WO2014044277A1

WO2014044277A1 - Gear assembly

Info

Publication number: WO2014044277A1
Application number: PCT/DE2013/200184
Authority: WO
Inventors: Benedikt GEIER; Jürgen OSTERLÄNGER; Ralf Wagner
Original assignee: Schaeffler Technologies AG & Co. KG
Priority date: 2012-09-24
Filing date: 2013-09-23
Publication date: 2014-03-27
Also published as: DE102012217102A1

Abstract

The invention relates to a gear assembly (1) comprising a sun gear (3) that is driven about an axis (a) by a drive motor (2) and comprises an outer toothing (4); a number of planetary gears (5) that are arranged radially outside of the sun gear (3) and are provided with a toothing (6) with which the planetary gears mesh with the outer toothing (4) of the sun gear (3); a stationary ring gear (7) with an inner toothing (8), the toothing (6) of the planetary gears (5) meshing with the inner toothing (8) of said ring gear (7); and an output ring gear (9) that is arranged so as to be rotatable about the axis (a) and comprises an inner toothing (10). The planetary gears (5) are provided with another toothing (11) that is axially offset relative to the aforementioned toothing (6) and meshes with the inner toothing (10) of the output ring gear (9). The aim of the invention is to provide a compact and highly efficient gear mechanism. According to the invention, this is achieved in that the planetary gears (5) are provided with three toothings (6', 6", 11) that are offset relative to one another in the axial direction (a). The first toothing (6') forms the meshing engagement between the sun gear (3) and the planetary gear (5) and lies on a first plane (E₁), the second toothing (6") forms the meshing engagement between the stationary ring gear (7) and the planetary gear (5) and lies on a second plane (E₂), and the third toothing (11) forms the meshing engagement between the output ring gear (9) and the planetary gear (5) and lies on a third plane (E₃), all three planes (E₁, E₂, E₃) being axially offset relative to one another.

Description

Name of the invention

transmission assembly

description

Field of the invention

The invention relates to a gear arrangement, comprising a driven by a drive motor about an axis sun gear with an external toothing, a number of planet gears, which are arranged radially outside the sun gear and which are provided with a toothing, with which they mesh with the external toothing of the sun gear , A stationary ring gear with an internal toothing, wherein the planetary gears mesh with their teeth with the internal teeth of the ring gear, and a rotatably mounted about the output shaft arranged ring gear with an internal toothing, wherein the planetary gears with a toothed axially offset further arranged further teeth are provided, which meshes with the internal teeth of the output ring gear.

Background of the invention

Such a gear arrangement is referred to as Wolfrom gear (or Wolfrum epicyclic gear) and is described for example in DE 93 18 360 111. A similar solution is shown in DE 20 2009 018 547 U1.

Previous drive concepts provide, for example, direct motors (internal rotor motors) with a hollow shaft as the drive element, by means of which a linear movement can be generated; Hereby, an actuator can be actuated, as required for example in a rear-wheel steering. Furthermore, axially parallel drives with internal rotor motor are known, which transmit their drive torque via a spur gear or a belt drive. Furthermore, axial drives with internal rotor motor commonly used, which are connected to a flanged spur or planetary gear (planetary gear).

The combination of an external rotor motor with different types of transmission, in particular with a planetary gear, is described for example in DE 44 23 902 A1.

If the transmission must have a high gear ratio, for example a ratio of i = 40: 1, the Wolfrom gearbox has proven itself, as shown in a schematic diagram in Fig. 1.

The gear assembly 1 has an only indicated here drive motor 2, which drives a sun gear 3 about an axis a. The sun gear has an outer toothing 4, which meshes with a number of planetary gears 5, which have a toothing 6; three or more planet gears 5 can be arranged equidistantly around the sun gear 3. A ring gear 7 is arranged stationary and has an internal toothing 8, which meshes with the toothing 6 of the planet gears 5. The sun gear, the planet gears - as far as their teeth 6 is concerned - and the ring gear 7 lie in one plane.

