DE102018117560B4 - Device for torque transmission - Google Patents

Abstract

Device (31) for transmitting torque from a drive unit (30) to a working device (41), in particular from a tractor to a working device (41), via a transmission (39) with a torque switch (38), for changing the transmission ratio of the transmission (39) operable by a drive shaft (40) as a function of a torque difference between the drive shaft (40) and a transmission input shaft (45) of the transmission (39), wherein the drive shaft (40) can be driven by the drive unit (30), characterized in that the torque switch (38) has a device for generating a hydraulic output signal, that the torque switch (38) has a rotary slide with a first shaft (13) and a second shaft (14), wherein these have a common axis of rotation (38a) and are mounted so as to be rotatable relative to one another and are coupled via a first spring (4), and that the first shaft (13) has at least one first hydraulic inlet channel (6) and a first hydraulic return channel (7), each with at least one channel opening (6a, 7a), and the second shaft (14) has at least one second inlet channel (11) and a second return channel (12), each with at least one channel opening (11a, 12a), wherein the first inlet channel (6) and the second inlet channel (11) are fluidly connected to one another via their channel openings (6a, 11a) in at least one first rotational position of the two shafts (13, 14) relative to one another, while the first return channel (7) and the second return channel (12) are not fluidly connected via their channel openings (7a, 12a) in this position, and that the first return channel (7) and the second return channel (12) are fluidly connected to one another via their channel openings in at least one second rotational position of the two shafts (13, 14) relative to one another, while the first inlet channel (6) and the second inlet channel (11) are not fluidly connected via their channel openings in this position (6a, 11a) are separated from each other.

Description

The invention relates to a device for transmitting torque from a drive unit to a working device, in particular from a tractor to a working device, via a transmission with a torque switch, for changing the gear ratio of the transmission operable by a drive shaft as a function of a torque difference between the drive shaft and a transmission input shaft of the transmission, wherein the drive shaft can be driven by the drive unit, and to a method for operating a working device, wherein a torque is transmitted from a drive unit, in particular a tractor, to the working device, the working device has a transmission operated by a drive shaft, and the transmission is switched automatically by a torque switch as a function of the torque of the drive shaft.

Work equipment operated by drive units is used in many parts of the economy, but particularly in agriculture in the form of work equipment pulled and driven by tractors or similar tractors, such as harrows, plows and others. Work equipment is understood to mean all work machines or driven devices, particularly in the agricultural sector, which absorb energy in the form of mechanical work and are used to carry out a specific work or a specific work step and for this purpose must be supplied with at least a torque by a drive unit. Drive units are understood to mean power machines that emit mechanical energy and are suitable for driving work equipment. Drive units therefore include, for example, internal combustion engines including drive trains. The work equipment can often, but not always, be moved by the drive unit when it is in operation; for example, bar mowers are used while the tractor is moving. However, this is not advantageous for all drive units, for example circular saws or wood splitters, which are supplied with torque by tractors when they are stationary. In most cases, the work equipment can be separated from the drive unit, or a drive unit can operate different work equipment simultaneously or one after the other. As a rule, the torque is transmitted via a power take-off shaft or auxiliary drive on the drive unit to which the implement is connected.

The torque with which the implement is operated should not exceed a certain maximum value in order to avoid damage to the mechanics of the implement and the power take-off shaft. For this purpose, it is advisable to provide a gearbox in the implement. A torque switch is often provided for this purpose, which measures the torque of a drive shaft and a gearbox that can be operated by the drive shaft is switched on the basis of this measured value in order to prevent the maximum value from being exceeded.

The DE 28 05 619 A1 shows a vehicle that has an overload protection device that decouples a drive shaft from a device shaft when excessive torque occurs. This effectively prevents the system from being overloaded. The disadvantage, however, is that decoupling automatically leads to freewheeling and thus an interruption of the torque supply to the device that is driven via the device shaft. This temporarily renders this device inoperable.

From the EN 10 2012 212 936 A1 Control devices are known which are used to control a transmission of a drive train, whereby the torque of an input shaft is measured by means of a sensor connected to a vehicle computer and the transmission is switched depending on the measured torque so that the torque does not exceed a threshold value. However, devices of this type are prone to malfunctions and errors.

