DE102017215685A1 - PTO drive for an agricultural or construction work vehicle and method for operating a PTO clutch serving as an overload clutch of a PTO drive - Google Patents

Abstract

A PTO drive for a farm or construction work utility vehicle has a PTO clutch (3) via which one of an internal combustion engine (1) driven input shaft (2) with a drivingly connected to a PTO stub shaft (17) output shaft is coupled. The PTO clutch (3) is hydraulically actuated via a proportional valve in an engaged position and serves as an overload clutch on which by means of transducers and an electronic control unit when exceeding a limit value of a torque transmitted by this detectable slippage is determined. The occurrence of a slip via the electronic control unit (25) and the proportional valve (20) to an actuation of the PTO clutch (3) in its disengaged position. In order to avoid overloading and slippage leading to wear on the PTO clutch serving as an overload clutch in all operating states, a pressure p present in a hydraulic actuator (21) of the PTO clutch (3) is applied directly to it in its engaged position As proportional to the transmitted by means of the PTO clutch (3) torque Man, wherein via the electronic control unit (25) based on a characteristic of each transmittable torque, a corresponding pressure p, with which the PTO clutch (3) of the PTO drive is operated.

Description

The invention relates to a PTO drive for a farm or construction work vehicle, in which by means of a hydraulically actuated via a proportional valve PTO clutch driven by an internal combustion engine input shaft with a drivingly connected to a PTO shaft stub output shaft is coupled, wherein the force-locking PTO clutch acts as an overload clutch, in which, when a limit value of a torque transmitted by it is exceeded, a slip detectable by transducers and an electronic control unit is ascertained, which leads to actuation of the PTO clutch via the electronic control unit and the proportional valve into its disengaged position.

Furthermore, the invention also relates to a method for operating a PTO clutch serving as an overload clutch of a PTO, is detected at the exceeding of a limit of a torque transmitted by this one detectable by transducers and an electronic control unit slip, which is to a hydraulic actuation of the PTO clutch via the electronic Control unit and a proportional valve leads to its disengaged position.

Agricultural or construction work vehicles are rear or front side provided with a PTO (power take-off) designated power take-off. This has a provided with a spline shaft PTO stub, can be driven from the working equipment via a propeller shaft. Some of these implements may experience torque peaks during operation that can cause significant damage to the drive train of the work vehicle or components of the implement. A sudden increase in torque usually occurs when the operation of a driven assembly of the implement is blocked. For example, in the case of a rotationally driven tillage implement, such as a tiller or harrow, a stone or foreign object may be caught by the tools and block the entire tillage implement. A similar state may occur in a work implement designed as a harvester. Thus, for example, due to the condition of the crop or too large amount of crop, a jam can form within the harvester, which also leads to a sudden increase in torque. Examples include balers and maize forage harvesters.

For this reason, the manufacturers of appropriate tools to their customers point out that between the PTO stub of the machine and a transmission input of the implement an overload protection is provided. This can, inter alia, structurally combined with the propeller shaft and be designed as a star ratchet, cam clutch or friction clutch. However, corresponding overload protection devices have considerable disadvantages. A star ratchet does not have sufficient fatigue strength and wears over time. In friction clutches, which are arranged between the PTO stub and the implement, the so-called sudden slip can not be detected immediately by the driver, so that this friction coupling wears relatively quickly.

Incidentally, such overload protection of heavy pollution and increased corrosion are exposed so that they are no longer functional after prolonged use. In part, however, is recommended by the manufacturers of the implements to purchase separate overload clutches, which should preferably be arranged between the PTO stub shaft and the propeller shaft. Since in this area of the work vehicle can be raised and lowered components of a three-point linkage and coupling elements for coupling trailers, a corresponding space for the arrangement of such overload protection is not available.

