DE19926697B4 - Method for increasing the operational safety of a motor vehicle equipped with an automated clutch - Google Patents

Abstract

A method for controlling a motor vehicle whose drive train connecting the engine (1) to the drive wheels contains a friction clutch (3) that automatically disconnects the drive train, the method on the one hand preventing the motor vehicle from starting when it is not ready to drive due to the motor drive, whereby to determine the not In the ready-to-drive state, a sensor (45) is provided which responds to the actuation of a brake pedal, and the non-ready-to-drive state is present when the brake pedal is not actuated, with the friction clutch (3) switched to disconnection and the running engine (1) when the vehicle is stationary. the vehicle is not ready to drive, a drive of the vehicle by the engine (1) is prevented by shifting a transmission (5) contained in the drive train into a neutral state, characterized in that the method, on the other hand, when the vehicle is stationary, the friction clutch ( 3) with the engine running be (5) switches to neutral and the clutch (3) closes if, since the vehicle came to a standstill, there has been a ...

Description

The invention relates to a method for controlling a motor vehicle whose drive train connecting the engine to the drive wheels contains a friction clutch automatically separating the drive train and optionally an automated multi-speed transmission, in particular an automated transmission, whereby when the vehicle is in a non-running state , a departure of the vehicle is prevented.

A device of this kind is in the DE 197 43 674 A1 known. If, with the ignition off, ie the engine stopped, and the control unit of an automated transmission and an automated clutch switched off, a driver's activity, e.g. As a brake operation is detected, the control unit is activated, for example, to disengage the clutch and to be able to switch the transmission immediately to restart. When the ignition is switched off and thus the engine is stopped and the gear engaged, the previously opened clutch can be automatically closed to prevent rolling.

A method according to the preamble of claim 1 is known from DE 39 18 428 A1 known.

Other methods for increasing the reliability of a motor vehicle are from the DE 20 45 423 A1 and the DE 197 10 975 A1 known.

A method for determining the gripping point of a clutch is known from DE 44 26 260 A1 known.

Further, a vehicle has become known in which, when the engine is running, a gear is engaged and with the clutch open within a predetermined period of time, the foot brake has not been operated, the engine is turned off.

Increasingly, motor vehicles between the engine and the transmission are being equipped with an automatically separating friction clutch. These are single-disc or multi-disc dry clutches, which are opened and closed by means of an approximately electric or hydraulic actuator in accordance with clutch control signals of a central control unit. The control unit again automatically generates the clutch control signals programmatically or by signals input by the driver.

The automated transmission may be an automatic planetary gear automatic transmission with brake clutches or a countershaft transmission with several gears to be engaged via synchronizers, which are switched by electric or hydraulic actuators in accordance with transmission control signals of the control unit. The control unit generates the transmission control signals either automatically programmatically or by signals input by the driver.

If an automatically separating friction clutch is kept in the disengaged state by the actuator for a long time with the engine running, there is a risk that the control unit, sensors connected to it, such as current and / or position detection, signal transmission, actuator fault or the power transmission from the actuator to the clutch or the like., The clutch unintentionally engages slowly and the vehicle begins to roll, which is particularly dangerous if the driver has left the vehicle with the engine running.

Such an undesired torque transmission can also occur in the event of failure of the hydraulic unit, such as pressure supply, supply lines, valves; in case of failure of the control unit, such as valve control, control of the hydraulic pump with hydraulic actuator, motor control with electromechanical actuator.

In hydraulic power transmission between the actuator and the clutch with master cylinder and slave cylinder a compensation hole is usually provided in the region of the master cylinder piston, which is released when the clutch is not actuated by the piston and a compensation of the trapped between master cylinder and slave hydraulic fluid in a surge tank allowed.

The hydraulic medium between the master and slave cylinders is subject to temperature-dependent volume changes. When the compensation hole is closed then there is a change in position of the clutch. If a position sensor fed back to the control unit is arranged on the master cylinder, then it can not recognize this change, since only the slave cylinder moves.

