WO1999037940A1 - Tensioning device for traction means provided with a hydraulic damper - Google Patents

Abstract

The invention relates to a tensioning device for traction means, especially a belt, comprising a tensioning arm (2) on which a tension roller (2a) is provided. The tensioning arm (2) is held against the traction means by a spring element (3). In addition, a hydraulic damper element (9) is provided whose piston (13) which plunges inside a cylinder (12) delimits a pressure chamber (14) with said cylinder (12). The pressure chamber communicates with a reservoir (7) provided for hydraulic fluid. In order to reduce the necessary installation space, the housing (1) is provided with chambers (7, 8) which are separated by a parting wall (6) in a liquid-tight manner, whereby the spring element (3) is provided in one chamber (8) and the hydraulic damper element (9) is provided in the other chamber (7), said chamber (7) forming the reservoir.

Description

 Tensioning device for traction devices with hydraulic damping

The present invention relates to tensioning devices for traction means, such as belts and chains. Such tensioning devices are preferably used in the belt or chain drive of internal combustion engines in motor vehicles.

DE 196 14 546 A1, for example, discloses a tensioning device for belts, in which a tensioning roller is rotatably mounted on a tensioning arm designed as an eccentric. The eccentric is pivotally mounted on a bolt and spring-loaded against the belt by means of a spring element. Furthermore, a hydraulic damping element is provided, which dampens retrograde movements of the tensioning arm away from the belt. This hydraulic damping element is a separate component which has a cylinder in which a piston is immersed, the piston and the cylinder delimiting a pressure space which communicates via a one-way valve with a reservoir for hydraulic fluid likewise provided in this component. Such tensioning devices have the advantage that the tensioning and damping elements each already form a unit, but it is disadvantageous that the damping element provided with the reservoir takes up a relatively large amount of installation space, which can be considerable under the tight conditions in the engine compartment of motor vehicles Effort for the assembly or disassembly of the clamping device entails. In particular, if the damping element is to be integrated into a housing of the tensioning device, a correspondingly large housing must be provided.

Summary of the invention

The object of the present invention is therefore to provide a tensioning device known according to the features of the preamble of claim 1, which 2 comparatively less space is required and, as a result, can be provided more easily in the belt or chain drive, in particular of internal combustion engines. According to the invention, this object is achieved in that a housing is provided with chambers which are liquid-tightly separated by a partition, the spring element being provided in one chamber and the damping element in the other chamber, which other chamber forms the reservoir. With the tensioning device according to the invention, a separate reservoir of the damping element can be dispensed with. In particular in the case of tensioning devices in which a housing is provided in which the damping element is arranged, the space required can be considerably reduced with the further development according to the invention. Since space is provided in the housing for the damping element in any case, this space is used simultaneously for receiving the damping element and as a reservoir for hydraulic fluid. The partition prevents hydraulic fluid from getting into the other chamber. Of course, connection openings in the partition are conceivable, for example for ventilation. Since the damping element used in the tensioning device according to the invention does not contain its own reservoir and therefore less enclosed space is created, the tensioning device according to the invention has less mass, which is desirable in modern motor vehicles. The damping element is provided for damping movements of the tensioning arm, which it executes in the opposite direction to the resilience of the tensioning arm by the spring element.

A further development according to the invention provides a shaft which is guided through the partition. On the one hand the shaft is rotatably the clamping arm and on the other hand the partition is rotatably arranged a lever, the damping element supported on the housing acting on the lever. With pivoting movements of the tensioning arm, the effective lever length for the damping element changes, which consequently changes its position in the chamber. Accordingly, the supports on the housing and on the lever must be such that pivoting of the damping element on the support is possible. This can preferably be ensured by rotating joints. 3 are performed, which are arranged between the damping element and the lever or between the damping element and the housing. Such a swivel joint can have a spherical head accommodated in a socket, wherein the socket can be formed in the reservoir on the housing side and on the lever on the clamping arm side. In such an arrangement, the cylinder and the piston each have a spherical head at their opposite ends. Instead of a spherical surface, for example, a partially cylindrical surface can also be provided. In a known manner, a spring element, for example a helical compression spring, is provided which acts on the one hand on the piston and on the other hand on the cylinder in such a way that the ball heads of the piston and cylinder are spring-loaded against the pans.

