EP2583006A1

EP2583006A1 - Method for engaging at least one speed-increasing or speed reduction stage in a transfer box

Info

Publication number: EP2583006A1
Application number: EP11718715.3A
Authority: EP
Inventors: Markus Maurer
Original assignee: ZF Friedrichshafen AG
Current assignee: ZF Friedrichshafen AG
Priority date: 2010-06-17
Filing date: 2011-05-04
Publication date: 2013-04-24
Also published as: WO2011157477A1; KR20130118740A; US20130087018A1; US8869642B2; DE102010030242A1

Abstract

Proposed is a method for engaging at least one speed-increasing stage (H) and/or at least one speed reduction stage (L) in a claw-shift transfer box (VG) in a drivetrain of a vehicle having a drive engine and a shift transmission (SG) that can be shifted under load, wherein the transfer box (VG) is shifted into the neutral position (N) and, after the synchronization, is shifted into the speed-increasing stage (H) or into the speed reduction stage (L). According to the invention, during the synchronization, the shift transmission (SG) is braked or accelerated, by the actuation of at least one additional shift element, such that the output rotational speed (n_SG) of the shift transmission (SG) is aligned with the output rotational speed (n_VG) of the transfer box (VG) multiplied by the target transmission ratio in the transfer box (i_VG).

Description

Method for switching at least one over- or Untersetzunqsstufe

at a distributor transmission

The present invention relates to a method for switching at least one transmission stage and / or at least one reduction stage in a jaw-connected transfer case in a drive train of a vehicle according to the closer defined in the preamble of claim 1. Art.

From the vehicle technology it is known that to increase the spread of a gearbox, a jaw-connected, not synchronized transfer case is connected downstream. The transfer case, for example, be carried out in two stages with a gear ratio as street gear and a reduction stage as off-road gear.

For example, from the document WO 2010/006872 A1 a method for controlling a drive train of a vehicle with a drive motor and a main transmission and a transfer case is known with the automated circuit can be performed in the transfer case while driving. For this purpose, the drive train is disconnected from the power shift, the transfer case switched and inserted in the powershift again the appropriate gear. This process is inevitably associated with an interruption of the tractive effort, as for switching the gear ratio or the reduction stage in the transfer case an interruption of the traction is necessarily required.

The present invention is based on the object to propose a method of the type described above, in which the time of traction interruption is reduced to a minimum.

This object is achieved by the features of claim 1, wherein further advantageous embodiments of the dependent claims and the drawings. It is thus proposed a method for switching at least one gear ratio and / or at least one reduction stage in a jaw-connected transfer case in a drive train of a vehicle with a drive motor and a powershift transmission, in particular an automatic transmission, wherein the transfer case in the neutral position or switched to neutral and after synchronization, the gear stage or the reduction stage in the transfer case is switched. According to the invention, the transmission is temporarily braced by driving at least one additional switching element during synchronization, so that the output speed of the gearbox to the output speed of the transfer case multiplied as quickly as possible with the target ratio in the transfer case.

In this way, the inherent in the circuit of the transfer case gear train interruption is reduced by means of the power shift to a minimum, is braked or accelerated by controlled braking or acceleration of the drive train in the power shift transmission, the output of the transmission to synchronous speed of the transfer case in the new gear, depending according to whether there is an upshift or a downshift. Advantageously, the shortening of the interruption of traction in upshifts without engine brake interventions and downshifts without speed specification on the engine is realized with the inventive method.

As part of a particularly advantageous embodiment of the invention, it is provided in the method that for braking or accelerating the gearbox, an additional switching element for synchronizing a higher or lower gear is controlled in the transmission until the desired synchronous speed is reached. The choice of the switching element to be synchronized depends on the gear ratio to be switched or gear ratio.

For example, in an upshift the transfer case can be switched from the reduction stage to neutral and then a switching element of a lower gear of the gearbox be controlled such that the Output speed of the gearbox is reduced by controlled bracing until the output speed of the transmission and the output speed of the transfer case are multiplied multiplied by the target ratio in the transfer case, so that the transfer case can be switched from neutral to the desired gear ratio.