With disengaged clutch and pressurized hydraulic fluid can escape due to manufacturing tolerances hydraulic medium past the seal of the master cylinder in the balancing bore, so that the volume of the hydraulic medium is lower and changes the position of the clutch. When integrated with the actuator donor or slave cylinder, the reverse may occur, namely that the trapped between master cylinder and slave cylinder volume increases.

As a result, the case may arise that the position sensor arranged on the master cylinder Output signal that does not correspond to the actual clutch position and then by overpressure the release system and / or the clutch is damaged. Furthermore, it may happen that the clutch unintentionally partially engages and then the gear can no longer properly insert or even the vehicle anfährt unintentionally.

A critical situation may arise when the driver leaves the vehicle with the engine running and about reverse gear engaged and he or another driver later wants to get back in and drive off. Likewise, he could inadvertently signal a driving request, for example by accelerating or releasing the brake, so that the vehicle then moves inadvertently or in an undesired direction.

Another critical situation may arise when the bonnet is opened while the engine is running and gear engaged to perform engine maintenance. The person working in front of the vehicle could signal a driving request by actuating the accelerator pedal linkage so that the vehicle unintentionally starts moving and endangers the person.

Another critical situation may arise when the vehicle is parked on a slope with not or not sufficiently tightened handbrake and running engine and the vehicle is inadvertently set in motion after leaving the driver.

If the automated clutch is operable in a partially engaged state in a creep mode, the creep mode may respond only after a certain time delay after switching on, if the clutch is engaged very slowly. This can not be ruled out by accidentally switching on the crawl mode, leaving the vehicle and only after leaving the vehicle does the creep mode begin to operate and the vehicle unintentionally starts.

The object of the invention is therefore to prevent further critical situations in an equipped with an automated friction clutch motor vehicle with the engine running even when unintentionally engaging clutch.

The object is achieved by a method according to claim 1. Further advantageous embodiments are the subject of the dependent claims.

According to the invention, the coupling is closed in order to be able to carry out the compensation of the hydraulic medium, for example in hydraulic systems with displacement sensing on the master cylinder.

The method according to the invention is carried out by a control device of the motor vehicle.

Preferably, the controller turns on the neutral state only after lapse of a predetermined period of time since the beginning of the non-running state, to prevent too frequent switching to the neutral state. The time span can be in the range of about 10 seconds.

In order not to irritate the driver, it is preferable for the time of Gangauslegens no change of the indicated by the selector lever position or an additional display gangs, d. H. it remains the last engaged gear in the display.

With the engine running and the gearbox automatically switched to the neutral state, the clutch can be closed again to equalize the hydraulic fluid between the master and slave cylinders. It is also possible to leave the clutch open and to close the clutch for a short time, about 6 seconds, at regular intervals, say every 2 minutes, especially when the vehicle is equipped with a dual mass flywheel. As a result, an idling rattle of dual mass flywheel and clutch can effectively suppress. Furthermore, shortens the time to re-gear, since then the transmission shaft is and no longer needs to be synchronized.

To determine the non-ready state, a sensor may be provided which is responsive to the opening state of a hood and / or door of the vehicle, the control device only in open hood and / or door, the transmission switches to the neutral state. The door may be the driver or passenger door, or a loading door of a delivery van. The layout of the gear in the neutral state can also take place when the door is closed again with the engine running, because then it is not clear whether the driver has actually left the vehicle.

To detect the door operation can be used in any case already existing door contact switch for the interior lighting.

If the hood is around the hood of the vehicle, a special hood contact is required to be able to sense the opening of the hood. This should be redundant to detect a failure of a contact and / or to distinguish an open hood from a not completely locked or closed hood. Different signals from both contacts could be used, the Gangauslegen not or at least with to activate changed times or / and to allow start-up until the gear is laid out. Here, for safety reasons with the bonnet open, the transmission can be switched to the neutral state without delay.

