JPS60129659A - Air-fuel ratio detecting apparatus - Google Patents

Abstract

PURPOSE:To make it possible to accurately detect an air-fuel ratio, by providing a solid electrolyte oxygen concentration cell element provided with a porous electrode and a solid electrolyte oxygen pump element to both terminal surfaces of an oxygen ion conductive solid electrolyte. CONSTITUTION:A small gap (f) is formed between the surface of an oxygen pump element 3 in the side of the porous platinum electrode layer 4 thereof and the surface of an oxygen concn. cell element 10 in the porous platinum layer 12 thereof and both elements are mutually fixed at foot parts thereof through a heat resistant insulating spacer 19 in order to be arranged in opposed relation to each other within an exhaust pipe 1. In detecting the change in a resistance value, an arbitrary reference point is provided to the middle of a max. resistance value and a min. one so as to sense a resistance value smaller or larger than said reference point. Then, when operation is performed in a fuel super-concn. region, the resistance value of a metal oxide semiconductor 17 is smaller than said reference point and the output signal corresponding to the pump current of the oxygen pump element 3 is detected on the basis of this information at this time to enable control or measurement in the fuel super-concn. region. Similarly, control and measurement in a fuel dilute region can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [〃No] The present invention relates to a detection device for measuring or controlling oxygen concentration or air-fuel ratio in exhaust gas of a combustion device such as an internal combustion engine or gas combustion equipment.

[Prior art] Conventionally, an oxygen sensor made by depositing a porous electrode layer (for example, a porous layer made of platinum) on an ion-conducting solid electrolyte (for example, stabilized zirconia) has been used to detect oxygen in exhaust gas. It is generally known that, for example, an automobile engine can be controlled to operate at the stoichiometric air-fuel ratio by detecting the stoichiometric air-fuel ratio and the combustion state in the vicinity based on the change in electromotive force caused by the difference between the oxygen partial pressure and the oxygen partial pressure of the air. Being and being.

By the way, the above-mentioned acid sensor can obtain a large change in output when the air/fuel ratio (A/F) is an unreasonable air-fuel ratio of 14.7 during operation when the weight ratio of air and fuel is 1; There is little change in the operating air-fuel ratio range, and when the engine is operated at an air-fuel ratio other than the stoichiometric air-fuel ratio, 1. ii [! Oxygen sensor output cannot be used.

In JP-A No. 58-153155, two elements each having an electrode layer provided on both sides of the front side of a plate-shaped oxygen ion conductive solid electrolyte are arranged in parallel with a gap between them, and a gap is formed on the front side. The pixel elements are fixed with a step (pump), one element is used as an oxygen pump element, and the other element is used as an oxygen pump between the ambient atmosphere and the gap.
We have proposed an oxygen concentration detection device using an oxygen concentration battery element that operates depending on the degree difference. Although such an oxygen i11 low-cost detection device has good responsiveness, if it is operated in a rich fuel region that is lower than the stoichiometric air-fuel ratio number 14.7 corresponding to the output signal, it will produce an output in the same direction as when it is in a lean fuel region. The characteristics that occur are now clear. In other words, since two air-fuel ratios correspond to the output, there is a problem that air-fuel ratio control can only be applied in cases where it is clear whether the area is rich in fuel or lean in fuel. .

[Object of the Invention] The first object of the present invention is to provide an air-fuel ratio detection system that can correctly detect the operating air-fuel ratio (A/F) of a combustion device such as an internal combustion engine in the entire region or a part of the region from the fuel excess region to the fuel lean region. A second object of the present invention is to provide an air-fuel ratio detection device that has the advantage of being able to easily perform feedback control in M degrees when performing feedback control of the air-fuel ratio.

[Structure of the Invention] The air-fuel ratio detection device of the present invention includes a solid electrolyte oxygen concentration battery element and a solid electrolyte oxygen pump element in which porous electrodes are provided on both end faces of an oxygen ion conductive solid electrolyte, and at least one piece thereof. A highly thermally conductive substrate having a window opening the porous electrode portion on the side surface and having a built-in electric heater therein is provided, and metal oxidation is applied to the side surface of the highly thermally conductive substrate of the oxygen concentration battery element or the oxygen pump element. Established physical semiconductors (
], the oxygen 8I dilute battery element and the oxygen pump element are arranged facing each other through a small gap, and the change in the electrical property given by the metal oxide semiconductor and the electromotive force of the oxygen concentration battery element or the Detecting the air-fuel ratio based on the output signal given by one of the pump currents of the oxygen pump element is defined as a 4i configuration.

[Effects of the Invention] The air-fuel ratio detection device of the present invention has the following effects in the above configuration. □ The air-fuel ratio (△/[) can be accurately detected in the entire region or in a part of the range from the fuel-rich region to the fuel-lean region by using one sen brotor.

[Practical Example] Next, the present invention will be explained based on an example shown in the drawings.
- Figures 1 to 6 show embodiments of the present invention.

1 is an exhaust pipe of an internal combustion engine, which is a combustion device, and 2 is a detection frame portion of an air-fuel ratio detection device disposed in the exhaust pipe 1. 3 is the solid electrolytic oxygen pump element of the air-fuel ratio sensing electrode part 2, and porous platinum electrode layers 4 and 5 with a thickness of approximately 20μ are provided on both sides using thick film technology (
) with a thickness of about 0.5 mm and a flat plate-shaped ion conductive solid electrolyte (e.g. stabilized zirconia) 6, and one side of the ion conductive solid electrolyte 6, for example, a porous platinum electrode layer 5 is provided (). The side surface has a window a which is an opening adapted to the shape of the porous platinum electrode layer 5 so as not to block the part of the porous platinum electrode layer 5 attached airtightly.
, a 251 m flat plate-like high thermal conductive substrate 7 made of an electrically insulating material (such as alumina or spinel), and a high thermal conductive substrate 7 on the side of the ion conductive solid electrolyte 6 of the high thermal conductive substrate 7. An IC electric heater 8 and an electric heater 8 are provided at the outer periphery of the window a on the opposite side to the surface with a □ gap between the outer periphery of the window a and the outer periphery of the highly thermally conductive substrate 7.
An electric heater 8 is installed inside the surface of the highly thermally conductive substrate 7 provided with the high thermally conductive substrate 7, which is connected to the outside.
It is constructed of a flat plate having a window 1) opening a porous platinum electrode layer 5 similar to that of 6 and a conductive base 9. Reference numeral 10 denotes a solid electrolyte oxygen concentration battery element of the air-fuel ratio detection frame portion 2, which is constructed by providing porous platinum electrode layers 11J5 and 12 on both sides using the thick film technology in the same manner as the porous platinum electrode layers 4 and 5. A flat plate-shaped ion conductive solid electrolyte 13 similar to the ion conductive solid electrolyte 6 and a porous platinum electrode layer 11 on one side of the ion conductive solid electrolyte 13 similar to the high thermal conductivity substrate 7. Attach the porous platinum electrode layer 11 to the surface on which the porous platinum electrode layer 11 is provided (the porous platinum electrode layer 11 is attached to a highly thermally conductive substrate 14 having an opening J8 window C, and ions of the highly thermally conductive substrate 14 like the electric heater 8 etc. An electric heater 15 is provided on the outer periphery of the window C on the surface opposite to the surface of the conductive solid electrolyte 13, and an electric heater 15 is provided on the surface of the highly thermally conductive base 14 on which the electric heater 15 is provided. A flat plate-shaped high thermal conductive substrate 16 having a window portion d opening the porous platinum electrode layer 11, similar to the high thermal conductive substrate 14 which is installed inside and isolated from the outside, A metal oxide semiconductor (for example, a titania element) is formed to a thickness of about 50μ using thick film technology on the surface of the substrate 16 opposite to the surface on which the electric heater 15 is installed. ) 17. Note that the oxygen pump element 3 and the oxygen concentration battery element 1olL: Each of the provided electric cords (4, 5, 8,
11, 12, 15, and 17) are each provided with a lead wire element 18 using thick film technology so as to be electrically conductive to the outside.