To generate the tensioning force for the belt, a helical torsion spring is preferably provided which is wound around the shaft and which is supported on the one hand on the housing and which on the other hand engages the tensioning arm.

The damping element is arranged in the other chamber such that its check valve is immersed in the hydraulic fluid of the reservoir. In further developments according to the invention, which provide for the passage of the shaft through the partition, it is advantageous that an annular gap present between the shaft and the partition is closed by means of at least one sealing ring.

In known damping elements, the cylinder is designed in a straight line, so that movements of the piston in the cylinder also take place along a straight line. A particularly favorable development according to the invention provides that the cylinder is curved. The piston which is arranged to be longitudinally displaceable therein is consequently not displaced along a straight line but rather along a curved line. This curved cylinder is preferably arranged at least approximately concentrically with the shaft. In this development according to the invention, a large piston travel can be provided in the cylinder without the risk that this cylinder projects beyond the housing in the radial direction. Rather, the curvature of the 4

Cylinder achieves that an extension of the possible piston travel is achieved within the available space without providing additional radial space for the cylinder.

Brief description of the drawings

The invention is explained in more detail below with the aid of three tensioning devices shown in a total of five figures. Show it:

FIG. 1 shows a longitudinal section through a tensioning device according to the invention,

FIG. 2 shows a cross section through the tensioning device from FIG. 1,

FIG. 3 shows the damping device from FIG. 2 in a view rotated by 90 °,

Figure 4 shows a cross section through a further tensioning device according to the invention and

Figure 5 shows a cross section through a further tensioning device according to the invention.

Detailed description of the drawings

In the tensioning device according to the invention according to FIG. 1, a housing 1 and a tensioning arm 2 which is arranged pivotably with respect to the housing 1 are provided, at one end of which a tensioning roller 2a, which is only shown in broken lines, is arranged and which rests on a belt, not shown. The tensioning arm 2 is spring-loaded against the belt (not shown) by means of a helical torsion spring 3, the helical torsion spring 3 being supported on the one hand on the housing 1 and on the other hand engaging the tensioning arm 2 while exerting a torsional moment. The tension arm 2 is non-rotatably on a shaft 4 5 arranged, which is accommodated in the housing 1 and is pivotally mounted relative to the housing 1 by means of two radial bearings 5. The housing 1 is provided with a partition 6, which is arranged transversely to the shaft 4 and which is pierced by the shaft 4. This partition 6 separates two chambers 7, 8 from one another, one chamber 7 being designed as a reservoir for receiving hydraulic fluid, and the other chamber 8 being provided for receiving the helical torsion spring 3. A damping element 9 is arranged in the chamber 7, which acts on the shaft 4 via a lever 10, the lever 10 being arranged on the shaft 4 in a rotationally fixed manner. An annular space formed by the shaft 4 and the partition 6 is closed by means of a sealing ring 11, so that the two chambers 7, 8 are separated from one another in a liquid-tight manner. The chamber 7 is closed to the environment in a liquid-tight manner by means of a cover 11 a.

FIG. 2 clearly shows the cut damping element 9, which comprises a cylinder 12, a piston 13 immersed therein, a pressure chamber 14 delimited by the cylinder 12 and the piston 13, the pressure chamber 14 communicating with the reservoir 7 via a check valve 15. The damping element 9 is arranged in the chamber 7 such that the check valve 1 5 is below a liquid level of the hydraulic fluid.

FIG. 3 shows the damping element 9 in a view rotated by 90 °, this view clearly showing that the ends of the piston 13 and the cylinder 12 on pivot arms 16, 17 provided on the tension arm side and housing side via bearing eyes 18, 19 are pivotally received, the bearing eye 18 on the piston 13 and the bearing eye 19 on the cylinder 12 are formed.

