DE19849494C1 - Method of setting speed of motor vehicle when almost stationary involves maintaining any movement opposite to desired direction with speed limited to maximum value greater than zero - Google Patents

Abstract

The method involves determining the desired direction of motion (Rsoll) of the vehicle set via the gearbox; determining the current actual direction (Rist) of motion; comparing them; if there is a directional discrepancy, maintaining the movement opposite to the desired direction whereby the speed (Vist) is limited to a maximum value greater than zero. An Independent claim is also included for a control arrangement for a vehicle when almost stationary.

Description

The invention relates to a method and a control unit direction for setting the speed of a motor vehicle 11 near-standstill according to claim 1 or 11.

It is already known from the publication DE 196 11 360 C2 become a brake system of a motor vehicle in silence to automatically operate standing phases for safety reasons, to prevent the vehicle from accidentally rolling away. This is to ensure that the stationary drive testifies with the engine running, for example when stopping at sloping lane stops without accidentally getting in To set movement and in this way a dangerous situation to create.

So that the vehicle's brake system is actuated automatically, Several conditions must be met cumulatively, which from On output signals, which are obtained from sensors, in one Control device can be formulated and checked. It will checks whether the vehicle is at a standstill, whether it is in use of an automatic transmission the selection level for forward travel, for Reverse or idle whether the engine runs and whether the brake system is already operated by the driver becomes. If all of these conditions exist, the braking system automatically applied a high brake pressure, the one prevents the vehicle from accidentally rolling away.

From the document DE 29 11 372 C1 it is known for one  Stop applying the brakes on the slope and release them again, so soon the vehicle has come to a standstill. The vehicle starts again after releasing the brakes, wor then the brake is automatically applied again.

The publication DE 196 54 670 A1 deals with a method for Controlling the reverse lock of an automatic transmission. The current direction of travel is evaluated and the vehicle is by adjusting the engine speed while rolling back in the Slope prevented.

Furthermore, DE 196 48 559 A1 describes a downhill Speed controller known, in addition to the engine power also use the service brake to set the speed is pulled.

Based on this prior art, the invention is Problem, safety when the vehicle is at a standstill or Increase almost standstill while the engine is still running.

This problem is solved according to the invention with the features of the Proverbs 1 and 11 solved.

According to the innovation, the vehicle is allowed to be at slow speed that is less than or equal to is a predetermined, maximum permissible maximum value the desired direction of movement - the target Direction of movement - moved. For example, the vehicle with forward gear engaged with a maximum of one of the maximum value roll backwards at the appropriate speed. In correspond Conversely, in the opposite case, it is allowed that Vehicle with reverse gear engaged with the permissible Ge speed rolls forward. As a result, at ab sloping lane the vehicle without driver intervention does not come to a standstill, but moves slowly speed against the set direction of movement moved. Forces and moments opposing the actual movement te, for example motor drive torques that are conventional Operating mode can cancel the slope downforce, so that the vehicle does not roll even when the road is inclined advises are manipulated so that the vehicle is low compliant movement against the target direction of movement.

The driver is due to the unintentional and not by him intentionally induced vehicle movement to concentration forced to handle his vehicle so that an ir Leading feeling of security, which changes when the Can adjust vehicle is avoided. The driver is ge forced to pay attention to the vehicle and Take action that continues movement of the Vehicle against the desired direction of movement  other. These measures are in particular actuating the hard parking brake, operating the wheel brake or operating the accelerator dals to increase the motor drive torque.

The driver's active active action helps prevent that if the engine stops or dies, the Han output suddenly opposing engine drive torque falls and a previously stationary vehicle unexpectedly gets into Movement sets. Situations in which the driver is at a standstill vehicle, but the engine is running for a short time leaves are prevented.

In the vehicle, the actual actual direction of movement is that Desired direction of movement and the absolute value of the drive tool speed determined. Is the actual Direction of movement does not match the target direction of movement, so is the case that the vehicle due to an external embossed forces, such as downhill forces the set direction of movement is moved. In this Case, the actual direction of movement is maintained according to the invention and just ensured that the vehicle speed is less than or equal to a predeterminable maximum value. About the Specifying the maximum value ensures that the vehicle move very slowly without conscious driver intervention can, so that no dangerous situation can arise and the Driver sufficient time is available, measures to Ver hindrance to the direction of the desired movement To seize vehicle movement.

