JPH01212343A - Semiconductor exhaust gas sensor - Google Patents

Abstract

PURPOSE:To enhance the detection accuracy of the concn. of oxygen in exhaust gas, by arranging both of an N-type semiconductor and a P-type semiconductor to each of two substrates holding a heater member therebetween and setting the arrangement positions of said semiconductors to reverse positions between both substrates. CONSTITUTION:This gas sensor is constituted of an alumina substrate 3 having an N-type semiconductor 1a and a P-type semiconductor 2a arranged to the surface thereof, an alumina substrate 4 having N-type and P-type semiconductors 1b, 2b arranged thereto in the same way and the heater member 5 arranged between the rears of both substrates 3, 4. The member 5 is fixed to the substrate 3 by printing and bonded to the substrate 4 by a bonding agent 6 composed of cement. The substrates 3, 4 are provided so that the arrangement positions of the N-type and P-type semiconductors are set to reverse positions each other and the N-type and P-type semiconductors 1a, 1b as well as the N-type and P-type ones 2a, 2b are mutually connected in series. Therefore, the heating degree by the member 15 is mutually different between the substrates 3, 4 but the temp. differences between the semiconductors of the substrates 3, 4 are set off and the temps. of both substrates 3, 4 become the same temp. value. Therefore, by the change of an engine operating state, the temp. difference between the N-type and P-type semiconductors can be eliminated.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention includes an n-type semiconductor and a p-type semiconductor, and detects the oxygen concentration in exhaust gas based on the change in resistance value due to oxygen adsorption of both semiconductors. This invention relates to improvements in semiconductor exhaust gas sensors.

(Prior Art) Conventionally, this type of semiconductor exhaust gas sensor has been disclosed, for example, in the specification and drawings of Japanese Patent Application No. 1984-1981. As shown in FIG. 12, this includes a substrate with an n-type semiconductor a disposed on its surface, a substrate d with a p-type semiconductor C disposed on its surface, and a substrate placed between the back surfaces of both substrates a and c. , a heater member e for heating the n-type semiconductor a and the p-type semiconductor C in order to use the semiconductors a and c within a set temperature range; It consists of a three-layer structure sintered and bonded with bonding materials f and f made of cement. By disposing this semiconductor exhaust gas sensor in the exhaust passage of the engine, and forming an electrical bridge circuit with the semiconductors a and c and the two reference resistors,
, When C adsorbs oxygen in the exhaust gas and its resistance value changes, the negative equilibrium voltage (output voltage) generated in the bridge circuit is measured, and the oxygen concentration in the exhaust gas (air-fuel ratio of the mixture) is calculated as follows. As shown in FIG. 11, detection is performed linearly on the lean side of the air-fuel ratio of the air-fuel mixture.

(Problem to be Solved by the Invention) By the way, the heater member e disposed between the substrates d and
Since the change in resistance of the n-type semiconductor a and the p-type semiconductor C depends on their temperature, each of the semiconductors a and c is heated to maintain them within a set temperature range.

However, the above-mentioned conventional devices have a drawback that the output value changes depending on the operating condition such as the engine rotation speed even when the oxygen concentration value is the same.

Therefore, the applicant conducted experiments and research to find out the cause of this problem, and found that, as shown in FIG. 13, when the temperature of the heater member is kept constant at a predetermined temperature, the In the region above p and m, the exhaust gas temperature is high and the temperature difference between the n-type semiconductor and the p-type semiconductor is a minute value. The temperature difference in semiconductors becomes significant. In other words, when the exhaust gas temperature is low, the power consumption of the heater member is large and heating of both semiconductors is performed almost exclusively by the heater member, and in this situation, the temperature difference between the two semiconductors is caused by the following: It was learned that this is due to non-uniform heating of both semiconductors by the heater member.

Therefore, in the present invention, in view of these points, as a means of solving the problem, a structure is adopted to cancel out the influence of the temperature difference between the two semiconductors, and a structure to cancel the temperature difference or the change in the temperature difference is implemented by adjusting the engine operation. The objective is to obtain the same output value under the same oxygen concentration regardless of changes in conditions.