As part of the upshift can be a total of z. B of the fifth gear in the sixth gear, with the originally selected gear is preferably reduced by one or more ratios in the transmission and is switched in the transfer case from the reduction stage or low in the translation stage or high. However, it is possible that z. B. in the gearbox several gear increments during the switching operation in the transfer case are carried out to realize other translations.

In a downshift of the transfer case is switched in the context of the inventive method of the gear ratio high to neutral and then a switching element of a higher gear of the gearbox to accelerate the output speed of the gearbox controlled until the output speed of the gearbox is synchronized with the output speed of the transfer case, so that the transfer case from the neutral position in the reduction stage can be switched low.

As part of the downshift, a gear change in the drive train total z. B. from the sixth gear in the fifth gear, whereby in the manual transmission, the originally selected gear is preferably increased by one or more gear ratios and is switched low in the transfer case from the translation stage or high in the reduction stage. However, it is possible that z. B. in the gearbox several gear increments during the switching operation in the transfer case are carried out to realize other translations. Regardless of the type of switching operation to be performed can be provided in the proposed method that for decoupling the drive motor during synchronization of the drive pressure of the torque converter lockup clutch before the neutral circuit of the transfer case to open the lockup clutch is reduced and that the control pressure of the lockup clutch after switching the transmission stage or the reduction stage in the transfer case is increased again to close the lockup clutch.

In this way, the output of the gearbox alone by the

Bracing the drive train braked or accelerated because the drive motor is decoupled by the opening of the lock-up clutch from the other drive train. Thus, the manual over the torque converter is only hydraulically coupled thrust side to the engine. The switching elements must therefore only slow down the moment of inertia of the gearbox, the secondary side of the torque converter and the output shaft to the shift claw of the transfer case. In this case, the engine mass does not have to be braked, as it is decoupled from the manual transmission through the opened converter lockup clutch.

If the tension of the drive train in the context of the method according to the invention takes place with non-decoupled drive motor, there is the difference that the converter lock-up clutch is not opened or immediately after the transfer case has reached the neutral position, is closed again. In this state, the switching elements of the power shift also slow down the moments of inertia of the drive motor and the inertia of the gearbox. After reaching the synchronous speed, the lock-up clutch is briefly opened and lowered the control pressure of the corresponding switching elements to then switch the transfer case from the neutral position to the desired gear ratio and close the corresponding switching elements in the gearbox accordingly, so that then engine torque can be transmitted. In this embodiment, there is the advantage that a higher control pressure is required for driving the switching elements, whereby the acceleration and braking can be better controlled with the manual transmission.

Hereinafter, the present invention will be further explained with reference to the drawings. Show it:

Figure 1 is a schematic representation of a drive train of a

Vehicle in which the inventive method is applicable;

FIGS. 2a to 2f show a shift upshift from a fifth gear step to a sixth gear step in the context of the method according to the invention, illustrated by different diagrams; and

3a to 3f, a push downshift from a sixth gear in a fifth gear in the context of the inventive method, illustrated with reference to various diagrams.

The drive train of a vehicle illustrated by way of example in FIG. 1 comprises a drive motor, not shown further, which acts on a torque converter DW with a converter lockup clutch WK with an engine speed n_Mot. The torque converter DW is coupled to the input of a power-shiftable automatic transmission SG. The output of the gearbox SG is coupled to the input of a jaw-connected transfer case VG. The transfer case VG can be switched via a shift claw from a neutral position N either to a transmission ratio H (high) or to a reduction ratio L (low) in order to increase or decrease the output speed n_VG of the transfer case VG. The illustration of the drive train is only an example because the method according to the invention can also be used with other drive trains, possibly modified accordingly.

The inventive method is exemplified on the one hand on the basis of a Zughochschaltung ZH 5-6, starting from a fifth gear in a sixth Gear stage of the drive train and on the other hand based on a push downshift SR 6-5, starting from a sixth gear in a fifth gear stage of the drive train described by way of example.