If the bonnet contact, for reasons of cost, is not redundant, the starting should only after a predetermined time, eg. B. 5 seconds can be prevented so that the vehicle remains mobile, for example, in case of failure of the hood signal, in which an open bonnet is permanently displayed. By visual or / and audible warning can be announced in the absence of driver activity imminent start-up prevention.

In the presence of the conditions for gear interpretation in the neutral state, after a predetermined time, for. B. a second, the driver to be notified by an optical or acoustic signal to the imminent laying out. The warning can remain active even after completed gear interpretation in the neutral state or be switched off completely or partially.

Regardless of the safety function, a visual and / or audible warning can always be given with the engine running and the door open.

A new gear should be able to be re-engaged only after the driver has moved the selector lever to the neutral position to ensure that it has actually detected the existing neutral condition of the gearbox.

In certain countries, there may be a requirement that the driver in an emergency situation can drive away even when the driver's door is open, for example, if he is asked under pressure of physical violence to leave the vehicle to steal the vehicle (criminal attack). For this purpose, the control device with the driver's door open without any delay engage a gear when a driving control of the vehicle, in particular the accelerator pedal is pressed. By pressing the accelerator pedal, the driver can immediately take flight with his vehicle, without having to laboriously engage a gear.

Another way to determine the non-ready state is to additionally provide a sensor that responds to the occupancy of the driver's seat, so that the controller switches only when not occupied driver's seat, the transmission in the neutral state. In this case, there is the possibility that when the seat contact is reactivated and the door closed again, the last used gear is automatically re-inserted.

When the clutch is hydraulically operated, it is possible for the control device to shift the transmission to the neutral state when the vehicle is not running when the temperature of the hydraulic fluid exceeds a predetermined maximum temperature or a change in temperature of the hydraulic fluid exceeds a predetermined maximum temperature change. This prevents that by temperature-induced increase in volume of the hydraulic fluid, the opened clutch gradually closes again and the vehicle begins to roll.

In this case, in the case of a non-running vehicle and switching to the neutral state, the clutch is closed for a short time due to increased hydraulic temperature or change, and then disconnected again in order to allow compensation of the hydraulic fluid volume through the compensation bore. The threshold values of the temperature change are then chosen so that, on the one hand, no overpressing of the coupling takes place and, on the other hand, the coupling still reliably separates.

As part of the remaining path of the master cylinder can be a correction of the transmission characteristic of the clutch via the temperature change, z. B. in the form of a shift of the coupling engagement point or the positions for the end positions, as long as the mentioned threshold values of the temperature change were not reached, provided that the clutch position sensor is provided on the master cylinder.

In a hydraulic actuation of the clutch, it may be necessary to move the master cylinder piston in the disengaged position to a stop to reduce the pump duty cycle of the hydraulic unit, so that the coupling valve can leave the blocking area and leakage can be prevented. If the minimization of leakage takes precedence over the temperature compensation - this decision can be made by the ambient temperature of the hydraulic power unit or of the motor driving the pump - the clutch position to be adjusted can not be corrected until the stop has been re-written. As a result, another threshold for the permissible temperature increase may be necessary.

To detect the temperature change of the hydraulic fluid, a temperature sensor is required. In this case, the temperature should be measured as close as possible to the main volume of the enclosed hydraulic medium, for example by a separate temperature sensor. For the sake of simplicity, it is also possible to use an ambient air temperature sensor or intake air temperature sensor which is generally present anyway. whose values are exchanged via a data interface between engine and transmission control unit.

The temperature can also be determined from a change in resistance of one of the connected solenoid valves. Since the flow through the valve must be set very accurately to control the hydraulic pressure or the flow rate of a valve, this setting is made via a current control. Here, the actual current is measured and compared with a target current value. In adaptation of the control deviation, the drive signal is adjusted so that the control deviation becomes zero. From the drive signal for a constant current, the resistance of the magnetic coil can now be calculated, and it can be concluded from the known nominal resistance and the likewise known temperature coefficient of the coil material to the temperature of the valve. If the nominal resistance is subject to large tolerances and a more accurate absolute temperature detection is necessary, it may be necessary to introduce the nominal resistance at the end of the production line.

