DE4241171C2 - Method for controlling an automatic transmission - Google Patents

Description

The invention relates to a method for control an automatic transmission according to the preamble of the first claim.

Many begin with vehicles with automatic transmissions Cases with inserting the driving position and engine idling Vehicle to crawl because the engine connects to the transmission Output torque even if no accelerator pedal is pressed.

From DE 41 18 474 A1 is an anti-creep control known for an automatic vehicle transmission. The anti Creep control is activated when vehicle speed speed and opening angle of the engine throttle valve zero or are almost zero and the brake is applied. During the Anti-creep control will take the torque transmission under broken or diminished by loosening a clutch or the Engaging force is reduced.

To control the transition anti-creep control too Normal driving state is a method from DE 35 04 417 C2 known in which the pressure in the starting clutch ends the creep control is raised after a time function.

The invention has for its object the transition from anti-creep control to normal driving condition.  

The object is achieved in that at the end of the anti-creep control, the pressure in one pass Travel clutch increases after a time function. This can z. B. be a ramp or exponential function.

With the end of the anti-creep control, a final pressure value of the Ramp or exponential function calculated. The final print value is a sum of partial pressures. The partial pressures are formed from the current vehicle parameters, e.g. B. Mo. Torque, engine speed, load position and temperature of the Pressure medium of a transmission hydraulic control.  

Another solution is that the Pressure in the starting clutch according to a speed ratio increases. The speed ratio is calculated from the Ratio gearbox input speed to gearbox output speed number.

Both solution variants offer the advantage that the Printing is continuous. This will transition from Application phase to the closing phase of the starting clutch smoothly. A pressure increase after an exponential function causes that the drive train before the actual load transfer is already preloaded without play.

The second solution has the additional advantage that the Pressure value constantly activated from the end of the anti-creep control becomes. Thus, driving state changes, e.g. B. suddenly accelerating the driver, an immediate change in pressure in the starting clutch.

In an embodiment of the invention it is proposed that when changing from anti-creep control to normal driving condition the engine torque is reduced. The reduction of the engine moments is controlled by an electronic transmission control triggered by an electronic engine control. The electro African engine control reduces the engine moments in a known manner that z. B. an ignition angle or an injection time or a position of the throttle valve is changed.

A reduced engine torque means that the starting clutch takes over the load at low pressure level. This ver reduces the friction on the clutch plates and the lifespan increases.

The engine torque reduction begins when the engine speed number or the engine torque or the torque at the transmission input exceed a first setpoint.  

This ensures that the engine torque is not greater is than the torque that can be transmitted by the clutch. A skull The friction linings of the clutch are prevented. The reduction in engine torque ends as soon as the engine rotation number and / or the engine torque a second setpoint below stride. The reduction also ends after the time function has expired, e.g. B. 10 msec later. The second solution variant, the reduction in engine torque ends as soon as that Speed ratio falls below a limit value. This Limit is greater than or equal to the gear ratio the starting stage of the transmission.

In the drawing, an embodiment is Darge provides.

Show it:

Fig. 1 shows the system diagram of an automatic transmission;

Fig. 2 shows the timing diagram for a transition from anti-creep control to normal operation.

In Fig. 1, an automatic transmission 3 is connected to a motor 1 through a drive shaft 2 . The automatic transmission 3 contains clutches, not shown, which are actuated by electromagnetic valves, not shown, which are contained in a hydraulic control unit 4 . Also in the hydraulic control unit 4 are not shown, electromagnetic pressure regulator, via which the pressure level of the couplings is set. The electromagnetic valves and pressure regulators are controlled by an electronic control unit 5 .

The electronic control unit 5 contains the usual components of a microprocessor system, such as input and output part, memory and arithmetic unit. The electronic control unit 5 processes the input signals 6 . The input signals 6 are known for. B. a vehicle speed signal, an engine speed signal, a signal for an engine torque, a load signal, a signal for the position of the drive lever and a signal of a brake light switch or brake pressure switch.

The electronic control unit 5 is connected to an electronic motor control 8 via a line 7 . The electronic control unit 5 in the electronic engine control unit 8 controls the start and the end of the engine torque reduction via the signal line 7 . The electronic engine control 8 causes a reduction in the engine torque z. B. by changing the ignition angle or the injection time or the position of the throttle valve. At the electronic engine control 8 , the sensor signals 9 of the engine 1 are connected.

