DE102006022154A1 - Shaft-hub e.g. rotary hub, arrangement for use in e.g. multi-axes industrial robot, has hub with recess sealed at side, that is turned towards shaft, in air-tight, so that shaft hub connection is sealed completely - Google Patents

Abstract

The arrangement (1) has a hub (3) e.g. rotary hub, connected with a shaft (2), where the shaft has an end (2.1) that engages in a retainer. The retainer is arranged at an end (3.2) of the hub, where the end of the shaft is connected with the inner circumference section of a recess of the hub in a torque-proof manner. The recess of the hub is sealed at a side, that is turned towards the shaft, in an air-tight, so that a shaft hub connection (5) is sealed completely against the environment in an air-tight manner. An independent claim is also included for a method for connecting a shaft with a hub.

Description

The The invention relates to an arrangement with at least one shaft and at least one hub connected thereto, one shaft end engages in a arranged at one end of the hub receptacle and by means of a shaft-hub connection at least along an outer peripheral portion the shaft end rotationally fixed with at least one inner peripheral portion the recess of the hub is connected, wherein the shaft facing away from the shaft Side of the recess is substantially hermetically sealed. The invention further relates to a robot, which at least has a drive equipped with such an arrangement, and a method of connecting a shaft to a hub, wherein a shaft end so arranged in one at one end of the hub Recess inserted that is, at least along an outer peripheral portion of the shaft end by means of a shaft-hub connection rotatably with at least one Inner peripheral portion of the recess of the hub is connected, wherein the side facing away from the shaft of the recess substantially airtight is closed.

On In the field of mechanical engineering, shaft-hub connections are widespread, to torques from a shaft or an axle to a rotating one Hub to transfer. In particular special in robotics, for example, find application for connecting motors with transmission elements, e.g. Cardan shafts, or with gears. These are usually standardized Types of connection, such as positive Connections, for example, a serration, or non-positive connections with security elements for a positive connection, for example a conical seat combined with a Woodruff key, inserted.

Problematic in known shaft-hub connections in particular the occurrence the so-called Tribokorrosion and resulting fretting rust. This can be done with very precisely matched components, such as a wave profile and a hub profile due to micromotion a destruction of the material become. In extreme cases, this has a release of the shaft-hub connection entail, so that, for example, the operative connection between the Drive motor and a robot arm of a robot is interrupted and this one fails. Especially with positive locking Shaft-hub connections can be found in the Trap of misalignment, e.g. between a motor and Gear shaft, wobble between shaft and hub element occur, due to the relative movement between these elements superficially Passungsrost can arise, resulting in a resolution of the positive connection can. Even with non-positive shrinking or pressing connections occur relative movements in the exit area the shaft from the hub, in which case the occurrence of fretting corrosion to a notch effect in the highly loaded shaft and finally to cause a permanent break can.

predominant Cause of the fit grid is an entry of oxidative acting Oxygen in the shaft-hub connection. In addition to the relative movement in the contact area of hub and shaft take other parameters Influence on the Oxida tion process, such. the material combination the shaft and hub, the surface oxidation-friendly, the Ambient atmosphere, the surface pressure in the contact area or the friction conditions. It is with common manufacturing processes and in economic production of the shaft-hub connection the Relative movement between shaft and hub not completely closed avoid. Also stainless materials contain technical disadvantages and are often economically unprofitable.

to Prevention of tribocorrosion and consequent fretting corrosion it is known, a centering diameter before and / or behind the respective form-fitting To arrange parts of the shaft-hub connection. However, it is still there the high manufacturing costs a relative movement in the field of positive engagement and thus the occurrence of fretting corrosion is not excluded. To the Compensation of misalignment is also the use of couplings known, however, an increased Cause inertia and thus the performance the arrangement in the power transmission reduce and also additional Take up space and are expensive.

Further In the prior art, coatings on the contact surfaces, such as Special lubricants or lubricants used, their effectiveness however due to limited Durability is limited in time and, moreover, largely significant Claim additional costs.

Of the Invention is therefore based on the object, an arrangement with at least a shaft and at least one hereby connected hub of the beginning mentioned type and a method for producing such Arrangement while avoiding the above-mentioned disadvantages to simple and cost-effective To further develop the way to the occurrence of fretting corrosion to effectively prevent, without affecting the operability of the arrangement, but rather, if necessary, to be able to improve them.

