JPS60111935A - Combustion monitoring apparatus - Google Patents

Abstract

PURPOSE:To attain to enhance the detection accuracy of the internal pressure of a cylinder, by constituting the title apparatus so that the output of a cylinder internal pressure sensor is corrected by subtracting an output value at a predetermined crank angle corresponding to a drift. CONSTITUTION:Sensor output S1 is drifted because the temp. of a sensor 4 is raised after an engine is accelerated and sensor outputs at exhaustion upper dead points t4-t6 come to DELTAV1, DELTAV2 and DELTAV3 and do not come to 0V. Sensor output values DELTAV1, DELTAV2 and DELTAV3 at exhaustion upper dead points are latched in synchronous relation to the 180 deg. signal S3 of a crank angle sensor 8 by an output correcting circuit 11 and the latched values are successively subtracted from the sensor output S1 in the next combustion cycle. Thus subtracted value is converted to an analogue value S2 by a D/A converter 12. Therefore, output drift due to pyroelectricity generated by the change in the temp of a piezoelectric element is corrected by the detection signal S2 obtained from the D/A converter 12 as shown by the solid line. As mentioned above, the detection accuracy of cylinder internal pressure is enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a combustion monitoring device for monitoring the combustion state of an internal combustion engine, etc., and particularly to a combustion monitoring device that corrects the output of a cylinder internal pressure sensor in accordance with drift.

Conventionally, this type of combustion monitoring device was the Tokko Sho+/-5i.
slI number, for example, Figure 1 (4) and Figure 1 (B
) are shown below. That is, a ring-shaped cylinder internal pressure sensor l is formed by sandwiching a pair of piezoelectric elements between electrodes 2 and 3, and this sensor l is used as a washer for a spark plug j, as shown in Fig. It is attached to the cylinder head 7, which is the outer wall of the combustion chamber B, with a constant initial pressure applied thereto. Then, the internal pressure of the seven rings inside the combustion chamber during combustion is applied to this cylinder internal pressure sensor via the spark plug j, and the electric charge generated in the piezoelectric element l in response to the force acting on the seven cylinder is taken out. The combustion state within the combustion chamber 6 is monitored based on the change in .

However, in such a conventional combustion monitoring device ff, since the cylinder internal pressure - the heat h1 conducted to the piezoelectric element of the sensor changes due to engine temperature changes, pyroelectricity is generated in the piezoelectric element and the cylinder internal pressure changes. The electric charge generated by the sensor drifts, and the drift makes it impossible to accurately detect the cylinder internal pressure, especially under engine acceleration/deceleration operating conditions. There was a problem that internal pressure could not be detected.

The present invention has been made by focusing on such conventional problems, and solves the above problems by correcting the output of the cylinder internal pressure sensor by the output difference at a predetermined crank angle corresponding to drift. The purpose is to provide a combustion monitoring device that

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 3 shows an example of the +1 configuration of the combustion monitoring device of the present invention,
Here, several cylinder internal pressure sensor tags are installed in the cylinder head 7 of the combustion chamber B as washers for the ignition plug S, and generate a cylinder internal pressure sensor output S/ corresponding to the cylinder internal pressure. A crank angle sensor 9 detects the engine crank angle and generates an rO0 signal S3 and a signal St/, and a crank angle sensor 9 latches the signal S+ from the crank angle sensor l and outputs a
This is a latch circuit that operates the D (analog-defthal) converter IO, and the A/D converter IO changes the output S/ of the cylinder internal pressure sensor l to A/ every 10 crank angles in synchronization with the output from the latch circuit. D-convert. //A is a memory circuit, and the latch circuit 9A performs A/D conversion W every /100.
Write down the output of /θ1. Leave it a. The output of this memory circuit//A and the output of the A/D converter/θ are connected to the output correction circuit l.
/, and every '1gO°, the A/D converter I
The output of the memory circuit //A is subtracted from the output of O. /
2 is the signal corrected by this output correction circuit // to the NIA
It is a D/A converter that performs (digital to analog) conversion.

Next, an example of the operation of the output correction circuit /l shown in FIG. 3 will be described with reference to the signal waveform diagram shown in FIG. First, as shown in FIG. 3, the cylinder internal pressure sensor l is attached to the cylinder head 7 as a washer for the spark plug 5, so 2'J4
As shown in the figure, the cylinder internal pressure sensor output S/ has a potential of OV when the cylinder internal pressure is equal to atmospheric pressure.

Therefore, when the temperature of sensor t (hereinafter referred to as sensor temperature) is normal temperature, the exhaust valve closes at exhaust top dead center (1
, to 13), the cylinder internal pressure sensor output S/ becomes OV. However, after accelerating the engine, the sensor temperature rises and pyroelectricity is generated, so the sensor output S/ drifts and reaches exhaust top dead center (t4 to t6).
) Tenosensor output S/ is Δv1. Δv2 and Δ■3, which does not result in OV.

Therefore, in the output correction circuit//, the i of the crank angle sensor is
In synchronization with the ro° signal S3, the above-mentioned sensor output value Δv1. Latch Δ■2 and ΔV3,
This latched value is sequentially subtracted from the sensor output S/ during the next combustion cycle. The value subtracted in this way is D
/A converter/2 converts it to an analog value of 8.2. Therefore, from D/A converter/2? i) Detection signal S2 spreading from
As shown by the solid line in the figure, the output drift due to pyroelectricity caused by changes in the humidity of the piezoelectric element is corrected.

・ FIG. 5 shows another embodiment of the present invention, where 73 is an intake pipe pressure sensor that detects the pressure in the intake pipe, which is not shown in the figure;
This is caused by the crank angle sensor r. 'Latch converter that latches signal S6 and signal S7, /6 is A
/7 is an output correction circuit that corrects the output of the D converter; /7 is a D/A conversion circuit that D/A converts the output of the output correction circuit /4;
1g is a throttle valve fully closed switch that detects the throttle valve fully closed, and the output of the throttle valve fully closed switch /g is supplied to a correction circuit /7. NIA is a launch circuit, and there is a memory circuit/
Latch 6A. This memory circuit /l is A/D conversion H
g ts ratio output input and the output of the memory circuit/4A as the input of the output correction circuit/B.

As in the previous embodiment, the cylinder internal pressure sensor l is attached to the cylinder head 7 of the combustion chamber B as a washer for the spark plug j, and generates the desired output SS to the cylinder internal pressure.
! is supplied to the A/D converter/s together with the output s9 of the intake air pressure sensor. On the other hand, the /100 signal S6 and the 10 signal S7 generated from the crank angle sensor are latched by the latch circuit /G and used to operate the A/D converter /3. The A/D converter/S is actuated by the latch circuit/4I, converts the cylinder internal pressure sensor output Sj into a digital signal for each crank angle, and also converts the cylinder internal pressure sensor output Sj to a digital signal at each crank angle/ramp.
Inhale every °? '? The output of the pressure sensor 13 is converted into a digital signal and sent to the output correction circuit/6.

The latch circuit /FA generates a latch signal every time /00 to operate the memory circuit /i. Note 1. @Circuit/6A is A/
The intake pipe pressure sensor output of D conversion 8H15 is stored for each ito'. Output correction circuit/6ba A/D conversion 1'f, /
The cylinder internal pressure sensor output of No. 3 is corrected by the output of the memory circuit/4A. The thus corrected output is converted into an analog signal S by the D/A converter/7.

In addition, in the embodiment shown in Fig. 3, only the output drift of the cylinder Yamakawa sensor was corrected, but in this example, in addition to this output drift ()'fIli positive, correction is also made for variations in sensor output characteristics and changes over time. This is what I decided to do.

Next, an example of the operation of the output correction circuit lB shown in FIG. 5 will be described with reference to the signal waveform diagram shown in FIG.

Under idling operating conditions in which the output of the throttle valve fully closed switch/g is in the ON state indicating that the throttle valve is fully closed, and the output generation rate at the crank angle is below a predetermined value, the output absolute value shown below The correction gX number is calculated by the output correction circuit/B. That is, first, as in the embodiment shown in FIG. 3, the output Sj of the cylinder internal pressure sensor t is calculated by calculating the deviation Δv1. between the atmospheric pressure at exhaust top dead center (1, to 16) and the sensor output. ΔV2 and Δ■
5, and this correction value (seventh correction value) is set as the cylinder internal pressure sensor output Sj'.

On the other hand, under the idle condition of one engine, the ignition advance value is small,
In addition, since the initial combustion is slow, the cylinder internal pressure at compression top dead center is the compressed intake pipe pressure P. The value obtained by subtracting the output value V of the sensor output S5 at the intake bottom dead center (crank angle T1) from the output value V2 of the sensor output SS at the compression top dead center (crank angle T2) is "■2 - ■1 ``' is equal to the value 1 (x (ρ - /) It is a ratio.

Therefore, next, a correction value V' is calculated based on equation (1) below, and this correction value V' is
A converter/7 performs D/A conversion to obtain signals s and r. Here, V in equation (1) is the cylinder internal pressure sensor output st'
is the value (primary correction value).

Therefore, the corrected output S obtained from the D/A converter/7
As shown in the figure, in addition to the output drift correction using pyroelectricity, the absolute value of variations in sensor output characteristics and changes over time are also corrected, making it possible to accurately detect cylinder internal pressure and monitor combustion. y, +1 degree improvement can be obtained.

As explained above, according to the present invention, the output of the cylinder internal pressure sensor is corrected by subtracting the output value at a constant crank angle, which corresponds to the drift.
It is possible to correct output drift due to pyroelectricity caused by temperature changes in the piezoelectric element. Furthermore, in the present invention, a predetermined calculation is performed using the output value of the sensor output at the compression top dead center and the output value of the sensor'V- output at the intake bottom dead center under idle conditions.
In addition to correcting the output drift, by changing f to t],
This provides the advantage of being able to correct variations in sensor output characteristics and changes over time.

Although the cylinder internal pressure sensor of this example is used as a washer for a spark plug, it is of course not limited to this and may be used as a washer for a cylinder head bolt.

[Brief explanation of drawings]

Figure 1 (A) is a plan view showing an example of the configuration of the cylinder internal pressure sensor, Figure 1 (B) is a vertical cross-sectional view taken along line I-1, and Figure 1 shows the cylinder internal pressure sensor installed in the engine. FIG. 3 is a block diagram showing the configuration of an embodiment of the present invention; FIG. 7 is a timing chart showing an example of signal waveforms of each part thereof; FIG. 5 is a diagram showing other embodiments of the present invention. FIG. 6 is a block diagram showing the configuration of the embodiment. FIG. 6 is a timing chart showing an example of signal waveforms of each part. l...Piezoelectric element, 2.3...Electrode, l...Cylinder internal pressure sensor, j...Ignition plug, 6...Combustion chamber, 7...Cylinder head, Z...Crank angle sensor , wa, /4'...Latch circuit, /θ, /3...A/D converter, //, , #;...Output correction circuit, /2, /7
...D/A converter, /3...Intake pipe pressure sensor, 1g...Throttle valve fully closed switch, S/, S! ;...Cylinder internal pressure sensor output, S2
, 3g...D/A converter output, S3, 34 ./
100 signal, S4 (, 87... 10 signal, S9... intake pipe pressure sensor output. Fig. 1 (A)

Claims (1)

[Scope of Claims] 1) A cylinder internal pressure sensor that detects the internal cylinder pressure of an engine and generates a detection output V, and a crank angle sensor that detects the crank angle of the engine and generates a detection signal T. , combustion that measures the output value Vo of the cylinder internal pressure sensor at a predetermined crank angle To at which the cylinder internal pressure becomes atmospheric pressure, and outputs the calculated value Ma of V-Vo, which is obtained by subtracting the output value Vo from the output V. Monitoring equipment. 2. Scope of patent claims! fl. In the apparatus described in item 1,
A combustion monitoring device characterized in that the crank angle To is a crank angle at which an exhaust valve of a cylinder to which the cylinder internal pressure sensor is attached closes.