DE102007056174B3 - Method for controlling automatic friction clutch arranged between engine and gearbox of vehicle, involves carrying out slip regulation of clutch for preventing torque impulse in alteration of load - Google Patents

Abstract

The method involves carrying out a slip regulation of the clutch for preventing torque impulse in alteration of load. The change of the clutch torque (4) is limited by the slip regulation. The change of the clutch torque is limited depending on the slip speed. The dependability is determined by linear, quadratic or logarithmic functions or by an engine operating map of the change of the clutch torque over the slip speed.

Description

at Driven in vehicles where a friction clutch as a starting element is used, it comes with locked clutch in case of sudden load changes at the drive to torque surges, the Problems such. Eg noises, Wear and tear can cause uncomfortable driving at low speeds. specially load load surges during accelerator operation (tip-in or back-out).

These Torque shocks are for manual transmissions through suitable functionality in engine management reduced. Here's a sudden change the driver's request torque implemented only filtered, as possible low torque change gradients to get. A disadvantage of this method, however, is that desired sudden torque changes (eg in dangerous situations in the crossing area) also only delayed further are given. Another disadvantage is that the comfort (also because a compromise with spontaneity must be found) here only increased to a certain extent can be.

Around the torque shock problem It is also known to counteract the torque shock at sudden Load changes take place through a targeted increase in clutch slip to dampen. This can be achieved in different ways.

From the EP 1 058 019 B1 is a method for controlling a clutch that transmits a torque between an engine and a transmission system of a motor vehicle, in which the engagement of the clutch is performed in such a way that the torque transmitted by them is a certain amount above the engine torque, and recording the amount of slip of the clutch during load change as the torque transmitted by the engine increases rapidly, comparing the amount of slip that occurs during load cycling with a model number that provides the ideal slip for the absolute torque, the torque gradient and represents the engine speed, as well as correcting the friction coefficient of the clutch to equate the ideal slip with the actual slip. In this case, the clutch is normally controlled completely closed by a feed-forward control. In the event that a tip-in is detected (by evaluation, for example, by the accelerator pedal), a parameter of the control (the coefficient of friction of the clutch) is changed so that the feed-forward portion is no longer sufficient, the clutch closed hold. As a result, the desired clutch slip is generated, which is possibly degraded slowly by the rule share.

From the DE 102 37 793 A1 A method and system for controlling an automatic friction clutch disposed between an engine and a transmission of a motor vehicle is known in which operating state quantities of the powertrain are detected and the clutch is controlled so as to transmit a clutch torque resulting from a substantially one of Motor torque dependent component and a slip-dependent component is composed, wherein the engine torque dependent component is calculated according to operating state variables of the drive train and adapted according to an i-portion of a controller and the slip-dependent share of the controller according to a deviation between an actual slip and one of operating state variables of the drive train Setpoint slip is determined, wherein parameters of the controller from operating state variables of the drive train are calculated and corrected and the engine torque-dependent portion of the clutch torque by the i-part of the Re glers in the sense of a reduction of the i-portion is adapted. Thus, a slip control of a clutch is generally described, which also includes transitions into a feed-forward control and modifications of the controlled variables. In order to prevent a tip-in or back-out load shock, a faster change of the setpoint slip is permitted here when a tip-in or back-out situation is detected. Furthermore, a dependence of the control characteristics of the derivative of the nominal slip deviation or of the duration of the nominal slip deviation is presented.

From the DE 39 18 254 C2 is a method for preventing load changes due to sudden changes in the accelerator pedal position in vehicles, especially passenger cars, known, which are equipped with an internal combustion engine, a transmission and arranged between the engine and the transmission and controllable with respect to the transmittable torque clutch, wherein at an adjustment the accelerator pedal from a load position into a push position, the clutch is initially controlled automatically in the disengagement and then operated again until reaching a predetermined slip between the speed of the engine and the transmission input in the direction of engagement, the clutch before the change of the internal combustion engine from train to Pushing operation is automatically completely disengaged, and the clutch in response to the adjustment of the accelerator pedal or in response to the adjustment speed of the accelerator pedal ausgeüc kt is. In other words, when detecting a back-out (or tip-in) based on the engine speed and the accelerator pedal position (or the operating speed), the slip is increased by the clutch is completely disengaged. The slip is then degraded by controlled engagement of the clutch to a desired slip value.

