DE102010040737A1 - Vehicle drive strand operating method for agriculture machine, involves raising current rotational torque based on slippage-free operating mode of wheels of drivable vehicle axle upto transition of wheels into slippage operation - Google Patents

Abstract

The method involves determining supportable rotational torque within a region of wheels (9, 10, 18, 19) of drivable vehicle axles (11, 17) by a torque sensor device (14). Current rotational torque is raised based on a slippage-free operating mode of the wheels in the drivable vehicle axle upto a transition of the wheels into a slippage operation, lying close in the region of the wheels. The slippage-free operating mode of the wheels is represented during a reversing process between driving forward and reverse movements of a vehicle (1) implemented with a vehicle drive strand (2).

Description

The invention relates to a method for operating a vehicle drive train according to the closer defined in the preamble of claim 1. Art.

Usually known from practice vehicle drive trains are each carried out with a prime mover, with a transmission device and with an output with at least one drivable vehicle axle. A current actual torque of engine drives of the vehicle drive trains designed as internal combustion engines is known to be determined as a function of the injection quantity and in the region of an engine control unit. The actual torque is available to further control units connected to the engine control unit via a CAN bus, in each case as an input variable for specific control and regulating routines.

Furthermore, the transmission devices of the vehicle drive trains are assigned sensors for measuring torque values carried in the vehicle drive train. In this case, for example, angles of rotation of solid or hollow shafts via strain gauged waves or magnetically coded waves are determined by measurement. Depending on the angle of rotation, in each case the torques guided in each case via the shafts can be determined.

A torque guided via a hydrostatically-mechanically split power transmission device is calculated, for example, as a function of a measured or calculated operating pressure in the region of a hydrostatic drive, the latter procedure being only a rough estimate of the torque currently to be transmitted via a transmission device.

About vehicle drivelines of agricultural machinery is known to constitute a so-called power reversing, during which is switched by switching between two frictional clutches between a forward drive operation and a reverse drive operation in the forward drive operation traction interruption-free. In this case, depending on the particular application, the deceleration process and the subsequent acceleration process are coordinated by a suitable parameterization so that the wheels of the output or the drivable vehicle axle of the output at the highest possible dynamics do not spin and the substrate, preferably a turf, do not damage. Since the friction conditions between the wheels and the currently traveled underground can vary greatly, a compromise must always be provided for this and the vehicle can not be operated with a desired high tractive effort.

The currently available traction of a vehicle is known to be dependent on the tire slip and thus significantly on the current soil conditions of the traveled ground. The current tire slip is determined in particular in tractors via a vehicle-side radar sensor, by means of which a current vehicle speed with respect to the ground can be determined, and a speed sensor in the region of the transmission output via which the current tire speed can be determined. A driver of the tractor can manually set a desired slip of the wheels via a corresponding vehicle-side control. However, the optimum for obtaining the maximum traction power slippage in the range of the wheels is not known because the current condition of the ground or the ground conditions are the driver at least locally often not known with the required accuracy.

If a vehicle is designed with a so-called hoist control, the vehicle performance during operation is predominantly utilized at least approximately optimally. The hoist control is known to be operated in conjunction with a Zugkraftmessbolzen in the range of a hoist mounted on the vehicle, by means of a traction is always exploitable to a predetermined limit. If the soil load in the area of the wheels exceeds this limit, for example, the plow is lifted out of the ground by a certain height, thus reducing the working depth of the field and thus the load acting on the vehicle. This approach is essentially during a heavy tillage, such as plowing, but also increasingly in order combinations, d. H. in sowing machines with upstream and / or downstream tillage processes.

About the above-described Hubwerksregelung the preset slip in the wheel is stable, but the hoist control is performed without a control loop, by means of which the slip in the area of the wheels is optimized depending on the current soil conditions to a vehicle always in the range of its maximum traction power to be able to operate.

The present invention is therefore based on the object of providing a method for operating a vehicle drive train, by means of which a respective requested operating state of the wheels can be optimally adapted to the respective present ground conditions.

According to the invention this object is achieved by a method having the features of claim 1.

In the method according to the invention for operating a vehicle drive train with a drive machine, with a transmission device and with an output with at least one drivable vehicle axle, a torque which can be supported in the region of wheels of the drivable vehicle axle is determined by means of a torque sensor device and the torque currently applied in the region of the wheels starting from a slip-free operating state of the wheels of the drivable vehicle axle up to a transition of the wheels in a slipping operation raised.

