JPS5812467B2 - Engine exhaust gas recirculation device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in an exhaust gas recirculation device that suppresses the generation of NOx by recirculating a portion of exhaust gas emitted from an engine into an intake passage. This also appropriately controls the amount of recirculated exhaust gas at the same time.

Generally, when exhaust gas is recirculated into the intake passage when the engine is cold, the combustion efficiency deteriorates when the engine is cold, and the air-fuel mixture is diluted by inert exhaust gas, which prevents normal combustion. becomes impossible and the output decreases. It has defects that cause deterioration of drivability, especially:
Since the above-mentioned problems become noticeable immediately after the engine is started, it is not preferable to recirculate the exhaust gas when the engine is cold.

However, when warm-up progresses to a certain extent and the engine temperature rises, in order to suppress NOx emissions, a certain amount of exhaust gas is recirculated within a range that does not impede drivability. It is necessary to increase the amount of gas to achieve desired reflux characteristics and to reduce NOx.

However, with conventional exhaust gas recirculation systems, the control of the amount of recirculated exhaust gas when the engine is cold is insufficient, and the system merely cants the recirculation of exhaust gas when the engine is cold. If an attempt is made to control the amount of recirculation, the structure becomes extremely complicated, which poses a practical problem.3 On the other hand, one type of exhaust gas recirculation system is an exhaust gas recirculation system that connects the exhaust passage and the intake passage. The passage is provided with an orifice and a reflux control valve located downstream of the orifice and used as an opening source for negative pressure generated downstream of or near the throttle valve in the intake passage. The passage pressure and the venturi negative pressure generated in the venturi part of the intake passage are used as operating sources, and as the passage pressure or venturi negative pressure increases, the amount of negative pressure leaking to the atmosphere, which becomes the operating source for opening the recirculation control valve, is reduced. A device equipped with a negative pressure adjustment device that increases the opening degree of the recirculation control valve has been proposed. Although this exhaust gas recirculation device has a relatively simple configuration, It is recognized that an appropriate amount of recirculated exhaust gas can be supplied depending on the amount of recirculated exhaust gas.

The present invention analyzes the characteristics of the proposed device and appropriately controls the exhaust gas recirculation when the engine is cold. It is easy to prevent recirculation, allow a relatively small amount of exhaust gas to be recirculated until the temperature rises and warm-up is completed, and then recirculate a large amount of exhaust gas with predetermined characteristics once warm-up is complete. This is what I am trying to do.

The present invention will be described in detail below with reference to embodiments shown in the drawings.

Embodiment 1 In FIG. 1, 1 is an intake passage for supplying intake air to the engine 2, and the flow rate of intake air flowing into the intake passage 1 from the direction of the arrow is linked to an accelerator pedal (not shown). It is controlled by a throttle valve 3.

Reference numeral 4 denotes an exhaust passage connected to the engine 2. One end of an exhaust gas recirculation passage 5 is opened to the exhaust passage 4, and the other end is opened to the intake passage 1 downstream of the throttle valve 3. An orifice 6 is provided in the middle of the orifice 5, and a reflux control valve γ is provided downstream of the orifice 6.

Reference numeral 8 indicates a venturi portion provided in the intake passage 1, and reference numeral 9 indicates a catalyst device interposed in the middle of the exhaust passage 4.

The recirculation control valve 7 includes a diaphragm 7C to which a valve body 7a for opening and closing the exhaust gas recirculation passage 5 is attached via a rod 7b.
and a negative pressure chamber 7 partitioned by this diaphragm 7c.
d, an atmospheric chamber 1e, and a spring 7f that urges the valve body 7a to close.The negative pressure acting on the negative pressure chamber 7d serves as an opening source, and this negative pressure acts as an opening source for the spring 7f.
The diaphragm 7c is biased against the spring force, and the biasing of the diaphragm 7c opens the valve body 7a.

One end of a negative pressure passage 10 communicates with the negative pressure chamber 7d of the recirculation control valve 7, and the other end of this negative pressure passage 10 communicates with a first negative pressure outlet 10a opened in the intake passage 1. .