A small gap f of about 0.1 mm is formed between the surface of the oxygen pump element 3 on the porous platinum electrode layer 4 side and the surface of the oxygen concentration battery element 1O on the porous platinum electrode layer 12 side to form an exhaust pipe. 1, the foot parts are fixed to each other via heat-resistant and insulating spacers 19 (filling adhesive may be used). A support base 21 having a screw portion 20 is attached to the outer edge of the foot of the oxygen pump element 3 and the oxygen concentration battery element 10, which are fixed to each other by a spacer 19, and is attached by a heat-resistant and insulating adhesive member 22. installed.

The air-fuel ratio detection frame portion 2 is attached to the exhaust pipe 1 by screwing the threaded portion 20 of the support base 21 into the sensor mounting screw portion 23 of the air-fuel ratio detection frame portion 2 provided on the exhaust pipe 1.

Here, to manufacture the air-fuel ratio detection frame part 2, a porous platinum electrode layer and its lead wire elements are formed on both sides of a flat ion-conducting solid electrolyte, such as a zirconia solid electrolyte green sheet, using thick film technology. 1. Print each with a predetermined pattern. On one side, a platinum resistor used as an electric heater and its lead wire element are sandwiched between two green sheets of a highly thermally conductive material such as spinel with a flat plate shape and a window. The oxygen pump element 3 has a ceramic laminated structure obtained by integrally sintering after pressure bonding, and the surface without the porous platinum electrode layer of the element formed by the same process as the oxygen pump element 3 is coated with a material such as titania. Oxygen concentration battery element 10 is made by printing lead wire elements for metal oxide semiconductors in a predetermined pattern using thick film technology and sintering them (the metal oxide thick film is made by sintering the above element and then firing it in an atmosphere). It is advantageous to bond and fix the foot portions of the two (forming) with a spacer (heat-resistant lamic adhesive) 19 in a state where they are placed one on top of the other with the seekness gauge in between.

24 is an example of an attached electronic control unit part, in which the electromotive force e generated between the porous platinum electrodes @ 11 and 12 of the oxygen concentration battery element 10 is transferred to an operational amplifier (
The output of the operational amplifier (A) is proportional to the difference between the reference voltage (Vr) applied to the inverting input terminal of A) and the non-inverting input terminal of the operational amplifier (A) and the electromotive force e. The device has a function of controlling the pump current Tp flowing between the porous platinum electrode layers 4.5 of the oxygen pump cord 3 by driving the transistor (Tr).That is, the electromotive force e is set as a constant value reference. It functions to supply the pump current II) necessary to maintain the voltage (Vr). DC power supply (
In order to obtain an output signal corresponding to the pump current I11 supplied from B) at the output terminal 25, a resistor (Ro) is provided. (C) is a capacitor. In addition, the oxygen concentration battery element 10 is a metal oxide semiconductor 17 generated in accordance with the difference in the oxygen area within the exhaust pipe 110.
The electric heater 8 heats the metal oxide semiconductor 17 and the porous platinum electrode layers 4.5 and 11.12 in the air tube 1.
．． Power sources 27 and 28 for heating are electrically connected to the power sources 15, respectively.

FIGS. 7 and 8 are characteristic diagrams of the air-fuel ratio detection device shown in FIGS. 1 to 6 shown in -.

Figure 7 shows the change in the resistance value of the metal oxide semiconductor 17 at the output terminal 26, and shows a small resistance value in the air-fuel ratio range (fuel rich range) smaller than the stoichiometric air-fuel ratio 14.7. and increases rapidly around the stoichiometric air-fuel ratio of 14.7,
In an air-fuel ratio range (fuel lean range) greater than the stoichiometric air-fuel ratio of 14.1, a large resistance value is exhibited. Figure 8 shows the reference voltage (
Vr) is kept constant at, for example, 20 mV, and in order to make the electromotive force e 20 mV, the pump current tp in the pumping direction is set at The air-fuel ratio range (fuel @ V
ilffl), the pump current 1p increases as the air-fuel ratio increases.

This embodiment utilizes the characteristics shown in FIGS. 7 and 8.

For the output terminal 26 that detects a change in resistance value, an arbitrary reference point P point is set between the maximum resistance value and the minimum resistance value, and when the resistance value is smaller than point J: area)
It is designed to detect when the fuel is greater than the P point (fuel lean region). Therefore, when the engine is operated in a fuel rich region, the resistance value of the metal oxide semiconductor 17 is smaller than point P, and this information corresponds to the pump current fp of the oxygen pump element 3 at this time. By detecting the output signal, it is possible to perform detailed control or measurement in the fuel rich region. Further, when the engine is operated in a fuel lean region, the resistance value of the metal oxide semiconductor 17 is greater than point P, and this information and the output signal corresponding to the pump current lp of the oxygen pump element 3 at this time are used. By detecting this, fine-grained control or i1+11 constant in the fuel lean region can be performed.

Further, when controlling the above engine at a stoichiometric air-fuel ratio of 14.7, the output terminal 26 for detecting the resistance value has a stoichiometric air-fuel ratio of 14.7.
Utilizing the characteristic that the resistance value rapidly decreases around 7, the air-fuel ratio is controlled as a direct feedback control signal. With the above configuration, it is possible to obtain an air-fuel ratio detection device that can accurately measure the numerical value of the air-fuel ratio of the engine even in a wide range of fuel-rich and fuel-lean regions. Using this fact, if you set the desired air-fuel ratio, the exhaust pipe 1
The current air-fuel ratio is detected by the air-fuel ratio detection frame portion 2 attached to the air-fuel ratio, and the desired air-fuel ratio can be continuously controlled based on the feedback.