By means of the method according to the invention, a current ground condition of the ground currently being driven over by a vehicle or a coefficient of friction between wheels of the drivable vehicle axle and the ground can be determined with little control effort. The procedure according to the invention is based on the knowledge that when the force transmission limit between the wheels and the ground is exceeded, the power transmission mechanism abruptly changes from sticking to sliding and the associated abrupt change in the coefficient of friction between the wheels and the ground leads to a significant reduction in the transmittable torque in the area of the wheels leads. With the aid of the direct torque measurement according to the invention, the sudden change in the torque in the drive train can be detected at high frequency and, at the same time, at least the momentarily maximum transferable or supportable torque in the region of the wheels is known.

If there is a corresponding requirement, the torque applied to the wheels is set to represent a substantially slip-free operating state of the wheels as a function of the maximum torque which can be supported in the region of the wheels. This is with little knowledge of the maximum in the range of wheels supportable torque and the current coefficient of friction between the wheels of the drivable vehicle axle and the ground feasible.

In a further advantageous variant, it is provided that the substantially slip-free operating state of the wheels is represented during a reversing between a forward drive and a reverse drive of a running with the vehicle drive train vehicle. For this purpose, so-called power shuttle clutches are so regulated that slippage of the wheels of the drivable vehicle axle is avoided and the currently traveled by the vehicle surface or the ground is spared.

The voltage applied to the wheels torque is high frequency adjustable in a further advantageous variant of the method, since the substantially slip-free operating condition of the wheels is produced by limiting the voltage applied to the wheels torque via a controlled and / or regulated operated torque limiting device of the vehicle drive train.

In this case, the torque limiting device can be configured as an electric brake arranged in the region of the vehicle drive train, preferably in the region of a differential gear mechanism of the drivable vehicle axle, via which a drive torque provided by the drive machine can be reduced with greater dynamics than by a corresponding activation of the drive engine.

Furthermore, it is also possible to use a hydrostat of a mechanical-hydraulic power-split transmission as a torque limiting device, in which case a ratio for reducing the applied in the wheels of the drivable vehicle axle drive torque is reduced as needed in the hydrostatic.

In addition, it is also possible to provide modulatable friction clutches as a torque limiting device and to reduce a torque applied in the wheels of the drivable vehicle axle torque due to continuous adjustment of the transmission capabilities of the friction clutches according to requirements to avoid slipping operation of the wheels of the drivable vehicle axle according to requirements.

If a vehicle drive train is designed with a hybrid system, an electric machine of the hybrid system can also be used as a torque limiting device, wherein a highly dynamic adjustment of the output torque applied to the wheels of the drivable vehicle axle can be limited as required by regenerative operation of the electric machine.

If a maximum traction power supply is to be made available via a vehicle, the torque applied to the wheels is set in a further advantageous variant of the method according to the invention for displaying an operating state of the wheels with defined slip as a function of the maximum torque which can be supported in the region of the wheels.

For this purpose, it is in a further advantageous variant of the method according to the invention provided that the defined slip to be set in the region of the wheels, with which a maximum traction power supply is available, by means of at least one the relationship between the coefficient of friction in the area between the wheels and the ground, the current slip of the wheels and a tensile force in the area of the output imaging model can be determined as a function of the maximum torque which can be supported in the region of the wheels.

In addition, there is the possibility that a defined slip for a performance-oriented or for an economical operation of the vehicle drive train can be determined by means of the model.

In a further advantageous variant of the method according to the invention, the vehicle drive train can be operated in the range of its optimum performance by varying a load acting on the vehicle as a function of the maximum torque which can be transmitted in the region of the wheels.

If the torque which can be transmitted by the wheels is respectively determined metrologically in the regions of the vehicle drive train facing the wheels, the determination of the torque can be determined with high accuracy, since in the region between a torque sensor device positioned at another point in the vehicle drive train and the wheels drivable vehicle axle in the power flow arranged components occurring, preferably temperature-dependent, to determine losses to a lesser extent and must be taken into account.

In order to map the real vehicle system with high accuracy, a current gradient of a driven speed is determined in a further advantageous variant of the method according to the invention and in the calculation of each of the wheels of the drivable vehicle axle maximum transmissible torque and the coefficient of friction between the wheels and a currently used underground. This results from the fact that the current gradient of the output speed depends on a dynamic axle load distribution and thus the friction torque which can be transmitted in each case in the region of the wheels of the drivable vehicle axle.

