BELT TRANSMISSION AND METHOD FOR OPERATION THEREOF

Description

[0001] The present application relates to a belt transmission according to the preamble of claim 1. Furthermore, the present application relates to a method for operating a belt transmission according to the preamble of claim 7.

[0002] The belt drive generally comprises at least one drive pulley, at least one driven pulley, at least one belt, and at least one belt tensioner. The drive pulley can interact, in particular, with a drive shaft of a drive device, which can be formed, for example, by an internal combustion engine. By means of the belt, which interacts with both the drive pulley and the driven pulley, it is possible to transfer a torque provided by the drive pulley to the driven pulley. For this purpose, the belt must be applied to the drive pulley and the driven pulley under a certain tension in order to prevent the belt from slipping, known as "slippage." It is understood that if slippage occurs between the belt and the drive and / or driven pulley, only a reduced or even no power transmission takes place.

[0003] In order to tension the belt to an operating tension and to maintain it at the operating tension during operation of the belt drive, the belt drive comprises a belt tensioner. This comprises a tensioning roller arranged on a holding arm, wherein the holding arm is pivotally mounted, in particular on a higher-level structure, for example a fixed frame, to form a pivot axis. An axis of rotation, about which the tensioning roller can rotate relative to the holding arm, is arranged at a distance from the pivot axis of the holding arm, such that the tensioning roller can be moved on a circular path about the pivot axis by pivoting the belt tensioner. The pivot axis is oriented in particular perpendicular to a belt plane, within which the belt continuously rotates on a belt path.

[0004] To apply a tensioning torque to the belt tensioner, it interacts with a tensioning device by means of which the tensioning torque can be exerted. The tensioning device can, in particular, comprise a tension spring provided with a preload. Furthermore, the belt tensioner interacts with a damper that dampens a pivoting movement of the belt tensioner about the pivot axis. In this way, sudden or jerky movements of the tensioning pulley relative to the pivot axis are at least partially prevented.

[0005] Belt drives of the above type are already known in the prior art. Reference is made to German patent application DE 37 18 227 A1. This relates to a tensioning device for belts, which can be used in particular in conjunction with motor vehicle engines. According to the cited document, the special feature is the provision of a damping mechanism for the tensioning device, by means of which the tensioning device can be damped depending on its movement. This means that pivoting of the tensioning device in a first direction of rotation about the pivot axis is free from the influence of the damper, while pivoting in the opposite direction of rotation is damped by the damper. WO01 / 84014A also shows a prior art belt drive.

[0006] In some applications, particularly in agricultural machinery, it has proven problematic that the drive pulley is subject to relatively sudden changes in the applied torque. This is passed on via the belt directly to the driven pulley and thus to the associated output device, e.g. a fan, which means that the output device - as well as the belt itself - is subject to increased wear. A further problem is that sudden changes in the torque at the drive pulley can lead to a load reversal in the belt. This occurs when the torque at the drive pulley decreases, so that at least briefly a transfer of torque from the output to the drive takes place. This is accompanied by the slack side of the belt briefly becoming the load side and vice versa.Thus, the section of the belt that forms the slack side in normal operating conditions is briefly "tightened," which also affects the belt tensioner, which usually acts on the slack side. The tensioner is deflected in a direction away from the belt. The tensioning device then causes the belt tensioner to track the belt as the load is released, returning it to its typical operating condition, so that the belt regains its operating tension. Both the sudden change in the belt's condition and the associated sudden re-tensioning of the belt by the belt tensioner lead to comparatively high wear on the components involved.

[0007] The present application is based on the object of providing a belt transmission which as such is subject to less wear and tear and which also protects the components of the respective drive train from excessive wear.

[0008] The object is achieved according to the invention by means of a belt drive according to claim 1. Advantageous embodiments emerge from the subclaims 2 to 6.

[0009] The belt transmission according to the invention is characterized in that the damper has direction-dependent damping constants, wherein a first damping constant for damping a pivoting movement of the belt tensioner about the pivot axis, which corresponds to a movement of the tension pulley toward the belt, is greater than a second damping constant for damping a pivoting movement of the belt tensioner about the pivot axis, which corresponds to a movement of the tension pulley away from the belt. Advantageously, the damper remains ineffective during the pivoting movement that corresponds to the movement of the tension pulley away from the belt (second damping constant negligibly small). In this special case, the damper is designed to be single-acting, so that it only acts when the pivoting movement occurs that corresponds to a movement of the tension pulley toward the belt.

