JPH0639938B2 - Smoke detection device for diesel engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a detector for detecting smoke in exhaust gas from a diesel engine, and more particularly to a smoke detector in a diesel engine in which the detector is improved. Regarding the device.

[Prior Art] Controlling the amount of smoke (soot) in the exhaust gas of a diesel engine has become a major problem in terms of pollution prevention. The control of the amount of smoke is performed by measuring the amount of smoke in the exhaust gas and feeding it back to the arithmetic and control unit to control the fuel injection amount and injection timing. In this case, the amount of smoke is measured by the electrostatic induction method as described in US SAE 860012 report. In this method, a positively charged smoke is passed along a sensor made of a metal plate to generate an induced current in the sensor. Then, the output from the smoke sensor is amplified by the amplifier, and the quantity of electricity is obtained by integrating the output voltage with respect to time.

[Problems to be Solved by the Invention] However, the insulation resistance between the smoke sensor and the ground electrode temporally changes depending on the operating conditions, and a decrease in insulation resistance causes a leakage current. Then, this leakage current is superimposed on the output from the smoke sensor. Therefore, it becomes difficult to accurately measure a minute output. Along with this, a change in insulation resistance affects a leakage current, and the voltage waveform of the smoke sensor has a poor correlation with the amount of smoke. Therefore, the output obtained by integrating the voltage has a disadvantage that the accuracy of detecting the smoke amount is poor.

[Object of the Invention] The present invention has been made so as to eliminate the above problems, and its object is to reduce the noise superimposed on the output from the smoke sensor, to enable accurate measurement of a minute output, and to use a peak value detection circuit. An object of the present invention is to provide a smoke detection device for a diesel engine, which has an excellent correlation between the output from the smoke sensor and the actual amount of smoke, and can perform accurate fuel injection control.

[Means for Solving the Problems] The present invention includes a smoke sensor that is provided in an exhaust pipe of a diesel engine to generate a current when smoke in a charged state passes, and a high-pass filter circuit that outputs an output signal from the smoke sensor. An amplifier circuit that amplifies via
A peak value detection circuit having an input, an output and a reset terminal, respectively, and an output side of the amplification circuit is connected to an input terminal of the peak value detection circuit, and an output side of the peak value detection circuit is connected through a comparator. It employs a configuration including a monostable circuit connected to a reset terminal and an arithmetic and control unit for controlling fuel injection timing or injection amount according to an output signal from the output terminal of the peak value detection circuit.

[Operation] According to the present invention, it is possible to eliminate the superimposition of the leakage current output by the high-pass filter circuit. The influence of the deviation of the voltage waveform from the initial value of the zero level is reduced by resetting the peak value by the peak value detection circuit for each combustion cycle. For this reason, the correlation between the output from the smoke sensor and the actual smoke amount becomes good, and the width of the output signal from the smoke sensor can be sufficiently secured by the monostable circuit, and the calculation control device can obtain sufficient time for calculation. Will be able to.

[Effect of the Invention] According to the present invention, it is possible to eliminate the superimposition of the leakage current output by the high-pass filter circuit. The influence of the deviation of the voltage waveform from the initial value of the zero level is reduced by resetting the peak value by the peak value detection circuit for each combustion cycle. For this reason, the correlation between the output from the smoke sensor and the actual smoke amount becomes good, the smoke amount can be accurately measured, and the monostable circuit can secure a sufficient width dimension of the output signal from the smoke sensor. A diesel engine having a superior effect that the control device can sufficiently obtain the time required for the calculation, and this effect is combined to enable the calculation control device to accurately control the fuel injection amount or the injection timing. It is possible to provide the smoke detection device.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

