JPH0850108A - Resistance changing type oxygen sensor with heater and use thereof - Google Patents

Abstract

PURPOSE:To prevent the deterioration in the detectability of the oxygen concentration due to the lead damage of a sensor by integrally providing a comparison resistance for bridging between the lead wire connected to a sensor output taking-out terminal at the intermediate part of the lead wire and the lead wire connected to a grounding terminal, together with the lead wire. CONSTITUTION:When a connector C is connected to the prescribed input terminal of the air-fuel ratio A/F control circuit E of a vehicle to be substituted, a heater power supply voltage VB is applied between the heater voltage applying terminals 33, 34 of sensor elements through the terminals 51, 52 on the side of the circuit E. The electric potential divided by the resistance Rh due to the large part on the non-grounding side of a heat-generating resistance pattern 32 for a heater and by the resistance R'h on the remaining grounding side is applied to the electrode on one side of a metallic oxide semiconductor 11. The resistance Rs of the semiconductor 11 varies more than two figures while denoting the resistance changing ratio from Rsmin when the oxygen concentration in the exhaust gas is lambda<1, to Rsmax when it is lambda>1. On the other hand, the resistance Rc of a comparison resistance 40 for bridging between the grounding side terminal 34 and the output taking-out terminal 37 is selected to a value nearly equal to an equal ratio division value of both extreme values of the resistance change of the semiconductor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxygen sensor with a heater used to control the air-fuel ratio of a vehicle internal combustion engine to λ (excess air ratio) = 1, and particularly to a resistance change type metal oxide semiconductor such as titania. The present invention relates to an oxygen sensor with a heater and a method of using the oxygen sensor.

[0002]

2. Description of the Related Art As an oxygen sensor for detecting λ = 1 used for controlling an air-fuel ratio of a vehicle internal combustion engine, oxygen of a concentration cell type using an oxygen ion conductive solid electrolyte such as stabilized or partially stabilized zirconia. Sensors are currently most widely used. Further, among them, one of the pair of lead wires for the heater applied voltage, the non-ground side lead wire and the other ground side lead wire, and at least the non-ground side lead wire of the pair of lead wires for extracting the sensor output. An oxygen concentration battery type oxygen sensor with a heater, which has a total of three or four lead wires, is widely used. However, since this oxygen concentration cell type oxygen sensor utilizes an electrochemical reaction concerning oxygen between three phases of a solid electrolyte, a porous platinum electrode deposited on the surface of the solid electrolyte, and an exhaust gas which is a measurement gas, if If leaded fuel is refueled and used, the porous platinum electrode has a lead capturing effect, so that the above-mentioned electrochemical reaction is immediately inhibited by so-called lead poisoning such as the formation of a lead film on the surface. Therefore, the electromotive force performance of the oxygen concentration battery is weakened, and the deterioration of the detection accuracy at λ = 1 point cannot be avoided. This problem is a major problem in areas where leaded gasoline is still in circulation.

[0003]

DISCLOSURE OF THE INVENTION The inventor has found that a resistance change type oxygen sensor, that is, an oxygen sensor using a metal oxide semiconductor whose resistance value changes according to the oxygen concentration of titania or the like,
Unlike the oxygen concentration cell type oxygen sensor, the electrode part does not take part in the electrochemical reaction, but merely needs to fulfill the function of electrically conductive contact with the metal oxide semiconductor. The present invention was carried out by focusing on the fact that the resistance change characteristic is not directly affected even if it is contaminated with, and it is extremely advantageous in avoiding the lead poisoning problem of the oxygen sensor. That is, the problem to be solved by the present invention is the most widely used oxygen concentration battery type oxygen sensor with a heater, that is, a pair of lead wires for supplying heater power and at least one lead wire for extracting sensor output. As a lead poisoning countermeasure for the oxygen sensor for a vehicle that performs air-fuel ratio control using an oxygen concentration cell type oxygen sensor with a heater equipped with a total of 3 to 4 lead wires, only the oxygen sensor is used as necessary. The present invention provides an advantageous oxygen sensor that can be used in place of an oxygen concentration cell type oxygen sensor, and a method of using the oxygen sensor as a lead poisoning countermeasure for the vehicle.

