planetary gear

Abstract

Planetary gear (1) comprising an internally toothed ring gear (13) with a ring gear toothing (15), and a planet gear (17) with a planet gear toothing (19) for meshing with the ring gear toothing, wherein the ring gear toothing has a ring gear tooth number of at least 135, and wherein a first profile overlap of the ring gear toothing and the planet gear toothing is at least 1.1.

Description

Field of invention

[0001] The disclosure relates to planetary gears, in particular planetary gears with low-loss gearing. State of the art

[0002] Planetary gearboxes with increased efficiency are known from the prior art. Known planetary gearboxes can feature low-loss gearing, also known as "low-loss gearing." Such planetary gearboxes are frequently used in industrial applications requiring particularly low power loss. In known planetary gearboxes, it is common to incorporate low-loss gearing with a high pressure angle and low contact ratios.

[0003] However, planetary gearboxes with known low-loss gears may, for example, be louder in operation or have a lower pitting load capacity compared to other planetary gearboxes. Disclosure of the invention

[0004] The purpose of this disclosure is to specify a planetary gear unit that is an improvement over the prior art. In particular, it should specify a planetary gear unit that has low power loss, low noise, low excitation characteristics, or high load-carrying capacity.

[0005] The problem is solved with a planetary gear unit according to claim 1.

[0006] According to one aspect, a planetary gear set is specified. The planetary gear set comprises an internally toothed ring gear with ring gear teeth. The planetary gear set includes a planet gear with planet gear teeth for meshing with the ring gear teeth. The ring gear teeth have a minimum of 135 teeth. The first profile overlap of the ring gear teeth and the planet gear teeth is at least 1.1.

[0007] In typical embodiments, the planetary gear is designed as a single-stage planetary gear with exactly one gear stage. In other embodiments, the planetary gear can be designed as a multi-stage planetary gear, for example, as a two-stage or three-stage planetary gear. Planetary gears according to typical embodiments are used in drive trains in industrial drive technology, particularly in machine tools, packaging machines, industrial robots, lathes or milling machines, printing presses, handling and automation technology, medical technology, logistics, automotive engineering, or construction machinery. Typical planetary gears can enable a reduction in speed or a reduction in speed.

[0008] Typically, a gear stage of a planetary gear set, particularly of a single-stage or multi-stage planetary gear set, comprises the internally toothed ring gear and the planet gear according to the embodiments described herein. The gear stage typically has an efficiency of at least 98.5%, particularly at least 99% or at least 99.3%. For example, the gear stage may have an efficiency of at least 99.5%. The gear stage typically features low-loss teeth.

[0009] In particular, the ring gear teeth of the ring gear and the planet gear teeth of the planet gear can be designed as low-loss gearing of the gear stage. Specifically, the planetary gear set, and especially the gear stage with the low-loss gearing, is designed for power transmission with low power loss.

[0010] In typical embodiments, the internal gear teeth of the ring gear are designed as internal teeth. In typical embodiments, the internal gear teeth have a minimum of 135 teeth, particularly a minimum of 140. Typically, the internal gear teeth have a maximum of 162 teeth, particularly a maximum of 155 or a maximum of 150. Specifically, the internal gear teeth can have a minimum of 135 and a maximum of 162 teeth, a minimum of 135 and a maximum of 155 teeth, a minimum of 135 and a maximum of 150 teeth, a minimum of 140 and a maximum of 162 teeth, a minimum of 140 and a maximum of 155 teeth, or a minimum of 140 and a maximum of 150 teeth. For example, the internal gear teeth can have a minimum of 144 teeth. According to further examples, the internal gear teeth can have a minimum of 135 or 162 teeth.

[0011] In certain embodiments, the ring gear teeth have a module of at most 1.5 mm, in particular at most 1.0 mm or at most 0.65 mm. In other embodiments, the module is at least 0.2 mm, in particular at least 0.3 mm. The module of a gear indicates the ratio of the pitch circle diameter of the gear to the number of teeth on the gear. According to typical embodiments, the pitch circle diameter of the ring gear is at least 35 mm, in particular at least 40 mm, or at most 230 mm, in particular at most 220 mm. For example, the pitch circle diameter can be at least 40 mm and at most 220 mm.

