JPS59190652A - Rich-burn sensor - Google Patents

Abstract

PURPOSE:To obtain an air-fuel ratio sensor which can detect rich-burn by a method wherein a measurement chamber is equipped with an oxygen control and supply means and a chemical equivalent point detection means and exhaust gas is introduced into this measurement chamber. CONSTITUTION:An oxygen control and supply means is composed of zirconia solid electrolytic plates 11a, 12a and a chemical equivalent point detection means is composed of zirconia solid electrolytic plates 11b, 12b. Measured gas (exhaust gas) is introduced into a space chamber (measurement chamber) B through a fine diffusion hole 14. The difference between the oxygen density in a reference air chamber A' and the oxygen concentration in the space chamber B is detected by the chemical equivalent point detection means. As an output voltage of an oxygen concentration cell which is the chemical equivalent point detection means changes step by step in the rich-side from a theoretical air-fuel ratio point, the theoretical air-fuel ratio point can be detected. Because the quantity of the oxygen introduced into the space chamber B can be optionally controlled by an oxygen pump which is the oxygen control and supply means, the air-fuel ratio can be shifted to the rich-side from the theoretical air-fuel ratio point and the optional air-fuel ratio can be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rich pan sensor for measuring the air-fuel ratio in exhaust gas of a combustion engine.

Conventionally, a Trufea oxygen concentration battery sensor has been used as an air-fuel ratio detection element. This sensor detects the combustion state at the stoichiometric air-fuel ratio by changing the output voltage stepwise at the stoichiometric air-fuel ratio point. For example, it is used in a system that controls an automobile internal combustion engine to operate at a stoichiometric air-fuel ratio. However, with the oxygen sensor mentioned above, there is almost no change in the electromotive force in a rich atmosphere, so it is impossible to accurately measure the air-fuel ratio on the rich side. Various devices were installed on the side to perform open control. However, such a control system has the disadvantage that air-fuel ratio control is expensive and responsiveness is low, making it impossible to perform highly accurate control.

In addition, conventionally, as a sensor for detecting the entire air-fuel ratio,
Sensors such as those described in the above publication have been proposed, but all of them are technically difficult and have not yet reached the practical stage.

The above-mentioned Japanese Patent Publication No. 53-34077 discloses that in order to measure the air-fuel ratio at a richer side than the stoichiometric air-fuel ratio point, A
u.

Oxygen sensors using non-catalytic electrodes such as Ag have been described, but even with the above electrodes, the catalytic action is poor, gas adsorption occurs, and the reproducibility of the output voltage is poor. The sensor had poor durability and could not be put to practical use. In addition, Japanese Patent Publication No. 57-49860 describes a method that can measure rich and lean air-fuel ratios, but the current used is extremely low, requires careful electrical processing, and manufacturing is also difficult. Durability in technically difficult, high-temperature, high-speed gas environments.

It had drawbacks such as poor responsiveness.

This invention was made in order to eliminate the drawbacks of the conventional ones as described above.It is relatively inexpensive and has excellent practicality, and the stoichiometric air-fuel ratio point is not measured at the stoichiometric point but at the rich side and the in-line side. The purpose is to provide a sensor that can This invention also provides a fuel-burning engine for improving the combustion efficiency of an automobile engine and making exhaust gas harmless.

The present invention aims to provide a sensor that measures the air-fuel ratio in exhaust gas for closed control of the air-fuel ratio of a lean burn engine.

The feature of the rich burn sensor according to this invention is that it uses oxygen in the air as an oxygen supply source, and as a result, it supplies a sufficient amount of oxygen to change the combustible gas concentration and oxygen concentration in the gas being measured. can do. This means that the chemical equivalence point of the gas to be measured can be moved to the oxygen-deficient side, which is lower than the stoichiometric air-fuel ratio point.
This means that the air-fuel ratio on the side can be detected.

An embodiment of the invention will be described below with reference to FIG.