[0004]

According to a first aspect of the present invention, there is provided a pair of terminals for applying a heater voltage, which are respectively connected to both ends of a heating resistor for a heater and at least one of which is grounded. Is internally connected to the voltage dividing point of the voltage applied to the heater and is connected to the other electrode of the metal oxide semiconductor element to which a predetermined potential is applied. A variable resistance oxygen sensor having a heater having a variable resistance oxygen sensor element, a lead wire having one end connected to each of the terminals, and a connector having the other end of the lead wire connected thereto. A comparative resistor bridging between the lead wire connected to the sensor output take-out terminal and the lead wire connected to the ground terminal at an intermediate portion of A heater with variable resistance-type oxygen sensor, characterized in that provided in the line integral form.

Here, a pair of terminals for applying a heater voltage, which are respectively connected to both ends of the heater heating resistor and at least one of which is grounded and used, and one electrode are internally connected to a voltage dividing point of the heater applied voltage. A variable resistance oxygen sensor element with a heater having a terminal for taking out a sensor output from the ground potential connected to the other electrode of the metal oxide semiconductor element to which a predetermined potential is applied, A resistance change type oxygen sensor with a heater, which is provided with a lead wire whose one end is connected to each terminal and a connector whose other end is connected to the terminal, is disclosed in, for example, JP-A-60-11.
It is described outside the 7140 and is known. Further, the comparison resistor is connected between the ground potential and the terminal potential for extracting the sensor output on the air-fuel ratio control circuit side, and the voltage generated across the comparison resistor is used as the sensor output to perform the air-fuel ratio control. It is known, for example, to describe it in JP-A-62-217150. By the way, in the present invention, the comparative resistor is bridged between the intermediate portions of the lead wire connected to the sensor output take-out terminal and the lead wire connected to the grounding terminal, and along the lead wire. It is characterized in that it is provided integrally. Here, the provision of the comparative resistor integrally along the lead wire means that the resistor having a general shape that is long in the axial direction is placed along the longitudinal direction of the lead wire, and is covered with, for example, an insulating cylinder to be integrally formed. By fixing, etc., it is said that the lead wire or lead wire assembly is mounted in a state in which it can be handled almost the same as a conventional lead wire or lead wire assembly.

According to a second aspect of the present invention, in the resistance variable oxygen sensor with a heater according to the first aspect, a protective tube for covering a portion of the lead wire provided with a comparative resistor is at least watertight inside the protective tube. A resistance change type oxygen sensor with a heater provided with the protective tube fixed to the lead wire.

According to a third aspect of the present invention, there is provided a method of using the resistance variable oxygen sensor with a heater according to the first aspect of the present invention, for a vehicle for performing air-fuel ratio control using an oxygen concentration cell type oxygen sensor with a heater. As a measure against lead poisoning of the oxygen concentration battery type oxygen sensor, there is provided a method of using a resistance variable oxygen sensor with a heater, characterized in that only the oxygen sensor is used in place of the oxygen concentration battery type oxygen sensor.

[0008]

In the variable resistance oxygen sensor with a heater according to the present invention as defined in claim 1, the lead wire is a resistor which electrically bridges the two lead wires at an intermediate portion between the two lead wires. After preparing a lead wire group that is provided along with it in an integrated form,
A connector having the same structure as the connector of the oxygen concentration cell type oxygen sensor to be replaced is prepared at one end side of the lead wire group, and a lead wire assembly with a connector attached to one end side of the lead wire group is prepared. For example, a resistance change type oxygen sensor with a heater having a well-known compact structure (that is, one for applying a heater voltage, which is connected to both ends of a heating resistor for a heater and at least one of which is grounded) is used.
A sensor output is provided between the pair of terminals and the ground potential connected to the other electrode of the metal oxide semiconductor element to which one electrode is internally connected to the voltage division point of the heater applied voltage and a predetermined potential is applied. A resistance variable oxygen sensor element having a terminal for taking out, a resistance variable oxygen sensor element, a lead wire having one end connected to each of the terminals, and a connector having the other end of the lead wire connected thereto. The resistance change type oxygen sensor with a heater of the present invention can be obtained easily and at low cost only by assembling the sensor in the same manner as the assembling procedure. The obtained oxygen sensor can be immediately mounted in place of the oxygen concentration battery type oxygen sensor on the vehicle to be replaced, and once it is mounted, the oxygen concentration battery type oxygen sensor can be replaced with a predetermined air-fuel ratio. By outputting the control feedback signal, the predetermined air-fuel ratio control for the vehicle can be immediately performed.