The fact that the pump current (P) changes in proportion to the air-fuel ratio in the fuel lean region as described above is described in, for example, Japanese Patent Laid-Open No. 153155/1983.

That is, by changing the oxygen partial pressure of the exhaust gas introduced into the small gap by the action of the oxygen pump element 3, a difference is created between the oxygen partial pressure of the exhaust gas flowing inside the exhaust pipe 1, and this oxygen partial pressure is changed. When controlling the pump current I0 supplied to the oxygen pump element 3 so that the electromotive force e of the oxygen concentration battery element 1 () generated by the difference in 13- is constant, this pump current II
) was found to change in proportion to the oxygen concentration in the exhaust gas. The reason for the above operation in the oxygen pumping mode in the fuel-rich region is thought to be that it is sensitive to CO gas. - Fig. 9 shows another embodiment of the air-fuel ratio detection frame portion 2.

゛In this embodiment, the outer peripheries of the highly thermally conductive substrates 1.9 and 14.16 in which the electric heaters 8 and 15 are installed extend outward from the portions forming the ion conductive solid electrolytes 6 and 13, respectively. It is formed in an overhanging manner.

This results in high thermal conductivity substrates 7.9 and 14.16.
Since each area of the high thermal conductivity substrate increases by 1.9 J:
The electric heaters 8.15 and 14.16, the metal oxide semiconductor 17, and each lead wire element 18 can be easily installed.

14- In the above embodiment, the resistance value of the metal oxide semiconductor 17 was used as a criterion for determining the fuel rich region and the fuel r3+ lean region, but as shown in FIG. The characteristics of the change in the ratio of the voltage passing through the semiconductor 17 (% of the applied voltage) may also be used.

The direction of the pump current Ip of the oxygen pump element 3 was to flow in the direction (up>0) that pumps out oxygen from the small gap f, but on the contrary, it flows in the direction that pumps oxygen from the exhaust gas in the exhaust pipe 1 (, Il).
The pump current I11, which keeps the output of the oxygen concentration cell element 10 constant even when the current is applied to <9), is as shown in FIG. Good too.

Also, the pump current II of the oxygen pump element 3) (small gap f
Oxygen concentration battery element 10 when the oxygen concentration (including both the case of pumping out oxygen and the case of pumping it in) is controlled to be constant
Since the generated electromotive force e also changes according to the air-fuel ratio, the characteristics when doing so can also be utilized.