In device technical terms, this object is ge in an arrangement of the above Type mentioned solved in that the recess of the hub is sealed on its side facing the shaft substantially airtight, so that the shaft-hub connection is substantially completely sealed airtight to the environment.

In procedural terms, the invention provides for the solution of this Task in a method of the type mentioned above further, that the recess of the hub on its side facing the shaft essentially sealed airtight, so that the shaft-hub connection essentially entirely sealed against the environment.

By the solution according to the invention can Occurrence of fretting corrosion can be effectively avoided. The tribo-corrosion-causing oxygen can no longer from the outside get to the shaft-hub connection and remains if necessary to the amount of oxygen originally present in the recess of the hub limited, where In any case, no atmospheric oxygen from the environment to those in the Recess of the hub trailing shaft-hub connection can flow. With "airtight" within the meaning of the invention is the rest addressed a substantially gas-tight connection, in particular for one effective barrier for the oxidizing agent oxygen, also in the form of atmospheric oxygen, provides.

According to one structurally simple embodiment of the invention has the essence airtight sealing of the shaft against the hub, at least one sealing element, like a sealing ring, on which between the outer circumference the shaft and the inner circumference of the hub arranged. It can be advantageous if the sealing element compliant, in particular elastic, is designed to work for a reliable one To ensure sealing function. In the simplest and cheapest case the sealing element is a conventional one O-ring. Alternatively, the seal can of course also by gluing or Sealants, such as silicone, etc., or any other, known as such Be realized way. In terms of process engineering is preferred the substantially airtight sealing of the shaft against the hub Insert at least one sealing element, such as a sealing ring between produced the same, of course, in this regard, the the above alternatives.

In Advantageous configuration can be provided that the Sealing element arranged by means disposed in the recess of the hub itself around its inner circumference extending seat, such as a shoulder, in Axialrichtung is held, and / or that the sealing element by means of a seat extending around a circumference of the shaft, such as a Shoulder, held in the axial direction. The example in shape A seat formed the shoulder of the hub and / or the shaft can / in Essentially step-shaped formed or formed by a, in particular substantially constant, taper In addition, in the latter case, a simpler Introduce reaches the end of the shaft in the recess of the hub in the manner of a chamfer can be.

The Sealing function of between the shaft and the hub, e.g. between a shoulder of the shaft and one of the hub, arranged sealing element Thus, not only radially, but alternatively or additionally axially against the shoulder of the respective element (shaft / hub), i.e. the respective shoulder (s) can only be used for position fixing the sealing element in the axial direction as well as the actual Forming an airtight boundary between hub and sealing element serve in the axial direction. The sealing element can in this case e.g. in the axial direction fed to the respective -. in the form of a step or a rejuvenation trained - shoulder abut the shaft or the hub.

While the Shaft-hub-connection itself basically practically arbitrary, e.g. in the form of a positive, positive or cohesive connection formed It can be, in many cases he wishes when used by a splined connection or a compression or clamping connection is formed. However, the invention is not on any special connection for non-rotatable coupling of the shaft with the hub limited.

In order to achieve an improvement in the dynamic running properties of the drive or transmission shaft, a development of the invention provides that in the cavity between the shaft-hub connection and the substantially airtight seal the recess of the hub on the side facing away from the shaft Overpressure relative to the environment is adjustable. If an overpressure prevails in this cavity of the recess of the hub, this has the advantage that the shaft can be acted upon by a force directed axially from the hub, which force acts on the end face of the shaft end located in the recess of the hub as a result of the internal overpressure to ensure a smooth running. As a result, for example, a so-called "greasing" of a rolling body commonly associated with the shaft, eg a bearing, can be avoided. The effect of "greasing" occurs primarily when the rolling elements undergo a sliding phase during dynamic movements due to inertia before they can follow the rotational speed of the shaft, the effect being favored by a relatively low specific load of the shaft bearing. To achieve such an axial bias of the shaft-hub connection between the drive motor and shaft as a result of acting on the latter overpressure in the recess of the hub is preferably an overpressure in the range of about 0.1 bar to about 1 bar, for example of about 0.5 bar, provided. In this way, it is ensured that the motors used are exposed only to axial forces that do not exceed a range of axial forces permissible for the engine. With a maximum permissible axial force of, for example, 40 N and an end face of the motor shaft of approx. 800 mm ² , the overpressure should not exceed 0.5 bar.