[0012] In typical embodiments, the planetary gear system comprises one or more planet gears, each of which has a planet gear toothing according to the embodiments described herein for meshing with the ring gear toothing of the ring gear. Typically, the planetary gear system includes at least one planet gear for meshing with the ring gear toothing, in particular exactly one, exactly two, exactly three, exactly four, or exactly five planet gears, for example, exactly three or exactly five planet gears for meshing with the ring gear toothing. Typically, the planetary gear system includes a planet carrier for receiving the at least one planet gear.

[0013] In typical embodiments, the first contact ratio of the ring gear teeth and the planet gear teeth is at least 1.1, in particular at least 1.4 or at least 1.5. A contact ratio greater than 1 can, for example, enable particularly robust operation. Typically, the first contact ratio is a maximum of 1.8, in particular at most 1.7. For example, the first contact ratio can have a value in the range of 1.1 to 1.8, in particular from 1.4 to 1.8, or from 1.5 to 1.7. Typically, the contact ratio of two gear teeth gives the ratio l / p. b the engagement length l of the gear teeth to the engagement pitch p b the gear teeth (see also Fig. 2 and Fig. 3) Typically, the planetary gear has the same module as the ring gear.

[0014] In embodiments, the planetary gear set, in particular the gear stage of the planetary gear set, comprises a sun gear with sun gear teeth. Typically, the sun gear teeth are configured to mesh with the planet gear teeth of the planet gear set. In embodiments, the ring gear teeth, the planet gear teeth, and the sun gear teeth are designed as low-loss gears. Typically, the sun gear has the same module as the ring gear, in particular the same module as the ring gear and the planet gear set.

[0015] According to typical embodiments, the second profile overlap of the planetary gear teeth and the sun gear teeth is at least 1.05, in particular at least 1.1, or at most 1.6. For example, the second profile overlap can be at least 1.05 and at most 1.6, in particular at least 1.1 and at most 1.6. A high first or second profile overlap according to the embodiments described herein can, for example, provide reduced excitation behavior, in particular reduced noise generation. Furthermore, an increased load-carrying capacity of the planetary gear set can be achieved.

[0016] In certain embodiments, the pressure angle between the ring gear teeth and the planetary gear teeth, or between the sun gear teeth and the planetary gear teeth, is at least 18°, in particular at least 19° or at least 20°, or at most 27°, in particular at most 25° or at most 23°. For example, the pressure angle can be at least 18° and at most 27°, in particular at least 19° and at most 25°, or at least 20° and at most 23°. For example, the pressure angle can be 20°. A pressure angle of 20° can advantageously provide high load-bearing capacity through high profile overlap and simultaneously low noise generation.

[0017] In typical embodiments, the ring gear teeth, in particular the ring gear teeth and the planet gear teeth, are designed as helical teeth. In embodiments with a sun gear, the sun gear teeth are also typically designed as helical teeth. The helical teeth are typically involute helical teeth. In typical embodiments, the helical teeth have a helix angle of at least 6° or at most 12°, for example, a helix angle of 7.5°. The planet gear teeth, in particular the planet gear teeth and the sun gear teeth, typically have the same helix angle as the ring gear teeth.

[0018] Gear designs according to the embodiments described herein can, for example, achieve sufficient root safety, sufficient flank safety, low gear power loss, or combinations thereof with low excitation behavior. Gear losses can be reduced by up to 50%, for example. In particular, the efficiency of the gear stage or the planetary gear can be increased. In these embodiments, the rated speed or the power of the planetary gear can be significantly increased, in particular by up to 50%. Typical gears have a rated speed between 2,500 and 12,000 rpm. Surface coatings of the gears can be omitted in these embodiments.

[0019] In typical embodiments, the ring gear teeth and the planetary gear teeth, and in particular the sun gear teeth, each have a surface roughness with a mean roughness value Ra of less than 0.2. In embodiments, the ring gear teeth and the planetary gear teeth, and in particular the sun gear teeth, are hardened.

[0020] In typical embodiments, the planetary gear, in particular the gear stage comprising the internally toothed ring gear and the planet gear, has a gear ratio of at least 2.5, in particular at least 4, or of a maximum of 14, in particular a maximum of 13. The gear ratio can, for example, be a value between 2.5 and 14.

[0021] In typical embodiments, the planetary gear includes a planetary gear bearing for supporting the planet gear. In some embodiments, the planetary gear bearing is designed as a cage bearing with needle rollers, particularly for gear ratios below 7. A planetary gear bearing with a cage bearing can also be referred to here as a cage-guided planetary gear bearing. A cage bearing with needle rollers can advantageously reduce friction in the planetary gear or simplify its assembly. In further embodiments, the planetary gear bearing can be designed as a full complement needle roller bearing, particularly for gear ratios of at least 7. Typically, for high gear ratios, gear losses dominate, while for lower gear ratios, load-independent losses or losses in the planetary gear bearing dominate.

