JPH04330320A - Air suction system - Google Patents

Abstract

PURPOSE:To prevent deterioration of exhaust purifying performance in an air suction system for purifying exhaust gas in an internal combustion engine by regulating a flow rate of secondary air in such a manner that an air-fuel ratio on the upstream side of a three-way catalyst becomes a theoretical air-fuel ratio when a rich air-fuel ratio of an intake passage is determined on the basis of an exhaust component value detected by an exhaust sensor and an exhaust temperature is lower than a predetermined temperature. CONSTITUTION:A controller 28 selectively supplies a negative pressure and an atmospheric pressure to a negative pressure chamber 52 of an opening/closing valve mechanism 46 by a negative changeover valve mechanism 60 of a flow rate regulator 44 if an air-fuel ratio of an intake passage 4 is richer than a theoretical air-fuel ratio on the basis of concentration of oxygen detected by an oxygen sensor 36 and an exhaust temperature detected by an exhaust temperature sensor 42 is lower than a predetermined temperature, to operate a diaphragm 50. Consequently, an opening/closing valve body 54 is displaced so that an air-fuel ratio of an exhaust passage 6 on the upstream side of a three- way catalyst 24 from a secondary air passage 18 can be maintained in the theoretical air-fuel ratio.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] This invention relates to an air suction system, and in particular improves the performance of exhaust purification under high-load operating conditions of an internal combustion engine that is supplied with a mixture having a richer air-fuel ratio than the stoichiometric air-fuel ratio. The present invention relates to an air suction system that can be improved without causing a decrease in performance.

0002

2. Description of the Related Art Some internal combustion engines installed in vehicles are equipped with an air suction system. The air suction system includes a secondary air passage that supplies secondary air to the exhaust passage by utilizing negative pressure generated by exhaust pulsation in the exhaust passage of an internal combustion engine. The air suction system supplies secondary air to the exhaust passage through a secondary air passage to perform secondary combustion of the exhaust gas, oxidizes harmful exhaust gas components such as HC and CO, and purifies the exhaust gas.

An example of such an air suction system is shown in FIG. In the figure, 102 is an internal combustion engine, 104 is an intake passage, and 106 is an exhaust passage. The intake passage 104 of the internal combustion engine 102 includes an air cleaner 108 at the upstream end, a throttle body 110 continuous to the air cleaner 108, and an intake manifold 112 communicating the throttle body 110 to the internal combustion engine 102. The exhaust passage 106 is connected to the internal combustion engine 102.
The exhaust manifold 114 is connected to the exhaust manifold 114, and the exhaust pipe 116 is continuous with the exhaust manifold 114.

The air suction system includes a secondary air passage 118 that communicates upstream with the air cleaner 108 at the upstream end of the intake passage 104 and communicates downstream with the exhaust manifold 114 of the exhaust passage 104 . This secondary air passage 118 is provided with a check valve 120 that prevents backflow of exhaust gas. The check valve 120 prevents the exhaust gas from flowing back into the secondary air passage 118 in the reverse direction region, and allows the secondary air to flow into the exhaust passage 106 in the forward direction region. In addition, the secondary air passage 118
An oxidation catalyst 122 is provided in the exhaust passage 104 on the downstream side of the portion communicating with the exhaust passage 104 .

[0005] As a result, the air suction system:
Using the negative pressure generated by exhaust pulsation in the exhaust passage 106 of the internal combustion engine 102, the intake passage 104 is
Secondary air is supplied from the air cleaner 108 to the exhaust passage 106, and the exhaust gas is subjected to secondary combustion to remove HC, which is a harmful component of the exhaust gas.
It oxidizes and CO and purifies exhaust gas. In addition, oxidation catalyst 1
22 oxidizes HC and CO to purify exhaust gas.