The overpressure can by the way e.g. ambient air or a trapped in the recess Inert gas or other corrosion inhibitor such as e.g. liquid or pasty lubricant, be generated.

to Achieving overpressure in said cavity of the recess of the hub is in procedural It is preferably provided that during or after insertion of the Shaft into the recess of the hub in the cavity between the shaft-hub connection and the substantially airtight completion of the recess of the Hub on the side facing away from the shaft overpressure relative to the Environment is generated.

• – Ineinanderfügen des Wellenendes und der Nabe in Axialrichtung, bis das Wellenende und die Nabe an wenigstens einem Dichtungselement im Wesentlichen luftdicht zur Anlage kommen;
• – Erzeugen eines Überdrucks in der Ausnehmung durch weiteres Ineinanderfügen des Wellenendes in Axialrichtung, bis der gewünschte Überdruck in der Ausnehmung erreicht worden ist; und
• – Festlegen der axialen Relativposition des Wellenendes bezüglich der Nabe.

This can be done, for example, by means of a method comprising the following steps:

• - Joining the shaft end and the hub in the axial direction until the shaft end and the hub come to rest on at least one sealing element substantially airtight;
• - Generating an overpressure in the recess by further joining the shaft end in the axial direction until the desired overpressure has been reached in the recess; and
• - Determining the axial relative position of the shaft end with respect to the hub.

The Generation of overpressure can therefore exclusively while of insertion the shaft made in the recess of the hub, wherein the pressure in particular by compression of the seal according to the invention gas space enclosed between the shaft / hub when (further) pushed in the shaft can be generated in the hub. The remaining void volume is suitably chosen so that the resulting overpressure not inadmissible high axial forces on the shaft / hub exercise can and e.g. an overpressure in the order of magnitude of 0.5 bar is achieved.

alternative or additionally can be provided that the generation of the overpressure either by introducing a fluid, such as an inert gas, air or even a lubricant as a corrosion inhibitor or as a friction-reducing additive or like, into the cavity. In this case can be provided be that the cavity between the shaft-hub connection and the essentially airtight completion of the recess of the hub their side facing away from the shaft by means of an air-tight sealable channel corresponds to the environment, wherein the channel to a compressed gas source, preferably with egg nem inert gas or air, etc., can be connected, to pressurize the cavity.

Of the essentially airtight completion of the recess of the hub whose side facing away from the shaft, for example, by a be formed on the hub fixed, separate part, which for example, airtight on the shaft remote from the end of the recess can be pressed or otherwise mounted. In the separate Part can be e.g. around a machine part, such as in the form of a robot link, act. Alternatively, the hub can of course also a one-piece with this have trained closure, the recess thus in shape be formed of a blind hole.

Otherwise it concerns the invention also a robot, in particular a multi-axis Industrial robot, with at least one drive, which thereby is characterized in that the drive at least one arrangement of having the aforementioned type. Such, often six-axis industrial robots usually include a carousel rotatably mounted on a pedestal, one on top pivotally arranged rocker with a turn on the latter pivotally fixed robotic arm which terminates a e.g. around three axes carrying movable robot hand.

following the invention with reference to preferred embodiments with reference closer to the drawings explains on the basis of which there are further advantages and features of the invention. Showing:

1 a schematic sectional view of an embodiment of a shaft-hub connection according to the invention with a radially to the shaft axis we kenden air seal of the hub interior between the shaft and hub;

2 a detailed view of in 1 illustrated shaft-hub connection with an alternative embodiment of the air seal of the hub interior, which in the region adjacent to the hub has an axial sealing effect and in the region adjacent to the shaft has a sealing effect with an axial and radial component with respect to the shaft axis;

3 a detailed view of in 1 illustrated shaft-hub connection with a further alternative embodiment of the air seal of the hub interior, through which a purely axial sealing effect is formed both in the adjoining the hub and of the shaft to the shaft region;

4 a schematic sectional view of another embodiment of a shaft-hub connection according to the invention, which has a hermetically sealable channel between the inner and outer space of the hub; and

5 a schematic sectional view of a shaft-hub connection, in which the advantages of the invention are compared to the problems of conventional shaft-hub connections.