In an expedient further development, the road slope is determined and the increase in vehicle speed in actual Direction of movement calculated depending on the slope of the road, to delay especially in the case of high road gradients realized, braked increase in vehicle speed and give the driver enough time for the  To initiate countermeasures. The duration of the ge slowed speed increase can be predetermined, mathematically determined or read from a map. After Ab There is an unbraked speed over the period rose until the maximum was reached. But there may be should also be appropriate, the speed increase without time limit until the speed is reached To be carried out with maximum braking, or else in a wide range ren appropriate execution, first the speed rose unrestrained and the time interval with the ge slowed speed increase in the range of the maximum value to move, so that first a steeper and then a flatter increase in speed results.

There can also be a maximum total taxiway to the wrong one Direction can be specified after the vehicle is forcibly is braked, for example by braking and connecting inserting the parking lock; the driver then needs a new one execute start.

The manipulation of the vehicle speed, especially the Limitation to the permissible maximum value can be different Way. The wheel brakes are preferably applied and / or manipulated the engine drive torque and / or the Mo ment transmission in the drive train of the vehicle influences, being a combination of engaging the wheel brakes and Stei reduction of the motor drive torque advantageous only for one be limited, predeterminable period of time may be increased brake wear or overheating of the torque wall avoid overexertion.

The maximum allowed vehicle speed is chosen advantageously small enough that a average driver response time enough time is available for the change from brake pedal to accelerator pedal.  Especially in connection with a braked speed This increases the driver's panic reaction avoided.

A maximum value for that distance is preferred ben, the vehicle regardless of external embossed forces ten, in particular regardless of that due to the road gradient caused downhill force, against the target Maximum direction of movement. This will si made that the vehicle slowed even or lack of driver response just a short distance can travel in the wrong direction, so the The emergence of a dangerous situation is practically impossible is.

The control device that is useful for performing the Procedure is used, controls or regulates the vehicle speed to the specified or determined maximum value, by generating a control signal from input signals, wel ches a vehicle composition influencing the speed can be fed. As input signals are via sensors the actual vehicle speed and the actual Direction of movement determined, for example via sensors Anti-lock braking system and / or a traction control system, so that no additional measurement effort is required. As further input signal is in the control device Target movement direction processed in the vehicle transmission is set and for example via a transmission control or a gearbox detection is determined. From the one gating signals according to the above-described regulation Control signal for setting and limiting vehicle movement generated.

Further advantages and practical embodiments are the further claims, the description of the figures and the drawing  conditions. Show it:

Fig. 1 is a schematic representation of a Brennkraftmaschi ne with automatic transmission and control device for setting the vehicle speed,

Fig. 2 is a flowchart of a method for speed adjustment.

Referring to FIG. 1, the Mo generated in the internal combustion engine 1 tor driving torque is transmitted via a drive train 2 to the wheels 3, 4. The drive train 2 comprises a transmission 5 which, in the exemplary embodiment shown, leads out as an automatic transmission, the transmission position being predetermined by the driver via a selector lever 7 . The engine speed of the internal combustion engine 1 is set via an accelerator pedal 8 , the pedal movement of which is indirectly transmitted via an E-gas 6 to a throttle valve of the internal combustion engine.

The vehicle control is designed as a drive-by-wire function. Adjustment movements of the accelerator pedal and the selector lever exercised by the driver are transmitted as input signals via signal lines 9 , 10 to a control device 11 , in which steep signals are generated and are fed via a further signal line 12 to engine electronics 13 . The control signals who prepared the in the engine electronics 13 for the e-gas 6 and supplied to the e-gas 6 via a signal line 14 .

The control device 11 communicates via further signal lines 15 , 16 with an ignition lock 17 for starting and starting the internal combustion engine, and with a control unit 18 which contains an anti-lock braking system and a traction control system and via signal lines 19 , 20 the wheel speed sensors 21 , 22 measured wheel speeds of the wheels 3 , 4 can be supplied as input signals.