[0010] Applied to the problem outlined above, the invention ensures that, in the event of a sudden drop in torque at the drive pulley and the associated brief reversal of the slack side into the tight side of the belt, the belt tensioner can be "displaced" in a direction away from the belt due to the resulting "tightening" of the belt, counteracting a very small damping constant of the damper. In other words, the damper counteracts this pivoting of the belt tensioner only slightly. Conversely, however, the effect of the damper prevents the belt tensioner to a much greater extent from suddenly pivoting back toward the belt after its deflection and immediately retensioning the belt to its full operating tension.Instead, the belt tensioner is deliberately delayed, and as a result, in the absence of the belt tensioner's full effect, the belt operates for a certain period at a low tension level below the operating tension, allowing the belt to slip on the drive pulley and / or the driven pulley. This slippage is accompanied by only a limited transfer of the torque applied to the drive pulley to the driven pulley.

[0011] The belt drive according to the invention has many advantages. In particular, as a result of the aforementioned and deliberately induced slippage, an unplanned and undesired torque peak acting on the drive pulley is, as desired, transmitted neither to the belt itself nor to the driven pulley and the connected output device, thus protecting the belt and the output device from excessive wear. Meanwhile, the belt tensioner, under the influence of the tensioning device and the direction-dependent damper, is adjusted only with a delay after its deflection, so that the belt is relatively gently retensioned to its operating tension. Even in normal operating conditions, the belt is constantly at its operating tension, so that the normal transmission of torque from the drive pulley to the driven pulley is not negatively affected by the damper.

[0012] Such a design of the belt transmission is preferred in which the first damping constant of the damper is at least 5 times, preferably at least 7.5 times, more preferably at least 10 times, as large as the second damping constant.

[0013] As already indicated above, it can also be particularly advantageous if the damper is designed to be single-acting, so that the damper only damps the pivoting movement of the belt tensioner around the pivot axis, which corresponds to the movement of the tension pulley toward the belt. In this case, the second damping constant is zero, neglecting minimal frictional resistance, which is always present due to the design of the damper.

[0014] In an advantageous embodiment of the belt drive according to the invention, the damper is formed by a piston-cylinder unit. This can, in particular, be provided with a bypass line fluidically connecting the two working chambers on either side of the piston. The bypass line is equipped with a check valve so that the flow of a corresponding working fluid in one direction is prevented, while flow in the opposite direction is barely impeded or even unhindered. The flow of the working fluid in the direction prevented by the check valve is then only possible, for example, through throttle openings that impede the flow and thus achieve the desired damping effect. In the opposite direction, however, the damper acts to a significantly reduced extent or even not at all due to the bypass line.In this way, a direction-dependent damper can be implemented particularly easily. In general, the damper is advantageously designed in the form of a viscous damper.

[0015] Furthermore, it is particularly advantageous if the belt tensioner interacts with a slack side of the belt, at least during normal operating conditions of the belt drive. This makes it particularly easy to adjust the belt tension.

[0016] In a further advantageous embodiment of the belt drive according to the invention, the tensioning device comprises a tension spring, the spring force of which can be transmitted to the holding arm of the belt tensioner by means of at least one tensioning lever. In particular, the tensioning lever is arranged on the holding arm in such a way that a lever arm between a line of action of the spring force of the tension spring and the pivot axis of the belt tensioner changes as the belt tensioner pivots about the pivot axis. In this way, it is possible to automatically change the tensioning torque acting on the belt tensioner as a result of a pivoting movement of the belt tensioner. This is advantageous in that, depending on the position of the belt tensioner, the belt and the tensioning pulley of the belt tensioner form different wrap angles around which the belt is guided on the tensioning pulley.Depending on the position of the belt tensioner, the belt tension varies, which also causes the force acting on the belt tensioner to vary. Using the aforementioned design, it is possible to counteract the change in the force acting on the belt tensioner with a corresponding change in the tensioning torque, so that the spring force of the tensioning device and the belt tension are in an at least essentially constant relationship to one another. In this way, it is possible, for example, to make a precise statement about the tension acting on the belt by measuring the spring force.

