Method for controlling a shift process of an automatic gearbox and controller

Abstract

A method for controlling a shift process of an automatic gearbox for a vehicle with an internal combustion engine as its engine, including specifying a shift strategy in a controller, by continuously predictively determining the behaviour of the engine following any shift process into a target gear on the basis of a current detected vehicle dynamic value, a current detected vehicle specific actual value, and/or a current detected engine specific actual value. The prediction results are taken into account and adapted shift thresholds are determined and specified as upshift thresholds or downshift thresholds for a fuel efficient shift. A control command for a corresponding automatic shift process is output after exceeding a shift threshold. The current temperature of at least one component of the engine exhaust system is taken into account during the specification of an adapted shift threshold.

Claims

1. A method for controlling a shift process of an automatic gearbox in a vehicle with an internal combustion engine as its engine, comprising the steps of: specifying, by a controller, a shift strategy by continuously predictively determining a behavior of the engine following any shift process into a target gear based on at least one of current detected vehicle dynamic, vehicle specific actual values, and engine specific actual values; determining adapted shift thresholds as upshift thresholds or downshift thresholds taking into account the predictively determined behaviour for a fuel efficient shift and a current temperature of at least one component of an engine exhaust system; and outputting, after exceeding one of the shift thresholds, a control command for a corresponding automatic shift process.

2. The method according to claim 1, wherein the at least one component of the exhaust system is at least one of an exhaust turbine of an exhaust turbocharger and an exhaust manifold.

3. The method according to claim 1, further comprising the steps of directly measuring the current temperature by at least one temperature sensor and sending a current temperature signal to the controller.

4. The method according to claim 1, further comprising the step of indirectly calculating the current temperature from a load profile of the internal combustion engine.

5. The method according to claim 4, wherein the step of indirectly calculating uses at least one of a revolution rate, a charging pressure, an injection quantity, and an air mass flow of the internal combustion engine.

6. The method according to claim 1, further comprising the step of precalculating a build-up of torque as a load step response of the internal combustion engine following a shift process during the step of predictively determining the behaviour of the internal combustion engine.

7. The method according to claim 6, wherein a lower component temperature compared to a defined specified component temperature threshold value causes a slower build-up of torque with correspondingly less power of the internal combustion engine than is the case for component temperatures corresponding to or higher than the defined specified component threshold temperature, and the build-up of torque associated with the current temperature is taken into account during the step of specifying a shift threshold and when making a decision for a shift process whether a necessary power for a current speed demand of the vehicle will be available for the current temperature conditions of the internal combustion engine.

8. A controller storing a computer executable program for carrying out a method for controlling a shift process of an automatic gearbox in a vehicle with an internal combustion engine as its engine, the program comprising steps executable by the controller for: specifying a shift strategy by continuously predictively determining a behavior of the engine following any shift process into a target gear based on at least one of current detected vehicle dynamic, vehicle specific actual values, and engine specific actual values; determining adapted shift thresholds as upshift thresholds or downshift thresholds taking into account the predictively determined behaviour for a fuel efficient shift and a current temperature of at least one component of an engine exhaust system; and outputting, after exceeding one of the shift thresholds, a control command for a corresponding automatic shift process.

9. A vehicle with an automatic gearbox, an internal combustion engine, and a controller the controller storing a computer executable program for carrying out a method for controlling a shift process of the automatic gearbox, the program comprising steps executable by the controller for: specifying a shift strategy by continuously predictively determining a behavior of the engine following any shift process into a target gear based on at least one of current detected vehicle dynamic, vehicle specific actual values, and engine specific actual values; determining adapted shift thresholds as upshift thresholds or downshift thresholds taking into account the predictively determined behaviour for a fuel efficient shift and a current temperature of at least one component of an engine exhaust system; and outputting, after exceeding one of the shift thresholds, a control command for a corresponding automatic shift process.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the figures:

(2) FIG. 1 shows a flow chart of a method for controlling a shift process of an automatic gearbox for a vehicle with an internal combustion engine as its engine,

(3) FIG. 2 shows a load step diagram for a build-up of torque following a shift process as a function of an exhaust turbine temperature.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(4) A flow chart 1 for a method for controlling a shift process of an automatic gearbox for a vehicle with an internal combustion engine as its engine is shown in FIG. 1. For this the actual state of the engine is determined continuously in Block 2 by a controller, wherein recorded input variables are used for the calculation, as shown schematically with Block 3 and the input arrow 4. The recorded input variables are recorded by various sensors and the controller is, for example, a processor running a program. In particular the fuel feed and the air feed, the water temperature and possibly other recorded variables are used as input variables for this.

(5) A precalculation of the build-up of torque for possible characteristic field points of a possible target gear is carried out in Block 6 based on the results of Block 2 (input arrow 5). In addition to the values for the actual state of the engine from Block 2, further input variables are used and are taken into account for this, as shown schematically with Block 7 and the input arrow 8. Block 7 represents schematically the input variables including charging pressure, revolution rate, injection quantity and air mass flow which are used in particular for indirect model calculation of the temperature of an exhaust turbine of an exhaust turbocharger and said temperature is taken into account in the precalculation of the build-up of torque.

(6) Alternatively or additionally, such a temperature can also be directly measured with at least one temperature sensor 9, whose measurement value is fed to Block 6 to be taken into account during the precalculation.

(7) Block 10 schematically represents a gearbox controller, which may be integrated within an engine controller, and in which the decision is made as to whether a possible shift process will be fuel efficient and should be carried out or omitted. For this purpose, the gearbox controller corresponding to Block 10 interrogates Block 6 for the precalculation results, as shown schematically with query arrow 11. Accordingly, the precalculation result from Block 6 is output to the gearbox controller of Block 10, as shown schematically by the transmission arrow 12.

(8) In FIG. 2 the step response of an engine following a shift process is shown in relation to a build-up of torque by way of example. For this purpose the torque is shown qualitatively towards the top and the time profile in seconds is shown towards the right in a coordinate system:

(9) The five graphs shown correspond by way of example to a load step response of an engine during a shift process at a revolution rate of 1200 revolutions per minute. A thermal model of an exhaust turbine is integrated within the engine controller and relies on measurement variables or computed variables of the engine controller.

(10) The model provides a temperature, using which the load step response of the engine can be described/calculated according to FIG. 2.

(11) In the diagram according to FIG. 2, the bottom graph 13 corresponds to a temperature of the exhaust turbine of 140 C. and, moving up, graph 14 corresponds to a temperature of 300 C., graph 15 to a temperature of 400 C., graph 16 to a temperature of 460 C. and the topmost graph 17 to a temperature of 500 C.

(12) It can be clearly seen from the diagram that the step response of the engine depends significantly on the thermal state of the exhaust turbine, wherein a colder exhaust turbine causes a slower build-up of torque following a shift process. Said dependency is determined according to the invention and is taken into account when making the decision for a possible shift process.

(13) TABLE-US-00001 Reference character list 1 flow chart 2 block 3 block 4 input arrow 5 input arrow 6 block 7 block 8 input arrow 9 temperature sensor 10 block 11 query arrow 12 transmission arrow 13 bottom graph 14 graph 15 graph 16 graph 17 top graph