[0006] Such an air suction system is disclosed in Japanese Unexamined Patent Publication No. 56-60814. The device disclosed in this publication includes an air-fuel ratio control device that controls the air-fuel ratio in the intake passage of the internal combustion engine to a stoichiometric air-fuel ratio based on the exhaust gas component value detected by an exhaust sensor provided in the exhaust passage of the internal combustion engine. In an internal combustion engine equipped with a three-way catalyst in the exhaust passage, the secondary air passage that supplies secondary air to the exhaust passage is provided with an on-off valve that opens when the internal combustion engine is cold. This is to promote the combustion of HC by supplying secondary air to the reactor, thereby rapidly activating the three-way catalyst.

[0007]

By the way, an internal combustion engine is supplied with an air-fuel mixture having a rich air-fuel ratio, which is richer than the stoichiometric air-fuel ratio, in a high-load operating state. However, the three-way catalyst can sufficiently exhibit exhaust purification performance when the air-fuel ratio is around the stoichiometric air-fuel ratio (window).

[0008] For this reason, the air suction system disclosed in the above-mentioned publication, in high-load operating conditions such as accelerated operation,
There is an inconvenience that exhaust purification performance deteriorates. Additionally, a three-way catalyst can reduce thermal load by setting the air-fuel ratio to a rich air-fuel ratio that is richer than the stoichiometric air-fuel ratio. If the air-fuel ratio deviates from the above range and becomes a rich air-fuel ratio, there is a disadvantage that the exhaust purification performance deteriorates.

[0009]

[Means for Solving the Problems] In order to eliminate such inconveniences, the present invention provides an air suction system equipped with a secondary air passage that supplies secondary air to the exhaust passage of the internal combustion engine. An air-fuel ratio control device that controls the air-fuel ratio in the intake passage of the internal combustion engine to a stoichiometric air-fuel ratio based on the exhaust component value detected by an exhaust sensor installed in the exhaust passage; A primary catalyst is provided, an exhaust passage upstream of the three-way catalyst is connected to the downstream side of the secondary air passage, and an exhaust temperature sensor is provided for detecting exhaust temperature, and the exhaust gas components detected by the exhaust sensor are provided. According to the value, when the air-fuel ratio of the intake passage is a rich side air-fuel ratio that is richer than the stoichiometric air-fuel ratio and the exhaust temperature detected by the exhaust temperature sensor is below a predetermined temperature, the secondary air flow rate of the secondary air passage. The present invention is characterized in that a flow rate adjusting means is provided for controlling the air-fuel ratio in the exhaust passage upstream of the three-way catalyst to the stoichiometric air-fuel ratio by adjusting the air-fuel ratio.

0010

[Operation] According to the structure of the present invention, the air-fuel ratio in the intake passage is set to a rich-side air-fuel ratio richer than the stoichiometric air-fuel ratio according to the exhaust component value detected by the exhaust sensor, and the exhaust temperature sensor When the detected exhaust temperature is below a predetermined temperature, the secondary air flow rate in the secondary air passage is adjusted so that the air-fuel ratio in the exhaust passage upstream of the three-way catalyst becomes the stoichiometric air-fuel ratio. The air-fuel ratio of the exhaust gas flowing into the three-way catalyst can be controlled to the stoichiometric air-fuel ratio in high-load operating conditions such as accelerated driving.

[0011]

Embodiments Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIGS. 1 and 2 show an embodiment of the present invention. In FIG. 1, 2 is an internal combustion engine, 4 is an intake passage, and 6 is an exhaust passage. The intake passage 4 of the internal combustion engine 2 includes an air cleaner 8 at an upstream end, a throttle body 10 continuous to the air cleaner 8, and an intake manifold 12 communicating the throttle body 10 to the internal combustion engine 2. The exhaust passage 6 is composed of an exhaust manifold 14 communicating with the internal combustion engine 2 and an exhaust pipe 16 continuous with the exhaust manifold 14.

The air suction system includes a secondary air passage 18 that communicates upstream with the air cleaner 8 at the upstream end of the intake passage 4 and communicates downstream with the exhaust manifold 14 of the exhaust passage 4. This secondary air passage 18 is provided with a check valve 20 that prevents backflow of exhaust gas. The check valve 20 prevents the exhaust gas from flowing back into the secondary air passage 18 in the reverse direction region, and allows the secondary air to flow into the exhaust passage 6 in the forward direction region.