(Means for Solving the Problem) In order to achieve the above object, the invention according to the present application includes an n-type semiconductor and a p-type semiconductor as a semiconductor exhaust gas sensor, and changes in resistance value due to oxygen adsorption of both semiconductors. It is assumed that the configuration is such that the oxygen concentration in exhaust gas is detected based on the following.

In the first invention according to the present application, two substrates having an n-type semiconductor and a p-type semiconductor device arranged on their surfaces are provided as a configuration to offset the influence of the temperature difference between the two semiconductors, and
A heater member for heating each n-type semiconductor and p-type semiconductor through each substrate is arranged between the back surfaces of the two substrates, and further, the n-type semiconductor and p-type semiconductor device placement positions on the two substrates are set on the side. The configuration is such that the substrates are set at opposite positions to each other.

In addition, in the second invention of the present application 1, as a configuration for eliminating the temperature difference between both semiconductors, an n-type semiconductor and a p-type semiconductor are arranged in the longitudinal direction on the surface of the substrate, and a heater is installed on the back surface of the substrate. Place the parts.

The heat transfer coefficient to the n-type semiconductor and the p-type semiconductor by the heater member is set to be lower as the semiconductor side is located on the inner side of the substrate.

Furthermore, in the third invention according to the present application, as another structure for eliminating the temperature difference between both semiconductors, a substrate having an n-type semiconductor disposed on the surface and a substrate having a p-type semiconductor disposed on the surface are provided. In contrast to the basic configuration in which a heater member is disposed between the back surfaces of both substrates, the heater member is formed integrally with a bonding material for bonding the heater member to both substrates.

(Function) With the above configuration, in the first invention according to the present application, the n-type semiconductor of one substrate and the p-type semiconductor of the other substrate are
Although the same temperature difference as before occurs between the two substrates, the n-type semiconductor and p-type semiconductor devices are arranged in opposite positions between the side substrates, so that the p-type semiconductor and the p-type semiconductor on the one substrate are opposite to each other. Since the temperature difference between the n-type semiconductor of the other substrate and the temperature difference opposite to the above temperature difference occurs, the influence of that temperature difference can be canceled out, and from the perspective of the semiconductor as a whole, all of the This can be equivalent to a situation similar to that of heating to approximately the same temperature.

Moreover, in the second invention according to the present application, the n-type semiconductor and the p-type semiconductor on the front surface are heated by the heater member through the same substrate on which they are placed. In this case, the semiconductor located on the outer side of the substrate has a large amount of heat dissipation, and its temperature is lower than that of the semiconductor located on the inner side. Since the heat transfer coefficient from the heater member is lower than that from the outer side, the temperature difference between both semiconductors is suppressed to a small value, and the temperature is adjusted to almost the same value.

Furthermore, in the third invention according to the present application, the n-type semiconductor and the p-type semiconductor are heated through separate substrates by the intermediate heater member, but the heater member is formed integrally with the bonding material of both the substrates. As a result, the thicknesses of the two bonding layers between the heater member and each substrate are made uniform, and the heat transfer coefficients from the heater member to each semiconductor are about the same, and the temperature of both semiconductors becomes the same value. Secured.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

1 to 5 show an embodiment of the first invention of the present application. Figure 1 shows the overall configuration of an engine using a semiconductor exhaust gas sensor, where 11 is an engine and 12 is an engine 1.
A combustion chamber 15 having a variable volume is formed by a piston 14 slidably inserted into the cylinder 13 of 1, and the combustion chamber 15 has one end communicating with the atmosphere and the other end opening into the combustion chamber 12 for supplying intake air. The intake passage 16 is an exhaust passage that communicates with the combustion chamber 2 at one end and opens to the atmosphere at the other end for discharging exhaust gas. The intake passage 15 is provided with a throttle valve 17 that adjusts the amount of intake air, and a fuel injection valve 18 that injects and supplies fuel downstream of the throttle valve 17. Further, in the combustion chamber 12, an intake valve 20 is arranged at the opening of the intake passage 15, and an exhaust valve 21 is arranged at the opening of the exhaust passage 16. In addition, 23 is an ignition coil that generates a high voltage, and 24 is an igniter that cuts off the primary current of the ignition coil 23, and has a function as a crank angle sensor that detects the crank angle (engine speed).