From the DE 10 2005 033 965 A1 is a method for actively damping a powertrain in a vehicle powertrain that includes an internal combustion engine responsive to an accelerator pedal position and controllably coupled to the driveline via a torque transmitting device, in which an engagement command is provided that includes a powertrain feedback portion an acceleration term and an over-acceleration term, the acceleration term is determined as a function of the acceleration of a drive train element and the over-acceleration expression is determined as a function of the overdrift of the drive train element, and the engagement of the torque transmission device is controlled in accordance with the engagement command. So a complex tip-in management is presented, in which a tip-in is first recognized. Subsequently, the current clutch torque is frozen until a certain target slip is exceeded. Thereafter, the slip control is reset again to reduce the slip to the usual desired slip value.

From the EP 0 240 283 B1 discloses a system for controlling a clutch for a motor vehicle with an accelerator pedal for actuating a throttle valve of an engine having first means for progressively increasing the clutch torque when the accelerator pedal is depressed, with first detection means for detecting the rotational speed of the engine and for generating a corresponding An engine speed signal, comprising second detector means for detecting the opening angle of the throttle valve and for generating a corresponding throttle valve signal, second means for increasing the idle speed of the engine during engine operation in the cold state to provide a fast idle state, and third detector means for detecting the fast idle state and generating a fast idle signal having first control means responsive to the fast idle signal for reducing the slew rate of clutch torque upon depression of the accelerator pedal and second Control means responsive to the fast idle signal, the engine speed signal and the throttle valve signal for increasing the slew rate of the clutch torque with the increase of the engine speed and / or the throttle valve opening angle.

at the above solutions is always provided that a tip-in or back-out situation, z. B. by monitoring of the accelerator or the throttle, is explicitly recognized and only then it reacts accordingly.

at Automatic transmissions that use a transducer as a starting element, It is also known, the torque surge in the converter by increased slip catch. The transducer characteristic offers by the with The slip increasing torque is a useful compromise between spontaneity and ride comfort in the low gears. However, this would be Compromise in higher courses not necessary, because here the effect of the torque shocks on the Vehicle of translation correspondingly lower and thus here a much more direct Tuning of the converter desirable would.

From the DE 195 04 847 A1 For example, a method of controlling an automatic clutch between an engine and a transmission is known, wherein the clutch torque is composed of a first component dependent on the engine torque and a second component, the second component being dependent on the slip in the clutch. To avoid shocks of the clutch torque is provided to correct the first portion by a corresponding function. The function is to ensure that the clutch torque is limited in its change. However, the function for limiting the change in the clutch torque does not detect the second part dependent on the slip, so that large changes in the slip result in large changes in the clutch torque, which has an influence on the driving comfort.

In contrast there is the object of the present invention to provide a method which Counteract load shocks can, without requiring a detection of a tip-in or back-out situation necessary is. In addition, the process should be as simple as possible be feasible and as possible all courses Be active without compromising spontaneity and ride comfort in the low gears and the higher one courses suffers.

These The object is achieved by the reproduced in claim 1 method.

Thereby, that in the slip control the change of the clutch torque is limited, it is possible To make a slip control, without a separate detection a tip-in or back-out situation or other sudden load changes necessary is. The process can therefore be carried out continuously. This is the change the coupling torque in dependence limited by the slip speed.

The dependence can be represented by linear, quadratic or logarithmic functions or be determined or defined by a map of the slew rate above the slip speed. If a map is used, this can be described by the area enclosed by intersecting quadratic and logarithmic functions.

Logically, will only increase the change the clutch torque is limited, especially at low slip speeds, in particular less than 100 per min. It makes sense, the clutch in the slip control according to the invention So operated in micro-slip.

To gets in the low gears, preferably the 1st and 2nd gear, the clutch operated in micro-slip. These are to be understood as slip speeds between 1 and 50 per minute.

By the slip control automatically becomes the torque transmitted by the clutch adapted to the engine torque. This regulation must normally as quickly as possible happen to excessive slippage and the associated energy input and to avoid the deterioration of efficiency. According to the invention will now this scheme artificial slowed down / limited in certain areas, making it sudden changes the motor torque comes to an increased slip while the Clutch torque only comparatively slow to the new target value brought becomes. However, since the clutch torque is crucial for the driving experience Torque is, thereby can be a significant improvement in driving behavior be achieved.

