Method for operating an internal combusting engine, and corresponding internal combustion engine

Abstract

A method for operating an internal combustion engine having multiple cylinders. A warm-up operation is carried out after the internal combustion engine has been started, during which a speed of the internal combustion engine is limited to a limit value. The limit value is selected during the warm-up operation at least temporarily as a function of a starting temperature of the internal combustion engine.

Claims

1. A method for operating an internal combustion engine having a plurality of cylinders, comprising: carrying out a warm-up operation after the internal combustion engine has been started, wherein a speed of the internal combustion engine is normally controlled to a target speed commanded by at least one of a driver and a driver assistance system, wherein, during the warm-up operation, the speed of the internal combustion engine is controlled to a speed limit value which differs from the target speed, wherein, during the warm-up operation, at least one charge limit value limits a cylinder charge of each of the plurality of cylinders, and wherein the speed limit value and the at least one charge limit value are each selected based on at least a starting temperature of the internal combustion engine, wherein the speed limit value and the at least one charge limit value are each set to a starting value at a beginning of the warm-up operation and progress towards an end value during the warm-up operation, wherein the starting values and the end values are each determined as a function of the starting temperature of the internal combustion engine.

2. The method according to claim 1, wherein the starting temperature is determined according to a computer model based on a previous operating duration of the internal combustion engine and a duration of a standstill of the internal combustion engine preceding a start.

3. The method according to claim 1, wherein the warm-up operation is only carried out when the starting temperature of the internal combustion engine is less than a minimum temperature.

4. The method according to claim 1, wherein progression of the speed limit value and the at least one charge limit value takes place linearly or in steps.

5. The method according to claim 1, wherein progression of the speed limit value and the at least one charge limit value takes place as a function of a cumulative amount of air supplied to the internal combustion engine since the internal combustion engine was started.

6. The method according to claim 1, wherein the warm-up operation is ended when at least one of the speed limit value and the at least one charge limit value have reached their respective end value.

7. An internal combustion engine having a plurality of cylinders and a control device for carrying out the method according to claim 1.

8. The method according to claim 3, wherein the minimum temperature is determined as a function of at least an ambient temperature.

9. The method according to claim 1, wherein determination of the starting values is bounded by a minimum value corresponding to a minimum torque to be supplied by the internal combustion engine.

10. The method according to claim 1, wherein the starting values are further determined based on a progression of cooling of the internal combustion engine.

11. The method according to claim 6, wherein the warm-up operation is ended when both the speed limit value and the at least one charge limit value have reached the end value.

12. The method according to claim 5, wherein the warm-up operation is ended when the cumulative amount of air supplied to the internal combustion engine since the internal combustion engine was started exceeds a predetermined threshold.

13. The method according to claim 1, wherein a torque provided by the internal combustion for driving a motor vehicle is reduced due to the warm-up operation.

14. The method according to claim 1, wherein the starting values and the end values are further determined based on an ambient temperature.

Description

BRIEF DESCRIPTION OF THE FIGURE

(1) In the following, the invention will be explained in greater detail with reference to the exemplary embodiments depicted in the drawings, without this restricting the invention. In the sole figure,

(2) FIG. 1 shows a schematic illustration of an internal combustion engine.

(3) The FIGURE shows a schematic illustration of an internal combustion engine 1, which has multiple cylinders 2 in the exemplary embodiment shown here. Each of the cylinders 2 has at least one inlet valve 3 and at least one outlet valve 4. Fresh gas can be supplied to the respective cylinder 2 from an intake tract 5 via each of the inlet valves 3, whereas exhaust gas can escape from the corresponding cylinder 2 through each of the outlet valves 4, namely in the direction of an exhaust tract 6. Downstream of the exhaust tract 6 there can be an exhaust gas purification device 8, which is fluidically connected to the outlet valves 4 via an exhaust gas line 7. The exhaust gas purification device 8 can, for example, have at least one catalytic converter.

(4) The internal combustion engine 1 is operated by means of a method according to which a warm-up operation is carried out after the internal combustion engine has been started. The speed of the internal combustion engine 1 is limited to the limit value. Fresh gas is supplied to the cylinders 2 via the intake tract 5, wherein this fresh gas supply can additionally be limited to a limit value during the warm-up operation. In this respect, two limit values can thus exist, namely one for the speed of the internal combustion engine and one for the cylinder charge. The limit value or values are selected during the warm-up operation at least temporarily as a function of a starting temperature of the internal combustion engine 1.

(5) For example, the internal combustion engine 1 is designed to determine the combustion chamber temperature at the time of the start of the internal combustion engine 1 in order to use this as the starting temperature. To determine the combustion chamber temperature, temperature sensors can be provided in the internal combustion engine 1. Additionally or alternatively, the combustion chamber temperature can be determined on the basis of a model calculation. The model calculation can calculate the combustion chamber temperature or the starting temperature using sensor data, such as an outside temperature, as well as the time curve of a standstill of the internal combustion engine 1 preceding the start of the internal combustion engine 1. If the measured or calculated starting temperature is below a minimum temperature, the warm-up operation is thus carried out.

(6) At the beginning of the warm-up operation, the limit value is set to a starting value. During the warm-up operation, the limit value is increased starting from the starting value in the direction of an end value. The end value is selected, for example, so that the limit value of the speed reaches a maximum permissible speed which, in normal operation, may be present after the operating temperature has been reached, without damage to the internal combustion engine 1 occurring or being expected. In addition, a maximum permissible end value can also be defined for the limit value of the cylinder charge.

(7) The limit value is increased in the direction of the end value, wherein the increase takes place as a function of the amount of air supplied cumulatively to the cylinders 2 via the intake tract 5 since the start. When the limit value reaches the end value, the warm-up operation is ended. Additionally or alternatively, it can be provided that the warm-up operation is ended as soon as the amount of air supplied cumulatively to the cylinders 2 since the start exceeds a threshold value. In this way, the internal combustion engine 1 is heated to an operating temperature in a controlled manner during the warm-up operation, and the pollutant emissions of the internal combustion engine 1 are accordingly significantly reduced during the warm-up operation.