In such an air suction system, the internal combustion engine 2 includes an air-fuel ratio control device 22 and a three-way catalyst 24. The air-fuel ratio control device 22 is an internal combustion engine 2
As a fuel system, a single fuel injection valve 26 is provided in the intake passage 4 on the upstream side of the throttle body 10. This fuel injection valve 26 is connected to a control section 28. Control part 2
8 includes a throttle sensor 32 provided in the throttle body 10 to detect the opening degree of the throttle valve 30, a pressure sensor 34 to detect the intake pressure in the intake passage 4, and an exhaust manifold to detect the exhaust gas component value in the exhaust passage 6. An oxygen sensor 36, which is an exhaust sensor provided at 14, is connected. Note that the reference numeral 38 is an ignition coil, and the reference numeral 40 is a battery.

Thereby, the air-fuel ratio control device 22 controls the internal combustion engine 2 by the control section 28 based on the opening degree of the throttle valve 30 detected by the throttle sensor 32 and the intake pressure in the intake passage 4 detected by the pressure sensor 34. The fuel injection valve 26 is controlled so that the air-fuel ratio of the intake passage 4 becomes the required air-fuel ratio according to the operating state of the intake passage 4, and the intake air is The fuel injection valve 26 is controlled so that the air-fuel ratio in the passage 4 becomes the stoichiometric air-fuel ratio.

Further, the three-way catalyst 24 is connected to the exhaust passage 6 downstream of the oxygen sensor 36 constituting the air-fuel ratio control device 22.
It is provided in the exhaust pipe 16 that constitutes the. The exhaust passage 6 upstream of the three-way catalyst 24 is provided in communication with the downstream side of the secondary air passage 18, and is also provided with an exhaust temperature sensor 42 for detecting exhaust temperature.

The secondary air passage 18 is provided with a flow rate adjusting means 44 . In this embodiment, the flow rate adjusting means 44 includes an on-off valve mechanism 46 in the secondary air passage 18 on the upstream side of the check valve 20. The on-off valve mechanism 46 has a negative pressure chamber 52 partitioned into a main body 48 by a diaphragm 50, and the diaphragm 50 is provided with an on-off valve body 54 for opening and closing the secondary air passage 18. A closing spring 56 is provided that biases the diaphragm 50 in a direction to close the passageway 18.

The negative pressure chamber 52 of the on-off valve mechanism 46 is connected to the intake passage 4 of the intake manifold 12 through a negative pressure passage 58. A negative pressure switching valve mechanism 60 is provided in the negative pressure passage 58. The negative pressure switching valve mechanism 60 selectively connects the first negative pressure passage 58-1 on the negative pressure chamber 52 side to the manifold side negative pressure passage 58-2 on the intake manifold 12 side and the atmospheric hole 62. A switching valve body 64 is provided, and a switching solenoid 66 for switching and driving the switching valve body 64 is provided. The switching solenoid 66 is connected to the control section 28 .

[0019] Thereby, the control unit 28, according to the detected values of the oxygen sensor 36 and the exhaust temperature sensor 42,
Power is supplied to and discharged from the switching solenoid 66 of the negative pressure switching valve mechanism 60 to operate the switching valve body 64, and negative pressure and atmospheric pressure are selectively supplied to the negative pressure chamber 52 of the opening/closing valve mechanism 46, so that the diaphragm 50 The secondary air flow rate is adjusted by operating the on-off valve body 54 to open and close the secondary air passage 18.