Furthermore, agricultural or construction work utility vehicles with a PTO are known in which between a driven by an internal combustion engine input shaft and the PTO stub driving output shaft and a disengageable PTO clutch is arranged. Such a PTO, which is considered generic, is from the DE 40 01 398 A1 known. Here, designed as a friction clutch PTO clutch between a power train of an internal combustion engine and serving to drive attachments PTO stub should be arranged. A control valve, which is designed as a proportional valve, controls the pressure medium supply in the hydraulic actuation of the PTO clutch and thus their engagement or disengagement. Furthermore, the arrangement has an electronic evaluation unit, are connected to the sensors for detecting vehicle-specific values. These vehicle-specific values should be the input-side and output-side rotational speeds of the PTO clutch, which are used to determine the slip of the clutch. Furthermore, the sensors should also pick up torsional vibrations at the PTO clutch input and / or output. If critical vehicle-specific values, ie, for example, exceeding a limit value of the slip over a given Minimum period beyond, the PTO clutch shall be permanently disengaged.

Furthermore, from the DE 101 45 588 A1 a method and a device for controlling a clutch, wherein also the clutch slip of a PTO clutch is determined by means of sensors from a rotational speed between the input and output of the PTO clutch. In this case, the clutch slip is to be set and maintained continuously to a constant value, wherein from the constant slip value and a value corresponding to the clutch pressure, the load transmitted through the clutch, in particular the torque, is determined. To set or control the clutch slip, the clutch pressure via a valve, preferably a proportional pressure control valve, varies and the valve current used as a controlled variable for slip control. With the help of this regulation, a maximum torque is to be set, which is not exceeded at the PTO shaft stub during operation. This is to provide a protective function for the vehicle drive train, PTO transmission and the drive of the attachment.

Starting from the generic state of the art, it is an object of the present invention, with little structural effort to serve as overload clutch PTO clutch such that on the one hand in all operating conditions of the PTO overload and on the other leading to wear of the PTO clutch slip are avoided.

This object is solved by the features of the respective characterizing part of claims 1 and 8. Advantageous embodiments are specified in particular in the dependent claims of patent claim 1, each taken alone or in various combinations with each other can represent an aspect of the invention.

According to claim 1, a PTO drive for a agricultural or construction work utility vehicle on a PTO clutch via which an input shaft driven by an internal combustion engine with a drivingly connected to a PTO shaft stub output shaft is coupled. Such a PTO clutch is designed as a frictional clutch, so friction clutch and is actuated hydraulically via a proportional valve in an engaged position. In this case, the non-positively acting PTO clutch serves as an overload clutch on which by means of transducers and an electronic control unit when exceeding a limit value of a torque transmitted by this detectable slip is determined. The occurrence of a slip via the electronic control unit and the proportional valve to actuate the PTO clutch in its disengaged position.

According to the invention, a pressure present in a hydraulic actuating device of the PTO clutch, with which it is acted upon in its engaged position, is to be directly proportional to the torque which can be transmitted by the latter and thus used to determine the torque which can be transmitted by means of the PTO clutch. From this relationship of the pressure to the transmittable torque, a characteristic curve can be derived, which indicates at which adjusted and a resulting maximum torque the PTO clutch is set in a slip state. In this case, the electronic control unit based on the characteristic of each permissible torque, which is specified by the manufacturer of the implement, a corresponding pressure be assigned. Consequently, in this overload function, the PTO clutch can only transmit a certain torque, so that it is repealed at a higher torque, so a shock when blocking the implement, the stiction. The then entering slip state of the PTO clutch is detected by the electronic control unit, which controls a disengagement of the same via the proportional valve, so that damage is avoided.

In contrast, after the DE 40 01 398 A1 not in principle a separation of the drive train by a disengagement of the PTO clutch when this slip occurs. Rather, this should only be the case when the slip exceeds a predetermined value. However, the occasional slip will lead to premature wear of the PTO clutch.

After DE 101 45 588 A1 the PTO clutch is maintained in a controlled slip state, from the constant slip value and a value corresponding to the clutch pressure permanently determined by the PTO clutch torque is determined. The permanent slip condition causes the PTO clutch to wear out in a short period of operation so that it can no longer fulfill its function.

In a further embodiment of the invention, the power take-off stub to be driven with different output speeds, wherein between the output shaft and the PTO stub, at least one switchable gear ratio is provided. In this case, a characteristic curve is provided for each of the output speeds, based on which the transmittable torque can be determined via the set pressure. About a corresponding PTO, the PTO stub is preferably driven at output speeds of 540 min ^-1 or 1,000 min ^-1 . Furthermore, output speeds of 750 min ^-1 and 1,400 min ^{-1 can be} provided. At the given output speeds 540 min ^-1 and 1,000 min ^-1 can each have a normal level N, in which this output speed is reached with the rated speed of the engine and an ECO stage E, at the corresponding output speed with speeds of the engine of 1,500 - 1,600 min ^{-1 is} reached.

