JPH11200913A - Arrangement structure for exhaust gas sensor of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably sense oxygen concentration and control an air-fuel ratio inside of a range for a short period from the starting time by heating an element part to be in high temperature for a short period from the starting time, by the use of high temperature exhaust gas immediately after combustion. SOLUTION: An oxygen concentration sensor 9 is composed of an element part 23 in direct contact with exhaust gas 49, and a main body part 23 for supporting the element part 23. The main body part 24 is a closed type sensor which has no air introduction port. The element part 23 is arranged inside an exhaust port 8, while the main body part 24 is arranged outside the exhaust port 8 and in cooling water 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an arrangement structure of an exhaust gas sensor of an internal combustion engine.

[0002]

2. Description of the Related Art FIG. 7 is a principle diagram of a typical three-way catalyst purifying system. This purifying system 100 includes an oxygen sensor 101 for detecting an oxygen concentration, a control unit 102 for performing feedback control, and a fuel injection valve. 103
And a three-way catalyst 104 for purifying exhaust gas. A throttle sensor 106 and an air cleaner 107 are attached to the intake pipe 105, and a water temperature sensor 10 is attached to the main body 108.
9, the cooling water 111, the spark plug 112 and the thermostat 113 are shown. 114 is an exhaust pipe, 115
Is the radiator.

[0003] three-way catalyst 104 is harmful 3 component in the exhaust gas in the oxidation and reduction reactions were cleaned (carbon monoxide (CO), hydrocarbons (HC), nitrogen oxides (NO _X)) at the same time,
It emits harmless exhaust gas to the atmosphere. In order to purify with high efficiency, the three components must be balanced, and the air-fuel ratio becomes important.

[0004] The control unit 102 controls the air-fuel ratio to be kept within a predetermined range. The oxygen concentration in the exhaust gas is detected by the oxygen sensor 101, the intake air amount is detected by the throttle sensor 106, the water temperature is detected by the water temperature sensor 108, and the control unit 102 performs comprehensive processing together with other information. The output signal is sent to the fuel injection valve 103 to supply a fuel amount corresponding to the intake air amount, thereby keeping the air-fuel ratio within the range.

FIGS. 8A and 8B are cross-sectional views of a conventional typical oxygen sensor, FIG. 8A is a partial cross-sectional view of the entire oxygen sensor, and FIG. 8B is an enlarged view of a main part. Oxygen sensor 101
Has a platinum electrode 122 provided inside a test tubular zirconia element 121 and a platinum electrode 123 provided outside, and the outer platinum electrode 123 is further coated with a ceramic 124 as a porous layer. A ventilation hole 12 for introducing air into a main body 125 supporting the zirconia element 121 is provided.
6 (... indicates a plurality; the same applies hereinafter). Air is introduced into the inside of the zirconia element 121 (toward the platinum electrode 122) through the ventilation holes 126, and the air is used as a reference for the oxygen concentration. On the other hand, holes 127 for passing exhaust gas are provided in a cover 126 surrounding the zirconia element 121, and exhaust gas is passed through the holes 127.
(To the platinum electrode 123 side). 128 is a lead wire.

[0006] One side of the zirconia element 121 is brought into contact with the atmosphere, and the other side is brought into contact with exhaust gas having a low oxygen concentration. As a result, oxygen ions move from the atmosphere side having a high oxygen partial pressure toward the exhaust gas side, and an electromotive force is generated. The electromotive force increases as the concentration difference increases.

However, the above zirconia element 121 is
At low temperatures, the internal resistance becomes very large, so that the movement of oxygen ions is hindered and the generation of electromotive force becomes insufficient. Therefore, the zirconia element 121 needs to be used under relatively high temperature conditions.

For this reason, as a technique for touching the oxygen sensor before the exhaust gas temperature decreases so much, there is, for example, Japanese Utility Model Publication No. Sho 59-13308 "Exhaust Gas Purification System for Multi-Cylinder Engine".

According to the drawings in the above publication, the first exhaust pipe group 2
5 is characterized in that an exhaust gas component detecting device 33 is disposed in the collecting section 32. Compared to the case where an exhaust gas component detection device is arranged in the collecting portion 29 of the first and second connecting pipes 27 and 28,
The exhaust gas having a relatively high temperature is detected by the exhaust gas component detection device 33.
Therefore, the exhaust gas component detection device 33 can be operated more accurately.

[0010]

However, the technique disclosed in the above publication also has a problem that it takes time to raise the temperature due to the heat capacity of the sensor itself. On the other hand, if the heat capacity itself is simply reduced, the influence of the fluctuation of the exhaust gas temperature due to the fluctuation of the operation state of the internal combustion engine and the influence of the fluctuation of the sensor temperature by the cooling due to the running wind or the like are received. . Also, if the sensor is moved further upstream of the exhaust pipe,
Since the sensor element comes into contact with the hotter exhaust gas, the temperature rise can be expected to be faster, but this time, there is a risk that other lead wires of the sensor body may be overheated.

