Control drive with electric motor and planetary gear mechanism

1. Field of the Invention

The invention concerns a control drive, consisting of an electric motor and a planetary gear mechanism, comprising a ring gear, a planet carrier and several planet gears mounted on the planet carrier, the planet gears each having a front surface in the assembly direction F in the region of their external teeth, and the ring gear having, in the region of its internal teeth, several angle areas assigned to the planet gears of the end opposite the assembly direction F in a defined angle position of the planet carrier to ring gear.

2. Description of Related Art

A generic control drive is described in DE 197 29 988 C1, in which the angle areas of the end opposite the assembly direction are arranged in a single plane and the ends of the planet gears in front in the assembly direction are also arranged in a single plane, so that the individual spacings between the ends of the planet gears and the angle areas of the ring gear are the same in each assembly step, and also in the final assembly position. This geometric arrangement is problematical at the moment of assembly, in which the teeth of the three planet gears simultaneously engage with the teeth of the ring gear. Joining problems frequently occur here, because the angle position of the planet gears to each other and to the ring gear are not automatically aligned correctly. This leads at least to a reduction of assembly speed. Additionally, damage to the teeth can also occur.

The object of the present invention is therefore to ensure in a generic control drive that an economical and rapid assembly of the three planet gears in the ring gear is possible without increasing the manufacturing expense and assembly time, in which case only slight changes to the existing shapes are necessary.

This task is accomplished according to the present invention in that the axial spacing (A 1 ) between the front surface ( 7 a ) of the first planet gear ( 6 a ) and the first angle area ( 8 a ) of the ring gear ( 4 ) assigned to it differs from the axial spacing (A 2 ) between the front surface ( 7 b ) of the second planet gear ( 6 b ) and the second angle area ( 8 b ) of the ring gear ( 4 ) assigned to it. Through this arrangement, the individual planet gears enter the assembly-critical tooth area of the ring gear independently of each other during the time of assembly, so that easier self-alignment of the planet gears is possible. This increases the assembly speed and reduces the frequency of errors during assembly. The invention can be applied to planetary gear mechanisms with two or more planet gears in the same gear stage.

When three planet gears are used in the same gear stage, it is prescribed that the axial spacing (A 2 ) between the front surface ( 7 a ) of the second planet gear ( 6 a ) and the second angle area ( 8 a ) of ring gear ( 4 ) assigned to it differs from the axial spacing (A 3 ) between the front surface ( 7 b ) of the third planet gear ( 6 b ) and the third angle area ( 8 b ) of ring gear ( 4 ) assigned to it and the axial spacing (A 1 ) between the front surface ( 7 c ) of the first planet gear ( 6 c ) and the angle area ( 8 c ) of the ring gear ( 4 ) assigned to it.

In order to reliably accomplish the previously described task, it is important that the differences in spacings (A 1 , A 2 , A 3 ) are greater than the axial displacements of the engagement edges 23 of the planet gears and the engagement edges 22 of the ring gear possibly through unavoidable tolerances, so that during assembly of the planet gears ( 6 a , 6 b , 6 c ), only one planet gear ( 6 a , 6 b , 6 c ) can reach the beginning of an engagement area between planet gears ( 6 a , 6 b , 6 c ) and ring gear ( 4 ). Ordinarily during assembly, angle inaccuracies can occur leading to there being slight play among the gears. Manufacturing tolerances are also always present. These influences add up to a calculable dimension that must absolutely be maintained, in order to achieve the mentioned advantages.

Specific embodiments of the invention are further explained below by means of the drawing. In the drawing:

FIG. 1 shows a sectional view through a control drive according to the invention,

FIG. 2 shows an assembled planet carrier according to a first embodiment,

FIG. 3 shows a connector of a planet carrier according to a second embodiment,

FIG. 3 b shows an assembled planet carrier according to FIG. 3 a,

FIG. 4 shows a stylized sectional view of a third embodiment,

FIG. 5 a shows a three-dimensional depiction of a ring gear according to the fourth embodiment,

FIG. 5 b shows a three-dimensional depiction of the ring gear from FIG. 5 a from a different perspective,

FIG. 5 c shows a mounted planet carrier according to the third embodiment,

FIG. 6 a shows a partial sectional view of a planetary gear mechanism before assembly of the planet carrier,

FIG. 6 b shows a partial sectional view of the planetary gear mechanism in a first assembly phase,

FIG. 6 c shows a partial sectional view of the planetary gear mechanism in a second assembly phase,

FIG. 6 d shows a partial sectional view of the planetary gear mechanism in a third assembly phase, and

FIG. 6 e shows a partial sectional view of the planetary gear mechanism in the final assembled position.

