JPS6120291Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improvement of an engine exhaust gas recirculation device that aims to reduce NOx in the exhaust gas by recirculating a portion of the engine exhaust gas to the intake system.

Exhaust gas recirculation devices for engines of this type have been well known.

By the way, in conventional engine exhaust gas recirculation devices, one exhaust gas recirculation control valve is interposed in the middle of the exhaust gas recirculation passage that guides a part of the exhaust gas to the intake system. Therefore, in order to ensure the necessary and sufficient recirculation amount, the stroke amount of the exhaust gas recirculation control valve must be increased, and when starting the exhaust gas recirculation, There is a problem in that a large amount of exhaust gas is temporarily recirculated, which deteriorates the running performance of the engine.

In addition, in the conventional exhaust gas recirculation control valve controlled by the intake negative pressure downstream of the throttle valve, in order to maintain the exhaust pressure upstream of the exhaust gas recirculation control valve constant, a negative pressure adjustment device is provided to control the amount of intake negative pressure leaked into the exhaust gas recirculation control valve into the atmosphere according to the exhaust pressure, thereby obtaining a constant exhaust gas recirculation amount according to the amount of intake air supplied to the engine. However, if the stroke amount of the exhaust gas recirculation control valve is set large as described above, when the intake negative pressure starts to act on the exhaust gas recirculation control valve, the exhaust pressure becomes high and the exhaust gas recirculation amount becomes large. Since there is almost no leakage to the atmosphere due to the negative pressure regulating device, a large intake negative pressure acts on the control valve, greatly increasing the stroke of the control valve and also causing large fluctuations in the exhaust pressure upstream of the exhaust gas recirculation control valve. As a result, the amount of intake negative pressure leaked to the atmosphere by the negative pressure regulating device also fluctuates, making the operation of the exhaust gas recirculation control valve unstable and causing hunting. Furthermore, during acceleration, the amount of exhaust gas recirculated increases significantly as the exhaust pressure rises, causing a problem of deterioration in acceleration performance.

The present invention has been made to solve these conventional problems, and is capable of controlling the amount of exhaust gas recirculation in multiple stages using two exhaust gas recirculation control valves installed in parallel. By correlating the operations of both exhaust gas recirculation control valves, hunting can be prevented and stable exhaust gas recirculation amount control can be performed, and requests during transient engine operation can be appropriately responded to. The basic objective is to provide an exhaust gas recirculation system for engines that can be used.

Therefore, in the present invention, the first and second exhaust gas recirculation control valves are arranged in parallel in the exhaust gas recirculation passage of the engine, and for the first exhaust gas recirculation control valve, the throttle valve is set to a first set opening. A first negative pressure passage is provided that applies intake negative pressure downstream of the throttle valve when the throttle valve is opened to a second setting. A second valve that applies negative intake pressure downstream of the throttle valve when the throttle valve is opened beyond the opening degree.
For the first exhaust gas recirculation control valve that is provided with a negative pressure passage and opens first, as in the past, the amount of intake negative pressure leaking to the atmosphere is determined according to the exhaust pressure upstream of the first exhaust gas recirculation control valve. A negative pressure regulating device is provided to adjust the exhaust gas recirculation control valve, and the first and second negative passages are communicated with each other through a restriction by a communication passage, and the first and second exhaust gas recirculation control valves are operated in a correlated manner. The basic feature is that

Hereinafter, the present invention will be explained in more detail based on the illustrated embodiments.

In FIG. 1, reference numeral 1 denotes an exhaust gas recirculation passage that recirculates part of the exhaust gas taken out from the exhaust passage of an engine (not shown) to the downstream of the throttle valve 3 of the intake passage 2; The downstream side of the orifice 4 interposed in the middle is branched into two to form a first exhaust gas recirculation passage 5 and a second exhaust gas recirculation passage 6.

Negative pressure operated first and second exhaust gas recirculation control valves 7 and 8 are interposed in the first and second exhaust gas recirculation passages 5 and 6, respectively, to open and close the respective exhaust gas recirculation passages 5 and 6. Basically, the amount of exhaust gas recirculated is controlled by the first and second exhaust gas recirculation control valves 7 and 8.