The upshift ZH 5-6 is explained below with reference to the diagrams shown in Figures 2a to 2f.

In Figure 2a, the course of the motor torque applied by the drive motor M_Mot, in Figure 2b, the curve of the engine speed n_Mot, in Figure 2c, the curve of the output speed n_SG, in Figure 2d, the course of the respective shift position N, L, H of the shift claw of the transfer case VG in Figure 2e, the curves of the respective control pressure SE_1, SE_2, SE_3, SE_WK the switching elements and the lockup clutch WK and in Figure 2f the curves of the respective switching states of the gearbox SG, the transfer case VG and the resulting entire drive train over time during the upshift shown.

In particular, from the Ansteuerdruckverläufen according to Figure 2e shows that for switching a gear always two switching elements must be pressurized, wherein in preparation for the activation of a switching element in advance an approximately rectangular course of the control pressure is provided. In the upshift, for example, the first shift element and the second shift element are assigned to the fifth gear of the shift transmission SG and the first shift element and the third shift element to the fourth gear of the shift transmission SG. During the synchronization according to the invention, in addition to the first switching element, the second and third switching element are additionally controlled, which is illustrated by the corresponding courses of the drive pressures SE_1, SE_2 and SE_3, so that the shift transmission SG is briefly jammed.

At the beginning of the upshift, the engine torque M_Mot for opening the lockup clutch WK is reduced. Meanwhile, the shift claw is switched by the reduction stage L in the neutral position N, which in particular particular from Figure 2d (t_Klaue_loesen) can be seen. For this only a time of about 0.1 -0.2 s is needed.

To open the converter lockup clutch WK, the drive pressure SE_WK of the lockup clutch WK is reduced to a minimum, as shown in FIG. 2e. As a result, the drive motor is decoupled from the further drive train, namely the manual transmission SG and in the transfer case VG. In this state, the manual transmission SG is briefly switched to the neutral position N, which can be seen in particular from Figure 2f.

When the torque converter lockup clutch WK is opened, the drive pressure SE_2 of the second shift element, which is assigned to the fifth gear in the manual transmission SG, is simultaneously reduced to a predetermined value. At the same time, the drive pressure SE_3 of an additional third shift element which is associated with the fourth gear of the gearbox is increased to thereby clamp the gearbox SG and reduce the output speed n_SG of the gearbox SG, which can be seen in particular from FIG. 2c (t_development_n_vspann). This requires a time of about 0.2-0.4 s.

In this time, the output speed n_SG of the gearbox SG is constantly compared with the value of the output speed n_VG multiplied by the target ratio i_VG of the transfer case VG. As soon as the synchronous rotational speed has been reached, the drive pressure SE_2 and SE_3 of the second and third shift element is reduced to a minimum and the transfer case VG or the shift claw is switched from the neutral position N to the transfer stage H, which can be seen from FIG. 2d (t_claw_inclamping). Overall, only a time of about 0.1 -0.2 s is needed.

If the switched ratio stage H is detected in the transfer case VG, the engine torque M_Mot can be released again and the AnSteuerdruck SE_3 of the required switching element can be increased depending on the engine torque M_Mot, so that the complete traction is available again. Subsequently, the control pressure SE_WK the lockup clutch WK for Close again increased. With the method according to the invention, the traction interruption for shifting the transfer case VG can thus be reduced to significantly less than 1 s.

As can be seen in particular from FIG. 2f, the manual transmission SG is in fifth gear prior to the shifting of the transfer case VG, while the synchronization is synchronized to decelerate or equalize the output rotational speed n_SG of the fourth and fifth gear in the manual transmission SG and after the shift of the Transfer case, the fifth gear of the gearbox SG is switched. The transfer case VG is located before the circuit in the reduction stage L and after the shift in the gear ratio H, so that a total of six gear stage results in the drive train before switching the transfer case VG a fifth gear and after the circuit of the transfer case VG.