According to a second aspect of the present invention, there is provided a resistance variable oxygen sensor with a heater according to the first aspect of the present invention. Since it is tightly sealed, the damage due to the collision of external objects and the deterioration of the insulation due to the intrusion of water can be surely prevented, and moreover, the handling similar to the conventional handling of the lead wire or the lead wire assembly becomes possible.

In the method of using the resistance variable oxygen sensor with a heater according to the first aspect of the invention according to the third aspect, deterioration of exhaust gas purifying ability due to lead poisoning of the oxygen concentration battery type oxygen sensor is expected. When installed in a vehicle, it becomes possible to perform a predetermined air-fuel ratio control in place of the oxygen concentration cell type oxygen sensor, and during the air-fuel ratio control operation for the vehicle in place of the oxygen concentration cell type oxygen sensor, the sensor element is leaded. Even if the vehicle is used with leaded gasoline, for example, even if leaded gasoline is temporarily used, it will not be emptied because lead poisoning such as the sensor element of the oxygen concentration battery type oxygen sensor does not occur even if it is contaminated by the components. The quality of the fuel ratio control does not deteriorate and the exhaust gas continues to maintain a clean state.

[0011]

Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 shows an overall view of a resistance change type oxygen sensor with a heater according to an embodiment of the present invention. A is a sensor probe main body, and B is a lead wire assembly extending from the sensor probe main body and provided with a connector C having a predetermined shape on the front side. Reference numeral D is a resistor mounting portion in which a comparative resistor is integrally provided so as to bridge between two specific intermediate portions of the lead wire B and along the lead wire. . The sensor probe main body A has, for example, the structure shown in FIG. Reference numeral 10 denotes a metal oxide semiconductor element 11 whose resistance value changes according to oxygen concentration on a ceramic substrate, a heating resistor (32) for a heater, and three terminals (33) connected to them so as to achieve a predetermined electrical connection. , 34, 3
It is a resistance change type oxygen sensor element with a heater consisting of 7). Reference numeral 12 denotes a metal shell formed in a tubular shape for gripping the sensor element 10 and mounting the sensor probe on an internal combustion engine mounted on a vehicle. Reference numeral 13 denotes the metal oxide semiconductor 11 mounted on the tip of the metal shell 12 on the internal combustion engine side. A protector for protecting the sensor element 14 is an inner cylinder for holding the sensor element 10 together with the metal shell 12, and the sensor element 10 includes the spacer 15, the filling powder 16, and the glass seal 1.
It is gripped by the metal shell 12 and the inner cylinder 14 via 7.
Further, a threaded portion 12a for mounting the internal combustion engine is engraved on the outer periphery of the metal shell 12, and the gasket 1 is provided so as not to leak gas when mounted on the exhaust gas pipe of the internal combustion engine.
8 are provided.

Reference numeral 19 denotes a metal shell 12 so as to cover the inner cylinder 14.
The outer cylinders, 21, 22, and 23 attached to the
Three intermediary metal leads 20, 20, 20 (of which one is not shown) are connected to the three terminals (3
3, 34, 37), which are electrically insulated lead wires made of three synthetic resins such as fluorine resin and silicon rubber in this case. Reference numeral 24 denotes an elastic sealing material made of silicon rubber, which is made of glass.
It serves to insulate and protect the connection portion with 3. The oxygen sensor element 10 has the laminated structure shown in FIG. still,
(A) is a plan view and an AA cross-sectional view showing the substrate upper layer of the device and the metal oxide semiconductor 11 by rupture removal, and (B) is a plan view and AA taken only from the metal oxide semiconductor 11. A cross-sectional view, (C) is a plan view of the sensor element and a cross-sectional view taken along line AA. 30 and 31 are lower layers of the substrate of alumina,
The upper layer of the substrate. Numerals 32 to 38 are metallic conductive patterns formed on the lower substrate layer 30 and containing platinum in the range of more than 10%, of which 32 is a heating resistor pattern for a heater and 33 is a heating resistor pattern 32. Of the non-grounded side terminal pattern, 34 is a ground side terminal pattern of the heating resistor pattern 32, and 35 is an applied voltage division provided with one electrode for the metal oxide semiconductor 11 and provided near the ground side of the heating resistor pattern 32. One electrode pattern connected to the point 38, 36 is the other electrode pattern for the metal oxide semiconductor 11 and the other electrode pattern connected to the output extraction terminal pattern 37. Reference numeral 39 denotes an opening provided in the upper substrate layer 31. In the opening, here, the metal oxide semiconductor 11 in which platinum powder is dispersed and supported on porous titania is exposed as the electrodes 35 and 36. It is provided so as to be laminated on the surface and cover it. The non-ground side terminal pattern 33 of the heating resistor pattern 32 is electrically connected to the lead wire 21, the ground side terminal pattern 34 is electrically connected to the lead wire 23, and the output extracting terminal pattern 3 is formed.
7 is connected to the lead wire 22 and is connected to the sensor probe main body A.
Built into.

