JPH039273A - Disconnection detector for inside lead wire in oxygen sensor - Google Patents

Abstract

PURPOSE:To surely detect and display a disconnection and a normal condition of lead wire by providing a NOT circuit, electrostatic capacitance measuring circuit, comparator and disconnection display circuit on connector terminals at the heater side and electrode side, and providing a NOR circuit and display circuit on the output side. CONSTITUTION:The electrode side 1b for sensor element of an oxygen sensor S can be consid ered as a capacitor and the heater side 1c2 can be considered as a resistor. When the sensor S is inserted to the connector of an inspection device H, a transistor Tr1 is connected by an output signal of the NOT circuit 13 at the time of disconnection of the lead wire 3 and a pilot lamp D1 is lightened. When the electrostatic capacitance measured by an electrostatic capacitance measuring circuit 14 is decided to be out of the set range by the comparator 15, that is the lead wire 2 is being disconnected, the output of an OR circuit is made to be H-level by the output signal of a comparator in the circuit 14, then a transistor Tr2 is connected and a pilot lamp D2 is lightened. When the lead wire 3 at the heater side and the lead wire 2 at the electrode side are both normal (when each output signal of the NOT circuit 13 and the comparator 15 are 0), a transistor Tr3 is connected by the output signal of the NOR circuit 17 and a pilot lamp D3 is lightened to display that each lead wire 2, 3 are both in the normal condition.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention detects the presence or absence of disconnection of the lead wires inside the sensor (heater and electrode lead wires for heating the sensor), which is one of the failures of oxygen sensors. It relates to a device for detecting.

[Conventional technology]

First, the basic configuration and operation of the oxygen sensor will be briefly explained.

As shown in FIG. 3(A,)(B), the oxygen sensor S is
Solid electrolyte pellet 1a [e.g., zirconium oxide (ZrO: 'zirconia) with metal oxide (e.g., Y
an electrode 1b formed on both sides of the pellet 1a (e.g., porous platinum, etc.), and an electrode 1b integrally sealed on the cathode side of the pellet 1a of the electrode 1b. A sensor element 1 consisting of a capsule 1c having a gas diffusion hole 1ct and a heater IC2 for heating the sensor formed on the upper surface is connected to the lead wires 2 and 3 of the electrode 1b and the heater C2. It consists of a stem 6 having terminals 4 and 5 (two each) for holding the sensor element 1, and a mesh cover 7 that is joined to the stem 6 and covers the sensor element 1.

Then, by applying the voltage E1 between the picture electrodes lb and the voltage E2 to the heater C, the pellets 1a under the height are
Due to the oxygen bombing effect, a current using oxygen ions as carriers flows between the electrodes lb, and the oxygen molecules that have entered the gas reaction chamber in the capsule IC through the gas diffusion hole let are discharged via the pellet 1a.

At this time, since there is a one-to-one relationship between the flat region of the current that appears in the voltage region of the voltage-current characteristic, that is, the limiting current value and the oxygen concentration, a constant voltage is applied to the electrode 1b and the heater IC2. The oxygen concentration is detected from the temperature and limit current value of the sensor element 1 at that time.

As described above, the oxygen sensor has a circuit for measuring the limiting current value and a heating circuit for the sensor element as essential elements in its configuration. , Heater C2 or terminal 4
, 5) affects the function of the oxygen sensor, so detecting the presence or absence of breakage of the lead wire is one of the important methods for detecting failure of the oxygen sensor.

By the way, the following means have been conventionally adopted to detect the presence or absence of lead wire breakage.

(a) Remove the mesh cover 7 of the oxygen sensor S and visually check the condition of the lead wires 2 and 3.

(b) Connect the detection device T shown in FIG. 4 to the terminal 4.5 of the oxygen sensor S.

That is, the battery E is connected to the connector 8 that can be inserted into and removed from the terminal 4 on the electrode side.
, a switch 9 and a resistor 10 are connected in series, and the resistor 1
The electrode side detection part has a voltmeter V connected in parallel to TI 0, and the ammeter A and TI
It consists of an E pond E4 and a heater side detection unit which is connected in series with a switch 12 (which works in conjunction with the above-mentioned switch).

[Problem to be solved by the invention]

The above-mentioned detection means (a) is adopted because a normal continuity tester can detect the presence or absence of a break in the lead wire 3 of the heater example, but cannot detect the presence or absence of a break in the lead wire 2 on the electrode side. However, since this detection means destroys a part of the oxygen sensor S, there is a problem in that repair after detection is troublesome.

