METHOD FOR CALIBRATING A CHARACTERISTIC DIAGRAM OFA WORK MACHINE AND WORK MACHINE

Abstract

A method is described for calibrating a characteristic diagram of a working machine. The characteristic diagram includes a brake pedal characteristic of a brake system and at least one clutch characteristic of a drive input clutch which, in the calibrated condition, have a nominal relationship to one another. The method having the steps of: determining a wheel-side drive output torque; determining an actual brake pedal characteristic with reference to the drive output torque; determining an actual relationship that differs from the nominal relationship by comparing the actual brake pedal characteristic with a nominal brake pedal characteristic; and calibrating the brake pedal characteristic or the clutch characteristic in such manner that the actual relationship corresponds to the nominal relationship. In addition a working machine with a control unit for carrying out the method is described.

Claims

1-15. (canceled)

16. A method of calibrating a characteristic diagram (13) of a working machine (2), the characteristic diagram (13) having a brake pedal characteristic (14; 16) of a brake system (11) and at least one clutch characteristic (15; 17) of a drive input clutch (5) which, in a calibrated condition, have a nominal relationship to one another, the method comprising: determining a wheel-side drive output torque, determining an actual brake pedal characteristic (16) with reference to the drive output torque, determining an actual relationship that deviates from the nominal relationship by comparing the actual brake pedal characteristic (16) determined with a nominal brake pedal characteristic (14), and calibrating the brake pedal characteristic (14; 16) or the clutch characteristic (15; 17) in such manner that the actual relationship corresponds to the nominal relationship.

17. The method according to claim 16, further comprising either: maintaining an actual clutch characteristic (17) unchanged and calibrating the actual brake pedal characteristic (16) toward the nominal brake pedal characteristic (14), or maintaining the actual brake pedal characteristic (16) unchanged and calibrating the actual clutch characteristic (17) toward a nominal clutch characteristic (15).

18. The method according to claim 16, further comprising determining a turbine wheel torque to determine the drive output torque, from a converter characteristic of a hydrodynamic torque converter (4) connected upstream from the drive input clutch (5) in the power flow direction, and the converter characteristic being stored in an electronic control unit (12).

19. The method according to claim 16, further comprising calculating the drive output torque with reference to at least one of the turbine wheel torque, a clutch parameter of the drive input clutch (5), and at least one transmission parameter of a transmission (9) connected downstream from a hydrodynamic torque converter (4).

20. The method according to claim 16, further comprising determining, from the drive output torque, a brake characteristic magnitude with reference to which a braking torque of the brake system (11) is determined either indirectly or directly.

21. The method according to claim 16, further comprising determining a value of the brake characteristic magnitude that corresponds with a brake pedal position to determine the actual brake pedal characteristic (16).

22. The method according to claim 16, further comprising determining the actual brake pedal characteristic by a discrete process in which a number of Bezier control points (19, 20, 21, 22) are determined.

23. The method according to claim 22, further comprising determining one of the Bezier control points (19, 20, 21, 22) by setting the brake pedal position to a value and, during the determination of the corresponding value of the brake characteristic magnitude, keeping the brake pedal position constant at that value.

24. The method according to claim 7, further comprising engaging a gear in the transmission (9) while the working machine (2) is at rest and increasing a motor rotational speed until the working machine (2) starts moving.

25. The method according to claim 22, further comprising, at least one of: when movement is detected, shifting the transmission (9) automatically to an idling mode via the electronic control unit (12), and when movement begins, at least one of determining and storing the value of the brake characteristic magnitude existing at the moment.

26. The method according to claim 16, further comprising determining the actual brake pedal characteristic (16) by a continuous process in which the brake pedal position is continuously varied and, at the same time, the corresponding values of the brake characteristic magnitude are determined.

27. The method according to claim 26, further comprising accelerating the working machine (2) up to a maximum speed attainable in a gear and then braking the working machine to rest, during a deceleration phase, by continuously increasing actuation of the brake pedal, and determining the corresponding values of the brake characteristic magnitude during the deceleration phase.

28. The method according to claim 16, further comprising carrying out the continuous process for determining an initiation point of the actual brake pedal characteristic (16), first at a first motor rotational speed and then at a higher second motor rotational speed, by comparing the second motor rotational speed with the first motor rotational speed.

