WO2002099301A1

WO2002099301A1 - Control method for hill-descent in a vehicle with an automatically operated clutch

Info

Publication number: WO2002099301A1
Application number: PCT/DE2002/001939
Authority: WO
Inventors: Jürgen GERHART; Klaus KÜPPER; Olaf Werner; Georg Schneider
Original assignee: Luk Lamellen Und Kupplungsbau Beteiligungs Kg
Priority date: 2001-06-05
Filing date: 2002-05-27
Publication date: 2002-12-12
Also published as: DE10223467A1; ITMI20021210A1; BR0205113A; FR2825435A1; DE10223467B4; FR2825435B1; ITMI20021210A0; DE10292470D2

Abstract

The invention relates to a control method for hill-descent in a vehicle with an automatically operated clutch, whereby said driving situation is detected and on descending a hill, the clutch is automatically released when the gearbox speed is less than a set first value and the clutch engaged again when the gearbox speed exceeds a set second value, characterised in that the clutch is released or engaged at a speed the value of which is less than a set value, or that the clutch is only released far enough to permit the transfer of a set torque from the gearbox to the engine, or accelerating the vehicle to a set value, or the speed of the vehicle corresponds to a set value or the difference between gearbox speed and engine speed corresponds to a set value.

Description

Control method for rolling down a vehicle with an automatic clutch

The invention relates to a control method for rolling down a vehicle with an automatically actuated clutch, in which this driving situation is detected and the clutch is automatically opened when rolling downhill when the transmission speed falls below a presettable first value, and the clutch is closed again when the transmission speed is a presettable one exceeds the second value.

In vehicles with an automatic clutch, when rolling downhill, which in the sense of the invention is a downhill run with little or no or without accelerator and / or brake pedal actuation, the clutch can be opened and closed cyclically at low speed. This leads to a vehicle vibration that is uncomfortable for the vehicle driver. This vibration arises from the fact that the vehicle is decelerated by the drag torque of the engine when driving slowly downhill (engine brake). In order to prevent the engine from stalling if the speed is too low, depending on the gear engaged, the clutch is opened when the gearbox speed falls below a specified gearbox speed. When the clutch is open, the vehicle is then accelerated again when rolling downhill until the engagement threshold is exceeded, whereupon the clutch is closed. This re-engagement takes place to restore the flow of power and is generally desired by the driver. The vehicle then decelerates again with the drag torque of the engine until the clutch disengagement threshold is undershot and the clutch is opened. This cyclical behavior leads to vehicle vibration or jerking of the vehicle, which is pronounced and disruptive in vehicles with a high drag torque, in particular in vehicles with a diesel engine. Because the clutch has to be opened and closed several times, the driver experiences an uncomfortable and incomprehensible driving situation over a longer downhill stretch. The invention is therefore based on the object of providing a control method in which the disengagement and engagement when rolling downhill is detected and vehicle vibration is avoided or at least reduced by a slip control with targeted slip or by a targeted modulation of the torque on the clutch which can be transmitted by the clutch ,

This object is achieved according to the invention by the method mentioned at the outset in such a way that the clutch is opened or closed at a speed whose amount is less than a preset value. The opening or closing of the clutch preferably extends over a period of at least three seconds, preferably at least ten seconds.

The method according to the invention is usually implemented in control software, which in turn is implemented in a programmable, electronic control device.