The 1 shows an embodiment of an arrangement according to the invention 1 in which the cylindrical end 2.1 a wave 2 in the interior of a recess I of a substantially tubular hub 3 along the inner wall 3.1 the same by means of a shaft-hub connection 4 is attached. Such a shaft-hub connection 4 can be formed both positively and non-positively or cohesively or in a combination of these versions. The hub 3 has an open end 3.2 for receiving the shaft end 2.1 and an airtight end 3.3 which is on the shaft 3 opposite end of the hub 2 located. The airtight closure of the end 3.3 , is in the present case by pressing the same on an axis 5 a robot arm (not shown), wherein an end portion of the axle 5 enters a region I.3 of the interior I and completely fills this region I.3. Thus, the interior I of the hub 3 from a joint area I.1 for receiving the shaft 2 , an entry region I.3 of the axis 5 and an interposed, for example, filled with air cavity I.2 together.

At that to its open end 3.2 extending end portion 3.5 has the hub 3 a radially arranged, in the direction of the environment or of the outer space A of the hub 3 pointing shoulder 3.3 on. The latter borders essentially in its inner diameter the outer diameter of the shaft 2 corresponding main section 3.4 the hub 3 from the end portion 3.5 where also the end section 3.5 the hub 3 a substantially constant, but larger inner diameter compared to the main portion 3.4 has.

The wave 2 points in its entry section 2.3 in the interior of the recess I at the open end 3.2 the hub 3 a region of constant, substantially the inner diameter of the end portion 3.5 the hub 3 corresponding outer diameter, the circumference in the direction of the interior I in a tapered shoulder portion 2.2 opens at which the shaft end 2.1 followed. In this way, the shaft end engages 2.1 in the recess I of the hub 3 one, being between the shoulder 2.2 the wave 2 and the shoulder 3.3 the hub 3 a cavity 6 is formed.

In the cavity 6 is a - preferably elastic - sealing ring 7 arranged such that this one hand in the axial direction along its in 1 lower side 7.4 to the shoulder 3.3 the hub 3 on the other hand, in the radial direction along its inside 7.1 to the tail 2.1 the wave 2 and along its outside 7.3 to the end section 3.5 the hub 3 borders. Here is the sealing ring 7 in the radial direction between the tail 2.1 the wave 2 and the end section 3.5 the hub 3 pressed in such a way that in this radial connection area an airtight seal between the outer space A and the shaft-hub connection 4 in the interior I of the hub 3 is formed. This can in particular by means of a permanent radial deformation of the sealing ring 7 be effective. Thus, in particular, a pressure equalization between a in the interior I of the hub 3 prevailing overpressure and the outside space A prevented.

The 2 shows a detail view of in 1 illustrated arrangement, wherein in an alternative embodiment of the sealing ring 7 in the cavity 6 placed so that this only along its bottom 7.4 to the shoulder 3.3 the hub 3 and at its top 7.2 to the shoulder 2.2 the wave 2 adjoins and is pressed in between. This is an air seal in the axial direction to the hub 3 and a conical air seal to the shaft 2 causes, the latter having both a radial, and an axial component. Here too, a radial or axial deformation of the sealing ring 7 respectively.

The 3 shows one of the 2 corresponding detail view of in 1 illustrated arrangement in a further alternative to the design of the air seal. It takes in contrast to 2 the shoulder 2.2 the wave 2 a stepped course, so that by the pressed-on this stage sealing ring 7 an air seal to the shaft 2 can be effected only in the axial direction.

The 4 shows a further education in 1 reproduced arrangement. It is similar to the in 3 Shown detail view of the shoulder section 2.2 the wave 2 formed by a step against which a spacer ring 8th is applied, through which a power transmission in the axial direction and thereby squeezing the with the spacer ring 8th in contact with the sealing ring 7 With a resulting air seal takes place. By adequate design of the contact pressure of the spacer ring 8th to the sealing ring 7 can also be effected here an axial and radial air seal.