First, in the diesel engine shown in FIG. 1, 1 is a cylinder in which a piston 2 is arranged, 3 and 4 are intake ports and exhaust ports communicating with the cylinder 1, and 5 is a cylinder in which light oil as fuel is atomized. It is an injection nozzle which injects into 1. An exhaust pipe 6 is connected to the exhaust port 4, and is composed of two pipes 7 and 8 connected to each other via flanges 7a and 8a. Reference numeral 9 is a smoke detecting device, which is arranged in the exhaust pipe 6 so as to be located at the connecting portion of the flanges 7a and 8a, as shown in FIG. The detection device 9 includes a support 10 formed by bending a rectangular plate made of alumina ceramic into a cylindrical shape.
have. A detection electrode 11 as a smoke sensor is formed on the inner surface of the support 10 by metallizing platinum paste. A lead wire 12 is led out from the detection electrode 11, and the lead wire 12 is connected to an input terminal 14 of a high pass filter circuit 13 shown in FIG. This input terminal 14 is connected to an inverting input terminal 18 of an operational amplifier 17 via capacitors 15 and 16,
The output terminal 19 of the operational amplifier 17 is connected to the inverting input terminal 22 of the operational amplifier 21 in the amplifier circuit 20.
The output terminal 23 of the operational amplifier 21 is connected to the non-inverting input terminal 26 of the operational amplifier 25 in the peak value detection circuit 24. The output terminal 27 of the operational amplifier 25 is connected to the non-inverting input terminal 29 of the operational amplifier 25 via the diode 28, and is also grounded from the diode 28 via the capacitor 30. The inverting input terminal 31 of the operational amplifier 25 is connected to the output terminal 27 via the diode 32. On the other hand, diode 2
A transistor 33 is connected in parallel with the capacitor 30 between 8a and the non-inverting input terminal 29 of the operational amplifier 25, and an output terminal 34 of the operational amplifier 25 is connected to a central processing unit 35 as an operational control device. There is. The central processing unit 35 is a RAM (random access memory) or RO.
It is configured by M (read only memory) and the like, and calculates the injection amount or injection timing of fuel to the injection nozzle 5 according to the output from the detection electrode 11. Further, from the common bus 36 of the output terminal 23 of the operational amplifier 21 and the non-inverting input terminal 26 of the operational amplifier 25, the comparator 3
7 is connected to an inverting input terminal 38, and its output terminal 39 is connected to an input terminal 41 of a multivibrator 40 as a monostable circuit. This multi-vibrator 40 is a well-known one composed of transistors 42, 43, a resistor 44 and a capacitor 45, and its output terminal 46 has another monostable circuit, that is, the multi-vibrator 4.
7 are connected to the input terminal 48. This multi-vibrator 47 is also a well-known one made up of transistors 49, 50, a resistor 51 and a capacitor 52.
Reference numeral 3 is connected to the base 33a of the transistor 33 as a reset terminal in the peak value detection circuit 24.

Then, when the engine is operating, exhaust gas is exhausted from the exhaust port 4, the pipe 7 of the exhaust pipe 6, the support 10 and the pipe 8.
Are sequentially discharged to the outside. In this exhaust gas,
The positively charged smoke (soot) is included, and in the process of passing the smoke through the detection electrode 11, a current corresponding to the amount of smoke is generated in the detection electrode 11. The output of this current passes through the high-pass filter circuit 13 and the amplifier circuit 20,
After passing, the trigger-pulse signal shown in (a) of FIG. 4 appears. The pulse signal of (a) is output from the common bus 36 through the inverting input terminal 38 of the comparator 37 and the output terminal 39 as the pulse signal shown in (b) of FIG. The pulse signal of (B) is input to the input terminal 41 of the multivibrator 40 and appears from the output terminal 46 as the pulse signal of (C) of FIG. This pulse signal (c) is output from the output terminal 53 via the input terminal 48 of the multivibrator 47 as the pulse signal shown in (d) of FIG. This output is given to the base 33a of the transistor 33 in the peak value detection circuit 24.

