WO2008055783A1

WO2008055783A1 - Eccentric clamping device

Info

Publication number: WO2008055783A1
Application number: PCT/EP2007/061395
Authority: WO
Inventors: Niels FLÄMIG; Rainer BAUMÜLLER
Original assignee: Schaeffler Kg
Priority date: 2006-11-09
Filing date: 2007-10-24
Publication date: 2008-05-15

Abstract

The present invention relates to an eccentric clamping device for clamping a traction mechanism designed as a flat or toothed belt of a traction mechanism drive. The object of the invention is to provide advantageous solutions resulting in assembly-related advantages during the installation of clamping devices and the integration of the traction mechanism into the traction mechanism drive. Said task is solved, according to the invention, by an eccentric clamping device for a traction mechanism drive, comprising a roller device having a rotor disk and for the storage thereof a roller bearing, a working eccentric disk for supporting the roller device such that it can be displaced according to a pivot of the working eccentric disk in a direction radial to the revolving axis of the roller bearing, furthermore a torsion spring for pretensioning of the working eccentric disk, a fastening device for securing the working eccentric disk in a mounting position, in which the torsion spring is in a pretensioned state, and a base plate structure that can be rotationally secured to a flanging surface intended for connecting the eccentric clamping device, wherein the fastening device is designed such that it is automatically released if a fastening screw, by which the eccentric clamping device is screwed on the mounting surface, is tightened.

Description

Name of the invention

Eccentric tensioning device

Field of the invention

The present invention relates to an eccentric tensioning device for tensioning a traction means, for example a flat or toothed belt, of a traction mechanism. In particular, the invention relates in this case to an eccentric clamping device provided for incorporation into a traction mechanism drive of an internal combustion engine which automatically ensures a required pretensioning of the traction means by means of an adjusting torque generated by a spring device.

A clamping device of the aforementioned type is known for example from DE 40 33 777 AI. This conventional tensioning device, also referred to as a double eccentric tensioning device, comprises a setting eccentric which has an eccentrically arranged bore provided for receiving a fastening screw. By means of the fastening screw, the tensioning device is fastened to a housing, in particular a housing of the internal combustion engine, wherein the adjustment eccentric is supported on the housing via a base plate. In this adjustment eccentric a working or operating eccentric is placed, being provided in an annular gap between a lateral surface of the adjustment eccentric and an inner wall of the operating eccentric a sliding bearing. On the outside, a roller bearing surrounds the operating eccentric whose outer ring acts directly as a running disk which, as such, rests on the traction means of the traction mechanism drive in the installed state, thereby acting on it with a transverse force directed transversely to the running direction. In order to achieve a frictional engagement of the running disk on the traction means, a torsion spring is arranged between the base plate and the operating eccentric, which permanently urges the operating eccentric and the associated running disk into a position exciting the traction means. The invention has for its object to provide solutions by which advantages in the installation of tensioning devices and the involvement of the traction means in the traction mechanism under Montagetechnischen aspects.

This object is achieved by an eccentric tensioning device for a traction drive, with:

a roller device which, as such, comprises a running disc and a bearing provided for supporting the same,

a working eccentric for supporting the roller device such that it is displaceable in accordance with a pivoting of the working eccentric in a direction radial to the axis of rotation of the bearing,

a torsion spring for biasing the working eccentric, a fixing device for securing the working eccentric in a mounting position in which the torsion spring is in a prestressed state, and

- A base plate structure which is rotatably anchored to a provided for connection of the Exzenterspannvor- direction Anflanschfläche, - wherein the fixing device is designed such that it automatically releases in the context of tightening a fastening screw by which the eccentric tensioning device is connected to the Anflanschfläche.

