JPH11257150A - Control method for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control conforming to a cylinder internal pressure change in the current engine cycle by engine parameters including a cylinder internal pressure signal, by converting a variation in cylinder internal pressure in a crank angle position after the termination of a suction stroke, to a cylinder internal pressure parameter. SOLUTION: A cylinder internal pressure sensor 21 of a cylinder terminated with a suction stroke out of the cylinder internal pressure 21 installed in each cylinder is selected by an MPX 31, and a cylinder internal pressure signal out of this selected cylinder internal pressure sensor 21 is analog-to-digital converted 32 at every specified crank angle and fed to a central processing unit 34. Next, whether the suction stroke is terminated or not is judged, and when the suction stroke is terminated, a cylinder internal pressure p1 at a crank angle θ1 and another cylinder internal pressure p1 +Δp at the crank angle θ1 +Δθ are taken in, thereby calculating a variation in the cylinder internal pressure. With this cylinder internal pressure variation and engine speed, referring to a map, the volumetric efficiency of an engine 1 is determined, and thus a fuel injection quantity and an ignition angle are determined from this volumetric efficiency and the engine speed or the cylinder internal pressure variation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling an internal combustion engine using an in-cylinder pressure sensor for detecting a pressure in a cylinder (hereinafter, referred to as an in-cylinder pressure).

[0002]

2. Description of the Related Art As a method for controlling an internal combustion engine such as an automobile engine, as disclosed in Japanese Patent Application Laid-Open No. 62-129571, a method of controlling a pressure signal in accordance with a cylinder pressure from a cylinder pressure sensor is used. 2. Description of the Related Art A technique for controlling an engine by determining an ignition timing of the engine is known.

Hereinafter, this conventional technique will be described with reference to FIG. FIG. 1 is a diagram showing a change in the in-cylinder pressure that changes according to the crank angle. θ _IG indicates an ignition angle which is an ignition timing. At this θ _IG , the air-fuel mixture in the cylinder is ignited by a spark discharge generated from a spark plug and enters a combustion stroke. The volume of the mixture by the combustion of the mixture increases, also increases sharply with cylinder pressure thereto, the cylinder pressure at theta _PX maximum value P
Becomes Thereafter, the in-cylinder pressure decreases, and the exhaust valve is opened at θ _A to enter the exhaust stroke.

[0004] In the prior art, the method of determining the ignition timing of the engine is as follows. First, the maximum value P of the in-cylinder pressure is detected, the crank angle _θPX at this time is obtained, and then the _θPX and the piston The ignition angle θ _IG is determined based on the relationship with the crank angle θ _TDC when the point is reached. The ignition angle is determined by comparing θ _PX with an amount θ _ID obtained by adding an ideal angle α previously determined in a preliminary experiment such as an actual machine test to θ _TDC .
If θ _PX is larger than θ _ID , it is determined that the ignition timing is late, θ _IG is set to a small value, the ignition timing in the next engine cycle is advanced, and θ _PX becomes smaller than θ _ID In this case, it is determined that the ignition timing is too early, and θ _IG is set to a large value to delay the ignition timing of the next engine cycle.

[0005]

As described above, the control of the engine according to the prior art utilizes the position information of the crank angle when the in-cylinder pressure becomes maximum. Therefore, since the ignition timing of the current engine cycle has already passed after θ _IG is determined, the ignition timing for the current engine cycle is controlled by the in-cylinder pressure in the engine cycle one cycle before the current engine cycle. This means that proper ignition timing control could not always be performed during startup, such as when the engine speed fluctuates greatly, or during rapid acceleration / deceleration.

Further, in a control method of an internal combustion engine using the in-cylinder pressure for controlling not only the ignition timing but also the fuel supply amount, an average effective pressure is obtained based on the in-cylinder pressure change in the previous engine cycle. And the other engine parameters, the fuel supply amount is adjusted, so that a fuel supply amount suitable for the current cycle is not always obtained.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has as its object to enable control in response to a change in in-cylinder pressure in a current engine cycle by using an engine parameter including an in-cylinder pressure signal. An object of the present invention is to provide an engine control method.

[0008]

A control method for an internal combustion engine according to the present invention obtains a control command for the internal combustion engine based on engine parameters including an in-cylinder pressure signal parameter and controls the internal combustion engine based on the control command. Wherein the rate of change of the in-cylinder pressure at the crank angle position after the end of the suction stroke is used as the in-cylinder pressure signal parameter.