The invention will now be explained by means of embodiments with reference to the accompanying drawings.

1 shows a first embodiment with automated hydraulic actuation of the clutch and transmission;

1A shows a clutch master cylinder with position sensor in 1 shown hydraulic unit 11 ;

2 shows a second embodiment similar 1 but with a position sensor arranged on the clutch slave cylinder;

3 shows a third embodiment with automated electromechanical actuation of the clutch and transmission; and

First, a first execution based on the 1 explained. An engine 1 to drive a motor vehicle is via a single or multi-plate friction clutch 3 , optionally in combination with a dual-mass flywheel, and a multi-speed manual transmission 5 connected to not shown wheels of the vehicle. The coupling 3 and the gearbox 5 are in accordance with control signals of a common central electronic control unit 7 automated, ie programmatically or in response to operator signals, operated.

For controlling the clutch 3 is the control unit 7 via a signal line 9 with a hydraulic unit 11 connected. The hydraulic unit 11 includes a motor-operated hydraulic oil pump, electromagnetic control and switching valves, an oil reservoir (not shown) and an integrated clutch master cylinder 13 with reservoir 15 as detailed in 1A shown. The master cylinder 13 limited with a piston 17 a working chamber 19 over a line 21 with a slave cylinder 23 mechanically connected via a release (not shown) of the clutch 3 connected is. By pressure supply from the hydraulic pump of the hydraulic unit 11 over the line 25 the piston moves 17 according to

1A to the right while reducing the volume of the working chamber 19 , against the force of one in the working chamber 19 attached compression spring 27 to go over the line 21 and the slave cylinder 23 the coupling 3 to open and thereby a torque transmission from the engine 1 to the gearbox 5 completely prevent. Without pressure supply from the oil pump of the hydraulic unit 11 the piston moves 17 by pressure of a clutch release spring and the compression spring 27 according to 1A to the left and gives a radial bore 29 free in the cylinder wall, which is the working space 19 with the expansion tank 15 combines. Here is the clutch 3 indented. During the disengagement movement to open the clutch 3 according to 1A to the right the piston locks 17 the hole 29 and allows a pressure build-up between the master and slave cylinders 13 . 23 , The piston 17 is with a position sensor 31 connected, the longitudinal position of the master piston 17 determined, which is used as a measure of the respective coupling position. The position sensor 31 is via a signal line 33 to the control unit 7 fed back.

The hydraulic unit 11 is also via transmission control lines 35 hydraulically with a selector cylinder 37 and a shift cylinder 39 connected to in response to corresponding signals of the control unit 7 The gear 5 - Here in the form of a synchronized multi-shaft transmission - to be able to switch between multiple forward speeds, a reverse gear and a neutral stage. The control unit 7 receives - except from the position sensor 31 - Signals from an engine ignition switch 41 , a gear lever 43 , a brake pedal position sensor 45 , an accelerator pedal position sensor 47 , one in the transmission 5 provided gear recognition sensor 49 , a transmission speed sensor 51 , Wheel speed sensors 53 and of the shift and the dial cylinder 37 . 39 assigned position sensors 37a . 39a ,

Further, the control unit 7 via a data bus line with a motor control unit 55 of the motor 1 connected, and outputs signals to one diagnostic switch 57 and an audible or visual warning buzzer 59 ,

The operation of the execution is as follows:
When the engine is running 1 the wheel speed sensors 53 indicate that the vehicle is stationary, the brake pedal sensor 45 indicates a non-operation of the foot brake, the gear selector lever 43 is engaged in a forward or reverse gear, the clutch position sensor 31 indicates that the clutch 3 is closed and since the beginning of the existence of all the above conditions, a first predetermined waiting time - here about 3 seconds - has expired, gives the control unit 7 via the warning buzzer 59 an acoustic warning signal.

By brake application and a corresponding signal from the brake pedal sensor 45 the warning signal is ended.

