AT508077B1 - METHOD FOR OPERATING A MOTOR VEHICLE HAVING A LASER SWITCH - Google Patents

Description

Austrian Patent Office AT508 077B1 2012-01-15

Description: The invention relates to a method for operating a motor vehicle having a powershift reversing transmission, wherein the powershift reversing transmission has a first and a second directional coupling, wherein the two directional clutches formed by clutches in at least one switching operation by a preferably hydraulic actuator via a Controllers are controlled.

The AT 506.868 A1 describes a gear assembly for commercial vehicles with a multi-stage, switchable under load power shift gearbox and a multi-stage power shift reversing gearbox with two directional couplings. A similar power shift reversing transmission (Po-wer-Shuttle transmission) is known from EP 1 013 967 A2.

In numerous vehicles in the field of agricultural and construction machinery are power shift reversing gearboxes. These generally have two independent directional couplings which allow forward and reverse travel. With these, it is also possible to activate a direction of travel before the directional coupling of the opposite direction has been completely resolved. As a result, the change of the direction of travel can be completed without there being an interruption of the power flow in between.

Known power shift reversing gear use electro-hydraulic control systems with proportional valves for the control of these two directional couplings. During the change of direction, the drive torque is transferred from one directional coupling to the other by controlling both directional couplings or control of a directional coupling and control of the other directional clutch. The disadvantage is that the switching behavior is dependent on external conditions. In the case of conventional control systems, for example, which are based only on speed, problems with a change in direction under thrust, for example when driving downhill, can occur because the vehicle starts to roll freely on the opening clutch due to the increasingly reducing clutch torque.

The object of the invention is to propose a method with which a constant switching behavior of the vehicle under different external conditions can be achieved.

According to the invention, this is achieved in that during the switching at any time in each case a directional clutch in an open loop and the other directional clutch is driven in a closed loop, the decision of which of the two directional clutches in the closed and which controlled in the open loop is taken in response to at least one operating parameter.

It can be provided that the decision of which of the two directional clutches in the closed and which is controlled in the open loop, is made depending on whether the transmitted clutch torque exceeds a defined Momen tengrenzwert and / or that the decision which the two directional clutches in the closed and which is controlled in the open loop, is made in response to whether a defined limit for the vehicle speed and / or the vehicle acceleration is exceeded.

The clutch torque may be determined based on the engine torque based on the engine speed and the drive motor drive signal based on a torque measurement point between the prime mover and the transmission and / or based on the breakaway torque of an opening directional clutch.

The torque limit can be calculated as a function of vehicle-specific variables, preferably on the basis of the engine torque at the beginning of the switching operation. In this case, a uniform torque curve and thus a constant deceleration or acceleration is sought during the reversing process. [0010] It is preferably provided that a change takes place dynamically between the open and the closed control loop during the switching process. As a result, a flexible adaptation to changing external conditions can be realized.

The control of the directional clutch in the closed loop is advantageously carried out in dependence on at least one target speed, which is compared with the actual vehicle speed. Alternatively or additionally, it can be provided that the directional clutch controlled in the closed loop is regulated as a function of a desired acceleration, which is compared with the actual vehicle acceleration.

In the context of the invention, it is provided that in the case when during a reversal process, the actual vehicle speed and / or the actual acceleration is smaller than the corresponding setpoint, preferably a first setpoint, in a further step, the current clutch torque compared with the torque limit and that the closing force at the opening directional clutch is reduced when the current clutch torque is greater than the torque limit, and that the closing force at the closing clutch is increased when the actual clutch torque is less than the torque limit. Furthermore, it can be provided that in the case when during a reversal process, the actual vehicle speed and / or the actual acceleration is greater than the corresponding setpoint, preferably a second setpoint, the current clutch torque is compared with the torque limit, wherein the closing force at the closing directional clutch is reduced when the current clutch torque is greater than the torque limit, and wherein the closing force is increased at the opening directional clutch, when the current clutch torque is smaller than the torque limit.