In Figure 3a, the course of the motor torque applied by the drive motor M_Mot, in Figure 3b, the curve of the engine speed n_Mot, in Figure 3c, the curve of the output speed n_SG of the gearbox, in Figure 3d, the course of the respective shift position N, L, H of the shift claw 3e, the curves of the respective control pressure SE_1, SE_2, SE_3, SE_4, SE_WK of the switching elements and the lockup clutch WK and in Figure 3f, the curves of the respective switching states of the gearbox SG, the transfer case VG and the resulting entire drive train on the Time during the push downshift shown.

In particular, from the Ansteuerdruckverläufen according to Figure 3e shows that for switching a gear always two switching elements must be pressurized, wherein in preparation for the activation of a switching element in advance an approximately rectangular course of the control pressure is provided. In the push-down shift, the first shift element and the second shift element are exemplified by the fifth speed of the shift transmission SG and the first shift element and the third shift element the fourth speed of the shift transmission SG and the first shift element and the fourth shift element the sixth gear assigned. During the synchronization according to the invention in addition to the first switching element additionally the second and fourth switching element is driven, which is illustrated by the corresponding courses of the drive pressures SE_1, SE_2 and SE_4, so that there is a brief acceleration of the output of the gearbox SG.

At the beginning of the push-down, the control pressure SE_WK the torque converter lockup clutch, as shown in Figure 3e, is reduced to a minimum to open the lockup clutch WK. At the same time the AnSteuerdruck SE_3 of the third switching element, which is assigned to the fourth gear of the gearbox SG, reduced to a minimum. While the manual transmission SG is briefly switched to the neutral position N, the shift claw of the transfer case VG is shifted from the translation stage H in the neutral position N, which in particular from Figure 3d (t_Klaue_loesen) can be seen.

After the transfer case VG is in the neutral position N, the drive pressure SE_4 of the fourth shift element associated with the sixth speed of the transmission is increased to also increase the output speed n_SG of the transmission. Meanwhile, the switching element associated with the fifth speed of the gearbox is prepared. Once the synchronous speed of the shift claw of the transfer case has been reached, the shift claw of the transfer case VG can be switched or retracted from the neutral position N in the reduction stage L, which can be seen in Figure 3d (t_Klaue_einfahren). As soon as the transfer case VG is switched to the reduction stage L, the drive pressure SE_2 of the second shift element, which is assigned to the fifth gear of the manual transmission SG, is continuously increased, so that the drive train is closed. Subsequently, the control pressure SE_WK of the lockup clutch WK is increased to close the same.

As can be seen in particular from FIG. 3f, the manual transmission SG is in fourth gear before the shifting of the transfer case VG. During synchronization, the sixth gear is used for acceleration or equal to the output speed n_SG ansynchronisiert. After the shift of the transfer case VG, the fifth speed of the shift transmission SG is switched. The transfer case VG is before the circuit in the translation stage H and after the circuit in the reduction stage L, so that a total of six times and in the drive train before switching the transfer case VG a sixth gear and after the shift of the transfer case VG results in a fifth gear.

REFERENCE CHARACTERS

WK converter lockup clutch

DW torque converter

SG manual transmission

VG transfer case

n_Mot engine speed

M_Mot engine torque

n_SG Output speed of the gearbox

n_VG Output speed of the transfer case i_VG Target ratio in the transfer case

p_SE control pressure

SE_WK Control pressure of converter lockup clutch

SE_1 driving pressure of the first switching element

SE_2 control pressure of the second switching element

SE_3 driving pressure of the third switching element

SE_4 driving pressure of the fourth switching element

L reduction level low

H translation level high

N neutral position

Pos_Klaue switching claw position

Claims

claims

1 . Method for switching at least one transmission stage (H) and / or at least one reduction stage (L) in a jaw-connected transfer case (VG) in a drive train of a vehicle with a drive motor and a power-shiftable transmission (SG), wherein the transfer case (VG) in the neutral position (N) is switched and after the synchronization, the ratio stage (H) or the reduction stage (L) in the transfer case (VG) is switched, characterized in that during the synchronization, the transmission (SG) is braced or accelerated by driving at least one additional switching element such that the output speed (n_SG) of the gearbox (SG) is adjusted to the output speed (n_VG) of the transfer case (VG) multiplied by the target gear ratio in the transfer case (i_VG).

