JPS626102B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for controlling the ratio of the amount of exhaust gas recirculated to the engine intake amount (EGR rate) in a device for recirculating exhaust gas into the intake pipe downstream of the throttle valve of an internal combustion engine.

In recent years, the performance of electronic computers,
As reliability has improved and it has come to be installed in automobiles, there are attempts to control the amount of EGR using an actuator controlled by a computer, but the movement of the actuator uniquely corresponds to the amount of EGR. Therefore, the control range of the actuator has become very wide. For example, in order to control the EGR rate within the range of 3% at engine speed 1000rpm to 10% at 3000rpm, the EGR amount changes over a range of 10 times from minimum to maximum, and the actuator also requires a correspondingly wide control range. Therefore, it was difficult to manufacture the actuator. In addition, when the engine is operated in a place where the intake pipe pressure is low, there is a large amount of burned gas blown back into the intake pipe, and it is generally a light load range and it is necessary to reduce disturbances in engine torque due to the introduction of EGR gas. It is said that it is better to reduce the EGR rate. In view of the above, the present invention provides means for controlling the EGR rate with the actuator, thereby narrowing the range of protection of the actuator, and enabling faster response in a feedback system including a surge meter that senses the degree of surging of the vehicle. The first purpose is to provide. A second object is to provide an exhaust gas recirculation amount control device in which the EGR rate decreases as the intake pipe pressure decreases in locations where the intake pipe pressure is low.

Next, details of the present invention will be explained based on embodiments shown in the drawings.

In FIG. 1, an exhaust pipe 2 of an engine 1 is connected to a pipe 3, an EGR control valve 4, a passage 5, and an EGR valve 6.
An EGR passage is formed which passes through the throttle valve 7 and communicates with the intake pipe 8 downstream of the throttle valve 7. The EGR valve 6 is connected to the throttle valve 7 by a link 9.
The vacuum modulator 10 has a passage 5 and an intake pipe 8.
It consists of a diaphragm 11 that senses the pressure difference ΔP, a valve 12 that is opened and closed by the diaphragm 11, and a spring 13 that pushes the diaphragm in a direction that opens the valve 12 when the pressure difference ΔP becomes small. The EGR control valve 4 is fixed to the diaphragm 14 and is driven by the pressure within the diaphragm chamber 15 and the force of a spring 16 located within the diaphragm chamber 15 that pushes the diaphragm 14 in the direction of closing the EGR control valve 4. be done. A passage is formed that passes through the variable throttle 17, the throttle 18, and the valve 12 and leads to the intake pipe 8.
The passage between the variable throttle 17 and the throttle 18 is connected to the diaphragm chamber 15. The variable throttle 17 consists of an annular throttle 17a and a needle valve 17b driven axially therein by a step motor 20. The upstream side of the variable throttle 17 is open to approximately atmospheric pressure upstream of the carburetor bench lily section 21. Drive wheels 22 of the vehicle are driven by the engine 1 via a torque sensor 23 and a torque transmission shaft 24 . The computer 25 receives electrical signals representing the opening of the throttle valve 7, the pressure of the intake pipe 8, torque fluctuations from the torque sensor 23, etc., and outputs electrical signals for driving the step motor 20. 19 is a transducer that converts the pressure in the intake pipe 8 into voltage.

The embodiment of FIG. 2 differs from that of FIG. 1 in that the upstream side of the variable throttle 17 is connected to a port 27 that opens into the intake passage 26 upstream of the throttle valve 7 and downstream of the vent lily portion 21.

In the embodiment shown in FIG. 3, the variable throttle 17 is opened to almost atmospheric pressure upstream of the bench lily portion 21, as in FIG. The port 27 is connected to the port 27 at the same position as in FIG.

