JPS59120770A - Egr control device of internal-combustion engine - Google Patents

Abstract

PURPOSE:To allow the highly precise EGR control without being influenced by the EGR valve characteristics and exhaust pressure by providing an oxygen sensor on a suction passage downstream an EGR feedback port and controlling the opening of the EGR valve so as to maintain the detected value of the oxygen density at a target value. CONSTITUTION:The oxygen density is detected by an oxygen sensor 14 provided downstream the EGR feedback port 12b of a suction passage 4, and the detected value O2a is compared with a predetermined value O2L of the oxygen density set in accordance with a load T. When O2a<O2L, a switch circuit 16 is opened to de-energize a solenoid 20, a valve 22 is switched to the open side of the atmosphere opening 29, the atmospheric pressure is introduced into an actuator 26, thus the opening of an EGR valve 10 is decreased. On the other hand, when O2b>O2L, the switch circuit 16 is closed and the solenoid 20 is energized through an amplifier 18, and the valve 22 is moved downward against a spring 24. Thereby, the negative pressure in a vacuum pump 28 is introduced into the actuator 26, and the opening of the EGR valve 10 is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an EGR control device for an internal combustion engine, and in particular detects the oxygen concentration in intake air on the downstream side of exhaust gas recirculation and maintains this oxygen concentration at a target value. The present invention relates to an EGR control device for an internal combustion engine that accurately controls the amount of EGR corresponding to engine conditions such as engine speed.

Some EGR control devices for internal combustion engines control the amount of EGR by adjusting the EGR valve opening based on the carburetor throttle valve opening and the intake negative pressure associated with the carburetor throttle valve opening. The above-mentioned measures have successfully reduced the amount of nitrogen oxides (NOx) that are harmful components in exhaust gas. However, controlling the EGR amount by changing the opening degree of the carburetor throttle valve or the intake negative pressure has the disadvantage that the EGR amount cannot be accurately controlled due to the influence of the EGR valve characteristics and exhaust pressure.

Therefore, an object of the present invention is to detect the oxygen concentration of the air-fuel mixture using an air-fuel ratio sensor such as an oxygen sensor installed downstream of the EGR recirculation port in the intake passage, and to maintain this oxygen concentration at a target value to reduce the load. To realize an EGR control device for an internal combustion engine that can accurately perform EGR control corresponding to engine conditions such as engine speed without being affected by EGR valve characteristics or exhaust pressure, and can reduce NOx emissions. .

Therefore, in order to achieve this object, this invention controls the opening degree of the EGR valve to maintain the oxygen concentration detected by the oxygen sensor installed in the intake passage downstream of the EGR recirculation port at a target value, thereby performing EGR control. It is characterized by

Embodiments of the present invention will be described in detail below based on the drawings.

In FIG. 1, 2 is an engine, 4 is an intake passage, 6 is an exhaust passage, 8 is an EGR recirculation passage, 10 is an EGR valve, 1
2a is an EGR intake port, and 12b is an EGR reflux port. An oxygen sensor is provided on the downstream side of the EGR recirculation port 121) of the intake passage 4, and the relationship between the oxygen concentration, EGR amount, and load T at this point A is shown in FIG. As shown in FIG. 2, the oxygen concentration is inversely proportional to the increase or decrease in EGRI.

Further, FIG. 3 shows the relationship between the NOx concentration, the EGR amount, and the load at point B on the upstream side of the EGRI inlet 12a of the exhaust passage 6. As shown in FIG. 3, the NOx concentration is inversely proportional to the increase or decrease in the amount of EGR.

From the graph of FIG. 2, the graph of FIG. 4 showing the relationship between the load T and the EGR amount is derived. That is, as shown in FIG. 4, when the oxygen concentration is constant (for example, OZa, or 02°), the load T and the EGR amount are inversely proportional at a predetermined rate. Therefore, in order to bring the detected value of oxygen concentration closer to the target value according to the load T, the EGR valve opening degree is adjusted, thereby making it possible to perform accurate EGR control.

5 to 9 show a first embodiment of the present invention.

The EGR control circuit will be explained with reference to FIG.

An oxygen sensor 14 is provided downstream of the EGR recirculation port 12b of the intake passage 4, and a sui-nochi circuit 16 is connected to the oxygen sensor 14. As shown in FIG. 6.9, the switch circuit No. 16 is normally open until the oxygen sensor output (2), which is proportional to the oxygen concentration, exceeds a predetermined oxygen sensor output vL. Then, an amplifier 1B and a solenoid 20 are connected in series to the switch circuit 16. The solenoid 20
The opening/closing mechanism of the solenoid valve 22 is constructed as follows.

The solenoid valve 22 has a solenoid 20 and a biasing means 2.
It is configured to be opened and closed by 4. That is, when the switch circuit 16 is opened, the solenoid valve 20 is energized, and the solenoid valve 22 is moved in the direction B against the energizing means 24, and the actuator 26 and the vacuum pump 28
The structure is such that the nozzle opening 27 is communicated with the nozzle opening 27. Further, when the switch circuit 16 is opened, the solenoid valve 22 is moved in the direction A by the urging means 24, thereby communicating the actuator 26 and the atmospheric opening 29.

The configuration is such that the opening degree of the EGR valve 10 can be controlled by operating the actuator 26. Further, the solenoid valve 22 has a three-way valve function that closes the atmospheric opening 29 when the vacuum opening 27 is opened, and, conversely, opens the atmospheric opening 29 when the vacuum opening 27 is closed.

