Agricultural utility vehicle having a power takeoff and method for operating the power takeoff

An agricultural utility vehicle includes a working power takeoff drivable by means of an internal combustion engine for operating an implement. The utility vehicle further includes an auxiliary power takeoff, which can be driven by an energy storage device and is coupled to the working power takeoff in such a manner that the working power takeoff is additionally driven at least transiently by the auxiliary power takeoff.

RELATED APPLICATIONS

This application claims priority to German Application Ser. No. 102016221311.3, filed Oct. 28, 2016, the disclosure of which is hereby expressly incorporated by reference in its entirety.

FIELD OF THE DISCLOSURE

The present disclosure relates to an agricultural utility vehicle having a power takeoff for operating an implement. The method further relates to a method for driving a power takeoff of an agricultural utility vehicle.

BACKGROUND

A work system consisting of a tractor and a square baler is known from U.S. Publication Ser. No. 2010/0115902A1. The square baler is driven via a power takeoff of the tractor. The rear power takeoff is in turn driven via a gear unit by the internal combustion engine of the tractor. The output torque of the internal combustion engine is modified depending on the determined load data from the square baler.

The invention addresses the problem of driving a power takeoff of an agricultural vehicle in an energy-efficient manner for operating an implement with low expense.

SUMMARY

In one embodiment of the present disclosure, an agricultural utility vehicle (e.g. a traction vehicle or a tractor) has an internal combustion engine which, in particular by means of a suitable clutch, gear stage or the like, drives a power takeoff of the utility vehicle. This power takeoff (hereinafter “working power takeoff”) in turn operates, with its kinetic energy, an implement (e.g., a big baler). The utility vehicle additionally includes a further power takeoff (hereinafter “auxiliary power takeoff”) that can be driven by the stored energy and energy storage device. It is provided that the auxiliary power takeoff is coupled to the working power takeoff in such a manner that the working power takeoff can be driven not only by the internal combustion engine, but also by the auxiliary power takeoff, at least transiently.

In this manner, discrete or cyclically occurring peak loads of the implement, which are transmitted via the gear unit thereof to the working power takeoff of the utility vehicle, can be compensated at the working power takeoff by additionally driving it transiently with the auxiliary power takeoff. Thereby, conventional effects when operating the implement, such as a drop in the rotational speed of the internal combustion engine and the speed of the utility vehicle when torque or load peaks occur at the working power takeoff, can be reduced or completely eliminated in a technically simple manner. This supports the internal combustion engine of the utility vehicle and a uniform working operation for the implement. It is also possible to operate the internal combustion engine in a virtually stationary state, whereby a corresponding reduction of the fuel consumption or emission values is achieved.

The term “at least transiently” includes defined or predetermined times or periods of time in which the auxiliary power takeoff is driven by the energy storage device and is drivingly coupled to the working power takeoff. At these times or in these periods of time, the auxiliary power takeoff is then in an assistance mode for assisting the rotational driving of the working power takeoff.

Depending on the respective embodiment of the utility vehicle and the gear stages between the internal combustion engine and the power takeoffs, the auxiliary power takeoff can be driven under certain operating conditions by the internal combustion engine or the working power takeoff if the auxiliary power takeoff is not in the above-mentioned assistance mode thereof. It is also possible in principle for the working power takeoff and the auxiliary power takeoff to be driven independently of one another and, when necessary (e.g., during an assistance mode), coupled to one another in a defined manner.

In order for the auxiliary power takeoff to be able to efficiently assist the working power takeoff, an energy storage device is designed as a device that enables storage and regulated or controlled output of energy to the auxiliary power takeoff.

The energy storage device supplies the auxiliary power takeoff with kinetic energy if an elevated load torque or a load torque peak is acting on the working power takeoff.

In principle, an energy accumulator of the energy storage device can be implemented in different manners. For example, electrical energy storage, mechanical energy storage (e.g., by means of a spring mechanism) or hydraulic energy storage (e.g., by means of a pressure accumulator) are conceivable.

