WO2012110133A1

WO2012110133A1 - Harmonic drive with laterally guided spur gear

Info

Publication number: WO2012110133A1
Application number: PCT/EP2011/072081
Authority: WO
Inventors: Jens Schäfer; Mike Kohrs; Jeffrey S. BALKO
Original assignee: Schaeffler Technologies AG & Co. KG
Priority date: 2011-02-14
Filing date: 2011-12-07
Publication date: 2012-08-23
Also published as: DE102011004075A1

Abstract

The invention relates to a harmonic drive comprising at least one internally toothed ring gear (02, 04), an externally toothed flexible spur gear (06) mounted inside the ring gear (02, 04) and a wave generator (07), mounted inside the spur gear (06), for bending the spur gear (06) in the radial direction, a torque-transmitting connection being established between the ring gear (02, 04) and the spur gear (06) on two opposite locations of the spur gear (06), and the wave generator (07) having a ring with an elliptical outer circumference and an elliptically deformed bearing (08) attached to the outer circumference. The harmonic drive according to the invention is characterized in that the spur gear (06) is axially supported on each side by a cap (09, 10).

Description

Name of the invention

Corrugated gear with lateral guidance of the spur gear Description

The invention relates to a harmonic drive according to the preamble of the attached claim 1. Well gear are known from the prior art, this reference is made, for example, to DE 102 22 695 A1. Wellular gears usually 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 inserted into the interior of the flexible gear. fits. The wave generator is constituted by a rigid wave gear insert having an elliptical outline and a wave gear bearing fitted on an outer peripheral surface of the wave gear insert, so that the flexible gear is bent into an elliptical shape and the external teeth thereof are bent at both ends of the main axis is arranged in the elliptical 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. It is men 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 fast rotation of the wave generator with low torque, a relative rotation of the two ring gears occurs. 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 phase adjusters or camshaft adjusters in 3-shaft systems. The shaft system is supplied via the drive shaft, such as camshaft sprocket, the drive power, which is discharged via the output shaft, eg camshaft again. Serving as an actuator phase divider is seen as a link between the drive shaft and the shaft to be driven in the power flow. This allows, via a third shaft, the adjusting shaft, superimposed on the drive power, to additionally couple mechanical power into or out of the shaft system. As a result, the predetermined by the drive shaft movement function can be changed to the output shaft, for example, a phase offset can be realized. As actuators in such three-shaft systems are often electric motors for adjusting the adjusting used. But it is also possible to use electrical, mechanical or hydraulic brakes, rotary or linear-acting electromagnets, solenoid valves or linear motors or actuators to allow the Phasenver position.

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 generally limited by limiting 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 drive and output shafts, between the drive and adjusting shafts or between the output and the adjusting shafts. be net. 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 takes place in the prior art always just between two transmission shafts, never twice, so between the output and drive and between see adjusting shaft and drive or between the adjusting and output.

Furthermore, wave gear can be used in 2-shaft arrangements of a 3-shaft gear in Versteilantrieben. 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. The stop can be seen here between adjusting and output shaft, be formed between the output shaft and 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. In this case, the path of the output shaft is primarily determined by the actuating path defined by the control. Preset shaft specified. 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 gear elements as soon as the output side reaches the limit of the rotation angle. enough. 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, the principle of the wave gear is based on a thin-walled flexible spur gear, which can be ovalized by the wave generator circumferentially. The resulting in the wave gear on the flexible spur gear due to the operating or momentum load tooth forces cause in addition to the transverse thrust in the teeth also attributable to the elasticity of the spur gear, unwanted twisting of the spur gear. This twisting simplifies the avoidance of the corresponding teeth and thus the terminals or snapping over.

The object of the present invention is therefore to provide an improved wave gear, with which the twists of the flexible spur gear occurring under load are prevented or minimized, whereby deviations in the tooth contact are prevented or minimized, whereby the gear parts against overloads be better protected, and jamming or damage to the gear parts are largely prevented.

To achieve the object of the invention, a harmonic drive is used according to the appended claim 1. The corrugated transmission according to the invention is characterized in that the spur gear is axially supported on both sides by a respective cover. An essential advantage of the harmonic drive according to the invention is that by the additional axial support of the spur gear possibly occurring under load twisting of the spur gear can be avoided or minimized. Tilts of the spur gear or of the entire wave generator occurring due to operating cycles can be restricted by the narrow lateral guidance of the spur gear. As a result, a high torsional stiffness can be achieved.

