FORAGE HARVESTER

Abstract

A forage harvester has multiple working elements for carrying out a crop handling process, a drive system which is divided into a main drive train that includes mechanically driven working elements, and an auxiliary drive train that includes hydraulically driven working elements, a driver assistance system which comprises a memory for storing data and a computing device for processing data stored in the memory, as well as a graphical user interface. The working elements consist of at least one adjustable crop handler, at least one actuator system for adjusting and/or actuating the crop handler, and a control unit for controlling the actuator system. The working element is designed as an automatic adjuster whose mode of operation can be optimized by the driver assistance system. The driver assistance system feeds a throughput-proportional load signal, which can be determined by at least one sensor system, to the particular automatic adjuster.

Claims

1. A forage harvester comprising: multiple working elements for carrying out a crop handling process, the working elements comprising at least one adjustable crop handler, at least one actuator system configured for adjusting and/or actuating the at least one crop handler, as well as a control unit for controlling the actuator system, a drive system which is divided into a main drive train that includes mechanically driven working elements of the multiple working elements, and an auxiliary drive train that includes at least partially hydraulically driven working elements of the multiple working elements, a driver assistance system which comprises a memory for storing data and a computing device for processing data stored in the memory, as well as a graphical user interface, and a sensor system configured for determining a throughput-proportional load signal of the drive system, wherein each working element is designed as an automatic adjuster (A.sub.1, A.sub.2, A.sub.3, A.sub.4, A.sub.n), wherein a mode of operation of each automatic adjuster (A.sub.1, A.sub.2, A.sub.3, A.sub.4, A.sub.n) is configured to be optimized, individually or depending on at least one further automatic adjuster (A.sub.1, A.sub.2, A.sub.3, A.sub.4, A.sub.n), by the driver assistance system, wherein the driver assistance system is configured for feeding the throughput-proportional load signal of the drive system to a particular automatic adjuster (A.sub.1, A.sub.2, A.sub.3, A.sub.4, A.sub.n).

2. The forage harvester as claimed in claim 1, wherein the at least one sensor system is assigned to at least one working element in the main drive train, in order to determine the throughput-proportional load signal, in order to detect changes in a power uptake of the at least one working element.

3. The forage harvester as claimed in claim 1, wherein the at least one sensor system is assigned to at least one working element in the auxiliary drive train, in order to determine the at least one throughput-proportional load signal, in order to detect changes in power uptake of the at least one working element.

4. The forage harvester as claimed in claim 1, wherein the at least one sensor system is configured for transmitting measuring signals acquired by the sensor system to the driver assistance system in order to generate throughput-proportional load signals.

5. The forage harvester as claimed in claim 1, wherein the automatic adjusters (A.sub.1, A.sub.2, A.sub.3, A.sub.4, A.sub.n) are configured for utilizing the load signals during optimization of the mode of operation of the particular working element, the mode of operation being optimization a power requirement of the particular working element.

6. The forage harvester as claimed in claim 1, wherein the at least one sensor system is configured for indirectly measuring a load of the drive system.

7. The forage harvester as claimed in claim 1, wherein the at least one sensor system is configured for determining elongation slip in a drive belt upstream and downstream from a pulley of the main drive train.

8. The forage harvester as claimed in claim 7, wherein the sensor system comprises at least one guide roller positioned downstream from a pulley of the at least one working element in the main drive train, wherein sensors of the at least one sensor system are configured to detect rotational speed of the guide roller and of the pulley of the at least one working element in the main drive train.

9. The forage harvester as claimed in claim 1, wherein the at least one sensor system is configured for determining bending vibrations in a drive belt of the main drive train.

10. The forage harvester as claimed in claim 9, wherein the at least one sensor system comprises two distance sensors, wherein one of the distance sensors is assigned to a slack side upstream from the at least one working element and a second one of the distance sensors is assigned to a load side downstream from the working element, wherein the at least one sensor system is configured for determining a deflection of the drive belt of the main drive train.

11. The forage harvester as claimed in claim 1, wherein the at least one sensor system is configured for determining a hydraulic power of at least one hydraulic motor situated in the auxiliary drive train of the drive system.

12. The forage harvester as claimed in claim 11, wherein the at least one sensor system comprises two pressure sensors, a first one of the pressure sensors being positioned upstream from the at least one hydraulic motor and a second one of the pressure sensors being positioned downstream from the at least one hydraulic motor.