The present invention utilizes the characteristic characteristics obtained from the air-fuel ratio detection frame 2, or multiple modes, and performs feedback control, continuously over the entire operating range while frequently switching modes as necessary. This system performs feedback control of the air-fuel ratio.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram showing an embodiment of the air-fuel ratio detection device of the present invention, Fig. 2 is a cross-sectional view taken along line II in Fig. 1, and Fig. 3 is a cross-sectional view taken along line II-II in Fig. 2. Cross-sectional view, Figure 4 is shown in Figure 2.
5 is an exploded view of the oxygen concentration battery element, 6 is an exploded view of the oxygen pump element, and 7 is the change in the air-fuel ratio and the resistance value of the metal oxide semiconductor. A characteristic diagram, FIG. 8 is a characteristic diagram showing the change in the pump current II) of the oxygen pump element with respect to the air-fuel ratio when the electromotive force e of the oxygen concentration cell element is constant, and FIG. 9 is another implementation of the air-fuel ratio detection part. A cross-sectional view showing an example, Fig. 10 is a characteristic diagram showing the change in air-fuel ratio and applied voltage (%), Fig. 11 is a forced pump current of the oxygen pump element assuming that the electromotive force e of the oxygen concentration battery element is constant. 111 is a characteristic diagram showing changes with respect to the air-fuel ratio. In the figure: 1...Exhaust pipe 3...Solid electrolyte oxygen pump element 10...Solid electrolyte oxygen concentration battery element alb
, c, d... window f... small gap agent Ken Ishiguro = 17- Fig. 7 □ Fig. 8 □ Complete explosion w (A/F) Fig. 9 Fig. 10 Sha) I Todo (Δ/F) ZE > kX: LL1% M/l / May 21, 1980 for procedural amendment Director-General of the Patent Office Air-fuel ratio detection device 3, relation to the case of the person making the amendment Patent applicant address 14-18, Takatsuji-cho, Mizuho-ku, Nagoya Name: Nippon Tokushu Togyo Co., Ltd. (454) Representative: Kozuki □Oshuji 4, Osamu Hito 465 Phone: 052-773-24/
19G, Full text of the specification subject to amendment Fuji Specification 1, Title of the invention Air-fuel ratio detection device 2, Claims 1) Solid electrolyte oxygen concentration battery element in which porous electrodes are provided on both sides of an oxygen ion conductive solid electrolyte and solid electrolyte m
A pump element is provided, and an electrically insulating base is provided on at least one side of the element, excluding the porous electrode part,
A metal oxide semiconductor is provided on the surface of the electrically insulating base of the oxygen concentration battery element or the oxygen pump element, the oxygen concentration battery element and the oxygen pump element are disposed facing each other with a small gap interposed therebetween, and the metal oxide The air-fuel ratio is detected by a change in electrical properties provided by a semiconductor and an output signal provided by either the electromotive force of the oxygen concentration battery element or the pump current of the oxygen pump element. Device. 3. Detailed Description of the Invention [Field] This invention relates to the combustion 4i! of internal combustion engines, gas combustion equipment, etc.
The present invention relates to a detection device for measuring or controlling the oxygen concentration or air-fuel ratio in exhaust gas at a location. [Prior art 1] Conventionally, an oxygen sensor constructed by depositing a porous electrode layer (for example, a porous layer made of platinum) on an ion-conducting solid electrolyte (for example, stabilized zirconia) is used to measure the oxygen partial pressure of exhaust gas. It is generally known that, for example, an automobile engine can be controlled to operate at the stoichiometric air-fuel ratio by detecting the combustion state near the stoichiometric air-fuel ratio based on the change in electromotive force caused by the difference in the oxygen partial pressure of air. . By the way, the above oxygen sensor can obtain a large change in output when the operating air-fuel ratio (A/F), which is the weight ratio of air and fuel, is the stoichiometric air-fuel ratio of 14.7, but changes in other operating air-fuel ratio ranges. The output of the oxygen sensor cannot be used when the engine is operated at an air-fuel ratio other than the stoichiometric air-fuel ratio 2-. In JP-A No. 58-153155, two elements each having an electrode layer provided on both sides of the front side of a plate-shaped oxygen ion conductive solid electrolyte are arranged in parallel with a gap between them, and a gap is formed on the front side. is provided to fix the pixel element, one element is used as an oxygen pump element, and the other element is used as an oxygen pump element between the surrounding atmosphere and the above-mentioned gap.
We have proposed an oxygen concentration detection device using an oxygen concentration battery element that operates based on the difference in oxygen concentration. Although such an oxygen concentration detection device has good responsiveness, the stoichiometric air-fuel ratio number corresponding to the output signal is 14.7.
It has been found that operating at lower fuel levels produces more power in the same direction as in the lean fuel range. In other words, since two air-fuel ratios correspond to the output, there is a problem that air-fuel ratio control can only be applied when it is clear whether it is in the fuel excess region or the fuel lean region. there were. [Object of the Invention] 3- The first object of the present invention is to provide an air-fuel ratio system in which the operating air-fuel ratio (Δ/F) of a combustion device such as an internal combustion engine can be correctly detected in the entire region or a part of the range from the fuel-rich region to the fuel-lean region. A second object of the present invention is to provide an air-fuel ratio detection device that has the advantage of being able to perform accurate and easy feedback control when performing air-fuel ratio feedback control. [Configuration of the Invention] The air-fuel ratio detection device of the present invention includes a solid electrolyte oxygen concentration battery element and a solid electrolyte oxygen pump element in which porous electrodes are provided on both sides of an oxygen ion conductive solid electrolyte, and at least one side of the solid electrolyte An electrically insulating base is provided in a portion other than the porous electrode, and a metal oxide semiconductor is provided on the surface of the electrically insulating base of the oxygen concentration battery cable or oxygen pump element. The oxygen concentration battery element and the oxygen pump element are arranged opposite to each other with a small gap interposed therebetween, and the change in electrical properties provided by the metal oxide semiconductor and the electromotive force of the oxygen concentration battery element or the pump of the oxygen pump element are controlled. The configuration is such that the air-fuel ratio is detected based on an output signal given by J: to either of the currents. [Effects of the Invention] The air-fuel ratio detection device of the present invention has the following effects due to the above configuration. Using one lens probe, the air-fuel ratio (A/F) can be correctly detected in the entire region or a partial region from a fuel-rich region to a fuel-lean region. [Example] Next, the present invention will be explained based on an example shown in the drawings. 1 to 6 show embodiments of the present invention. 1 is an exhaust pipe of an internal combustion engine which is a combustion device, 2 is the exhaust pipe 1
This is the detection frame part of the air-fuel ratio detection device installed inside. ,
3 is the solid electrolyte oxygen pump element of the air-fuel ratio detection frame part 2, and porous platinum electrode layers 4 and 5 with a thickness of about 20 μm are provided on both sides using thick film technology (the thickness is about 20 μm). 0.
A 5 mm flat plate-shaped ion conductive solid electrolyte (e.g. stabilized zirconia) 6 and one side of the ion conductive solid electrolyte 6, for example, a porous platinum electrode layer 5, It has a flat plate shape with a thickness of about 0.2511111 mm and is thermally conductive and has a window part a that is an opening adapted to the shape of the porous platinum electrode layer 5 so as not to block the part of the porous platinum electrode layer 5 that has been removed. Highly thermally conductive electrically insulating substrate 1 made of an excellent electrically insulating material (such as alumina or spinel), etc.