2. The method according to claim 1, characterized in that for bracing or for accelerating the gearbox (SG), the additional switching element for Ansynchronisieren a higher or lower gear in the transmission (SG) for accelerating or decelerating the output speed (n_SG) of the gearbox (SG) is driven until the desired synchronous speed is reached.

3. The method according to any one of the preceding claims, characterized in that the transfer case (VG) of the reduction stage (L) is switched to the neutral position (N) at a traction upshift, and that thereafter a switching element of a lower gear of the gearbox (SG) such is controlled, that the output speed (n_SG) of the gearbox (SG) is reduced until the output speed (n_SG) of the gearbox (SG) and the output speed (n_VG) of the transfer case (VG) are synchronized, so that the transfer case (VG) off the neutral position (N) in the translation stage (H) is switched.

4. The method according to claim 3, characterized in that in a power upshift in the drive train from a fifth gear in the sixth gear after the neutral shift of the transfer case (VG), the drive pressure (SE_2) of the fifth speed associated shift element is lowered to a predetermined value while increasing the drive pressure (SE_3) of the fourth speed shift element.

5. The method according to claim 4, characterized in that during the lowering of the control pressure (SE_2) of the switching element of the fifth gear and increasing the control pressure (SE_3) of the switching element of the fourth gear, the output speed (n_SG) of the gearbox (SG) with the output speed (n_VG) of the transfer case (VG) multiplied by the target ratio in the transfer case (i_VG) is continuously compared until equal speed exists and the control pressure (SE_2, SE_3) of both switching elements is reduced and the gear ratio (H) of the transfer case (VG) is switched, after which the driving pressure (SE_3) of the fourth-speed shifting element is increased.

6. The method according to any one of the preceding claims, characterized in that the transfer case (VG) of the translation stage (H) is switched to the neutral position (N) in a push-down, and that thereafter a switching element of a higher gear of the gearbox (SG) such is controlled so that the output speed (n_SG) of the gearbox (SG) is increased until the output speed (n_SG) of the gearbox (SG) with the output speed (n_VG) of the transfer case (VG) is multiplied by the target ratio in the transfer case (i_VG) synchronized , so that the transfer case from the neutral position (N) in the reduction stage (L) is switched.

7. The method according to claim 6, characterized in that is reduced at a push-down in the drive train from the sixth gear to the fifth gear during the neutral circuit of the transfer case (VG), the driving pressure (SE_3) of the switching element of the fourth gear to a minimum and after the Neutral circuit of the transfer case (VG) of the driving pressure (SE_4) of the sixth-speed switching element is increased.

8. The method according to claim 6 or 7, characterized in that during the lowering of the control pressure (SE_3) of the switching element of the fourth gear and increasing the driving pressure (SE_4) of the switching element of the sixth gear, the output speed (n_SG) of the gearbox (SG) with the output speed (n_VG) of the transfer case (VG) multiplied by the target ratio in the transfer case (i_VG) is continuously compared until equal speed and the drive pressure (SE_4) of the sixth-speed shift element is reduced to a minimum and the transfer case (VG) the neutral position (N) in the reduction stage (L) is switched, after which the driving pressure (SE_2) of the switching element of the fifth gear is increased.

9. The method according to any one of the preceding claims, characterized in that for decoupling the drive motor during synchronization of the control pressure (SE_WK) of the torque converter lockup clutch (WK) of the torque converter (DW) before the neutral circuit of the transfer case (VG) to open the lockup clutch (WK) is reduced and that the AnSteuerdruck (SE_WK) of the lockup clutch (WK) after switching the gear ratio (H) or the reduction stage (L) is increased again to close the lockup clutch (WK).