However, the planet gears 6 are axially extended beyond this level and have a toothed portion which carries a toothing 1 1. This toothing meshes with an internal toothing 10, which has a driven ring gear 9. The driven ring gear 9 is mounted concentrically around the axis a rotatably. When driving the sun gear 3 thus the output ring gear 9 rotates with a strong reduction in the slow.

This transmission is already relatively compact and uses conventional gearing techniques; only one planetary bridge is needed. However, in-line planetary gearboxes required several stages, including several planetary webs. However, the previously known drive concepts or the known Wolfrom transmission also have disadvantages:

When driving by means of a direct motor with a hollow shaft, the motor is relatively large or oversized and thus heavy and expensive. The cost of materials is high. In the case of drives that are parallel to the axis, difficult installation space conditions usually arise. Furthermore, a high manufacturing accuracy is required here. In the case of coaxial drives with flanged gear unfavorable utilization of the radial space is available.

The combination of an external rotor motor with a simple planetary gear can not realize a high gear ratio in one stage. The series connection of several stages increases the construction costs significantly, as more parts and bearings are required.

With regard to the described Wolfrom transmission is to be noted as a disadvantage that radially a relatively large space is needed. Furthermore, the efficiency of the transmission is not particularly high. The efficiency drops significantly with increasing overall ratio for this type of transmission. This is due to the fact that in the sub-transmission (part of the planetary gears with the teeth 1 1 and output ring gear 9), a poor power flow predominates due to coupling reactive power. The higher the translation ratio in the sub-transmission, the worse the efficiency. Accordingly, the efficiency increases when the ratio of the ratio in the main gear (sun gear 3, planet gears with their teeth 6 and ring gear 7) increases. To increase the ratio in the main transmission, however, the Planetenraddurchmesser would disadvantageously be increased. The already relatively large radial space would be even greater. Object of the invention

The present invention is based on the A u fg abe, a transmission arrangement of the type mentioned in such a way that a more compact design can be achieved. Here, a coaxial drive concept can be achieved wisely. Here, a coaxial drive concept will be proposed, in which both the axial and the radial space can be optimized. Furthermore, the efficiency of the transmission should be increased in comparison with previously known solutions and in particular compared with the known Wolfrom transmission.

The gear arrangement should be optimized in particular as a combined motor-gear unit, for example, to drive an electromechanical actuator of a rear-wheel steering. Of course, other applications of the arrangement are also conceivable.

Summary of the invention

The solution to this problem by the invention is characterized in that the planetary gears are provided with three toothings, which are each arranged offset from one another in the axial direction, wherein the first toothing forms the toothed engagement between sun gear and planetary gear and lies in a first plane, wherein the second toothing forms the meshing between stationary ring gear and planetary gear and lies in a second plane, wherein the third toothing forms the toothed engagement between output ring gear and planetary gear and lies in a third plane, wherein all three planes are axially offset from one another.

The first level preferably lies between the second level and the third level.

The planet gears preferably consist of an integrally formed base body, in which the three gears are incorporated. The teeth of the planet gears preferably have all different pitch circle diameter. The pitch circle diameter of the first toothing is preferably larger than the pitch circle diameter of the second toothing; the pitch circle diameter of the third toothing is preferably smaller than the pitch circle diameter of the first toothing; Finally, the pitch circle diameter of the third toothing is preferably smaller than the pitch circle diameter of the second toothing. The toothing modules of the three gears can not all be the same. Preferably, the modules of the three gears are all different in size. Of course, it can also be provided that the modules of the three gears are the same size. The planet gears can be held by a planet carrier.

The drive motor is preferably designed as an external rotor motor, wherein the rotor of the drive motor is fixedly connected to the sun gear. Thus, the invention is based on the idea that the main gear (sun gear, planetary gear and stationary ring gear) is provided with stepped planetary gears. Thus, the ratio of translation in the main transmission can be increased, which increases the overall efficiency of the transmission. Furthermore, the proposed concept builds - compared to the previously known solution - radially smaller.