The first negative pressure outlet 10a is located near the throttle valve 3 and on the upstream side of the throttle valve 3 when the throttle valve 3 is fully closed, so that the intake negative pressure does not act and the throttle valve 3 is opened to the set opening degree. When the throttle valve 3
The negative pressure acting on the first negative pressure outlet 10a is introduced into the negative pressure chamber 7d of the reflux control valve 7 through the negative pressure passage 10. A leak opening 10b open to the atmosphere is provided in the middle of the negative pressure passage 10.

When the amount of leak from this leak opening 10b increases,
Even if the negative pressure acting on the first negative pressure outlet 10a is constant, the negative pressure acting on the negative pressure chamber 7d of the reflux control valve 7 decreases, and the valve element 7a moves downward in the figure to control the reflux. The opening degree of valve 7 decreases.

On the other hand, when the leak opening 10b is closed and the leak amount decreases, the opening degree of the reflux control valve 7 increases.

Reference numeral 11 denotes a negative pressure passage 10 which is an opening source for the recirculation control valve 7.
A negative pressure adjustment device that adjusts the opening degree of the leak opening 10b of the case 12 to adjust the amount of negative pressure leaking to the atmosphere.
A first diaphragm 13 with a small diameter, a second diaphragm 14 with a large diameter, and a third diaphragm 15 with a small diameter are arranged side by side in order from the top of the drawing, and the inner space of the case 12 is partitioned by each diaphragm 13 to 15. Leak chamber 1 formed by diaphragm 13 and case 12 and open to the atmosphere
1a, the first diaphragm 13 and the second diaphragm 14
A first chamber 11b formed by the second diaphragm 14 and the third diaphragm 15, an atmospheric chamber 11c formed by the third diaphragm 15 and the case 12, and a second chamber 11d formed by the third diaphragm 15 and the case 12.

The first diaphragm 13 also has a valve portion 13a at its center facing the leak opening 10b of the negative pressure passage 10.
The first diaphragm 1 opens and closes the leak opening 10b, that is, increases and decreases the amount of leakage.
3, and the second and third diaphragms 14, 15 are integrally connected via a rod 16 and are provided so as to move together, and a first spring 17 is provided in the leak chamber 11a, and further, A second spring 18 is provided in the second chamber 11d, and the first spring 17 biases the leak opening 10b and the second spring 18 biases the leak opening 10b so as to close the leak opening 10b.

The urging force of the first spring 17 is the same as that of the second spring 18.
When the pressure inside the first chamber 1lb and the second chamber 11d is atmospheric pressure, the leak opening 10b is fully opened, and even if there is negative pressure at the first negative pressure outlet 10a. Even if it acts, this negative pressure will leak, the recirculation control valve 7 will be fully closed, and the exhaust gas recirculation passage 5 will be closed by the valve body 7a.

19 is the second chamber 11 of the negative pressure adjustment device 11
d, one end of which is in communication with the first passage 1.
The other end of 9 is a passage pressure outlet 19 provided downstream of the orifice 6 of the exhaust gas recirculation passage 5 and upstream of the recirculation control valve γ.
The passage pressure acting on the passage pressure outlet 19a is introduced into the second chamber 11d.

20 is a first on-off valve provided in this first passage 19.

On the other hand, 21 is a second passage whose one end communicates with the first chamber 1lb of the negative pressure adjustment device 11, and the other end of this second passage 21 is connected to a second negative pressure passage opened in the venturi portion 8 of the intake passage 1. It communicates with the outlet 21a, and the venturi negative pressure generated in the penturi portion 8 is introduced into the first chamber 11b.

22 is a second on-off valve provided in this second passage 21.

