DE102011105505A1 - Method for operating motor vehicle on mountain, involves capturing and utilizing road inclination to assist driver of motor vehicle in hill hold mode when accelerating or driving on mountain - Google Patents

Abstract

The method involves capturing and utilizing a road inclination to assist a driver of a motor vehicle in a hill hold mode when accelerating or driving on the mountain. A coupling torque (9) is specified with a constant value at a slope, where the size of the constant value depends on the road inclination. The clutch torque is maintained at the constant value for a limited period of time after releasing the foot brake.

Description

The invention relates to a method for operating a motor vehicle on the mountain, wherein a road inclination is detected and used to assist a driver of the motor vehicle in a Hillhold mode when starting or driving on the mountain.

From the German patent application DE 196 53 203 A1 For example, a method of preventing a vehicle from rolling backward by automatically maintaining partial engagement of the clutch while the vehicle is stopped at a grade is known. From the German patent application DE 10 2006 032 853 A1 A method for speed change control in motor vehicles is known in which a brake control unit is dependent on a current roadway inclination command for gear change control to a transmission control unit. The brake control unit also queries the transmission control unit for a momentary creep torque and, when starting, controls the release of wheel brakes as a function of this creep torque. Alternatively, the brake control unit gives the transmission control unit a desired creep torque.

The object of the invention is to further optimize the operation of a motor vehicle in a Hillhold mode when starting or driving on the mountain.

The object is in a method for operating a motor vehicle on the mountain, wherein a road inclination is detected and used to assist a driver of the motor vehicle in a hillhold mode when starting or driving on the mountain, achieved in that in hillhold mode on a slope Clutch torque is given a constant value, the size of which depends on the road inclination. Hillhold mode means mountain mode. In Hillhold mode, the driver is assisted when starting on the mountain, for example, after releasing a foot brake for some time a braking effect is maintained. Then, in automated clutch systems according to a vehicle reaction, the clutch torque can be changed, for example, to reduce unwanted rollback on the mountain. The road inclination is preferably the road inclination in the longitudinal direction. As a mountain every increase is considered. The roadway is the ground on which the motor vehicle drives. It can also be a terrain that has no roadway. According to an essential aspect of the invention, the clutch torque at the constant value is already given at the beginning of the hillhold mode, not just at the end of the hillhold mode or after. As a result, the ride comfort when starting on the mountain can be significantly improved. The inventive method is used in particular in combination with automated coupling systems.

A preferred embodiment of the method is characterized in that the clutch torque is kept at a constant value for a limited period of time after releasing a foot brake. The duration is for example a few seconds and coincides with the duration of Hillhold mode.

A further preferred embodiment of the method is characterized in that the constant value of the clutch torque in Hillhold mode is changed during operation by an adaptation. In the adaptation, for example, a rolling back of the motor vehicle is evaluated after releasing the foot brake.

A further preferred embodiment of the method is characterized in that the constant value of the clutch torque in Hillhold mode is raised / lowered by a defined amount when the motor vehicle rolls too fast forward / forward. The road inclination is taken into account. Default values for the raising or lowering of the clutch torque can be stored in a memory of a control unit.

A further preferred embodiment of the method is characterized in that the constant value of the clutch torque in Hillhold mode is lowered by a defined amount at excessive engine speed drops of the motor vehicle. The engine speed is detected, for example, with a known speed sensor device and evaluated in a corresponding control unit.

A further preferred embodiment of the method is characterized in that the clutch is controlled in Hillhold mode with a constant torque of a defined order of magnitude. The constant torque has, for example, a value of about twenty Newton meters.

A further preferred embodiment of the method is characterized in that the phase with a constant clutch torque after a defined period of time is replaced by a phase with a variable clutch torque. The variable clutch torque can be calculated according to the invention by an algorithm which provides a speed control. This mode is used to implement appropriate requirements for a defined crawl speed. At this stage, the Clutch torque for safety reasons are limited.

A further preferred embodiment of the method is characterized in that the clutch torque is lowered from the constant value to zero after a defined period of time. The lowering of the clutch torque after a defined period serves for coupling protection. This ensures that if a fault occurs in a Hillhold system, the clutch does not remain closed or applied unnecessarily long. To record the defined period, a counter can be used. The defined period is preferably such that normally no impairment is noticeable.

A further preferred embodiment of the method is characterized in that the driver of the motor vehicle is informed of a malfunction in the event of a fault before lowering the clutch torque to zero. For this purpose a pulsing of the coupling with a defined superimposition, for example with a rectangular or sinusoidal pulse, can be used.

A further preferred embodiment of the method is characterized in that an engine idle speed is raised in hillhold mode and / or in time shortly after the hillhold mode. During and after leaving the Hillhold mode can be expected with an increased load on an engine, in particular an internal combustion engine, the motor vehicle. By raising the engine idle speed, the ride comfort when starting on the mountain can be further improved.

