transmission

Abstract

A transmission (1) for reducing the input speed of an input shaft (2) to a slow speed, comprising a spur gear stage (5) and a planetary gear stage (6) downstream of it, which are arranged in a transmission housing (4), wherein the input shaft (2) drives a sun gear (9) of the planetary gear stage (6) via the spur gear stage (5), which consists of a drive gear (7) and an output gear (8), the planet gears (11) of which are arranged on a planet carrier (13, 40, 46) by means of bearing journals (27, 39, 47) mesh with the sun gear (9) and a ring gear (14), characterized in that a drive shaft (10) of the planetary gear stage (6), which is rotationally fixed to the sun gear (9), is also rotationally fixed to the output gear (8) of the spur gear stage (5), wherein the latter has hub sections (15 and 16) projecting axially on both sides of its transverse central plane with cylindrical outer surfaces (21 and 22). 22) shows,and that the output gear (8) is mounted on the planet carrier (13, 40, 46) via the outer surface (21) of the first hub section (15) in the gearbox housing (4) and via the outer surface (22) of the second hub section (16).

Description

[0001] The invention relates to a transmission for reducing the input speed of an input shaft to a slow speed, comprising a spur gear stage and a planetary gear stage downstream thereof, which are arranged in a transmission housing, wherein the input shaft drives a sun gear of the planetary gear stage via the spur gear stage consisting of a drive gear and an output gear, the planet gears of which are arranged on a planet carrier by means of bearing journals in engagement with the sun gear and a ring gear.

[0002] Such transmissions are designed to reduce a high input speed, such as that of an electric motor, to a lower speed using a spur gear stage and a planetary gear stage, thereby increasing the torque. These transmissions can be configured as multi-stage spur gear transmissions or planetary gear transmissions. If, as in the present case, a planetary gear stage follows the spur gear stage, further planetary gear stages can be added to increase the gear ratio towards the output. Such transmissions are particularly suitable for use in the wheel drives of vehicles.

[0003] A gearbox of the type specified in the preamble of claim 1 is known from DE 40 10 742 C1. According to this patent, a gearbox of a drive unit is housed in a gearbox casing closed at one open side by a cover, with an electric motor screwed to the cover. A motor shaft of the electric motor, which forms an input shaft of the gearbox, receives a drive gear of a spur gear stage in a rotationally fixed manner, which is in mesh with an output gear. This output gear is rotatably mounted on a journal extending from the cover and receives a disc carrier of a multi-disc brake, wherein this disc carrier is connected via a cylindrical extension to a sun gear of a so-called spur gear planetary gearbox serving as a planetary stage.

[0004] The sun gear meshes with planet gears, which also engage with the internal teeth of a ring gear fixed in the gearbox housing. The planet gears are rotatably mounted on bearing journals of a planet carrier, which is connected to a wheel shaft via a toothed connection. A wheel flange, formed integrally with the wheel shaft, is designed to accommodate a vehicle wheel. The multi-disc brake is actuated by a two-armed lever, which causes a push pin to displace the multi-disc carrier, along with the output gear, the extension, and the sun gear, relative to the other elements of the planetary stage, thus compressing the brake plates. It is intended to use such a gearbox for driving a forklift truck, with the multi-disc brake positioned between the spur gear stage and the planetary gear stage.

[0005] The object of the present invention is to provide an improved bearing arrangement for the output gear, which can be arranged within the gearbox housing in a space-saving manner in order to achieve a compact gearbox design.

[0006] This problem is solved starting from the preamble of claim 1 in conjunction with its characterizing features. The subsequent dependent claims each describe advantageous embodiments of the invention.

[0007] According to the invention, a transmission is provided for reducing the input speed of an input shaft to a slower speed and for this purpose comprises a spur gear stage and a planetary gear stage downstream thereof, which are arranged in a transmission housing. The input shaft drives a sun gear of the planetary gear stage via the spur gear stage, which consists of a drive gear and an output gear. The planet gears of the planetary gear stage, arranged on a planet carrier by means of bearing journals, mesh with the sun gear and a ring gear.