That is, according to the characteristics of the present invention, the volumetric efficiency of the intake cylinder can be estimated from the rate of change of the in-cylinder pressure.
The fuel injection amount and the ignition timing can be controlled based on the estimated volume efficiency.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 shows a control device for an internal combustion engine according to an embodiment of the present invention. In FIG. 2, the internal combustion engine 1 includes air sucked from an intake pipe 11 and a combustion chamber 13.
The fuel is injected from the injector 12 that directly injects the air-fuel mixture, and the air-fuel mixture is burned by spark discharge in the spark plug 14, and the volume of the air-fuel mixture at this time is increased to move the piston 15 downward. The movement of the crankshaft 16 is transmitted to the crankshaft 16 and converted into a rotational movement of the crankshaft 16.

An in-cylinder pressure sensor 21 for generating an in-cylinder pressure signal corresponding to the in-cylinder pressure in the combustion chamber 13 is provided, for example, in a washer portion of a spark plug 14 which is screwed into an engine cylinder head. The in-cylinder pressure signal emitted from the in-cylinder pressure sensor 21 is supplied to an amplification circuit 28,
The output of the amplifier circuit 28 is a multiplexer (hereinafter, MPX).
) 31 to a high-speed A / D converter 32. The high-speed A / D converter 32 is connected to the input / output bus 3
The output signal from the high-speed A / D converter 32 is supplied to an input / output bus 33. The input / output bus 33 inputs and outputs a data signal or an address signal to / from the CPU 34. On the other hand, MPX
Reference numeral 31 denotes a switch for selectively supplying any one of the signals supplied to the MPX 31 to the high-speed A / D converter 32 in accordance with a command issued from the CPU 34 at a predetermined timing. With such a configuration, for example,
In the case of an internal combustion engine having multiple cylinders, an in-cylinder pressure signal generated from an in-cylinder pressure sensor provided for each cylinder can be captured.

The crankshaft reference position detecting device 22 and the crank angle detecting device 23 are provided near the crankshaft 16. The crankshaft reference position detecting device 22 is connected to an input terminal of the waveform shaping circuit 24, and an output terminal of the waveform shaping circuit 24 is connected to the input / output bus 33. The crankshaft reference position detecting device 22 generates one pulse signal when the crankshaft reaches a predetermined reference position, for example, when the piston is located at the top dead center. On the other hand, the crank angle detecting device 23 is a device that generates one pulse signal at every predetermined crank angle, for example, every one degree, and its output signal is waveform-shaped by the waveform shaping circuit 25, It is supplied to the angular position counter 27. The rotation speed counter 26 outputs a digital value corresponding to the rotation speed of the internal combustion engine. The angular position counter 27 outputs a digital value according to the crank angle position.
With such a configuration, the CPU 34 can detect the reference position of the crankshaft, the rotation speed of the internal combustion engine, and the crank angle.

With the above-described configuration, according to the present invention, the in-cylinder pressure sensor of the cylinder that has completed the intake stroke among the in-cylinder pressure sensors provided in each cylinder is MPX.
An in-cylinder pressure signal selected from the selected in-cylinder pressure sensor 31 and output from the selected in-cylinder pressure sensor is supplied to the high-speed A / D converter 32 at every predetermined crank angle, for example, every 1 degree of the crank angle, and is converted into a digital signal. It is supplied to the CPU 34.

The input / output bus 33 has a ROM 3
5, an ignition plug drive circuit 41 for driving the RAM 36 and the ignition circuit, and an injector drive circuit 42 for driving the injector 12 are connected. CPU34
Is supplied to the ignition plug 14, the ignition plug 14 is ignited to burn the air-fuel mixture in the fuel chamber. On the other hand, when an injector control command is supplied from the CPU 34 to the injector 12, the fuel injection valve (not shown) of the injector 12 is controlled, and the fuel supply amount is controlled. The ROM 35 stores a program for executing the control processing of the internal combustion engine according to the flowchart described in FIG. 3, a correspondence relationship for determining the volume efficiency from the engine speed and the in-cylinder pressure change rate, and a fuel efficiency based on the volume efficiency. And a map in which the correspondence for determining the injection time and the correspondence for determining the ignition angle from the volumetric efficiency are stored. This correspondence is determined, for example, by a preliminary experiment such as an actual machine test.

With the above-described configuration, the in-cylinder pressure corresponding to the crank angle can be sampled and taken in, and the taken-in crank angle value and the taken in-cylinder pressure value are stored in the RAM 36. In the following description,
Initial settings such as initialization of variables used by the CPU 34 have been completed, and it is assumed that the internal combustion engine, for example, a direct injection engine is operating.

