DE102017203545A1 - Method for operating a vehicle with a continuously variable transmission - Google Patents

Abstract

The invention relates to a method for operating a vehicle (1) with a continuously variable transmission (3), the transmission ratio of which can be varied continuously. The transmissibility of two friction-locking directional couplings (5, 6) is infinitely variable. If there is a request for a change of direction, first the ratio of the continuously variable transmission (3) is raised. When falling below a defined speed of the output (4) the currently engaged directional control clutch (5 or 6) is switched off and switched on the currently switched-off direction clutch (6 or 5). As a function of a requested on the driver side target speed of the output (4) and a corresponding target rotational speed of the drive machine (2) to be displayed at the end of the direction of change target ratio of the continuously variable transmission (3) is determined. When determining a desired ratio of the continuously variable transmission (3), which is in another transmission range of the continuously variable transmission (3) than during the operation of the directional control clutches (5, 6) in the continuously variable transmission (3) set actual ratio, in the continuously variable transmission (3 ) during the actuation of the direction-of-travel clutch (5, 6) changed in the transmission range in which the determined target ratio is.

Description

The invention relates to a method for operating a vehicle with a continuously variable transmission according to the closer defined in the preamble of claim 1. Art.

During a reversing operation requested by the driver, for example, a tractor designed as a tractor whose drive train is formed with a continuously variable transmission or a so-called CVT transmission (Continuously Variable Transmission) with several driving ranges, within which the ratio of the continuously variable transmission is continuously variable via a variator is first the translation of the continuously variable transmission adjusted such that the vehicle speed or a speed of an output of the vehicle decreases. From a defined speed of the output, the gear ratio is kept constant or frozen and realized the requested direction of travel change over a coordinated operation of two so-called directional control clutches. About the two direction of travel couplings whose transmission capacity is continuously variable, the vehicle is drivable via a defined drive rotational movement of a drive device in a direction of travel or in a direction opposite thereto.

It is during the operation of the directional control clutches or during the well-known as power reversing process, the currently switched-direction clutch disconnected and switched off the directional control clutch. As a result, the vehicle changes according to the requirements and with high dynamics the direction of travel, the vehicle is delayed by the operation of the directional control clutches first with a larger gradient in the direction of vehicle standstill as is the case by adjusting the ratio of the continuously variable transmission and then in the direction of travel the vehicle standstill opposite direction accelerated. If after the change of direction further acceleration in the direction of speeds of the defined speed of the output or above the so-called power reversal threshold is desired, this is realized by an adjoining the power reversing adjustment of the ratio of the continuously variable transmission.

From the DE 198 30 953 A1 is a corresponding procedure for carrying out a reversing operation of a vehicle requested by the driver known.

If the operating points to which in the continuously variable transmission in each case a change between the transmission ranges are unfavorable with respect to the power reversing threshold, there is the possibility during unfavorable operating state curves in the previously known approaches that immediately after completion of the power reversing a driving range change is performed, for its implementation a corresponding drive range clutch of the continuously variable transmission is to be filled before the vehicle can be further accelerated to the required extent. However, this delays the vehicle acceleration and causes discontinuities in the course of the output torque, which affect driving comfort to an undesirable extent.

In addition, due to the system behavior described in detail above, a high reversing dynamics is achieved when the power reversal threshold is set as high as possible, since the actuation of the direction-of-travel clutches then starts earlier compared to lower power reversal thresholds.

The present invention has for its object to provide a method for operating a vehicle with a continuously variable transmission and with at least two travel direction clutches available, by means of which a requested direction of change with the highest possible reversing dynamics at the same time good ride comfort can be implemented.

In the inventive method for operating a vehicle, such as a work machine, in particular a tractor, with a continuously variable transmission, the ratio is infinitely variable within different transmission ranges by adjusting a variator, and with at least two frictional direction-control couplings whose transmission capacity is continuously variable and by means of which Vehicle can be driven via a defined drive rotational movement of a drive device in a direction of travel or in an opposite direction, is in the presence of a request for a change of direction starting from a current direction in the opposite direction of travel to implement the requested direction change initially raised the translation of the continuously variable transmission and falls below a defined speed of the output or a corresponding vehicle speed the currently switched direction clutch off and switched on the currently switched-off direction clutch.

