DE102010001282A1 - Method for controlling drive system of car, involves introducing control process of transducer lockup clutch under consideration of threshold value that is predetermined as control difference rotation speed - Google Patents

Abstract

The method involves requesting a state change of a transducer lockup clutch (6) from an open state into a partially or completely closed state in a drive operation. Difference rotation speed between a drive side and a power take-off side of a torque converter (2) is detected and evaluated during request for the state change of the lockup clutch. Rotation speed-relevant motor control intervention takes place depending on the evaluation of the speed. A control process of the lockup clutch is introduced under consideration of a threshold value predetermined as control difference rotation speed.

Description

The invention relates to a method for controlling a drive system of a vehicle according to the preamble of patent claim 1.

Propulsion systems for vehicles, which have a transmission with controllable means for switching various ratios and a mechanically bridgeable hydraulic torque transmission element for transmitting power in a drive train between a drive motor and the driven vehicle wheels, are known per se. In particular, such drive systems with a stepped automatic transmission and a hydrodynamic torque converter arranged between the drive motor and the automatic transmission are widespread, the latter being bridgeable by a friction clutch.

The hydrodynamic torque converter usually consists of an oil-filled housing in which an impeller is connected as a drive with a crankshaft of the drive or internal combustion engine and a turbine wheel as output with a transmission input shaft. Between the impeller and the turbine wheel, a rotatable in one direction stator is arranged as a support element for torque conversion. During operation, the pump wheel driven by the vehicle's internal combustion engine sets the oil in motion. The kinetic flow energy of the oil is absorbed by the turbine wheel and converted into a rotational movement, which is transmitted via the transmission input shaft to the transmission. The stator deflects the oil flowing back from the turbine wheel, so that the torque of the turbine wheel delivered to the transmission is higher than the torque of the pump wheel received by the internal combustion engine. The torque converter thus operates as a continuously variable transmission.

Since the impeller always precedes the turbine wheel, however, there is a differential speed-dependent increasing slip, which reduces the efficiency of the torque converter. Therefore, the hydrodynamic torque converter is usually used only for a short time in acceleration phases, for example for starting in train operation or in deceleration phases, for example as an aid in gear changes in overrun mode for torque transmission. Otherwise, the impeller and the turbine wheel are frictionally bridged by means of said lock-up clutch.

A transmission system with a torque converter and a lockup clutch, as for example in the DE 101 10 374 A1 described works via two parallel transmission paths for the input torque of the motor. On the one hand via the lock-up clutch and on the other hand via a hydraulic circuit of the torque converter. The actuation of the lock-up clutch is generally carried out by means of a hydraulically actuated piston, the adjusting movement of which is controlled by a software stored in a control unit.

In a request for a state change of such a lock-up clutch starting from an open state, the corresponding torque-transmitting partners, for example, the friction torque transformer of a disk set, are selectively brought into abutment against each other in a Einregelvorgang. Usually, by means of a pressure control of the converter lockup clutch, a clutch piston is first brought close to a friction torque transformer of the disk pack in a controlled application phase. Following this is usually followed by a slip control of the lock-up clutch to realize a compromise between a gentle and a direct connection of the engine to a transmission input shaft. On the one hand, the lock-up clutch without unnecessary loss of time close to save fuel and to achieve high driving dynamics, on the other hand, the diversion transition of the drive torque from the torque converter to the lock-up clutch as comfortable as possible, gentle component and without noticeable shock loads. Thus, the slip control can use at the right time, therefore, the application of the torque transfer means in the lock-up clutch must be detected as close to the event.

This may provide a method of investor identification and launch control, which in the unpublished DE 10 2008 043 495.7 the applicant is described. It is based on the fact that the lockup clutch and the hydraulic circuit of the torque converter are two parallel transmission paths for the engine torque to be transmitted, so that an incipient torque transmission via the torque converter lockup clutch is associated with a decreasing pump torque compared to the engine torque. This corresponds to a pump torque gradient, which is more negative by a certain threshold compared to the gradient of the engine torque. By means of a suitable gradient evaluation of the converter pump torque and of the engine torque, wherein the current converter pump torque is calculated from a stored converter identifier and the current engine and converter turbine speeds and the current engine torque is made available, for example, by an engine controller, it can be achieved that a slip control of the converter lockup clutch only then starts when a manipulated variable penetration of a slip controller is certainly given, but early enough so that the lock-up clutch is not closed surprisingly jerky.

In principle, the pressure control of the lockup clutch and the engine and transmission controls can be varied so that switching operations in a relatively large speed range of the output can be carried out. This allows, depending on the requirements, to set particularly low-consumption and / or particularly dynamic switching operations and the shortest possible switching times. In particular, in the train operation during a vehicle acceleration, a switching point for a pending circuit can be selected at a comparatively high output speed.