29. A working machine (2) with a drive unit (3), a hydrodynamic torque converter (4), a drive input clutch (5), a transmission (9), a brake system (11), and an electronic control unit (12) in which a characteristic diagram (13) is stored, which diagram includes a brake pedal characteristic (14, 16) of the brake system (11) and at least one clutch characteristic (15, 17) of the drive input clutch (5) which, in a calibrated condition, have a nominal relationship to one another, the electronic control unit (12) is designed to carry out a method of calibrating the characteristic diagram (13) including: determining a wheel-side drive output torque; determining an actual brake pedal characteristic (16) with reference to the drive output torque; determining an actual relationship that deviates from the nominal relationship by comparing the actual brake pedal characteristic (16), determined with a nominal brake pedal characteristic (14); and calibrating the brake pedal characteristic (14; 16) or the clutch characteristic (15; 17) in such manner that the actual relationship corresponds to the nominal relationship.

30. The working machine according to claim 29, wherein a converter characteristic of the torque converter (4) is stored in the electronic control unit (12).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Below, the invention is explained in greater detail with reference to drawings, which show:

[0025] FIG. 1: A schematic view of a drive-train of a working machine, and

[0026] FIG. 2: A characteristic diagram for the working machine in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] FIG. 1 shows a drive-train 1 of a working machine 2. The drive-train 1 comprises a drive unit 3, which drives one or more consumers by way of a hydrodynamic torque converter 4 and a drive input clutch 5. The working machine 1 drives wheels 6 and at least one power take-off 7 such as hydraulic pumps for actuating loading scoops.

[0028] The torque converter 4 is on the one hand functionally connected to the drive unit 3 so that torque of the drive unit 3 can be transmitted to an impeller 8 of the torque converter 4. On the other hand, on the wheel side the torque converter 4 is connected to the drive input clutch 5 and/or to a transmission 9. A turbine wheel 10 of the hydrodynamic torque converter 4 receives the flow energy produced by the impeller 8 and supplies it in the form of mechanical energy to the drive input clutch 5 and the transmission 9, whereby preferably at least one wheel 6 is driven.

[0029] On the drive input side, the power take-off 7 is connected upstream from the torque converter 4 and drives for example a high-pressure pump, a concrete mixer or a moving blade. The torque supplied to the power take-off 7 is preferably a function of the torque of the drive unit 3 transmitted to the impeller 8 of the torque converter 4.

[0030] Connected upstream from the wheels 6 is a hydraulic brake system 11 such that the wheels 6, for example during driving, can be braked in accordance with the position of a brake pedal (not shown) or prevented from rotating when the vehicle is at rest. To brake the wheels 6, the brake system 11 produces a braking pressure by means of which the braking process takes place.

[0031] In addition the working machine 2 comprises an electronic control unit 12 by means of which a calibration process can be carried out. In the control unit 12 at least one characteristic diagram 13 (see FIG. 2) of the working machine 2 is stored, which enables the braking torque of the brake system 11 to be determined.

[0032] FIG. 2 shows the characteristic diagram 13 for the working machine 2, wherein by comparison with FIG. 1 the same indexes are used for features whose design and/or mode of operation is identical or at least comparable. Insofar as these are not again explained in detail, their design and/or mode of operation corresponds to the design and mode of operation of the features already described earlier.

[0033] The x-axis of the characteristic diagram 13 represents a pedal displacement of the brake system 11 and the y-axis represents the braking torque of the brake system 11 (see FIG. 1). The characteristic diagram 13 comprises a nominal brake pedal characteristic 14 of the hydraulic brake system 11 and at least a first actual clutch characteristic 17 of the drive input clutch (see FIG. 1). In the calibrated condition the nominal brake pedal characteristic 14 and the actual clutch characteristic 17 have a nominal relationship with one another. In the calibrated condition an actual brake pedal characteristic 16 and/or an actual clutch characteristic 17 are compared with the respective nominal brake pedal characteristic 14 and/or the nominal clutch characteristic 15. The nominal relationship depicts at least one point of intersection 18 between the nominal brake pedal characteristic 14 and the actual clutch characteristic 17. The position of the point of intersection 18 represents the pedal position at which the drive input clutch 5 is released. The calibrated characteristic diagram 13 makes it possible to determine the braking torque of the brake system 11 independently of the major tolerances thereof.