[0011]

According to one aspect of the present invention, there is provided an internal combustion engine having a combustion chamber, an intake passage and an exhaust passage connected to the combustion chamber, wherein the refrigerant cools the internal combustion engine itself. In a device having a passage and an exhaust gas sensor on the discharge side from the combustion chamber, the exhaust gas sensor includes an element portion directly in contact with the exhaust gas and a main body portion supporting the element portion, and an air introduction hole is provided in the main body portion. , Wherein the element portion is arranged in the exhaust passage, and the main body portion is arranged outside the exhaust passage and in the refrigerant. Since the exhaust gas sensor is disposed in the exhaust passage connected to the combustion chamber and the element section is brought into direct contact with the high-temperature exhaust gas, the temperature of the element section can be quickly raised. In addition, the adoption of the sealed sensor allows the main body to be forcibly cooled by the refrigerant, thereby preventing overheating of the main body despite the arrangement of the exhaust gas sensor in the exhaust passage near the combustion chamber of the internal combustion engine. Can be.

[0012] The refrigerant according to claim 2 is characterized in that it is cooling water for an internal combustion engine. Since the temperature of the cooling water of the internal combustion engine is controlled, the main body of the exhaust gas sensor can be maintained at a predetermined temperature, and the performance of the exhaust gas sensor can be maintained well.

According to a third aspect of the present invention, the exhaust gas sensor is an oxygen concentration sensor. It is particularly suitable for an oxygen concentration sensor that requires a trade-off that the element part of the sensor is at a higher temperature and the body part of the sensor is near normal temperature, and that the performance of the oxygen concentration sensor is exhibited and maintained well. Can be.

[0014]

Embodiments of the present invention will be described below with reference to the accompanying drawings. The drawings should be viewed in the direction of reference numerals. FIG. 1 is a perspective view of an internal combustion engine according to the present invention. The internal combustion engine 1 includes a cylinder block 2, a crankcase 3 mounted below the cylinder block 2, and a cylinder head 4 mounted on the cylinder block 2. And an oxygen sensor arrangement portion 5 provided on a side surface of the cylinder head 4.
And a cylinder head cover 6 mounted on the cylinder head 4. 7 are intake ports.

FIG. 2 is a sectional view taken along line 2-2 of FIG. Specifically, the oxygen concentration sensor 9 is inserted from the storage section 12 side, the element section 23 of the oxygen concentration sensor 9 faces the exhaust port 8, the main body section 24 is left in the storage section 12, and thereafter the blind portion is covered by the cover 14. By doing so, the cooling water 13 can be made to flow into the storage section 12. Reference numeral 15 denotes a grommet, and reference numeral 16 denotes a spark plug mounting screw.

FIG. 3 is a sectional view taken along line 3-3 of FIG. 1, showing an example of the arrangement of the intake valve 18, the exhaust valve 19, the cams 22a and 22b, and also shows the mounting position of the oxygen concentration sensor 9. That is, this indicates that the oxygen concentration sensor 9 is mounted very close to the exhaust valve 19.

FIGS. 4A and 4B are cross-sectional views of an oxygen concentration sensor according to the present invention, wherein FIG.
(B) is sectional drawing which expanded the b part of (a). The oxygen concentration sensor 9 includes an element unit 23 that directly contacts the exhaust gas,
The main body 24 supports the element portion 23. The element section 23 includes a base layer 25 composed of multiple layers and a first platinum (P
t) an electrode 26, a thin-film zirconia layer 27, a second platinum electrode 28, a protective cap 29 surrounding these, a terminal crimping portion 35 for connecting to the heater 25c,
It comprises a terminal crimping portion 36 for connecting to the second platinum electrodes 26, 28, and lead wires 37, 37 crimped to the terminal crimping portions 35, 36. 38 are ventilation holes for passing exhaust gas. The base layer 25 includes a thin zirconia layer 25a, an insulating layer 25b, a heater 25c, an insulating layer 25d, and a thin zirconia layer 25e. Note that the zirconia layer 27 is yttria - stabilized zirconia with (Y ₂ O ₃ yttrium oxide) - was the the (Z _R O ₂ zirconium oxide) is thinned solid electrolyte, stabilizers and solid electrolyte limited to Absent.

The main body 24 includes a main body 41, a seal 42 fitted into a longitudinal hole of the main body 41 and holding the base 25, a pipe 43 welded to an end of the main body 41, And a rubber stopper 44 for closing the opening of the pipe 43. 45 is a gasket.