Furthermore, due to the required output rotational speed, the pressure of the driver of the work vehicle should be manually adjustable on the control unit on the basis of the characteristic curve associated with this output rotational speed. In this case, the driver is provided with the graph containing the characteristics, and he can read from this to the respective stage of the output speed, in which he has previously switched the PTO, and the predetermined limit of the torque, the clutch pressure, he manually over adjusts the proportional valve. The characteristics themselves are stored in the gearbox control unit. This automatically recognizes all influencing variables (for example selected power take-off, speeds, temperature) and uses them to regulate the clutch pressure according to the torque selected by the driver. The driver does not have to look at the characteristics themselves, but can easily only the desired max. select transmissible torque, the transmission control unit then takes over the appropriate pressure control.

As an alternative to the manual setting of the input speed, this can be detected by a sensor and fed to the electronic control unit, wherein the pressure in the hydraulic actuation of the PTO clutch is adjusted by means of the predetermined torque on the basis of the corresponding characteristic curve. It is also possible that the specific data that are transmitted from the implement via an interface to the electronic control unit of the work vehicle, the target speed and the maximum torque include. Then an automatic adjustment based on the map. Such an interface to the work vehicle is in some work tools, such as. Round balers, in the form of a data cable available and can be used accordingly.

The transducers, which serve to monitor a slip occurring at the PTO clutch, can be designed as speed sensors associated with the input shaft and the output shaft. Through the electronic control unit, which are fed to the respective speeds, then takes place due to a possible speed difference, the slip determination. It is also envisaged to form the PTO clutch as a multi-plate clutch.

In a further embodiment of the invention, the electronic control unit is to be connected to a display and / or an acoustic warning device, via which the driver can be informed about a slip state of the PTO clutch and its disengaged state. The driver himself does not have to react. If the control unit detects a slippage of the clutch (for example due to a torque shock), the message is sent to the driver, but the control unit also reacts immediately and opens the clutch, which prevents it from being damaged. If one were to wait for the driver to intervene, the clutch could already be damaged.

Finally, it is to be determined according to the patent claim 8 in a method for operating a serving as an overload clutch PTO clutch of a power take-off when exceeding a limit value of a torque transmitted by a detectable by transducers and an electronic control unit slip. This is to lead via the electronic control unit and a proportional valve to a hydraulic actuation of the PTO clutch in its disengaged position.

In this case, the invention provides that a determined under consideration of a speed and a temperature pressure-torque curve for the PTO clutch is determined and used, starting from a maximum torque and a drive speed, which are each predetermined for a connectable to the PTO implement To determine the hydraulic pressure that is applied to the PTO clutch in its engaged position, and that this pressure is adjusted with the proportional valve.

The invention is not limited to the specified combination of the features of independent claim 1 with the features of the dependent claims. In addition, there are further possibilities of combining individual features, in particular if they result from the patent claims, the following description of the exemplary embodiments or directly from the figures. In addition, the reference of the claims to the figures by the use of reference numerals is not intended to limit the scope of the claims to the illustrated embodiments.

• 1 eine schematische Darstellung eines Zapfwellenantriebs mit einer als Lamellenkupplung ausgebildeten Zapfwellenkupplung und
• 2 ein Diagramm, in welchem Kennlinien zu unterschiedlichen Schaltstufen eines Zapfwellengetriebes angeben ist, mit welchem Kupplungsdruck ein präziser Grenzwert eines von der Zapfwellenkupplung übertragbaren Drehmoments einstellbar ist.

To further explain the invention is based on the following description of a preferred embodiment of the invention. Show it:

• 1 a schematic representation of a power take-off with a trained as a multi-plate clutch PTO clutch and
• 2 a diagram in which indicate characteristics to different switching stages of a PTO, with which clutch pressure a precise limit of a transferable from the PTO clutch torque is adjustable.