In addition, the detection means (b) includes the connectors 8 and 11 of the detection device T inserted into the terminals 4.5 of the oxygen sensor S, and the switches 9 and
12, the presence or absence of a break in the lead wire 3 on the heater side can be detected by the pointer display of the ammeter A.

The presence or absence of disconnection of the lead wire 2 on the electrode side is determined by (a)
If it is determined that there is no breakage in the lead wire 3 detection described above (as indicated by the ammeter A), if there is no breakage in the lead wire 2, there will be a gap between the electrodes lb due to the oxygen bombing effect caused by the heating of the heater IC2. Current flows and the voltage drop value across resistor 10 is indicated on voltmeter V, but if there is a disconnection, no current flows between electrodes lb, so the indicated value on voltmeter V is detected as 0. .

(b) If there is a break in the lead wire 3, the oxygen bombing effect will not occur and it will be impossible to detect whether the lead wire 2 is broken, so first repair the lead wire 3.

As described above, it is possible to reliably detect whether the lead wires 2 and 3 are disconnected.
It is necessary for the temperature to be normal, and a waiting time of 2 to 3 minutes is required until the heater IC2 is energized, the temperature rises to a predetermined value, and the oxygen bombing action occurs, making rapid detection impossible. There is a problem.

The present invention has been made in view of such problems, and an object of the present invention is to provide an internal lead in an oxygen sensor in which the presence or absence of disconnection of each lead wire can be displayed quickly and in relation to each other without damaging the appearance of the oxygen sensor. An object of the present invention is to provide a wire breakage detection device.

[Means to solve the problem]

In order to achieve the above object, the detection device of the present invention includes a heater side lead wire disconnection detection section in which the N07 circuit and the disconnection indicator circuit are connected to a connector that can be inserted into and removed from the heater side terminal, and an electrode side lead wire disconnection detection section. A disconnection detection section of the electrode side lead wire with a capacitance measurement circuit, a comparison circuit, and a disconnection display circuit connected to a connector that can be inserted and removed from the terminal, and a NOR circuit and display circuit on each output side of the N07 circuit and comparison circuit. The device is characterized by comprising a normal state detecting section for each lead wire on the heater side and the electrode side connected to the heater side and the electrode side.

[For production]

The N07 circuit indicates a break in the lead wire on the heater side.

The capacitance of the pellet and two electrodes, which is considered to be a capacitor, is measured by the capacitance measuring circuit, and if the comparison circuit determines that the value is outside the set range, it is displayed as a disconnection of the electrode lead wire. do.

Further, the NOR circuit indicates that both the lead wires on the heater side and the electrode side are in a normal state.

Therefore, by displaying both the lead wire breakage and the normal state, it is possible to reliably recognize whether or not the oxygen sensor is malfunctioning.

〔Example〕

Embodiments of the present invention will be described with reference to the drawings.

As mentioned above, the electrode side of the sensor element 1 in the oxygen sensor S has the dielectric material of the pellet 1a and the two electrodes 1b.
The heater side can be viewed as a resistor.

And the capacitance of the capacitor on the electrode side is several 10 to several 1
000 pF, and the resistance value of the resistor on the heater side is normally set in the range of 1 to 5 Ω.

From the above viewpoint, the detection device H, as shown in FIG.
A NOT circuit 13 for continuity check is connected to the connector 1 which can be inserted into and removed from the terminal 5 on the heater side.
The output side of the circuit 13 is connected to the transistor T via the protective resistor R.
Connect to the base of rl.

An indicator light (for example, a light emitting diode lamp) is connected to the transistor T through a protective resistor R2.

Note that R1 is a grounding resistance.

Therefore, when the lead wire 3 is disconnected, the transistor "rl becomes conductive due to the output signal of the NOT circuit 13, and the indicator light D1 is turned on.
lights up.

When the lead wire 3 is normal, there is no output signal from the NOT circuit 13 and the indicator light D1 does not light up.

In addition, a capacitance measuring circuit 14 is connected to the connector 8 that can be inserted into and removed from the terminal 4 on the electrode side, a comparison circuit 15 is connected to the measurement circuit 14, and the output side of the comparison circuit 15 is connected to a protective resistor R.
6 to the base of transistor "r2.

