JPH0565821A - Engine exhaust system - Google Patents

Abstract

(57) [Abstract] [Purpose] To supply secondary air to the catalytic converter of the exhaust system of the engine and improve the torque in the low and medium speed rotation range. [Structure] A first catalytic converter 10 is connected to an exhaust manifold 9 of an engine body 8, and a second catalytic converter is connected in series to the first catalytic converter 10 via an exhaust pipe 11. The exhaust pipe 11 and the air cleaner 18 are connected via the secondary air passage 15 and the air pipe 16 of the case 13. When secondary air is required for the exhaust gas purification reaction of the second catalytic converter 12, the control device 26 opens the solenoid valve 26 to introduce the secondary air into the exhaust pipe 11, and otherwise, the solenoid valve is used. By closing 26, the volume chamber 24 is formed by the air pipe 16 and the secondary air passage 15, and the exhaust pipe effect is utilized to improve the torque in the low and medium speed rotation range of the engine.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved exhaust system for an engine equipped with a secondary air introducing device.

[0002]

2. Description of the Related Art When purifying engine exhaust gas by a catalytic converter provided in an exhaust system, it is necessary to supply air (secondary air) required for a catalytic purifying reaction to the catalytic converter.

Therefore, conventionally, as shown in FIG. 7, an exhaust manifold 2 of an engine 1 and a catalytic converter 3 are attached to an exhaust manifold 2.
Is connected to connect the upstream side of the catalytic converter 3 and the air cleaner 5 provided in the intake system 4 of the engine 1 with an air pipe 6. Further, in the middle of the air pipe 6, one side from the air cleaner 5 side to the catalytic converter 3 side is connected. A reed valve 7 (check valve) that allows air to flow only in the direction is provided.

With this structure, the secondary air is introduced from the air cleaner 5 side to the catalytic converter 3 through the air pipe 6 by the negative pressure generated by the exhaust pulsation of the engine 1, and the reed valve 7 moves the catalytic converter 3 side to the air cleaner 5 side. Prevents backflow of exhaust gas.

Further, Japanese Laid-Open Patent Publication No. 57-153922 has a reed valve having a valve body and a valve seat made of a magnetic material, an exciting coil for magnetizing the valve seat, and an engine speed sensor.
Disclosed is a secondary air supply device that prevents the abnormal overheat of a catalytic converter by stopping the introduction of secondary air by magnetizing a valve seat and fixing the reed valve in a closed state when the engine is rotating at high speed. ing.

[0006]

However, in the conventional device shown in FIG. 7, since the secondary air is introduced into the catalytic converter 3 by the negative pressure due to the exhaust pulsation regardless of the engine speed, the throttle opening, etc., The supply of secondary air more than necessary increases the load on the catalyst, and there is a problem that operating noise is frequently generated when the reed valve 7 is opened and closed.

By the way, in a 4-cycle engine,
An exhaust pipe effect is known in which exhaust pulsation influences intake efficiency by selecting an exhaust pipe. Then, generally, when the exhaust pipe is made longer, the intake efficiency in the low and medium speed rotation regions is improved and the torque is increased. Also, the same effect can be obtained by connecting a volume chamber in the middle of the exhaust pipe.

The present invention has been made in view of the above points, and supplies the secondary air required for the catalytic converter and improves the torque in the low and medium speed rotation regions by utilizing the exhaust pipe effect. It is an object of the present invention to provide an exhaust system for an engine that can be made to operate.

[0009]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention connects an exhaust pipe and an air cleaner with an air pipe having a check valve, and utilizes exhaust pulsation to remove the air cleaner from the air cleaner. In an exhaust system of an engine equipped with a secondary air introducing device for introducing secondary air into the exhaust pipe through an air pipe, valve means for opening and closing the air pipe is provided between the check valve of the air pipe and the exhaust pipe, A control device for controlling the operation of the valve means is provided, and by closing the valve means, a volume chamber is formed between the valve means of the air pipe and the exhaust pipe.

[0010]

With this configuration, the controller opens the valve means to introduce the secondary air into the exhaust pipe when the secondary air is required, and otherwise closes the valve means. As a result, the volume chamber is formed, and the exhaust pipe effect can improve the intake efficiency in the low and medium speed rotation range of the engine.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a diagram schematically showing an intake / exhaust system of an engine to which the exhaust system of the present invention is applied.

As shown in FIG. 1, the exhaust system for an engine of this embodiment is equipped with a two-stage catalytic converter, and an exhaust manifold 9 is connected to the exhaust port side of an engine body 8 to form an exhaust manifold. A first catalytic converter 10 is connected to the outlet side of 9. Further, a second catalytic converter 12 is connected in series to the first catalytic converter 10 via an exhaust pipe 11. First
The case 13 of the catalytic converter 10 is provided with a secondary air passage 15 communicating with the downstream side of the catalyst carrier 14.

One end of an air pipe 16 is connected to the secondary air passage 15 of the first catalytic converter 10.
The other end of 16 is connected to an air cleaner 18 of an intake system 17 connected to the engine body 8. In the middle of the air pipe 16, a reed valve 19 (check valve) that allows air to flow from the air cleaner 18 side to the first catalytic converter 10 side only in one direction is provided. Further, the air pipe 16 is provided with a solenoid valve 20 as a valve means for opening and closing the air pipe between the reed valve 19 and the first catalytic converter 10. The solenoid valve is fixed to the front surface of the cylinder head 8a of the engine body 8 by a bolt 21 as shown in FIG.

In the solenoid valve 20, for example, as shown in FIG. 4, the valve body 22 is normally urged by a spring (not shown) to be in a closed state, and the solenoid 23 is energized to energize the valve body 22.
It is possible to use one having a structure in which the valve is opened by sucking.