[0008] In such an arrangement, the output is preferably via the planet carrier, with the ring gear then being non-rotatably connected to the gearbox housing. Alternatively, it is also possible to design the planetary stage so that the planet carrier is fixed and the output is driven via the ring gear.

[0009] According to the invention, a drive shaft of the planetary stage, which is non-rotatably connected to the sun gear, is also non-rotatably connected to the output gear of the spur gear stage.

[0010] An external toothing on the drive shaft and an internal toothing provided in a hub of the output gear engage in a positive-locking manner. Furthermore, the hub on the output gear is designed with hub sections projecting axially on both sides from its transverse center plane, each of which has a cylindrical outer surface.

[0011] These features ensure that the output gear is supported in the gearbox housing via the outer surface of the first hub section and on the planet carrier via the outer surface of the second hub section. In a corresponding gear where the hub is connected to the ring gear via a disc, the hub sections project beyond the disc on both sides. This results in a space-saving arrangement for the radial support of the output gear in the gearbox housing and relative to the planet carrier.

[0012] In contrast, the output gear in the transmission according to DE 40 10 742 C1 is mounted on the journal extending from the cover via a centrally arranged cylindrical roller bearing, and no hub sections projecting on both sides are provided. When the brake is applied, the output gear and the lamellar carrier bolted to it undergo axial movement on the journal, causing the sun gear to also shift. Consequently, no bearing is provided between the planetary gear carrier and the output gear.

[0013] According to a further embodiment of the invention, the first hub section is mounted in a recess of the gearbox housing via a first radial bearing. The radial bearing can be a radial rolling bearing, preferably a ball bearing, angular contact ball bearing, angular contact shoulder bearing, or tapered roller bearing, which is pressed directly into the cylindrical recess by means of its outer ring. This results in a space-saving arrangement that allows for easy assembly of the spur gear stage.

[0014] Furthermore, the second hub section is supported on the planet carrier's bearing journal via a second radial bearing. This means the spur gear stage is supported radially and axially by the adjacent bearing journal of the planet carrier, resulting in a smaller installation space requirement. This also leads to a longer bearing lifespan, as the bearing is positioned between two gear elements with comparatively small speed differences. Therefore, the number of rolling element passes is reduced.

[0015] The second radial roller bearing can also be designed as a ball bearing, angular contact ball bearing, angular contact shoulder bearing, or tapered roller bearing. If, as proposed, the planetary stage is operated with a rotary gear ratio, the ring gear is fixed in the gearbox housing, and an output shaft, non-rotatably connected to the planet carrier, is at least indirectly supported in the gearbox housing. Preferably, a hub ring is integrally connected to a gear flange, with the hub ring that receives the output shaft being supported in the gearbox housing.

[0016] Preferably, the gearbox is designed as a wheel hub gearbox for a forklift truck, wherein the input shaft can be driven by an electric motor and the output shaft is connected to a wheel flange. In such an electric wheel drive, the electric motor is operated at a relatively high speed and low output torque. The present gearbox ensures a relatively low speed and high torque at its output shaft. Furthermore, one of the essential requirements is that the gearbox, located directly in the area of ​​the forklift truck's wheel, has an extremely compact design.

[0017] It is particularly advantageous if the bearing journals have recessed extensions at their ends facing the driven gear, with each extension forming a curved side surface through the recess, and all side surfaces align on a common circle to accommodate the outer ring of the second radial bearing. These extensions, with their curved side surfaces adapted to the radius of the outer ring, engage in partial circumferential areas of the outer ring.

[0018] Furthermore, it is also possible to design the bearing journals such that they each have a curved groove at their ends facing the output gear, with all grooves running on a common circle. In this context, a hollow cylindrical retaining ring is provided, which is equipped with axial projections that engage in the grooves. The retaining ring, which can be manufactured using a chipless forming process, thus accommodates the second radial roller bearing at its outer ring. The projections, which are designed as curved tabs, engage in the respective grooves of the bearing journals.

