Patent Application
20190153909
This disclosure relates to an actuating gear mechanism which can be used, in particular, in a motor vehicle and the housing of which has a cylindrical basic shape, wherein there is a rotation angle limiter between the housing and an output shaft that can be connected to an output element of the actuating gear mechanism.
DE 10 2004 038 681 A1 discloses an electric-motor camshaft adjuster in which there is a rotation angle limiter between an output flange and a stop washer. The rotation angle limitation is achieved through the interaction of a nose on the output flange with two stops on the stop washer. The gear mechanism of the known electric-motor camshaft adjuster can be designed as a swashplate mechanism or simple internal eccentric mechanism.
In a camshaft adjustment system known from DE 10 2008 039 008 A1, there is rotation angle limitation between a stop washer, which is connected to a camshaft, and a chain sprocket.
For rotation angle limitation, a transmission device which is disclosed in DE 10 2010 050 814 A1 and is likewise suitable for a camshaft adjuster has a plurality of noses, which each interact with stops on a pocket. In this case, those parts which can pivot relative to one another are provided with sliding support.
Further actuating gear mechanisms are disclosed by DE 10 2008 043 673 A1, DE 10 2006 028 554 A1 and US 2015/0033906 A1. DE 10 2011 004 070 A1 discloses a camshaft adjuster in which a first mechanical stop is provided between the input part and the output part, and a second mechanical stop is provided between the actuating element and either the input part or the output part. A device of this kind may solve the problem of jamming of the actuating element but is not of compact construction. In particular, it is not possible to dispense with a stop washer on the output side.
It is the underlying object of the disclosure to further develop an actuating gear mechanism which has a rotation angle limiter between an output shaft and a housing relative to the cited prior art in respect of a particularly compact, easy-to-manufacture construction.
According to the disclosure, this object is achieved by an actuating gear mechanism having the features described herein and illustrated in the Figures. This is an actuating gear mechanism that has a housing with a cylindrical basic shape. Connections to an actuating motor, on the one hand, and to an output shaft, on the other hand, are provided on the two ends of the housing. The output shaft to be connected to an output element of the actuating gear mechanism can be pivoted over only a limited angular range relative to the housing, wherein a rotation angle limiter provided for this purpose is arranged not on the output-side end but on the input-side end of the housing, which faces the actuating motor, i.e. facing away from the output shaft.
The initially paradoxical rotation angle limiter between the output shaft and the housing of the actuating gear mechanism on the end thereof facing away from the output shaft has the advantage that there is no need for any special stop element on the output side of the mechanism, and therefore the connection between the output element of the actuating gear mechanism and the output shaft can be of particularly space-saving configuration. Instead, the rotation angle limiter is relocated into the actuating gear mechanism, namely to the input-side end thereof.
The rotation angle limiter itself can be formed with parts that are present in the actuating gear mechanism in any case and have geometrical features known per se. The interaction between a nose or some other projection on a first part with flanks of recesses in a second part may be mentioned by way of example. As known, in principle, from the cited DE 10 2010 050 814 A1, for example, it is possible here for a plurality of pairs of stop contours to be distributed uniformly over the circumference of the parts that can be pivoted to a limited extent relative to one another. At least one of the parts that can be pivoted relative to one another is processed by means of machining methods, for example. This has the advantage that different maximum adjustment angles can be defined by means of different machining processes, based on starting components of identical geometry.
If a plurality of stops, at which stop contact takes place simultaneously, is provided for mechanical limitation of the adjustment range, the loads are distributed between the individual stops and the material thickness thereof can be reduced. Even more installation space is saved as a result. A gear mechanism of this kind is of axially compact construction if the stops are arranged offset relative to one another in the circumferential direction. They are preferably situated in the same axial plane.
In a development of the stops, these are arranged symmetrically in order to reduce the unbalance of the gear mechanism. If the gear mechanism has an unbalance owing to other components, arc-shaped recesses with two stop walls can be provided, only one of which is used as a mechanical adjustment angle limiter. The arc-shaped recess is “open” toward the other stop, with the result that no mechanical stop contact takes place here, the recess in the material serving instead for unbalance compensation, for example. Two or more arc-shaped recesses can then jointly delimit an adjustment range in both directions of rotation.