In another embodiment, the energy storage device has an energy accumulator that stores energy generated by the auxiliary power takeoff itself (other than in assistance mode). This avoids expensive additional energy sources on the utility vehicle and supports the energy-saving character in the desired assistance of the working power takeoff by the auxiliary power takeoff.

The energy storage device has a flywheel mass. The flywheel mass can store energy and then output it. In particular, the flywheel mass is designed as a flywheel. For an efficient usage of the flywheel mass, it can be simply connected to the auxiliary power takeoff. When the auxiliary power takeoff is coupled to the working power takeoff in the assistance mode, the flywheel mass of the auxiliary power takeoff supplements the drive torque of the working power takeoff and thus the working energy of the implement (e.g., a flywheel mass of the implement). In comparison to a correspondingly larger flywheel mass on the implement, the flywheel mass on the auxiliary power takeoff has the advantage that the total drive torque is less because the working power takeoff and the auxiliary power takeoff are coupled to one another only to compensate for load peaks on the working power takeoff.

In another embodiment, the energy storage device has an electrical energy storage unit. It may it be designed, for example, as a super-capacitor.

It is advantageous in this regard to connect the electrical energy storage unit to an electrical machine that is coupled to the auxiliary power takeoff. The electrical machine has at least one motor function and can output electrical energy from the energy storage unit as kinetic energy to the auxiliary power takeoff.

The electrical machine advantageously also has a generator function so that kinetic energy produced by the auxiliary power takeoff outside of assistance mode can be stored as electrical energy and output again as kinetic energy to the auxiliary power takeoff when necessary. In this way, the electrical machine can be actuated to perform a motor or generator function depending on operating information from the implement. This may be derived, for example, from the temporally expected load torques at the working power takeoff.

The working power takeoff is designed as a rear-end power takeoff and the auxiliary power takeoff as a front-end power takeoff. In particular, the energy storage device can be removable so that it can be mounted optionally at the front or rear power takeoff acting as the working power takeoff, in which case the respective other power takeoff constitutes the auxiliary power takeoff.

The energy storage device is advantageously arranged mechanically stably in a three-point hitch available as standard on the utility vehicle. In addition, the distance between the auxiliary power takeoff and the energy storage device can be kept small and any losses in energy transmission between the two parts can be negligible.

The method for driving a working power takeoff of an agricultural utility vehicle presumes that an internal combustion engine of the utility vehicle drives the power takeoff of the utility vehicle, and in particular, via a suitable clutch, gear stage or the like.

In one embodiment of a method in this disclosure, an item of operating information (e.g., pressing force, implement status, pressing piston position, etc.) of the active or operating implement is determined. Depending on the operating information, a time or period of time is defined in which a further power takeoff, or an auxiliary power takeoff, of the utility vehicle is coupled to the working power takeoff such that the working power takeoff is additionally driven by the auxiliary power takeoff, the auxiliary power takeoff being supplied for this purpose with kinetic energy from an energy storage device. At defined or predetermined times or periods of time, the auxiliary power takeoff is thus in an assistance mode for assisting the rotary driving of the working power takeoff. With regard to the advantages of this assistance mode (such as compensating for peak loads appearing at the working power takeoff, reducing or avoiding decreasing the rotational speed of the internal combustion engine and the speed of the utility vehicle when torque or load peaks occur at the working power takeoff, etc.), the reader is referred to the above explanations.

The above-mentioned assistance mode of the auxiliary power takeoff is used with a big baler as the implement. When the big baler is active, heavy cyclical peak loads are caused by the pressing piston and are transmitted via the gear unit of the baler to the working power takeoff of the utility vehicle. The torque peaks of the working power takeoff resulting from this can be compensated in the assistance mode of the auxiliary power takeoff.

DETAILED DESCRIPTION

InFIG. 1, an embodiment of an agricultural utility vehicle10is in the form of a tractor having a cab, a front axle14, and an internal combustion engine16for driving at least a rear axle18. An implement20is operated with respect to its working function by means of a rear power takeoff (hereinafter working power takeoff22) and is present at the rear area of the utility vehicle10. A front three-point hitch24, which supports a removable energy supply device26, is present at the front end of the utility vehicle10. The energy storage device26has the purpose of driving a front power takeoff (hereinafter auxiliary power takeoff28).

