JPS626101B2 - - Google Patents

Description

Detailed Description of the Invention The present invention is a device for controlling the ratio of the amount of exhaust gas recirculated to the amount of engine intake air (hereinafter referred to as the EGR rate) in a device that recirculates exhaust gas into the intake pipe downstream of the throttle valve of an internal combustion engine. Regarding.

Conventionally, as an EGR rate control device, from the exhaust pipe
An EGR gas passage is configured that connects to the intake pipe downstream of the throttle valve via the EGR control valve and the EGR valve. By using a vacuum modulator that uses intake pipe negative pressure and variable and fixed throttles to maintain constant pressure.
There was one that drives the EGR control valve, but in the region where the engine speed is low and the intake pipe negative pressure is low.
There was a drawback that the EGR rate tended to be higher than the required value necessary for engine compatibility.

The purpose of the present invention is to eliminate the above-mentioned drawbacks, by changing the relationship between the variable throttle and the fixed throttle in the vacuum modulator, and increasing the amount of intake air in the intake pipe upstream of the throttle valve instead of atmospheric pressure. The use of a negative pressure source improves the performance of conventional configurations with only minor changes.

Next, it will be explained based on the drawings.

In the embodiment shown in FIG. 1, EGR gas is connected from an exhaust pipe 2 of an engine 1 to an intake pipe 8 downstream of a throttle valve 7 through a passage 3, an EGR control valve 4, a passage 5, and an EGR valve 6 having a butterfly shape. A passage is constructed. The EGR valve 6 is connected to a throttle valve 7 by a link 9. The vacuum modulator 10 includes a chamber A 11, a chamber B 12, a diaphragm 13 separating the chamber A 11 and the chamber B 12, and a spring 14 located inside the chamber B 12 that pushes the diaphragm 13 toward the chamber A.
and a variable throttle (valve) 15 located within the B chamber 12 and opened and closed by a diaphragm 13. Room A 11 communicates with passage 5. The B chamber 12 is connected to the intake pipe 8. The EGR control valve 4 is fixed to the diaphragm 16 and controls the pressure inside the diaphragm chamber 17 and the pressure inside the diaphragm chamber 17.
It is opened and closed by the force of the spring 18 pressing the EGR control valve 4 in the closing direction. The variable throttle 15 connects through a throttle 19 to the diaphragm chamber 17 and through a throttle 20 to a port 22 that opens into an intake passage 21 upstream of the throttle valve 7. To describe the position of the port 22 in detail, the throttle valve 7
When the throttle valve 7, which is located on the right side and has a butterfly shape, rotates counterclockwise to increase its opening area, it opens at the position of the port 22 where such negative pressure increases, or into the bench lily portion 23. That is, in the intake passage upstream of the throttle valve, it opens to a first pressure source where the negative pressure increases as the intake air amount increases, for example, as the engine speed increases.

FIG. 2 shows a conventional configuration in which the throttle 20 is open upstream of the bench lily portion 23, that is, to substantially atmospheric pressure.

The air flow rate G _A taken into the engine is determined by the opening area A _A of the throttle valve 7 and the corresponding pressure difference.
The amount is determined by the opening area A _E of the EGR valve 6 and the corresponding pressure difference.

Diaphragm 1 of vacuum modulator 10
The pressure difference between the front and rear of the EGR valve 6 acts on the valve 1 due to the balance between the force generated thereby and the biasing force of the spring 14.
5 opens and closes, and if the differential pressure between the front and rear becomes too small, the valve 15 opens and transmits more negative pressure from the intake pipe 8 to the diaphragm chamber 17 of the diaphragm 16 that drives the EGR control valve 4 via the throttle 19. hand,
The EGR control valve 4 is opened further and the differential pressure across the EGR valve 6 is corrected to increase. In this way, the vacuum regulator stabilizes the differential pressure across the EGR valve 6. The diaphragm chamber 17 also communicates via the throttle 20 with a port 22 opening into the intake pipe 21 upstream of the throttle valve 7, so that the pressure in the diaphragm chamber 17 relative to the diaphragm 16 is equal to the intake pipe pressure. Value of P _B , opening/closing degree of valve 15, port 2
It is related to the pressure P ₁ of the intake passage at 2 and the opening area of the throttle 20. Here, from port 22 to aperture 2
0. Considering the change in pressure along the flow path of air flowing into the intake pipe 8 via the throttle 19 and valve 15,
The pressure between the throttle 20 and the valve 15, that is, the pressure P in the diaphragm chamber 17, is approximately expressed as shown in FIG. In FIG. 3, the horizontal axis shows the ratio of the opening area A ₁ of the valve 15 including the throttle 19 to the area A ₂ of the throttle 20, and the vertical axis shows the pressure P. If the valve 15 is fully closed, the value of the pressure P will be equal to the pressure _P1 of the port 22, and if the opening area _A1 is sufficiently larger than the area _A2 of the throttle 20, the value of the pressure P will be equal to the pressure of the intake pipe 8. Approach P _B. However, in reality, the maximum value of the aperture area A ₁ is limited by the aperture 19.

