JPS581266B2 - 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 for an engine.

Conventionally, an exhaust system has been designed to reduce the generation of nitrogen oxides (NOx) in the exhaust gas by recirculating a portion of the exhaust gas emitted from the engine into the intake system and suppressing the combustion temperature in the combustion chamber. Gas reflux devices (hereinafter abbreviated as EGR devices) are well known.

Conventionally, such an EGR device has an orifice in an EGR 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. An EGR control valve is provided, and passage pressure in a constant pressure passage downstream of the orifice and upstream of the EGR control valve is used as an operating source, and as the passage pressure increases, the EGR control valve is opened to negative pressure in the atmosphere. By providing a negative pressure regulator that reduces the amount of leakage and increases the opening degree of the EGR control valve, the amount of EGR can be adjusted in proportion to the exhaust pressure, which is approximately proportional to the amount of intake air of the engine, that is, the passage pressure. A so-called exhaust pressure utilization type EGR device has been proposed, in which the EGR rate is always controlled at a constant level by increasing or decreasing the EGR rate. Static or dynamic pressure is used.

However, in the above-mentioned conventional exhaust pressure utilization type EGR device, the EGR rate when the static pressure of the passage pressure is used as the operating source of the negative pressure adjustment device is as shown in FIG. Compared to the EGR rate when using the dynamic pressure of the passage pressure, the EGR rate is smaller in the entire operating range of the engine, so engine operability is good, but sufficient NOx suppression cannot be achieved. If the engine is running, the EGR rate is higher than when static pressure is used, so while sufficient NOx can be suppressed, drivability deteriorates, especially when the engine is cold or when the engine is running at low speeds and high loads, or when the engine is running at low speeds and under low loads. There is a problem with doing so.

The present invention has been made in view of the above-mentioned points, and is applicable to the exhaust pressure utilization type EGR system as described above, during specific operations where engine drivability is a problem (when the engine is cold or when the engine is running at low speeds and under high load). (at high speed and low load)
By using the static pressure of the passage pressure in the constant pressure passage as the operating source of the negative pressure regulator, the EGR rate is reduced and NOx
While trying to improve driveability while suppressing other factors to some extent, during normal operation when other driveability is not an issue, by using the dynamic pressure of the passage pressure in the constant pressure passage, the EGR rate is increased and NOx is sufficiently suppressed. Therefore, the present invention provides an engine EGR device for the purpose of obtaining an EGR rate adapted to the operating state of the engine.

That is, the present invention provides the above exhaust pressure utilization type EGR device in which the constant pressure passage is formed by a single passage, and the static pressure and dynamic pressure of the passage pressure of the constant pressure passage are taken out respectively, and the negative pressure regulating device is activated. A first pressure passage and a second pressure passage are respectively provided as a source, and during a specific operation of the engine, the first pressure passage is opened and the second pressure passage is closed, and the static pressure of the passage pressure is provided as a source of operation of the negative pressure regulating device. While using
A control device is provided that closes the first pressure passage and opens the second pressure passage during normal operation of the engine, and uses the dynamic pressure of the passage pressure as an operating source for the negative pressure regulating device. It is something to do.

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

In FIG. 1, 1 is an engine, 2 is an intake passage that supplies air-fuel mixture to the engine 1, and 3 is an exhaust passage connected to the engine 1.The intake passage 2 is connected to a venturi 4 and an accelerator pedal ( A throttle valve 5 is disposed in conjunction with a catalytic converter (not shown), and a catalyst device 6 is provided in the middle of the exhaust passage 3.
is interposed.

7 is an EGR passage whose one end opens upstream of the catalyst passage 6 of the exhaust passage 3 and the other end opens downstream of the throttle valve 5 of the intake passage 2, and the passage 7 directs a portion of the exhaust gas emitted from the engine 1 to the intake passage 2. It is something that refluxes.

An orifice 8 is disposed in the middle of this EGR passage 7 to measure the amount of EGR, and is located downstream of the orifice 8 to control the negative pressure generated near the throttle valve 5 (or downstream of the throttle valve 5) in the intake passage 2. An EGR control valve 9 is provided as an opening source.

The EGR control valve 9 has a rod 11 attached to a diaphragm 10.
The valve body 12 is supported via the diaphragm 1 and controls opening and closing of the passage area of the EGR passage 7.
The negative pressure chamber 13 has a negative pressure chamber 13 and an atmospheric chamber 14 separated by a
The negative pressure outlet is located upstream of the throttle valve 5 of the intake passage 2 until it is opened to a predetermined opening degree, and when the throttle valve 5 is opened to a predetermined opening degree or more, the negative pressure outlet is located downstream of the throttle valve 5 of the intake passage 2. 16, and a spring 17 is compressed in the negative pressure chamber 13, and the negative pressure introduced into the negative pressure chamber 13 from the negative pressure outlet 16 causes the diaphragm 10 to be connected to the spring 1.
The opening degree of the valve body 12 is controlled by being biased against the spring force 7, and the degree of opening of the valve body 12 is increased as the negative pressure in the negative pressure chamber 13 increases.