In order to avoid too frequent switching between the open and closed loop, it is provided that the control of directional couplings taking into account a hysteresis function of at least one controlled variable, wherein lower first setpoint values of the controlled variable for falling, and upper second setpoints for increasing current values of the controlled variable apply, wherein preferably the controlled variable is the vehicle speed, the vehicle acceleration and / or the clutch torque.

The invention will be explained in more detail below with reference to the figures.

1 shows a gear unit with a powershift reversing transmission for carrying out the method according to the invention; FIG. 2 FIG. 3 FIG. 4 FIG Representation of the powershift reversing gear, a diagram for explaining the method according to the invention, a diagram for explaining a reversal process, a speed-time diagram and Fig. 6 is a torque-time diagram.

Fig. 1 shows a transmission assembly 1 with a multi-stage, switchable under load power shift transmission 2 and a multi-stage power shift reversing gearbox 3. The power shift transmission 2 consists of a drive shaft 4, an intermediate intermediate shaft 5 and a plurality of pairs 6, 7, 8 of continuously meshing gears, one gear of each pair 6, 7, 8 being drivingly connected to a shaft 4, 5 and the other gear of this pair being connected to one of a fluid pressure (hydraulic pressure) operable clutch A, B, C, D to the other shaft 5, 4 can be coupled. The four-stage power-shift transmission 2 is arranged on the transmission input of the transmission assembly 1 and is used for both directions of travel. It consists of three spur gear stages 6, 7, 8 and four clutches A, B, C, D. By opening and closing of corresponding combinations of the clutches A, B, C, D are with the three spur gears 6, 7, 8 four powershift gears realized. The powershift reverse gear 3 is provided with two designed as hydraulic clutches directional clutches F, R, the forward (F) and backward (R) optionally by a flow medium pressure (hydraulic pressure ) are activated. The powershift reverse gear 3 is designed as a multi-stage group transmission, for different speed range for forward and reverse.

The clutches A, B, C, D, F, R are formed by hydraulically actuated multi-plate clutches. The directional clutches F, R of the powershift reversing transmission 3 are arranged concentrically to the clutch shaft 9 of the powershift reversing transmission 3. The coupling shaft 9 is connected to the intermediate shaft 5 via a connecting gear stage 10, wherein a first gear 11 of the connecting gear stage 10 with the intermediate shaft 5 and a second gear 12 of the connecting gear stage 10 with the coupling shaft 9 via the directional couplings F, R is drehverbindbar. The power-shift transmission 2, which is physically separate from the power-shift transmission 2, has two drive-compatible multi-plate clutches and allows a reversing operation without power interruption. The return gear of the powershift reversing transmission 3 uses the same output gear 11 as the forward gear, the power flow via a countershaft 15 to the return wheel 16, which is connected to the clutch bell 17 of the return direction clutch R.

Fig. 2 shows a schematic representation of the powershift reversing transmission 3, for which the method described is applicable. In this case, reference numeral 18 designates a drive machine and 19 an output shaft. Via a torque measuring device 20, the clutch torque MK can be determined based on the engine torque ME, act of the engine 18. A speed sensor 21 is used to determine the vehicle speed. The measured data are supplied to an electronic control unit 22, which actuates the power shift reversing gear 3 via a first proportional valve 23 for the first directional clutch F and a second proportional valve 24 for the second directional clutch R.

Similar to known methods, the method according to the invention also provides a pilot control in order to carry out the change of the directional couplings. In addition, there are four possible ways of controlling both directional clutches F, R. These are: - increasing the closing force on the closing directional coupling by increasing the hydraulic pressure; - Reduction of the closing force at the closing directional coupling by Verminde tion of the hydraulic pressure; Increasing the closing force at the opening directional clutch by increasing the hydraulic pressure; and [0029] Reducing the closing force at the opening directional clutch by decreasing the hydraulic actuating pressure.

