JP7708020B2 - Engine Control Unit - Google Patents

Description

This invention relates to a control device for an engine having multiple cylinders, and in particular to an engine control device that can halt the supply of fuel to only one or some of the cylinders (partial cylinder fuel cut) while the engine is running.

Patent Document 1 describes a determination device for an internal combustion engine that aims to appropriately determine deterioration of exhaust properties even when partial cylinder fuel cut is performed.

JP 2022-65266 A

As with the internal combustion engine described in Patent Document 1 above, when an engine having multiple cylinders is in operation, fuel supply to only one or some of the cylinders is suspended, in other words, partial cylinder fuel cut (or cylinder deactivation operation) is performed, thereby improving the fuel efficiency of the engine. However, if the engine transitions to a partial cylinder fuel cut state when the engine output torque is large, the engine output torque will drop significantly, which may cause a shock.

This invention was conceived with a focus on the technical issues discussed above, and aims to provide an engine control device that can appropriately perform partial cylinder fuel cut while suppressing the occurrence of shocks.

To achieve the above object, the present invention provides a control device for an engine having multiple cylinders, comprising a controller that controls the engine and executes partial cylinder fuel cut by suspending fuel supply to only one or some of the cylinders of the engine while the engine is in operation, the controller outputs a command engine torque for controlling the torque of the engine, obtains an actual engine torque by detecting or estimating the actual torque of the engine operated in accordance with the command engine torque, and prohibits execution of the partial cylinder fuel cut if the greater of the command engine torque or the actual engine torque exceeds a predetermined load threshold for determining a high torque state of the engine (or permits execution of the partial cylinder fuel cut if both the command engine torque and the actual engine torque are less than the load threshold).

According to the engine control device of this invention, the high torque state of the engine is determined based on the greater of the indicated engine torque and the actual engine torque. If it is determined that the engine is in a high torque state, the execution of partial cylinder fuel cut is prohibited. This makes it possible to appropriately execute partial cylinder fuel cut while suppressing the occurrence of shock.

FIG. 13 is a time chart for explaining a problem in the engine control device of the present invention, showing changes in engine torque (indicated engine torque and actual engine torque) and changes in a partial cylinder fuel cut permission flag. FIG. 1 is a diagram for explaining the control executed by the engine control device of the present invention, and is a time chart showing the change in engine torque (indicated engine torque and actual engine torque) and the change in the partial cylinder fuel cut permission flag.

The embodiment of the present invention will be described with reference to the drawings. Note that the embodiment shown below is merely an example of how the present invention can be realized, and is not intended to limit the present invention.

The engine to be controlled in the embodiment of the present invention is, for example, an internal combustion engine such as a gasoline engine or a diesel engine that is mounted on a vehicle as a driving force source, and is configured to electrically control the output adjustment and operating state such as starting and stopping. In the case of a gasoline engine, the throttle valve opening, the amount of fuel supplied or injected, the ignition on/off, and the ignition timing are electrically controlled. In the case of a diesel engine, the fuel injection amount, fuel injection timing, or the throttle valve opening (in the EGR system) are electrically controlled.

Furthermore, the engine to be controlled in the embodiment of the present invention has multiple cylinders and is configured to perform partial cylinder fuel cut (or cylinder deactivation operation) in which fuel supply is suspended only to one or some of the multiple cylinders. A specific example of the engine configuration is an engine (internal combustion engine) having four cylinders as shown in the above-mentioned "Figure 1 of Patent Document 1". The engine control device in the embodiment of the present invention includes a controller similar to "control device 70" in "Figure 1 of Patent Document 1". The controller in the embodiment of the present invention controls the operating state of the engine and executes the above-mentioned partial cylinder fuel cut.

As mentioned above, if partial cylinder fuel cut is performed when the engine is operating and the engine is outputting a large torque (engine torque) (high torque state), the amount of engine torque reduction caused by partial cylinder fuel cut, i.e., the drop in engine torque, becomes large, causing a shock. As a countermeasure, it is possible to set a threshold value for the magnitude of engine torque, and prohibit partial cylinder fuel cut when the engine torque exceeds the threshold value. For example, as shown in the time chart of Figure 1, a load threshold value TH' is set as a threshold value for determining whether the engine is in a high torque state. When the engine torque exceeds the load threshold value TH', the engine is determined to be in a high torque state.