In an advantageous embodiment, at least one of the lids is integral with the ring gear. This has manufacturing and assembly advantages, since fewer components are used. The other cover may also be part of the ring gear. Alternatively, a cover may be designed as a separate component or both covers as separate components. The inner contact surface of the cover to the spur gear may have interruptions on the circumference. For example, there may be formed ribs or recesses. In this way, the weight of the lid can be reduced, also the lubrication and Kühlmittelzu- and removal is facilitated. Furthermore, one or both lids can be laminar constructed of several part lids to achieve a separation of functions. For example, a thinner inner part cover, z. As steel or sintered steel, for wear protection and an outer part cover made of softer material, eg. As aluminum or plastic, are used. The partial covers may be additionally adhesively bonded to one another, for example. by welding or material / form-fitting z. B. be connected by punching packages.

According to an advantageous embodiment, the axial guide clearance of the spur gear between the covers is less than 2 mm. Even cheaper are designs with a guide clearance of less than 1, 5 mm. Embodiments with a guide play of less than 1 mm have proved to be particularly advantageous. To comply with the required leadership game manufacturing tolerances and the tolerance chains are to be limited accordingly. The guiding game can be positively supported by the additional measures described below in order to minimize them. Thus, the use of insertion discs between the covers and the ring gear has proved to be useful. In this case, insert discs can be used with different thickness, depending on the determined axial play the corresponding insertion discs are selected.

Furthermore, it is advantageous if at least one of the two covers has a shoulder or bulges on its side facing the spur gear. The bulges may in this case be circular, ring or rod-shaped, for example. The heel or the bulge immersed in the internal toothing of the ring gear and can compensate for the depth of the shoulder or the bulge according to the game.

According to an advantageous embodiment, the lids have a wall thickness of at least 0.7 mm. With covers designed in this way, the axial pressure rigidity required to support the spur gear can be realized. In this sense, the use of additional ribbing on the lids has proven to be beneficial. Alternatively, other additional radial and axial stiffeners can be attached. It is possible, for example, the attachment of collar on the inner and / or outer diameter of the lid. Furthermore, to achieve the required axial compressive rigidity, the lids can be manufactured as packetized lids consisting of several sheet metal layers. In this case, individual sheet metal layers may have recesses for weight reduction. Through the recesses and the Schmiermittelbzw. Coolant guide facilitates. The sheets are either loose or interconnected. In a further expedient embodiment, the covers have local material compaction or material consolidations. In this way, the axial compressive stiffness can also be positively influenced. It is advantageous if, in an advantageous embodiment, the spur gear has a width of> 5 mm. As even more favorable, a width of the spur gear of more than 8 mm has been found. Particularly preferred embodiments are those in which the spur gear is more than 10 mm wide. Due to these spur wheel widths, twisting of the spur gear within the gearing game in the region of the meshing engagement can additionally be made more difficult.

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 shows a longitudinal section of a wave gear according to the invention in a first embodiment;

2 shows a longitudinal section of the harmonic drive according to the invention in a second embodiment; Fig. 3: a lid with a paragraph;

Fig. 4: a lid with a collar on the inner diameter;

Fig. 5: sectional views of several lids in different designs.

Fig. 1 shows a longitudinal section of a wave gear according to the invention in a first embodiment. The corrugated transmission comprises a first ring gear 02, which is connected to a drive unit 01, with internal teeth, and a second ring gear 04, which is connected to an output unit 03, with internal teeth. First and second Holrad 02, 04 are arranged side by side. The selected embodiment is a 3- Shaft arrangement. Of course, 2-shaft arrangements are also possible. In 2-shaft arrangements, the first ring gear 02 is arranged fixed to the housing. A flexible spur gear 06 with external teeth is located inside the ring gears 02, 04.

Within the spur gear 06, a wave generator 07 is arranged. In the embodiment shown here, the wave generator 07 comprises a ring with an elliptical outer circumference and an elliptically deformed rolling bearing 08 mounted on the outer circumference. Instead of a rolling bearing, a plain bearing can also be used. By means of wave generator 07, the flexible spur gear 06 is bent in the radial direction. The elliptically deformed spur gear 06 engages with its external teeth in the regions of the two intersection points of the ellipse circumference with the main axis of the ellipse in the internal teeth of the first and second ring gears 02, 04, whereby a torque-transmitting connection is made.

The spur gear 06 should preferably have a width of more than 5 mm. Even more favorable is a spur wheel width of more than 8 mm. Particularly preferred are spur gears widths of more than 10 mm. With such executed spur gears 06, a twisting of the spur gear 06 within the teeth play in the field of meshing can be difficult.

The spur gear 06 is located between a first and a second cover 09, 10. The cover 09, 10 are used for axial support of the spur gear 06. The cover 09, 10 may be designed as separate components or be part of the gear members. In the embodiment shown here, the first cover 09 is designed as a separate component. The second cover 10 is part of the second ring gear 04. The entire axial guide clearance of the spur gear 06 between the covers 09, 10 should preferably be less than 2 mm. As even more favorable, an axial guide play of less than 1, 5 mm has been found. In particularly preferred embodiments, the axial guide clearance is less than 1 mm. To comply with the specified axial Leadership game is to pay special attention to the minimization of manufacturing tolerances.