Next, control of the EGR amount of the entire system will be explained.

First, the conventional device shown in FIG. 2 will be described. The pressure P ₁ at the opening of the passage communicating with the throttle 20 to the intake passage 21 is atmospheric pressure, and the maximum value of the opening area A ₁ is usually selected to be about three times the area A ₂ as shown in FIG. As can be seen, the vacuum modulator 10 controls the pressure P in the diaphragm chamber 17 by using more than 90% of the negative pressure (P ₁ - P _B ) in the intake pipe 8, and controls the differential pressure across the EGR valve 6. We are trying to keep it at a constant value (ΔP) as much as possible. The amount of intake air G _A passing through the throttle valve 7 is proportional to A _A √ ₁ - _B , and EGR
The EGR amount G _E passing through the valve 6 is proportional to A _E √△.
Also, the relationship between the opening area A _A of the throttle valve and the opening area A _E of the EGR valve 6 is determined by the link 9 as A _E /A _A
= Assuming that it is kept constant, the ratio between the EGR amount G _E and the intake air G _A is It is expressed as However, C is a constant value.

Thus, as shown in equation (1), the EGR rate obtained by the conventional device shown in Fig. 2 seems to be independent of the engine speed and depends only on the intake pipe pressure P _B , but in reality, the EGR rate depends on the intake pipe pressure P B the higher the number
As the EGR amount increases, the piping resistance increases, so the EGR rate tends to decrease when the intake pipe pressure P _B approaches the atmospheric pressure P ₁ as shown in FIG. By the way, when the engine speed is low and the intake pipe pressure P _B is close to the atmospheric pressure P ₁ , the EGR is lower than when the engine speed is high due to engine performance compliance.
need to reduce the rate.

In the conventional device shown in FIG.
Consider a case where the full open area A' ₁ of the valve 15 including the throttle 19 is kept constant and the area A ₂ of the throttle 20 is gradually increased. Figure 5 shows that when the engine speed is constant,
The characteristics when the area A ₂ is changed are shown. When A' ₁ /A ₂ is about 3 or more than the conventional value, the intake pipe pressure P _B at the peak of the EGR rate characteristic curve does not change much, but when it changes from 3 to A' As ₁ / _A2 is decreased, the peak intake pipe pressure P _B gradually decreases. The reason is that the vacuum modulator 10 supplies the pressure P to the diaphragm chamber 17 to control the EGR control valve 4.
This is because it is limited to the shaded area in FIG. Furthermore, if the area A ₂ is increased (in other words, if A' ₁ /A ₂ is decreased), even when the intake pipe pressure P _B is small,
There is a tendency for the EGR rate to decrease. The reason is that even when obtaining the same pressure P value, the larger A ₂ is, the larger A ₁ needs to be correspondingly larger.
In other words, since the valve 15 is opened more, the set length of the spring 14 becomes longer, and the load on the spring 14 is reduced, so that the EGR
The pressure difference across the valve 6 becomes smaller and the EGR rate decreases.

Next, consider the case where the pressure P ₁ applied to the throttle 20 is gradually reduced from atmospheric pressure in a state where A' ₁ /A ₂ =1, for example. In this case, the EGR rate characteristic curve is A' ₁ /A
As in the case where ₂ is large, the peak value moves to the larger side of P _B again. The reason for this is that as the value of P ₁ decreases in FIG. 3, the limit value of the possible values of the pressure P approaches P _B.