As soon as the driving situation of rolling downhill is recognized, the clutch opens slowly and remains open until the driver applies the brakes or the accelerator pedal. If the clutch remains open, the vehicle may slowly accelerate by rolling downhill. From a certain speed limit, which can be significantly higher than the disengagement threshold, the clutch must then be slowly closed again. Under certain circumstances, this can still result in a cyclical oscillation, the frequency of which, however, is considerably lower than when the vehicle is jerked due to the slow engagement of the clutch and is therefore not as noticeable. In a special embodiment, the vehicle vibration is greatly reduced by very slowly closing and opening the clutch. Is disengaged very slowly when rolling downhill, for. B. over at least 3 sec or in particular over at least 10 sec, and at the same time the disengagement speed is set very low, the clutch opens much later than in the known methods and the vehicle is accelerated again much later by rolling downhill with the clutch open. This reduces the frequency of the vibration very much. By lowering the disengagement threshold with a small hysteresis for the re-engagement, the amplitude of the vibration can also be reduced, so that the driver can hardly feel the vibration. In another procedure, the clutch is kept fully or partially closed after the driving situation of rolling downhill has been detected. With a partially closed clutch, this is done, for example, by applying a clutch torque that is somewhat greater than the drag torque of the engine. It can also be done by applying a constant z. B. happen gear-dependent moment. As a result, the engine is decelerated evenly. If the idle speed is reached, the idle speed can be maintained via an idle controller. This prevents the engine from stalling. Vibration of the vehicle can thus be largely suppressed. In addition, the clutch can be opened shortly before idling speed is reached and can remain open until the driver applies the brakes or the accelerator pedal.

In the context of the task, a variant of the control method is characterized in that the clutch is only kept open enough that a presettable clutch torque is transmitted from the transmission to the engine.

Further solutions to the problem consist in the control methods mentioned at the outset, in which the acceleration or the speed of the vehicle or the clutch slip is regulated. For the purposes of this invention, this means that the clutch is opened, held open or closed so far that the speed or the acceleration or the clutch slip takes on a presettable value.

If a downhill roll is detected, in the event of a solution, the vehicle acceleration is switched to a control of the vehicle acceleration. The acceleration is either measured or determined from the gearbox speed (optionally also speedometer or wheel speed) by derivation. By specifying a target acceleration, the actual acceleration is approximated to the target acceleration and the clutch torque is changed in such a way that a variable slip speed is set which ultimately regulates the vehicle acceleration.

If a downhill roll is detected, in the event of a solution, the vehicle speed is switched to a control of the vehicle speed. The GE- Speed is either measured or from the gearbox speed (optionally also

Speedometer or wheel speed) determined. By specifying a target speed, the actual speed is approximated to the target speed and the clutch torque is changed in such a way that a variable slip speed is set which ultimately regulates the vehicle speed.

If a downhill roll is detected, the solution is switched to a slip speed control by regulating the slip speed. By specifying a target slip speed, the actual slip speed is approximated to the target slip speed and the clutch torque is changed so that a constant slip speed is established.

The invention is explained in more detail below with reference to the drawings. Show it

Fig. 1 shows the schematic course of transmission input speed n _get , engine speed n _mot and clutch torque M _κ , each in dependence on the time t during the rolling downhill in the prior art and

Fig. 2 shows the schematic course of the transmission _input speed n _gθt , engine speed n _mot and the slip control _according to the invention of the clutch torque M «, each as a function of the time t during rolling downhill, shown as an example for the case of regulating the slip speed.

1, the transmission input speed n _get and the engine speed nm _ot ei closed clutch are initially of the same size and decrease with time, when a vehicle with an automated clutch begins to roll downhill, with neither the brake nor the accelerator pedal being actuated. The clutch torque M _κ is constant. As soon as the transmission _input speed n _{gθt falls below} a predetermined disengagement speed at time t _A , the known clutch control system opens the clutch in order to avoid the engine stalling. The drop below the disengagement speed is caused, for example, by the drag torque of the engine that is transmitted when the clutch is stuck, which slows the vehicle down sharply when rolling downhill. If the driver does not intervene by operating the brake after opening the clutch, the vehicle accelerates (sailing) due to the gradient of the Travel distance, and the transmission _input speed n _get increases, while the engine speed n _mot remains constant and the clutch torque M _κ is zero (open clutch). As soon as the transmission _input speed n _ge t exceeds a predetermined engagement speed at the time t _E , the clutch closes and the clutch torque MK increases, as does the engine speed nmot. The engine speed nm ₀ t adjusts itself to the transmission input speed n _get until an intermediate maximum is reached. If the brake is still not actuated, the transmission _input speed n _gθ t drops due to the clutch control of the automated clutch, the clutch torque MK decreases, the engine speed n _mot and _if the clutch _input speed _{falls below} the disengagement speed n _get opens the clutch and the one described above The process is repeated. In extreme cases, this process is repeated cyclically and causes an unwanted jerking of the vehicle or vehicle vibrations, which the driver perceives as uncomfortable and dangerous.

