Epicyclic gear train

Abstract

The invention relates to a self-locking epicyclic gear train (1) comprising a pinion (2) having at least one helical gear tooth (21), a ring gear (3) having a plurality of helical gear teeth (31), and a plurality of planetary gears (4) between the pinion (2) and the ring gear (3). Each planetary gear (4) comprises a plurality of helical gear teeth (41) that engage the teeth (31, 21) of the ring gear (3) and the pinion gear (2). The helical gear teeth (21, 31, 41) have a helical angle of less than 20 DEG, and the pinion (2) is always in contact with at least one tooth (41) of the or each planetary gear (4).

Description

Technical Field

[0001] The present invention relates to the field of epicyclic gear trains. More particularly, but not exclusively, the present invention also relates to a drive assembly comprising an electric motor coupled to a pinion of an epicyclic gear train; and a tubular electric motor comprising said assembly. Background Art

[0002] Tubular motor assemblies comprising a motor coupled to a pinion of an epicyclic gear train are commonly used, for example, in devices having a windable motor element.

[0003] Such tubular motor assemblies are also commonly used in electric rolling door devices. EP 3 470 616 A1 describes such a device in which the tubular motor assembly comprises an epicyclic gear train driven by a brushless motor. Summary of the invention

[0004] The present invention aims to alleviate the problems observed when using a motor assembly with an epicyclic gear train in applications where reversibility is not desired (where it is not desired to drive a gearbox input via output rotation). The present invention also aims to improve the efficiency of the epicyclic gear train while minimizing the impact on its noise and wear characteristics.

[0005] The present invention relates to a self-locking epicyclic gear train, comprising: a pinion having at least one helical gear tooth; a ring gear having a plurality of helical gear teeth; and one or more planetary gears between the pinion and the ring gear, the or each planetary gear comprising a plurality of helical gear teeth engaging the gear teeth of the pinion and the gear teeth of the ring gear.

[0006] The helix angle of helical gear teeth may be less than 20°.

[0007] In some examples, the or each tooth of the pinion gear is always in contact with at least one tooth of the or each planet gear.

[0008] The present invention also relates to a self-locking epicyclic gear train, comprising: a pinion having at least one helical gear tooth; a ring gear having a plurality of helical gear teeth; and one or more planetary gears between the pinion and the ring gear, the or each planetary gear comprising a plurality of helical gear teeth, the plurality of helical gear teeth engaging the teeth of the ring gear and the teeth of the pinion; wherein the helical gear teeth have a helix angle of less than 20°, and the pinion is always in contact with at least one tooth of the or each planetary gear.

[0009] The inventors have found that by minimising the helix angle whilst maintaining at least one of the teeth of the or each planet gear in contact with the pinion, the efficiency of the self-locking epicyclic gear train can be improved whilst minimising the impact on its noise and wear characteristics.

[0010] In particular, the inventors have found, quite surprisingly, that such a reduction in the helix angle increases the efficiency of the gear train, despite a reduction in the number of teeth in contact, without significantly reducing the contact surface.

[0011] The helix angle of the helical gear teeth may be less than or equal to 18°, such as less than or equal to 15°. The helix angle of the helical gear teeth may be at least 8°, such as at least 10°. The helix angle of the helical gear teeth may be between 8° and 18°, such as between 9° and 15°. The helix angle of the helical gear teeth may be between 10° and 12°, such as about 11°.

[0012] More specifically, the helix angle of the helical gear teeth may be between 10° and 12°.

[0013] The pinion gear and / or the ring gear may comprise or be molded from metal.The planet gears may comprise or be molded from a polymer.

[0014] One or more teeth of the pinion gear and / or teeth of the planet gear may be configured such that the coefficient of friction therebetween is at least 0.10, such as at least 0.11.

[0015] More specifically, the coefficient of friction between the or each tooth of the pinion gear and each tooth of the planet gear may be at least 0.11.

[0016] A coefficient of friction of at least 0.11 is preferred to ensure the self-locking function.

[0017] One or more teeth of the pinion and / or teeth of the planet gear may be configured such that the coefficient of friction therebetween is comprised between 0.08 and 0.14, preferably between 0.10 and 0.12, for example between 0.11 and 0.12, or about 0.11.

[0018] The teeth of the planetary gears and / or the teeth of the ring gear may also be configured such that the coefficient of friction therebetween is comprised between 0.08 and 0.14, preferably between 0.10 and 0.12, for example approximately 0.11.