However, there is a risk that a Einregelvorgang the lockup clutch run relatively uncomfortable and uncomfortable for the driver unpleasant as shock can be felt because at unfavorable, especially at too high differential speeds between the drive side and output side the so-called unwanted "converter snap" can use.

From the DE 100 40 657 A1 a method for controlling a drive system of a vehicle with an automatic transmission and a hydrodynamic torque converter is known, in which a positive engine control intervention takes place during a gear engagement or when adjusting a lockup clutch in a coasting operation. The term "motor control intervention" is understood here as a control technology intervention in the otherwise usual sequence of a program for controlling and regulating the operation of the drive motor.

In this engine control intervention during a transition of the lockup clutch from an open to a slipping or closed state, the rotating masses of the drive motor is accelerated so that a perceived as uncomfortable for the driver vehicle deceleration is limited during the shift in overrun. Such vehicle decelerations are caused when, upon restoration of traction of the drive train during a coasting engagement, the speed of the engine is less than the speed at the transmission input, which is due to the need for kinetic energy to accelerate the rotatory masses of the engine. In particular, with the aid of the aforementioned positive engine control intervention, the engagement of a target gear at relatively high rotational speeds can take place without sacrificing ride comfort. However, this method is limited to a Schubeinregelung a lockup clutch and not readily transferable to a Einregelvorgang in train operation.

Furthermore, methods are already known which use a motor torque reduction when closing a lockup clutch in transmissions with a hydrodynamic torque converter to make the closing process as comfortable as possible.

The DE 199 49 118 B4 describes such a method, in which a motor torque reduction is adjusted using a characteristic map in which the amount of reduction over the measured speed ratio of turbine and pump is stored. The engine torque reduction begins with a starting value which is approached via an output torque ramp in the area of engagement of the friction parts of the clutch.

From the DE 102 42 821 A1 Another method for closing a lockup clutch is known, in which the closing operation or adjusting a certain differential speed from the open state via a pressure control and / or an engine control intervention takes place such that the driving sequence corresponds to the sequence of a switching operation of a step machine, the driver not perceived as disturbing.

In the known methods with a motor torque reduction, this takes place during the Einregelns a lock-up clutch. Thus, although the closing process can be designed as pleasant for the driver and possibly relatively short Einregelzeiten be realized. However, these Einregelvorgänge are not adapted to a speed-favorable starting point for the adjustment in the train operation of the vehicle. A common disadvantage of the known method is thus that they are less optimal when considering a switching strategy of such a transmission system with lockup clutch with regard to the control of the lockup clutch in train operation, taking into account a highly effective and at the same time reliably comfortable Einregelvorgangs.

Against this background, the invention has for its object to provide a method for controlling a drive system with a hydraulic transmission element with a bridging element that realizes an improved control sequence of the bridging element in particular in a train operation while ensuring a high level of effectiveness and high comfort.

The solution of this problem arises from the features of the main claim, while advantageous embodiments and further developments of the invention are the dependent claims can be removed.

The invention is based on the finding that in a train-Einregelung a converter lockup clutch of a hydrodynamic torque converter via a targeted deceleration of a Einregelvorgangs with the help of a motor torque reduction and a differential speed rating of the converter, a drive sequence is represented, with the always a betriebspunktrelevante maximum allowable Einregeldifferenzdrehzahl is maintainable.

Accordingly, the invention is based on a method for controlling a drive system of a vehicle, with a drive motor and a transmission with a hydraulic transmission element and with a bridging element, in particular with an automatic transmission with a hydrodynamic torque converter and a lockup clutch, in which a state change of the Bridging element is required from an open state to a partially closed or closed state. To achieve the object, the invention provides that when a request for the state change of the lock-up element initially a differential speed between a drive side and an output side of the transmission element is detected and evaluated, and that depending on the evaluation, a speed-relevant engine control intervention takes place, wherein a Einregeivorgang of Bridging element is introduced taking into account a predetermined as Einregeldifferenzdrehzahl threshold value.

In particular, it may be provided that the actual differential speed is continuously compared with the Einregeldifferenzdrehzahl that at differential speeds above the Einregeldifferenzdrehzahl a motor torque reduction takes place that when reaching or falling below the Einregeldifferenzdrehzahl the Einregelvorgang is started, and that within the Einregelvorgangs or a closing operation the motor control intervention is withdrawn.

Accordingly, in the presence of a request for a state change of the lockup clutch from an open state to a controlled state, for example in the context of a shift strategy of the automatic transmission, the current differential speed, formed from the current engine speed or the pump speed of the converter and the current turbine speed, with a permissible Einregeldifferenzdrehzahl compared. If the current differential speed is above the threshold value, a rotation or motor torque reduction is triggered.