13. The forage harvester as claimed in claim 11, wherein the hydraulic motor is designed as a fixed displacement motor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention is explained in greater detail in the following with reference to exemplary embodiments represented in the drawings.

[0027] In the drawings:

[0028] FIG. 1 shows a schematic representation of a side view of a self-propelled forage harvester;

[0029] FIG. 2 shows a schematic representation of the structure of an automatic adjuster:

[0030] FIG. 3 shows a schematic overview of the structure of a driver assistance system;

[0031] FIG. 4 shows a schematic partial view of a main drive train of a drive system comprising a sensor system for indirectly measuring the load;

[0032] FIG. 5 shows a schematic view of the main drive train comprising a sensor system according to a second embodiment for indirectly measuring the load; and

[0033] FIG. 6 shows a schematic view of an auxiliary drive train of the drive system comprising a sensor system according to a third embodiment for indirectly measuring the load.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] FIG. 1 shows a schematic representation of a side view of a self-propelled forage harvester 1. The forage harvester 1 comprises a front attachment 2 for harvesting, in particular, stalk crop. The front attachment 2 can be designed, inter alia, as a so-called corn header or as a corn picker. For the purpose of harvesting grass, the front attachment 2 can be designed as a mower unit.

[0035] The crop picked up by the front attachment 2 is fed to an intake conveyor device 3. The intake conveyor device 3 comprises at least a first roller pair 4a, 4b and a second roller pair 5a, 5b which are situated on a frame or a housing. The at least two roller pairs 4a, 4b and 5a, 5b are utilized for drawing in and compressing the picked-up crop. The roller pairs 4a, 4b and 5a, 5b form an adjustable crop handling means. Thus, for example, the compression force as well as the drive speed of the roller pairs 4a, 4b and 5a, 5b can be changed in order to be adapted to changing crop quantities.

[0036] A chopper 6 is positioned downstream from the intake conveyor device 3. The chopper 6 comprises a rotationally driven chopper drum 7 equipped with a plurality of chopper knives 8. The chopper knives 8 rotating with the chopper drum 7 interact with a fixedly situated shear bar 9 of the chopper 6 in order to chop up the crop supplied by the intake conveyor device 3 in the form of a compressed crop mat. The spacing of the shear bar 9 in relation to the enclosing circle of the chopper knives 8 can be adjusted or readjusted. A preferably small spacing contributes to a reduced force requirement during cutting and to a constant cut quality. A sharpening device (not represented) assigned to the chopper 6 is utilized for sharpening the chopper knives 8, as necessary, in order to counter a deteriorating chopping quality resulting from dull chopping knives and to counter an increased energy requirement for driving the chopper 6.

[0037] The chopped up crop emerging from the chopper 6 can be fed to an optionally provided after-treatment device 10. The after-treatment device 10, which is also referred to as a conditioning unit or corn cracker, is utilized for the comminution of corn kernels in order to increase the usability or energy efficiency when utilized as feed or in a biogas plant. These types of after-treatment devices 10 consist of a pair of rollers having profiled surfaces, wherein the rollers are driven at different rotational speeds. The speed ratio of the roller pair of the after-treatment device 10 is variable.

[0038] The comminution of the grain is determined, in particular, by a gap width between the two rollers of the after-treatment device 10. The smaller the gap width is, the greater the comminution of the grain is. The gap width is adjustable. The after-treatment device 10 can be removed from the crop flow path of the forage harvester 1 as necessary, for example, in order to harvest grass.

[0039] From the chopper 6 or the optional after-treatment device 10, the chopped up crop reaches an accelerating device 11 which transfers the crop, through a conveying shaft 12 and an adjoining discharge device 13 designed as a discharge spout, to a transport vehicle (not represented) traveling adjacently to the forage harvester 1. An ensilage agent metering device 14 is situated in the area of the accelerating device 11, which introduces a fluid into the conveying shaft 12 with the aid of a variable-capacity supply pump 15. For this purpose, an injector 16 is provided, which terminates in the conveying shaft 12 and opens in the flow direction of the crop, whereby the fluid is applied in a finely sprayed form onto the crop flowing past. At least one sensor 17 is situated on the discharge device 13, which is configured at least for determining the moisture content of the chopped up crop with respect to the dry mass. The at least one sensor 17 can be designed as an NIR sensor which is also configured for detecting components such as raw ash or the raw protein content of the crop flowing past. One or multiple further sensors 18 for determining the length of cut, the flow speed of the crop, and/or the mass flow of the crop flowing past may be assigned to the discharge device 13.