The axially slightly larger design is irrelevant in many applications, for example, in actuators for a rear-wheel steering, since the electric motor builds longer here anyway. The proposed concept advantageously requires no additional bearing point, since - as in the conventional Wolfrom gear - there is only one common planetary web.

According to the proposed solution, an external rotor motor is used and this integrated directly into the transmission. So can be dispensed with a flanged solution. A heavy and expensive direct motor, which is considered as a drive solution is replaced with the present invention by a motor-gearbox combination. The proposed transmission concept allows a high ratio - preferably in the range of i = 40: 1 - which can be realized with minimal construction costs.

Both the required installation space and the efficiency of the transmission are optimized. Thus, there is a small and powerful drive concept.

The proposed transmission concept is suitable in a special way - but not exclusively - for use in an electromechanical actuator, which is required for example in a rear-wheel steering of a vehicle. In general, the use of the solution according to the invention is recommended wherever large torques have to be generated by small electric motors.

Brief description of the figures

In the figures, an embodiment of the invention is shown. Show it:

1 shows schematically the transmission concept of a Wolfrom transmission according to the prior art,

Fig. 2 shows schematically the transmission concept according to the present invention, the radial section through a structurally implemented gear arrangement according to an embodiment of the invention and

4 is a perspective view of the transmission arrangement according to FIG. 3. Detailed description of the figures

In Fig. 2, the schematic diagram of the transmission assembly 1 according to the invention is outlined. The only indicated here drive motor 2 drives directly the sun gear 3 with its external teeth 4. The sun gear 3 meshes with the planet gears 5, of which at least three are usually arranged around the circumference of the sun gear 3.

The planetary gears 5 are formed as stepped planets, ie they have three teeth 6 ', 6 "and 1 1, which are in three different levels Ei, E ₂ and E ₃ , each axially, ie offset in the direction of the axis a, offset from each other are.

As can further be seen, the three pitch diameters Di, D ₂ and D _{3 of} the three gears 6 ', 6 "and 1 1 are of different sizes The gear 6' has the largest pitch diameter D-, the gear 6" has a smaller pitch Pitch circle diameter D ₂ ; the smallest pitch circle diameter D ₃ has the teeth 1 1. As can be seen, lies in the plane E-, the sun gear 3 and the part of the planet gears 5, which has the teeth 6 '. Axially offset, namely arranged in the plane E ₂ , the part of the planet gears 5 with the teeth 6 "and the stationary arranged ring gear 7. Again axially offset thereto, namely arranged in the plane E ₃ , the portion of the planet gears 5 with the Gearing 1 1 and the internal teeth 10 of the output ring gear. 9

Depending on the choice of the pitch diameters Di, D ₂ and D ₃ in conjunction with the pitch diameters of the teeth 4 of the sun gear 3, the teeth 8 of the ring gear 7 and the teeth 10 of the output ring gear 9, the overall ratio of the gear assembly 1 results in high efficiency , One possibility of constructive implementation of the transmission concept according to FIG. 2 is shown in FIG. 3 and in FIG. 4 (FIG. 3 shows the gear arrangement according to FIG. 2 in a mirrored arrangement). The drive motor is designed as a permanently excited motor and consists of a stator 14 and a rotor driven by this 13. The rotor 13 is axially and rotatably connected to the sun gear 3. Axial next to the sun gear 3 is sufficient space for receiving other elements, such as an angular position sensor 15; Analogously, other engine control components can be accommodated.

The planet gears 5 are formed as a sleeve-shaped body having a base body, on the outer circumference of the three teeth 6 ', 6 "and 1 1 are incorporated (the teeth are not shown in detail) A planetary carrier 12 is not mandatory, however, it can also be used with cantilever planetary gears 5. It is not shown that the ring gear 7 is fixed in a housing element, not shown, the gear assembly Ring gear 7 is received on its outer cylindrical surface in a corresponding portion of the housing.