In the 1 1 is an internal combustion engine of an agricultural or construction work vehicle, such as an agricultural tractor or system vehicle, which is an input shaft 2 a PTO clutch 3 drives. The PTO clutch 3 is designed as a multi-plate clutch and has a plurality of friction discs 4 on, between which after engaging the PTO clutch 3 a frictional connection is made. Concentric to the input shaft 2 goes from the PTO clutch 3 a trained as a hollow shaft output shaft 5 out, on the drive wheels 6 and 7 freely rotatable and with the output shaft 5 via a sliding sleeve 8th are arranged detachable.

This arrangement of the drive wheels 6 and 7 are two provided with corresponding gears countershafts 9 and 10 associated with gears of the countershaft 10 with output wheels 11 and 12 comb. These output wheels 11 and 12 are freely rotatable on an output shaft 13 arranged and optionally via a sliding sleeve 14 with this detachable. The aforementioned waves 5 . 9 . 10 and 13 and the corresponding gears form a PTO transmission 15 ,

By appropriate switching operations of the two sliding sleeves 8th and 14 via a switching device 16 can be as specified in addition to the display, switch different switching stages for standardized output speeds of 540 min ^-1, 750 min ^-1, 1,000 min ^-1 and 1400 min ^-1. The output shaft 13 forms at its end a PTO stub 17 with which a propeller shaft 18 is positively coupled. About this cardan shaft 18 becomes from the working vehicle in the power take-off a working device 19 driven.

An input or disengagement process as well as a control of a clutch pressure p _K takes place by means of a proportional valve 20 and one at the PTO clutch 3 provided slave cylinder 21 , A pressure medium supply of the slave cylinder 21 via the proportional valve 20 via a hydraulic pump 22 , As can be seen from the illustration, the proportional valve 20 , which is electromagnetically operated, via control lines 23 and 24 from an electronic control unit 25 actuated. This electronic control unit 25 be over other control lines 26 and 27 as well as speed sensors 28 and 29 as input values, the respective rotational speeds of the input shaft 2 and the output shaft 13 fed.

Alternatively, there is also the option of the speed sensor 29 instead of the output shaft 12 at the output shaft 5 provided. When in the present arrangement of the speed sensor 29 a predetermined speed difference between the input shaft 2 and the output shaft 13 changed, so this change from the electronic control unit 25 detected as slippage at the PTO clutch 3 occurs and suggests that an allowable torque is exceeded.

As continues from the 1 indicates in the electronic control unit 25 a map 30 be in the following in connection with the 2 will be received. Furthermore, in the present case, a data cable 31 provided, that of the electronic control unit 25 specific data of the implement 19 supplies, wherein these data, for example, a predetermined speed stage of the PTO transmission 15 and a limit value of an allowable torque should act. Furthermore, there is the electronic control unit 25 with the switching device 16 of the PTO gearbox 15 via a control line 32 in connection, by means of which a gear stage can be specified, or, if the gear stage is switched manually, this information to the electronic control unit 22 is transmitted.

In the 2 a diagram is shown that already related to the 1 listed map 30 represents. In this diagram, on the abscissa of a coordinate system, the clutch pressure p _K in bar and on the ordinate a predetermined limit of the transmittable torque M _A in Nm. A first curve, shown as a solid line, shows the relation between the clutch pressure p _K and the corresponding tearing moment M _A for a transmission stage of the PTO with 540 min ^-1 . Further, in the diagram as shown in dashed curve a step 750 min ^-1, a dotted curve for a level of 1.000 min ^-1 and a curve illustrated as a dotted line for one stage of 1.400 min ^-1 are shown.

The following is an example of the determination of a required clutch pressure by means of the diagram explained: Starting from a maximum torque, the 500 Nm and provided that the PTO 15 is operated in the stage with a target speed of 1,000 min ^-1 , can be on the abscissa of the diagram, a clutch pressure p _K read off 5.4 bar. With this clutch pressure p _K becomes the PTO clutch 3 acted in their engaged position, so that only when exceeding the limit value of the torque of 500 Nm, a clutch slip may occur, which then via the speed sensors 28 and 29 as well as the electronic control unit 25 is detected. In this case, it can be assumed that the drive of the implement 19 is blocked. By means of the electronic control unit 25 therefore becomes the PTO clutch 3 adjusted in its disengaged state, so that no torque is transmitted to the implement. This overload function of the PTO clutch is signaled to the driver. As already explained, both the determination of the required clutch pressure based on the parameter target speed and maximum torque and the adjustment of the clutch pressure by means of the electronic control unit 25 be automated.