It is essential that the controller 25 Although both directional clutches F, R controls, but at any time of the hydraulic actuating pressure only at one of the two directional clutches F, R is changed by the controller 25. To determine the controlled variable, the following input variables are used, for example: a) Measured vehicle speed vakt: This value is determined by the speed sensor 21.

B) calculated desired speed course vs (t): At the beginning of the process to Rich change direction a target speed curve is determined. Input variables for this can be, for example, the current speed vakt and the position of the accelerator pedal. An adaptation of this desired speed curve vs (t) during the reversal process is possible.

C) Current engine torque ME, act of the prime mover 18: Conventional internal combustion engine can transmit this value to the electronic control unit 22.

D) torque limit MG: This limit can be determined as a fixed value or by a loading calculation from other input variables. During the reversal process, the current measured vehicle speed vakt is constantly compared with the desired speed curve vs (t). If the actual acceleration in the new direction of travel is too low, ie if the measured vehicle speed changes more slowly than it corresponds to the desired speed profile vs (t), then the control system can intervene in two ways: Increasing the pressure at closing clutch [0035] 0036] Reduction of the pressure at the opening clutch In a further calculation, the current engine torque ME, akt is compared with the torque limit value Mg. If the current moment ME, act of the prime mover 18 is greater than the torque limit MG, the controller 25 responds by reducing the hydraulic actuation pressure at the opening directional clutch. If the current engine torque ME, akt smaller than the torque limit Mc, so there is an increase in the hydraulic actuation pressure at the closing directional clutch.

In the alternative case, that the measured vehicle speed vak, changes faster than it corresponds to the target speed course vs (t), the current engine torque ME, akt is again compared with the torque limit MG. Here, the following procedure is implemented: If the current engine torque ME, akt on the prime mover 18 is greater than the torque limit Mg, the controller 25 responds by reducing the hydraulic actuation pressure at the closing directional clutch. If, however, the current engine torque ME> act is smaller than the torque limit value MG, an increase in the hydraulic actuating pressure takes place at the opening directional clutch.

A switching operation is shown schematically in Fig. 3. 30 denotes the beginning of the switching process. It is checked whether the current clutch torque MK determined, for example, from the current engine torque ME, akt is above a torque limit value MG, and whether the current acceleration aak is above the target acceleration as. If both are the case, then in step 31, pressure control is performed on the opening directional clutch by pressure reduction and control on the closing directional clutch. If the clutch torque M << is greater than the torque limit MG and the vehicle acceleration aak is less than the target acceleration as, pressure control is performed on the closing direction clutch by pressure reduction and control is performed on the opening direction clutch. This step is indicated by reference numeral 32. If it is determined that the clutch torque MK is smaller than the torque limit value Mg and the actual vehicle acceleration aakt is greater than the setpoint acceleration as, then in step 33 pressure regulation is performed on the closing directional clutch by pressure increase and control on the opening direction clutch. Finally, if it is determined that the clutch torque MK is smaller than the torque limit Mg and the actual vehicle acceleration aakt is less than the target acceleration as, pressure control at the opening direction clutch by pressure increase and control at the closing direction clutch are performed at a step 34. These interrogations are repeated until the differential speed nK at the closing clutch is> 0. If no speed difference is detected, the switching process is terminated in step 35.

In Figs. 4, 5 and 6, a reversal process from forward to backward is exemplified. On the one hand, the current vehicle speed vakt and on the other hand, the current clutch torque MK, which is determined on the basis of the current engine torque ME / akt the prime mover, measured, and on the other hand determines the time course of the target speed vs (t). If the measured vehicle speed is less than the 4/10 Austrian Patent Office AT508 077 B1 2012-01-15