[0040] A drive device 19 designed as an internal combustion engine is provided for driving the forage harvester 1. The drive device 19 is drivingly connected to a drive system 20. The drive system 20 is divided into a main drive train which includes mechanically driven working elements such as the chopper 6, the optional after-treatment device 10, as well as the accelerating device 11, and an auxiliary drive train which includes mechanically and/or hydraulically driven working elements such as the front attachment 2 and the intake conveyor device 3.

[0041] The chopper 6 and the accelerating device 11 are driven with the aid of a drive belt 20a. The after-treatment device 10 is drivingly connected to the accelerating device 11 by one further belt. The front attachment 2 and the intake conveyor device 3 can be driven by the auxiliary drive train which can be mechanically coupled to the chopper 6, can be operated mechanically and hydrostatically in a power-split manner, or can be hydrostatically operated independently of the chopper 6. A hydraulic pump 28, which drives a hydraulic motor 29, is provided for the purely hydrostatic drive of the front attachment 2 and the intake conveyor device 3. The hydraulic pump 28 is preferably designed as an axial piston pump having an adjustable displacement volume. The hydraulic motor 29 is designed as a fixed displacement motor. Moreover, a hydrostatic ground drive 21 is provided, with the aid of which the ground speed of the forage harvester 1 can be regulated.

[0042] The forage harvester 1 comprises a cab 22, in which an input/output device 23 is provided, which is available to an operator of the forage harvester 1 for the purpose of setting and adjusting operating parameters, for example, and informing the operator about present operating and harvesting conditions. The input/output device 23 is connected to a driver assistance system 25 of the forage harvester 1 by a bus system 24. The bus system 24 also connects the sensors 17, 18 to the discharge device 13 and connects a sensor 26 to the intake conveyor device 3, and connects further sensors and sensor systems 34 and actuators 32 (not represented in FIG. 1) for monitoring as well as adjusting and/or actuating the front attachment 2, the intake conveyor device 3, the chopper 6, the sharpening device, the after-treatment device 10, the accelerating device 11, the ensilage agent metering device 14, the discharge device 13, as well as the ground drive 21, which are referred to in the following as working elements 30, to the driver assistance system 25. The sensors 17, 18 and 26 are described in general in the following under the term sensor system 34. Each of these working elements 30 includes at least one adjustable crop handler 31, with the aid of which the crop is manipulated throughout the crop handling process through the forage harvester 1, from the point of having been picked up by the front attachment 2 until it is discharged by the discharge device 13. The at least one actuator system 32 of each working element 30 is utilized for setting, adjusting, and/or actuating the at least one crop handler 31 of a working element 30 according to the particular prevailing harvesting conditions. The sensors or sensor systems 34 monitor operation- and working element-specific parameters of the working elements 30 and of the crop handled by the working elements 30. The term crop handler 31 is understood to mean, inter alia, the roller pairs 4a, 4b and 5a, 5b of the intake conveyor device 3, and the chopper knives 8 of the chopper 6.

[0043] FIG. 2 shows a schematic view of the structure of an automatic adjuster A.sub.n. The working element 30 designed as an automatic adjuster A.sub.n comprises at least one crop handler 31, an actuator system 32, as well as a control unit 33. Control signals are transmitted from the control unit 33 to the actuator system 32 with the aid of the data bus 24. The at least one crop handler 31 is adjusted with the aid of the actuator system 32. A sensor system 34 monitors the at least one crop handler 31 of the working element 30 and, if necessary, the actuator system 32. The sensor system 34 makes the data it generates available to the control unit 33 for evaluation, by way of the bus system 24. In addition, external information 35 is made available to the control unit 33, which is transmitted to the forage harvester 1, for example, from other working machines and/or a central computer system, and which can influence the crop handling process. The data made available by the sensor system 34, as well as the external information 35, form input signals I.sub.En of the automatic adjuster A.sub.n. Output signals of the automatic adjuster A.sub.n are designated as I.sub.An. The automatic adjuster A.sub.n autonomously optimizes the mode of operation of the working element 30, i.e., the automatic adjuster A.sub.n is configured for continuously autonomously determining and specifying the required adjustments of operating parameters of the working element 30. Operating parameters which have been optimally adapted to the particular present operating and harvesting conditions are made available by the automatic adjuster A.sub.n.