This makes it possible in an advantageous manner to provide a clamping device in which is fixed during the assembly of the traction means of the working or the operating eccentric under bias of the torsion spring in a pivoted away from the Zugmittellaufpfad end position, said securing state are repealed in the context of Verbaus the tensioning device can. The working eccentric is preferably fixed in that locking or mounting position so that relative movements between the working eccentric and the base plate are prevented. According to a particularly preferred embodiment of the invention, the fixing device is designed such that it by means of tightening the fastening screw by which the eccentric tensioning device, in particular a setting eccentric thereof is screwed to the, the tensioning device bearing Anflanschfläche, automatically triggers. This automatic Lösebzw. Activation procedure of the fixing device can be introduced in particular by running over the free-switching path under the effect of the axial force applied by the fastening screw in the connection of the eccentric clamping device to the Anflanschfläche of components of the clamping device or a first in the clamping device provided axial clearance is eliminated , By way of the elimination of this axial play, in particular against an axial force applied by the torsion spring or by auxiliary support structures, an engagement structure of the fixing device can be brought into a release state.

The engagement structure is preferably rigidly coupled to the working eccentric. In particular, it is possible to design the engagement structure in such a way that it is connected to the working eccentric via a pointer arm, or, in particular, is designed as a pointer produced in one piece with the working eccentric.

The fixing device according to the invention is preferably designed so that in the mounting position, the engagement structure is engaged with a holding element which is provided by the base plate. The transfer of the engagement structure into the release state is preferably carried out by axial displacement of the engagement structure relative to the retaining element.

The spring device provided for generating the torsional moment which pivots the working eccentric is preferably designed as a helical spring. This coil spring may be formed so that it has a plurality of spring coils. The helical spring can be embodied as a limbless helical spring, so that the forces generated by this helical spring can be transmitted over the end faces of the spring ends and, if necessary, over an end thereof around a NEN angle of typically 90 ° offset circumferential portion are introduced into the respective, loaded by the spring components. The spring may also be provided with anchoring structures, in particular in the form of hook sections, in the area of the spring ends. These hook sections can in particular be made by radially inwardly or outwardly bent-off wire ends of the spring structure. With regard to the cross section of the spring wire, the spring device can be designed such that it has a polygonal, in particular square or flat cross section. Furthermore, the spring device is preferably designed so that it is compressed in the installed state, at least slightly, for example, to 30% of its length in the axially unloaded state.

The tensioning device according to the invention preferably comprises a damping or braking device, which as such serves to generate an eccentric braking torque, by means of which the pivoting of the working eccentric is braked. This damping or braking device can be formed by an axially loaded disk structure, by a radially loaded bushing structure, or by an axially loaded cone structure. Preferably, at least part of the loading force acting on this damping or braking device is generated or transmitted by the torsion spring. At least one of the frictional force generating frictional partner is preferably made of a possibly loaded with fillers plastic material.

The working eccentric can be made of a plastic material. It is also also possible to perform the working eccentric integral with the inner ring of the bearing. Furthermore, it is also possible to carry out the running disk in one piece with the outer ring of the rolling bearing.

According to a particularly preferred embodiment of the invention, the working eccentric is mounted on a setting eccentric. By the fixing device according to the invention, or in particular by an additional, for example designed as a shear structure fixing device is preferably the Position of the working eccentric also set against the setting eccentric. It is possible to make the clamping device constructive in such a way that the adjusting eccentric is axially displaceable by a small distance relative to the working eccentric or a base plate, wherein the release state of the fixing device can be brought about by means of the axial displacement of the adjusting eccentric, in particular under the action of the fastening screw.

The base plate is preferably designed in such a way that it comprises a ring disk section provided for clamping onto the flange surface. This annular disc portion may be designed so that it is rotatably coupled in the region of an inner peripheral edge with a bearing bush.

On the base plate, a projection or other engagement structure may be formed, which serves as such / such the rotationally fixed anchoring of the base plate to the Anflanschfläche. Preferably, the approach is such that the rotationally fixed anchoring of the base plate is achieved at the Anflanschfläche before the fixing device enters a release state, or before the axial release path is overcome.