[0019] The axial contact surface length between the or each tooth of the pinion and the or each tooth of the or each planet gear may be at least 20% of the value of the diameter of the pinion head, for example at least 30%, 35% or 40%. The axial contact surface length between the or each tooth of the pinion and the or each tooth of the or each planet gear may be between 35% and 50% of the value of the diameter of the pinion head, for example between 40% and 45%. In some examples, the axial contact surface length between the or each tooth of the pinion and the or each tooth of the or each planet gear is about 43% of the value of the pinion head diameter.

[0020] More specifically, the axial contact surface length between the or each tooth of the pinion and the or each tooth of the or each planet gear may be at least 35% of the value of the diameter of the pinion head.

[0021] The area of ​​the contact surface between the or each tooth of the pinion and the or each tooth of the or each planet gear may be at least 0.15 times, for example at least 0.2 times, the axial contact surface length L. The area of ​​the contact surface between the or each tooth of the pinion and the or each tooth of the or each planet gear may comprise between 0.2 and 0.3 times, for example between 0.20 and 0.25 times, for example about 0.23 times, the axial contact surface length L.

[0022] More specifically, the area of ​​the contact surface between the or each tooth of the pinion and the or each tooth of the or each planet gear may be comprised between 0.2 and 0.3 times the axial contact surface length L.

[0023] In some examples, at most two teeth of the or each planet gear are in contact with the or each tooth of the pinion gear at any one time.

[0024] The teeth may be profiled such that, in use, rotating the pinion gear causes a corresponding rotation of the planet gear, whilst rotating the planet gear causes a force insufficient to cause a corresponding rotation of the pinion gear.

[0025] Thus, the present invention provides an epicyclic gear train having a gear profile that ensures a self-locking function when the output of the gearbox is driving. Thus, this self-locking function is particularly useful in applications where the output of the gearbox may be driving. This may be the case, for example, when the gear train is coupled to a brushless motor.

[0026] This also enables a high reduction ratio to be achieved.

[0027] In use, rotating the pinion gear may cause an effective force extending away from the centre of the or each planet gear to cause a corresponding rotation of the planet gear. Rotating the planet gear may cause an effective force travelling near the centre of the pinion gear to avoid causing a corresponding rotation of the pinion gear.

[0028] In some examples, the teeth are profiled such that, in use, rotating the pinion causes an effective force extending away from the center of the or each planet gear so as to cause a corresponding rotation of the planet gear, while rotating the planet gear causes an effective force travelling near the center of the pinion which is insufficient to cause a corresponding rotation of the pinion so as to avoid causing a corresponding rotation of the pinion gear.

[0029] The teeth may be profiled such that the pressure angle shared by the or each planet gear and pinion gear is such that, in use, rotating the pinion gear causes a corresponding rotation of the planet gear whilst rotating the planet gear causes a force insufficient to cause a corresponding rotation of the pinion gear.

[0030] The pinion gear may include three or fewer teeth.The pinion gear may include two or fewer teeth.

[0031] The pinion may comprise a single tooth.

[0032] The pressure angle shared by the or each planet gear and the pinion, in particular the transverse pressure angle, may be comprised between 30° and 60°, for example about 35°. The pressure angle shared by the or each planet gear and the pinion, in particular the transverse pressure angle, may be comprised between 35° and 55°. The pressure angle shared by the or each planet gear and the pinion, in particular the transverse pressure angle, may be comprised between 35° and 45°. The pressure angle shared by the or each planet gear and the pinion, in particular the transverse pressure angle, is preferably comprised between 35° and 40°, for example about 39°.

[0033] More specifically, the lateral pressure angle common to the or each planet gear and pinion gear may be comprised between 35° and 55°.

[0034] The planetary gear may include at least three planetary gears.

[0035] The planetary gear may include four planetary gears. The planetary gear may include a plurality of planetary gears. The plurality of planetary gears may include at least three planetary gears, for example four planetary gears.

[0036] The ring gear may comprise at least one spline, for example to mesh with a tubular housing within which the self-locking epicyclic gear train is to be housed.

[0037] The invention also relates to a drive assembly comprising an electric motor coupled to a pinion of a self-locking epicyclic gear train as described above.

[0038] The motor may include a brushless motor.