Furthermore, at the in 4 shown arrangement, the hermetically sealed end 3.6 the hub 3 integral with the axle 5 formed of the robot arm. Here is the axis 5 inside of a canal 9 permeated, which a Luftab- or supply of the or in the interior I of the hub 3 in and out of the outer space A allows. The channel 9 is at its free end with an airtight closure mechanism 10 Mistake. As a result, if necessary ventilation of the interior of the hub I 3 and in particular a regulation of an overpressure located in the interior I possible.

The 5 illustrates the advantages of the arrangement according to the invention (left) compared to a conventional shaft-hub connection (right). In this case, in a schematic sectional view of a shaft-hub connection 4 between a wave 2 and a hub 3 represented, for example, may be formed by a non-positive compression composite or a cohesive adhesive or welding composite. At the in 5 Right edge region, the connection according to the prior art is directly exposed to the located in the environment A atmospheric oxygen. This can be in the smallest bumps and imperfections of the connection between the shaft 2 and the hub 3 penetrate, causing tribo-corrosion with a resulting fretting corrosion 11 occurs. The tribo-corrosion arises in the presence of atmospheric oxygen by a relative movement, eg due to rotational deflection of a radially loaded, rotating shaft or due to changing torsional load due to reversal of direction of the shaft. The in 5 left edge area of the shaft-hub connection 4 is according to the invention by means of a sealing ring 7 delimited by the oxygen present in the outer space A, whereby the formation of fretting corrosion is reliably contained.

Below is a method according to the invention by way of example in the 2 illustrated embodiment of an inventive arrangement explained.

In a first step, the tail is 2.1 the wave 2 through the open end 3.2 the hub 3 from the outside space A into the joining area I.1 of the interior I of the hub 3 introduced and along the end portion 3.5 the hub 3 moved into the interior I. In the process, the atmospheric oxygen displaced from the cavity I.2 of the interior I escapes completely into the exterior space A through the circumference between the shaft 2 and hub 3 extending cavity 6 ,

In a second step, the tail is 2.1 the wave 2 along the main section 3.4 the hub 3 moved further into the joint area I.1 of the interior I. The compressed in the decreasing cavity I.2 of the interior of the hub I air oxygen can along the shaft-hub connection 4 and over the cavity 6 leak to a complete or partial pressure equalization in the outer space A, until the sealing ring 7 finally in contact with the shoulder 2.2 the wave 2 arrives.

In a third step, the tapered shoulder section 2.2 the wave 2 continue against the sealing ring 7 Pressed so that the sealing ring 7 deformed both in radial and in axial direction. In this case, a complete air seal of the cavity I.2 is generated in the interior I.2, so that - if the volume of the interior I.2 due to further insertion of the shaft 2 in the recess I of the hub 3 reduced - the internal pressure in the cavity I.2 increases.

At the in 1 shown embodiment of the sealing ring 7 with a radial sealing effect, the air seal of the interior can already at a radial crushing of the sealing ring 7 through the tail 2.1 the wave 2 take place before this in the second step deeper into the recess I of the hub 3 is introduced. Consequently, in this case, an increase in pressure in the cavity I.2 already take place before the shaft end 3.1 has reached the intended position in the joint area I.1.

In addition, in a fourth step, the internal pressure of the cavity I.2 by a vent / aeration device 9 . 10 as they are in the 4 shown arrangement to be regulated to a desired value.

1

Shaft-hub arrangement

2

wave

2.1

shaft end

2.2

shoulder portion the wave

2.3

entry section the wave

3

hub

3.1

Hub inner wall

3.2

Restricted End of the hub

3.3

shoulder

3.4

main section the hub

3.5

end the hub

3.6

completed End of the hub

4

Shaft-hub connection

5

axis

6

radial Cavity around the shaft circumference

7

sealing ring

7.1 7.3

top, Bottom of the sealing ring

7.2 7.4

Inside-, outside of the sealing ring

8th

spacer

9

air discharge

10

locking mechanism

11

fretting

I

inner space the hub

A

outer space the hub

Claims (14)

