JP2000145500A - Combustion control method for internal combustion engine by means of ion current - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent erroneous control of combustion conditions during a period through which accurate measurement of ion current is not possible by inhibiting control of combustion conditions in an operating condition of an internal combustion engine where a discharge time is long or an engine speed is high as measured in terms of a signal level of ion current. SOLUTION: An electronic control unit 6 receives output signals from an intake vacuum sensor 13, a cam position sensor 14, a vehicle speed sensor 15, an idle switch 16, a water temperature sensor 17, an oxygen sensor 21, and other detecting devices and, according to these signals, controls fuel injection. An ion current measurement circuit 25 is also employed to measure ion current that flows in each ignition and the results of these measurements are reflected on the control of combustion conditions of an engine 100. The electronic control unit determines, at this time, to see if an engine speed is lower than a criterion speed set to a level higher than an engine speed that is the limit in ordinary detection of misfire. If the engine speed is higher than the criterion speed, the unit inhibits combustion control by means of ion current.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion control method using an ionic current of an internal combustion engine, which mainly controls a combustion state in an automobile engine based on a signal level of an ionic current generated in a combustion chamber after ignition.

[0002]

2. Description of the Related Art Conventionally, for controlling the combustion state of an internal combustion engine, for example, knock control, a knock control system using a vibration type knock sensor has been known. In such a knock control system, a vibration when a knock is generated is detected by a vibration type knock sensor, it is determined whether or not the vibration is caused by the knock, and if it is determined that the knock is generated, the ignition timing is retarded. The purpose is to control the combustion state of the internal combustion engine so as to eliminate knock.

As a method for detecting the occurrence of knock, a method for detecting the occurrence of knock using an ion current is disclosed in, for example, Japanese Patent Application Laid-Open No. 58-7536. There is known an apparatus that detects (determines) the occurrence of knock from the amplitude and width of an ion signal corresponding to. Also in this example, in order to prevent the spark noise from being superimposed on the ion signal, the detection of the ion signal is performed after a predetermined time delay from the ignition. And even in the case of such a method of detecting the occurrence of knock due to the ion current, a predetermined frequency band (knock frequency component) of the ion current similarly to the case of the knock sensor described above.
Is known that performs signal processing by peak-holding the signal.

[0004]

By the way, in the system utilizing ion current, the ignition current is measured using a spark plug, and the combustion state is controlled based on the measurement result. During the discharging period, normal detection of the ion current cannot be performed. Typically,
In such a system, when the discharge time is short or the engine speed is low, the discharge period does not overlap with the period during which the ionic current is generated, so that the ionic current can be measured. If the discharge time is short and the discharge period is long or the engine speed is high, the discharge may not be completed when measuring the ion current, and the ion current may not be measured normally. As a result, since the ion current cannot be measured accurately, the combustion state of the internal combustion engine such as knock detection cannot be controlled in some cases.

[0005] An object of the present invention is to solve such a problem.

[0006]

In order to achieve the above object, the present invention takes the following measures. That is, in the combustion control method using the ionic current of the internal combustion engine according to the present invention, when the signal level of the ionic current is measured, the operating state of the internal combustion engine may be such that the discharge time is long or the engine speed is low as described above. If you say it is expensive,
The control of the combustion state of the internal combustion engine is prohibited based on at least the engine speed.

[0007]

DETAILED DESCRIPTION OF THE INVENTION The invention according to the present invention measures a signal level of an ionic current generated for each ignition through a spark plug in a combustion chamber of an internal combustion engine, and determines a combustion state of the internal combustion engine based on the measured signal level. A combustion control method using an ion current of an internal combustion engine that controls an internal combustion engine, wherein an operation state of the internal combustion engine when a signal level of the ion current is measured is detected, and at least the engine speed is preset in the detected operation state of the internal combustion engine. A combustion control method using an ionic current of the internal combustion engine, wherein control of the combustion state of the internal combustion engine is prohibited when the rotation speed exceeds the determined rotation speed.