Further, a reference numeral 18 is connected to a negative pressure atmosphere downstream of the orifice 8 of the EGR passage 7 and upstream of the EGR control valve 9 (valve body 12) using the passage pressure P of the constant pressure passage 7a as an operation source to become an operation source for opening the EGR control valve 9. This is a negative pressure regulating device for controlling the leakage amount of the negative pressure introducing passage 15, which includes a pressure chamber 20 and an atmospheric chamber 21 separated by a diaphragm 19.
A negative pressure leak passage 22 is branched from the middle, and an opening 22a of the negative pressure leak passage 22 is exposed into the atmospheric chamber 21 close to the diaphragm 19, and a spring 23 is compressed in the atmospheric chamber 21. The diaphragm 19 is biased by the pressure of the pressure chamber 20 against the spring force of the first spring 23, and the opening area of the negative pressure leak passage opening 22a is controlled by the bias of the diaphragm 19. The negative pressure in the negative pressure chamber 13 of the EGR control valve 9 is increased by controlling the amount of negative pressure leaking to the atmosphere from the EGR control valve 9 and reducing the amount of negative pressure leaking as the pressure in the pressure chamber 20 increases. The opening degree of the valve body 12 is increased by this.

The constant pressure passage γa is formed by a single passage.

Further, 24 is a static pressure P of the passage pressure P of the constant pressure passage γa in the pressure chamber 20 of the negative pressure adjustment device 18.

a first pressure passage 25 for introducing the pressure chamber 20;
A second pressure passage for introducing dynamic pressure P1 of the passage pressure P of the constant pressure passage 7a into the constant pressure passage 7a. The static pressure P of the passage pressure P in the constant pressure passage 7a.

One end 25a of the second pressure passage 25 has a dynamic pressure P of the passage pressure P of the constant pressure passage 7a between the orifice 8 of the EGR passage 7 and the EGR control valve 9. While the other ends of both pressure passages 24 and 25 are brought together and communicated with the pressure chamber 20 via a common pressure passage 26,
A detection signal from a specific operating state detection device 27 for detecting a specific operating state of the engine (cold operating state of the engine, low rotational high load operating state, and high rotational low load operating state) is provided at the gathering point of both pressure passages 24 and 25. A switching valve 28 is provided, which is operated to open the first pressure passage 24 and open the second pressure passage 25 by switching the switching valve 28 when the specific operating state detection device 27 detects the specific operating state detection device 27, that is, when the engine is in a specific operation. is closed, and the static pressure Po of the passage pressure P is used as the operating source for the negative pressure adjustment device 18 (pressure chamber 20). When the engine is completed (or when the engine is operating at a time other than low speed, high load, or high speed and low load), the first pressure passage 24 is closed by the switching valve 28, and the second pressure passage 25 is opened, and the negative pressure regulator 1 is closed.
A control device 29 is configured to use the dynamic pressure P1 of the passage pressure P as the operating source of the control device 8.

Therefore, in the above embodiment, during specific operations such as when the engine is cold or when the engine is at low rotational speeds and high loads, and when the engine is at high rotational speeds and low loads, when engine drivability is emphasized, the negative pressure regulator 18 is controlled by the control device 29. The pressure chamber 20 is connected to E through the first pressure passage 24 and the common pressure passage 26.
Static pressure P of the passage pressure P of the single constant pressure passage 7a between the orifice 8 of the GR passage 7 and the EGR control valve 9.

is introduced as an operating source, the pressure in the pressure chamber 20 is relatively low, and the diaphragm 19 is pushed down by the spring 23, opening 22a of the negative pressure leak passage 22 is wide open, allowing negative pressure to flow into the atmosphere. Since there is a large amount of leakage, E
The negative pressure in the negative pressure chamber 13, which is the source for opening the GR control valve 9, is diluted with the atmosphere and is low, and the opening degree of the valve body 12 is relatively small, so the EGR amount is small and the EGR rate is as shown in FIG. Low as shown.

Therefore, good drivability can be ensured while suppressing NOx in the exhaust gas to some extent.