Prefers is it when the change the clutch torque in both negative and positive Load changes is limited.

The Although presented method is suitable for a constant use ("always on"), d. H. for all gears, however the application of the method in small gears is preferred because here by the big translations the gear wheels of small courses changes the engine torque to larger torque changes lead the transmission output shaft. As a result, the ride comfort can be influenced more targeted. at high passageways are through the smaller translation the gear wheels changes of engine torque is not felt as strongly.

In addition, can the limitation depending on one or more of the following parameters: engine speed, Engine torque, engaged gear, vehicle speed, transmitted torque.

Further Details, features and advantages of the invention will become apparent the following description with reference to the drawing, in which

1 a schematic representation of the speed and torque curves in the use of the invention with an increase in the engine torque shows;

2 shows a schematic representation of the speed and torque curves when using the invention in a drop in engine torque;

3 a schematic representation of possible dependencies of the limitation of the clutch torque as a function of the slip speed shows.

1 and 2 show the course of the above speed and torque values in the case of a rise ( 1 ) or waste ( 2 ) of the engine torque 1 , z. Example, in a tip-in or back-out situation, using the specified method for controlling an arranged between the engine and the transmission of a motor vehicle automatic friction clutch in which a slip control of the clutch to prevent torque surges during load changes is performed.

In the 1 and 2 are the engine speed 1 as dashed line, the input shaft speed 2 as a dotted line, the engine torque 3 as dash-dotted line, the limited clutch torque 4 as a solid line and the unlimited theoretical clutch torque 5 shown as a dotted line. The range of limiting the clutch torque is with 6 designated.

The engine torque 3 rises in 1 along with the engine speed 1 because the user is getting more power, e.g. B. by pressing the accelerator pedal or turning on consumers.

A locked clutch would theoretically meet these requirements with unlimited clutch torque 5 follow, which would lead to a load shock, which is perceived as unpleasant and is also unfavorable due to the mechanical stress.

To prevent this, the clutch is operated in micro-slip and by the slip control, the torque transmitted by the clutch 4 automatically to the motor torque 3 customized.

This regulated adjustment should normally be made as soon as possible to prevent excessive slippage and related problems Energy input and the deterioration of efficiency to avoid.

However, according to the invention, this control becomes artificial in a certain area 6 slows or limits, so that there is an increased slip, while the clutch torque 4 only comparatively slowly to the new target value. For this purpose, the gradient of the clutch torque ∂T / ∂t in the slip control as a function of the slip speed Δn is limited (see. 3 ).

This results in the in 1 shown speed and torque curves, the regulated range with 6 is designated.

Because the clutch torque 4 However, for the driving feel is the crucial torque, thereby a significant improvement in driving performance can be achieved.

In this case, the restriction depending on the clutch slip may be such that the torque increase is greatly limited at low slip, while at high slip (eg, 200 per minute slip speed), the control speed is no longer limited (see. 3 ).

3 shows the relationship between the torque gradient ∂T / ∂t and the slip speed Δn. It becomes clear that with a small slip the change of the torque 4 in a clutch would be small. If the slip speed Δn increases, the gradient ∂T / ∂t also increases.

The course of the dependence of the gradient on the slip speed can be as in 3 illustrated, be different. Preference is given to the progressive (square) variant. The characteristics go in 3 not by the zero point, since a minimum gradient ∂T / ∂t for controlling the slip must be present, otherwise no control of a micro-slip would be possible.

These dependence can by linear, quadratic or logarithmic functions or by a map of the slew rate ∂T / ∂t over slip speed .DELTA.n done.

In 3 the first three variants are indicated. With 7 is the linear, with 8th the square and with 9 the logarithmic dependence indicated. A corresponding map 10 could be located within the area enclosed by the square and logarithmic curves.

In 3 A sign change takes place whenever a load change (train -> push or vice versa) happens, so that the curves 7 . 8th . 9 and the map 10 each have a "negative" and "positive" branch.

2 on the other hand shows the course of the above parameters in the event of a drop in engine torque 1 , z. B. in a back-out situation.

To change the load to negative engine torques 3 To filter, also the clutch control is slowed down. However, due to the different torque levels, different limits than in positive load cases make sense here. Again, only the positive increase of the clutch torque is 4 (which only starts after the engine torque 3 has become negative).

