JPS6233090Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to an intake system for a fuel-injected engine, and in particular, to a measure to prevent clogging of the idle passage due to carbon particles in recirculated exhaust gas recirculated into a surge tank. .

Generally, in a fuel injection engine, when performing so-called exhaust recirculation, in which a part of the exhaust gas flowing through the exhaust passage is returned to the intake system to reduce NOx, etc. in the exhaust, a throttle valve is inserted in the intake passage downstream of the throttle valve. The downstream end of the exhaust gas recirculation passage is opened near the upstream end of the surge tank, and the recirculated exhaust gas is evenly distributed to the intake air in the surge tank, improving the distribution of the recirculated exhaust gas to each cylinder of the engine. things are being done.

However, in this case, since the recirculated exhaust gas is recirculated to the upstream portion of the surge tank, the recirculated exhaust gas may flow back to the intake passage upstream of the surge tank due to intake pulsation. As a result, carbon particles in the recirculated exhaust gas adhere to and accumulate on the passage walls of the bypass passage, which opens on the upstream side wall of the surge tank and is used to supply intake air during idling, and block the bypass passage. As a result, there was a problem in that the idling performance of the engine was impaired.

Therefore, conventionally, as disclosed in, for example, Japanese Utility Model Application Publication No. 150713/1983, a cylindrical sheath is protruded into the collector chamber (surge tank) at the downstream end of the barrel of a throttle chamber having a throttle valve. The cylindrical sheath increases the flow rate of the intake air flowing from the throttle chamber to the collector chamber, thereby preventing the recirculated exhaust gas in the collector chamber from flowing back into the bypass passage. has been proposed.

However, in the above-mentioned conventional type, the throttle valve opens and the intake air flows into the cylindrical sheath in order to increase the flow velocity of the intake air flowing from the throttle chamber to the collector chamber and prevent the backflow of recirculated exhaust gas. It is effective during constant speed operation, but during deceleration operation when the throttle valve is closed and almost no intake air flows, recirculated exhaust gas remains in the dead volume between the exhaust recirculation amount control valve and the downstream end opening of the exhaust recirculation passage. Or, due to the response delay of the exhaust gas recirculation amount control valve, the recirculated exhaust gas that has passed through the control valve is sucked out into the surge tank by the intake negative pressure, and the recirculated exhaust gas is also sucked into the bypass passage. The pulsation causes carbon particles in the exhaust gas to flow backwards and adhere to the walls of the bypass passage, which cannot provide an essential solution. Another disadvantage is that once carbon particles adhere to the walls of the bypass passage in this manner, the bypass passage cannot be cleaned thereafter.

Therefore, the present invention aims to transfer a portion of the intake air on the upstream side of the throttle valve to the downstream side of the bypass passage through a passage separate from the regular bypass passage when the throttle valve is opened to a predetermined opening degree or more. This increases the amount of intake air flowing through the idle passage when the engine is running at a constant speed, prevents carbon particles in the recirculated exhaust gas from adhering to the wall of the idle passage, and reduces deceleration. The purpose is to clean the bypass passage by removing carbon particles that have adhered during operation.

To achieve this purpose, the configuration of the present invention is to recirculate a part of the exhaust gas into a surge tank provided in the intake passage downstream of the throttle valve, and to circulate the exhaust gas through the idle adjust screw to the throttle valve. In an intake system for a fuel-injected engine, which is provided with a bypass passage that bypasses the idle adjustment screw, the bypass passage downstream of the idle adjust screw is inserted into the intake passage downstream of the throttle valve when the throttle valve is at an idle opening. In addition, when the opening of the throttle valve is greater than the set opening, a communication passage is provided that communicates with the intake passage upstream of the throttle valve, so that when the throttle valve opens more than the set opening, the throttle is closed. A part of the intake air on the upstream side of the valve is made to flow through the communication passage to the downstream part of the bypass passage to increase the intake air flow rate in the downstream part.