[0034] The nominal brake pedal characteristic 14 has an initiation point 24, which indicates from which pedal position of the brake system 11 the latter engages and thus brakes the working machine 2 or keeps it at rest (see FIG. 1).

[0035] To get to the calibrated condition, a wheel-side drive output torque is determined. In the control unit 12, a converter characteristic (not shown) of the hydrodynamic torque converter 4 is stored, which represents the relationship of the rotational speed ratio between the impeller 8 and the turbine wheel 10 on the one hand, and the torque of the turbine wheel 10 on the other hand (see FIG. 1). The drive output torque is calculated with reference to the turbine torque and/or at least one clutch and/or transmission parameter of the drive input clutch 5 or the transmission 9. The clutch and/or transmission parameters are for example the transmission ratio, the pressure at a brake valve which increases in line with pedal displacement, friction values, and/or piston values for producing the braking force.

[0036] The drive output torque determined enables the determination of a brake characteristic magnitude, in particular the brake pressure, by means of which a braking torque of the brake system 11 can be characterized.

[0037] With reference to the drive output torque an actual brake pedal characteristic 16 can be determined, and for that purpose the brake characteristic magnitude is determined for at least one brake pedal position and a value that corresponds to that brake pedal position. This can be done with the help of a discrete and/or a continuous method.

[0038] In the discrete method, the actual brake pedal characteristic 16 is determined by determining several Bezier control points 19, 20, 21, 22 and plotting those points in the characteristic diagram 13.

[0039] At the beginning of this method the working machine according to FIG. 1 is preferably at rest. By the control unit 12, which is configured for calibration, or by a driver (not shown), the calibration process is started in that the brake system 11, specifically its brake pedal, is actuated to a first Bezier control point 19. To reach the first Bezier control point 19 the brake system 11 is actuated in such manner that the brake pedal is fully depressed as far as the maximum pedal displacement. At least during the next step the brake pedal remains constantly held at the maximum pedal displacement.

[0040] With the working machine 2 at rest a gear is now engaged in the transmission 9. Preferably, the gear engaged is that gear in which the maximum sustainable traction force is produced by the brake system 11. For this, the drive unit 3 is accelerated in the form of a motor rotational speed increase until rolling of the working machine 2 is detected. For that purpose a drive output rotational speed indicator (not shown) or a sensor is preferably installed, in order to be able to detect rotation of at least one wheel 6. The drive input of the drive unit 3 can for example be produced manually by way of an accelerator pedal or brought about automatically by the control unit 12.

[0041] When rolling of at least one wheel 6 is detected, the transmission 9 is automatically shifted to idling mode by the electronic control unit 12. At the point when the rolling of the wheel 6 is detected, the associated drive output torque is stored in the control unit 12. The drive output torque is determined by way of the turbine wheel torque stored in the converter characteristic, which in turn in determined by the pump and turbine rotational speed of the impeller 8 and the turbine wheel 10 of the torque converter. Then, from the established drive output torque a braking torque is determined, with reference to which a braking torque of the brake system 11 (see FIG. 1) can be determined. The value existing at the moment of rolling, that corresponds to the braking characteristic magnitude, specifically the brake pressure, is determined and plotted as a braking torque into the characteristic diagram 13 along the y-axis.

[0042] Thus, in the characteristic diagram 13 the braking force or braking torque is determined by way of the pedal displacement at a first Bezier control point 19. Preferably the steps, from setting a particular pedal displacement of the brake system 11 while at rest, engaging a gear of the transmission 9 and operating the drive unit 3 at an elevated motor rotational speed until rolling movement of the wheel 6 is first detected, are carried out for different pedal displacements. As shown in FIG. 2, this is carried out a number of times for different pedal displacements of 75%, 60% and 23% to obtain additionally at least a second, third and fourth Bezier control points 20, 21 and 22. The number of Bezier control points 19, 20, 21, 22 can be varied arbitrarily in order to determine as exact an actual brake pedal characteristic 16 as possible.

[0043] After determining the actual brake pedal characteristic 16, the actual clutch characteristic 17 is calibrated by forming a nominal clutch characteristic 15 on the basis of the actual brake pedal characteristic 16. Since the nominal relationship is defined by the common point of intersection 18 of the two characteristics 14 and 17, the actual brake pedal characteristic 16 is calibrated on the basis of the nominal brake pedal characteristic 14, in particular in the characteristic diagram 13 displaced in parallel so that the actual clutch characteristic 17, together with the actual brake pedal characteristic 16, form the original point of intersection 18 which essentially represents the nominal relationship.

