JPH0315023B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to transferring part of the exhaust gas from the exhaust system to the intake system in order to reduce nitrogen oxides (NOx) contained in the exhaust gas in an internal combustion engine. The present invention relates to an exhaust gas recirculation (hereinafter referred to as EGR) amount control device.

[Conventional technology]

Since the amount of NOx emissions varies depending on the operating state of the engine, various methods have been proposed to control the amount of EGR in response to this. However, in consideration of the operability and fuel consumption rate of the engine, there are conventionally known systems that control the air-fuel ratio to the lean side (λ>1) in the medium load range of the engine.

[Problem to be solved by the invention]

If the EGR amount is set to the same amount as in a conventional engine (an engine that does not have a system for controlling the air-fuel ratio to the lean side in the medium-load range) in such a medium load range, the actual air-fuel ratio will be even leaner, and the engine will become leaner. drivability deteriorates.
Additionally, if EGR is uniformly cut off when the engine's air-fuel ratio shifts to the lean side, EGR will be cut off in either the engine's light load range or high load range, resulting in a significant reduction in NOx. The problem is that

An object of the present invention is to solve such problems, and to provide an EGR amount control device that controls EGR to be cut or to reduce the amount of EGR in a medium load range of an engine.

[Means to solve the problem]

In order to solve the above problems, the present invention is equipped with a mechanism that controls the air-fuel ratio to the lean side in the medium load range of the engine, and also transmits control negative pressure from the EGR port to the negative pressure operated EGR valve through vacuum piping. In an internal combustion engine that controls the amount of exhaust gas recirculated from the exhaust system to the intake system through the EGR valve, an auxiliary valve is provided in the middle of the vacuum piping, and the auxiliary valve is operated by a diaphragm having a valve body. The first chamber is connected to the intake manifold negative pressure outlet port downstream of the throttle valve, and the second chamber is connected to the control port immediately downstream of the throttle valve. The valve body of the diaphragm opens and closes a bleed port branching from the vacuum piping due to a pressure difference acting on the exhaust gas, so that when the bleed port is opened, the bleed port communicates with the control port. A recirculation flow control device is provided.

[Effect]

In the present invention, in the medium load range of the engine, EGR is cut and the EGR rate becomes 0 or a value close to 0.
Therefore, even in an internal combustion engine where the air-fuel ratio is set to lean toward the lean side in the medium load range, the air-fuel ratio does not become so lean that it impedes engine drivability, and good drivability is maintained. maintained.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a schematic diagram of an EGR amount control device according to the present invention. Part of the exhaust gas is controlled by negative pressure
It is controlled by the EGR valve 1 and circulated from the exhaust system to the intake system. As is well known, the negative pressure for controlling the EGR valve 1 is supplied from the EGR port 3 of the throttle body 2 through the vacuum piping 4.
The negative pressure is transmitted to the negative pressure working chamber 11 of the EGR valve 1, and the spring 1
By suctioning the diaphragm 13 against pressure 2, the valve body 14 is pulled up and the amount of EGR recirculated from the exhaust system to the intake system is controlled. The negative pressure modulator 5 installed in the middle of the vacuum piping is the EGR valve 1.
This is the final adjustment of the control negative pressure that operates the system, and is well known in the art.

In the present invention, an auxiliary valve 2 is provided in the middle of the vacuum piping 4 between the EGR port 3 and the negative pressure modulator 5.
0 was set. The auxiliary valve 20 has two chambers 23 separated by a diaphragm 22 having a valve body 21;
24, and the first chamber 23 on the lower side of the figure is connected to an intake negative pressure outlet port 26 in the intake manifold section 7 downstream of the throttle valve 6 via a vacuum piping 25.
The second chamber 24 on the upper side of the figure is connected via vacuum piping 27 to a control port 28 provided in the throttle body 2 immediately downstream of the throttle valve 6. A spring 29 is provided in the lower first chamber 23 to press the valve body 21 upward. That is, the valve body 21 is pressed in a direction to close the bleed port 30 branched from the vacuum pipe 4. In FIG. 1, 8 indicates an air cleaner, arrow P indicates the direction in which intake air flows, and arrow Q indicates the direction in which the throttle valve 6 opens and closes.

In the idle operating range, the throttle valve 6 is almost closed as shown in FIG. At this time, the EGR port 3 is located upstream of the throttle valve 6, so the required negative pressure does not act on the EGR port 3, and the EGR valve 1 closes its valve body 14 under the action of the spring 12. EGR is not being performed.

In the light load range, the throttle valve 6 opens slightly, and the EGR port 3 is positioned very slightly downstream of the throttle valve 6. Therefore,
Negative pressure acts on EGR port 3. however,
In this position, since the control port 28 is still located downstream of the throttle valve 6, negative pressure is also acting on the control port 28. Naturally, a negative pressure similar to the negative pressure of the control port 28 also acts on the intake negative pressure extraction port 26, and these negative pressures act on the first chamber 23 and the second chamber 24 of the auxiliary valve 20 at the same time. At this time, the valve body 21 closes the bleed port 30 by the action of the spring 29, so the negative pressure in the EGR port 3 is transferred to the negative pressure working chamber 11 of the EGR valve 1 via the negative pressure modulator 5.
, the valve body 14 is pulled up, and EGR is performed in the same manner as in the conventional device.

