DE102011004077A1 - Harmonic drive used as electromechanical camshaft phaser for three-wave system, has wave generator having ring with elliptical outer periphery mounted on outer periphery of bearing, and axial spacing is formed between ring gears - Google Patents

Abstract

The harmonic drive has a primary ring gear (01) with internal tooth (02), and secondary ring gear (03) with internal tooth (04). An axial spacing (05) is formed between primary and secondary ring gears. A flexible spur gear with external teeth is arranged within primary ring, and spur gear within wave generator is arranged to bend in radial direction of spur gear. The wave generator has a ring with elliptical outer periphery mounted on the outer periphery of bearing that is elliptically deformed. The axial spacing between primary and secondary ring gears is 0.2 mm to 4 mm.

Description

The invention relates to a wave gear according to the preamble of the appended claim 1.

Wave gears are known from the prior art, this is for example on the DE 102 22 695 A1 directed. Shaft gears normally include a cylindrical rigid ring with an internal toothing or alternatively also two cylindrical rigid rings with an internal toothing, a flexible externally toothed gear, which is arranged inside the rigid ring gear, and a wave generator, which is fitted in the interior of the flexible gear , The wave generator is constituted by a rigid wave gear insert having an elliptical outline and a wave gear bearing fitted on an outer circumferential surface of the wave gear insert, so that the flexible gear is bent into an elliptical shape and the outside teeth thereof is bent at both ends of the major axis of the ellipse shape , meshes with the internal teeth of the rigid gear. When the wave generator is rotated by a motor or the like, the meshing parts of the two gears move in the circumferential direction. Since there is a difference in the number of teeth between the external gear and the internal gear, relative rotation occurs between the gears according to the difference in the number of teeth. Typically, the difference in the number of teeth is two.

Corrugated gearboxes are subdivided according to their design into pot gearboxes and sleeve gears or flat gears. When Topfgetriebe the flexible gear is designed in a pot shape, the bottom is flanged to the output shaft. The translating ring gear is used as a flange for connection to the periphery. In the case of the sleeve gear, the flexible gear is designed in a ring shape. There are two ring gears used, a gear and a clutch gear, wherein the clutch gear has the same number of teeth of the flexible gear and the transmission gear has more teeth than the flexible gear. With rapid rotation of the wave generator with low torque creates a relative rotation of the two ring gears. Between the ring gears, the reduced speed and the high torque can be tapped. The flat gear is often used in camshaft drives.

Shaft drives can be used as electromechanical phasing or camshaft adjuster in 3-shaft systems. The shaft system is connected via the drive shaft, z. B. camshaft sprocket, the drive power supplied, which via the output shaft, z. B. camshaft, is discharged again. Serving as an actuator phaser is arranged as a link between the drive shaft and the shaft to be driven in the power flow. This allows a third wave, the adjusting shaft, superimposed on the drive power additionally inject mechanical power into the shaft system or remove it. As a result, the predetermined by the drive shaft movement function can be changed to the output shaft, z. B., a phase offset can be realized. As actuators in such three-shaft systems are often electric motors for adjusting the adjusting used. However, it is also possible to use electrical, mechanical or hydraulic brakes, rotary or linear electromagnets, solenoid valves or linear motors or actuators to enable the phase adjustment.

In order to protect the periphery in the event of control errors of the actuators from undesired collisions of components, the adjustment range or drive range is usually restricted by the limitation of the angle of rotation of one of the three shafts relative to a second shaft or relative to the housing. For this purpose, a mechanical stop is used as an integral part of the device. The stop can be arranged between the input and output shafts, between the drive and adjusting shaft or between the output and the adjusting shaft. The stop is realized in the known state of the art usually between the output shaft and drive unit. The limitation of the output angle is done in the prior art always just between two transmission shafts, never twice, ie between the output and drive and between the adjusting and drive or between the adjusting and output.

Furthermore, wave gear can also be used in 2-shaft arrangements of a 3-shaft gear in adjusting drives. Here, they are primarily used as reduction devices for actuators in the automotive sector and in industrial applications. Reduction devices are used to convert a high-speed, low-load drive power of an actuator into a low-speed, high-load output. Only power is transferred between the adjusting shaft and the output shaft. The third shaft of the gearbox is fixed to the housing. The angle of the output shaft can be more than 360 °.