In addition, various measures have proven useful in this context. Thus, for example, between the covers 09, 10 thin insertion discs are arranged. The use of a set of differently thick insertion wastes is particularly useful. Thus, depending on which axial guide play has been determined, correspondingly thick slices can be selected.

In the embodiment shown in Fig. 2, another way to comply with the axial guide clearance is shown. Here, in contrast to the embodiment shown in Fig. 1, the inside of the first cover 09 is not flat, but provided with a shoulder 12. A detailed representation of the thus executed first cover 09 can be seen in FIG. The shoulder 12 of the first cover 09 dips into the internal toothing of the first ring gear 02. As a result, the depth of the paragraph 12 can be compensated according to leadership game. Instead of a paragraph 12, the first cover 09 may also be provided with partial recesses. These deposits can be, for example, circular, ring-shaped or rod-shaped.

Due to the lateral support of the spur gear on the two covers 09, 10 increased demands on the axial compressive stiffness of the cover 09, 10 are to be made. Thus, the wall thickness of both lids 10 should preferably be at least 0.7 mm. In this context, it is also beneficial to additional ribs or other radial and axial stiffeners to the covers 09, 10 to install. Thus, for example, at the inner and / or outer diameter of the cover 09 collar can be attached. Fig. 4 shows a cover 09, 10 with a collar 13 at the inner diameter. Furthermore, the cover 09, 10 may be designed as a packetized lid with multiple sheet metal layers. The individual sheets are either loose or interconnected. The covers 09, 10 may be used to achieve increased axial pressure strength also have local material compaction and / or material compaction.

Fig. 5 shows lids in different versions, each in a sectional view. In the embodiment shown in Fig. 5a, a plurality of recesses 14 are inserted into the lid, which serve to reduce weight and / or lubricant or coolant supply. In the embodiment of Fig. 5b, the lid consists of a thinner inner through hardened part cover 15 and an outer part cover 16 made of a softer material. The inner Teilde- disgust 15 may for example consist of steel. The outer part cover 16 is made of aluminum or plastic, for example. In the cover shown in Fig. 5c, the embodiments shown in Fig. 5a and 5b are combined. The recesses 14 are arranged in the thicker outer part cover 16. The lid shown in Fig. 5d consists of several sheet metal layers 17, in which partial recesses 14 are introduced. Through the recesses 14, the weight of the lid can be reduced. In addition, the lubricant or coolant supply are facilitated.

Reference character list - drive unit

- first wooden wheel

- Output unit

- second wheel

- - spur gear

- wave generator

- Roller bearing

- first cover

- second lid

- -- Paragraph

- collar

- recesses

- inner part cover

- outer part cover

- Sheet metal layers

Claims

claims

1. wave gear with at least one ring gear (02, 04) with an internal toothing, one within the ring gear (02, 04) arranged, flexible spur gear (06) with an external toothing and within the spur gear (06) arranged wave generator (07) for bending the spur gear (06) in the radial direction, wherein between the ring gear (02, 04) and the spur gear (06) at two opposite points of the spur gear (06) is made a torque transmitting connection, wherein the wave generator (07) has a ring with elliptical outer circumference and on The outer circumference mounted elliptically deformed bearing (08), characterized in that the spur gear (06) on both sides by a respective cover (09, 10) is axially supported.

Wave gear according to claim 1, characterized in that at least one of the covers (09, 10) integrally with the ring gear (02, 04) is out leads.

Wave gear according to claim 1 or 2, characterized in that the axial guide clearance of the spur gear (06) between the covers (09, 10) <2 mm.

Wave gear according to one of claims 1 to 3, characterized in that between the covers (09, 10) and the ring gear (02, 04) insert discs are arranged.

Wave gear according to one of claims 1 to 4, characterized in that at least one of the cover (09, 10) on the spur gear (06) facing side has a shoulder (12) and / or bulges, wherein the bulges circular, annular or rod-shaped.

6. wave gear according to one of claims 1 to 5, characterized in that the cover (09, 10) have a wall thickness of at least 0.7 mm.

7. wave gear according to one of claims 1 to 6, characterized in that the cover (09, 10) have ribs.

8. wave gear according to one of claims 1 to 7, characterized in that the cover (09, 10) consist of several sheet metal layers.

9. wave gear according to one of claims 1 to 8, characterized in that the cover (09, 10) have local material compaction and / or Werkstoffverfestigungen.

10. Wave gear according to one of claims 1 to 9, characterized in that the spur gear (06) has a width of> 5 mm.