The operation of the exhaust gas sensor arrangement structure of the internal combustion engine described above will be described with reference to FIGS. In FIG.
When the intake valve 18 is opened by the intake process of the piston 21 and the cam 22a, the air-fuel mixture 48 passes through the intake port 7 and reaches the combustion chamber of the cylinder 17. After the compression and expansion steps, when the exhaust valve 19 is opened by the exhaust step of the piston 21 and the cam 22b, the exhaust gas 49 is pushed out and passes through the exhaust port 8. At this time, the high-temperature exhaust gas 49
Comes into contact with the oxygen concentration sensor 9,
Reaches a predetermined temperature in a short time.

Returning to FIG. 2, the temperature of the element section 23 becomes high.
On the other hand, since the main body 24 is surrounded by the cooling water 13 for cooling the cylinder head 4, there is no need to worry about high temperatures. As a result, there is no fear that the temperature of the lead wire 37 and the rubber stopper 44 becomes higher than the heat resistant temperature.

Referring to FIG. 4, when a positive voltage is applied to the first platinum electrode 26 and a negative voltage is applied to the second platinum electrode 28 via a detection resistor (not shown), the second platinum electrode 28 is exposed to exhaust gas. Contained in the zirconia layer 27 receives the electrons and becomes oxygen ions, and the oxygen ions pass through the zirconia layer 27 and release electrons on the first platinum electrode 26 side to remain as oxygen. Since a current is generated between the electrodes depending on the occurrence of the oxidation-reduction reaction of oxygen, a change in the oxygen concentration in the exhaust gas is detected as a voltage change across the detection resistor. Power supply control and measurement of voltage fluctuation for oxygen generation are controlled by a controller. Since the oxygen concentration sensor 9 uses the zirconia layer 27 as a solid electrolyte to detect the oxygen concentration in the exhaust gas as its redox reaction, it does not need oxygen in the atmosphere, so the main body 24 does not need an air introduction hole. , Can be sealed.

Compared to the conventional oxygen sensor 101 shown in FIG. 8, the oxygen concentration sensor 9 of this embodiment shown in FIG. 4 is different in the following points. Since there is no need to introduce air, the main body 24 can be reduced in size to a small diameter. Since there is no need to introduce air, the test tubular zirconia element 121 is not required, and the protective cap 29 at the distal end is not required.
Can be reduced to a small diameter. As a result, in the oxygen concentration sensor 9 of the present embodiment, the heat capacity becomes extremely small, and reaches the predetermined temperature in a short time. However, conventionally, the main body 125 was cooled by the atmosphere, but in the present embodiment, since this is stopped, the main body portion 24 needs to be cooled by another means. This embodiment is characterized in that this cooling is performed by a coolant such as cooling water.

FIG. 5 is a cross-sectional view of another embodiment of the exhaust gas sensor arrangement structure of the present invention. This embodiment is characterized in that lubricating oil is used as a refrigerant. The same components as those in FIGS. 1 to 4 are denoted by the same reference numerals, and description thereof will be omitted.
In the internal combustion engine 60, a finned cylinder block 61
And a cylinder head 62 mounted on the cylinder block 61, camshafts 63, 63 disposed on the cylinder head 62, and an oxygen concentration sensor disposed portion 64 disposed on the exhaust side of the cylinder head 62. Is shown. In this embodiment, the oxygen concentration sensor 9 is inserted from the storage portion 65 side, the element portion 23 of the oxygen concentration sensor 9 faces the exhaust port 8, the main body portion 24 remains in the storage portion 65, and thereafter the blind portion is blinded by the cover 66. By doing so, the lubricating oil 6
7 is made to flow. 68 is a return oil passage opened at the bottom of the storage section 65.

The lubricating oil 67 uses the intake and exhaust valves 18, 19
And the lubrication of the camshafts 63 and 63, and further cools the main body 24 of the oxygen concentration sensor 9 with the splash of the lubricating oil 67. Since cooling is performed by the lubricating oil 67, there is no fear that the temperature of the lead wire 37 and the rubber stopper 44 becomes higher than the heat resistant temperature. Therefore, even in the air-cooled internal combustion engine 60, the oxygen concentration sensor 9 can be disposed in the high-temperature exhaust port 8.

FIGS. 6 (a) and 6 (b) show still another embodiment of the exhaust gas sensor arrangement structure of the present invention. The internal combustion engine 70 is a two-cycle water-cooled engine, and a scavenging hole and an exhaust port are provided in a cylinder block. It is provided. FIG. 3A is a perspective view of an internal combustion engine 70, which includes a cylinder block 72, a crankcase 73 mounted below the cylinder block 72, a cylinder head 74 mounted on the cylinder block 72, Cylinder block 7
And an oxygen sensor arrangement portion 75 provided on the side surface of the second sensor. 7
6 is an exhaust timing control valve cover, and 77 is a thermostat cap.