[Example 1] y2os 10 Stable ZrO2 sintered body 5
Cut out two boards of ×20 × 5m sail, and 3 × on both sides of this board.
Approximately 2,000 ptsm of PT was vapor-deposited to the size of a cod, and then electroplated to a thickness of 1 μm to produce a solid electrolyte plate 12a (12b) with electrodes as shown in FIG. Next 5 X
The solid electrolyte plate 11 shown in FIG. 3 is made by cutting out two plates of 20 X i, 5 m in diameter and providing a hole so as to form a hole communicating with the air side when bonded to the solid electrolyte plate 12a (12b). a(llb) was produced. Further 5X5
Cut out a board of 1.5 wa and cut out 4
Drill a hole of X4m+ and become a diffusion pore 14 0,07
A spacer 13 shown in FIG. 4 with a slI++ hole was manufactured. Each of the above members is attached to the exhaust pipe 1 as shown in Figure 1.
It is assembled through the holding part 3 inside, and NaO-8 is attached to the adhesive part.
After coating and bonding glass frit 2, which has a softening point at xooot of the system
were heated and bonded.

Next, the functions of the sensor configured as described above will be explained with reference to FIG. In the figure, a Trufea solid electrolyte oxygen pump as an oxygen amount control supply means is connected to a solid electrolyte plate 11.
It is composed of a T 12 a.

In addition, a Sorconia solid electrolyte oxygen concentration cell serving as a chemical equivalence point detection means is constituted by solid electrolyte plates 1 lb and 12 b. The spacer 13 forms a space chamber B having diffusion pores 14 through which the gas to be measured is introduced and measured. When a voltage is applied to the electrodes 15a and 15b of the oxygen pump, oxygen in the reference air chamber A, which is open to the air, moves into the space chamber B. Further, the oxygen concentration cell generates a voltage depending on the oxygen concentration in the air chamber A' and the oxygen concentration in the space chamber B, which are open to the air so that air can be used as a reference gas. This voltage is expressed by the well-known Nernst equation.

F-...Faraday constant P Ot...Oxygen partial pressure in the reference gas POr...Oxygen partial pressure in the measured gas By the way, the air-fuel ratio is at the stoichiometric air-fuel ratio point. Because the oxygen concentration is extremely low and combustible gas rapidly increases, the output voltage of the zirconia solid electrolyte oxygen concentration battery changes in a stepwise manner from the stoichiometric air-fuel ratio point to the 1/2 side.Using this phenomenon, the stoichiometric air-fuel ratio point can be reached. It is known to be used as a means of detection. On the other hand, in this invention, the oxygen concentration cell operates in the same manner as described above, but since oxygen is introduced into the measured gas by the oxygen pump, the chemical equivalence point between the oxygen in the measured gas and the combustible gas is the theoretical point. The air-fuel ratio point also moves to the rich side, and the amount of this movement can be freely controlled depending on the amount of oxygen introduced, so it is possible to detect any air-fuel ratio on the rich side, as shown in Figure 6.7. can.

[Example 2] ZrO stabilized with 10% by weight of Y2O3, sintered body 5
Cut out two 5tm x 20 x 0 plates, deposit approximately 20,001 ptsm of PT on both sides of the plate to a size of 3 x 4m, and then electroplate to a thickness of 1μ to create a solid electrolyte plate with electrodes. 12a and 12b were manufactured. Next 5X
The above solid electrolyte plate 12 was cut out from two 20x1.5m plates.
solid electrolyte plates 11'a and llb provided with holes to form holes communicating with the air side when bonded to solid electrolyte plates 11'a and 12b;
was produced. Furthermore, in order to provide a gap chamber C, a spacer 4 is used.
I cut out a board of 5 x s x O, 075.

The above members were assembled as shown in Fig. 5, and after applying 7 liters of Na0-8i02-At20s glass, which has a softening point at 1000°C, to the bonded parts, they were heated to 1150°C in a furnace.
It was heated and bonded. Regarding the function of the sensor configured in this manner, the gap chamber C achieved the same effect as the space chamber B provided with the diffusion pores 14 of Example 1, and the output characteristics were also similar.

