Input gear stage for planetary gearbox

Abstract

An input gear stage (1) for eccentric drive of a planetary gearbox is disclosed, the input gear stage (1) comprising a gear (2) and an input pinion (4), where the input pinion (4) is eccentrically positioned with respect to the gear (2) and configured to transmit a driving force to the gear (2), where the input gear stage (1) comprises two intermediate pinions (6, 8) arranged between the input pinion (4) and the gear (2), the transmission device is used for transmitting the motion of the input pinion (4) to the gear (2).

Description

Technical Field

[0001] The invention relates to an input gear stage for a planetary gearbox according to claim 1 and to a planetary gearbox having such an input gear stage according to claim 8 . Background Art

[0002] High-precision gearboxes that can be used, for example, in industrial robots or machine tools usually consist of a two-stage design. The first stage, also called the input gear stage, is the stage that converts the input speed and torque from the motor. This input gear stage can be designed as a spur gear with a sun-like input pinion that drives one or more planet-like gears. Alternatively, the input pinion can be located eccentrically and can drive a larger gear that then acts on the sun-like pinion or, for example, on the carrier of the high-precision gearbox.

[0003] In the case of an eccentrically positioned pinion, the gear is usually an integral part of the gearbox and its diameter is limited. This may be the case, for example, due to geometrical restrictions and in particular due to the requirements of the mounting interface. The diameters of the pinion and gear are in turn limited by the number of teeth and the module of the gears. Therefore, in order to achieve high torques at a given diameter limit, a large module is used. However, a large module limits the number of teeth and therefore the reduction ratio of the input gear stage. In turn, in order to achieve high reduction ratios at a given diameter limit, a high number of teeth is used. However, this high number of teeth limits the size of the module and therefore the torque capacity of the input gear stage. Summary of the invention

[0004] It is therefore an object of the present invention to provide an eccentrically driven input gear stage which is able to support high reduction ratios and / or high torques even for restricted diameter dimensions of the input pinion and gear.

[0005] This object is achieved by an input gear stage for an eccentric drive of a planetary gearbox according to claim 1 and by a planetary gearbox according to claim 8 .

[0006] An eccentrically driven input gear stage can be used in any kind of planetary gearbox comprising an eccentrically arranged input drive. For example, such a planetary gearbox can be used in a high-precision gearbox, particularly in the field of industrial robots. In order to transmit the driving force from the input drive to the input gear stage, the input gear stage comprises an input pinion and a gear. The input pinion is positioned eccentrically relative to the gear and is configured to transmit the driving force from the input drive (e.g. an electric motor) to the gear. The gear can be attached to a sun gear or a carrier, which can be part of the second stage of the planetary gearbox. Thus, the input driving force can be transmitted from the input pinion to the second stage of the planetary gearbox via the gear.

[0007] In order to provide an input gear stage capable of supporting a high reduction ratio and / or high torque, the input gear stage described herein includes two intermediate pinions. The two intermediate pinions are arranged between the input pinion and the gear for transmitting the movement of the input pinion to the gear. Therefore, the input driving force is transmitted from the input pinion to the intermediate pinion and then to the gear. Instead of having one load path from the input pinion to the gear, the input gear stage described herein has two load paths: one from the input pinion to the gear via the first intermediate pinion and one from the input pinion to the gear via the second intermediate pinion. By having two load paths, the contact stress between the input pinion and the gear is reduced because the input pinion is in contact (or more accurately meshed) with the two intermediate pinions and the gear is also in contact or meshed with the two intermediate pinions. The load path and the corresponding stress or load are therefore divided into two, thereby reducing the stress or load on the input pinion and the gear.

[0008] Having two intermediate pinions not only increases the second load path, but also has the advantage of at least two tooth pairs in contact. More precisely, the input pinion is in contact with the first intermediate pinion and at the same time with the second intermediate pinion. The same applies to the gear in a similar manner, i.e. the gear is in contact with the first intermediate pinion and at the same time with the second intermediate pinion. Having two load paths and the increased contact between the pinion and the gear allows for higher torque loads or a greater reduction ratio or both, while the load on the input pinion and / or the gear is reduced or at least not increased.

