Engine control device

Abstract

To provide a control device of an engine capable of suppressing generation of shock to appropriately execute partial cylinder fuel cut.SOLUTION: A control device of an engine having a plurality of cylinders, outputs an instruction engine torque for controlling the torque of the engine; obtains an actual engine torque by detecting or estimating an actual torque of the engine operated following the instruction engine torque; and when larger one of the instruction engine torque and the actual engine torque exceeds a predetermined load threshold for determining a high torque state of the engine, prohibits execution of partial cylinder fuel cut in which fuel supply is stopped to only one or some of the cylinders of the engine.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a control device for an engine having a plurality of cylinders, and more particularly to a control device for an engine capable of suspending the fuel supply of only one or some of the cylinders (partial cylinder fuel cut) during engine operation.

Background Art

[0002] Patent Document 1 describes a determination device for an internal combustion engine aimed at appropriately determining the deterioration of exhaust characteristics even when partial cylinder fuel cut is executed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By executing so-called partial cylinder fuel cut (or cylinder cut-off operation) in which the fuel supply of only one or some of the cylinders is suspended during the operation of an engine having a plurality of cylinders like the internal combustion engine (engine) described in the above Patent Document 1, the fuel efficiency of the engine can be improved. However, when shifting to the partial cylinder fuel cut state when the output torque of the engine is large, the drop in the output torque of the engine becomes large, and there is a risk of generating a shock.

[0005] The present invention has been conceived by paying attention to the above technical problems, and an object thereof is to provide a control device for an engine capable of suppressing the generation of a shock and appropriately executing partial cylinder fuel cut.

Means for Solving the Problems

[0006] To achieve the above object, the present invention provides a control device for an engine having a plurality of cylinders, which includes a controller that controls the engine and executes a partial cylinder fuel cut for suspending the fuel supply only to one or some of the cylinders of the engine during the operation of the engine. The controller outputs a commanded 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 following the commanded engine torque, and prohibits the execution of the partial cylinder fuel cut when the larger one of the commanded engine torque and the actual engine torque exceeds a load threshold value determined in advance for determining a high torque state of the engine (or permits the execution of the partial cylinder fuel cut when both the commanded engine torque and the actual engine torque are less than the load threshold value).

Advantages of the Invention

[0007] According to the engine control device of the present invention, a high torque state of the engine is determined based on the larger value of either the commanded engine torque or the actual engine torque. When it is determined that the engine is in a high torque state, the execution of the partial cylinder fuel cut is prohibited. Therefore, the occurrence of shock can be suppressed and the partial cylinder fuel cut can be appropriately executed.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0009] Embodiments of the present invention will be described with reference to the drawings. Note that the embodiments shown below are merely examples of implementing the present invention and do not limit the present invention.

[0010] The engine to be controlled in the embodiments of the present invention is, for example, an internal combustion engine such as a gasoline engine or a diesel engine mounted on a vehicle as a driving power source, and is configured such that the output adjustment and operating states such as starting and stopping are electrically controlled. In the case of a gasoline engine, the opening degree of the throttle valve, the fuel supply amount or injection amount, the execution and stop of ignition, and the ignition timing are electrically controlled. Also, in the case of a diesel engine, the fuel injection amount, the fuel injection timing, or the opening degree of the throttle valve (in the EGR system) is electrically controlled.

[0011] Furthermore, the engine to be controlled in the embodiments of the present invention has a plurality of cylinders, and is configured such that partial cylinder fuel cut (or cylinder cut operation) in which only one or some of these plurality of cylinders have their fuel supply suspended is possible. As a specific example of the engine configuration, for example, an engine (internal combustion engine) having four cylinders as shown in "FIG. 1 of Patent Document 1" described above can be cited. And the engine control device in the embodiments of the present invention includes a controller similar to the "controller 70" in "FIG. 1 of Patent Document 1". The controller in the embodiments of the present invention controls the operating state of the engine and executes the above-described partial cylinder fuel cut.

[0012] As described above, when the engine is in a state of outputting a large torque (engine torque) (high torque state) during engine operation and partial cylinder fuel cut is executed, the amount of decrease in engine torque due to the partial cylinder fuel cut, that is, the drop in engine torque becomes large, and a shock occurs. As a countermeasure, it is conceivable to provide a threshold value with respect to the magnitude of the engine torque and prohibit the execution of the partial cylinder fuel cut when the engine torque exceeds the threshold value. For example, as shown in the time chart of FIG. 1, a load threshold value TH' is set as a threshold value for determining the high torque state of the engine. When the engine torque exceeds the load threshold value TH', the engine is determined to be in the high torque state.