Arrangement with at least one shaft ( 2 ) and at least one hub connected thereto ( 3 ), whereby a shaft end ( 2.1 ) into one at one end ( 3.2 ) the hub ( 3 ) arranged receptacle ( 2 ) and by means of a shaft-hub connection ( 4 ) at least along an outer peripheral portion of the shaft end ( 2.1 ) rotatably with at least one inner peripheral portion of the recess ( 21 ) the hub ( 3 ), whereby that of the shaft ( 2 ) facing away from the recess ( 2 ) is substantially hermetically sealed, characterized in that the recess (I) of the hub ( 3 ) at her of the wave ( 2 ) facing side is sealed substantially airtight, so that the shaft-hub connection ( 5 ) is substantially completely airtight sealed against the environment (A). Arrangement according to claim 1, characterized in that the substantially airtight seal of the shaft ( 2 ) against the hub ( 3 ) at least one sealing element ( 7 ), such as a sealing ring, which between the outer circumference of the shaft ( 2 ) and the inner circumference of the hub ( 3 ) is arranged. Arrangement according to claim 2, characterized in that the sealing element ( 7 ) by means of a in the recess (I) of the hub ( 3 ), extending around its inner circumference extending seat, for example a shoulder ( 3.3 ) is held in the axial direction. Arrangement according to one of claims 2 or 3, characterized in that the sealing element ( 7 ) by means of a around a circumference of the shaft ( 2 ) extending seat, eg a shoulder ( 2.2 ) is held in the axial direction. Arrangement according to claim 3 or 4, characterized in that the seat ( 3.3 ) the hub ( 3 ) and / or the seat ( 2.2 .) the wave ( 2 ) is substantially stepped or formed by a, in particular substantially constant, taper is / are. Arrangement according to one of claims 1 to 5, characterized in that in the cavity (I.2) between the shaft-hub connection ( 4 ) and the substantially airtight completion of the recess (I) of the hub ( 3 ) at the shaft ( 2 ) facing away from an overpressure relative to the environment (A) is adjustable. Arrangement according to claim 6, characterized that the overpressure ambient air or an inert gas trapped in the recess (I) or another corrosion inhibitor, such as a lubricant, is generated. Arrangement according to one of claims 1 to 7, characterized in that the cavity (I.2) between the shaft-hub connection ( 4 ) and the substantially airtight completion of the recess (I) of the hub ( 3 ) at whose the Wel le ( 2 ) facing away by means of a hermetically sealable channel ( 9 . 10 ) corresponds to the environment (A). Arrangement according to one of claims 1 to 8, characterized in that the substantially airtight completion of the recess (I) of the hub ( 3 ) at the shaft ( 2 ) facing away by a at the hub ( 3 ) fixed, separate part is formed. Robots, in particular multi-axis industrial robots, with at least one drive, characterized in that the drive at least one arrangement according to one the claims 1 to 9. Method for connecting a shaft ( 2 ) with a hub ( 3 ), whereby a shaft end ( 2.1 ) into one at one end ( 3.2 ) the hub ( 3 ) arranged recess (I) is inserted so that it at least along an outer peripheral portion of the shaft end ( 2.1 ) by means of a shaft-hub connection ( 5 ) rotatably with at least one inner peripheral portion of the recess (I) of the hub ( 3 ), whereby that of the shaft ( 2 ) facing away from the recess (I) is substantially hermetically sealed, characterized in that the recess (I) of the hub ( 3 ) at her of the wave ( 2 ) facing side is sealed substantially airtight, so that the shaft-hub connection ( 4 ) is substantially completely airtight sealed against the environment (A). Method according to claim 11, characterized by the following steps: - joining of the shaft end ( 2.1 ) and the hub ( 3 ) in the axial direction until the shaft end ( 2.1 ) and the hub on at least one sealing element ( 7 ) come to be substantially airtight to the plant; Generating an overpressure in the recess (I) by further joining the shaft end ( 2.1 ) in the axial direction until the desired overpressure has been reached in the recess; and - Determining the axial relative position of the shaft end ( 2.1 ) with respect to the hub ( 3 ). A method according to claim 12, characterized in that the generation of the overpressure exclusively during the insertion of the shaft ( 2 ) in the recess (I) of the hub ( 3 ) he follows. WEG method according to claim 11 or 12, characterized characterized in that the generation of an overpressure in the recess (I) by introducing a fluid, such as an inert gas, air or Like, into the cavity (I.2) takes place.