In one embodiment, a ring gear is provided as the output element of the actuating gear mechanism which is to be connected to the output shaft. This ring gear can be of single- or multi-part construction and preferably has a pot shape, wherein the pot base faces the output-side end. A cylindrical section of the pot-shaped ring gear is accordingly open toward the input-side end of the actuating gear mechanism, wherein the rotation angle limiter is preferably formed directly on that edge of the cylindrical section of the ring gear which faces the input-side end. In this case, the rotation angle limiter can be formed directly between the ring gear and the housing. As an alternative, the rotation angle limiter can be formed between the ring gear and a thrust washer connected in a fixed manner to the housing.
The housing as a whole can be provided as the input element of the actuating gear mechanism. For this purpose, the housing can have an external toothing, which interacts with a traction means, namely a chain or a toothed belt, or, as part of a gearwheel mechanism, with at least one further gearwheel, for example. It is likewise possible to implement embodiments in which the housing forms a non-rotatable machine element and is connected, for example, to an engine block of an internal combustion engine, namely a reciprocating-piston engine, or is an integral component of such an engine block.
Irrespective of whether the housing of the actuating gear mechanism is a rotatable or a non-rotatable machine part, the actuating gear mechanism is designed as a strain wave gear. By virtue of the principle involved, a strain wave gear has a flexible toothed transmission ring. The flexible transmission ring can be a flex spline, for example. A flexible, ring-shaped, toothed transmission ring without a flange or rim is referred to as a flex spline. As an alternative, the flexible transmission ring can have a pot shape. In one embodiment, the flexible transmission ring is a collared sleeve. In this case, a radially outward-oriented flange, also referred to as a collar, adjoins a cylindrical, toothed section of the transmission ring. The collar of the flexible transmission ring is preferably arranged on the input-side end of the housing, in front of the rotation angle limiter, i.e. is mounted in front of the rotation angle limiter. It is possible, in turn, for a cover to be mounted in front of the collar on the input-side end of the housing.
In respect of a possible geometrical configuration of a flexible gearwheel designed as a collared sleeve which is suitable for a strain wave gear, attention is drawn by way of example to EP 0 741 256 B1.
According to one possible embodiment, the actuating motor, in particular electric motor, which is provided for the adjustment of the actuating gear mechanism, is coupled by means of a compensating coupling to mechanism elements of the actuating gear mechanism. The compensating coupling, which is also referred to as an Oldham coupling, allows the compensation of a parallel misalignment and, to a small extent, also the compensation of angular errors, between the actuating motor and the actuating gear mechanism. The compensating coupling, or at least one Oldham disk as the core element of the compensating coupling, is preferably arranged axially between the rotation angle limiter and an external toothing on the flexible transmission ring.
The actuating gear mechanism is suitable both for stationary applications and for applications in vehicles. In particular, the actuating gear mechanism is suitable for use in an electric camshaft adjuster of an internal combustion engine or in a device for adjusting the compression ratio of a reciprocating piston engine.
An illustrative embodiment of the disclosure is explained in greater detail below with reference to a drawing, in which, in simplified form:
An actuating gear mechanism denoted overall by the reference character 1 is designed as a strain wave gear and is provided for use in an electric camshaft adjuster of an internal combustion engine. A substantially cylindrical housing 2 of the actuating gear mechanism 1 has an external toothing 3, which enables the housing 2 and hence the entire actuating gear mechanism 1 to be driven with the aid of a traction means (not shown), namely a chain or a toothed belt.
The housing 2 rotates in a manner known per se at half the speed of the crankshaft of the internal combustion engine.
An output element 4 of the actuating gear mechanism 1, which is arranged within the housing 2, is designed as a ring gear and is provided for connection to a camshaft (not shown), in particular an inlet camshaft, of the internal combustion engine.
In the illustrative embodiment shown, the output element 4 is a one-piece transmission ring, wherein a cylindrical, internally toothed section of the output element 4 is denoted by 5 and an end section adjoining the latter is denoted by 6. In the end section 6 there is a central opening 7, which is concentric with the rotational axis of the actuating gear mechanism 1 and hence also with the camshaft. Connecting elements by means of which the end section 6 of the output element 4 is connected to the camshaft are not shown in the figures.