After expiration of a second waiting time since the beginning of the above conditions, which is longer than the first waiting time, here about 10 seconds, gives the control unit 7 to the hydraulic unit 11 a transmission control signal to enable it via the hydraulic lines 35 and the control and dial cylinders 37 . 39 The gear 5 is set to neutral, with the selector lever remains in the previously set position, a gear position display, not shown, but switched to "neutral".

Then there is the control unit 7 to the hydraulic unit 11 a clutch control signal, so that these on the master cylinder 13 , The administration 21 and the slave cylinder 23 the coupling 5 engages, causing the master piston 17 the hole 29 releases and the working chamber 19 with the expansion tank 15 is connected.

By switching the gearbox 5 to neutral, whereby the transmission input shaft is decoupled from the transmission output shaft, the driving force transmission from the engine 1 inevitably interrupted on the wheels, so that unintentional driving off of the vehicle is reliably prevented. This in turn opens up the possibility of the clutch 3 close and relieve the hydraulic system between the master cylinder and slave cylinder. A slight pressure leakage between master piston 17 and master cylinder 13 to the expansion tank 15 There is no consequences, ie the clutch 3 can not accidentally engage and the vehicle can not roll off.

The warning by the warning device 59 remains in effect until the footbrake is applied or the selector lever is set to neutral.

If the driver steps on the brake, the clutch opens 5 , and the previously engaged gear is engaged again and the warning is switched off. Just by pressing the accelerator pedal you can immediately start again without any further operating steps.

In addition, the system may be designed so that after switching to neutral and closing the clutch 5 After a further waiting time, the engine 1 parked and the first gear is not set to secure the vehicle from rolling away. By brake operation, the clutch 5 open and the engine 1 started again.

It is also possible to use the control unit 7 with a door opening sensor 61 , a seat occupancy sensor 62 and / or a hood opening sensor 63 connect to. When the engine is running 1 , standing vehicle, gear engaged and non-actuation of the gas and brake the driver's or loading door and / or the bonnet of the vehicle is opened or the driver leaves the seat, after a first waiting -. B. 3 seconds - first issued a warning signal, and after another waiting time, the transmission 5 set to neutral and the clutch 3 indented. This prevents the vehicle from starting when the driver has left the vehicle, for example through the driver's door or a loading door, or the bonnet has been opened for maintenance purposes.

Another option is the control unit 7 with a temperature sensor 65 To connect, as a separate sensor in the area of the hydraulic system between clutch master and slave cylinder 13 . 23 is arranged or the temperature of the ambient or intake air to the engine measures to a strong temperature change in the hydraulic system between the clutch and slave cylinder 13 . 23 to be able to measure. When the engine is running 1 , stationary vehicle, engaged gear and not actuated accelerator pedal and brake not actuated the sensor 65 outputs a signal that causes too rapid an increase in the temperature of the hydraulic system between the master and slave cylinders 13 . 23 indicates the gearbox becomes 5 set to neutral and the clutch 3 closed. Due to the increasing temperature, the hydraulic medium expands between the master and slave cylinders 13 . 23 out, so that the clutch 3 could unintentionally disengage gradually without this on the master cylinder 13 mounted Posistionssensor 31 can capture. By engaging the clutch 3 it comes to a volume compensation with the expansion tank 15 , so that the signal of the position sensor 31 the position of the coupling 3 is properly assigned again and also a positive pressure of the clutch 3 is avoided.

2 shows a similar embodiment as 1 in which the same parts are provided with the same reference numerals. The essential difference from the first embodiment is that here the clutch position sensor 131 on the clutch slave cylinder 123 is attached so that the sensor 131 regardless of temperature changes in the hydraulic system between the master and slave cylinders via the line 133 always the correct position of the coupling 3 detected. The control unit 7 can be connected to other input and output elements, as in 1 are drawn. With 67 is called a transmission oil temperature sensor. Otherwise, the design is similar in function and design of the first embodiment.