Fig. 2 shows the transition from the end of the anti-Kriechsteue tion to the normal driving state, comprising a Zustandsdia grams of the anti-creep control 10, a pressure-time diagram of the starting clutch 11 and a state diagram of the reductive tion of the engine torque 12th

The pressure timing diagram of the starting clutch 11 consists of a pressure drop from the pressure level P2 to the pressure level P0, a time function F1 which begins at point A and ends at point B and a normal driving state which is represented by the pressure value P1. The solid line of the time function F1 shows an increase in pressure in the form of a ramp. The dashed line shows an increase in pressure in the form of an exponential function.

Anti-creep control is activated at time t0. In the upper diagram, this is the transition from 0 to 1. At the same time, the pressure of the starting clutch 11 is reduced from the pressure level P2 to the pressure level P0 at the time t0. The engaging force of the starting clutch 11 is determined via the pressure level P0. Anti-creep control is deactivated at time t1. This is the transition from 1 to 0 in the upper diagram. At the end of the anti-creep control, the time function F1 of the starting clutch 11 begins at point A. The Zeitfunk tion F1 of the starting clutch 11 is terminated at point B at time t3. The pressure level P1 belonging to the ramp end point B is a sum of partial pressures. The partial pressures are formed from the current vehicle parameters, e.g. B. Engine torque, engine speed, load position and temperature of the pressure medium of the transmission hydraulics. The pressure level P1 is selected so that the starting clutch remains securely closed. The load takeover point of the starting clutch falls in the period t1 to t3 during the time function F1. The starting clutch takes over the transmission input torque at the load transfer point. During the period t1 to t3, the engine speed or the engine torque change very strongly, e.g. B. by a driver accelerating, the pressure level in the clutch is not sufficient to take the load safely. Therefore, the engine torque is reduced when the engine speed or the engine torque or transmission input torque is exceeded. In the diagram below, this is the transition from 0 to 1 at time t2.

The torque reduction remains activated until the engine speed and / or engine torque a second setpoint below stride. In addition, the torque reduction is deactivated fourth after the time function F1 has expired. This is the time t4 and in the lower diagram the transition from 1 to 0.  

reference numeral

1

engine

2

drive shaft

3

transmission

4

hydraulic control unit

5

electronic control unit

6

input signals

7

signal line

8th

Electronic engine control

9

input signals

10

Status signal anti-creep control

11

Starting clutch pressure curve

12

Status signal reduction of engine torque
F1 time function

Claims (10)

1. A method for controlling an automatic transmission, in which an electronic control unit ( 5 ) via electromagnetic valves and pressure regulators controls clutches in an automatic transmission ( 3 ) and starts and ends a reduction in engine torque in an electronic engine control ( 8 ) and with an anti-creep control, which is activated as a function of operating parameters of the vehicle, thereby causing an interruption or reduction in the torque transmission in a starting clutch, characterized in that after the end of the anti-creep control, the pressure in the starting clutch after a continuous time function (F1) increases and the engine torque is temporarily reduced during the time function. 2. The method according to claim 1, characterized indicates that the engine torque is reduced, as soon as an engine speed exceeds a first setpoint tet. 3. The method according to claim 1, characterized indicates that the engine torque is reduced, as soon as a moment at the transmission input a first setpoint exceeds. 4. The method according to claim 1, characterized records that the reduction in engine torque en det when the engine speed and / or the moment at the transmission fall below a second setpoint.   5. The method according to claim 1, characterized records that the reduction in engine torque en shortly after the time function has expired. 6. Method for controlling an automatic transmission, in which an electronic control unit ( 5 ) controls clutches in an automatic transmission ( 3 ) via electromagnetic valves and pressure regulators and starts and stops a reduction of the engine torque in an electronic engine control ( 8 ) and with an anti-creep control, which is activated as a function of operating parameters of the vehicle, thereby causing an interruption or reduction in the torque transmission in a starting clutch, characterized in that after the end of the anti-creep control, the pressure in the starting clutch after a speed ratio increases, which is calculated from the transmission input speed to the transmission output speed. 7. The method according to claim 6, characterized indicates that the engine torque is reduced, if this is larger than that transmitted by the clutch real moment. 8. The method according to claim 6, characterized records that the reduction in engine torque en det if the speed ratio, calculated from gearbox input speed to gearbox output speed, one Falls below the limit. 9. The method according to claim 8, characterized shows that the limit value is a function of Gear ratio of the starting stage is.   10. The method according to claim 6, characterized records that the reduction in engine torque is limited in time.