The camshaft, referred to in general as the output shaft, which is connected in a fixed manner to the output element 4, can be pivoted to only a limited extent relative to the housing 2, which acts as an input element of the actuating gear mechanism 1. For this purpose, a rotation angle limiter 8 is formed which is arranged on the end of the housing 2 facing away from the output shaft. To distinguish it from the output-side end of the housing 2, the end on which the rotation angle limiter 8 is situated is referred to as the input-side end. A thrust washer 9, which forms a component of the rotation angle limiter 8, is connected in a fixed manner to the housing 2 on the input-side end. The additional component of the rotation angle limiter 8 is formed directly by the cylindrical section 5 of the output element 4, i.e. the ring gear.
An electric motor (not shown), which is provided as an actuating motor for actuating the actuating gear mechanism 1, is arranged on the first, input-side end of the actuating gear mechanism 1, that is on the left in the arrangement according to
Via the Oldham disk 11, the actuating motor drives an inner ring 12 of a wave generator 13. As long as the inner ring 12 rotates at the speed of the housing 2, the phase relation between the camshaft coupled to the output element 4 and the crankshaft of the internal combustion engine remains unchanged. The inner ring 12 of the wave generator 13 is intrinsically rigid and has an elliptical outer contour. Rolling elements, namely balls 14, rolling on the inner ring 12 are in contact with an outer ring 15, which is flexible and adapts continuously to the elliptical shape of the inner ring 12. The outer ring 15, in turn, is surrounded directly by a flexible transmission ring 16, namely a collared sleeve. The collared sleeve 16 has an external toothing 17, which meshes with an internal toothing of the cylindrical section 5 of the output element 4. Owing to the elliptical shape of the inner ring 12, the external toothing 17 of the flexible transmission ring 16 is in engagement with the internal toothing of the ring gear 4 only in two diametrically opposite circumferential regions. As the inner ring 12 is rotated, these engagement regions travel along the circumference of the two transmission rings 4, 16. A slight difference in the number of teeth of the external toothing 17, on the one hand, and the internal toothing of the ring gear 4, on the other hand, ensures that the ring gear 4 is turned slightly relative to the housing 2 for each full revolution of the inner ring 12. The actuating gear mechanism 1 designed as a strain wave gear thus forms a gear mechanism with a large reduction ratio.
Several full revolutions of the inner ring 12 are required to pivot the ring gear 4 from one stop position to the other stop position, which is in each case determined by the rotation angle limiter 8. On the first, input-side end of the housing 2, the rotation angle limiter 8 is directly adjacent to a collar 18 of the flexible transmission ring 16. The collar 18 of the flexible transmission ring 16, i.e. the collared sleeve, merges into a cylindrical section, denoted by 19, of the flexible transmission ring 16, on which the external toothing 17 is located. The entire flexible transmission ring 16, including the external toothing 17, is manufactured as a one-piece sheet-metal component. When viewed in the axial direction of the actuating gear mechanism 1, the Oldham disk 11 is situated between the rotation angle limiter 8 and the external toothing 17 of the collared sleeve 16. A cover 20, which—like the flexible transmission ring 16—has the shape of a cylindrical sleeve with an integrally formed flange, is mounted in front of the flexible transmission ring 16 on the input-side end of the housing 2. In the axial direction, i.e. the longitudinal direction of the central axis of the actuating gear mechanism 1, the cover 20 extends beyond the rotation angle limiter 8 as far as the Oldham disk 11 and ends with a radially inward-oriented rim 21 directly in front of the wave generator 13. By virtue of the overlap between various elements of the actuating gear mechanism 1 in the axial direction, in particular between the rotation angle limiter 8 and the flexible transmission ring 16, the actuating gear mechanism 1 is of very compact construction overall.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2016 209 362.2 | May 2016 | DE | national |
This application is the U.S. National Phase of PCT Application No. PCT/DE2017/100455 filed May 30, 2017 which claims priority to DE 102016209362.2 filed May 31, 2016.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/DE2017/100455 | 5/30/2017 | WO | 00 |