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

1 and 2, 1 is a four-cylinder engine, 2 is an intake pipe forming an intake passage 3 for supplying intake air to the engine 1;
consists of one collecting part 4 and four intake manifolds 5, 5, . . . branched from the downstream end of the collecting part 4. An air cleaner 6 and an air flow meter 7 are attached to the gathering part 4 of the intake pipe 2 in order from the upstream side, and the intake pipe 2 downstream of the air flow meter 7
A throttle body 8 is formed therein. As shown in enlarged detail in FIG. 2, the throttle body 8 is provided with a throttle valve 9 that throttles and opens and closes the intake passage 3 to control the amount of intake air, and an idle adjuster that adjusts the idling speed. A bypass passage 11 is formed that bypasses the throttle valve 9 via the screw 10, and the bypass passage 11 supplies intake air during idling operation when the throttle valve 9 is substantially fully closed. Further, the intake passage 3 downstream of the throttle valve 9, that is, the intake pipe 2
A surge tank 12 for storing intake air is interposed at the connection portion between the collecting portion 4 and the intake manifolds 5, 5, .

On the other hand, 13, 13, ... denote exhaust manifolds forming a part of an exhaust passage (not shown) for discharging exhaust gas from the engine 1, 14 denotes an exhaust gas recirculation passage for recirculating a part of the exhaust gas flowing through the exhaust passage into the surge tank 12, and a downstream end opening 14a of the exhaust gas recirculation passage 14 is connected to the surge tank 12.
2 and downstream of a downstream end opening 11a of the bypass passage 11 so as to face said opening 11a. An exhaust gas recirculation amount control valve 15 for controlling the amount of exhaust gas recirculated is disposed in the exhaust gas recirculation passage 14, and this control valve 15 opens to allow exhaust gas recirculation when the engine 1 is operating at a constant speed, but closes to cut off the exhaust gas recirculation when the engine 1 is decelerating.

Further, 16 indicates the surge tank 12 during deceleration.
The downstream end of the air passage 16 is an air passage for a vacuum limiter for supplying air for the vacuum limiter to increase the filling efficiency of intake air and prevent misfires of the engine 1. It opens into the bypass passage 11 downstream of the strike screw 10.

Furthermore, a communication passage 18 is provided in the partition wall 17 between the bypass passage 11 and the intake passage 3 at a position corresponding to the throttle valve 9, and the communication passage 18 is a bypass passage downstream of the idle adjustment screw 10. 11, throttle valve 9
When the throttle valve 9 is at the idle opening (approximately fully closed state) as shown by the phantom line in Figure 2, the intake passage 3 downstream of the throttle valve 9 is connected to the intake passage 3, and the throttle valve 9 is at the set opening as shown by the solid line in the figure. When the above conditions exist, the intake passages 3 upstream of the throttle valves 9 are communicated with each other. And the communication path 18
The passage area of is set larger than the maximum passage area of the bypass passage 11 set in the idle adjusting screw 10. In addition, in Figure 1, 1
9, 19, . . . are fuel injection valves that inject and supply fuel to the engine 1.

Therefore, in the embodiment described above, when the engine 1 is operating at a constant speed, the throttle valve 9 is opened and the intake air (air) is pumped into the surge tank 12.
Immediately before entering each cylinder of the engine 1, the fuel is mixed with fuel from the fuel injection valves 19, 19, . . . to form an air-fuel mixture.
Further, the exhaust gas recirculation amount control valve 15 is opened and the recirculated exhaust gas in an amount corresponding to the intake air amount is recirculated into the surge tank 12 from the opening 14a of the exhaust gas recirculation passage 14, thereby reducing NOx, etc. in the exhaust gas. and improve fuel efficiency.

From this state, when the throttle valve 9 closes to the idling opening and the engine 1 shifts to a deceleration operating state, the exhaust recirculation amount control valve 15
is closed and the exhaust gas recirculation is cut off, but due to the delayed response of the exhaust gas recirculation amount control valve 15 to the closing operation of the throttle valve 9, the recirculated exhaust gas that has passed through the control valve 15 and the exhaust gas recirculation amount are control valve 15
The recirculated exhaust gas remaining in the dead volume portion between the exhaust gas recirculation passage 14 and the downstream end opening 14a of the exhaust recirculation passage 14 is sucked out into the surge tank 12 by the intake negative pressure generated within the surge tank 12. Also,
At the same time, air is blown into the surge tank 12 from the vacuum limiter air passage 16 so as to reduce the intake negative pressure in the surge tank 12.