As an alternative to the above-described measures, it is also possible to design the tensioning device according to the invention so that the release state is not achieved by axial loading of the tensioning roller device, but, for example, by pivoting back the working eccentric against the pivoting direction caused by the torsion spring. In this even further swung back state, for example, resiliently preloaded into a release position locking member can be unlocked and release the working eccentric so that it is pivoted under the action of the torsion spring to the Zugmittellaufpfand out and thus the running disk is lowered onto the traction means.

It is also possible to design the tensioning device in such a way that the release condition is brought about by an additionally inserted into the working eccentric. guided, acting in the direction of the torsional spring generated by the clamping torque acting overload torque takes place.

Preferably, securing means are provided by which re-engagement of the fixing device is prevented. This makes it possible to ensure that no unintentional reclosing of the fixing device takes place during operation of the clamping device.

The invention includes in particular the following embodiment variants:

version 1

Before mounting the clamping device, this is pretensioned in the delivery condition. A connected to the operating eccentric, radially aligned pointer is non-positively and / or positively supported on a support member of the base plate or the adjustment eccentric. In this case, the work eccentric and the pointer connected thereto are pressed in a force-fitting manner against the retaining element of the base plate by the force of the torsion spring and thus fixed in position. The pointer assumes this position by a limited axial displacement of the working eccentric relative to the adjustment eccentric or the base plate, wherein this displacement takes place in the direction of a Axialkraftkompo- component of the torsion spring.

Starting from this starting position, the tensioning device is loosened by means of the fastening screw, i. without rigid attachment, positioned on the internal combustion engine. About the base plate in conjunction with an axially projecting lug, which engages in a corresponding bore or receiving the internal combustion engine in the region of the Anflanschfläche, a position-oriented installation position of the clamping device sets. In the mounting position, the operating eccentric is fixed in an end stop, which is also referred to as a hot stop, whereby the traction means, in particular a belt, mounted simplified, i. can be placed on all pulleys of the traction drive.

After the Zugmittelmontage the clamping device is rigidly attached to the housing of the internal combustion engine by means of the fastening screw. Synchronously for tightening the fastening screw, the adjusting eccentric and the base plate connected thereto shifts axially in the direction of the internal combustion engine, whereby the pointer integrally connected to the base plate is released from the retaining element and the torsion spring the operating eccentric twisted into a position biasing the traction means. The release of the pointer and thus the working eccentric from the lock during the mounting position is thus achieved as soon as an axial play "S" between the working eccentric and the base plate or the adjusting eccentric is compensated or reduced by screwing on the clamping device.

Variant 2

To achieve an effective transport lock, which prevents a relative movement between the working eccentric and the base plate in the mounting position, is a communicating with the working eccentric pointer or a similar shaped object with a stop of the base plate in an operative connection. The locking can be achieved by suitable shaping of the base plate alone or with the aid of additional elements such as e.g. Cotter pins or a sheet done, which are removed after applying traction means to tension the traction means.

Variant 3

Another embodiment for positioning the operating or working eccentric in a mounting position provides to make the locking device for maintaining the prestressed torsion spring so that it does not exceed the radial outer contour of the clamping unit. For this purpose, for example, a frontally on the flange of the engine adjacent side of the working eccentric introduced groove or recess in the working eccentric or in the base plate, in which engages a form fit, adhesion or by a combination of both ways intervening fuse to a rotational movement of the To prevent working sexzenters against the base plate or the adjustment eccentric in the assembly position.

The cooperating with the groove or the recess counterpart, the Depending on the arrangement of the backdrop either on the base plate or the working eccentric can be designed as a bent part, casting or as an attachment (eg as a dowel pin). The exit of the counterpart from the groove or the recess in the direction of Nutanfangs is prevented by the caulking of the working eccentric and the associated limitation of the axial play of the clamping unit. According to another embodiment, the counterpart surrounds the working eccentric. In the mounting position engages a particular standing in connection with the base plate molding in a groove or recess of the working eccentric due to the axial force of the torsion spring is between the base plate and the working eccentric an effective backup in the mounting position.

