JPS608113Y2 - Secondary air supply device - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improvement of a secondary air supply device in an exhaust system of an internal combustion engine related to exhaust gas treatment technology.

In recent years, exhaust gas regulations for automobiles and the like have become stricter, and there is a catalytic exhaust gas treatment method in which exhaust gas from an internal combustion engine is treated with a catalyst by introducing secondary air.

However, in an exhaust system where the catalyst is placed close to the exhaust manifold (see Figure 1), the exhaust manifold pulsating pressure decreases in the low rotation range, especially when idling, because resonance does not occur between the catalyst and the catalyst. This has the drawback that the negative pressure required to open the check valve d provided in the secondary air introduction pipe C communicating with the exhaust manifold a becomes extremely small, and the amount of intake air decreases. During idling, the amount of CO and HC discharged increases, so a large amount of intake air is required in this state.

In view of the above problems, this invention was devised for the purpose of providing a secondary air supply device for the exhaust system that can obtain sufficient secondary air introduction in the low rotation range. A resonant pipe is provided, and a secondary air introduction pipe is connected to the resonant pipe to amplify the pulsating negative pressure generated within the resonant pipe, thereby increasing the amount of secondary air supplied by the check valve.

An embodiment of the secondary air supply system of the present invention will be described below with reference to a schematic diagram of an internal combustion engine exhaust system shown in FIG.

Reference numeral 1 denotes an exhaust manifold provided on the exhaust side of the engine 2, and a catalyst 4 is provided in a portion of an exhaust pipe 3 that is continuous with the exhaust manifold 1 and is close to the exhaust manifold 1.

Reference numeral 5 designates a resonant pipe that communicates the upstream side 1a and downstream side 1b of the exhaust manifold 1, and a secondary air introduction pipe 7 provided with a check valve 6 is connected to the middle of the resonant pipe 5.

The length of the resonance tube 5 is determined according to the resonance condition of the idling rotational frequency of the engine 2. When the upstream side 1a and the downstream side 1b of the exhaust manifold 1 are connected by the resonance tube 5, the exhaust manifold Even when the pulsating negative pressure in the resonant tube 5 is small, the pulsating negative pressure in the resonant tube 5 is amplified by the resonance effect, and this pulsating negative pressure passes through the secondary air introduction tube 7 communicating with the resonant tube 5 to the check valve 6. This negative pressure opens the check valve 6 to supply a large amount of secondary air.

Therefore, a large amount of secondary air can be obtained especially during idling, and CO and HC, which are generated in large quantities in the low rotation range, can be sent to the catalyst 4 together with the secondary air, and can be efficiently purified. Therefore, the exhaust gas discharged from the exhaust pipe 3 can be made stable even when the engine 2 is running at low speed.

In addition, in the exhaust system of an internal combustion engine, if the secondary air supply device of the present invention requires the amount of secondary air at a specific rotational speed even when not idling, it will resonate with a unique length that resonates with that rotational frequency. Since the desired air can be introduced by selecting the tube 5, it is also possible to determine the amount of secondary air introduced in a complicated rotation range by providing a plurality of resonance tubes 5 each having a different length. It is something.

As explained above, the secondary air supply device of the present invention has a secondary air introduction pipe of a specific length that communicates the upstream and downstream sides of the exhaust manifold in an exhaust system where the catalyst is placed close to the exhaust manifold. By connecting to the resonant tube,
Even in the rotation range where the pulsating negative pressure in the exhaust manifold is small, the amplification effect of the resonance tube increases the pulsating negative pressure and allows sufficient secondary air to be introduced, allowing the catalytic exhaust gas treatment device to work efficiently. This means that it has extremely high practical effects.

[Brief explanation of the drawing]

The drawings show an embodiment of the secondary air supply device of the present invention, and FIG. 1 is a schematic diagram of an exhaust system equipped with a conventional device, and FIG. 2 is a schematic diagram of an exhaust system equipped with a device of the present invention. 1...Exhaust manifold, 1a...upstream side, 1b...downstream side, 2...engine, 3...exhaust pipe, 4 ...Catalyst, 5.
...Resonance tube, 6...Check valve, 7...
...Secondary air introduction pipe.

Claims (1)

[Scope of utility model registration request] In an exhaust system in which a catalyst is provided close to an exhaust manifold, a secondary air introduction pipe provided with a check valve is connected to the middle of a resonance pipe of a specific length that communicates the upstream and downstream sides of the exhaust manifold. A secondary air supply device characterized in that the pulsating negative pressure in the exhaust manifold is amplified by resonance to increase the amount of secondary air introduced in a specific rotation range.