JPS6235252A - Smoke detector - Google Patents

Abstract

PURPOSE:To perform detection with invariably high precision and simple structure by detecting the sticking-incineration period of carbon particles in exhaust gas between electrode from the detected value of a current detecting circuit and outputting a pulse signal corresponding to the period. CONSTITUTION:When smoke in exhaust gas, i.e. carbon particles stick between platinum electrodes 11 and 12, a current begins to flow between them and a voltage signal VA increases with the amount of the stuck carbon particles. When the signal reaches a reference level VB, the carbon particles fire themselves and burn and the voltage signal falls to 0 again. The sticking-incineration period of the carbon particles varies with the amount of carbon particles in the exhaust gas, i.e. smoke concentration. Then, a comparator 33 compares the signal VA with the level VB to output a pulse signal VS which goes up to a high level when VA>VB, and then the signal VS varies at a period corresponding to the smoke concentration. Consequently, the signal VS is used as an input signal to a smoke controller.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a smoke detection device for detecting the amount of carbon particles, that is, the smoke concentration, present in the exhaust gas of various combustion devices such as internal combustion engines.

[Prior Art] Conventionally, in internal combustion engines, especially diesel engines, in order to prevent the generation of smoke caused by carbon particles remaining in exhaust gas, a smoke detection device that outputs a signal according to the smoke concentration in exhaust gas has been used. There is a control device that performs so-called feedback control, which directly detects the smoke concentration in exhaust gas and optimally controls the ignition timing and fuel supply amount according to the detected smoke concentration to prevent smoke from occurring.

The smoke detection device used in the above control device includes a light transmission type that detects smoke concentration from changes in the light transmittance of smoke, and an ion current type that detects smoke concentration based on changes in ion current caused by smoke. There is also a method using a Co sensor that detects the smoke concentration by detecting the amount of change in CoII degree by utilizing the correlation between the increase in Co generation in exhaust gas and the smoke concentration.

[Problems to be Solved by the Invention] As described above, in order to detect the smoke concentration in the exhaust gas and perform feedback control on the ignition timing and fuel supply amount, a control circuit consisting of a microcomputer or the like is used as a control device. However, since the conventional smoke detection device described above is configured to output an analog signal whose detection level changes depending on the smoke concentration, the input section of the control circuit receives that signal at the detection level. An A/D converter is required to convert the signal into a digital signal corresponding to the signal, which causes a problem that the circuit becomes complicated.

SUMMARY OF THE INVENTION Therefore, the present invention has been made for the purpose of providing a smoke detection device which can directly input a detection signal to a control circuit without going through an A/D converter or the like, and which has a simple structure. , the following configuration was adopted.

[Means for Solving the Problems] That is, the structure of the present invention in C and the means for solving the above problems is as follows: a detection section comprising an electrode, a voltage application means for applying a predetermined voltage between the electrodes of the detection section, a current detection means for detecting a current flowing between the electrodes, and a current detected by the current detection means. pulse signal output means for detecting the adhesion-incineration cycle of carbon particles in the exhaust gas between the electrodes caused by the application of voltage by the voltage application means from periodic changes in the voltage, and outputting a pulse signal according to the cycle; The gist of this invention is a smoke detection device characterized by the following.

[Function] In the smoke detection device of the present invention configured as described above, first, since the detection section is provided in the exhaust gas,
Carbon particles in the exhaust gas, which causes smoke, adhere to the heat-resistant insulating substrate.

Then, since a voltage is applied between the electrodes on the heat-resistant insulating substrate by the voltage applying means, a current flows between the electrodes due to the conductivity of the carbon particles.

This current increases by &N as the number of attached carbon particles increases, but due to this increase in current, the carbon particles self-ignite and are incinerated. Then, current no longer flows between the electrodes, and carbon begins to adhere between the electrodes again, allowing current to flow again. Such carbon particle adhesion and incineration operations are repeated at intervals depending on the amount of carbon particles in the exhaust gas, that is, the smoke concentration. - In the power tree invention, current detection means for detecting the current flowing between the electrodes is provided, and the pulse signal output means is configured to output a pulse signal in accordance with periodic changes in the current. Therefore, the pulse signal output from the pulse signal output means is a signal corresponding to the smoke concentration in the exhaust gas,
This pulse signal can now be directly input to the control circuit as a detection signal.