A further preferred embodiment of the method is characterized in that a load precontrol in hillhold mode and / or in time shortly after the hillhold mode is increased. As a result, as an alternative or in addition to raising the engine idle speed, the increased load on the engine during and after leaving the hillhold mode can be taken into account.

Further advantages, features and details of the invention will become apparent from the following description in which, with reference to the drawings, various embodiments are described in detail.

The only enclosed 1 shows a Cartesian coordinate diagram in which two different torque curves are plotted over time.

1 shows a Cartesian coordinate diagram 1 with an x-axis 4 and a y-axis 5 , On the x-axis 4 the time is plotted in seconds. On the y-axis 5 is a torque in Newton meters plotted. In the Cartesian coordinate diagram 1 is the course of a motor torque 8th along with the course of a clutch torque 9 applied over time.

At a first time 11 For example, after eight seconds, a motor vehicle crawls up a hill. The engine torque 8th and the clutch torque 9 go up to a second time 12 from, for example, twelve seconds. At the second time 12 For example, a Hillhold system is activated by footbrake. The Hillhold system remains from the second time 12 until a third time 13 , for example fifteen seconds, in a Hillhold mode.

In hillhold mode, the vehicle is in a so-called hillhold phase, in which after releasing a foot brake by the driver on the slope of the mountain, the braking force is maintained. In this case, according to an essential aspect of the invention, the clutch torque 9 set to a defined but constant value.

The value of this constant torque is dependent on the slope or slope. The slope or slope of the road can be detected, for example, by a tilt sensor. It is also conceivable to calculate the slope by a mathematical algorithm.

In Hillhold mode between times 12 and 13 In accordance with the method according to the invention, a constant torque of approximately twenty Newton meters is activated at the clutch. At the time 13 the Hillhold system is disabled. Due to the increased clutch torque, the vehicle does not roll back. After the time 13 is switched to the mode with variable clutch torque (speed control).

According to a further aspect of the invention, the constant torque on the clutch when driving on the mountain is changed by an adaptation during operation. In the adaptation, for example, rolling back or forward rolling of the vehicle is evaluated after releasing the foot brake on the mountain.

If the rollback is too strong, the constant clutch torque in the hillhold phase is increased by a defined amount. If too much forward rolling takes place, the constant clutch torque in the hillhold phase is reduced by a defined amount. Similarly, at too high engine speed drops during the Hillhold phase lowered the predetermined constant clutch torque by a defined amount.

To ensure that in an error in Hillhold system, the clutch is not unnecessarily long or remains closed, according to a further aspect of the invention, a counter is installed in the motor vehicle, which reduces the constant clutch torque to zero after a defined time. The period of time is preferably such that normally no impairment is noticeable. According to a further aspect, in the case of an error, before the constant coupling torque is reduced, the driver is informed of a malfunction, for example by a pulse of the clutch with a defined superimposition (rectangle or sine).

During and after leaving the Hillhold mode can be expected with increased load of an internal combustion engine of the motor vehicle. Therefore, it makes sense to raise the engine idle speed during the hillhold phase or shortly thereafter or to prepare the engine for the increased load, for example by increasing the load precontrol.

LIST OF REFERENCE NUMBERS

1

Cartesian coordinate diagram

4

X axis

5

y-axis

8th

engine torque

9

clutch torque

11

time

12

time

13

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 19653203 A1 [0002]
• DE 102006032853 A1 [0002]

Claims (10)

A method for operating a motor vehicle on a mountain, wherein a road inclination is detected and used to assist a driver of the motor vehicle in a hillhold mode when starting or driving on the mountain, characterized in that in Hillhold mode on a slope a clutch torque ( 9 ) is given with a constant value whose size depends on the road inclination. Method according to claim 1, characterized in that the clutch torque ( 9 ) is held at a constant value for a limited period of time after releasing a foot brake. Method according to one of the preceding claims, characterized in that the constant value of the clutch torque ( 9 ) is changed in the Hillhold mode during operation by an adaptation. Method according to one of the preceding claims, characterized in that the constant value of the clutch torque ( 9 ) is raised / lowered by a defined amount in Hillhold mode when the vehicle rolls too fast forward / forward. Method according to one of the preceding claims, characterized in that the constant value of the clutch torque ( 9 ) is lowered by a defined amount in Hillhold mode at excessive engine speed drops of the motor vehicle. Method according to one of the preceding claims, characterized in that the clutch is driven in Hillhold mode with a constant torque in the order of 20 Newton meters. Method according to one of the preceding claims, characterized in that the phase with a constant clutch torque after a defined period of time is replaced by a phase with a variable clutch torque. Method according to one of the preceding claims, characterized in that the phase are calculated with a variable clutch torque by an algorithm which provides a speed control. Method according to one of the preceding claims, characterized in that the clutch torque ( 9 ) is lowered from the constant value to zero after a defined period of time. A method according to claim 7, characterized in that the driver of the motor vehicle before lowering the clutch torque ( 9 ) is pointed to zero in case of error on a malfunction.

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