Target speed vs (t), the measured speed thus changes slower than it corresponds to the target speed curve vs (t), the control system can intervene in two ways: Increasing the closing force and thus the transmitted torque the closing directional clutch F or reduction of the closing pressure and thus of the transmitted torque at the

opening directional clutch R

The decision on one of these two measures is made by comparing the measured clutch torque MK with the torque limit MG, which is calculated at the beginning of the switching operation on the basis of the engine torque ME, 0. If the measured clutch torque MK is smaller than the torque limit value MG, an increase in the closing force of the closing second directional clutch R is performed in step 41. If the measured current vehicle speed vakt is smaller than the setpoint speed vs (t), but the clutch torque MK is greater than the torque limit value MG, a reduction of the closing force is performed in the opening first directional clutch R in a step 42.

If, on the other hand, it is determined within the speed-sensitive control 40 that the measured current vehicle speed vakt is greater than the setpoint speed vs (t), the measured speed therefore changes faster than corresponds to the desired speed course vs (t), Thus, the control system can intervene in two ways: • Reduction of the closing force and thus the torque transmitted to the closing directional coupling F F or • Increasing the closing pressure and thus the transmitted torque at the

opening directional clutch R

Again, the decision can be made on one of these two measures by comparing the measured clutch torque MK with the torque limit MG, which is calculated at the beginning of the switching operation on the basis of the engine torque MEO. If the measured clutch torque MK is greater than the torque limit value MG, a reduction of the closing force at the closing second directional clutch R is performed in step 43. In step 44, an increase in the closing force at the opening first directional clutch F is caused as soon as the measured current vehicle speed vak, greater than the target speed vs (t) and the measured clutch torque MK is less than the torque limit MG.

In Fig. 5 the speed vakt of the vehicle in the new direction, and the target speed vs over the time t is plotted. As can be seen, a hysteresis function can be used for the target speed vs, wherein increasing current vehicle speeds vak, vkt with a target upper speed vSo and declining current vehicle speeds vakt are compared with a lower target speed vSu. Analogously to the vehicle speed vakt, corresponding lower and upper desired accelerations aSu, aso can also be used for the current vehicle acceleration aakt.

Conventional control systems based only on speed lead to problems with a change of direction under thrust, e.g. when driving downhill. Here it can happen that the vehicle starts to roll freely downhill, because the pressure at the opening direction clutch due to the regulation continues to reduce. In contrast, in the described method at lower engine load, the closing direction clutch is pressurized with more pressure and thus ensures the adhesion of the vehicle.

Furthermore, in a turning maneuver under load, a vehicle often decelerates very abruptly, as the actuation pressure at the controlled interpretive directional coupling is reduced too quickly. With the method described under these conditions, the pressure of the opening clutch is increased again, whereby the vehicle slows down more slowly.

Too frequent switching between the open and closed loop 5/10

Claims (14)