[0044] Displacement of the actual brake pedal characteristic 16 preferably takes place along an offset 25 between the initiation point 24 and a mirror point 26 relative thereto. In the characteristic diagram 13 or FIG. 2, for the sake of simplicity the offset 25 is displaced along the brake pedal characteristics 14, 16. The initiation point 24 of the brake system 11 depends decisively on the wear of the brake system. The greater the wear, as a rule the later the brake system 11 engages or the higher must be the braking torque. Thus, if the actual brake pedal characteristic 16 deviates from the nominal brake pedal characteristic 14, the initiation point 24 also is displaced to the mirror point 26. In the characteristic diagram 13 the mirror point 26 and the initiation point 24 are connected with one another by the offset 25. Preferably, the offset 25 remains the same size throughout the length of the nominal and actual brake pedal characteristics 14, 16. To calibrate the actual brake pedal characteristic 16, it is displaced by the offset 25 relative to the nominal brake pedal characteristic 14, so that the drive input clutch 5 is released at the ideally chosen pedal position corresponding to the intersection point 18 of the actual relationship.

[0045] Alternatively, it is conceivable to displace the actual clutch characteristic 17 along the offset 25 relative to a nominal clutch characteristic 15, so that a new calibration point 23 is defined at which the actual relationship corresponds to the nominal relationship at the intersection point 18.

[0046] The calibration of the characteristic diagram 13 takes place by the continuous method as previously described, but the actual brake pedal characteristic 16 is determined in this case by continuously varying the brake pedal position instead of moving to individual, discrete Bezier control points 19, 20, 21, 22 as before. At the same time as the continuous variation of the pedal displacement, the corresponding values of the braking characteristic magnitudes, in particular the braking pressure, are determined in order to determine the braking torque. The working machine 2 is accelerated by the drive unit 3 up to the maximum speed attainable in the gear of the transmission 9 engaged at the time. Then, the working machine 2 is slowly braked to rest by continuously increasing the actuation of the brake system 11, in particular its brake pedal (see FIG. 1). During this deceleration phase, in which the working machine 2 is progressively braked, the values of the braking magnitudes that correspond to the pedal displacement are determined so that the braking torque as a function of the pedal displacement can be documented in the characteristic diagram 13. This produces an essentially flowing actual brake pedal characteristic 16, which can be corrected in accordance with the previously described calibration method.

[0047] The calibration takes place by correcting either the actual clutch characteristic 17 or the actual brake pedal characteristic 16, in such manner that the actual relationship corresponds to the nominal relationship.

[0048] By means of the discrete or the continuous method, the initiation point 24 of the actual brake pedal characteristic 16 can be determined. This enables the calibration of the characteristic diagram 13 to be carried out, so that the opening of the drive input clutch 5 is permanently matched to the braking force or pedal displacement of the brake system 11 and wear or the brake system 11 is prevented. The readjustment of the drive-train 1 can if necessary take place several times during the service life of the working machine 2, so that it is optimally calibrated for any driving situation. The adjustment process takes place at least partially automatically.

[0049] The present invention is not limited to the example embodiments illustrated and described. Variations within the scope of the claims are also possible, such as a combination of features, even where these have been illustrated and described in different example embodiments.

INDEXES

[0050] 1 Drive-train [0051] 2 Working machine [0052] 3 Drive unit [0053] 4 Torque converter [0054] 5 Drive input clutch [0055] 6 Wheel [0056] 7 Power take-off [0057] 8 Impeller [0058] 9 Transmission [0059] 10 Turbine wheel [0060] 11 Brake system [0061] 12 Control unit [0062] 13 Characteristic diagram [0063] 14 Nominal brake peal characteristic [0064] 15 Nominal clutch characteristic [0065] 16 Actual brake pedal characteristic [0066] 17 Actual clutch characteristic [0067] 18 Point of intersection [0068] 19 First Bezier control point [0069] 20 Second Bezier control point [0070] 21 Third Bezier control point [0071] 22 Fourth Bezier control point [0072] 23 Calibration point [0073] 24 Initiation point [0074] 25 Offset [0075] 26 Mirror point