In the region of the cab12there is an operating element30for activating and deactivating the working power takeoff22and an operating element32for activating and deactivating the auxiliary power takeoff28, among other things. In addition, an appropriate transmission ratio can be preselected and the power takeoff rotational speed can be limited by means of the operating elements30,32.

FIG. 2schematically shows individual details of the interaction of the utility vehicle10with the implement20. The two power takeoffs22,28can be driven by a suitable gearbox device34and the drivetrain of the utility vehicle independently of one another by the internal combustion engine16.

The auxiliary power takeoff28can additionally be coupled via the gearbox device34to the working power takeoff22in such a manner that the auxiliary power takeoff28simply runs at the speed of the working power takeoff22, which is achieved by the driving of the working power takeoff22by the internal combustion engine16. In addition, the auxiliary power takeoff28can be coupled in an assistance mode to the working power takeoff22in such a manner that, at defined times or periods of time, the working power takeoff22is not driven only by the internal combustion engine16, but also by the auxiliary power takeoff28, in order to compensate for elevated load torques or load torque peaks at the working power takeoff22.

InFIG. 2, an implement20in the form of a large baler36is operated by means of the working power takeoff22. The big baler36includes a flywheel38which, optionally via intervening additional components for transmitting force, is drivingly coupled to the working power takeoff22. A pressing gear unit40, which operates a pressing piston42, is connected to the flywheel38. Depending on the design, additional components for force transmission (not shown) can be provided between the flywheel38, the pressing gear unit40and the pressing piston42.

The energy storage device26according toFIG. 2contains an alternating current machine44that can be used as a motor and a generator, an AC/DC converter46, an energy storage unit48designed as a super-capacitor, and a control unit50. The control unit50is connected via a data bus52of the utility vehicle10to a control unit54of the implement20or the large baler36. In this way, the control unit50of the energy storage device26can receive data and information regarding expected load cycles of the implement20or the large baler36. The energy storage device can be controlled in such a manner that the alternating current machine44is active as a generator during a low-load period of time (e.g., with torques M of approximately MN), so that mechanical energy available at the auxiliary power takeoff is stored as electrical energy in the energy storage unit48. During the elevated load or peak load generated by the implement20or the large baler36(e.g., in the period t1to t2), the alternating current machine44operates as a motor and outputs the stored energy back to the auxiliary power takeoff28, which thereby additionally drives the drive shaft22in an assistance mode. The control unit50regulates the torque of the alternating current machine44operating as a motor, based on received or determined predictive load information from the implement20or the large baler36.

Due to the pressing piston42in the large baler36, high cyclical peak loads, i.e., torques M that are greater than a low-load torque MNand can reach a peak torque MS(see schematic diagram inFIG. 1) are generated and can be transmitted via the pressing gear unit40to the working power takeoff22of the utility vehicle10. This can lead to a decrease of the rotational speed of the internal combustion engine16and a decrease of the forward speed of the utility vehicle10in working operation. In order to compensate for the elevated loads or peak loads, the working power takeoff22is additionally driven by the auxiliary power takeoff28at defined times or periods of time (e.g., tS, or t1to t2). For this purpose, an information item of the active big baler36is determined in the embodiment according toFIG. 2. This operating information item can be a position PKand a pressing force FPof the pressing piston42, for example. On the basis of this information, predictive load information is determined, particularly a load torque M to be expected or a load peak M>MNand the associated time t1, tS, t2or time period t1to t2. It is thereby possible to define times or periods of time in which the auxiliary power takeoff28is coupled to the working power takeoff22and supplied with kinetic energy in such a manner that the working power takeoff22is additionally driven by the auxiliary power takeoff28.

While the energy storage device26according toFIG. 2can be considered an electrically active flywheel mass or electrically active flywheel, the energy storage device26in the embodiment ofFIG. 3has a mechanical flywheel mass56that is connected to the auxiliary power takeoff28.