The process sequence for setting the speed when the vehicle is almost at a standstill in accordance with a “quasi-hill holder” function or a “quasi roll-off preventer” is shown in FIG. 2 as a flow chart. In a first step 101 it is checked whether the actual direction of movement of the vehicle - the actual direction of movement of the vehicle - matches the target direction of movement - the direction of movement set in the transmission. Such a situation, in which the vehicle is moving against the set direction of movement, can occur after braking on a gradual road, if the speed is reduced to a standstill of the vehicle, but the vehicle under the influence of downhill force or other external factors Forces slowly rolling back.

The signal R _ist representing the actual direction of movement _is generated in a wheel speed sensor assigned to the anti-lock system, which, in addition to the wheel speed from which the vehicle speed is determined, also supplies information about the direction of movement - forwards or backwards. The signal R _soll representing the target direction of movement is taken from a control module or a sensor assigned to the gearbox to detect the gearbox state.

According to step 101 of the control device, is checked in a comparison unit whether the directions of movement representing signals R and _{R should} coincide. If this is the case, then there is no situation that requires intervention by the control device; it can return to the starting point and be checked again at regular intervals.

If the signals R and _{R should} not match, a control signal S _St in step 102 generates, that _is v as a function of actual vehicle speed, the target speed v _soll and optionally the beginning of the stoppage of the vehicle elapsed time t, and other parameters or state variables is determined. The control signal S _St is expediently formed in accordance with a predetermined control law, wherein a control difference, which is formed from the difference between the actual and target speed and has a significant influence on the control signal, is differentiated, integrated and / or subjected to a constant factor.

The actual vehicle speed v _{ist is} determined from the signals of the wheel speed sensors. The target speed _is v t may depend on the beginning of the stoppage of the vehicle elapsed time and in a characteristic of the controller box and be stored in accordance ei ner writing in a calculation unit stored Berechnungsvor be determined. In principle, any manipulation of the setpoint is possible; in particular, a degressi ver, but also a progressive course up to a given maximum value can be realized.

As a further dependency, a maximum distance can be taken into account that the vehicle can travel against the target direction of movement. For this purpose, the distance traveled in the opposite direction since the vehicle came to a standstill is determined and compared with a permissible maximum value for this distance. If the distance covered reaches the permissible maximum value, the control signal S _{St is set} to a value that brakes the vehicle to a standstill. This value can remain suppressed as long as the brake pedal is pressed by the driver at the same time.

The target velocity v _soll is in any case greater than the given maximum value of the velocity, which is small enough to give rise to no danger situation during movement of the vehicle and towards the set movement direction.

The point in time at which the vehicle comes to a standstill is expediently determined, for example by the fact that the wheel speed sensors do not deliver any signals or the signal value zero. The time elapsed since the standstill is relevant with regard to the calculation of the target speed or the control signal S _St. The time of the standstill, together with the information that the vehicle is moving against the required direction of movement, is used as the starting point of the function calculation.

The control signal S _St generated in step 102 is optionally supplied to the brake shown in step 103 , in particular the wheel brake, the motor shown in step 104 and / or the drive train shown in step 105 for setting the current speed to the desired speed. In the wheel brake, the braking force acting on the vehicle is increased or decreased, in the engine the engine drive torque is increased or decreased by adjusting the engine speed and in the drive train the drive torque to be transmitted to the wheels is adjustable by releasing or closing clutches, torque converters or the like enlarged or reduced.

When rolling in the wrong direction, the driving torque and Braking torque always in the same direction; support them each other. When the accelerator pedal is pressed, the Propulsion management a smooth transition from the rolling motion in the wrong direction towards the desired direction of travel posed by the influencing torques continuously to be changed. This also applies analogously to the superimposed one Effect of the service brake via the brake pedal.

The method and the control device can both  Vehicles with automatic transmissions as well as vehicles with Manual transmissions are used.

Claims (19)

1. Method for adjusting the speed of a motor vehicle at near standstill, wherein

• 1. the target direction of movement (R target) set via the gearbox ( 5 ) of the motor vehicle _is determined,
• 2. the actual actual direction of movement _(R) is determined of the vehicle,
• 3. the actual direction of movement (R _ist ) is compared with the target direction of movement (R _soll ),
• 4. If the actual direction of movement (R _ist ) deviates from the target direction of movement (R _soll ), the movement of the vehicle against the target direction of movement (R _soll ) is maintained, the vehicle speed (v _ist ) being limited to a maximum value , which is set to a value greater than zero.