The negative pressure adjustment device 11 has a first chamber 1lb and a second chamber 11d.
The leak opening 10b of the negative pressure passage 10 is opened and closed by the displacement of the diaphragms 13 to 15 due to the increase/decrease in the passage pressure and the penturi negative pressure acting on the reflux control valve I, and the negative pressure that is the source of opening of the reflux control valve I leaks to the atmosphere. The opening degree of the recirculation control valve 7, that is, the amount of recirculation of exhaust gas is controlled.

That is, when only the passage pressure from the first passage 19 acts on the negative pressure adjustment device 11, when this passage pressure increases, the third diaphragm 15 moves upward in the figure, and the valve portion 13a of the first diaphragm 13 moves in the direction of closing the leak opening 10b, reduces the amount of negative pressure in the negative pressure passage 10 leaking to the atmosphere, increases the negative pressure acting on the negative pressure chamber 7d of the reflux control valve 7, and closes the reflux control valve 7. 7 to increase the amount of recirculated exhaust gas, and the exhaust gas recirculation rate due to the effect of only the passage pressure is as shown by the broken line 1 in Fig. 2, when the load (engine speed is kept constant) Throttle valve 3 when
The reflux rate increases to a certain value as the opening degree of the reflux rate increases, and then decreases slightly at the maximum point, and is set to have a small reflux rate as a whole.

Further, when only the venturi negative pressure from the second passage 21 is acting on the negative pressure adjustment device 11, when this venturi negative pressure increases, the second diaphragm 14 has a larger diameter than the first diaphragm 13, that is, the effective pressure receiving Due to the dog-shaped area, the second diaphragm 14 moves upward in the figure, and the valve portion 13a of the first diaphragm 13 closes to the leak opening 10b.
The venturi moves in the direction of closing, reduces the amount of negative pressure leaking to the atmosphere in the negative pressure passage 10, and increases the opening degree of the recirculation control valve 7. The exhaust gas recirculation rate due to the action of only this venturi negative pressure changes with the characteristics shown by the chain line ■ in FIG.

Furthermore, the change in the exhaust gas recirculation rate when both the venturi negative pressure and the passage pressure act simultaneously on the negative pressure regulating device 11 is as shown by the solid line ■ in FIG. Until the outlet 10a reaches the downstream side of the throttle valve 3, the recirculation control valve 7 is closed and there is no recirculation of exhaust gas.After this point, as the load increases, the synergistic effect of the venturi negative pressure and the passage pressure occurs. As a result, the recirculation rate (2) is set to be greater than the exhaust gas recirculation rate (I) due to passage pressure alone.

Next, 23 is a detection device that detects the cooling water temperature of the engine 2 and detects its warm-up state. 1 signal is issued, and the engine cooling water temperature warms up from the first cold state until the temperature exceeds the first set value and reaches the second set value higher than the first set value, that is, warm-up is completed. The second signal is configured to be emitted during the period up to.

Further, 24 is a first signal from the detection device 23 and a second signal from the detection device 23.
An operating device that receives a signal and operates the first and second on-off valves 20 and 22. This operating device 24 and the first and second on-off valves 2
0 and 22 constitute a control device that controls the amount of recirculated exhaust gas when the engine 2 is cold, that is, the negative pressure in the negative pressure passage 10, which is the source of the opening operation of the recirculation control valve 7, in accordance with the cold state of the engine 2. ing.

The operating device 24 includes a first on-off valve 20 interposed in the first passage 19 that guides the passage pressure to the second chamber 11d of the negative pressure adjustment device 11, and a venturi negative pressure in the intake passage 1 that controls the negative pressure adjustment device 1.
1 to the first chamber 11b of the second passageway 21.
The on-off valve 22 is operated, the first on-off valve 20 is closed when the detection device 23 is emitting the first signal, and the second on-off valve 22 is closed when the detection device 23 is emitting the first and second signals. Closed is activated.

That is, when the detection device 23 emits the first signal (first cold machine state), the first on-off valve 20 and the second on-off valve 22
(The first and second on-off valves 20 and 22 are three-way valves, and when they are closed, the atmosphere is introduced into the second chamber 11d1 and the first chamber 11b.