[Example 3] In the sensor manufactured in Example 1, the oxygen in space chamber B was exhausted using a solid electrolyte oxygen pump, and the air-fuel ratio was adjusted so that the output voltage of the solid electrolyte acid concentration battery was 100 mV. When I changed the pump current accordingly and measured it, I found that it was 800.
The characteristics shown in FIG. 7 were confirmed at an exhaust gas temperature of .degree. Due to this characteristic, the air-fuel ratio can be measured at one time by measuring the pump current. Further, similar characteristics were obtained with the sensor manufactured in Example 2. Incidentally, FIG. 8 shows a characteristic diagram of the relationship between pump current and fuel ratio during lean operation.

As described above, according to the present invention, the acid system amount control supply means for supplying a predetermined amount of oxygen and the chemical equivalence point detection means are provided, and both means introduce and measure an arbitrary amount of the gas to be measured. By forming a space chamber with a gap chamber or diffusion pores, it becomes a small and inexpensive sensor that can measure the oxygen concentration and air-fuel ratio in the exhaust gas of an internal combustion engine, and the stoichiometric air-fuel ratio as a reference. Since the oxygen concentration and air-fuel ratio can be corrected, the air-fuel ratio can be accurately and stably controlled to any desired rich or lean air-fuel ratio. Furthermore, the sensor of the present invention can be applied to automobile engines as well as 2. It has the effect of being widely applicable to industrial burners and heating combustion devices.

[Brief explanation of drawings]