In the JP S61- 155 716 A discloses a torque switch that is suitable for outputting a hydraulic output signal at a specific torque. For this purpose, two coaxial shafts are connected to one another via a rubber member. If the amount of the torque difference between the shafts exceeds a maximum value, a flow connection is established by twisting the rubber member between two hydraulic channels and a hydraulic signal is output. If the torque difference is below this maximum value, no signal is output and it is not possible to tell whether the torque difference is just below the maximum value or whether it is falling too much and is far below it. This makes optimal switching between different gears difficult.

In the EN 10 2013 110 315 A1 Drive units such as tractors are described, which transmit torque to a working device via a power take-off shaft, whereby a power take-off shaft transmission is switched depending on at least one operating parameter. The type of sensor or signal transmission is not described in more detail.

The object of the invention is therefore to provide a device for transmitting torque from a To provide a drive unit for a work device or a method for operating a work device which is as simple and robust as possible and prevents damage to the work device during normal operation due to the transmission of excessive torque from the drive unit and/or enables optimal gear shifting during normal operation.

This object is achieved according to the invention in that the torque switch has a device for generating a hydraulic output signal, in that the torque switch has a rotary slide with a first shaft and a second shaft, wherein these have a common axis of rotation and are mounted so as to be rotatable relative to one another and are coupled via a first spring, and in that the first shaft has at least one first hydraulic inlet channel and a first hydraulic return channel, each with at least one channel opening, and the second shaft has at least one second inlet channel and a second return channel, each with at least one channel opening, wherein the first inlet channel and the second inlet channel are fluidly connected to one another via their channel openings in at least one first rotational position of the two shafts relative to one another, while the first return channel and the second return channel are not fluidly connected via their channel openings in this position, and in that the first return channel and the second return channel are fluidly connected to one another via their channel openings in at least one second rotational position of the two shafts relative to one another, while the first inlet channel and the second inlet channel are fluidly connected to one another via their channel openings in this position. are separated.

This is also achieved by the torque switch generating a hydraulic output signal at at least one defined torque and sending it to the transmission, a first shaft and a second shaft of a rotary slide valve of the torque switch being mounted so that they can rotate relative to one another and these shafts have a common axis of rotation and they are coupled via a first spring and that at at least a first torque of the drive shaft a flow connection is established between a first inlet channel of the first shaft with at least one channel opening and a second inlet channel of the second shaft with at least one channel opening via their channel openings, while a flow connection between a first return channel of the first shaft with at least one channel opening and a second return channel of the second shaft with at least one channel opening is interrupted in this position via their channel openings with at least one channel opening, and that a flow connection between the first return channel and the second return channel is established at at least a second torque of the drive shaft via their channel openings, while the flow connection of the first inlet channel and the second inlet channel is interrupted in this position via their channel openings.

By generating a hydraulic output signal or by sending hydraulic output signals, a signal is transmitted between the torque switch and the gearbox in a very simple manner. Since hydraulic systems are very robust and durable, and the use of electrical systems and structurally complex and error-prone mechanical devices is avoided, the longest possible service life of the work equipment can be ensured. It also eliminates the sometimes complicated power supply. Since most drive units have a hydraulic interface to provide hydraulic power anyway, the use of a hydraulic system is particularly advantageous, as the hydraulic power usually does not have to be generated by the work equipment itself. The integration of the switching function into the work equipment also makes the system very cost-effective and fast.

In many known systems with comparable simplicity and as few connections as possible between the drive unit and the implement, it is often only possible for the person setting up the device to manually shift the gear, which must be done directly on the implement. This is disadvantageous because usually only one person operates the work setup and this person is usually busy with the drive unit, for example steering a tractor. This means that the person has to leave their position, shift the gear directly on the implement and only then can they continue working. This is not necessary with the devices and methods described and work therefore no longer needs to be interrupted.

Such a device or method can also achieve optimal gear shifting behavior, since the gear shifting occurs automatically and is determined by the torque of the drive shaft, which represents the optimal parameter for determining the gear shifting time.