[0017] The underlying problem is further solved from a procedural point of view by means of the method having the features of claim 9. This method is characterized by the method step that the pivoting of the belt tensioner in the direction towards the belt is damped by means of a direction-dependent damper, wherein the damper damps the pivoting of the belt tensioner in a direction away from the belt to a lesser extent than the pivoting of the belt tensioner towards the belt.

[0018] The method according to the invention can be carried out particularly easily using the belt drive according to the invention. This achieves the advantages already mentioned above. In particular, the effect achieved is that after deflection of the belt tensioner, in particular as a result of a sudden drop in torque at the drive pulley and a concomitant reversal of the slack side and tight side of the belt, the adjustment of the belt tensioner is only delayed due to the action of the direction-dependent damper, so that the belt is subject to slippage for a certain period of time because it is not at its operating tension. As a result, sudden fluctuations in torque at the drive pulley are only transmitted to the belt and the output device at a reduced level or not at all, thereby protecting both the belt and the output device.The belt is then tensioned back to its operating tension using the belt tensioner.

[0019] Advantageously, the method is designed such that a tensioning torque acting on the belt tensioner, by means of which the belt tensioner can be tensioned against the belt and thus the latter can be maintained at its operating tension, is changed as a result of a pivoting movement of the belt tensioner. This change preferably takes place automatically or independently, with the tensioning torque preferably being changed proportionally to the belt tension.

[0020] The underlying object is further achieved according to the invention by means of an agricultural work machine having the features of claim 10. This comprises a drive device, which can in particular be formed by an internal combustion engine. Furthermore, the work machine comprises at least one output device that can be driven by the drive device. Finally, the work machine comprises at least one belt transmission according to the invention, by means of which a torque provided by the drive device can be transmitted to the output device. The latter can, for example, be formed by a working element of the work machine. This can be seen in the following exemplary embodiment.

[0021] The device according to the invention is explained in more detail below using an exemplary embodiment shown in the figures. It shows: Fig. 1: A side view of a belt transmission according to the invention, Fig. 2: A perspective view of the belt transmission according to Figure 1 , Fig. 3:A detail of a belt tensioner of the belt transmission according to Figure 1 in cooperation with a tensioning device and a damper and Fig. 4: A schematic side view of an agricultural working machine which is equipped with a belt transmission according to the invention.

[0022] An example of implementation that is shown in the Figures 1 to 4 shown, a belt transmission according to the invention comprises 1, which is a drive pulley 2, a driven pulley 3 and a drive pulley 2 and the output pulley 3 connecting straps 4 The drive pulley 2 is connected to a drive shaft in a torque-transmitting manner 22 which in turn is connected to a gearbox 24Furthermore, the belt transmission includes 1 in the example shown a calming role 21, which, however, is not relevant for achieving the advantages of the present invention. Finally, the belt transmission comprises 1 a belt tensioner 5, which has a slack strand 11 of the belt 4 By means of the belt tensioner 5 the belt 4 tensioned to an operating voltage so that a slip-free and therefore reliable transmission of torque from the drive pulley 2 on the output pulley 3 can be done.

[0023] The belt tensioner 5 includes a holding arm 6 and one at one end of the support arm 6 arranged tension pulley 7. The latter is around a rotation axis 23 freely rotatable on the holding arm 6 stored. The holding arm 6is in turn attached to one of the tension pulleys 7 opposite end forming a pivot axis 8 pivoted on a higher, stationary component. The latter is here supported by a rigid frame 20 formed. The pivot axis 8 In the example shown, it is arranged perpendicular to a belt plane within which a path of the belt 4, on which the belt 4 constantly moving, located.

[0024] The belt tensioner 5 works with a clamping device 9 together, by means of which a tensioning torque is applied to the belt tensioner 5 exercised and in this way the tension roller 7 in one direction on the belt 4 To this end, the clamping device has 9 via a tension spring 13, which is preloaded with a spring force. Said spring force acts along a line of action 16on a tension lever 14, which transmits torque to the holding arm 6 the belt tensioner 5 The line of action 16 the spring force extends to form a lever arm 15 relative to the swivel axis 8 the belt tensioner 5, so that the spring force creates a clamping moment around the swivel axis 8 causes.