[0019] In a further embodiment of the invention, a bushing with a base can be inserted into the recess of the gearbox housing, into which an outer ring of the first radial bearing is pressed. The bushing with the base can be manufactured in one piece without machining, the base preferably having a thinner wall than the bushing. The recess in the gearbox housing provided for receiving the bushing can penetrate its wall.

[0020] According to a further embodiment of the invention, a retaining ring is connected to the end faces of the bearing journals, the retaining ring enclosing an outer ring of the second radial bearing. In a further development of this solution, the retaining ring is provided with bores for its fixation to the bearing journals, wherein grooved pins, dowel pins or locating pins extending in the bores engage in blind holes of the bearing journals.

[0021] Finally, the retaining ring can be fixed to the bearing journal by means of a screw or adhesive connection.

[0022] The invention is not limited to the specified combination of features of the main claim and the dependent claims. Furthermore, it is possible to combine individual features, even those that arise from the claims, the subsequent description of preferred embodiments of the invention, or directly from the drawings. The reference in the claims to the drawings by means of reference numerals is not intended to limit the scope of protection of the claims.

[0023] Advantageous embodiments of the invention, which are explained below, are illustrated in the drawings. They show: Fig. 1 a gear diagram of a transmission which forms the basis of the present invention, Fig. 2 a first embodiment of the transmission in which radial roller bearings for supporting an output gear are arranged directly in a recess of a transmission housing and in a planet carrier of a planet stage, in longitudinal section, Fig. 3 a perspective single view of the after the Fig. 2 planetary gear carriers used, Fig. 4 a second embodiment of a transmission in longitudinal section, wherein bearing journals of a planetary gear carrier receive on their end faces a retaining ring which encloses a radial roller bearing on its outer surface, Fig. 5 as a perspective representation, a scaled-down individual representation of the after the Fig. 4 planetary gear carriers used, Fig. 6 as a perspective representation after the Fig. 4 provided retaining rings, Fig. 7 a longitudinal section of a third embodiment of a transmission in which a hollow cylindrical retaining bushing is arranged in curved grooves of bearing journals of a planetary gear carrier, Fig. 8 as a perspective representation, a scaled-down individual representation of the after the Fig. 7 used planetary gear carrier and Fig. 9 as a perspective representation of the after the Fig. 7 used retaining bushings.

[0024] In the gearbox diagram according to the Fig. The transmission 1 is designated as a gearbox driven by an electric motor 3 via an input shaft 2. A spur gear stage 5 and a planetary gear stage 6 are arranged in a gearbox housing 4, forming the gearbox 1. Within the spur gear stage 5, the input shaft 2 drives an output gear 8 via a drive gear 7 fixedly mounted on it. Both the output gear 8 and a sun gear 9 are fixedly connected to a drive shaft 10. Four planet gears 11 mesh with the sun gear 9, only one of which is visible in the gearbox diagram. These planet gears 11 are rotatably mounted in a planet carrier 13 connected to an output shaft 12 and mesh with a ring gear 14 fixedly mounted in the gearbox housing 4.

[0025] As can be further seen from the schematic diagram, the output gear 8 is to have hub sections 15 and 16, which extend on both sides of its transverse center plane. Hub section 15 is supported in a recess 18 of the gearbox housing 4 by a first radial roller bearing 17. The other hub section 16 extends towards the planet carrier 13 and is supported therein by a second radial roller bearing 19.

[0026] In the following described Fig. 2, Fig. 4 and Fig. Figure 7 shows different embodiments of the bearing arrangement of the output gear 8. Where the other components of the gearbox 1 are identical, corresponding reference numerals are used for them.

[0027] After Fig. The drive wheel 7, which is fixedly mounted on the input shaft 2, drives the output wheel 8. The output wheel has hub sections 15 and 16 that extend axially on both sides of its disk 20. The radial roller bearings 17 and 19 are mounted on the stepped outer surfaces 21 and 22 of the hub sections 15 and 16.