In principle, the method according to the invention can be used both for vehicle drive trains having a drivable vehicle axle and for vehicles having a plurality of drivable vehicle axles, wherein in the operation of the vehicle drive train, in each case the wheel is considered in the representation of the slip-free operating state of the wheels or the operating state with defined slip Range of lowest coefficient of friction is determined.

Both the features specified in the claims and the features specified in the following exemplary embodiment of the method according to the invention are each suitable alone or in any combination with each other to further develop the subject matter according to the invention. The respective feature combinations represent no limitation with respect to the development of the subject matter according to the invention, but essentially have only an exemplary character.

Further advantages and advantageous embodiments of the method according to the invention will become apparent from the claims and the embodiment described in principle below with reference to the drawings.

The sole figure of the drawing shows a highly schematic block diagram representation of a vehicle which is formed with a vehicle drive train operated according to the invention.

The figure shows a vehicle 1 with a vehicle powertrain 2 that with a prime mover 3 , a transmission device 4 and a downforce 5 is trained. The downforce 5 In this case comprises two drivable vehicle axles 11 and 17 , wherein a vehicle rear axle 11 represents a permanently driven vehicle axle and the vehicle front axle 17 in a manner known per se via a switching element not shown in detail in the drawing operating state-dependent switched on or off. In the field of transmission equipment 4 is a switching element 6 provided on the basis of the respectively set transmission capacity torque by frictional contact between a portion of a first switching element half 7 and a portion of a second switching element half 8th is feasible.

Depending on the respective present embodiment of the vehicle drive train 2 can the at least partially frictionally executed switching element 6 to illustrate a translation of the transmission device 4 be provided or be designed as a so-called power shuttle clutch for switching between a forward drive operation and a reverse drive operation. In addition, there is also the possibility that the switching element 6 is a component of a vehicle drive train is to be guided by the torque and which is at least phased to operate one of the functions of the vehicle powertrain described in more detail below to operate slipping.

An in the range of wheels 9 . 10 the permanently drivable vehicle rear axle 11 the downforce 5 Transmittable torque is transmitted via a present two torque sensors 12 . 13 comprehensive torque sensor device 14 determined, the torque sensors 12 and 13 each between a differential gear unit 15 and the wheel 9 or the wheel 10 are arranged. This makes it possible in a simple way, in each case in the area of the wheel 9 as well as in the area of the wheel 10 currently supportable torque via the torque sensor device 14 independent of a balancing operation in the range of Differentialachsgetriebeeinrichtung 15 to determine.

The present running as a tractor vehicle 1 is additionally equipped with an attachment designed as a hoist 16 equipped, which in the present case is coupled with a plow whose processing depth is variable via a so-called hoist control for setting an optimal utilization of vehicle performance.

Will the vehicle 1 used for maintenance work, during which a surface of a currently traveled surface by the wheels 9 . 10 of the vehicle should not be damaged, there is a corresponding requirement for a slip-free operation of the wheels 9 and 10 the downforce 5 in front.

Of course, this requirement applies when switched on another drivable vehicle axle 17 also for wheels 18 and 19 the vehicle axle 17 , which other torque sensors 20 . 21 the torque sensor device 14 assigned. The other torque sensors 20 and 21 are also between one of the vehicle axle 17 associated further differential differential gear device 22 and the wheels 18 respectively. 19 positioned. To a substantially slip-free operation of the wheels 9 and 10 respectively. 18 and 19 the drivable vehicle axles 11 and 17 to be able to guarantee is the vehicle 1 or its vehicle drive train 2 to calibrate before driving on the area or subsoil which is not desired to be damaged in the manner described in more detail below.

During the calibration process, for example, an often causing damage reversing process between forward drive and reverse drive is carried out while using the torque sensor device 14 Gradients of the wheels 9 . 10 18 . 19 Abstützbaren Torque monitors whether a current from the prime mover 3 provided drive torque a slip of the wheels 9 and 10 respectively. 18 and 19 caused or not.

The monitoring is based on the knowledge that exceeding the power transmission limit between the tires 9 and 10 respectively. 18 and 19 and the currently run-over surface a sudden change in the power transmission mechanism of sticking to sliding result and also an abrupt change in the current coefficient of friction between the wheels 9 and 10 respectively. 18 and 19 and the underground. The sudden change in the coefficient of friction leads to a significant reduction of the transmittable torque in the area of the wheels 9 and 10 respectively. 18 and 19 via the torque sensor device 14 high frequency is detectable. At the same time, via the torque sensor device 14 the momentarily maximum transferable torque in the range of the wheels 9 and 10 respectively. 18 and 19 determined.