In order to protect the peripherals against collisions of components in the event of control errors of the actuators, the output rotation angle can in turn be limited by a mechanical limitation. Of the Stop can be formed between the adjusting and driven shaft, between the output shaft and the housing or between adjusting or drive shaft and housing. The stop is usually realized between the output shaft and the housing. It can also be exclusively or additionally control-side limitations of the adjustment made. Here, the path of the output shaft is primarily determined by the travel of the drive or adjusting shaft defined by the controller. The attack then only serves to safeguard fail-safe states.

As just described, the Verstellbereichsbegrenzung usually takes place between the input and output shaft and between the output shaft and the housing of the device. The adjustment shaft, which is not limited directly in the adjustment angle or drive angle, is braked via the transmission kinematics and the rigidity of the transmission elements as soon as the output side reaches the limit of the rotation angle. In the prior art, no measures are defined which attenuate occurring impulse loads in the effect of reaching the stop in the actuator. As a result of high loads, gear members can deform so much that they collide with each other and cause the actuator to jam. Furthermore, gear parts can tire early or must be oversized for normal operation to endure the high loads in the unbraked stop. This condition can also occur if, outside of a possibly existing stop, the controller is abruptly decelerated by the controller or due to a collision (stop outside the system).

As already described, two ring gears are used in the corrugated transmission in sleeve design, wherein in the 3-shaft arrangements, a first ring gear is connected to a drive unit and a second ring gear is connected to the output unit. In the 2-shaft arrangements, the first ring gear is fixed to the housing and the second ring gear in turn connected to the output unit. The two Holräder are arranged spaced from each other. The axial distance between the ring gears should be as small as possible. Too large a distance between the ring gears results in a higher tangential bending and twist in the flexible spur gear. The toothed spur gears - first ring gear and spur gear - second ring gear move away in this case from inside to outside increasingly relative to each other. This can lead to interference in the lateral edge areas. In order to prevent these negative effects, therefore, as far as possible a minimum distance between the ring gears should be realized. However, if the distance is too small, problems may arise with the lubricating oil supply of the wave gear, since there may not be sufficient plenums for the lubricating oil.

The subject of the lubricating oil supply of variable speed drives is exemplified in the DE 10 2005 059 841 A1 directed. The lubrication oil supply of variators can be done, among other things by dripping, spray nozzles, oil mist or a central bore. Regardless of the type of feed, the 01 is distributed in the interior of the variable by the centrifugal force or by gravity.

The object of the present invention is therefore to provide an improved wave gear available, with which a sufficiently rigid support of the teeth can be ensured to prevent or minimize occurring under load twists of the flexible spur gear, thereby preventing deviations in the tooth contact or ., which protects the gear parts from overloads and prevents jamming or damage to the gear parts as far as possible. Furthermore, in the improved wave gear sufficient collecting spaces for the provision of the amount of lubricant required for lubricating the wave gear available.

To achieve the object of the invention, a harmonic drive according to the appended claim 1 is used.

The corrugated transmission according to the invention is characterized in that the axial distance between the first and second ring gear is 0.2 mm to 4 mm. By such a selected distance between the ring gears a sufficiently large lubrication gap is present to ensure optimum supply of the toothing of the corrugated transmission with lubricant. At the same time an optimal radial and tangential support of the teeth can be ensured. In this way, the intervention disturbances possibly occurring at too large a distance of the ring gears can be effectively avoided. Due to the seized stiff support of the teeth twisting of the flexible spur gear, which can lead to evasion of corresponding teeth and thus for clamping of transmission parts and over-snap, can be prevented.

According to an advantageous embodiment, the axial distance between the first and second ring gear is 1 mm to 4 mm. Even more favorable has an axial distance between the first and second Ring gear from 0.5 mm to 2 mm proved. In a particularly preferred embodiment, an axial distance between the first and second ring gear of 0.2 mm to 1 mm is selected. With this last-mentioned distance range, the compromise between sufficiently rigid support of the toothing and the provision of sufficiently large collecting chambers for the provision of the lubricant quantity required for lubrication can be achieved particularly well.

In an advantageous embodiment, the axial contact surfaces of the first and second ring gear recesses. Through these recesses a lubricant passage to the wave generator storage is facilitated. Alternatively, in other embodiments, the axial abutment surfaces of the first and / or second ring gear may have an axial waviness. Due to the waviness of the contact surfaces, the lubricant passage to the wave generator storage can also be facilitated. Due to the presence of the recesses or the wavy designed contact surfaces a good lubricant passage is ensured, even if there is no axial distance between the ring gears substantially due to axial forces between the two ring gears.