These cyclical oscillation processes are to be avoided or minimized by the invention. 2 explains how the situation of rolling downhill, which triggers disengagement and engagement, is recognized and the clutch control is replaced by a slip control (or one of the other methods described) by means of targeted modulation of the clutch torque on the clutch the generation of vibrations is suppressed. As the speed curve for the transmission input speed nget and engine speed nmot as well as the curve of the clutch torque MK in FIG. 2 show, these curves up to the point in time tE largely correspond to the processes in the known clutch control as shown in FIG. 1. Event a)

namely disengagement without brake actuation detected at time t _A and then event b)

this is the engagement at constant engine speed nm _ot - As soon as event a) is recognized, a flag "Motor_bremst_Fahrzeug" is set in the control program. If event b) is recognized, the two conditions, the flag "Motor_bremst_Fahrzeug" and the event b ) to the fact that a flag "clutch when rolling downhill" is set. The following action is then carried out in the case of the slip control: The clutch torque M _κ (initially equal to zero) is built up in a controlled manner, e.g. For example, the structure is ramped or stepped until the transmission input speed n _{get is} less than / equal to a speed interval, formed from the motor speed n _mot plus a constant control deviation (offset) of, for example, 50, 100, 150 rpm. The clutch torque M _κ is then modulated so that a negative slip speed n _s = n _mo t - n _{gθt is} established at the clutch. The negative slip speed n _s according to n _s > (-) offset results from the two relationships n _gθt ≤ nm _0t + offset and n _s = n _mo t - n _gθt . Examples of the target slip speed n _s are then -50 rpm, -100 rpm, -150 rpm or further multiples of a base slip speed n _s = -50 rpm, n _s = -40 rpm or -60 rpm.

During the slip control, the clutch torque MK is modulated uniformly, as shown in FIG. 2, and there is no disengagement, i. H. the clutch torque never becomes zero. The control speed of the clutch torque is expediently reduced in order to avoid excessive modulation of the clutch torque and largely to avoid vehicle vibrations. The vehicle then rolls downhill at largely constant vehicle speed as a result of the slip control when the engine is idling and cyclical opening and closing of the clutch is largely avoided.

As an entry condition for the re-engagement when rolling downhill according to the invention, the condition of a limit value for the clutch temperature is also provided, which must not be exceeded. This limit value is, for example, 300 ° C. For this purpose, a sensor continuously measures the clutch temperature or this is calculated by the clutch control using a calculation method, which increases the more the transmitted drag torque of the engine increases.

The targeted coupling modulation to combat vehicle vibrations when rolling downhill is terminated when exit conditions are present, which will be described below.

In one embodiment, the control method according to the invention with targeted clutch modulation to combat vehicle vibrations when rolling downhill is configured as follows: In the control process, the control software initially monitors two successive events: a) disengaging without brake actuation; b) Recoupling after disengaging without increasing the engine speed. This corresponds to the driving behavior desired by the driver. The disengagement can be detected when the transmission input speed nget is less than the disengagement threshold and the change over time dnget / dt (gradient nget) is less than 0 or a negative threshold value (corresponds to nget falling) and a brake (service and / or parking brake) is not or only slightly actuated. In addition, the last two conditions can be observed over a certain speed interval: The disengagement is detected when nget of a speed, which is composed of the disengagement threshold (nausk) and an offset value (e.g. 50 rpm), falls below the disengagement threshold nausk without applying a brake (strongly). After detecting the disengagement, a flag "Motor_bremst_Fzg" is set, which is reset as soon as the driver intervenes by (more) pressing the accelerator pedal and / or the brake. If the clutch falls below the disengagement threshold, the clutch is opened according to a standard strategy. The re-engagement is determined by the transmission input speed nget exceeding the engagement threshold, with the Motor_bremst_Fzg flag still being set.