Next, the comparative resistor 40 was integrally attached to the lead wire as shown in FIG. FIG. 4 is a side view showing a part of the attachment portion D of the comparative resistor 40 in a cutaway manner.
41 is an intermediate portion of the insulation-coated lead wire 22 (which is electrically connected to the output extraction terminal pattern 37).
One crimping connection terminal for integrally crimping and connecting the two core wires and one lead wire 40a of the resistor 40 placed substantially along the extending direction of the lead wire, and 42 is the insulation coating lead wire 23
The core wire of the lead wire 23 and the other lead wire 40 of the resistor 40 at an intermediate portion (conducting to the ground side terminal pattern 34).
The other crimp connection terminal for crimp-connecting with b integrally, 43
Is a resistor 4 for each of the lead wire 22 and the lead wire 23.
A protective tube (here made of stainless steel), preferably made of metal (stainless steel or other steel materials, aluminum or its alloys, copper or its alloys, etc.), through which the connection portion with 0 is inserted, 44 and 45 are here The elastic sealing members are made of silicon rubber, and the lead wires 22 and 23 are inserted and fitted at both open end sides of the protective tube 43 made of metal, respectively, and then side caulking 43a, 43a.
.., which is fixed by .., 46 is a glass braided insulating sheet, and the lead wire 2 to which the resistor 40 is attached
It is arranged in the protective tube 43 in a form of winding and wrapping the portions 2 and 23.

An example of an electric circuit for explaining the operation of the resistance change type oxygen sensor with the heater of the above-mentioned embodiment when it is mounted and used in the vehicle to be replaced instead of the oxygen concentration battery type oxygen sensor. As shown in FIG. When the connector C is connected to a predetermined input terminal portion of the air-fuel ratio (A / F) control circuit device E of the destination vehicle, the heater power supply voltage Vb (for example, 12V) passes through the terminals 51 and 52 on the control circuit device E side. It is applied between the heater voltage application terminals 33 and 34 of the sensor element. A potential (for example, about 1 with respect to the ground potential) divided by the resistance value Rh due to most of the non-ground side of the heater heating resistor pattern 32 and the remaining ground side resistance value Rh ′
V) is applied to one electrode of the metal oxide semiconductor 11. The resistance value Rs of the metal oxide semiconductor 11 indicates a resistance value change ratio of about two digits or more from (Rs) min when the oxygen concentration in the exhaust gas is λ <1 to (Rs) max when the oxygen concentration in the exhaust gas is λ> 1. Change. On the other hand, the resistance value Rc of the comparison resistor 40 bridging between the ground side terminal 34 and the output extraction terminal 37.
Is a value approximately equal to a geometrically divided value of both ends of the resistance change of the metal oxide semiconductor 11, that is, Rc≈ ((Rs) min.
Since (Rs) max) ^1/2 is selected, the applied voltage is applied between the terminal 37 and the ground side terminal 34, that is, between the ground potential and the input terminal 53 of the voltage follower 55 on the control circuit device E side. An output change that swings in a range of about 80% or more of 1 V is obtained as an output. Since the value of this output change and its change pattern are substantially the same as when the oxygen concentration battery type oxygen sensor is installed, the air quality of the air-fuel ratio control state when the oxygen concentration battery type oxygen sensor is installed is almost the same. A fuel ratio control state will be obtained. Reference numeral 56 denotes an operational amplifier which is a front stage of a normal negative feedback control circuit. The output terminal of the voltage follower 55 is connected to the inverting input terminal of the operational amplifier, and the reference potential Vs (for example, the above output change) is connected to the non-inverting input terminal. The negative feedback control of λ = 1 is performed by giving a middle value of about 500 mV.