At the outer periphery of the window a on the side of the ion conductive solid electrolyte 69 side of the highly thermally conductive electrically insulating substrate 7 and the surface opposite to 4, the outer periphery of the window a and the highly thermally conductive electrically insulating substrate 7 The electric heater 8 is installed inside the high heat conductive electrically insulating base 79 on which the electric heater 8 is installed, and the electric heater 8 is installed on the surface of the high heat conductive electrically insulating base 79, so that there is a gap between the outer peripheral edge of the electric heater 8 and the electric heater 8. It is composed of a highly thermally conductive electrically insulating substrate 1 provided to block the outside ζ and a flat highly thermally conductive electrically insulating substrate 9 having a window portion opening a similar porous platinum electrode layer 5. - It is. 10 is a solid electrolyte oxygen concentration battery element of the air-fuel ratio detection frame portion 2, and porous platinum electrode layers 116 are formed on both sides using the thick film technology similar to the porous platinum electrode layers 4 and 5.
A flat ion-conducting solid electrolyte 1p similar to the ion-conducting solid electrolyte 6 configured with a half-fiber 12;
Similar to the highly thermally conductive electrically insulating base 7, a porous platinum electrode layer 11 is attached to one side of the ion conductive solid electrolyte 13, which is the side 9 on which the porous platinum electrode layer 11 is provided.
Similar to the electric heater 8, the surfaces of the highly thermally conductive electrically insulating material 14 having the window portion C that opens the ion conductive solid electrolyte 13 are on the opposite side. The electric heater 15 is placed on the outer periphery of the window C on the surface thereof, and the electric heater 15 is folded inwards on the surface of the highly thermally conductive electrically insulating substrate 14 on which the electric heater 15 is provided, so as to isolate the heat from the outside. Provided highly thermally conductive electrically insulating substrate 1
Similar to 4, a flat plate-shaped highly thermally conductive electrically insulating substrate 16 having a window d opening the porous platinum electrode layer 11 and a highly thermally conductive electrically insulating substrate 1697 - the side surface in which the electric heater 15 is installed inside. On the opposite side of the window d, a metal oxide semiconductor (for example titania element) 17 is formed to a thickness of approximately 50μ using thick film technology. Note that each electric element (4, 5, 8, 11, 12, 15, 17) provided in the oxygen pump element 3 and the oxygen concentration battery element 10 is provided with a lead wire 18 using a thick film technology so as to be electrically conductive to the outside. This is provided by the following. The surface of the oxygen pump element 3 on the porous platinum electrode layer 4 side and the surface of the oxygen concentration battery element 10 on the porous platinum electrode layer 12 side are O, 1 mm Pi! In order to form a small gap f with a spacing dimension of 100 degrees, and to dispose them facing each other inside the exhaust pipe 1, the foot portions are fixed to each other via a heat-resistant and insulating spacer 19 (filling adhesive may be used). A support base 21 having a threaded portion 20 is attached to the outer edge of the foot of the oxygen pump element 3 and the oxygen concentration battery element 1O, which are fixed to each other by a spacer 19, using a heat-resistant and insulating adhesive member 22. ing. The air-fuel ratio detection frame portion 2 is attached to the exhaust pipe 1 by inserting the threaded portion 20 of the support base 21 into the mounting screw portion 23 of the air-fuel ratio detection frame portion 2 provided on the exhaust pipe 1. Here, in order to manufacture the air-fuel ratio detection frame part 2, as shown in FIG. Each of the lead wires is printed in a predetermined pattern using thick film technology, and one side of each is covered with two green sheets of highly thermally conductive and electrically insulating material, such as spinel green sheets that are flat and have windows. In between, a platinum resistor used as an electric heater and its lead wire' are sandwiched between the two, and an oxygen pump element 3 made of a ceramic laminated structure 1i obtained by laminated pressure bonding and integral sintering, as shown in FIG. Next, lead wires for metal oxide semiconductors such as titania are formed in a predetermined pattern using thick film technology on the surface of the highly thermally conductive electrically insulating base of the element, which is formed by the same process as the oxygen pump element 3. Printed and sintered oxygen concentration battery element 10 (a thick film of metal oxide is formed after sintering the above element)
It is advantageous to bond and fix the foot portions of the two (formed by firing in an atmosphere) with a spacer (heat-resistant ceramic adhesive) 19 in a state where they are overlapped with a seekness gauge in between. 24 is an example of an attached electronic control device part, and the above-mentioned oxygen 'm pale Nlt! ! Porous platinum electrode layer 11 of element 1O.
Apply the electromotive force e generated in the 12th question to the inverting input terminal of the equal width amplifier (A) through the resistor (R1).
A) quasi-voltage (Vr) applied to the non-inverting input terminal of
') and the electromotive force e, the transistor <Tr) is driven by the output of the operational amplifier (A), and a pump current is caused to flow between the porous platinum electrode layers 4.5 of the oxygen pump element '3. It has a function to control r6. That is, it functions to maintain the electromotive force e at a constant value of the reference voltage (Vr), and to supply the exhausting pump current (2) of 0. The above pump current 1 supplied from the DC power supply (B)
A resistor (Ro) is provided for obtaining an output signal corresponding to the output terminal 25 at the output terminal 25. (C) is a capacitor. In addition, the oxygen concentration battery element 1O is equipped with an output terminal 26 for detecting a change in the resistance value of the metal oxide semiconductor 17 that occurs in the exhaust pipe 1 according to a difference in oxygen concentration. physical semiconductor 17 and porous platinum electrode layer 4.
Heating power supplies 27 and 28 are connected to electric heaters 8.15 and 11.12, respectively. FIGS. 7 and 8 are characteristic diagrams of the air-fuel ratio detection device shown in FIGS. 1 to 6 above. Figure 7 shows the change in the resistance value of the metal oxide semiconductor 17 at the output terminal 26, and shows a small resistance value in the air-fuel ratio range (fuel rich range) smaller than the stoichiometric air-fuel ratio 14.7. and increases rapidly around the stoichiometric air-fuel ratio of 14.7,
In an air-fuel ratio range (fuel lean range) greater than the stoichiometric air-fuel ratio of 14.7, a large resistance value is exhibited. Figure 8 shows the reference voltage (
■For example, 2' (1111V constant),
In order to make the electromotive force e 20111■, the theoretical air-fuel ratio is 14.7.
In a smaller air-fuel ratio range (fuel ratio 11-), the pump current in the pumping direction decreases as the air-fuel ratio increases, and in a range larger than the stoichiometric air-fuel ratio 14.7, the pump current in the pumping direction decreases as the air-fuel ratio increases. (fuel lean region), the above pump current 1
p increases with increasing air-fuel ratio. This embodiment utilizes the characteristics shown in FIGS. 7 and 8. For the output terminal 26 that detects a change in resistance value, a point P, which is an arbitrary M single point, is set between the maximum resistance value and the minimum resistance value, and when the resistance value is smaller than the P point (fuel rich area ) is larger than point P (fuel lean region). Therefore, if the above engine is operated in a rich fuel region,
The resistance value of the metal oxide semiconductor 17 is smaller than point P,
This information and the pump current I of the oxygen pump element 3 at this time
By detecting the output signal corresponding to t1, detailed control or measurement in the fuel rich region can be performed. Further, when the engine is operated in a fuel lean region, the resistance value of the metal oxide semiconductor 17 is greater than point P, and this information and the output signal corresponding to the pump current Ip of the oxygen pump element 3 at this time are used. By detecting this, it is possible to perform detailed control or measurement in the fuel lean region. Further, when controlling the above engine at a stoichiometric air-fuel ratio of 14.7, the output terminal 26 for detecting the resistance value has a stoichiometric air-fuel ratio of 14.7.
