JPH0248655Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an air suction system for a gasoline engine.

Secondary combustion (oxidation) of exhaust gases (especially HC, CO) emitted from gasoline engines in the exhaust system
Air suction systems are known for supplying secondary air to the exhaust system for the purpose of An air suction system generally has an air suction case containing an air suction filter disposed in an air suction passageway that communicates with an exhaust pipe via a reed valve. The reed valve opens and closes according to exhaust pulsation.
Atmosphere (secondary air) from the air suction system
is supplied to, for example, a catalytic converter for exhaust gas purification in the exhaust pipe. However, in a gasoline engine equipped with such an air suction system, if too much secondary air is supplied, afterburn occurs, so a control valve is required to appropriately cut or reduce the supply of secondary air depending on the operating conditions. be.
Particularly when the temperature is low, the chioke valve is closed and the air-fuel ratio becomes rich, so if secondary air is supplied to the exhaust system, afterburn is likely to occur.

However, in the past, a control valve that was opened and closed by a signal from a temperature sensor or the like was provided separately from the suction case, resulting in a complicated structure and high manufacturing cost.

In view of these points, the present invention aims to realize an inexpensive and simple air suction system in which a temperature-sensitive control valve is integrated into a suction case.

This will be explained below with reference to the drawings.

The air suction system according to the present invention has an air suction case 10 in which an air suction filter 1 is incorporated. The filter 1 has an annular shape, and an air introduction passage 13 is formed around its outer periphery.
The atmosphere introduction passage 13 is connected to an engine room (not shown) via a conduit 15. The conduit 15 may be connected not only to the engine room but also to any atmospheric region where the engine temperature can be detected. Inside the case 10, two chambers 21 and 23 are formed by the plate 4.
The internal space 25 of the filter 1 is divided into a chamber 21.
It is connected to the chamber 21 through a central opening 29 in a plate 27 provided therein. The valve housing 2 is fixed to the plate 4 with bolts and nuts 6. A central opening 31 connected to the interior space of the valve housing 2 is formed in the center of the plate 4 . The interior space of the valve housing 2 is separated into chambers 33 and 34 by a plate 35. The chambers 33 and 34 are connected by several holes 37 formed in the plate 35. A valve support portion 39 is formed in the center of the plate 35, and a temperature-sensitive control valve in the form of a bimetallic plate 3, for example, is engaged with this valve support portion. Bimetal plate 3
The center thereof is pressed against the valve support portion 39 by a spring 41 provided within the chamber 34. Alternatively, the bimetal plate 3 may be fixed to the valve support portion 39 so as to be capable of bimetal movement (curving movement). The holes 37 in the plate 35 are selectively opened and closed by the bimetal plate 3. That is,
The bimetal plate 3 is in the open position shown in the figure (at high temperatures) and in the closed position (at low temperatures) bent to the opposite side.
and occupies. In the valve-closing position, the bimetal plate 3 is warped, and both ends thereof contact the plate 35 to cut off communication between the hole 37 and the chamber 34. The chamber 34 of the valve housing 2 is connected to the interior space 25 of the filter 1 via an inlet passage 51 .

A bypass 53 is formed around the valve housing 2, opening the opening 29 so that a portion of the secondary air that has passed through the filter 1 always flows into the chamber 21. The secondary air passing through the bypass 53 flows into the chamber 23 through the opening 5 formed in the plate 4. Chamber 23 is connected by conduit 50 to an exhaust pipe (not shown) via a reed valve (not shown).
The bypass 53 is used to constantly expose the bimetal plate 3 to secondary air representing the engine ambient temperature, and even when the valve is closed, for example, HC in the catalytic converter,
It is provided to send in the minimum amount of air necessary for CO oxidation treatment. That is, if there is no bypass 53, especially if the flow of secondary air stops when the valve is closed, the engine temperature will not directly act on the bimetal plate 3, and therefore the bimetal plate 3 will be opened and closed according to the engine temperature. I can't. The passage area of the opening 31 is equal to or larger than the sum of the total passage area of the holes 37, and the opening 3
1 does not act as an intake resistance (restriction).

In the air suction system constructed as described above, the holes 37 are closed by the bimetallic plate 3 at low temperatures, so secondary air is supplied only through the bypass system, and the amount of secondary air is reduced. Therefore, even if the intake valve is closed and the air-fuel ratio is rich, afterburn is prevented from occurring. This is because not enough secondary air is supplied to cause afterburn.

When the engine temperature eventually rises and reaches a predetermined temperature, the bimetal plate 3 is reversed to the valve opening position shown, and the hole 37 is opened. As a result, secondary air is supplied not only through the bypass passage 53 but also through the control valve, thereby ensuring a sufficient amount of secondary air necessary for secondary combustion of HC and CO. Incidentally, at this time, the engine has already been warmed up sufficiently, so the chioke valve is open and the air-fuel ratio is appropriate, so even if the secondary air is increased, no afterburn will occur.

In addition, conventionally, when decelerating or changing a transmission shift, the negative pressure of exhaust gas increases, so the reed valve that responds to exhaust pulsation sucks in excess secondary air, which tends to cause afterburn.However, according to the present invention, Afterburn in such cases can also be prevented. This is because when a large amount of secondary air flows through the control valve at once, the flow pressure causes the bimetallic plate 3 to be temporarily pushed back to the valve-closed position regardless of the ambient temperature.

In addition, in this invention, as the temperature source for operating the temperature-sensitive control valve, the engine ambient temperature is used, which has few sudden temperature changes and can be precisely controlled from low to high temperatures. Can be controlled.

As described above, the present invention prevents afterburn particularly at low temperatures, and also effectively prevents afterburn during deceleration or shift change when the negative pressure of exhaust gas increases rapidly.

In the present invention, a temperature-sensitive valve consisting of a bimetallic plate 3 and a housing 2 is housed in a suction case 10, and an annular chamber 21 is formed around the temperature-sensitive valve in the suction case. Air from 53 is constantly circulated. Since the chamber 21 has a certain volume, the air that enters the atmospheric chamber 21 stays for a while, and the bimetal 3 can always react accurately to the temperature of the air to be detected, and can accurately detect the secondary air. Amount control can be performed.

Furthermore, since the bypass is built into the case, the configuration itself is compact.

[Brief explanation of the drawing]

The drawing is a partially cutaway diagram showing the internal structure of the suction case of the air suction system according to the present invention. 1... Air suction filter, 2... Suction case, 3... Bimetal plate, 31...
...opening, 37...hole, 53...bypass.

Claims (1)

[Scope of utility model registration request] In an air suction system for a gasoline engine, the suction case has a built-in air suction filter installed upstream of the reed valve in an air suction passage that supplies secondary air to the exhaust system via a reed valve. The air inlet upstream of the air suction filter inside is opened into the engine room, and a bimetallic temperature-sensitive control is installed approximately in the center of the air suction case downstream of the air suction filter, which opens and closes depending on the engine ambient temperature. an annular atmospheric chamber is formed in an air suction case at an outer periphery of the temperature-sensitive control valve; an inlet passage formed in the valve case and open to the filter side;
It is also formed in the valve case and consists of an outlet passage opened to the exhaust pipe side, and a bimetallic valve body that controls the communication between the inlet passage and the outlet passage according to the air temperature and controls the amount of air suction. An annular bypass is provided on the end face of the air suction filter side of the valve case of the temperature control valve to constantly communicate the downstream side of the air suction filter with the annular atmospheric chamber,
An air suction system for a gasoline engine, characterized in that a predetermined amount of air in the engine room is always guided to the reed valve side, bypassing the temperature-sensitive control valve via the bypass passage.