On the other hand, in the peak value detection circuit 24, the capacitor 30
Is equal to the voltage V3 at the output terminal of the operational amplifier 25, and the voltage V1 at the non-inverting input terminal 26 of the operational amplifier 25 is
Is controlled to be equal to the voltage V3 of the inverting input terminal 31. Therefore, the voltage of the output terminal 27 of the operational amplifier 25 is increased by the amount of the forward voltage drop of the diode 28a. Therefore, the diodes 28a and 32 are turned on and off, and the voltage V3 follows the voltage V1.
Further, when the voltage V1 becomes lower than the voltage V2, the voltage of the output terminal 27 of the operational amplifier 25 also decreases, and the diode 28
Since a is turned off and the voltage V3 is equal to the voltage V2, the peak value of the voltage V1 is held. Therefore, when the pulse signal of (a) of FIG. 4 is input to the peak value detecting circuit 24, the peak value of the pulse signal is held and the pulse of (d) of FIG. Each time a signal is input, the capacitor 30 discharges and the voltage V2 becomes zero potential, so that the pulse signal shown in (e) of FIG. 4 is obtained at the output terminal 34. In this (e) pulse signal, the peak value of the pulse is kept at the peak value corresponding to (a), and the pulse width dimension is the sum of the width dimensions of the (b) pulse signal and (c) pulse signal. Shown. The pulse signal shown in (e) of FIG. 4 is input to the central processing unit 35, and based on this pulse signal, the central processing unit 35 calculates an appropriate injection amount or injection timing of the fuel for the injection nozzle 5 and pollutes the pollution. Keep the amount of smoke in the exhaust gas to a minimum to prevent it.

As described above, according to the above configuration, the leakage current output is prevented by the high-pass filter circuit 13, and in the pulse signal input to the central processing unit 35, the peak value of the pulse is (a) in FIG. ) Is maintained at the peak value, the correspondence with the actual smoke amount in the exhaust gas becomes accurate, and their correlation becomes good. Further, the pulse width dimension becomes wide as shown as the sum of the width dimensions of the pulse signal of (b) and the pulse signal of (c) in FIG. 4, and is necessary for the central processing unit 35 to calculate the amount of smoke. Sufficient time can be secured. Therefore, the injection timing or injection amount of the fuel to the 3-injection nozzle 5 can be accurately implemented, and the amount of smoke in the exhaust gas can be always kept to the minimum without being erroneous.

Further, in the above-described embodiment, since the detection device 9 is disposed at the position where the flanges 7a and 8a of the exhaust pipe 6 are present, there is an effect in the embodiment that the mounting is easy even inside the pipe. In this case, it goes without saying that the detection device 9 may be arranged at any position in the exhaust pipe 6.

In addition, although the support 10 is formed in a cylindrical shape in the above-described embodiment, the shape is not limited to the cylindrical shape, and may be a square tube shape or a hexagonal tube shape. In this case, the exhaust pipe has a square tubular shape or a hexagonal tubular shape depending on the shape of the support.

The material of the support is not limited to alumina ceramics, and ceramics such as mullite, zircon, silicon nitride, aluminum titanate can be used as appropriate.

In addition, in concrete implementation, various modifications can be made without departing from the scope of the present invention.

[Brief description of drawings]

1 shows an embodiment of the present invention, FIG. 1 is an exploded perspective view showing an exhaust pipe portion of a diesel engine, and FIG. 2 is an enlarged vertical cross-sectional view showing a main part, particularly a mounting state of a detection device to an exhaust pipe. 3 is an electric circuit diagram, and FIG. 4 is a time chart. In the figure, 1 ... Cylinder, 2 ... Piston, 3 ... Intake port,
5 ... Injection nozzle, 6 ... Exhaust pipe, 9 ... Detection device, 10 ... Support, 11 ... Detection electrode (smoke sensor), 12 ... Lead wire, 13 ... High pass filter circuit, 20 ... Amplification circuit,
24 ... Peak value detection circuit, 33 ... Transistor (reset terminal), 40, 47 ... Multivibrator (monostable circuit), 35 ... Central arithmetic unit (arithmetic control unit)

Claims (1)

[Claims] 1. A smoke sensor, which is provided in an exhaust pipe of a diesel engine and produces a current when smoke in a charged state passes, an amplifier circuit for amplifying an output signal from the smoke sensor through a high-pass filter circuit, and an input. A peak value detection circuit having an output terminal and a reset terminal respectively, and an output side from the amplifier circuit is connected to an input terminal of the peak value detection circuit, and an output side thereof is reset through a comparator. Smoke detection device in a diesel engine, comprising a monostable circuit connected to a terminal, and an arithmetic control device for controlling fuel injection timing or injection amount according to an output signal from the output terminal of the peak value detection circuit. .