In a further embodiment, the following aspect is also required:

The downhill run will include with the brake not actuated or the accelerator pedal not actuated detected as follows: If the clutch is opened while rolling downhill, the engine speed changes compared to the gearbox speed shortly before the clutch is fully open. The gearbox speed is then greater than the engine speed, since the vehicle is accelerated downhill with the clutch open or partially open. The gearbox speed can also be greater than the engine speed by being slower than the engine speed. So there is a negative slip.

It may also be required that the transmission speed be greater than the engine speed for more than a predetermined period of time (eg 300 ms). This effect can be used as a condition for the existence of a downhill run. In contrast, when stopping in the plane, the engine speed is always greater than the transmission speed, since the vehicle slows down in the plane. In this case there is a positive hatch.

Another criterion for the presence of a downhill run is that the gear speed remains constant after the disengagement or becomes greater. Accordingly, the transmission speed or a corresponding, derived variable such as the wheel speed or the speed of the speedometer shaft is detected or the time derivative of these variables (gradient of the transmission speed, the wheel or speedometer speed) is used

In a further embodiment, it is also required that the currently transmitted clutch torque is 0.

The entry condition for re-engaging when rolling downhill is that the "Motor_bremst_Fzg" flag is set and re-engaging is recognized. In addition, a further condition may be that the clutch temperature is below a limit value of, for example, 300 ° C. If three conditions are met, a "clutch engagement when rolling downhill" flag is set in the software.

In addition, a further condition can be required that the clutch control is not in a state that is present during or shortly after a gear change.

The mode of targeted clutch modulation to combat vehicle vibrations when rolling downhill is exited, i.e. the flag "Einkuppeln_beim Bergabrollen" is reset if one or more of the following conditions is (are) fulfilled:

The brake is actuated for a time t1 of, for example, longer than 0s or 1 s (with a certain strength); the accelerator pedal is actuated by a minimum value (threshold value) greater than, for example, 0 °, preferably for longer than, for example, 0 s to 0.5 s; the transmission input speed nget is greater than a threshold of 3000 rpm, for example, for safety reasons; the transmission input speed nget is less than an idle speed offset (e.g. offset = 0 to 50 rpm) serves as protection against stalling for the engine, and the clutch temperature is greater than a threshold value of e.g. 300 ° C. Another exit condition may be requesting or recognizing a gear change.

When leaving the mode of the targeted clutch modulation to combat the vehicle vibrations when rolling downhill, the previously effective clutch control is switched over again. The transition can take place directly or after an adjustment of the target torques from the modulation when rolling downhill and the clutch control used in other driving situations (e.g. ramp-shaped).

A programmable electronic control device which has inputs which are connected to means for detecting the speed of a motor and / or a transmission and / or a speedometer shaft and / or the wheels and / or an engaged and / or an engaged gear of the transmission and which Outputs to send control signals to an electrically controllable coupling device, characterized in that the control device is connected or programmed so that each of the above control methods can be carried out.

With regard to the electronic regulating and control devices with the corresponding sensors and actuating means and with regard to the corresponding regulating and regulating methods in vehicles with automated clutches and manual transmissions, reference is made to DE 40 11 850 A1, DE 44 26 260 A1, DE 197 45 677 A1 and EP 1 010 606 A1 expressly referenced in this context, the disclosure contents of which relating to the control device and the sensors are also the content of this application.

The patent claims submitted with the application are proposals for formulation without prejudice for the achievement of further patent protection. The applicant reserves the right to claim further combinations of features previously only disclosed in the description and / or drawings. Back relationships used in subclaims indicate the further development of the subject matter of the main claim through the features of the respective subclaim; they are not to be understood as a waiver of the achievement of independent, objective protection for the combinations of features of the related subclaims.

Since the subjects of the subclaims can form their own and independent inventions with regard to the prior art on the priority date, the applicant reserves the right to make them the subject of independent claims or declarations of division. They can furthermore also contain independent inventions which have a design which is independent of the objects of the preceding subclaims.