[0009] According to an embodiment, the intermediate pinions have the same size and / or the same number of teeth. This provides the advantage that the same intermediate pinions can be used, which reduces manufacturing costs. Advantageously, the input pinions can also have the same size and / or the same number of teeth, thereby further reducing manufacturing costs.

[0010] Alternatively, the intermediate pinions have different sizes and / or different numbers of teeth. When using two intermediate pinions of different sizes, the risk of resonance frequencies (which may occur in the case of intermediate pinions of the same size) can be reduced or eliminated.

[0011] Basically, the size of the input pinion as well as the intermediate pinion is a matter of design and load considerations. When limited installation space is available, the size of the input pinion and / or the intermediate pinion can be reduced. When more installation space is available, the size of the input pinion and / or the intermediate pinion can be increased, allowing for improved load distribution.

[0012] The input pinion, the intermediate pinions and the gears can each have an external gear, wherein the gearing of each intermediate pinion meshes with the gearing of the input pinion and the gearing of the gear. Also in this case, the exact arrangement can be based on design considerations, taking into account the available installation space. For example, when the installation space is limited, the input pinion can be arranged between the two intermediate pinions, as close to the gears as possible without meshing with the gears. When there is more installation space, the input pinion can be arranged as far away from the gears as possible, as long as the input pinion can mesh with the two intermediate pinions.

[0013] The gearing of the input pinion, intermediate pinion and gear can be straight or can be helical. All gearing must be the same, either helical or straight. The gearing type can be chosen appropriately.

[0014] Where axial reaction of the pinion is not permitted or the diameter is limited, a spur type gear arrangement may be preferred. Particularly when high torque, low noise or low vibration are required, a helical type gear arrangement may become advantageous.

[0015] As mentioned above, the input gear stage may be part of a planetary gearbox. Thus, the gear may be coupled to another wheel of the planetary gearbox, for example to a sun wheel or a carrier of the planetary gearbox. The input pinion may be coupled to an input drive, in particular an electric motor. The input drive may be arranged eccentrically and may be particularly configured to drive the input pinion in an eccentric manner relative to the gear.

[0016] According to another aspect, a planetary gearbox is disclosed, comprising an input gear stage as described above. In addition, the planetary gearbox comprises at least one further stage, such as an output stage. As described above, the gear of the input gear stage is coupled to another wheel of the output stage, and the input pinion of the input gear stage is coupled to the input drive.

[0017] By having such an input gear stage, the contact force between the input pinion and the intermediate pinion is less than the contact force that exists between the input pinion and the gear when the intermediate pinion is not used, and the input pinion directly contacts the gear. For example, the contact force can be reduced by about 50%. In addition, the contact pressure can be reduced, for example, to about 60% to 70%, compared to previously used designs without intermediate pinions.

[0018] By reducing the loads, contact forces and / or contact pressures, the service life of the input gear stage and thus of the entire planetary gearbox can be increased. Furthermore, as described above, since the installation space requirement of the input gear stage can be reduced, the installation space requirement of the entire planetary gearbox can also be reduced. This allows the gearbox to be utilized also in environments with only a small installation space. Since the gearbox can support higher torques and / or higher reduction ratios and at the same time can be constructed in a smaller manner than previously used gearboxes, such a gearbox can be used in particular in industrial robotics or automotive applications, which usually have high constraints with regard to installation space and high requirements with regard to torque and / or reduction ratios.

[0019] Further preferred embodiments are defined in the dependent claims as well as in the description and the drawings. Hence, elements described or shown in combination with other elements may exist alone or in combination with other elements without departing from the scope of protection.

[0020] In the following, preferred embodiments of the present invention are described in conjunction with the accompanying drawings, wherein the accompanying drawings are only exemplary and are not intended to limit the scope of protection. The scope of protection is limited only by the attached claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings show:

[0022] Figure 1 is a schematic top view of a first embodiment of an eccentrically driven input gear stage;

[0023] Figure 2 is a schematic top view of a second embodiment of an eccentrically driven input gear stage; and

[0024] Figure 3 is a schematic top view of a third exemplary embodiment of an eccentrically driven input gear stage. DETAILED DESCRIPTION

[0025] In the following, identical or similar functional elements are denoted by the same reference numerals.