Fig. 1 is a sectional view of the adhesive sensor according to the present invention;
The figure is a perspective view of a solid electrolyte plate with electrodes, Figure 3 is a perspective view of a solid electrolyte plate, Figure 4 is a perspective view of a spacer, Figure 5 is a sectional view showing another embodiment of the beam sensor, and Figure 6 is a perspective view of a solid electrolyte plate with electrodes. Figure 7 is a characteristic diagram showing changes in battery voltage when pump current is applied, Figure 7 is a characteristic diagram showing changes in chemical equivalence point in terms of pump current and air-fuel ratio, and Figure 8 is a characteristic diagram showing changes in battery voltage when pump current is applied. FIG. 3 is a characteristic diagram showing the relationship between fuel ratios. 2...Glass frit joint, 4...Spacer, 1
1a, 11b - Solid electrolyte plate, 12a, 12b... Solid electrolyte plate with electrode, 13... Spacer, 14 - Diffusion pore, 15a, 151>... Pump part electrode, 16
a, 16b-battery section electrode, A, A'--reference air chamber, B... space chamber, C... gap chamber. In addition, in the figures, the same reference numerals indicate the same or corresponding parts. Fig. 1 Fig. 5 Fig. 6
City Pump Figure 7 Figure 8 Procedural amendment (voluntary) 2. Name of the invention Rich burn sensor 3. Relationship to the person making the amendment Patent applicant address 2-2-3 Marunouchi, Chiyoda-ku, Tokyo Name Name (601) Mitsubishi Electric Co., Ltd. Representative Hitoshi Katayama 4, Agent address 2-2-3-5 Marunouchi, Chiyoda-ku, Tokyo, Claims column 6 of the specification to be amended, Attachment to the contents of the amendment Amend the claims of the specification as follows. Claims (1) Oxygen amount control supply means for supplying a predetermined amount of oxygen;
chemical equivalence point detection means; both means form a space chamber equipped with a gap chamber or diffusion pore for introducing and measuring an arbitrary amount of the gas to be measured; The oxygen concentration is controlled by the oxygen amount control supply means to control the gas to be measured in the space chamber to a chemical equivalence point at a predetermined air-fuel ratio, and the air-fuel ratio of the gas to be measured outside the space chamber is controlled by the chemical equivalence point detection means. A rich burn sensor characterized by measuring. (2) The rich burn sensor according to claim 1, wherein a solid electrolyte oxygen pump is used as the oxygen amount control supply means and oxygen in the air is used as the oxygen source. (3) The rich burn sensor according to claim 1, wherein a solid electrolyte oxygen concentration battery is used as the chemical equivalence point detection means, and oxygen in the air is used as the reference gas. (4) In the lean state, the detection means is operated so that the oxygen concentration in the gas to be measured in the space chamber has a predetermined concentration difference from the oxygen concentration in the reference gas of the chemical equivalence point detection means; The oxygen concentration is determined based on the current value of the air-fuel ratio of the gas to be measured outside the space chamber, and the air-fuel ratio of the gas to be measured outside the space chamber is determined. Indication of the case: Japanese Patent Application No. 58-66022 2, Name of the invention Air-fuel ratio sensor 3, Person making the amendment 4, Agent I'Kibi', 5. Full text of the specification to be amended. 6. Details of the amendment The entire text has been amended as shown in the attached document. Description 1, Name of the invention Air-fuel ratio sensor 2, Claims (1) Oxygen amount control supply means for supplying a predetermined amount of oxygen and chemical equivalence point detection means Both means form a space chamber equipped with a gap chamber or a diffusion pore for introducing and measuring an arbitrary amount of the gas to be measured, and the oxygen concentration in the gas to be measured in this chamber is adjusted to the above amount of oxygen. An air-fuel ratio sensor characterized in that the air-fuel ratio of the gas to be measured in the indoor and outdoor areas is controlled by a control supply means to a desired air-fuel ratio to the chemical equivalence point.(2) As the oxygen amount control supply means, a solid electrolyte oxygen (3) The air-fuel ratio sensor according to claim 1, characterized in that a pump is used and oxygen in the air is used as an oxygen source. The air-fuel ratio sensor as set forth in claim 1, item 2. Conventionally, a zirconia oxygen concentration battery sensor has been used as an air-fuel ratio detection element.This sensor detects the combustion state at the stoichiometric air-fuel ratio by changing the output voltage stepwise at the stoichiometric air-fuel ratio point. For example, it is used in a system that controls an automobile internal combustion engine to operate at a stoichiometric air-fuel ratio.However, in the oxygen sensor mentioned above, there is almost no change in electromotive force in a rich atmosphere, and therefore It is impossible to precisely measure the air-fuel ratio, so in order to maintain an almost constant rich atmosphere, open control is performed by installing various devices on the intake system side.However, with this control method, Air-fuel ratio control has the drawbacks of high cost and inability to perform high-precision control. Conventionally, as a sensor for detecting the entire air-fuel ratio, there are sensors such as those disclosed in Japanese Patent Publication No. 58-84077 and Japanese Patent Publication No. 57-4986.
Sensors such as those described in Publication No. 0 have been proposed, but all of them are technically difficult and have not yet reached the practical stage. The above-mentioned Japanese Patent Publication No. 58-84077 describes the use of materials such as Au and Ag as a measuring electrode located in the exhaust gas of a zirconia tube in order to measure the air-fuel ratio when the air-fuel ratio is richer than the stoichiometric air-fuel ratio point. Oxygen sensors using non-catalytic electrodes have been described, but even the above electrodes have a catalytic effect, causing gas adsorption phenomena, resulting in poor output voltage reproducibility and poor durability in high-temperature, high-temperature gases. It was a sensor that could not be put to practical use. In addition, Japanese Patent Publication No. 57-49860 describes a method that can measure rich and lean air-fuel ratios, but the current used is extremely low, requires careful electrical processing, and is technically difficult to manufacture. However, it has drawbacks such as poor durability and poor responsiveness in high-temperature, high-speed gas environments. This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and it is a sensor that is relatively inexpensive, has excellent practicality, and can measure not only the stoichiometric air-fuel ratio point but also the air-fuel ratio on the rich side and lean side. is intended to provide. This invention also provides a rich burn engine for improving the combustion efficiency of an automobile engine and making exhaust gas harmless;