In a preferred design variant of the device, the gear can only be switched by the torque switch. Due to the independence from the drive unit, on the one hand, the structure of the device is simplified, and on the other hand, disadvantageous gear shifting is prevented. The person operating the drive unit can no longer cause gear states that are disadvantageous for the implement by actively shifting gears, as they place unnecessary strain on it. At the same time, the operator no longer has to worry about shifting the gears and can concentrate on other aspects of the work, which is a relief for them. At the same time, the implement does not have to be additionally connected to the drive unit, as no transmission of switching signals is required. This means that the implement can also be used with simple drive units that do not have complex logic for shifting the implement's gears. In addition, this also prevents interface problems when such logic is present.

If the transmission is designed as a powershift transmission, this improves the performance of the implement, as work does not have to be interrupted during the gearshift process. Two-stage powershift transmissions in particular are easy to implement and are often sufficient to ensure good function.

In order to prevent the gearbox from switching back and forth unnecessarily when the torque of the drive shaft moves between values just above and just below the threshold value at which switching takes place, it is advantageous to provide a torque hysteresis. This refers to a switching behavior in which the threshold value for switching in one direction and the threshold value for switching in the other direction are different. If a multi-stage gearbox is used rather than a two-stage gearbox, this refers to the transition between two successive stages. Different hystereses can be provided for different stage transitions.

The form in which the generated signals influence the transmission can vary depending on the design. For example, in a design with two signals and a two-stage transmission, it can be useful to emit a signal until a gear change is required. If this occurs, the signal is terminated and a second signal is started to be emitted. Once the gear change has been completed, the second signal remains until another gear change is required, which is indicated by a change to the first signal. Another possibility is for the signals to only represent short sequences that are terminated shortly after the desired gear change or, if necessary, before it.

According to the invention, the torque switch has a rotary slide with a first shaft, which is preferably connected to the drive shaft, and with a second shaft, which is preferably connected to the gear, whereby these have a common axis of rotation. The shafts can be arranged at least partially concentrically to one another or one behind the other, or even only touch one another at one end; in any case, they are mounted so that they can rotate relative to one another and are coupled via a first spring.

Furthermore, the first shaft has at least one first hydraulic inlet channel and a first hydraulic return channel, each with at least one channel opening, and the second shaft has at least one second hydraulic inlet channel and a second hydraulic return channel, each with at least one channel opening. Depending on the design variant, several channels can also be provided, in particular if the transmission has more than two stages. It is essential that the first inlet channel and the second inlet channel are fluidly connected to one another via their channel openings in at least one first rotational position of the two shafts relative to one another, while the first return channel and the second return channel are not fluidly connected to one another via their channel openings in this position, i.e. are separated, and that the first return channel and the second return channel are fluidly connected to one another via their channel openings in at least one second rotational position of the two shafts relative to one another, while the first inlet channel and the second inlet channel are not fluidly connected to one another via their channel openings in this position, i.e. are separated. Depending on the design, the channel openings can be located either on the inner or outer casing of the shafts if the shafts at least partially run into each other, or can also be located on the end faces facing each other. The openings do not necessarily have to be round; they can also have an elongated shape, for example, in order to increase the range of rotation in relation to the shafts in which the inlet channels or return channels are fluidly connected. If necessary, the shafts can change their shape or diameter in the area close to the other shaft. For example, they can be reinforced or have flange-like ends to provide more space for the inlet channels and return channels or their openings. An example of a cheap and simple method of manufacturing the inlet channels and return channels is to drill the channels into the shafts.

By using such a torque switch, the torque difference between the torques of the first shaft and the torques of the second shaft can cause the two shafts to rotate relative to one another. The degree of rotation therefore reflects the size of the torque difference. If a torque difference is so large that the shafts assume the described first rotational position relative to one another, a hydraulic flow of the actuating fluid can take place via at least one first and second inlet channel, while this is not the case via at least one first and second return channel. If the torque changes in such a way that the shafts move into the second rotational position relative to one another, a hydraulic flow of the actuating fluid can take place via at least one first and second return channel, while this is not the case via at least one first and second inlet channel. This allows at least two different signals to be generated depending on the torque acting. The same applies to a method in which pressure sources or pressure sinks are connected to hydraulic control lines of the transmission, depending on the torque of the drive shaft.