With such a configuration, in an operating state in which the engine speed is higher than the determined engine speed, control of the combustion state of the internal combustion engine is prohibited. State control is not performed by mistake. Therefore, for example, in the case of controlling the occurrence of knock, it is possible to solve the problem that the engine is retarded even though knock is not generated and the operating performance of the internal combustion engine is reduced. .

[0009]

An embodiment of the present invention will be described below with reference to the drawings. The engine 100 schematically shown in FIG. 1 is of a three-cylinder type for an automobile, and has a throttle valve 2 that opens and closes in response to an accelerator pedal (not shown) in an intake system 1 thereof.
The surge dunk 3 is provided on the downstream side. In the vicinity of one end communicating with the surge tank 3, a fuel injection valve 5 is further provided. The fuel injection valve 5 is controlled by the electronic control unit 6 so as to be independently injected for each cylinder. ing. A spark plug 18 that generates sparks and serves as an electrode for ion current is attached to a cylinder head 31 that forms the combustion chamber 30. Further, an O ₂ sensor 21 for measuring the oxygen concentration in the exhaust gas is attached to the exhaust system 20 at a position upstream of a three-dimensional catalyst 22 disposed in a pipe leading to a muffler (not shown). I have.

The electronic control unit 6 includes a central processing unit 7
, A storage device 8, an input interface 9, an output interface 11, and an A / D converter 10. The input interface 9 has an intake pressure signal a output from an intake pressure sensor 13 for detecting the pressure in the surge tank 3 and a cylinder output from a cam position sensor 14 for detecting the rotation state of the engine 100. Vehicle speed sensor 1 for detecting discrimination signal G1, crank angle reference position signal G2, engine speed signal b, and vehicle speed
5, an IDL signal d output from an idle switch 16 for detecting the open / close state of the throttle valve 2, and a water temperature signal e output from a water temperature sensor 17 for detecting the engine coolant temperature. , The current signal h output from the O ₂ sensor 21 and the like are input. On the other hand, the output interface 11 outputs a fuel injection signal f to the fuel injection valve 5 and an ignition pulse g to the spark plug 18. The spark plug 18 is connected via a high voltage diode 23 to a bias power supply 24 for measuring an ion current. This bias power supply 24
Various methods known in the art can be used for the circuit 25 for measuring the ion current and the measurement method itself. In this embodiment, the ion current can be detected for each cylinder, so that the combustion state can be controlled for each cylinder.

The electronic control unit 6 includes an intake pressure signal a output from the intake pressure sensor 13 and a cam position sensor 14.
The basic injection time is corrected by various correction coefficients determined according to the operating state of the engine 100 to determine the fuel injection valve opening time, that is, the injector final energization time T, with the rotation speed signal b output from the main information as main information. A program for controlling the fuel injection valve 5 based on the determined energizing time and injecting fuel corresponding to the engine load into the intake system 1 is built in.

In addition, while controlling the fuel injection of the engine 100 as described above, the ionic current flowing at each ignition is measured, the combustion state of the engine 100 is detected, and the combustion state is controlled based on the detection result. The electronic control unit 6 is programmed. The control of the combustion state detects, for example, the occurrence of knock based on a knock signal superimposed on the ion current, and in the case where knock has occurred, retards the ignition timing to eliminate the occurrence of knock. Or detecting the occurrence of misfire from the current value of the ion current.

Further, a signal level of an ion current generated at each ignition in the combustion chamber 30 of the engine 100 via the spark plug 18 is measured, and the combustion state of the engine 100 is controlled based on the measured signal level. And the engine 1 when measuring the signal level of the ion current
The electronic control unit 6 includes a program that detects the operating state of the engine 100 and prohibits the control of the combustion state of the engine 100 when at least the engine speed exceeds a predetermined determination speed in the detected operating state of the engine 100. It is. The operating state of the engine 100 is detected based on, for example, the engine speed, load (intake pressure), and the like.