The tensioning device according to the invention shown in FIG. 4 differs from the tensioning device described above essentially by modified rotary joints for the damping element. The cylinder 12 and the piston 13 are each provided at their ends facing away from one another with a spherical head 20, 21, which are each pivotably arranged in a pan 22, 23. 6 are net, the pans 22, 23 are provided in the chamber 7 on the housing 1 and on the lever 10. Furthermore, a helical compression spring 24 is arranged in the space delimited by the piston 13 and the cylinder 12, which acts on the one hand on the piston 13 and on the other hand on the cylinder 12 in such a way that the ball heads 20, 21 are spring-loaded against the pans 22, 23. The helical compression spring 24 shown here can of course also be arranged outside the space delimited by the piston 1 3 and by the cylinder 12, ie externally. Instead of the helical compression spring 24, an externally arranged leg spring is also conceivable, which engages the cylinder with one leg and the piston with the other leg.

The tensioning device according to the invention shown in FIG. 5 differs from that from FIG. 4 essentially in that the piston 13 and the cylinder 12 are curved. Accordingly, displacements of the piston 13 relative to the cylinder 12 do not take place along a straight line, but rather along a curved line which, as shown, is preferably designed as a circular path and is arranged concentrically to the shaft 4. With this development according to the invention, long displacement paths on the piston can be realized without an additional radial expansion on the housing 1 being necessary to accommodate an enlarged damping element 9.

LIST OF REFERENCE NUMBERS

1 housing

2 tension arm 2a tension roller

3 helical torsion spring

4 shaft 5 radial bearings

6 partition

7 chamber

8 chamber

9 damping element 10 lever

1 1 sealing ring

1 1 a lid

12 cylinders

13 pistons 14 pressure chamber

15 check valve

16 pivot pins

17 pivot pins

18 bearing eye 19 bearing eye

20 ball heads

21 ball head

22 pan

23 pan 24 helical compression spring

Claims

Patent claims 1 . Tensioning device for traction means, in particular belts, which comprises a tensioning arm (2) provided with a tensioning means, in particular tensioning roller (2a) for the traction means, which is sprung against the traction means by means of a spring element (3), and a hydraulic damping element (9) The piston (13) immersed in a cylinder (12) and the cylinder (12) delimit a pressure chamber (14) which communicates with a reservoir (7) for hydraulic fluid via a one-way valve (15), characterized in that a Housing (1) with chambers (7, 8) separated by a partition (6) in a liquid-tight manner is provided, the spring element (3) in one chamber (8) and the damping element (9) in the other chamber (7) are provided, which other chamber (7) forms the reservoir. 2. Clamping device according to claim 1, in which a through the partition wall (6) shaft (4) is provided, on the one hand the partition wall (6) rotatably the clamping arm (2) and on the other hand the partition wall a lever (10) are arranged, the damping element (9) supported on the housing (1) engaging the lever (10). 3. Clamping device according to claim 2, wherein the damping element (9) via a pivot joint (16, 1 7, 18, 19, 22, 21) on the lever (10) and on the Housing (1) is supported. 4. Clamping device according to claim 3, wherein the swivel joint has a spherical head (20, 21) received in a socket (22, 23). 5. Clamping device according to claim 4, in which on the housing side in the reservoir (7) and on the clamping arm side on the lever (10) one of the pans (22, 23) is formed. y 6. Clamping device according to claim 2, in which a helical torsion spring (3) wound around the shaft (4) is provided, which is supported on the one hand on the housing (1) and on the other hand engages the tensioning arm (2). 7. Clamping device according to claim 1, wherein the check valve (15) is immersed in the hydraulic fluid of the reservoir (7). 8. Clamping device according to claim 2, in which at least one sealing ring (1 1) is provided, which closes an existing between the shaft (4) and the partition (6) existing annular gap. 9. Clamping device according to claim 1, wherein the cylinder (12) and the piston (13) are curved. 10. Clamping device according to claim 9, wherein the cylinder (12) and the piston (13) are arranged at least approximately concentrically to the shaft (4).