In addition, 25 is an intake air temperature sensor that detects the intake air temperature on the upstream side of the throttle valve 17, 26 is an air flow sensor that detects the amount of intake air, 27 is an opening sensor that detects the opening of the throttle valve 17, and 2g is a throttle valve. 17 is a negative pressure sensor for detecting intake negative pressure on the downstream side; 29 is a vehicle speed sensor for detecting vehicle speed. Further, A is a semiconductor exhaust gas sensor according to the present invention arranged in the exhaust passage 16.

Each of the sensors 24 to 29 and the semiconductor exhaust gas sensor A are each connected to a controller 32 having a CPU or the like therein so as to be able to send and receive signals. The combustion injection amount and the ignition timing of the air-fuel mixture in the combustion chamber 12 are adjusted and controlled.

As shown in FIGS. 2 to 4, the semiconductor exhaust gas sensor A includes an alumina substrate 3 on which an n-type semiconductor 1a and a p-type semiconductor 2a are arranged in the width direction, and a An alumina substrate 4 on which an n-type semiconductor 1b and a p-type semiconductor 2b are arranged in the width direction, and both alumina substrates 3
．． 4 and a heater member 5 disposed between the rear surfaces of the heater member 4. Thus, the n-type semiconductors 1a, lb and the p-type semiconductor 2
a.

2b both have resistance characteristics in which the resistance value changes when oxygen is adsorbed. Further, the heater member 5 is fixed to one alumina substrate 3 by printing, and
The other alumina substrate 4 is bonded with a bonding material 6 made of cement, forming a three-layer structure in which a heater member 5 is arranged between the substrates 3 and 4.

In the semiconductor exhaust gas sensor A, as shown in FIG.
It is configured to heat the type semiconductors 1a, lb and each p-type semiconductor 2a, 2b.

In addition, in the same figure, two n-type semiconductors 1a and lb and two p-type semiconductors 2a of the semiconductor exhaust gas sensor A are shown.
, 2b are arranged so as to be able to adsorb oxygen in the exhaust gas flowing through the exhaust passage 16 so as to face the inside of the exhaust passage 16, and are electrically connected in series with each other as n-type and p-type. These electrically constitute a bridge circuit 43 with two load resistors 41 and 42, and when the bridge power supply 44 is energized, the two n-type semiconductors 1a, lb and the p-type semiconductors 2a, 2b are connected to the exhaust gas. When the resistance value changes due to oxygen adsorption in the bridge circuit 43, an unbalanced voltage corresponding to the amount of adsorbed oxygen is generated in the bridge circuit 43. This unbalanced voltage signal (output voltage) is input to the controller 32, and the voltage shown in FIG. It is configured to grasp the oxygen concentration in exhaust gas using the output voltage characteristics as shown, and linearly detect the air-fuel ratio of the air-fuel mixture. In addition, in FIGS. 2 and 3, 7 is an electrode wire for forming a bridge circuit.

In FIG. 4, the semiconductor exhaust gas sensor A has two alumina substrates 3.4 in which the n-type semiconductor and p-type semiconductor devices are arranged in opposite positions.
In one alumina substrate 3, an n-type semiconductor 1a is shown at the bottom in the figure.
However, while the p-type semiconductors 2a are arranged on the upper side in the figure, on the other alumina substrate 4, the n-type semiconductor 1b is arranged on the upper side in the figure, and the p-type semiconductor 2b is arranged on the lower side in the figure. There is.

Therefore, in the embodiment according to the first invention,
The heater member 5 is bonded to one substrate 3 by printing, and to the other substrate 4 by bonding material (cement).
6, the degree of heating by the heater member 5 differs between the two substrates 3 and 4. As a result, in one substrate (for example, 3), n-type and p-type semiconductors 1a, 2a
The temperatures of the n-type and p-type semiconductors 1a and 2a of the other substrate 4 are the same and low. but,
In the bridge circuit 43 shown in FIG. 5, the n-type semiconductors 1a and lb on both substrates 3°4 are connected in series to form one side, and the p-type semiconductors 2a and 2b are similarly connected in series on one side. Therefore, the n-type semiconductors 1a, l connected in series
When viewed from the whole of b and the whole of similar p-type semiconductors 2a and 2b, the temperature difference between the semiconductors of each substrate 3.4 is canceled out,
The temperature value becomes the same. Therefore, changes in engine operating conditions (
The temperature difference between the n-type semiconductor and the p-type semiconductor can also be eliminated or made uniform due to changes in the temperature effect due to exhaust gas, and the accuracy of detecting the oxygen concentration in the exhaust gas can be improved.