In describing preferred embodiments of the present invention illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the invention is not intended to be limited to the specific terminology so selected, and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner to accomplish a similar purpose.

According to a first embodiment of the invention, the planet gears ( 6 a , 6 b , 6 c ) have different thicknesses in the axial direction. Time sequencing during assembly can therefore be achieved. However, a drawback is that different individual parts are necessary. In addition, this solution might lead to undesired noise at higher speeds, for which reason this embodiment is not preferred.

A second embodiment is characterized by the fact that the planet gears ( 6 a , 6 b , 6 c ) are mounted in different axial arrangements on the planet carrier ( 5 ), the planet gears having the same shape. Time decoupling of the engagement time of the planet gears is also achieved with this solution. Only one component must be changed, depending on the design of the planet carrier.

A drawback in the two embodiments just mentioned is also the axial mounting of the planet carrier in the installed state. This must occur on the planet carrier itself, because a contact surface in the ring gear or gear housing would require either an additional component or large axial play would have to be tolerated in at least two planet gears.

In order to implement the second embodiment, the planet carrier ( 5 ) has stud axles ( 10 a , 10 b , 10 c ), on which the planet gears ( 6 a , 6 b , 6 c ) are radially mounted, and the planet carrier ( 5 ) has stationary seat surfaces ( 11 a , 11 b , 11 c ), on which the planet gears ( 6 a , 6 b , 6 c ) are axially mounted, the stationary seat surfaces ( 11 a , 11 b , 11 c ) protruding axially to different extents. In a one-piece design of the planet carrier, for example, in a planet carrier originally made of plastic, these stationary seat surfaces can be produced without problem. In a planet carrier assembled from several individual parts, the advantages relative to the first embodiment can be lost.

In a third embodiment of the invention, it is proposed that the front surfaces ( 7 a , 7 b , 7 c ) of the planet gears ( 6 a , 6 b , 6 c ) be arranged in different axial positions in the assembled state, the planet gears ( 6 a , 6 b , 6 c ) having the same tooth width and stationary seat surfaces ( 15 a , 15 b , 15 c or 16 a , 16 b , 16 c ) axially protruding on both sides of the teeth of planet gears ( 6 a , 6 b , 6 c ) to different extents. The ring gears are designed in one piece with hubs or connected by press-fit, the ring gears being arranged axially offset to different extents relative to the hub. With the planet gears assembled, identical parts can be used and the desired geometry achieved merely by different press-fit heights.

For the first and third planet gears ( 6 a , 6 c ), they can be identically designed, being merely rotated by 180°, in order to achieve a different axial offset. The second planet gear ( 6 b ) differs from the first and third planet gears, but can be shaped symmetrically to a center plane and therefore mounted in both possible alignments.

The third embodiment makes it possible for the stationary seat surfaces ( 16 a , 16 b , 16 c ) of the side facing away from the planet carrier ( 5 ) to be arranged in the assembled state in connector one plane, on the one hand, and, on the other hand, for the stationary seat surfaces ( 15 a , 15 b , 15 c ) of the side facing the planet carrier to be arranged in one plane in the assembled state.

A fourth embodiment is particularly preferred, because the drawbacks of the previous embodiments can largely be avoided by it. In the fourth embodiment, it is proposed that none of the angle areas ( 8 a , 8 b , 8 c ) of the end ( 9 ) of ring gear ( 4 ) opposite the assembly direction (F) be part of a plane ( 12 a , 12 b , 12 c ), to which one of the other angle areas ( 8 a , 8 b , 8 c ) belongs, the planes ( 12 a , 12 b , 12 c ) being aligned parallel to each other and at right angles to the axis of symmetry of the control drive. The combinations among these three embodiments are also contemplated.

The following practical examples each show three planet gears per gear stage, and also only one gear stage, but the invention also includes planetary gear mechanisms with two, four or more planet gears per gear stage, and also multistage planetary gear mechanisms. The control drives can also include additional gear stages of other types of gears, like spur, worm or bevel gearing, and the motor axis need not be flush with the planetary gear mechanism axis.

FIG. 1 shows a sectional view through a control drive 1 , consisting of an electric motor 2 and a planetary gear mechanism 3 . The electric motor is a commutator motor with a housing canister 18 , a wound rotor 19 with a commutator 20 and a brush rocker that serves as an end bracket 13 . The planetary gear mechanism includes a ring gear 4 , a sun gear 14 , a planet carrier 5 and planet gears 6 a , 6 b , 6 c . The output of the planetary gear mechanism 3 in the present practical example is connected to a rack-and-pinion drive. The control drive serves as an EGR drive.