In order to generate a hydraulic signal, a pressure source or pressure sink can be provided in the torque switch itself, which automatically increases or decreases the pressure of the actuating fluid for the signal, but a corresponding pressure source or sink could also be provided elsewhere in the work device. However, it is particularly advantageous if the pressure source or pressure sink is located in the drive unit and the torque switch is subjected to at least two different pressure levels of the actuating fluid through hydraulic connections between this and the first hydraulic inlet channel or first hydraulic return channel. In the case of more than one inlet channel and one return channel, it can also be advantageous to supply the different inlet channels or return channels with different hydraulic pressure strengths, or to provide several pressure sources or pressure sinks in general, which may differ in the size of the pressure or negative pressure.

In order to fix a defined rotational position of the first and second shaft until defined minimum torques are applied, an advantageous embodiment can provide locking bodies which are brought into a locking position in at least one rotational position of the two rotatable shafts relative to one another. These should generally be designed in such a way that the rotational position between the shafts is not changed within a certain first minimum torque in one direction and a second minimum torque in the other direction. In most cases, the first minimum torque and second minimum torque should be selected in such a way that they can occur during the intended use of the tool. If necessary, however, the locking body can also be designed to prevent the shafts from rotating too much relative to one another and can only be released in one direction of rotation. Depending on the application, the first minimum torque and the second minimum torque can therefore be selected symmetrically, i.e. so that both minimum torques have the same amount and only differ in the direction of rotation, or they can be selected asymmetrically. A similar result can also be achieved if a method is used in which a locking body is brought into a locking position in at least one rotational position of the two rotatable shafts relative to each other.

The design of such a locking body can provide that the locking body sits on one shaft and is moved into a recess provided for this purpose in the other shaft in a specific rotational position. This provides an easy-to-construct embodiment that defines a rotational position within a specific torque band between the first minimum torque and the second minimum torque. The locking body can preferably be moved into the recess by a spring. The torque band is determined by the shape of the locking body, the shape and above all the depth of the recess and other factors, such as the characteristic curve of the spring provided if necessary.

The characteristic curve of the first spring largely determines the rotational behavior of the two shafts in relation to each other. It is therefore advantageous to provide at least one adjusting screw in order to be able to precisely adjust the tension force of the first spring. These adjusting screws can be attached to the mechanical stops and exert additional force on the first spring when turned. This allows the sensitivity and spring travel to be adjusted.

In order to prevent the shafts from over-rotating relative to one another, at least one stop can be provided in an advantageous embodiment to limit the rotational movement of the first shaft and the second shaft relative to one another. For example, such stops in the form of protruding fingers can be provided directly on the first spring or on its suspension. This represents a very simple and cost-effective variant in order to prevent maximum rotation. If the shafts are in a position in which at least one stop prevents further rotation in one direction, no minimum torque needs to be applied so that the shafts can rotate in the other direction - provided that the rotational position is not additionally determined by a locking body, if present.

It is advantageous if, in a rotational position in which at least one locking body is in a locking position, at least two inlet channels or return channels running in different shafts are fluidically connected. By fixing the first shaft and second shaft in a rotational position when at least one channel is fluidically connected, it is ensured that the actuating fluid flows through the corresponding channels in this rotational position for a longer period of time and thus a sufficiently long and clear signal can be passed on to the gearbox. This also means that the signal remains until a minimum torque acts on the locking body and it moves from its locking position.