Further, FIG. 6 shows an embodiment according to the second invention of the present application, and in the semiconductor exhaust gas sensor A° shown in the same figure, an n-type semiconductor 1 and a p-type semiconductor similar to those described above are provided on the surface of an alumina substrate 3°. 2 are arranged in the longitudinal direction, and a heater member 5° for heating the n-type semiconductor 1 and the p-type semiconductor 2 through the substrate 3° is printed on the back surface of the alumina substrate 3°.

The semiconductor exhaust gas sensor A° is arranged with its substrate 3° surface side facing the upstream side of the exhaust passage 6, and as shown in FIG. The embedding depth tp of the p-type semiconductor 2 into the substrate 3° is set to be shallow, less than the embedding depth tN of the upper n-type semiconductor 1 located on the outer side. That is, compared to the n-type semiconductor 1 on the outer side, the inner p-type semiconductor 2 is farther from the heater member 5° due to the shallower embedding depth and is less likely to be heated from the heater member 5°. The coefficient of heat transfer from 0 to the p-type semiconductor 2 is set lower than the coefficient of heat transfer to the n-type semiconductor 1 located on the outer side.

Therefore, in this embodiment, since both the n-type semiconductor 1 and the p-type semiconductor 2 are arranged at 3° on the same substrate, there is no difference in the thickness of the bonding layer between printing and bonding material (cement) as in the conventional case. The resulting differences in the degree of heating are eliminated. Moreover, the exhaust passage 16 for both the n-type and p-type semiconductors 1 and 2
Since they are located on the upstream side of each other, the temperature influence due to exhaust gas is also the same. Furthermore, since the n-type semiconductor 1 and the p-type semiconductor 2 are arranged in the longitudinal direction, the width of the substrate 3' is narrow, and even if they are arranged facing each other on the upstream side of the exhaust passage 16, there will not be much resistance.

In this case, the n-type semiconductor 1 located on the outer side has a better heat dissipation property due to its outer position, and the width of the temperature decrease is larger than that of the p-type semiconductor 2 on the inner side. However, the p-type semiconductor 2 on the inner side is far from the heater member 5°, and the heat transfer coefficient from the heater member 5° is set lower than that of the n-type semiconductor 1 on the outer side. Temperature rise is suppressed,
The temperature is almost the same as that of the outer n-type semiconductor 1 which has good heat dissipation properties. Therefore, by keeping the n-type semiconductor 1 and the p-type semiconductor 2 at the same temperature, the same output value can be obtained at the same oxygen concentration regardless of changes in engine operating conditions, and the detection accuracy of the oxygen concentration in exhaust gas can be improved. be able to.

Further, FIG. 8 shows a first modification example of the configuration in which the heat transfer coefficients between the outer n-type semiconductor 1 and the inner p-type semiconductor 2 are different, and in FIG. Although the depth was changed, the shape of the alumina substrate 3° was changed.

That is, in FIG. 8, n-type semiconductor 1 and p-type semiconductor 2
The embedding depths of the 3° alumina substrate are the same, but the back shape of the alumina substrate 3° is inclined upward in the figure toward the surface side.

The thickness is set to be thicker on the inner side and thinner on the outer side. This makes it more difficult to heat the p-type semiconductor 2 on the inner side by the distance from the heater member 5°, and reduces the heat transfer coefficient from the heater member 5° to the n-type semiconductor 1 on the outer side. The heat transfer coefficient is set lower than the heat transfer coefficient.

Furthermore, FIG. 9 shows a second modification of the configuration in which the heat transfer coefficients are different. In this modification, the heater member 5° is divided into two parts, and a heater portion 5a' with a dense heater pattern is arranged in the outer part corresponding to the n-type semiconductor 1, and the inner part corresponds to the p-type semiconductor 1. A heater portion 5b' with a rough heater pattern is arranged in a portion corresponding to the semiconductor 2, and the heat transfer coefficient from the heater member 5° to the p-type semiconductor 2 on the inner side is adjusted to the n-type semiconductor 1 on the outer side.
The heat transfer coefficient is set lower than the heat transfer coefficient.