[0022] In some embodiments, the planetary gear unit comprises a first shaft. The first shaft can, for example, be non-rotatably connected to the sun gear or the planet carrier of the planetary gear unit. The first shaft can also be referred to as the input shaft. In some embodiments, the planetary gear unit has a sealing ring on the first shaft, in particular a low-friction sealing ring. In other embodiments, the planetary gear unit comprises a second shaft. The second shaft can, for example, be non-rotatably connected to the ring gear or the planet carrier of the planetary gear unit. The second shaft can also be referred to as the output shaft. Typical planetary gear units can also be operated in reverse, with the second shaft serving as the input shaft and the first shaft as the output shaft.A low-friction sealing ring, provided the mating surface of the first or second shaft is sufficiently smooth, robust, and free of twist, can have a low spring preload or an optimized sealing profile, or be made of a friction-optimized material. In some embodiments, a low-friction sealing ring can be a non-contact sealing ring, for example, a labyrinth seal. In other embodiments, the planetary gear can be designed without sealing rings.

[0023] Typically, a planetary gear system incorporates a lubricant, in particular grease or oil. Specifically, the lubricant can be grease. Grease-lubricated planetary gear systems offer the advantage that no contact seals, such as radial shaft seals, are required. In particular, the service life of the seals can be significantly longer than in oil-lubricated planetary gear systems. Low power loss in planetary gear systems according to the embodiments described herein can be particularly advantageous in a grease-lubricated planetary gear system, since heat dissipation is usually not as efficient in grease-lubricated planetary gear systems as in oil-lubricated planetary gear systems. Furthermore, low power loss reduces heat input, resulting in less or slower lubricant degradation.The reduction in lubricant degradation is typically more pronounced in grease-lubricated planetary gears than in oil-lubricated planetary gears.

[0024] Typical embodiments of planetary gears can offer advantages over prior art, such as the ability to provide a planetary gear with low-loss, low-noise, or low-excitation, yet high-load-carrying gearing. In particular, the gearing can exhibit high pitting resistance compared to known low-loss gears. Typical planetary gears can be provided for a wide transmission range. They also offer the advantage of high power transmission. In particular, the planetary gears described herein typically generate less heat than conventional gears. The operating temperature limit for the planetary gear is typically reached only at higher power levels than with conventional gears.

[0025] Typical planetary gearboxes can offer the advantage that CO2 savings or energy savings can be achieved due to their high efficiency.

[0026] Furthermore, embodiments can offer the advantage of increasing the rated speed by more than 40%. In typical embodiments, an electric motor connected to a typical planetary gearbox of a specific size can advantageously be operated more efficiently, particularly because a high number of teeth in the ring gear allows for higher gear ratios within the size of the planetary gearbox. Furthermore, embodiments can offer the advantage of reduced idle times in intermittent operation of a drive comprising a typical planetary gearbox. In particular, the typical planetary gearbox does not heat up as much as conventional planetary gearboxes, even at high operating torques.Furthermore, in certain embodiments, friction in the planetary gear can be reduced by friction-reducing measures described herein on the planetary gear bearing or on the sealing surfaces.

[0027] Typical planetary gear sets with different gear ratios can advantageously be manufactured from a modular gear set. In particular, a ring gear according to an embodiment described herein can be used for a plurality of planetary gear sets of the same size with different gear ratios. Using a ring gear as a common component for different gear ratios can be cost-effective. Furthermore, assembly advantages can arise if a cage-guided planetary gear bearing according to typical embodiments can be used for different gear ratios, especially for those ratios where the cage-guided planetary gear bearing does not offer significant efficiency advantages over a full needle roller planetary gear bearing. Brief description of the drawings

[0028] Further advantages and features of preferred embodiments of the invention are explained below with reference to the accompanying drawings, the figures showing: Fig. Figure 1 shows a schematic sectional view of a planetary gear unit according to a typical embodiment; Fig. Figure 2 shows a schematic sectional view of the engagement of a ring gear toothing of a ring gear with a planet gear toothing of a planet gear according to typical embodiments; and Fig. Figure 3 shows a schematic sectional view of the engagement of a planet gear toothing of a planet gear with a sun gear toothing of a sun gear according to typical embodiments. Description of embodiments

[0029] Typical embodiments are described below with reference to the figures. The invention is not limited to these embodiments; rather, the scope of the invention is defined by the claims. The same reference numerals are used for identical or similar parts in the description of the figures. For the sake of clarity, some features already described in connection with other figures are not described again.