In this manner, the flow rate adjusting means 44 controls the air-fuel ratio of the intake passage 4 to be a rich-side air-fuel ratio richer than the stoichiometric air-fuel ratio according to the exhaust gas component value detected by the oxygen sensor 42. , when the exhaust gas temperature detected by the exhaust gas temperature sensor 42 is below a predetermined temperature that does not cause deterioration of the three-way catalyst 24 or the oxygen sensor 36, two of the secondary air passages 18
The air-fuel ratio in the exhaust passage 6 upstream of the three-way catalyst 24 is controlled to be the stoichiometric air-fuel ratio by adjusting the secondary air flow rate. Note that the check valve 20 of the secondary air passage 18 prevents the secondary air from flowing back into the secondary air passage 18 in the reverse direction area, and prevents the secondary air from flowing back into the exhaust passage 6 in the forward direction area. Next air circulation is allowed. Therefore, the flow rate adjustment means 44 controls the secondary air passage 1 in the forward direction region.
8 is controlled so that the air-fuel ratio in the exhaust passage 6 upstream of the three-way catalyst 24 becomes the stoichiometric air-fuel ratio.

Next, the operation will be explained.

When the internal combustion engine 2 is in an operating state other than acceleration, for example, in an idling state, the air-fuel ratio control device 22 uses the control section 28 to control the opening degree of the throttle valve 30 and the pressure detected by the throttle sensor 32. sensor 3
4 controls the fuel injection valve 26 so that the air-fuel ratio in the intake passage 4 becomes the stoichiometric air-fuel ratio. At this time, the three-way catalyst 24 can sufficiently exhibit exhaust purification performance because the air-fuel ratio of the inflowing exhaust gas is controlled to the stoichiometric air-fuel ratio.

At this time, since the air-fuel ratio in the intake passage 4 is the stoichiometric air-fuel ratio based on the oxygen concentration detected by the oxygen sensor 36, the control section 28 causes the negative pressure switching valve mechanism 60 of the flow rate adjustment means 44 to close the valve. Atmospheric pressure is supplied to the negative pressure chamber 52 of the valve mechanism 46, and the secondary air passage 18 is closed to prevent the supply of secondary air to the exhaust passage 6. This can prevent the air-fuel ratio from becoming a lean air-fuel ratio that is leaner than the stoichiometric air-fuel ratio, and can prevent the three-way catalyst 24 and the like from deteriorating.

When the internal combustion engine 2 is in a high-load operating state such as during acceleration, the air-fuel ratio in the intake passage 4 is richer than the stoichiometric air-fuel ratio due to the oxygen concentration detected by the oxygen sensor 36. When the exhaust gas temperature detected by the temperature sensor 42 is below a predetermined temperature, the control unit 28 causes the negative pressure switching valve mechanism 60 of the flow rate adjustment means 44 to cause the negative pressure chamber 52 of the on-off valve mechanism 46 to have a negative pressure and atmospheric pressure. is selectively supplied to operate the diaphragm 50 and displace the on-off valve body 50 to open and close the secondary air passage 18, thereby adjusting the air-fuel ratio in the exhaust passage 6 upstream of the three-way catalyst 24 to stoichiometric air. Adjust the secondary air flow rate to match the fuel ratio.

[0025] Accordingly, the flow rate adjusting means 44 controls the air-fuel ratio of the exhaust gas flowing into the three-way catalyst 24 to the stoichiometric air-fuel ratio in the forward direction region of the check valve 20 in a high-load operating state such as during acceleration operation. be able to.

Therefore, in a high-load operating state such as during acceleration of the internal combustion engine 2 supplied with a mixture having a rich air-fuel ratio that is richer than the stoichiometric air-fuel ratio, the air-fuel ratio of the exhaust gas flowing into the three-way catalyst 24 changes. By controlling the air-fuel ratio to the stoichiometric air-fuel ratio, exhaust purification performance can be improved. Further, in a high-load operating state, the exhaust gas purification performance of the three-way catalyst 24 can be improved without controlling the air-fuel ratio of the intake passage 4 to the stoichiometric air-fuel ratio, so that no deterioration in drivability occurs.

Furthermore, even in a high-load operating state such as during acceleration, the check valve 20 prevents the flow rate adjusting means 44 from supplying secondary air to the exhaust passage 6 in the reverse direction region. . Therefore, inconveniences caused by backflow of exhaust gas can be avoided.