It is particularly advantageous if a locking body can assume two locking positions and, when assuming a first locking position, the first inlet channel and the second inlet channel are fluidly connected to one another via their channel openings, while the first return channel and the second return channel are not fluidly connected to one another via their channel openings in this locking position, and that, when assuming the second locking position, the first return channel and the second return channel are fluidly connected to one another via their channel openings, while the first inlet channel and the second inlet channel are not fluidly connected to one another via their channel openings in this locking position. Something similar can also be achieved if a method is used in which, with two torques, on the one hand a pressure source is connected to a control line and a control line is separated from a pressure sink, or on the other hand a control line is separated from a pressure source and a pressure sink is connected to a control line. These embodiments or these methods are particularly advantageous in two-stage transmissions, since in a reduced embodiment it can be ensured that at least two different switching signals are generated by the torque switch in two different rotational positions. It is particularly advantageous here if the switching signals are assigned to different hydraulic pressure levels of the actuating fluid, at which actuators of the transmission's clutches are actuated via hydraulic control lines. These are therefore clear switching signals for the transmission in order to change the gear ratio. In this sense, it is particularly advantageous if the rotational behavior of the shafts in relation to one another is selected such that the minimum torque that must be applied so that the locking body leaves the first locking position in the direction of the second locking position corresponds to the torque at which a shift in the transmission is desired. When such a torque is applied, the locking body leaves the first locking position, the inlet channels that were previously flow-connected are rotationally displaced in such a way that they are no longer flow-connected, and the hydraulic signal emitted to the control line through the flow connection is terminated. The first and second shafts continue to rotate against each other in the direction specified by the torque due to the action of the torque. This torque is usually made up of the difference between the external torques transmitted to the first and second shafts by the drive shaft or the gearbox, and primarily counteracts the spring torque exerted by the first spring. The shafts therefore continue to rotate until the locking body reaches the second locking position and is pushed into it. This fluidly connects the return channels, which generate a signal that is preferably the opposite of the signal described for the first rotational position. This can trigger a gear shift in the gearbox. When the torque is reduced, this second rotational position is maintained by the locking device until the torque in the opposite direction exceeds a minimum torque, so that the locking body is released from its second locking position and the shafts rotate against each other again in the direction of the first rotational position. The first and second rotational positions described can be so close to one another that when the rotational position changes, there is a direct transition from the flow connection of the inlet channels to the flow connection of the return channels. This is achieved by the angular difference between the described rotational positions being only a few degrees, for example 45°, depending on the size of the channel openings. However, it can also be advantageous to provide a distance of more than just a few degrees, thus clearly ending one signal before the other signal begins to be generated.

A similar system can also be used for multi-stage transmissions. In such cases, there would be several locking positions for one locking body, or there would be more locking bodies with different different locking positions can be provided so that more than two rotational positions can be determined by the locking bodies. In each rotational position in which at least one locking body is in a locking position, at least two inlet channels or return channels running in different shafts are fluidically connected.

A variant is also possible in which a locking body can assume at least one locking position in a rotational position between the first and second rotational positions. In this intermediate rotational position, preferably neither the inlet channels nor the return channels are fluidically connected, as a result of which no output signal is generated. This can be advantageous if the device is designed in such a way that the transmission does not shift in this state, but shifts a gear higher or lower when one of the two signals is received. It may be advantageous to fluidically connect the inlet channels or return channels in this intermediate position as well, but the routing of just a first and second inlet channel and just a first and second return channel can be sufficient to obtain a device that can shift a three-stage or even more-stage transmission.

• 1 eine erfindungsgemäße Vorrichtung in einer schematischen Darstellung;
• 2 einen Drehmomentschalter einer erfindungsgemäßen Vorrichtung in einer ersten Drehstellung in einem Schnitt gemäß einer Linie I-I in 3;
• 3 den Drehmomentschalter in einem Schnitt gemäß der Linie III-III in 2;
• 4 diesen Drehmomentschalter in einer Zwischendrehstellung in einem Schnitt analog zu 2;
• 5 den Drehmomentschalter in einer zweiten Drehstellung in einem Schnitt gemäß der Linie V-V in 5;
• 6 den Drehmomentschalter in einem Schnitt gemäß der Linie VI-VI in 5.