The engine torque reduction can be advantageously updated to increasing differential speeds, so that the speed difference decreases in the sequence. For falling differential speeds above the Einregeldifferenzdrehzahl the motor control intervention can be kept constant, for example.

The magnitude and the course of the engine control intervention may be determined by various parameters, in particular as a function of the differential speed, an engine speed gradient, a relevant temperature, for example a transmission temperature and / or variables derived therefrom.

The adjustment of the lock-up clutch is delayed in the sequence in the further continuous differential speed rating until the permitted for the relevant operating point Einregeldifferenzdrehzahl is reached or fallen below. Subsequently, the delay of the Einregelanforderung is terminated and started the Einregelvorgang.

The withdrawal of the engine control intervention is preferably carried out as soon as there is an application of an actuating element of the bridging element to a torque transmission means thereof. This can advantageously be ascertained by means of a method for applying the lock-up clutch to the contact detection, as is not previously published, for example, in the already mentioned above DE 10 2008 043 495.7 is described.

With the method according to the invention, an improved traction control of the converter lockup clutch with respect to a shift strategy with favorable shift times and shift points is achieved while maintaining consistently high comfort and reliably avoiding increased clutch wear.

To clarify the invention, the description is accompanied by a drawing of an embodiment. In this shows

1 a diagram of the torque transmission paths on a hydrodynamic torque converter with lockup clutch, and

2 a time chart with representations of speed characteristics of a drive motor and a turbine of the lockup clutch, with a control curve of the lockup clutch, with a differential speed curve of the drive motor and turbine, and with the course of a motor control intervention.

Accordingly, in 1 two parallel transmission paths of a converter lockup clutch system 1 shown as it is For example, in the drive train of a motor vehicle with an automatic transmission can be provided. An input torque m_mot of an internal combustion engine, not shown, branches into a converter torque m_p of a transmission element designed as a hydrodynamic torque converter 2 and in a bridging torque m_wk a bypass element designed as a lockup clutch 6 ,

The torque converter 2 includes a pump wheel in conventional construction 3 driven by the internal combustion engine, a turbine wheel 4 as an output to drive a transmission input shaft, not shown, and a stator 5 for torque conversion.

The torque converter lockup clutch 6 is in a conventional manner as a friction clutch with a disk set as a torque transmitting means 8th formed, the input and output side friction partners by a hydraulic actuating piston 7 can be brought into frictional contact.

The torque converter lockup clutch 6 and a hydraulic circuit of the torque converter 2 are controllable via control means, not shown. Depending on the activated closing or opening degree no, only a certain part or the complete drive torque m_mot on the lock-up clutch 6 transfer. Because of the parallel transmission paths via the converter clutch 6 and the hydraulic circuit of the torque converter 2 cause the two input torques m_wk and m_p each other.

At the exit of the system 1 , ie at the transmission input, is thus at fully open lock-up clutch 6 a turbine speed n_t, by the slip, ie the speed ratio of the torque converter 2 is determined. At a beginning torque transmission of the lock-up clutch 6 results at the transmission input, a speed from the converter slip and an incipient clutch slip. When the lock-up clutch is fully closed 6 the speed at the transmission input n_t corresponds to the engine speed n_mot.

An inventive method for controlling a drive system, which can be carried out with such an arrangement is carried out according to a in 2 shown driving sequence.

This is in a diagram 2a the rotational speeds of the drive motor n_mot and the converter turbine n_t are plotted as a function of the time t during a vehicle acceleration in a train operation. Starting from an initial converter slip, the rotational speed n_mot of the drive motor initially increases more than the rotational speed n_t of the turbine 4 , wherein both increases substantially continuously, so that a growing differential speed nd_wk = n_mot - n_t and therefore an increasing converter slip at the converter lockup clutch system 1 results.

At a time t_0 is a request of a shift strategy of the automatic transmission for a state change of the lock-up clutch 6 from open to regulated in front of what's in 2 B is illustrated.

Since the current differential speed nd_wk whose time course in 2c is shown, is above a predetermined maximum allowable Einregeldifferenzdrehzahl nd_wk_regel, the Einregelung or the controlled closing of the lock-up clutch 6 initially not allowed and issued a motor control intervention.

The in 2d illustrated engine control intervention results in a motor torque reduction, which is plotted as a function of the time t. The engine control intervention is as a function f (nd_wk, ng_mot, c_getr) of the current differential speed nd_wk, a determined speed gradient ng_mot of the drive motor and a relevant temperature, for example a measured transmission temperature c_getr, which is equivalent to a pressure medium temperature of the lockup clutch 6 is presented, layed out.