However, in order to ensure a sufficiently large lubricant passage without the recesses or the waviness, the functional clearance of the sliding bearing used in a preferred embodiment between the first and second ring gear should be designed within certain limits. The lower limit ensures sufficient lubricant passage. The upper limit of the functional games ensures that the position of the two ring gears to each other or the flexible spur does not deviate too much. Too large a deviation can lead to the above-mentioned interference interferences and deformations of the flexible spur gear. A thrust bearing clearance sLa and a radial bearing clearance sLr of at least 0.1 mm and a maximum of 0.2 mm has proved favorable. In connection with the function plays on the 4 and the related description.

In alternative embodiments, a rolling bearing can be used for storage between the first and second ring gear. The lubricant passage is ensured by the gaps between the rolling elements.

In order to prevent the axial lubrication gap from being pulled out of the chain (pulling means) or the camshaft as a result of an axially acting force, in a further advantageous embodiment a minimal tilting is generated by a correspondingly positioned drive wheel relative to the center plane of the sliding bearing. For the drive wheel, an offset pk between BL · 0.1 and BL · 1 has proved favorable in this connection (see 6 ). The limitation of the maximum offset to the top is to ensure that the position and angle deviations of the two ring gears to each other or to the flexible spur not deviate too much.

The limitation of the tilt is determined by the design. The design should be selected such that the tilt angle between the input and output unit is limited by sole contact in the radial bearing and / or by combined contact / support in the radial bearing and thrust bearing.

Further advantages, details and developments of the invention will become apparent from the following description of preferred embodiments, with reference to the drawing. Show it:

1 a simplified sectional view of a first and second ring gear of a wave gear according to the prior art;

2 a simplified sectional view of a first and second ring gear of a wave gear according to the invention;

3 a ring gear with recesses in the axial contact surfaces in perspective view;

4 an inventive wave gear with plain bearing between the first and second ring gear in a first embodiment;

5 : the wave gear according to 4 with tilted drive unit;

6 : the wave gear according to the invention with sliding bearing between the first and second ring gear in a second embodiment;

7 : the corrugated transmission according to the invention 6 with tilted drive unit.

1 shows a simplified representation of a first and second ring gear of a wave gear according to the prior art. The wave gear comprises a first ring gear 01 with an internal toothing 02 and a coaxial with the first ring gear arranged second ring gear 03 with an internal toothing 04 , Between the first and second ring gear 01 . 03 is an axial distance 05 available. At the in 1 contained, known arrangement, this distance 05 chosen relatively large, usually greater than 4 mm. The distance 05 is chosen so large in the known solutions to provide a large plenum for the provision of the required amount of lubricant available. A major disadvantage of this large distance is that the teeth between the two ring gears 01 . 03 As a result, tangentially are not clamped. The wave gear is thereby too yielding, which can lead to unwanted twists in the flexible spur gear of the wave gear.

2 shows a simplified representation of a first and second ring gear of a wave gear according to the invention. In the wave gear according to the invention, the axial distance 05 between the first and second ring gear 01 . 03 much lower than in the known from the prior art solutions (see 1 ). The axial distance 05 between the first and second ring gear 01 . 03 is 0.2 mm to 4 mm. As advantageous has an axial distance 05 between 1 mm and 4 mm. Even more advantageous is an axial distance 05 between 0.5 mm and 2 mm. The most advantageous is an axial distance 05 from 0.2 mm to 1 mm. By choosing an axial distance 05 in the aforementioned limits, the teeth are supported sufficiently rigid, which among other things, unwanted twists of the flexible spur gear of the wave gear can be effectively avoided. At the same time, the axial distance 05 however, large enough to provide sufficient plenums to provide the required amount of lubricant.

3 shows the ring gear 01 . 03 with recesses in the axial contact surfaces. The axial contact surfaces of the first and second ring gear 01 . 03 may recesses according to a preferred embodiment 06 exhibit. Through these recesses 06 Lubricating the passage to the Wellgeneratorlager is facilitated. In other embodiments, instead of the recesses 06 a wavy design of the axial contact surfaces are made. The wavy design fulfills the same purpose as the recesses 06 and also facilitates lubricant passage to the wave generator bearing.