Next, EGR rate control shown in FIG. 1 representing a specific example of the present invention will be explained. The negative pressure in the intake pipe 21 at the port 22 changes depending on the rotational speed and the intake pipe pressure P _B as shown in FIG. Generally, the higher the rotational speed, the greater the negative pressure in the port 22. Area A ₂ of the throttle 20 and opening area of the valve 15 including the throttle 19 when fully open
If the ratio A' ₁ /A ₂ to A' ₁ is made smaller than the conventional value of about 3, and the throttle 20 is connected to the port 22, the EGR rate characteristics will be the same as before when the engine speed is high, as shown in Figure 7. As the engine speed decreases, the peak value decreases and moves toward the side where the intake pipe pressure is lower.

Regardless of the fuel supply system, the port 22 location shown in FIG.
Even in the variable bench lily type or each cylinder fuel injection type, the port 22
A similar result is obtained because the negative pressure at is increased or decreased.
The same applies to the fixed bench lily type because the negative pressure in the bench lily increases and decreases with the engine speed.

According to this invention, compared to conventional configurations, it is possible to reduce the number of rotations in a region where the rotational speed is low and the intake pipe pressure is close to atmospheric pressure (when the vehicle speed is low and the throttle valve is wide open) without adding substantially any devices. EGR rate can be reduced. Conventionally, in order to reduce the flow rate of air flowing from the atmosphere into the intake pipe 8 through the throttle 20 and the valve 15 by bypassing the air amount measuring unit (the bench lily unit 23 in FIG. 2), the throttle 20 has been set at a limit that is suitable for mass production. A jet with a diameter of about 0.6 mm is used, and the aperture 19 has a diameter of 1 mm, which is three times the area of the aperture 20.
However, since the aperture 20 is too small, there is a risk of clogging, and the aperture 19 is too large, making it difficult to make the vacuum modulator compact.

According to the present invention, the aperture 20 is made large and the aperture 19
Since it can be made smaller, mass productivity can be improved. Further, since the air flowing through the throttles 20 and 19 can be the one that has passed through the air measuring section, there is an advantage that no error is caused in the air-fuel ratio measurement.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 2 is a block diagram of a conventional device, and Fig. 3 is a diagram of pressure P and A ₁ /A ₂
Figure 4 is a diagram showing the EGR rate characteristics of the conventional system, Figure 5 is a diagram showing changes in the EGR rate characteristics of the conventional system, and Figure 6 is the graph showing the EGR rate characteristics of the conventional system. A diagram showing changes in the negative pressure of the intake pipe 21 at the port 22 of the device, and FIG. 7 is a diagram showing the EGR rate characteristics in the control device of the present invention. 1...engine, 2...exhaust pipe, 3...passage, 4...
EGR control valve, 5...Passage, 6...EGR valve, 7...Throttle valve, 8...Intake pipe, 9...Link, 10...Vacuum modulator, 15...Variable throttle (valve), 1
6...Diaphragm, 17...Diaphragm chamber, 20
... Throttle, 21... Intake passage, 22... Port, 23...
Bench lily.

Claims (1)

[Claims] 1 Connects from the engine exhaust to the EGR control valve and the intake downstream of the throttle valve via the EGR valve.
Consists of EGR gas passage, throttle valve and EGR
A vacuum modulator 10 includes a valve that opens and closes in conjunction with the EGR valve and opens and closes by sensing the differential pressure across the EGR valve, and a first pressure source that connects the throttle and the vacuum modulator. a passage leading to the intake pipe through 10 valves, and the pressure between the throttle and the valve of the vacuum modulator 10 is equal to
In an exhaust gas recirculation amount control device configured to transmit information to a diaphragm chamber that drives an EGR control valve, the effective area A′ ₁ of the vacuum modulator when the valve is fully open and the effective area A ₂ of the throttle When the ratio is less than 3, the first pressure source is the intake passage upstream of the throttle valve, where negative pressure increases as the engine speed increases, and the port connecting this first pressure source and the throttle is a circular butterfly type throttle valve. Exhaust gas recirculation amount control device that opens between the top surface of the throttle valve and the bench lily when the throttle valve is fully closed.