) The negative pressure regulator 11 is inactivated, and the negative pressure regulator 11 opens the leak opening 10b to the maximum (the first diaphragm 13 is biased downward by the first spring 17), and the recirculation control valve 7 is opened. This prevents the action of negative pressure, which is the operating source, and maintains the reflux control valve 7 in a fully closed state.

On the other hand, when the detection device 23 is emitting the second signal (until the warm-up is completed beyond the first cold state), the second on-off valve 2
2 remains closed, the first on-off valve 20 opens, and the negative pressure regulator 1
Only passage pressure acts on 1.

In this case, as described above, the exhaust gas is recirculated at a small recirculation rate as indicated by the broken line ■ in FIG.

Furthermore, when warm-up is completed, the first and second on-off valves 20
, 220 are both opened so that the venturi negative pressure and passage pressure act on the negative pressure regulator 11, and as mentioned above, a large amount of exhaust gas is recirculated with the desired characteristics as shown by the solid line ■ in Fig. 2. It is something to do.

Embodiment 2 As shown in FIG. 3, the exhaust gas recirculation system of this embodiment receives the first signal from the detection device 23 that is emitted according to the cold state of the engine.
In response to the signal and the second signal, a control device that adjusts the recirculation rate of exhaust gas is connected to a third on-off valve 26 interposed in the negative pressure passage 10 by which negative pressure, which is the source for opening the recirculation control valve 7, is introduced. , a second on-off valve 22 (same as the previous example) interposed in the second passage 21 that guides the venturi negative pressure to the negative pressure adjustment device 11, and a detection device 23.
The operating device 25 operates the third and second on-off valves 26 and 22 based on the first and second signals 72 from the detection device 2.
3 emits the first signal, the second on-off valve 22 closes.
is operated to open when the first and second signals are being issued, as in the first embodiment.

Other structures are provided in the same manner as in the first embodiment, and the same structures are given the same reference numerals and their explanations are omitted.

In this example, when the detection device 23 is in the first cold state in which it emits the first signal, the third on-off valve 26 is open, so that the negative pressure passage 10 to the recirculation control valve 7 is blocked. As a result, no negative pressure is applied, the recirculation control valve 7 is fully closed, and the exhaust gas is not recirculated.

Further, while the detection device 23 is emitting the second signal, the third on-off valve 26 is open and the second on-off valve 22 is closed, so that only the passage pressure is introduced into the negative pressure regulating device 1.
1, the exhaust gas is recirculated at a small recirculation rate as shown by the broken line (■) in FIG.

Further, when the warm-up is completed, both the on-off valves 22 and 26 are opened, and the exhaust gas is recirculated at the desired large recirculation rate as shown by the solid line ■ in FIG.

In each of the above embodiments, the extraction of the negative pressure, which is the source for opening the reflux control valve 7, is located at the upstream side of the throttle valve 3 when the throttle valve 3 is fully closed, and after the throttle valve 3 reaches the set opening degree. This is performed by the first negative pressure outlet 10a provided downstream of the throttle valve 3, but this negative pressure can also be extracted downstream of the throttle valve 3 even when the throttle valve 3 is fully closed. This may be carried out using a negative pressure outlet provided as shown in FIG.

Furthermore, the control device may be constructed electrically or mechanically, and although it will not be described in detail, it goes without saying that any known system can be applied.

Therefore, according to the present invention as described above, when the engine is in the first cold state at an extremely low temperature, the recirculation of exhaust gas is stopped, and until the engine exceeds the first cold state and warm-up is completed, the exhaust gas is recirculated at a small recirculation rate. By refluxing the exhaust gas and refluxing the exhaust gas at the desired high reflux rate after warm-up is completed,
By preventing changes in combustion conditions and deterioration of drivability due to excessive recirculation of exhaust gas when the engine is cold, and by recirculating exhaust gas in stages as the engine warms up,
It has excellent effects such as being able to suppress the generation of NOx, having a simple structure, and being highly practical.

[Brief explanation of the drawing]

The drawings illustrate embodiments of the present invention, and FIG. 1 is a schematic diagram of the overall configuration of Embodiment 1, FIG. 2 is a graph showing the relationship between exhaust gas recirculation rate and load, and FIG. 3 is Embodiment 2. FIG. 2 is a schematic diagram of the overall configuration. 1... Intake passage, 2... Engine, 3... Throttle valve, 4 items...
Exhaust passage, 5i...Exhaust gas recirculation passage, 6...-orifice, 7...Recirculation control valve, 7a...Valve body, 7b...Load,
7c...Diaphragm, 7d...Negative pressure chamber, 7e...Dog air chamber, 7f...Spring, 8...Venturi section, 9...
Catalyst device, 10... Negative pressure passage, 10a... First negative pressure outlet, 10b... Leak opening, 11... Negative pressure adjustment device,
11a...Leak chamber, 1lb...First chamber, 11c...Atmospheric chamber, 11d...Second chamber, 12...Case, 13...First diaphragm, 13a...Valve section, 14...Second diaphragm , 15... third diaphragm, 16... rod,
17...first spring, 18...second spring, 1
9...first passage, 19a...passage pressure outlet, 20...
First on-off valve, 21... Second passage, 21a... Second negative pressure outlet, 22n... Second on-off valve, 23... Stomach detection device, 24,
25 Crystal operating device, 26... Stomach third opening/closing valve.

Claims (1)

[Claims] 1. An orifice in an exhaust gas recirculation passage that communicates an exhaust passage and an intake passage, and a negative pressure opening source located downstream of the orifice and generated downstream of or near a throttle valve in the intake passage. A reflux control valve is provided, and the reflux is controlled by using the passage pressure downstream of the orifice and upstream of the reflux control valve and the venturi negative pressure generated in the venturi portion of the intake passage as the actuation source as the passage pressure or venturi negative pressure increases. This system detects the warm-up state of the engine in an engine exhaust gas recirculation system equipped with a negative pressure adjustment device that reduces the amount of negative pressure leaking into the atmosphere and increases the opening of the recirculation control valve. , a detection device is provided which issues the first and second signals respectively during a period when the engine is in the first cold state and during a period when the engine warms up from the first cold state until the warm-up is completed; During the period when the device is emitting the first signal, the negative pressure, which is the source of the opening operation of the reflux control valve, is prevented from acting on the reflux control valve to maintain the reflux control valve in a fully closed state, and the detection device generates the second signal. During the period when the signal is being emitted, the effect of the venturi negative pressure on the negative pressure regulator is blocked, and the amount of negative pressure leaking to the atmosphere, which is the source of opening the reflux control valve, is controlled in accordance with the increase/decrease in the passage pressure. An exhaust gas recirculation device for an engine, characterized in that it is provided with a control device that makes it possible to 2. The detection device detects the engine cooling water temperature, and issues a first signal during a period when the engine cooling water temperature is lower than the first set value, and when the engine cooling water temperature exceeds the first set value, a second set value higher than the first set value is generated. 2. The exhaust gas recirculation system for an engine according to claim 1, wherein the second signal is emitted until the second signal reaches . 3. The control device is interposed in the first passage that leads the passage pressure to the negative pressure regulator, and includes a first on-off valve that closes when the detection device emits the first signal, and a venturi negative pressure to the negative pressure regulator. A detection device is interposed in the second passage leading to the first and second passages.
An exhaust gas recirculation device for an engine according to claim 1 or 2, comprising a second on-off valve that closes when a signal is issued. 4. The control device is interposed in a negative pressure passage that guides negative pressure, which is the source of the opening operation of the reflux control valve, to the reflux control valve, and includes a third on-off valve and a venturi that close when the detection device emits the first signal. Claim 1 or claim 1, further comprising a second on-off valve that is disposed in a second passage that guides negative pressure to the negative pressure adjustment device and that closes when the detection device emits the first and second signals. An exhaust gas recirculation device for an engine according to item 2.