First, the operation will be explained with reference to FIG. The amount of intake air GA taken into the engine 1 through the throttle valve is determined by the opening area A _A of the throttle valve 7 and the pressure difference between the pressure P ₁ upstream thereof and the pressure P _B of the intake pipe 8 downstream. The EGR amount G _E taken into the engine 1 is the opening area A _E of the EGR valve 6 and the differential pressure △ before and after it.
It is determined by P. Vacuum modulator 10 is
By sensing the differential pressure △P across the EGR valve 6, if △
When P becomes smaller, the valve 12 is opened to supply more negative pressure from the intake pipe 8 to the diaphragm chamber 15, and the EGR
The control valve 4 is opened to try to increase ΔP. Conversely, when ΔP increases, the valve 12 is closed, and since the diaphragm chamber 15 communicates with atmospheric pressure via the variable throttle 17, the EGR control valve 4 is closed to decrease ΔP. Thus, the vacuum modulator 10
maintains the differential pressure △P across the EGR valve 6 at a constant value. Assuming that the ratio between the opening area A _A of the throttle valve 7 and the opening area A _E of the EGR valve 16 is kept constant by the link 9, G _A ∝A _A √ ₁ - _B G _E ∝A _E √ △ Therefore, the ratio between G _E and G _A is However, C is a constant. Here, assuming that P ₁ is approximately atmospheric pressure, it can be seen that the EGR rate depends only on the pressure P _B of the intake pipe 8. Here, let us consider the pressure at each part of the air passageway that flows into the intake pipe 8 via the variable throttle 17, fixed throttle 18, and valve 12. Assuming that the opening area of the variable throttle 17 is A ₂ , the opening area of the valve 12 including the throttle 18 is A ₁ , and the pressure upstream of the variable throttle 17 is P ₀ , the pressure in the passage between the variable throttle 17 and the throttle 18 is The pressure P in the diaphragm chamber 15 is expressed as shown in FIG. However, the ratio A ₁ /A ₂ of A ₁ and A ₂ is set on the horizontal axis. That is, when the valve 12 is closed and A ₁ =0, the pressure P becomes equal to Pa,
When the valve 12 opens and A ₁ becomes sufficiently large compared to A ₂ , P becomes sufficiently close to P _B . Conventionally, variable aperture 17
Instead, there is one that has a fixed throttle and opens the upstream to atmospheric pressure, and in order to satisfy formula (1) as much as possible, the opening area of the valve 12 including the throttle 18 when fully open is
The ratio of A' ₁ and A ₂ is set to 3 or more, that is, according to Fig. 4, more than 90% of the pressure difference between P ₀ and P _B is utilized, and its characteristics are shown in Fig. 5. Something was warm. FIG. 5 shows the EGR rate characteristics when the horizontal axis represents the intake pipe pressure P _B and the engine speed is kept constant.

Here, if we consider the case where the opening area _A2 of the variable diaphragm 17 is increased, the valve 1 including the diaphragm 18
The area A' ₁ when the valve 2 is fully open is determined by the throttle 18, and as A ₂ increases and A' ₁ /A ₂ becomes smaller than 3, the possible range of the pressure P becomes, for example, It is limited to the shaded area in Figure 4. As a result, the EGR rate moves from curve a to curve c shown in FIG. Here, curve a is the conventional
A′ ₁ /A ₂ is about 3, and curve c shows the characteristics when A′ ₁ /A ₂ is smaller than 3. That is, the position of the peak of the EGR rate gradually shifts to the side where the intake pipe pressure P _B is smaller. This is because the lower limit of the range of pressure P increases, and the limit intake pipe pressure P _B that lifts the diaphragm 14 and opens the EGR control valve 4 becomes smaller. At the same time, curve c tends to decrease compared to curve a even when the intake pipe pressure P _B is small. The reason for this is that when _the area A ₂ of the variable throttle 17 is increased, the intake air _is The flow rate of air flowing into the pipe 8 increases, and therefore, in order to maintain the same pressure P, the valve 12 is slightly opened, and the length of the spring 13 during regulation is used in an extended state, so the EGR This is thought to be because the differential pressure ΔP across the valve is controlled to be smaller. That is, by changing the area _A2 of the variable aperture 17, the EGR rate changes as shown in FIG.

It is known that the riding comfort of a vehicle is closely related to the torque fluctuation rate sensed by the torque meter 23 attached to the torque transmission shaft 24 that transmits torque from the engine 1 to the wheels. When operating at a lean air-fuel ratio, the more EGR the better.
On the other hand, if the EGR is increased, the torque fluctuation rate increases and the riding comfort deteriorates, so a feedback system that senses the torque fluctuation rate and corrects the EGR amount has already been established as a known technology. Therefore,
Enters the computer 25 from the torque sensor 23,
A detailed description of the electric circuit that drives the step motor 20 will be omitted. The step motor 20 is configured to rotate the rotor around the axis by a predetermined angle stepwise by an electric step input, and to move the needle valve 17b forward and backward in the axial direction by turning a screw fixed to the rotor. However, since the step motor is well known, the explanation thereof will be omitted. Furthermore, there are other mechanisms for changing the degree of aperture based on electrical signals, such as a method for changing the opening/closing time ratio of a solenoid valve, but these are out of the scope of the present invention and will not be explained here. The opening degree of the throttle valve 7 and the intake pipe pressure are input into the computer in order to detect the idle state and sudden acceleration/deceleration and correct the feedback control by the torque sensor 23 and the step motor 20.