[0013] Normally, the engine is controlled so that the actual engine torque (actual engine torque) follows the command value of the engine torque (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 in a range where the indicated engine torque L1' is lower than the load threshold value TH'. That is, during the period before time t1 and after time t2, the execution of the partial cylinder fuel cut (partial cylinder FC) is permitted. When the indicated engine torque L1' exceeds the load threshold value TH', the partial cylinder fuel cut permission flag FL' is turned OFF. That is, during the period from time t1 to time t2, the execution of the partial cylinder fuel cut (partial cylinder FC) is prohibited.

[0014] However, the actual engine torque L2' (the detected value or estimated value of the actual engine torque) inevitably changes with a delay time with respect to the indicated engine torque L1'. Therefore, when the high torque state of the engine is determined as described above, even when the actual engine torque L2' is greater than the load threshold TH' between the time t2 and the time t3 in FIG. 1, the execution of the partial cylinder fuel cut is permitted. Even when the high torque state of the engine is determined based on the actual engine torque L2', due to the control delay when the partial cylinder fuel cut is executed, there may be a case where the actual engine torque L2' is already greater than the load threshold TH' at the timing when the partial cylinder fuel cut is actually executed. Therefore, in the conventional control technology, when the partial cylinder fuel cut is executed, the engine torque drop becomes large, and there is a possibility that a shock may occur.

[0015] Therefore, in the engine control device according to the embodiment of the present invention, an indicated engine torque for controlling the engine torque is output, and an actual engine torque detected or estimated that is output by the engine operated following the indicated engine torque is obtained. Then, when either the indicated engine torque or the actual engine torque, whichever is larger, exceeds a load threshold predetermined for determining the high torque state of the engine, the execution of the partial cylinder fuel cut is prohibited.

[0016] Specifically, as shown in the time chart of FIG. 2, the partial cylinder fuel cut permission flag FL is turned ON when the larger of the indicated engine torque L1 or the actual engine torque L2 is in a range lower than the load threshold TH. That is, before the time t10 when both the indicated engine torque L1 and the actual engine torque L2 become smaller than the load threshold TH, and in the period after the time t20, the execution of the partial cylinder fuel cut (partial cylinder FC) is permitted. When the larger 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, between the time t10 when the indicated engine torque L1 larger than the actual engine torque L2 becomes larger than the load threshold TH and the time t20 when the actual engine torque L2 larger than the indicated engine torque L1 becomes larger than the load threshold TH, the execution of the partial cylinder fuel cut (partial cylinder FC) is prohibited.

[0017] By determining the high torque state of the engine as described above and judging whether to execute the partial cylinder fuel cut according to the determination result, when the engine torque has an increasing trend, based on the indicated engine torque L1 that becomes larger earlier than the actual engine torque L2, the execution of the partial cylinder fuel cut is prohibited prior to the increase in the actual engine torque L2. On the other hand, when the engine torque has a decreasing trend, based on the actual engine torque L2 that becomes smaller later than the indicated engine torque L1, the execution of the partial cylinder fuel cut is permitted after waiting for the decrease in the actual engine torque L2. As a result, when the execution of the partial cylinder fuel cut is permitted (the partial cylinder fuel cut permission flag FL is turned ON) and the partial cylinder fuel cut is actually executed, the actual engine torque L2 is in a state smaller than the load threshold TH. Therefore, it is possible to avoid the execution of the partial cylinder fuel cut in the high torque state of the engine and suppress the occurrence of shocks associated with the execution of the partial cylinder fuel cut.

[0018] Therefore, according to the engine control device in the embodiment of the present invention, the determination of the high torque state of the engine is made based on the larger value of either the indicated engine torque L1 or the actual engine torque L2. And when it is determined that the engine is in the high torque state, the execution of the partial cylinder fuel cut is prohibited. In other words, the execution of the 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 for determining the high torque state of the engine. Therefore, the occurrence of shock can be suppressed and the partial cylinder fuel cut can be appropriately executed.

Explanation of Signs

[0019] L1, L1’ Indicated engine torque L2, L2’ Actual engine torque FL, FL’ Partial cylinder fuel cut permission flag TH, TH’ Load threshold

Claims

【Claim 1】 A control device for an engine having a plurality of cylinders, comprising: a controller that controls the engine and executes a partial cylinder fuel cut for suspending the supply of fuel only to one or a part of the cylinders of the engine during operation of the engine; the controller: outputs a commanded 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 following the commanded engine torque; when either the commanded engine torque or the actual engine torque, whichever is greater, exceeds a load threshold value determined for determining a high torque state of the engine, prohibits execution of the partial cylinder fuel cut; A control device for a vehicle, characterized by the above.

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