[0025] As can be seen in particular from the illustration in accordance with Figure 1 The clamping lever is 14 designed in such a way that a pivot point of the spring force on the clamping lever 14 with swiveling of the belt tensioner 5 around the swivel axis 8 on a circular path around the latter. This means that when the belt tensioner pivots 5 the lever arm 15 is changed. Consequently, the tensioning device also changes 9caused tensioning torque, under the effect of which the belt tensioner 5 the belt 4 The design is advantageously chosen in such a way that a pivoting movement of the belt tensioner 5 or its tension pulley 7 on the belt 4 which is associated with an increase in the wrap angle 27 between belts 4 and tension pulley 7 and an increase in the tension of the belt 4 , directly results in an increase in the clamping torque. Ideally, the geometric relationships between the clamping device 9 and belt tensioner 5 using a clamping lever 14 selected so that the tension of the belt 4 and the clamping torque caused by the spring force change proportionally to each other.

[0026] According to the invention, the belt tensioner acts 5 also with a damper 10which acts in a direction-dependent manner according to the invention. In the example shown, the damper is 10 single-acting, so that its second damping constant, under which the damper 10 a pivoting of the belt tensioner 5 dampens, which with a movement of the tension pulley 7 from the belt 4 away, is equal to zero. The damper 10 is here from one with a piston 25 and a cylinder 26 equipped piston-cylinder unit, whereby the damper 10 with its first end on the holding arm 6 and its opposite second end to the stationary frame 20 The damper 10 is aligned in such a way that it allows a pivoting movement of the belt tensioner 5 around the swivel axis 8 - based on the representation according to Figure 1- clockwise rotation is not obstructed or dampened. Consequently, the belt tensioner 5 free from the effect of the damper 10 around the pivot axis 8 be pivoted so that the tension pulley 7 from the belt 4 This functionality allows the belt tensioner 5 in the course of a sudden tightening of the slack strand 11 of the belt 4, particularly as a result of load reversal when the torque on the drive pulley falls 2, the suddenly increasing tension in the slack strand 11 In this constellation, the empty strand 11 briefly to the load strand, while a load strand 12 of the belt 4 briefly becomes a slack strand.

[0027] By means of the damper 10 is then a pivoting movement of the belt tensioner 5counterclockwise, that is, in such a way that the tension roller 7 on the belt 4 to move, damped, whereby the first damping constant takes effect. This prevents the belt tensioner 5 after relieving the belt 4 in the empty strand 11 immediately the belt 4 Instead, the belt is 4 operated for at least a moment with a voltage that is below the actually desired operating voltage. This results in a tension between the belt 4 and the drive pulley 2 or the output pulley 3 slippage occurs, which causes a transmission of torque between the drive pulley 2 and the output pulley 3 This has the positive effect that torque peaks, which occur particularly on the drive pulley 2 may be present, not directly on the belt4 and to the output pulley 3 This protects both components from excessive wear.

[0028] Such torque peaks and sudden load reversals in the belt 4 can occur, for example, when starting an internal combustion engine used as a drive device. After overcoming the "rough operation," the belt can 4 be tensioned back to its operating tension. The time delay with which the belt tensioner 5 on the belt 4 is acted upon, is achieved by means of the damper 10 which allows the belt tensioner to be adjusted 5, which is caused by the tensioning device 9 This results in the effect that during the period of "unsteady operation" torque peaks due to the slip between belts 4and drive pulley 2 and driven pulley 3 be excluded to some extent and the effect of the belt tensioner 5 only starts again once this period has passed. During normal operation, the belt transmission transmits 1 then, as desired, the drive pulley 2 applied torque, since the belt 4 using the belt tensioner 5 is tensioned to its operating voltage.