When the solenoid valve 20 is closed, the volume chamber 24 connected to the exhaust pipe 11 is provided between the solenoid valve 20 of the air pipe 16 and the connecting portion with the secondary air passage 15. To be formed. The air pipe 16 and the secondary air passage 15 that form the volume chamber 24 are formed in a shape such that the exhaust pipe effect is obtained so that the intake efficiency is improved in the low and medium speed rotation range of the engine. Further, the air pipe 16 is provided with an exhaust temperature sensor 25 for detecting the exhaust temperature in the volume chamber 24.

A control device 26 is connected to the solenoid valve 20. The controller 26 uses the ECU in advance according to the engine speed detected by each sensor (not shown), the throttle opening, the negative pressure of the inlet manifold, and the exhaust temperature in the volume chamber 24 detected by the exhaust temperature sensor 25. The opening / closing of the solenoid valve 20 is controlled by turning on / off the output current based on the set conditions. The ECU of the control device 26 opens the solenoid valve 20 when the negative pressure of the inlet manifold is 0 to 80 mmHg and the engine speed and the throttle opening are in the conditions shown by "open" in FIG. Closes solenoid valve 20. Further, the temperature detected by the exhaust temperature sensor 25 is an allowable temperature (for example, the allowable temperature of the solenoid valve 20 is 800
20 ° C), solenoid valve 20 for cooling
Open to introduce secondary air.

The operation of this embodiment having the above-mentioned structure will be described below. The exhaust gas discharged from the engine body 8 is purified by the first catalytic converter 10 and further purified by the second catalytic converter 12.

When the negative pressure of the inlet manifold is 0 to 80 mmHg and the engine speed and throttle opening are in the condition shown by "open" in FIG. 5, that is, when the engine speed is in the low speed range, Throttle opening is 1 /
When the value is 2 or less, it is determined that the secondary air is necessary for the exhaust gas purification reaction by the second catalytic converter, and the solenoid valve
Energize 20 to open it. Then, due to the negative pressure generated on the exhaust pipe 11 side by the exhaust pulsation, the secondary air is introduced from the air cleaner 18 to the exhaust pipe 11 through the air pipe 16 through the reed valve 19, and is supplied to the second catalytic converter 12 for purification. Accelerate the reaction.

In the case other than the above, that is, when the negative pressure of the inlet manifold is other than 0 to 80 mmHg by the control device 26, or when the engine speed and the throttle opening are the conditions shown as "closed" in FIG. Since the secondary air is not required for the exhaust gas purification reaction by the second catalytic converter, the solenoid valve 20 is de-energized and closed. In this state, a volume chamber 24 is formed between the solenoid valve 20 of the air pipe 16 and the connection portion of the first catalytic converter 10 with the secondary air passage 15, and the secondary air passage 15 forms a volume chamber 24. As shown in, the intake efficiency is improved in the low and medium speed rotation range of the engine, and the torque is increased. In FIG. 6, the solid line shows the characteristics of the engine to which the exhaust system of this embodiment is applied, and the broken line shows the characteristics of the conventional engine.

Further, the control device 26 controls the exhaust temperature sensor.
When the detected temperature of 25 exceeds the allowable temperature, the solenoid valve 20 is opened to introduce the secondary air into the air pipe 16 to cool the exhaust gas.

In this embodiment, the one provided with a two-stage catalytic converter has been described, but the first catalytic converter is omitted and the air pipe is directly connected to the exhaust pipe on the upstream side of the second catalytic converter. You can

[0022]

As described in detail above, according to the present invention, the air pipe for introducing the secondary air into the exhaust pipe is provided with the valve means for opening and closing by the control device, and the valve means is opened when the secondary air is required. The valve is operated to introduce secondary air into the exhaust pipe, and at other times, the valve means is closed to form a volume chamber to improve the intake efficiency in the low and medium speed engine range by the exhaust pipe effect. Therefore, the secondary air required for the catalytic converter can be supplied, and the torque in the low and medium speed rotation range of the engine can be improved. Also, by preventing unnecessary introduction of secondary air into the exhaust pipe, it is possible to reduce the generation of operating noise of the check valve (reed valve) of the air pipe, which is an excellent effect. Further, the air pipe for introducing the secondary air is used as the volume chamber, so that no space is required.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an entire intake / exhaust system of an engine to which an exhaust system according to an embodiment of the present invention is applied.

FIG. 2 is a vertical cross-sectional view of a main part of the device shown in FIG.

3 is a partial vertical cross-sectional view of a mounting portion of a solenoid valve of the apparatus of FIG.

FIG. 4 is a schematic view showing a longitudinal section of a solenoid valve of the apparatus shown in FIG.

5 is a diagram showing opening / closing conditions of a solenoid valve of the control device of the apparatus of FIG.

6 is a diagram showing the relationship between the rotational speed and torque of an engine to which the device of FIG. 1 is applied and a conventional engine.

FIG. 7 is a schematic diagram showing a conventional secondary air introducing device.

[Explanation of symbols]

 8 engine body 11 exhaust pipe 16 air pipe 18 air cleaner 19 reed valve (check valve) 20 solenoid valve (valve means) 24 volume chamber 26 controller

Claims (1)

[Claims] 1. A secondary air introducing device for connecting an exhaust pipe and an air cleaner by an air pipe having a check valve interposed therebetween and introducing secondary air from the air cleaner to the exhaust pipe through the air pipe by utilizing exhaust pulsation. In an exhaust system for an engine, the valve means for opening and closing the air pipe is provided between the check valve of the air pipe and the exhaust pipe, a control device for controlling the operation of the valve means is provided, and the valve means is closed. An exhaust system for an engine, wherein a volume chamber is formed between the valve means of the air pipe and the exhaust pipe by valveing.