[0044] The representation in FIG. 3 shows the schematic overview of the structure of the driver assistance system 25. The driver assistance system 25 comprises multiple automatic adjusters A.sub.1, A.sub.2, A.sub.3, A.sub.4, . . . , A.sub.n. In principle, each of the automatic adjusters A.sub.1, A.sub.2, A.sub.3, A.sub.4, . . . , A.sub.n operates autonomously. It is conceivable, however, to combine two automatic adjusters A.sub.1, A.sub.2 into one unit, as indicated in FIG. 3 by way of example. It makes sense to combine two automatic adjusters A.sub.1, A.sub.2 when a respective autonomous optimization provides no added value over the direct interaction or dependence between these two automatic adjusters A.sub.1, A.sub.2. Thus, in the case of the forage harvester 1, the automatic adjuster A.sub.1 designed as an automatic front attachment adjuster, which is utilized for optimizing the operating parameters of the front attachment 2, and the automatic adjuster A.sub.2 designed as an automatic intake conveyor device adjuster, which is utilized for optimizing the operating parameters of the intake conveyor device 3, are combined to form one shared automatic adjuster, which is referred to as an automatic feed adjuster 36. Further automatic adjusters are an automatic chopper adjuster A.sub.3, an automatic after-treatment adjuster A.sub.4, and an automatic acceleration adjuster A.sub.5. Further automatic adjusters are conceivable.

[0045] The driver assistance system 25 comprises a computing device 37, a memory 38, and a graphical user interface 39. The computing device 37 is configured for processing data stored in the memory 38. In addition, the computing device 37 of the driver assistance system 25 receives and processes data of sensor system 34 as well as external information 35 which has been made available.

[0046] The driver assistance system 25 comprises sets of rules stored in the memory 38 and/or in a memory unit of the control units 33 of the automatic adjusters A.sub.1, A.sub.2, A.sub.3, A.sub.4, . . . , A.sub.n, which are assigned to the particular automatic adjusters A.sub.1, A.sub.2, A.sub.3, A.sub.4, . . . , A.sub.n. The set of rules assigned to the particular automatic adjuster A.sub.1, A.sub.2, A.sub.3, A.sub.4, . . . , A.sub.n brings about an optimization of the mode of operation of the particular working element 30 regardless of the mode of operation of the other working elements 30. The sets of rules encompass expert knowledge as well as adaptable characteristic curves or families of characteristics.

[0047] The automatic adjusters A.sub.1, A.sub.2, A.sub.3, A.sub.4, . . . , A.sub.n are integrated into the driver assistance system 25, which is of a higher order in terms of control hierarchy, wherein the mode of operation of each automatic adjuster A.sub.1, A.sub.2, A.sub.3, A.sub.4, . . . , A.sub.n can be optimized by the driver assistance system 25 individually or depending on at least one further automatic adjuster A.sub.1, A.sub.2, A.sub.3, A.sub.4, . . . , A.sub.n. Thus, input signals I.sub.E1, I.sub.E2, I.sub.E3, I.sub.E4, . . . , I.sub.En corresponding to each automatic adjuster A.sub.1, A.sub.2, A.sub.3, A.sub.4, . . . , A.sub.n, respectively, are made available by the higher-order driver assistance system 25 and are processed according to the particular set of rules of the automatic adjusters A.sub.1, A.sub.2, A.sub.3, A.sub.4, . . . , A.sub.n. In order to optimize the mode of operation of the particular automatic adjuster A.sub.1, A.sub.2, A.sub.3, A.sub.4, . . . , A.sub.n, an output signal I.sub.A1, I.sub.A2, I.sub.A3, I.sub.A4, . . . , I.sub.An is generated, which is utilized for controlling the particular actuator system 32 of the working element 30 controlled by the automatic adjuster A.sub.1, A.sub.2, A.sub.3, A.sub.4, . . . , A.sub.n. In addition, the output signals I.sub.A1, I.sub.A2, I.sub.A3, I.sub.A4, . . . , I.sub.An are transmitted to the computing device 37 of the driver assistance system 25. The driver assistance system 25 makes the output signals I.sub.A1, I.sub.A2, I.sub.A3, I.sub.A4, . . . , I.sub.An available to the other automatic adjusters A.sub.1, A.sub.2, A.sub.3, A.sub.4, . . . , A.sub.n as additional control input signals S.sub.A1, S.sub.A2, S.sub.A3, S.sub.A4, . . . , S.sub.An. As a result, additional information is available to the driver assistance system 25 and the automatic adjusters A.sub.1, A.sub.2, A.sub.3, A.sub.4, . . . , A.sub.n, whereby it is made possible to take interactions with one or multiple other working elements 30, which arise due to changed settings of one working element 30, into account during the optimization of the working elements 30.

