Camshaft adjusting device

Abstract

A camshaft adjusting device having improved lubricant management including adjusting gearing for adjusting the angular position of a camshaft is proposed, the adjusting gearing having an input shaft, which can be coupled to a crankshaft, an output shaft, which can be coupled to the camshaft and an adjusting shaft, which can be coupled to an actuator. The adjusting gearing defines a rotational axis and the gearing forms a gearing interior, in which the input shaft, the output shaft and the adjusting shaft are operatively interconnected. The camshaft adjusting device has a lubricant supply for supplying the gearing interior with a lubricant and the lubricant supply is designed to form a lubricant sump in the gearing interior, the sump being radially outwards situated relative to the rotational axis.

Claims

1. A camshaft adjusting device, comprising: a variator, wherein the variator has an input shaft, arranged to be coupled to a crankshaft; an output shaft, arranged to be coupled to a camshaft; an adjusting shaft, arranged to be coupled to an actuator, wherein the variator forms an internal gear chamber, wherein the input shaft, the output shaft and the adjusting shaft are in operative connection with each other in the internal gear chamber; and, a lubricant supply unit for supplying the internal gear chamber with a lubricant; wherein: the lubricant supply unit forming a lubricant sump, which is arranged radially outside of an axis of rotation, in the internal gear chamber; the lubricant sump covers at least one rolling bearing point; and, the lubricant supply unit has a lubricant feed line and a lubricant discharge line, wherein the lubricant discharge line comprises a lubricant overflow, wherein a radial expansion of the lubricant sump is defined radially inwards by the lubricant overflow in such a way that an outer ring of a rolling bearing is arranged in a region of the lubricant sump; and an inner ring is arranged outside of the lubricant sump.

2. The camshaft adjusting device of claim 1, wherein the lubricant overflow is arranged as an outlet port out of the internal gear chamber.

3. The camshaft adjusting device of claim 1, wherein the lubricant discharge line has a lubricant outflow, wherein said lubricant outflow is arranged radially outside of the lubricant sump.

4. The camshaft adjusting device of claim 3, wherein a volumetric flow rate of the lubricant feed line is greater than a volumetric flow rate of the lubricant outflow, so that the lubricant sump is formed.

5. The camshaft adjusting device of claim 4, wherein a sum of mass flow rates of the lubricant outflow and the lubricant overflow is greater than or equal to the volumetric flow rate of the lubricant feed line, so that the lubricant sump is defined inwards in a radial direction by the lubricant overflow.

6. The camshaft adjusting device of claim 3, wherein the lubricant feed line includes a first radius, the lubricant outflow includes a second radius, and the lubricant overflow includes a third radius in relation to the axis of rotation, where the first radius is smaller than the third radius which is smaller than the second radius.

7. The camshaft adjusting device of claim 1, wherein the variator comprises a harmonic drive, wherein the harmonic drive includes the rolling bearing and a deformable steel bushing, which has external gear teeth and which is arranged on the rolling bearing, wherein the rolling bearing and/or the steel bushing is/are immersed at least in sections in the lubricant sump.

Description

DESCRIPTION OF THE DRAWINGS

(1) Additional features, advantages and effects of the invention will become apparent from the following description of preferred exemplary embodiments of the invention as well as the accompanying figures, in which:

(2) FIG. 1 is a schematic diagram of a camshaft adjusting device according to one exemplary embodiment of the invention;

(3) FIG. 2 is a cross-sectional view of the variator of the camshaft adjusting device in FIG. 1;

(4) FIG. 3 is the same view as in FIG. 2 the variator with a lubricant sump;

(5) FIG. 4 is an alternative embodiment of the variator in FIG. 2; and,

(6) FIG. 5 is a plan view of the variator in FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

(7) FIG. 1 shows in a diagrammatic representation a camshaft adjusting device 1 for an engine, in particular, an internal combustion engine of a vehicle, as a first exemplary embodiment of the invention. The camshaft adjusting device 1 comprises a camshaft 2, which has a plurality of cams 3, which are designed to actuate the valves of the engine.

(8) The drive of the camshaft 2 is provided by way of a drive gear 4, which is coupled to a crankshaft (not shown) of the engine by means of a chain, a belt or a transmission. A variator 5 is interposed between the drive gear 4 and the camshaft 2. Said variator allows an angular adjustment of the camshaft 2 to be effected in a controlled fashion relative to the drive gear 4 and, as a result, relative to the crankshaft (not shown). In order to control the variator 5, this variator is coupled to an electric motor 6 by means of a motor shaft 13, which is arranged so as to be stationary relative to the variator 5. That is, said motor shaft does not rotate along with said variator.

(9) The camshaft adjusting device 1 comprises a lubricant supply unit 7, which introduces, starting from an oil pan or more specifically an oil tank 8, transmission oil as a lubricant into the camshaft 2 through a motor oil pump 9 and optionally a motor oil filter 10 by means of a rotary transmitter (not shown) for oil. The lubricant is fed through a lubricant feed line 11 from the camshaft 2 into the variator 5, in order to lubricate the variator 5 and is then discharged again from the variator 5 through a lubricant discharge line 12, so that the lubricant supply unit 7 is designed as a lubricant circuit.

(10) FIG. 2 shows the variator 5 in a cross-sectional view taken along an axis of rotation D, which is defined, for example, by the camshaft 2 or the motor shaft 13 (FIG. 1).

(11) The variator 5 is also designed as a so-called wave gear (also called a harmonic drive gear). The wave gear 5 is also referred to as an ellipto-centric gear or in English a strain wave gear (SWG). The variator 5 has an input shaft 14, which is coupled in a torsion proof manner to the drive gear 4 or is formed by this drive gear. Furthermore, the variator 5 has an output shaft 15, which is connected to the camshaft 2 in a torsion proof manner. In contrast, an adjusting shaft 16 is connected to the motor shaft 13 in a torsion proof manner. The adjusting shaft 16 has a generator section 17, which has a cross section that is perpendicular to the axis of rotation D and which is designed so as to be not round, in particular, is designed to be elliptical. A rolling bearing 18 is disposed on said generator section in such a way that the inner ring 19 of the rolling bearing 18 rests on a shell surface of the generator section 17; and the outer ring 20 bears a deformable, cylindrical steel bushing 21 with external gear teeth. The steel bushing 21 is also referred to as a flex spline. The steel bushing 21 is designed with a cross section, which is perpendicular to the axis of rotation D, and is designed elliptical as well.

(12) The input shaft 14 bears internal gear teeth 22, which mesh with the external gear teeth of the steel bushing 21. Even the output shaft 15 bears internal gear teeth 23, which also mesh with the external gear teeth of the steel bushing 21. By rotating the adjusting shaft 16 at an angular velocity that is different from the angular velocity of the input shaft 14 it is possible to adjust the input shaft 14 and the output shaft 15 in terms of the angular position to each other. Such a harmonic drive gear is also described, for example, in the publication DE 10 2005 018 956 A1.

(13) The input shaft 14, the output shaft 15 and the adjusting shaft 16 come into operative connection in an interaction region 28 in a radius RG by means of the internal gear teeth 22, 23 and the external gear teeth of the steel bushing 21. In addition, the variator 5 has a sliding bearing section 24 in a radius RL between a carrier of the internal gear teeth 23 of the output shaft 15 and the input shaft 14.

(14) The variator 5 forms an internal gear chamber 25, which is formed by the input shaft 14, on the one hand, by a supporting member 26 and, on the other hand, by a cover 27, where in this case the rolling bearing 18 and the interaction region 28 of the external gear teeth of the steel bushing 21 and the internal gear teeth 22 and 23 are disposed in the internal gear chamber 25 of the sliding bearing section 24.

(15) The lubricant feed line 11 comprises one or more axially oriented outlet ports 29, which are arranged on an end face S of the output shaft 15 at a distance RZ from the axis of rotation D. The outlet ports 29 are supplied with lubricant through the channels in the camshaft 2. In the normal operating mode the lubricant issues from the outlet ports 29 and is distributed in the internal gear chamber due to the rotation of the output shaft 15, where in this case the end face S acts as a lubricant guide surface. The lubricant is fed through the outlet ports 29 into the internal gear chamber 25.

(16) The lubricant discharge line 12 is divided into a lubricant outflow 30 and a lubricant overflow 31. The lubricant outflow 30 is located at a distance RA from the axis of rotation D. The lubricant overflow 31 is disposed at a distance RU from the axis of rotation D.

(17) The outlet ports 29, the lubricant outflow 30 and the lubricant overflow 31 as well as the distances RA, RZ and RU are dimensioned in such a way that a lubricant sump 32 is formed in the internal gear chamber 25, as is shown in a highly schematic form in FIG. 3, superimposed on the cross sectional view of the variator 5. It can be seen that the lubricant sump 32 extends from the radial outer side of the internal gear chamber 25 up to a radially outer edge of the lubricant overflow 31. The sliding bearing section 24 as well as the interaction region 28 of the internal gear teeth 22, 23 and the external gear teeth of the steel bushing 21 and the outer ring 20 of the rolling bearing 18 are disposed in this region of the lubricant sump 32. Thus, by generating the lubricant sump 32 it is ensured that both the sliding bearing section 24 and the interaction region 28 are supplied with sufficient lubricant. In contrast, the inner ring 18 is arranged outside of the lubricant sump 32, in order to avoid unnecessary churning of the lubricant.

(18) If the volumetric flow rates of the lubricant supply unit 7 are taken into consideration, then the volumetric flow rate QZ of the lubricant feed line 11 is adjusted by the configuration of the outlet ports 29 and other flow-relevant components in such a way that said volumetric flow rate is always less than or equal to the volumetric flow rate of the lubricant discharge line 12 that is made up of the volumetric flow rate QA of the lubricant outflow 30 and the volumetric flow rate QU of the lubricant overflow 31.

(19) In particular, it is provided that the volumetric flow rate QA of the lubricant outflow 30 is less than the volumetric flow rate QZ of the lubricant feed line 11. In this way it is ensured in the normal operating mode that, first, the lubricant sump 32 is filled until it reaches the radially outer edge of the lubricant outflow 30 and then flows out with certainty, so that an overflow of the internal gear chamber 25 is prevented. This arrangement achieves the objective that when the variator 5 is running, the radial expansion of the lubricant sump 32 is always constant, irrespective of the angular velocity of the input shaft 14.

(20) FIG. 4 shows an additional exemplary embodiment of the variator 5, where, in contrast to the exemplary embodiment in the preceding figures, the lubricant outflow 30 is divided into two different axial outflow ports, with one of the outflow ports being disposed in the supporting member 26 and the other outflow port being disposed in the cover 27. The flow of the lubricant is indicated in schematic form by the arrows.

(21) FIG. 5 shows a plan view of the variator 5, in order to illustrate the external ports of the lubricant discharge line 12. The lubricant outflows 30, which are provided as passage ports out of the internal gear chamber 25, for example, into a chain case of the motor, can be seen in the circumferential direction. An intermediate angle beta is provided in each instance between the passage ports of the lubricant outflows, so that the internal gear chamber 25 may idle when the variator 5 is shut down. In contrast, the lubricant overflow 31 is designed as an annular gap between the cover 27 and a circular collar of the generator section 17.

(22) The variables of the variator 5 satisfy preferably at least one condition or any selection of the following conditions or all of the following conditions: RZ<RU<RA. RA≧1.00*RG and/or RA≧1.00*RL, in particular, RA≧1.05*RG and/or RA≧1.05*RL. QZ>QA, preferably 0.9*QZ>QA. The total area AA of the ports of the lubricant outflow 30 is less than the total area of the AZ of the outlet ports 29 of the lubricant feed line 11, in particular, AA≦0.9*AZ holds true. The total area AU of the ports of the lubricant overflow 31 is greater than the total area of the AZ of the outlet ports 29 of the lubricant feed line 11, in particular, AU≧2.0*AZ holds true. QU>QZ−QA, where QZ=QA+QU holds true. Ri≧1.0*RU, preferably Ri≦0.9*RU.

LIST OF REFERENCE NUMERALS

(23) TABLE-US-00001 1 camshaft adjusting device 2 camshaft 3 cam 4 drive gear 5 variator 6 electric motor 7 lubricant supply unit 8 oil tank 9 motor oil pump 10 motor oil filter 11 lubricant feed line 12 lubricant discharge line 13 motor shaft 14 input shaft 15 output shaft 16 adjusting shaft 17 generator section 18 rolling bearing 19 inner ring 20 outer ring 21 steel bushing 22 internal gear teeth 23 internal gear teeth 24 sliding bearing section 25 internal gear chamber 26 supporting member 27 cover 28 interaction region 29 axially oriented outlet ports 30 lubricant outflow 31 lubricant overflow 32 lubricant sump D axis of rotation QA, QU, QZ volumetric flow rates RA, RZ, RO, RG, RL radii AA, AZ, AU total areas