In this embodiment, the flow rate adjusting means 44 is composed of an on-off valve mechanism 46 and a negative pressure switching valve mechanism 60.
Although shown as an example, a control valve mechanism 68 whose duty is controlled may be provided as shown in FIG. The control valve mechanism 68 includes a tapered control valve body 70 that extends and retracts from the secondary air passage 18, and a closing spring that pushes and urges the control valve body 70 in a direction to close the secondary air passage 18. 72, and a control solenoid 74 that pulls and biases the control valve body 70 in the direction of opening the secondary air passage 18. The control solenoid 74 of the control valve mechanism 68 is connected to the control unit 28, and as described above, the air-fuel ratio of the intake passage 4 is set to a rich side air-fuel ratio richer than the stoichiometric air-fuel ratio according to the oxygen concentration detected by the oxygen sensor 36. If the exhaust gas temperature detected by the exhaust temperature sensor 42 is below a predetermined temperature, the control valve mechanism 68 of the flow rate adjustment means 44 opens and closes the secondary air passage 18 to open and close the exhaust passage upstream of the three-way catalyst 24. The secondary air flow rate can also be adjusted so that the air-fuel ratio of 6 becomes the stoichiometric air-fuel ratio.

As described above, by using the control valve mechanism 68 whose duty is controlled as the flow rate adjusting means 44, the same effects as those of the above-mentioned embodiment can be achieved, and furthermore, the control valve mechanism 68
By controlling the duty by , the secondary air flow rate can be controlled more finely, and control accuracy can be improved.

[0030]

As described above, according to the present invention, the air-fuel ratio of the exhaust gas flowing into the three-way catalyst can be controlled to the stoichiometric air-fuel ratio during high-load operating conditions such as during acceleration.

Therefore, in a high-load operating state such as during acceleration operation of an internal combustion engine that is supplied with a mixture having a rich air-fuel ratio that is richer than the stoichiometric air-fuel ratio, the air-fuel ratio of the exhaust gas flowing into the three-way catalyst is Exhaust purification performance can be improved by controlling the air-fuel ratio to the stoichiometric air-fuel ratio, and the exhaust purification performance of the three-way catalyst can be improved without controlling the air-fuel ratio in the intake passage to the stoichiometric air-fuel ratio under high-load operating conditions. As a result, drivability does not deteriorate.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of an air suction system showing an embodiment of the present invention.

FIG. 2 is a sectional view showing another embodiment of the flow rate adjusting means.

FIG. 3 is a schematic configuration diagram of an air suction system showing a conventional example.

[Explanation of symbols]

2 Internal combustion engine 4 Intake passage 6 Exhaust passage 8 Air cleaner 10 Throttle body 12 Intake manifold 14 Exhaust manifold 16 Exhaust pipe 18 Secondary air passage 20 Check valve 22 Air-fuel ratio control device 24 Three-way catalyst 26 Fuel injection valve 28 Control section 30 Throttle valve 32 Throttle sensor 34 Pressure sensor 36 Oxygen sensor 42 Exhaust temperature sensor 44 Flow rate adjustment means 46 Opening/closing valve mechanism 60 Negative pressure switching valve mechanism 68 Control valve mechanism

Claims (1)

[Claims] Claims: 1. An air suction system comprising a secondary air passage supplying secondary air to an exhaust passage of an internal combustion engine, wherein the internal combustion engine an air-fuel ratio control device for controlling the air-fuel ratio in the intake passage to a stoichiometric air-fuel ratio, a three-way catalyst in the exhaust passage downstream of the exhaust sensor, and a three-way catalyst in the exhaust passage upstream of the three-way catalyst; An exhaust temperature sensor is provided to connect the downstream side of the secondary air passage and detect the exhaust temperature, and the air-fuel ratio of the intake passage is on the richer side than the stoichiometric air-fuel ratio based on the exhaust component value detected by the exhaust sensor. When the air-fuel ratio is on the rich side and the exhaust temperature detected by the exhaust temperature sensor is below a predetermined temperature, the secondary air flow rate in the secondary air passage is adjusted to reduce the air in the exhaust passage upstream of the three-way catalyst. An air suction system characterized by being provided with a flow rate adjustment means that controls the fuel ratio to be the stoichiometric air-fuel ratio.