[0048] Due to the detection of load changes in the drive system 20 and due to the transmission of the throughput-proportional load signals 40, which reflect these load changes, from the driver assistance system 25 to all automatic adjusters A.sub.1, A.sub.2, A.sub.3, A.sub.4, . . . , A.sub.n, a prompt adaptation of the operating parameters can be carried out by the particular automatic adjusters A.sub.1, A.sub.2, A.sub.3, A.sub.4, . . . , A.sub.n of a working element 30, in order to continuously optimize the operation of the working element 30. For this purpose, in order to determine a particular load signal 40 in the main drive train and/or in the auxiliary drive train, at least one sensor system 41, 42, 43 is assigned to the main drive train and/or the auxiliary drive train, which is illustrated in FIGS. 4 to 6. The sensor systems 41, 42, 43 are each configured for indirectly measuring the load in the drive system 20.

[0049] FIG. 4 shows a partial view of the main drive train of the drive system 20 comprising a sensor system 41 for indirectly measuring the load, which is configured for determining elongation slip in the drive belt 20a upstream and downstream from a pulley 44 of the main drive train, with the aid of which the chopper drum 7 is driven. An arrow DR indicates the direction of rotation of the pulley 44 operating as the output. The sensor system 41 comprises a guide roller 45 which rests against the load side 49 of the drive belt 20a and is driven thereby. The guide roller 45 is positioned as close as possible to the pulley 44 in order to be able to measure the belt speed at the exit point AP of the chopper drum 7 The guide roller 45 is essentially unloaded, in order to avoid the occurrence of slip. The circumferential speed of the guide roller 45 therefore essentially corresponds to the belt speed at the exit point AP. A sensor 47, in particular, a Hall sensor, is provided for measuring the rotational speed of the guide roller 45. One further sensor 46, which is also designed as a Hall sensor, is utilized for detecting the rotational speed of the chopper drum 7. The sensors 46, 47 are connected, for the purpose of signaling, to the driver assistance system 25 by the bus system 24. The driver assistance system 25 evaluates the signals of the rotational speeds received from the sensors 46, 47.

[0050] The belt speed at the entry point EP of the slack side 48 of the drive belt 20a can be determined on the basis of the rotational speed of the chopper drum 7. On the basis of the difference of the belt speeds between the entry point EP and the exit point AP, the resultant elongation slip can be determined, which, in turn, correlates with the torque taken up by the chopper 6, and so the power uptake of the chopper 6 can be inferred. By way of the continuous measurement carried out with the aid of the sensor system 41, the throughput-proportional load signals 40 are generated by the driver assistance system 25 and are made available to the automatic adjusters A.sub.1, A.sub.2, A.sub.3, A.sub.4, . . . , A.sub.n, and so the automatic adjusters can promptly respond to changes in the throughput of crop.

[0051] The representation in FIG. 5 shows a schematic view of the main drive train comprising a sensor system 42 according to a second embodiment for indirectly measuring the load. A drive pulley, which is driven by the drive device 19, is designated with the reference numeral 50. Jockey pulleys 53 are utilized for maintaining the belt tension of the drive belt 20a. The hydraulic pump 28 is driven by a pulley 51. One further pulley 52 drives the accelerating device 11 as well as the after-treatment device 10 which is drivingly connected to the accelerating device 11. The sensor system 42 is configured for determining bending vibrations in the drive belt 20a of the main drive train. For this purpose, the sensor system 42 comprises a distance sensor 54 on the slack side 48 upstream from the working element chopper 6 and a distance sensor 54 on the load side 49 downstream from the working element chopper 6, with the aid of which a deflection of the drive belt 20a of the main drive train can be determined on the basis of belt vibrations. The continuously detected belt vibrations can be subjected to a frequency analysis in order to determine the frequency of the belt vibrations of the drive belt upstream and downstream from the pulley of the working element driven by the pulley. The determination of the frequencies of the belt vibrations of the drive belt 20a makes it possible to infer a difference of the belt-side forces on the slack side 48 upstream from the pulley 44 and on the load side 49 downstream from the pulley 44. The force given off to the chopper 6, which, in turn, is required for determining the torque, can be inferred from the difference of the belt-side forces.