FIG. 3 is a flowchart showing a subroutine for processing the control of the internal combustion engine according to the embodiment of the present invention. First, it is determined whether or not the suction stroke has been completed (step S1). If the suction stroke has not been completed, this subroutine is immediately terminated. On the other hand, when the intake stroke is completed in step S1, the engine speed Ne is taken from the engine speed signal (step S1).
2). Next, the in-cylinder pressure p ₁ (step S3) at the crank angle θ ₁ (for example, 270 degrees after intake TDC) and the crank angle θ ₁ + Δθ (for example, 320 after intake TDC)
(Ie, Δθ is 50 degrees), the in-cylinder pressure p ₁ + Δp (step S4) is taken. Then, θ ₁ , Δθ, p ₁
And the rate of change of the in-cylinder pressure dp / dθ = Δp / Δθ, which is a parameter of the in-cylinder pressure signal, is calculated from step S and Δp (step S
5). Using the in-cylinder pressure change rate dp / dθ and the engine speed Ne taken in step S2, the volume efficiency η _v of the internal combustion engine is determined with reference to the map as described above (step S6). In this map, a correspondence relationship based on a relationship as shown in FIG. 4 described later is stored in the ROM 35 as numerical data, and one map of the in-cylinder pressure change rate dp / dθ and the engine speed Ne is used for one internal combustion engine. it is to determine the volumetric efficiency eta _v. The volume efficiency η _v of the internal combustion engine is, for example, a volume expressed as a ratio of a stroke volume to a volume obtained by converting the volume of fresh air such as intake air or air-fuel mixture into a standard state (normal temperature, normal pressure). Ratio. Next, based on the volume efficiency η _v and the rotation speed Ne or the in-cylinder pressure change rate dp / dθ, referring to a map stored in the ROM 35, a fuel injection time T _i for determining a fuel injection amount and an ignition angle for determining an ignition timing. θ _IG is determined (step S7). Thereafter, the CPU 34 proceeds to step S
Issues a valve opening command to the injector drive circuit 42 based on the fuel injection time T _i determined in 7 (step S
8) An ignition command is issued to the ignition plug drive circuit 41 based on the ignition angle θ _IG (step S9), and this subroutine is terminated.

FIG. 4 is a graph showing a correspondence relationship for determining the volumetric efficiency from the in-cylinder pressure change rate and the engine speed.
This relationship is a linear relationship as described in JP-A-59-221433. When the in-cylinder pressure change rate dp / dθ is large, the volume efficiency is large and it is determined that a large amount of air has been inhaled. On the other hand, when the in-cylinder pressure change rate dp / dθ is small, the volume efficiency is small and the air It is determined that a small amount has been inhaled.

When the volumetric efficiency is high, the fuel injection time T _i is increased and the ignition angle θ _IG is reduced. On the other hand, when the volumetric efficiency is small, the fuel injection time T _i is reduced,
The ignition angle θ _IG is increased. Further, in the case of an internal combustion engine having multiple cylinders, as described above, it is possible to obtain an in-cylinder pressure signal for each cylinder, so that the volume efficiency is calculated for each cylinder, and the ignition angle and the fuel injection time are calculated. It can be adjusted.

In the above-described embodiment, the concept of estimating the state of change of the in-cylinder pressure in one engine cycle based on the rate of change in the rise of the in-cylinder pressure and calculating the volumetric efficiency based on this is estimated. It depends. Also,
In the present specification, the engine parameters refer to parameters necessary for engine control, such as an engine speed and an intake negative pressure, in addition to the in-cylinder pressure signal parameters. Further, the internal combustion engine refers to a fluid combustion engine including a direct injection engine, a hybrid engine, and the like.

[0020]

As described above, according to the control method for an internal combustion engine according to the present invention, it is possible to perform preferable control in response to a change in in-cylinder pressure in the current engine cycle.

[Brief description of the drawings]

FIG. 1 is a graph showing an in-cylinder pressure that changes according to a change in a crank angle.

FIG. 2 is a block diagram showing an apparatus for controlling an internal combustion engine according to an embodiment of the present invention.

FIG. 3 is a flowchart showing a subroutine for controlling an internal combustion engine according to the embodiment of the present invention.

FIG. 4 is a graph showing a correspondence relationship for determining volumetric efficiency from an in-cylinder pressure change rate and an engine speed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Internal combustion engine 21 In-cylinder pressure sensor 22 Crank angle detecting device 23 Crank shaft reference position detecting device 27 Angular position counter 32 High-speed A / D converter 34 CPU 35 ROM 36 RAM

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazunori Sawamura 1-4-1 Chuo, Wako-shi, Saitama Prefecture Inside Honda R & D Co., Ltd. (72) Hironao Fukuchi 1-4-1 Chuo, Wako-shi, Saitama (72) Inventor Hideyuki Oki 1-4-1 Chuo, Wako-shi, Saitama Prefecture Honda Research Institute Co., Ltd. (72) Kenji Abe 1-4-1 Chuo, Wako-shi, Saitama Company Honda R & D Center

Claims (1)

[Claims] 1. A control method for obtaining a control command for an internal combustion engine based on engine parameters including an in-cylinder pressure signal parameter and controlling the internal combustion engine based on the control command. A control method, wherein a change rate of an internal pressure is used as the in-cylinder pressure signal parameter.