[0030] The Fig. Figure 1 shows a typical planetary gear 1 with a first shaft 5 rotatable about a gear axis 3, which serves in particular as the drive shaft of the planetary gear 1. A second shaft 7 of the planetary gear 1, which serves in particular as the output shaft of the planetary gear 1, is arranged coaxially to the first shaft 5. The planetary gear 1 of the Fig. 1 is designed as a single-stage planetary gear with one gear stage 11. The gear stage 11 comprises a ring gear 13 with a ring gear tooth 15. The ring gear 13 is in Fig. 1 formed integrally with a housing 9 of the planetary gear 1. The gear stage 11 further comprises several planet gears 17, each of which has a planet gear toothing 19, whereby only one planet gear 17 is visible in the sectional view of the Fig. Figure 1 shows the planet gear 17 rotatably mounted on a bolt 31 of a planet carrier 29 of the planetary gear 1 about a planetary axis of rotation 23. The planet gear bearing 21 of the planet gear 17 on the bolt 31 is specifically designed as a full complement bearing with needle rollers. The planet carrier 29 is non-rotatably connected to the second shaft 7.

[0031] The planetary gear set 1 comprises a sun gear 25 with a sun gear tooth 27. The sun gear 25 is non-rotatably connected to the first shaft 5. The first shaft 5 is rotatably mounted relative to the housing 9 in a first bearing area 41 via a first bearing 43. A first sealing ring 45 is arranged between the housing 9 and the first shaft 5. The second shaft 7 is rotatably mounted relative to the housing 9 in a second bearing area 47 via second bearings 49. A second sealing ring 51 is arranged between the housing 9 and the second shaft 7. The planetary gear set 1 of the Fig. Example 1 is a grease-lubricated planetary gear. The first sealing ring 45 and the second sealing ring 51 are in Fig. 1 each designed as a labyrinth sealing ring.

[0032] In Fig. 1. The planet gear teeth 19 engage with the ring gear teeth 15 and the sun gear teeth 27. The ring gear teeth 15, the planet gear teeth 19, and the sun gear teeth 27 are designed according to the embodiments described herein, in particular as described below in connection with the Fig. 2 and Fig. 3 explained.

[0033] The Fig. Figure 2 schematically shows an engagement between the ring gear teeth 15 of the ring gear 13 and the planet gear teeth 19 of the planet gear 17 of a typical planetary gear set 1, wherein the ring gear 13 has a ring gear tooth count of at least 135. The ring gear 13 has a first pitch circle 14, and the planet gear 17 has a second pitch circle 18. The pitch point C1 is located at the point of contact between the first pitch circle 14 and the second pitch circle 18. The engagement between the ring gear teeth 15 and the planet gear teeth 19 occurs along a line of action 201, specifically between a point of engagement A1 and a point of engagement E1 along the line of action 201. The distance A1-E1 from the point of engagement A1 to the point of engagement E1 is typically referred to as the engagement path l. Furthermore, the flanks of the ring gear teeth 15 and the planet gear teeth 19 touch at a first point of contact, in which Fig. 2 at the point of engagement A1, and at a second point of contact D1. The distance A1-D2 between the first point of contact and the second point of contact is typically called the engagement pitch p. b The first profile overlap of the ring gear teeth 15 and the planet gear teeth 19 results from the ratio l / p. b the intervention path l to the intervention division p b The ratio l / p b corresponds to Fig. 2 the ratio of the distance A1-E1 to the distance A1-D1. The first profile overlap of the ring gear toothing 15 and the planet gear toothing 19 is between 1.1 and 1.8.