[0052] For this purpose, a distance sensor 54 is assigned to the slack side 48 upstream from the chopper 6 and a distance sensor 54 is assigned to the load side 49 downstream from the chopper 6, with the aid of which a deflection of the drive belt 20a of the main drive train can be determined. The distance sensors 54 are preferably designed as contactlessly operating sensors, in order to detect the distance changes of the drive belt 20a caused by the belt vibrations. The signals of the distance sensors 54 are forwarded to the driver assistance system 25 via the bus system 24 for evaluation by the driver assistance system 25. The driver assistance system 25 generates the throughput-proportional load signals 40 and makes them available to the automatic adjusters A.sub.1, A.sub.2, A.sub.3, A.sub.4, . . . , A.sub.n.

[0053] FIG. 6 shows a schematic view of the auxiliary drive train of the drive system 20 comprising a sensor system 43 according to a third embodiment for indirectly measuring the load. The sensor system 43 is configured for determining a hydraulic power of at least one hydraulic motor 29 situated in the auxiliary drive train. In the exemplary embodiment shown, the drive of the front attachment 2 and the intake conveyor device 3 takes place purely hydrostatically by a hydraulic motor 29 in each case. The drive of the hydraulic motor 29 takes place due to a pressure differential between the pressure line and the suction line of a closed hydraulic system 55, and so the displacement volume of the hydraulic motor 29 is identical during every revolution. The hydraulic motor 29 comprises an output shaft 57. A constant volumetric flow is made available by the hydraulic pump 28, the drive shaft 56 of which is drivingly connected to the pulley 51 which is driven by the drive belt 20a of the main drive train. The hydraulic pump 28 is designed as an axial piston pump having an adjustable displacement volume, and so the rotational speed of the hydraulic motor(s) 29 is adjustable. In order to determine the power taken up by the hydraulic motor 29, it is necessary to know the pressure difference at the inflow and the outflow of the hydraulic motor 29. For this purpose, the sensor system 43 comprises two pressure sensors 58 which are utilized at the inflow and the outflow of the hydraulic motor 29 for determining the pressure difference.

[0054] The power taken up by the particular hydraulic motor 29 can be determined on the basis of the output rotational speed at the pulley 51 of the hydraulic pump as well as the pressure difference at the inflow and the outflow of the hydraulic motor 29. The evaluation takes place with the aid of the driver assistance system 25, as described above in conjunction with the two other embodiments.

TABLE-US-00001 List of reference characters 1 forage harvester 29 hydraulic motor 2 front attachment 30 working element 3 intake conveyor device 31 crop handling means 4a roller 32 actuator system 4b roller 33 control unit 5a roller 34 sensor system 5b roller 35 external information 6 chopper 36 automatic feed adjuster 7 chopper drum 37 computing device 8 chopper knife 38 memory 9 shear bar 39 graphical user interface 10 After-treatment device 40 load signal 11 accelerating device 41 sensor system 12 conveying shaft 42 sensor system 13 discharge device 43 sensor system 14 ensilage agent metering device 44 pulley 15 supply pump 45 guide roller 16 injector 46 sensor 17 sensor 47 sensor 18 sensor 48 slack side 19 drive device 49 load side 20 drive system 50 drive pulley 21 ground drive 51 pulley 22 cab 52 pulley 23 input/output device 53 jockey pulleys 24 bus system 54 distance sensor 25 driver assistance system 55 hydraulic system 26 sensor 56 drive shaft 27 drive belt 57 output shaft 28 hydraulic pump 58 pressure sensor A.sub.1 automatic adjuster DR rotational direction A.sub.2 automatic adjuster EP entry point A.sub.3 automatic adjuster AP exit point A.sub.4 automatic adjuster A.sub.n automatic adjuster I.sub.E1 input signal I.sub.E2 input signal I.sub.E3 input signal I.sub.E4 input signal I.sub.En input signal I.sub.A1 output signal I.sub.A2 output signal I.sub.A3 output signal I.sub.A4 output signal I.sub.An output signal S.sub.A1 control input signal S.sub.A2 control input signal S.sub.A3 control input signal S.sub.A4 control input signal S.sub.An control input signal