Normally, the engine is controlled so that the actual engine torque follows the engine torque command value (indicated engine torque) output by the controller. Therefore, in the conventional control technology, as shown in the time chart of FIG. 1, the partial cylinder fuel cut permission flag FL' is turned ON when the indicated engine torque L1' is lower than the load threshold TH'. That is, the execution of partial cylinder fuel cut (partial cylinder FC) is permitted before time t1 and after time t2. When the indicated engine torque L1' exceeds the load threshold TH', the partial cylinder fuel cut permission flag FL' is turned OFF. That is, the execution of partial cylinder fuel cut (partial cylinder FC) is prohibited between time t1 and time t2.

However, the actual engine torque L2' (detected value or estimated value of the actual engine torque) inevitably changes with a delay time with respect to the command engine torque L1'. Therefore, when the high torque state of the engine is determined as described above, even if the actual engine torque L2' is greater than the load threshold TH', as in the case of the period from time t2 to time t3 in FIG. 1, the execution of partial cylinder fuel cut is permitted. Note that even when the high torque state of the engine is determined based on the actual engine torque L2', due to a control delay when the partial cylinder fuel cut is actually executed, the actual engine torque L2' may already be greater than the load threshold TH' at the time when the partial cylinder fuel cut is actually executed. Therefore, with conventional control technology, when the partial cylinder fuel cut is executed, the drop in engine torque becomes large, which may cause a shock.

In the engine control device according to the embodiment of the present invention, a command engine torque for controlling the engine torque is output, and an actual engine torque is obtained by detecting or estimating the engine torque that is actually output by the engine operated in accordance with the command engine torque. If the larger of the command engine torque or the actual engine torque exceeds a load threshold value that is predetermined for determining the high torque state of the engine, execution of partial cylinder fuel cut is prohibited.

Specifically, as shown in the time chart of FIG. 2, the partial cylinder fuel cut permission flag FL is turned ON in a range in which the greater of the indicated engine torque L1 or the actual engine torque L2 is lower than the load threshold TH. That is, the execution of partial cylinder fuel cut (partial cylinder FC) is permitted before time t10 when both the indicated engine torque L1 and the actual engine torque L2 are smaller than the load threshold TH, and in the period after time t20. When the greater of the indicated engine torque L1 or the actual engine torque L2 exceeds the load threshold TH, the partial cylinder fuel cut permission flag FL is turned OFF. That is, the execution of partial cylinder fuel cut (partial cylinder FC) is prohibited between time t10 when the indicated engine torque L1, which is greater than the actual engine torque L2, becomes greater than the load threshold TH, and time t20 when the actual engine torque L2, which is greater than the indicated engine torque L1, becomes greater than the load threshold TH.

By judging the high torque state of the engine as described above and judging whether partial cylinder fuel cut should be performed based on the judgment result, when the engine torque is increasing, the execution of partial cylinder fuel cut is prohibited before the increase of the actual engine torque L2 based on the command engine torque L1, which becomes larger before the actual engine torque L2. On the other hand, when the engine torque is decreasing, the execution of partial cylinder fuel cut is permitted after the actual engine torque L2 decreases based on the actual engine torque L2, which becomes smaller after the command engine torque L1. As a result, when the execution of partial cylinder fuel cut is permitted (the partial cylinder fuel cut permission flag FL is ON) and the partial cylinder fuel cut is actually performed, the actual engine torque L2 is smaller than the load threshold value TH. Therefore, the execution of partial cylinder fuel cut is avoided when the engine is in a high torque state, and the occurrence of shocks associated with the execution of partial cylinder fuel cut can be suppressed.

Therefore, according to the engine control device of this embodiment of the present invention, the high torque state of the engine is determined based on the greater of the indicated engine torque L1 and the actual engine torque L2. If it is determined that the engine is in a high torque state, the execution of partial cylinder fuel cut is prohibited. In other words, the execution of partial cylinder fuel cut is permitted only when both the indicated engine torque L1 and the actual engine torque L2 are lower than the load threshold TH that determines the high torque state of the engine. Therefore, the occurrence of shock can be suppressed and partial cylinder fuel cut can be executed appropriately.

L1, L1': Indicated engine torque L2, L2': Actual engine torque FL, FL': Partial cylinder fuel cut permission flag TH, TH': Load threshold

Claims (1)

A control device for an engine having a plurality of cylinders,
a controller that controls the engine and executes a partial cylinder fuel cut to stop the supply of fuel to only one or some of the cylinders of the engine during operation of the engine;
The controller:
outputting a command engine torque for controlling the torque of the engine;
An actual engine torque is obtained by detecting or estimating an actual torque of the engine operated in accordance with the indicated engine torque;
A vehicle control device characterized in that, when the greater of the indicated engine torque or the actual engine torque exceeds a load threshold value set for determining a high torque state of the engine, execution of the partial cylinder fuel cut is prohibited.