[0026] Figure 1 An eccentrically driven input gear stage 1 is shown. Such an input gear stage 1 can be used, for example, in a planetary gearbox, which can be used in particular in (industrial) robotics or in any other type of application in different areas of technology, such as automotive. The planetary gearbox can be, for example, a high-precision gearbox. Independently of the type of application, the gearbox is eccentrically driven, which means that the input gear stage 1 is driven by a motor which is arranged eccentrically with respect to the main axis of rotation of a gear 2 which is connected to another stage of the gearbox.

[0027] Gear 2 may be connected, for example, to a carrier or sun gear of another gearbox stage. Gear 2 is driven by an input pinion 4. Input pinion 4 is located eccentrically relative to gear 2 and is configured to transmit a driving force (e.g. from an electric motor or the like) to gear 2.

[0028] In order to support higher torques and / or reduction ratios than previously used input gear stages, the input gear stage 1 further comprises two intermediate pinions 6, 8. Figures 1 to 3 As shown, intermediate pinions 6 , 8 are arranged between input pinion 4 and gear 2 for transmitting the movement of input pinion 4 to gear 2 .

[0029] To transmit the motion, gear 2 has an external gear arrangement 10, input pinion 4 has an external gear arrangement 12, and intermediate pinions 6, 8 also have external gear arrangements 14, 16. The gear arrangement 12 of input pinion 4 meshes with the gear arrangements 14, 16 of intermediate pinions 6, 8, and the gear arrangements 14, 16 of intermediate pinions 6, 8 mesh with the gear arrangement 10 of gear 2. Therefore, when input pinion 4 is driven by the input drive, the motion of input pinion 4 is transmitted to gear 2 via the interposed intermediate pinions 6, 8.

[0030] By having two intermediate pinions 6, 8, instead of a single load path being formed between the input pinion 4 and the gear 2, two load paths are formed: a first load path is formed from the input pinion 4 via the first intermediate pinion 6 to the gear 2, and a second load path is formed from the input pinion 4 via the second intermediate pinion 8 to the gear 2. More precisely, the first and second load paths are formed due to the meshing of the gear arrangements 12, 14, 10 and 12, 16, 10 and the corresponding contacts between the input pinion 4, the intermediate pinion 6 and the gear 2 and the contacts between the input pinion 4, the intermediate pinion 8 and the gear 2.

[0031] Having two load paths spreads the total load over the two load paths, effectively reducing the load, contact force and / or contact pressure acting on the input pinion 4 and the gear 2. As a result, a smaller pinion 4 can be used while supporting the same amount of load, contact force and / or contact pressure compared to previous input gear stages. The smaller input pinion 4 also results in a smaller overall diameter of the input gear stage 1, thereby reducing the installation space requirements. In addition, the arrangement of the input pinion 4, the intermediate pinions 6, 8 and the gear 2 supports a higher reduction ratio and a higher torque because the load on each individual element of the input gear stage 1 is reduced due to the two load paths.

[0032] Furthermore, due to the use of two intermediate pinions 6, 8, the backlash in the input gear stage 1 can be eliminated. For this purpose, the two intermediate pinions 6, 8 can be preloaded in the opposite direction to the input pinion 2.

[0033] It should be noted that although the gear arrangements 10, 12, 14, 16 are shown as spur gear arrangements, they may also be helical gear arrangements when appropriate. In addition, the gear 2, the input pinion 4 and / or the intermediate pinion 6, 8 may each have an inner hole 18, 20, 22, 24. These inner holes 18, 20, 22, 24 may be used to support the gear 2, the input pinion 4 and / or the intermediate pinion 6, 8, or may be used as a passage for cables, etc. The inner holes 18, 20, 22, 24 may also be omitted when appropriate.