The first and second exhaust gas recirculation control valves 7 and 8 are
Basically, they have the same structure, and the casing 7a,
8a is compressed with coil springs 7c, 8c by diaphragms 7b, 8b to form negative pressure chambers 7d, 8d.
and atmospheric chambers 7f, 8f communicated with the atmosphere through atmospheric communication ports 7e, 8e, and the diaphragms 7b, 8b have valves provided in the first and second exhaust gas recirculation passages 5, 6. Inverted cone-shaped valve bodies 7g and 8g that open and close seats 5a and 6a are placed in atmospheric chamber 7.
Actuation rods 7h and 8h extend through f and 8f
It has a structure supported through.

Negative pressure chamber 7d of the first exhaust gas recirculation control valve 7
is located upstream of the throttle valve 3 when the throttle valve 3 is fully closed, and is located downstream of the throttle valve 3 when the throttle valve 3 is opened to a preset first opening degree. The first exhaust gas recirculation control valve 7 is communicated with the first negative pressure outlet 9 through a first negative pressure passage 10, and basically controls the first exhaust gas recirculation control valve 7 by the intake negative pressure acting on the first negative pressure outlet 9. .

Reference numeral 11 denotes a negative pressure adjusting device provided for a negative pressure leak passage 12 that communicates with one end midway through the first negative pressure passage 10. The device 11 is configured as a kind of diaphragm device, and A diaphragm 11b is attached with a valve body 11a that opens and closes the end of the diaphragm 11b.
The casing 11c is connected to the negative pressure leak passage 12 by
The atmospheric chamber 11d is divided into an open atmospheric chamber 11d and a pressure chamber 11e, and the atmospheric chamber 11d is equipped with a coil spring 11f that always biases the diaphragm 11b in the open direction. Downstream of the orifice 4, the passage pressure (exhaust pressure) of that part is introduced by a pressure passage 13 having one end open at the branch part of the first and second exhaust gas recirculation passages 5 and 6, so that the passage pressure is When the pressure is high, the diaphragm 11b is lifted against the spring force of the coil spring 11f, and the supported valve body 11a closes the negative pressure leak passage 12, thereby reducing the amount of leakage and increasing the first exhaust gas recirculation control valve 7. On the other hand, when the passage pressure is low, the leak amount is increased and the first exhaust gas recirculation control valve 7 is closed, thereby maintaining the passage pressure almost constant.

On the other hand, the negative pressure chamber 8d of the second exhaust gas recirculation control valve 8 attached to the first exhaust gas recirculation device valve 7 opens into the intake passage 2 upstream from the first negative pressure outlet 9,
When the throttle valve 3 is opened to a second set opening degree that is larger than the first set opening degree, it communicates with a second negative pressure outlet 14 provided downstream thereof through a second negative pressure passage 15. Basically, when the throttle valve 3 is opened to a second set opening degree or more, the second exhaust gas recirculation control valve 8 is opened by the applied negative intake pressure.

The second negative pressure passage 15 that leads negative pressure to the second exhaust gas recirculation control valve 8 and the first negative pressure passage 10 that leads negative pressure to the first exhaust gas recirculation control valve 7 are connected through a communication path in the middle thereof. communicated with each other by 16,
In the middle of the communication path 16, there is a throttle 1 that acts in both directions.
7, the first and second exhaust gas recirculation control valves 7,
The operation of 8 is given a certain degree of relevance.

Next, the operation of the exhaust gas recirculation device will be explained.

() During idling operation During idling operation, the throttle valve 3 is fully closed, and the first and second negative pressure outlets 9 and 14 are both located upstream of the throttle valve 3, so that the first and second exhaust gas Atmospheric pressure acts on the negative pressure chambers 7d and 8d of the recirculation control valves 7 and 8, and the first and second exhaust gas recirculation control valves 7 and 8
are the first and the first, respectively, by the supported valve bodies 7g and 8g.
The second exhaust gas recirculation control passages 5 and 6 are completely closed to cut off the recirculation of exhaust gas.

() 1st set opening ≦ Throttle valve opening < 2nd set opening In the operating state in which the throttle valve 3 is opened to an opening greater than or equal to the 1st set opening and smaller than the 2nd set opening, the first The negative pressure outlet 9 is located downstream of the throttle valve 3 , and the second negative pressure outlet 14 is still located upstream of the throttle valve 3 .