In the following, the present invention is explained in more detail with reference to the embodiments shown in the non-limiting figures. They show:

• 1 a device according to the invention in a schematic representation;
• 2 a torque switch of a device according to the invention in a first rotational position in a section along a line II in 3 ;
• 3 the torque switch in a section along the line III-III in 2 ;
• 4 this torque switch in an intermediate rotation position in a section analogous to 2 ;
• 5 the torque switch in a second rotational position in a section along the line VV in 5 ;
• 6 the torque switch in a section along the line VI-VI in 5 .

1 shows a device 31 according to the invention for transmitting torque from a drive unit 30 to a working device 41 via a universal joint shaft 32. The drive unit 30 has an internal combustion engine 33 which is connected to a transmission 35 via a clutch 34. This transmission 35 represents the main transmission of the drive unit 30 and is connected, among other things, to a power take-off shaft 37 via a power take-off shaft clutch 36. This power take-off shaft 37 is connected to a drive shaft 40 of the working unit 31 via the universal joint shaft 32. The drive torque is thus transmitted to the torque switch 38. The torque switch 38 transmits the drive torque of the drive unit 30 via a transmission input shaft (45) to a two-stage powershift transmission 39, the transmission output 39a of which drives the working device 41 of the device 31.

The transmission 39 is designed, for example, as a powershift transmission and, in the exemplary embodiment, has two gear ratios S1, S2, which are switched via a first clutch 42 and a second clutch 43. The first clutch 42 and the second clutch 43 are automatically switched by the torque switch 38, which generates a hydraulic output signal, depending on the drive torque of the drive shaft 40, with one of the two clutches 42, 43 being engaged and the other clutch 43, 42 being disengaged. In the idle state, i.e. in the pressure-free state, the first clutch 42 is closed and the second clutch 43 is opened. The respective actuator 42a, 43a of the first clutch 42 or second clutch 43 is connected to a pressure source 50 or pressure sink 51 via the torque switch 38 and the hydraulic control lines 42b, 43b.

In the 2 to 6 an embodiment of a torque switch 38 is shown, which has a first inlet channel 6, a second inlet channel 11, as well as a first return channel 7 and a second return channel 12. The first inlet channel 6 and the first return channel 7 extend inside a first shaft 13 and each have a channel opening 6a, 7a on the outer casing 13a of the first shaft 13, the second inlet channel 11 and the second return channel 12 run inside a second shaft 14 and each have a channel opening 11a, 12a on the inner casing 14a of the second shaft 14. The first shaft 13 is in drive connection with a power take-off shaft 32 of the working machine 30, the second shaft 14 is connected to a gearbox 39, as can be seen from 1 can be seen. The power take-off shaft 32 transmits a drive torque to the first shaft 13. The first shaft 13 runs partly inside the second shaft 14, whereby these can be rotated relative to each other. A first spring 4 has a first end element 15 and a second end element 5, whereby the first end element 15 is firmly connected to the first shaft 13 and the second end element 5 is firmly connected to the second shaft 14. Along a guide in which When the first spring 4 moves, end stops 8 are provided on the first shaft 13 and on the second shaft 14, which limit the movement of the first spring 4.

In the 2 and 3 In the first rotational position of the shafts 13, 14 shown, the channel openings 7a, 12a of the first return channel 7 and the second return channel 12 lie one above the other, whereby these channels are fluidically connected, while the channel openings 6a, 11a of the first inlet channel 6 and the second inlet channel 11 are rotated relative to one another, whereby these inlet channels 6, 11 are not fluidically connected. In the first rotational position shown, a hydraulic flow 20 of the actuating fluid can therefore take place. In this position, the actuators 42a, 43a of the clutches 42, 43 are connected to the pressure sink 51. In this configuration, a first gear ratio is set. The gear ratio is changed depending on the load. Furthermore, a locking unit is provided, which consists of a cylindrical locking body 1, for example, which is guided in a radial bore in the first shaft 13. The locking body 1 is pressed against the second shaft 14 by the pre-tension of a second spring 2, for example a helical spring. The second shaft 14 has recesses 3a, 3b, which are matched to the geometry of the locking body 1, whereby the position of each recess 3a, 3b is assigned to a defined rotational position of the two shafts 13, 14. In the 2 In the first rotational position shown, the locking body 1 engages in the first recess 3a and in a 4 shown second rotational position into the second recess 3b. Each recess 3a, 3b has lateral ramps 3c, 3d. The slope of the ramps 3c, 3d and the second spring 2 are coordinated such that the locking body 1 is released when the drive shaft 40 has a defined torque. When the defined torque is reached, the locking body 1 is pressed out of the recess 3a by the lateral ramps 3c, 3d against the force of the second spring 2.

In 4 an intermediate rotation position is shown in which the 2 the hydraulic flow 20 shown is no longer possible because when the first shaft 13 rotates in relation to the second shaft 14, the flow of the actuating fluid from the clutch to the tank is interrupted. In this phase, the first spring 4 is compressed. As a result, the circumferential force on the first spring 4 increases due to the further rotation of the first shaft 13. The first spring 4 must be able to store the mechanical energy to ensure a downshift when the drive torque decreases, which occurs due to the changed gear ratio. At the end of this compression phase, the spring force reaches its maximum force and the locking body 1 engages in a further recess 3. There, there is a balance of forces between the circumferential force and the spring force (plus the inertia force of the shaft 13 to accelerate the shaft 13 in the locking position 3b).

In 5 and 6 the locking body 1 has moved into the further recess 3. Further rotation of the first shaft 13 is prevented on the one hand by the locking mechanism itself and on the other hand by the pre-tensioned first spring 4. In this rotational position, the two channel openings 7a, 12a of the first return flow channel 7 and the second return flow channel 12 overlap. A hydraulic return flow 20 can now take place via the control lines 42b, 43b to the pressure sink 51. The pressure reduction in the control lines 42b, 43b causes pressure to build up in the gear 39 and a gear ratio change occurs. Within the further recess 3, the locking body 1 is able to absorb changes in the drive torque. However, if the drive torque falls below a minimum torque of the further recess 3, the transition to an intermediate rotational position is initiated. With appropriate design of the spring stiffness and the recesses 3, a hysteretic behavior with regard to drive torque can be achieved.

Claims (15)

Device (31) for transmitting torque from a drive unit (30) to a working device (41), in particular from a tractor to a working device (41), via a transmission (39) with a torque switch (38), for changing the transmission ratio of the transmission (39) operable by a drive shaft (40) as a function of a torque difference between the drive shaft (40) and a transmission input shaft (45) of the transmission (39), wherein the drive shaft (40) can be driven by the drive unit (30), characterized in that the torque switch (38) has a device for generating a hydraulic output signal, that the torque switch (38) has a rotary slide with a first shaft (13) and a second shaft (14), wherein these have a common axis of rotation (38a) and are mounted so as to be rotatable relative to one another and are coupled via a first spring (4), and that the first shaft (13) has at least one first hydraulic inlet channel (6) and one first hydraulic return channel (7) with each having at least one channel opening (6a, 7a), and the second shaft (14) has at least one second inlet channel (11) and a second return channel (12) each having at least one channel opening (11a, 12a), wherein the first Inlet channel (6) and the second inlet channel (11) are fluidly connected to one another via their channel openings (6a, 11a) in at least a first rotational position of the two shafts (13, 14) relative to one another, while the first return channel (7) and the second return channel (12) are not fluidly connected to one another via their channel openings (7a, 12a) in this position, and that the first return channel (7) and the second return channel (12) are fluidly connected to one another via their channel openings in at least a second rotational position of the two shafts (13, 14) relative to one another, while the first inlet channel (6) and the second inlet channel (11) are separated from one another via their channel openings (6a, 11a) in this position. Device (31) according to Claim 1 , characterized in that the transmission (39) can be switched exclusively by the torque switch (38), independently of the drive unit (30) operating the drive shaft (40). Device (31) according to Claim 1 or 2 , characterized in that the transmission (39) is a, preferably two-stage, powershift transmission. Device (31) according to one of the Claims 1 until 3 , characterized in that the switching behavior of the torque switch (38) has a torque hysteresis. Device (31) according to one of the Claims 1 until 4 , characterized in that at least one first inlet channel (6) can be connected to at least one pressure sink (51) and at least one first return channel (7) can be connected to at least one pressure source (50). Device (31) according to one of the Claims 1 until 5 , characterized in that at least the first shaft (13) or the second shaft (14) of the torque switch (38) has at least one locking body (1) which can be brought into a locking position in at least one rotational position of the two rotatable shafts (13, 14) relative to one another. Device (31) according to Claim 6 , characterized in that the at least one locking body (1) - preferably by a second spring (2) - is displaced in at least one locking position into a recess (3a, 3b) of the other shaft (13, 14). Device (31) according to one of the Claims 1 until 7 , characterized in that the torque switch (38) has at least one adjusting screw for adjusting the preload force of the first spring (4). Device (31) according to one of the Claims 1 until 8th , characterized in that the torque switch (38) has at least one stop (8, 18) for limiting the rotational movement of the first shaft (13) and the second shaft (14) relative to one another. Device (31) according to one of the Claims 7 until 9 , characterized in that at least one first inlet channel (6) running in the first shaft (13) and at least one second inlet channel (11) running in the second shaft (14) or at least one first return channel (7) running in the first shaft (13) and at least one second return channel (12) running in the second shaft (14) are flow-connected when at least one locking body (1) is in a locking position. Device (31) according to Claim 10 , characterized in that a locking body (1) can assume at least two locking positions and that when assuming a first locking position, the first inlet channel (6) and the second inlet channel (11) are fluidly connected to one another via their channel openings (6a, 11a), while the first return channel (7) and the second return channel (12) are not fluidly connected via their channel openings (7a, 12a) in this locking position, and that when assuming the second locking position, the first return channel (7) and the second return channel (12) are fluidly connected to one another via their channel openings (7a, 12a), while the first inlet channel (6) and the second inlet channel (11) are not fluidly connected via their channel openings (6a, 11a) in this locking position. Device (31) according to one of the Claims 7 until 11 , characterized in that the locking body (1) can be deflected into a first recess (3a) in the first locking position and into a second recess (3b) in the second locking position. Method for operating a working device (41), wherein a torque is transmitted from a drive unit (30), in particular a tractor, to the working device (31), the working device (41) has a transmission (39) which is operated by a drive shaft (40), and the transmission (39) is switched automatically by a torque switch (38) depending on the torque of the drive shaft (40), characterized in that a hydraulic output signal is generated by the torque switch (38) at at least one defined torque and is sent to the gear (39), that a first shaft (13) and a second shaft (14) of a rotary slide of the torque switch (38) are mounted so as to be rotatable relative to one another and these shafts (13, 14) have a common axis of rotation (38a) and they are coupled via a first spring (4) and that in at least a first rotational position of the two shafts (13, 14) relative to one another, a flow connection is established between a first inlet channel (6) of the first shaft (13) with at least one channel opening (6a) and a second inlet channel (11) of the second shaft (14) with at least one channel opening (11a) via their channel openings (6a, 11a), while a flow connection between a first return channel (7) of the first shaft (13) with at least one channel opening (7a) and a second return channel (12) of the second shaft (14) with at least one channel opening (12a) in this position via their channel openings (7a, 12a) is interrupted with at least one channel opening (12a), and that a flow connection between the first return channel (7) and the second return channel (12) is established in at least a second rotational position of the two shafts (13, 14) relative to one another via their channel openings (7a, 12a), while the flow connection of the first inlet channel (6) and the second inlet channel (11) is interrupted in this position via their channel openings (6a, 11a). Procedure according to Claim 13 , characterized in that at least the first torque of the drive shaft (40) a flow connection is established between at least one pressure source (50) and at least one hydraulic control line (42b, 43b) of the transmission (39) and the flow connection between at least one pressure sink (51) and the hydraulic control line (42b, 43b) is interrupted. Procedure according to Claim 13 or 14 , characterized in that at the second torque of the drive shaft (40) a flow connection is established between at least one pressure sink (51) and at least one hydraulic control line (42b, 43b) of the transmission (39) and the flow connection between at least one pressure source (50) and the hydraulic control line (42b, 43b) is interrupted.

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