Here, the heat-resistant insulating substrate constituting the detection section is as follows:
For example, plate-shaped alumina (AAzOa), magnesia (M
ood, berylia (Be O), mullite (3A standing Z
Oa・2SiOz＞, Spinel (M(110・A20
Insulating porcelain such as 3) may be used, and as a result, the heat resistance and corrosion resistance of the detection element portion can be improved compared to conventional detection devices.

The pair of electrodes provided on this heat-resistant insulating substrate may be made of a heat-resistant, corrosion-resistant metal such as platinum (Pt), and may be printed on the substrate in a desired pattern. The structure can be simplified and productivity can be improved.

Next, the voltage applying means applies a voltage between the electrodes. For example, if the combustion equipment to be smoke controlled is a diesel engine of a vehicle, the battery installed in the vehicle may be used as is. good. The current detection means detects the current flowing between the electrodes due to the adhesion of the carbon particles; for example, a resistor is provided in series with the signal line from the voltage application means to the electrode, What is necessary is to detect the voltage.

The pulse signal detection means outputs periodic changes in the current value detected by the current detection means as a pulse signal, and for example, the pulse signal detection means outputs periodic changes in the current value detected by the current detection means (specifically, A simple comparator circuit configured to output a high level signal when the voltage value (corresponding to the current value) exceeds a predetermined value may be used.

[Practical theory 11i! l] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram showing the overall configuration of the smoke detection device of this embodiment, and FIG. 2 is a partially broken pressure surface view showing the detection section.

As shown in FIG. 1, this smoke detection device operates a detection section 2 provided in an exhaust pipe 1 of a diesel engine (not shown), and outputs a pulse signal according to the smoke concentration in exhaust gas. It is composed of a detection circuit 3 that performs

As shown in FIG. 2, the detection unit 2 has an alumina substrate 13 provided with a pair of platinum electrodes 11 and 12 fixed inside the exhaust pipe 1, and a detection circuit 3 detects carbon particles in the exhaust gas from each platinum electrode 11. 12, a housing 14 for gripping and fixing the alumina substrate 13 to the exhaust pipe 1, and lead wires 15 and 16 connecting each platinum electrode 11, 12 and the detection circuit 3 are provided. There is. Further, the housing 14 is formed into a cylindrical shape in order to hold the alumina substrate 13 and to insulate and protect the connecting portions between the platinum electrodes 11 and 12 on the alumina substrate 13 and the lead wires 15 and 16 inside. A spacer 17 for gripping the alumina substrate 13 is provided at the tip of the hollow exhaust pipe 1 side, and an insulating material 18 is provided around the connecting portion between the platinum electrodes 11 and 12 and the lead wires 15 and 16. . Further, the hollow portion above the insulating material 18 of the housing 14 is filled with a sealing material 19 made of glass or the like to prevent exhaust gas from leaking to the outside. In the figure, 20 represents a protective cap for protecting the sealing material 19, and 21 represents a threaded portion carved around the periphery of the housing 14 for airtightly fixing the detection unit 2 to the exhaust pipe 1. .

Next, the detection circuit 3 includes a battery 31 that applies a voltage between the platinum electrodes 11 and 12 on the alumina substrate 13, and a battery 31 that applies voltage between the platinum layers wA11 and 12 on the alumina substrate 13, and
A resistor 32 detects the current flowing between the two as a voltage signal.
and a buffer circuit 34 that inputs the voltage signal V^ detected by this resistor 32 to a comparator 33 constituted by an operational amplifier OP1. Compared with vA, VA
> v8, the pulse signal Vs is configured to output a @high level. Furthermore, buffer circuit 3
4 is configured using an operational amplifier OP2.