Next, the effect will be explained.

An oxygen sensor 14 provided downstream of the EGR recirculation port 12b of the intake passage 4 detects the oxygen concentration.

When the relationship between this detected oxygen concentration value OZa and the predetermined value 02L of oxygen concentration according to the load T is 02a<02L, from FIG. 9, the oxygen sensor output also becomes Va<■1.

For this reason, the Sui 7,000 circuit 16 was opened, and the amplifier 18
Since no voltage is applied to the solenoid 20 or the solenoid 20, the solenoid 20 is not energized, and the solenoid valve 22 is activated by the biasing means 2.
4 in the direction A, and the actuator 26 and the atmospheric opening 29 communicate with each other. Then, the EGR valve opening degree is reduced by the spring force of the actuator 26 to reduce the EGR amount, and the oxygen concentration is increased to control the oxygen concentration from the detected value 02a to the target value 02L. That is, as a result, the EGR amount is accurately limited.

Further, when the relationship between the detected value 02b of the oxygen concentration and the predetermined value 02L is 0□6>02L, the oxygen sensor output also becomes vb>vL from FIG. 9. Therefore, the switch circuit 16
becomes open state and 1. The oxygen sensor output vb is amplified by the amplifier 18 and reaches the solenoid 20. This results in
The solenoid 20 is energized and moves the solenoid valve 22 in the direction B against the biasing means 24, thereby communicating the vacuum opening 27 of the vacuum pump 28 and the actuator 26. The actuator 26 is actuated in the inward direction by the negative pressure of the vacuum pump 28, the EGR amount is increased by adjusting the EGR valve opening degree, and the oxygen concentration is controlled from the detected value 02b to the target value 02L. It is something.

As a result, the EGR valve opening degree can be adjusted according to the detected value of the oxygen concentration, the EGR amount can be controlled, and the target value of the oxygen concentration can be set to 021- according to the load T, as shown in FIG. be. In other words, as a result, the EGR amount is increased accurately.

10 to 12 show a second embodiment of this invention,
This is an example of an electronic control system. In this second embodiment, parts that perform the same functions as those in the first embodiment described above are given the same reference numerals and will be explained.

The feature of this second embodiment is that the oxygen concentration is electronically controlled by the control unit 30 according to the load T and the engine speed Ne. In other words, the load T
Converts the detected value of 32 into an electric signal, and also converts the detected value of the engine rotation speed Ne and oxygen concentration into an electric signal 34.
36 and input the respective electrical signals to the control unit 30. Then, as shown in FIG.
The EGR pulp opening degree is adjusted 38 in order to control the oxygen concentration 40 according to the load T and engine speed Ne.
The configuration is such that the amount of EGR is controlled.

In this case, if the detected value of the oxygen concentration is smaller than the target value according to the load T and the engine speed Ne, the control unit 30 makes the EGR valve opening small, reduces the EGR amount, and reduces the oxygen concentration. This is to raise the value and set it as a target value. Further, if the detected value of oxygen concentration is larger than the target value, the control unit 30
The R valve opening degree is increased and EGRi is increased to lower the oxygen concentration to the target value. As a result, the EGR amount is controlled to a predetermined amount.

As described in detail above, according to the present invention, the EGR valve opening degree is controlled to maintain the oxygen concentration detected by the oxygen sensor provided in the intake passage downstream of the EGR recirculation port at a target value, thereby performing EGR control. Therefore, the EG of the intake passage
An oxygen sensor installed downstream of the R recirculation port detects the oxygen concentration of the air-fuel mixture, and by maintaining this oxygen concentration at a target value, the E
GR control can be performed accurately while eliminating the adverse effects of EGR valve characteristics and exhaust pressure, and the amount of NOx exhaust can be effectively reduced.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of the EGR device of the present invention, Figure 2 is a graph showing the relationship between EGR amount and oxygen concentration according to load, and Figure 3 is a graph showing the relationship between EGR amount and oxygen concentration according to load.
The figure shows EGR amount and N according to load. A graph showing the relationship between the X concentration and FIG. 4 is a graph showing the relationship between the load and the EGR amount depending on the oxygen concentration. 5 to 9 show a first embodiment of this invention,
Figure 5 is a schematic explanatory diagram of the EGR control device, Figure 6 is a graph showing the open/closed state of the switch circuit, Figure 7 is a graph showing the relationship between EGR amount and oxygen concentration according to load, and Figure 8 is oxygen concentration. 9th graph showing the relationship between load and EGR amount according to
FI! J is a graph showing the relationship between oxygen concentration and oxygen sensor output. 10 to 12 show a second embodiment of the present invention, in which FIG. 10 is a schematic diagram of the EGR device, FIG. 11 is a system diagram of the electronic control circuit, and FIG. 12 is a diagram showing the load, engine speed, It is a graph showing each relationship of oxygen concentration three-dimensionally. In the figure, 2 is the engine, 4 is the intake passage, 6 is the exhaust passage, 8 is the recirculation passage, 1o is the EGR valve, 14 is the oxygen sensor, 16 is the sui 7,000 circuit, 18 is the amplifier, and 20 is the solenoid. . Agent Patent Attorney Yoshimi Saigo

Claims (1)

[Claims] An EGR control device for an internal combustion engine, characterized in that the EGR control device performs EGR control by controlling an EGR valve opening to maintain an oxygen concentration detected by an oxygen sensor provided in an intake passage downstream of an EGR recirculation port at a target value.