Therefore, the intake negative pressure downstream of the throttle valve 3 acting on the first negative pressure outlet 9 is introduced into the negative pressure chamber 7d of the first exhaust gas recirculation control valve 7 through the first negative pressure passage 10, As a result, the first exhaust gas recirculation control valve 7 is opened. However, in this case, since the second negative pressure outlet 14 is located upstream of the throttle valve 3, part of the intake negative pressure introduced into the first negative pressure passage 10 is
The second negative pressure outlet 1 through the throttle 17 of the communication path 16
4 side, and the intake negative pressure is diluted to a certain extent. As a result, the first exhaust gas recirculation control valve 7 is opened relatively slowly without being opened suddenly, and the exhaust gas recirculation is It will start gradually.

Further, the negative pressure regulator 11 is configured to control the negative pressure leak passage 1 in order to maintain the passage pressure downstream of the orifice 4 constant.
The opening degree of the first exhaust gas recirculation control valve 7 is controlled moment by moment by adjusting the amount of intake negative pressure leaking to the atmosphere.

At this stage, the second exhaust gas recirculation control valve 8 is fully closed, so the amount of exhaust gas recirculation is basically controlled by the first exhaust gas recirculation control valve 7.

() Throttle valve opening ≧ second set opening When the throttle valve 3 is opened to the second set opening or more, the first and second negative pressure outlets 9 and 14 are both located downstream of the throttle valve 3, Intake negative pressure downstream of the throttle valve 3 acts on the first and second negative pressure outlets 9 and 14 . However, the intake negative pressure that suddenly acts on the second negative pressure outlet 14 is passed through the communication passage 16 through the throttle 17, and the second negative pressure outlet 14 is controlled by the negative pressure regulating device 11. 1 to the negative pressure passage 10 side, and further leaked to the atmosphere through the negative pressure leak passage 12.
The intake negative pressure introduced into the exhaust gas recirculation control valve 8 is diluted to a certain extent, and as a result, the opening operation of the second exhaust gas recirculation control valve 8 is relaxed, and the opening operation of the second exhaust gas recirculation control valve 8 is reduced. Therefore, the amount of recirculation of exhaust gas does not suddenly and temporarily increase. For this reason,
The amount of recirculation of exhaust gas is increased almost continuously.

Further, at the same time as the second exhaust gas recirculation control valve 8 is opened, the passage downstream of the orifice 4 is lowered, and as the passage pressure decreases, the first exhaust gas recirculation control valve 7 is opened by the action of the negative pressure regulator 11. When the second exhaust gas recirculation control valve 8 is fully opened, only the first exhaust gas recirculation control valve 7 is operated. It is possible to obtain an exhaust gas recirculation amount proportional to the intake air amount.

() During acceleration operation For example, when the throttle valve 3 is shifted from an opening degree larger than the first set opening degree and smaller than the second set opening degree to an accelerated operation of the engine in which the throttle valve 3 is opened wide to the second set opening degree or more, the The intake negative pressure suddenly acts on the second negative pressure outlet 14, and the intake negative pressure slightly leaks from the negative pressure adjustment device 11 acts on the negative pressure chamber 8d of the second exhaust gas recirculation control valve 8, and the control valve The opening action of No. 8 is relatively relaxed. At this time, the exhaust pressure decreases and the passage pressure downstream of the orifice 4 also decreases, so the negative pressure regulator 11 opens the negative pressure leak passage 12 by the valve body 11a supported by the displacement of the diaphragm 11b.
The amount of leakage increases, the intake negative pressure in the negative pressure chamber 7d decreases, and the first exhaust gas recirculation control valve 7 is suddenly closed. Further, the first and second exhaust gas recirculation control valves 7,
Since the stroke amount of No. 8 is set smaller than the conventional single exhaust gas recirculation control valve, it is possible to prevent the exhaust recirculation gas from increasing significantly at the beginning of acceleration, without impairing drivability at the beginning of acceleration. Additionally, exhaust gas can be recirculated during accelerated driving. Also, during acceleration when the throttle valve 3 is opened from fully closed to below the second set opening and above the first set opening, the intake negative pressure acting on the first exhaust gas recirculation control valve 7 is throttled as described above. To leak through 17,
It is possible to prevent the exhaust gas recirculation amount from increasing significantly at the beginning of acceleration.

Furthermore, during sudden acceleration operation in which the throttle valve is suddenly opened from fully closed to an opening equal to or higher than the second set opening, the first and second
Since the intake negative pressure acts on both the negative pressure outlets 9 and 14 and is simultaneously introduced into the first and second negative pressure passages, the initial leakage due to the throttle 17 does not occur, and the first and second negative pressure The second exhaust gas recirculation control valves 7 and 8 are simultaneously opened. Therefore, during rapid acceleration, a large amount of exhaust gas is quickly recirculated, and the required amount during rapid acceleration can be quickly secured.