On the other hand, during normal operation, such as when the engine has been warmed up or when the engine is not operating at low speeds and high loads or when the engine is running at high speeds and low loads, when the engine drivability is not so much of a problem, the control device 29 controls the negative pressure regulator 18. Since the dynamic pressure P1 of the passage pressure P of the single constant pressure passage 7a is introduced into the pressure chamber 20 through the second pressure passage 25 and the common pressure passage 26 as an operating source, the pressure in the pressure chamber 20 increases. The diaphragm 19 is biased against the spring force of the spring 23, and the negative pressure leak passage opening 22a is narrowed to reduce the amount of negative pressure leaking to the atmosphere. As the negative pressure in a certain negative pressure chamber 13 increases and the opening degree of the valve body 12 increases, the EGR amount increases and the EGR rate reaches the second level.
Increase as shown in the figure.

Therefore, NOx in the exhaust gas can be sufficiently suppressed.

In the above embodiment, the negative pressure outlet 16, which is the opening source for the EGR control valve 9, is located upstream of the throttle valve 5 in the intake passage 2 until the throttle valve 5 is opened to a predetermined opening degree. The throttle valve 5 is provided so as to be located downstream of the throttle valve 5 when the throttle valve 5 is opened to a predetermined opening degree or more.
When the engine is idling, the EGR control valve 9 is deactivated so that EGR is not performed.However, the negative pressure outlet is provided downstream of the throttle valve 5 in the intake passage 2, and the EGR control valve 9 is activated. Of course, it is also good.

As explained above, according to the present invention, in the exhaust pressure utilization type EGR device, when the engine is operating in a specific manner (when the engine is cold, when the engine is at low speed and high load, and when the engine is under high speed and low load), negative pressure is applied. While the static pressure of the passage pressure of a constant pressure passage formed by a single passage is used as the operating source of the regulating device,
By using the dynamic pressure of the passage pressure in the constant pressure passage as the operating source for the negative pressure regulator during normal engine operation, the EGR rate can be lowered during specific operations where engine operability is a problem. While it is possible to improve drivability and suppress NOx to a certain extent, it is also possible to increase the EGR rate during normal operation of the engine, so that sufficient NOx can be suppressed.
Therefore, it is possible to satisfy both the demands of suppressing NOx and improving drivability depending on the operating state of the engine.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram illustrating an embodiment of the present invention, and FIG.
3 and 3 are constant EGR rate curve diagrams in the entire operating range of the engine when dynamic pressure and static pressure of the passage pressure of the constant pressure passage are used, respectively. 1...Engine, 2...Intake passage, 3...Exhaust passage, 4
... Venturi, 5... Throttle valve, 6... Catalyst device, 7...
EGR passage, 7a... constant pressure passage, 8... orifice, 9
... EGR control valve, 10 ... diaphragm, 11 ... rod, 12 ... valve body, 13 ... negative pressure chamber, 14 ... atmospheric chamber, 15 ... negative pressure introduction passage, 16 ... negative pressure outlet , 17...
... Spring, 18 ... Negative pressure adjustment device, 19 ... Diaphragm, 20 ... Pressure chamber, 21 ... Atmospheric chamber, 22 ... Negative pressure leak passage, 2'2a ... Opening, 23 ... Spring, 24 ...First pressure passage, 24a...One end opening, 2
5...Second pressure passage, 25a...One end opening, 26...
Common pressure passage, 27... Specific operating state detection device, 28...
...Switching valve, 29...control device.

Claims (1)

[Scope of Claims] 1. An orifice in an exhaust gas recirculation passage communicating 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 passage pressure of the constant pressure passage downstream of the orifice and upstream of the reflux strut valve is used as an operating source, and as the passage pressure increases, a negative pressure atmospheric air is provided that becomes an operating source for opening the reflux control valve. In an exhaust gas recirculation system for an engine equipped with a negative pressure regulating device that increases the opening degree of a recirculation control valve by reducing the amount of leakage to the engine, the constant pressure passage is formed by a single passage, and A first pressure passage and a second pressure passage are respectively provided to take out static pressure and dynamic pressure and serve as an operating source for the negative pressure regulating device, and the first pressure passage is opened and the second pressure passage is opened during a specific operation of the engine. is closed, and the static pressure of the passage pressure is used as an operating source for the negative pressure regulator, while the first pressure passage is closed and the second pressure passage is opened during normal operation of the engine to operate the negative pressure regulator. 1. An exhaust gas recirculation device for an engine, comprising a control device that uses the dynamic pressure of the passage pressure as a source. 2 Claim 1 in which the specific operation is defined as the time when the engine is cold, while the normal operation is defined as the time when the engine has been warmed up.
Exhaust gas recirculation device for the engine described in Section 1. 3. The exhaust gas recirculation system for an engine according to claim 1, in which the specific operation is a low engine speed and high load and the high engine speed and low load, while the normal operation is an operation other than the above. .