JPS5856323Y2 - Engine secondary air supply system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a secondary air supply device for an engine that supplies secondary air from an air cleaner to the exhaust system of the engine to reburn exhaust gas.

Conventionally, this type of secondary air supply device has been provided with a secondary air supply passage that connects the air cleaner and the exhaust system, and a reed valve that opens and closes depending on the exhaust pulsation in the exhaust passage is interposed in this secondary air supply passage. The reed valve is opened when negative pressure is generated due to exhaust pulsation, and secondary air is supplied to the exhaust system via the secondary air supply passage (hereinafter referred to as
It is abbreviated as reed valve type secondary air supply device.

) is well known.

However, in this conventional glued valve type secondary air supply device, the reed of the reed valve may resonate when the engine is running at high speeds, causing the reed to remain open. There have been cases where exhaust gas from the passage flows backward into the secondary air supply passage.

In order to prevent the backflow of exhaust gas due to the lead of the single-door valve being left open as described above, conventionally, there was a
A system in which two reed valves are interposed at predetermined intervals has been proposed (see Japanese Unexamined Patent Publication No. 51-19230). There is also a possibility that the leads may cause resonance, and there is a problem that it is not possible to reliably prevent the exhaust gas from flowing back.

Furthermore, in order to improve the above proposal, the natural frequency of the reed valve on the air cleaner side is increased by increasing the thickness of the reed, and the natural frequencies of the two reed valves are made to differ. However, in this one,
Although it is possible to prevent the above-mentioned backflow of exhaust gas by changing the resonance generation range of each reed valve, the thicker reeds deteriorate the response to exhaust pulsation and make it difficult to secure a sufficient amount of secondary air. There were some drawbacks.

The present invention has been developed in view of these points, and is intended to reduce the amount of exhaust gas generated when the reed of the reed valve is left open due to resonance of the reed of the reed valve at high engine speeds in the above reed valve type secondary air supply system. An object of the present invention is to provide a secondary air supply device for an engine that can reliably prevent gas backflow and ensure a sufficient amount of secondary air.

That is, the present invention provides a reed valve type secondary air supply device in which a case is provided in the secondary air supply passage upstream of the reed valve and is inclined so that the air cleaner side of the bottom is lower than the reed valve side. A check ball that moves on the bottom of the case by its own weight is installed in the case,
When positive pressure of exhaust pulsation occurs, the check ball is seated on a seat provided on the air cleaner side of the case, while when negative pressure of exhaust pulsation occurs, the movement of the check ball is determined by a stopper provided on the reed valve side of the case. It is designed to be regulated within a certain range.

Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.

In the drawing, 1 has one end opening into the air filter 2a of the air cleaner 2, and the other end opening into the exhaust manifold 3.
A reed valve 4 is interposed in the middle of the secondary air supply passage 1 and is opened and closed by the exhaust pulsation in the exhaust manifold 3.
The reed valve 4 is equipped with a reed 4C that opens and closes a valve seat 4b formed in the valve box 4a, and a stopper 4d that restricts the opening operation of the reed 4C. , secondary air is supplied from the air cleaner 2 to the exhaust manifold 3 via the secondary air supply passage 1, and when positive pressure is generated due to exhaust pulsation, the lead 4C of the reed valve 4 is closed to supply secondary air from the exhaust manifold 3. It is configured to prevent exhaust gas from flowing back into the passage 1.

Reference numeral 5 denotes a cylindrical case interposed in the secondary air supply passage 1 on the upstream side of the reed valve 4, and this case 5 has a through hole 5a inside, and an air cleaner 2 on the bottom surface 5b of the through hole 5a. The check ball 6 is inclined at an angle of inclination θ such that the side thereof is lower than the side of the reed valve 4, and a check ball 6 is inserted into the through hole 5a of the case 5 and moves on the bottom surface 5b by its own weight.

Further, a seat 7 on which the check ball 6 is seated is provided on the air cleaner 2 side of the through hole 5a of the case 5, and a stopper 8 is provided on the reed valve 4 side of the through hole 5a of the case 5. When positive pressure is generated due to exhaust pulsation, the check ball 6 is seated on the dust 7 by its own weight and positive pressure, while when negative pressure is generated due to exhaust pulsation, the check ball 6 is pushed toward the side of the valve 4 due to the negative pressure. The stopper 8 is configured to restrict movement within a predetermined range.