LIST OF REFERENCE NUMBERS

1

internal combustion engine

2

Input shaft of 3

3

PTO

4

Friction discs of 3

5

Output shaft of 3

6

drive wheel

7

drive wheel

8th

sliding sleeve

9

Countershaft

10

Countershaft

11

output gear

12

output gear

13

output shaft

14

sliding sleeve

15

PTO

16

switching device

17

Zapfwellenstummel

18

propeller shaft

19

implement

20

proportional valve

21

slave cylinder

22

hydraulic pump

23

control line

24

control line

25

electronic control unit

26

control line

27

control line

28

Speed sensor

29

Speed sensor

30

map

31

data cable

32

control line

p _K

Clutch pressure [bar]

M _A

maximum torque (breaking torque) [Nm]

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 4001398 A1 [0006, 0012]
• DE 10145588 A1 [0007, 0013]

Claims (8)

PTO drive for a agricultural or construction work vehicle, in which by means of a hydraulically via a proportional valve (20) actuated PTO clutch (3) by an internal combustion engine (1) driven input shaft (2) with a drivingly connected to a PTO stub shaft (17) output shaft ( 5) can be coupled, wherein the non-positively acting PTO clutch (3) serves as an overload clutch, at which a threshold of a torque transmitted by this one of transducers and an electronic control unit (25) detectable slip is determined, which is to actuate the PTO clutch ( 3) via the electronic control unit (25) and the proportional valve (20) leads to its disengaged position, characterized in that in a hydraulic actuator (21) of the PTO clutch (3) existing pressure p _K , with this in its engaged position is charged is directly proportional to the torque M _{A which} can be transmitted by means of the PTO clutch (3) and that via the electronic control unit (25) a corresponding pressure p _K , with which the PTO clutch (3) of the power take-off drive is operated, can be assigned to each transmittable torque is. PTO drive to Claim 1 , characterized in that the PTO stub (17) is drivable with different output speeds, between the output shaft (5) and the PTO stub (17) at least one shiftable ratio stage is provided, and that for each of the output speeds, a characteristic is provided, based on which the set pressure p _K, the transmittable torque M _{A can be} determined. PTO drive after one of the Claims 1 or 2 , characterized in that determined by the driver due to the required output speed of the PTO drive on the basis of this output speed associated characteristic of the pressure p _K and manually on the hydraulic actuator (21) is adjustable. PTO drive after one of the Claims 1 or 2 , characterized in that via a speed sensor (29) detected output speed of the electronic control unit (25) is supplied, wherein by means of the predetermined torque M _A based on the corresponding output speed associated characteristic of the pressure p _K in the hydraulic actuation (21) of the PTO clutch (3) is set. PTO drive to Claim 1 , characterized in that the transducers as the input shaft (2) and the output shaft (5) associated with speed sensors are formed. PTO drive to Claim 1 , characterized in that the PTO clutch (3) is designed as a multi-plate clutch. PTO drive to Claim 1 , characterized in that the electronic control unit (25) is connected to a display and / or an acoustic warning device, via which the driver can be informed about a slip state of the PTO clutch (3) and its disengaged state. Method for operating a PTO clutch (3) of a power take-off drive serving as an overload clutch, at which a slip detectable by transducers and an electronic control unit (25) is detected when a limit value of a torque M _A transmitted by the latter is exceeded, resulting in hydraulic actuation of the PTO clutch ( 3) via the electronic control unit (25) and a proportional valve (20) in its disengaged position, characterized in that a determined in consideration of a speed and a temperature pressure-torque characteristic curve for the PTO clutch (3) is determined and used, in order, starting from a maximum torque M _A and a drive speed, which are predetermined for each connectable to the PTO implement (19) to determine the hydraulic pressure, which is applied to the PTO clutch (3) in its engaged position, and that this Dr uck is adjusted with the proportional valve (20).

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