[0028] The output gear 8 is mounted in the recess 18 of the gearbox housing 4 via the first radial roller bearing 17, the recess 18 being partially enclosed by a stepped, annular collar 24 into which an outer ring 23 of the radial roller bearing 17 is pressed. The second radial roller bearing 19 is fixed with its inner ring on the outer surface 22 of the second hub section 16, its outer ring 25 being fixed to the planet carrier 13.

[0029] As can be seen in particular from the Fig. 3, which follow the Fig. As can be seen from the 2 planetary gear carrier used, the planetary gear carrier 13 consists of a disk body 26 and from this extend on the one hand the output shaft 12 and on the other hand bearing journals 27 with axial extensions 28, each of which has a recess 29, wherein each of the recesses 29 is bounded by a curved outer surface 30.

[0030] All outer surfaces 30 run on a circle concentric to the planet carrier 13 and engage the circumference of the outer ring 25. Thus, the output gear 8 and the planet carrier 13 are rotatably mounted relative to each other. The output shaft 12 is rotationally fixed to a wheel flange 31, which is supported in a wheel hub housing 34 by two tapered roller bearings 32 and 33. Fig. 2).

[0031] The next example of how to design this Fig. 4 differs from the one after the Fig. 2 with regard to the design of the bearing arrangement of the output gear 8 and the planet carrier. Otherwise, the components of the transmission 1 essentially correspond to the components described in the figure. It is immediately apparent that the first radial roller bearing 17 is received by a bushing 35, which has a base 36. This bushing 35 is in turn inserted into a recess 37 of the transmission housing 4.

[0032] The second radial roller bearing 19 is in accordance with the one in the Fig. The bearings shown in Figure 2 are arranged on the outer surface 22 of the hub section 16, while the outer ring 25 of the second radial roller bearing 17 is pressed into a retaining ring 38. This retaining ring 38 is fixed to bearing journals 39 of a planetary gear carrier 40, for which purpose the bearing journals 39 are provided with blind holes 41 on their end faces. Grooved pins 42 are passed through bores 43 of the retaining ring 38 and engage in the blind holes 41.

[0033] In the Fig. Figure 5 shows the planet carrier 40 separately, with the blind bores 41 produced in the bearing journals 39 visible. The planet carrier also consists of a disk body 44 and an output shaft 45 formed integrally with it. Fig. Figure 6 shows the retaining ring 38 with the bores 43 formed in it.

[0034] The Fig. Figure 7 shows a third embodiment of the invention, wherein the general structure of this gearbox is again similar to that of the embodiments according to the Fig. 2 and Fig. 4 is the same, therefore the same reference numerals are used for essentially identical components and these are not explained again. There is no difference compared to the design according to the Fig. 4 consists in the design of the bearing provided between the output wheel 8 and a planet carrier.

[0035] In this case, a planetary gear carrier 46 is provided with bearing journals 47 extending from a disk body 49 connected to an output shaft 48, the end faces 50 of which have curved grooves 51. These grooves 51 run on a common circle and accommodate a retaining ring 52 into which the outer ring 25 is pressed.

[0036] From the Fig. Figure 8 shows the course of the grooves 51 arranged in the end faces 50 of the bearing journals 47. As the Fig. As can be seen from Figure 9, the retaining ring 52, which is designed as a pipe section, is to have four axial projections 53, which correspond to the Fig. 7 engage in the grooves 51. Reference sign 1 gearbox 2 Input wave 3 Electric motor 4 Gearbox housings 5 spur gear stage 6th planetary stage 7 drive wheel 8 Output wheel 9 Sun wheel 10 Drive shaft 11 planetary gears 12 Output shaft 13 planetary gear carriers 14 Ring gear 15 Hub section 16 Hub section 17 first radial roller bearing 18 Exclusion 19 second radial roller bearing 20 slices of 8 21 Outer surface area of ​​15 22 Outer surface area of ​​16 23 outer ring of 17 24 ring-shaped bundle 25 outer ring of 19 26 disc bodies of 13 27 bearing journals 28 axial processes 29 Exclusion 30 curved outer surface of 28 31 Wheel flange 32 tapered roller bearings 33 tapered roller bearings 34 wheel hub housings 35 socket 36 floor of 35 37 Exclusion in 4 38 retaining ring 39 bearing journals out of 40 40 planetary gear carriers 41 blind hole drilling in 39 42 Grooved pin 43 bore 44 disc bodies out of 40 45 Output shaft 46 planetary gear carriers 47 bearing journals 48 Output shaft 49 disc bodies out of 46 50 end faces of 47 51 Nut in 50 52 retaining ring 53 protrusions