Then, an indicator light D2 (for example, a light emitting diode lamp) is connected to the transistor T through a protective resistor R3.

An example of the capacitance measurement circuit 14 and comparison circuit 15 is shown in FIG.

That is, the capacitance measurement circuit 14 includes an oscillation circuit 14a whose frequency changes depending on the capacitance on the electrode side, and the oscillation circuit 14a.
F-V converter 4 that converts the frequency of a into DC voltage
It is composed of b.

The comparison circuit 15 also includes a comparator OP1 that outputs an output signal when the input terminal from the F-V converter 4b is lower than the reference voltage vr1 (when the capacitance is several tens of pF or less), and a When the input terminal is higher than the reference voltage Vr2 (the capacitance is several thousand pins)
It consists of a comparator OP2 that outputs an output signal when the voltage is higher than F), and an OR circuit 16 that outputs an output signal when the human input signal is lower than the reference voltage V or higher than ■r2. The output side is connected to the protection resistor R6 and the NOR circuit 17.

Therefore, the capacitance determined by Δt1 by the capacitance measurement circuit 14 is determined to be several tens to several thousand pF in the comparator circuit 15.
When it is determined that the lead wire 2 is within the setting range of
When is normal, there are no output signals from the comparators op and op2, and therefore, there is no output signal from the OR circuit 16, so the indicator lamp D2 does not light up.

Also, when it is determined that the capacitance is outside the setting range,
In other words, when lead wire 2 is disconnected, the comparator OP
, op2 causes the output of the OR circuit 16 to go high, the transistor T becomes conductive, and the indicator lamp D2 lights up.

2 Furthermore, a NOR circuit 17 is connected to each output side of the N07 circuit 13 and the comparison circuit 15, and the output side of the NOR circuit 17 is connected to the base of the transistor Tr3 via a protective resistor R7.

Then, an indicator light D3 (for example, a light emitting diode lamp) is connected to the transistor T through a protective resistor R4.

Therefore, the lead wire 3 on the heater side and the lead wire 2 on the electrode side
When both are normal (when the output signals of the NOT circuit 13 and the comparison circuit 15 are O), the output signal of the NOR circuit 17 makes the transistor T conductive, the indicator light D3 lights up, and each lead "3" Displays that both 2 and 3 are in normal condition.

〔effect〕

The present invention has the following effects.

(a) Since the detection device has a connector that can be inserted into and removed from the terminal of the oxygen sensor, it is possible to reliably detect the presence or absence of internal lead wire breakage without damaging the appearance of the sensor.

(b)? ! ! Since disconnection of the lead wire on the pole side is detected by comparing capacitance, there is no need to wait for the oxygen pumping action to occur as in the conventional case, and rapid detection is possible.

(C) Since the normal state of the lead wire is also displayed using the NOR circuit, both the disconnected state and the normal state can be recognized, improving reliability.

(d) Since the circuit configuration of the detection device is simple and low power consumption is possible, it can also be used for portable use.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram of a detection device according to the present invention, Fig. 2 is an explanatory diagram of a capacitance measuring circuit and a comparison circuit, and Fig. 3 is an explanatory diagram of the basic configuration of an oxygen sensor. FIG. 4 is a cross-sectional view of the sensor element, FIG. 4 is a -HE side view of the sensor unit, and FIG. 4 is a circuit configuration diagram of a conventional detection device. 1...Sensor element, 1a...Pellet, 1b
...Electrode, IC...Capsule, 102...Heater, 2゜3...Lead wire, 4.5...Terminal, 8,11
...Connector, 13...N07 circuit, 14...Capacitance measurement circuit, 15...Comparison circuit, 17...NO
R circuit, D, D2゜■ D3... Indicator light.

Claims (1)

[Claims] A disconnection detection part of the lead wire on the heater side, in which a NOT circuit and a disconnection indicator circuit are connected to a connector that can be inserted and removed from the terminal on the heater side, and a connector that can be inserted and removed from the terminal on the electrode side. A disconnection detection section of the lead wire on the electrode side to which a capacitance measurement circuit, a comparison circuit, and a disconnection indication circuit are connected, and a heater side and electrode side to which a NOR circuit and a display circuit are connected to each output side of the NOT circuit and comparison circuit. A disconnection detection device for an internal lead wire in an oxygen sensor, comprising: a normal state detection section for the lead wire;