Utilizing the characteristic that the resistance value rapidly decreases around 7, the air-fuel ratio is controlled as a direct feedback control signal. With the above configuration, the fuel excess lI range and the fuel excess lI range and the fuel excess lI range and the fuel excess lI range and ! This makes it possible to obtain an air-fuel ratio detection device that can accurately measure the air-fuel ratio of the engine even in a wide lean range. By utilizing this fact, once the desired air-fuel ratio is set, the current air-fuel ratio is detected by the air-fuel ratio detection frame portion 2 attached to the exhaust pipe 1, and the desired air-fuel ratio can be continuously controlled based on the feedback. I can do it. The fact that the pump current Ip changes in proportion to the air-fuel ratio in the fuel lean region as described above is described in, for example, Japanese Patent Laid-Open No. 153155/1983. That is, by changing the oxygen partial pressure of the exhaust gas introduced into the small gap f by the action of the oxygen pump element 3, it is made different from the oxygen partial pressure of the exhaust gas flowing inside the exhaust pipe 1, and this oxygen content is changed. When controlling the pumping pump current Ip supplied to the oxygen pump element 3 so that the electromotive force e of the oxygen concentration battery cable 10 generated in response to the difference in pressure is constant, this pump current It1 is Oxygen I in gas
It was found that it changes in proportion to Nmaro. The reason for the above-mentioned operation in the oxygen pumping mode in the fuel-rich region is considered to be an attempt to respond to CO gas. FIG. 9 shows another embodiment of the air-fuel ratio detection frame portion 2. In this embodiment, the outer peripheries of the φ high thermal conductive electrically insulating substrates 7.9 and (4, 16) in which the electric heaters 8 and 15 are installed are located outward from the portions forming the ion conductive solid electrolytes 6 and 13, respectively. As a result, the highly thermally conductive electrically insulating substrates 7.9 and 14.
16, the installation of the electric heater 8.15, the metal oxide semiconductor 17, and each lead wire 18 provided on the highly thermally conductive electrically insulating substrates 7.9 and 14, 14-16 is facilitated. Become. In the above embodiment, the heater is disposed on the surface of either the m-element pump element or the oxygen concentration battery element, and is embedded inside a highly thermally conductive electrically insulating base for maintaining the metal oxide semiconductor on the surface. However, if the temperature of the gas to be measured is always sufficiently high, each element can be heated without special heating.
In cases where the metal oxide semiconductor and metal oxide semiconductor are activated, the heater may be omitted. In the above embodiment, the resistance value of the metal oxide semiconductor 17 was used as a criterion for determining the fuel rich region and the fuel portion Mbli, but as shown in FIG. The characteristic of change in the ratio of voltage passing through (% of applied voltage) may be used. The direction of the pump current II) of the oxygen pump element 3 is determined by the small gap f.
The flow was carried out in the direction of pumping out oxygen from the exhaust pipe 1 (Ip>0), but on the other hand, it was flowed in the direction of drawing oxygen from the exhaust gas in the exhaust pipe 1 (It
l<0), the oxygen concentration voltage is 15-? l! ! Since the pump current 1p that keeps the output of the element 10 constant changes in accordance with the air-fuel ratio as shown in FIG. 11, the characteristics when doing so may be utilized. Also, the electromotive force e generated in the oxygen concentration battery element 10 when the pump current Ip of the oxygen pump element 3 (including both the case of pumping the M cable from the small gap f and the case of pumping it in) is controlled to be constant. Since it changes depending on the air-fuel ratio, the characteristics when doing so can also be utilized. The present invention uses one or more of the characteristics obtained from the air-fuel ratio detection frame 2 to perform feedback control, so that the air-fuel ratio is continuously controlled over the entire operating range while frequently switching modes as necessary. This is to perform feedback control. 4. Brief description of the drawings Fig. 1 is a configuration diagram showing an embodiment of the air-fuel ratio detection device of the present invention, Fig. 2 is a cross-sectional view taken along line I-I in Fig. 1, and Fig. 3 is A cross-sectional view along the X-V line of FIG. 4 is l1r in FIG.
- A cross-sectional view along line II, Figure 5 is an exploded view of the oxygen concentration battery element, Figure 6 is an exploded view of the oxygen pump element, and Figure 7 shows changes in the air-fuel ratio and the resistance value of the metal oxide semiconductor. Characteristic diagram,
FIG. 8 is a characteristic diagram showing the change in the pumping current Ip of the oxygen pump element with respect to the air-fuel ratio when the electromotive force e of the oxygen concentration battery element is constant, and FIG. 9 is a cross-section showing another embodiment of the air-fuel ratio detection part. Figure 10 is a characteristic diagram showing changes in the air-fuel ratio and applied voltage as a percentage, and Figure 11 is a characteristic diagram showing the change in the air-fuel ratio and the % of the applied voltage. FIG. 3 is a characteristic diagram showing changes. In the figure 1...Exhaust pipe 3...Solid electrolyte oxygen pump element 7.9.14.16...High thermal conductivity electrically insulating base material 10...Solid electrolyte oxygen concentration battery cord 17.
...Metal oxide semiconductor f...Small gap agent Kenji Ishiguro Procedural Amendment November 5, 1982 2, Name of the invention Air-fuel ratio detection vi 3, Relationship with @Correct Person Case Patent Applicant Address: No. 18, 141 Takatsuji-cho, Mizuho-ku, Nagoya
NGK Spark Plug Co., Ltd. (454') Representative: Shuho Ogawa 4, Agent: 465 Phone: 052"773-24'49
1-511 Miscellaneous & Specification 1, Name of the invention Air-fuel ratio detection device 2, Claims 1) Solid electrolyte oxygen concentration battery element and solid electrolyte oxygen pump in which porous electrodes are provided on both sides of an oxygen ion conductive solid electrolyte comprising an element, and providing an electrically insulating base on at least one side of the element excluding the porous electrode,
A metal oxide semiconductor is provided on the surface of the electrically insulating base of the oxygen concentration battery element or the oxygen pump element, and the oxygen concentration battery element and the oxygen pump element are arranged facing each other with a small gap therebetween, and the metal- Air-fuel ratio detection B that detects an air-fuel ratio based on a change in electrical properties given by a compound semiconductor and an output signal given by either an electromotive force of the oxygen concentration cell element or a pump current of the oxygen pump element. It! . 3. Detailed Description of the Invention [Field] The present invention relates to a detection device for measuring or controlling the oxygen concentration or air-fuel ratio in exhaust gas of a combustion device such as an internal combustion engine or gas combustion equipment. [Prior art] Conventionally, an oxygen sensor composed of an ion-conductive solid electrolyte (e.g., stabilized zirconia) coated with a porous electrode layer (e.g., a porous layer made of platinum) has been used to determine the oxygen partial pressure of exhaust gas and By detecting the combustion state near the stoichiometric air-fuel ratio based on the change in electromotive force caused by the difference between the oxygen partial pressure of the air and the oxygen partial pressure of the air, it is possible to
It is generally known that lilJ m-J. By the way, the above-mentioned oxygen sensor can obtain a large change in output when the operating air-fuel ratio (A/F), which is the weight ratio of air and fuel, is the stoichiometric air-fuel ratio of 14.7, but when there is a change in other operating air-fuel ratio ranges, When the engine is operated at an air-fuel ratio other than the stoichiometric air-fuel ratio, the output of the oxygen sensor cannot be used. Two elements having electrode layers on both sides of the front side are arranged parallel to each other with an interval between them, and a gap is provided on the front side to fix the pixel element, and one element is attached to an oxygen pump element. , the other element is connected to the surrounding atmosphere and oxygen m between the gap.
We have proposed an oxygen concentration detection device using an oxygen concentration battery element that operates based on temperature differences. Although such an oxygen concentration detection device has good responsiveness, the stoichiometric air-fuel ratio corresponding to the output signal is 14.
It has been found that when operated in a fuel-rich region lower than 7, it has the characteristic of generating output in the same direction as in a fuel-lean region. In other words, the problem was found that since two air-fuel ratios correspond to the output, air-fuel ratio control can only be applied in cases where it is determined whether the fuel rich region or the fuel lean region is in the fuel rich region. It was done. It has also been found that with this detection device, it is difficult to detect or control the stoichiometric air-fuel ratio or the air-fuel ratio in the vicinity thereof with accuracy or responsiveness. [Object of the Invention] The first object of the present invention is to ensure that the operating air-fuel ratio (A/F, And respond≦