[0029] Figure 4 shows an example of an agricultural working machine according to the invention 17, in which the belt transmission according to the invention 1 is installed. The working machine 17 includes a drive device 18, which is designed here in the form of an internal combustion engine. Furthermore, the working machine comprises 17 an output device 19,which is formed here, for example, by a separating device, namely a tray shaker. By means of the belt drive 1 a drive device 18 torque provided to the output device 19 so that the latter can be operated. List of reference symbols

[0030] 1Belt drive 2Drive pulley 3Drive pulley 4Belt 5Belt tensioner 6Holding arm 7Tension pulley 8Pivot axis 9Tensioning device 10Damper 11Slack side 12Load side 13Tension spring 14Tension lever 15Lever arm 16Line of action 17Working machine 18Drive device 19Output device 20Frame 21Stabilizing pulley 22Drive shaft 23Rotary axis 24Gearbox 25Piston 26Cylinder 27Wrap angle

Claims

1. A belt drive (1), comprising - at least one belt (4) - at least one belt tensioner (5) - at least one tensioning device (9), as well as - at least one damper (10), wherein the belt tensioner (5) has a retaining arm (6) which can be pivoted about a pivot axis (8), as well as a tensioning roller (7) disposed on the retaining arm (6), wherein, by means of the tensioning device (9), a tensioning moment acting with respect to the pivot axis (8) can be exerted on the belt tensioner (5), wherein, by means of the damper (10), a pivoting movement of the belt tensioner (5) about the pivot axis (8) can be damped and the damper (10) has directional damping constants, characterized in that a first damping constant for damping a pivoting movement of the belt tensioner (5) about the pivot axis (8) which corresponds to a movement of the tensioning roller (7) onto the belt (4) is larger than a second damping constant for damping a pivoting movement of the belt tensioner (5) about the pivot axis (8) which corresponds to a movement of the tensioning roller (7) away from the belt (4), wherein the second damping constant is negligibly small, wherein the damper (10) is single-acting in construction so that, by means of the damper (10), only the pivoting movement of the belt tensioner (5) about the pivot axis (8) which corresponds to the movement of the tensioning roller (7) onto the belt (4) can be damped.

2. The belt drive (1) according to claim 1, characterized in that the damper (10) is formed by a piston and cylinder unit.

3. The belt drive (1) according to one of claims 1 to 2, characterized in that the damper (10) is formed by a viscosity damper.

4. The belt drive (1) according to one of claims 1 to 3, characterized in that the belt tensioner (5) cooperates with a no-load side (11) of the belt (4).

5. The belt drive (1) according to one of claims 1 to 4, characterized in that the tensioning device (9) comprises a tension spring (13) the spring force of which can be transmitted to the retaining arm (6) of the belt tensioner (5) by means of at least one tension lever (14).

6. The belt drive (1) according to claim 5, characterized in that the tension lever (14) is disposed on the retaining arm (6) in a manner such that a lever arm of a force (15) between a line of action (16) of the spring force of the tension spring (13) and the pivot axis (8) of the belt tensioner (5) is changed as the belt tensioner (5) is pivoted about the pivot axis (8).

7. A method for operating a belt drive (1), wherein the belt drive (1) comprises a drive pulley (2), a driven pulley (3), a belt (4), a belt tensioner (5), a tensioning device (9) as well as a damper (10), comprising the following steps of the method: a) a tensioning roller (7) of the belt tensioner (5) is tensioned against the belt (4) with the application of a tensioning moment which is applied to a retaining arm (6) of the belt tensioner (5) by means of the tensioning device (9), so that the belt (4) is tensioned to an operating tension, b) during the course of a reduction in a drive torque acting on the drive pulley (2) which is associated with a reversal of load between a no-load side (11) and a load side (12) of the belt (4), the belt tensioner (5), which cooperates with the no-load side (11), is pivoted about a pivot axis (8) in the direction away from the belt (4), so that a tension of the belt (4) drops below the operating tension, c) by means of the action of the tensioning device (9), the belt tensioner (5) is pivoted back again in the direction onto the belt (4), so that the belt (4) is again tightened to its operating tension, characterized by the following step of the method: d) the pivoting of the belt tensioner (5) in the direction onto the belt (4) is more strongly damped by means of one of the dampers (10) than the pivoting of the belt tensioner (5) in the direction away from the belt (4), namely in that the damper (10) is single-acting in construction so that, by means of the damper (10), only the pivoting movement of the belt tensioner (5) about the pivot axis (8) which corresponds to the movement of the tensioning roller (7) onto the belt (4) can be damped.

8. An agricultural working machine (17), comprising - a drive device (18), - at least one driven device (19) which can be driven by means of the drive device (18), as well as - at least one belt drive (1) as claimed in one of claims 1 to 6, by means of which a torque made available by the drive device (18) can be transmitted to the driven device (19).