The present invention aims to provide a sensor that measures the air-fuel ratio in exhaust gas for closed control of the air-fuel ratio of a lean burn engine. A feature of the air-fuel ratio sensor according to the present invention is that it uses oxygen in the air as an oxygen supply source, and as a result, it supplies a sufficient amount of oxygen to change the combustible gas concentration and oxygen concentration in the gas being measured. This means that the chemical equivalence point of the gas being measured can be moved to the oxygen-deficient side, which means that the air-fuel ratio can be detected on the richer side than the stoichiometric air-fuel ratio point. There is. An embodiment of the invention will be described below with reference to FIG. [Example IJ Y208 10 Juya% Z, O2 sintered body 5×
Two 20 x 0.5 mm plates were cut out, and approximately 200 OA of Pt was deposited on both sides of the plates to a size of 8 x 4 m +++.
Thereafter, the solid electrolyte plates (12a) and (12b) with electrodes shown in FIG. 2 were manufactured by electroplating to a thickness of 1 μm. Next, two plates of 5 x 20 x 1.5 mm were cut out, and a hollow was formed so as to form a hole communicating with the air side when the solid electrolyte plates (12a) and (12b) were bonded to the solid electrolyte shown in Fig. 8. A plate (lla) (Hb) was manufactured. Furthermore, a 5x5x1.5mm plate was cut out, and a 4x4. A spacer 18 as shown in FIG. 4 was manufactured in which a hole of 0.07 nnn was formed to serve as the diffusion pore 14. Each of the above members is assembled into the exhaust pipe 1 via the holding part 8 as shown in FIG.
O-S i 02 AA'20B series O After applying and bonding glass frit 2 which exhibits a softening point at 1000°C,
They were heated to 1150"C in a furnace and bonded. Next, the function of the sensor configured as described above will be explained with reference to FIG. 11a
, 12a. Further, a zirconia solid electrolyte oxygen concentration cell serving as a chemical equivalence point detection means is composed of a solid electrolyte plate 11b and a plate 2b. The spacer 18 forms a space chamber B having diffusion pores 14 for introducing and measuring the gas to be measured. When a voltage is applied to the electrodes 15a and 15b of the oxygen pump, oxygen in the reference air chamber A, which is open to the air, moves into the space chamber B. Further, the oxygen concentration cell generates a voltage depending on the oxygen concentration in the air chamber A' and the oxygen concentration in the space chamber B, which are open to the air so that air can be used as a reference gas. This voltage is expressed by the well-known Nernst equation. R...Gas constant PO2...Oxygen partial pressure in the reference gas Pσ2...Oxygen partial pressure in the measured gas By the way, when the air-fuel ratio is richer than the stoichiometric air-fuel ratio point, the oxygen concentration in the measured gas is Because combustible gas increases rapidly at extremely low temperatures, the output voltage of zirconia solid electrolyte oxygen concentration batteries changes stepwise on the richer side than the stoichiometric air-fuel ratio point, and this phenomenon is used as a means to detect the stoichiometric air-fuel ratio point. It is publicly known that On the other hand, in this invention, the oxygen concentration cell operates in the same manner as described above, but since oxygen is introduced into the gas to be measured in the space chamber B by the oxygen pump, the oxygen in the gas to be measured and the flammable The chemical equivalent of the gas moves to the richer side than the stoichiometric air-fuel ratio point of the gas to be measured outside the space chamber B, and the amount of this movement can be freely controlled by the amount of oxygen introduced. As shown in the figure, any air-fuel ratio on the rich side can be detected. [Example 2] Two plates of 5 x 20 x 0.5 mm were cut out from a Z r O 2 sintered body stabilized with 10% by weight of Y2O8, and about 200 O of PT was applied to both sides of the plate to a size of F3 x 4 m+n.
Solid electrolyte plates 12a and 12b with electrodes were manufactured by depositing A and then electroplating to a thickness of 1 μm. Next, two plates of 5 x 20 x 1.5 mm are cut out, and a solid electrolyte plate 1 is provided with a recess so as to form a hole communicating with the air side when bonded to the solid electrolyte plates 12a and 12b.
1a. 11b was produced. Furthermore, in order to provide a gap chamber C, a plate of 5×5×0.075 mm was cut out as a spacer 4. Each of the above members was assembled as shown in Fig. 5, and Na0-5i02-Al□Oa system (D 1000'
After applying a glass frit exhibiting a CTE softening point, it was heated to 1150°C in a furnace and bonded. In the function of the sensor configured in this way, the gap chamber C is the diffusion pore 14 of the first embodiment.
The same effect as that of the space chamber B equipped with the above was obtained, and the output characteristics were also the same. [Example 3] In the sensor manufactured in Example 1, the oxygen in space chamber B was exhausted using a solid electrolyte oxygen pump, and the output voltage of the solid electrolyte oxygen concentration battery was 100 mV. When we measured the pump current by changing the pump current according to the air-fuel ratio so that the oxygen partial pressure in chamber B and reference air chamber A' became the set value, we found the characteristics shown in Figure 8 at an exhaust gas temperature of 800'C. was confirmed. Based on this characteristic, in order to measure the air-fuel ratio during lean conditions, it is sufficient to measure the pump current. Further, similar characteristics were obtained with the sensor manufactured in Example 2. As described above, according to the present invention, the oxygen amount control supply means for supplying a predetermined amount of oxygen and the chemical equivalence point detection means are provided. By forming a space chamber with a gap chamber or diffusion pores, it becomes a small and inexpensive air-fuel ratio sensor that can measure the oxygen concentration and air-fuel ratio in the exhaust gas of an internal combustion engine, and also detects the stoichiometric air-fuel ratio as a reference. Since the oxygen concentration and air-fuel ratio can be corrected, any rich or lean air-fuel ratio can be measured accurately and stably. Furthermore, the sensor of the present invention has the effect of being widely applicable not only to automobile engines but also to industrial burners and chamber combustion devices. 4. Brief description of the drawings Figure 1 is a cross-sectional view of the air-fuel ratio sensor of the present invention, Figure 2 is a perspective view of a solid electrolyte plate with electrodes, Figure 8 is a perspective view of a solid electrolyte plate, and Figure 4 is a spacer. 5 is a sectional view showing another embodiment of the air-fuel ratio sensor, FIG. 6 is a characteristic diagram showing changes in battery voltage when pump current is applied, and FIG. FIG. 8 is a characteristic diagram showing the relationship between the pump current and the air-fuel ratio in a lean state. 2...Glass frit joint, 4...Spacer, 1
1a, llb... one solid electrolyte plate, 12a, 1
2b =-Solid electrolyte plate with electrode, 1g... Spacer, Work 4... Diffusion pore, 15a, 15b... Pump part electrode, 16a, 16b... Battery part electrode, ^,
A'...Reference air chamber, B...Space chamber, C...Gap chamber. In addition, in the figures, the same reference numerals indicate the same or corresponding parts. Agent Masuo Oiwa