An outline of the combustion control program based on the ion current is as shown in FIG. Step S1
Then, it is determined whether or not the engine speed is lower than a predetermined determination speed KIONMASK. The determination rotational speed KIONMASK in this embodiment is shown in FIG.
As shown in FIG. 2, the setting is such that the load is high when the load of the engine 100 is small, and decreases as the load increases. This is because when the engine speed is high, the initial discharge energy for spark discharge can be small,
Similarly, even when the load is light, it is based on the fact that the discharge time becomes longer because the initial discharge energy is small. In other words, it may be set based on the engine speed at which the discharge continues even during the period in which combustion continues in the explosion stroke. Normally, such an engine speed is relatively high, and thus the determination engine speed KIONMASK is set to a value higher than the engine speed which is a limit in normal misfire detection.

If it is determined in step S1 that the engine speed is lower than the determination speed KIONMASK, this program is terminated. On the other hand, when the engine speed is equal to or higher than the determination speed KIONMASK,
Proceeding to step S2, the combustion control by the ion current is prohibited. This is because the ion current is detected by the spark plug 18 when a high voltage is applied to the spark plug 18 after combustion starts and flows into the combustion gas. This is because the ion current flows only after the discharge, so that the period during which the ion current flows is shortened and the combustion state is not reflected. When such an ion current is detected, the detected ion current does not accurately reflect the state of combustion. Therefore, when various types of combustion control are performed based on the signal level of the ion current, the operation state of the engine 100 is reduced, so that the combustion control is prohibited.

As described above, the duration of the discharge period is detected based on the number of revolutions of the engine, and the combustion control using the ion current is prohibited in the operation state where the discharge period is long and the generation period of the ion current is long. Accordingly, the operating state of the engine 100 can be accurately grasped, and appropriate control of the combustion state can be performed. The present invention is not limited to the embodiments described above.

In the above embodiment, in order to detect the operating state of the engine 100, the combustion state is controlled by combining the magnitude of the load and the determined rotational speed. However, the operating state is detected only by the engine rotational speed. May be used. In addition, the configuration of each unit is not limited to the illustrated example, and various modifications can be made without departing from the spirit of the present invention.

[0018]

As described above, according to the present invention, the control of the combustion state of the internal combustion engine is prohibited in the operating state in which the engine speed is higher than the determined engine speed, so that the ion current can be measured accurately. At least, it is possible to prevent erroneous control of the combustion state. Therefore, for example, in the case of controlling the occurrence of knock, it is possible to solve the problem of delaying the operation performance of the internal combustion engine even though knock has not been generated.

[Brief description of the drawings]

FIG. 1 is a schematic structural explanatory view showing one embodiment of the present invention.

FIG. 2 is a flowchart showing a schematic control procedure of the embodiment.

FIG. 3 is an operation explanatory view of the embodiment.

[Explanation of symbols]

 Reference Signs List 6 ... Electronic control device 7 ... Central processing unit 8 ... Storage device 9 ... Input interface 10 ... A / D converter 11 ... Output interface 18 ... Spark plug 30 ... Combustion chamber

Continued on the front page F term (reference) 3G019 AB01 AB02 CD06 GA01 GA05 GA08 GA09 GA11 GA14 GA18 LA05 3G084 BA13 BA16 DA38 FA05 FA10 FA11 FA20 FA25 FA29 FA33 FA38 3G301 JA22 LA00 MA13 NE00 PA07Z PA14Z PC08Z PD03Z PE01Z PE03Z PE05Z PE08Z

Claims (1)

[Claims] An ion engine of an internal combustion engine controls a combustion state of an internal combustion engine based on a signal level of an ion current generated at each ignition through a spark plug in a combustion chamber of the internal combustion engine. A combustion control method using current, wherein an operating state of the internal combustion engine at the time of measuring a signal level of an ion current is detected, and at least the engine speed exceeds a predetermined determination speed in the detected operating state of the internal combustion engine. Control of the combustion state of the internal combustion engine by ionic current.