The internal teeth 10 in the output ring gear 9 can be incorporated directly into a hollow cylindrical portion of the output ring gear 9; but it is also just possible that a gear with the toothing 10 is made separately and then inserted into the output ring gear 9. LIST OF REFERENCE NUMBERS

1 gear arrangement

2 drive motor

3 sun wheel

4 external toothing

5 planetary gear

6 toothing

6 'toothing (first toothing of the planetary gear) 6' toothing (second toothing of the planetary gear)

7 ring gear

8 internal toothing

9 output ring gear

10 internal toothing

1 1 toothing (third toothing of the planetary gear)

12 planet carriers

13 rotor

14 stator

15 angular position sensor

Egg first level

E ₂ second level

E ₃ third plane Di pitch circle diameter

D ₂ pitch circle diameter

D ₃ pitch circle diameter a axis

Claims

claims

Transmission arrangement (1) comprising a sun gear (3) driven by a drive motor (2) about an axis (a) with external teeth (4), a number of planet gears (5) arranged radially outside the sun gear (3) and are provided with a toothing (6), with which they mesh with the outer toothing (4) of the sun gear (3), a stationary ring gear (7) with an internal toothing (8), wherein the planet wheels (5) with their toothing (6) with the internal toothing (8) of the ring gear (7) mesh, and about the axis (a) rotatably mounted output ring gear (9) with an internal toothing (10), wherein the planetary gears (5) with a toothing to their (6) axially offset arranged further teeth (1 1) are provided, which meshes with the internal toothing (10) of the output ring gear (9), characterized in that the planetary gears (5) with three teeth (6 ', 6 ", 1 1) are provided, which are each offset in the axial direction (a) to each other, wherein the first toothing (6 ') forms the meshing engagement between the sun gear (3) and the planetary gear (5) and lies in a first plane (Ei), wherein the second toothing (6 ") engages the meshing between stationary ring gear (7) and planet wheel (5 ) and lies in a second plane (E ₂ ), wherein the third toothing (1 1) forms the toothed engagement between output ring gear (9) and planetary gear (5) and in a third plane (E ₃ ), all three planes (Ei, E ₂ , E ₃ ) axially offset from each other are arranged.

Gear arrangement according to claim 1, characterized in that the first plane (Ei) between the second plane (E ₂ ) and the third plane (E ₃ ) is arranged.

Gear arrangement according to claim 1 or 2, characterized in that the planet wheels (5) consist of an integrally formed base body, in which the three toothings (6 ', 6 ", 1 1) are incorporated.

Gear arrangement according to one of claims 1 to 3, characterized in that the toothings (6 ', 6 ", 1 1) of the planetary gears (5) all have different pitch circle diameters (Di, D ₂ , D ₃ ).

Gear arrangement according to claim 4, characterized in that the pitch circle diameter (Di) of the first toothing (6 ') is greater than the pitch circle diameter (D ₂ ) of the second toothing (6 ").

Gear arrangement according to claim 4, characterized in that the pitch circle diameter (D ₃ ) of the third toothing (1 1) is smaller than the pitch circle diameter (Di) of the first toothing (6 ').

Gear arrangement according to claim 4, characterized in that the pitch circle diameter (D ₃ ) of the third toothing (1 1) is smaller than the pitch circle diameter (D ₂ ) of the second toothing (6 "). Gear arrangement according to one of claims 1 to 7, characterized in that the modules of the three toothings (6 ', 6 ", 1 1) are not all the same, wherein preferably the modules of the three toothings (6', 6", 1 1) all are different.

Gear arrangement according to one of claims 1 to 8, characterized in that the planet wheels (5) by a planet carrier (12) are held.

Gear arrangement according to one of claims 1 to 9, characterized in that the drive motor (2) is designed as an external rotor motor, wherein the rotor (13) of the drive motor (2) is fixedly connected to the sun gear (3).