The exemplary embodiments are not to be understood as a restriction of the invention. Rather, numerous changes and modifications are possible within the scope of the present disclosure, in particular such variants, elements and combinations and / or materials, which, for example, by combining or modifying individual ones in conjunction with and described in and in the general description and embodiments and the claims Features or elements or procedural steps contained in the drawings can be taken by a person skilled in the art with regard to the solution of the task and, by means of combinable features, lead to a new object or to new procedural steps or procedural step sequences, also insofar as they relate to manufacturing, testing and working methods.

Claims

claims

1.Control method for rolling down a vehicle with an automatically actuatable clutch, in which this driving situation is detected and the clutch is automatically opened when rolling downhill when the transmission speed falls below a presettable first value and the clutch is closed again when the transmission speed falls below a presettable second value exceeds, characterized in that the clutch is opened or closed at a speed whose amount is less than a preset value.

2. Control method according to claim 1, characterized in that a period of, for example, at least three seconds, in particular at least ten seconds, is provided for opening or closing the clutch.

3.Control procedure for rolling down a vehicle with an automatically actuatable clutch, in which the driving situation is detected and the clutch is automatically opened when rolling downhill when the transmission speed falls below a presettable first value and the clutch is closed again when the transmission speed falls below a presettable second value exceeds, characterized in that the clutch is only kept so wide open that a preset clutch torque is transmitted from the transmission to the engine.

4. Control method according to claim 3. Characterized in that the preset clutch torque corresponds essentially to 0 Nm.

5. Control method according to claim 3, characterized in that the preset clutch torque depends on the gear selected.

6. Control method according to claim 3, 4 or 5, characterized in that the preset clutch torque is chosen slightly larger than the drag torque of the engine.

7. Control method according to one of claims 3 to 6, characterized in that the clutch is opened completely when the engine speed corresponds to the idling speed.

8.Control method for rolling down a vehicle with an automatically actuatable clutch, in which the driving situation is detected and the clutch is automatically opened when rolling downhill when the transmission speed falls below a presettable first value, and the clutch is closed again when the transmission speed falls below a presettable second value exceeds, characterized in that the clutch is opened only so far that the vehicle is accelerated to a preset value.

9. Control method according to claim 8, characterized in that the acceleration is measured via the change in speed over time or is determined from the transmission speed, the wheel speed or the speed of the speedometer cable.

10.Control method for rolling down a vehicle with an automatically actuatable clutch, in which the driving situation is detected and the clutch is automatically opened when rolling downhill when the transmission speed falls below a presettable first value and the clutch is closed again when the transmission speed falls below a presettable second value exceeds, characterized in that the clutch is only opened so far that the speed of the vehicle corresponds to a preset value.

11. Control method according to claim 10, characterized in that the speed is measured via the transmission speed or determined from the wheel speed or the speed of the speedometer shaft.

12.Control method for rolling down a vehicle with an automatically actuatable clutch, in which the driving situation is detected and the clutch is automatically opened when rolling downhill when the transmission speed falls below a presettable first value and the clutch is closed again when the transmission speed falls below a presettable second value exceeds, characterized in that the clutch is only opened so far that the differential limit between gearbox speed and engine speed corresponds to a preset value (slip control).

13. Control method according to claim 12, characterized in that the preset value for the slip control is selected in a range from -40 to -100 1 / min.

14. Control method according to claim 12 or 13, characterized in that the slip control is terminated when the actuation of a brake or the accelerator pedal is detected, the transmission speed is greater than a preset safety threshold, the engine speed is less than the idle speed or the clutch temperature is greater than is a preset threshold temperature.

15. Control method according to one or more of claims 1 to 14, characterized in that the engine speed, the transmission speed, the actuation of the accelerator pedal and the brake are continuously monitored and a hill roll is determined in such a way that when disengaging and not or only slightly or slightly depressed accelerator pedal and no or only slightly or slightly actuated brake when disengaging the transmission speed is greater than the engine speed.

16. Control method according to claim 14, characterized in that a further condition for the presence of the rolling downhill is that the transmission speed remains constant after the disengagement or becomes greater.

17. Control method according to claim 14 or 15, characterized in that instead of or in addition to the transmission speed, the wheel speed, the vehicle speed or the speed of the tachometer shaft is detected to determine a rolling downhill.