In addition, the reed valve 4 of the secondary air supply passage 1 and the case 5
A cylindrical expansion chamber 9 in which the diameter of the secondary air supply passage 1 is expanded is provided between the case 5 and the case 5 on the immediate downstream side.

Therefore, in the above embodiment, when positive pressure is generated due to exhaust pulsation in the exhaust manifold 3, the reed 4C of the reed valve 4 is closed to prevent the exhaust gas from flowing back into the secondary air supply passage 1; When the reed 4C of the reed valve 4 is left open due to resonance etc. during high rotation, the check ball 6 in the case 5 closes the through hole 5a due to its own weight and positive pressure.
By moving over the bottom surface 5b toward the air cleaner 2 and sitting on the seat 7, the secondary air supply passage 1 is closed, and the backflow of the exhaust gas can be reliably prevented.

In addition, if an expansion chamber 9 is provided in the secondary air supply passage 1 between the case 5 and the reed valve 4, the expansion chamber 9 can reduce the backflow speed of the exhaust gas and reduce its pressure. , it is possible to more reliably prevent the backflow of the exhaust gas.

On the other hand, when negative pressure is generated due to exhaust pulsation in the exhaust manifold 3, the reed 4C of the reed valve 4 is opened, and
Due to negative pressure, the check ball 6 is inserted into the through hole 5a of the case 5.
moves on the bottom surface 5b of the air to the reed valve 4 side and is restricted within a predetermined range by the stopper 8, creating a gap between the check ball 6 and the case 5, so the secondary air supply passage 1 is opened and the air Secondary air from 2 is sent to secondary air supply passage 1
The air is supplied to the exhaust manifold 3 through the air, and the amount of secondary air is adjusted in the gap between the check ball 6 and the case 5, thereby ensuring a sufficient amount of secondary air.

As explained above, according to the present invention, in the reed valve type secondary air supply device, the secondary air supply passage on the upstream side of the reed valve is sloped so that the air cleaner side at the bottom is lower than the air cleaner side. At the same time, a check ball is provided in the case that moves by its own weight on the bottom surface of the case, and a seat is provided on the air cleaner side of the case on which the check ball sits when positive pressure of exhaust pulsation is generated. By providing a stopper on the reed valve side of the case that restricts the movement of the check ball within a predetermined range when negative pressure occurs due to exhaust pulsation, the reed of the reed valve is prevented from resonating when positive pressure occurs due to exhaust pulsation. Even if the check ball is left open, its own weight and positive pressure will cause it to 2
Since the secondary air supply passage is closed, backflow of exhaust gas to the secondary air supply passage can be reliably prevented.

Furthermore, since the timing of opening and closing of the check ball is determined by the weight of the check ball and the angle of inclination of the bottom of the case, the intake of secondary air is greater than when a spring is installed on the back of the check ball. The resistance is small and a sufficient amount of secondary air can be secured.

In addition, by providing an expansion chamber in the secondary air supply passage between the case and the reed valve, there is an advantage that backflow of the exhaust gas can be more reliably prevented.

[Brief explanation of drawings]

The drawings are schematic configuration diagrams illustrating embodiments of the present invention. 1...Secondary air supply passage, 2...Air cleaner, 2a...Air filter, 3...
...Exhaust manifold, 4...Reed valve, 4a
...Valve box, 4b...Valve seat, 4C...
...Lead, 4d...Stopper, 5...
...Case, 5a...Through hole, 5b...
・Bottom, 6...Check ball, 7...
- Seat, 8... Stopper, 9... Expansion chamber.

Claims (1)

[Scope of utility model registration request] In a secondary air supply system for an engine, a secondary air supply passage is provided that connects an air cleaner and an exhaust system, and a reed valve that opens and closes according to exhaust pulsation is interposed in the secondary air supply passage. A case is installed in the secondary air supply passage, the bottom of which is inclined so that the air cleaner side is lower than the reed valve side, and a check ball that moves under its own weight on the bottom of the case is installed within the case to further reduce exhaust pulsation. A seat on which the check ball sits when positive pressure is generated is provided on the air cleaner side of the case, while a stopper is provided on the side of the case to prevent the check ball from moving within a predetermined range when negative pressure is generated due to exhaust pulsation. A secondary air supply device for an engine, characterized in that it is provided with: