercuts acting at least along and perpendicular to an axis of rotation of the gear, wherein acting at least along and perpendicular to the axis of rotation of the gear prevents movement of the outer part relative to the connecting part along and perpendicular to the axis of rotation, and wherein the plurality of corresponding projections comprise adjacent projections, and a projection has a length along the axis of rotation that is different than a length along the axis of rotation of an adjacent projection, and wherein the plurality of depressions of the outer part comprise adjacent depressions, and a depression has a depth along the axis of rotation that is different than a depth along the axis of rotation of an adjacent depression.

13. The method as claimed in claim 12, further comprising: forming undercuts in the connecting part collinear with the axis of rotation of the gear.

14. The method as claimed in claim 12, wherein injection molding the outer part is carried out using a pinpoint gate method.

15. A gear for use in a gear unit, comprising: an outer part having a gear rim made of a first plastic and having a number of injection-molded portions, an inlay part made of metal, and a connecting part made of a second plastic, the connecting part arranged between the inlay part and the outer part for a connection between the inlay part and the outer part, wherein the outer part has a plurality of depressions that mate to a plurality of corresponding projections of the connecting part, and wherein the plurality of depressions and corresponding projections are interlocked when mated, wherein the connecting part overlaps the injection-molded portions, and the connecting part has undercuts acting at least along and perpendicular to an axis of rotation of the gear, wherein acting at least along and perpendicular to the axis of rotation of the gear prevents movement of the outer part relative to the connecting part along and perpendicular to the axis of rotation, and wherein the plurality of corresponding projections comprise adjacent projections, and a projection has a length along the axis of rotation that is different than a length along the axis of rotation of an adjacent projection, and wherein the plurality of depressions of the outer part comprise adjacent depressions, and a depression has a depth along the axis of rotation that is different than a depth along the axis of rotation of an adjacent depression.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) Exemplary embodiments of the present application will be explained in greater detail hereafter with reference to the appended drawings. In the figures

(2) FIG. 1 shows a perspective illustration of one embodiment of a gearwheel pair according to the present application,

(3) FIG. 2 shows a schematic sectional illustration through a second spur gear according to the present application,

(4) FIG. 3 shows a perspective, exploded illustration through a second spur gear according to the present application,

(5) FIG. 4a shows a perspective illustration of the outer part of the second spur gear,

(6) FIG. 4b shows an enlarged illustration of the detail A identified in FIG. 4a,

(7) FIG. 4c shows a perspective illustration of the connecting part of the second spur gear,

(8) FIG. 4d shows an enlarged illustration of the detail B identified in FIG. 4c,

(9) FIG. 4e shows a schematic sectional illustration through the connecting part of the detail C identified in FIG. 4d,

(10) FIGS. 5a-5b each show a schematic unrolling of the outer part,

(11) FIGS. 6a-6c show various schematic illustrations of the injection molding method for producing the outer part of the second spur gear: a: disk gate, b: radial star gate, frontal pinpoint gate

(12) FIG. 7a shows a top view of a second spur gear after the demolding from the injection-molding tool,

(13) FIG. 7b shows a schematic sectional illustration through an injection-molding tool for producing a second spur gear according to the present application in the disk gate method using the section plane A-A defined in FIG. 7a,

(14) FIG. 7c shows a perspective illustration of a second spur gear after the demolding from the injection molding tool,

(15) FIG. 8 shows a schematic illustration to explain the pinpoint gate method,

(16) FIG. 9 shows a schematic illustration of a spur gear unit having a gearwheel pair according to the present application, and

(17) FIG. 10 shows a schematic unrolling of the gear rims of the first and the second spur gear.

DETAILED DESCRIPTION

(18) FIG. 1 shows an exemplary embodiment of a gearwheel pair 10 according to the present disclosure on the basis of a perspective illustration. The gearwheel pair 10 comprises a first spur gear 12 and a second spur gear 14, which are meshed. The first spur gear 12 is completely produced from one material in this case, for example, from plastic or from metal. The second spur gear 14 has an outer part 16, which forms a gear rim 18 having a number of teeth 19, an inlay part 20, and a connecting part 22 arranged between the inlay part 20 and the outer part 16. The connecting part 22 connects the inlay part 20 and the outer part 16 in an interlocked and/or materially-bonded manner.

(19) The outer part 16 is manufactured from a first plastic and the connecting part 22 is manufactured from a second plastic, while the inlay part 20 consists of metal. The inlay part 20 can be formed as a hub, shaft, or a preinstalled functional assembly.

(20) An embodiment in which the first spur gear 12 is constructed precisely like the second spur gear 14 is not shown, and therefore the first spur gear 12 also has the outer part 16, the inlay part 20, and the connecting part 22.

(21) In FIG. 2, an embodiment of the second spur gear 14 is shown on the basis of a schematic sectional illustration. The second spur gear 14 has a spur gear diameter D.sub.SR2, while the inlay part 20 has an inlay part diameter D.sub.ET. The ratio between the inlay part diameter D.sub.ET and the spur gear diameter D.sub.SR2 is between 0.1 and 0.8. In the illustrated example, the ratio is approximately 0.46.

(22) In FIG. 3, the second spur gear 14 illustrated in FIG. 1 is shown on the basis of a perspective exploded illustration. It can be seen that the inlay part 20 has recesses 17, for providing interlocking with the connecting part 22, on its outer lateral surface 24, with which it comes into contact with the connecting part 22. The connecting part 22 is formed corresponding to the recesses 17 where the connecting part 22 comes into contact with the inlay part 20.

(23) It can be seen both from FIG. 3 and in particular from FIGS. 4a to 4e that the outer part 16 has a number of depressions 29 delimited radially inward, to produce an interlock with the connecting part 22, on its inner lateral surface 26, with which it comes into contact with the connecting part 22. The connecting part 22 has corresponding hooked projections 27. As already explained, the interlock between the outer part 16 and the connecting part 22 has to be designed such that slipping of the outer part 16 in relation to the connecting part 22 is prevented both along and also about the axis of rotation T of the second spur gear 14 (see FIG. 9). It is clear in particular from FIGS. 4d and 4e that as a result of this requirement, the projections 27 are shaped such that they form undercuts 39, which are not producible without the use of a gate in the injection molding method.

(24) To be able to illustrate this situation more accurately, FIG. 4e shows a schematic illustration in partial section through the connecting part 22, wherein the plane of section extends through the axis of rotation T.sub.2 of the second spur gear 14. It can be seen in particular from FIG. 4e that the projections 27 are arranged on two different planes, which each have a different diameter and which are arranged offset in relation to the axis of rotation T.sub.2. The depressions 29 of the outer part 16 are designed accordingly. Both the outer part 16 and also the connecting part 22 therefore have a stepped construction. As a result of the arrangement of the projections 27 and the depressions 29, the number of the projections 27 and the depressions 29 can be increased, and therefore the above-described slipping of the outer part 16 in relation to the connecting part 22 can be prevented particularly effectively.

(25) It is clear in particular from FIGS. 4c to 4e that the connecting part 22 not only has an undercut 39 along the axis of rotation T.sub.2, but rather also perpendicular to the axis of rotation T.sub.2.

(26) Furthermore, it is recognizable from FIG. 3 that the connecting part 22 has reinforcements 28 in the form of ribs, using which the axial rigidity can be enhanced with little material use.

(27) A schematic unrolling of the outer part 16 is shown in each of FIGS. 5a and 5b, wherein the view is toward the inner lateral surface 26 of the outer part. The exemplary embodiment of the outer part 16 illustrated in FIG. 5a has an injection-molded portion 21, which is formed in the form of a coherent injection-molded surface 25. As will be explained in greater detail hereafter, for the case in which the outer part 16 is produced in the disk gate method, after completion of the disk gate method, an excess arises which has to be removed by cutting, for example, in a separate method step. As a result of the removal of the excess, the injection-molded surface 21 results, which differs in its quality from the other surfaces of the outer part 16 which are not treated accordingly.

(28) The exemplary embodiment of the outer part 16 illustrated in FIG. 5b has a number of injection-molded portions 21, which are formed in the form of multiple injection-molded points 23. The injection-molded points 23 arise if the pinpoint gate method is used where the injection-molding channels of the injection-molding tool end and discharge into the cavity of the tool.

(29) Various embodiments of the injection-molding method for producing the outer part 16 are shown on the basis of schematic illustrations in FIGS. 6a to 6c. FIG. 5a shows a disk gate, in which a tool insert 31 is used to produce the outer part 16. The tool insert 31 is enclosed by the upper tool (not shown) and by the lower tool (not shown).

(30) In the star gate method illustrated in FIG. 6b, the tool insert 31 has a main injection-molding channel 33 extending along the axis of rotation of the outer part 16, which discharges into a total of six subchannels 35 extending in a star shape and perpendicularly to the axis of rotation.

(31) In FIG. 5c, a total of six injection-molding channels 37 are provided, which are arranged on the relevant upper or lower tool and extend parallel to the axis of rotation. This is a point gating method in this case.

(32) In both cases, where the subchannels 35 or the injection-molding channels 37, respectively, end and discharge into the cavity, the injection-molding points 23 also illustrated in FIGS. 2 and 5b form in the resulting outer part 16. Depending on the course of the subchannels 35 and the injection-molding channels, the injection-molding points 23 are arranged on the inner lateral surface 26 (FIG. 6b or on the end face of the outer part 16 (FIG. 6c).

(33) FIG. 7a shows a schematic sectional illustration through an injection-molding tool 30 for producing a second spur gear 14 according to the present disclosure in the disk gate method. The already finished inlay part 20 and the also finished outer part 16 are laid on a bottom 32 of the injection-molding tool 30 concentrically to a tool axis A.

(34) The injection-molding tool 30 has an upper tool 34 having a conical portion, which is movable along the tool axis A. Concentrically to the tool axis A, the upper tool 34 has an injection-molding channel 36, through which a plastic melt can be introduced into the interior of the injection-molding tool 30.

(35) To produce the connecting part 22, the upper tool 34 is closed until it rests on the outer part 16. The plastic melt is subsequently injected into the interior of the injection-molding tool 30. To prevent the plastic melt from penetrating into a cavity 38 enclosed by the inlay part 20 (cf. FIG. 2), a tool insert 40 is inserted into the cavity 38, which fills it up completely and protrudes out of it, before the closing of the tool. The tool insert 40 is typically concentrically connected to the bottom 32.

(36) FIG. 7b shows the second spur gear 14 in a perspective illustration after the demolding from the injection-molding tool 30. It can be seen that the connecting part 22 has a conical excess 42, which has to be removed in a cutting work step.

(37) FIG. 8 shows a schematic illustration to depict the pinpoint gate method. In the pinpoint gate method, the plastic melt is injected through a number of injection-molding channels 36, which are typically arranged concentrically around the inlay part 20, into the intermediate space between the outer parts 16 and the inlay part 20. In the illustrated example, three injection-molding channels 36 are provided. Weld seams 44 arise where the flow fronts of the plastic melts, which have been injected through adjacent injection-molding channels 36 into the intermediate space, meet one another. In contrast to the disk gate method, a tool insert 40 is not necessary to prevent the plastic melt from reaching the cavity 38 enclosed by the inlay part 20. The upper tool 34 can be designed such that it can be closed extensively until it rests both on the inlay part 20 and also on the outer part 16. No excess 42 which has to be removed after the demolding results.

(38) FIG. 9 shows a schematic illustration of a spur gear unit 46 having a gearwheel pair 10 according to the present disclosure. The first spur gear 12 is connected in a rotationally-fixed manner to a driveshaft 48 rotatable about a first axis of rotation T.sub.1 and the second spur gear 14 is connected in a rotationally-fixed manner to an output shaft 50 rotatable about a second axis of rotation T.sub.2. The driveshaft 48 and the output shaft 50 extend parallel but offset in relation to one another. The first spur gear 12 and the second spur gear 14 are arranged meshing in an interior of a gearing housing 52. The driveshaft 48 and the output shaft 50 are supported in a way not shown in greater detail. The connecting part 22 is manufactured from a material which is adapted to the thermal expansion of the gearing housing 52 and the first spur gear 12. The goal in this case is to design the gearing housing 52 in such a way that the thermal expansion of the gearing housing 52 is approximately equal to the total of the thermal expansions of the two spur gears 12, 14 of the gearwheel pair 10, in order to minimize the occurrence of excessively large or excessively small tooth clearance and the negative effects accompanying this on the engagement of the two spur gears 12, 14.

(39) The first spur gear 12 and the second spur gear 14 are shown on the basis of a schematic unrolling in FIG. 10. The first spur gear 12 has a first width B.sub.SR1 and the second spur gear 14 has a second width B.sub.SR2. The first width B.sub.SR1 is greater than the second width B.sub.SR2, which prevents the sharp front edge of the gear rim, in particular made of metal, of the first spur gear 12 from running into the gear rim 18 made of the first plastic and thus resulting in increased wear. As is also recognizable from FIGS. 1 and 3, the gearwheel pair 10 has a helical gearing, and therefore the first spur gear 12 and the second spur gear 14 have a helix angle β, which is between 10° and 30° and is approximately 20° in the illustrated example. A profile overlap ε.sub.α, which is between 1 and 2, results from the profile (not shown in greater detail) of the teeth 19. In particular as a result of the selected helix angle β, an overlap ratio ε.sub.β results, which is to have a value of 1 or 2 in the present case.

LIST OF REFERENCE SIGNS

(40) 10 gearwheel pair 12 first spur gear 14 second spur gear 16 outer part 17 recess 18 gear rim 19 tooth 20 inlay part 21 injection-molded portion 22 connecting part 23 injection-molded point 24 outer lateral surface 25 injection-molded surface 26 inner lateral surface 27 projection 28 reinforcement 29 depression 30 injection-molding tool 31 tool insert 32 bottom 33 main injection-molding channel 34 upper tool 35 lower channel 36 injection-molding channel 37 injection-molding channel 38 cavity 39 undercuts 40 tool insert 42 excess 44 weld seams 46 spur gear unit 48 driveshaft 50 output shaft 52 gearing housing A tool axis b.sub.SR1 first width b.sub.SR2 second width d.sub.SR2 spur gear diameter d.sub.ET inlay part diameter T.sub.1 first axis of rotation T.sub.2 second axis of rotation β helix angle ε.sub.α profile overlap ε.sub.β overlap ratio