The invention is particularly directed to tensioning devices that ensure a nearly constant biasing force of the traction device under all operating conditions and with which continue a long life can be achieved. The measures according to the invention enable a semi-automated adjustment of the required traction force during the initial assembly and a service to compensate for:

- Diameter and position tolerances of the individual disks of the traction mechanism drive;

Length tolerances of the traction means, in particular toothed belts; Belt wear; Temperature differences; and effects due to the dynamic behavior of the internal combustion engine.

Further details and features of the invention will become apparent from the following description in conjunction with the drawings. It shows: Figure 1 is an axial sectional view for illustrating the construction of a tensioning device according to the invention with an operating eccentric and a setting eccentric and a fixing device according to the invention;

FIG. 2 shows a detailed representation to illustrate the structure of a shear structure of the tensioning device according to FIG. 1;

FIG. 3 a perspective view of a tensioning device in the pretensioned, locked state;

FIG. 4 shows a side view of the clamping device according to FIG. 3 in a state in which the fixing device is just entering a release position;

Figure 5 is an illustration of the tensioning device in a state in which the unlocked pointer just passes under the holding device;

Figure 6 is a perspective view of another clamping device in the pretensioned or locked state with a slightly modified design of the holding device and the pointer cooperating therewith;

FIG. 7 shows a further perspective view of a third variant of a tensioning device, also in the pretensioned or locked state;

8 shows a perspective view of a base plate of a clamping device with a further fixing device or securing structure for fixing the working eccentric in an assembly position. FIG. 1 shows a first variant of a tensioning device 1b according to the invention, in which a setting eccentric 2b is fastened to a housing 12 via a fastening screw 11. The adjustment eccentric 2b is inserted into a hollow cylindrical support body 13, via which the tensioning device 1b is supported on the housing 12. The tensioning device comprises an operating eccentric 4b which is rotatably mounted on the support body 13 via a sliding bearing 5b.

On the outside, the operating eccentric 4b is enclosed by a roller bearing 6b which carries a running disk 7b. A torsion spring 9b is disposed between a base plate 10b and the operating eccentric 4b. A pointer 14 arranged locally on the operating eccentric 4b has, in particular, the task of visually indicating the position of the operating eccentric 4b with respect to the base plate 10b. The construction of the tensioning device 1b includes an axial clearance "s" between an end face of the operating eccentric 4b and the base plate 10b. With regard to the further reference numerals 20 to 25 shown in this illustration, reference is made to the following explanations regarding FIG.

2 shows the detail "Z" on an enlarged scale according to FIG 1. For the initial fixation of the adjustment eccentric 2b, a friction disc 21 is inserted between an end face of the operating eccentric 4b and a rim 20 of the adjustment eccentric 2b, which has an axially protruding pin 22 of the form fit engages in a designed as a blind hole receptacle 23. Furthermore, the friction disc 21 includes on the inner circumference a radially inwardly directed shear pin 24, which engages in an end-side groove 25 of the support body 13.

This makes it possible to initially rigidly couple the operating eccentric 4b and the adjusting eccentric 2b in a position which gives a maximum distance of the running disk 7b (FIG. 1) from a traction means path. In a first partial assembly state, the base plate 10b is already secured in a rotationally fixed manner to the housing 12 via its projection 10b. measure preloaded, but in itself secured clamping device not yet unlocked.

The operating eccentric 4b and the adjusting eccentric 2b are aligned with one another such that the circumferential wall of the running disk 7b occupies its greatest possible distance from the running path of the tensioning means of the traction mechanism drive to be tensioned. In this state, the traction means can be easily placed on the associated pulleys of the belt drive.

As can be seen from FIG. 3, the pointer 14 of the operating eccentric 4b is in an operative connection with a holding element 15a assigned to the base plate IOb. By locking the pointer 14 on the retaining element 15a, it becomes possible to secure the operating eccentric 4b, which is rigidly coupled to the pointer 14, in particular in one piece, to the preloaded position shown here.