Subsequently, during the intended driving on the surface to be protected, for example, a reversing process in the transmission device 4 using the switching element 6 so regulated that slipping of the wheels 9 and 10 respectively. 18 and 19 is avoided and the soil is spared. For this example, the transfer capability of the switching element 6 reduced to reduce the torque applied in the area of the output, if that at the output 5 applied torque in the area of the wheels 9 and 10 respectively. 18 and 19 maximum transmittable torque exceeds.

Furthermore, the vehicle drive train 2 with a torque limiting device 23 carried out by means of the at the wheels 9 and 10 respectively. 18 and 19 applied torque is controlled and / or regulated limited.

Depending on the particular application, this is the output 5 applied torque, for example, limited by a control unit, by means of which of the prime mover 3 provided drive torque is reduced operating state-dependent.

If the control of the prime mover 3 by the control of the control device of the torque limiting device 23 has too little dynamics to the desired slip-free operation of the wheels 9 and 10 respectively. 18 and 19 To be able to guarantee, in addition or alternatively to the possibility, in each case one in the range of Differentialachsgetriebeeinrichtung 15 respectively. 22 intended to operate electric brake and by raising the transmission capacity of the electric brakes that the wheels 9 and 10 respectively. 18 and 19 to reduce each supplied torque to a level at which a slip-free operation of the wheels 9 and 10 respectively. 18 and 19 is guaranteed.

Again cumulatively or alternatively, there is also the possibility of that at the output 5 applied torque by varying the transmission capacity of one between the prime mover 3 and the downforce 5 arranged frictional switching element on the for the slip-free operation of the wheels 9 and 10 respectively. 18 and 19 to lower the required level.

Furthermore, a current gradient of the speed of the vehicle 1 determined to determine a dynamic axle load distribution and the respective transmissible friction torque in the range of vehicle axles 11 and 17 or the wheels 9 and 10 such as 18 and 19 to determine with high quality. Depending on the additionally determined values, this is that of the wheels 9 and 10 respectively. 18 and 19 each supportable torque determined in a further improved extent.

On the other hand, there is a corresponding requirement for representing an operation of the vehicle drive train 2 with maximum traction, this is via the torque sensor device 14 in the field of wheels 9 and 10 respectively. 18 and 19 Measured maximum transmittable torque used to provide a defined slip in the area of the wheels 9 and 10 respectively. 18 and 19 adjust.

For this purpose, for example, at the beginning of a plowing work in the field that at the output 5 applied torque to the above-mentioned waste in the range of the wheels 9 and 10 respectively. 18 and 19 transmittable torque increases. This is preferably by driver side lowering the hoist 16 or by appropriate actuation of another attachment, via an ISO bus connection with a suitable control unit of the vehicle 1 connected, self-triggering. By means of this procedure, the current coefficient of friction between the wheels 9 and 10 respectively. 18 and 19 and that of the vehicle 1 currently underway. Based on the measured coefficient of friction, the defined slip value in the region of the wheels is stored by means of mathematical relationships between the coefficient of friction, the tire slip and the actual tractive force stored in the vehicle control 9 and 10 respectively. 18 and 19 determined, which is required to represent the maximum traction power supply.

The mathematical relationships are present, for example, in the form of curves or interpolatable tables, where desired either an economic or a performance-oriented operation depending on the mathematical relationships can be realized. In addition, the real vehicle speed can be determined via a vehicle-side wheel sensor and the optimum tire slip can be set by appropriate control of the engine speed.

In order to be able to operate the vehicle permanently at optimum performance during operation, for example, the control of the lifting mechanism 16 usable, in contrast to known from practice, instead of the Zugkraftmessbolzens the hoist 16 the signal of the torque sensor device 14 is used. This is based on the current operating point of the vehicle 1 the drive torque of the prime mover 3 increased or decreased accordingly to the area of the wheels 8th . 9 18 . 19 to be able to provide the maximum traction power supply.

In general, during the method according to the invention, a monitoring of the output-side torque curve is performed and as a function of the monitoring result of the tires 9 . 10 . 18 . 19 slippage operating state-dependent or set according to requirements. This will be the downforce 5 applied torque to represent a slip-free operation of the wheels 9 and 10 respectively. 18 and 19 the downforce 5 or an operating condition of the wheels 9 and 10 respectively. 18 and 19 with defined slip depending on the wheel 9 . 10 . 18 or 19 performed in the range of the lowest supportable torque is determined. This procedure is not required if the differential gear units 15 and 22 are each carried out with a differential lock, by means of which in each case a balancing operation in the range of Differentialachsgetriebeeinrichtungen 15 and 22 can be deactivated and also a corresponding means for blocking a compensation function between vehicle axles 11 and 17 in the vehicle longitudinal direction, such as a longitudinal lock or the like, is provided.

