JPS6239250B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a secondary air supply device for exhaust purification provided in a motorcycle engine.

As an exhaust purification device for automobile engines, a secondary air supply passage communicating with the atmosphere is provided at the exhaust port,
Some devices are designed to oxidize and remove air pollutants in the exhaust gas by introducing air from the atmosphere into the exhaust port.

On the other hand, motorcycles do not have as large an installation space as automobiles due to the structure of their body frames, and therefore it is desirable for attached equipment to be as compact as possible. When a secondary air supply device such as the one described above is provided in the engine of such a motorcycle, it is necessary to ensure that it does not interfere with the miniaturization of the secondary air supply device. However, from the viewpoint of compactness, if the cross-sectional area of the secondary air supply passage is narrowed down, the exhaust port is heated to a high temperature, and the oxygen supply becomes insufficient due to air expansion. There is a problem in that the purifying effect of exhaust gas is reduced.

In addition, since the secondary air supply device mentioned above has a passageway that communicates with the atmosphere, if the seal is incomplete, the airtightness of the engine combustion chamber may be disrupted, which may affect output. .

The purpose of the present invention is to solve the above-mentioned problems,
To provide a secondary air supply device which enables sufficient oxygen supply while having a small mechanism suitable for motorcycles, and also enables complete airtightness and does not cause a decrease in engine output.

To achieve the above object, the present invention provides a motorcycle equipped with an air-cooled engine in which cooling fins are provided around the cylinder and an exhaust port is provided in the front side of the cylinder head. A nozzle portion of the passage is opened, and a duct portion that communicates with the atmosphere via a check valve is opened on the front side of the cylinder so as to be sandwiched between cooling fins, and the duct portion and the nozzle portion are connected to each other. The cylinder head is characterized by communication across the joint surface of the cylinder.

Hereinafter, the present invention will be explained with reference to embodiments shown in the drawings.

In the motorcycle shown in FIG. 1, 1 is an air-cooled engine mounted on a body frame 2, 3 is an exhaust pipe, and 4 is an intake pipe. The intake pipe 4 is provided with a carburetor 6 and an air cleaner 7, and the exhaust pipe 3 is provided with a muffler 5 at its tail end.

As shown in FIG. 3, the engine 1 has a cylinder 8
The cylinder head 10 and the cylinder head 10 are assembled at their joint surfaces via a patch 20, a piston 9 is inserted into the cylinder, and a combustion chamber 11 is formed in the upper part of the piston 9. The cylinder head 10 is provided with an exhaust port 13 on the front side and an intake port 17 on the rear side so as to be in a cross-flow type. Further, the exhaust port 13 is provided with an exhaust valve 22 and the intake port 17 is provided with an intake valve 16, and the exhaust port 13 is connected with an exhaust pipe 3, and the intake port 17 is connected with an intake pipe 4. .

In the exhaust port 13, a nozzle portion 15 of a secondary air passage 14 is opened on the lower inner wall thereof.
This nozzle section 15 is connected to a pipe 20 via a duct section 19 as shown in FIG. 2, and further communicates with the atmosphere via a check valve 21. Check valve 21
is the same as a conventionally known configuration, allowing only airflow from the atmosphere side toward the exhaust port 13 side, and opens when the exhaust port 13 becomes negative pressure with respect to atmospheric pressure due to engine operation. The air introduced by opening the check valve 21 is supplied from the nozzle portion 15 into the exhaust port 13, a portion of which enters the combustion chamber 11 via the stem of the exhaust valve 22, and the remainder of the air that enters the exhaust port 13. It mixes with the exhaust gas from the exhaust pipe 3 and oxidizes and removes air pollutants.

The nozzle portion 15 of the secondary air passage 14 is provided on the cylinder head 10 side, but the duct portion 1
9 is provided on the cylinder 8 side. The nozzle portion 15 and the duct portion 19 communicate with each other across the joint surface between the cylinder head 10 and the cylinder 8. Further, the duct portion 19 is configured such that a connection portion to the pipe 20 opens at a position sandwiched between the cooling fins 18, 18 on the front side of the cylinder 8.

According to the above-described secondary air supply device for an air-cooled engine, the duct portion 19 that first introduces secondary air from the atmosphere into the high-temperature engine side through the check valve 21 and the pipe 20 constantly supplies cooling air. Since it is located on the front side of the cylinder 8 that is receiving and being cooled, and is sandwiched between the cooling fins 18, 18 and is open at a position where heat is actively radiated, the length passing through the high temperature part is shortened. can, thereby
Secondary air is not heated and expanded unnecessarily. Therefore, even if the cross-sectional area of the duct portion 19 of the secondary air passage 14 is made smaller to make it more compact to be advantageous for motorcycles, a sufficient amount of oxygen can be delivered to the exhaust port 13.
This enables good exhaust gas purification.

In addition, since the duct part 19 and the nozzle part 15 are connected across the relatively wide joint surfaces of the cylinder 8 and cylinder head 10, the joint surfaces can be completely airtight. Therefore, the engine output will not be reduced due to insufficient sealing. In addition, the nozzle part 1
5 is provided on the lower side of the inner wall of the exhaust port 13 with respect to the cylinder head 10, so machining can be made much easier than when it is provided on the upper side of the exhaust port where the valve train etc. are arranged. .

[Brief explanation of the drawing]

Fig. 1 is a partial side view of a motorcycle equipped with a secondary air supply device according to an embodiment of the present invention, Fig. 2 is an external view of the engine of the motorcycle, and Fig. 3 is an enlarged cross-section of the main parts of the engine. It is a diagram. 1... Air-cooled engine, 8... Cylinder, 10...
...Cylinder head, 13...Exhaust port, 14...
... Secondary air passage, 15 ... Nozzle section, 18 ... Cooling fin, 19 ... Duct section, 21 ... Check valve,
23...Patsukin.

Claims (1)

[Claims] 1. In a motorcycle equipped with an air-cooled engine in which cooling fins are provided around the cylinder and an exhaust port is provided on the front side of the cylinder head, a nozzle portion of a secondary air passage is opened on the inner wall on the lower side of the exhaust port, and A duct portion communicating with the atmosphere via a check valve is opened at the front side of the cylinder so as to be sandwiched between cooling fins, and the duct portion and the nozzle portion are connected to each other, and the joint surface between the cylinder head and the cylinder is opened. A secondary air supply device for exhaust purification of a motorcycle engine, characterized in that the device communicates with the air in a transverse manner.