As shown in FIG. 4, the holding element 15a comprises, for example, on the end side a U-shaped offset 16 which forms a free radially inwardly directed rim 17. To achieve the unlocking position that can be recognized here, the running disk 7b is initially displaced in the direction of the base plate IOb in opposition to an axial force exerted by the torsion spring 9b in conjunction with the operating eccentric 4b. The shift is made possible by the axial release path S permitted between the operating eccentric 4b and the base plate IOb.

Subsequently, under the action of the torsion spring 9b, a limited relative rotation between the pointer 14 and the holding element 15a takes place. The permitted maximum swivel angle W is defined by swivel stop structures B1, B2. These pivot stop structures form part of the operating eccentric 4b. Between these two pivot stop structures B1, B2 is an integral with the base plate 10b executed inner stop A1 displaced. The safety device realized between the pointer and the holding element 15a can be realized structurally in some other way, in particular as will be explained in more detail below. In particular, it is possible to make this safety device so that, for example, a local overlap between the pointer 14 and the board 17 of the holding member 15a is rich enough, and is secured by appropriate the pointer in the direction of thrust supporting stops of the hands, under the action of the axial force of Torsion spring 9b of the pointer 14 is urged into the latching structure formed on the holding element 15a.

FIG. 5 shows the tensioning device in a state in which the pointer 14 is already outside of the retaining element 15a. In this system state, the operating eccentric 4b can pivot into its operating position in a spring-loaded manner until there is a balance of power between the radial force generated by the operating eccentric under the action of the torsion spring and the traction mechanism reaction forces acting on the running disk.

To secure the mounting position and create an effective transport lock, in addition to the non-positive support of the pointer 14, it is advisable to provide positive locking. For this purpose, for example, a local recess in the board 17 of the holding element 15a, in which the pointer 14 engages positively.

FIG. 6 shows a further variant of a tensioning device according to the invention. In this variant, the holding device 15a supporting the pointer 14 is designed such that under the action of the force acting on the holding device 15 by the pointer 14, a certain axial securing of the pointer 14 is achieved. In the area of the contact surfaces of the pointer 14 and the holding device 15 that come into contact with one another, for example, concave / convex geometries can be implemented.

In the variant according to FIG. 7, the holding device 15a is produced by a stop-lug portion which is formed integrally with the base plate 10b. In the area of the contact surface 14 of the hook-on lens section supporting the pointer 14, a slight recess may be formed, in which the pointer 14 is seated sufficiently secured under the action of the biasing force generated by the torsion spring.

FIG. 8 shows in a perspective the base plate 10 for a further variant of a fixing device. A retaining element I5b embodied here in one piece with the base plate 10b includes a plate following the radius of curvature of the running disk 7b. A slot 18 inserted in the sheet is intended to guide the pointer 14. In the prestressed position corresponding to the mounting position of the operating eccentric 4b relative to the base plate 10b, or the adjusting eccentric 2b, the pointer 14 is fixed in the end position by a separate pin 19.

The rolling bearing 6 of the clamping device is preferably designed as a radial roller bearing 6 which consists of an inner bearing ring and an outer bearing ring and a plurality between the bearing rings in grooved raceways rolling, held by a bearing cage at regular intervals held each other rolling elements and axially on both sides of its rolling elements in each case a seal with which of the trained as a grease deposit space is sealed between the bearing rings, this rolling bearing is characterized in that it is designed as a ball roller bearing whose rolling elements are designed as ball rollers with two symmetrically flattened from a spherical base and arranged parallel to each other side surfaces , This ball roller bearing offers over a comparable ball bearing by the higher number of mountable rolling elements increased load capacity and at the same time by the reduced space of the rolling elements an enlarged grease depot. The rolling elements of the radial roller bearing formed as ball rollers are preferably designed so that they preferably have a width between their side surfaces of about 70% of the diameter of their basic ball shape and by a distance of about 80% of the diameter of the ball basic shape of the rolling elements having distance between the concentric with each other arranged bearing rings initially axially "flat" into the radial roller bearing insertable and are pivotable by a corresponding rotation through 90 ° in the raceways of the bearing rings.The outer bearing ring can here directly form the running disk, the inner bearing ring can be formed directly by the working eccentric.

