JP2934799B2 - Combustion state monitoring device for multi-cylinder internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion state monitoring apparatus for an internal combustion engine which detects an internal pressure of a cylinder and detects abnormal combustion such as misfire or knock of the internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, a pressure sensor made of a piezoelectric element is inserted into the position of a washer of a spark plug of an internal combustion engine such as a two-stroke engine, a four-stroke engine or a rotary engine to tighten the spark plug and detect the cylinder internal pressure. In some cases, a combustion state such as misfire or knock is detected. In a conventional device of this type, in order to simplify the circuit, the outputs of the pressure sensors disposed in each cylinder are collectively connected to an amplifier (charge-voltage amplifier), and the output is integrated, an operation determination circuit, etc. To detect a combustion state such as misfire. However, in that case, the high-frequency output due to the seating of the intake valve and the exhaust valve of another cylinder is superimposed on the in-cylinder pressure output of the cylinder during the combustion stroke. Therefore, a filter has been added to the input circuit to remove a high-frequency output. Japanese Utility Model Laid-Open Publication No. 59-155532 proposes a configuration in which the output of a pressure sensor is input to an input circuit for each cylinder in which an explosion stroke and a compression stroke do not overlap.

[0003]

However, in the case where a filter is added to the input circuit, there is a problem that the input circuit becomes complicated and knock detection becomes difficult. In addition, in the case where the explosion stroke and the compression stroke are simply summarized for each cylinder that does not overlap, except for a two-stroke engine without an intake valve and an exhaust valve or a rotary engine, for example, when applied to a six-cylinder internal combustion engine, an intake valve The seating noise is superimposed or the exhaust valve seating noise is superimposed. For example, as shown in FIG. 3, when the pressure sensors of the first cylinder and the fifth cylinder are connected, the combustion state of the fifth cylinder falls within a range A1 from 60 degrees before top dead center to 60 degrees after top dead center for monitoring the combustion state. The intake valve seating noise C5 is superimposed. On the other hand, as shown in FIG.
When the pressure sensors of the first cylinder and the sixth cylinder are connected, the exhaust valve seating noise B1 of the first cylinder is superimposed on the range A6 from 60 degrees before top dead center to 60 degrees after top dead center for monitoring the combustion state. There was a problem that it would. The present invention has been made to solve the above problems, and an object of the present invention is to reduce the number of input circuits by inputting several pressure sensors to a single input circuit while reducing the number of input circuits. Provided is a combustion state monitoring device for a multi-cylinder internal combustion engine, which can eliminate a superposition of valve seating noise and exhaust valve seating noise, detect an accurate pressure change, and determine a combustion state with high reliability. It is in.

[0004]

In order to achieve the above object, the present invention provides a pressure sensor provided for each cylinder for converting the cylinder internal pressure of each cylinder into an electric signal corresponding to the pressure value, and detecting the pressure. A crank angle sensor for detecting the crank angle of the engine, an amplifier to which the output of the pressure sensor for each cylinder is connected and input, and a predetermined period before and after the top dead center of each cylinder based on a signal from the crank angle sensor And a selection means for passing an output signal from the amplifier only. Combining the outputs of the pressure sensors of cylinders whose explosion strokes are 240 degrees apart from each other by a crank angle, Is supplied to the amplifier, and a combustion state monitoring device for a multi-cylinder internal combustion engine is provided.

[0005]

In the combustion state monitoring apparatus for a multi-cylinder internal combustion engine configured as described above, the explosion strokes are set to be equal to each other at a crank angle of 240 degrees.
The outputs of the pressure sensors of three cylinders separated by degrees are input to one amplifier. Then, the intake valve sitting noise and the exhaust valve sitting noise of the three cylinders are generated at positions away from the vicinity of the top dead center of each cylinder, and are eliminated by the selection means and are not superimposed on the output signal.

[0006]

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a combustion state monitoring device.
A pressure sensor 3 is attached to each spark plug 2 of the six-cylinder internal combustion engine 1. The pressure sensor 3 is a piezoelectric sensor attached between the spark plug 2 and the cylinder block instead of the washer, and generates a charge Q proportional to the internal pressure of each cylinder. The outputs of the six pressure sensors 3 for each cylinder are connected in parallel three by three and input to a charge amplifier (charge-voltage amplifier) 4. The first charge amplifier 4 is connected to the pressure sensors 3 of the first, second and third cylinders, and the second charge amplifier 4 'is connected to the fourth and fourth cylinders.
The pressure sensors 3 of the fifth and sixth cylinders are connected. The charge amplifier 4 includes an operational amplifier 41, a feedback resistor 42 for preventing zero point drift, and a feedback capacitor 43, and converts the charge Q output from each pressure sensor 3 into a voltage V in a relation of V = Q / C.
And amplify.