(B) is a sectional view taken along the line bb of (a),
The cylinder block 72 mainly includes a scavenging hole 78, a cylinder 79, an exhaust timing control valve 81, and an exhaust port 82. In this embodiment, the oxygen concentration sensor 9 is inserted from the storage unit 83 side, and the element unit 2 of the oxygen concentration sensor 9 is inserted.
3 to the exhaust port 82, and
, And then blind by a cover 84 so that the cooling water 85 can flow into the storage portion 83.

In (b), the mixture 86 is supplied to the scavenging holes 78.
From the cylinder 79, and pushes out the exhaust gas 87. When the element portion 23 is disposed at the exhaust port 82 to which the exhaust gas 87 immediately after the combustion is applied, the exhaust gas 87
Is rapidly heated, the element section 21 reaches a predetermined temperature in a short time. On the other hand, the storage section 8 in which the cooling water 85 circulates
When the main body 24 of the oxygen concentration sensor 9 is disposed at 3, the cooling water 85 cools the main body 24, so that there is no concern that the lead wire 37 and the rubber plug 44 become higher than the heat resistant temperature.

The internal combustion engine of this embodiment is a four-cycle four-cylinder engine and a two-cycle single-cylinder engine, but is not limited thereto. For example, a V-type three-cylinder engine may be used, and the engine type is not limited.

[0029]

According to the present invention, the following effects are exhibited by the above configuration. In the first aspect, the exhaust gas sensor is disposed in the exhaust passage connected to the combustion chamber, and the element portion is brought into direct contact with the high-temperature exhaust gas. Therefore, the temperature of the element portion can be quickly raised.
In addition, the adoption of the sealed sensor allows the main body to be forcibly cooled by the refrigerant, thereby preventing overheating of the main body despite the arrangement of the exhaust gas sensor in the exhaust passage near the combustion chamber of the internal combustion engine. Can be. As a result, there is no fear that the covering material and the sealing material of the conductive wire become higher than the heat resistant temperature.

According to the second aspect of the present invention, since the refrigerant is controlled cooling water for cooling the internal combustion engine, the main body of the exhaust gas sensor can be efficiently cooled, can be cooled stably, and good performance can be maintained.

According to the third aspect of the present invention, since the exhaust gas sensor is an oxygen concentration sensor, the element section is particularly suitable for an oxygen concentration sensor in which the temperature of the element section is higher, and conversely, the main body section is kept at a high temperature. It can be exhibited and maintained well. In addition, since the exhaust gas brings the zirconia layer to a predetermined temperature in a short time, the detection of the oxygen concentration starts earlier,
The air-fuel ratio can be controlled within a predetermined range in a short time after starting. Therefore, the three components of the exhaust gas can be purified in a short time after the start.

[Brief description of the drawings]

FIG. 1 is a perspective view of an internal combustion engine according to the present invention.

FIG. 2 is a sectional view taken along line 2-2 of FIG.

FIG. 3 is a sectional view taken along line 3-3 in FIG. 1;

FIG. 4 is a sectional view of an oxygen concentration sensor according to the present invention.

FIG. 5 is a cross-sectional view according to another embodiment of the exhaust gas sensor arrangement structure of the present invention.

FIG. 6 is a view showing still another embodiment of the exhaust gas sensor arrangement structure of the present invention.

FIG. 7 is a principle diagram of a typical three-way catalyst purification system.

FIG. 8 is a cross-sectional view of a typical conventional oxygen sensor.

[Explanation of symbols]

1, 60, 70 ... internal combustion engine, 4 ... cylinder head, 7 ...
Intake port, 5, 64, 75 ... oxygen concentration sensor arrangement part,
8 Exhaust port, 9 Oxygen concentration sensor, 13 Refrigerant (cooling water), 23 Element part, 24 Body part, 37 Lead wire, 49, 87 Exhaust gas, 67 Refrigerant (lubricating oil), 7
2 ... Cylinder block.

Claims (3)

[Claims] 1. An internal combustion engine having a combustion chamber, an intake passage and an exhaust passage connected to the combustion chamber, comprising a refrigerant passage for cooling the internal combustion engine itself, and an exhaust gas sensor on the discharge side of the combustion chamber. In the exhaust gas sensor, the exhaust gas sensor is a hermetically sealed sensor having an element portion directly in contact with exhaust gas and a main body portion supporting the element portion, and having no air introduction hole in the main body portion. An exhaust gas sensor arrangement structure for an internal combustion engine, wherein the exhaust gas sensor is arranged in a passage and the main body is arranged outside the exhaust passage and in a refrigerant. 2. The exhaust gas sensor arrangement structure for an internal combustion engine according to claim 1, wherein the refrigerant is cooling water for an internal combustion engine. 3. The exhaust gas sensor arrangement structure for an internal combustion engine according to claim 1, wherein said exhaust gas sensor is an oxygen concentration sensor.