According to the invention during the execution of the change of direction in response to a driver-requested target speed of the output and a corresponding desired speed of the prime mover in a continuously variable transmission after completion of the Direction change to be displayed desired ratio of the continuously variable transmission determines. If a target ratio of the continuously variable transmission is determined, which is in a different range of the continuously variable transmission than the currently set during operation of the directional control clutches in the continuously variable transmission actual ratio is changed in the continuously variable transmission during operation of the directional control clutches in the compilation area in which the determined Target translation is.

It is possible to reduce the ratio of the continuously variable transmission defined by the change of the transmission range defined or increase the reciprocal ratio of the continuously variable transmission early in a defined extent.

By means of the procedure according to the invention, the acceleration process following the direction of travel change, which is characterized by a vehicle standstill, is performed faster and more homogeneously, as a result of which a requested change of direction can be implemented in a simple manner both with a desired high dynamics and with high ride comfort.

In an easily feasible variant of the method according to the invention, the defined rotational speed of the output or the power reversing threshold, from which the directional control clutches are operated to carry out the direction change, depending on the speed of the output at the time when the request for the direction of travel changes, to achieve a high ride comfort at the same time high reversing dynamics varies such that the speed of the output during the implementation of the requested direction change initially reduced by increasing the ratio of the continuously variable transmission and subsequently the direction of travel reversal of the vehicle is implemented by pressing the direction of travel clutches.

If the defined rotational speed of the output, from which the direction-control clutches are actuated to carry out the change of direction, is varied depending on a given dynamic with which the requested direction change is to be carried out, a requested direction change can be implemented with a desired high dynamic and simultaneously high driving comfort.

If the defined speed of the output is set higher, the greater the requested dynamics, the requested direction change is carried out starting from the current driving state of the vehicle with the respective desired dynamics.

The defined speed of the output, from which the directional control clutches are operated to carry out the direction change, is varied in a further advantageous variant of the method according to the invention in dependence on a load applied to the output, wherein the defined speed is increasingly reduced with increasing load. This ensures that the vehicle is defined at the output lying at high load and reproducibly delayed by an adjustment of the ratio of the continuously variable transmission to the beginning of the actuation of the directional control couplings on the one hand with high dynamics and on the other hand with a high level of comfort.

In a feasible with little effort variant of the method according to the invention, the load applied to the output is determined by measurement.

If the load applied to the output is determined as a function of a high pressure measured in the area of the variator designed as a hydraulic variator, the method according to the invention can be carried out inexpensively in known vehicles without additional expenditure on equipment.

In a particularly simple and with high spontaneity feasible variant of the method according to the invention, the load applied to the output is determined by means of a torque sensor.

The load applied to the output is determined in a variant of the method according to the invention that can also be implemented cost-effectively as a function of a torque provided by the drive machine.

By means of the above-described procedures, in contrast to conventional methods for operating vehicles with continuously variable transmissions with directional control clutches, which are based on fixed power reversing thresholds, a homogeneous and reproducible driving behavior can be represented during all load situations.

Alternatively or in addition to the previously described determination of the load applied to the output, an applied load can also be approximated via an indirect measured variable and used according to the invention. For example, the consideration of topographical information of the terrain used to determine the slope, level, slope should be mentioned. For this purpose, (digitized) topographic maps with elevation points and / or lines are suitable in conjunction with a position determination of the vehicle. Also pitch / tilt sensors can be used to control the approximate applied load. In this case, it may also be advantageous to consider vehicle-specific parameters (for example vehicle mass, direction of travel, yaw, roll and pitch rate, vehicle speed) in order to be able to make an even more precise approximation.

If a vehicle during a reversing process and during downhill driving in the forward or reverse direction due to a triggered by the reversing delay in a coasting operation, the vehicle without affecting the vehicle comfort by the current operating state history of the vehicle in the scope of the invention adapted closing the zuzuschaltenden direction clutch defined delayed and accelerated again after changing the direction of travel with high dynamics.

In contrast, a vehicle remains during an uphill drive in the forward or reverse direction during a reversing process thereby engaging the vehicle downgrade power or during a silage distribution in train operation, so a defined deceleration and re-acceleration of the vehicle by closing the new direction clutch not without affecting the ride comfort is possible. By way of the above-described procedures, the power reversing threshold is set to zero, for example, during such an operating state progression, whereby the vehicle deceleration is converted to represent the highest possible driving comfort solely by adjusting the ratio of the continuously variable transmission.