The crank angle sensor 5 optically detects the rotation angle of the crankshaft, and sends out a crank angle signal K corresponding to the rotation angle. In the analog switch circuits 6 and 6 'to which the outputs of the charge amplifiers 4 and 4' are inputted, based on the crank angle signal K, 60 degrees before the top dead center in the combustion state of each cylinder.
To 60 ° after the top dead center are input to the combustion state determination circuit 7. The combustion state determination circuit 7 includes a band pass filter 71, a knock determination circuit 72, and a display circuit 73. Signals from the speed sensor 81, the intake air amount sensor 82, and the like are input to the knock determination circuit 72. The display circuit 73 has, for example, six LEDs, and turns on the LED corresponding to the cylinder in which knock has occurred based on the signal from the knock determination circuit 72 and the crank angle signal K.

FIG. 2 is a timing chart showing the relationship between the stroke of each cylinder and the seating noise. Since the engine is a six-cylinder engine, the ignition sequence is the order of the first, fifth, third, sixth, second, and fourth cylinders, and the stroke of each cylinder is shifted by 120 degrees crank angle. The sections from 60 degrees before the compression top dead center to 60 degrees after the compression top dead center, which are sections necessary for monitoring the combustion state, are indicated by hatched portions A1 to A6 in the figure. Exhaust valve seating noise occurs at the beginning of each intake stroke, and is indicated by arrows B1 to B6 in the drawing.
Indicated by Further, the intake valve seating noise occurs at the beginning of each compression stroke, and is indicated by arrows C1 to C6 in the figure. Then, three cylinders whose strokes are separated from each other by 240 degrees, for example,
When the signals of the third and second cylinders are combined, combustion state monitoring sections A1, A3, and A2 appear at intervals of exactly 120 degrees, and the exhaust valve seating noises B1 to B3 and the intake valve seating noise C1 appear in the 120-degree intervals. To C3 occur. Each of the noises B1 to B3, C1 to C in the combustion state monitoring sections A1, A3, and A2.
Since 3 does not overlap, it is possible to accurately grasp the combustion state. The fourth, fifth and sixth steps are 240 degrees apart from each other
The same can be said for the combination of cylinders.

In the above embodiment, a six-cylinder engine has been described as an example. However, it is clear that the same holds true with a three-cylinder engine. In the case of a three-cylinder engine, the strokes of the respective cylinders are shifted by 240 ° crank angle, so that the outputs of the pressure sensors of the three cylinders may be combined into one.

In the above embodiment, the cylinder pressure is detected at regular intervals of 60 ° before and after the top dead center by the analog switch circuit 6. However, these crank angles are appropriately determined according to the number of cylinders of the internal combustion engine. The detection angle may be changed before and after the top dead center. Further, a pressure state in an arbitrary crank angle region can be detected.

[0011]

According to the present invention, the outputs of the pressure sensors of the cylinders having the above-mentioned construction and whose explosion strokes are separated from each other by 240 degrees in crank angle are combined, and the combined output is supplied to the amplifier. Therefore, with a configuration in which the number of amplifiers is smaller than the number of pressure sensors, the seating noise of the intake valve and the exhaust valve is not superimposed on the signal, and there is an excellent effect that the combustion state can be monitored accurately.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a combustion state monitoring device;

FIG. 2 is a timing chart showing a relationship between a stroke of each cylinder and a seating noise.

FIG. 3 is a timing chart,

FIG. 4 is a timing chart.

[Explanation of symbols]

1. . 1. internal combustion engine; . 2. spark plug, . Pressure sensor, 4. . Charge amplifier (amplifier),
5. . 5. Crank angle sensor, . 6. an analog switch circuit (selection means); . Combustion state determination circuit.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-203021 (JP, A) Fully open sho 59-155532 (JP, U) Really open sho 63-44133 (JP, U) (58) Field (Int.Cl. ⁶ , DB name) F02D 41/00-45/00 395

Claims (1)

(57) [Claims] A pressure sensor provided for each cylinder to convert and detect an internal pressure of each cylinder into an electric signal corresponding to the pressure value; a crank angle sensor to detect a crank angle of an internal combustion engine; An amplifier connected to and input to the output of the pressure sensor, and selection means for passing an output signal from the amplifier for a predetermined period before and after top dead center of each cylinder based on a signal from the crank angle sensor. In a combustion state monitoring device for a cylinder internal combustion engine, a multi-cylinder is characterized in that the outputs of pressure sensors of cylinders whose explosion strokes are separated from each other by 240 degrees in crank angle are combined and the combined output is supplied to the amplifier. A combustion state monitoring device for an internal combustion engine.