In the medium load range, the throttle valve 6 is further opened, and the control port 28 is at the same position as the throttle valve 6 or slightly upstream. Therefore, the control port 28 will be at near atmospheric pressure and the second chamber 24 of the auxiliary valve 20 will be at about atmospheric pressure. Since the intake manifold negative pressure is acting on the first chamber 23 of the auxiliary valve 20, the valve body 21 is sucked downward in the figure against the force of the spring 29, and the bleed port 30 is opened. Therefore, the control port 28 and the piping 2 are connected to the bleed port 30.
7. Atmospheric pressure acts through the second chamber 24.
Since the negative pressure transmitted from the EGR port 3 through the vacuum pipe 4 is bleed at the atmospheric pressure of the bleed port 30, the negative pressure does not act on the negative pressure modulator 5, and therefore EGR is cut off. Rather than completely cutting off EGR in the medium load range,
If weight loss is desired, bleed port 3
An appropriate aperture (not shown) may be provided at 0.

In a high load range where the throttle valve 6 is further opened, the negative pressure in the intake manifold 7 becomes smaller, and therefore the negative pressure acting on the first chamber 23 of the auxiliary valve 20 becomes smaller than the pressing force of the spring 29. Valve body 21 closes bleed port 30. Therefore, EGR is performed in the same way as in the light load range.

In the full load range (WOT) where the throttle valve 6 is fully open or close to fully open, the negative pressure in the intake manifold 7, which is the negative pressure source, is almost gone and the pressure is close to atmospheric pressure, so the EGR valve 1 cannot open. No, EGR will not be performed.

Figure 2 is a rough graph showing the relationship between the operating state (load state) of the engine and the EGR rate described above. As shown, in the medium load range
EGR is cut and the EGR rate becomes 0.

Various methods can be considered to control the air-fuel ratio to the lean side in the medium load range of the engine.
For example, there is a system in which air is bled into the fuel supply path only in the medium load range, and in a fuel injection type engine, a system in which the valve opening time of the fuel injector is controlled to be shortened by a certain percentage in the medium load range.

In addition, Figure 3 shows the engine load condition and air-fuel ratio (A/
It roughly shows the relationship with F),
The area where A/F is λ=1 is a region where the air-fuel ratio is controlled to the so-called stoichiometric air-fuel ratio.

〔Effect of the invention〕

As mentioned above, the present invention is applied to an internal combustion engine equipped with a mechanism that controls the air-fuel ratio to the lean side in the medium load range, but in the medium load range where the air-fuel ratio shifts to the lean side, the EGR Because it is cut or reduced in size,
The air-fuel ratio does not become so lean as to impede engine drivability, and good drivability can be maintained. In addition, EGR is performed effectively in the operating range where NOx emissions should be suppressed, ensuring drivability.
The two elements of reducing NOx can be satisfied at the same time.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of the exhaust gas recirculation (EGR) amount control device for an internal combustion engine according to the present invention, Fig. 2 is a graph roughly showing the relationship between engine load and EGR rate according to the present invention, and Fig. 3 is a graph showing the relationship between engine load and EGR rate according to the present invention. It is a graph roughly showing the relationship between engine load and air-fuel ratio when controlling the air-fuel ratio to the lean side in a medium load range. 1... EGR valve, 2... Throttle body, 3
...EGR port, 4...Vacuum piping, 6...
...Throttle valve, 7...Intake manifold, 2
0... Auxiliary valve, 21... Valve body, 22... Diaphragm, 23, 24... Chamber, 26... Intake manifold negative pressure extraction port, 28... Control port.

Claims (1)

[Claims] 1 Equipped with a mechanism to control the air-fuel ratio to the lean side in the medium load range of the engine, and controlling negative pressure from the EGR port 3 through vacuum piping 4 to the negative pressure operated EGR
In an internal combustion engine that controls the amount of recirculated exhaust gas flowing from the exhaust system to the intake system via the EGR valve by transmitting the signal to the valve 1, an auxiliary valve 20 is provided in the middle of the vacuum pipe 4, and the auxiliary valve is a valve. The first chamber 23 has an intake manifold negative pressure outlet port 26 downstream of the throttle valve 6, and the second chamber 24 has a throttle valve 6. 6 are connected to each other, and the valve body 21 of the diaphragm opens and closes the bleed port 30 branching from the vacuum pipe 3 due to the pressure difference acting on both chambers 23 and 24, An exhaust gas recirculation flow rate control device in which the bleed port communicates with the control port 28 when the bleed port is opened.