JPS6344927B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device that controls the introduction of secondary air in accordance with an air-fuel ratio signal from an air-fuel ratio sensor provided in an exhaust system of an internal combustion engine.

In an internal combustion engine in which a catalytic converter is provided in the exhaust system, if poor quality gasoline is used as fuel, there is a problem in that the catalyst generates a strange odor while the air conditioner is operating under idling operation. That is, a small amount of sulfur contained in the fuel produces sulfur dioxide SO ₂ as a result of combustion within the combustion chamber. The exhaust gas containing SO ₂ is introduced into the catalytic converter. On the other hand, due to feedback control based on signals from an air-fuel ratio sensor placed in the exhaust pipe, the exhaust gas is microscopically divided into an atmosphere with an excess of air or an atmosphere with an excess of air ( It is thought that the atmosphere goes back and forth between an oxidizing atmosphere (lean in air-fuel ratio) and an atmosphere lacking in air (reducing atmosphere = rich in air-fuel ratio). In an oxidizing atmosphere, SO ₂ is oxidized to sulfur trioxide SO ₃ , and in a reducing atmosphere, hydrogen is added to SO ₃ to produce hydrogen sulfide H ₂ S. The H ₂ S generated in this way is the cause of the strange odor in the first place, but since the amount of exhaust gas is large during normal driving, the amount of H ₂ S relative to the amount of exhaust gas is negligible.
There is no noticeable odor. However, when the engine is idling, the amount of exhaust gas itself is small, and when the engine is idling up, the amount of air is large, so the chemical reaction at the catalyst takes place more actively than when the engine is simply idling, so the temperature of the catalyst bed becomes relatively high. The above-mentioned oxidation-reduction reaction is promoted, and the amount of H ₂ S that is the source of odor increases, making the odor noticeable.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a secondary air introduction device for an internal combustion engine that can suppress the generation of such abnormal odors. In order to achieve this object, the present invention detects when the air conditioner is in idle operation, and introduces a large amount of secondary air into the exhaust system during this operation, regardless of the signal from the O ₂ sensor.
Therefore, the exhaust gas atmosphere is constantly on the lean side with respect to the stoichiometric air-fuel ratio. In other words, the time period in which H ₂ S, which causes off-flavors, is generated is occupied by a reducing atmosphere (rich side in terms of air-fuel ratio), or the oxidizing atmosphere is always maintained, and as a result, the occurrence of off-odor is suppressed. It is.

To explain with reference to the drawings below, in the internal combustion engine shown in FIG.
It is introduced into the engine main body 16 via. Exhaust gas is removed to exhaust manifold 18 and purified by catalytic converter 22 in exhaust pipe 20.

Exhaust gas recirculation (EGR) to exhaust manifold 18
A passage 24 is connected to the EGR valve 2.
6 and EGR passage 28 to the intake manifold 1
Connected to 4. The EGR valve 26 is connected to a diaphragm 30, and a negative pressure from a sensing port 34 provided slightly upstream of the idle position of the throttle valve 32 acts on the diaphragm 30.
As is well known, a constant pressure chamber 36 is provided upstream of the EGR valve 26, and a pressure regulating valve 38 maintains the pressure in the constant pressure chamber 36 at a constant value close to atmospheric pressure.

The secondary air passage 42 is connected at one end to the EGR passage 24 upstream of the EGR valve 26. A reed valve 43 and a secondary air control valve 44 are provided at the other end of the passage 42 . The secondary air control valve 44 is the diaphragm 4
6, this diaphragm 46 connects to the negative pressure port 5 of the intake manifold 14 via a negative pressure signal passage 48, an electromagnetic negative pressure switching valve 50, and a negative pressure signal passage 52.
Connect to 6.

The electromagnetic switching valve 50 is driven by a control circuit 58. The control circuit 58 has an OR gate 60 having one input connected to the exhaust manifold 18.
It is connected via line 62 to an O ₂ sensor 64 .
As shown in Fig. 2, the _O2 sensor 64 has the characteristic of outputting a high level (ON) signal when the air-fuel ratio is below a predetermined value (rich) and outputting a low level (OFF) signal when the air-fuel ratio is above a predetermined value. There is. The other input of OR gate 60 is connected to the output of AND gate 66.
The output of OR gate 60 is also connected to solenoid valve 50 by line 68. One input of AND gate 66 is connected to rotation speed sensor 70 . As shown in FIG. 3, this sensor 70 is turned ON at a speed of N ₁ and turned OFF at a speed of N ₂ (>N ₁ ) when the engine is idling. An air conditioner switch 72 is connected to the other side of the AND gate 66.