[0034] The Fig. Figure 3 schematically shows the engagement between the planet gear teeth 19 of the planet gear 17 and the sun gear teeth 27 of the sun gear 25. The sun gear 25 has a third pitch circle 26. The pitch point C2 is located at the point of contact between the second pitch circle 18 of the planet gear 17 and the third pitch circle 26 of the sun gear 25. The engagement between the planet gear teeth 19 and the sun gear teeth 27 occurs along the line of action 301. Point T2 indicates the tangential point of contact of the line of action 301 on a base circle 28 of the sun gear 25. The engagement takes place between a start of engagement A2 and a finish of engagement E2. Along the line of action 301 lies a first point of contact and a second point of contact D2 of the flanks of the planet gear teeth 19 and the sun gear teeth 27, the first point of contact being in the Fig. 3 at the start of engagement A2. A second profile overlap of the planetary gear teeth 19 and the sun gear teeth 27 results from the ratio l / p. b the intervention path l to the intervention division p b The ratio l / p b corresponds to Fig. 3 the ratio of the distance A2-E2 to the distance A2-D2. The second profile overlap of the planet gear teeth 19 and the sun gear teeth 27 is between 1.05 and 1.6. This can enable particularly robust operation.

[0035] According to the following examples, the ring gear 15, the planet gear 19, and the sun gear 27 of a typical planetary gear set 1 are each designed as helical involute gears. The helix angle of the involute gears is 7.5° in each case. The pressure angle between the sun gear 27 and the planet gear 19, or between the ring gear 15 and the planet gear 19, is 20°. The gear ratio is approximately 10 in each case.

[0036] According to a first example, the planetary gear 1 has a ring gear tooth count of 144, a ring gear module of 0.6 mm, a pitch circle diameter of the first pitch circle 14 of the ring gear 13 of 86.4 mm, a first profile overlap of 1.7 and a second profile overlap of 1.4.

[0037] According to a second example, the planetary gear 1 has a ring gear tooth count of 135, a module of the ring gear 13 of 0.6 mm, a pitch circle diameter of the first pitch circle 14 of the ring gear 13 of 81 mm, a first profile overlap of 1.5 and a second profile overlap of 1.1.

[0038] According to a third example, the planetary gear 1 has a ring gear tooth count of 162, a module of the ring gear 13 of 0.53 mm, a pitch circle diameter of the first pitch circle 14 of the ring gear 13 of 85.86 mm, a first profile overlap of 1.5 and a second profile overlap of 1.1. The examples and typical embodiments described herein provide, in particular, planetary gears with low-loss, low-excitation, yet load-bearing gear teeth.

Claims

[1] Planetary gear (1) comprising - an internally toothed ring gear (13) with a ring gear toothing (15), and - a planet gear (17) with a planet gear toothing (19) for meshing with the ring gear toothing, wherein the ring gear toothing has a ring gear tooth number of at least 135, and wherein a first profile overlap of the ring gear toothing and the planet gear toothing is at least 1.

1. [2] Planetary gear according to claim 1, wherein a gear stage (11) comprising the internally toothed ring gear and the planet gear has an efficiency of at least 98.5%. [3] Planetary gear set according to claim 1 or 2, wherein the number of teeth on the ring gear is a maximum of 162. [4] Planetary gear set according to any of the preceding claims, wherein the number of teeth of the ring gear is at least 140 and / or at most 150. [5] Planetary gear set according to any of the preceding claims, wherein the first profile overlap is at least 1.4 and / or at most 1.

8. [6] Planetary gear according to one of the preceding claims, further comprising a sun gear (25) with a sun gear toothing (27) for meshing with the planet gear toothing, wherein a second profile overlap of the planet gear toothing and the sun gear toothing is at least 1.05 and / or at most 1.

6. [7] Planetary gear according to one of the preceding claims, wherein the ring gear toothing is designed as helical toothing. [8] Planetary gear according to claim 7, wherein the helical gearing is a helical involute gearing. [9] Planetary gear according to claim 7 or 8, wherein the helical gearing has a helix angle of at least 6° and / or a maximum of 12°. [10] Planetary gear set according to one of the preceding claims, wherein the ring gear toothing has a module of a maximum of 1.5 mm. [11] Planetary gear according to one of the preceding claims, wherein the pressure angle between the ring gear toothing and the planet gear toothing is at least 18° and / or at most 27°. [12] Planetary gear set according to one of the preceding claims, wherein the pitch circle diameter of the ring gear is at least 35 mm and / or at most 230 mm. [13] Planetary gear according to one of the preceding claims, wherein a gear stage comprising the internally toothed ring gear and the planet gear has a gear ratio of at least 2.5 and / or at most 14. [14] Planetary gear according to one of the preceding claims, wherein the ring gear toothing and the planet gear toothing each have a mean roughness value of less than 0.

2. [15] Planetary gear according to one of the preceding claims, further comprising a planet gear bearing (21) for supporting the planet gear, wherein the planet gear bearing is designed as a cage bearing with needle rollers.

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