[0039] The drive assembly may include a first stage formed by a self-locking epicyclic gear train. The drive assembly may include a second epicyclic gear train stage. The drive assembly may include one or more additional epicyclic gear train stages. The second stage or additional stages of the epicyclic gear train may not be self-locking.

[0040] The invention also relates to a tubular motor assembly comprising a drive assembly as described above.

[0041] For the avoidance of doubt, all features described herein are also applicable to any aspect of the present invention.

[0042] As part of this application, it is expressly provided that the various aspects, embodiments, examples and alternatives disclosed in the preceding paragraphs, claims and / or the following description and drawings, and in particular their individual features, can be presented individually or in any combination. In other words, all embodiments and / or features of any embodiment can be combined in any way, unless these features are incompatible.

[0043] For the avoidance of doubt, the terms "can", "and / or", "for example", "such as" and any other similar terms used herein must be interpreted as non-limiting such that any feature described herein is not necessarily required to be present.

[0044] Indeed, any combination of optional features is expressly envisioned without departing from the scope of the present invention, whether explicitly claimed or not. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Other features and advantages of the present invention will become apparent from the following detailed description, which will be read with reference to the accompanying drawings, in which:

[0046] [ Figure 1 ] Figure 1 shows a gear train according to the present invention;

[0047] [ Figure 2 ] Figure 2 Shows Figure 1 An exploded view of the gear train in

[0048] [ Figure 3 ] Figure 3 Shows Figure 1 and Figure 2 A cross-sectional view of the gear train in FIG. 1 showing the contact forces between the teeth of the pinion gear and one of the planet gears;

[0049] [ Figure 4 ] Figure 4 Shows Figures 1 to 3 A planetary gear in a planetary gear train in a gear train to indicate the helix angle;

[0050] [ Figure 5 ] Figure 5 showing a pinion gear and, when in use, a view of the contact surfaces between the teeth of the pinion gear and the teeth of one of the planet gears;

[0051] [ Figure 6 ] Figure 6 shows a pinion from a similar gear train, but with a Figure 5 and a view of the contact surfaces between the pinion gear teeth and each of the three teeth of the planet gear;

[0052] [ Figure 7 ] Figure 7 The drive assembly is shown;

[0053] [ Figure 8 ] Figure 8 Shown include Figure 7 A tubular motor assembly of a drive assembly in the embodiment of the present invention. DETAILED DESCRIPTION

[0054] The following reference is made to the attached Figures 1 to 8 Different aspects of different embodiments of the invention are described in more detail.

[0055] Figures 1 to 3 An overall view of a self-locking epicyclic gear train 1 according to the invention is shown. The gear train comprises a pinion 2 having helical gear teeth 21, a ring gear 3 having a plurality of helical gear teeth 31, and four planetary gears 4 between the pinion and the ring gear. Each planetary gear 4 comprises a plurality of helical gear teeth 41 which engage the teeth 21, 31 of the ring gear 3 and the pinion 2.

[0056] The gear train is mounted on a carrier 11 which includes a shaft 12 on which the pinion 2 is mounted and a corresponding shaft 14 for each planetary gear 4. Those skilled in the art will appreciate that the pinion 2 will include a coupling means (not shown) for coupling to a motor when in use. The carrier 11 also includes an output gear 16. The ring gear 3 includes four splines 5 to mesh with a tubular housing in which the self-locking epicyclic gear train will be housed.

[0057] Figure 3 Schematic diagram of the effective contact force F from pinion 2 to planetary gear 4 1 / 2 and the reaction force F from planetary gear 4 to pinion 2 2 / 1 In this example, the pinion 2 and the ring gear 3 are molded from metal, and the planetary gears 4 are molded from polymer. In use, the coefficient of friction between the gear teeth 21, 41 of the pinion 2 and the planetary gears 4 is about 0.11. The lateral pressure angle shared by each planetary gear 4 and the pinion 2 is about 39°.

[0058] As shown, in use, rotating the pinion 2 causes an effective force F extending to a distance rb2 from the center of each planet gear 4. 1 / 2 , so as to cause a corresponding rotation of the planetary gear 4. Conversely, the rotating planetary gear 4 causes an effective force F to travel to a distance rb1 near the center of the pinion 2 2 / 1 , so as not to cause corresponding rotation of pinion 2.

[0059] Thus, the gear teeth of the self-locking epicyclic gear train 1 are profiled so that, in use, rotating the pinion causes a corresponding rotation of the planet gear, while rotating the planet gear causes a force insufficient to cause a corresponding rotation of the pinion.