The operation of the present invention will be described below. When the air conditioner is not operating and is idling, the cooler switch 7
2 is OFF, a low level signal is always output from the output of the AND gate 66 to the OR gate 60. Therefore, the OR gate 60 is operated only by the signal from the O ₂ sensor 64. Also, since the throttle valve 32 takes the fully closed position shown in the figure during idling, the sensing port 34
becomes atmospheric pressure, and atmospheric pressure also acts on the diaphragm 30, closing the EGR valve 26. _O2 sensor 64
If the air-fuel ratio is below a predetermined value (rich), the second
Output high level output as shown in the figure, OR gate 60
A high level output is also output from the solenoid valve 50, and as a result, the solenoid valve 50 assumes the port position indicated by the black mark. Therefore, the negative pressure from the negative pressure port 56 is allowed to act on the diaphragm 46, the secondary air control valve 44 is opened, and the secondary air control valve 44 is opened.
The next air passes through passages 42 and 24 to the exhaust manifold 1.
8, and the richness of the air-fuel ratio is avoided. Conversely, when the air-fuel ratio is above a predetermined value (lean), the O ₂ sensor 64 outputs a low level output, so the OR gate 60 is not turned on by the signal from the O ₂ sensor 64.
The solenoid valve 50 takes the port position marked in white, and the negative pressure supply to the diaphragm 46 is cut off. Therefore, the secondary air control valve 44 is closed and the introduction of secondary air is stopped, so that a lean air-fuel ratio is avoided.

When the air conditioner is in operation, the cooler switch 72 is ON or in idle operation, so naturally the rotation speed sensor 70 is also outputting an ON signal. Therefore, a high level signal appears at the output of AND gate 66. Thus, OR gate 60
is turned on regardless of the rich or lean signal from the O ₂ sensor 64 as shown in FIG. Therefore, the solenoid valve is maintained at the open position indicated by the black mark, and the secondary air control valve 44 is kept open. Thus, the secondary air flows through the passages 42, 24.
A large amount is introduced into the exhaust system via the This large amount of 2
Since the air-fuel ratio is controlled to the lean side (i.e., oxidizing atmosphere) by the secondary air, the reduction reaction that generates H ₂ S is suppressed, which eliminates the occurrence of abnormal catalyst odor that appears to be idling up when the air conditioner is operating. This problem does not occur even under easy conditions.

In the modification shown in FIG. 4, the sensing port 34
is the throttle valve 32 in the idle position as in the first
It is located downstream rather than upstream. Therefore,
Even during idle, negative pressure acts on the diaphragm 30 (FIG. 1) and the EGR valve 26 opens. As a result, 2
The secondary air can enter not only the exhaust manifold 18 but also the intake manifold 14, allowing a large overall flow rate. Fig. 1 alone is suitable when the amount of secondary air is insufficient.

In the modification shown in FIG. 5, the auxiliary secondary air supply passage 7
6 is connected to the intake manifold 14, and is connected to an air filter 78, which is an atmospheric source, by an electromagnetic on-off valve 77. Solenoid valve 77 is connected to the output of AND gate 66 via line 79. When the above-mentioned high-level signal appears at the output of the AND gate 66 while the air conditioner is operating at idle, the solenoid valve 77 is activated.
is turned on, and an amount of secondary air determined according to the throttle 80 is introduced in addition to the secondary air from the secondary air control valve 44 (FIG. 1). This embodiment is suitable when the amount of secondary air is insufficient even with the configuration shown in FIG.

[Brief explanation of drawings]

Figure 1 is an overall diagram of the system of the present invention, Figure 2 is
FIG. 3 is an output characteristic diagram of an O ₂ sensor, FIG. 3 is an output characteristic diagram of a rotation speed sensor, FIG. 4 is a diagram showing an example in which the position of the sensing port is changed, and FIG. 5 is a partial diagram of yet another modification. 18... Exhaust manifold, 44... Secondary air control valve, 64... O ₂ sensor, 70... Rotation speed sensor, 72... Cooler switch.

Claims (1)

[Claims] 1. Equipped with a valve means for controlling the amount of secondary air to the internal combustion engine according to an air-fuel ratio signal from an air-fuel ratio sensor provided in the exhaust system of the internal combustion engine, and equipped with an engine rotation speed detection sensor and an air conditioner operation detection sensor, A secondary air introduction device for an internal combustion engine, wherein the valve means is always maintained in an open state during operation of an air conditioner under engine idling operation.