2. The method according to claim 1, characterized in that the road inclination is determined and the increase in vehicle speed (v _ist ) in the actual direction of movement (R _ist ) _is calculated as a function of the road inclination. 3. The method according to claim 1 or 2, characterized in that the increase in vehicle speed (v _ist ) in the actual direction of movement (R _ist ) _is braked for a given period. 4. The method according to any one of claims 1 to 3, characterized in that a brake intervention to limit the vehicle speed (v _ist ) is carried out to the maximum value. 5. The method according to any one of claims 1 to 4, characterized in that the (R _to) the vehicle in the desired direction of motion be impacting drive torque is influenced. 6. The method according to claim 5, characterized, that the engine speed is affected. 7. The method according to claim 5 or 6, characterized in that in the drive train ( 2 ) of the motor vehicle, the torque transmission between the engine ( 1 ) and wheels ( 3 , 4 ) is influenced. 8. The method according to claim 7, characterized, that when using an automatic transmission in addition to another gear step is engaged.   9. The method according to claims 4, 5 and 6, characterized, that a simultaneous brake intervention and an Er increase in engine speed only for a limited period of time is maintained. 10. A method according to any one of claims 1 to 9, characterized in that a maximum value for the ke _(to R) of the vehicle opposite to the direction of movement ge desired target distance Wegstrec be predetermined. 11. Control device for a motor vehicle in near standstill, in particular control device for performing the method according to one of claims 1 to 10, with the following features:

• a) there are sensors for determining the vehicle speed (v _ist ), the desired direction of movement (R _soll ) set in the transmission ( 5 ) and the actual actual direction of movement (R _ist );
• b) the signals picked up by the sensors (v _ist , R _ist , R _soll ) can be fed as input signals to the control device ( 11 ), with control signals (S _St ) in the control device ( 11 ) depending on the input signals for influencing the vehicle speed ( v _is ) can be generated;
• c) the signal representing the actual direction of movement (R _ist ) and the signal representing the desired direction of movement (R _soll ) can be fed to a comparison unit in the control device ( 11 );
• d) in the event of a deviation of these signals, the signal representing the vehicle speed (v _ist ) can be fed to a comparison unit and can be compared with a maximum value, an actuating signal (S _St ) to limit the vehicle speed (v _ist ) can be generated to the maximum value.

12. Control device according to claim 11, characterized in that an inclination sensor is provided for generating a signal representing the road tendency and, depending on this signal, the control signal (S _St ) influencing the vehicle speed (v _ist ) can be manipulated such that the increase the vehicle speed (v _ist ) is reduced. 13. Control device according to claim 11 or 12, characterized in that the sensor for determining the vehicle speed (v _is ) is part of an anti-lock braking system or an on-slip control. 14. Control device according to one of claims 11 to 13, characterized in that the control signal (S _St ) influencing the vehicle speed (v _is ) can be fed to a brake system for setting the brake pressure. 15. Control device according to one of claims 11 to 14, characterized in that the control signal (S _St ) influencing the vehicle speed (v _is ) can be fed to the engine control ( 13 ) for setting the engine speed. 16. A control apparatus according to any one of claims 11 to 15, characterized in that the vehicle speed (v _ist) influencing the control signal _(R) of the control of the transmission (5) to the SET of the torque transmission between the motor lung (1) and wheels (3, 4 ) can be fed. 17. Control device according to claim 11 and 12, characterized in that the feedforward control also the weight of the vehicle, for. B. on the air spring pressure, is considered as an influencing variable for the control signal (S _St ). 18. Control device according to one of claims 11 to 17, characterized, that only a limited maximum taxiway in the wrong direction approved and that the vehicle is then fixed brakes and is permanently locked, which may be a subsequent restart by the driver can. 19. Control device according to one of claims 11 to 18, characterized, that when you press the accelerator or brake pedal continuously che torque transitions are created.