Next, FIG. 2 will be explained. The variable throttle 17 is not open to the atmosphere as shown in FIG. 1, but communicates with the intake passage on the upstream side of the throttle valve 7. Therefore, the variable throttle 17 is not opened to the atmosphere as shown in FIG. Since there is no air flow flowing into the intake pipe 8 through the valve 12, there is an advantage that the air-fuel ratio metering system is not obstructed, but the EGR rate control is essentially the same as in FIG. 1.

In Fig. 1, we explained that when the opening area _A2 of the variable diaphragm 17 is increased, the curve shifts from curve a to c in Fig. 6, but in state c, the pressure upstream of the variable diaphragm 17 is decreased from atmospheric pressure. It is known that it returns to the direction of and a. That is, by locating the port 27 upstream of the throttle valve 7 at a location where the negative pressure increases as the opening degree of the throttle valve 7 increases, the EGR rate characteristics shown in FIG. 6 can be changed depending on the engine speed. However, the relationship between the change in the EGR rate and the variable throttle 17 is essentially the same as that shown in FIG. Further, in FIG. 3, two types of EGR rate characteristics are obtained by fully closing and fully opening the actuator.

According to this invention, by simply changing the area _A2 of the variable aperture 17, the EGR rate can be increased or decreased around the curve b showing the basic characteristics as shown in FIG. Since it is known that it is not affected much by the rotation speed, the torque sensor 23,
By being incorporated into the EGR feedback system composed of the computer 25, step motor 20, and variable throttle 17, it is possible to quickly respond even if the engine operating load changes suddenly.
Further, since the range of movement of the actuator can be narrow, there is an advantage that there is no need to ensure accuracy as in the conventional case. Furthermore, when the intake pipe pressure is lower than the intake pipe pressure when the EGR rate is at its peak value, as shown in FIG. 6, a desirable control characteristic for engine operation is obtained in which the EGR rate decreases as the intake pipe pressure decreases.

In the example shown in FIG. 3, different EGR rate characteristics can be obtained by fully closing and fully opening the variable diaphragm, so it can also be used for simple EGR rate correction.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing an embodiment of this invention;
The figure shows another embodiment, Fig. 3 shows a further another embodiment, Fig. 4 shows a diagram showing the relationship between pressure P and A ₁ /A ₂ , and Fig. 5 shows the EGR rate and intake pipe in the conventional configuration. FIG. 6 is a diagram showing the relationship between the change in the EGR rate and _{the intake pipe pressure P B in} the embodiment shown in FIG. 1. 1... Engine, 2... Exhaust pipe, 4... EGR control valve, 6... EGR valve, 7... Throttle valve, 8... Intake pipe, 9... Link, 10... Vacuum modulator, 12... Valve, 14... Diaphragm, 15...Diaphragm chamber, 17...Variable throttle, 19...Pressure-voltage transducer, 20...Step motor, 23
...Torque sensor, 25...Computer, 26...Intake passage, 27...Port.

Claims (1)

[Claims] 1 Connects from the engine exhaust pipe to the intake pipe downstream of the throttle valve through the EGR control valve and EGR valve.
The EGR gas passage consists of a throttle valve and an EGR
A vacuum modulator is equipped with a valve that opens and closes in conjunction with the EGR valve, and is opened and closed by sensing the differential pressure across the EGR valve, and operates in the direction of closing as the differential pressure increases, and a valve upstream of the throttle valve. Alternatively, it has a passage communicating from the atmosphere to the intake pipe through a variable throttle and the valve of the vacuum modulator, and the pressure between the variable throttle and the valve of the vacuum modulator drives the EGR control valve. The EGR control valve has a configuration in which the pressure is transmitted to a diaphragm chamber, and the smaller the pressure transmitted to the diaphragm chamber, the wider the EGR control valve opens, and the opening area of the variable throttle is changed according to the operating state of the engine. Let EGR
Exhaust gas recirculation rate control device.