Therefore, in both of the above-described modifications, the n-type semiconductor 1 and the p-type semiconductor 2 can be similarly heated to approximately the same temperature regardless of changes in engine operating conditions, and the accuracy of detecting the oxygen concentration in exhaust gas is improved. be able to.

Further, FIG. 10 shows an embodiment according to the third invention of the present application. In the semiconductor exhaust gas sensor A'' shown in the same figure, n
an alumina substrate 3°°°° on which a type semiconductor 1° is arranged;
It includes an alumina substrate 4°゛°゛ with a p-type semiconductor 2° arranged on its surface, and a heater member 5°゛ arranged between the back surfaces of both the alumina substrates 3'' and 4°゛°°. The configuration of the heater member 5° is a heat generating resistor such as ruthenium oxide, and borosilicate glass or the like as a bonding material between the alumina substrates 3°'', 4°°° and the heater member 5°. The resistance paste is made by pasting a low melting point glass with an organic resin, and is formed integrally with the bonding material (low melting point glass).

Therefore, to join the alumina substrates 3°'', 4°°°° and the heater member 5°°, first, paste the heater member 5° and both substrates 3°'', 4°°. After applying to the back side of °° and bonding, this champion is heated to 8
Heat to 50°C to melt the glass layer, impregnate the porous parts of both alumina substrates at 3°'' and 4°°°, and form a diffusion reaction layer between the alumina and glass to bring them into close contact. The resistance value of the heater member 5° is set according to the content ratio of ruthenium oxide in the resistance paste.

Therefore, in this embodiment, since the heater member 5° is integrally formed with the resistor (ruthenium oxide) and the bonding material (borosilicate glass), the two substrates 3°'',
In the three-layer structure in which the heater member is joined with 5° between them, the thickness of each joining layer is uniform and there is no cement layer interposed between the substrate and the heater member as in the conventional case. As a result, separate substrates 3 from the heater member 5°
Although the n-type semiconductor 1 and the p-type semiconductor 2 are heated through the heater member 5 and 4 degrees, since there is no cement layer and the bonding layer has a uniform thickness,
The heat transfer coefficients to the type semiconductor 1' and the p-type semiconductor 2' become similar, and both semiconductors 1' and 2 can be heated to approximately the same temperature. Further, the conventional bonding process using a separate bonding material (cement) can be eliminated, and the work process for forming the semiconductor exhaust gas sensor A'' can be simplified.

Therefore, similarly to the first and second inventions, even if the engine operating condition changes, the output value of the semiconductor exhaust gas sensor A'' can be maintained at the same value at the same oxygen concentration, and the oxygen concentration in the exhaust gas can be changed. Detection accuracy can be improved.

(Effects of the Invention) As explained above, according to the semiconductor exhaust gas sensor of the first invention according to the present application, both the n-type semiconductor and the p-type semiconductor are arranged on each of the two substrates sandwiching the heater member. At the same time, the n-type semiconductor and p-type semiconductor are arranged in opposite positions between the side substrates, so that if a temperature difference occurs in the semiconductor between the side substrates due to a difference in the heat transfer coefficient from the heater member, However, this temperature difference between the semiconductors can be canceled out, and when the oxygen concentration is the same, the same output value can be obtained regardless of changes in engine operating conditions. be able to.

Further, according to the second invention of the present application, an n-type semiconductor and a p-type semiconductor device are arranged in the longitudinal direction of one substrate, and the heat transfer coefficient from the heater member is adjusted to the side of the semiconductor located inwardly. In this case, since the temperature of both semiconductors is set lower than that of the semiconductor side which is located on the outer side and has good heat dissipation property, the temperature of both semiconductors can be maintained at the same temperature regardless of the engine operating state, or the change in temperature difference can be eliminated. Similar to the invention, the same output value can be obtained regardless of changes in engine operating conditions, and the accuracy of oxygen concentration detection can be improved.