Furthermore, the procedures explained in greater detail in each case offer the possibility of raising the power reversal thresholds close to the vehicle standstill and, thus, close to the change in direction of travel, in order to avoid undesired delayed reactions which result from actuation of the direction-of-travel clutches only shortly before reaching the vehicle standstill. Therefore, taking into account the desired reversing dynamics and the difference between the rotational speed of the output, to which the request for the direction change is made, and the power reversing limit the earliest possible start of the actuation of the direction-control clutches is sought, the inventive specification of the power reversing limit is based on the knowledge that the comfort during the actuation of the directional control clutches depends on the desired reversing dynamics and the latter difference.

If the currently specified power reversing threshold is, for example, 1 km / h and if a reversing process with high dynamics is to be carried out at 10 km / h, there is a high level of vehicle idleness due to the inertia of the vehicle with the power reversal threshold of 1 km / h without an undesirable delay time during the change of direction Reversing comfort achievable. In contrast, reversing with low dynamics or starting from a vehicle speed close to the power reversal threshold causes a reversing process that is characterized to an undesirable extent by a sudden change of direction.

Both the features specified in the claims and the features specified in the following embodiment of the subject invention are each suitable alone or in any combination with each other to further develop the subject invention.

Further advantages and advantageous developments of the invention will become apparent from the claims and the embodiment described in principle with reference to the drawings.

• 1 eine schematische Darstellung eines Fahrzeuges mit einer Antriebsmaschine, einem Stufenlosgetriebe mit Fahrtrichtungskupplungen und einem Abtrieb;
• 2 einen Verlauf einer Fahrzeuggeschwindigkeit des Fahrzeuges gemäß 1 über der Zeit t; und
• 3 mehrere Verläufe verschiedener Betriebsgrößen des Fahrzeuges gemäß 1 über der Zeit t.

It shows:

• 1 a schematic representation of a vehicle with a prime mover, a continuously variable transmission with directional control clutches and an output;
• 2 a course of a vehicle speed of the vehicle according to 1 over time t; and
• 3 several courses of different operating variables of the vehicle according to 1 over time t.

1 shows a highly schematic representation of a vehicle 1 with a prime mover 2 as well as with a continuously variable transmission 3 and a downforce 4 , In the area of the continuously variable transmission 3 are several driving ranges or translation areas can be inserted, within which via a variator, not shown, the ratio of the continuously variable transmission 3 is infinitely variable. In addition, the vehicle powertrain of the vehicle includes 1 two friction-locking directional couplings 5 . 6 whose transmission capacity is infinitely variable and by means of which the vehicle 1 via a defined drive rotational movement of the drive machine or the drive device 1 is drivable in a forward direction or in a reverse direction opposite thereto.

If there is a request for a change of direction from an actual direction of travel to the respective one opposite direction of travel is to implement the requested direction change initially the translation of the continuously variable transmission 3 raised in more detail later extent described or reduced a reciprocal translation value and falls below a defined speed of the output 4 or a corresponding limit value v_fzgPS of the vehicle speed v_fzg the currently engaged direction-control clutch 5 or 6 switched off and the currently switched-off direction clutch 6 or 5 connected in a conventional manner.

In 2 is a curve of a vehicle speed v_fzg over time t during the execution of a requested direction change shown. At a time T0 corresponds to the vehicle speed v_fzg in the present example about 20 km / h. At a subsequent point in time T1, a driver-side request for a change of direction results from a drive of the vehicle 1 in the forward or reverse direction in the opposite direction of travel. Due to the requirement for the change of direction, an in 3 illustrated course of a reciprocal of a desired translation i_nom from one with the vehicle speed v_fzg corresponding value at time T1 i_sollT1 is lowered along a ramp up to a time T2 to a value i_sollT2 to the actual translation i_ist of the continuously variable transmission 3 from the translation value i_istT1 at time T1, the present case the target value i_sollT1 corresponds to the extent necessary to carry out the requested direction change.