LIST OF REFERENCE NUMBERS

1

vehicle

2

Vehicle powertrain

3

prime mover

4

transmission device

5

output

6

switching element

7

first switching element half

8th

second switching element half

9, 10

wheel

11

drivable vehicle axle

12, 13

torque sensor

14

Torque sensor device

15

Differentialachsgetriebeeinrichtung

16

Hoist, attachment

17

vehicle axle

18, 19

wheel

20, 21

torque sensor

22

another Differentialachsgetriebeeinrichtung

23

Torque limiting device

Claims (11)

Method for operating a vehicle drive train ( 2 ) with a prime mover ( 3 ), with a transmission device ( 4 ) and with an output ( 5 ) with at least one drivable vehicle axle ( 11 . 17 ), characterized in that a range of wheels ( 9 . 10 . 18 . 19 ) of the drivable vehicle axle ( 11 . 17 ) supportable torque by means of a torque sensor device ( 14 ) and that currently in the area of the wheels ( 9 . 10 . 18 . 19 ) applied torque from a slip-free operating state of the wheels ( 9 . 10 . 18 . 19 ) of the drivable vehicle axle ( 11 . 17 ) until a transition of the wheels ( 9 . 10 . 18 . 19 ) is raised into a slip operation. A method according to claim 1, characterized in that the at the wheels ( 9 . 10 . 18 . 19 ) applied torque for representing a substantially slip-free operating condition of the wheels ( 9 . 10 . 18 . 19 ) depending on a maximum in the range of the wheels ( 9 . 10 . 18 . 19 ) Abstützbaren torque is set. A method according to claim 2, characterized in that the substantially slip-free operating condition of the wheels ( 9 . 10 . 18 . 19 ) during a Reversiervorganges between a forward drive and a reverse drive of a with the vehicle drive train ( 2 ) running vehicle ( 1 ) is pictured. A method according to claim 2 or 3, characterized in that the substantially slip-free operating condition of the wheels ( 9 . 10 . 18 . 19 ) by limiting the at the wheels ( 9 . 10 . 18 . 19 ) applied torque via a controlled and / or regulated operated torque limiting device ( 23 ) of the vehicle drive train ( 2 ) will be produced. Method according to one of claims 1 to 4, characterized in that the at the wheels ( 9 . 10 . 18 . 19 ) applied torque to represent an operating condition of the wheels ( 9 . 10 . 18 . 19 ) with defined slip depending on a maximum in the area of the wheels ( 9 . 10 . 18 . 19 ) Abstützbaren torque is set. Method according to claim 5, characterized in that in the region of the wheels ( 9 . 10 . 18 . 19 ) defined slip, by means of which a maximum traction power supply is available, by means of at least one the relationship between coefficient of friction in the area between the wheels ( 9 . 10 . 18 . 19 ) and the road surface, the actual slip of the wheels ( 9 . 10 . 18 . 19 ) and a tensile force in the region of the output ( 5 ) imaging model depending on the maximum in the range of wheels ( 9 . 10 . 18 . 19 ) Abstützbaren torque is determined. A method according to claim 6, characterized in that by means of the model a defined slip for a performance-oriented operation of the vehicle drive train ( 2 ) is determinable. Method according to one of claims 1 to 7, characterized in that the vehicle drive train ( 2 ) by varying one on the vehicle ( 1 ) acting load as a function of the area of the wheels ( 9 . 10 . 18 . 19 ) maximum transmittable torque in the range of its optimum performance is operable. A method according to claim 7 or 8, characterized in that by means of the model a defined slip for an economical operation of the vehicle drive train ( 2 ) is determinable. Method according to one of claims 1 to 9, characterized in that the of the wheels ( 9 . 10 . 18 . 19 ) transmissible torque each in the wheels ( 9 . 10 . 18 . 19 ) facing areas of the vehicle drive train ( 2 ), preferably in the area of the wheels ( 9 . 10 . 18 . 19 ), is determined by measurement. Method according to one of claims 1 to 10, characterized in that a current gradient of a vehicle output speed ( 1 ) is determined.

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