Claims (4)

[Claims] (1) oxygen amount control supply means for supplying a predetermined amount of oxygen;
chemical equivalence point detection means; both means form a space chamber equipped with a gap chamber or diffusion pore for introducing and measuring an arbitrary amount of the gas to be measured; The oxygen concentration is controlled by the oxygen amount control supply means to control the gas to be measured in the space chamber to a chemical equivalence point at a predetermined air-fuel ratio, and the air-fuel ratio of the gas to be measured outside the space chamber is controlled by the chemical equivalence point detection means. Ritsuchipan sensor characterized by measuring. (2) The multi-burn sensor according to claim 1, characterized in that a solid electrolyte oxygen pump is used as the oxygen amount control supply means and oxygen in the air is used as the oxygen source. (3) The multi-bar sensor according to claim 1, characterized in that a solid electrolyte oxygen concentration battery is used as the chemical equivalence point detection means, and oxygen in the air is used as the reference gas. (4) In the lean state, the detection means is operated so that the oxygen concentration in the gas to be measured in the space chamber has a predetermined concentration difference from the oxygen concentration in the reference gas of the chemical equivalent detection means, and the current at that time is The sensor according to claim 1, characterized in that the oxygen concentration is determined based on the value, and the air-fuel ratio of the measurement gas outside the space chamber is determined.