FIG. 2 shows an assembled planet carrier 5 according to a first embodiment, in which it is equipped with three planet gears 6 a , 6 b , 6 c of different widths. The faces 7 a , 7 b , 7 c of the respective planet gears 6 a , 6 b , 6 c lie in different planes parallel to each other, so that during assembly of the equipped planet carrier 5 , the planet gear 6 a initially, then 6 b and finally 6 c engage with the teeth of the ring gear in assembly direction F.

FIG. 3 a shows a planet carrier 5 of a second embodiment of the invention (without stud axle 10 ), in which the planet carrier has stationary seat surfaces 11 a , 11 b , 11 c , which consist of different parallel planes, i.e., the stationary seat surfaces protrude to different extents from the plane of the planet carrier (connector). The same planet carrier 5 is equipped with planet gears 6 a , 6 b , 6 c in FIG. 3 a . The planet gears have stationary seat surfaces 16 a , 16 b , 16 c facing away from the planet carrier. On the opposite side of the planet gears 6 a , 6 b , 6 c (concealed here), there are stationary seat surfaces 15 a , 15 b , 15 c , which face the stationary seat surfaces 11 a , 11 b , 11 c . The stationary seat surfaces 15 a , 15 b , 15 c and 16 a , 16 b , 16 c form the face surfaces of planet gear hubs 17 a , 17 b , 17 c . The width of the planet gears in the second practical example is the same and the planet gears 6 a , 6 b , 6 c are identically designed.

A third embodiment of the invention is shown in stylized fashion in FIG. 4 . A planet carrier 5 has stud axles 10 a , 10 b , 10 c , on which planet gears 6 a , 6 b , 6 c are mounted to rotate. The planet gears have hubs 17 a , 17 b , 17 c , whose front surfaces face the planet carrier 5 as stationary seat surfaces 15 a , 15 b , 15 c , and whose opposite front surfaces face away from planet carrier 5 and serve as stationary seat surfaces 16 a , 16 b , 16 c . The stationary seat surfaces 15 a , 15 b , 15 c , as well as 16 a , 16 b , 16 c , protrude to different extents and delimit the installation space of the planet gears 6 a , 6 b , 6 c . An axial bearing washer, which can be arranged in the ring gear or can also be a component of the planet carrier, serves as axial support and limitation for the planet gears 6 a , 6 b , 6 c . The planet gears 6 a , 6 b , 6 c can be designed with their hub 17 a , 17 b , 17 c in one piece as a plastic injection molded part. In this case at least two different die nests are required. Planet gear 6 a is identical to planet gear 6 c by rotation of 180°. Planet gear 6 b differs from planet gears 6 a and 6 c , but can be designed symmetrically. It is also conceivable that the hub is mounted in the planet gears and fastened by press-fitting. In this embodiment, identical parts can be used, which need only be mounted differently.

FIGS. 5 a and 5 b show a ring gear 4 from a different perspective. This ring gear is part of the fourth and preferred embodiment of the invention. Here the planet gears are designed identically and the end 9 of the ring gear is divided into three areas 8 a , 8 b , 8 c , each of which occupies about 120° of the periphery. The areas 8 a , 8 b , 8 c protrude to different extents from the end 9 of ring gear 4 .

FIGS. 6 a to 6 e show the assembly phases in succession during assembly of an equipped planet carrier 5 in ring gear 4 of the planetary gear mechanism. FIG. 6 a shows the assembly right before engagement of the first planet gear 6 a . The first planet gear 6 a in FIG. 6 b is already engaged with ring gear 4 and planet gear 6 b is right before engagement. The planet gear 6 b in FIG. 6 c is also already engaged with ring gear 4 and gear 6 c is still not engaged. Only in FIG. 6 d are all three planet gears 6 a , 6 b , 6 c engaged. The final position is reached in FIG. 6 d , in which the faces of planet gears 7 a , 7 b , 7 c have different spacings in the assembly direction A 1 , (A 2 ), A 3 to the corresponding angle areas 8 a , 8 b , 8 c of the end 9 of the ring gear.

Modifications and variations of the above-described embodiments of the present invention are possible, as appreciated by those skilled in the art in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims and their equivalents, the invention may be practiced otherwise than as specifically described and illustrated.

1 Control drive

2 Electric motor

3 Planetary gear mechanism

4 Ring gear

5 Planet carrier

6 Planet gears

7 Front surface

8 Angle area

9 End

10 Stud axle

11 Stationary seat surface of the planet carrier

12 Plane

13 End bracket

14 Sun gear

15 Stationary seat surface of planet gears (facing planet carrier)

16 Stationary seat surface of planet gears (facing away from planet carrier)

17 Hub

18 Housing canister

19 Rotor

20 Commutator

21 Axial bearing washer

22 Engagement edge

23 Engagement edge