The second object is to provide an air-fuel ratio detection device capable of detecting the air-fuel ratio, which has the advantage of allowing accurate and easy feedback control when performing air-fuel ratio feedback control within the above-mentioned air-fuel ratio range. An object of the present invention is to provide an air-fuel ratio detection device. ,. [Structure of the Invention] The air-fuel ratio detection device of the present invention includes a solid electrolyte oxygen concentration battery element and a solid electrolyte quasi-cumulative pump element, each of which has porous electrodes on both sides of an oxygen ion-conducting solid electrolyte, at least one of which An electrically insulating base is provided on a portion of one side of the electrode other than the porous electrode, a metal oxide semiconductor is provided on the surface of the electrically insulating base of the oxygen concentration battery element or the oxygen pump element-4, and a metal oxide semiconductor is provided on the surface of the electrically insulating base of the The oxygen concentration battery element and the oxygen pump element are arranged in pairs with a small gap interposed therebetween, and changes in electrical properties given by the metal oxide conductor and electromotive force of the oxygen concentration battery element or pump current of the oxygen pump element are controlled. The configuration is such that the air-fuel ratio is detected based on an output signal given by one of the following. [Effects of the Invention] The air-fuel ratio detection device of the present invention has the following effects due to the above configuration. Using one sensor probe, the air-fuel ratio (A/F) can be correctly detected in the entire region or a partial region from the fuel-rich region to the fuel #J lean region. [Example] Next, the present invention will be explained based on an example shown in the drawings. 1 to 6 show embodiments of the present invention. Reference numeral 1 indicates an exhaust pipe of an internal combustion engine, which is a combustion device, and reference numeral 2 indicates a detection frame portion of an air-fuel ratio detection device disposed within the exhaust pipe 1. 3 is the solid electrolyte oxygen pump element of the air-fuel ratio detection frame part 2, and porous platinum electrode layers 4 and 5 with a thickness of about 20μ are provided on both sides using thick film technology, respectively, and the thickness is about o. , a 5 mm flat plate-shaped ion conductive solid electrolyte (e.g. stabilized zirconia) 6 and a porous electrolyte attached to one side of the ion conductive solid electrolyte 6, for example the side on which the porous platinum electrode layer 5 is provided. It has a flat plate shape with a thickness of about 0.25n+m and has a window a that is an opening adapted to the shape of the porous platinum electrode M5 so as not to block the part of the platinum electrode layer 5, and has excellent thermal conductivity and electrical insulation. A highly thermally conductive electrically insulating substrate 1 (the substrate may be a molded board or a printed film) made of a material (such as alumina or spinel) 1, and a highly thermally conductive electrically insulating substrate 1 A gap is formed between the outer periphery of the window a and the outer periphery of the highly thermally conductive electrically insulating substrate 7 at the outer periphery of the window a on the side opposite to the surface on the side of the ion conductive solid electrolyte 6. The electric heater 8 is installed inside the high heat conductive electrically insulating base 70 on which the electric heater 8 is provided, and the high heat conductive electrical It is composed of an insulating base 7 and a flat plate-shaped highly thermally conductive electrically insulating base 9 having a window portion opening the same porous platinum electrode layer 5. 10 is a solid of the air-fuel ratio detection frame portion 2. In the electrolyte oxygen concentration battery element, porous platinum electrode layers 11 and 12 are formed on both sides using the same thick film technology as the porous platinum electrode layers 4 and 5.
A plate-shaped ion conductive solid electrolyte 13 similar to the ion conductive solid electrolyte 6 is provided, and one side of the ion conductive solid electrolyte 13 is similar to the high thermal conductive electrically insulating base 7. A highly thermally conductive electrically insulating substrate 14 having a window portion C that opens a portion of the porous platinum electrode layer 11 attached to the side surface on which the porous platinum electrode layer 11 is provided.
And, like the electric heater 8, it has a high heat transfer rate of 13f! An electric heater 15 is provided on the outer periphery of the window C on the surface of the electrically insulating rope 14 opposite to the ion conductive solid electrolyte 13 side. A highly thermally conductive electrically insulating material 14 is provided with an electric heater 15 therein and is isolated from the outside.
A flat plate-shaped highly thermally conductive electrically insulating material 16 having a window d that opens the porous platinum electrode layer 11 and the surface of the highly thermally conductive electrically insulating material 1G on the side facing the electric heater 15 are as follows. At the top of the window d on the opposite side, use thick film technology to
0μ is composed of a metal oxide semiconductor (for example, a ditania element) 17 provided at any thickness. It should be noted that each electric element (4, 5, 8, 11, 12, 15) provided in the oxygen pump element 3 and the oxygen concentration battery element 10
, 17) are each connected with a lead wire 18 for continuity to the outside.
is provided using thick film technology. The surface of the oxygen pump resistor 3 on the porous platinum electrode layer 4 side and the surface of the oxygen concentration battery element 10 on the porous platinum electrode layer 12 side are separated by a small distance of about 0.1 to 0.05 mm. Gap f
In order to form a heat-resistant and insulating spacer (filling adhesive may be used) 19 at the foot of the exhaust pipe 1,
They are fixed to each other via 8-. At the outer edge of the feet of the oxygen pump water element 3 and the oxygen concentration battery element 10, which are fixed by the spacer 19, there is a support base 21 with a threaded part 20 on the right. Installed by 22. The air-fuel ratio detection frame portion 2 is attached to the exhaust pipe 1 by screwing the threaded portion 20 of the support base 21 into the mounting screw portion 23 of the air-fuel ratio detection frame portion 2 provided on the exhaust pipe 1. Here, in order to manufacture the air-fuel ratio detection frame part 2, as shown in FIG. The lead wires are each printed in a predetermined pattern using thick film technology, and one side of the lead wires is coated with a highly thermally conductive and electrically insulating base, for example, two flat spinel green sheets with windows. In Fig. 9-5, there is an oxygen pump element 3 with a ceramic @layer structure obtained by laminating a platinum resistor such as an electric heater and a lead wire of the metal and then integrally sintering it. As shown, lead wires for metal oxide semiconductors such as ditania are formed using thick film technology on the surface of the highly thermally conductive electrically insulating base of the element, which is formed in the same process as oxygen pump element 3. An oxygen concentration battery element 10 printed in a predetermined pattern and sintered (the thick film of metal oxide is formed by sintering the above element and then firing in an atmosphere) was stacked with a seekness gauge in between. In this state, it is advantageous to adhesively fix the foot part with a spacer (if thermal ceramic adhesive) 19. Reference numeral 24 is an example of an attached electronic control unit part, in which the electromotive force e generated in the porous platinum electrode layer 11 and 12 of the oxygen concentration battery element 10 is transferred to an operational amplifier (
The reference voltage (Vr) applied to the inverting input terminal of A) and the non-inverting input terminal of the operational amplifier CA>
The operational amplifier (A
It has a function of controlling the pump current ip flowing through the porous platinum electrode layer 4.5 of the S pump cable 3 by driving a transistor (Tr) by the output of . That is,
It functions to supply the pump current Ip necessary to maintain the electromotive force e at a constant reference voltage (Vr). A resistor (Ro) is used to obtain an output signal corresponding to the pump current Ill supplied from the DC power supply (B) to the output terminal 25.