At time T2 reaches the vehicle speed v_fzg the so-called power reversion threshold v_fzgPS , below which the ratio of the continuously variable transmission 3 constant on the value of the actual translation i_istT2 is held until the vehicle speed v_fzg of the vehicle 1 in the requested direction of travel, ie in the forward direction of travel or in the reverse direction, the power reversal threshold v_fzgPS again, what happens at the course v_fzg according to 2 underlying operating state history of the vehicle 1 at the time T3 is the case.

Since the value i_setpoint T2 specified at the time T2 is the target ratio i_nom of the continuously variable transmission 3 below the value i_istT2 the actual translation i_ist of the continuously variable transmission 3 lies and the actual translation i_ist of the continuously variable transmission 3 between times T2 and T3, between which the actuation of the direction-of-travel clutches 5 and 6 to represent the change of direction takes place, should be left substantially constant, the target ratio i_nom of the continuously variable transmission 3 at time T2 to the value of the actual translation i_istT2 raised and initially held at this value.

During the reversing process of the vehicle requested at time T1 1 becomes in dependence of a driver side on a power request element, such as an accelerator pedal or the like, requested target speed of the output 4 or a corresponding vehicle speed v_fzg of the vehicle 1 and a requested target speed of the prime mover 2 one in the continuously variable transmission 3 to be displayed after completion of the change of direction target ratio i_nom of the continuously variable transmission 3 certainly.

As in the present case, a nominal ratio of the continuously variable transmission 3 is determined in another translation area or in a higher transmission range of the continuously variable transmission 3 is as the while the direction of the clutch 5 and 6 currently in the continuously variable transmission 3 constant actual translation i_istT2 , is in continuously variable transmission 3 during operation of the directional control clutches 5 and 6 changed to the translation area in which the determined target translation lies. The ratio of the continuously variable transmission 3 is defined by the change of the transmission range defined reduced or the reciprocal of the ratio of the continuously variable transmission 3 in the 3 raised amount shown.

In order not to influence the translation change due to the range change or to influence in the least possible extent, the range change is present by raising the course of the target ratio i_nom of the continuously variable transmission 3 triggered at the time T4, to which the vehicle 1 at standstill. From the jump-shaped lifting of the course of the desired ratio i_soll of the continuously variable transmission 3 At time T4 results due to a system-inherent response only a delayed increase in the course of the actual translation i_ist of the continuously variable transmission 3 in the direction of the course of the desired translation i_nom , The actual translation i_ist of the continuously variable transmission 3 reaches the target specification at the time T5, which lies between the times T4 and T3. From the time T5, the actual translation i_ist of the continuously variable transmission 3 set constant by an appropriate target specification.

After time T3, to which the actuation of the directional control clutches 5 and 6 is completed and zuzuschaltende direction clutch 5 or 6 is completely closed while the turn-off clutch to be disconnected 6 or 5 is in the open operating state, the target ratio i_nom of the continuously variable transmission 3 in the extent shown in the direction of requested value, in this case the target ratio i_sollT1 at time T1. Raising the target ratio i_nom in turn causes an increase in the actual translation i_ist of the continuously variable transmission 3 that at a time T6 the value of the target translation i_nom reached and then kept constant at this value. Thus, at time T6, the direction change requested at time T1 is completely completed, and the actual gear ratio is the value of the target gear ratio i_nom of the continuously variable transmission 3 that triggered the range change made at time T4.

To the reversing process of the vehicle 1 each with a desired high dynamics at the same time to be able to perform high driving comfort, the power reversion threshold v_fzgPS depending on one each in the area of the output 4 varying load varies. This is the power reversion threshold v_fzgPS shifted towards lower vehicle speeds when during the requested reversing process in the field of output 4 a high load is applied. This is for example during a downhill descent of the vehicle 1 and / or during a Reversiervorganges during a driving operation of the vehicle 1 in the plane of the case, if this has a high payload.

Additionally or alternatively, the power reversion threshold v_fzgPS depending on a difference between the vehicle speed v_fzg at the time the request for the direction change is made and the power reversal threshold v_fzgPS varies to the vehicle speed during the reversing process v_fzg To reduce in the above scope first by adjusting the ratio of the continuously variable transmission and with reaching the power reversing threshold v_fzgPS via a corresponding actuation of the direction-of-travel couplings 5 and 6 decelerate to zero and accelerate in the opposite direction.