Furthermore, according to the third invention of the present application, the heater member located between the two substrates having both an n-type semiconductor and a p-type semiconductor is formed integrally with the bonding material, so that the two Since the thickness of the bonding layer can be made almost uniform, the degree of heating of each semiconductor by the heater member can be made uniform, and the temperature difference between the two-handed conductors can be reduced to the same level at the same oxygen concentration as in the first and second inventions. By obtaining an output value, it is possible to improve the detection accuracy of oxygen concentration.

[Brief explanation of the drawing]

1 to 5 show an embodiment of the first invention according to the present application, in which FIG. 1 is a general schematic diagram of the air-fuel ratio control of an engine, FIG. 2 is a front view of a semiconductor exhaust gas sensor, and FIG. 3 is a side view of the same, FIG. 4 is a plan view of the same, and FIG. 5 is an electric circuit diagram of the semiconductor exhaust gas sensor. 6 to 9 show an embodiment according to the second invention of the present application, in which FIG. 6 is a perspective view of a semiconductor exhaust gas sensor, FIG. 7 is a sectional view of essential parts of the semiconductor exhaust gas sensor, and FIG. The figure is a cross-sectional view of a main part of a semiconductor exhaust gas sensor showing a first modification of a configuration in which the heat transfer coefficient is different between an outer semiconductor and an inner semiconductor.
The figure is a rear view of the main parts of the semiconductor exhaust gas sensor showing the second modification. FIG. 10 is a perspective view of a semiconductor exhaust gas sensor showing the third invention of the present application, and FIG. 11 is a diagram showing the oxygen concentration detection characteristics of the semiconductor exhaust gas sensor. 12 and 13 show a conventional example, FIG. 12 is a perspective view of a semiconductor exhaust gas sensor, and FIG. 13 is a diagram showing the change characteristics of the temperature difference between the semiconductors enclosed in the engine speed. A%A', A''...Semiconductor exhaust gas sensor, 1.
1°, 1a, 1b...n-type semiconductor, 2, 2° 2a. 2b...p-type semiconductor, 3.3°, 3°°, 3”°, 3
°°°°・・・Alumina substrate, 4.4°, 4°°°'・
... Alumina substrate, 5.5', 5°°... Heater member, 6... Bonding material. Patent applicant Mazda Corporation Figure 9 Figure 6 Figure 8 Figure 7 Figure 11 Left Daisai: rshi 10 vl pe<7:'*:x□2 Figure 13 Engine speed: ( r, p, m) Figure 12

Claims (3)

[Claims] (1) A semiconductor exhaust gas sensor that includes an n-type semiconductor and a p-type semiconductor and detects the oxygen concentration in exhaust gas based on the change in resistance value due to oxygen adsorption of both semiconductors, the sensor having an n-type semiconductor and a p-type semiconductor on the surface. two substrates on which type semiconductors are arranged,
A heater member is disposed between the back surfaces of the two substrates and heats each n-type semiconductor and p-type semiconductor through each substrate, and the two substrates are arranged such that the n-type semiconductor and the p-type semiconductor are arranged in the same position as each other. A semiconductor exhaust gas sensor characterized by being set in a reverse position. (2) A semiconductor exhaust gas sensor that includes an n-type semiconductor and a p-type semiconductor and detects the oxygen concentration in exhaust gas based on a change in resistance value due to oxygen adsorption of both semiconductors, the sensor having an n-type semiconductor and a p-type semiconductor on the surface. It includes a substrate on which semiconductors are arranged in the longitudinal direction, and a heater member that is arranged on the back side of the substrate and heats each of the n-type and p-type semiconductors through the substrate. A semiconductor exhaust gas sensor characterized in that the heat transfer coefficient to the p-type semiconductor is set to be lower as the semiconductor side is located on the inner side of the substrate. (3) A semiconductor exhaust gas sensor that includes an n-type semiconductor and a p-type semiconductor and detects the oxygen concentration in exhaust gas based on the change in resistance due to oxygen adsorption of both semiconductors, with the n-type semiconductor disposed on the surface. a substrate on which a p-type semiconductor is disposed, a heater member disposed between the back surfaces of both substrates and heating the n-type semiconductor and the p-type semiconductor through each substrate, the heater member . A semiconductor exhaust gas sensor, characterized in that the heater member is integrally formed with a bonding material that bonds the heater member to both of the substrates.