It is equipped with (C) is a capacitor. Further, the oxygen concentration battery element 10 is provided with an output terminal 26 for detecting a change in the resistance value of the metal oxide semiconductor 17 that occurs in the exhaust pipe 1 according to a difference in oxygen concentration. Metal oxide semiconductor 17 and porous platinum electrode layer 4.5 and 11.
The electric heaters 8 and 11) for heating 12 are electrically connected to heating power sources 27 and 28, respectively. 7 and 8 are characteristic diagrams of the air-fuel ratio detection device shown in FIGS. 1 to 6 above. FIG. 7 shows the change in the resistance value of the metal oxide semiconductor 17 at the output terminal 26. In the air-fuel ratio range smaller than the stoichiometric air-fuel ratio 14.7 (fuel stone excess m range), the resistance value is small. and increases rapidly around the stoichiometric air-fuel ratio of 14.7,
In an air-fuel ratio range (fuel lean range) greater than the stoichiometric air-fuel ratio of 14.7, a large resistance value is exhibited. Figure 8 shows the reference voltage (
Vr) is kept constant at, for example, 20 mV, and in order to make the electromotive force e 20 mV, the pump current I11 in the pumping direction is set at an air-fuel ratio range smaller than the stoichiometric air-fuel ratio 14.7 (fuel rich range). The above pump current I11. increases with increasing air-fuel ratio. This embodiment utilizes the heather characteristics shown in FIGS. 7 and 8. Regarding the output terminal 26 that detects a change in resistance value, PQ is located at an arbitrary reference point between the maximum resistance value and the minimum resistance value.
The resistance value is set to detect when the resistance value is smaller than point P (fuel rich area) and when it is larger than point P (fuel lean area). Therefore, if the above engine is operated in a rich fuel region,
The resistance value of the metal oxide semiconductor 17 is smaller than point P,
This information and the pump current 1 of the oxygen pump element 3 at this time
By detecting the output signal corresponding to p, detailed control or measurement can be performed in the fuel rich region. In addition, when the above engine is operated in a fuel lean region, the metal oxide semiconductor 1
The resistance value of point 7 is larger than point [), and by detecting this information and the output signal corresponding to oxygen, pump current of pump element 3, and flow at this time, detailed control in the fuel lean region is possible. Or you can measure it.・In addition, when controlling the engine described in 1-1 at a theoretical air-fuel ratio of 14.7, the resistance value is detected at the stoichiometric air-fuel ratio of 14.7 (near -1, the low value decreases rapidly). The air-fuel ratio fi control is performed by using the characteristics of It is difficult to obtain an air-fuel ratio detection device that can accurately and responsively measure the air-fuel ratio of the engine mentioned above.You can also use this to set the desired air-fuel ratio and adjust the exhaust pipe. Air-fuel ratio detection frame part 2 attached to 1
The current air-fuel ratio can be detected quickly, and the desired air-fuel ratio can be continuously controlled based on the feedback. The fact that the pump current lp changes in proportion to the air-fuel ratio in the fuel lean region as described above is described in, for example, Japanese Patent Laid-Open No. 153155/1983. That is, by changing the oxygen partial pressure of the exhaust gas introduced into the small gap f by the action of the oxygen pump element 3, a difference is created between the oxygen partial pressure of the exhaust gas flowing in the 1-1 trachea 1, When controlling the pump current Ip supplied to the oxygen pump cord 3 so that the electromotive force C of the oxygen concentration battery element 10 is constant, the pump It was found that the current Ip changes in proportion to 8M of oxygen in the v1 gas. The reason for the above-described operation in the oxygen pumping mode in the fuel-rich region is thought to be that it is sensitive to CO gas. FIG. 9 shows another embodiment of the air-fuel ratio detection frame portion 2. In this embodiment, the outer peripheries of the highly thermally conductive electrically insulating substrates 7.9 and 14.16, which hold the electric heaters 8 and 15, are exposed to external forces from the portions connecting the ion conductive solid electrolytes 6, 13, and 13, respectively. It is formed by overhanging the. This increases the area of each of the highly thermally conductive electrically insulating substrates 7.9a3 and 14.16, so the electric heater 8.15 installed on the highly thermally conductive electrically insulating substrates 7.9 and 14.16 increases. In the above embodiment, the metal oxide semiconductor 17 and each lead wire 18 are easily installed. In this case, the temperature of the gas to be measured is always sufficiently high and the temperature of each element and metal oxide 4 is maintained even without special heating. If the conductor is activated, the heater can be omitted. In the above embodiment, the resistance value of the metal oxide semiconductor 17 is used as the criterion for determining the fuel-rich region and the fuel-lean N region, but as shown in FIG. The characteristic of a change in the ratio of voltage (% of applied voltage) passing through the oxide semiconductor 17 may be used. The direction of the Bonle current I11 of the oxygen pump element 3 is determined by the small gap f.
Although the flow was carried out in the direction of pumping out oxygen from the exhaust pipe 1 ('I p ＞' O), even if it was flowed in the direction of pumping oxygen from the ``i1 gas'' in the exhaust pipe 1 up < 0), the oxygen 81 light cell Element 1
Since the pump current It), which maintains a constant output of 0, changes in accordance with the air-fuel ratio as shown in FIG. 6, the characteristic number when doing so may be used. In addition, the oxygen concentration battery element 10 is constructed by controlling the pump current 1p of the oxygen pump element 3 (including both the case of pumping out oxygen from the small gap f and the case of pumping it in) to a constant value.
The generated electromotive force. Since the air-fuel ratio also changes depending on the air-fuel ratio, the characteristics obtained when the air-fuel ratio is changed are used.The present invention performs feedback control by using one or more of the characteristics obtained from the air-fuel ratio detection frame 2. Thus, feedback control of the air-fuel ratio is continuously performed over the entire operating range while frequently switching modes as needed. 4. Brief description of the drawings Fig. 1 is a configuration diagram showing an embodiment of the air-fuel ratio detection device of the present invention, Fig. 2' is a sectional view taken along line 1'-'I in Fig. 1, and Fig. 3
The figure is a cross-sectional view taken along the F-I line in Figure 2, Figure 4 is a cross-sectional view taken along the side line in Figure 2, Figure 5 is an exploded view of the oxygen concentration battery confectionery, and Figure 6 is the oxygen pump. An exploded diagram of the device, Figure 7 is a characteristic diagram showing the ice formation of the air-fuel ratio and the resistance value of the gold m1lHts semiconductor, and Figure 8 is the pump current of the oxygen pump element when the electromotive force e of the oxygen concentration battery element is constant. 9 is a cross-sectional view showing another embodiment of the air-fuel ratio detection portion; FIG. 10 is a special diagram showing changes in air-fuel ratio and applied voltage %; FIG. 11 is a characteristic diagram showing the change in the push-pump current I'p of the oxygen pump element 8 with respect to the air-fuel ratio, with the electromotive force of the oxygen concentration cell element constant at zero. In the diagram: 1...Exhaust pipe 3...Solid electrolyte oxygen cylinder 1
7- Element 7.9.14.16...High thermal conductivity electrically insulating base material 10...Solid electrolyte oxygen ii! Light cell battery element...Metal oxide semiconductor f...Kenji Ishiguro 18-

Claims (1)

[Scope of Claims] 1) A porous electrode, a single-digit solid electrolyte, a fine dielectric cell element, and a solid electrolyte Pon Y element are provided on both end faces of an oxygen ion conductive solid electrolyte, at least one of which A high heat conductive material having a window opening the porous electrode portion and having a built-in electric heater inside is provided on one side of the material, and in front of the quasi-elementary cell element or oxygen pump material. A metal oxide semiconductor is provided on the side surface of the high thermal conductivity element, and the oxygen concentration battery and the oxygen bomb/element are placed facing each other with a small gap between them. j given by either the electromotive force of the oxygen-concentrated battery or the pump current of the oxygen pump element.
An air-fuel ratio detection device that detects the air-fuel ratio at the same time as the signal.