[0060] The invention thus provides an epicyclic gear train with a gear profile that ensures a self-locking function. This makes it possible to achieve high reduction ratios and prevents the motor from being driven when the output is being driven, which may be useful in certain applications, for example when the gear train is coupled to a brushless motor with low or no cogging (reluctant torque).

[0061] According to the present invention and Figure 4 As shown, the helical gear teeth 41 (21, 31, 41) have a helix angle β, which in this example is 11°. The inventors have found that this helix angle β makes it possible to obtain a contact ratio slightly higher than one, which means that the pinion 2 is always in contact with at least one tooth 41 but at most two teeth 41 of each planet gear 4.

[0062] Figure 5 A pinion 2 is shown, highlighting the contact surface S between the pinion 2 and one of the planetary gears 4. The contact surface S has an axial length L extending over a large portion of the width of one side of the tooth 21. The contact surface S also has a surface area corresponding to the highlighted area. In this example of the invention, the diameter of the pinion head 2 is 7.5 mm, the axial length L is approximately 3.2 mm, and the contact surface area S is approximately 0.74 mm. The basic gear efficiency (fixed planetary gear carrier) of this arrangement is approximately 62%.

[0063] Figure 6 A pinion 2' is shown for an epicyclic gear train (not shown), wherein the helical gear teeth have a helix angle of 30°, highlighting the three contact surfaces S between the pinion 2' and one of the planetary gears a , S b , S c Each contact surface S a , S b , S c With axial length L a , L b , L c , said axial length extending over a portion of the width of one side of the tooth 21 '. The contact surface S a , S b , S c Provides an aggregate area corresponding to the sum of the highlighted areas shown.

[0064] In this example, the diameter of the pinion head 2 is 7.5 mm, the concentrated surface area axial length (La +L b +L c ) is about 3.6 mm, and the aggregate contact surface area (S a +S b +S c ) is about 0.75 mm. The basic gear efficiency of this arrangement (fixed planet carrier) is about 57%.

[0065] It is generally desirable to provide helical gear teeth with a larger helix angle as this should enable the contact surface to be larger and more dispersed, thereby reducing wear and noise in the gear train 1. It is also known that increasing the helix angle has a negative impact on the efficiency of the gear train as it increases the axial component of the force transmitted between the gear teeth.

[0066] However, the inventors have found, quite surprisingly, that a helix angle β of 11° used with a self-locking gear profile, as described herein, actually provides a similarly arranged converging contact surface S having a helix angle of 30°. a , S b , S c (See Figure 6 ) equivalent contact surface S (see Figure 5 ), which results in a contact ratio of three.

[0067] A person skilled in the art will recognize that this reduction in the helix angle β has a considerable effect on the efficiency of the gear train 1. Thus, the inventors have determined that the efficiency of the gear train 1 can be significantly improved without significantly compromising the wear and noise of the gear train 1. Although the distribution of the contact surface S is less dispersed in the gear train 1 according to the invention, this appears to have a relatively small effect on its wear and noise in many applications.

[0068] The axial length L of the contact surface S between the tooth 21 of the pinion 2 and the tooth 41 of each planet gear 4 is about 43% of the value of the diameter of the pinion head 2. The inventors have found that this length can be smaller, for example up to 20%, but preferably greater than 35%, and ideally greater than 40%.

[0069] Furthermore, the area of ​​the contact surface S between the tooth 21 of the pinion 2 and the tooth 41 of each planet gear 4 is approximately 0.23 times the axial length L of the contact surface S. The inventors have found that this length may be smaller, for example up to 0.15 times, but is preferably greater than 0.2 times the axial contact surface length L.

[0070] like Figure 7As shown in , the invention also relates to a drive assembly 100 comprising an electric motor 10 coupled to a pinion 2 of the above-mentioned self-locking epicyclic gear train 1. In this example, the electric motor 10 comprises a brushless motor. The drive assembly 100 comprises a first stage formed by the self-locking epicyclic gear train 1 and two additional epicyclic gear train stages 110, 120. In this example, the additional stages 110, 120 are not self-locking.

[0071] like Figure 8 As shown in , the present invention also relates to a tubular motor assembly 1000 , which includes the above-mentioned drive assembly 100 .