Note that when the engine is decelerating, the throttle valve 3 is fully closed and atmospheric pressure acts on the first and second negative pressure outlets 9 and 14, so the first and second exhaust gas recirculation control valves 7 and 8 are closed. It is fully closed, and as a result, the recirculation of exhaust gas is cut off.

As described above, the present invention provides exhaust gas recirculation passage 1
In the middle of the process, the first and second exhaust gas recirculation control valves 7, 8
Since the two control valves 7 and 8 are arranged in parallel and the operation of both control valves 7 and 8 is controlled in a correlated manner, the individual stroke amounts of the first and second exhaust gas recirculation control valves 7 and 8 can be set relatively small. In addition, when the second exhaust gas recirculation control valve 8 operates to open, the first exhaust gas recirculation control valve 7 can be operated in the closing direction, thereby stabilizing the amount of exhaust gas recirculation. .

Therefore, as shown schematically in Fig. 2, the variation in the EGR rate A of the present invention can be significantly reduced compared to the variation in the EGR rate B due to a single conventional exhaust gas recirculation control valve. This makes it possible to ensure a stable exhaust gas recirculation amount proportional to the intake air amount and therefore the exhaust pressure, and it is also possible to substantially eliminate the so-called hunting phenomenon.

That is, according to the engine exhaust gas recirculation device according to the present invention, it is possible to slow down the rise characteristic of the recirculation amount at the start of exhaust gas recirculation, and at the same time, it is possible to prevent the hunting phenomenon. During slow acceleration operation, the opening action of the first and second exhaust gas recirculation control valves can be relaxed, and the first and second exhaust gas recirculation control valves with small stroke amounts can perform good control, so that so-called overflow can be prevented. This has the effect of preventing shoots and not impairing the acceleration performance of the engine.

Furthermore, during sudden acceleration of the engine in which the throttle valve is suddenly opened from fully closed to more than the second set opening, the first and second exhaust gas recirculation control valves 7 and 8 may be opened simultaneously. As a result, a large amount of exhaust gas can be quickly supplied, and demands during sudden acceleration can be appropriately met.

[Brief explanation of the drawing]

Fig. 1 is a schematic overall explanatory diagram of an engine exhaust gas recirculation device according to an embodiment of the present invention, and Fig. 2 shows the time fluctuation of the EGR rate according to the present invention with a solid line A, and the conventional one with a dotted line B. It is a graph. 1...Exhaust gas recirculation passage, 2...Intake passage, 3
... Throttle valve, 4... Orifice, 7, 8... 1st,
Second exhaust gas recirculation control valve, 9...First negative pressure outlet, 10...First negative pressure passage, 11...Negative pressure adjustment device, 12...Negative pressure leak passage, 14... Second negative pressure Outlet port, 15...second negative pressure passage, 16...communication passage, 17...throttle.

Claims (1)

[Scope of utility model registration request] An orifice and first and second exhaust gas recirculation control valves located downstream of the orifice and arranged in parallel to control opening/closing of the exhaust gas recirculation passage are provided in an air intake gas recirculation passage that communicates the intake passage with the intake passage. intervene,
The negative pressure chamber of the first exhaust gas recirculation control valve is opened into the intake passage, which is located upstream of the throttle valve when it is fully closed, and which is located upstream of the throttle valve when it is opened to the first set opening degree. A first negative pressure passage communicating with the negative pressure outlet is provided, and the pressure in the passage downstream of the orifice and upstream of the first and second exhaust gas recirculation control valves is used as an operating source, and as the passage pressure increases, the first exhaust A negative pressure regulating device is provided to increase the degree of opening of the first exhaust gas recirculation control valve by reducing the amount of negative pressure leaking to the atmosphere, which is the source of the opening operation of the gas recirculation control valve, and the second exhaust gas recirculation control valve The negative pressure chamber is communicated with a second negative pressure outlet that opens into the intake passage located downstream of the first negative pressure outlet when the throttle valve is opened to a second set opening degree or more, upstream of the first negative pressure outlet. A second negative pressure passage is provided, and the first negative pressure passage is connected to a second negative pressure passage through a throttle.
An exhaust gas recirculation device for an engine, characterized in that it communicates with a negative pressure passage.