In the smoke detection device of this embodiment configured as described above, as shown in FIG. The voltage signal vA increases depending on the amount of carbon particles that flow out and adhere. When the voltage signal VB reaches a predetermined level, that is, when the current exceeds a predetermined current, the carbon particles self-ignite and are incinerated, and the voltage signal V^ becomes "o" again. The deposition and incineration cycle of carbon particles changes depending on the amount of carbon particles in the exhaust gas, that is, the smoke concentration, and when the smoke concentration is high, the voltage signal V^- as shown by the dotted line in Fig. 3 (a).
The change period of is shortened. By the way, in this embodiment, comparator 3
In step 3, this voltage signal vA is compared with the reference voltage vB, and when VA > VB as shown in FIG. has been done. Therefore, this pulse signal VS changes with a period corresponding to the smoke density, and this pulse signal Vs can be used as it is as an input signal to the smoke control device. In addition, Fig. 3 (b) shows the voltage signal V^ shown by the solid line in Fig. 3 (a).
The pulse signal V obtained by comparing and the reference voltage V,3
s, and FIG. 3(c) shows the pulse signal Vs' obtained by comparing the voltage signal vA - shown by the dotted line in FIG. 3(a) with the reference voltage VB. This indicates that the cycles are different.

As explained above, in the smoke detection device of this embodiment, the detection signal is a pulse signal whose cycle changes according to the smoke concentration in the exhaust gas, so if smoke control is performed using this detection device, the control When inputting to the circuit, there is no need to provide an A/D converter input circuit as in the conventional case, and the circuit can be simplified. Furthermore, the detection section can be realized with a simple structure such as providing a platinum electrode on a ceramic substrate, and productivity can be improved. Furthermore, since the carbon in the exhaust gas is attached and incinerated, there is no change in the detection signal over time, and the smoke concentration can always be detected with high accuracy.

In the above embodiment, the platinum electrodes on the alumina substrate were simply arranged facing each other in the figure, but the platinum electrodes may have any shape as long as they are a pair, for example, two electrodes may be formed. The electrode patterns may be formed in a meandering parallel manner.

In addition, in the detection section of the above embodiment, the alumina substrate is made to protrude outside (into the exhaust pipe) as it is, but by providing a mesh-like protective cover around it, for example, the alumina substrate can be attached to the exhaust pipe during work. Damage to the board can be prevented, and workability during installation can be improved.

[Effects of the Invention] As detailed above, according to the smoke detection device of the present invention, the detection signal can be a pulse signal whose period changes depending on the smoke concentration in the exhaust gas, and when input to the control circuit, It can be input directly without going through an input circuit such as an A/D converter. Further, since the carbon particles in the exhaust gas are attached and incinerated in the detection section, the detection characteristics are not deteriorated by the carbon particles, and highly accurate detection can be performed at all times. Furthermore, the detection section only needs to be provided with a pair of electrodes on a heat-resistant insulating substrate, so the structure is simple and productivity can be improved.

[Brief explanation of the drawing]

1 to 3 show a practical example of the present invention, FIG. 1 is a schematic configuration diagram showing the entire smoke detection device of this embodiment, and FIG. 2 is a part showing the structure of the detection section 1. Broken front view,
FIG. 3 is a time chart illustrating the operation and detection signals of this embodiment. 1... Exhaust pipe 2... Detection section 3... Detection circuit 11.12... Platinum electrode 13... Alumina substrate 31... Battery 32... Resistor 33... Comparator

Claims (1)

[Claims] A voltage application that applies a predetermined voltage between a detection unit that is provided in exhaust gas and includes a heat-resistant insulating substrate and a pair of electrodes provided on the substrate, and the electrodes of the detection unit. current detection means for detecting a current flowing between the electrodes, and exhaust gas generated between the electrodes by application of voltage by the voltage application means from periodic changes in the current detected by the current detection means; A smoke detection device comprising: pulse signal output means for detecting an adhesion-incineration cycle of carbon particles therein and outputting a pulse signal according to the cycle.