In the 2 In the first phase there is no deceleration of the clutch torque 4 instead, because the engine control in this phase, no large engine torque changes 3 allowed and the present method is applied only at a small slip speed. Only when the engine is in the overrun phase, higher engine torque changes must be damped by the operated by the method controller.

The dismantling of the clutch torque 4 respectively. 5 zero moment during the first phase of the load change should be done as quickly as possible to allow the best possible decoupling of the drive train.

Here is a support the process in the first phase by a suitable engine control (a filtering of the driver's request torque, dashpot function) makes sense, otherwise the removal of the torque was otherwise perceived as uncomfortable can be.

There the application of the method according to the invention - as above already mentioned - mainly in low gears and at low speeds and torques makes sense in addition to the slip speed dependency a dependency the gradient of the active gear, the engine speed or vehicle speed as well as the transferred Torque done. This can be done by adjusting the limiting characteristics or by disabling the feature in unwanted ones Areas.

This makes it possible, in situations where a direct coupling of the engine torque to the drive train is not disturbing (high speeds or torques, high gears) to allow a quick response of the vehicle to the change of the driver's desired torque, without the comfort in low gears at low speeds and torques. This is in Compared to the torque converter a significant advantage of the regulated clutch system.

at the implementation of the procedure is to pay attention that the slip control only makes a limitation of the torque increase. This is included a simple proportional controller of the case. However, when using an integrator member for it be ensured that this is not "full", so unnecessarily high manipulated variables generated. This can be done by not only limiting the manipulated variable, too the I share of the regulation in the area of the limit of the appropriate Value is reduced.

Also is at a feedforward of the slip control by the engine torque to pay attention to the final Manipulated variable limited where, if necessary, the gain factor similar to the pilot control like the I share of the scheme during the limitation phase must be modified.

is the regulator is designed accordingly so that he has such a rate limit without "side effects", needs thus no change the original one Regulation performed become. Otherwise, the element must be sensitive to a limitation responds accordingly (eg the I component) accordingly also in dependence the sizes mentioned modified become.

To In any case, the present method does not require separate recognition a tip-in or back-out situation. This can also be done unforeseen torque fluctuations from the internal combustion engine (z. B. air conditioning inrush) intercepted become.

1

Engine speed

2

Input shaft speed

3

engine torque

4

clutch torque

5

unlimited theoretical clutch torque

6

Area the limit of change the clutch torque

7

linear Curve

8th

square Curve

9

logarithmic Curve

10

Map range

∂T / ∂t

gradient the clutch torque T

.DELTA.n

Slip speed

Claims (10)

Method for controlling an automatic friction clutch arranged between an engine and a transmission of a motor vehicle, in which a slip control of the clutch for preventing torque surges during load changes is carried out, whereby in the slip control the change (∂T / ∂t) of the clutch torque ( 4 ), characterized in that the change (∂T / ∂t) of the coupling torque ( 4 ) is limited as a function of the slip speed (Δn). A method according to claim 1, characterized in that the dependence by linear ( 7 ), square ( 8th ) or logarithmic ( 9 ) Functions or through a map ( 10 ) of the change (∂T / ∂t) of the coupling torque ( 4 ) is determined above the slip speed (Δn). Method according to claim 2, characterized in that the characteristic field ( 10 ) is determined by an area defined by intersecting square ( 8th ) and logarithmic ( 9 ) Functions is enclosed. Method according to one of claims 1 to 3, characterized in that only the increase of the change (∂T / ∂t) of the clutch torque ( 4 ) is limited. A method according to claim 4, characterized in that the increase in the change (∂T / ∂t) of the clutch torque ( 4 ) is limited only at low slip speeds. Method according to Claim 5, characterized in that the increase in the change (∂T / ∂t) of the clutch torque ( 4 ) is limited at slip speeds of less than 100 per minute. Method according to one of claims 4 to 6, characterized in that the change (∂T / ∂t) of the coupling torque ( 4 ) is limited in both negative and positive load changes. Method according to one of the preceding claims, characterized characterized in that the clutch in the slip control in the micro-slip is operated. Method according to one of the preceding claims, characterized characterized in that the slip control is operated at low speeds. Method according to one of the preceding claims, characterized characterized in that the limit is additionally dependent one or more of the following parameters occurs: engine speed, Engine torque, gear engaged, vehicle speed, transmitted Torque.