LIST OF REFERENCE NUMBERS

1 a clamping device

1 b clamping device

2a Adjustment eccentric

2b Adjustment eccentric

3 receiving hole

4a operating eccentric

4b operating eccentric

5a slide bearing

5b sliding bearing

6a rolling bearings

6b rolling bearings

7a running disk

7b running disk

8 traction means

9a torsion spring

9b torsion spring

10a base plate

10b base plate

11 fixing screw

12 housing

13 supporting body

14 pointers

15a retaining element

15b retaining element

16 crank

17 board

18 slot

19 pen

Claims

claims

1. Eccentric clamping device for a traction drive, comprising:

- A roller device as such a running disc (7) and a bearing for the same provided rolling bearing (6), - a working eccentric (5) for supporting the roller device such that it in accordance with a pivoting of the working eccentric (5) in one to the axis of rotation (X) of the rolling bearing is displaceable in the radial direction,

- A torsion spring (9) for biasing the working eccentric (5), and

- A fixing device for securing the working eccentric in a mounting position in which the torsion spring (9) is in a prestressed state, and

a base plate structure which can be anchored in a rotationally fixed manner to a flange surface provided for connecting the eccentric tensioning device,

- Wherein the fixing device is designed such that it is released in the context of tightening a fixing screw by which the eccentric tensioning device is screwed to the Anflanschfläche automatically.

2. Eccentric clamping device according to claim 1, characterized in that by means of the attachment of the eccentric tensioning device to the Anflanschfläche by the fastening screw an axial clearance (S) is eliminated.

3. Eccentric clamping device according to claim 2, characterized in that the elimination of the axial clearance (S) against a force applied by the torsion spring axial force.

4. Eccentric clamping device according to claim 3, characterized in that in the course of the elimination of the axial clearance with the working eccentric (5) connected engagement structure enters a release state.

5. Eccentric clamping device according to claim 4, characterized in that the engagement structure is connected via a pointer arm (11) to the working eccentric (5).

6. Eccentric tensioning device according to claim 5, characterized in that in the mounting position, the engagement structure is engaged with a holding element which is provided by a base plate.

7. Eccentric clamping device according to at least one of claims 1 to 6, characterized in that the movement of the engagement structure in the release state by axial displacement of the engagement structure relative to the holding element.

8. Eccentric clamping device according to at least one of claims 1 to 7, characterized in that the spring device is designed as a helical spring.

9. Eccentric clamping device according to at least one of claims 1 to 8, characterized in that a damping device is provided for generating a radial displacement of the roller device counteracting Exzenterbremsmomentes.

10. Eccentric clamping device according to at least one of claims 1 to 9, characterized in that the working eccentric is mounted on a setting eccentric.

11. Eccentric clamping device according to at least one of claims 1 to 10, characterized in that the working eccentric is axially displaceable, and that the release state can be brought about by axial displacement of the adjustment eccentric under the action of the fastening screw

12. Eccentric clamping device according to at least one of claims 1 to 11, characterized in that the base plate (8) comprises an opening provided for clamping on the Anflanschfläche annular disc portion, and that the annular disc portion in the region of an inner peripheral edge rotatably with a support body (5) is coupled, and that on the base plate (8) in an outer edge region of the same that retaining element is formed.

13. Eccentric clamping device according to at least one of claims 1 to 12, characterized in that on the base plate (8) has a projection (10) is formed for non-rotatable anchoring of the base plate (8) on the Anflanschfläche.

14. Eccentric clamping device according to at least one of claims 1 to 13, characterized in that the projection (10) is designed such that the rotationally fixed anchoring of the base plate (8) is reached on the Anflanschfläche before the axial release path (S) is overcome.