The variable resistance oxygen sensor with a heater of the above-mentioned embodiment can easily and easily protect the comparative resistor mounting portion from damage due to collision of an external object and deterioration of insulation due to water intrusion. It can be done at low cost.

In the resistance variable oxygen sensor with the heater of the above embodiment, the material of the protective tube is made of metal, which is advantageous in that the sealing process inside the protective tube is relatively easy when the synthetic resin coated lead wire is used. However, the material is not limited to this, and any material having a protective function in a relatively high temperature atmosphere such as ceramics or synthetic resin can be used. Further, in the resistance variable oxygen sensor with the heater of the above-mentioned embodiment, the protective tube is made to pass only two lead wires electrically bridging each other by the comparative resistor. It is also possible to insert them and bundle them with a protective tube.

[0017]

EFFECTS OF THE INVENTION In a vehicle in which an air-fuel ratio is controlled by using an oxygen concentration battery type oxygen sensor, the oxygen concentration detection ability deteriorates due to lead poisoning of the oxygen sensor, and therefore the exhaust gas purification ability deteriorates. It is a serious problem depending on the situation, and it is a problem that it is difficult to easily take measures as long as the oxygen concentration battery type oxygen sensor is used. It has an extremely large effect that it can be adopted.

[Brief description of drawings]

FIG. 1 is an overall perspective view of a resistance change type oxygen sensor with a heater according to an embodiment of the present invention.

FIG. 2 is a fragmentary side view of the main part (A) of the resistance variable oxygen sensor with a heater according to the above embodiment.

FIG. 3 is a view for explaining the structure of the oxygen sensor element (10) of the resistance variable oxygen sensor with a heater of the above embodiment, (a) is a substrate upper layer part (31) and a metal oxide semiconductor (11). ) And the plan view and AA sectional drawing which showed and removed,
(B) is a plan view and AA sectional view showing only the metal oxide semiconductor (11) removed, and (C) is a plan view and AA sectional view of the oxygen sensor element (10).

FIG. 4 is a side view showing a part of a mounting portion (D) of a comparative resistor 40 of the resistance change type oxygen sensor with a heater of the above-mentioned embodiment in a partially cutaway manner.

FIG. 5 is an example of an electric circuit for explaining the operation as a sensor when the resistance change type oxygen sensor with a heater according to the above-described embodiment is mounted and used in a vehicle to be replaced instead of the oxygen concentration battery type oxygen sensor. FIG.

[Explanation of symbols]

10: Resistance change type oxygen sensor element with heater 21, 22, 23: Lead wire C: Connector 32: Heater resistor for heater 33: Terminal on grounded side of a pair of terminals for applying heater voltage 34: Heater Of a pair of terminals for voltage application, a ground side terminal 37: a terminal for taking out a sensor output 40: a comparative resistor 43: a protective tube

Claims (3)

[Claims] 1. A pair of terminals for applying a heater voltage, which are respectively connected to both ends of a heating resistor for a heater and at least one of which is grounded, and one electrode is internally connected to a voltage dividing point of the heater applied voltage. A variable resistance oxygen sensor element with a heater having a terminal for taking out a sensor output from the ground potential connected to the other electrode of the metal oxide semiconductor element to which a predetermined potential is applied, Lead wires with one end connected to each terminal and extending long,
In a resistance change type oxygen sensor having a connector to which the other end of the lead wire is connected, a lead wire connected to the sensor output takeout terminal and a grounding terminal are connected at an intermediate portion of the lead wire. A variable resistance oxygen sensor with a heater, characterized in that a comparative resistor bridging with a lead wire is provided integrally with the lead wire along the lead wire. 2. The resistance change type oxygen sensor with a heater according to claim 1, wherein a protective tube covering a portion of the lead wire provided with the comparative resistor is sealed so that at least the inside of the protective tube is watertight. A variable resistance oxygen sensor with a heater, characterized in that a protective tube is fixed to the lead wire. 3. As a measure against lead poisoning of an oxygen concentration battery type oxygen sensor for a vehicle for performing air-fuel ratio control using the oxygen concentration battery type oxygen sensor with a heater, only the oxygen concentration battery type oxygen sensor is used as a measure against lead poisoning. A method of using a resistance variable oxygen sensor with a heater, which is used by replacing the sensor.