[0034] like Figure 1 As shown, the input pinion 4 and the intermediate pinions 6, 8 can have the same size. Advantageously, the input pinion 4 and the intermediate pinions 6, 8 can be identical. This has the advantage that only one type of pinion needs to be manufactured. This can reduce manufacturing costs and can also save costs in the event of a pinion replacement. However, when using identical pinions 4, 6, 8, the resonant frequency increases.

[0035] Therefore, in a further embodiment, the input pinion 4 and the intermediate pinions 6, 8 may have different sizes. In this case, at least one pinion 4, 6, 8 is different from the other pinions, and all three pinions 4, 6, 8 may be different. For example, Figure 2 As shown, the intermediate pinion 6 may be smaller than the input pinion 4 and the intermediate pinion 8. This arrangement may lower the resonant frequency but still provide the advantage of having two load paths.

[0036] In another embodiment, the input pinion 4 can be arranged closer to the gear 2. Figure 3 As shown, the input pinion 4 is arranged as close as possible to the gear 2 without touching the gear 2. Nevertheless, two load paths are provided through the two intermediate pinions 6, 8, but at the same time, the overall diameter of the input gear stage 1 is further reduced. This arrangement may be advantageous when the installation space of the input gear stage 1 is strictly limited.

[0037] It should be noted that Figure 1 , 2 The embodiments of and 3 can also be combined. For example, in Figure 3 In the embodiment of the present invention, pinions 4, 6, 8 of different sizes can be used.

[0038] In summary, the input gear stage described herein uses two intermediate pinions, inserted between the input pinion and the gear, which provides two load paths instead of only a single load path. The two load paths allow for a smaller module of the input pinion and / or the intermediate pinion, which in turn allows for more teeth and therefore a higher reduction ratio. Since the input gear stage allows for more load (since the load is distributed over two load paths, there is less load on each path), the torque capacity of the input gear stage can be increased.

[0039] Reference numerals list

[0040] 1 Input gear stage

[0041] 2 Gear

[0042] 4 Input pinion

[0043] 6 Intermediate pinion

[0044] 8 Intermediate pinion gear

[0045] 10 Gear

[0046] 12 Gear

[0047] 14 Gear

[0048] 16 Gear

[0049] 18 inner hole

[0050] 20 inner hole

[0051] 22 inner hole

[0052] 24 inner hole

Claims

1. An eccentrically driven input gear stage (1) for a planetary gearbox, the input gear stage (1) comprising a gear (2) and an input pinion (4), wherein the input pinion (4) is eccentrically positioned relative to the gear (2) and is configured to transmit a driving force to the gear (2), It is characterized in that The input gear stage (1) comprises two intermediate pinions (6, 8) arranged between the input pinion (4) and the gear (2) for transmitting the movement of the input pinion (4) to the gear (2).

2. The input gear stage according to claim 1, in, The intermediate pinions (6, 8) have the same size and / or the same number of teeth.

3. The input gear stage according to claim 1, in, The intermediate pinions (6, 8) have different sizes and / or different numbers of teeth.

4. An input gear stage according to any one of the preceding claims, in, The input pinion (4), the intermediate pinions (6, 8) and the gear (2) each have an external gear arrangement (10, 12, 14, 16), wherein the gear arrangement (14, 16) of each intermediate pinion (6, 8) meshes with the gear arrangement (12) of the input pinion (4) and the gear arrangement (10) of the gear (2).

5. The input gear stage according to claim 4, in, The gearing (10, 12, 14, 16) of the input pinion (4), the intermediate pinions (6, 8) and the gear (2) is straight.

6. The input gear stage according to claim 4, in, The gear arrangement (10, 12, 14, 16) of the input pinion (4), the intermediate pinions (6, 8) and the gear (2) is helical.

7. An input gear stage according to any one of the preceding claims, in, The gear (2) can be coupled to another wheel of the planetary gearbox, and wherein the input pinion (4) can be coupled to an input drive device, in particular to an electric motor.

8. A planetary gearbox comprising an input gear stage (1) and an output stage according to any of the preceding claims, wherein a gear (2) of the input gear stage (1) is coupled to another wheel of the output stage, and wherein an input pinion (4) of the input gear stage (1) is coupled to an input drive.

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