Austrian Patent Office AT508 077B1 2012-01-15 control of the directional couplings F, R, including a hysteresis function also for the torque limit, as demonstrated in the torque diagram shown in Fig. 6 by means of a switching operation, in which the current clutch torque MK is plotted over the time t. In the example, the vehicle is switched over from forward to reverse by opening the first directional clutch F and closing the second directional clutch R. During the time phase tF, the first directional clutch F and during the time tR, the second directional clutch R is controlled in the closed loop. The other directional clutch R, F is controlled in the open loop. In this case, different torque limit values MGu or MGo are used for increasing and decreasing clutch torques M ". The first directional clutch F is controlled in a closed loop until the increasing clutch torque MK exceeds an upper limit MGo. From this time, the second directional clutch R is controlled in a closed loop until the clutch torque MK falls below the lower torque limit MGu, while the first directional clutch F is controlled in the open loop. If the clutch torque MK falls below the lower limit value MGu, then again the first directional clutch F in the closed loop and the second directional clutch R in the open loop are controlled. 1. A method for operating a motor vehicle having a powershift reversing transmission (3), wherein the power shift reversing transmission (3) has a first and a second directional clutch (F; R), wherein the two directional clutches (F; R) formed by clutches be controlled by at least one switching operation by a preferably hydraulic actuator via a regulator (25), characterized in that during the switching at each time each a directional clutch (F; R) in an open loop and the other directional clutch (R; F) in a closed-loop control is triggered, the decision as to which of the two directional clutches (F; R) is controlled in the closed loop and which in the open loop is made as a function of at least one operating parameter. 2. Method according to claim 1, characterized in that the decision as to which of the two directional clutches (F; R) is controlled in the closed loop and which in the open loop is made as a function of whether the transmitted clutch torque (MK) has a defined torque limit value (F). MG). 3. The method according to claim 1 or 2, characterized in that the decision which of the two directional clutches (F; R) is controlled in the closed and which in the open loop, is made depending on whether a defined setpoint (vs, as) for the vehicle speed (v) and / or the vehicle acceleration (a) is exceeded. 4. The method according to claim 2 or 3, characterized in that the clutch torque (MK) is determined on the basis of the current engine torque (ME, akt) of the drive machine. 5. The method according to claim 2 or 3, characterized in that the clutch torque (MK) is determined on the basis of the engine speed of the drive machine and a signal for controlling the drive machine. 6. The method according to claim 2 or 3, characterized in that the clutch torque (MK) by a torque measuring device (20) between the drive machine and the power shift reversing gear (3) is determined. 6/10 Austrian Patent Office AT508 077 B1 2012-01-15 7. The method according to claim 2 or 3, characterized in that the clutch torque (MK) on the basis of a demolition torque of an opening directional clutch (F; R) is determined. 8. The method according to any one of claims 2 to 7, characterized in that the Mo-mentengrenzwert (MG) as a function of vehicle-specific variables, preferably based on the engine torque (ME, 0) at the beginning of the switching operation is calculated. 9. The method according to any one of claims 1 to 8, characterized in that there is a dynamic change between the open and closed loop during the switching process. 10. The method according to any one of claims 1 to 9, characterized in that the controlled in the closed loop directional clutch (F; R) is controlled in dependence on a target speed (vs), which is compared with the actual vehicle speed (vakt). 11. The method according to any one of claims 1 to 9, characterized in that the controlled in the closed loop directional clutch (F; R) is controlled in dependence on a target acceleration (as), which is compared with the actual vehicle acceleration (aakt). 12. The method according to any one of claims 1 to 11, characterized in that in the case when, during a reversal process, the actual vehicle speed (vakt) and / or the actual acceleration (aakt) is smaller than the corresponding desired value (vs, as), preferably a first setpoint value (vsu, asu), in a further step the actual clutch torque (MK) is compared with the torque limit value (MG), and that the closing force at the opening directional clutch is reduced if the actual clutch torque (MK) is greater than that Torque limit (MG), and that the closing force on the closing clutch is increased when the current clutch torque (MK) is smaller than the torque limit (MG). 13. The method according to any one of claims 1 to 11, characterized in that in the case when during a reversal process, the actual vehicle speed (vakt) and / or the actual acceleration (aakt) is greater than the corresponding desired value (vs, as), preferably a second setpoint value (vso, aso), the current clutch torque (MK) is compared with the torque limit value (MG), wherein the closing force at the closing directional clutch is reduced if the actual clutch torque (M ") is greater than the torque limit value (MG) , and wherein the closing force at the opening directional clutch is increased when the actual clutch torque (MK) is smaller than the torque limit value (MG). 14. The method according to any one of claims 1 to 13, characterized in that the control of the directional couplings (F; R) takes place involving a hysteresis function of at least one controlled variable, wherein lower first setpoints (vsu,, aSu, MGu) of the controlled variable for falling, and upper second setpoints (vso, aso MGo) apply to increasing current values of the controlled variable, wherein preferably the controlled variable is the vehicle speed (v), the vehicle acceleration (a) and / or the clutch torque (MK). 3 sheets of drawings 7/10