3 shows a similar embodiment as 1 in which, however, the clutch 3 and the gearbox 5 be operated by electromechanical actuators, which without hydraulic components via control lines 321 and 335 from the control unit 7 be controlled directly. Here is the clutch 3 from an electromotive actuator 323 engaged and disengaged, and the transmission 5 is powered by a dial motor 337 and a switching motor 339 connected. Otherwise, the embodiment is similar in function and structure of the first embodiment, wherein like parts are provided with the same reference numerals. With 3a is the releaser of the clutch 3 designated.

Claims (15)

Method for controlling a motor vehicle, of which the engine ( 1 ) with the drive wheels connecting drive train a drive train automatically separating friction clutch ( 3 ), wherein the method prevents on the one hand, that the motor vehicle drives off in a non-running state by motor drive, wherein a sensor is used to determine the non-running state ( 45 ) is provided, which is responsive to the operation of a brake pedal, and wherein the non-driving condition is present when the brake pedal is not operated, wherein, when the vehicle is on separation of switched friction clutch ( 3 ) and running engine ( 1 ) the vehicle is not ready to drive, a drive of the vehicle by the engine ( 1 ) is prevented by a transmission contained in the drive train ( 5 ) is switched to a neutral state, characterized in that the method on the other hand, when the vehicle is on separation-switched friction clutch ( 3 ) and running engine the transmission ( 5 ) switches to the neutral state and the clutch ( 3 ) closes when the vehicle's parking brake has been continuously applied for a predetermined period of time since the vehicle stopped. Method according to claim 1, characterized in that the transmission ( 5 ) is switched to the neutral state only after a predetermined period since the beginning of the non-ready state. A method according to claim 1 or 2, characterized in that the sensor is a brake pressure switch ( 45 ). Method according to one of the preceding claims, characterized in that, when the vehicle is not ready to drive and the transmission is in the neutral state ( 5 ) the motor ( 1 ) stops, a gear is engaged again. A method according to claim 4, characterized in that a highly translated gear is engaged. Method according to one of the preceding claims, characterized in that, when the vehicle is not ready to drive and the transmission is in the neutral state ( 5 ) the coupling ( 3 ) is closed. Method according to one of the preceding claims, characterized in that, to determine the non-ready state, a sensor ( 61 . 63 ) is provided, which responds to the opening state of a hood and / or door of the vehicle, and the transmission ( 5 ) is switched to the neutral state only when the hood and / or door is open. Method according to one of the preceding claims, characterized in that a predetermined time before switching of the transmission ( 5 ) is issued in the neutral state when the vehicle is not running a perceptible by the driver warning signal. Method according to one of the preceding claims, characterized in that a re-engagement of a gear is released only when the driver before a gear selector lever of the transmission ( 5 ) has placed in the neutral position. Method according to one of claims 7 to 9, characterized in that when the driver's door is opened a gear without delay is engaged when the accelerator pedal ( 47 ) is pressed. Method according to one of the preceding claims, characterized in that, to determine the non-ready state, a sensor ( 62 ) is provided, which responds to the occupancy of the driver's seat, and the transmission ( 5 ) is switched to neutral only when the driver's seat is not occupied. Method according to one of the preceding claims, characterized in that the coupling ( 3 ) is hydraulically actuated and the transmission ( 5 ) is switched to the non-running vehicle only in the neutral state, when a temperature of the hydraulic fluid exceeds a predetermined maximum temperature or a temperature change of the hydraulic fluid exceeds a predetermined maximum temperature change. Method according to claim 12, characterized in that the coupling ( 3 ) when the vehicle is not ready to drive, after switching to the neutral state due to increased hydraulic temperature or hydraulic temperature change, it is briefly closed and then disconnected again. A method according to claim 12 or 13, characterized in that for the evaluation of the temperature of the hydraulic fluid, a signal from a temperature sensor ( 65 ), which is the temperature of the ambient air, the engine intake air or the temperature of a hydraulic control unit ( 11 ) of the coupling. Method according to one of the preceding claims, characterized in that the engine ( 1 ) is switched off after the passage of a predetermined period of time since the shift in the neutral state and in the transmission ( 5 ) a gear is engaged.

Images