[0072] Those skilled in the art will appreciate that numerous modifications to the embodiments described above are conceivable without departing from the scope of the present invention.

[0073] Reference numerals list

[0074] 1Self-locking epicyclic gear train

[0075] 10 Motor

[0076] 11 Bracket

[0077] 12 Pinion shaft

[0078] 14 Planetary gear shaft

[0079] 16 Output gear

[0080] 100 drive components

[0081] 110 Additional Epicyclic Gear Train Stage

[0082] 120 additional epicyclic gear train stages

[0083] 1000 Tubular Motor

[0084] 2 small gears

[0085] 20 Rotation axis of pinion

[0086] 21 pinion teeth

[0087] 3 Ring gear

[0088] 31 ring gear teeth

[0089] 4Planetary gears

[0090] 41 planetary gear teeth

[0091] 5 splines

[0092] L Axial contact surface length

[0093] L a Axial contact surface length

[0094] L b Axial contact surface length

[0095] L c Axial contact surface length

[0096] S contact surface

[0097] S a Contact surface

[0098] S b Contact surface

[0099] S c Contact surface

Claims

1. A self-locking epicyclic gear train (1), comprising: A pinion (2) having at least one helical gear tooth (21); A ring gear (3) having a plurality of gear teeth (31); as well as one or more planetary gears (4) between the pinion gear (2) and the ring gear (3), the or each planetary gear (4) comprising a plurality of helical gear teeth (41) engaging teeth (21, 41) of the ring gear (4) and the pinion gear (2); The helical gear teeth (21, 31, 41) have a helix angle of less than 20°, and the pinion (2) is always in contact with at least one tooth (41) of the or each planetary gear (4).

2. The self-locking epicyclic gear train according to claim 1, wherein the helix angle of the helical gear teeth (21, 31, 41) is between 10° and 12°.

3. A self-locking epicyclic gear train according to claim 1 or claim 2, wherein the coefficient of friction between the or each tooth (21) of the pinion (2) and the or each tooth (41) of the planetary gear (4) is at least 0.

11.

4. A self-locking epicyclic gear train according to any one of the preceding claims, wherein the axial length (L) of the contact surface (S) between the or each tooth (21) of the pinion (2) and the or each tooth (41) of the or each planetary gear (4) is at least 35% of the value of the diameter of the pinion head (2).

5. A self-locking epicyclic gear train according to claim 4, wherein the area of ​​the contact surface (S) between the or each tooth (21) of the pinion (2) and the or each tooth (41) of the or each planetary gear (4) is between 0.2 and 0.3 times the axial length L of the contact surface (S).

6. A self-locking epicyclic gear train according to any one of the preceding claims, wherein at most two teeth (41) of the or each planet gear (4) are in contact with the or each tooth (21) of the pinion (2) at any one time.

7. A self-locking epicyclic gear train according to any one of the preceding claims, wherein the teeth (21, 31, 41) are profiled so that, in use, rotating the pinion (2) causes a corresponding rotation of the planet gear (4), while rotating the planet gear (4) causes a force that is insufficient to cause a corresponding rotation of the pinion (2).

8. A self-locking epicyclic gear train according to claim 7, wherein the teeth (21, 31, 41) are profiled so that, in use, rotating the pinion (2) causes an effective force (F) extending away from the centre of the or each planet gear (4). 1 / 2 ) so as to cause a corresponding rotation of the planetary gear (4), while rotating the planetary gear (4) causes an effective force (F) to travel near the center of the pinion (2) 2 / 1 ), the effective force is insufficient to cause a corresponding rotation of the pinion (2), so as to avoid causing a corresponding rotation of the pinion (2).

9. A self-locking epicyclic gear train according to any one of the preceding claims, wherein the pinion (2) comprises a single tooth (21).

10. A self-locking epicyclic gear train according to any one of the preceding claims, wherein the lateral pressure angle shared by the or each planet gear (4) and the pinion (2) is comprised between 35° and 55°.

11. The self-locking epicyclic gear train according to any one of the preceding claims, wherein the planetary gears (4) comprise at least three planetary gears (4).

12. A drive assembly (100) comprising an electric motor (10) coupled to a pinion (2) of a self-locking epicyclic gear train (1) according to any one of the preceding claims.

13. The drive assembly of claim 12, wherein the motor (10) comprises a brushless motor.

14. A tubular motor assembly (1000) comprising a drive assembly (100) according to claim 12 or claim 13.

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