As a result of said engine control intervention, the speed curve n_mot bends in 2a decreases and rises less strongly approximately steadily, while the turbine speed n_t continues to rise steadily continues to rise. The engine torque reduction is initially adjusted to increasing differential speeds nd_wk out, so that the differential speed nd_wk steadily decreases after exceeding a vertex corresponding to a now constant engine torque reduction ( 2c ).

At a time t_1, the decreasing differential speed nd_wk reaches the threshold value of the regulation differential speed nd_wk_regel. Then the Einregelvorgang the lock-up clutch 6 released and started. The engine control intervention is subsequently canceled, as an indicator of the withdrawal of the engine control intervention, for example, a torque detection of the torque transfer means 8th based on the already mentioned DE 10 2008 043 495.7 is being used. The engine speed n_mot rises more nearly steadily at a later time t_2, gradually approaching the turbine speed n_t.

The method according to the invention thus proceeds essentially in two phases: In an initial deceleration phase with a reduction in the engine torque, an admissible regulation difference rotational speed nd_wk_regel is actuated, and in an adjustment phase, starting from this differential rotational speed, the regulating process is permitted and initiated. The engine control intervention is then turned off based on a landing detection program. Thus, for all operating points, the maximum possible Einregeldifferenzdrehzahl nd_wk_regel be adhered to when controlling the lockup clutch.

LIST OF REFERENCE NUMBERS

1

Converter lockup clutch system

2

Transmission element, torque converter

3

impeller

4

turbine

5

stator

6

Bypass element, torque converter lockup clutch

7

Actuator, clutch piston

8th

Torque transmission means, disc pack

c_getr

Relevant temperature, transmission temperature

n

rotation speed

nd_wk

Differential speed

nd_wk_regel

Einregeldifferenzdrehzahl, threshold value

ng_mot

engine speed gradient

n_mot

Engine speed

n_P

pump wheel

n_t

Output speed, turbine speed

m_mot

engine torque

M_p

Pumpenradmoment

m_wk

Torque of the lockup clutch

t

Time

t_0

time

t_1

time

t_2

time

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 10110374 A1 [0005]
• DE 102008043495 [0007, 0025, 0041]
• DE 10040657 A1 [0010]
• DE 19949118 B4 [0013]
• DE 10242821 A1 [0014]

Claims (8)

Method for controlling a drive system of a vehicle, comprising a drive motor and a transmission with a hydraulic transmission element ( 2 ) and a bridging element ( 6 ), for example, with an automatic transmission with a hydrodynamic torque converter and with a lockup clutch, wherein in a train operation, a state change of the bridging element ( 6 ) is requested from an open state to a partially closed or closed state, characterized in that in the request for the state change of the bridging element ( 6 ) First, a differential speed (nd_wk) between a drive side and an output side of the transmission element ( 2 ) is detected and evaluated, and that, depending on the evaluation, a speed-relevant motor control intervention takes place, wherein an intervention process of the bridging element ( 6 ) is introduced taking into account a predetermined threshold as Einregeldifferenzdrehzahl (nd_wk_regel). A method according to claim 1, characterized in that continuously the current differential speed (nd_wk) with the Einregeldifferenzdrehzahl (nd_wk_regel) is compared that at differential speeds (nd_wk) above the Einregeldifferenzdrehzahl (nd_wk_regel) an engine torque reduction takes place, that at a decrease in the differential speed (nd_wk) is started to the Einregeldifferenzdrehzahl (nd_wk_regel), the Einregelvorgang, and that in the context of the Einregelvorgangs or a closing operation of the engine control intervention is withdrawn. A method according to claim 1 or 2, characterized in that the differential speed (nd_wk) from the difference of the engine speed (n_mot) and an output speed (n_t) of the transmission element ( 2 ) is determined. Method according to one of claims 1 to 3, characterized in that the engine control intervention as a function of the differential speed (nd_wk), an engine speed gradient (ng_mot), a relevant temperature (c_getr) and / or variables derived therefrom is determined. Method according to one of claims 1 to 4, characterized in that the engine torque reduction is updated to increasing differential speeds (nd_wk) out. Method according to one of claims 1 to 5, characterized in that the engine torque reduction at falling differential speeds (nd_wk) above the Einregeldifferenzdrehzahl (nd_wk_regel) is kept constant. Method according to one of claims 1 to 6, characterized in that the engine control intervention is withdrawn when an application of an actuating element ( 7 ) of the bridging element ( 6 ) to a torque transmission means ( 8th ) is recognized. Method according to one of claims 1 to 7, characterized in that the request of the state change of the bridging element ( 6 ) is issued via a shift strategy of the transmission.

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