There is also the option of the power reversal threshold v_fzgPS to vary depending on an aggressiveness setting or a dynamic adjustment for the reversing process to be carried out. The power reversal threshold v_fzgPS is thereby increased with increasing dynamics, while the power reversal threshold v_fzgPS is set to lower values when requested smaller dynamics in order to implement the requested dynamics to the desired extent.

The last two specifications for setting the power reversal threshold or limit v_fzgPS offer the possibility of a reversing process with a desired dynamic at the same time high comfort from a variety of driving situations of the vehicle 1 implement.

In contrast, by means of the load-dependent change of the power reversal threshold v_fzgPS achieved that the vehicle 1 defined at high load and reproducible by adjusting the ratio of the continuously variable transmission 3 until the beginning of the actuation of the direction-of-travel couplings 5 and 6 is delayed, thus for a driver of the vehicle 1 almost over the entire operating range of the vehicle 1 an expected driving behavior can be represented.

LIST OF REFERENCE NUMBERS

1

vehicle

2

prime mover

3

CVT

4

output

5, 6

Direction clutch

i_ist

Actual gear ratio of the continuously variable transmission

i_istT1

discrete value of the actual translation

i_istT2

discrete value of the actual translation

i_nom

Target ratio of the continuously variable transmission

i_sollT1

discrete value of the target translation

i shouldT2

discrete value of the target translation

T0 to T6

time

t

Time

v_fzg

vehicle speed

v_fzgPS

Powerreversierschwelle

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 19830953 A1 [0004]

Claims (9)

Method for operating a vehicle (1) with a continuously variable transmission (3) whose ratio is infinitely variable within various transmission ranges by adjusting a variator, and with at least two frictional direction-control clutches (5, 6) whose transmission capacity is continuously variable and by means of which the vehicle (1) via a defined drive rotational movement of a drive device (2) in a direction of travel or in an opposite direction is driven, in the presence of a request for a direction change from a current direction in the opposite direction of travel, wherein the implementation of the requested direction change first the ratio of the continuously variable transmission (3) is raised and when falling below a defined speed of the output (4) the currently engaged directional control clutch (5 or 6) is switched off and the currently switched off Fahrtric Coupling (6 or 5) is switched on, characterized in that during the implementation of the change of direction in response to a driver requested requested speed of the output (4) and a corresponding target speed of the drive machine (2) in a continuously variable transmission (3) In the continuously variable transmission (3) in determining a desired ratio (i_soll) of the continuously variable transmission (3), which is located in another transmission range of the continuously variable transmission (3) when the actual ratio 8 (i_act) currently set in the continuously variable transmission (3) during actuation of the direction-of-travel clutches (5, 6) is changed during the actuation of the direction-of-travel clutches (5, 6) into the transmission range in which the determined nominal transmission ratio is determined (i_soll) lies. Method according to Claim 1 , characterized in that the defined speed of the output (4), from which the direction of travel clutches (5, 6) are operated to carry out the direction change, depending on the speed of the output (4) at the time (T1), to which the requirement for the direction of travel is changed, is varied such that the speed of the output (4) during the implementation of the requested direction change first by increasing the ratio (i_ist) of the continuously variable transmission (3) is reduced and then reversing the direction of travel of the vehicle (1) by pressing the Direction of travel clutches (5, 6) takes place. Method according to Claim 1 or 2 , characterized in that the defined speed of the output (4), from which the direction of travel clutches (5, 6) are actuated to carry out the direction change, depending on a predetermined dynamics with which the requested direction change is to be performed, is varied. Method according to Claim 3 , characterized in that the defined speed of the output (4) is set higher, the greater the requested dynamics. Method according to one of Claims 1 to 4 , characterized in that the defined speed of the output (4), from which the direction of travel clutches (5, 6) are operated to carry out the direction change is varied in dependence on the output (4) applied load, wherein the defined speed with increasing load increasingly reduced. Method according to Claim 5 , characterized in that the load applied to the output (4) is determined by measurement. Method according to Claim 6 , characterized in that the load applied to the output (4) is determined as a function of a measured in the region of the formed as a hydraulic variator variator high pressure. Method according to Claim 6 or 7 , characterized in that the load applied to the output (4) is determined by means of a torque sensor. Method according to one of Claims 6 to 8th , characterized in that the load applied to the output (4) is determined as a function of a torque provided by the drive machine (2).

Images