Claims

[1] Gearbox (1) for reducing the input speed of an input shaft (2) to a slow speed, comprising a spur gear stage (5) and a planetary gear stage (6) downstream of it, which are arranged in a gearbox housing (4), wherein the input shaft (2) drives a sun gear (9) of the planetary gear stage (6) via the spur gear stage (5) consisting of a drive gear (7) and an output gear (8), the planet gears (11) of which are arranged on a planet carrier (13, 40, 46) by means of bearing journals (27, 39, 47) are in mesh with the sun gear (9) and a ring gear (14), characterized by, that a drive shaft (10) of the planetary stage (6) which is non-rotatably connected to the sun gear (9) is also non-rotatably connected to the output gear (8) of the spur gear stage (5), wherein the latter has hub sections (15 and 16) projecting axially on both sides of its transverse central plane with cylindrical outer surfaces (21 and 22), and that the output gear (8) is supported in the gearbox housing (4) via the outer surface (21) of the first hub section (15) and on the planet carrier (13, 40, 46) via the outer surface (22) of the second hub section (16). [2] Gearbox according to claim 1, characterized by , that the first hub section (15) is supported by a first radial bearing (17) in a recess (18) of the gearbox housing (4). [3] Gearbox according to claim 1, characterized by , that the second hub section (16) is supported on the bearing journals (27, 39, 47) of the planet carrier (13, 40, 46) via a second radial bearing (19). [4] Gearbox according to claim 1, characterized by , that the planetary stage (6) is operated with a rotary transmission in which the ring gear (14) is fixed in the gearbox housing (4) and an output shaft (12) which is non-rotatably connected to the planet carrier (13, 40, 46) is at least indirectly mounted in the gearbox housing (4). [5] Gearbox according to claim 1, characterized by , that the gearbox (1) is designed as a wheel hub gearbox for a forklift truck, wherein the input shaft (29) can be driven via an electric motor (3) and the output shaft (12) is connected to a wheel flange (31). [6] Gearbox according to claim 3, characterized by, that the bearing journals (27) have extensions (28) provided with recesses (29) at their ends facing the output gear (8), wherein in each of the extensions (28) a curved outer surface (30) is formed by the recess (29) produced in it, and all outer surfaces (30) run on a common circle to accommodate an outer ring (25) of the second radial bearing (19). [7] Gearbox according to claim 3, characterized by , that the bearing journals (39) each have a curved groove (51) at their ends facing the output gear (8) and that all grooves (51) run on a common circle. [8] Gearbox according to claim 7, characterized by , that a hollow cylindrical retaining ring (52) is provided with axial projections (53) which each engage in the grooves (51). [9] Gearbox according to claim 2, characterized by, that a bushing (35) provided with a base (36) is inserted into the recess (29) of the gearbox housing (4), into which an outer ring (23) of the first radial bearing (17) is pressed. [10] Gearbox according to claim 3, characterized by , that a retaining ring (38) is connected to the end faces of the bearing journals (39), which surrounds an outer ring (25) of the second radial bearing (19). [11] Gearbox according to claim 10, characterized by , that the retaining ring (38) is provided with bores (43) for its fixation to the bearing journal (39), wherein grooved pins (42), tension pins or dowel pins running in the bores (43) engage in blind holes (41) of the bearing journal (39). [12] Gearbox according to claim 10, characterized by , that the retaining ring (38) is fixed to the bearing pin (39) by a screw or adhesive connection.

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