At that time, the air passage 1 for the vacuum limiter
The opening 11a of the bypass passage 11 where the downstream end of the exhaust gas recirculation passage 14 is opened is located upstream of the opening 14a of the exhaust gas recirculation passage 14 and is provided toward the opening 14a of the exhaust gas recirculation passage 14. , the air for the vacuum limiter is connected to the exhaust recirculation passage 1.
4 and deflects the gas toward the intake downstream side. This prevents the recirculated exhaust gas from flowing back into the throttle valve 9 section or into the bypass passage 11, and thus
It is possible to prevent carbon particles in the recirculated exhaust gas from adhering to the peripheral edge of the bypass passage 11 and the passage wall of the bypass passage 11.

Then, after the idling state, when the throttle valve 9 enters a constant speed operation state in which the throttle valve 9 is opened from the idling opening to the set opening or more, the amount of intake air flowing into the bypass passage 11 from its upstream end decreases. At the same time, the intake passage 3 upstream of the throttle valve 9 and the bypass passage 11 downstream of the idle adjustment screw 10 are communicated through a communication passage 18, and the passage area of the communication passage 18 is regulated by the idle adjustment screw 10. Since the area is larger than the maximum passage area of the bypass passage 11, a portion of the intake air on the upstream side of the throttle valve 9 is passed through the communication passage 18 to the bypass passage downstream of the idle adjust screw 10 so as to compensate for the decrease in the intake air amount. 11, thereby increasing the amount of intake air passing through the bypass passage 11. As a result, it is possible to prevent carbon particles in the recirculated exhaust gas in the surge tank 12 from entering the bypass passage 11 due to intake pulsation and adhering to the passage wall. Even if particles enter the bypass passage 11 and adhere to the passage wall, the bypass passage 11 can be cleaned by scattering and removing the carbon particles.

As explained above, according to the present invention, there is provided an idle bypass passage that recirculates a portion of the exhaust gas into the surge tank downstream of the throttle valve and bypasses the throttle valve via the idle adjustment screw. In the intake system for a fuel injection type engine, the bypass passage downstream of the idle adjust screw is connected to the intake passage downstream of the throttle valve when the throttle valve is at idle opening, and the throttle valve setting By providing communication passages that communicate with the intake passages upstream of the throttle valve when the opening degree is exceeded, the amount of intake air in the bypass passage is increased in a constant speed operation region of the engine where the amount of intake air flowing through the bypass passage decreases. As a result, it is possible to prevent carbon particles in the recirculated exhaust gas from adhering to the walls of the bypass passage and to clean the bypass passage, thereby improving the idling performance of the engine. .

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is an overall plan view, and FIG. 2 is an enlarged sectional view of the main part. 1...Engine, 3...Intake passage, 9...Throttle valve, 10...Idle adjustment screw,
DESCRIPTION OF SYMBOLS 11...Bypass passage, 11a...Opening part, 12...Surge tank, 14...Exhaust gas recirculation passage, 14a...Opening part, 15...Exhaust gas recirculation amount control valve, 16...Air passage for vacuum limiter, 18...Communication passage.

Claims (1)

[Scope of utility model registration request] A fuel injection engine equipped with a bypass passage that recirculates a portion of the exhaust gas into a surge tank provided in the intake passage downstream of the throttle valve and bypasses the throttle valve via an idle adjust screw. In this intake system, the bypass passage downstream of the idle adjust screw is connected to the intake passage downstream of the throttle valve when the throttle valve is at idle opening, and the throttle valve is connected to the intake passage downstream of the throttle valve when the opening is at or above the throttle valve's set opening. An intake device for a fuel injection type engine, characterized in that a communication passage is provided that communicates with each intake passage upstream of a tutle valve.