4 shows a corrugated transmission according to the invention with a sliding bearing between the first and second ring gear in a first embodiment. In this embodiment, the functional clearance of the sliding bearing is designed within certain limits, on the one hand to ensure the supply of lubricant and on the other hand, an excessive deviation of the position of the two ring gears 01 . 03 to avoid each other or to the flexible spur gear. The function games are defined as follows: axial clearance: sLa = BL - bl 0.0005 · DL ≤ sLa ≤ 0.004 · DL where sLa is at least 0.01 mm and at most 0.2 mm Radial clearance: sLr = DL -dl 0.0005 · DL ≤ sLr ≤ 0.002 · DL where sLr is at least 0.01 mm and at most 0.2 mm

5 shows the harmonic drive according to 4 with displaced drive unit. In the embodiment shown here is the with the first ring gear 01 related drive unit 08 for example, by the action of one of a drive wheel 09 applied force F shifted. As a result, closes the axial lubrication gap, which could result in problems in the lubricant supply.

To remedy this, will be at the in 6 shown embodiment, a minimal tilting of the drive unit 08 by a correspondingly positioned drive wheel 09 realized. For the drive wheel 08 an offset pk between BL · 0.1 and BL · 1 with respect to the symmetry position SL of the between the first and second ring gear 01 . 03 arranged plain bearing proved to be favorable.

7 shows the harmonic drive according to 6 with tilted drive unit. The tilting of the drive unit 08 is bounded by the bases A, B. The illustration shows that an axial lubrication gap is still available.

LIST OF REFERENCE NUMBERS

01

first ring gear

02

Internal toothing of the first ring gear

03

second ring gear

04

Internal toothing of the second ring gear

05

axial distance between the ring gears

06

Recesses in the contact surface

07

08

drive unit

09

drive wheel

A,

B bases

SL

Symmetry line slide bearing

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10222695 A1 [0002]
• DE 102005059841 A1 [0010]

Claims (10)

Wave gear with a first ring gear ( 01 ) with an internal toothing ( 02 ), coaxial with the first ring gear ( 01 ) arranged second ring gear ( 03 ) with an internal toothing ( 04 ), wherein between the first and second ring gear ( 01 . 03 ) an axial distance ( 05 ) is present, at least partially within the first ring gear ( 01 ) arranged, flexible spur gear with an external toothing and a corrugated generator disposed within the spur gear for bending the spur gear in the radial direction, wherein between the first ring gear ( 01 ), second wheel ( 03 ) and spur gear at two opposite points of the spur gear, a torque transmitting connection is made, wherein the wave generator comprises an elliptical outer circumference ring and an elliptically deformed bearing mounted on the outer circumference, characterized in that the axial distance ( 05 ) between the first and second ring gear ( 01 . 03 ) Is 0.2 mm to 4 mm. Wave gear according to claim 1, characterized in that the axial distance ( 05 ) between the first and second ring gear ( 01 . 03 ) Is 1 mm to 4 mm. Wave gear according to claim 1, characterized in that the axial distance ( 05 ) between the first and second ring gear ( 01 . 03 ) Is 0.5 mm to 2 mm. Wave gear according to claim 1, characterized in that the axial distance ( 05 ) between the first and second ring gear ( 01 . 03 ) Is 0.2 mm to 1 mm. Wave gear according to one of claims 1 to 4, characterized in that the axial contact surfaces of the first and / or second ring gear ( 01 . 03 ) Recesses ( 06 ) exhibit. Wave gear according to one of claims 1 to 4, characterized in that the axial contact surfaces of the first and / or second ring gear ( 01 . 03 ) have an axial waviness. Wave gear according to one of claims 1 to 6, characterized in that the first ring gear ( 01 ) via a sliding bearing on the second ring gear ( 03 ) is stored. Wave gear according to claim 7, characterized in that the axial bearing clearance of the sliding bearing is 0.0005 · DL ≤ sLa ≤ 0.004 · DL and / or that the radial bearing clearance is 0.0005 · DL ≤ sLr ≤ 0.002 · DL. Wave gear according to claim 7 or 8, characterized in that with the first ring gear ( 01 ) a drive wheel ( 09 ) and that an offset between the median plane of the drive wheel ( 09 ) and the median plane of the sliding bearing. Wave gear according to one of claims 7 to 9, characterized in that the sliding bearing at least one capillary connection for the lubricant supply between the axial end faces and the radial outer surfaces of the corresponding surfaces of the first and second ring gear ( 01 . 03 ) having.

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